JP7018295B2 - Conductive paste - Google Patents

Description

The present invention relates to a conductive paste.

In recent years, various developments have been made on materials used for wiring constituting elastic wiring boards. As a technique of this kind, for example, the technique described in Patent Document 1 is known. According to the same document, it is described that the binder rubber polymer and the conductive powder were mixed at a ratio of 2: 8 (weight ratio), dispersed in a three-roll mill, and then the viscosity was adjusted with a solvent to obtain a conductive paste. (Paragraph 0037 of Patent Document 1).

JP-A-2015-55615

However, as a result of examination by the present inventor, it has been found that the conductive paste described in the above document has room for improvement in terms of printability and durability.

As a result of further studies, the present inventor has further investigated and found that by further adding silica particles to a conductive paste containing a conductive filler, printability and durability are obtained in a conductive resin film such as wiring using the conductive paste. It was found that the present invention can be improved, and the present invention has been completed.

According to the present invention
An elastomer composition containing silica particles (C) and
With conductive filler ,
A conductive paste containing a solvent and
The conductive filler contains a lint-like metal powder (G) and contains.
The content of the conductive filler is 40 % by mass or more and 85% by mass or less with respect to the entire conductive paste.
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.
The content of the silica particles (C) is 1% by mass or more and 15% by mass or less with respect to the entire conductive paste , and the total amount of the silica particles (C) and the conductive filler is 100% by mass. 1% by mass or more and 20% by mass or less with respect to%.
The viscosity of the conductive paste as measured at a shear rate of 20 [1 / s] at room temperature of 25 ° C. is 1 Pa · s or more and 100 Pa · s or less.
A conductive paste is provided.

According to the present invention, it is possible to provide a conductive paste having excellent printability and durability.

It is sectional drawing which shows the outline of the electronic apparatus in this embodiment. It is sectional drawing which shows the outline of the manufacturing process of the electronic device in this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by the same reference numerals, and description thereof will be omitted as appropriate. Further, in the present specification, "-" indicates the following from the above unless otherwise specified.

The outline of the conductive paste of this embodiment will be described.
The conductive paste of the present embodiment contains an elastomer composition containing silica particles (C) and
It can contain a conductive filler and a solvent.

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

Since the conductive paste of the present embodiment contains silica particles in addition to the conductive filler, it is possible to improve the mechanical strength and durability of the elastomer composed of the cured product of the conductive paste. 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. This makes it possible to enhance the stretchable electrical characteristics of the stretchable wiring board provided with the wiring formed of the conductive paste of the present embodiment.

Hereinafter, each component of the conductive paste of the present embodiment will be described.

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, appropriate elasticity can be exhibited with respect to the elastomer. Further, the conductive paste of the present embodiment can contain silica particles (C). This makes it possible to improve the durability and mechanical strength of the elastomer.

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

(Elastomer)
As the elastomer, silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, ethylene propylene rubber and the like can be used. Among these, the elastomer can include one or more thermosetting elastomers selected from the group consisting of silicone rubber, urethane rubber, and fluororubber. Further, 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 the 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 product of the thermoplastic elastomer. In the present specification, the elastomer of the conductive paste means an elastomer formed by drying or curing the conductive paste.

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

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 which is a main component of the silicone rubber-based curable composition of the present embodiment.

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

The vinyl group-containing linear organopolysiloxane (A1) has a linear structure and contains a vinyl group, and the vinyl group serves as a cross-linking point at the time of curing.

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

In the present specification, the vinyl group content is the mol% of the vinyl group-containing siloxane unit when all the units constituting the vinyl group-containing linear organopolysiloxane (A1) are 100 mol%. .. However, it is considered that there is one vinyl group for each vinyl group-containing siloxane unit.

The degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably in the range of, for example, preferably about 1000 to 10000, and more preferably about 2000 to 5000. The degree of polymerization can be determined, for example, as the polystyrene-equivalent number average degree of polymerization (or number average molecular weight) in GPC (gel permeation chromatography) using chloroform as a developing solvent.

Further, 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.

By using a vinyl group-containing linear organopolysiloxane (A1) having a degree of polymerization and specific gravity within the above range, the silicone rubber obtained has heat resistance, flame retardancy, chemical stability, etc. Can be improved.

The vinyl group-containing linear organopolysiloxane (A1) preferably has a structure represented by the following formula (1).

In formula (1), R ¹ is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an alkenyl group, an aryl group, or a hydrocarbon group in which these are combined. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, a butenyl group and the like, and among them, a vinyl group is preferable. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group and the like.

Further, R ² is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an alkenyl group, an aryl group, or a hydrocarbon group in which these are combined. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

Further, R ³ is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group in which these are combined. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group.

Further, examples of the substituent of R ¹ and R ² in the formula (1) include a methyl group, a vinyl group and the like, and examples of the substituent of R ³ include a methyl group and the like.

In the equation (1), the plurality of R ^1s are independent of each other and may be different from each other or may be the same. The same applies to R ² and R ³ .

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

Moreover, as a specific structure of the vinyl group-containing linear organopolysiloxane (A1) represented by the formula (1), for example, the one represented by the following formula (1-1) can be mentioned.

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

Further, the vinyl group-containing linear organopolysiloxane (A1) contains a first vinyl group having a vinyl group content of 2 or more in the molecule and 0.4 mol% or less. 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 it. As raw 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 direct having a high vinyl group content. By combining with a chain organopolysiloxane (A1-2), the vinyl group can be unevenly distributed, and the cross-linking density can be more effectively formed in the cross-linking network of the silicone rubber. As a result, the tear strength of the silicone rubber can be increased more effectively.

Specifically, as the vinyl group-containing linear organopolysiloxane (A1), for example, in the above formula (1-1), a unit in which R ¹ is a vinyl group and / or a unit in which R ² is a vinyl group is used. , 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 the unit in which ² is a vinyl group.

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

Further, when the first vinyl group-containing linear organopolysiloxane (A1-1) and the second vinyl group-containing linear organopolysiloxane (A1-2) are blended in combination (A1-1). The ratio of 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: It is more preferably 10.

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

Further, the vinyl group-containing organopolysiloxane (A) may contain a vinyl group-containing branched organopolysiloxane (A2) having a branched structure.

<< Organohydrogen Polysiloxane (B) >>
The silicone rubber-based curable composition of the present embodiment can contain organohydrogenpolysiloxane (B).
The organohydrogenpolysiloxane (B) is classified into a linear organohydrogenpolysiloxane (B1) having a linear structure and a branched organohydrogenpolysiloxane (B2) having a branched structure. Either one or both can 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 a vinyl group-containing organopolysiloxane (A). In addition to the vinyl group, it is a polymer that undergoes a hydrosilylation reaction with the vinyl group contained in the components contained in the silicone rubber-based curable composition to crosslink these components.

The molecular weight of the linear organohydrogenpolysiloxane (B1) is not particularly limited, but for example, the weight average molecular weight is preferably 20000 or less, and more preferably 1000 or more and 10000 or less.

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.

Further, the linear organohydrogenpolysiloxane (B1) is usually preferably one having no vinyl group. This makes it possible to accurately prevent the cross-linking reaction from proceeding 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), ^R4 is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an alkenyl group, an aryl group, a hydrocarbon group combining these, or a hydride group. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, a butenyl group and the like. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

Further, R5 is a substituted or unsubstituted alkyl group having 1 to ¹⁰ carbon atoms, an alkenyl group, an aryl group, a hydrocarbon group combining these, or a hydride group. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group and a propyl group, and among them, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, a butenyl group and the like. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In the equation (2), the plurality of R ^4s are independent of each other and may be different from each other or may be the same. The ^same applies to R5. However, of the plurality of R ⁴ and R ⁵ , at least two or more are hydride groups.

Further, R ⁶ is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group in which these are combined. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. The plurality of ^R6s are independent of each other and may be different from each other or may be the same.

Examples of the substituent of R ⁴ , R ⁵ , and R ⁶ in the formula (2) include a methyl group and a vinyl group, and a methyl group is preferable from the viewpoint of preventing an intramolecular cross-linking reaction.

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

The linear organohydrogenpolysiloxane (B1) may be used alone or in combination of two or more.

Since the branched organohydrogenpolysiloxane (B2) has a branched structure, it forms a region having a high crosslink density and is a component that greatly contributes to the formation of a dense structure having a crosslink density 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 hydrosilylates with the vinyl group of the component contained in the rubber-based curable composition and crosslinks these components.

The specific gravity of the branched organohydrogenpolysiloxane (B2) is in the range of 0.9 to 0.95.

Further, the branched organohydrogenpolysiloxane (B2) is usually preferably one having no vinyl group. This makes it possible to accurately prevent the cross-linking reaction from proceeding in the molecule of the branched organohydrogenpolysiloxane (B2).

The branched organohydrogenpolysiloxane (B2) is preferably represented by the following average composition formula (c).

Average composition formula (c)
(H _a (R ⁷ ) _3-a SiO _1/2 ) _m (SiO _4/2 ) _n
(In the formula (c), R ⁷ is a monovalent organic group, a is an integer in the range of 1 to 3, m is _a number of Ha (R ⁷ ) _3-a SiO _1/2 units, and n is SiO _{4 /.} It 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 in combination thereof. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

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

Further, in the formula ( _c ), m is the number of Ha (R ⁷ ) _3-a SiO _1/2 unit, and n is the number of SiO _4/2 unit.

The branched organohydrogenpolysiloxane (B2) has a branched structure. The linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) differ in that their structure is linear or branched, and the Si is the same as when the number of Si is 1. The number of alkyl groups R to be bonded (R / Si) is 1.8 to 2.1 for the linear organohydrogenpolysiloxane (B1) and 0.8 to 1 for the branched organohydrogenpolysiloxane (B2). It is in the range of 0.7.

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

Further, 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, or a hydrocarbon group in combination thereof, or a hydrogen atom. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. Examples of the substituent of R ⁷ include a methyl group and the like.

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

Further, in the equation (3), "-O-Si≡" indicates that Si has a branched structure that spreads three-dimensionally.

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

Further, 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, the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpoly are added to 1 mol of the vinyl group in the vinyl group-containing linear organopolysiloxane (A1). The total amount of hydride groups of siloxane (B2) is preferably 0.5 to 5 mol, more preferably 1 to 3.5 mol. This ensures that a crosslinked network is formed between the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) and the vinyl group-containing linear organopolysiloxane (A1). Can be made to.

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, based on the entire conductive paste. The above is more preferable. 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 more preferably 15% by mass or less with respect to the entire conductive paste. Is even more preferable.
By setting the content of the elastomer composition to the above lower limit value 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 value or less, the mechanical strength of the elastomer can be improved.

<< Silica particles (C) >>
The conductive paste of the present embodiment may contain silica particles (C), if necessary. This makes it possible to improve the hardness and mechanical strength of the elastomer formed from the conductive paste.

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

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

By using the silica particles (C) within the range of the specific surface area and the average particle size, it is possible to improve the hardness and mechanical strength of the formed silicone rubber, particularly the tensile strength.

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, based on the whole of the conductive paste. It is more preferably 3% by mass or more. 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 whole of the conductive paste. The following is more preferable.
By setting the content of the silica particles (C) to the above lower limit value or more, the elastomer of the conductive paste can have an appropriate mechanical strength. Further, by setting the content of the silica particles (C) to the above upper limit value or less, the elastomer can have an appropriate conductive property.

<< Silane Coupling Agent (D) >>
The silicone rubber-based curable composition of the present embodiment can contain a silane coupling agent (D).
The silane coupling agent (D) can have a hydrolyzable group. The hydrolyzing group is hydrolyzed by water to become a hydroxyl group, and this hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl group on the surface of the silica particles (C), whereby the surface of the silica particles (C) can be modified.

Further, the silane coupling agent (D) can include a silane coupling agent having a hydrophobic group. As a result, this hydrophobic group is imparted to the surface of the silica particles (C), so that the cohesive force of the silica particles (C) is reduced in the silicone rubber-based curable composition and thus in the silicone rubber (hydrogen due to the silanol group). 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. As a result, the interface between the silica particles and the rubber matrix increases, and the reinforcing effect of the silica particles increases. Further, it is presumed that the slipperiness of the silica particles in the matrix is improved when the rubber matrix is deformed. Then, by improving the dispersibility and slipperiness of the silica particles (C), the mechanical strength (for example, tensile strength, tear strength, etc.) of the silicone rubber due to the silica particles (C) is improved.

Further, the silane coupling agent (D) can include a silane coupling agent having a vinyl group. As a result, a vinyl group is introduced on the surface of the silica particles (C). Therefore, when the silicone rubber-based curable composition is cured, that is, the vinyl group of the vinyl group-containing organopolysiloxane (A) and the hydride group of the organohydrogenpolysiloxane (B) undergo a hydrosilylation reaction. When the network (crosslinked structure) formed by these is formed, the vinyl group of the silica particles (C) is also involved in the hydrosilylation reaction with the hydride group of the organohydrogenpolysiloxane (B). Silica particles (C) will also be incorporated into. 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).

Y _n -Si- (X) _4-n ... (4)
In the above equation (4), n represents an integer of 1 to 3. Y represents any 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 them is. 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 in which these are combined, and examples thereof include a methyl group, an ethyl group, a propyl group, a phenyl group, and the like. Methyl groups are preferred.

Examples of the hydrophilic group include a hydroxyl group, a sulfonic acid group, a carboxyl group, a carbonyl group and the like, and 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, examples of the hydrolyzable group include an alkoxy group such as a methoxy group and an ethoxy group, a chloro group or a silazane group, and among them, a silazane group is preferable because it has high reactivity with the silica particles (C). A group having a silazane group as a hydrolyzable group has two structures of ( _Yn —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 methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, and methyltri, as those having a hydrophobic group as a functional group. Alkoxysilanes such as ethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane; methyltrichlorosilane , Chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane; hexamethyldisilazane, examples of which have a vinyl group as a functional group include methacrypropyltriethoxysilane, methacrypropyltrimethoxysilane, methacryoxy. Ekalkylsilanes such as propylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane, vinylmethyldichlorosilane; divinyltetramethyldi Examples thereof include silazanes, but in consideration of the above description, hexamethyldisilazane is particularly preferable as having a hydrophobic group, and divinyltetramethyldisilazane is preferable as having a vinyl group.

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 5% by mass or more, and further preferably 5% by mass or more. The upper limit of the content of the silane coupling agent (D) is preferably 100% by mass or less, preferably 80% by mass or less, based on 100 parts by mass of the total amount of the vinyl group-containing organopolysiloxane (A). It is more preferably present, and further preferably 40% by mass or less.
By setting the content of the silane coupling agent (D) to the above lower limit value or more, the elastomer of the conductive paste has an appropriate adhesion to the substrate, and when the silica particles (C) are used, the elastomer It can contribute to the improvement of mechanical strength as a whole. Further, by setting the content of the silane coupling agent (D) to the above upper limit value or less, the elastomer can have appropriate mechanical properties.

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

As the platinum or the platinum compound (E), known ones can be used, for example, platinum black, platinum supported on silica, carbon black or the like, platinum chloride acid or an alcohol solution of platinum chloride acid, chloride. Examples thereof include a complex salt of platinum acid and olefin, and a complex salt of platinum chloride acid and vinyl siloxane.

As the platinum or the platinum compound (E), only one type may be used alone, or two or more types may be used in combination.

In the present embodiment, the content of platinum or the platinum compound (E) in the conductive paste is preferably 0.0001% by mass or more, preferably 0.0002% by mass or more, based on the total amount of the conductive paste. It is more preferably present, and further preferably 0.0003% by mass or more. The content of platinum or the platinum compound (E) in the conductive paste is preferably 1% by mass or less, more preferably 0.5% by mass or less, based on the whole conductive paste. , 0.1% by mass or less is more preferable.
By setting the content of platinum or the platinum compound (E) to the above lower limit value or more, the conductive paste can be cured at an appropriate rate. Further, by setting the content of platinum or the platinum compound (E) to the above upper limit value or less, 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) functions as a dispersion medium for dispersing each component contained in the silicone rubber-based curable composition, and is a component that contributes to the reaction between the silica particles (C) and the silane coupling agent (D). .. Therefore, in the silicone rubber, the silica particles (C) and the silane coupling agent (D) can be more reliably connected to each other, and uniform characteristics can be exhibited as a whole.

Further, when water (F) is contained, the content thereof can be appropriately set, but specifically, for example, 10 to 100 parts by weight with respect to 100 parts by weight of the silane coupling agent (D). It is preferably in the range of 30 to 70 parts by weight, and more preferably in the range of 30 to 70 parts by weight. This makes it possible to more reliably proceed the reaction between the silane coupling agent (D) and the silica particles (C).

(Other ingredients)
Further, 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. Examples thereof include additives such as inorganic fillers, reaction inhibitors, dispersants, pigments, dyes, antioxidants, antioxidants, flame retardants, and thermal conductivity improvers.

(Conductive filler)
The conductive paste of the present embodiment may contain a conductive filler. As the conductive filler, a known conductive material may be used, but the following metal powder (G) can be contained.
The metal constituting the metal powder (G) is not particularly limited, but for example, at least one of copper, silver, gold, nickel, tin, lead, zinc, bismuth, antimon, or an alloyed metal powder thereof. , Or two or more of these can be included.
Of these, the metal powder (G) preferably contains silver or copper, that is, silver powder or copper powder, because of its high conductivity and high availability.
As these metal powders (G), those coated with other kinds of metals can also be used.

In the present embodiment, the shape of the metal powder (G) is not limited, but conventionally used metal powders (G) such as dendritic, spherical, and lint-like can be used. Among these, phosphorus flake-shaped metal powder (G) may be used.

Further, the particle size of the metal powder (G) is not limited, but for example, the average particle size _D50 is preferably 0.001 μm or more, more preferably 0.01 μm or more, still more preferably 0.1 μm or more. be. The particle size of the metal powder (G) is, for example, preferably 1,000 μm or less, more preferably 100 μm or less, and further preferably 20 μm or less with an average particle size _D50 .
By setting the average particle size D ₅₀ in such a range, it is possible to exhibit appropriate conductivity as an elastomer of the conductive paste.
The particle size of the metal powder (G) is defined as an average value of 200 arbitrarily selected metal powders, for example, by observing the conductive paste or this elastomer with a transmission electron microscope or the like and performing image analysis. be able to.

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, based on the whole of the conductive paste. % Or more is more preferable. 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 whole of the conductive paste. It is more preferable to have.
By setting the content of the metal powder (G) to the above lower limit value or more, the elastomer of the conductive paste can have appropriate conductive properties. Further, by setting the content of the metal powder (G) to the above upper limit value or less, the elastomer can have appropriate flexibility.

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. It is preferably 3% by mass or more, and more preferably 5% by mass or more. This makes it possible to improve the mechanical strength of the elastomer of the conductive paste. 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. It is preferably 15% by mass or less, and more preferably 10% by mass or less. This makes it possible to balance the expansion and contraction electrical characteristics and the mechanical strength of the elastomer of the conductive paste.

(solvent)
The conductive paste of this embodiment contains a solvent. As the 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. This makes it possible to improve printing stability such as screen printing. 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 at the time of wiring formation can be suppressed, so that damage to the underlying substrate and the shape of the wiring formed of the conductive paste can be satisfactorily maintained.

The solvent of the present embodiment can be appropriately selected from the viewpoint of solubility and boiling point of the elastomer composition. For example, an aliphatic hydrocarbon having 5 or more and 20 or less carbon atoms, preferably 8 or more and 18 or less carbon atoms. Aliphatic hydrocarbons, more preferably aliphatic hydrocarbons having 10 or more and 15 or less carbon atoms can be contained.

Further, 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. , Aromatic hydrocarbons such as mesitylene, trifluoromethylbenzene, benzotrifluoride; diethyl ether, diisopropyl ether, dibutyl ether, cyclopentylmethyl ether, cyclopentyl ethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol mono Ethers such as butyl ether, dipropylene glycol dimethyl ether, dipropylene glycol methyl-n-propyl ether, 1,4-dioxane, 1,3-dioxane, tetrahydrofuran; dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane , 1,1,1-Trichloroethane, 1,1,2-trichloroethane and other haloalkanes; N, N-dimethylformamide, N, N-dimethylacetamide and other carboxylic acid amides; , Esters such as diethyl carbonate can be exemplified. These may be used alone or in combination of two or more.
The solvent used here may be appropriately selected from the solvents capable of uniformly dissolving or dispersing the composition components in the above-mentioned conductive paste.

The upper limit of the polarity term (δ _p ) of the Hansen solubility parameter of the solvent is, for example, 10 MPa ^1/2 or less, preferably 7 MPa ^1/2 or less, and more preferably 5.5 MPa ^1/2 or less. It can contain a first solvent. This makes it possible to improve the dispersibility and solubility of the elastomer composition such as the silicone rubber-based curable resin composition in the conductive paste. The lower limit of the polarity term (δ _p ) of the first solvent is not particularly limited, but may be, for example, 0 Pa ^1/2 or more.

The upper limit of the hydrogen bond term (δ _h ) of the Hansen solubility parameter in the first solvent is, for example, 20 MPa ^1/2 or less, preferably 10 MPa ^1/2 or less, and more preferably 7 MPa ^1/2 or less. be. Thereby, in the conductive paste, the dispersibility and solubility of the elastomer composition such as the silicone rubber-based curable resin composition can be improved. The lower limit of the hydrogen bond term (δ _h ) of the first solvent is not particularly limited, but may be, for example, 0 Pa ^1/2 or more.

The Hansen solubility parameter (HSP) is an indicator of how soluble a substance is in another substance. HSP represents solubility as a three-dimensional vector. This three-dimensional vector can be typically represented by a dispersion term (δ _d ), a polarity term (δ _p ), and a hydrogen bond term (δ _h ). And it can be judged that those having similar vectors have high solubility. It is possible to judge the similarity of vectors by the distance of Hansen solubility parameter (HSP distance).

The Hansen solubility parameter (HSP value) used in the present specification can be calculated using software called HSPiP (Hansen Solubility Parameter in Practice). Here, the computer software HSPiP developed by Hansen and Abbott includes a function to calculate the HSP distance and a database describing various resin and solvent or non-solvent Hansen parameters.
The solubility of each resin in a pure solvent and a mixed solvent of a good solvent and a poor solvent was investigated, and the results were input to the HSPiP software. Is calculated.

As the solvent of the present embodiment, for example, an elastomer or a solvent having a small difference in HSP distance, polarity term and hydrogen bond term between the constituent unit constituting the elastomer and the solvent can be selected.

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 forming property can be improved. In addition, the shape retention can be improved even when a thick film is formed. 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. This makes it possible to improve the printability of the conductive paste.

In the conductive paste in the present embodiment, the viscosity measured at a shear rate of 1 [1 / s] at room temperature of 25 ° C. is η1, and the viscosity measured at a shear rate of 5 [1 / s] is η5. The thixotropy is defined as the viscosity ratio (η1 / η5). At this time, the lower limit of the thixotropic index is, for example, 1.0 or more, preferably 1.1 or more, and more preferably 1.2 or more. As a result, the shape of the wiring obtained by the printing method can be stably maintained. On the other hand, the upper limit of the thixotropic index is, for example, 3.0 or less, preferably 2.5 or less, and more preferably 2.0 or less. This makes it possible to improve the printability of the conductive paste.

In the present embodiment, the viscosity and thixotropic index can be controlled by appropriately selecting, for example, the type and blending amount of each component contained in the conductive paste, the method for preparing the conductive paste, and the like. Among these, for example, the type of solvent such as a hydrophobic solvent, a hydrocarbon solvent, a solvent having a high boiling point suitable for printing, or a solvent having a small polar term or a hydrogen bond term should be appropriately selected, and silica particles (C). ), The amount and ratio of the conductive filler, and the use of a vinyl group-containing organopolysiloxane (A) having a vinyl group at the end to control the crosslink density of the resin and the uneven distribution of the crosslink structure. To more reliably proceed the reaction between the silane coupling agent (D) and the silica particles (C), such as surface modification of the silica particles (C) with the silane coupling agent (D) and addition of water. And the like are mentioned as factors for setting the above-mentioned viscosity and the thixoindex in a desired numerical range.

(Manufacturing method of conductive paste)
Hereinafter, a method for producing a conductive paste according to this embodiment will be described.

The conductive paste of the present embodiment can be produced, for example, by going through the following steps.

First, each component of the silicone rubber-based curable composition is uniformly mixed by an arbitrary kneading device to prepare a 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 a predetermined amount and then kneaded by an arbitrary kneading device. A kneaded product containing each of these components (A), (C) and (D) is obtained.

The kneaded product is preferably obtained by kneading the vinyl group-containing organopolysiloxane (A) and the silane coupling agent (D) in advance, 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) as needed. This makes it possible to more reliably proceed the reaction between the silane coupling agent (D) and the silica particles (C).

Further, it is preferable that the kneading of each component (A), (C), and (D) goes through a first step of heating at the first temperature and a second step of heating at the second temperature. Thereby, 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) are combined. By-products produced by the reaction can be reliably removed from the kneaded product. Then, 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 ° C., and more preferably about 60 to 90 ° C., for example. The second temperature is, for example, preferably about 130 to 210 ° C, more preferably about 160 to 180 ° C.

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

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

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

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

When kneading the respective 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 product with platinum or the platinum compound (E), and then knead the respective kneaded products. This ensures that each component (A) to (E) is contained in the silicone rubber-based curable composition without proceeding with the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B). Can be dispersed in.

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

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

By setting the temperature within the above range in the above step [1] and the above step [2], the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) is more accurately performed. Can be prevented or suppressed. Further, in the above steps [1] and the above steps [2], by setting the kneading time within the above range, each component (A) to (E) is more reliably dispersed in the silicone rubber-based curable composition. Can be done.

The kneading device used in each of the steps [1] and [2] is not particularly limited, and for example, a kneader, a two-roll, a Banbury mixer (continuous kneader), a pressurized kneader, or the like can be used.

Further, in this 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) is more accurately prevented or suppressed. be able to.

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

[Use]
Hereinafter, an example of the use of the conductive paste of the present embodiment will be described with reference to FIG. FIG. 1 shows an outline of an electronic device 100 provided with such wiring as a cross-sectional view.

As shown in FIG. 1, the electronic device 100 can include a wiring board 50 and an electronic component 60. The wiring board 50 is configured by providing the wiring 10 on the board 20. As the substrate 20, an insulating substrate having elasticity can be used. On the other hand, the wiring 10 can be made of a cured product obtained by curing the conductive paste of the present embodiment. The electronic component 60 may be configured to be electrically connected to the wiring 10 constituting such an elastic wiring board (wiring board 50).

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

Further, the substrate 20 constituting the electronic device 100 of the present embodiment is usually made of a flexible material.
As this material, the same material as the above-mentioned elastomer can be adopted. 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 depending on the application and the like. can. Further, the substrate 20 may be composed of a cured product of the above-mentioned silicone rubber-based curable composition.

Further, as the substrate 20, an elastomer composed of the above-mentioned elastomer composition can be used. Further, the elastomer may be composed of an insulating paste containing an elastomer composition containing silica particles and a solvent. As the solvent, the same solvent type as the above-mentioned solvent can be used, and among these, a solvent exhibiting solubility in the above-mentioned conductive paste or a conductive sheet which is a cured product of the above-mentioned conductive paste is used. be able to. As a specific solvent for the insulating paste, for example, a solvent having a high boiling point or a solvent having a polar term (δ _p ) or a hydrogen bond term (δ _h ) of HSP of not more than the above upper limit can be used.

Further, the electronic component 60 may be appropriately selected from known components according to the intended use. Specific examples thereof include semiconductor devices and resistors and capacitors other than semiconductor devices. Examples of the semiconductor element include a transistor, a diode, an LED, a capacitor and the like. In the electronic device 100 of the present 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 the cover material 30 as needed. By providing the 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.
Further, the cover material 30 can be made of the same material as the substrate 20. Since the cover material 30 follows the expansion and contraction of the substrate 20 and the wiring 10, the electronic device 100 as a whole can be expanded and contracted without bias, and can contribute to extending the life of the electronic device 100.

Next, an example of the manufacturing process of the electronic device 100 of the present 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 in the present embodiment.

First, as shown in FIG. 2A, the support 120 is installed on the workbench 110, and the insulating paste 130 is applied onto the support 120. As the coating method, various methods can be used, and for example, a printing method such as a squeegee method using a squeegee 140 can be used. Subsequently, the coating film-like insulating paste 130 can be dried to form an insulating layer 132 (dried 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, and for example, the drying temperature may be 150 ° C. to 180 ° C., the drying time may be 1 minute to 30 minutes, or the like. can.

Subsequently, as shown in FIG. 2B, a mask 160 having a predetermined opening pattern shape is arranged on the insulating layer 132. Then, as shown in FIGS. 2 (b) and 2 (c), the conductive paste 150 is applied onto the insulating layer 132 via the mask 160. As the coating method, the same method as the coating method of the insulating paste 130 can be used, and for example, squeegee printing with the 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. After that, these may be collectively cured. The curing treatment can be appropriately set depending on the thermosetting elastomer composition, and for example, the curing temperature can be 160 ° C. to 220 ° C., the curing time can be 1 hour to 3 hours, or the like. As shown in FIG. 2D, the mask 160 can be removed after the curing treatment or before the curing treatment. As a result, it is possible to form wiring which is a cured product of the conductive layer 152 and has a predetermined pattern shape on the substrate composed of the cured product of the insulating layer 132.

Subsequently, as shown in FIG. 2 (e), the insulating paste 170 is further coated on the insulating layer 132 and the patterned conductive layer 152, and the insulating layer 172 is provided 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 a result, the electronic device 100 shown in FIG. 2 (f) can be obtained.

When an insulating sheet is used instead of the insulating paste, the process may be started from the step shown in FIG. 2 (b). That is, the insulating sheet may be placed on the support 120, dried for a predetermined period, and then the conductive paste 150 may be applied onto the insulating sheet via the mask 160. Subsequent steps can be performed according to the above steps. This makes it possible to obtain the electronic device 100 shown in FIG. 2 (f).

The present invention is not limited to the above-described embodiment, and modifications, improvements, and the like to the extent that the object of the present invention can be achieved are included in the present invention.
Hereinafter, an example of the reference form will be added.
1. 1. An elastomer composition containing silica particles (C) and
With conductive filler,
Conductive paste, including solvent.
2. 2. 1. 1. The conductive paste described in 1.
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.
3. 3. 1. 1. Or 2. The conductive paste described in 1.
A conductive paste used to form the wiring that makes up an elastic wiring board.
4. 1. 1. From 3. The conductive paste according to any one of the above.
A conductive paste containing a high boiling point solvent having a boiling point of 100 ° C. or higher and 300 ° C. or lower.
5. 1. 1. From 4. The conductive paste according to any one of the above.
A conductive paste in which the solvent contains an aliphatic hydrocarbon having 5 or more and 20 or less carbon atoms.
6. 1. 1. From 5. The conductive paste according to any one of the above.
A conductive paste containing a first solvent in which the polarity term (δ _p ) of the Hansen solubility parameter is 10 MPa ^1/2 or less.
7. 1. 1. From 6. The conductive paste according to any one of the above.
A conductive paste having a viscosity of 1 Pa · s or more and 100 Pa · s or less when measured at a shear rate of 20 [1 / s] at a room temperature of 25 ° C.
8. 1. 1. From 7. The conductive paste according to any one of the above.
The viscosity of the conductive paste when measured at a shear rate of 1 [1 / s] at a room temperature of 25 ° C. is η1, and the viscosity when measured at a shear rate of 5 [1 / s] is η5. A conductive paste having a thixotropy index of 1.0 or more and 3.0 or less, which is a ratio (η1 / η5).
9. 1. 1. From 8. The conductive paste according to any one of the above.
The conductive filler is a conductive paste containing metal powder (G).
10. 1. 1. From 9. The conductive paste according to any one of the above.
A conductive paste in which the content of the conductive filler is 30% by mass or more and 85% by mass or less with respect to the entire conductive paste.
11. 1. 1. From 10. The conductive paste according to any one of the above.
A conductive paste in which the content of the silica particles (C) is 1% by mass or more and 20% by mass or less with respect to 100% by mass of the total amount of the silica particles (C) and the conductive filler.
12. 1. 1. From 11. The conductive paste according to any one of the above.
A conductive paste in which the elastomer composition contains a silicone rubber-based curable composition.
13. 12. The conductive paste described in 1.
A conductive paste in which the silicone rubber-based curable composition contains a vinyl group-containing organopolysiloxane (A).
14. 12. Or 13. The conductive paste described in 1.
A conductive paste in which the silicone rubber-based curable composition further contains organohydrogenpolysiloxane (B).
15. 12. From 14. The conductive paste according to any one of the above.
A conductive paste in which the silicone rubber-based curable composition further contains platinum or a platinum compound (E).
16. 1. 1. From 15. The conductive paste according to any one of the above.
A conductive paste in which 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.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

The materials used in the 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), Vinyl group-containing dimethylpolysiloxane synthesized by the following synthesis scheme 1 (structure represented by the above formula (1-1)).
(A1-2): Second vinyl group-containing linear organopolysiloxane: Vinyl group content is 0.92 mol%, vinyl group-containing dimethylpolysiloxane synthesized by the following synthesis scheme 2 (the above formula (1-). Structure represented by 1) in which R ¹ and R ² are vinyl groups)

(Organohydrogenpolysiloxane (B))
(B1): Organohydrogenpolysiloxane: Momentive, "88466"

(Silica particles (C))
(C1): Silica fine particles (particle size 7 nm, specific surface area 300 m ² / g), manufactured by Nippon Aerosil Co., Ltd., "AEROSIL 300"

(Silane Coupling Agent (D))
(D1): Hexamethyldisilazane (HMDZ), manufactured by Gelest, "HEXAMETHYLDISILAZANE (SIH6110.1)".

(Platinum or platinum compound (E))
(E1): Platinum compound, PLATINUM DIVINYLTETRAMETHYLDISILOXANE COMPLEX (in xylene) (manufactured by Gelest, trade name "SIP6831.2")

(Water (F))
(F1): Pure water

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

(Metal powder (G))
(G1): Silver powder, manufactured by Tokuriki Kagaku Kenkyusho, trade name "TC-101", median diameter d ₅₀ : 8.0 μm, aspect ratio 16.4, average major axis 4.6 μm

(Synthesis of vinyl group-containing organopolysiloxane (A))
[Synthesis scheme 1: Synthesis of first vinyl group-containing linear organopolysiloxane (A1-1)]
The 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 silicate were placed in a 300 mL separable flask having a cooling tube and a stirring blade substituted with Ar gas, heated, and heated at 120 ° C. for 30 minutes. Stirred. At this time, an increase in viscosity was confirmed.
Then, the temperature was raised to 155 ° C., and stirring was continued for 3 hours. Then, 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.
After 4 hours, it was diluted with 250 mL of toluene and then washed 3 times with water. The organic layer after washing was washed with 1.5 L of methanol several times for reprecipitation purification, and the oligomer and the polymer were separated. The obtained polymer was dried under reduced pressure at 60 ° C. overnight to obtain a first vinyl group-containing linear organopolysiloxane (A1-1) (Mw = 573,903, Mn = 227,734). The vinyl group content calculated by 1 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), in addition to 74.7 g (252 mmol) of octamethylcyclotetrasiloxane, 2,4,6,8-tetramethyl 2,4,6,8-tetravinylcyclotetrasiloxane 0. By performing the same as the synthesis step of (A1-1) except that 86 g (2.5 mmol) was used, a second vinyl group-containing linear organopolysiloxane (A1-2) was used as shown in the following formula. ) Was synthesized. The vinyl group content calculated by 1 H-NMR spectrum measurement was 0.92 mol%.

[Preparation of conductive paste]
(Preparation of Silicone Rubber Curable Compositions 1 to 3)
Silicone rubber-based curable compositions 1 to 3 were prepared as follows. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (F) is kneaded in advance at the ratio shown in Table 1 below, and then silica particles (silica particles ()) are added to the mixture. 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) is carried out in the first step of kneading under a nitrogen atmosphere at 60 to 90 ° C. for 1 hour for the coupling reaction, and the removal of the by-product (ammonia). Therefore, it is carried out by going through the second step of kneading under a reduced pressure atmosphere under the condition of 160 to 180 ° C. for 2 hours, and then cooling, and the remaining 10% of the vinyl group-containing organopolysiloxane (A) is added twice. It was added separately and kneaded for 20 minutes.
Subsequently, the organohydrogenpolysiloxane (B), platinum or platinum compound (E) and the reaction inhibitor were added to 100 parts by weight of the obtained kneaded product (silicone rubber compound) at the ratio shown in Table 1 below. , Kneaded with a roll to obtain silicone rubber-based curable compositions 1 to 3 (elastomer compositions 1 to 3).

(Elastomer Composition 4)
As the elastomer composition 4, the trade name “C6-135 ELASTOMER (including silica particles)” manufactured by Toray Dow Corning Co., Ltd. was used.

(Elastomer Composition 5)
Silica particles surface-treated with 9.2 g of urethane diacrylate (manufactured by Toa Synthetic Co., Ltd., trade name "Aronix M-1200") and 0.9 g of silane coupling agent (hexamethyl disilazane (manufactured by Gelest)). (Manufactured by Nippon Aerosil Co., Ltd., trade name "AEROSIL300") 3.5 g and an organic peroxide initiator (manufactured by Nippon Oil & Fat Co., Ltd., trade name "Perhexa 3M") 0.1 g were mixed to obtain an elastomer composition 5. ..

<Example 1: Conductive paste 1>
The obtained 13.7 parts by weight of the silicone rubber-based curable composition 1 (elastomer composition 1) was immersed in 31.8 parts by weight of tetradecane, and subsequently stirred with a rotation / revolution mixer to 54.5 parts by weight. A liquid conductive paste 1 was obtained by kneading with three rolls after adding the silver powder G1 of the portion.

<Example 2: Conductive paste 2>
The obtained 13.7 parts by weight of the silicone rubber-based curable composition 2 (elastomer composition 2) was immersed in 31.8 parts by weight of decan, and then stirred with a rotation / revolution mixer to 54.5 parts by weight. A liquid conductive paste 2 was obtained by kneading with three rolls after adding the silver powder G1 of the portion.

<Example 3: Conductive paste 3>
The obtained 13.7 parts by weight of the silicone rubber-based curable composition 1 (elastomer composition 1) was immersed in 31.8 parts by weight of toluene, and subsequently stirred with a rotation / revolution mixer to 54.5 parts by weight. A liquid conductive paste 3 was obtained by kneading with three rolls after adding the silver powder G1 of the portion.

<Example 4: Conductive paste 4>
The obtained 13.7 parts by weight of the elastomer composition 4 (containing 3.0 parts by weight of silica particles) was immersed in 31.8 parts by weight of decan, and subsequently stirred with a rotation / revolution mixer, 54. After adding 5 parts by weight of silver powder G1, the mixture was kneaded with three rolls to obtain a liquid conductive paste 4.

<Example 5: Conductive paste 5>
The obtained 13.7 parts by weight of the elastomer composition 5 was immersed in 31.8 parts by weight of toluene, subsequently stirred with a rotation / revolution mixer, 54.5 parts by weight of silver powder G1 was added, and then three pieces were added. By kneading with a roll, a liquid conductive paste 5 was obtained.

<Example 6: Conductive paste 6>
The obtained 13.7 parts by weight of the elastomer composition 1 was immersed in 31.8 parts by weight of mesitylene, subsequently stirred with a rotation / revolution mixer, 54.5 parts by weight of silver powder G1 was added, and then three pieces were added. By kneading with a roll, a liquid conductive paste 6 was obtained.

<Example 7: Conductive paste 7>
The obtained 13.7 parts by weight of the elastomer composition 2 was immersed in 31.8 parts by weight of dipropylene glycol dimethyl ether, subsequently stirred with a rotation / revolution mixer, and 54.5 parts by weight of silver powder G1 was added. Later, the mixture was kneaded with three rolls to obtain a liquid conductive paste 7.

<Example 8: Conductive paste 8>
The obtained 13.7 parts by weight of the elastomer composition 1 was immersed in 31.8 parts by weight of diethyl carbonate, subsequently stirred with a rotation / revolution mixer, 54.5 parts by weight of silver powder G1 was added, and then three. By kneading with this roll, a liquid conductive paste 8 was obtained.

<Example 9: Conductive paste 9>
The obtained 12.0 parts by weight of the elastomer composition 1 was immersed in 32.4 parts by weight of tetradecane, subsequently stirred with a rotation / revolution mixer, 55.6 parts by weight of silver powder G1 was added, and then three pieces were added. By kneading with a roll, a liquid conductive paste 9 was obtained.

<Example 10: Conductive paste 10>
The obtained 15.5 parts by weight of the elastomer composition 2 was immersed in 32.6 parts by weight of decan, subsequently stirred with a rotation / revolution mixer, 51.9 parts by weight of silver powder G1 was added, and then three pieces were added. By kneading with a roll, a liquid conductive paste 10 was obtained.

<Comparative Example 1: Elastomer Composition>
20 parts by weight of the obtained elastomer composition 1 (containing 5.2 parts by weight of silica particles (C)) is not immersed in a solvent, 80 parts by weight of silver powder G1 is added, and then kneaded with three rolls. As a result, it was used as it was as a sample of Comparative Example 1.

<Comparative Example 2: Conductive paste 11>
The obtained 13.7 parts by weight of the elastomer composition 3 (not containing silica particles (C)) was immersed in 31.8 parts by weight of tetradecane, and subsequently stirred with a rotation / revolution mixer to 54.5 parts by weight. A liquid conductive paste 11 was obtained by kneading with three rolls after adding the silver powder G1 of the portion.

In the solubility parameter (HSP) of Hansen of the solvent in Table 2, the dispersion term (δ _d ) of tetradecane: 15.8 MPa ^1/2 , the polarity term (δ _p ): 0 MPa ^1/2 , the hydrogen bond term (δ _h ). : 0 MPa ^1/2 , decan dispersion term (δ _d ): 15.7 MPa ^1/2 , polarity term (δ _p ): 0 MPa ^1/2 , hydrogen coupling term (δ _h ): 0 MPa ^1/2 . , Toluene dispersion term (δ _d ): 17.8 MPa ^1/2 , polar term (δ _p ): 3.0 MPa ^1/2 , hydrogen bond term (δ _h ): 0 MPa ^1/2 , and mesitylen dispersion term. (Δ _d ): 18.0 MPa ^1/2 , polar term (δ _p ): 0.6 MPa ^1/2 , hydrogen bond term (δ _h ): 0.6 MPa ^1/2 , dispersion term of dipropylene glycol dimethyl ether. (Δ _d ): 15.1 MPa ^1/2 , polar term (δ _p ): 6.3 MPa ^1/2 , hydrogen coupling term (δ _h ): 4.9 MPa ^1/2 , and dispersion term of diethyl carbonate (δ). _d ): 15.7 MPa ^1/2 , the polarity term (δ _p ): 5.1 MPa ^1/2 , and the hydrogen coupling term (δ _h ): 3.5 MPa ^1/2 . The boiling point of tetradecane is 253 ° C, the boiling point of decane is 174 ° C, the boiling point of toluene is 111 ° C, the boiling point of mesitylene is 165 ° C, and the boiling point of dipropylene glycol dimethyl ether is 175 ° C. The boiling point of diethyl carbonate was 126 ° C.
Further, "-" in Comparative Example 1 in Table 2 indicates that each evaluation item could not be measured because the coating operation could not be performed on the Comparative Example 1 sample. Therefore, the sample of Comparative Example 1 could not be used as a paste, and it was judged that the coatability and printability were poor.

[Evaluation of conductive paste]
The obtained conductive pastes 1 to 11 were evaluated according to the following items.

<Viscosity>
The viscosity of the obtained conductive paste at a shear rate of 20 [1 / s] at room temperature of 25 ° C. was measured immediately after the production of the conductive paste using TPE-100H manufactured by Toki Sangyo Co., Ltd. The unit of viscosity is Pa · s.
<Thixotropic index>
The viscosity of the obtained conductive paste when measured at a shear rate of 1 [1 / s] at a room temperature of 25 ° C. using TPE-100H manufactured by Toki Sangyo Co., Ltd. was η1 and a shear rate of 5 [1 / s]. ], The viscosity at the time of measurement was set to η5, and each viscosity was measured immediately after the conductive paste was prepared. The unit of viscosity is Pa · s. The thixotropic index was determined as the viscosity ratio (η1 / η5).

<Measurement of volume resistivity>
The conductive paste obtained in each example and each comparative example was applied onto a slide glass to a size of 10 mm square and a thickness of 60 μm, and cured in an oven at 170 ° C. for 120 minutes, and then the volume resistivity of the cured product was measured by 4 probes. Measured by method. The results are shown in Table 2.

<Evaluation of printability>
The conductive pastes of Examples and Comparative Examples are placed on silicone rubber with a stencil plate having an opening L / S = 500/500 μm so that the height after curing at 170 ° C. for 120 minutes falls within the range of about 50 to 100 μm. The pattern was printed. The pattern obtained by observing with an optical microscope without bleeding was marked with ⊚, the pattern with bleeding of 50 μm or more at 10 points or less was marked with ◯, and the pattern with shunt or disconnection was marked with ×. The results are shown in Table 2.

(Durability test)
First, the obtained silicone rubber-based curable composition 1 (elastomer composition 1) was cured at 170 ° C. for 120 minutes, molded into a sheet, and formed of silicone rubber, width 2 cm × height 500 μm × length. A 5 cm substrate was prepared.
Subsequently, using the conductive pastes obtained in each Example and each Comparative Example, a wiring pattern was drawn on the obtained substrate, and this was cured under the condition of 170 ° C. for 120 minutes, and the width was 500 μm × the height. A test piece having a wiring pattern of 50 μm × 30 mm in length was prepared.

The test piece thus obtained was stretched by 20% in the length direction of the test piece, and the operation of releasing the stretch was performed 1000 times.
◎ is the wiring that is sufficiently conductive even when this extension operation is performed 1000 times, ○ is the one that is sufficiently conductive even when the extension operation is performed 500 times, and when the extension operation is performed 500 times. Those with broken wiring were evaluated as x. The results are shown in Table 2.

The conductive pastes obtained in Examples 1 to 10 are excellent in coatability and printability as compared with Comparative Example 1, and have excellent stretch durability as compared with Comparative Example 2. It turned out that can be realized. It was found that such conductive pastes of Examples 1 to 10 are suitable for forming elastic wiring.

10 Wiring 20 Board 30 Cover material 50 Wiring board 60 Electronic components 100 Electronic components 110 Worktable 120 Support 130 Insulation paste 132 Insulation layer 140 Squeegee 150 Conductive paste 152 Conductive layer 160 Mask 170 Insulation paste 172 Insulation layer

Claims (13)

An elastomer composition containing silica particles (C) and
With conductive filler ,
A conductive paste containing a solvent and
The conductive filler contains a lint-like metal powder (G) and contains.
The content of the conductive filler is 40 % by mass or more and 85% by mass or less with respect to the entire conductive paste.
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.
The content of the silica particles (C) is 1% by mass or more and 15% by mass or less with respect to the entire conductive paste , and the total amount of the silica particles (C) and the conductive filler is 100% by mass. 1% by mass or more and 20% by mass or less with respect to%.
The viscosity of the conductive paste as measured at a shear rate of 20 [1 / s] at room temperature of 25 ° C. is 1 Pa · s or more and 100 Pa · s or less.
Conductive paste. The conductive paste according to claim 1.
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 claim 1 or 2.
A conductive paste used to form the wiring that makes up an elastic wiring board. The conductive paste according to any one of claims 1 to 3.
A conductive paste containing a high boiling point solvent having a boiling point of 100 ° C. or higher and 300 ° C. or lower. The conductive paste according to any one of claims 1 to 4.
A conductive paste in which the solvent contains an aliphatic hydrocarbon having 5 or more and 20 or less carbon atoms. The conductive paste according to any one of claims 1 to 5.
A conductive paste containing a first solvent in which the polarity term (δp) of the Hansen solubility parameter is 10 MPa ^1/2 or less. The conductive paste according to any one of claims 1 to 6.
The viscosity of the conductive paste when measured at a shear rate of 1 [1 / s] at a room temperature of 25 ° C. is η1, and the viscosity when measured at a shear rate of 5 [1 / s] is η5. A conductive paste having a thixotropy index of 1.0 or more and 3.0 or less, which is a ratio (η1 / η5). The conductive paste according to any one of claims 1 to 7.
A conductive paste in which the elastomer composition contains a silicone rubber-based curable composition. The conductive paste according to claim 8.
A conductive paste in which the silicone rubber-based curable composition contains a vinyl group-containing organopolysiloxane (A). The conductive paste according to claim 8 or 9.
A conductive paste in which the silicone rubber-based curable composition further contains organohydrogenpolysiloxane (B). The conductive paste according to any one of claims 8 to 10.
A conductive paste in which 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 11.
Conductive paste for printing. The conductive paste according to any one of claims 1 to 12.
A conductive paste having an average particle size D ₅₀ of the metal powder (G) of 0.001 μm or more and 1,000 μm or less.

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