Conductive paste and method for manufacturing the same

Abstract

To provide a conductive paste excellent in inhibiting variations of conductivity before and after expansion and contraction.SOLUTION: A conductive paste of the present invention includes an elastomer composition, a conductive filler, and a non-aqueous solvent. A value of fineness gage of the conductive paste measured according to JIS K5600-2-5:1999 is 40 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a conductive paste and a method for producing the conductive paste. [Background technology]

[0002] Various developments have been made on conductive pastes. For example, a known example of this type of technology is described in Patent Document 1. Paragraph 0015 of Patent Document 1 states that the conductive paste is produced by adding a predetermined amount of flaky silver powder to a silicone resin, and optionally adding an organic solvent and kneading the resulting mixture. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-150837 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that the conductive paste described in Patent Document 1 has room for improvement in terms of suppressing fluctuations in conductivity before and after expansion and contraction. [Means for solving the problem]

[0005] As a result of further investigation, the inventors discovered that by appropriately controlling the initial mixing conditions of the conductive filler and the elastomer composition, it is possible to suppress fluctuations in the conductivity of the produced conductive paste before and after expansion and contraction, and thus completed the present invention.

[0006] According to one aspect of the present invention, there are provided the following conductive paste and method for manufacturing the conductive paste.

[0007] 1. an elastomer composition; A conductive filler; A conductive paste comprising: A conductive paste having a particle gauge value of 40 μm or less as measured in accordance with JIS K5600-2-5:1999. 2. The conductive paste according to 1., The conductive paste has a grain gauge value of 5 μm or more. 3. The conductive paste according to 1. or 2., A conductive paste whose viscosity, when measured at 25°C and at a shear rate of 20 [1 / s], is 1 Pa·s or more and 100 Pa·s or less. 4. The conductive paste according to any one of 1. to 3., The conductive paste has a thixotropy index calculated by η1 / η5, where η1 is the viscosity when measured at a shear rate of 1 [1 / s] at 25°C and η5 is the viscosity when measured at a shear rate of 5 [1 / s], of 1.0 or more and 3.0 or less. 5. The conductive paste according to any one of 1. to 4., A conductive paste comprising a non-conductive filler. 6. The conductive paste according to any one of 1. to 5., The 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. 7. The conductive paste according to any one of 1. to 6., The conductive paste, wherein the non-aqueous solvent contains a high-boiling-point non-aqueous solvent having a boiling point of 100°C or higher and 250°C or lower. 8. The conductive paste according to any one of 1. to 7., A conductive paste, wherein the content of the conductive filler is 30% by mass or more and 85% by mass or less, based on 100% by mass of the conductive paste. 9. The conductive paste according to any one of 1. to 8., The BET specific surface area of ​​the conductive filler is 0.1 m 2 / g or more 5m 2 / g or less. 10. A method for producing a conductive paste, comprising a mixing step of stirring raw material components including an elastomer composition, a conductive filler, and a non-aqueous solvent in a stirring tank using stirring blades, and then kneading the components using a planetary mixer to obtain a conductive paste. 11. A method for producing the conductive paste according to 10., A method for producing a conductive paste, wherein the conductive paste obtained in the mixing step has a particle gauge value of 40 μm or less as measured in accordance with JIS K5600-2-5:1999. 12. A method for producing a conductive paste according to 10. or 11., a method for producing a conductive paste, wherein in the mixing step, the mixture of the elastomer composition and the non-aqueous solvent has a viscosity of 1 Pa·s or more and 100 Pa·s or less when measured at 25°C and at a shear rate of 20 [1 / s]. 13. A method for producing a conductive paste according to any one of items 10 to 12, comprising: The method for producing a conductive paste, wherein the non-aqueous solvent contains a high-boiling-point non-aqueous solvent having a boiling point of 100°C or higher and 250°C or lower. 14. A method for producing a conductive paste according to any one of items 10 to 13, comprising: The BET specific surface area of ​​the conductive filler is 0.1 m 2 / g or more 5m 2 / g or less. [Effects of the Invention]

[0008] According to the present invention, a conductive paste that is excellent in suppressing fluctuations in conductivity before and after expansion and contraction, and a method for producing the same are provided. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by similar reference numerals, and descriptions thereof will be omitted where appropriate. Furthermore, the drawings are schematic diagrams and do not correspond to actual dimensional proportions.

[0010] An outline of the conductive paste of this embodiment will be described.

[0011] The conductive paste of this embodiment contains an elastomer composition, a conductive filler, and a non-aqueous solvent. This conductive paste satisfies the requirement that the particle gauge value measured in accordance with JIS K5600-2-5:1999 is 40 μm or less.

[0012] According to the findings of the present inventors, it has been found that the dispersibility of the conductive filler can be improved by performing appropriate stirring during the initial mixing of raw material components including an elastomer composition, a conductive filler, and a non-aqueous solvent. In other words, even when the specific gravity of the conductive filler is higher than that of the elastomer composition and the viscosity of the raw material components is relatively high, a decrease in the dispersibility of the conductive filler can be suppressed by appropriate stirring. The particle gauge value is an appropriate index for expressing such dispersibility. Although the detailed mechanism is unclear, it is believed that the conductive paste obtained by such a stirring treatment can suppress the occurrence of conductive filler that separates from the elastomer composition and floats in the solvent, and therefore the conductive member formed using the conductive paste exhibits the property of suppressing fluctuations in conductivity even before and after expansion and contraction.

[0013] The upper limit of the particle gauge value of the conductive paste is 40 μm or less, preferably 35 μm or less, and more preferably 30 μm or less, which makes it possible to minimize fluctuations in conductivity before and after expansion and contraction. On the other hand, the lower limit of the particle gauge value of the conductive paste is not particularly limited, but is, for example, 5 μm or more, preferably 10 μm or more, and more preferably 15 μm or more. This improves the ease of handling and also suppresses an increase in resistance value after expansion and contraction.

[0014] The lower limit of the viscosity of the conductive paste when measured at room temperature (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 or more. This improves film-forming properties. It also improves shape retention even when forming thick films. On the other hand, the upper limit of the viscosity of the conductive paste at room temperature (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 improving the printability of the conductive paste.

[0015] In the conductive paste of this embodiment, when the viscosity measured at room temperature 25°C at a shear rate of 1 [1 / s] is η1 and the viscosity measured at a shear rate of 5 [1 / s] is η5, the thixotropy index is calculated from the viscosity ratio (η1 / η5). The lower limit of the thixotropy index is, for example, 1.0 or more, preferably 1.1 or more, and more preferably 1.2 or more, which allows the shape of the wiring obtained by the printing method to be stably maintained. On the other hand, the upper limit of the thixotropy index is, for example, not more than 3.0, preferably not more than 2.5, and more preferably not more than 2.0, which can improve the ease of printing of the conductive paste.

[0016] The conductive paste of this embodiment has excellent applicability and film-forming properties on a substrate, and / or excellent printability such as screen printing.

[0017] The conductive paste of this embodiment can be used to form various conductive members such as electrodes, wiring, sensors, heating elements, adhesives, etc. That is, a cured product of the conductive paste can be used as an expandable conductive member for at least one of the various applications described above. Examples of the electrode include a bioelectrode and a flexible sheet electrode. Examples of the wiring include elastic wiring. Examples of the sensor include a displacement sensor, a pressure sensor, and a sensor for measuring the flow rate of the inner layer material of the tube. Examples of the heating element include heaters used in devices, vehicles, medical equipment, and the like. Examples of adhesives include conductive adhesives used in electronic devices. In this embodiment, a structure including such a conductive member can be provided.

[0018] The conductive paste of the present embodiment may contain silica particles in addition to the conductive filler, which can improve the mechanical strength and durability of the conductive member formed using the conductive paste.

[0019] Here, an example of a method for producing the conductive paste of this embodiment will be described.

[0020] The method for producing the conductive paste may include a mixing step in which raw material components including, for example, an elastomer composition, a conductive filler, and a non-aqueous solvent are stirred in a stirring tank using stirring blades (stirring treatment), and then kneaded using a planetary mixer (kneading treatment) to obtain a conductive paste (mixture). By performing the stirring process using a stirring blade, it is possible to further improve the dispersibility of the conductive filler in the conductive paste. Furthermore, when stirring using a stirring blade, it is preferable to use one that gives the raw material components (mixture) containing the elastomer composition and the non-aqueous solvent a viscosity of 1 Pa·s or more and 100 Pa·s or less, which allows for stable stirring operation when using a stirring blade that applies high shear force. Here, the viscosity is measured at 25° C. and a shear rate of 20 [1 / s]. Note that the raw material components (mixture) to be subjected to viscosity measurement do not need to contain a conductive filler.

[0021] The volume of the stirring vessel and the shape of the bottom of the stirring vessel can be appropriately selected depending on the viscosity and volume of the raw material components. The rotation speed and rotation time of the stirring blades can also be appropriately selected depending on the viscosity and volume of the raw material components.

[0022] The stirring blade may be a stirring blade for low viscosity such as a propeller blade, a turbine blade, a paddle blade, or a three-bladed swept blade, or a stirring blade for high viscosity such as an anchor blade, a helical ribbon blade, etc. Among these, a stirring blade that can stir the entire conductive paste evenly and efficiently is preferred from the viewpoint of suppressing sedimentation of the conductive filler during stirring.

[0023] In this embodiment, the particle gauge value can be controlled by appropriately selecting, for example, the type and amount of each component contained in the conductive paste, the method for preparing the conductive paste, etc. Among these, factors for setting the particle gauge value within a desired range include, for example, performing an appropriate stirring process using a stirring blade or the like, appropriately controlling the viscosity of the raw material components used for stirring, and the BET specific surface area of ​​the metal powder.

[0024] In the manufacturing method of this embodiment, it is preferable not to use a three-roll mill during the mixing step, as the evaporation of the solvent during the three-roll mill may cause an increase in the viscosity of the paste after rolling, and the recovery rate may decrease due to drying on the three-roll mill, which may result in a decrease in manufacturing stability.

[0025] The manufacturing method of this embodiment may also include a filtration step in which the mixture obtained in the mixing step is subjected to a filtration treatment. The manufacturing method of this embodiment may also include a degassing step of performing a degassing treatment on the mixture obtained in the kneading step. At least one or both of the filtration step and the defoaming step may be carried out. The order of carrying out these steps is not particularly limited, but the defoaming step may be carried out after the filtration step. Other known treatments may also be carried out.

[0026] The manufacturing method of this embodiment may also include an evaluation step of determining whether the mixture obtained in the mixing step satisfies predetermined conditions for one or more properties selected from the group consisting of viscosity, solid content, and gel time. This improves the manufacturing stability of the conductive paste. The evaluation step may be performed between the above steps, or after the final step.

[0027] Each component of the conductive paste will be described in detail below.

[0028] The conductive paste of this embodiment contains an elastomer composition, a conductive filler, and a non-aqueous solvent.

[0029] (Elastomer composition) The elastomer composition may be silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, ethylene propylene rubber, etc. Among these, the elastomer is a composition for forming at least one elastomer selected from the group consisting of silicone rubber, urethane rubber, and fluororubber. Among these, the elastomer composition may be a thermosetting elastomer composition or a composition containing a thermoplastic elastomer, preferably a thermosetting elastomer composition, and more preferably a silicone rubber composition.

[0030] The silicone rubber composition is preferably a silicone rubber-based curable composition containing, for example, a silicone compound, a crosslinking agent, and a catalyst. Here, an example of a silicone rubber-based curable composition will be described. In one example of the silicone rubber-based curable composition, the silicone compound contains a vinyl group-containing organopolysiloxane (A), silica particles (C), and a silane coupling agent (D), as described below; the crosslinking agent contains an organohydrogenpolysiloxane (B); and the catalyst may contain platinum or a platinum compound (E).

[0031] The lower limit of the content of the elastomer composition or silicone rubber-based curable composition in the conductive paste is, for example, preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on 100% by mass of the conductive paste. On the other hand, the upper limit of the content of the elastomer composition or silicone rubber-based curable composition in the conductive paste is, for example, preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the conductive paste. By setting the content of the elastomer composition or silicone rubber-based curable composition to be equal to or greater than the above lower limit, the elastomer of the conductive paste can have appropriate flexibility, while by setting the content of the elastomer composition or silicone rubber-based curable composition to be equal to or less than the above upper limit, the mechanical strength of the elastomer can be improved.

[0032] The lower limit of the content of the conductive filler or metal powder (G) in the conductive paste is, for example, preferably 30 mass% or more, more preferably 40 mass% or more, and even more preferably 50 mass% or more, based on 100 mass% of the conductive paste. On the other hand, the upper limit of the content of the conductive filler or metal powder (G) in the conductive paste is, for example, preferably 85 mass% or less, more preferably 75 mass% or less, and even more preferably 65 mass% or less, based on 100 mass% of the conductive paste. By setting the content of the conductive filler or metal powder (G) to the above lower limit or more, the elastomer of the conductive paste can have appropriate conductivity. By setting the content of the conductive filler or metal powder (G) to the above upper limit or less, the elastomer can have appropriate flexibility.

[0033] The conductive paste may contain a non-conductive filler such as silica particles (C) as needed. In this case, the lower limit of the content of silica particles (C) in the conductive paste is, for example, preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, based on 100% by mass of the conductive paste. On the other hand, the upper limit of the content of silica particles (C) in the conductive paste is, for example, preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the conductive paste. By setting the content of the silica particles (C) or non-conductive filler to the above lower limit or more, the elastomer of the conductive paste can have an appropriate mechanical strength. On the other hand, by setting the content of the silica particles (C) or non-conductive filler to the above upper limit or less, the elastomer can have an appropriate conductivity.

[0034] The lower limit of the content of the silica particles (C) in the conductive paste can be, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more, based on 100% by mass of the total amount of the silica particles (C) and the conductive filler. This can improve the mechanical strength of the elastomer in the conductive paste. On the other hand, the upper limit of the content of the silica particles (C) in the conductive paste can be, for example, 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less, based on 100% by mass of the total amount of the silica particles (C) and the conductive filler. This can achieve a balance between the elastic electrical properties and the mechanical strength of the elastomer in the conductive paste.

[0035] The lower limit of the content of the silane coupling agent (D) in the conductive paste is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, relative to 100% by weight of the total amount of the vinyl group-containing organopolysiloxane (A). On the other hand, the upper limit of the content of the silane coupling agent (D) is preferably 100% by mass or less, more preferably 80% by mass or less, and even more preferably 40% by mass or less, relative to 100% by weight of the total amount of the vinyl group-containing organopolysiloxane (A). By setting the content of the silane coupling agent (D) in the conductive paste 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, this contributes to improving the mechanical strength of the elastomer as a whole. Furthermore, by setting the content of the silane coupling agent (D) to the above upper limit or less, the elastomer can have appropriate mechanical properties.

[0036] The lower limit of the content of platinum or platinum compound (E) in the conductive paste is, for example, preferably 0.0001 mass% or more, more preferably 0.0002 mass% or more, and even more preferably 0.0003 mass% or more, based on 100 mass% of the conductive paste. On the other hand, the upper limit of the content of platinum or platinum compound (E) in the conductive paste is preferably 1 mass % or less, more preferably 0.5 mass % or less, and even more preferably 0.1 mass % or less, based on the total amount of the conductive paste. 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 rate. Furthermore, by setting the content of platinum or platinum compound (E) to the above upper limit or less, the cost of producing the conductive paste can be reduced.

[0037] <<Vinyl group-containing organopolysiloxane (A)>> The silicone rubber-based curable composition may contain a vinyl group-containing organopolysiloxane (A). The vinyl group-containing organopolysiloxane (A) may be the main component of the silicone rubber-based curable composition.

[0038] The vinyl group-containing organopolysiloxane (A) can contain a vinyl group-containing linear organopolysiloxane (A1) having a linear structure.

[0039] The vinyl group-containing linear organopolysiloxane (A1) has a linear structure and contains vinyl groups, which become crosslinking points during curing.

[0040] The vinyl group content of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but for example, it is preferable that the vinyl group content be 15 mol % or less, and more preferably 0.01 to 12 mol %, and that the vinyl group content be two or more in the molecule. This optimizes the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1), ensuring the formation of networks with the components described below.

[0041] In this specification, the vinyl group content refers to the mole percent of vinyl group-containing siloxane units when all units constituting the vinyl group-containing linear organopolysiloxane (A1) are taken as 100 mole percent, where it is considered that there is one vinyl group per vinyl group-containing siloxane unit.

[0042] The degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably within a range of, for example, about 1,000 to 10,000, and more preferably about 2,000 to 5,000. The degree of polymerization can be determined, for example, as the polystyrene-equivalent number-average degree of polymerization (or number-average molecular weight) measured by GPC (gel permeation chromatography) using chloroform as a developing solvent.

[0043] In this specification, unless otherwise specified, the symbol "to" indicates that the upper and lower limits are included.

[0044] 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.

[0045] By using a vinyl group-containing linear organopolysiloxane (A1) having a degree of polymerization and specific gravity within the above ranges, it is possible to improve the heat resistance, flame retardancy, chemical stability, etc. of the resulting silicone rubber.

[0046] As the vinyl group-containing linear organopolysiloxane (A1), those having a structure represented by the following formula (1) are particularly preferred.

[0047] [ka]

[0048] In formula (1), R 1 is a hydrocarbon group selected from substituted or unsubstituted alkyl groups, alkenyl groups, aryl groups, or combinations thereof having 1 to 10 carbon atoms. Examples of alkyl groups having 1 to 10 carbon atoms include methyl groups, ethyl groups, and propyl groups, with methyl groups being preferred. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl groups, allyl groups, and butenyl groups, with vinyl groups being preferred. Examples of aryl groups having 1 to 10 carbon atoms include phenyl groups.

[0049] Also, R 2 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group combining these groups, each having 1 to 10 carbon atoms. Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl, allyl, and butenyl groups. Examples of aryl groups having 1 to 10 carbon atoms include phenyl groups.

[0050] Also, R 3is a substituted or unsubstituted alkyl group or aryl group having 1 to 8 carbon atoms, or a hydrocarbon group consisting of a combination thereof. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of aryl groups having 1 to 8 carbon atoms include phenyl groups.

[0051] Furthermore, R in formula (1) 1 and R 2 Examples of the substituent of R include a methyl group and a vinyl group. 3 Examples of the substituent include a methyl group.

[0052] In addition, in formula (1), multiple R 1 are independent of each other and may be different or the same. 2 , and R 3 The same is true for .

[0053] Furthermore, m and n are the numbers of repeating units constituting the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1), where m is an integer of 0 to 2000 and n is an integer of 1000 to 10000. m is preferably 0 to 1000, and n is preferably 2000 to 5000.

[0054] Specific examples of the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1) include those represented by the following formula (1-1).

[0055] [ka]

[0056] 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.

[0057] Furthermore, the vinyl group-containing linear organopolysiloxane (A1) preferably contains a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more vinyl groups in the molecule and a vinyl group content of 0.4 mol% or less, and a second vinyl group-containing linear organopolysiloxane (A1-2) having a vinyl group content of 0.5 to 15 mol%. Combining a first vinyl group-containing linear organopolysiloxane (A1-1) with a typical vinyl group content for raw rubber, the raw material for silicone rubber, with a second vinyl group-containing linear organopolysiloxane (A1-2) with a high vinyl group content allows for uneven distribution of vinyl groups, more effectively creating a crosslink density distribution within the crosslinked network of the silicone rubber. As a result, the tear strength of the silicone rubber can be more effectively increased.

[0058] Specifically, the vinyl group-containing linear organopolysiloxane (A1) may be, for example, a vinyl group-containing linear organopolysiloxane represented by the above formula (1-1), 1 is a vinyl group and / or R 2 a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more units in the molecule in which R is a vinyl group and containing 0.4 mol % or less of the unit; 1 is a vinyl group and / or R 2 It is preferable to use a second vinyl group-containing linear organopolysiloxane (A1-2) containing 0.5 to 15 mol % of units in which each of the units is a vinyl group.

[0059] The first vinyl group-containing linear organopolysiloxane (A1-1) preferably has a vinyl group content of 0.01 to 0.2 mol %, and the second vinyl group-containing linear organopolysiloxane (A1-2) preferably has a vinyl group content of 0.8 to 12 mol %.

[0060] Furthermore, when the first vinyl group-containing linear organopolysiloxane (A1-1) and the second vinyl group-containing linear organopolysiloxane (A1-2) are combined and blended, the ratio of (A1-1) to (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 more preferably 80:20 to 90:10.

[0061] The first and second vinyl group-containing linear organopolysiloxanes (A1-1) and (A1-2) may each be used alone or in combination of two or more.

[0062] The vinyl group-containing organopolysiloxane (A) may also contain a vinyl group-containing branched organopolysiloxane (A2) having a branched structure.

[0063] <<Organohydrogenpolysiloxane (B)>> The silicone rubber-based curable composition may contain an 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, and may contain either one or both of these.

[0064] The linear organohydrogenpolysiloxane (B1) has a linear structure and a structure in which hydrogen is directly bonded to Si (≡Si-H), and is a polymer that undergoes a hydrosilylation reaction with the vinyl groups of the vinyl group-containing organopolysiloxane (A) and with vinyl groups of the components blended into the silicone rubber-based curable composition, thereby crosslinking these components.

[0065] The molecular weight of the linear organohydrogenpolysiloxane (B1) is not particularly limited, but for example, the weight average molecular weight is preferably 20,000 or less, and more preferably 1,000 or more and 10,000 or less.

[0066] The weight average molecular weight of the linear organohydrogenpolysiloxane (B1) can be measured, for example, by gel permeation chromatography (GPC) using chloroform as a developing solvent, in terms of polystyrene.

[0067] Furthermore, it is generally preferred that the linear organohydrogenpolysiloxane (B1) does not contain a vinyl group, which can reliably prevent the crosslinking reaction from proceeding within the molecule of the linear organohydrogenpolysiloxane (B1).

[0068] As the linear organohydrogenpolysiloxane (B1) described above, for example, one having a structure represented by the following formula (2) is preferably used.

[0069] [ka]

[0070] In formula (2), R 4 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, a hydrocarbon group combining these, or a hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, with a methyl group being preferred. 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.

[0071] Also, R 5is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, a hydrocarbon group combining these, or a hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, with a methyl group being preferred. 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.

[0072] In addition, in formula (2), multiple R 4 are independent of each other and may be different or the same. 5 The same applies to multiple R 4 and R 5 At least two of these are hydride groups.

[0073] Also, R 6 is a substituted or unsubstituted alkyl group or aryl group having 1 to 8 carbon atoms, or a hydrocarbon group combining these. Examples of alkyl groups having 1 to 8 carbon atoms include methyl groups, ethyl groups, and propyl groups, with methyl groups being preferred. Examples of aryl groups having 1 to 8 carbon atoms include phenyl groups. 6 are independent of each other and may be different from each other or may be the same.

[0074] In addition, R in formula (2) 4 ,R 5 ,R 6 Examples of the substituent include a methyl group and a vinyl group, and a methyl group is preferred from the viewpoint of preventing intramolecular crosslinking reactions.

[0075] Furthermore, m and n are the numbers of repeating units constituting the linear organohydrogenpolysiloxane (B1) represented by formula (2), where m is an integer of 2 to 150 and n is an integer of 2 to 150. Preferably, m is an integer of 2 to 100 and n is an integer of 2 to 100.

[0076] The linear organohydrogenpolysiloxane (B1) may be used alone or in combination of two or more.

[0077] Because the branched organohydrogenpolysiloxane (B2) has a branched structure, it forms regions with high crosslink density, and is a component that significantly contributes to the formation of a sparsely crosslinked structure in the silicone rubber system. Like the linear organohydrogenpolysiloxane (B1), it has a structure in which hydrogen is directly bonded to silicon (≡Si-H), and undergoes a hydrosilylation reaction with the vinyl groups of the vinyl-group-containing organopolysiloxane (A) and with the vinyl groups of other components incorporated into the silicone rubber-based curable composition, forming a polymer that crosslinks these components.

[0078] The specific gravity of the branched organohydrogenpolysiloxane (B2) is in the range of 0.9 to 0.95.

[0079] Furthermore, it is generally preferred that the branched organohydrogenpolysiloxane (B2) does not contain vinyl groups, which can reliably prevent crosslinking reactions from occurring within the molecules of the branched organohydrogenpolysiloxane (B2).

[0080] The branched organohydrogenpolysiloxane (B2) is preferably one represented by the following average composition formula (c).

[0081] 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, and m is H a (R 7 ) 3-a SiO 1 / 2 The number of units, n, is SiO 4 / 2 (the number of units)

[0082] In formula (c), R 7 is a monovalent organic group, preferably a substituted or unsubstituted alkyl group or aryl group having 1 to 10 carbon atoms, or a hydrocarbon group consisting of a combination thereof. Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of aryl groups having 1 to 10 carbon atoms include phenyl groups.

[0083] In formula (c), a is the number of hydride groups (hydrogen atoms directly bonded to Si), and is an integer ranging from 1 to 3, preferably 1.

[0084] In addition, in formula (c), m is H a (R 7 ) 3-a SiO 1 / 2 The number of units, n, is SiO 4 / 2 The number of units.

[0085] The branched organohydrogenpolysiloxane (B2) has a branched structure. The linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) differ in their structures, that is, whether they are linear or branched. The number of alkyl groups R bonded to Si (R / Si), where the number of Si is 1, is in the range of 1.8 to 2.1 for the linear organohydrogenpolysiloxane (B1) and 0.8 to 1.7 for the branched organohydrogenpolysiloxane (B2).

[0086] Because the branched organohydrogenpolysiloxane (B2) has a branched structure, it leaves a residue amount of 5% or more when heated, for example, in a nitrogen atmosphere to 1000°C at a heating rate of 10°C / min. In contrast, because the linear organohydrogenpolysiloxane (B1) is linear, it leaves almost no residue amount after heating under the above conditions.

[0087] Specific examples of the branched organohydrogenpolysiloxane (B2) include those having a structure represented by the following formula (3).

[0088] [ka]

[0089] In formula (3), R 7 R is a substituted or unsubstituted alkyl group or aryl group having 1 to 8 carbon atoms, or a hydrocarbon group combining these, or a hydrogen atom. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of aryl groups having 1 to 8 carbon atoms include phenyl groups. 7 Examples of the substituent include a methyl group.

[0090] In addition, in formula (3), multiple R 7 are independent of each other and may be different from each other or may be the same.

[0091] In addition, in formula (3), "-O-Si≡" indicates that Si has a branched structure that spreads three-dimensionally.

[0092] The branched organohydrogenpolysiloxane (B2) may be used alone or in combination of two or more.

[0093] Furthermore, the amount of hydrogen atoms (hydride groups) directly bonded to Si in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is not particularly limited. However, in the silicone rubber-based curable composition, the total amount of hydride groups in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is preferably 0.5 to 5 moles, more preferably 1 to 3.5 moles, per mole of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1). This ensures the reliable formation of a crosslinked network between the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) and the vinyl group-containing linear organopolysiloxane (A1).

[0094] <<Silica particles (C)>> The silicone rubber-based curable composition may optionally contain silica particles (C) as a non-conductive filler. The non-conductive filler is not limited to silica particles (C), and other non-conductive fillers may also be included. This can improve the hardness and mechanical strength of the elastomer formed from the conductive paste. As the non-conductive filler, known materials can be used, such as silica particles, silicone rubber particles, talc, etc. These may be used alone or in combination of two or more.

[0095] The silica particles (C) are not particularly limited, but examples thereof include fumed silica, calcined silica, precipitated silica, etc. These may be used alone or in combination of two or more.

[0096] The silica particles (C) have a specific surface area measured by the BET method of, for example, 50 to 400 m 2 / g, and 100 to 400m 2 / g is more preferable, and 200 to 400m 2 / g is more preferred. 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.

[0097] By using silica particles (C) having a specific surface area and average particle size within the above ranges, it is possible to improve the hardness and mechanical strength of the silicone rubber formed, particularly the tensile strength.

[0098] <<Silane coupling agent (D)>> The silicone rubber-based curable composition may contain a silane coupling agent (D). The silane coupling agent (D) may have a hydrolyzable group, which is hydrolyzed by water to form a hydroxyl group, which undergoes a dehydration condensation reaction with the hydroxyl groups on the surface of the silica particles (C), thereby modifying the surface of the silica particles (C).

[0099] The silane coupling agent (D) may also contain a silane coupling agent having a hydrophobic group. This provides the surface of the silica particles (C), thereby reducing the cohesive strength of the silica particles (C) in the silicone rubber-based curable composition and, ultimately, in the silicone rubber (reducing aggregation due to hydrogen bonding via silanol groups). This is thought to result in improved dispersibility of the silica particles in the silicone rubber-based curable composition. This increases the interface between the silica particles and the rubber matrix, enhancing the reinforcing effect of the silica particles. Furthermore, it is thought that the sliding properties of the silica particles within the matrix are improved during deformation of the rubber matrix. The improved dispersibility and sliding properties of the silica particles (C) contribute to improved mechanical strength (e.g., tensile strength, tear strength, etc.) of the silicone rubber.

[0100] Furthermore, the silane coupling agent (D) may contain a silane coupling agent having a vinyl group. This introduces a vinyl group onto the surface of the silica particles (C). Therefore, during curing of the silicone rubber-based curable composition, i.e., when the vinyl groups of the vinyl group-containing organopolysiloxane (A) and the hydride groups of the organohydrogenpolysiloxane (B) undergo a hydrosilylation reaction to form a network (crosslinked structure), the vinyl groups of the silica particles (C) also participate in the hydrosilylation reaction with the hydride groups of the organohydrogenpolysiloxane (B), thereby incorporating the silica particles (C) into the network. This allows for a silicone rubber with a low hardness and a high modulus to be formed.

[0101] 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.

[0102] Examples of the silane coupling agent (D) include those represented by the following formula (4).

[0103] Y n -Si-(X) 4-n ···(4) In the above formula (4), n represents an integer of 1 to 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 the groups is a hydrophobic group. X represents a hydrolyzable group.

[0104] The hydrophobic group is an alkyl group having 1 to 6 carbon atoms, an aryl group, or a hydrocarbon group formed by combining these groups, such as a methyl group, an ethyl group, a propyl group, or a phenyl group, with a methyl group being particularly preferred.

[0105] Examples of the hydrophilic group include a hydroxyl group, a sulfonic acid group, a carboxyl group, and a carbonyl group, and among these, a hydroxyl group is particularly preferred. Although a hydrophilic group may be contained as a functional group, it is preferable that the hydrophilic group is not contained from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

[0106] Further, examples of the hydrolyzable group include alkoxy groups such as methoxy and ethoxy groups, chloro groups, and silazane groups. Among these, silazane groups are preferred because of their high reactivity with the silica particles (C). Note that, those having a silazane group as the hydrolyzable group have structural characteristics such that (Y n -Si-) structures.

[0107] Specific examples of the silane coupling agent (D) represented by the above formula (4) include those having a hydrophobic group as a functional group, such as alkoxysilanes like methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, and decyltrimethoxysilane; chlorosilanes like methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and phenyltrichlorosilane; and hexamethyldisilazane. Examples of the vinyl group-containing silane include alkoxysilanes such as methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane and vinylmethyldichlorosilane; and divinyltetramethyldisilazane. Among these, taking into consideration the above, hexamethyldisilazane is particularly preferred as the silane having a hydrophobic group, and divinyltetramethyldisilazane is particularly preferred as the silane having a vinyl group.

[0108] <<Platinum or platinum compounds (E)>> The silicone rubber-based hardenable composition of this embodiment may contain platinum or a platinum compound (E). Platinum or 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.

[0109] As the platinum or platinum compound (E), known compounds can be used, such as platinum black, platinum supported on silica or carbon black, chloroplatinic acid or an alcohol solution of chloroplatinic acid, a complex salt of chloroplatinic acid and an olefin, and a complex salt of chloroplatinic acid and a vinylsiloxane. The platinum or platinum compound (E) may be used alone or in combination of two or more.

[0110] Alternatively, a catalyst other than component (E) may be used in place of or in combination with platinum or platinum compound (E). Examples of catalysts other than component (E) include organic peroxides such as ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peresters, peroxyesters, and peroxydicarbonates.

[0111] <<Water(F)>> The silicone rubber-based hardening composition of this embodiment may contain water (F) in addition to the above components (A) to (E).

[0112] Water (F) functions as a dispersion medium to disperse the components contained in the silicone rubber-based curable composition, and also contributes to the reaction between the silica particles (C) and the silane coupling agent (D). This allows the silica particles (C) and the silane coupling agent (D) to be more reliably bonded to each other in the silicone rubber, allowing the composition to exhibit uniform properties overall.

[0113] <<Other ingredients>> Furthermore, the silicone rubber-based curable composition of this embodiment may further contain other components in addition to the above components (A) to (F), such as inorganic fillers other than the 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, as well as additives such as reaction inhibitors, dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, and thermal conductivity improvers. Examples of inorganic fillers other than the silica particles (C) include diatomaceous earth, iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide, cerium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, glass wool, and mica.

[0114] Here, an example of a method for producing a silicone rubber-based hardening composition will be described.

[0115] First, the components of the silicone rubber-based hardening composition are mixed uniformly using any kneading device to prepare the silicone rubber-based hardening composition.

[0116] [1] For example, a predetermined amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D) are weighed, and then kneaded using any kneading device to obtain a kneaded product containing these components (A), (C), and (D).

[0117] The kneaded mixture is preferably obtained by first kneading the vinyl group-containing organopolysiloxane (A) with the silane coupling agent (D) and then kneading the silica particles (C) in the mixture, which further improves the dispersibility of the silica particles (C) in the vinyl group-containing organopolysiloxane (A).

[0118] Furthermore, when obtaining this kneaded mixture, water (F) may be added to the kneaded mixture of the components (A), (C), and (D) as needed, which allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

[0119] Furthermore, when water (F) is contained, its content can be appropriately set, but specifically, for example, it is preferably in the range of 10 to 100 parts by weight, more preferably in the range of 30 to 70 parts by weight, per 100 parts by weight of the silane coupling agent (D), which allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

[0120] Furthermore, the kneading of components (A), (C), and (D) is preferably carried out through a first step in which the components are heated at a first temperature and a second step in which the components are heated at a second temperature. This allows the surfaces of the silica particles (C) to be surface-treated with the coupling agent (D) in the first step, and allows by-products formed by the reaction between the silica particles (C) and the coupling agent (D) to be reliably removed from the kneaded mixture in the second step. If necessary, component (A) may then be added to the resulting kneaded mixture, followed by further kneading. This improves the compatibility of the components in the kneaded mixture.

[0121] The first temperature is preferably, for example, about 40 to 120° C., and more preferably, for example, about 60 to 90° C. The second temperature is preferably, for example, about 130 to 210° C., and more preferably, for example, about 160 to 180° C.

[0122] 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.

[0123] Furthermore, the time for the first step is, for example, preferably about 0.3 to 1.5 hours, more preferably about 0.5 to 1.2 hours, and 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.

[0124] By setting the conditions for the first and second steps as described above, the above-mentioned effects can be more significantly obtained.

[0125] [2] Next, predetermined amounts of organohydrogenpolysiloxane (B) and platinum or a platinum compound (E) are weighed out, and then, using any kneading device, the components (B) and (E) are kneaded into the mixture prepared in the above step [1] to obtain a silicone rubber-based curable composition (elastomer composition).

[0126] When kneading components (B) and (E), it is preferable to first knead the mixture prepared in step [1] with the organohydrogenpolysiloxane (B), and then knead the mixture prepared in step [1] with platinum or a platinum compound (E), and then knead the respective mixtures together. This ensures that components (A) to (E) are dispersed in the silicone rubber-based curable composition without promoting the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B).

[0127] The temperature at which the components (B) and (E) are kneaded is, for example, preferably about 10 to 70°C, more preferably about 25 to 30°C, as the roll temperature.

[0128] Furthermore, the kneading time is, for example, preferably about 5 minutes to 1 hour, and more preferably about 10 to 40 minutes.

[0129] In steps [1] and [2], by maintaining the temperature within the above range, it is possible to more effectively prevent or inhibit the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B). Furthermore, by maintaining the kneading time within the above range in steps [1] and [2], it is possible to more reliably disperse the components (A) to (E) in the silicone rubber-based curable composition.

[0130] The kneading device used in each of steps [1] and [2] is not particularly limited, but for example, a kneader, a two-roll mill, a Banbury mixer (continuous kneader), a pressure kneader, etc. can be used.

[0131] Furthermore, in step [2], a reaction inhibitor such as 1-ethynylcyclohexanol may be added to the kneaded mixture, which makes it possible to more effectively prevent or inhibit the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) even when the temperature of the kneaded mixture is set at a relatively high temperature. By the above step [2], a silicone rubber-based curable composition is obtained as an elastomer composition.

[0132] (Conductive filler) The conductive filler may be a known conductive material, but may also contain one or more selected from the group consisting of powdery or fibrous metal-based fillers, carbon-based fillers (conductive carbon materials), metal oxide fillers, and metal-plated fillers. Among these, metal-based fillers may be used, and metal powder (G) as described below may also be used.

[0133] The metal constituting the metal powder (G) is not particularly limited, but may include, for example, at least one of copper, silver, gold, nickel, tin, lead, zinc, bismuth, antimony, or metal powders alloyed with these, or two or more of these. Of these, the metal powder (G) preferably contains silver or copper, that is, silver powder or copper powder, because of their high conductivity and easy availability. These metal powders (G) may also be coated with other metals.

[0134] The shape of the metal powder (G) is not particularly limited, and conventionally used shapes such as dendritic, spherical, scale-like, etc. Among these, scale-like metal powder (G) may be used.

[0135] The lower limit of the particle size of the metal powder (G) or the flaky metal powder (G) is not particularly limited, but the average particle size D 50 For example, it is 0.001 μm or more, preferably 0.01 μm or more, more preferably 0.1 μm or more, and even more preferably 1 μm or more. The particle size of the metal powder (G) or flaky metal powder (G) is the average particle size D 50 For example, it is 1,000 μm or less, preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 20 μm or less. Average particle size D 50 By setting the value of the elastomer in this range, the conductive paste can exhibit appropriate conductivity. The lower limit of the BET specific surface area of ​​the conductive filler or metal powder (G) is, for example, 0.1 m 2 / g or more, preferably 0.5m 2 / g or more, more preferably 1.0m 2 / g or more, which increases the electrical conductivity when stretched. On the other hand, the upper limit of the BET specific surface area of ​​the conductive filler or metal powder (G) is, for example, 5 m 2 / g or less, preferably 3 μm or less, more preferably 2 m 2 / g. This allows the paste viscosity to be kept low. The particle size of the metal powder (G) can be defined as the average value of 200 arbitrarily selected metal powder particles after observing the conductive paste or the elastomer with a transmission electron microscope or the like and performing image analysis.

[0136] (non-aqueous solvent) As the non-aqueous solvent, various known non-aqueous solvents can be used, including, for example, high-boiling point non-aqueous solvents. These may be used alone or in combination of two or more.

[0137] The lower limit of the boiling point of the high-boiling-point non-aqueous solvent is, for example, 100°C or higher, preferably 130°C or higher, and more preferably 150°C or higher. This can improve printing stability in screen printing and the like. On the other hand, the upper limit of the boiling point of the high-boiling-point non-aqueous solvent is not particularly limited, and may be, for example, 300°C or lower, 290°C or lower, or 280°C or lower. This can suppress excessive thermal history during wiring formation, thereby preventing damage to the base substrate and maintaining a good shape of the wiring formed from the conductive paste. The upper limit of the boiling point of the high-boiling-point non-aqueous solvent may be 250° C. or lower, 240° C. or lower, or 200° C. This makes it possible to suppress the solvent from remaining in the cured product when the conductive paste is cured.

[0138] The non-aqueous solvent can be appropriately selected from the viewpoint of the solubility and boiling point of the elastomer composition, and may include, for example, an aliphatic hydrocarbon having 5 to 20 carbon atoms, preferably an aliphatic hydrocarbon having 8 to 18 carbon atoms, and more preferably an aliphatic hydrocarbon having 10 to 15 carbon atoms.

[0139] Examples of non-aqueous solvents include aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane, methylcyclohexane, ethylcyclohexane, octane, decane, dodecane, and tetradecane; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, xylene, mesitylene, trifluoromethylbenzene, and 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, and diethylene glycol. Examples of suitable solvents include ethers such as glycol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol methyl-n-propyl ether, 1,4-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 dimethyl sulfoxide and diethyl sulfoxide; and esters such as diethyl carbonate. These may be used alone or in combination of two or more. The solvent used here may be appropriately selected from among solvents that can uniformly dissolve or disperse the components in the conductive paste.

[0140] In addition, the polarity term (δ p ) is, for example, 10 MPa 1 / 2 or less, preferably 7 MPa 1 / 2 or less, more preferably 5.5 MPa 1 / 2 The conductive paste may contain a first non-aqueous solvent having the following polarity term (δ): This makes it possible to improve the dispersibility and solubility of an elastomer composition such as a silicone rubber-based curable resin composition in the conductive paste. p The lower limit of the pressure is not particularly limited, but may be, for example, 0 Pa. 1 / 2More than that is fine.

[0141] The hydrogen bond term (δ h ) is, for example, 20 MPa 1 / 2 or less, preferably 10 MPa 1 / 2 or less, more preferably 7 MPa 1 / 2 This allows the dispersibility and solubility of elastomer compositions such as silicone rubber-based curable resin compositions to be improved in the conductive paste. h The lower limit of the pressure is not particularly limited, but may be, for example, 0 Pa. 1 / 2 More than that is fine.

[0142] Hansen solubility parameter (HSP) is an index that indicates the solubility of a substance, i.e., how much a substance dissolves in another substance. HSP expresses solubility as a three-dimensional vector. This three-dimensional vector is typically expressed as a dispersion term (δ d ), polarity term (δ p ), hydrogen bond term (δ h ) and those with similar vectors can be judged to have high solubility. The similarity of vectors can be judged by the distance of the Hansen solubility parameter (HSP distance).

[0143] The Hansen solubility parameters (HSP values) used in this specification can be calculated using software called HSPiP (Hansen Solubility Parameters in Practice). The computer software HSPiP, developed by Hansen and Abbott, includes a function for calculating HSP distances and a database listing the Hansen parameters for various resins and non-aqueous or non-non-aqueous solvents. The solubility of each resin in pure non-aqueous solvents and mixed non-aqueous solvents of good and poor non-aqueous solvents is investigated, and the results are entered into the HSPiP software to calculate D: dispersion term, P: polar term, H: hydrogen bond term, and R0: radius of the solubility sphere.

[0144] As the non-aqueous solvent, for example, one can be selected in which the difference in HSP distance, polarity term, or hydrogen bond term between the elastomer or the structural units constituting the elastomer and the non-aqueous solvent is small.

[0145] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. Below, examples of reference forms are added. 1. an elastomer composition; A conductive filler; A conductive paste comprising: A conductive paste having a degree of dispersion of 40 μm or less as measured using a particle gauge in accordance with JIS K5600-2-5:1999. 2. The conductive paste according to 1., A conductive paste whose viscosity, when measured at 25°C and at a shear rate of 20 [1 / s], is 1 Pa·s or more and 100 Pa·s or less. 3. The conductive paste according to 1. or 2., The conductive paste has a thixotropy index calculated by η1 / η5, where η1 is the viscosity when measured at a shear rate of 1 [1 / s] at 25°C and η5 is the viscosity when measured at a shear rate of 5 [1 / s], of 1.0 or more and 3.0 or less. 4. The conductive paste according to any one of 1. to 3., A conductive paste comprising a non-conductive filler. 5. The conductive paste according to any one of 1. to 4., The 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. 6. The conductive paste according to any one of 1. to 5., The conductive paste, wherein the non-aqueous solvent contains a high-boiling-point non-aqueous solvent having a boiling point of 100°C or higher and 300°C or lower. 7. The conductive paste according to any one of 1. to 6., A conductive paste, wherein the content of the conductive filler is 30% by mass or more and 85% by mass or less, based on 100% by mass of the conductive paste. 8. A method for producing a conductive paste, comprising a mixing step of stirring raw material components including an elastomer composition, a conductive filler, and a non-aqueous solvent in a stirring tank using stirring blades, and then kneading the components using a planetary mixer to obtain a conductive paste. [Example]

[0146] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0147] <Elastomer composition> The vinyl group-containing organopolysiloxane (A), the silane coupling agent (D), and the water (F) were mixed in a predetermined ratio, and a predetermined amount of silica particles (C) was added and further mixed to obtain a silicone rubber compound. To the silicone rubber compound, predetermined amounts of organohydrogenpolysiloxane (B) as a crosslinking agent, platinum or a platinum compound (E) as a catalyst, and a reaction inhibitor were added and mixed to obtain an elastomer composition (silicone rubber-based curable composition).

[0148] <Conductive paste manufacturing> [Example 1] A predetermined amount of decane (non-aqueous solvent, boiling point 174°C) was added to the obtained elastomer composition and mixed to obtain a mixture. The viscosity of the mixture measured at 25°C and a shear rate of 20 [1 / s] using an E-type viscometer (Toki Sangyo Co., Ltd., TPE-100H) was 15 Pa s. The resulting mixture was further mixed with silver powder A (conductive filler, BET specific surface area: 1.5 m 2After mixing the ingredients (100g / g), the mixture was stirred at 15 rpm for 10 minutes using a stirrer with anchor blades (Three-One Motor (registered trademark), manufactured by Shinto Scientific Co., Ltd.). The mixture was then thoroughly kneaded using a planetary centrifugal mixer (Awatori Rentaro (registered trademark), manufactured by Thinky Corporation) to obtain a conductive paste of Example 1. [Example 2] A predetermined amount of tetradecane (non-aqueous solvent, boiling point 253°C) was added to the obtained elastomer composition and mixed to obtain a mixture. The viscosity of the mixture measured using an E-type viscometer (Toki Sangyo Co., Ltd., TPE-100H) at 25°C and a shear rate of 20 [1 / s] was 20 Pa s. The resulting mixture was further mixed with silver powder A (conductive filler, BET specific surface area: 1.5 m 2 After mixing the ingredients (100g / g), the mixture was stirred at 15 rpm for 10 minutes using an anchor blade mixer (Three-One Motor (registered trademark), manufactured by Shinto Scientific Co., Ltd.). The mixture was then thoroughly kneaded using a planetary centrifugal mixer (Awatori Rentaro (registered trademark), manufactured by Thinky Corporation). Additional kneading was then carried out using a three-roll mill to obtain the conductive paste of Example 2. [Example 3] A predetermined amount of decane (non-aqueous solvent, boiling point 174°C) was added to the obtained elastomer composition and mixed to obtain a mixture. The viscosity of the mixture measured using an E-type viscometer (Toki Sangyo Co., Ltd., TPE-100H) at 25°C and a shear rate of 20 [1 / s] was 12 Pa s. The resulting mixture was further mixed with silver powder B (conductive filler, BET specific surface area: 0.7 m 2 After mixing the ingredients (100g x 100g), the mixture was stirred at 15 rpm for 10 minutes using a stirrer with anchor blades (Three-One Motor (registered trademark), manufactured by Shinto Scientific Co., Ltd.). The mixture was then thoroughly kneaded using a planetary centrifugal mixer (Awatori Rentaro (registered trademark), manufactured by Thinky Corporation) to obtain a conductive paste of Example 3.

[0149] [Comparative Example 1] A conductive paste of Comparative Example 1 was obtained in the same manner as in Example 1, except that the above-mentioned mixer and rotation-revolution mixer were not used, and the mixture was stirred and kneaded by hand. In Comparative Example 1, lumps were found scattered throughout the obtained conductive paste. These lumps are presumed to be derived from the elastomer composition. In Examples 1 to 3, the presence of such lumps was not confirmed in the mixture after stirring. Comparative Example 2 The same conditions as in Example 1 were used, except that the amount of decane added to the mixture was reduced to obtain a mixture with a viscosity of 130 Pa s, and silver powder A was added to this mixture, followed by stirring with an anchor blade stirrer. In Comparative Example 2, stirring was started using a stirrer with anchor blades, but the mixture became unable to be stirred midway through. When stirring became impossible, the production process was terminated.

[0150] [Evaluation of conductive paste] The obtained conductive paste was evaluated according to the following items.

[0151] <Measuring the grain gauge value> The particle gauge value of the obtained conductive paste was measured in accordance with JIS K5600-2-5:1999 as follows. First, a clean, dry grain gauge was placed on a smooth, level, non-slip surface. Next, at room temperature of 25°C, the sample was thoroughly stirred using a spatula, and then a sufficient amount of sample (conductive paste) was poured into the deeper end of the groove, allowing it to slightly overflow from the groove. Next, the scraper was held between the thumbs and fingers of both hands, with the long side of the scraper parallel to the width of the gauge and the cutting edge in contact with the deep end of the gauge groove. While holding the scraper perpendicular to the surface of the gauge, it was pulled at a uniform speed across the surface of the gauge, perpendicular to the long side of the groove, over 1 to 2 seconds, down to the depth of 0. Sufficient force was applied to the scraper so that the groove was filled with the sample and the excess was removed. Then, within 3 seconds of finishing pulling, the sample was observed by shining a light on it so that the pattern on the sample was easily visible, at a viewing angle perpendicular to the long side of the groove and at an angle of 20° to 30° to the surface of the gauge. In the above observation, the gauge scale was read at the position of the first speck that appeared among a plurality of specks that appeared in the groove, and this was taken as the grain gauge value (μm).

[0152] (Grain gauge used in the above measurements) Material: Stainless steel Dimensions: length approx. 165mm, width 35mm, thickness 13mm Grooves: 2, length approx. 125mm, width 12mm Maximum groove depth: 100 μm Scale interval: 10μm Measurement range: 0 to 100 μm

[0153] (Scraper used in the above measurements) Material: Stainless steel Cutting edge: both sides, long side is straight, R: approx. 0.25 Dimensions: Approximately 50mm long, 38mm wide, 5mm thick

[0154] The above particle gauge value was measured three times, and the average value was calculated. As a result, the grain gauge value is Example 1 is 21 μm, Example 2 is 8 μm, Example 3 is 32 μm, Comparative Example 1 was over 40 μm.

[0155] <Viscosity> The viscosity of the obtained conductive paste was measured immediately after preparation at 25°C and a shear rate of 20 [1 / s] using a TPE-100H (E-type viscometer) manufactured by Toki Sangyo Co., Ltd. The unit of viscosity is Pa·s. In Example 1, the viscosity at 25°C was 20 Pa·s.

[0156] <Thixotropy index> The resulting conductive paste was measured immediately after preparation using a Toki Sangyo TPE-100H (E-type viscometer) at 25°C, with the viscosity measured at a shear rate of 1 (1 / s) as η1 and the viscosity measured at a shear rate of 5 (1 / s) as η5. The viscosity is measured in Pa·s. The thixotropy index was calculated from the η1 / η5 viscosity ratio. In Example 1, the thixotropy index was 1.7.

[0157] <Measurement of resistance value before and after expansion> The resulting elastomer composition was cured at 170°C for 120 minutes and molded into a sheet to prepare a silicone rubber substrate measuring 5 cm wide x 500 µm high x 5 cm long. Next, a rectangular wiring pattern was drawn on the obtained substrate using the obtained conductive paste, and this was cured under conditions of 170°C for 120 minutes to form a wiring pattern with a width of 30 mm, length of 30 mm, and thickness of 70 μm. The rectangular wiring pattern was stretched by 50% in the diagonal direction and then released from the stretched state, and this stretching operation was repeated 100 times. The resistance of the unstretched diagonal wiring pattern was measured before and immediately after the 100th stretching operation. In Example 1, the resistance value before the stretching operation was 0.4Ω, the resistance value after the stretching operation was 0.6Ω, In Example 2, the resistance value before the stretching operation was 0.3Ω, the resistance value after the stretching operation was 0.5Ω, In Example 3, the resistance value before the stretching operation was 0.4Ω, the resistance value after the stretching operation was 0.7Ω, In Comparative Example 1, the resistance value before the stretching operation was 3.2Ω, and the resistance value after the stretching operation was 27Ω. [Reference example 1] Primary particle diameter is 0.4 μm (BET specific surface area is 4 m 2 A conductive paste of Reference Example 1 was obtained in which silver powder C (at 1000 ppm / g) was used and the particle gauge value was 3 μm. It was confirmed that the resistance value of Reference Example 1 after the stretching operation, measured based on the above <Measurement of resistance value before and after stretching>, was lower than that of Comparative Example 1, but higher than that of Examples 1 to 3.

[0158] The conductive pastes of Examples 1 to 3 showed results in which the difference between the initial resistance value and the resistance value after stretching was smaller than that of Comparative Example 1. It was found that the conductive pastes of such Examples were able to suppress fluctuations in conductivity before and after stretching.

[0159] The conductive pastes of Examples 1' to 3' were obtained using the same raw material components, mixing, and kneading conditions as in Examples 1 to 3, except that the content ratios of the elastomer composition, silver powder, and non-aqueous solvent in the non-aqueous solvent were the same. The obtained Examples 1' to 3' were subjected to a curing treatment at 170°C for 120 minutes, and the degree of remaining solvent in the obtained cured products was evaluated. It was confirmed that the conductive pastes of Examples 1' and 3' had a lower degree of remaining solvent in the cured products than the conductive paste of Example 2', which used a non-aqueous solvent with a boiling point of over 250°C.

[0160] This application claims priority based on Japanese Patent Application No. 2023-144192, filed September 6, 2023, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. an elastomer composition; A conductive filler; A conductive paste comprising: A conductive paste having a particle gauge value of 40 μm or less as measured in accordance with JIS K5600-2-5:1999.

2. The conductive paste according to claim 1, A conductive paste, wherein the grain gauge value of the conductive paste is 5 μm or more.

3. The conductive paste according to claim 1 or 2, 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 25°C.

4. The conductive paste according to any one of claims 1 to 3, The conductive paste has a thixotropy index calculated by η1 / η5, where η1 is the viscosity when measured at a shear rate of 1 [1 / s] at 25°C and η5 is the viscosity when measured at a shear rate of 5 [1 / s], of 1.0 or more and 3.0 or less.

5. The conductive paste according to any one of claims 1 to 4, A conductive paste comprising a non-conductive filler.

6. The conductive paste according to any one of claims 1 to 5, The 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.

7. The conductive paste according to any one of claims 1 to 6, The conductive paste, wherein the non-aqueous solvent contains a high-boiling-point non-aqueous solvent having a boiling point of 100°C or higher and 250°C or lower.

8. The conductive paste according to any one of claims 1 to 7, A conductive paste, wherein the content of the conductive filler is 30% by mass or more and 85% by mass or less, based on 100% by mass of the conductive paste.

9. The conductive paste according to any one of claims 1 to 8, The BET specific surface area of ​​the conductive filler is 0.1 m ２ / g or more 5m ２ / g or less.

10. A method for producing a conductive paste, comprising a mixing step of stirring raw material components including an elastomer composition, a conductive filler, and a non-aqueous solvent in a stirring tank using stirring blades, and then kneading the components using a planetary centrifugal mixer to obtain a conductive paste.

11. The method for producing a conductive paste according to claim 10, The conductive paste obtained in the mixing step has a particle gauge value of 40 μm or less as measured in accordance with JIS K5600-2-5:1999.

12. 12. The method for producing a conductive paste according to claim 10 or 11, a viscosity of the mixture of the elastomer composition and the non-aqueous solvent measured at 25°C and a shear rate of 20 [1 / s] of 1 Pa s or more and 100 Pa s or less in the mixing step.

13. A method for producing the conductive paste according to any one of claims 10 to 12, The method for producing a conductive paste, wherein the non-aqueous solvent contains a high-boiling-point non-aqueous solvent having a boiling point of 100°C or higher and 250°C or lower.

14. A method for producing the conductive paste according to any one of claims 10 to 13, The BET specific surface area of ​​the conductive filler is 0.1 m ２ / g or more 5m ２ / g or less.

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