Conductive paste, RFID inlay, and RFID inlay production method

Abstract

Provided is a conductive paste capable of 1) enhancing jetting stability, 2) enhancing storage stability, and 3) enhancing curability when mounted at a relatively low temperature in a relatively short time in an air atmosphere or the like.　A conductive paste according to the present invention contains a cationically polymerizable compound, a polymerization initiator, and a conductive filler. The cationically polymerizable compound contains an oxetane compound or an epoxy compound. The polymerization initiator contains a sulfonium salt or an ammonium salt. The viscosity of the conductive paste at 25°C is at least 10 Pa·s and at most 100 Pa·s.

Description

Conductive paste, RFID inlay, and method for manufacturing RFID inlay

[0001] This invention relates to a conductive paste containing a conductive filler. Furthermore, this invention relates to an RFID inlay using the above conductive paste and a method for manufacturing the RFID inlay. Finally, this invention relates to the use of a conductive paste for obtaining an RFID inlay.

[0002] RFID (Radio Frequency Identification) inlays, which enable contactless data transmission and reception, are widely used in contactless RFID tags and contactless RFID cards. In particular, UHF (Ultra High Frequency) band (860 MHz to 960 MHz) RFID inlays are attracting attention due to their long communication range. UHF band RFID inlays are used for various items and purposes, such as commuter passes, inventory management, distribution management, and history management.

[0003] In RFID inlays, a conductive paste containing a conductive filler and a binder resin is sometimes used to bond and connect a chip having electrodes on its surface to a substrate having wiring (antenna patterns) on its surface.

[0004] In recent years, with the miniaturization of electronic components using RFID inlays, the chips used in RFID inlays have also become smaller. Therefore, there is a demand for conductive pastes that have high adhesive properties and can be positioned with even greater precision on the wiring. When positioning conductive paste on the wiring, a dispensing method is sometimes used. For this reason, conductive pastes with excellent dispensing stability are required.

[0005] Patent Document 1 below discloses an adhesive applicable to electronic components. The adhesive is an acrylic adhesive composition comprising a radical initiator having a 10-hour half-life temperature of 80°C or lower, a vinylene-containing oligomer, and at least one diluent. The adhesive can be snap-cured at low temperatures, and its pot life at room temperature is 24 hours or more.

[0006] Patent Document 2, described below, discloses a conductive adhesive comprising a polymerizable acrylic compound, an organic peroxide, and solder particles, wherein the one-minute half-life temperature of the organic peroxide is lower than the solidus temperature of the solder particles.

[0007] Japanese Patent Publication No. 2006-144018 Japanese Patent Publication No. 2013-124330

[0008] Conventional adhesives (conductive pastes) as described in Patent Documents 1 and 2 can improve adhesion to a certain extent. However, with conventional conductive pastes, when electronic components are manufactured (mounted) in an atmospheric environment using the conductive paste, the polymerization reaction of the conductive paste may not proceed sufficiently due to the influence of oxygen, and uncured portions may remain in the cured conductive paste. As a result, there is a problem in that the conductivity reliability between the upper and lower electrodes that should be connected in the resulting electronic component (RFID inlay) decreases, and the connection reliability between the adhesive part and the electrodes decreases. This problem is particularly pronounced when mounting is done at relatively low temperatures (e.g., below 180°C) and for a relatively short time (e.g., within 15 seconds).

[0009] Furthermore, generally speaking, increasing the curing properties of an adhesive (conductive paste) tends to shorten its pot life (working time). With conventional adhesives (conductive pastes), it is difficult to increase both the curing properties and storage stability.

[0010] Furthermore, with conventional conductive pastes, when the conductive paste is dispensed using a dispensing method such as a jet dispensing method, liquid accumulation may occur or the amount of liquid dispensed may change.

[0011] The object of the present invention is to provide a conductive paste that can 1) improve dispensing stability, 2) improve storage stability, and 3) improve curability when mounted at relatively low temperatures and for a relatively short time in an atmospheric environment. The present invention also aims to provide an RFID inlay using the above conductive paste and a method for manufacturing an RFID inlay. Furthermore, the present invention aims to provide the use of a conductive paste for obtaining an RFID inlay.

[0012] This specification discloses the following conductive paste, RFID inlay, method for manufacturing an RFID inlay, and use of the conductive paste to obtain an RFID inlay.

[0013] Item 1. A conductive paste comprising a cationic polymerizable compound, a polymerization initiator, and a conductive filler, wherein the cationic polymerizable compound comprises an oxetane compound or an epoxy compound, the polymerization initiator comprises a sulfonium salt or an ammonium salt, and the viscosity of the conductive paste at 25°C is 10 Pa·s or more and 100 Pa·s or less.

[0014] Item 2. The conductive paste according to Item 1, wherein the cationic polymerizable compound comprises an alicyclic epoxy compound.

[0015] Item 3. The conductive paste according to item 1 or 2, wherein the cationic polymerizable compound comprises a cationic polymerizable compound having a molecular weight of 1,000 or more and 6,000 or less.

[0016] Item 4. The conductive paste according to Item 3, wherein the cationic polymerizable compound comprises a cationic polymerizable compound having a molecular weight of 1,000 or more and 6,000 or less, and a cationic polymerizable compound having a molecular weight of less than 1,000.

[0017] Item 5. The conductive paste according to item 3 or 4, wherein the cationic polymerizable compound with a molecular weight of 1000 to 6000 is a liquid at 25°C.

[0018] Item 6. The conductive paste according to any one of items 3 to 5, wherein the epoxy equivalent of the cationic polymerizable compound having a molecular weight of 1000 to 6000 is 150 g / eq to 200 g / eq.

[0019] Item 7. The conductive paste according to any one of items 3 to 6, wherein the cationic polymerizable compound with a molecular weight of 1000 to 6000 comprises epoxidized polybutadiene.

[0020] Item 8. A conductive paste according to any one of items 3 to 7, wherein the content of the cationic polymerizable compound having a molecular weight of 1000 to 6000 is 50% to 90% by weight in 100% by weight of the conductive paste.

[0021] Item 9. The conductive paste according to any one of items 3 to 8, wherein the weight ratio of the content of the cationic polymerizable compound having a molecular weight of 1,000 to 6,000 to the content of the polymerization initiator is 50 to 90.

[0022] Item 10. The conductive paste according to any one of items 1 to 9, wherein the polymerization initiator comprises a quaternary ammonium salt.

[0023] Item 11. The conductive paste is the conductive paste according to any one of items 1 to 10, used to obtain an RFID inlay.

[0024] Item 12. An RFID inlay comprising a substrate having wiring on its surface, a chip having electrodes on its surface, and an adhesive portion bonding the substrate and the chip, wherein the material of the adhesive portion is the conductive paste described in any one of items 1 to 11, and the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

[0025] Item 13. A method for manufacturing an RFID inlay, comprising: a first placement step of placing a conductive paste according to any one of items 1 to 11 on the surface of a substrate having wiring on its surface; a second placement step of placing a chip having electrodes on its surface on the surface of the conductive paste opposite to the substrate side; and an bonding step of heating and pressurizing the conductive paste to form an adhesive portion that bonds the substrate and the chip, and electrically connecting the wiring and the electrodes with the conductive filler in the adhesive portion.

[0026] Item 14. The method for manufacturing an RFID inlay according to Item 13, wherein the substrate is elongated, and the elongated substrate is transported in a roll-to-roll manner during the first placement step, the second placement step, and the bonding step to manufacture the RFID inlay.

[0027] Item 15. Use of any one of the conductive pastes described in items 1 to 11 to obtain an RFID inlay.

[0028] Item A. The conductive paste according to any one of items 1 to 11, wherein the cationic polymerizable compound includes an epoxy compound that does not have an aromatic skeleton.

[0029] Item B. A conductive paste according to any one of items 1 to 11 and A, wherein the total content of the cationic polymerizable compound, the polymerization initiator, and the conductive filler in 100% by weight of the conductive paste is 60% by weight or more.

[0030] The conductive paste according to the present invention comprises a cationic polymerizable compound, a polymerization initiator, and a conductive filler, wherein the cationic polymerizable compound comprises an oxetane compound or an epoxy compound, and the polymerization initiator comprises a sulfonium salt or an ammonium salt. In the conductive paste according to the present invention, the viscosity of the conductive paste at 25°C is 10 Pa·s or more and 100 Pa·s or less. Because the conductive paste according to the present invention has the above configuration, it is possible to 1) improve the discharge stability, 2) improve the storage stability, and 3) improve the curability when mounted at a relatively low temperature and for a relatively short time in an atmospheric environment.

[0031] Figure 1 is a schematic cross-sectional view showing an RFID inlay using a conductive paste according to the first embodiment of the present invention.

[0032] The details of the present invention will be described below.

[0033] (Conductive Paste) The conductive paste according to the present invention comprises a cationic polymerizable compound, a polymerization initiator, and a conductive filler. In the conductive paste according to the present invention, the cationic polymerizable compound comprises an oxetane compound or an epoxy compound, and the polymerization initiator comprises a sulfonium salt or an ammonium salt. In the conductive paste according to the present invention, the viscosity of the conductive paste at 25°C is 10 Pa·s or more and 100 Pa·s or less.

[0034] In conventional conductive pastes, when electronic components are fabricated (mounted) using the conductive paste in an air atmosphere, the polymerization reaction of the conductive paste may not proceed sufficiently due to the influence of oxygen, and there may be uncured portions in the cured product of the conductive paste. As a result, there are problems such as a decrease in the conduction reliability between the upper and lower electrodes to be connected in the obtained electronic component (RFID inlay), or a decrease in the connection reliability between the adhesive portion and the electrode. This problem is particularly more prominent when mounting is performed at a relatively low temperature (for example, 180°C or lower) and within a relatively short time (for example, within 15 seconds). Also, in conventional conductive pastes, it is difficult to enhance the curability of the conductive paste and to enhance the storage stability.

[0035] The inventors of the present invention have found that by using a combination of specific materials and setting the viscosity of the conductive paste within a specific range, the above problems can be solved.

[0036] That is, in the conductive paste according to the present invention, since the above configuration is provided, the discharge stability of the conductive paste can be enhanced, and the conductive paste can be arranged with high precision on a fine wiring. Also, in the conductive paste according to the present invention, since the above configuration is provided, the pot life (usable time) can be lengthened (storage stability can be enhanced). Further, in the conductive paste according to the present invention, since the above configuration is provided, even when mounting is performed at a relatively low temperature and within a relatively short time in an air atmosphere or the like, the curability can be enhanced and sufficient curing can be achieved. As a result, it is possible to suppress the presence of uncured conductive paste in the adhesive portion of the obtained electronic component, enhance the conduction reliability between the upper and lower electrodes to be connected, and enhance the connection reliability between the adhesive portion and the electrode.

[0037] Furthermore, the conductive paste according to the present invention can suppress the presence of uncured conductive paste in the cured product even when mounted in an atmosphere other than air. Moreover, the conductive paste according to the present invention can suppress the presence of uncured conductive paste in the cured product even when mounted over a medium to long period of time. The conductive paste according to the present invention can suppress the presence of uncured conductive paste in the cured product under various mounting conditions.

[0038] The conductive paste according to the present invention is in paste form at 25°C. The conductive paste is used by dispensing it, for example, at 20°C to 50°C. The conductive paste according to the present invention is preferably used by dispensing it using a dispenser, and more preferably by dispensing it using a jet dispenser or a quantitative dispenser. The quantitative dispenser is preferably a micro-quantitative dispenser.

[0039] The viscosity (η25) of the conductive paste at 25°C is 10 Pa·s or more and 100 Pa·s or less. Preferably, the viscosity (η25) is 11 Pa·s or more, more preferably 15 Pa·s or more, even more preferably 17 Pa·s or more, particularly preferably 20 Pa·s or more, preferably 95 Pa·s or less, more preferably 90 Pa·s or less, even more preferably 80 Pa·s or less, particularly preferably 70 Pa·s or less, and most preferably 65 Pa·s or less. If the viscosity (η25) is above the lower limit, the outflow of conductive paste from around the chip and from the wiring can be suppressed, and the curability and adhesion of the conductive paste can be further improved. If the viscosity (η25) is below the upper limit, the discharge stability of the conductive paste can be further improved.

[0040] The above viscosity (η25) can be measured, for example, using an E-type viscometer, for the conductive paste immediately after production, under the conditions of 25°C and 0.5 rpm. Examples of the above E-type viscometer include the "TV35 type viscometer" manufactured by Toki Sangyo Co., Ltd. When the measured value of the above viscosity (η25) is less than 40 Pa·s, the measurement is carried out under the conditions of a cone rotor R04 (3°×R14) and a sample volume of 0.4 mL. When the measured value of the above viscosity (η25) is 40 Pa·s or more, the measurement is carried out under the conditions of a cone rotor R07 (3°×R7.7) and a sample volume of 0.1 mL.

[0041] The ratio of the viscosity (ηA) at 25°C of the conductive paste after storage at 25°C and 50% RH for 24 hours to the viscosity (η25) at 25°C of the conductive paste immediately after production is defined as the ratio (ηA / η25). The above ratio (ηA / η25) is preferably 0.7 or more, more preferably 0.8 or more, still more preferably 0.9 or more, preferably 2.0 or less, more preferably 1.5 or less, still more preferably 1.25 or less, particularly preferably 1.2 or less, and most preferably 1.1 or less. When the above ratio (ηA / η25) is at least the above lower limit, the storage stability can be further enhanced, and the outflow of the conductive paste from the wiring can be suppressed. When the above ratio (ηA / η25) is at most the above upper limit, the conductive paste can be accurately arranged on a fine wiring.

[0042] The above viscosity (ηA) after storage can be measured, for example, after storing the conductive paste in a thermo-hygrostat at 25°C and 50% RH for 24 hours, using an E-type viscometer, under the conditions of 25°C and 0.5 rpm. Examples of the above E-type viscometer include the "TV35 type viscometer" manufactured by Toki Sangyo Co., Ltd. The above viscosity (ηA) after storage can be measured in the same manner as the above viscosity (η25).

[0043] The volume shrinkage rate of the cured product obtained by heating the conductive paste at 150°C for 30 minutes is preferably 10.0% or less, more preferably 8.0% or less, even more preferably 7.5% or less, and particularly preferably 7.0% or less. When the volume shrinkage rate of the cured product is below the above upper limit, the occurrence of voids in the cured product of the conductive paste can be suppressed, the conductivity reliability between the upper and lower electrodes to be connected can be improved, and the connection reliability between the adhesive part and the electrodes can be improved. The lower limit of the volume shrinkage rate of the cured product is not particularly limited. The volume shrinkage rate of the cured product may be 0% or more, or 1.0% or more. The range of the volume shrinkage rate of the cured product can be set by appropriately selecting the above lower limit and upper limit. The volume shrinkage rate of the cured product is the volume shrinkage rate of the conductive paste when it is heated at 150°C for 30 minutes.

[0044] The volume shrinkage rate of the above-mentioned cured product is measured, for example, as follows. First, the specific gravity of the conductive paste (before curing) at 23°C is measured using a densimeter. Next, the conductive paste is filled into a disc-shaped mold with a diameter of 1 mm and a height of 1 mm, and the top and bottom surfaces of the filled material are sandwiched between release-treated glass plates. The mold is then heated at 150°C for 30 minutes to obtain a cured product. Eight of these cured products are stacked to create a measurement sample. The specific gravity of the obtained measurement sample at 23°C is measured using a densimeter, and the obtained measurement value is taken as the specific gravity of the cured product. The volume shrinkage rate of the above-mentioned cured product is calculated using the following formula. Examples of the hydrometer used include a dry-type densimeter (for example, Shimadzu Corporation's "AccuPic II 1345").

[0045] Volume shrinkage rate (%) of the above cured product = (G1 - G2) × 100 / G2 G1: Specific gravity of conductive paste (before curing) at 23°C G2: Specific gravity of the above cured product at 23°C

[0046] The following are some methods for easily adjusting the volume shrinkage rate of the cured product to a preferred range: a method using a preferred cationic polymerizable compound described later; a method for adjusting the content of the cationic polymerizable compound; a method using a preferred polymerization initiator described later; a method for adjusting the content of the polymerization initiator; a method for adjusting the amount of conductive filler described later; and a method for adjusting the amount of non-conductive filler described later.

[0047] The above conductive paste has good adhesive properties. The above conductive paste is suitable for use as an adhesive. The above conductive paste is particularly suitable for bonding a substrate to a chip.

[0048] From the viewpoint of further improving conductivity reliability, the conductive paste is preferably an anisotropic conductive paste. The conductive paste is suitably used for electrical connection of electrodes. The conductive paste is suitably used to obtain connection structures. The conductive paste is suitably used to obtain electronic components. The conductive paste is particularly suitably used to obtain RFID inlays (use of the conductive paste to obtain RFID inlays). The conductive paste is suitably used for bonding and connecting a chip having electrodes on its surface to a substrate having wiring (antenna patterns) on its surface (use of the conductive paste to bond and connect a chip having electrodes on its surface to a substrate having wiring (antenna patterns) on its surface).

[0049] RFID inlays require mass production and are manufactured, for example, by transporting long substrates using a roll-to-roll method. Therefore, in the manufacturing of RFID inlays, even slight irregularities in ejection can easily lead to poor adhesion and poor conductivity, requiring excellent ejection stability. Furthermore, in the manufacturing of RFID inlays, it is necessary that they can be mounted at relatively low temperatures and in a relatively short time under atmospheric conditions. The conductive paste according to the present invention 1) enhances ejection stability and 3) enhances curability when mounted at relatively low temperatures and in a relatively short time under atmospheric conditions, making it particularly suitable for RFID inlays.

[0050] The conductive paste described above is preferably thermosetting. It is more preferably a thermosetting conductive paste, and more preferably a thermosetting anisotropic conductive paste.

[0051] The following explains each component contained in the conductive paste.

[0052] In this specification, "(meth)acrylate" refers to acrylate and methacrylate. "(meth)acrylic" refers to acrylic and methacrylic.

[0053] <Cationically Polymerizable Compounds> The above cationic polymerizable compounds preferably have a cationic polymerizable group. Examples of the above cationic polymerizable group include vinyl ether group, epoxy group, oxetanyl group, allyl ether group, vinyl group, and hydroxyl group.

[0054] Examples of the cationic polymerizable compounds mentioned above include epoxy compounds, oxetane compounds, vinyl ether compounds, and the like. The cationic polymerizable compounds may be used individually or in combination of two or more.

[0055] Examples of the epoxy compounds mentioned above include bisphenol A type epoxy compounds, bisphenol E type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, bisphenol O type epoxy compounds, 2,2'-diallylbisphenol A type epoxy compounds, alicyclic epoxy compounds, hydrogenated bisphenol type epoxy compounds, propylene oxide-added bisphenol A type epoxy compounds, resorcinol type epoxy compounds, biphenyl type epoxy compounds, sulfide type epoxy compounds, diphenyl ether type epoxy compounds, dicyclopentadiene type epoxy compounds, naphthalene type epoxy compounds, phenol novolac type epoxy compounds, orthocresol novolac type epoxy compounds, dicyclopentadiene novolac type epoxy compounds, biphenyl novolac type epoxy compounds, naphthalene phenol novolac type epoxy compounds, glycidylamine type epoxy compounds, alkyl polyol type epoxy compounds, rubber-modified epoxy compounds, glycidyl ester compounds, and 1,6-hexanediol diglycidyl ether.

[0056] Examples of the above oxetane compounds include allyloxyoxetane, phenoxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 3-ethyl-3-(4-hydroxybutyl)oxymethyloxetane, 3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane, 3-ethyl-3-((3-(triethoxysilyl)propoxy)methyl)oxetane, 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane, oxetanylsilsesquioxane, phenol novolac oxetane, and 1,4-bis(((3-ethyl-3-oxetanyl)methoxy)methyl)benzene.

[0057] Examples of the vinyl ether compounds mentioned above include benzyl vinyl ether, cyclohexanedimethanol monovinyl ether, dicyclopentadiene vinyl ether, 1,4-butanediol divinyl ether, cyclohexanedimethanol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol divinyl ether, and tripropylene glycol divinyl ether.

[0058] The above cationic polymerizable compound includes an oxetane compound or an epoxy compound. The above cationic polymerizable compound may contain an oxetane compound, an epoxy compound, or both an oxetane compound and an epoxy compound. In the above conductive paste, since the above cationic polymerizable compound includes an oxetane compound or an epoxy compound, the curing properties of the conductive paste can be further enhanced when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment.

[0059] The above oxetane compound preferably contains 3-ethyl-3-(phenoxymethyl)oxetane, 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane, or 3-ethyl-3-(4-hydroxybutyl)oxymethyl-oxetane. The above oxetane compound more preferably contains 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane, or 3-ethyl-3-(4-hydroxybutyl)oxymethyl-oxetane, and even more preferably contains 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane. When the above oxetane compound is one of these preferred compounds, the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment.

[0060] Commercially available oxetane compounds may be used. Examples of commercially available oxetane compounds include OXT-221 (manufactured by Toagosei Co., Ltd.) and ETERNACOLL HBOX (manufactured by Ube Industries, Ltd.).

[0061] The molecular weight of the above oxetane compound is preferably 110 or more, more preferably 180 or more, even more preferably 200 or more, and preferably 2000 or less. When the molecular weight of the above oxetane compound is above the lower limit and below the upper limit, the kneadability during the preparation of the conductive paste can be improved, and the uniformity of the conductive paste can be improved.

[0062] The above molecular weight refers to the molecular weight that can be calculated from the structural formula of the oxetane compound, if the oxetane compound is not a polymer, or if the structural formula of the oxetane compound can be identified. If the oxetane compound is a polymer, it refers to the weight-average molecular weight.

[0063] From the viewpoint of improving the kneadability during the preparation of conductive paste and enhancing the uniformity of the conductive paste, it is preferable that the above-mentioned cationic polymerizable compound contains an oxetane compound and an epoxy compound.

[0064] From the viewpoint of further improving the curability of the conductive paste when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment, it is preferable that the cationic polymerizable compound includes an epoxy compound that does not have an aromatic skeleton. From the viewpoint of improving the kneadability during the preparation of the conductive paste and improving the uniformity of the conductive paste, it is more preferable that the cationic polymerizable compound includes an alicyclic epoxy compound. In this specification, "alicyclic epoxy compound" refers to a compound that has an epoxy group on an alicyclic skeleton (i.e., shares some of the carbon atoms in the alicyclic skeleton with the epoxy group, i.e., has an alicyclic epoxy group). The alicyclic epoxy compound may be an epoxy compound that does not have an aromatic skeleton, or it may be an epoxy compound that has an aromatic skeleton. From the viewpoint of further improving the curability of the conductive paste when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment, it is preferable that the alicyclic epoxy compound does not have an aromatic skeleton. The oxetane compound may or may not have an aromatic skeleton.

[0065] Examples of the above-mentioned alicyclic epoxy compounds include dicyclopentadiene-type epoxy compounds, epoxy compounds having an adamantane skeleton, epoxy compounds having a tricyclodecane skeleton, naphthylene ether-type epoxy compounds, 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 1,2-epoxy-4-vinylcyclohexane, and 1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol, and tetrakis-(3-cyclohexenylmethyl) modified epsilon-caprolactone of epoxidized butanetetracarboxylic acid. The above-mentioned alicyclic epoxy compounds may have a double bond in part of their alicyclic skeleton. Only one of the above-mentioned alicyclic epoxy compounds may be used, or two or more may be used in combination.

[0066] Commercially available alicyclic epoxy compounds may be used. Examples of commercially available alicyclic epoxy compounds include Celoxide 2000, Celoxide 2021P, Celoxide 2081, Celoxide 3000, Celoxide 8000, Epolid GT401 (all manufactured by Daicel Corporation), and Sansosizer EPS (manufactured by Shin Nippon Rika Kogyo Co., Ltd.).

[0067] The molecular weight of the above alicyclic epoxy compound is preferably 200 or more, more preferably 220 or more, even more preferably 250 or more, preferably 6500 or less, more preferably 6000 or less, even more preferably 4000 or less, particularly preferably 2000 or less, and most preferably 1000 or less. When the molecular weight of the above alicyclic epoxy compound is above the lower limit and below the upper limit, the kneadability during the preparation of the conductive paste can be improved, and the uniformity of the conductive paste can be improved.

[0068] The above molecular weight refers to the molecular weight that can be calculated from the structural formula of the alicyclic epoxy compound if it is not a polymer, or if the structural formula of the alicyclic epoxy compound can be identified. If the alicyclic epoxy compound is a polymer, it refers to the weight-average molecular weight.

[0069] From the viewpoint of further improving the discharge stability of the conductive paste, it is preferable that the above cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of 6000 or less. From the viewpoint of further improving the discharge stability of the conductive paste and improving the uniformity of the conductive paste, it is preferable that the above cationic polymerizable compound includes an oxetane compound with a molecular weight of 6000 or less or an epoxy compound with a molecular weight of 6000 or less, and it is more preferable that it includes an oxetane compound with a molecular weight of 6000 or less and an epoxy compound with a molecular weight of 6000 or less. The above cationic polymerizable compound may or may not include a cationic polymerizable compound with a molecular weight exceeding 6000. From the viewpoint of further improving the discharge stability of the conductive paste, it is preferable that the above cationic polymerizable compound does not include a cationic polymerizable compound with a molecular weight exceeding 6000.

[0070] From the viewpoint of further improving the discharge stability of the conductive paste, it is even more preferable that the above-mentioned cationic polymerizable compound includes a cationic polymerizable compound (first cationic polymerizable compound) with a molecular weight of 1000 to 6000.

[0071] From the viewpoint of improving the uniformity of the conductive paste, it is particularly preferable that the above cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of 1,000 to 6,000 (first cationic polymerizable compound) and a cationic polymerizable compound with a molecular weight of less than 1,000 (second cationic polymerizable compound). The above cationic polymerizable compound may also include an oxetane compound with a molecular weight of 1,000 to 6,000 and an oxetane compound with a molecular weight of less than 1,000, or it may include an epoxy compound with a molecular weight of 1,000 to 6,000 and an oxetane compound with a molecular weight of less than 1,000. The above cationic polymerizable compound may also include an oxetane compound with a molecular weight of 1,000 to 6,000 and an epoxy compound with a molecular weight of less than 1,000, or it may include an epoxy compound with a molecular weight of 1,000 to 6,000 and an epoxy compound with a molecular weight of less than 1,000. From the viewpoint of improving the uniformity of the conductive paste, it is particularly preferable that the above-mentioned cationic polymerizable compound includes an epoxy compound with a molecular weight of 1000 to 6000 and an oxetane compound with a molecular weight of less than 1000.

[0072] From the viewpoint of further improving the discharge stability of the conductive paste, when the above-mentioned cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of 1,000 to 6,000, it is preferable that the above-mentioned cationic polymerizable compound with a molecular weight of 1,000 to 6,000 is liquid at 25°C.

[0073] When the above-mentioned cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of less than 1000, the state of the above-mentioned cationic polymerizable compound with a molecular weight of less than 1000 at 25°C is not particularly limited. The above-mentioned cationic polymerizable compound with a molecular weight of less than 1000 may be a liquid or a solid at 25°C.

[0074] When the above-mentioned cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of 1,000 to 6,000, it is preferable that the cationic polymerizable compound with a molecular weight of 1,000 to 6,000 includes an epoxy compound. That is, it is preferable that the above-mentioned cationic polymerizable compound includes an epoxy compound with a molecular weight of 1,000 to 6,000. In this case, the discharge stability of the conductive paste can be further improved, and the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment.

[0075] When the above cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of 1000 to 6000, the epoxy equivalent of the above cationic polymerizable compound with a molecular weight of 1000 to 6000 is preferably 150 g / eq to 200 g / eq. The epoxy equivalent of the above cationic polymerizable compound with a molecular weight of 1000 to 6000 is preferably 150 g / eq or more, preferably 200 g / eq or less, and more preferably 170 g / eq or less. If the epoxy equivalent of the above cationic polymerizable compound with a molecular weight of 1000 to 6000 is above the above lower limit, shrinkage of the conductive paste during curing can be suppressed. If the epoxy equivalent of the above cationic polymerizable compound with a molecular weight of 1000 to 6000 is below the above upper limit, the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment.

[0076] When the above cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of less than 1000, the epoxy equivalent of the cationic polymerizable compound with a molecular weight of less than 1000 is preferably 100 g / eq or more, preferably 250 g / eq or less, more preferably 200 g / eq or less, and even more preferably 150 g / eq or less. If the epoxy equivalent of the cationic polymerizable compound with a molecular weight of less than 1000 is above the above lower limit, shrinkage of the conductive paste during curing can be suppressed. If the epoxy equivalent of the cationic polymerizable compound with a molecular weight of less than 1000 is below the above upper limit, the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment.

[0077] When the above cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of 1,000 to 6,000, it is preferable that the above cationic polymerizable compound with a molecular weight of 1,000 to 6,000 includes epoxidized polybutadiene (an epoxy compound having a polybutadiene skeleton). That is, it is preferable that the above cationic polymerizable compound includes epoxidized polybutadiene with a molecular weight of 1,000 to 6,000. In this case, the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. From the viewpoint of further improving the discharge stability of the conductive paste and further improving the curability of the conductive paste when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment, it is particularly preferable that the above cationic polymerizable compound includes epoxidized polybutadiene with a molecular weight of 1,000 to 6,000 and which is liquid at 25°C.

[0078] In 100% by weight of the conductive paste, the content of the cationic polymerizable compound is preferably 40% by weight or more, more preferably 45% by weight or more, even more preferably 50% by weight or more, particularly preferably 55% by weight or more, most preferably 60% by weight or more, preferably 95% by weight or less, more preferably 90% by weight or less, even more preferably 85% by weight or less, and particularly preferably 80% by weight or less. If the content of the cationic polymerizable compound is above the lower limit, the discharge stability of the conductive paste can be further improved. If the content of the cationic polymerizable compound is below the upper limit, the conductivity reliability can be further improved.

[0079] When the above cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of less than 1000, the content of the cationic polymerizable compound with a molecular weight of less than 1000 in 100% by weight of the conductive paste is preferably 5% by weight or more, more preferably 7.5% by weight or more, even more preferably 10% by weight or more, preferably 75% by weight or less, more preferably 50% by weight or less, even more preferably 35% by weight or less, particularly preferably 30% by weight or less, and most preferably 25% by weight or less. When the content of the cationic polymerizable compound with a molecular weight of less than 1000 is above the above lower limit, the uniformity of the conductive paste can be improved, and the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. When the content of the cationic polymerizable compound with a molecular weight of less than 1000 is below the above upper limit, the discharge stability of the conductive paste can be further improved.

[0080] When the above cationic polymerizable compound includes a cationic polymerizable compound with a molecular weight of 1000 to 6000, the content of the cationic polymerizable compound with a molecular weight of 1000 to 6000 in 100% by weight of the conductive paste is preferably 40% by weight or more, more preferably 45% by weight or more, even more preferably 50% by weight or more, preferably 90% by weight or less, more preferably 85% by weight or less, and even more preferably 80% by weight or less. If the content of the cationic polymerizable compound with a molecular weight of 1000 to 6000 is above the lower limit, the discharge stability of the conductive paste can be further improved. If the content of the cationic polymerizable compound with a molecular weight of 1000 to 6000 is below the upper limit, the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment.

[0081] In 100% by weight of the conductive paste, the content of the cationic polymerizable compound with a molecular weight exceeding 6000 is preferably 25% by weight or less, more preferably 22% by weight or less, even more preferably 20% by weight or less, still more preferably 15% by weight or less, particularly preferably 10% by weight or less, and most preferably 0% by weight (not present). When the content of the cationic polymerizable compound with a molecular weight exceeding 6000 is below the above upper limit, the discharge stability of the conductive paste can be further improved. In 100% by weight of the conductive paste, the content of the cationic polymerizable compound with a molecular weight exceeding 6000 may be 0% by weight or more, 1% by weight or more, or 3% by weight or more. In 100% by weight of the conductive paste, the range of the content of the cationic polymerizable compound with a molecular weight exceeding 6000 can be set by appropriately selecting the above lower limit and upper limit.

[0082] When the above cationic polymerizable compound contains the above oxetane compound, the content of the above oxetane compound in 100% by weight of the conductive paste is preferably 3% by weight or more, more preferably 5% by weight or more, even more preferably 7.5% by weight or more, particularly preferably 10% by weight or more, preferably 60% by weight or less, more preferably 50% by weight or less, even more preferably 35% by weight or less, particularly preferably 30% by weight or less, and most preferably 25% by weight or less. When the content of the above oxetane compound is above the lower limit, the uniformity of the conductive paste can be improved, and the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. When the content of the above oxetane compound is below the upper limit, the discharge stability of the conductive paste can be further improved.

[0083] When the above cationic polymerizable compound contains the above epoxy compound, the content of the epoxy compound in 100% by weight of the conductive paste is preferably 15% by weight or more, more preferably 30% by weight or more, even more preferably 35% by weight or more, still more preferably 40% by weight or more, particularly preferably 45% by weight or more, most preferably 50% by weight or more, preferably 75% by weight or less, more preferably 65% ​​by weight or less, and still more preferably 60% by weight or less. If the content of the epoxy compound is above the lower limit, the discharge stability of the conductive paste can be further improved. If the content of the epoxy compound is below the upper limit, the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment.

[0084] When the cationic polymerizable compound contains the alicyclic epoxy compound, the content of the alicyclic epoxy compound in 100% by weight of the conductive paste is preferably 3% by weight or more, more preferably 10% by weight or more, even more preferably 14% by weight or more, preferably 68% by weight or less, more preferably 60% by weight or less, and even more preferably 55% by weight or less. When the content of the alicyclic epoxy compound is above the lower limit, the curability of the conductive paste can be further improved when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. When the content of the alicyclic epoxy compound is below the upper limit, the discharge stability of the conductive paste can be further improved.

[0085] When the above cationic polymerizable compound contains the above epoxidized polybutadiene, the content of the above epoxidized polybutadiene in 100% by weight of the conductive paste is preferably 25% by weight or more, more preferably 35% by weight or more, even more preferably 40% by weight or more, particularly preferably 45% by weight or more, most preferably 50% by weight or more, preferably 70% by weight or less, and more preferably 64% by weight or less. When the content of the above epoxidized polybutadiene is above the lower limit and below the upper limit, the discharge stability of the conductive paste can be further improved.

[0086] <Polymerization Initiators> Examples of polymerization initiators include photopolymerization initiators and thermal polymerization initiators. Only one polymerization initiator may be used, or two or more may be used in combination.

[0087] From the viewpoint of further improving the curability of the conductive paste when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment, the polymerization initiator preferably contains a thermal polymerization initiator. The thermal polymerization initiator preferably contains a thermal cationic polymerization initiator (thermal acid generator), and is preferably a thermal cationic polymerization initiator.

[0088] The above thermal cationic polymerization initiator has an anionic portion of BF ４ － , PF ６ － SbF ６ － , or (BX４ ) － Examples include sulfonium salts, phosphonium salts, iodonium salts, and ammonium salts, which consist of (wherein X represents a phenyl group substituted with at least two fluorine or trifluoromethyl groups).

[0089] Examples of the above-mentioned sulfonium salts include triphenylsulfonium tetrafluoroborate and triphenylsulfonium hexafluoroantimonate.

[0090] Examples of the phosphonium salts mentioned above include ethyltriphenylphosphonium hexafluoroantimonate and tetrabutylphosphonium hexafluoroantimonate.

[0091] Examples of the above ammonium salts include dimethylphenyl(4-methoxybenzyl)ammonium hexafluorophosphate, dimethylphenyl(4-methoxybenzyl)ammonium hexafluoroantimonate, dimethylphenyl(4-methoxybenzyl)ammonium tetrakis(pentafluorophenyl) borate, dimethylphenyl(4-methylbenzyl)ammonium hexafluorophosphate, dimethylphenyl(4-methylbenzyl)ammonium hexafluoroantimonate, dimethylphenyl(4-methylbenzyl)ammonium hexafluorotetrakis(pentafluorophenyl) borate, and methylphenyldibenzylammonium hexafluorophosphate. Examples include methylphenyldibenzylammonium hexafluoroantimonate, methylphenyldibenzylammonium tetrakis(pentafluorophenyl)borate, phenyltribenzylammonium tetrakis(pentafluorophenyl)borate, dimethylphenyl(3,4-dimethylbenzyl)ammonium tetrakis(pentafluorophenyl)borate, N,N-dimethyl-N-benzylanilinium hexafluoroantimonate, N,N-diethyl-N-benzylanilinium tetrafluoroborate, N,N-dimethyl-N-benzylpyridinium hexafluoroantimonate, and N,N-diethyl-N-benzylpyridinium trifluoromethanesulfonic acid.

[0092] Commercially available thermal cationic polymerization initiators may be used. Examples of commercially available thermal cationic polymerization initiators include San-Aid SI-60, San-Aid SI-80, San-Aid SI-100L, San-Aid SI-B3, San-Aid SI-B3A, San-Aid SI-B4 (all manufactured by Sanshin Chemical Industry Co., Ltd.), K-PURE CXC1612, and K-PURE CXC1821 (all manufactured by King Industries).

[0093] The polymerization initiator described above contains a sulfonium salt or an ammonium salt. The polymerization initiator may contain a sulfonium salt, an ammonium salt, or both. In the conductive paste described above, since the polymerization initiator contains a sulfonium salt or an ammonium salt, the storage stability of the conductive paste can be further enhanced, and the curability of the conductive paste can be further enhanced when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment.

[0094] From the viewpoint of further improving the storage stability of the conductive paste and further enhancing its curability when mounted at relatively low temperatures and for a relatively short time in an atmospheric environment, the polymerization initiator more preferably contains an ammonium salt, and even more preferably contains a quaternary ammonium salt. From the viewpoint of further improving the storage stability of the conductive paste and further enhancing its curability when mounted at relatively low temperatures and for a relatively short time in an atmospheric environment, the polymerization initiator is particularly preferably K-PURE CXC1821 (manufactured by King Industries).

[0095] In 100% by weight of the above conductive paste, the content of the polymerization initiator is preferably 0.1% by weight or more, more preferably 0.3% by weight or more, even more preferably 0.5% by weight or more, particularly preferably 0.6% by weight or more, preferably 5.0% by weight or less, more preferably 4.0% by weight or less, even more preferably 3.0% by weight or less, and particularly preferably 2.5% by weight or less. When the content of the polymerization initiator is above the lower limit and below the upper limit, the discharge stability and storage stability of the conductive paste can be further enhanced, and the curability of the conductive paste can be further enhanced when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. In particular, when the content of the polymerization initiator is above the lower limit, the curability of the conductive paste can be further enhanced when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. When the content of the polymerization initiator is below the upper limit, the discharge stability and storage stability of the conductive paste can be further enhanced.

[0096] With respect to 100 parts by weight of the above cationic polymerizable compound, the content of the polymerization initiator is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, even more preferably 0.7 parts by weight or more, preferably 6.0 parts by weight or less, more preferably 5.0 parts by weight or less, even more preferably 4.0 parts by weight or less, particularly preferably 3.0 parts by weight or less, and most preferably 2.5 parts by weight or less. When the content of the polymerization initiator is above the lower limit and below the upper limit, the storage stability of the conductive paste can be further enhanced, and the curability of the conductive paste can be further enhanced when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. In particular, when the content of the polymerization initiator is above the lower limit, the curability of the conductive paste can be further enhanced when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. When the content of the polymerization initiator is below the upper limit, the discharge stability and storage stability of the conductive paste can be further enhanced.

[0097] The weight ratio of the content of the cationic polymerizable compound with a molecular weight of 1000 to 6000 to the content of the polymerization initiator (content of cationic polymerizable compound with a molecular weight of 1000 to 6000 / content of polymerization initiator) is preferably 20 or more, more preferably 40 or more, even more preferably 50 or more, particularly preferably 60 or more, preferably 200 or less, more preferably 150 or less, even more preferably 99 or less, particularly preferably 95 or less, and most preferably 90 or less. When the weight ratio (content of cationic polymerizable compound with a molecular weight of 1000 to 6000 / content of polymerization initiator) is above the lower limit and below the upper limit, the storage stability of the conductive paste can be further enhanced, and the curability of the conductive paste can be further enhanced when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. In particular, when the weight ratio (content of cationic polymerizable compound with a molecular weight of 1000 to 6000 / content of polymerization initiator) is above the lower limit, the curability of the conductive paste can be further enhanced when it is mounted at a relatively low temperature and for a relatively short time in an atmospheric environment. When the above weight ratio (content of cationic polymerizable compound with a molecular weight of 1000 to 6000 / content of polymerization initiator) is below the above upper limit, the discharge stability and storage stability of the conductive paste can be further improved.

[0098] <Conductive Filler> The conductive filler described above is not particularly limited. The conductive filler may be conductive particles or carbon fibers.

[0099] The shape of the conductive filler is not particularly limited. The conductive filler may be spherical, or it may have a shape other than spherical, or it may be flattened, etc.

[0100] The conductive filler is preferably a conductive particle. The conductive particles may be solder particles or metal particles. The metal particles may be metal powder. The conductive particles may comprise a base particle and a conductive portion disposed on the surface of the base particle. From the viewpoint of further improving conductivity reliability, it is preferable that the conductive particles comprise a base particle and a conductive portion disposed on the surface of the base particle.

[0101] The particle size (diameter) of the conductive filler (or, if the conductive filler is a conductive particle, the particle size of the conductive particle) is preferably 0.1 μm or more, more preferably 1 μm or more, even more preferably 2 μm or more, preferably 100 μm or less, more preferably 30 μm or less, even more preferably 20 μm or less, particularly preferably 15 μm or less, and most preferably 10 μm or less. When the particle size of the conductive filler is above the lower limit and below the upper limit, adhesion and conductivity reliability can be further improved when mounted at relatively low temperatures and for a relatively short time in an atmospheric environment.

[0102] The particle diameter of the conductive filler described above is preferably the average particle diameter, and more preferably the number-average particle diameter. The average particle diameter of the conductive filler can be determined, for example, by observing 50 arbitrary conductive fillers with an electron microscope or optical microscope and calculating the average value of the particle diameter of each conductive filler, or by performing a laser diffraction particle size distribution measurement.

[0103] In 100% by weight of the above conductive paste, the content of the above conductive filler is preferably 0.1% by weight or more, more preferably 1.0% by weight or more, even more preferably 3.0% by weight or more, particularly preferably 5.0% by weight or more, preferably 80.0% by weight or less, more preferably 60.0% by weight or less, even more preferably 50.0% by weight or less, particularly preferably 45.0% by weight or less, and most preferably 40.0% by weight or less. When the content of the above conductive filler is above the lower limit and below the upper limit, adhesion and conductivity reliability can be further improved when mounted at relatively low temperatures and for a relatively short time in an atmospheric environment.

[0104] In 100% by weight of the above conductive paste, the total content of the cationic polymerizable compound, the polymerization initiator, and the conductive filler is preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, particularly preferably 85% by weight or more, most preferably 90% by weight or more, preferably 99.9% by weight or less, more preferably 99.8% by weight or less, and even more preferably 99.7% by weight or less. If the total content of the cationic polymerizable compound, the polymerization initiator, and the conductive filler is above the lower limit, the conductivity reliability can be further improved. If the total content of the cationic polymerizable compound, the polymerization initiator, and the conductive filler is below the upper limit, the discharge stability of the conductive paste can be further improved.

[0105] The conductive filler described above preferably contains a metal. Examples of such metals include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. In addition, tin-doped indium oxide (ITO) may be used as the metal. Only one of the metals may be used, or two or more may be used in combination.

[0106] From the viewpoint of further lowering the connection resistance between electrodes, the conductive filler preferably contains a tin-containing alloy, nickel, palladium, ruthenium, silver, copper, or gold, and more preferably contains nickel or palladium. From the viewpoint of improving the corrosion resistance of the conductive filler and maintaining high conductivity reliability, the conductive filler preferably contains nickel or gold, and more preferably contains nickel. From the viewpoint of improving the corrosion resistance of the conductive filler and maintaining high conductivity reliability, it is particularly preferable that the conductive filler contains nickel on its outer surface.

[0107] When the conductive filler is a metal filler (when the conductive particles are metal particles), examples of metals that make up the metal filler include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder. From the viewpoint of further effectively improving conductivity reliability, it is preferable that the material of the metal filler contains nickel or a nickel alloy, and it is more preferable that the material of the metal filler contains nickel or a nickel alloy. From the viewpoint of further effectively improving conductivity reliability, it is preferable that the outer surface portion of the metal filler contains nickel or a nickel alloy.

[0108] The details of conductive particles comprising a base particle and a conductive portion disposed on the surface of the base particle will be described below.

[0109] (Base Particles) Examples of the base particles include resin particles, inorganic particles excluding metal particles, organic-inorganic hybrid particles, and metal particles. The base particles are preferably base particles excluding metal particles, and more preferably resin particles, inorganic particles excluding metal particles, or organic-inorganic hybrid particles. The base particles may also be core-shell particles comprising a core and a shell disposed on the surface of the core. The core may be an organic core, and the shell may be an inorganic shell.

[0110] The above-mentioned base material particles are more preferably resin particles or organic-inorganic hybrid particles, and may be resin particles or organic-inorganic hybrid particles. The effects of the present invention are exhibited even more effectively by using these preferred base material particles.

[0111] Various resins are suitably used as the material for the above-mentioned resin particles. Examples of materials for the above-mentioned resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polyalkylene terephthalate, polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamide-imide, polyetheretherketone, polyethersulfone, divinylbenzene polymer, and polymers obtained by polymerizing one or more polymerizable monomers having ethylenically unsaturated groups. The above-mentioned divinylbenzene polymer may also be a divinylbenzene-based copolymer. Examples of the above-mentioned divinylbenzene copolymers include divinylbenzene-styrene copolymers and divinylbenzene-(meth)acrylic acid ester copolymers.

[0112] Since it is possible to design and synthesize resin particles having any desired compression characteristics suitable for conductive pastes, and the hardness of the resin particles can be easily controlled within a suitable range, it is preferable that the material of the above resin particles is a polymer obtained by polymerizing polymerizable monomers having multiple ethylenically unsaturated groups. In this case, only one type of polymer obtained by polymerizing polymerizable monomers having multiple ethylenically unsaturated groups may be used, or two or more types may be used in combination.

[0113] When the above resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, the polymerizable monomer having an ethylenically unsaturated group can be a non-crosslinked monomer or a crosslinked monomer.

[0114] The above non-crosslinked monomers include styrene monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; alkyl (meth)acrylate compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; and 2-hydroxyethyl Examples include oxygen atom-containing (meth)acrylate compounds such as (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; vinyl acid ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; and halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene.

[0115] The above crosslinkable monomers include tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly) Examples include polyfunctional (meth)acrylate compounds such as pyrene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; and silane-containing monomers such as triallyl(iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallylacrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.

[0116] The above-mentioned polymerizable monomer having an ethylenically unsaturated group can be polymerized by known methods to obtain the resin particles. Examples of such methods include suspension polymerization in the presence of a radical polymerization initiator, and polymerization by swelling the monomer together with a radical polymerization initiator using non-crosslinked seed particles.

[0117] When the above-mentioned base material particles are inorganic particles excluding metal particles or organic-inorganic hybrid particles, examples of inorganic materials for the base material particles include silica, alumina, barium titanate, zirconia, and carbon black. Preferably, the inorganic material is not a metal. Examples of particles formed from silica include particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, and then firing them as needed. Examples of organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a crosslinked alkoxysilyl polymer and an acrylic resin.

[0118] The above organic-inorganic hybrid particles are preferably core-shell type organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. The core is preferably an organic core. The shell is preferably an inorganic shell. From the viewpoint of more effectively lowering the connection resistance between electrodes, the base particles are preferably organic-inorganic hybrid particles having an organic core and an inorganic shell disposed on the surface of the organic core.

[0119] Examples of materials for the organic core mentioned above include the resin particle material described above.

[0120] Examples of materials for the inorganic shell include the inorganic substances listed above as materials for the base particles. The material for the inorganic shell is preferably silica. The inorganic shell is preferably formed by forming a shell-like substance from a metal alkoxide on the surface of the core using a sol-gel method, and then firing the shell-like substance. The metal alkoxide is preferably a silane alkoxide. The inorganic shell is preferably formed from a silane alkoxide.

[0121] When the above-mentioned base material particles are metal particles, examples of metals that make up the metal particles include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder.

[0122] The particle size of the above-mentioned base material particles is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.5 μm or more, even more preferably 1 μm or more, particularly preferably 3 μm or more, preferably 50 μm or less, more preferably 30 μm or less, even more preferably 20 μm or less, and particularly preferably 10 μm or less. When the particle size of the above-mentioned base material particles is above the lower limit, the conductivity reliability is further increased. Furthermore, aggregation becomes less likely when forming conductive parts on the surface of the base material particles, and aggregated conductive particles are less likely to form. When the particle size of the above-mentioned base material particles is below the upper limit, the conductive particles are easily compressed, and the connection resistance between electrodes connected via the conductive particles can be further effectively reduced.

[0123] The particle size of the above-mentioned substrate particles is preferably the average particle size, and more preferably the number-average particle size. The number-average particle size of the above-mentioned substrate particles can be measured, for example, as follows: Conductive particles are added to Kulzer's "Technovit 4000" so that the content of conductive particles is 30% by weight, and dispersed to create an embedded resin body for substrate particle inspection. An ion milling device (Hitachi High-Technologies Corporation's "IM4000") is used to cut out a cross-section of the conductive particles dispersed in the above-mentioned embedded resin body for substrate particle inspection, passing through the vicinity of the center of the substrate particles. Then, using a field emission scanning electron microscope (FE-SEM), the image magnification is set to 25,000 times, 50 conductive particles are randomly selected, and the substrate particles of each conductive particle are observed. The particle size of the substrate particles in each conductive particle is measured, and these are arithmetically averaged to obtain the average particle size of the substrate particles.

[0124] (Conductive part) The conductive part preferably contains a metal. The metal constituting the conductive part is not particularly limited. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. In addition, tin-doped indium oxide (ITO) may be used as the metal. Only one type of metal may be used, or two or more types may be used in combination. From the viewpoint of further lowering the connection resistance between electrodes, alloys containing tin, nickel, palladium, ruthenium, silver, copper, or gold are preferred, and nickel or palladium are more preferred.

[0125] From the viewpoint of more effectively improving conductivity reliability, it is preferable that the conductive part contains nickel, and it is more preferable that the outer surface portion of the conductive part contains nickel.

[0126] The nickel content in 100% by weight of the nickel-containing conductive part is preferably 10% by weight or more, more preferably 50% by weight or more, even more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 90% by weight or more. The nickel content in 100% by weight of the nickel-containing conductive part may be 100% by weight or less, 99% by weight or less, 90% by weight or less, or 70% by weight or less. The range of nickel content in 100% by weight of the nickel-containing conductive part can be set by appropriately selecting the above lower limit and upper limit.

[0127] The conductive portion may be formed by a single layer. The conductive portion may be formed by multiple layers. That is, the conductive portion may have a laminated structure of two or more layers. When the conductive portion is formed by multiple layers, the metal constituting the outermost layer is preferably an alloy containing gold, silver, nickel, palladium, ruthenium, copper, or tin, and more preferably nickel. When the metal constituting the outermost layer is one of these preferred metals, the connection resistance between electrodes becomes even lower.

[0128] The method for forming the conductive portion on the surface of the above-mentioned substrate particles is not particularly limited. Examples of methods for forming the conductive portion include electroless plating, electroplating, physical impact, mechanochemical reaction, physical vapor deposition or physical adsorption, and coating the surface of the substrate particles with metal powder or a paste containing metal powder and a binder. The method for forming the conductive portion is preferably electroless plating, electroplating, or physical impact. Examples of physical vapor deposition methods include vacuum deposition, ion plating, and ion sputtering. In the physical impact method, for example, a theta composer (manufactured by Tokuju Kogyosho) can be used.

[0129] The thickness of the conductive portion is preferably 0.005 μm or more, more preferably 0.01 μm or more, preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 0.3 μm or less. When the thickness of the conductive portion is above the lower limit and below the upper limit, sufficient conductivity can be obtained, and the conductive particles can be sufficiently deformed during connection without becoming too hard.

[0130] When the conductive portion is formed by multiple layers, the thickness of the outermost conductive layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, preferably 0.5 μm or less, and more preferably 0.1 μm or less. When the thickness of the outermost conductive layer is above the lower limit and below the upper limit, the conductive layer of the outermost layer becomes uniform, corrosion resistance is sufficiently high, and the connection resistance between electrodes can be sufficiently low.

[0131] The thickness of the conductive portion can be measured, for example, by observing the cross-section of the conductive particles using a transmission electron microscope (TEM).

[0132] Core material: The conductive particles preferably have multiple protrusions on the outer surface of the conductive portion. An oxide film is often formed on the surface of the electrodes connected by the conductive particles. When conductive particles with protrusions on the outer surface of the conductive portion are used, the oxide film can be effectively removed by the protrusions when the conductive particles are placed between the electrodes and pressed together. As a result, the electrodes and the conductive portion make contact more reliably, and the connection resistance between the electrodes becomes even lower. Furthermore, when connecting electrodes, the protrusions of the conductive particles can effectively remove fillers between the conductive particles and the electrodes. As a result, the conductivity reliability between electrodes becomes even higher.

[0133] Methods for forming the above-mentioned protrusions include a method in which a core material is attached to the surface of a base particle and then a conductive part is formed by electroless plating, and a method in which a conductive part is formed on the surface of a base particle by electroless plating, then a core material is attached, and then a conductive part is formed by electroless plating. Alternatively, to form the protrusions, a method may be used in which a conductive part is formed on the base particle by electroless plating without using the above-mentioned core material, then a plating is deposited on the surface of the conductive part in the form of protrusions, and then a conductive part is formed by electroless plating.

[0134] Methods for attaching a core material to the surface of base particles include, for example, adding the core material to a dispersion of base particles and accumulating and attaching the core material to the surface of the base particles by van der Waals forces, and adding the core material to a container containing base particles and attaching the core material to the surface of the base particles by mechanical action such as rotating the container. From the viewpoint of controlling the amount of core material to be attached, the method of attaching the core material to the surface of base particles is preferably one in which the core material is accumulated and attached to the surface of base particles in a dispersion.

[0135] The materials constituting the core material mentioned above include conductive materials and non-conductive materials. Examples of conductive materials include metals, metal oxides, conductive nonmetals such as graphite, and conductive polymers. Examples of conductive polymers include polyacetylene. Examples of non-conductive materials include silica, alumina, titanium oxide, tungsten carbide, and zirconia. From the viewpoint of further improving the conductivity reliability between electrodes, it is preferable that the core material is a metal.

[0136] The above metals are not particularly limited. Examples of the above metals include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys composed of two or more metals such as tin-lead alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. From the viewpoint of further improving the conductivity reliability between electrodes, the above metals are preferably nickel, copper, silver, or gold. The above metals may be the same as or different from the metals constituting the conductive part.

[0137] The shape of the core material described above is not particularly limited. The core material is preferably in the form of a lump. Examples of the core material include particulate lumps, aggregates formed by the aggregation of multiple fine particles, and irregularly shaped lumps.

[0138] The particle size (diameter) of the core material is preferably 0.001 μm or larger, more preferably 0.05 μm or larger, preferably 0.9 μm or smaller, and more preferably 0.2 μm or smaller. When the particle size of the core material is above the lower limit and below the upper limit, the connection resistance between electrodes can be effectively reduced.

[0139] The particle size (diameter) of the core material described above is preferably the average particle size (average diameter), and more preferably the number-average particle size (number-average diameter). The particle size of the core material can be determined, for example, by observing 50 arbitrary core material samples with an electron microscope or optical microscope and calculating the average value of the particle size of each core material, or by performing laser diffraction particle size distribution measurement.

[0140] <Non-conductive filler> The conductive paste described above may or may not contain a non-conductive filler. The conductive paste described above optionally contains a non-conductive filler.

[0141] Examples of the nonconductive fillers mentioned above include silica, alumina, titanium oxide, calcium oxide, zinc oxide, and boron nitride. Only one type of nonconductive filler may be used, or two or more types may be used in combination.

[0142] From the viewpoint of improving the applicability of the conductive paste, it is preferable that the conductive paste contains a non-conductive filler. From the viewpoint of improving the applicability of the conductive paste, it is preferable that the non-conductive filler contains silica or titanium oxide, and more preferably silica.

[0143] In 100% by weight of the conductive paste, the content of the non-conductive filler is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, preferably 10.0% by weight or less, more preferably 7.5% by weight or less, and even more preferably 5.0% by weight or less. If the content of the non-conductive filler is above the lower limit, the applicability of the conductive paste can be improved and the conductivity reliability can be increased. If the content of the non-conductive filler is below the upper limit, the adhesion can be further improved.

[0144] In 100% by volume of the above conductive paste, the total content of the conductive filler and the non-conductive filler is preferably 5.0% by volume or more, more preferably 10.0% by volume or more, preferably 40.0% by volume or less, more preferably 30.0% by volume or less, even more preferably 25.0% by volume or less, particularly preferably 20.0% by volume or less, and most preferably 15.0% by volume or less. When the total content of the conductive filler and the non-conductive filler is above the lower limit and below the upper limit, the applicability of the conductive paste can be improved and the conductivity reliability can be increased.

[0145] <Other Components> The conductive paste described above may contain components other than the cationic polymerizable compound, the polymerization initiator, the conductive filler, and the non-conductive filler. The conductive paste may also contain other components such as solvents, inorganic fillers, organic fillers, silane coupling agents, colorants, polymerization inhibitors, chain transfer agents, antioxidants, ultraviolet absorbers, defoamers, leveling agents, surfactants, slip agents, antiblocking agents, waxes, masking agents, deodorizers, fragrances, preservatives, antibacterial agents, antistatic agents, and adhesion enhancers.

[0146] Further, the conductive paste may or may not contain a non-cationic polymerizable compound. Examples of the non-cationic polymerizable compound include phenoxy resin, phenol resin, and melamine resin. The conductive paste may or may not contain a compound having no polymerizable functional group.

[0147] (Use of the conductive paste) The use according to the present invention is for adhering a chip having a planar area of 0.50 mm ２ or less. In the use according to the present invention, since a specific conductive paste and a chip having a specific planar area are used, 1) the discharge stability can be enhanced, 2) the storage stability can be enhanced, and 3) the curability can be enhanced when mounting is performed at a relatively low temperature and in a relatively short time in an air atmosphere or the like.

[0148] Further, the use according to the present invention is for obtaining an RFID inlay using the above-described conductive paste. In the use according to the present invention, since a specific conductive paste is used, 1) the discharge stability can be enhanced, 2) the storage stability can be enhanced, and 3) the curability can be enhanced when mounting is performed at a relatively low temperature and in a relatively short time in an air atmosphere or the like.

[0149] (RFID inlay and method for manufacturing RFID inlay) The RFID inlay according to the present invention includes a substrate having wiring on its surface, a chip having an electrode on its surface, and an adhesive portion bonding the substrate and the chip. In the RFID inlay according to the present invention, the material of the adhesive portion is the above-described conductive paste. In the RFID inlay according to the present invention, the wiring and the electrode are electrically connected by the conductive filler in the adhesive portion.

[0150] FIG. 1 is a cross-sectional view schematically showing an RFID inlay using the conductive paste according to the first embodiment of the present invention.

[0151] The RFID inlay 81 shown in Figure 1 comprises a substrate 82 having wiring on its surface, a chip 83 having electrodes on its surface, and an adhesive portion 84 that bonds the substrate 82 and the chip 83. The material of the adhesive portion 84 is a conductive paste containing a conductive filler 1. The adhesive portion 84 is formed from a conductive paste containing a conductive filler 1. Preferably, the adhesive portion 84 is formed by curing a conductive paste containing a conductive filler 1.

[0152] The substrate 82 has wiring 82a on its surface (top surface). The chip 83 has electrodes 83a on its surface (bottom surface). The wiring 82a and electrodes 83a are electrically connected by a conductive filler 1 in the adhesive portion 84.

[0153] The method for manufacturing an RFID inlay according to the present invention comprises the following steps (1) to (3): (1) A first placement step of placing the conductive paste described above on the surface of a substrate having wiring on its surface. (2) A second placement step of placing a chip having electrodes on its surface on the surface of the conductive paste opposite to the substrate side. (3) An bonding step of heating and pressurizing the conductive paste to form an adhesive portion that bonds the substrate and the chip, and electrically connecting the wiring and the electrodes with the conductive filler in the adhesive portion.

[0154] In the RFID inlay and RFID inlay manufacturing method according to the present invention, a specific conductive paste is used, which makes it possible to suppress the generation of voids in the adhesive portion of the RFID inlay. Furthermore, in the RFID inlay and RFID inlay manufacturing method according to the present invention, a specific conductive paste is used, which makes it possible to improve the adhesion between the substrate and the chip and to improve conductivity reliability.

[0155] In the above-described method for manufacturing RFID inlays, it is preferable that the substrate is elongated, and that the elongated substrate is transported by a roll-to-roll method in the first placement step, the second placement step, and the bonding step to manufacture the RFID inlays. In this case, multiple RFID inlays can be manufactured continuously, further increasing the manufacturing efficiency of the RFID inlays.

[0156] When a roll-to-roll system is used, the transport speed of the substrate is not particularly limited.

[0157] Methods for distributing the conductive paste include, for example, application by a dispenser, screen printing, and ejection by an inkjet device.

[0158] The heating temperature in the bonding process described above is preferably 100°C or higher, more preferably 150°C or higher, preferably 400°C or lower, more preferably 300°C or lower, and even more preferably 250°C or lower. When the heating temperature in the bonding process described above is above the lower limit and below the upper limit, thermal damage to the substrate can be reduced, and good electrical connection between the chip and the substrate can be achieved.

[0159] The pressure applied during the bonding process is preferably 0.5 N or more, more preferably 1 N or more, preferably 3.5 N or less, more preferably 3 N or less, and even more preferably 2.5 N or less. When the pressure applied during the bonding process is above the lower limit and below the upper limit, the adhesion between the substrate and the chip can be improved, and the conductivity reliability can be enhanced.

[0160] The heating and pressing times in the bonding process described above are not particularly limited. The heating and pressing times in the bonding process described above may be 2 seconds or more, 15 seconds or less, 10 seconds or less, 9 seconds or less, 7 seconds or less, or 5 seconds or less.

[0161] The RFID inlay may be cut to a predetermined size as needed, or may be used after being cut. It is preferable to bond a plurality of the chips to a long substrate using a plurality of the adhesive portions. Multiple laminates of the chips and adhesive portions may be arranged on the long substrate. In the first arrangement step, it is preferable to place the conductive paste at a plurality of locations on the surface of the long substrate. In the second arrangement step, it is preferable to use a plurality of chips to place the chips on the surface opposite to the substrate side of each of the conductive pastes placed at the plurality of locations. After the chips are bonded to the long substrate using the adhesive portions, the long substrate may be cut.

[0162] The above-mentioned substrate is not particularly limited. Preferably, the substrate is a circuit board. Examples of the circuit board include resin films, flexible printed circuit boards, rigid-flexible circuit boards, glass substrates, and paper substrates. The substrate may be a resin substrate, a glass substrate, or a paper substrate.

[0163] The above substrate has wiring (antenna pattern) on its surface. Wiring (antenna pattern) is formed on the surface of the above substrate. Preferably, the above substrate has a base material and wiring (antenna pattern) arranged on the surface of the base material.

[0164] Examples of materials for the above-mentioned substrate include resin, glass, and paper. Examples of resins include PET (polyethylene terephthalate), PP (polypropylene), and PVC (polyvinyl chloride). The paper may be impregnated with epoxy resin or phenolic resin. From the viewpoint of further improving adhesion and from the viewpoint of manufacturing RFID inlays using a roll-to-roll method, the material of the above-mentioned substrate is preferably resin or paper, and more preferably PET (polyethylene terephthalate) or paper. The above-mentioned substrate may be resin, glass, or paper.

[0165] Examples of the above-mentioned wiring (antenna pattern) include gold wiring, nickel wiring, tin wiring, aluminum wiring, silver wiring, stainless steel wiring, copper wiring, molybdenum wiring, and tungsten wiring. From the viewpoint of improving the operating sensitivity in the UHF band (860 MHz to 960 MHz), aluminum wiring is preferred.

[0166] From the viewpoint of suppressing deformation of the substrate due to heat during chip (e.g., IC chip) mounting and improving flexibility, the thickness of the substrate is preferably 20 μm or more, more preferably 30 μm or more, preferably 200 μm or less, and more preferably 100 μm or less.

[0167] The shapes of the substrate and base material are not particularly limited. From the viewpoint of manufacturing RFID inlays using a roll-to-roll method, the substrate and base material are preferably elongated. The lengths of the substrate and base material are not particularly limited. The lengths of the substrate and base material may be 1 m or more, 10 m or more, 5000 m or less, or 1000 m or less.

[0168] Examples of the above-mentioned chips include semiconductor chips (IC chips), etc.

[0169] The above-mentioned chip has electrodes on its surface. Examples of such electrodes include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, silver electrodes, SUS electrodes, copper electrodes, molybdenum electrodes, and tungsten electrodes. From the viewpoint of further improving conductivity reliability, the electrodes are preferably copper electrodes or gold electrodes, and more preferably copper electrodes.

[0170] The number of electrodes per chip is not particularly limited. The number of electrodes per chip may be one or more, four or more, 20 or less, or 10 or less.

[0171] The shape of the chip described above is not particularly limited. The shape of the chip may be rectangular, triangular, or circular.

[0172] From the viewpoint of further improving adhesion (between the substrate and the chip) and further improving conductivity reliability, the surface area of ​​the chip is preferably 0.04 mm². ２ More preferably, 0.09 mm ２ More preferably 0.16 mm ２ The above is preferable, and preferably 0.50 mm ２ More preferably, 0.40 mm ２ Further preferably 0.30 mm ２ The following applies: The above-mentioned area is the area on a plane (area in a planar view). If the area of ​​the chip is greater than or equal to the lower limit, the conductive paste can be placed on fine wiring with high precision. If the area of ​​the chip is less than or equal to the upper limit, the conductivity reliability can be maintained even when the RFID inlay is left in a high-temperature, high-humidity environment for a long time. The conductive paste according to the present invention can be suitably used for bonding relatively small chips.

[0173] The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to the following examples.

[0174] The following materials were prepared.

[0175] Cationic polymerizable compounds: (Oxetane compounds) "OXT-221" manufactured by Toagosei Co., Ltd. (3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane, molecular weight 214, liquid at 25°C) "ETERNACOLL HBOX" manufactured by Ube Industries, Ltd. (3-ethyl-3-(4-hydroxybutyl)oxymethyl-oxetane, molecular weight 188, liquid at 25°C)

[0176] (Epoxy Compounds) Nissan Chemical Corporation's "TEPIC-FL" (Epoxy compound without an aromatic skeleton, epoxy equivalent 169 g / eq, molecular weight 507.7, liquid at 25°C) Daicel Corporation's "Celoxide 2021P" (3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, alicyclic epoxy compound without an aromatic skeleton, epoxy equivalent 130 g / eq, molecular weight 252.3, liquid at 25°C) Daicel Corporation's "Epolleed GT401" (Epoxidized butanetetracarboxylic acid tetrakis-(3-cyclohexenylmethyl) modified epsiloncaprolactone, alicyclic epoxy compound without an aromatic skeleton, epoxy equivalent 220 g / eq, molecular weight 788.9, liquid at 25°C) Daicel Corporation's "Epolide PB3600" (epoxidized polybutadiene without an aromatic skeleton, epoxy equivalent 193 g / eq, molecular weight 5400, liquid at 25°C) Daicel Corporation's "Epolide PB4700" (epoxidized polybutadiene without an aromatic skeleton, epoxy equivalent 165 g / eq, molecular weight 3100, liquid at 25°C) Daicel Corporation's "Epofriend AT501" (epoxy compound of styrene-butadiene block copolymer, epoxy compound without an aromatic skeleton, epoxy equivalent 1055 g / eq, molecular weight over 6000, solid at 25°C)

[0177] Non-cationic polymerizable compound: "Phenotote YP-70" manufactured by Nippon Steel Chemical & Material Co., Ltd. (phenoxy resin, solid at 25°C)

[0178] Compounds without polymerizable functional groups (non-polymerizable compounds): Nippon Soda Co., Ltd.'s "1,2-SBS (solid)" (1,2-styrenebutadienestyrene, molecular weight 35,000, solid at 25°C)

[0179] Polymerization initiators: King Industries "K-PURE CXC1821" (quaternary ammonium salt), Sanshin Chemical Industry Co., Ltd. "San-Aid SI-100L" (sulfonium salt), San-Apro Co., Ltd. "IK-1" (iodonium salt)

[0180] Conductive filler: Nikko Rica Co., Ltd. "CN050" (nickel particles, average particle size: 5 μm)

[0181] Additive: KBM-403 (3-glycidoxypropyltrimethoxysilane) manufactured by Shin-Etsu Silicone Co., Ltd.

[0182] Chip: IC chip (copper electrode, NXP "UCODE9", surface area: 0.22 mm²) ２ )

[0183] Substrate: PET film (long-length resin film with aluminum wiring operating in the UHF band (860 MHz to 960 MHz))

[0184] (Example 1) (1) Preparation of conductive paste The materials shown in Table 1 below were mixed in the amounts (parts by weight) shown in Table 1 below, and stirred using a planetary stirring device (Thinky Co., Ltd. "Awatori Rentaro") to obtain a conductive paste (anisotropic conductive paste).

[0185] (2) Fabrication of RFID Inlay The obtained conductive paste was applied to the PET film using a jet dispensing method to form a conductive paste layer (adhesive layer) with a diameter of 800 μm (first placement step). Next, an IC chip (450 μm × 450 μm) was laminated on the surface of the conductive paste layer (adhesive layer) so that the wiring on the surface of the PET film and the electrodes on the surface of the IC chip faced each other (second placement step). Then, the conductive paste layer (adhesive layer) was cured by heat pressing under the conditions of an upper heat tool at 180°C, a lower heat tool at 175°C, a pressure of 0.05 MPa, and a pressing time of 3 seconds, thereby forming an adhesive part. Furthermore, the wiring on the surface of the PET film and the electrodes on the surface of the IC chip were electrically connected by a conductive filler in the adhesive part to obtain a connection structure (bonding step). The first placement step, the second placement step, and the bonding step described above were performed using a Muhlbauer "DDA40000" (roll-to-roll type). The resulting connection structure was cut to a size of 5 cm x 1.5 cm to obtain 50 RFID inlays.

[0186] (Examples 2-14 and Comparative Examples 1-8) Conductive pastes and RFID inlays were obtained in the same manner as in Example 1, except that the components and amounts of the conductive paste were set as shown in Tables 1, 3, 5, 7, 9, and 11.

[0187] (Evaluation) (1) Viscosity of conductive paste at 25°C The viscosity (η25) of the conductive paste at 25°C was measured using the method described above for the conductive paste immediately after preparation. In Comparative Example 6, the viscosity at 25°C exceeded the upper limit of the E-type viscometer, so the viscosity (η25) could not be measured (unmeasurable). In Comparative Example 8, the viscosity (η25) exceeded 100 Pa·s. In Comparative Example 7, pellet-like material remained in the conductive paste, and it did not become a uniform paste, so the viscosity (η25) could not be measured.

[0188] (2) Dispensing stability The conductive paste that obtained the required dispensing stability was dispensed using a jet dispensing method to a diameter of 800 μm. The dispensing stability of the conductive paste was judged according to the following criteria.

[0189] [Criteria for determining dispensing stability] ○: Conductive paste can be dispensed continuously from the jet dispenser for 10 hours or more. ○: Conductive paste can be dispensed continuously from the jet dispenser for 10 hours or more, but slight dispensing irregularities occur during the 10 hours of continuous dispensing. ×: Conductive paste cannot be dispensed at the initial stage of dispensing from the jet dispenser, or conductive paste can be dispensed continuously from the jet dispenser, but cannot be dispensed continuously for 10 hours or more.

[0190] (3) A conductive paste was applied to a curable glass plate to a thickness of 30 μm. The glass plate was placed on the surface of a hot plate (set temperature 160°C) with the side opposite to the side on which the conductive paste was applied facing upwards, and the time elapsed until the conductive paste gelled was measured. The curability (gel time) of the conductive paste was determined according to the following criteria. After 3 seconds and 10 seconds, stringing was checked using a needle with a handle, and gelling was determined when the string no longer broke.

[0191] [Criteria for determining curability] ○○: The time elapsed until the conductive paste gels is 3 seconds or less. ○: The time elapsed until the conductive paste gels is more than 3 seconds but 10 seconds or less. ×: The time elapsed until the conductive paste gels is more than 10 seconds.

[0192] (4) Storage Stability (Pot Life) The viscosity (ηA) of the conductive paste at 25°C and 0.5 rpm after storing the conductive paste immediately after preparation at 25°C and 50% RH for 24 hours was measured in the same manner as the viscosity (η25) and the ratio (ηA / η25) was calculated. The storage stability of the conductive paste was determined according to the following criteria.

[0193] [Storage Stability Criteria] ○○: Ratio (ηA / η25) is 1.2 or less ○: Ratio (ηA / η25) is greater than 1.2 and 2.0 or less ×: Ratio (ηA / η25) is greater than 2.0

[0194] The composition and details of the conductive paste, as well as the evaluation results, are shown in Tables 1 to 12 below.

[0195]

[0196]

[0197]

[0198]

[0199]

[0200]

[0201]

[0202]

[0203]

[0204]

[0205]

[0206]

[0207] 1...Conductive filler 81...RFID inlay 82...Substrate with wiring on its surface 82a...Wiring 83...Chip with electrodes on its surface 83a...Electrode 84...Adhesive part

Claims

1. A conductive paste comprising a cationic polymerizable compound, a polymerization initiator, and a conductive filler, wherein the cationic polymerizable compound comprises an oxetane compound or an epoxy compound, the polymerization initiator comprises a sulfonium salt or an ammonium salt, and the viscosity of the conductive paste at 25°C is 10 Pa·s or more and 100 Pa·s or less.

2. The conductive paste according to claim 1, wherein the cationic polymerizable compound comprises an alicyclic epoxy compound.

3. The conductive paste according to claim 1 or 2, wherein the cationic polymerizable compound comprises a cationic polymerizable compound having a molecular weight of 1,000 or more and 6,000 or less.

4. The conductive paste according to claim 3, wherein the cationic polymerizable compound comprises a cationic polymerizable compound having a molecular weight of 1,000 or more and 6,000 or less, and a cationic polymerizable compound having a molecular weight of less than 1,000.

5. The conductive paste according to claim 3 or 4, wherein the cationic polymerizable compound with a molecular weight of 1000 to 6000 is a liquid at 25°C.

6. The conductive paste according to any one of claims 3 to 5, wherein the epoxy equivalent of the cationic polymerizable compound having a molecular weight of 1000 to 6000 is 150 g / eq to 200 g / eq.

7. The conductive paste according to any one of claims 3 to 6, wherein the cationic polymerizable compound with a molecular weight of 1000 to 6000 comprises epoxidized polybutadiene.

8. The conductive paste according to any one of claims 3 to 7, wherein the content of the cationic polymerizable compound having a molecular weight of 1000 to 6000 is 50% to 90% by weight in 100% by weight of the conductive paste.

9. The conductive paste according to any one of claims 3 to 8, wherein the weight ratio of the content of the cationic polymerizable compound having a molecular weight of 1,000 to 6,000 to the content of the polymerization initiator is 50 to 90.

10. The conductive paste according to any one of claims 1 to 9, wherein the polymerization initiator comprises a quaternary ammonium salt.

11. The conductive paste according to any one of claims 1 to 10, which is used to obtain an RFID inlay.

12. An RFID inlay comprising a substrate having wiring on its surface, a chip having electrodes on its surface, and an adhesive portion bonding the substrate and the chip, wherein the material of the adhesive portion is the conductive paste described in any one of claims 1 to 11, and the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

13. A method for manufacturing an RFID inlay, comprising: a first placement step of placing a conductive paste according to any one of claims 1 to 11 on the surface of a substrate having wiring on its surface; a second placement step of placing a chip having electrodes on its surface on the surface of the conductive paste opposite to the substrate side; and an bonding step of heating and pressurizing the conductive paste to form an adhesive portion that bonds the substrate and the chip, and electrically connecting the wiring and the electrodes with the conductive filler in the adhesive portion.

14. The method for manufacturing an RFID inlay according to claim 13, wherein the substrate is elongated, and the elongated substrate is transported by a roll-to-roll method in the first placement step, the second placement step, and the bonding step to manufacture the RFID inlay.

15. Use of the conductive paste according to any one of claims 1 to 11 for obtaining an RFID inlay.

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