Hot melt adhesive sheet containing conductive particles, method for manufacturing smart card, and smart card

Abstract

To provide a conductive particle-containing hot-melt adhesive sheet capable of improving adhesive force between a card member and an IC chip even after a smart card having a hardly adhesive card member (for example, a card member using polylactic acid as a core material) is left in a high temperature and high humidity environment.SOLUTION: A conductive particle-containing hot-melt adhesive sheet 1 includes a first layer 2 containing 40 mass% or more of a crystalline polyamide resin having a carboxyl group, and a second layer 3 containing a crystalline polyurethane resin and a carbodiimide compound. In the conductive particle-containing hot-melt adhesive sheet 1, the content of the crystalline polyurethane resin is more than 10% by mass and the content of the carbodiimide compound is less than 15% by mass with respect to the total mass of the crystalline polyurethane resin and the carbodiimide compound in the second layer 3. The conductive particle-containing hot-melt adhesive sheet 1 contains conductive particles 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present technology relates to a conductive particle-containing hot melt adhesive sheet, a method for manufacturing a smart card, and a smart card. [Background technology]

[0002] 2. Description of the Related Art So-called smart cards, such as credit cards, are known in which electrodes of an IC (Integrated circuit) chip are connected to antenna wiring inside the card member.

[0003] Smart cards are formed, for example, by laminating a film with an antenna wiring printed thereon or a film with a surface printing, etc., around a plastic plate made of various resins as a core. In addition, a recess is formed by milling part of the laminated plastic plate or film, and an IC chip is mounted and bonded in this recess, and the IC chip and the antenna wiring are electrically connected.

[0004] Plastics used in smart cards have traditionally included PVC (Polyvinyl Chloride) and PET (Polyethylene terephthalate). However, in response to recent demands for reducing environmental impact, the use of resins with improved biodegradability, recycled resins, and recyclable resins has been increasing. One example of such a resin is polylactic acid (PLA). Adhesives used in conventional smart cards (see, for example, Patent Document 1) tend to have low adhesive strength to card components with polylactic acid as a core material, i.e., poor adhesion. Therefore, for example, when manufacturing a smart card including a card component with polylactic acid as a core material, the adhesive strength between the card component and the IC chip may be poor, resulting in poor durability (e.g., bending resistance) of the smart card. In particular, it is desirable for smart cards including a card component with polylactic acid as a core material (hereinafter also referred to as a PLA card) to have good wet-heat reliability, specifically, good adhesive strength between the card component and the IC chip even after the smart card is left in a high-temperature, high-humidity environment.

[0005] On the other hand, adhesives for smart cards have been developed, for example, with two layers of adhesive corresponding to the area to be attached, with compositions tailored to the area to be attached (see, for example, Patent Document 2). However, the adhesive film described in Patent Document 2 is considered insufficient as an adhesive for mounting an IC chip to a card member, for example, in smart cards using biodegradable plastics.

[0006] Furthermore, for example, Patent Document 3 discloses a latent reactive polyurethane adhesive film containing a crystalline polyurethane component and a conductive filler. However, the adhesive film described in Patent Document 3 requires a long heating process, and is considered to be undesirable in terms of production efficiency as an adhesive for mass-produced smart cards. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6966659 [Patent Document 2] Special Publication No. 2007-514006 [Patent Document 3] Special Publication No. 2022-515327 Summary of the Invention [Problem to be solved by the invention]

[0008] The present technology was proposed in consideration of the current situation, and provides a hot melt adhesive sheet containing conductive particles that can maintain good adhesion between a card member and an IC chip even after a smart card equipped with a poorly adhesive card member (e.g., a PLA card) is left in a high-temperature, high-humidity environment. [Means for solving the problem]

[0009] The conductive particle-containing hot melt adhesive sheet according to the present technology comprises a first layer containing 40% by mass or more of a crystalline polyamide resin having a carboxyl group, and a second layer containing a crystalline polyurethane resin and a carbodiimide compound, and in the second layer, the content of the crystalline polyurethane resin is more than 10% by mass and the content of the carbodiimide compound is less than 15% by mass relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound.

[0010] The method for manufacturing a smart card according to the present technology comprises: a first layer containing 40% by mass or more of a crystalline polyamide resin having a carboxyl group; a crystalline polyurethane resin; and a carbodiimide compound; wherein the second layer contains more than 10% by mass of the crystalline polyurethane resin and less than 15% by mass of the carbodiimide compound relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound; and a conductive particle-containing hot melt adhesive sheet is interposed between a card member and an IC chip so that the first layer faces the IC chip, and the two are thermally compressed together.

[0011] The smart card according to the present technology comprises a card member, an IC chip, and an adhesive layer that bonds the card member and the IC chip, and the adhesive layer contains a reaction product of a crystalline polyamide resin having a carboxyl group and a carbodiimide compound, and conductive particles.

[0012] The smart card according to the present technology comprises a card member, an IC chip, and an adhesive layer that bonds the card member and the IC chip, the adhesive layer comprising a first layer containing 40% by mass or more of a crystalline polyamide resin having a carboxyl group, and a second layer containing a crystalline polyurethane resin and a carbodiimide compound, and the second layer comprises a conductive particle-containing hot melt adhesive sheet in which the content of the crystalline polyurethane resin in the second layer is more than 10% by mass and the content of the carbodiimide compound is less than 15% by mass relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound. [Effects of the Invention]

[0013] This technology can maintain good adhesive strength between a card member and an IC chip even after a smart card equipped with a poorly adhesive card member (for example, a PLA card) is left in a high-temperature, high-humidity environment. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a conductive particle-containing hot melt adhesive sheet. [Figure 2] FIG. 2 is a schematic perspective view showing an example of a smart card. [Figure 3] FIG. 3 is a top view showing an example of an IC chip area of ​​a card member. [Figure 4] FIG. 4 is a perspective view illustrating an example of a step of attaching a conductive particle-containing hot-melt adhesive sheet to the connection surface of an IC chip in a method for manufacturing a smart card. [Figure 5] FIG. 5 is a cross-sectional view illustrating an example of a step of thermocompression bonding an IC chip and a card member in a method for manufacturing a smart card. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Hot melt adhesive sheet containing conductive particles> FIG. 1 is a cross-sectional view showing an example of a conductive particle-containing hot melt adhesive sheet. The conductive particle-containing hot melt adhesive sheet 1 according to this embodiment comprises a first layer 2 (hereinafter simply referred to as "first layer 2") containing 40% by mass or more of a crystalline polyamide resin having carboxyl groups, and a second layer 3 (hereinafter simply referred to as "second layer 3") containing a crystalline polyurethane resin and a carbodiimide compound. In the second layer 3, the content of the crystalline polyurethane resin is greater than 10% by mass and the content of the carbodiimide compound is less than 15% by mass, based on the total mass of the crystalline polyurethane resin and the carbodiimide compound. The conductive particle-containing hot melt adhesive sheet 1 contains conductive particles 4. Here, crystalline polyamide resins and crystalline polyurethane resins having carboxyl groups are collectively referred to as binders.

[0016] In the conductive particle-containing hot melt adhesive sheet 1, the first layer 2 contains a crystalline polyamide resin having a carboxyl group, and the second layer 3 contains a carbodiimide compound, so that the first layer 2 and the second layer 3 mix and crosslink when they flow under heat and pressure. When the conductive particle-containing hot melt adhesive sheet 1 having such a configuration is used as an adhesive layer in a smart card that includes a card member, an IC chip, and an adhesive layer that bonds the card member and the IC chip, it can improve the adhesive strength between the card member and the IC chip.

[0017] In this specification, a smart card is a card incorporating an integrated circuit (IC) for recording and calculating information (data), and is also referred to as an "IC card" or "chip card." A smart card includes, for example, a card member, an IC chip, and an adhesive layer that bonds the card member and the IC chip. A smart card may also be a dual-interface card with a single IC chip that has two interfaces, contact and contactless, or a hybrid card equipped with a contact IC chip and a contactless IC chip. A smart card may also be a fingerprint authentication card equipped with a fingerprint authentication element, or a card equipped with a one-time password function that incorporates a battery element and a display element. These IC chips and elements have pads that are electrically connected to the electrode portions of the card member.

[0018] Here, "good adhesive strength between the card member and the IC chip" means both that the initial adhesive strength between the card member and the IC chip is good (OK) as evaluated by the method described in the Examples below, and that the moist heat reliability of the smart card (adhesion strength between the card member and the IC chip after being left in a high-temperature, high-humidity environment) is good (OK) as evaluated by the method described in the Examples below. "Good moist heat reliability" of the smart card, in other words, means that the adhesive strength between the card member and the IC chip does not decrease significantly even when the smart card is exposed to a high-temperature, high-humidity environment. Use of the conductive particle-containing hot melt adhesive sheet 1 can improve the moist heat reliability, particularly of smart cards that use a poorly adhesive PLA card as the card member.

[0019] For example, it is preferable that the conductive particle-containing hot melt adhesive sheet 1 has a first layer 2 and a second layer 3, and is interposed between the card member and the IC chip and thermocompression bonded, with the first layer 2 facing the IC chip, i.e., the second layer 3 facing the card member. This ensures good adhesion between the card member and the IC chip when the reaction product of the conductive particle-containing hot melt adhesive sheet 1 is used as an adhesive layer in a smart card.

[0020] Furthermore, when the conductive particle-containing hot melt adhesive sheet 1 is used as an adhesive layer in a smart card having a PLA card as the card member, the conductive particle-containing hot melt adhesive sheet 1 can improve the bending resistance of the smart card by providing the first layer 2 and the second layer 3. Here, good bending resistance of the smart card means that the result of the bending test of the smart card evaluated by the method described in the Examples below is good (OK).

[0021] The lower limit of the thickness of the conductive particle-containing hot melt adhesive sheet 1 can be, for example, 10 μm or more, 20 μm or more, 30 μm or more, or 35 μm or more. The upper limit of the thickness of the conductive particle-containing hot melt adhesive sheet 1 can be, for example, 100 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, or 45 μm or less. This makes the conductive particle-containing hot melt adhesive sheet 1 suitable for use in, for example, the production of smart cards.

[0022] Next, we will explain the conductive particles 4 contained in the conductive particle-containing hot melt adhesive sheet 1. Depending on the average particle diameter, the conductive particles 4 may be contained across the first layer 2 and the second layer 3, or may be contained in the first layer 2, or may be contained in the second layer 3, or may be contained in both the first layer 2 and the second layer 3, as shown in Figure 1 .

[0023] The conductive particle-containing hot melt adhesive sheet 1 contains, for example, solder particles as the conductive particles 4. The solder particles may be non-eutectic alloy solder particles or eutectic alloy solder particles, but it is preferable to use non-eutectic alloy solder particles. A non-eutectic alloy is an alloy that does not have a eutectic point. Non-eutectic alloy solder particles remain in a semi-molten state for a longer period of time during thermocompression bonding than eutectic alloy solder particles, allowing for sufficient removal of resin and achieving excellent connection reliability. The solder particles are preferably an alloy containing two or more elements selected from the group consisting of Sn, Bi, Ag, In, Cu, Sb, Pb, and Zn. The solder particles can be appropriately selected from, for example, Sn-Pb, Pb-Sn-Sb, Sn-Sb, Sn-Pb-Bi, Bi-Sn, Sn-Bi-Cu, Sn-Cu, Sn-Pb-Cu, Sn-In, Sn-Ag, Sn-Pb-Ag, Pb-Ag, etc., as specified in JIS Z 3282-2017 (corresponding international standard: ISO 9453:2014), depending on the terminal material, connection conditions, etc.

[0024] The lower limit of the solidus temperature (melting point) of the solder particles is, for example, preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 135°C or higher. The upper limit of the liquidus temperature of the solder particles may be, for example, 210°C or lower, preferably 200°C or lower, more preferably 195°C or lower, and even more preferably 190°C or lower. Here, the liquidus is a curve showing the relationship between the temperature (melting point) of the liquid phase in equilibrium with the solid phase and the composition of the liquid phase. The upper limit of the solidus temperature of the solder particles is, for example, preferably 155°C or lower, may be 150°C or lower, 145°C or lower, or may be 140°C or lower. Furthermore, a flux compound may be directly bonded to the surface of the solder particles for the purpose of surface activation. Activating the surface can promote metallic bonding with metal wires or electrodes.

[0025] In particular, the solder particles are preferably non-eutectic alloys with a solidus temperature (melting point) of 155°C or lower. For example, the solder particles preferably have a solidus temperature of 150°C or lower and are preferably one or more alloys selected from the group consisting of Sn-Bi-Cu alloy, Sn-Bi-Ag alloy, Sn-Bi alloy, Sn-Pb-Bi alloy, and Sn-In alloy. Specific examples of solder particles include Sn30Bi0.5Cu, Sn30Bi, Sn40Bi, Sn50Bi, Sn58Bi, Sn40Bi0.1Cu, Sn43Pb14Bi, and Sn20In. This allows for excellent connection reliability.

[0026] The lower limit of the content of solder particles in the conductive particle-containing hot melt adhesive sheet 1 is, for example, preferably 20 parts by mass or more, and more preferably 40 parts by mass or more, per 100 parts by mass of the binder (or the total mass of all components other than the solder particles) in the conductive particle-containing hot melt adhesive sheet 1. The upper limit of the content of solder particles is, for example, preferably 500 parts by mass or less, more preferably 400 parts by mass or less, and even more preferably 300 parts by mass or less, per 100 parts by mass of the binder (or the total mass of all components other than the solder particles) in the conductive particle-containing hot melt adhesive sheet 1, and may be 200 parts by mass or less, 150 parts by mass or less, 100 parts by mass or less, 80 parts by mass or less, or 70 parts by mass or less.

[0027] If the solder particle content is too low, it becomes difficult to obtain excellent conductivity. On the other hand, if the solder particle content is too high, it becomes difficult to obtain sufficient adhesive strength, and the insulation within the IC chip is easily impaired, making it difficult to obtain excellent conductivity reliability. When the solder particles are present in the binder, the volume ratio may be used, and when producing the conductive particle-containing hot melt adhesive sheet 1 (before the solder particles are present in the binder), the mass ratio may be used. The mass ratio can be converted to a volume ratio based on the specific gravity and compounding ratio of the compounds.

[0028] The solder particles may be kneaded and dispersed in the resin of the conductive particle-containing hot melt adhesive sheet 1, or may be arranged at a distance from one another, for example, arranged in a regular pattern. Examples of regular arrangements include lattice arrangements such as square lattices, hexagonal lattices, oblique lattices, and rectangular lattices. The solder particles may also be arranged as aggregates in which multiple particles are aggregated. In this case, the arrangement of the aggregates in the plan view of the conductive particle-containing hot melt adhesive sheet 1 may be regular or random, similar to the arrangement of the solder particles described above.

[0029] The average particle diameter of the solder particles is, for example, preferably 70% or more, more preferably 80% or more, and even more preferably 95% or more of the thickness of the conductive particle-containing hot melt adhesive sheet 1. This allows, for example, the solder particles to be more reliably sandwiched between the conductive parts of the IC chip and the conductive parts of the card member during thermocompression bonding of the conductive particle-containing hot melt adhesive sheet 1, thereby easily forming a metal bond.

[0030] The lower limit of the average particle diameter of the solder particles is, for example, preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. The upper limit of the average particle diameter of the solder particles is, for example, preferably 50 μm or less, more preferably 45 μm or less, and even more preferably 40 μm or less. The average particle diameter of the solder particles can be, for example, in the range of 25 to 45 μm. The maximum diameter of the solder particles is, for example, preferably 200% or less of the average particle diameter, more preferably 150% or less of the average particle diameter, and even more preferably 120% or less of the average particle diameter. By having the maximum diameter of the solder particles within the above range, the solder particles can be more reliably sandwiched between the conductive portions of the IC chip and the conductive portions of the card member, and the melting of the solder particles can more reliably form a metal bond between the conductive portions.

[0031] Furthermore, when the solder particles are aggregates of a plurality of solder particles, the size of the aggregates may be set to be equal to the average particle size of the solder particles. The size of the aggregates can be determined by observation with an electron microscope or an optical microscope.

[0032] Here, the average particle size refers to the average major axis diameter of particles measured, for example, at N=20 or more, preferably N=50 or more, and more preferably N=200 or more, in observation images using a metallurgical microscope, optical microscope, or electron microscope such as a scanning electron microscope (SEM). In the case of spherical particles, it refers to the average diameter of the particles. The observed images may also be measured using known image analysis software (such as "WinROOF" manufactured by Mitani Shoji Co., Ltd. or "Azo-kun (registered trademark)" manufactured by Asahi Kasei Engineering Co., Ltd.) or may be measured (N=1000 or more) using an image-based particle size analyzer (e.g., FPIA-3000 manufactured by Malvern Instruments). The average particle size determined from the observed images or an image-based particle size analyzer may be the average maximum length of the particles. When producing the conductive particle-containing hot melt adhesive sheet 1, it is possible to simply use manufacturer values ​​such as the particle size (D50) at which the cumulative frequency in the particle size distribution determined by the laser diffraction / scattering method is 50%, and the arithmetic mean diameter (preferably on a volume basis).

[0033] Next, examples of the configuration of the first layer 2 and the second layer 3 of the conductive particle-containing hot melt adhesive sheet 1 will be described.

[0034] [First layer] The first layer 2 contains at least a crystalline polyamide resin having a carboxyl group. The crystalline polyamide resin preferably has a carboxyl group at its terminal. Whether the first layer 2 contains a crystalline polyamide resin can be confirmed, for example, by observing an endothermic peak during the temperature rise process in differential scanning calorimetry.

[0035] The terminal carboxyl group concentration of the crystalline polyamide resin is not particularly limited and can be, for example, 0.5 mg KOH / g or more, 1.0 mg KOH / g or more, or 2.0 mg KOH / g or more. The terminal carboxyl group concentration of the crystalline polyamide resin can be, for example, 50 mg KOH / g or less, 30 mg KOH / g or less, or 10 mg KOH / g or less. The terminal carboxyl group concentration of the crystalline polyamide resin can be evaluated, for example, in accordance with JIS K 0070-1992 or ISO 2114. Specific examples of commercially available crystalline polyamide resins having carboxyl groups include "HX2519" and "M1276" manufactured by Arkema.

[0036] The content of the carboxyl group-containing crystalline polyamide resin in the first layer 2 is 40% by mass or more. As a result, when the reaction product of the conductive particle-containing hot melt adhesive sheet 1 is used as an adhesive layer of a smart card, for example, the adhesive strength between the card member and the IC chip can be improved, and the bending resistance of the smart card can also be improved.

[0037] The content of the carboxyl group-containing crystalline polyamide resin in the first layer 2 may be 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, or even 100% by mass. The content of the carboxyl group-containing crystalline polyamide resin in the first layer 2 may be in the range of 40 to 100% by mass. The carboxyl group-containing crystalline polyamide resin in the first layer 2 may be used alone or in combination of two or more. When two or more types of carboxyl group-containing crystalline polyamide resins are used in combination, it is preferable that the total amount thereof falls within the above content range. The content of the carboxyl group-containing crystalline polyamide resin may be based on the total mass of the first layer 2 excluding the conductive particles 4. In this case, the preferred range of the content of the crystalline polyamide resin having a carboxyl group is the same as the above-mentioned numerical range.

[0038] The first layer 2 may further contain a resin other than the carboxyl-containing crystalline polyamide resin, as needed. The other resin may be, for example, a crystalline resin, an amorphous resin, or the like, and can be selected appropriately depending on the purpose. The crystalline resin is not particularly limited as long as it has a crystalline region, and examples thereof include polyester resin, polyolefin resin, and polyurethane resin. Examples of polyester resins include polyethylene terephthalate resin and polybutylene terephthalate resin. Examples of polyolefin resins include polyethylene resin, polypropylene resin, and polybutylene resin. Examples of amorphous resins include those exemplified in the description of the crystalline resin. When the first layer 2 further contains a resin other than the carboxyl-containing crystalline polyamide resin, it is preferable to include a crystalline polyester resin, for example, from the viewpoint of adhesion at low temperature and in a short time.

[0039] For example, when the first layer 2 further contains a crystalline polyester resin, the content of the crystalline polyester resin in the first layer 2 can be, for example, 60% by mass or less, 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, or in the range of 1 to 60% by mass. The crystalline polyester resin may be used alone or in combination of two or more. When two or more crystalline polyester resins are used in combination, it is preferable that the total amount thereof satisfies the above-mentioned content range. The content of the crystalline polyester resin may be based on the total mass of the first layer 2 excluding the conductive particles 4. In this case, the preferred range of the crystalline polyester resin content is the same as the above-mentioned numerical range.

[0040] For example, if the first layer 2 further contains a carbodiimide compound in addition to the carboxyl-containing crystalline polyamide resin, the carbodiimide compound will react quickly with the carboxyl-containing crystalline polyamide resin, causing crosslinking. This increases the viscosity of the resin composition, making it difficult to apply the resin composition in a sheet (layer). Therefore, it is preferable that the first layer 2 is substantially free of a carbodiimide compound. For example, the content of the carbodiimide compound in the first layer 2 is preferably 0.1% by mass or less, or may be 0.05% by mass or less, 0.01% by mass or less, or even 0% by mass, based on the total mass of the components other than the conductive particles 4 in the first layer 2.

[0041] The lower limit of the thickness of the first layer 2 is not particularly limited and can be, for example, 5 μm or more, or 10 μm or more, or 15 μm or more. The upper limit of the thickness of the first layer 2 is not particularly limited and can be, for example, 35 μm or less, or 30 μm or less, or 25 μm or less.

[0042] [Second layer] The second layer 3 contains at least a crystalline polyurethane resin and a carbodiimide compound. The second layer 3 contains more than 10 mass % of the crystalline polyurethane resin relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound.

[0043] By containing a crystalline polyurethane resin and a carbodiimide compound in the second layer 3, hydrolysis of the crystalline polyurethane resin can be suppressed. For example, when the reaction product of the conductive particle-containing hot melt adhesive sheet 1 is used as the adhesive layer of a smart card, the adhesive strength between the card material and the IC chip can be improved both initially and after reliability, and the bending resistance of the smart card can also be improved. Whether the second layer 3 contains a crystalline polyurethane resin can be confirmed, for example, by observing an endothermic peak during the temperature rise process in differential scanning calorimetry.

[0044] The crystalline polyurethane resin that can be used is, for example, one having a viscosity of 300 to 3000 mPa·s in a 15% MEK (Methyl ethyl ketone) solution at 25°C.

[0045] Specific examples of commercially available crystalline polyurethane resins include Lubrizol's "Pearlstick 40-70 / 33 (viscosity of 15% MEK solution: 3000 mPa·s)" and "Pearlstick 40-70 / 03 (viscosity of 15% MEK solution: 300 mPa·s)."

[0046] The content of the crystalline polyurethane resin in the second layer 3 may be, for example, 12% by mass or more, 15% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more, based on the total mass of the crystalline polyurethane resin and the carbodiimide compound. The content of the crystalline polyurethane resin in the second layer 3 may be in the range of 15 to 99.9% by mass, based on the total mass of the crystalline polyurethane resin and the carbodiimide compound. The crystalline polyurethane resin may be used alone or in combination with two or more types. When two or more types of crystalline polyurethane resins are used in combination, it is preferable that the total amount thereof satisfies the above content range. The content of the crystalline polyurethane resin may be based on the total mass of the second layer 3 excluding the conductive particles 4. In this case, the preferred range of the content of the crystalline polyurethane resin is the same as the above-mentioned numerical range.

[0047] Furthermore, the content of the carbodiimide compound relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound in the second layer 3 is less than 15 mass %, which allows the conductive particle-containing hot melt adhesive sheet 1 to have good tackiness.

[0048] A carbodiimide compound is a compound having a carbodiimide group (-N=C=N-). The carbodiimide compound may be, for example, a solid or a liquid at room temperature. Room temperature refers to the range of 15 to 25°C as specified in JIS K 0050:2019 (General Rules for Chemical Analysis Methods). In the carbodiimide compound, the group bonded to the carbodiimide group is not particularly limited, and examples thereof include an aliphatic group, an alicyclic group, an aromatic group, or a group to which these organic groups are bonded (e.g., a benzyl group, a phenethyl group, a 1,4-xylylene group, etc.). Furthermore, the carbodiimide compound may be a cyclic carbodiimide compound having a carbodiimide group within a cyclic structure, from the viewpoint of suppressing the generation of isocyanate gas accompanying the reaction of the carbodiimide group.

[0049] Specific examples of commercially available carbodiimide compounds include Carbodilite V-02B (manufactured by Nisshinbo Chemical Inc.), Carbodista (manufactured by Teijin Limited), and solvent-soluble polycarbodiimide resins (solid content 70%) such as Carbodilite V-09GB (manufactured by Nisshinbo Chemical Inc.) and Elastostab H01 (manufactured by BASF Polyurethanes GmbH).

[0050] The content of the carbodiimide compound in the second layer 3 may be 14% by mass or less, 13% by mass or less, 12% by mass or less, 11% by mass or less, 10% by mass or less, 8% by mass or less, 6% by mass or less, 4% by mass or less, 2% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.2% by mass or less, based on the total mass of the crystalline polyurethane resin and the carbodiimide compound. The content of the carbodiimide compound in the second layer 3 may be 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.1% by mass or more but less than 15% by mass, or in the range of 0.1 to 10% by mass, based on the total mass of the crystalline polyurethane resin and the carbodiimide compound. One type of carbodiimide compound may be used alone, or two or more types may be used in combination. When two or more carbodiimide compounds are used in combination, it is preferable that the total amount thereof falls within the above content range. The content of the carbodiimide compounds may be based on the total mass of the second layer 3 excluding the conductive particles 4. In this case, the preferred range of the content of the carbodiimide compounds is the same as the above-mentioned numerical range.

[0051] The second layer 3 may further contain other components in addition to the crystalline polyurethane resin and the carbodiimide compound, as necessary. The other components may be, for example, a crystalline resin, an amorphous resin, or the like, and may be selected as appropriate depending on the purpose. As the crystalline resin and the amorphous resin, those exemplified as other components of the first layer 2 above can be used. When the second layer 3 further contains other components in addition to the crystalline polyurethane resin and the carbodiimide compound, it is preferable that the second layer 3 contains a crystalline polyester resin, for example, from the viewpoint of adhesion in a short period of time.

[0052] For example, when the second layer 3 further contains a crystalline polyester resin in addition to the crystalline polyurethane resin and the carbodiimide compound, the content of the crystalline polyester resin in the second layer 3 can be in the range of 1 to 80% by mass, based on the total mass of the crystalline polyurethane resin, the carbodiimide compound, and the crystalline polyester resin, and may be in the range of 10 to 80% by mass, 20 to 80% by mass, 30 to 80% by mass, 40 to 80% by mass, 50 to 80% by mass, 60 to 80% by mass, or 70 to 80% by mass. The crystalline polyester resin may be used alone or in combination with two or more types. When two or more types of crystalline polyester resins are used in combination, it is preferable that the total amount thereof satisfy the above-mentioned content range. The content of the crystalline polyester resin may be based on the total mass of the components other than the conductive particles 4 in the second layer 3. In this case, the preferred range of the content of the crystalline polyester resin is the same as the above-mentioned numerical range.

[0053] Here, for example, if the second layer 3 further contains a crystalline polyamide resin having carboxyl groups, the carbodiimide compound will react quickly with the crystalline polyamide resin having carboxyl groups, causing crosslinking, which will increase the viscosity of the resin composition too much, making it difficult to apply in a sheet (layer). Therefore, it is preferable that the second layer 3 is substantially free of a crystalline polyamide resin having carboxyl groups. For example, the content of the crystalline polyamide resin having carboxyl groups in the second layer 3 is preferably 0.1% by mass or less, or may be 0.05% by mass or less, 0.01% by mass or less, or even 0% by mass, based on the total mass of the components other than the conductive particles 4 in the second layer 3.

[0054] The lower limit of the thickness of the second layer 3 is not particularly limited and may be, for example, 5 μm or more, 10 μm or more, or 15 μm or more. The upper limit of the thickness of the second layer 3 is not particularly limited and may be, for example, 35 μm or less, 30 μm or less, or 25 μm or less.

[0055] The conductive particle-containing hot melt adhesive sheet 1 (first layer 2 and / or second layer 3) may further contain additives other than the above-mentioned components, as long as the effects of the present technology are not impaired. For example, nano-sized silica (primary particle diameter of 1 nm or more and less than 1000 nm) may be dispersed in the conductive particle-containing hot melt adhesive sheet 1 to further improve gas barrier properties and elastic modulus. Furthermore, to more uniformly control the height of the solder particles after compression bonding, the conductive particle-containing hot melt adhesive sheet 1 may also be dispersed with spacer particles such as resin particles, rubber particles, silicone rubber particles, silica, etc. of a specified size. Furthermore, as long as the effects of the present technology are not impaired, the conductive particle-containing hot melt adhesive sheet 1 may also contain a thermosetting resin or a curing agent.

[0056] Furthermore, the conductive particle-containing hot melt adhesive sheet 1 may further include layers other than the first layer 2 and the second layer 3, as long as the effects of the present technology are not impaired. Furthermore, the conductive particle-containing hot melt adhesive sheet 1 may also be used for applications other than smart cards, and may be used, for example, as an anisotropic conductive film.

[0057] <Method for producing a conductive particle-containing hot melt adhesive sheet> Next, we will explain an example of a method for producing the conductive particle-containing hot melt adhesive sheet 1. The conductive particle-containing hot melt adhesive sheet 1 includes, for example, a step of preparing a first layer 2, a step of preparing a second layer 3, and a step of laminating the first layer 2 and the second layer 3. This results in a conductive particle-containing hot melt adhesive sheet 1 as shown in Fig. 1, for example.

[0058] The process of preparing the first layer 2 includes, for example, a process of preparing a varnish by dissolving a resin composition (binder) containing a crystalline polyamide resin having at least a carboxyl group in a solvent, and a process of applying the prepared varnish to a predetermined thickness on a release substrate and drying it.

[0059] The process of preparing the second layer 3 includes, for example, the steps of dissolving a resin composition (binder) containing at least a crystalline polyurethane resin and a carbodiimide compound in a solvent to prepare a varnish, adding conductive particles 4 to the prepared varnish to obtain a conductive particle-containing resin composition, and applying the conductive particle-containing resin composition to a predetermined thickness on a release substrate and drying it. Note that if the conductive particles 4 in the conductive particle-containing hot melt adhesive sheet 1 are to be arranged spaced apart or regularly, the second layer 3 can be prepared without adding the conductive particles 4, and the conductive particles 4 can be arranged separately by a known method.

[0060] In the step of laminating the first layer 2 and the second layer 3, for example, the first layer 2 and the second layer 3 are bonded together using a roll laminator at 80 to 100° C., a speed of 0.5 m / min, and a pressure of 0.5 MPa.

[0061] In the above-described method for producing the conductive particle-containing hot melt adhesive sheet 1, the conductive particles 4 are added to the varnish in the step of preparing the second layer 3, but the present invention is not limited to this example. For example, the conductive particles 4 may be added to the varnish in the step of preparing the first layer 2, but not in the step of preparing the second layer 3. Furthermore, for example, the conductive particles 4 may be added to the varnish in both the step of preparing the first layer 2 and the step of preparing the second layer 3.

[0062] The solvent used in the process of preparing the varnish is not particularly limited and can be selected appropriately depending on the purpose. For example, a mixed solvent of methyl ethyl ketone:toluene:cyclohexanone in a ratio of 50:40:10 (by mass), or a mixed solvent of toluene:ethyl acetate in a ratio of 50:50 (by mass), can be used.

[0063] Furthermore, examples of the releasable substrate include those having a contact angle with water of 80° or more. Specific examples of the releasable substrate include silicone-based films, fluorine-based films, silicone-based films, and PET, PEN, and glassine paper that have been treated with a release agent such as a fluorine-based release agent. The thickness of the releasable substrate is not particularly limited and can be appropriately selected depending on the purpose, and can be, for example, 20 to 120 μm.

[0064] The conductive particle-containing hot melt adhesive sheet 1 may also be in the form of a film wound around a core, for example, formed into a tape. The diameter of the core is not particularly limited and can be selected appropriately depending on the purpose, and can be, for example, 50 to 1000 mm. The film length is also not particularly limited; for example, a length of 5 m or more allows for easy trial production using manufacturing equipment, while a length of 1000 m or less does not impose excessive burdens on workability and handling.

[0065] <Smart card> The conductive particle-containing hot melt adhesive sheet 1 can be suitably used, for example, as an adhesive layer in a smart card comprising a card member, an IC chip, and an adhesive layer bonding the card member and the IC chip. For example, a smart card according to this embodiment comprises a card member, an IC chip, and an adhesive layer bonding the card member and the IC chip, the adhesive layer containing a reaction product of a crystalline polyamide resin having carboxyl groups and a carbodiimide compound, and conductive particles. The adhesive layer contains, for example, solder particles, which are a non-eutectic alloy, in the reaction product of a crystalline polyamide resin having carboxyl groups and a carbodiimide compound.

[0066] Fig. 2 is a schematic perspective view showing an example of a smart card, and Fig. 3 is a top view showing an example of an IC chip area of ​​a card member. The smart card includes, for example, a card member 10 and an IC chip 20. The card member 10 is, for example, a laminate formed by stacking a first substrate, a second substrate including an antenna, and a third substrate in this order. The IC chip 20 has, for example, multiple contact terminals 21 on its front surface and electrodes covering the entire back surface.

[0067] The card member 10 is not particularly limited, and can be made of a plastic material typically used for smart cards, such as PVC or PET. As described above, the smart card according to this embodiment uses the reaction product of the conductive particle-containing hot melt adhesive sheet 1 as an adhesive layer between the card member 10 and the IC chip 20, so that even when a PLA card is used, the adhesive strength between the PLA card and the IC chip 20 is good and the bending resistance is good.

[0068] The card member 10 has, for example, a Cu wire on its surface facing the IC chip 20. The IC chip 20 has, for example, an Au plating (Au / Ni plating as an example) on its surface facing the card member 10. In a smart card including the card member 10 having such a configuration, the IC chip 20, and an adhesive layer that bonds the card member 10 and the IC chip 20, for example, solder particles as conductive particles 4 contained in the adhesive layer form an intermetallic compound (solder joint) with the IC chip 20 side that is plated with Au, and also form an intermetallic compound with the Cu wire on the card member 10. Here, the solder joint on the IC chip 20 side is more likely to be brittle than the solder joint on the card member 10 side. In other words, the solder joint on the card member 10 side is stronger than the solder joint on the IC chip 20 side.

[0069] Therefore, from the viewpoint of protecting the solder joints on the IC chip 20 side, which tend to be relatively brittle, the adhesive layer in the smart card may have, for example, a crystalline polyamide resin having a carboxyl group reacted with a carbodiimide compound unevenly distributed on the IC chip 20 side. Also, the adhesive layer in the smart card may or may not have a crystalline polyurethane resin unevenly distributed on the card member 10 side. This crystalline polyurethane resin does not need to be reacted or cured.

[0070] <Smart card manufacturing method> Next, an example of a method for manufacturing a smart card will be described. In the method for manufacturing a smart card according to this embodiment, for example, the conductive particle-containing hot melt adhesive sheet 1 having the above-described first layer 2 and second layer 3 is interposed between the card member 10 and the IC chip 20 with the first layer 2 facing the IC chip 20, and then thermocompression bonded.

[0071] In this way, by interposing the conductive particle-containing hot melt adhesive sheet 1 between the card member 10 and the IC chip 20 and thermocompressing it so that the first layer 2 of the conductive particle-containing hot melt adhesive sheet 1 is on the IC chip 20 side, i.e., the second layer 3 is on the card member 10 side, even when a PLA card is used, the second layer 3 can strongly adhere the adhesive layer consisting of the reaction product of the conductive particle-containing hot melt adhesive sheet 1 to the PLA card.

[0072] Furthermore, by placing the first layer 2 of the conductive particle-containing hot melt adhesive sheet 1 between the card member 10 and the IC chip 20 with the first layer 2 facing the IC chip 20 and then thermocompressing the sheet, the first layer 2 and the second layer 3 mix together due to the flow that occurs during thermocompression, and the carboxyl groups in the carboxyl-containing crystalline polyamide resin in the first layer 2 react (crosslink) with the carbodiimide compound in the second layer 3, thereby further increasing the adhesive strength between the card member 10 and the IC chip 20 and increasing the strength of the smart card.

[0073] Thus, the method for manufacturing a smart card using the conductive particle-containing hot melt adhesive sheet 1 can improve the adhesive strength between the PLA card as the card member 10 and the IC chip 20, thereby improving the bending resistance of the smart card.

[0074] 2 to 5, a specific example of a method for manufacturing a smart card will be described below. The method for manufacturing a smart card 50 includes, for example, step A of attaching a conductive particle-containing hot melt adhesive sheet 1 to the connection surface of an IC chip 20, step B of placing the IC chip 20 in the IC chip area of ​​a card member 10, and step C of thermocompression bonding the IC chip 20 and the card member 10 together.

[0075] [Process A] 4 is a perspective view illustrating an example of a step of attaching a conductive particle-containing hot melt adhesive sheet 1 to the connection surface of an IC chip 20 in a method of manufacturing a smart card. In step A, for example, as shown in FIG. 4, the conductive particle-containing hot melt adhesive sheet 1 is attached to the connection surface (back surface) of the IC chip 20. As described above, the conductive particle-containing hot melt adhesive sheet 1 is attached to the connection surface of the IC chip 20 with the first layer 2 facing the IC chip 20, i.e., with the second layer 3 facing the card member 10.

[0076] The conductive particle-containing hot melt adhesive sheet 1 can be shaped to cover the first exposed portion 12a and the second exposed portion 12b of the antenna pattern 12 on the card member 10 and have a cutout in the center, as shown in Figure 4, for example.

[0077] Process A may be a lamination process in which the conductive particle-containing hot melt adhesive sheet 1 is laminated onto the connection surface of the IC chip 20, or may be a temporary attachment process in which the conductive particle-containing hot melt adhesive sheet 1 is attached to the connection surface of the IC chip 20 at low temperature.

[0078] When process A is a lamination process, either a pressure laminator or a vacuum pressure laminator may be used. By using a lamination process as process A, a relatively large area can be mounted at once compared to a temporary attachment process. In addition, when process A is a temporary attachment process, only minimal changes such as the installation or modification of tools from the previous equipment are required, which is economically advantageous.

[0079] In step A, the temperature reached by the conductive particle-containing hot melt adhesive sheet 1 is preferably equal to or higher than the temperature at which the binder (e.g., a carboxyl-containing crystalline polyamide resin or crystalline polyurethane resin) flows, but lower than the temperature at which the solder particles (conductive particles 4) melt. The temperature at which the binder flows may be, for example, a temperature at which the melt viscosity of the conductive particle-containing hot melt adhesive sheet 1 is 100 to 1,000,000 Pa·s, preferably 1,000 to 100,000 Pa·s. This allows the conductive particle-containing hot melt adhesive sheet 1 to be attached to the connection surface of the IC chip 20 while maintaining the shape of the solder particles. The melt viscosity of the conductive particle-containing hot melt adhesive sheet 1 can be measured, for example, using a rotational rheometer (manufactured by TA Instrument) under the following conditions: measurement pressure: 5 g; temperature range: 30 to 200°C; heating rate: 10°C / min; measurement frequency: 10 Hz; measurement plate diameter: 8 mm; and load fluctuation on the measurement plate: 5 g.

[0080] [Process B] In step B, for example, the IC chip 20 is picked up using a tool equipped with an adsorption mechanism, and the IC chip area of ​​the card member 10 is aligned with the IC chip 20 as shown in FIG. 4, and the IC chip 20 is placed via the conductive particle-containing hot melt adhesive sheet 1.

[0081] [Process C] 5 is a cross-sectional view illustrating an example of a step of thermocompression bonding an IC chip 20 and a card member 10 in a method for manufacturing a smart card 50. In step C, a pressure bonding device 30 is used to thermocompress the IC chip 20 and the card member 10. The number of thermocompression bonding operations in step C can be set according to the objects to be connected. For example, it may be one time, but multiple times is preferable. This allows the binder in the conductive particle-containing hot melt adhesive sheet 1 to be sufficiently removed, and the IC chip 20 and the first exposed portion 12a and second exposed portion 12b of the antenna pattern 12 can be more reliably metal-bonded by melting the solder particles.

[0082] The thermocompression bonding temperature in step C is preferably equal to or higher than the melting point of the solder particles (conductive particles 4) of the conductive particle-containing hot-melt adhesive sheet 1. Here, the melting point refers to the solidus temperature. That is, the thermocompression bonding temperature in step C is preferably equal to or higher than the solidus temperature of the solder particles. Here, the solidus is a curve showing the relationship between the temperature (melting point) of the liquid phase in equilibrium with the solid phase and the composition of the solid phase. Specifically, the temperature reached by the conductive particle-containing hot-melt adhesive sheet 1 is preferably 120 to 170°C, more preferably 120 to 155°C, and even more preferably 120 to 150°C. This further suppresses thermal shock to the card member 10 and the IC chip 20, thereby more effectively preventing deformation of the card member 10.

[0083] As described above, in the method for manufacturing the smart card 50, the conductive particle-containing hot melt adhesive sheet 1 is interposed between the card member 10 and the IC chip 20 with the first layer 2 facing the IC chip 20, i.e., the second layer 3 facing the card member 10, and then thermocompressed. As a result, even when a PLA card is used as the card member 10, the crystalline polyurethane resin in the second layer 3 allows the adhesive layer 40 made of the reaction product of the conductive particle-containing hot melt adhesive sheet 1 to be strongly bonded to the card member 10.

[0084] In addition, the manufacturing method of the smart card 50 is such that the first layer 2 of the conductive particle-containing hot melt adhesive sheet 1 faces the IC chip 20, and is interposed between the card member 10 and the IC chip 20, and then thermocompressed to further increase the adhesive strength between the card member 10 and the IC chip 20, thereby increasing the strength of the smart card 50.

[0085] Thus, according to the method for manufacturing a smart card 50 using a conductive particle-containing hot melt adhesive sheet 1, the adhesive strength between the PLA card as the card member 10 and the IC chip 20 can be improved, and the bending resistance of the smart card 50 can be improved. [Example]

[0086] In this example, a conductive particle-containing hot melt adhesive sheet containing solder particles was prepared, and a smart card was produced using this sheet. The initial adhesive strength between the card member and the IC module (IC chip) in the smart card was then evaluated, and the smart card's bending test and wet heat reliability were evaluated. However, this example is not limited to these.

[0087] [Preparation of solder particles] The metal materials were placed in a heated container in a predetermined compounding ratio, melted, and then cooled to obtain a solder alloy. Powder was produced from the solder alloy by atomization, and the powder was classified to have a particle size in the range of 25 to 45 μm, obtaining solder particles with the following composition. ·Type 3 (particle size 25~45μm, IPC standard J-STD 005) Sn-40Bi (non-eutectic, solidus temperature: 139℃, liquidus temperature: 167℃)

[0088] [Preparation of conductive particle-containing hot melt adhesive sheet] The following compounds were prepared for the conductive particle-containing hot melt adhesive sheet. Platamid HX2592 (Arkema, crystalline polyamide resin with carboxyl groups) Aronmelt PES-111EE (crystalline polyester resin, manufactured by Toagosei Co., Ltd.) Pearlstick 40-70 / 33 (Lubrizol, crystalline polyurethane resin) Pearlstick 40-70 / 03 (Lubrizol, crystalline polyurethane resin) Pearlthane D12F75 (Amorphous polyurethane resin, manufactured by Lubrizol) Carbodilite V-02B (Nisshinbo Chemical Co., Ltd., carbodiimide compound)

[0089] <Examples 1 to 5 and Comparative Examples 1 to 6> [First layer] The compounds shown in Tables 1 and 2 were mixed and stirred to give the prescribed solid content (parts by mass) to obtain a mixed varnish for the first layer 2. The obtained mixed varnish for the first layer 2 was applied to a 50 μm thick PET film so that the average thickness after drying would be 20 μm, thereby obtaining the first layer 2.

[0090] [Second layer] The compounds shown in Tables 1 and 2 were mixed and stirred to a predetermined blend amount (parts by mass) in terms of solid content, to obtain a mixed varnish for the second layer 3. Next, 100 parts by mass of solder particles as conductive particles 4 per 100 parts by mass of the solid content of the mixed varnish for the second layer 3 was added to the obtained mixed varnish for the second layer 3, to obtain a conductive particle-containing resin composition. The obtained conductive particle-containing resin composition was applied to a 50 μm thick PET film so that the average thickness of the resin after drying (the average thickness of the resin portion excluding the conductive particles 4) would be 20 μm, to obtain the second layer 3.

[0091] The first layer 2 and the second layer 3 were bonded together using a roll laminate at a speed of 0.5 m / min at 80 to 100°C and a pressure of 0.5 MPa to produce a two-layer structure conductive particle-containing hot melt adhesive sheet 1 consisting of the first layer 2 and the second layer 3.

[0092] <Comparative Examples 7 to 9> In Comparative Examples 7 to 9, the compounds shown in Table 3 were mixed and stirred to the prescribed solid content (parts by mass) to obtain a mixed varnish. Subsequently, approximately 100 parts by mass of conductive particles 4 were added to the obtained mixed varnish per 100 parts by mass of the solid content of the mixed varnish to obtain a conductive particle-containing resin composition. The obtained conductive particle-containing resin composition was applied to a 50 μm-thick PET film so that the average thickness after drying would be 40 μm, producing a single-layer conductive particle-containing hot-melt adhesive sheet.

[0093] [Smart card creation] A dual interface PVC card (manufactured by Shoei Printing Co., Ltd.) with Cu wires arranged thereon was used as the card member 10 for the bending test. The Cu wires were exposed in the IC chip area of ​​this card member 10. A 6-pin IC module (manufactured by Wisecard Co., Ltd.) was used as the IC chip 20 for the bending test.

[0094] A PLA card without Cu wire (manufactured by Shenzhen Union Smart Card Co., Ltd.) or a dual interface PVC card with Cu wire (manufactured by Shoei Printing Co., Ltd.) was used as the card member 10 for adhesive strength evaluation or moist heat reliability evaluation. A 6-pin IC module (manufactured by Wisecard Co., Ltd.) was used as the IC chip 20 for adhesive strength evaluation or moist heat reliability evaluation.

[0095] The conductive particle-containing hot melt adhesive sheet 1 or a single-layer conductive particle-containing hot melt adhesive sheet was laminated onto the connection surface of an IC module at 3 bar. The IC module with the conductive particle-containing hot melt adhesive sheet 1 or the single-layer conductive particle-containing hot melt adhesive sheet attached was then placed on the IC chip area of ​​the card member 10, and thermocompression bonding was performed four times at 1.0 second intervals at 230°C and 90 N for 0.7 seconds to produce a smart card 50 of the example and a smart card of the comparative example.

[0096] [Adhesion strength between card material and IC module (initial)] The initial adhesive strength between the card material (PLA card or PVC card) and the IC module of the fabricated smart cards was evaluated in accordance with ISO 24789-2 "Adhesion of ICM to card-push test." An adhesive strength of 100 N or more was evaluated as OK for the initial adhesive strength, and an adhesive strength of less than 100 N was evaluated as NG for the initial adhesive strength. The results are shown in Tables 1 to 3. In the tables, "evaluation not possible" means that the viscosity of the resin composition (conductive particle-containing resin composition) had increased too much, making it difficult to apply it in a sheet (layer), and therefore evaluation of the initial adhesive strength was not possible.

[0097] [Bending test] According to ISO 10373-1 Dynamic Bending Stress, a periodic bending force was applied to the smart card at a specified strength and direction. Then, for the smart card after 4000 cycles of bending test, the Q value was measured using a resonance frequency checker MP300CL3 (manufactured by Micropross). A decrease in the Q value of 50% or more was evaluated as "NG," meaning that the smart card had poor bending resistance. Otherwise, the evaluation was evaluated as "OK," meaning that the smart card had good bending resistance. The results are shown in Tables 1 to 3. In the tables, "cannot be evaluated" means that the viscosity of the resin composition (conductive particle-containing resin composition) was too high to apply it in a sheet (layer), making it impossible to evaluate the bending test.

[0098] [Heat and humidity reliability] After a moist heat test (120 hours at 50°C and 95% RH) in accordance with ISO 24789-1 "Standalone Test Methods, Temperature and Humidity Aging," the smart cards were evaluated for adhesive strength (moisture and heat reliability) between the card material (PLA card or PVC card) and the IC module in accordance with ISO 24789-2 "Adhesion of ICM to card-push test." An adhesive strength of 50 N or greater was evaluated as OK for moist heat reliability, and an adhesive strength of less than 50 N was evaluated as NG for moist heat reliability. The results are shown in Tables 1 to 3. In the tables, "evaluation not possible" indicates that the viscosity of the resin composition (conductive particle-containing resin composition) was too high to apply it in a sheet (layer), making it impossible to evaluate the moist heat reliability.

[0099] [Table 1]

[0100] [Table 2]

[0101] [Table 3]

[0102] In Examples 1 to 5, a conductive particle-containing hot melt adhesive sheet 1 was used that included a first layer 2 containing 40% by mass or more of a crystalline polyamide resin having a carboxyl group, and a second layer 3 containing a crystalline polyurethane resin and a carbodiimide compound, with the crystalline polyurethane resin content exceeding 10% by mass and the carbodiimide compound content being less than 15% by mass relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound. As a result, the adhesive strength between the card member 10 and the IC chip 20 (IC module), i.e., the initial adhesive strength and the adhesive strength after exposure to a high-temperature, high-humidity environment, was good, and the bending resistance of the smart card 50 was also good. In particular, in Examples 1 to 5, the adhesive strength (humid heat reliability) between the PLA card and the IC chip 20 was good even after the smart card including the PLA card was exposed to a high-temperature, high-humidity environment.

[0103] In Comparative Example 1, a conductive particle-containing hot melt adhesive sheet that did not contain a carbodiimide compound was used, and therefore the moist heat reliability of the smart card equipped with a PLA card was found to be poor. This is thought to be because the carboxyl-containing crystalline polyamide resin in the first layer of the conductive particle-containing hot melt adhesive sheet did not crosslink, and the water resistance of the crystalline polyurethane resin was not sufficiently improved. Furthermore, it was found that the bending resistance of the smart card in Comparative Example 1 was also poor. This is thought to be because the carboxyl-containing crystalline polyamide resin in the first layer of the conductive particle-containing hot melt adhesive sheet did not crosslink, and therefore sufficient strength was not obtained.

[0104] In Comparative Example 2, a conductive particle-containing hot melt adhesive sheet was used that had a second layer in which the carbodiimide compound content was 15% by mass or more relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound, and it was found that the moist heat reliability of the smart card equipped with a PLA card was poor. One possible reason for this is that the content of the carbodiimide compound in the second layer of the conductive particle-containing hot melt adhesive sheet was too high, causing unreacted carbodiimide compound to bleed out after the moist heat reliability test.

[0105] In Comparative Example 3, a conductive particle-containing hot melt adhesive sheet was used that had a first layer with a carboxyl group-containing crystalline polyamide resin content of less than 40% by mass, and therefore the adhesive strength between the card member 10 and the IC chip 20 (initial adhesive strength and adhesive strength after exposure to a high-temperature, high-humidity environment) was poor, and the bending resistance of the smart card was also poor. In Comparative Example 3, the content of carboxyl group-containing crystalline polyamide resin in the first layer of the conductive particle-containing hot melt adhesive sheet was too low, which is thought to be one of the reasons for this, for example, the poor adhesion of the adhesive layer to the IC chip 20 and the low amount of crosslinked crystalline polyamide resin.

[0106] In Comparative Example 4, a conductive particle-containing hot melt adhesive sheet was used that had a second layer in which the content of crystalline polyurethane resin was 10% by mass or less relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound, and therefore it was found that the adhesive strength (initial adhesive strength and adhesive strength after being left in a high-temperature, high-humidity environment) between the PLA card as the card member 10 and the IC chip 20 was poor. In Comparative Example 4, for example, one possible reason for this is that the content of crystalline polyurethane resin in the second layer of the conductive particle-containing hot melt adhesive sheet was too low, resulting in poor adhesion of the adhesive layer to the PLA card.

[0107] Comparative Example 5 used a conductive particle-containing hot melt adhesive sheet having a second layer in which the content of crystalline polyurethane resin was 10% by mass or less relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound, in other words, a conductive particle-containing hot melt adhesive sheet having a second layer that did not contain a crystalline polyurethane resin but contained an amorphous polyurethane resin, and therefore it was found that the adhesive strength (initial adhesive strength and adhesive strength after being left in a high-temperature, high-humidity environment) between the PLA card and the IC chip 20 was poor. In Comparative Example 5, one possible reason for this is that, because the second layer did not contain a crystalline polyurethane resin but contained an amorphous polyurethane resin, for example, the wettability to the PLA card was poor after short-term pressure bonding.

[0108] In Comparative Example 6, the layer containing 40% by mass or more of a crystalline polyamide resin having carboxyl groups was positioned on the card member 10 side, in other words, the conductive particle-containing hot melt adhesive sheet 1 was interposed between the card member 10 and the IC chip 20. Therefore, it was found that the adhesive strength between the card member 10 and the IC chip 20 (initial adhesive strength and adhesive strength after being left in a high-temperature, high-humidity environment) was not good, and the bending resistance of the smart card was also not good. One possible reason for this in Comparative Example 6 is thought to be, for example, the weakened adhesion of the adhesive layer to the card member 10 side and the IC chip 20 side.

[0109] In Comparative Example 7, a mixture of a crystalline polyamide resin having carboxyl groups, a carbodiimide compound, and conductive particles 4 was used as the composition for the conductive particle-containing hot melt adhesive sheet, but the viscosity of the mixture increased too much to apply to a sheet, making it difficult to perform any evaluation. In Comparative Example 7, one possible reason for this is that, for example, the crystalline polyamide resin having carboxyl groups and the carbodiimide compound reacted during mixing, causing the viscosity of the mixture to increase too much, making it impossible to apply.

[0110] In Comparative Example 8, a single-layer conductive particle-containing hot melt adhesive sheet consisting of a mixture of crystalline polyamide resin having carboxyl groups and conductive particles was used, and it was found that the adhesive strength between the PLA card and the IC chip 20 (initial adhesive strength and adhesive strength after being left in a high-temperature, high-humidity environment) was not good.

[0111] In Comparative Example 9, a single-layer conductive particle-containing hot melt adhesive sheet consisting of a mixture of crystalline polyurethane resin, a carbodiimide compound, and conductive particles was used, and it was found that the adhesive strength between the card member 10 and the IC chip 20 (initial adhesive strength and adhesive strength after being left in a high-temperature, high-humidity environment) was not good, and the bending resistance of the smart card was also not good. [Explanation of symbols]

[0112] 1. A hot melt adhesive sheet containing conductive particles, 2 1st layer, 3 2nd layer, 4 conductive particles, 10 card member, 11 aperture, 12 Antenna patterns, 12a first exposed portion; 12b second exposed portion; 20 IC chips, 21 contact terminal, 30 crimping device, 40 adhesive layer, 50 Smart Cards

Claims

1. a first layer containing 40% by mass or more of a crystalline polyamide resin having a carboxyl group; a second layer containing a crystalline polyurethane resin and a carbodiimide compound; Equipped with a conductive particle-containing hot melt adhesive sheet, wherein in the second layer, the content of the crystalline polyurethane resin is more than 10 mass % and the content of the carbodiimide compound is less than 15 mass % relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound.

2. 2. The conductive particle-containing hot melt adhesive sheet according to claim 1, wherein the conductive particles are solder particles that are a non-eutectic alloy having a solidus temperature of 155°C or less.

3. 3. The conductive particle-containing hot melt adhesive sheet according to claim 1, wherein the content of the carbodiimide compound in the second layer is 0.1 mass% or more relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound.

4. A method for manufacturing a smart card, comprising: a first layer containing 40% by mass or more of a crystalline polyamide resin having a carboxyl group; and a second layer containing a crystalline polyurethane resin and a carbodiimide compound, wherein the content of the crystalline polyurethane resin in the second layer is more than 10% by mass and the content of the carbodiimide compound is less than 15% by mass relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound, and the conductive particle-containing hot melt adhesive sheet is interposed between a card member and the IC chip so that the first layer faces the IC chip, and then thermocompression bonded.

5. 5. The method for manufacturing a smart card according to claim 4, wherein the conductive particles are solder particles that are a non-eutectic alloy having a solidus temperature of 155[deg.] C. or less.

6. 6. The method for producing a smart card according to claim 4, wherein the content of the carbodiimide compound in the second layer is 0.1% by mass or more relative to the total mass of the crystalline polyurethane resin and the carbodiimide compound.

7. A card member; An IC chip, an adhesive layer that bonds the card member and the IC chip; A smart card, wherein the adhesive layer contains a reaction product of a crystalline polyamide resin having a carboxyl group with a carbodiimide compound, and conductive particles.

8. 8. The smart card of claim 7, wherein the adhesive layer further comprises a crystalline polyurethane resin.

9. a card member, an IC chip, and an adhesive layer that bonds the card member and the IC chip; A smart card, wherein the adhesive layer comprises the conductive particle-containing hot-melt adhesive sheet according to claim 1 or 2.

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