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

Abstract

Provided is a hot-melt adhesive sheet containing conductive particles that can improve the adhesive strength of a card member and an IC chip, and that can improve the moisture and heat reliability and the bending resistance of a smart card.　A hot-melt adhesive sheet 1 containing conductive particles comprises: a first layer 2 that contains 50 mass% or more a crystalline polyamide resin having a carboxyl group, and that has a storage modulus of 150 MPa or greater at 50°C; a crystalline polyester resin; and a second layer 3 that contains an amorphous polyester resin and that has a storage modulus of 30 MPa or greater at 50°C. The hot-melt adhesive sheet 1 containing conductive particles contains conductive particles 4.

Description

Conductive particle-containing hot melt adhesive sheet, smart card manufacturing method, and smart card

[0001] This application claims priority from Japanese Patent Application No. 2024-105795, filed on June 28, 2024, which is incorporated herein by reference.

[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] A smart card is formed by laminating, for example, a plastic plate made of various resins as a core, a film on which an antenna wiring is printed, a film with a printed surface, etc. A recess is formed by milling a portion 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] Traditionally, plastics used in smart cards have included PVC (Polyvinyl Chloride) and PET (Polyethylene terephthalate). However, due to recent demands for reducing environmental impact, there has been an increase in the use of resins with better biodegradability, recycled resins, and recyclable resins. Examples of such resins include recycled PET (hereinafter also referred to as recycled PET) and polylactic acid (PLA). Adhesives used in conventional smart cards (see, for example, Patent Document 1) tend to have low adhesive strength to recycled PET and polylactic acid, in other words, poor adhesion.

[0005] On the other hand, adhesives for smart cards have been developed, for example, by forming two layers of adhesive corresponding to the area to be attached, with the composition being adjusted according to the area to be attached (see, for example, Patent Document 2). However, the adhesive film described in Patent Document 2 is considered to be insufficient as an adhesive for mounting an IC chip to a card member, for example, in smart cards using recycled PET or polylactic acid.

[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 smart cards, which are mass-produced.

[0007] In particular, adhesives for smart cards are desirable that can improve the adhesive strength between, for example, recycled PET cards (eco-friendly cards) and IC chips, and that can improve the moist heat reliability and bending resistance of smart cards that include card members made of recycled PET. Here, moist heat reliability 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, for example.

[0008] Patent No. 6966659 Publication Special Publication No. 2007-514006 Publication Special Publication No. 2022-515327

[0009] The present technology has been proposed in consideration of the above-described conventional situation, and provides a hot melt adhesive sheet containing conductive particles that can improve the adhesive strength between the card member and the IC chip, and can improve the wet heat reliability and bending resistance of the smart card.

[0010] The conductive particle-containing hot melt adhesive sheet according to the present technology comprises a first layer containing 50 mass % or more of a crystalline polyamide resin having a carboxyl group and having a storage modulus of 150 MPa or more at 50°C, and a second layer containing a crystalline polyester resin and an amorphous polyester resin and having a storage modulus of 30 MPa or more at 50°C.

[0011] The method for manufacturing a smart card according to the present technology involves interposing a conductive particle-containing hot melt adhesive sheet between an IC chip and a card member, and thermocompression bonding the sheet and the card member, the conductive particle-containing hot melt adhesive sheet comprising: a first layer containing 50% by mass or more of a crystalline polyamide resin having a carboxyl group and having a storage modulus of 150 MPa or more at 50°C; and a second layer containing a crystalline polyester resin and an amorphous polyester resin and having a storage modulus of 30 MPa or more at 50°C.

[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, and the adhesive layer contains a mixture of a crystalline polyamide resin having a carboxyl group, a crystalline polyester resin, and an amorphous polyester resin, and conductive particles.

[0013] 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 being made of a conductive particle-containing hot melt adhesive sheet, the conductive particle-containing hot melt adhesive sheet comprising a first layer that contains 50% or more of a crystalline polyamide resin and has a storage modulus of 150 MPa or more at 50°C, and a second layer that contains a crystalline polyester resin and an amorphous polyester resin and has a storage modulus of 30 MPa or more at 50°C.

[0014] This technology can improve the adhesive strength between the card member and the IC chip, and can improve the wet heat reliability and bending resistance of the smart card.

[0015] Fig. 1 is a cross-sectional view showing an example of a conductive particle-containing hot melt adhesive sheet. Fig. 2 is a schematic perspective view showing an example of a smart card. Fig. 3 is a top view showing an example of an IC chip region of a card member. 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. 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. Fig. 6 is an electron microscope photograph showing an example of a cross-section of a smart card obtained in Comparative Example 2.

[0016] <Conductive Particle-Containing Hot Melt Adhesive Sheet> Figure 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 includes a first layer 2 (hereinafter simply referred to as "first layer 2") containing 50% by mass or more of a crystalline polyamide resin having a carboxyl group and having a storage modulus of 150 MPa or more at 50°C, and a second layer 3 (hereinafter simply referred to as "second layer 3") containing a crystalline polyester resin and an amorphous polyester resin and having a storage modulus of 30 MPa or more at 50°C. The conductive particle-containing hot melt adhesive sheet 1 contains conductive particles 4. In this specification, carboxyl group-containing crystalline polyamide resins, crystalline polyester resins, amorphous polyester resins, crystalline polyurethane resins, and the like are collectively referred to as binders.

[0017] Thus, the conductive particle-containing hot melt adhesive sheet 1 comprises a first layer 2 whose main component is a crystalline polyamide resin having a carboxyl group and whose lower limit of storage modulus is relatively high, and a second layer 3 whose main components are a crystalline polyester resin and an amorphous polyester resin and whose lower limit of storage modulus is relatively low. By comprising the first layer 2 and the second layer 3, which have different functions, the conductive particle-containing hot melt adhesive sheet 1 can more easily balance its properties than a single-layer structure.

[0018] The first layer 2 has good adhesion to the IC chip (e.g., glass epoxy resin in an IC module) 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. The second layer 3 also has good adhesion to the card member in a smart card, particularly to a card member (e.g., a recycled PET card) that uses recycled PET as its core material. Therefore, for example, when the conductive particle-containing hot melt adhesive sheet 1 is used as an adhesive layer in a smart card, good adhesion can be achieved between the card member and the IC chip.

[0019] "Good adhesive strength between the card member and the IC chip" means 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). "Good moist heat reliability" of the smart card 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. By using the conductive particle-containing hot melt adhesive sheet 1, it is possible to improve the moist heat reliability, particularly of smart cards that have card members made of recycled PET.

[0020] 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.

[0021] Furthermore, by providing the conductive particle-containing hot melt adhesive sheet 1 with the first layer 2 and the second layer 3, it is possible to improve the bending resistance, particularly the bending resistance in a high-temperature environment, of a smart card having a card member made of recycled PET. Here, "good bending resistance" of a smart card means that the result of a bending test of the smart card evaluated by the method described in the Examples below is good (OK).

[0022] For example, when the conductive particle-containing hot melt adhesive sheet 1 is used as an adhesive layer in a smart card having a card member made of recycled PET, the conductive particle-containing hot melt adhesive sheet 1 preferably 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 and good bending resistance of the smart card when the conductive particle-containing hot melt adhesive sheet 1 is used as an adhesive layer in the smart card.

[0023] In contrast, for example, a conductive particle-containing hot melt adhesive sheet consisting of only the first layer 2 or a conductive particle-containing hot melt adhesive sheet consisting of only the second layer 3 makes it difficult to improve the adhesive strength between a card member made of recycled PET and an IC chip, and the bending resistance of a smart card equipped with a card member made of recycled PET in a high-temperature environment.

[0024] 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 allows the conductive particle-containing hot melt adhesive sheet 1 to be suitably used, for example, in the manufacture of smart cards.

[0025] 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, the second layer 3, or both the first layer 2 and the second layer 3, as shown in Figure 1 .

[0026] 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 refers to 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.

[0027] 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. Furthermore, 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.

[0028] 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.

[0029] 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, 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.

[0030] If the solder particle content is too low, it is difficult to obtain excellent conductivity. On the other hand, if the solder particle content is too high, it is 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 or compounding ratio of the compound.

[0031] 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.

[0032] 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.

[0033] 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 melting of the solder particles can more reliably form a metal bond between the conductive portions.

[0034] 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.

[0035] Here, the average particle size is the average value of the 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, electron microscope such as SEM (Scanning Electron Microscope), or the like, and in the case of spherical particles, it is the average value of the diameter of the particles. Alternatively, the observed image may 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 distribution analyzer (for example, FPIA-3000 (manufactured by Malvern Instruments)). The average particle size determined from the observed image or image-based particle size distribution analyzer may be the average value of the maximum length of the particles. When producing the conductive particle-containing hot melt adhesive sheet 1, it is possible to use manufacturer values ​​such as the particle size (D50) at which the cumulative frequency in the particle size distribution determined by a simple laser diffraction / scattering method is 50%, and the arithmetic mean diameter (preferably on a volume basis).

[0036] 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.

[0037] [First Layer] The first layer 2 contains 50% by mass or more of a crystalline polyamide resin having a carboxyl group, and has a storage modulus of 150 MPa or more at 50° C. By providing the first layer 2 with this configuration, for example, it is possible to improve the adhesive strength between the recycled PET card and the IC chip, and to improve the moist heat reliability and bending resistance of a smart card including a card member using recycled PET.

[0038] 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.

[0039] The terminal carboxyl group concentration of the crystalline polyamide resin is not particularly limited and can be, for example, 0.5 mgKOH / g or more, 1.0 mgKOH / g or more, or 2.0 mgKOH / g or more. The terminal carboxyl group concentration of the crystalline polyamide resin can be, for example, 50 mgKOH / g or less, 30 mgKOH / g or less, or 10 mgKOH / 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 "HX2592" manufactured by Arkema.

[0040] The content of the carboxyl group-containing crystalline polyamide resin in the first layer 2 is 50% by mass or more. As a result, when 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.

[0041] The content of the carboxyl group-containing crystalline polyamide resin in the first layer 2 may be 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 50 to 100% by mass. The carboxyl group-containing crystalline polyamide resin in the first layer 2 may be used alone or in combination with two or more types. When two or more types of carboxyl group-containing crystalline polyamide resins are used in combination, it is preferable that the total amount thereof satisfy 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.

[0042] 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 or an amorphous resin, 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 temperatures and in a short time.

[0043] 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 is preferably 50% by mass or less, from the viewpoint of achieving a storage modulus of 150 MPa or more at 50°C of the first layer 2, and may be 45% by mass or less, 40% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, or in the range of 25 to 50% by mass. The crystalline polyester resin may be used alone, or two or more types may be used in combination. When two or more types of 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.

[0044] The first layer 2 has a storage modulus of 150 MPa or more at 50°C. This allows for improved adhesive strength between the card member and the IC chip. The first layer 2 may have a storage modulus of 160 MPa or more, 170 MPa or more, 180 MPa or more, 190 MPa or more, 200 MPa or more, 210 MPa or more, 220 MPa or more, 230 MPa or more, 240 MPa or more, or 250 MPa or more at 50°C. For example, from the viewpoint of improving adhesive strength between the card member and the IC chip, the first layer 2 preferably has a storage modulus of 200 MPa or more at 50°C.

[0045] The upper limit of the storage modulus of the first layer 2 at 50°C is not particularly limited and may be, for example, 300 MPa or less, 280 MPa or less, 270 MPa or less, 260 MPa or less, or 250 MPa or less. The storage modulus of the first layer 2 at 50°C may be in the range of 150 to 250 MPa, or in the range of 200 to 250 MPa. The storage modulus of the first layer 2 at 50°C is a value measured by the method described in the Examples section below.

[0046] The lower limit of the thickness of the first layer 2 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 first layer 2 is not particularly limited and may be, for example, 35 μm or less, 30 μm or less, or 25 μm or less.

[0047] [Second Layer] The second layer 3 contains at least a crystalline polyester resin and an amorphous polyester resin, and has a storage modulus of 30 MPa or more at 50° C. Such a configuration of the second layer 3 can, for example, improve the adhesive strength between the recycled PET card and the IC chip, and improve the moist heat reliability and bending resistance of a smart card including a card member using recycled PET.

[0048] On the other hand, if the second layer 3 does not contain a crystalline polyester resin or an amorphous polyester resin, or if the storage modulus of the second layer 3 at 50°C is less than 30 MPa, it becomes difficult to improve the wet heat reliability and bending resistance of a smart card having a card member made of recycled PET, for example.

[0049] Furthermore, if the second layer 3 does not contain, for example, a crystalline polyester resin, it will be difficult to improve the bending resistance of a smart card that includes a card member made of recycled PET.

[0050] Furthermore, if the second layer 3 does not contain, for example, an amorphous polyester resin, it becomes difficult to improve the wet heat reliability of a smart card including a card member made of recycled PET.

[0051] Whether the second layer 3 contains a crystalline polyester resin and an amorphous polyester resin can be confirmed, for example, by observing an endothermic peak during the temperature rise process in differential scanning calorimetry. A specific example of a commercially available crystalline polyester resin is Aronmelt PES-111EE (a crystalline polyester resin manufactured by Toagosei Co., Ltd.). A specific example of an amorphous polyester resin is Elitel UE3500 (manufactured by Unitika Ltd.).

[0052] The content of the crystalline polyester resin in the second layer 3 may be, for example, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more, preferably 30% by mass or more, relative to the total mass of the crystalline polyester resin, amorphous polyester resin, and crystalline polyurethane resin in the second layer 3. Furthermore, the content of the crystalline polyester resin in the second layer 3 may be, for example, 50% by mass or less, 45% by mass or less, or in the range of 25 to 50% by mass, 30 to 50% by mass, or 30 to 40% by mass, relative to the total mass of the crystalline polyester resin, amorphous polyester resin, and crystalline polyurethane resin in the second layer 3. The content of the crystalline polyester resin may be based on the total mass of the second layer 3 excluding the conductive particles 4 or the total mass of the resin in the second layer 3. In this case, the preferred range of the content of the crystalline polyester resin is the same as the numerical range described above.

[0053] The content of the amorphous polyester resin in the second layer 3 may be, for example, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more, preferably 30% by mass or more, relative to the total mass of the crystalline polyester resin, amorphous polyester resin, and crystalline polyurethane resin in the second layer 3. The content of the amorphous polyester resin in the second layer 3 may be, for example, 50% by mass or less, 45% by mass or less, or 40% by mass or less, or may be in the range of 25 to 50% by mass, 30 to 50% by mass, or 30 to 40% by mass, relative to the total mass of the crystalline polyester resin, amorphous polyester resin, and crystalline polyurethane resin in the second layer 3. The content of the amorphous polyester resin may be based on the total mass of the second layer 3 excluding the conductive particles 4 or the total mass of the resin in the second layer 3. In this case, the preferred range of the content of the amorphous polyester resin is the same as the above-mentioned numerical range.

[0054] The second layer 3 preferably contains a crystalline polyurethane resin in addition to the crystalline polyester resin and the amorphous polyester resin, and the content of the crystalline polyurethane resin is preferably more than 10% by mass relative to the total mass of the crystalline polyester resin, the amorphous polyester resin, and the crystalline polyurethane resin. Such a configuration of the second layer 3 can improve the adhesive strength between a PLA card and an IC chip, for example.

[0055] When the second layer 3 contains a crystalline polyurethane resin, the content of the crystalline polyurethane resin in the second layer 3 may be, for example, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more, preferably 20% by mass or more, relative to the total mass of the crystalline polyester resin, amorphous polyester resin, and crystalline polyurethane resin in the second layer 3. Furthermore, the content of the crystalline polyurethane resin in the second layer 3 may be, for example, less than 50% by mass, 45% by mass or less, or in the range of 20 to 40% by mass, relative to the total mass of the crystalline polyester resin, amorphous polyester resin, and crystalline polyurethane resin in the second layer 3. The crystalline polyurethane resin may be used alone, or two or more types may be used in combination. 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 or the total mass of the resin in the second layer 3. In this case, the preferred range of the content of the crystalline polyurethane resin is the same as the above-mentioned numerical range.

[0056] 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. A specific example of a commercially available crystalline polyurethane resin is "HK6503" manufactured by Henan Huike New Material Technology Co., Ltd.

[0057] As described above, the second layer 3 has a storage modulus of 30 MPa or more at 50°C. This can improve the moist heat reliability and bending resistance of, for example, a smart card including a card member made of recycled PET. The second layer 3 may have a storage modulus of 35 MPa or more, 40 MPa or more, 45 MPa or more, 50 MPa or more, 55 MPa or more, 60 MPa or more, 65 MPa or more, or 70 MPa or more at 50°C. The upper limit of the storage modulus of the second layer 3 at 50°C is not particularly limited and may be, for example, 200 MPa or less, 150 MPa or less, 100 MPa or less, 80 MPa or less, 75 MPa or less, or 70 MPa or less. The storage modulus of the second layer 3 at 50°C may be, for example, in the range of 30 to 45 MPa or 35 to 40 MPa. The storage modulus of the second layer 3 at 50° C. is a value measured by the method described in the examples below.

[0058] The second layer 3 may further contain, as necessary, a resin other than the crystalline polyester resin, the amorphous polyester resin, and the crystalline polyurethane resin, as long as the effect of the present technology is not impaired. The other resin may be, for example, a crystalline resin, an amorphous resin, or the like, and may be appropriately selected depending on the purpose. The other resin may be used alone or in combination of two or more.

[0059] 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.

[0060] 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.

[0061] 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 be used for applications other than smart cards, and may be used, for example, as an anisotropic conductive film.

[0062] <Method of Manufacturing Conductive Particle-Containing Hot Melt Adhesive Sheet> Next, a description will be given of an example of a method of manufacturing 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.

[0063] The process of preparing the first layer 2 includes, for example, the steps of dissolving a resin composition (binder) containing at least a crystalline polyamide resin having carboxyl groups 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.

[0064] The process of preparing the second layer 3 includes, for example, a process of preparing a varnish by dissolving a resin composition (binder) containing a crystalline polyester resin and an amorphous polyester resin in a solvent, and a process of applying the prepared varnish to a predetermined thickness on a release substrate and drying it.

[0065] The step of laminating the first layer 2 and the second layer 3 is, for example, performed by using a roll laminator to bond the first layer 2 and the second layer 3 together at a temperature of 80 to 100°C, a speed of 0.5 m / min, and a pressure of 0.5 MPa.

[0066] 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.

[0067] 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 at a ratio of 50:40:10 (by mass), or a mixed solvent of toluene:ethyl acetate at a ratio of 50:50 (by mass), can be used.

[0068] Furthermore, examples of the release substrate include those having a contact angle with water of 80° or more. Specific examples of the release substrate include silicone-based films, fluorine-based films, silicone-based films, PET, PEN, glassine paper, and the like that have been treated with a release agent such as a fluorine-based release agent. The thickness of the release substrate is not particularly limited and can be appropriately selected depending on the purpose, and can be, for example, 20 to 120 μm.

[0069] 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.

[0070] <Smart Card> The conductive particle-containing hot melt adhesive sheet 1 can be suitably used as an adhesive layer in a smart card, for example, 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 mixture of a carboxyl-containing crystalline polyamide resin, a crystalline polyester resin, and an amorphous polyester resin, and conductive particles. The adhesive layer contains, for example, solder particles that are a non-eutectic alloy in a mixture of a carboxyl-containing crystalline polyamide resin, a crystalline polyester resin, and an amorphous polyester resin. In particular, the smart card according to this embodiment preferably comprises a card member, an IC chip, and an adhesive layer bonding the card member and the IC chip, the adhesive layer being made of the conductive particle-containing hot melt adhesive sheet 1 described above.

[0071] 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 on the entire back surface.

[0072] The card member 10 is not particularly limited, and can be made of a plastic material typically used for smart cards, such as PVC, PET, PLA, etc. Furthermore, as described above, the smart card according to this embodiment uses the conductive particle-containing hot melt adhesive sheet 1 as an adhesive layer between the card member 10 and the IC chip 20. Therefore, even when a card member 10 made of recycled PET is used, the adhesive strength between the card member 10 made of recycled PET and the IC chip 20 is good, and the bending resistance is also good.

[0073] The card member 10 includes, for example, a Cu wire on the surface facing the IC chip 20. The IC chip 20 includes, for example, an Au plating (Au / Ni plating, for example) on the 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 bonding 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 Au-plated IC chip 20, 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.

[0074] The smart card according to the present embodiment uses the above-described conductive particle-containing hot melt adhesive sheet 1 as an adhesive layer, thereby preventing the resin constituting the adhesive layer from becoming easily stretched due to, for example, a humid heat environment or bending stress, thereby preventing the solder joint from being broken and causing poor electrical continuity. In particular, the smart card according to the present embodiment is obtained by interposing the conductive particle-containing hot melt adhesive sheet 1 between the card member 10 and the IC chip 20 and thermocompression bonding the two together, with the first layer 2 facing the IC chip 20. This effectively prevents the resin constituting the adhesive layer from becoming easily stretched due to a humid heat environment or bending stress, thereby preventing the solder joint from being broken and causing poor electrical continuity.

[0075] For example, 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 unevenly distributed on the IC chip 20 side. Also, the adhesive layer in the smart card may have, for example, a crystalline polyurethane resin, a crystalline polyester resin, and an amorphous polyester resin unevenly distributed on the card member 10 side, or may not have unevenly distributed.

[0076] <Method for Manufacturing a Smart Card> 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.

[0077] In this way, 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. Even when a card member 10 made of recycled PET is used, the second layer 3 allows the adhesive layer made of the conductive particle-containing hot melt adhesive sheet 1 to be strongly adhered to the card member 10 made of recycled PET.

[0078] 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 so that it faces 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, thereby further increasing the adhesive strength between the card member 10 and the IC chip 20 and increasing the strength of the smart card.

[0079] Thus, according to the method for manufacturing a smart card using the conductive particle-containing hot melt adhesive sheet 1, the adhesive strength between the card member 10 made of recycled PET and the IC chip 20 can be improved, and the bending resistance of the smart card can be improved.

[0080] 2 to 5, a specific example of a method for manufacturing a smart card will be described. 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.

[0081] [Step A] Figure 4 is a perspective view illustrating an example of a step in the manufacturing method of a smart card of attaching a conductive particle-containing hot melt adhesive sheet 1 to the connection surface of an IC chip 20. In step A, for example, as shown in Figure 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.

[0082] 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.

[0083] 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 a low temperature.

[0084] When process A is a lamination process, a pressure laminator or a vacuum pressure laminator may be used. By using process A as a lamination process, a relatively large area can be mounted at once compared to a temporary attachment process. Furthermore, 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.

[0085] 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, a crystalline polyurethane resin, a crystalline polyester resin, or an amorphous polyester resin) flows, but lower than the temperature at which the solder particles (conductive particles 4) melt. Here, 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, temperature rise rate 10°C / min, measurement frequency 10 Hz, measurement plate diameter 8 mm, and load fluctuation on the measurement plate 5 g.

[0086] [Step B] In step B, for example, the IC chip 20 is picked up using a tool equipped with a suction mechanism, and as shown in FIG. 4, the IC chip area of ​​the card member 10 is aligned with the IC chip 20, and the IC chip 20 is placed via the conductive particle-containing hot melt adhesive sheet 1.

[0087] [Step C] Figure 5 is a cross-sectional view illustrating an example of a step of thermocompression bonding the IC chip 20 and the card member 10 in the manufacturing method of the smart card 50. In step C, the IC chip 20 and the card member 10 are thermocompression bonded using a pressure bonding device 30. In step C, the number of thermocompression bonding operations can be set depending on the objects to be connected. For example, it may be one time, but it is preferable to perform multiple times. 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.

[0088] The thermocompression bonding temperature in step C, which is the temperature reached by the conductive particle-containing hot melt adhesive sheet 1, is preferably equal to or higher than the melting point of the solder particles (conductive particles 4). Here, the melting point refers to the solidus temperature. That is, the thermocompression bonding temperature in step C, which is the temperature reached by the conductive particle-containing hot melt adhesive sheet 1, 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 160°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, and more effectively prevents deformation of the card member 10.

[0089] 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. This allows the adhesive layer 40 made of the conductive particle-containing hot melt adhesive sheet 1 to be strongly adhered to the card member 10, even when a card member 10 made of recycled PET is used.

[0090] 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.

[0091] 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 card member 10 made of recycled PET and the IC chip 20 can be improved, and the bending resistance of the smart card 50 equipped with a card member made of recycled PET can be improved.

[0092] In this example, a conductive particle-containing hot melt adhesive sheet containing solder particles was prepared, and a smart card was fabricated using this sheet. The adhesive strength between the card member and the IC module (IC chip) in the smart card was then evaluated, the smart card's reliability under moist heat conditions was evaluated, and a bending test of the smart card was performed. However, this example is not limited to these.

[0093] [Preparation of solder particles] Metal materials were placed in a heated container in a predetermined compounding ratio, melted, and then cooled to obtain a solder alloy. Powder was prepared from the solder alloy using an atomization method, and the powder was classified to obtain solder particles with the following composition: Type 3 (particle diameter 25-45 μm, IPC standard J-STD 005) Sn-40Bi (non-eutectic, solidus temperature: 139°C, liquidus temperature: 167°C)

[0094] [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 having carboxyl groups) Aronmelt PES-111EE (Toagosei, crystalline polyester resin) Elitel UE3500 (Unitika, amorphous polyester resin) HK6503 (Henan Huike New Material Technology, crystalline polyurethane resin) Platamid HX2519 (Arkema, crystalline polyamide resin having carboxyl groups)

[0095] Examples 1 to 6, Comparative Examples 1 to 5 [First Layer (Layer A)] The compounds shown in Table 1 were mixed and stirred to a predetermined blend amount (parts by mass) in terms of solid content, to obtain a mixed varnish for the first layer 2. Subsequently, 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 first layer 2 was added to the obtained mixed varnish for the first layer 2, 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) was 20 μm, to obtain the first layer 2.

[0096] [Second Layer (Layer B)] The compounds shown in Table 1 were mixed and stirred to give predetermined solid content amounts (parts by mass) to obtain a mixed varnish for the second layer 3. The obtained mixed varnish for the second layer 3 was applied onto a 50 μm thick PET film so as to give an average thickness of 20 μm after drying, to obtain the second layer 3.

[0097] The first layer 2 and the second layer 3 were laminated together using a roll laminator at a temperature of 80 to 100°C at a speed of 0.5 m / min 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.

[0098] Comparative Examples 6 and 7 In Comparative Examples 6 and 7, the compounds shown in Table 1 were mixed and stirred to the predetermined 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, and the film was dried at 70° C. for 5 minutes and then at 120° C. for 5 minutes to produce a single-layer conductive particle-containing hot-melt adhesive sheet.

[0099] [Storage Modulus at 50°C] The storage modulus at 50°C was measured using a viscoelasticity tester (device name: Vibron, manufactured by A&D Co., Ltd.) in tension mode at 3°C / min and 11 Hz for the first layer 2 and second layer 3 produced in Examples 1 to 6 and Comparative Examples 1 to 5, and the single-layer conductive particle-containing hot melt adhesive sheets produced in Comparative Examples 6 and 7. The results are shown in Table 1. In Table 1, for example, "250 / 40" in Example 1 means that the storage modulus at 50°C of the first layer 2 (layer A) is 250 MPa, and the storage modulus at 50°C of the second layer 3 (layer B) is 40 MPa. Also, in Table 1, for example, "250" in Comparative Example 6 means that the storage modulus at 50°C of the single-layer conductive particle-containing hot melt adhesive sheet is 250 MPa.

[0100] [Fabrication of Smart Card] A recycled PET card for dual interface with a Cu wire arranged thereon was used as the card member 10 for the bending test. The Cu wire was exposed in the IC chip area of ​​this card member 10. A 6-pin IC module (manufactured by Smartflex) was used as the IC chip 20 for the bending test.

[0101] A PVC card without Cu wire (manufactured by Shoei Printing Co., Ltd.), a recycled PET card without Cu wire, or a PLA card without Cu wire (manufactured by Shenzhen Union Smart Card 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 Smartflex Co., Ltd.) was used as the IC chip 20 for adhesive strength evaluation or moist heat reliability evaluation.

[0102] The conductive particle-containing hot melt adhesive sheet 1 or a single-layer conductive particle-containing hot melt adhesive sheet was laminated to the connection surface of an IC module at 3 bar. The IC module to which the conductive particle-containing hot melt adhesive sheet 1 or the single-layer conductive particle-containing hot melt adhesive sheet was 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 under conditions of 230°C, 90 N, and 0.7 seconds, to produce a smart card 50 of the example and a smart card of the comparative example.

[0103] [Adhesion Strength Between Card Member and IC Module] The initial adhesion strength between the card member (PVC card, recycled PET card, or PLA card) and the IC module of the prepared 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, and an adhesive strength of less than 100 N was evaluated as NG. The results are shown in Table 1.

[0104] [Heat and humidity reliability] After a heat and humidity test (left for 500 hours in an environment of 60°C and 95% RH), the smart card was evaluated for adhesive strength (heat and humidity reliability) between the card material (recycled PET card) and the IC module in accordance with ISO 24789-2 "Adhesion of ICM to card-push test." When the adhesive strength was 80 N or more, the heat and humidity reliability was evaluated as OK, and when the adhesive strength was less than 80 N, the heat and humidity reliability was evaluated as NG. The results are shown in Table 1.

[0105] [Bending Test in a 50°C Environment] In accordance with ISO 10373-1 Dynamic Bending Stress, a periodic bending force was applied to the smart card in a specified strength and direction in a constant temperature bath at 50°C. The Q value of the smart card after 4000 cycles of bending testing was measured using a resonant 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 smart card was evaluated as "OK," meaning that the smart card had good bending resistance. The results are shown in Table 1.

[0106]

[0107] In Examples 1 to 6, a conductive particle-containing hot melt adhesive sheet 1 was used that included a first layer 2 containing 50% by mass or more of a crystalline polyamide resin having a carboxyl group and having a storage modulus of 150 MPa or more at 50°C, and a second layer 3 containing a crystalline polyester resin and an amorphous polyester resin and having a storage modulus of 30 MPa or more at 50°C. As a result, it was found that the initial adhesive strength between the card member 10 (recycled PET card) and the IC chip 20 (IC module) was good, and that the card member 10 using recycled PET also had good moist heat reliability and bending resistance for the smart card 50.

[0108] In particular, in Examples 1 to 4, the second layer 3 in the conductive particle-containing hot melt adhesive sheet 1 further contains a crystalline polyurethane resin, and the content of the crystalline polyurethane resin in the second layer 3 is more than 10 mass % relative to the total mass of the crystalline polyester resin, amorphous polyester resin, and crystalline polyurethane resin, and it was found that this also enables the initial adhesive strength between the PLA card and the IC chip 20 to be good.

[0109] In Comparative Example 1, the conductive particle-containing hot melt adhesive sheet 1 was interposed between the card member 10 and the IC chip 20 so that the first layer 2 containing 50% by mass or more of a crystalline polyamide resin having a carboxyl group was on the card member 10 side. Therefore, it was found that the initial adhesive strength between the card member 10 and the IC chip 20 was poor, and the moist heat reliability and bending resistance of the smart card were also poor. In particular, it was found that in Comparative Example 1, the initial adhesive strength between the card member 10 (recycled PET card or PLA card) and the IC chip 20 was poor, and the moist heat reliability and bending resistance of the smart card including a card member made of recycled PET were also poor.

[0110] In Comparative Example 2, 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 50% by mass and a storage modulus at 50°C of less than 150 MPa, and therefore it was found that the initial adhesive strength between the card member 10 and the IC chip 20 was poor, and the moist heat reliability and bending resistance of the smart card were also poor. In particular, in Comparative Example 2, it was found that the initial adhesive strength between the card member 10 (recycled PET card or PLA card) and the IC chip 20 was poor, and the moist heat reliability and bending resistance of the smart card 50 equipped with a card member using recycled PET were also poor.

[0111] Figure 6 is an electron microscope photograph showing an example of a cross section of a smart card obtained in Comparative Example 2 after a bending test. The smart card shown in Figure 6 has an IC module including an Au / Ni plating layer 60 and a Cu wire 61 disposed on the surface of the card member, and the solder joint 62 connecting the Au / Ni plating layer 60 and the Cu wire 61 is broken (cut). The conductive particle-containing hot melt adhesive sheet used in Comparative Example 2 had a first layer with a storage modulus at 50°C that was too low, which is thought to have caused the adhesive layer 63 (resin made of the conductive particle-containing hot melt adhesive sheet) protecting the solder joint 62 to elongate, resulting in the breakage of the solder joint 62 and, for example, poor electrical continuity.

[0112] In Comparative Example 3, a conductive particle-containing hot melt adhesive sheet was used that did not contain a crystalline polyester resin, but contained only a crystalline polyurethane resin and an amorphous polyester resin, and had a second layer with a storage modulus of less than 30 MPa at 50° C., and therefore it was found that the bending resistance of the smart card was poor. One possible reason for this result is that, for example, the second layer with a storage modulus of less than 30 MPa at 50° C. made the resin more likely to stretch, resulting in an unstable connection between the card member 10 and the IC chip 20.

[0113] In Comparative Example 4, a conductive particle-containing hot melt adhesive sheet was used that did not contain amorphous polyester resin and had a second layer that contained only crystalline polyurethane resin and crystalline polyester resin, and it was found that the wet heat reliability of the smart card was not good.

[0114] In Comparative Example 5, a conductive particle-containing hot melt adhesive sheet was used that did not contain a crystalline polyester resin or an amorphous polyester resin, but contained only a crystalline polyurethane resin, and had a second layer with a storage modulus of less than 30 MPa at 50° C., and therefore it was found that the wet heat reliability and bending resistance of the smart card were poor. One possible reason for this result is that, for example, the second layer with a storage modulus of less than 30 MPa at 50° C. made the resin more likely to stretch, resulting in an unstable connection between the card member 10 and the IC chip 20.

[0115] In Comparative Example 6, a conductive particle-containing hot melt adhesive sheet was used that contained only a layer (Layer A in Example 1) containing 50% or more by mass of crystalline polyamide having a carboxyl group and having a storage modulus of 150 MPa or more at 50°C (in other words, a conductive particle-containing hot melt adhesive sheet that did not include a layer containing a crystalline polyester resin, an amorphous polyester resin, and a crystalline polyurethane resin and having a storage modulus of 30 MPa or more at 50°C. Therefore, it was found that the initial adhesive strength between the card member 10 and the IC chip 20 was poor, and the moist heat reliability and bending resistance of the smart card were also poor. In particular, it was found that in Comparative Example 6, the initial adhesive strength between the card member 10 (recycled PET card or PLA card) and the IC chip 20 was poor, and the moist heat reliability and bending resistance of the smart card 50 including a card member made of recycled PET were also poor.

[0116] In Comparative Example 7, a conductive particle-containing hot melt adhesive sheet was used that contained only a layer containing a crystalline polyester resin, an amorphous polyester resin, and a crystalline polyurethane resin and having a storage modulus of 30 MPa or more at 50°C (the same as Example 1, except that conductive particles were added to Layer B), in other words, a conductive particle-containing hot melt adhesive sheet that did not include a layer containing 50% by mass or more of a crystalline polyamide having a carboxyl group and having a storage modulus of 150 MPa or more at 50°C. Therefore, it was found that the initial adhesive strength between the card member 10 and the IC chip 20 was poor, and the moist heat reliability and bending resistance of the smart card were also poor. In particular, it was found that in Comparative Example 7, the initial adhesive strength between the card member 10 (recycled PET card or PLA card) and the IC chip 20 was poor, and the moist heat reliability and bending resistance of the smart card 50 including a card member made of recycled PET were also poor.

[0117] REFERENCE SIGNS LIST 1 Conductive particle-containing hot melt adhesive sheet, 2 First layer, 3 Second layer, 4 Conductive particles, 10 Card member, 11 Opening, 12 Antenna pattern, 12a First exposed portion, 12b Second exposed portion, 20 IC chip, 21 Contact terminal, 30 Crimping device, 40 Adhesive layer, 50 Smart card, 60 Au / Ni plating, 61 Cu wire, 62 Solder joint, 63 Adhesive layer

Claims

1. A conductive particle-containing hot melt adhesive sheet comprising: a first layer containing 50% by mass or more of a crystalline polyamide resin having a carboxyl group and having a storage modulus of 150 MPa or more at 50°C; and a second layer containing a crystalline polyester resin and an amorphous polyester resin and having a storage modulus of 30 MPa or more at 50°C.

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. A conductive particle-containing hot melt adhesive sheet according to claim 1 or 2, wherein the second layer further contains a crystalline polyurethane resin, and the content of the crystalline polyurethane resin in the second layer is 20 mass% or more relative to the total mass of the crystalline polyester resin, the amorphous polyester resin, and the crystalline polyurethane resin.

4. A conductive particle-containing hot melt adhesive sheet according to claim 1 or 2, wherein the second layer further contains a crystalline polyurethane resin, and the content of the crystalline polyurethane resin in the second layer is more than 10 mass% relative to the total mass of the crystalline polyester resin, the amorphous polyester resin, and the crystalline polyurethane resin.

5. A method for manufacturing a smart card, in which a conductive particle-containing hot melt adhesive sheet having a first layer containing 50% by mass or more of a crystalline polyamide resin having a carboxyl group and having a storage modulus of 150 MPa or more at 50°C, and a second layer containing a crystalline polyester resin and an amorphous polyester resin and having a storage modulus of 30 MPa or more at 50°C is interposed between an IC chip and a card member and thermocompressed.

6. The method for manufacturing a smart card according to claim 5, wherein the first layer is interposed so as to face the IC chip side.

7. A method for manufacturing a smart card as described in claim 5 or 6, wherein the second layer further contains a crystalline polyurethane resin, and the content of the crystalline polyurethane resin in the second layer is 20 mass% or more relative to the total mass of the crystalline polyester resin, the amorphous polyester resin, and the crystalline polyurethane resin.

8. A smart card comprising: a card member; an IC chip; and an adhesive layer that bonds the card member and the IC chip, wherein the adhesive layer contains a mixture of a crystalline polyamide resin having a carboxyl group, a crystalline polyester resin, and an amorphous polyester resin, and conductive particles.

9. A smart card comprising a card member, an IC chip, and an adhesive layer that bonds the card member and the IC chip, wherein the adhesive layer is made of a hot melt adhesive sheet containing conductive particles, and the hot melt adhesive sheet containing conductive particles comprises: a first layer that contains 50% or more of a crystalline polyamide resin and has a storage modulus of 150 MPa or more at 50°C; and a second layer that contains a crystalline polyester resin and an amorphous polyester resin and has a storage modulus of 30 MPa or more at 50°C.

10. A smart card according to claim 8 or 9, wherein the card material is recycled PET (Poly Ethylene Terephthalate), PLA (Polylactic acid), or PVC (Polyvinyl Chloride).

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