Conductive film-provided resin substrate, electronic device, electromagnetic wave shield sheet, and planar heating element

Abstract

A conductive film-provided resin substrate according to the present invention comprises: a resin substrate that includes a thermoplastic resin layer; and a conductive film that is provided on at least a part of the surface of the resin substrate. The conductive film includes a sintered body of a plurality of conductive particles. The thermal shrinkage in the MD direction of the thermoplastic resin layer under conditions of 180°C for 30 minutes, as measured in accordance with JIS C 2318, satisfies at most 1.0%.

Description

Conductive film-coated resin substrates, electronic devices, electromagnetic shielding sheets, and planar heating elements.

[0001] The present invention relates to a resin substrate with a conductive film, an electronic device, an electromagnetic wave shielding sheet, and a planar heating element.

[0002] Studies have been conducted on forming conductive patterns, such as circuit patterns, on substrates using conductive compositions containing conductive particles. Conductive compositions containing conductive particles are sometimes referred to as conductive pastes, conductive inks, etc. Prior art relating to conductive pattern formation techniques using conductive compositions containing conductive particles can be found in the following patent documents 1 to 4.

[0003] Japanese Unexamined Patent Publication No. 2006-165467 Japanese Unexamined Patent Publication No. 2001-015893 Japanese Patent No. 6491032 Japanese Unexamined Patent Publication No. 11-289149

[0004] In the above-mentioned Patent Documents 1 to 4, a conductive paste containing conductive nanoparticles formed on a resin substrate is subjected to laser light, metal halide lamp, light irradiation, and YAG / CO2. ２ Techniques are used to sinter or dry conductive paste by irradiating it with a laser or the like. However, there has been insufficient study on methods for sintering a conductive particle-containing layer on a resin substrate using a hot press method (heat and pressure treatment). As a result of our studies, we found that when the heat and pressure treatment for sintering conductive particles is performed at high temperatures, thermal deformation of the resin substrate may occur, which may lead to an increase in the resistance value of the sintered body (conductive film) of conductive particles.

[0005] The present inventors have discovered that by using a resin substrate having the characteristic of having a small thermal shrinkage rate in the MD direction (i) or the characteristic of having a small anisotropy in the thermal shrinkage rate (ii), thermal deformation of the resin substrate can be suppressed when heat and pressure treatment is applied, thereby suppressing an increase in the resistance value of the sintered body (conductive film) of conductive particles, and have completed the present invention.

[0006] According to one aspect of the present invention, the following conductive film-coated resin substrate, electronic device, electromagnetic wave shielding sheet, and planar heating element are provided.

[0007] 1. A resin substrate with a conductive film, comprising a resin substrate containing a thermoplastic resin layer, and a conductive film provided on at least a portion of the surface of the resin substrate, wherein the conductive film contains a sintered body of a plurality of conductive particles, and the thermal shrinkage rate in the MD direction of the thermoplastic resin layer under the conditions of 180°C for 30 minutes, as measured in accordance with JIS C 2318, is 1.0% or less. 2. A resin substrate with a conductive film, comprising a resin substrate containing a thermoplastic resin layer, and a conductive film provided on at least a portion of the surface of the resin substrate, wherein the conductive film contains a sintered body of a plurality of conductive particles, and the difference in thermal shrinkage rates |MD-TD| between the MD direction and the TD direction of the thermoplastic resin layer under the conditions of 180°C for 30 minutes, as measured in accordance with JIS C 2318, is 0.7% or less. 3. 1. or 2. A conductive film-coated resin substrate as described above, wherein the thermal shrinkage rate in the MD direction of the thermoplastic resin layer under the conditions of 150°C for 30 minutes, as measured in accordance with JIS C 2318, is MD １５０ The thermal shrinkage rate in the MD direction of the thermoplastic resin layer under the conditions of 180°C for 30 minutes is defined as MD. １８０ In this case, the difference in thermal shrinkage coefficients |MD １８０ - MD １５０A conductive film-coated resin substrate in which the | is 0.5% or less. 4. A conductive film-coated resin substrate according to any one of 1 to 3, wherein the thermal shrinkage rate in the TD direction of the thermoplastic resin layer under the conditions of 180°C for 30 minutes, as measured in accordance with JIS C 2318, is 0.2% or less. 5. A conductive film-coated resin substrate according to any one of 1 to 4, wherein the thermoplastic resin layer is a biaxially oriented film. 6. A conductive film-coated resin substrate according to any one of 1 to 5, wherein the thermoplastic resin layer comprises one or more selected from the group consisting of polyester, polycarbonate, and polyimide. 7. A conductive film-coated resin substrate according to any one of 1 to 6, wherein the heat resistance temperature of the thermoplastic resin layer is 80°C or higher. 8. 1 to 7. A conductive film-coated resin substrate according to any one of the above, wherein at least a portion of the conductive film is embedded in the thermoplastic resin layer. 9. A conductive film-coated resin substrate according to any one of 1 to 8, wherein the particles contained in the conductive particles include dendritic particles. 10. A conductive film-coated resin substrate according to any one of 1 to 9, wherein the particle diameter D at the point where the cumulative volume from the smallest particle side reaches 50% in the volume-based cumulative distribution of particle diameters obtained when the particle diameter of the conductive particles is measured by laser diffraction scattering is ５０ A conductive film-coated resin substrate having a thickness of 0.5 μm or more and 100 μm or less. 11. A conductive film-coated resin substrate according to any one of 1 to 10, wherein the conductive particles contain copper. 12. An electronic device comprising a conductive film-coated resin substrate according to any one of 1 to 11. 13. An electronic device according to 12, wherein the electronic device is an RF tag. 14. An electromagnetic wave shielding sheet comprising a conductive film-coated resin substrate according to any one of 1 to 11. 15. A planar heating element comprising a conductive film-coated resin substrate according to any one of 1 to 11.

[0008] According to the present invention, a conductive film-coated resin substrate having a low-resistance conductive film, an electronic device using the same, an electromagnetic wave shielding sheet, and a planar heating element are provided.

[0009] This is a schematic cross-sectional view showing an example of the manufacturing process for a conductive film-coated substrate according to this embodiment. This is a schematic cross-sectional view showing an example of a conductive film-coated resin substrate according to this embodiment. This is a schematic top view showing an example of a conductive film-coated resin substrate according to this embodiment. This is an SEM image showing a cross-section of the conductive film-coated resin substrate of Example 1.

[0010] Embodiments of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted as appropriate. Also, the drawings are schematic diagrams and do not correspond to the actual dimensional ratios.

[0011] In this specification, the notation "X to Y" in descriptions of numerical ranges means X or more and Y or less, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less." In this specification, the notation "(meth)acrylic" represents a concept that encompasses both acrylic and methacrylic. The same applies to similar notations such as "(meth)acrylate." In this specification, the term "electronic device" is used to mean elements, devices, and final products to which electronic engineering technology is applied, such as semiconductor chips, semiconductor elements, printed circuit boards, electrical circuit display devices, information and communication terminals, light-emitting diodes, physical batteries, and chemical batteries.

[0012] The outline of the conductive film-coated resin substrate in this embodiment will be described.

[0013] The conductive film-coated resin substrate of the first embodiment comprises a resin substrate including a thermoplastic resin layer, and a conductive film provided on at least a portion of the surface of the resin substrate, wherein the conductive film includes a sintered body of a plurality of conductive particles, and satisfies the requirement that the thermal shrinkage rate in the MD direction of the thermoplastic resin layer under conditions of 180°C for 30 minutes, as measured in accordance with JIS C 2318, is 1.0% or less.

[0014] The conductive film-coated resin substrate of the second embodiment comprises a resin substrate including a thermoplastic resin layer, and a conductive film provided on at least a portion of the surface of the resin substrate, wherein the conductive film includes a sintered body of a plurality of conductive particles, and satisfies the condition that the difference in thermal shrinkage rates |MD-TD| between the MD direction and the TD direction in the thermoplastic resin layer under conditions of 180°C for 30 minutes, as measured in accordance with JIS C 2318, is 0.7% or less.

[0015] According to the inventors' findings, by using a resin substrate having a resin layer with the characteristic of having a small thermal shrinkage rate in the MD direction (i) or the characteristic of having small anisotropy in thermal shrinkage rate (ii), it is possible to suppress thermal deformation of the resin substrate even when relatively high temperatures are used during the heating and pressurizing process for sintering multiple conductive particles, thereby suppressing an increase in the resistance value of the conductive film including the sintered body.

[0016] Although the detailed mechanism is unclear, when the resin layer deforms due to thermal shrinkage, irregularities occur on the surface of the conductive particle-containing layer on the resin substrate, causing unevenness (variation) in the pressure received from the hot press. As a result, sintering may not be sufficient in areas where the pressure is relatively low, and therefore, it is presumed that the conductive film cannot be made low-resistance.

[0017] The first and second embodiments make it possible to suppress pressure unevenness applied to the conductive particle-containing layer during heating and pressurizing treatment, thereby achieving low resistance in the conductive film. It is also possible to suppress variations in the resistance value of the conductive film.

[0018] Furthermore, the above-described pressurized heat treatment may form an embedded structure in which at least a portion of the conductive film is embedded in a recess formed in the thermoplastic resin layer. Since the embedded structure functions as an anchor, it is presumed that delamination between the conductive film and the resin substrate is suppressed, and the physical adhesion between the two is increased.

[0019] The conductive film-coated resin substrate of this embodiment can be used for various applications, including, for example, electronic devices, electromagnetic shielding sheets, and planar heating elements. Preferably, as an electronic device, it can be used in RFID media such as inlays (sometimes called inlets) and tags (RF tags). RFID media can be used in inlays, tags, labels, tickets, cards, and other media formed by processing inlays. The RFID media incorporates an RFID-compliant IC chip. Such RFID media have visibly printed information about the object to be attached, the object to be affixed, or the wearer, and the incorporated IC chip can store various information about the object. The inlay comprises a substrate, an electrical circuit (such as an antenna), and an IC chip, and at least a portion of the metal pattern included in the substrate and electrical circuit may be made of the conductive film-coated resin substrate. The inlay may optionally include a meander pattern and / or a capacitor hat. In addition to the inlay, the tag may further include a sealing member to protect the IC chip. The inlay within the tag may be molded with a sealing material such as resin on the side where the IC chip is mounted or on both sides. Information (such as barcodes or text) may also be printed on the surface of the tag. In addition to the inlay, the label may further include adhesive for attachment to a substrate and printed information (such as barcodes or text).

[0020] The following describes the manufacturing method of the conductive film-coated resin substrate according to this embodiment, while detailing each component of the conductive film-coated resin substrate.

[0021] Figures 1(A) to 1(C) are cross-sectional views showing an example of a method for manufacturing a conductive film-coated resin substrate. Figure 2 is a schematic cross-sectional view showing an example of a conductive film-coated resin substrate 10. Figures 1(A) to 1(C) are cross-sectional views of the substrate in the thickness direction. In Figure 2, the Z direction means the same direction as the thickness direction. The Z direction may also be defined as the normal direction to the X-Y plane, when the plane of the surface 1A of the substrate 1 is defined as the X-Y plane.

[0022] An example of a method for manufacturing a conductive film-coated resin substrate according to this embodiment includes, as shown in Figure 1(A), a lamination step of forming a layer containing a plurality of conductive particles (conductive particle-containing layer 2) on the surface of a resin substrate (substrate 1); as shown in Figure 1(B), a surface modification step of softening or melting at least a portion of the surface side of the thermoplastic resin layer of the substrate 1 with a xenon flash 4; and as shown in Figure 1(C), a sintering step of sintering a plurality of conductive particles in the conductive particle-containing layer 2 by heating and pressurizing treatment to form a conductive film 3.

[0023] In the above manufacturing method, the surface modification step may be performed after the lamination step, or the lamination step may be performed after the surface modification step.

[0024] In the lamination process, a conductive particle-containing layer 2 can be formed on the surface 1A of the substrate 1 using a conductive paste containing multiple conductive particles and a solvent.

[0025] As a method for forming the conductive particle-containing layer 2, for example, a method can be used in which a film is formed using a conductive paste and the solvent contained in the film is dried, but this method is not limited to this.

[0026] As a method for forming a film, various coating and printing techniques can be applied. The conductive particle-containing layer 2 may be provided on the entire surface of the substrate 1, or may be provided only on a part of the surface of the substrate 1. In the former case, a coating method using an apparatus such as a blade coater, air knife coater, doctor coater, roll coater, bar coater (rod coater), curtain coater, or the like can be used. In the latter case, various printing methods, for example, screen printing, gravure printing, letterpress printing, offset lithography, inkjet method, transfer printing method, and the like can be used. By appropriately designing the "pattern" in printing, a substrate having a patterned structure such as a conductive film (circuit pattern) that can function as a circuit or a mesh pattern having electromagnetic wave shielding ability can be produced. When the conductive paste is provided only on a part of the surface of the base material 1, it is preferable that the "pattern" for printing is appropriately designed according to the application of the finally obtained conductive film. In order to prevent a film from being formed on the base material 1 at locations other than a desired position, for example, a film with holes hollowed out may be placed on the base material 1, the conductive paste may be applied or printed thereon, and then the film may be removed.

[0027] It is preferable that a heat treatment for drying the solvent contained in the conductive paste is performed to make the conductive particle-containing layer 2 a dried film. The conditions of the heat treatment are not particularly limited as long as the solvent is sufficiently dried, but are adjusted from the viewpoints of sufficient drying of the solvent and suppression of deterioration of the conductive particles caused by excessive heating. The temperature of the heat treatment is preferably 50 to 150°C, more preferably 80 to 120°C. The time of the heat treatment is preferably 30 seconds to 60 minutes, more preferably 1 minute to 30 minutes. The heat treatment for drying the solvent can be performed, for example, by applying hot air to the film. Of course, the heat treatment may be performed by other methods. The conductive particle-containing layer 2, which is a dried film, preferably contains a plurality of conductive particles that are not substantially sintered. In addition, when the conductive paste contains a curable resin, a crosslinking agent, or the like, it is preferable that the curable resin and the crosslinking agent in the dried film are substantially unreacted.

[0028] In this manner, a laminate including a base material 1 and a conductive particle-containing layer 2 can be obtained. Note that the lamination step is not limited only to the embodiment shown in FIG. 1(A), as long as a laminate including the base material 1 and the conductive particle-containing layer 2 can be obtained.

[0029] As another lamination step, for example, the above laminate may be obtained by bringing a provisional layer provided on the surface of an easily peelable base material with a conductive paste containing conductive particles into contact with the surface of a base material different from the easily peelable base material, and transferring the provisional layer onto the surface of the base material. The provisional layer is preferably dried to form a dried film before transfer. Furthermore, as another lamination step, a part of the conductive particle-containing layer 2 formed on the base material 1 may be removed to obtain a desired shape. That is, a part of the conductive particle-containing layer 2 may be removed in order to eliminate portions where excess conductive paste is printed, so-called pattern thickening, caused by printing of the conductive paste or the like. The removal method is not particularly limited, and a known method can be used; for example, ultraviolet laser etching and the like can be mentioned. This can improve the accuracy and stability of the finally obtained conductor pattern.

[0030] <Base Material> The base material 1 is a resin base material including a thermoplastic resin layer having a thermal shrinkage rate in the MD direction of 1.0% or less, or a resin base material including a thermoplastic resin layer having a thermal shrinkage difference between the MD direction and the TD direction |MD-TD| of 0.7% or less. The MD direction means the Machine Direction, and the TD direction means the Transverse Direction orthogonal to the machine direction. The thermal shrinkage rate is measured in accordance with JIS C 2318 under conditions of a predetermined temperature of 150°C or 180°C and a duration of 30 minutes. In the present embodiment, description is given using an example in which a resin base material including a thermoplastic resin layer with low thermal shrinkage is used, but the present invention is not limited thereto, and a resin base material including a thermosetting resin with a low thermal shrinkage rate and / or a small thermal shrinkage difference may also be used.

[0031] The upper limit of the thermal shrinkage rate in the MD direction of the thermoplastic resin layer at 150°C for 30 minutes is 1.0% or less, preferably 0.8% or less, and more preferably 0.5% or less. On the other hand, the lower limit of the thermal shrinkage rate in the MD direction is not particularly limited and may be 0% or 0.01% or more.

[0032] In the thermoplastic resin layer, the upper limit of the difference in thermal shrinkage rates between the MD direction and the TD direction |MD-TD| at 150°C for 30 minutes is 0.7% or less, preferably 0.6% or less, and more preferably 0.4% or less. On the other hand, the lower limit of the difference in thermal shrinkage rates |MD-TD| is not particularly limited and may be 0%, or 0.01% or more.

[0033] The upper limit of the thermal shrinkage rate in the TD direction of the thermoplastic resin layer at 150°C for 30 minutes is, for example, 0.2% or less, preferably 0.1% or less, and more preferably 0.05% or less. On the other hand, the lower limit of the thermal shrinkage rate in the TD direction is not particularly limited and may be 0% or 0.01% or more.

[0034] The upper limit of the thermal shrinkage rate in the MD direction of the thermoplastic resin layer at 180°C for 30 minutes is 1.0% or less, preferably 0.8% or less, and more preferably 0.5% or less. On the other hand, the lower limit of the thermal shrinkage rate in the MD direction is not particularly limited and may be 0% or 0.01% or more.

[0035] In the thermoplastic resin layer, the upper limit of the difference in thermal shrinkage rates between the MD direction and the TD direction |MD-TD| at 180°C for 30 minutes is 0.7% or less, preferably 0.6% or less, and more preferably 0.4% or less. On the other hand, the lower limit of the difference in thermal shrinkage rates |MD-TD| is not particularly limited and may be 0%, or 0.01% or more.

[0036] The upper limit of the thermal shrinkage rate in the TD direction of the thermoplastic resin layer at 180°C for 30 minutes is, for example, 0.2% or less, preferably 0.1% or less, and more preferably 0.05% or less. On the other hand, the lower limit of the thermal shrinkage rate in the TD direction is not particularly limited and may be 0% or 0.01% or more.

[0037] The thermal shrinkage rate in the MD direction of a thermoplastic resin layer under the conditions of 150°C for 30 minutes is MD １５０and let the heat shrinkage rate in the MD direction in the thermoplastic resin layer under the conditions of 180°C and 30 minutes be MD １８０ . At this time, the difference in heat shrinkage rate in the thermoplastic resin layer |MD １８０ -MD １５０ | has an upper limit of 0.5% or less, preferably 0.2% or less, more preferably 0.1% or less. On the other hand, the heat shrinkage difference |MD １８０ -MD １５０ | has no particular limitation on the lower limit, which may be 0% or 0.01% or more.

[0038] Examples of methods for reducing heat shrinkage of the thermoplastic resin layer include selecting a material with high heat resistance temperature, using a stretched film, and the like. The thermoplastic resin layer may preferably be composed of a biaxially stretched film. Furthermore, heat shrinkage can also be reduced by making at least a part of the surface of the thermoplastic resin layer amorphous (non-crystalline).

[0039] The lower limit of the heat resistance temperature of the thermoplastic resin layer is, for example, 80°C or higher, preferably 90°C or higher, more preferably 100°C or higher. On the other hand, the upper limit of the heat resistance temperature of the thermoplastic resin layer is, for example, 250°C or lower, preferably 220°C or lower, more preferably 200°C or lower. By using a thermoplastic resin layer having a heat resistance temperature equal to or higher than the above lower limit, thermal deformation of the entire resin base material caused by the heating and pressurizing treatment in the sintering step can be suppressed. By using a thermoplastic resin layer having a heat resistance temperature equal to or lower than the above upper limit, surface modification can be promoted. In general, heat resistance temperature is calculated as follows: when a product is placed in a machine and the temperature is increased by 10°C starting from 50°C, the temperature at which an abnormality (distortion, deformation, discoloration, change in functionality, etc.) occurs in the product is measured, and 10°C is subtracted from the temperature at which such abnormality occurs in the product to obtain the heat resistance temperature. In the present specification, it is preferable to use a heat resistance temperature that uses distortion and deformation as an index for abnormality.

[0040] Furthermore, in another embodiment, the resin base material may be composed of a thermoplastic resin layer having a surface-modified region where at least a part of the surface 1A is softened or melted, or may be composed of a thermoplastic resin layer in which a heat-softened coating layer is laminated on at least a part of the surface 1A.

[0041] The surface modification region can be formed by irradiating the surface 1A of the thermoplastic resin layer with a xenon flash, or by other means. As shown in Figure 1(B), in the surface modification step after the lamination step in which the conductive particle-containing layer 2 is provided on the substrate 1, it is preferable to irradiate with a xenon flash from the back surface 1B, which is opposite to the surface 1A side. Alternatively, when irradiating from the back surface 1B, the xenon flash may be transmitted through the substrate 1. The conductive particles contained in the conductive particle-containing layer 2 can suppress efficiency reduction due to light diffusion, etc., and can also suppress unintended sintering of conductive particles together.

[0042] Examples of energy sources include broadband waves from xenon flash lamps, LEDs, halogen lamps, metal halide lamps, and other UV lamps, as well as YAG lasers and CO2 lasers. ２ While there are various types of narrowband waves (single waves) such as lasers and semiconductor lasers, it is preferable to use xenon flash, which is a pulsed irradiation of broadband waves. By using broadband waves, surface irradiation becomes possible, and variations in the degree of surface modification in the in-plane direction of surface 1A can be suppressed. By using pulsed light emission such as xenon flash lamps, the effect can be localized more easily compared to continuous light emission such as halogen lamps and metal halide lamps, making it easier to control surface modification. In addition, by using pulsed light, copper particles near the resin are selectively heated, contributing to the surface modification of the resin. With continuous light, the entire copper particle film is heated, which can lead to oxidation of copper and be unfavorable for subsequent sintering.

[0043] In the surface modification process, the energy of the xenon flash is, for example, 10 to 5000 J, preferably 20 to 2500 J, and more preferably 50 to 2000 J.

[0044] Specifically, the surface modification step may involve the xenon flash described above, which may be applied to the dried film of the conductive particle-containing layer 2. This suppresses the occurrence of damage to the conductive particle-containing layer 2 due to sudden boiling of the solvent caused by xenon flash irradiation before drying. It also suppresses inhibition of modification of the thermoplastic resin layer. The dried film of the conductive particle-containing layer 2 is obtained by performing a heat treatment to dry the conductive particle-containing layer 2 during the lamination process.

[0045] The thermoplastic resin contained in the thermoplastic resin layer includes either an amorphous thermoplastic resin or a crystalline thermoplastic resin, or both. In this specification, surface modification is defined as a change in state of a portion of the surface of the thermoplastic resin layer due to irradiation with a xenon flash. Typically, the amorphous thermoplastic resin softens, and the crystalline thermoplastic resin melts. A portion of the melted crystalline thermoplastic resin may become amorphous and remain in an amorphous state. The amorphous region formed near the surface 1A of the thermoplastic resin layer can be identified using a cross-sectional SEM image. For example, when the surface of a crystalline PET substrate is melted with a xenon flash, the melted surface portion reflects electron beams more easily than the unmelted interior and appears slightly white. That is, the amorphous region can be observed as a region that appears relatively white in a cross-sectional SEM image.

[0046] In a preferred embodiment, the following sintering step may be carried out using a substrate 1 in which an amorphous region is formed on at least a portion of the vicinity of the surface 1A of the thermoplastic resin layer. In the first embodiment, an amorphous region may be formed on the surface 1A of the thermoplastic resin layer in the surface modification step, and preferably, an amorphous layer having a predetermined depth may be formed from the surface 1A. In the second embodiment, a substrate 1 including a thermoplastic resin layer having an amorphous region on at least a portion of the surface 1A can be prepared, and a lamination step can be carried out using this.

[0047] In another preferred embodiment, the surface modification process may create a state in which at least a portion of a plurality of conductive particles are embedded near the surface 1A of the thermoplastic resin layer. At least a portion of the plurality of conductive particles may be a single particle, a sintered product of multiple particles, or both. Although the detailed mechanism is not clear, it is presumed that the softened or molten state of the surface 1A makes it easier for the conductive particles to penetrate into the surface layer, and, if necessary, in combination with subsequent pressurizing treatment, the embedded state is formed.

[0048] The thermoplastic resin layer serves as the base material for the resin substrate. In this case, the thickness of the thermoplastic resin layer may be 10% to 100% of the thickness of the resin substrate, and preferably 20% to 100%.

[0049] Examples of thermoplastic resin materials that have a higher heat resistance temperature than polyolefins such as polyethylene and polypropylene include polyesters such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), polycarbonates, and polyimides. These may be used individually or in combination of two or more. Among the above, thermoplastic resin materials with high permeability to xenon flash are preferred. This suppresses thermal deformation of the substrate 1 caused by absorbing xenon flash and generating heat.

[0050] The base material 1 is typically in the form of a film, sheet, or plate. From the viewpoint of industrial productivity, any of these shapes of the base material is preferred.

[0051] The base material 1 is preferably flexible. By using a flexible base material, a flexible printed circuit board (FPC) can be manufactured. Using a flexible base material is preferable, for example, from the viewpoint of mass production.

[0052] The thickness of the substrate 1 is not particularly limited and can be set appropriately depending on the final application (electronic device, RF tag, electromagnetic shielding film, planar heating element, etc.) and various circumstances, as described later. The thickness of the substrate 1 is typically 10 to 250 μm, preferably 30 to 100 μm. However, from the viewpoint of suppressing curling during and after the manufacturing of the substrate with the conductive pattern, the thickness of the substrate is preferably 100 to 250 μm, more preferably 100 to 150 μm. Incidentally, the thickness of the substrate here can be determined by measuring the thickness of the portion of the substrate where the conductive pattern does not exist.

[0053] <Conductive Paste> An example of a conductive paste includes multiple conductive particles and a solvent.

[0054] The conductive particles preferably contain at least one element selected from the group consisting of silver and copper. Specifically, the conductive particles preferably contain at least one selected from the group consisting of particles mainly composed of silver and particles mainly composed of copper. Here, the expression "mainly composed of silver" means that the ratio of silver elements in the total constituent elements of the particles is preferably 50 mol% or more, more preferably 75 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more. Similarly, the expression "mainly composed of copper" means that the ratio of copper elements in the total constituent elements of the particles is preferably 50 mol% or more, more preferably 75 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more. The conductive particles may also contain elements other than silver and copper, as long as the desired conductivity is obtained. Examples of elements other than silver and copper include gold, aluminum, platinum, palladium, iridium, tungsten, nickel, tantalum, lead, zinc, and the like.

[0055] The conductive particles may contain two or more elements. For example, conductive particles in which the surface of copper particles is silver-plated (silver-coated copper particles) may be used. Silver-coated copper particles are particles mainly composed of copper, and for example, up to 35% by mass of silver, based on the total mass of the particles, is plated on the surface of the copper particles.

[0056] The conductive particles preferably contain dendritic metal particles, and more preferably contain dendritic copper particles. By using dendritic metal particles, adhesion to the thermoplastic resin layer can be further enhanced compared to spherical particles. It is presumed that dendritic metal particles are more likely to be embedded in the thermoplastic resin layer. However, the conductive particles may also contain metal particles of other shapes, such as spherical particles, in addition to dendritic metal particles. "Dendritic" usually refers to a shape having a main trunk that extends in one direction and at least one branch that branches off from the main trunk. Copper particles produced by electrolysis usually become dendrites due to the copper crystal formation mechanism. In the field of copper particles, dendritic copper particles produced by electrolysis are usually referred to as "dendritic copper particles." The meaning of the term "dendritic copper particles" in this specification is the same as the usual meaning of the term "dendritic copper particles" in the field of copper particles.

[0057] The proportion of dendritic copper particles in the total conductive particles is preferably 50% by mass or more, more preferably 75% by mass or more, and even more preferably 90% by mass or more. Of course, all of the copper particles (100% by mass) may be dendritic copper particles. Since dendritic copper particles are relatively inexpensive, a high proportion of dendritic copper particles in a mixture of copper particles (copper powder) leads to a reduction in the manufacturing cost of the conductive film.

[0058] In the volume-based cumulative particle size distribution curve obtained when conductive particles are measured by laser diffraction scattering, the particle size D at which the cumulative frequency reaches 50% is... ５０ The particle size is preferably 0.5 to 100 μm, more preferably 0.6 to 50 μm, even more preferably 0.7 to 30 μm, and particularly preferably 0.7 to 20 μm. ５０ A moderately large size allows for a reduction in the number of grain boundaries between conductive particles per unit volume. This is thought to lead to a lower resistivity in the resulting conductive pattern. D ５０ By keeping the size of the conductive particles small, the "gaps" between them are reduced, which is thought to lead to a lower resistivity in the resulting conductive pattern.

[0059] Conductive particles can be purchased from companies such as DOWA Electronics and Fukuda Metal Foil & Powder Industry. Two or more different conductive particles may be used in combination for adjusting and optimizing the particle size distribution or for other purposes.

[0060] The ratio of conductive particles to the total nonvolatile components of the conductive paste is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0061] The inclusion of a solvent in the conductive paste improves its applicability or printability on the substrate. The solvent typically includes an organic solvent. The solvent may also include water, as long as it can adequately disperse the conductive particles. The type of solvent is not particularly limited. The solvent should not substantially alter any of the components in the conductive paste. The amount of solvent used can be adjusted as appropriate depending on the application or printing method of the conductive paste. The amount of solvent used is, for example, 3 to 30% by mass, preferably 5 to 25% by mass, and more preferably 10 to 20% by mass, of the total conductive paste.

[0062] The conductive paste may, if necessary, contain resin components such as resins and binders, or dispersants for resin components, but may also substantially not contain resin components and dispersants. When resin components are included, the amount of resin components in the conductive paste is preferably 1 to 15 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1 to 5 parts by mass, per 100 parts by mass of conductive particles. Examples of resin components include polyvinylpyrrolidone, polyester, epoxy resin, (meth)acrylic resin, polyvinyl acetal, cellulosic resin (e.g., ethylcellulose), and phenolic resin. Here, "substantially not containing resin or binder" means either not containing any resin or binder at all, or containing resin or binder in amounts so small that the expected effects (specifically described below) from the use of resin or binder cannot be obtained (for example, 1% by mass or less, specifically 0.5% by mass or less, of the total nonvolatile components of the conductive paste).

[0063] The conductive paste may or may not contain various additive components found in conventional ink compositions and conductive pastes. Examples of additive components include antioxidants, silane coupling agents, and curing agents. These may be used individually or in combination of two or more.

[0064] In the manufacturing method of this embodiment, a laminate is used in which a conductive particle-containing layer 2 is laminated on the surface 1A of a softened or melted thermoplastic resin layer, and a sintering process is carried out. Immediately before the sintering process, the conductive particle-containing layer 2 of the laminate includes unsintered portions in which multiple conductive particles have not been sintered. In the sintering process, the multiple conductive particles contained in the conductive particle-containing layer 2 are sintered by heating and pressurizing treatment to form a conductive film 3.

[0065] The heating and pressing process can be carried out, for example, using a flat press device equipped with a heating mechanism. In other words, the laminate of the base material 1 and the conductive particle-containing layer 2 provided by conductive paste can be sandwiched between two (a pair of) flat plates and pressed while heating, thereby sintering the conductive particles in the conductive particle-containing layer 2.

[0066] In addition to a flat press device, heating and pressurization can also be performed using a roll press device or other devices. For example, a method may be employed in which a laminate comprising a base material 1 and a conductive particle-containing layer 2 is sandwiched between two opposing rolls and transported between these two rolls. Alternatively, a method may be employed in which the laminate is placed on a flat plate or on the flat surface of a table having a flat surface, a roll is brought into contact with it from above, and pressure is applied to the laminate while the roll is rotated. However, when heating and pressurizing using a roll press device, the heating and pressurizing time per unit area tends to be shorter compared to heating and pressurizing using a flat press device, so care should be taken to appropriately control the heating, pressurizing, transport speed (roll rotation speed), etc.

[0067] The heating temperature can be set appropriately depending on the heat resistance of the base material 1 and the type of conductive particles used, but for example, it is 50°C to 200°C, preferably 60°C to 180°C, and more preferably 80°C to 150°C. The pressurization is, for example, 5 MPa to 100 MPa, preferably 5 MPa to 80 MPa, and more preferably 10 MPa to 60 MPa. The processing time is, for example, 0.003 seconds to 10 seconds, preferably 0.006 seconds to 3 seconds, and more preferably 0.01 seconds to 1 second. When using a flat press device, the heating temperature is preferably 50°C to 200°C, more preferably 80°C to 160°C, the pressurization pressure is preferably 5 MPa to 80 MPa, more preferably 5 MPa to 75 MPa, and the heating and pressurization time is preferably 0.1 seconds to 60 seconds, and more preferably 0.5 seconds to 40 seconds.

[0068] Furthermore, it is preferable to cover part or all of the surface of the laminate on which the conductive particle-containing layer 2 is provided with a film-like material and then pressurize the conductive particle-containing layer 2 at least. The material of the film-like material can be a polyester film such as a PET film. From another viewpoint, in order to suppress peeling or damage to the conductive particle-containing layer 2, a release film can preferably be used as the film-like material. A release film is usually a resin film with a release agent coated on at least one side, and examples of release agents include silicone-based, fluorine-based, and non-silicone-based types. Release films are available, for example, from Fujimori Kogyo Co., Ltd. From yet another viewpoint, the film-like material may be a non-resin material such as paper or aluminum foil.

[0069] The manufacturing method of this embodiment may include other steps between the lamination step and the sintering step, and / or after the sintering step. For example, between the lamination step and the sintering step, a penetration step may be performed in which a component X capable of removing the oxide film on the surface of the conductive particles is permeated into the conductive particle-containing layer 2. The method of supplying the liquid in which component X is dissolved or dispersed in the penetration step to at least the surface of the conductive particle-containing layer 2 is not particularly limited. Known methods such as dropping, spraying, and immersion can be used as specific methods. In terms of ease of process implementation and ease of permeating component X into the conductive particle-containing layer 2, it is preferable that in the penetration step, a liquid in which component X is dissolved or dispersed is permeated into the conductive particle-containing layer 2. In this specification, "removal" of the oxide film includes not only cases where the oxide itself present on the surface of the conductive particles is removed, but also cases where the oxide returns to a non-oxide state through chemical changes such as reduction.

[0070] Component X may include one or more selected from the group consisting of carboxylic acids, phosphorus oxoacids, hydrazine compounds, inorganic acids, phenols, and other reducing substances. Examples of carboxylic acids include citric acid, formic acid, acetic acid, malonic acid, malic acid, tartaric acid, ascorbic acid, succinic acid, fumaric acid, and propionic acid. However, it is not limited to these, and organic acids other than carboxylic acids may be used. Examples of phosphorus oxoacids include phosphinic acid, phosphonic acid, phosphorous acid, phosphoric acid, diphosphate, triphosphate, and metatriphosphate. Examples of hydrazine compounds include hydrazine, hydrazine derivatives such as hydrazine salts including monohydrazine hydrochloride, hydrazine dihydrazine hydrochloride, monohydrazine hydrobromide, and hydrazine sulfate, phenylhydrazine, and others -NH-NH ２Examples of compounds with a specific structure include those mentioned above. Inorganic acids include, for example, hydrochloric acid, nitric acid, sulfuric acid, and hydrobromic acid. Phenols include, for example, pyrogallol, orthoaminophenol, and hydroquinone. Other reducing substances include, for example, pyrazolidone compounds. Phenidone is an example of a pyrazolidone compound. These may be used individually or in combination of two or more. Among these, component X can be a compound with a small pKa in water. Specifically, a compound with a pKa of -5.0 to 5.0 in water is preferred as component X, and a compound with a pKa of -4.0 to 4.5 is more preferred as component X. Incidentally, if component X is a polybasic acid, it is preferable that the smallest pKa among multiple pKa values ​​is within the above range. The pKa value here can be the value at room temperature (e.g., 25°C). The liquid containing component X is preferably water in which component X is dissolved or dispersed. Using water is preferable from the standpoint of reducing environmental impact and ensuring process safety (non-flammable). Of course, organic solvents in which component X is dissolved or dispersed can also be used. The concentration of component X in the liquid is, for example, 0.05 to 50 mol / L, preferably 0.1 to 40 mol / L, more preferably 0.1 to 30 mol / L, even more preferably 0.1 to 10 mol / L, and particularly preferably 0.15 to 5.0 mol / L. Of course, a liquid containing component X at a lower concentration than those shown herein may be used, or a liquid containing component X at a higher concentration than those shown herein (e.g., saturation concentration) may be used.

[0071] In the penetration process, it is preferable to treat the conductive particle-containing layer 2 with a carboxylic acid. In this case, component X preferably contains a carboxylic acid, preferably a carboxylic acid with 7 or fewer carbon atoms in the molecule, and more preferably contains formic acid.

[0072] When a sintering process is performed after the penetration process, component X that did not penetrate the conductive particle-containing layer 2 during the penetration process may or may not be removed before the sintering process. To prevent the formation of an oxide film again on the surface of the conductive particles from which the oxide film was removed during the penetration process, it is preferable that the time between the penetration process and the sintering process be short. Specifically, when a sintering process is performed after the penetration process, the time from the end of the penetration process to the start of the sintering process is preferably 1 hour or less, more preferably 30 minutes or less, even more preferably 10 minutes or less, and particularly preferably 1 minute or less. Alternatively, to prevent the formation of an oxide film again on the surface of the conductive particles from which the oxide film was removed during the penetration process, the laminate after the penetration process and before the sintering process may be temporarily stored in an inert gas atmosphere such as a rare gas or nitrogen gas, temporarily stored in a reducing atmosphere, or temporarily stored under vacuum or reduced pressure. After the sintering process, a removal process may be performed to remove any component X remaining on or inside the surface of the obtained conductive film.

[0073] The removal step for removing component X is not particularly limited, as long as it includes a process to reduce the amount of component X remaining in the conductive particle-containing layer 2. This can further reduce the resistivity of the final conductive film 3. For example, if component X has the property of volatilizing when heated, it is conceivable to perform a process to volatilize the component X remaining in the conductive particle-containing layer 2 by heating the conductive particle-containing layer 2 to an appropriate temperature. Another example is to perform a process to dissolve the component X remaining in the conductive particle-containing layer 2 by bringing the conductive particle-containing layer 2 into contact with a liquid such as water. More specifically, the following methods (i) to (v) can be used as processes to reduce the amount of component X remaining in the conductive particle-containing layer 2: (i) Applying an airflow to the conductive particle-containing layer 2. (ii) Injecting an inert gas such as nitrogen gas towards the conductive particle-containing layer 2. (iii) Pressing a liquid-absorbing material such as a sponge against the conductive particle-containing layer 2 to absorb a solution or dispersion containing component X. In a continuous process, it is preferable to use a roll-shaped sponge as the material that can absorb liquid. After absorbing the solution or dispersion, the conductive particle-containing layer 2 may be brought into contact with a liquid such as water (washing), and then the material that can absorb liquid may be pressed against the conductive particle-containing layer 2 again. (iv) The solution or dispersion containing component X is "squeezed" by applying pressure to the conductive particle-containing layer 2 using a roll. After that, the conductive particle-containing layer 2 may be brought into contact with a liquid such as water (washing), and then the liquid may be squeezed out again using a roll. Incidentally, by appropriately controlling the pressure and not heating when applying pressure, the solution or dispersion containing component X can be squeezed out without sintering the conductive particles in the conductive particle-containing layer 2. (v) A combination of two or more of the above (i) to (iv). For example, a combination of (i) and (ii), a combination of (iii) and (iv), etc.

[0074] Furthermore, a pre-pressure step may be included between the lamination step and the penetration step, in which the conductive particle-containing layer 2 is pressurized at least. Performing the pre-pressure step is optional, but performing this step makes it easier to maintain the shape of the conductive particle-containing layer 2 in the subsequent steps (especially the penetration step). When the pressure applied to the conductive particle-containing layer 2 in the pre-pressure step is P1, and the pressure applied to the conductive particle-containing layer 2 in the sintering step is P2, it is preferable that P1 < P2. More specifically, it is preferable that P1 is 0.9 times or less of P2, more preferably 0.75 times or less, and even more preferably 0.6 times or less. In other words, it is preferable that the pressure in the pre-pressure step is sufficiently smaller than the pressure required to compress or sinter the conductive particles in the sintering step.

[0075] By the above manufacturing method, a resin substrate 10 with a conductive film can be obtained.

[0076] Figure 2 is a schematic cross-sectional view showing an example of a conductive film-coated resin substrate 10. The conductive film-coated resin substrate 10 comprises a resin substrate (substrate 1) including a thermoplastic resin layer, and a conductive film 3 formed on at least a portion of the surface 1A of the substrate 1.

[0077] Multiple conductive particles in the conductive film 3 are sintered and connected to one another. Sintering means that, through heating and pressurizing, the particles fuse together at the contact points on the metal surfaces between them, and multiple conductive particles are joined (connected) to form an integrated structure.

[0078] In one embodiment, the conductive film-coated resin substrate 10 may have an embedded structure in which at least a portion of the conductive film 3 is embedded in a recess 5 formed by the surface 1A of the substrate 1 being recessed in the thickness direction.

[0079] In a cross-section of the conductive film-coated resin substrate 10 in the thickness direction, the conductive film 3 embedded in the recess 5 of the substrate 1 may occupy, for example, 50% or more of the total area, preferably 70% or more, and the entire conductive film may be embedded in the recess 5. However, a portion of the conductive film 3 may have a portion that is not embedded in the recess 5 and protrudes upward in the thickness direction.

[0080] In one embodiment, the thermoplastic resin layer in the substrate 1 may have a surface modification region 8 in at least a portion near the surface 1A. The surface modification region 8 may form a layer having a predetermined thickness in the depth direction from the surface 1A. This surface modification region 8 is composed of a softened or melted and solidified portion of the surface 1A of the thermoplastic resin layer, i.e., a softened layer or a molten layer. In one preferred embodiment, the surface modification region 8 may be configured to include part or all of the amorphous portion of the thermoplastic resin layer.

[0081] In another embodiment, in the cross-section in the thickness direction of the conductive film-coated resin substrate 10, an interface 9 may exist in at least a portion between the thermoplastic resin layer of the substrate 1 and the conductive film 3, and at the interface 9, the thermoplastic resin layer other than the surface modification region 8 may be in contact with the conductive film 3, and the surface modification region 8 may be in contact with the conductive film 3.

[0082] Figure 3 is a top view of an example of a conductive film-coated resin substrate 10, viewed from the direction normal to the surface 1A of the substrate 1. As shown in Figure 3, the conductive film 3 may have a conductive pattern including linear portions 3A. The linear portions 3A may be composed of straight lines or curves. The conductive pattern of the conductive film 3 is not limited to narrow linear portions 3A, but may also have pads or capacitor hats with a relatively large area. For example, the top view of the pads or capacitor hats may be circular, elliptical, square, or other polygonal shapes. Note that the cross-sectional view in Figure 2 may be a cross-section of the linear portion 3A of the conductive film 3 shown in Figure 3. When the plane of the surface 1A of the substrate 1 is defined as the X-Y plane, the X direction in Figure 3 may be defined as the short direction of the linear portion 3A, and the Y direction may be defined as the long direction of the linear portion 3A.

[0083] In Figure 3, the direction in which the line portion 3A of the conductive pattern extends is defined as the longitudinal direction, and the width direction of the line portion 3A is defined as the short direction. In this embodiment, in at least one of the cross-sections B that pass through the short direction and the thickness direction of the line portion 3A of the conductive pattern, the width of the line portion 3A in the short direction is, for example, 30 μm or more and 5000 μm or less, preferably 70 μm or more and 3000 μm or less, and more preferably 100 μm or more and 1000 μm or less. Even fine lines with a width of 500 μm or less, which are usually difficult to punch out, can be formed by the printing described above, and adhesion to the base material 1 can be provided to such fine line portions 3A.

[0084] <Electronic Devices> Electronic devices can be manufactured using a substrate (resin substrate with conductive film) equipped with the conductive film of this embodiment. By appropriately designing the pattern of the conductive film, a substrate equipped with a conductive film that can function as a circuit can be manufactured. Then, by combining this substrate with other electronic elements, an electronic device can be manufactured.

[0085] Here are some examples of electronic devices. It should be noted that electronic devices are, of course, not limited to these. • Sensors: For example, the conductive material with the conductive pattern of this embodiment can be applied to conductive members / circuits in sensors such as pressure sensors and vital signs sensors. • Solar cells: For example, the conductive material with the conductive pattern of this embodiment can be applied to the current collection wiring of solar cells. • Membrane switches: A membrane switch is a thin sheet-like switch made by printing circuits and contacts onto a film and then layering them. The conductive material with the conductive pattern of this embodiment can be applied to form the circuits and contacts of such switches. • Touch sensors / touch panels: For example, the conductive material with the conductive pattern of this embodiment can be applied to form lead wiring in touch sensors and touch panels. It is also conceivable to apply the manufacturing method of the conductive material with the conductive pattern of this embodiment to form transparent electrodes in touch sensors and touch panels. • Flexible substrates: Conventionally, circuits are formed by first coating the entire surface of a flexible film with a metal film, and then removing unnecessary parts of the metal film using chemicals. Instead of this conventional method, it is conceivable to form circuits using the manufacturing method of the conductive material with the conductive pattern of this embodiment.

[0086] In particular, in electronic devices where circuits were conventionally formed using conductive paste, using the manufacturing method of this embodiment for circuit formation can reduce the resistivity of the circuit, which can lead to improved performance of the electronic device.

[0087] A particularly preferred electronic device is the RF tag. Specifically, the substrate equipped with the conductive pattern of this embodiment is preferably used to manufacture conductive circuits such as the antenna portion of the RF tag. For the specific structure of the RF tag, refer to, for example, Japanese Patent Publication No. 2003-332714 and Japanese Patent Publication No. 2020-46834.

[0088] <Method for Manufacturing Electromagnetic Shielding Sheets> As an application other than electronic devices, it is conceivable to manufacture electromagnetic shielding sheets using the manufacturing method of the conductive film-equipped substrate (resin substrate with conductive film) of this embodiment. Specifically, by making the pattern used when printing the conductive paste in the lamination process a pattern specific to electromagnetic shielding sheets (such as a mesh pattern), electromagnetic shielding sheets can be manufactured.

[0089] <Method for Manufacturing a Planar Heating Element> As another application, it is conceivable to manufacture a planar heating element using the method for manufacturing a substrate (resin substrate with conductive film) equipped with the conductive pattern of this embodiment. A planar heating element is a material on which electrical wiring is provided, and heat is generated when an electric current is passed through the wiring. Specific examples of planar heating elements include those used for anti-fogging and cold protection, such as the rear windows of passenger cars.

[0090] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention.

[0091] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to the descriptions of these examples.

[0092] <Preparation of conductive paste> (Conductive paste) Electrolytic copper powder (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., D ５０ 82 parts by mass of (5 μm, dendritic), 2 parts by mass of polyester resin, and 16 parts by mass of organic solvent were weighed and kneaded with a spatula to obtain a mixture. This mixture was then stirred using a rotary-orbiting stirrer. In this manner, a conductive paste in paste form was obtained at 23°C.

[0093] <Manufacturing of conductive film-coated substrates> [Example 1] (Printing process) The conductive paste 1 described above was screen printed onto the surface of the substrate to form a patterned coating film (conductive particle-containing layer) and obtain a laminate. The printing process was carried out according to the following specific conditions. ・Substrate: Biaxially oriented PET film (thickness 50 μm, width 150 mm, heat resistance temperature 160°C) was used. ・Printing machine: Screen printing machine (Micro-Tech, Desk Top 38SA model) was used. ・Screen plate: A screen plate with a pattern having fine lines (325 mesh, mesh diameter 16 μm, emulsion thickness 20 μm) was used. ・Printing conditions: Printing pressure 0.18 MPa, squeegee speed 30 mm / sec, clearance (distance between screen plate and substrate) 2.0 mm, attack angle 80°.

[0094] For the biaxially oriented PET film used as the substrate in Example 1, the thermal shrinkage rate in the MD direction (MD) was measured in accordance with JIS C 2318 under the conditions of 150°C for 30 minutes. １５０ ), the thermal shrinkage rate in the MD direction (MD) under the conditions of 180°C for 30 minutes. １８０ ) and thermal shrinkage coefficient in the TD direction (TD １８０ ) was measured. As a result, MD １８０ 0.2%, TD １８０ 0.1%, | MD １８０ - MD １５０ The percentage for | was 0.05%.

[0095] (Drying process) The laminate obtained in the printing process was placed in a hot air circulating atmospheric oven and heated at 100°C for 15 minutes to evaporate the solvent and obtain a dried film of the conductive particle-containing layer. This formed a patterned dried film with a thickness of approximately 30 μm on the surface of the substrate.

[0096] (Surface modification process) After the drying process, the substrate, which did not have a patterned dried film formed on its back side, was irradiated with xenon flash using a xenon flash device (XENON Corporation, X-1100) under the conditions of applied voltage of 3000V, applied energy of 1500J, and irradiation time of 680μs.

[0097] (Immersion Process) After the surface modification process, the entire laminate was immersed in a formic acid aqueous solution (an aqueous solution containing formic acid as component X) for 10 seconds. Subsequently, the laminate was washed and drained.

[0098] (Sintering Process) After the penetration process, a film-like material (polyimide film) was placed in contact with the patterned conductive particle-containing layer to obtain a laminated body of the laminated body and the film-like material. The laminated body was placed on a metal plate (30 mm x 20 mm) set on the lower plate using a flat press machine (Housen Co., Ltd., HSSP008) equipped with two opposing flat plates (upper plate, lower plate), and hot-pressed under the following conditions to sinter the copper powder (multiple conductive particles) in the conductive particle-containing layer and form a sintered body (conductive film). After hot-pressing, the film-like material was peeled off to produce a conductive film-coated substrate with a conductive film provided on the surface of the substrate. ・Hot-pressing conditions: Heating temperature (pressing temperature): 140°C, pressure: 83 MPa, time: 30 seconds. However, the pressing temperature was not the machine's displayed value but was accurately measured and adjusted using a thermocouple. The pressure was calculated as follows. First, regarding the area of ​​the metal plate placed on the flat press machine (lower plate), 30 x 20 mm = 600 mm ２ This was calculated. The applied pressure was denoted as F. 600 mm ２ Since a force F was applied to this region, F ÷ 600 mm ２ The pressure was calculated using the following method.

[0099] [Comparative Example 1] A conductive film-coated substrate was manufactured in the same manner as in Example 1, except that a PET film having the following heat shrinkage rate was used as the substrate in the above printing process, instead of a biaxially oriented PET film. In accordance with the above method, the PET film of Comparative Example 1 had the following heat shrinkage rate (MD) １５０ ), the thermal shrinkage rate in the MD direction (MD) under the conditions of 180°C for 30 minutes. １８０ ) and thermal shrinkage coefficient in the TD direction (TD １８０ ) The results of measuring MD １８０ 1.3%, TD １８０ 0.2%, | MD １８０ - MD １５０ The percentage for | was 0.9%.

[0100] [Comparative Example 2] A conductive film-coated substrate was manufactured in the same manner as in Comparative Example 1, except that the heating temperature (pressing temperature) in the sintering process was changed to 120°C.

[0101] <Observation of the cross-section> The sample obtained by molding both sides of the conductive film-coated substrate with epoxy resin was cut using ion milling to expose the cross-section of the fine wire portion of the conductive pattern of the conductive film, perpendicular to the direction in which the conductive pattern extends. This cross-section was photographed with a scanning electron microscope (SEM) to obtain a cross-sectional image. In the cross-sectional image of Example 1, although the boundaries between copper particles were partially visible, it was confirmed that the particles were in close contact with each other and that electrical connections were formed. Furthermore, it was confirmed that a structure in which a part of the conductive film was embedded in the resin layer of the substrate was observed. The cross-sectional SEM image of Example 1 is shown in Figure 4.

[0102] <Measurement of Resistivity> The resistance of the fine-line portion (measurement width of 250 μm in the central region) of the conductive pattern of the conductive film on the obtained conductive film-coated substrate was measured using a four-terminal resistance meter, and the film thickness was measured using a film thickness gauge. The resistivity was calculated from the measured resistance and film thickness. A smaller resistivity value is preferable. The results are shown in Table 1.

[0103] <Deformation of Substrate> The obtained conductive film-coated substrates were visually inspected for any deformation. The presence or absence of deformation was determined based on whether or not "significant distortion or bending occurred in part or the entire substrate." The results are shown in Table 1.

[0104]

[0105] Based on the above results, the conductive film-coated substrate of Example 1 showed no deformation of the substrate compared to Comparative Example 1, and exhibited lower resistance of the conductive film compared to Comparative Examples 1 and 2.

[0106] This application claims priority based on Japanese Patent Application No. 2025-056748, filed on 28 March 2025, and incorporates all of its disclosures herein.

[0107] 1. Substrate 1A Front surface 1B Back surface 2. Conductive particle-containing layer 3. Conductive film 3A Line portion 4. Xenon flash 5. Recess 8. Surface modification region 9. Interface 10. Resin substrate with conductive film

Claims

1. A resin substrate with a conductive film, comprising: a resin substrate including a thermoplastic resin layer; and a conductive film provided on at least a portion of the surface of the resin substrate, wherein the conductive film comprises a sintered body of a plurality of conductive particles, and the thermal shrinkage rate in the MD direction of the thermoplastic resin layer under conditions of 180°C for 30 minutes, as measured in accordance with JIS C 2318, is 1.0% or less.

2. A resin substrate with a conductive film, comprising: a resin substrate including a thermoplastic resin layer; and a conductive film provided on at least a portion of the surface of the resin substrate, wherein the conductive film comprises a sintered body of a plurality of conductive particles, and the difference in thermal shrinkage rates |MD-TD| between the MD direction and the TD direction in the thermoplastic resin layer under conditions of 180°C for 30 minutes, as measured in accordance with JIS C 2318, is 0.7% or less.

3. A conductive film-coated resin substrate according to claim 1 or 2, wherein the thermal shrinkage rate in the MD direction of the thermoplastic resin layer under the conditions of 150°C for 30 minutes, as measured in accordance with JIS C 2318, is MD １５０ The thermal shrinkage rate in the MD direction of the thermoplastic resin layer under the conditions of 180°C for 30 minutes is MD １８０ In this case, the difference in thermal shrinkage coefficients |MD １８０ - MD １５０ A conductive film-coated resin substrate in which the | value is 0.5% or less.

4. A conductive film-coated resin substrate according to claim 1 or 2, wherein the thermal shrinkage rate in the TD direction of the thermoplastic resin layer under conditions of 180°C for 30 minutes, as measured in accordance with JIS C 2318, is 0.2% or less.

5. A conductive film-coated resin substrate according to claim 1 or 2, wherein the thermoplastic resin layer is a biaxially oriented film.

6. A conductive film-coated resin substrate according to claim 1 or 2, wherein the thermoplastic resin layer comprises one or more selected from the group consisting of polyester, polycarbonate, and polyimide.

7. A resin substrate with a conductive film according to claim 1 or 2, wherein the heat resistance temperature of the thermoplastic resin layer is 80°C or higher.

8. A resin substrate with a conductive film according to claim 1 or 2, wherein at least a portion of the conductive film is embedded within the thermoplastic resin layer.

9. A resin substrate with a conductive film according to claim 1 or 2, wherein the particles contained in the conductive particles include dendritic particles.

10. A resin substrate with a conductive film according to claim 1 or 2, wherein the particle diameter D at the point where the cumulative volume from the smallest particle side reaches 50% in the volume-based cumulative distribution of particle diameters obtained when the particle diameter of the conductive particles is measured by laser diffraction scattering is defined as the particle diameter D ５０ However, the conductive film-coated resin substrate is between 0.5 μm and 100 μm in thickness.

11. A resin substrate with a conductive film according to claim 1 or 2, wherein the conductive particles contain copper.

12. An electronic device comprising a resin substrate with a conductive film according to claim 1 or 2.

13. An electronic device according to claim 12, wherein the electronic device is an RF tag.

14. An electromagnetic shielding sheet comprising a resin substrate with a conductive film according to claim 1 or 2.

15. A planar heating element comprising a resin substrate with a conductive film according to claim 1 or 2.

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