HK1241321B - Conductive sheet - Google Patents

Description

Conductive sheet

This application is a divisional application of the invention patent application with application date of September 18, 2013, application number 201380048563.1, and invention name “Conductive Thin Sheet”.

Technical Field

The present invention relates to a conductive sheet suitable for achieving electrical continuity between a display control surface of a display control panel and its back surface.

Background Art

As a conventional electromagnetic wave sealant, a conductive sheet with a conductive adhesive layer formed on one side of a metal foil such as aluminum or copper has been proposed (Patent Document 1). To prevent short circuits caused by contact with other conductors, this conductive sheet has been improved as follows: a polyethylene terephthalate (PET) film is laminated as an insulating resin layer on the side of the conductive sheet not having the conductive adhesive layer, thereby imparting insulation properties to one side of the conductive sheet. Furthermore, a release film is attached to the conductive adhesive layer to improve handling.

However, in recent years, display surface control panels (so-called touch panels) have been used in smartphones, portable game consoles, ticket machines, etc., and conductive sheets have been used to achieve conduction from their display surface control surfaces to their back surfaces. For such conductive sheets, in order to prevent them from accidentally coming into contact with other conductive bodies such as metal frames and causing short circuits, insulating properties have been given to the single surface by laminating an insulating resin film on the single surface. When achieving conduction from the display surface control surface of the display surface control panel to its back surface through such a conductive sheet, attempts have been made to wrap the outer edge of the display surface control panel so that the insulating resin film of the conductive sheet becomes the outer side. In this case, in order to improve the quality of the image discernible through the display surface control panel or to prevent a decrease in image discernibility, attempts have been made to color the insulating resin film itself black, or to form a black printed layer on the insulating resin film so that the insulating resin film of the conductive sheet becomes a black frame.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Laid-Open No. 62-227985.

Summary of the Invention

Problems to be solved by the invention

However, when the conductive sheet of Patent Document 1 is passed through a coating machine or when the release film is peeled off, the metal layer is more susceptible to plastic deformation than the PET film, which is more susceptible to elastic deformation. This leads to the problem that the conductive sheet is prone to curling. Furthermore, when the conductive sheet is attached to the display surface control panel so as to wrap around the outer edge of the display surface control panel, the conductive sheet does not adequately follow the step (difference in plane) or corner shape of the attached portion, resulting in easy peeling and failure to achieve the required shape retention.

The object of the present invention is to solve the above-mentioned problems of the prior art and to impart to a conductive sheet a property that is not easy to curl, has good shape stability, and has shape-following properties. The conductive sheet is formed by laminating a conductive adhesive layer on one side of a base substrate (base substrate) and laminating a light-shielding insulating layer on the other side of the base substrate.

Means for solving problems

The present inventors have found that the above-mentioned object can be achieved by using a laminate having the same metal layer laminated on both surfaces of a resin film as a base substrate in the center portion in the thickness direction of a conductive sheet, and have completed the present invention.

That is, the present invention provides a conductive sheet, which is formed by laminating a conductive adhesive layer on one side of a base substrate and laminating a light-shielding insulating layer on the other side of the base substrate, wherein the base substrate has a structure in which the same metal layer is formed on both sides of a resin film.

In this case, the surface insulation level of the light-shielding insulating layer of the conductive sheet preferably has a surface resistance value of 1.0×10 ⁸ Ω/□ or more, and the light-shielding level preferably has a glossiness of 80% or less and an optical density of 1 or more.

In addition, the present invention also provides an image display module, which has a display surface control panel and an image display panel controlled by the display surface control panel, wherein the display surface control panel is connected to the conductive thin film of the above-mentioned present invention by a surface electrode provided on the surface outer edge portion of the display surface control panel and a back electrode provided on the back outer edge portion, which is configured to wrap the outer edge portion of the display surface control panel.

Effects of the Invention

The conductive sheet of the present invention, in which a conductive adhesive layer is laminated on one side of a base substrate and a light-shielding insulating layer is laminated on the other side of the base substrate, uses a base substrate having a structure in which the same metal layer is formed on both sides of a resin film as the base substrate. Therefore, even if the conductive sheet is stretched, the metal layers on both sides of the resin film show the same elongation, thereby significantly suppressing the occurrence of curling. In addition, since the metal layers are arranged on both sides of the insulating film, it can be attached with good shape tracking properties to changing shapes such as curved surfaces or bends (corners), and the shape retention is also excellent.

Furthermore, when the surface insulation level of the conductive sheet's light-blocking insulating layer reaches a surface resistance of 1.0×10 ⁸ Ω/□ or higher, short circuits caused by contact with other conductive materials can be suppressed. Furthermore, when the light-blocking level reaches a glossiness of 80% or lower and an optical density of 1 or higher, a grid-like black frame can be placed on the outer edge of the display control panel, significantly improving the visibility of images viewed through the display control panel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a cross-sectional view of a conductive sheet of the present invention;

FIG2 is a cross-sectional view of a conductive sheet of the present invention;

FIG3 is a cross-sectional view of the conductive sheet of the present invention.

DETAILED DESCRIPTION

Hereinafter, the conductive sheet of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a conductive sheet 100 of the present invention. The conductive sheet 100 has a structure in which a conductive adhesive layer 20 is formed on one surface of a base substrate 10 and a light-shielding insulating layer 30 is formed on the other surface.

＜Base material＞

The conductive sheet 100 of the present invention is characterized by a structure in which the base substrate 10 has the same metal layers 2 and 3 laminated on both surfaces of a resin film 1. This significantly reduces the occurrence of curling in the conductive sheet and provides the conductive sheet with excellent shape conformability and shape stability.

As the resin film 1 constituting the base substrate 10, a resin film used as a base film for a conductive sheet can be preferably used. Examples of such resin films include polyester films, polyolefin films, polyamide films, polyurethane films, and polystyrene films. Among these, polyester films, particularly polyethylene terephthalate films, are preferably used from the perspectives of availability, mechanical strength, heat resistance, cost, and rust resistance.

The thickness of the resin film 1 constituting the base substrate 10 is preferably 5 to 20 μm, more preferably 7 to 15 μm, in order to maintain the mechanical strength of the conductive sheet and ensure good shape conformability and shape stability.

Metal layers 2 and 3 constituting the base substrate 10 can be metal layers used in conventional conductive sheets. Examples of such metal layers 2 and 3 include aluminum, copper, nickel, gold, and silver. Among these, aluminum is preferably used in view of availability, mechanical strength, heat resistance, cost, and rust resistance.

In order to maintain the mechanical strength of the conductive sheet and ensure good shape followability and shape stability, the thickness of the metal layer 2 on the conductive adhesive layer 20 side and the metal layer 3 on the light-shielding insulating layer 30 side are preferably 5 to 20 μm, more preferably 7 to 15 μm.

From the perspective of both shape followability and shape retention, the ratio of the thickness [Mt1] of the metal layer 2 on the conductive adhesive layer 20 side, the thickness [Bt] of the resin film 1, and the thickness [Mt2] of the metal layer 3 on the light-shielding insulating layer 30 side is preferably [Mt1]:[Bt]:[Mt2] = 0.25~4:1:0.25~4, and more preferably 0.4~2.4:1:0.4~2.4.

The metal layers 2 and 3 can be formed on the resin film 1 using conventional methods. Examples include a method in which a metal foil is laminated onto the resin film 1 via an adhesive layer (not shown) formed from a dry adhesive such as a polyester adhesive or a polyurethane adhesive containing an isocyanate crosslinking agent; a method in which the metal layers 2 and 3 are formed by electroless metal plating and then electrolytic metal plating on both sides of the resin film 1; or a method in which the metal layers 2 and 3 are laminated on both sides of the resin film 1 by vacuum deposition. Among these, the method in which the metal layers are laminated via an adhesive layer is preferably employed from the perspectives of high productivity and low manufacturing costs.

In addition, if the linear expansion coefficient [ppm/°C] of the resin film 1 constituting the base substrate 10 is too large, curling is likely to occur, and if it is too small, the laminated structure tends to be unstable under a thermal environment, so there is a concern about interlayer delamination. Therefore, it is preferably 15 to 100 ppm/°C, and more preferably 20 to 70 ppm/°C.

The linear expansion coefficient (ppm/°C) of the metal layers 2 and 3 is preferably 12 to 25 ppm/°C, more preferably 16 to 23 ppm/°C, from the viewpoint of the stability of the laminated structure with the resin film 1 .

If the difference between the linear expansion coefficient of the resin film 1 and the linear expansion coefficient of the metal layers 2 and 3 is too large, curling tends to occur. Therefore, it is preferably 40 ppm/°C or less, and more preferably 25 ppm/°C or less.

The JIS K7113 tensile modulus [GPa] of the resin film 1 constituting the base substrate 10 tends to curl if too low, and tends to impair shape conformability if too high. Therefore, it is preferably 0.3 to 15 GPa, more preferably 2 to 7 GPa.

The metal layers 2 and 3 have a JIS K7113 tensile modulus [GPa] of preferably 45 to 200 GPa, more preferably 75 to 130 GPa, since too low a tensile modulus [GPa] tends to cause curling, and too high a tensile modulus tends to impair shape conformability.

If the difference in tensile modulus according to JIS K7113 between the resin film 1 and the metal layers 2 and 3 constituting the base substrate 10 is too large, curling tends to occur. Therefore, it is preferably 100 GPa or less, and more preferably 80 GPa or less.

＜Light-shielding insulating layer＞

The light-shielding insulating layer 30 constituting the conductive sheet 100 of the present invention is a layer that imparts light-shielding and insulating properties to the conductive sheet 100. If the insulating level of the surface of the light-shielding insulating layer 30 of the conductive sheet 100 is too low, short circuits may occur. Therefore, the surface resistance is preferably 1.0×10 ⁸ Ω/□ or greater, and more preferably 1.0×10 ¹⁰ Ω/□ or greater.

In addition, regarding the light-shielding level of the light-shielding insulating layer 30, in order to improve the image distinguishability, the glossiness of JIS Z8741 (incident angle 60°) is preferably less than 80%, more preferably less than 40%, and the optical density of JIS K7605 is preferably greater than 1, more preferably greater than 1.2, and further preferably greater than 1.4.

The thickness of the light-shielding insulating layer 30 is preferably 3 to 15 μm, more preferably 5 to 11 μm. If it is too thin, desired optical properties tend to be impaired, while if it is too thick, cracks tend to be easily generated.

Such a light-shielding insulating layer 30 can have various configurations with surface resistance, glossiness, and optical density within the above-mentioned ranges. Examples include a configuration comprising a single black resin layer formed of an insulating resin colored with a black colorant, as shown in FIG1 ; and a configuration comprising a black resin layer 30a formed of an insulating resin colored with a black colorant and an insulating primer layer 30b or matt varnish layer 30c formed on one surface thereof, as shown in FIG2 or FIG3 .

The insulating resin of the black resin layer constituting the light-shielding insulating layer 30 includes, for example, ethylene-α-olefin copolymers such as polyethylene, polypropylene, and ethylene-propylene copolymer; fluorine-based polymers such as polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl acetal, polyvinylidene fluoride, and polytetrafluoroethylene; thermoplastic resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer (ABS) resin, polyphenylene ether copolymer (PPE) resin, modified PPE resin, aliphatic polyamides, aromatic polyamides, polyimides, polyamide-imides, polymethacrylic acid, polymethyl methacrylate, polymethacrylates such as polyacrylic acid, polycarbonate, polyphenylene sulfide, polysulfone, polyethersulfone, polyether nitrile, polyether ketone, polyketone, liquid crystal polymer, silicone resin, and ionomer. In addition, thermoplastic elastomers such as styrene-butadiene block copolymers or their hydrogenated products, styrene-isoprene block copolymers or their hydrogenated products, styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and polyamide-based thermoplastic elastomers can also be mentioned. Other examples include cross-linked rubbers, epoxy resins, phenolic resins, polyimide resins, unsaturated polyester resins, and diallyl phthalate resins. Specific examples of cross-linked rubbers include thermosetting resins such as natural rubber, acrylic rubber, butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene-propylene copolymer rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, butyl rubber, halogenated butyl rubber, fluororubber, polyurethane rubber, and silicone rubber. Photocurable resins can also be used.

Examples of black colorants include well-known black dyes and pigments such as aniline black, carbon black, and titanium black. If the average particle size of these colorants is too small, uniform mixing into the insulating resin during manufacturing may be difficult. If the average particle size is too large, the smoothness of the light-blocking insulating layer 30 may be reduced. Therefore, the average particle size of the colorant is preferably 10 to 500 nm, more preferably 50 to 100 nm. Furthermore, if the content of the black colorant in the black resin layer is too low, the desired optical properties may not be achieved. If the content is too high, there is a risk of reduced adhesion to adjacent layers or peeling. Therefore, the content of the black colorant is preferably 10 to 40% by mass, more preferably 15 to 30% by mass.

In addition, as the insulating primer layer 30b shown in FIG. 2 , there can be mentioned a primer layer obtained by mixing a filler such as silica into the insulating resin exemplified as the black resin layer as necessary to prevent blocking.

If the thickness of the insulating primer layer 30b is too thin, the desired insulation properties tend not to be obtained, and if it is too thick, the desired shape retention tends not to be obtained. Therefore, the thickness of the insulating primer layer 30b is preferably 2 to 10 μm, more preferably 3 to 7 μm.

In addition, as the matte paint layer 30c shown in Figure 3, there can be listed: a matte paint layer obtained by preferably containing 30 to 80 mass % of fillers with an average particle size of 0.1 to 10 μm such as silica, barium sulfate, calcium carbonate, polyethylene beads, polystyrene beads, benzoguanamine beads, etc. in the insulating resin exemplified by the black resin layer, and forming a film to achieve a matte style preferred appearance and good coating strength in a well-balanced manner.

If the thickness of the matte varnish layer 30c is too thin, the desired insulation properties may not be obtained. If it is too thick, the desired shape retention or optical properties may not be obtained. Therefore, the thickness of the matte varnish layer 30c is preferably 2 to 10 μm, more preferably 3 to 7 μm.

It should be noted that when the light-shielding insulating layer 30 is a single black resin layer as shown in FIG1 , aniline black is preferably used as the black colorant, given its inherent insulating properties. Furthermore, when the light-shielding insulating layer 30 has a two-layer structure as shown in FIG2 or FIG3 , aniline black can be used as the black colorant for the black resin layer 30a. However, since the insulating primer layer 30b or the matte varnish layer 30c ensures insulation, carbon black, which inherently exhibits conductivity, can also be used without impairing the effects of the present invention.

<Conductive adhesive layer>

The conductive adhesive layer 20 constituting the conductive sheet 100 can be a conductive adhesive layer of an existing conductive sheet. For example, a conductive adhesive layer can be formed by mixing conductive particles such as carbon black or metal particles with an insulating resin, such as the black resin layer, in an amount sufficient to ensure conductivity of 500 mΩ/□ or less.

If the thickness of the conductive adhesive layer 20 is too thin, the desired adhesion tends not to be obtained, and if it is too thick, the desired conductive characteristics tend not to be obtained. Therefore, the thickness of the conductive adhesive layer 20 is preferably 10 to 35 μm, more preferably 15 to 25 μm.

<Manufacturing of Conductive Sheet>

The conductive sheet of the present invention can be manufactured using known methods. For example, a dry adhesive such as a polyurethane adhesive containing an isocyanate curing agent is applied to one side of a resin film such as a PET film and laminated with a metal layer such as aluminum foil. The dry adhesive is then applied to the other side in the same manner and laminated with a metal layer, thereby producing a base substrate with a double-sided metal layer. Next, a coating for a conductive adhesive layer is applied to a release sheet and dried to form a conductive adhesive layer, and then a base substrate is laminated thereon. Next, a black ink for forming a black resin layer is applied to the base substrate and dried to form a light-shielding insulating layer. Thus, the conductive sheet of FIG. 1 is obtained.

The conductive sheets of FIG. 2 and FIG. 3 can be manufactured basically in the same manner as the conductive sheet of FIG. 1 , except that a black resin layer and a matte varnish layer or an insulating primer layer are applied and dried to form films, respectively.

The conductive sheet of the present invention can be preferably used in an image display module in which conductive portions are arranged on a plane having undulations, or in which conductive portions are not arranged on the same plane.

As an example of the former, an image display module can be exemplified, in which a display panel of a notebook computer or the like is connected to a separate substrate via an arbitrary bend or step via a conductive sheet. This image display module exemplified in the notebook computer also forms part of the present invention.

As an example of the latter, an image display module can be exemplified, which combines a display surface control panel with an image display panel such as a liquid crystal display panel, which is the object of its control. The display surface control panel is formed by connecting a front electrode provided on the outer edge of the front surface of the display surface control panel, such as a touch panel, and a back electrode provided on the outer edge of the back surface of the display surface control panel, via a conductive sheet arranged so as to wrap around the outer edge of the display surface control panel. This image display module is also part of the present invention.

Example

Example 1

A polyester resin (UE3220, Yunichika (Strain)) using an isocyanate curing agent (Kolonate L, Nippon Polyuretane Industries (Strain)) was applied to one side of a 5 μm thick PET film (Maila, Teijin DuPont Foil (Strain)) at 3 g/ ^m2 (based on dry coating weight), and then a 7 μm thick soft aluminum foil (1030N-0 material, Nippon Foil (Strain)) was laminated. Similarly, a 7 μm thick soft aluminum foil (1030N-0 material, Nippon Foil (Strain)) was laminated to the other side of the PET film to prepare a base substrate.

A conductive black adhesive layer was formed by coating a conductive black adhesive (acrylic adhesive containing 10% by mass of carbon black) on a peelable PET film to a dry thickness of 25 μm and drying it, and the previously prepared base substrate was laminated on the conductive black adhesive layer.

Next, an insulating black ink (an ink obtained by dispersing aniline black (Tokyo Color Industry Co., Ltd.) in a polyester resin (Byron 200, Toyobo Co., Ltd.) (Dekselier Co., Ltd.)) was applied to the base substrate to a dry thickness of 3 μm and dried to form a light-shielding insulating layer. This produced a conductive sheet having the composition shown in Table 1.

Example 2

The same operation as in Example 1 was repeated except that a 12 μm thick PET film (E5100, Toyobo Co., Ltd.) was used instead of the 5 μm thick PET film of the base substrate, thereby obtaining a conductive sheet having the structure shown in Table 1.

Example 3

The same operations as in Example 1 were repeated except that a laminate of an insulating primer layer (polyester resin (Bilon 200, Toyobo Co., Ltd.) having a thickness of 3 μm from the base substrate side) and a carbon black ink layer (ink (Dekselair Co., Ltd.) obtained by dispersing carbon black (MA8, Mitsubishi Chemical Co., Ltd.) in polyester resin (Bilon 200, Toyobo Co., Ltd.)) formed thereon was used as the light-shielding insulating layer, thereby obtaining a conductive sheet having the structure shown in Table 1.

Example 4

The same operations as in Example 1 were repeated except that a laminate of a 3 μm thick carbon black ink layer {ink obtained by dispersing carbon black (MA8, Mitsubishi Chemical Corporation) in a polyester resin (Bilon 200, Toyobo Corporation) (Dekselair Co., Ltd.)} and a 3 μm thick matte varnish layer (LG6620, Tokyo Inki Co., Ltd.) was used as the light-shielding insulating layer. Thus, a conductive sheet having the structure shown in Table 1 was obtained.

Comparative Example 1

The same operations as in Example 1 were repeated, except that a 3 μm thick carbon black ink layer {ink obtained by dispersing carbon black (MA8, Mitsubishi Chemical Corporation) in a polyester resin (Bilon 200, Toyobo Corporation) (Dekselair Co., Ltd.)} was used as the light-shielding insulating layer, thereby obtaining a conductive sheet having the structure shown in Table 1.

Comparative Example 2

The polyurethane adhesive used in Example 1 was applied to the metal layer of the base substrate before the carbon black ink layer was formed, and a 5 μm thick PET film (MaiLa, Teijin DuPont Filmu Co., Ltd.) was laminated thereon before forming the carbon black ink layer. The same operations as in Comparative Example 1 were repeated, except that the carbon black ink layer was then formed. Thus, a conductive sheet having the structure shown in Table 1 was obtained.

Comparative Example 3

The same operation as in Comparative Example 2 was repeated except that a 12 μm thick PET film (E5100, Toyobo Co., Ltd.) was used instead of the 5 μm thick PET film sandwiched by the aluminum foil of the base substrate, thereby obtaining a conductive sheet having the structure shown in Table 1.

Comparative Example 4

A base substrate was used as the base substrate, in which a soft aluminum foil was laminated only on one side of a 5 μm thick PET film via the adhesive used in Example 1, and a layer of carbon black ink {ink (Dekselair Co., Ltd.) obtained by dispersing carbon black (MA8, Mitsubishi Chemical Co., Ltd.) in a polyester resin (Bilon 200, Toyobo Co., Ltd.)} was directly laminated on the side of the base substrate on which the soft aluminum foil was not laminated. The same operations as in Comparative Example 1 were repeated, thereby obtaining a conductive sheet having the structure shown in Table 1.

Comparative Example 5

The same operation as in Comparative Example 4 was repeated except that a 12 μm thick PET film (E5100, Toyobo Co., Ltd.) was used instead of the 5 μm thick PET film of the base substrate, thereby obtaining a conductive sheet having the structure shown in Table 1.

Comparative Example 6

The operation of Comparative Example 4 was repeated except that a 30 μm thick conductive nonwoven fabric reinforced adhesive film (Sui-80-M30, Celen Co., Ltd.) was laminated on the release PET film instead of forming the conductive adhesive layer, thereby obtaining a conductive sheet having the composition shown in Table 1.

Comparative Example 7

The same operation as in Comparative Example 6 was repeated except that a 12 μm thick PET film (E5100, Toyobo Co., Ltd.) was used instead of the 5 μm thick PET film of the base substrate, thereby obtaining a conductive sheet having the structure shown in Table 1.

＜Evaluation＞

The obtained conductive sheet was tested and evaluated for "curling properties," "shape retention," "shape conformability (resilience)," "insulation properties (surface resistance)," and "light-shielding properties (gloss and optical density)" as described below. The results are shown in Table 1.

"curl characteristics"

The conductive sheet was cut into strips 15 mm wide and 150 mm long. The release sheet on the conductive adhesive layer side of the test sample was peeled off in a 180° direction at a speed of 1000 mm/s, and any curling was visually inspected. A curl of less than one curl was considered good; a curl of more than one curl was considered unacceptable.

"Shape retention"

The conductive sheet was cut into strips 15 mm wide and 50 mm long. The release sheet on the conductive adhesive layer side of the test sample was peeled off in a 180° direction at a speed of 1000 mm/second. The sample was then folded 90° through the center toward the light-shielding insulating layer. The sample was visually inspected to see if it could maintain its shape for 10 seconds. If it could maintain its shape, it was rated as good; if it could not, it was rated as poor.

"Shape conformability (resilience)"

Cut the conductive sheet into a 15mm long, 10mm wide rectangle. Remove the release sheet from the conductive adhesive layer of the test sample. Apply the long side of the release sheet so that it covers the entire thickness of the 1mm thick aluminum plate and covers the 1mm edge of the aluminum plate. Bend the remaining portion 90° and apply it to the back of the aluminum plate. Place the sample in an environment of 80°C and 95% RH for 72 hours and visually inspect for any peeling. No peeling was considered good, while any peeling was considered unacceptable.

"Insulation (surface resistance)"

The surface resistance of the light-shielding insulating layer of the conductive sheet was measured using a resistance meter (HIRESTER, Mitsubishi Chemical Analytech Co., Ltd.) For practical purposes, the surface resistance is required to be 1×10 ⁸ Ω/□ or higher.

Light-blocking properties (glossiness and optical density)

The glossiness of the light-shielding insulating layer surface of the conductive sheet was measured using a gloss meter (Glossmeter IG-320, Horiba, Ltd.) according to JIS Z8741 (incident angle 60°). For practical purposes, the glossiness should be 80% or less. Furthermore, the optical density of the light-shielding insulating layer surface was measured using an optical densitometer (Reflection Densitometer RT924, Macbeth) according to JIS K7605. For practical purposes, the optical density should be 1.4 or higher. Conductive sheets that met both of these requirements were considered good.

Regarding the conductivity of the conductive adhesive layers of the conductive sheets of Examples 1-4 and Comparative Examples 1-5, and the conductive nonwoven fabric reinforced adhesive films of Comparative Examples 6 and 7, samples cut into 100 × 25 mm strips were applied to the ends of two copper foils (1 × 25 × 100 mm) placed parallel to each other at a distance of 50 mm. The electrical resistance between the two copper foils was measured using a resistance meter (milliohmmeter 4332B, Agilent). All samples exhibited very low resistance values of 50 to 60 mΩ, far below 500 mΩ.

The conductive sheets of Examples 1 to 4 obtained good results in all evaluation items.

In contrast, the conductive sheet of Comparative Example 1 has a light-shielding insulating layer formed using conductive carbon black ink instead of insulating black ink. Therefore, the surface resistance is low and the insulating properties sufficient for practical use are not exhibited.

In addition, although the conductive sheet of Comparative Example 2 does not use insulating black ink but uses carbon black ink to form a light-shielding insulating layer, an insulating PET film is arranged under the carbon black ink layer, so it shows good insulation properties. However, it loses the symmetry of the thickness direction of the base substrate, and thus has problems with the curling characteristics.

Since the conductive sheet of Comparative Example 3 is obtained by increasing the resin film thickness of the base substrate of the conductive sheet of Comparative Example 2 from 5 μm to 12 μm , the symmetry of the base substrate in the thickness direction is worse than that of Comparative Example 2, resulting in problems with shape tracking.

Since the conductive sheets of Comparative Examples 4 and 5 both used a base substrate having an aluminum foil laminated only on one side, they had good shape-following properties, but had problems with curling properties and shape retention.

The conductive sheets of Comparative Examples 6 and 7 use a non-woven fabric reinforced adhesive film as the conductive adhesive layer, so there is no problem with curling characteristics. However, since both use a base substrate with aluminum foil laminated only on one side, there are problems with shape retention and shape tracking.

Industrial Applicability

The conductive sheet of the present invention, in which one side of a base substrate is laminated with a conductive adhesive layer and the other side of the base substrate is laminated with a light-shielding insulating layer, uses a base material having a structure in which the same metal layer is formed on both sides of a resin film as the base substrate. Therefore, even if the conductive sheet is stretched, the metal layers on both sides of the resin film will show the same elongation, so the occurrence of curling can be greatly suppressed, and the shape of the curved surface or curved portion (corner) can be attached with good shape tracking, and the shape retention is also excellent. Therefore, the conductive sheet of the present invention can be used to manufacture an image display module in which the conductive portion is arranged on a plane with undulations, or an image display module in which the conductive portion is formed to form a configuration that does not exist in the same plane.

Explanation of symbols

1: resin film;

2: Metal layer on the conductive adhesive layer side;

3: Metal layer on the light-shielding insulating layer side;

10: Basic substrate;

20: conductive adhesive layer;

30: light-shielding insulating layer;

30a: black resin layer;

30b: insulating base coating;

30c: matte paint layer;

100: Conductive sheet.

Claims (16)

1. A conductive sheet, which is formed by laminating a conductive adhesive layer on one side of a base substrate and a light-shielding insulating layer on the other side of the base substrate, wherein the base substrate has a structure in which the same metal layer is laminated on both sides of a resin film, the metal layer being a metal foil, and the thickness of the metal layer on the resin film constituting the base substrate, the conductive adhesive layer side, and the insulating layer side are all 5 to 20 μm. 2. The conductive sheet according to claim 1, wherein the surface of the light-shielding insulating layer of the conductive sheet has a surface resistivity of 1.0 × ^10⁸ Ω/□ or higher, a gloss of 80% or less, and an optical density of 1 or more. 3. The conductive sheet according to claim 1, wherein the surface of the light-shielding insulating layer of the conductive sheet has a surface resistivity of 1.0 × ^10¹⁰ Ω/□ or higher, a gloss of 40% or less, and an optical density of 1.2 or higher. 4. The conductive sheet according to any one of claims 1 to 3, wherein the base substrate has a structure in which metal layers are laminated on both sides of the resin film via adhesive layers. 5. The conductive sheet according to any one of claims 1 to 4, wherein the coefficient of linear expansion of the resin film constituting the base substrate is 15 to 100 ppm/℃, and the coefficient of linear expansion of the metal layer is 12 to 25 ppm/℃. 6. The conductive sheet according to claim 5, wherein the difference in the coefficient of linear expansion between the resin film constituting the base substrate and the metal layer is less than 40 ppm/℃. 7. The conductive sheet according to any one of claims 1 to 6, wherein the tensile modulus of the resin film constituting the base substrate, JISK7113, is 0.3 to 15 GPa, and the tensile modulus of the metal layer is 45 to 200 GPa. 8. The conductive sheet according to claim 7, wherein the difference in tensile modulus between the resin film constituting the base substrate and the metal layer of JISK7113 is less than 100 GPa. 9. The conductive sheet according to claim 1, wherein the ratio of the thickness of the metal layer [Mt1] on the conductive adhesive layer side to the thickness of the resin film [Bt] to the thickness of the metal layer [Mt2] on the light-shielding insulating layer side is [Mt1]:[Bt]:[Mt2] = 0.25~4:1:0.25~4. 10. The conductive sheet according to any one of claims 1 to 9, wherein the light-shielding insulating layer is a black resin layer formed from an insulating resin colored with a black colorant. 11. The conductive sheet of claim 10, wherein the black colorant is aniline black. 12. The conductive sheet according to any one of claims 1 to 11, wherein the light-shielding insulating layer comprises a black resin layer formed of an insulating resin colored with a black colorant and an insulating base layer or matte varnish layer formed on at least one side thereof. 13. The conductive sheet of claim 12, wherein the black colorant is carbon black. 14. An image display module, wherein the conductive portion connected by the conductive sheet according to any one of claims 1 to 13 is disposed on a plane having undulations. 15. An image display module, wherein the conductive portions connected by the conductive sheet according to any one of claims 1 to 13 are configured not to exist in the same plane. 16. An image display module having a display surface control panel and an image display panel controlled by the display surface control panel, wherein a surface electrode provided on the outer edge of the surface of the display surface control panel and a back electrode provided on the outer edge of the back surface are connected by a conductive sheet according to any one of claims 1 to 13, the conductive sheet being arranged to cover the outer edge of the display surface control panel.