JPWO2016151898A1 - Connection sheet, flexible flat cable, flexible flat cable connection structure, and flexible flat cable connection method - Google Patents

Abstract

An object of the present invention is to provide a connection sheet that can enhance the electrical continuity between wirings to be connected, and can promote a reduction in thickness and space saving of a connection portion. The connection sheet of the present invention is a connection sheet used for electrical connection of a flexible flat cable having a plurality of wirings, arranged in parallel corresponding to the plurality of wirings in plan view, and conductive particles and a binder thereof And a plurality of strip-like conductive paste portions, and an adhesive portion that is disposed at least between the plurality of conductive paste portions and mainly contains a thermoplastic resin. The adhesive portion may be disposed so as to surround the plurality of conductive paste portions in a plan view. The average thickness of the conductive paste portion and the average thickness of the adhesive portion may be the same. The average width of the conductive paste portion may be smaller than the average width of the wiring. A pressure-sensitive adhesive part disposed in the same layer as the conductive paste part and the adhesive part may be further provided.

Description

  The present invention relates to a connection sheet, a flexible flat cable, a flexible flat cable connection structure, and a flexible flat cable connection method.

  A flexible flat cable is used for electrical connection of electronic components housed in an electrical device. This flexible flat cable has a configuration in which a plurality of flat strip conductors are covered with an insulating layer. This flexible flat cable is usually connected to a dedicated connector at the end, and is electrically connected to another conductor via this dedicated connector.

  However, when such a dedicated connector is used, the connecting portion becomes large, which violates the demand for thinning and space saving of electronic components.

  For this reason, a connection structure that can promote the thinning and space saving of electronic components by using no dedicated connector has been proposed today. As such a connection structure, for example, “a circuit board and an electrode connection body and a manufacturing method thereof” (see Japanese Patent Application Laid-Open No. 7-226569) can be cited.

  The connection structure described in this publication has a configuration in which a first conductor laminated on a base film via a thermoplastic adhesive layer is connected to another conductor (second conductor). The connection structure described in this publication is characterized in that the thickness of the thermoplastic adhesive layer that bonds the first conductor onto the base film is increased. In the connection structure described in this publication, when the first conductor and the second conductor are subjected to thermocompression bonding, the thermoplastic adhesive constituting the thermoplastic adhesive layer is formed between the first conductor and the second conductor. It is said that the first conductor and the second conductor can be firmly connected by flowing so as to fill the periphery.

JP-A-7-226569

  However, the connection structure described in the above publication connects the first conductor and the second conductor with a thermoplastic adhesive filled around the first conductor and the second conductor. Since the opposing surfaces of the first conductor and the second conductor are not electrically connected to each other, the first conductor and the second conductor cannot be accurately electrically connected. In the connection structure described in the above publication, the electrical conductivity of the first conductor and the second conductor is further deteriorated by the thermoplastic adhesive flowing between the opposing surfaces of the first conductor and the second conductor. Have a fear.

  The present invention has been made based on the above-described circumstances, and a connection sheet, a flexible flat cable, and a connection structure of a flexible flat cable, which can promote thinning and space saving of a connection portion while improving conductivity. And it aims at providing the connection method of a flexible flat cable.

  A connection sheet according to an aspect of the present invention made to solve the above-described problem is a connection sheet used for electrical connection of a flexible flat cable having a plurality of wirings, and corresponds to the plurality of wirings in a plan view. And a plurality of strip-shaped conductive paste portions including conductive particles and a binder thereof, and an adhesive portion that is disposed between at least the plurality of conductive paste portions and has a thermoplastic resin as a main component. With.

  A flexible flat cable according to another aspect of the present invention made to solve the above problems is a flexible flat cable having a plurality of wirings, in a region where at least one surface side of the plurality of wirings is exposed, The connection sheet is bonded so that the plurality of wirings and the plurality of conductive paste portions match in plan view.

  A flexible flat cable connection structure according to another aspect of the present invention made to solve the above problems is a flexible flat cable connection structure having a plurality of wirings, and at least one surface of the plurality of wirings. A flexible flat cable having an exposed side, the connection sheet bonded to the exposed region of the flexible flat cable so that the plurality of wirings and the plurality of conductive paste portions match in plan view, and a plurality of the connection sheets And a plurality of other wirings respectively bonded to the surface opposite to the bonding surface with the plurality of wirings of the conductive paste portion.

  A flexible flat cable connection method according to another aspect of the present invention made to solve the above-described problem is a flexible flat cable connection method having a plurality of wirings, wherein the plurality of wirings of the flexible flat cable are connected. An exposure process that exposes at least one surface side, and a first polymerization in which the connection sheet is overlapped with the exposed region of the flexible flat cable so that the plurality of wirings and the plurality of conductive paste portions match in plan view. A second superposition step of superimposing a plurality of other wirings to be connected to a surface opposite to a superposition surface of the plurality of wirings of the plurality of conductive paste portions, and the overlaid flexible flat A crimping step of thermocompressing the exposed region of the cable, the connection sheet, and other wirings.

  The connection sheet, the flexible flat cable, the flexible flat cable connection structure, and the flexible flat cable connection method of the present invention can promote the thinning and space saving of the connection portion while enhancing the electrical conductivity.

It is a typical perspective view containing the partial cross section of the flexible flat cable which concerns on one Embodiment of this invention. It is a typical exploded perspective view of the flexible flat cable of FIG. FIG. 2 is a schematic plan view of the flexible flat cable in FIG. 1. It is the AA line partial expanded sectional view of the flexible flat cable of FIG. It is a typical perspective view which shows the connection sheet | seat of the flexible flat cable which concerns on one Embodiment of this invention. It is a typical perspective view explaining the superposition | polymerization process of the manufacturing method of the flexible flat cable of FIG. It is a typical perspective view explaining the crimping | compression-bonding process of the manufacturing method of the flexible flat cable of FIG. It is a typical perspective view explaining the peeling process of the manufacturing method of the flexible flat cable of FIG. It is typical sectional drawing which shows the connection structure of the flexible flat cable which concerns on one Embodiment of this invention. It is a typical perspective view explaining the 2nd superposition | polymerization process of the connection method of the flexible flat cable which concerns on one Embodiment of this invention. It is a typical perspective view explaining the crimping | compression-bonding process of the connection method of the flexible flat cable which concerns on one Embodiment of this invention. It is a typical perspective view which shows the connection sheet which concerns on embodiment different from the connection sheet of FIG.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

  A connection sheet according to an aspect of the present invention is a connection sheet used for electrical connection of a flexible flat cable having a plurality of wirings, and is arranged in parallel corresponding to the plurality of wirings in a plan view, and is conductive. A plurality of strip-shaped conductive paste portions including particles and a binder thereof, and an adhesive portion that is disposed at least between the plurality of conductive paste portions and mainly includes a thermoplastic resin.

  The connection sheet is configured such that a plurality of conductive paste portions are bonded to the surfaces of a plurality of wirings of the flexible flat cable, respectively, and an adhesive portion is disposed between the plurality of conductive paste portions. Therefore, the connection sheet can be electrically connected while physically bonding the wiring and another wiring to be connected at the facing portion by the conductive paste portion. Moreover, the said connection sheet can improve the adhesiveness and electroconductivity with the wiring of a connection object, ensuring the insulation of adjacent wiring by the said adhesive agent part. Therefore, the connection sheet can enhance the electrical conductivity between the wirings to be connected, and can promote a reduction in the thickness and space saving of the connection portion by using no dedicated connector.

  The adhesive portion may be disposed so as to surround the plurality of conductive paste portions in a plan view. As described above, the adhesive portion is disposed so as to surround the plurality of conductive paste portions in a plan view, thereby promoting an effect of preventing a short circuit between adjacent wires and bonding with a connection target wire. The property can be further improved.

  The average thickness of the conductive paste portion and the average thickness of the adhesive portion may be the same. Thus, the average thickness of the conductive paste part and the average thickness of the adhesive part are the same, thereby promoting the effect of preventing a short circuit between adjacent wirings and further improving the adhesion to the wiring to be connected. Can be improved.

  The average width of the conductive paste portion may be smaller than the average width of the wiring. Thus, by making the average width of the conductive paste portion smaller than the average width of the wiring, it is possible to promote the effect of preventing a short circuit between adjacent wirings and further improve the adhesion to the wiring to be connected. it can.

  The softening temperature of the polymer constituting the binder of the conductive paste part and the polymer constituting the adhesive part is preferably 40 ° C. or higher and 70 ° C. or lower. Thus, when the softening temperature of the polymer constituting the binder of the conductive paste part and the polymer constituting the adhesive part is within the above range, these polymers are easily softened at a relatively low temperature. Therefore, it becomes easy to improve the adhesiveness by spreading the conductive paste part and the adhesive part in the gap between the connection objects.

  A pressure-sensitive adhesive part disposed in the same layer as the conductive paste part and the adhesive part may be further provided. Thus, by further providing an adhesive part disposed in the same layer as the conductive paste part and the adhesive part, the connection sheet and the flexible flat cable can be temporarily fixed by the adhesive part. . Thus, for example, by thermocompression bonding the connection sheet and the flexible flat cable in a temporarily fixed state, it is possible to prevent positional displacement at the time of thermocompression bonding of the connection sheet and the flexible flat cable. The cable can be easily and reliably joined at a desired position. Moreover, according to this structure, the effort which uses the jig | tool for positioning the said connection sheet | seat and a flexible flat cable can be saved.

  A release film laminated on one surface of the conductive paste portion and the adhesive portion may be further provided. Thus, handling property can be improved by further providing the release film laminated | stacked on one side of an electrically conductive paste part and an adhesive agent part. In addition, for example, by removing the release film immediately before connecting the objects to be connected, dust and dust are prevented from adhering to the plurality of conductive paste portions and adhesive portions, thereby improving conductivity and adhesion. can do.

  The flexible flat cable which concerns on 1 aspect of this invention is a flexible flat cable which has several wiring, Comprising: In the area | region where the at least one surface side of said several wiring was exposed, these wiring and said several wiring by planar view The connection sheet is bonded so that the conductive paste portion matches.

  The flexible flat cable electrically connects the wiring and other wiring to be connected with the conductive paste portion while physically bonding the facing portion to each other, and insulates adjacent wires by the adhesive portion. It is possible to improve the adhesiveness and conductivity with the wiring to be connected while securing the property. Therefore, the flexible flat cable can promote the thinning and space saving of the connection portion while enhancing the conductivity between the wirings to be connected.

  A flexible flat cable connection structure according to an aspect of the present invention is a flexible flat cable connection structure having a plurality of wirings, the flexible flat cable having at least one surface exposed of the plurality of wirings, and the flexible flat cable. The connection sheet joined to the exposed area of the cable so that the plurality of wirings and the plurality of conductive paste portions match in plan view, and the plurality of wirings of the plurality of conductive paste portions of the connection sheet; And a plurality of other wirings joined to the opposite surface.

  In the connection structure of the flexible flat cable, a plurality of conductive paste portions of the connection sheet are bonded to a plurality of wirings, respectively, and the surfaces of the plurality of conductive paste portions are opposite to the bonding surfaces with the plurality of wirings. Since a plurality of other wirings are joined to each other, as described above, it is possible to promote thinning and space saving of the connection portion while improving the conductivity between the wirings to be connected.

  The connection method of the flexible flat cable which concerns on 1 aspect of this invention is a connection method of the flexible flat cable which has several wiring, Comprising: The exposure process which exposes the at least one surface side of the several wiring of the said flexible flat cable, A first polymerization step of superimposing the connection sheet on the exposed area of the flexible flat cable so that the plurality of wirings and the plurality of conductive paste portions match in plan view; and the plurality of conductive paste portions A second overlapping step of overlapping a plurality of other wirings to be connected to the surface opposite to the overlapping surface with the plurality of wirings, an exposed region of the overlapped flexible flat cable, a connection sheet, and the other plurality A crimping step of thermocompression bonding the wiring.

  As described above, the flexible flat cable connection method can promote the thinning and space saving of the connection portion while improving the conductivity between the wirings to be connected.

  In the present invention, “the average thickness of the conductive paste portion and the average thickness of the adhesive portion” means that the average thickness of the plurality of conductive paste portions in the cross section cut in the width direction, It means that the average thickness of the adhesive part is the same, and “same” means that the average thickness ratio is 9/10 or more and 11/10 or less, preferably 19/20 or more and 21/20. It means the following. “Softening temperature” means a softening temperature measured according to JIS-K7196 (1991). “Strip shape” means that the shape in plan view is elongated.

[Details of the embodiment of the present invention]
Hereinafter, a connection sheet, a flexible flat cable, a flexible flat cable connection structure, and a flexible flat cable connection method according to an embodiment of the present invention will be described with reference to the drawings as appropriate.

[First embodiment]
<Flexible flat cable>
The flexible flat cable 1 shown in FIGS. 1 to 3 includes a flat cable body 2, a flexible flat cable connection sheet 3 (hereinafter, also simply referred to as “connection sheet 3”), and a reinforcing sheet 4. The flexible flat cable 1 has flexibility.

(Flat cable body)
The flat cable body 2 has a plurality of wires 5 arranged in a stripe shape and an insulating layer arranged on the front and back so as to surround the plurality of wires 5 (specifically, so as to surround the peripheral surfaces of the plurality of wires 5). It has mainly the adhesive bond layer 7 which is. In the flat cable main body 2, a pair of insulating films 6 a and 6 b cover the front and back of the plurality of wirings 5 with the adhesive layer 7 interposed therebetween. In addition, “front and back” is defined for the sake of convenience with one surface side as the front surface and the other surface side as the back surface, and does not specifically specify the configuration of the flexible flat cable of the present invention. Absent. In addition, “striped” means a state of being arranged substantially parallel (that is, a state of being arranged in parallel) in the same plane, and “substantially parallel” means that the angle formed by the central axis is ± 10 °. It is within.

(wiring)
The wiring 5 is composed of a conductor. The plurality of wirings 5 are formed in a long and flat shape. The plurality of wirings 5 are exposed on one surface side (one surface side in the present embodiment) on one end side. The wiring 5 is formed of a conductive material. An example of the main component of the wiring 5 is copper. The “main component” refers to a component having the highest content, for example, a component having a content of 50% by mass or more.

  As a minimum of the average length in the exposed part (exposed area B mentioned below) of a plurality of wirings 5, 2 mm is preferred and 3 mm is more preferred. On the other hand, the upper limit of the average length is preferably 10 mm, and more preferably 5 mm. If the average length is less than the lower limit, the adhesive strength and continuity with other wiring may be insufficient. On the contrary, if the average length exceeds the upper limit, the connecting portion may be unnecessarily large.

  The plurality of wirings 5 are plated on the surface, and a plating layer (not shown) is laminated on the surface by the plating process. Examples of the plating treatment include gold plating, silver plating, and tin plating. It is possible to prevent the exposed portions of the plurality of wirings 5 from being damaged by the plating process.

  The lower limit of the average thickness (including the plating layer) of the wiring 5 is preferably 10 μm, and more preferably 25 μm. On the other hand, the upper limit of the average thickness of the wiring 5 is preferably 100 μm, and more preferably 80 μm. If the average thickness of the wiring 5 is less than the above lower limit, the conductivity may be insufficient. Conversely, if the average thickness of the wiring 5 exceeds the upper limit, the flexible flat cable 1 may become unnecessarily thick.

  The lower limit of the average width (including the plating layer) of the wiring 5 is preferably 0.1 mm, and more preferably 0.2 mm. On the other hand, the upper limit of the average width of the wiring 5 is preferably 1 mm, and more preferably 0.4 mm. If the average width of the wiring 5 is less than the lower limit, the electrical conductivity may be insufficient. On the contrary, if the average width of the wiring 5 exceeds the upper limit, the width of the flexible flat cable 1 may become unnecessarily large.

  As a minimum of the average pitch of wiring 5, 0.2 mm is preferred and 0.3 mm is more preferred. On the other hand, the upper limit of the average pitch of the wiring 5 is preferably 1.5 mm, and more preferably 1.2 mm. If the average pitch of the wirings 5 is less than the lower limit, the adjacent wirings 5 may be in contact with each other. Conversely, if the average pitch of the wires 5 exceeds the above upper limit, the width of the flexible flat cable 1 may become unnecessarily large.

  The number of wirings 5 can be increased or decreased as necessary and is not particularly limited, but can be, for example, 10 or more and 60 or less.

(Adhesive layer)
Although it does not specifically limit as an adhesive agent which comprises the adhesive bond layer 7, The thing excellent in the softness | flexibility and heat resistance is preferable, for example, an epoxy resin, a polyimide, polyester, a phenol resin, a polyurethane, an acrylic resin, a melamine Various resin-based adhesives such as resins and polyamideimides can be used.

  The average thickness on the surface side of the adhesive layer 7 (average distance between the wiring 5 and the insulating film 6a) and the average thickness on the back surface side of the adhesive layer 7 (average distance between the wiring 5 and the insulating film 6b) are substantially equal. . The lower limit of the average thickness on the front surface side of the adhesive layer 7 and the average thickness on the back surface side of the adhesive layer 7 is preferably 5 μm, and more preferably 15 μm. On the other hand, the upper limit of the average thickness is preferably 50 μm, and more preferably 40 μm. If the average thickness is less than the lower limit, the adhesive strength between the plurality of wirings 5 and the insulating films 6a and 6b may be insufficient. Conversely, if the average thickness exceeds the upper limit, the flexible flat cable 1 may be unnecessarily thick.

(Insulating film)
The insulating films 6a and 6b are composed of a sheet-like member having flexibility and electrical insulation. Specifically, resin films can be employed as the insulating films 6a and 6b. As the main component of this resin film, for example, polyimide, polyethylene terephthalate or the like is preferably used.

  As a minimum of average thickness of insulating films 6a and 6b, 5 micrometers is preferred and 10 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the insulating films 6a and 6b is preferably 40 μm, and more preferably 20 μm. If the average thickness of the insulating films 6a and 6b is less than the lower limit, the strength of the insulating films 6a and 6b may be insufficient. Conversely, if the average thickness of the insulating films 6a and 6b exceeds the upper limit, the flexible flat cable 1 may be unnecessarily thick.

(Connection sheet)
The connection sheet 3 is used for electrical connection of a flexible flat cable having a plurality of wirings 5. Specifically, the connection sheet 3 is a flexible flat cable including a plurality of wirings 5 arranged in a stripe shape and an adhesive layer 7 that is an insulating layer arranged on the front and back sides so as to surround the plurality of wirings 5. Electrical connection with the wiring. The connection sheet 3 is joined to one surface side of the exposed region B where at least one surface side of the plurality of wirings 5 is exposed. The connection sheet 3 includes a plurality of conductive paste portions 8 disposed in parallel corresponding to the plurality of wirings 5 in plan view, and an adhesive portion 9 disposed between at least the plurality of conductive paste portions 8. Have That is, the flexible flat cable 1 has the connection sheet 3 so that the plurality of wirings 5 and the plurality of conductive paste portions 8 are aligned with each other in an exposed region B where at least one surface side of the plurality of wirings 5 is exposed. Are joined. As shown in FIG. 4, one surface of each of the plurality of conductive paste portions 8 and the adhesive portion 9 has a cross-sectional shape curved in an approximately arch shape based on the surface tension. This prevents mixing between the plurality of conductive paste portions 8 and the adhesive portion 9 when one surface of the plurality of conductive paste portions 8 and the adhesive portion 9 is thermocompression bonded to another wiring or substrate. Is done. As a result, it becomes easy to improve the continuity between the plurality of wirings 5 and other wirings to be connected, and it is easy to firmly bond the adhesive layer 9 to another substrate or the like.

(Conductive paste part)
The conductive paste portion 8 is formed of a conductive paste containing conductive particles and a binder thereof. The conductive paste portion 8 is formed in a strip shape.

  As said electroconductive particle, metal particles, such as silver, platinum, gold | metal | money, copper, nickel, palladium, a solder, are mentioned, for example, These can be used individually or in mixture of 2 or more types. Among these, silver powder, silver-coated copper powder, solder powder and the like exhibiting excellent conductivity are preferable, and scaly silver powder is particularly preferable. By using scale-like silver powder as the conductive particles, the contact area can be increased and the conductivity can be improved. In addition, “scale-like” means that the size in one direction (thickness direction) out of the three directions (length direction, width direction, thickness direction) perpendicular to each other is the other two directions (length A shape that is 1/2 or less, preferably 1/50 or more and 1/5 or less of the maximum value in the size in the width direction and the width direction).

  The lower limit of the average particle size of the conductive particles is preferably 0.3 μm, and more preferably 0.5 μm. On the other hand, the upper limit of the average particle size of the conductive particles is preferably 20 μm and more preferably 10 μm. If the average particle size of the conductive particles is less than the lower limit, there is a risk that sufficient conductivity cannot be obtained. On the contrary, when the average particle diameter of the conductive particles exceeds the upper limit, for example, when the conductive paste portion 8 is formed by screen printing, the screen plate may be clogged. The “average particle diameter” refers to a cumulative 50% average volume diameter (median diameter). For example, a particle size distribution measuring apparatus using a laser Doppler method (Nanotrack (registered trademark) particle size distribution measuring apparatus manufactured by Nikkiso Co., Ltd.). "UPA-EX150").

  As a minimum of content of the above-mentioned conductive particles in conductive paste part 8, 40 volume% is preferred and 45 volume% is more preferred. On the other hand, the upper limit of the content of the conductive particles is preferably 95% by volume, and more preferably 85% by volume. If the content rate of the said electroconductive particle is less than the said minimum, there exists a possibility that the electrical connectivity with the wiring 5 and the other wiring which is connection object may fall. On the contrary, if the content of the conductive particles exceeds the upper limit, the fluidity of the conductive paste is lowered, and it may be difficult to form the conductive paste portion 8, or the wiring 5 and other objects to be connected. There is a possibility that the adhesive strength of the wiring is lowered.

  Examples of the main component of the binder include thermoplastic resins such as acrylic resin, polyamide, polyolefin, fluororesin, polyester, and silicone resin.

  As a minimum of the softening temperature of the polymer which comprises the said binder, 40 degreeC is preferable and 50 degreeC is more preferable. On the other hand, the upper limit of the softening temperature of the polymer constituting the binder is preferably 70 ° C and more preferably 65 ° C. If the softening temperature of the polymer constituting the binder is less than the lower limit, the heat resistance may be insufficient. On the contrary, when the softening temperature of the polymer constituting the binder exceeds the upper limit, the conductive paste portion 8 is bonded to one surface of the wiring 5 and the wiring 5 and another wiring to be connected are bonded. There is a possibility that the thermocompression bonding temperature at the time of carrying out increases. As a result, the adhesive layer 11 of the reinforcing sheet 4 to be described later may be softened during the thermocompression bonding, and it may be difficult to stably hold the connection sheet 3 on one surface of the wiring 5.

  As a minimum of the glass transition temperature of the polymer which constitutes the above-mentioned binder, 30 ° C is preferred and 35 ° C is more preferred. If the glass transition temperature of the polymer constituting the binder is less than the lower limit, the strength of the conductive paste portion 8 may be insufficient. On the other hand, the upper limit of the glass transition temperature of the polymer constituting the binder is not particularly limited and can be, for example, 60 ° C. In addition, a glass transition temperature means the midpoint glass transition temperature measured based on JIS-K7121 (1987).

  A curing agent can be added to the binder. Examples of the curing agent include amine curing agents, polyaminoamide curing agents, isocyanate curing agents, acid and acid anhydride curing agents, basic active hydrogen compounds, tertiary aminos, and imidazoles. Furthermore, in addition to the components described above, auxiliary agents such as thickeners and leveling agents can be added to the binder.

  The conductive paste portion 8 is formed in a substantially rectangular shape in plan view as shown in FIG. As shown in FIG. 4, the central axis parallel to the longitudinal direction of the conductive paste portion 8 substantially coincides with the central axis of the wiring 5.

  The average width of the conductive paste portion 8 is smaller than the average width of the wiring 5. Further, both ends of the conductive paste portion 8 in the width direction are disposed inside both ends of the wiring 5 in the width direction. That is, the conductive paste portion 8 is included in the wiring 5 in plan view. Thus, when the conductive paste portion 8 is bonded to another wiring, the conductive paste portion 8 is attached to one surface of the wiring 5 because the average width of the conductive paste portion 8 is smaller than the average width of the wiring 5. It is easy to be held inside. Thereby, even if the conductive paste portion 8 flows somewhat when connected to other wiring, it is possible to prevent a short circuit from occurring between the plurality of wirings 5. The “average width of the conductive paste portion 8” refers to the average length at the joint surface of the conductive paste portion 8 with the wiring 5 in the direction parallel to the width direction of the wiring 5.

  As a minimum of the average width of conductive paste part 8, 0.08mm is preferred and 0.14mm is more preferred. On the other hand, the upper limit of the average width of the conductive paste portion 8 is preferably 0.5 mm, and more preferably 0.3 mm. If the average width of the conductive paste portion 8 is less than the lower limit, the electrical connectivity between the wiring 5 and other wiring to be connected may be reduced. Conversely, if the average width of the conductive paste portion 8 exceeds the above upper limit, the area of the adhesive portion 9 becomes small, and the adhesiveness to the substrate may be insufficient.

  The lower limit of the difference between the average width of the wiring 5 and the average width of the conductive paste portion 8 is preferably 0.02 mm, and more preferably 0.05 mm. On the other hand, the upper limit of the difference in average width is preferably 0.5 mm, and more preferably 0.2 mm. By setting the difference in the average width within the above range, it is possible to easily and reliably prevent a short circuit between the plurality of wirings 5 and improve the electrical connectivity between the wirings.

  As a minimum of average thickness of conductive paste part 8, 0.01 mm is preferred and 0.015 mm is more preferred. On the other hand, the upper limit of the average thickness of the conductive paste portion 8 is preferably 0.05 mm, and more preferably 0.035 mm. If the average thickness of the conductive paste portion 8 is less than the lower limit, the adhesive flows between the opposing surfaces of the conductive paste portion 8 and the wiring 5 to deteriorate the conductivity of the conductive paste portion 8 and the wiring 5. There is a risk. On the other hand, when the average thickness of the conductive paste portion 8 exceeds the above upper limit, the adhesion to the substrate may be insufficient.

  As a minimum of average length (average longitudinal direction length) of conductive paste part 8, 0.5 mm is preferred and 1 mm is more preferred. On the other hand, the upper limit of the average length of the conductive paste portion 8 is preferably 5 mm, and more preferably 3 mm. If the average length of the conductive paste portion 8 is less than the lower limit, the electrical connectivity between the wiring 5 and another wiring to be connected may be insufficient. Conversely, if the average length of the conductive paste portion 8 exceeds the upper limit, the connection sheet 3 may become unnecessarily large.

(Adhesive part)
The adhesive portion 9 is mainly composed of a thermoplastic resin. The adhesive portion 9 is constituted by a hot melt adhesive that melts by applying heat. The adhesive portion 9 is disposed so as to surround the plurality of conductive paste portions 8 in a plan view, and has, for example, a substantially rectangular outer edge. As described above, the adhesive portion 9 is disposed so as to surround the plurality of conductive paste portions 8 in a plan view, thereby accurately preventing a short circuit between adjacent wirings and connecting with the wiring to be connected. Adhesiveness can be further improved.

  Examples of the thermoplastic resin include acrylic resin, polyamide, polyolefin, fluororesin, polyester, and silicone resin. Among these, as the thermoplastic resin, a polyester excellent in moldability, insulation and the like is preferable.

  As a minimum of the softening temperature of the polymer which constitutes adhesive part 9, 40 ° C is preferred and 50 ° C is more preferred. On the other hand, the upper limit of the softening temperature of the polymer constituting the adhesive part 9 is preferably 70 ° C, and more preferably 65 ° C. If the softening temperature of the polymer constituting the adhesive part 9 is less than the lower limit, the heat resistance may be insufficient. On the contrary, when the softening temperature of the polymer constituting the adhesive part 9 exceeds the upper limit, the adhesive part 9 is adhered to one surface of the adhesive layer 11 of the reinforcing sheet 4 and to another substrate or the like. There is a possibility that the thermocompression bonding temperature at that time becomes high. As a result, the adhesive layer 11 may be softened during the thermocompression bonding, and the adhesive portion 9 may not be accurately bonded to another substrate or the like.

  Moreover, it is preferable that the softening temperature of the polymer constituting the conductive paste part 8 and the softening temperature of the polymer constituting the adhesive part 9 are both within the above range. Thus, by setting both the softening temperature of the polymer constituting the conductive paste portion 8 and the softening temperature of the polymer constituting the adhesive portion 9 within the above range, these polymers are easily softened at a relatively low temperature. . Therefore, the conductive paste portion 8 can be accurately connected to the wiring to be connected, and the adhesive portion 9 can be easily adhered to another substrate or the like. Moreover, according to this structure, it becomes easy to make the softening temperature of the said polymer lower than the softening temperature of the adhesive bond layer 11 of the reinforcement sheet 4. Thereby, softening of the adhesive layer 11 of the reinforcing sheet 4 is suppressed, and the conductive paste portion 8 and the adhesive portion 9 are easily bonded to desired positions.

  As a minimum of the glass transition temperature of the polymer which constitutes adhesive part 9, 30 ° C is preferred and 35 ° C is more preferred. If the glass transition temperature of the polymer constituting the adhesive part 9 is less than the lower limit, the strength of the adhesive part 9 may be insufficient. On the other hand, the upper limit of the glass transition temperature of the polymer constituting the adhesive part 9 is not particularly limited and can be set to 60 ° C., for example.

  Note that additives similar to those added to the binder, such as a curing agent, a thickener, and a rebilling agent, can be added to the adhesive portion 9.

  As a minimum of the average width of adhesive part 9 laminated between a plurality of conductive paste parts 8, 0.12 mm is preferred and 0.22 mm is more preferred. On the other hand, the upper limit of the average width of the adhesive portion 9 laminated between the plurality of conductive paste portions 8 is preferably 0.52 mm, and more preferably 0.42 mm. If the average width of the adhesive portions 9 laminated between the plurality of conductive paste portions 8 is less than the lower limit, the adhesive area may be small and the adhesion to the substrate may be insufficient. On the contrary, when the average width of the adhesive portion 9 laminated between the plurality of conductive paste portions 8 exceeds the upper limit, the width of the conductive paste portion 8 becomes narrower, and other wirings to be connected to the wiring 5 are connected. There is a risk that the electrical connectivity with will decrease.

  Note that, among the plurality of conductive paste portions 8, the average width of the adhesive portion 9 disposed outside the pair of conductive paste portions 8 stacked on both side ends is between the plurality of conductive paste portions 8. It is not necessary to be the same as the average width of the adhesive part 9 to be disposed. The average width of the adhesive portions 9 disposed outside the pair of conductive paste portions 8 disposed on both side ends is, for example, arranged between the plurality of conductive paste portions 8 in order to improve adhesiveness. It may be larger than the average width of the adhesive part 9 provided. In this case, the average width of the adhesive portion 9 disposed outside the pair of conductive paste portions 8 disposed on both side ends can be set to, for example, about 0.22 mm to 1 mm.

  As a minimum of average thickness of adhesive part 9, 0.01 mm is preferred and 0.015 mm is more preferred. On the other hand, the upper limit of the average thickness of the adhesive portion 9 is preferably 0.05 mm, and more preferably 0.035 mm. If the average thickness of the adhesive portion 9 is less than the above lower limit, the adhesiveness to other substrates may be insufficient. Conversely, when the average thickness of the adhesive portion 9 exceeds the above upper limit, the adhesive flows between the opposing surfaces of the conductive paste portion 8 and the wiring 5, so that the conductivity of the conductive paste portion 8 and the wiring 5 is increased. May get worse.

  The average thickness of the conductive paste portion 8 and the average thickness of the adhesive portion 9 are preferably the same. As described above, the average thickness of the conductive paste portion 8 and the average thickness of the adhesive portion 9 are the same, thereby promoting the effect of preventing a short circuit between the plurality of wirings 5, and other objects that are connected to the wirings 5. The electrical connectivity with the wiring can be further improved.

  The lower limit of the difference between the average length of the adhesive portion 9 (the length in the direction parallel to the longitudinal direction of the conductive paste portion 8) and the average length of the conductive paste portion 8 is preferably 1 mm, more preferably 1.5 mm. preferable. On the other hand, the upper limit of the difference in average length is preferably 5 mm, and more preferably 3 mm. If the difference in the average length is less than the lower limit, the conductive paste portion 8 may not be properly surrounded in plan view, and as a result, a short circuit may easily occur between the plurality of wirings 5. . Conversely, if the difference in the average length exceeds the upper limit, the planar area of the adhesive portion 9 may become unnecessarily large.

(Reinforcement sheet)
The reinforcing sheet 4 is disposed on one end side of the flexible flat cable 1 including the exposed region B. The reinforcing sheet 4 has an insulating layer 10 and an adhesive layer 11 laminated on one surface side of the insulating layer 10, and a plurality of wirings 5 are laminated on one surface of the adhesive layer 11. The reinforcing sheet 4 protects the plurality of wirings 5 exposed in the exposed region B from the other surface, and the conductive paste portion 8 is stably connected to other wirings to be connected at the time of thermocompression bonding, and an adhesive. The conductive paste portion 8 and the adhesive portion 9 are supported from the other surface so that the portion 9 is stably bonded to another substrate or the like. The reinforcing sheet 4 is preferably transparent and more preferably colorless and transparent.

(Insulating layer)
The insulating layer 10 is composed of a sheet-like member having flexibility and electrical insulation. Specifically, a resin film can be adopted as the insulating layer 10. As the main component of this resin film, for example, polyimide, polyethylene terephthalate or the like is preferably used.

  As a minimum of the softening temperature of the polymer which comprises the insulating layer 10, 100 degreeC is preferable, 110 degreeC is more preferable, and 120 degreeC is further more preferable. If the softening temperature of the polymer constituting the insulating layer 10 is less than the lower limit, there is a risk that the conductive paste portion 8 and the adhesive portion 9 may be softened and deformed during thermocompression bonding. On the other hand, the upper limit of the softening temperature of the polymer constituting the insulating layer 10 is not particularly limited, but may be, for example, 200 ° C.

  As a minimum of the glass transition temperature of the polymer which constitutes insulating layer 10, 50 ° C is preferred, 60 ° C is more preferred, and 65 ° C is still more preferred. If the glass transition temperature of the polymer constituting the insulating layer 10 is less than the lower limit, the strength after the pressure bonding may be insufficient. On the other hand, the upper limit of the glass transition temperature of the insulating layer 10 is not particularly limited, but may be, for example, 200 ° C.

  As a minimum of average thickness of insulating layer 10, 50 micrometers is preferred and 80 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the insulating layer 10 is preferably 200 μm, and more preferably 150 μm. If the average thickness of the insulating layer 10 is less than the lower limit, the strength of the insulating layer 10 may be insufficient. Conversely, if the average thickness of the insulating layer 10 exceeds the upper limit, heat may not be easily transmitted to the conductive paste portion 8 and the adhesive portion 9 during thermocompression bonding.

(Adhesive layer)
Although it does not specifically limit as an adhesive agent which comprises the adhesive bond layer 11, The thing excellent in the softness | flexibility and heat resistance is preferable, for example, an epoxy resin, a polyimide, polyester, a phenol resin, a polyurethane, an acrylic resin, a melamine Various resin-based adhesives such as resins and polyamideimides can be used. Among these, those which are thermoplastic and have a softening temperature higher than the polymer constituting the conductive paste part 8 and the polymer constituting the adhesive part 9 are preferable.

  As a minimum of the softening temperature of the polymer which constitutes adhesive layer 11, 70 ° C is preferred and 75 ° C is more preferred. If the softening temperature of the polymer constituting the adhesive layer 11 is less than the lower limit, the adhesive layer 11 softens during thermocompression bonding, and the conductive paste portion 8 laminated on one surface side of the adhesive layer 11 and There is a possibility that the adhesive portion 9 cannot be stably supported. As a result, the conductive paste portion 8 and the adhesive portion 9 are mixed with each other, which may result in insufficient electrical connectivity between the wires and may cause a short circuit between the plurality of wires 5. On the other hand, the upper limit of the softening temperature of the polymer constituting the adhesive layer 11 is not particularly limited, and can be, for example, 200 ° C.

  The softening temperature of the polymer constituting the adhesive layer 11 is preferably higher than the softening temperature of the polymer constituting the conductive paste portion 8 and the softening temperature of the polymer constituting the adhesive portion 9. The lower limit of the difference between the softening temperature of the polymer constituting the adhesive layer 11 and the softening temperature of the polymer constituting the conductive paste portion 8 and the softening temperature of the polymer constituting the adhesive portion 9 is 10 ° C. Preferably, 15 ° C. is more preferable. If the difference in the softening temperature is less than the lower limit, the adhesive layer 11 is likely to be softened during thermocompression bonding. On the other hand, the upper limit of the difference between the softening temperatures is not particularly limited, but may be 160 ° C., for example.

  As a minimum of the glass transition temperature of the polymer which constitutes adhesive layer 11, 50 ° C is preferred, 60 ° C is more preferred, and 70 ° C is still more preferred. If the glass transition temperature of the polymer constituting the adhesive layer 11 is less than the lower limit, the strength after the thermocompression bonding may be insufficient. On the other hand, the upper limit of the glass transition temperature of the polymer constituting the adhesive layer 11 is not particularly limited, and can be, for example, 200 ° C.

  The lower limit of the average thickness of the adhesive layer 11 is preferably 5 μm, and more preferably 15 μm. On the other hand, the upper limit of the average thickness of the adhesive layer 11 is preferably 50 μm, and more preferably 40 μm. If the average thickness of the adhesive layer 11 is less than the above lower limit, the adhesive strength may be insufficient. Conversely, if the average thickness of the adhesive layer 11 exceeds the upper limit, the flexible flat cable 1 may be unnecessarily thick.

<Advantages>
The flexible flat cable 1 can be electrically connected with the conductive paste portion 8 while physically bonding the wiring 5 and another wiring to be connected at the facing portion. In addition, the flexible flat cable 1 can improve the adhesiveness and electrical continuity with the wiring to be connected while ensuring the insulation between the adjacent wirings by the adhesive portion 9. Therefore, the flexible flat cable 1 can enhance the continuity between the wirings to be connected, and can promote thinning and space saving of the connecting portion by not using the dedicated connector.

  The connection sheet 3 is configured such that the plurality of conductive paste portions 8 are bonded to the surfaces of the plurality of wirings 5, and an adhesive portion 9 is disposed between the plurality of conductive paste portions 8. Yes. Therefore, the connection sheet 3 can be electrically connected by physically bonding the wiring 5 and the other wiring to be connected at the facing portion by the conductive paste portion 8. In addition, the connection sheet 3 can improve the adhesion and conductivity with the wiring to be connected while securing the insulation between the adjacent wirings by the adhesive portion 9. Therefore, the connection sheet 3 can enhance the electrical conductivity between the wirings to be connected, and can promote the thinning and space saving of the connection portion.

<Method for manufacturing flexible flat cable>
Next, the manufacturing method of the flexible flat cable 1 of FIGS. 1-3 is demonstrated. The manufacturing method of the flexible flat cable 1 includes an exposure process that exposes one surface side of the plurality of wirings 5 and a plurality of wirings 5 and a plurality of conductive paste portions in an exposed region B exposed by the exposure process in a plan view. 5 and the superposition | polymerization process (1st superposition | polymerization process) which overlaps the connection sheet 21 of FIG. 5, and the connection sheet | seat 21 so that the some wiring 5 and the some conductive paste part 8 may be joined by 1 to 1 correspondence. Is provided with a pressure-bonding step for thermocompression bonding to one surface of the plurality of wirings 5 and a peeling step for peeling the release film 22 of the connection sheet 21.

  First, the connection sheet 21 of FIG. 5 used in the method for manufacturing the flexible flat cable will be described.

(Connection sheet)
The connection sheet 21 includes the conductive paste portion 8 and the adhesive portion 9 and a release film 22.

  The release film 22 is laminated on one surface of the conductive paste portion 8 and the adhesive portion 9. As the release film 22, for example, a synthetic resin film mainly containing a synthetic resin such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyethylene terephthalate, rubber sheet, paper, cloth, etc. A suitable film-like body made of a nonwoven fabric, a net, a foam sheet, a metal foil, a laminate of these, or the like can be used. Further, the release film 22 may be provided with a release layer on the surface on which the conductive paste portion 8 and the adhesive portion 9 are laminated in order to improve the peelability, and may be treated with silicone treatment, long-chain alkyl treatment, fluorine A peeling treatment such as a treatment may be performed. Especially, it is preferable that the peeling layer which has a melamine resin as a main component is provided in the surface where the electroconductive paste part 8 and the adhesive agent part 9 of the release film 22 are laminated | stacked. Thus, by providing a release layer mainly composed of melamine resin, when the conductive paste portion 8 and the adhesive portion 9 are peeled from the release film 22, it is possible to accurately attach the release layer to the release surface. It is possible to prevent the adhesive force from being lowered due to the adhesion of the release layer. The connection sheet 21 can improve handleability by including the release film 22 laminated on one surface of the conductive paste portion 8 and the adhesive portion 9. Further, for example, by separating the release film 22 immediately before connecting the objects to be connected, it is possible to prevent dust and dust from adhering to the plurality of conductive paste portions 8 and the adhesive portion 9, thereby providing conductivity and adhesiveness. Can be improved.

  The connection sheet 21 is formed by laminating a plurality of conductive paste portions 8 on the surface of the release film 22 and further laminating an adhesive portion 9 between the plurality of conductive paste portions 8. Examples of the method for laminating the conductive paste portion 8 and the adhesive portion 9 include a method by printing or coating. Examples of the printing method include screen printing, gravure printing, offset printing, flexographic printing, inkjet printing, dispenser printing, and the like. Examples of the coating method include knife coating, die coating, and roll coating.

  The conductive paste portion 8 and the adhesive portion 9 may be formed using a solvent in order to improve printability or coatability. Examples of the solvent include, but are not limited to, organic solvents such as ester, ether, ketone, ether ester, alcohol, hydrocarbon, and amine. Among these, 1 type (s) or 2 or more types can be used. In addition, when forming the electrically conductive paste part 8 by printing, it is preferable to use the high boiling point solvent excellent in printability, and specifically, it is preferable to use carbitol acetate, butyl carbitol acetate, etc. Moreover, when forming the adhesive part 9 by printing, it is preferable to use isophorone, for example.

(Exposure process)
In the exposure step, first, the insulating films 6a and 6b on both sides on one end side of the plurality of wirings 5 are peeled, and the adhesive layer 7 is further removed. Subsequently, in the exposing step, the reinforcing sheet 4 is disposed on the other surface side of the exposed plurality of wirings 5. Specifically, the reinforcing sheet 4 is disposed so that the other surface of the plurality of wirings 5 abuts on one surface of the adhesive layer 11. Thereby, an exposed region B in which one surface side of the plurality of wirings 5 is exposed is formed. The reinforcing sheet 4 is disposed so that one end side in a plan view is in contact with the other surface of the plurality of wirings 5 and the other end side is overlapped with the insulating film 6b.

(Polymerization process)
In the polymerization step, as shown in FIG. 6A, the plurality of conductive paste portions 8 of the connection sheet 21 are overlapped with each other on the exposed one surface side of the plurality of wirings 5 in plan view. At this time, when the reinforcing sheet 4 is transparent, for example, the overlapping operation can be easily and reliably performed while confirming the positions of the plurality of conductive paste portions 8 and the plurality of wirings 5 from the other surface side of the reinforcing sheet 4. It can be carried out.

(Crimping process)
In the crimping step, as shown in FIG. 6B, the plurality of wirings 5 and the conductive paste portion 8 overlapped in the polymerization step are thermocompression-bonded and bonded between the plurality of conductive paste portions 8. The adhesive portion 9 and the plurality of wirings 5 and the adhesive layer 11 of the reinforcing sheet 4 are thermocompression bonded. Thereby, the said flexible flat cable 31 by which the release film 22 was laminated | stacked on the one surface of the electrically conductive paste part 8 and the adhesive agent part 9 is obtained.

  As a minimum of the thermocompression-bonding temperature in the said crimping | compression-bonding process, 70 degreeC is preferable and 80 degreeC is more preferable. On the other hand, as an upper limit of the said thermocompression bonding temperature, 110 degreeC is preferable and 100 degreeC is more preferable. If the said thermocompression bonding temperature is less than the said minimum, there exists a possibility that the adhesive strength between the connection sheet 21, the some wiring 5, and the adhesive bond layer 11 of the reinforcement sheet 4 may not fully be obtained. On the contrary, when the said thermocompression bonding temperature exceeds the said upper limit, there exists a possibility that it melt | melts to the adhesive bond layer 11 of the reinforcement sheet 4 and cannot adhere | attach the adhesive sheet 21 stably.

  As a minimum of the thermocompression bonding load in the above-mentioned pressure bonding process, 10N is preferred and 20N is more preferred. On the other hand, the upper limit of the thermocompression bonding load in the above-described crimping step is preferably 50N, and more preferably 40N. If the said thermocompression-bonding load is less than the said minimum, there exists a possibility that the adhesive strength between the connection sheet 21, the some wiring 5, and the adhesive bond layer 11 of the reinforcement sheet 4 may not fully be obtained. Conversely, if the thermocompression bonding load exceeds the upper limit, the adhesive layer 11 of the reinforcing sheet 4 may be melted and the adhesive sheet 21 may not be stably bonded.

  As a minimum of the thermocompression-bonding time in the said crimping | compression-bonding process, 1 second is preferable and 2 seconds is more preferable. On the other hand, the upper limit of the thermocompression bonding time in the pressure bonding step is preferably 6 seconds, and more preferably 4 seconds. If the said thermocompression bonding time is less than the said minimum, there exists a possibility that the adhesive strength between the connection sheet 21, the some wiring 5, and the adhesive bond layer 11 of the reinforcement sheet 4 may not fully be obtained. On the contrary, when the said thermocompression bonding time exceeds the said upper limit, there exists a possibility that it may melt | melt to the adhesive bond layer 11 of the reinforcement sheet 4, and cannot adhere | attach the adhesive sheet 21 stably.

  In the crimping step, when the softening temperature of the polymer constituting the adhesive layer 11 of the reinforcing sheet 4 is higher than the softening temperature of the polymer constituting the conductive paste portion 8 and the softening temperature of the polymer constituting the adhesive portion 9, Even if the polymer constituting the conductive paste portion 8 and the polymer constituting the adhesive portion 9 are softened, the softening of the polymer constituting the adhesive layer 11 is prevented. Therefore, the conductive paste portion 8 and the adhesive portion 9 can be stably bonded onto one surface of the adhesive layer 11 while supporting the other side by the adhesive layer 11. In addition, the other side is supported by the adhesive layer 11 in this manner, so that mixing of the conductive paste portion 8 and the adhesive portion 9 during thermocompression bonding is prevented. Thereby, the short circuit between the some wiring 5 is prevented.

(Peeling process)
In the peeling step, as shown in FIG. 6C, the release film 22 laminated on one surface of the conductive paste portion 8 and the adhesive portion 9 is peeled off. Thereby, the said flexible flat cable 1 of FIGS. 1-3 is obtained.

<Flexible flat cable connection structure>
Next, a connection structure of the flexible flat cable 1 will be described with reference to FIG.

  In the connection structure of FIG. 7, at least one surface side of the plurality of wirings 5 is exposed, and a plurality of conductive portions 23 are stacked on one surface of the exposed plurality of wirings 5. A plastic adhesive portion 24 is laminated. In the connection structure of FIG. 7, the connection sheet 3 is bonded to the exposed region B where at least one surface of the plurality of wirings 5 is exposed so that the plurality of wirings 5 and the plurality of conductive paste portions 8 match in plan view. Has been. That is, each conductive portion 23 is composed of the conductive paste portion 8 of the connection sheet 3, and the thermoplastic adhesive portion 24 is composed of the adhesive portion 9 of the connection sheet 3. 7 includes an electrode substrate 41 that is electrically connected to the flexible flat cable 1.

  The electrode substrate 41 includes a substrate 42 and a plurality of wirings (electrode layers) 43 stacked in a stripe pattern on the other surface side (bonding surface side with the flexible flat cable 1) of the substrate 42. In the connection structure of FIG. 7, a plurality of wirings 43 are bonded to the surface opposite to the bonding surface with the plurality of wirings 5 of the plurality of conductive paste portions 8. That is, the plurality of wirings 43 are disposed at positions overlapping the plurality of conductive parts 23 in plan view, and are directly laminated on one surface of the conductive part 23. The plurality of wirings 43 are directly laminated on one surface of the conductive part 23 to be electrically connected to the conductive part 23, and are electrically connected to the plurality of wirings 5 through the conductive part 23.

  The substrate 42 is preferably transparent, more preferably colorless and transparent. Examples of the main component of the substrate 42 include glass such as soda lime glass and non-alkali glass, and synthetic resin.

  The main components of the wiring 43 include, for example, indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), and fluorine tin oxide. Examples thereof include metal oxides such as a material (FTO), niobium titanium oxide (TNO), and cadmium tin oxide (CTO), and metals such as copper and silver.

  The average width of the wiring 43 is not particularly limited, and can be, for example, about 0.1 mm or more and 0.8 mm or less. Further, the average thickness of the wiring 43 is not particularly limited, and can be, for example, about 0.1 μm or more and 30 μm or less. The average pitch of the wiring 43 can be the same as the average pitch of the conductive portions 23.

<Advantages>
In the connection structure of the flexible flat cable, the plurality of conductive paste portions 8 of the connection sheet 3 are bonded to the plurality of wirings 5, respectively, and are opposite to the bonding surfaces of the plurality of conductive paste portions 8 with the plurality of wirings 5. Since the plurality of other wirings 43 are joined to the side surfaces, the conductivity between the plurality of wirings 5 and the plurality of wirings 43 can be increased, and the connection portion can be made thinner and space-saving. Can do.

<Flexible flat cable connection method>
Next, with reference to FIG. 8A and FIG. 8B, the connection method of the flexible flat cable 1 of FIGS. 1-3 is demonstrated.

  The flexible flat cable connection method includes an exposure step of exposing at least one surface side of the plurality of wirings 5, and an exposed region B where the plurality of wirings 5 are exposed. The first superposition step of superimposing the connection sheets 21 so that the paste portion 8 matches, and other surfaces that are to be connected to the surfaces opposite to the superposition surfaces of the plurality of wirings 5 of the plurality of conductive paste portions 8, respectively. A second superposition step of superimposing a plurality of wires, and a crimping step of thermocompression-bonding the exposed region B of the overlaid flexible flat cable 1, the connection sheet 21, and the other plurality of wires. In addition, in the following description, the case where the flexible flat cable 1 of FIGS. 1-3 and the electrode substrate 41 of FIG. 6 are connected is demonstrated.

  The exposure process is the same as the exposure process in the above-described flexible flat cable manufacturing method, and the first polymerization process is the same as the polymerization process in the above-described flexible flat cable manufacturing method, and thus the description thereof is omitted.

(Second polymerization step)
The said 2nd superposition | polymerization process is performed after the peeling process in the manufacturing method of the above-mentioned flexible flat cable. In the second polymerization step, as shown in FIG. 8A, the plurality of wirings 43 are overlapped on one surface of the plurality of conductive paste portions 8 bonded to one surface of the plurality of wirings 5. At this time, when the reinforcing sheet 4 is transparent and the substrate 42 is transparent, the overlapping operation is performed easily and reliably while confirming the positions of the plurality of conductive paste portions 8 and the plurality of wirings 43. Can do.

(Crimping process)
In the crimping step, as shown in FIG. 8B, the plurality of conductive paste portions 8 and the plurality of wirings 43 are thermocompression bonded, and the adhesive portion 9 and the substrate disposed between the plurality of conductive paste portions 8. 42 is thermocompression bonded. Accordingly, the plurality of conductive paste portions 8 become the plurality of conductive portions 23 and the adhesive portion 9 becomes the thermoplastic adhesive portion 24, whereby the connection structure of FIG. 7 is obtained.

  As a minimum of thermocompression bonding temperature in the above-mentioned press-bonding process, 80 ° C is preferred and 90 ° C is more preferred. On the other hand, as an upper limit of the said thermocompression bonding temperature, 140 degreeC is preferable and 130 degreeC is more preferable. If the said thermocompression bonding temperature is less than the said minimum, there exists a possibility that the adhesive strength between the some electroconductive paste part 8 and the adhesive agent part 9, and the board | substrate 42 and the wiring 43 may not fully be obtained. On the other hand, when the thermocompression bonding temperature exceeds the upper limit, the adhesive layer 11 of the reinforcing sheet 4 is melted and the plurality of conductive paste portions 8 and the adhesive portions 9, the substrate 42 and the wiring 43 are stably provided. There is a possibility that it cannot be bonded.

  As a minimum of the thermocompression bonding load in the above-mentioned pressure bonding process, 10N is preferred and 20N is more preferred. On the other hand, the upper limit of the thermocompression bonding load in the above-described crimping step is preferably 50N, and more preferably 40N. If the thermocompression bonding load is less than the lower limit, the adhesive strength between the plurality of conductive paste portions 8 and adhesive portions 9 and the substrate 42 and wiring 43 may not be sufficiently obtained. On the contrary, when the thermocompression bonding load exceeds the upper limit, the adhesive layer 11 and the like of the reinforcing sheet 4 are melted and the plurality of conductive paste portions 8 and the adhesive portions 9, the substrate 42 and the wiring 43 are stably formed. There is a possibility that it cannot be bonded.

  As a minimum of thermocompression-bonding time in the above-mentioned press-bonding process, 6 seconds are preferred and 8 seconds are more preferred. On the other hand, as an upper limit of the thermocompression bonding time in the above-described pressure bonding step, 14 seconds is preferable, and 12 seconds is more preferable. If the said thermocompression bonding time is less than the said minimum, there exists a possibility that the adhesive strength between the some conductive paste part 8 and the adhesive agent part 9, and the board | substrate 42 and the wiring 43 may not fully be obtained. On the contrary, if the said thermocompression bonding time exceeds the said upper limit, it will melt | dissolve to the adhesive bond layer 11 grade | etc., Of the reinforcement sheet 4, and the several electroconductive paste part 8 and the adhesive bond part 9, the board | substrate 42, and the electrode layer 43 will be stabilized. There is a possibility that it can not be adhered to.

  In the crimping step, when the softening temperature of the polymer constituting the adhesive layer 11 of the reinforcing sheet 4 is higher than the softening temperature of the polymer constituting the conductive paste portion 8 and the softening temperature of the polymer constituting the adhesive portion 9, Even if the polymer constituting the conductive paste portion 8 and the polymer constituting the adhesive portion 9 are softened, the softening of the polymer constituting the adhesive layer 11 is prevented. Therefore, it is possible to stably bond the plurality of conductive paste portions 8 and the adhesive portions 9 to the substrate 42 and the wiring 43 while supporting the other side by the adhesive layer 11. Further, the other side is supported by the adhesive layer 11 in this manner, so that mixing of the plurality of conductive paste portions 8 and the adhesive portion 9 during thermocompression bonding is prevented. Thereby, the short circuit between the some wiring 5 is prevented.

<Advantages>
The connection method of the flexible flat cable can enhance the continuity between the wirings to be connected, and can promote the thinning and space saving of the connection portion.

[Second Embodiment]
<Connection sheet>
The connection sheet 51 of FIG. 9 is used for electrical connection of a flexible flat cable having a plurality of wirings instead of the connection sheet 21 of FIG. The connection sheet 51 in FIG. 9 includes the conductive paste portion 8, the adhesive portion 59, the pressure-sensitive adhesive portion 60, and the release film 22. In the connection sheet 51 of FIG. 9, the release film 22 is laminated on one surface of the conductive paste part 8, the adhesive part 59, and the adhesive part 60. The conductive paste part 8, the adhesive part 59, and the adhesive part 60 are disposed in the same layer. The conductive paste portion 8 and the release film 22 in the connection sheet 51 of FIG. 9 are the same as the conductive paste portion 8 and the release film 22 of the connection sheet 21 of FIG. To do.

(Adhesive part)
The adhesive portion 59 is disposed between at least the plurality of conductive paste portions 8. Specifically, the adhesive portion 59 has a plurality of conductive pastes disposed between the plurality of conductive paste portions 8 and outside the pair of conductive paste portions 8 stacked on both side ends of the plurality of conductive paste portions 8. It is arranged in parallel with the paste part 8. Each adhesive part 59 is formed in a rectangular shape in plan view.

  The average width of the plurality of adhesive portions 59 disposed between the plurality of conductive paste portions 8 and the outside of the pair of conductive paste portions 8 stacked at both ends of the plurality of conductive paste portions 8. The average width of the pair of adhesive portions 59 provided and the average thickness of the plurality of adhesive portions 59 can be the same as those of the flexible flat cable 1 of FIGS.

  The average length of the plurality of adhesive portions 59 (the length in the direction parallel to the longitudinal direction of the conductive paste portion 8) is preferably the same as the average length of the plurality of conductive paste portions 8. Since the average length of the plurality of adhesive portions 59 and the average length of the plurality of conductive paste portions 8 are the same, the adhesive described later while ensuring the insulation between adjacent wires by the plurality of adhesive portions 59. It is easy to dispose the agent part 60 on both ends in the longitudinal direction of the plurality of conductive paste parts 8. Note that “the average length of the plurality of adhesive portions 59 and the average length of the plurality of conductive paste portions 8 are the same” means that the average length of the plurality of adhesive portions 59 and the plurality of conductive paste portions 8 are the same. It means that the difference in the average length is ± 1 mm or less, preferably ± 0.5 mm or less.

  The plurality of adhesive portions 59 are mainly composed of a thermoplastic resin. The plurality of adhesive portions 59 are configured by a hot melt adhesive that melts by applying heat. Examples of the thermoplastic resin include acrylic resin, polyamide, polyolefin, fluororesin, polyester, and silicone resin. Among these, as the thermoplastic resin, a polyester excellent in moldability, insulation and the like is preferable.

  As a minimum of the softening temperature of the polymer which constitutes a plurality of adhesives parts 59, 80 ° C is preferred and 100 ° C is more preferred. On the other hand, the upper limit of the softening temperature of the polymer constituting the plurality of adhesive portions 59 is preferably 130 ° C, more preferably 120 ° C. Since the adhesive sheet 60 described later has adhesiveness at room temperature, the connection sheet 51 is thermocompression bonded with the connection sheet 51 temporarily attached to the exposed region B of the flexible flat cable 1 by the adhesive part 60. Can do. Therefore, even if the softening temperature of the polymer constituting the adhesive portion 59 is high within the above range, the connection sheet 51 and the exposed region B can be joined at a desired position. Therefore, the said connection sheet 51 can fully improve heat resistance by making the softening temperature of the polymer which comprises the adhesive agent part 59 into the said minimum or more. On the other hand, when the softening temperature of the polymer constituting the adhesive portion 59 exceeds the upper limit, the thermocompression bonding temperature becomes too high, and the plurality of wirings 5 and the reinforcing sheet 4 may be deteriorated.

  As a minimum of the glass transition temperature of the polymer which constitutes adhesive part 59, 50 ° C is preferred and 60 ° C is more preferred. When the glass transition temperature of the polymer constituting the adhesive part 59 is equal to or higher than the above lower limit, the strength of the adhesive part 59 can be sufficiently increased. On the other hand, the upper limit of the glass transition temperature of the polymer constituting the adhesive part 59 is not particularly limited, and can be, for example, 100 ° C.

  The weight average molecular weight of the polymer constituting the adhesive part 59 can be, for example, 10,000 or more and less than 25,000. The weight average molecular weight is a value measured using a gel permeation chromatography (GPC) apparatus, using N-methyl-2-pyrrolidone as a developing solvent, and using monodisperse polystyrene as a standard.

  The lower limit of the intrinsic viscosity of the polymer constituting the adhesive part 59 is preferably 0.3 dl / g, more preferably 0.4 dl / g. On the other hand, the upper limit of the intrinsic viscosity of the polymer constituting the adhesive part 59 is preferably 0.7 dl / g, more preferably 0.6 dl / g. If the intrinsic viscosity of the polymer constituting the adhesive part 59 is less than the above lower limit, the moldability of the adhesive part 59 may be lowered. On the contrary, if the intrinsic viscosity of the polymer constituting the adhesive part 59 exceeds the above upper limit, the adhesion may be insufficient. The “intrinsic viscosity” refers to a value measured using a Ubbelohde viscometer in a mixed solvent of phenol and tetrachloroethane at 25 ° C.

  As a minimum of the hydroxyl value of the polymer which constitutes adhesive part 59, 1 mgKOH / g is preferred and 3 mgKOH / g is more preferred. When the hydroxyl value of the polymer constituting the adhesive part 59 is not less than the above lower limit, the substrate to be thermocompression bonded to the adhesive part 59 is a glass substrate or the like having a silanol group (—SiOH) on the surface. The bond strength can be improved by forming a bond (-Si-O-Si-). The upper limit of the hydroxyl value of the polymer constituting the adhesive part 59 is not particularly limited, and can be set to, for example, 30 mgKOH / g.

  It should be noted that additives such as a curing agent, a thickener, and a rebilling agent can be added to the adhesive portion 59 within a range that does not hinder the adhesive function of the adhesive portion 59.

(Adhesive part)
The pressure-sensitive adhesive part 60 is disposed on both ends in the longitudinal direction of the plurality of conductive paste parts 8 and the plurality of adhesive parts 59. Each pressure-sensitive adhesive part 60 is formed in a rectangular shape in plan view with the width direction of the plurality of conductive paste parts 8 and the plurality of adhesive parts 59 as the longitudinal direction. The length in the longitudinal direction of each adhesive portion 60 is the same as the total width of the plurality of conductive paste portions 8 and the plurality of adhesive portions 59. Thereby, the some electroconductive paste part 8, the some adhesive agent part 59, and a pair of adhesive part 60 are formed in the planar view rectangular shape as a whole.

  The lower limit of the average width of each pressure-sensitive adhesive part 60 (the average length in the direction parallel to the longitudinal direction of the plurality of conductive paste parts 8 and the plurality of adhesive parts 59) is preferably 0.5 mm, more preferably 0.8 mm. preferable. On the other hand, as an upper limit of the average width of each adhesive part 60, 3 mm is preferable and 2 mm is more preferable. If the average width of each adhesive part 60 is less than the said minimum, there exists a possibility that the temporary fix | stop function by the adhesive part 60 may not fully be acquired. Moreover, if the average width of each adhesive part 60 is less than the said minimum, it will become impossible to enclose the several electrically conductive paste part 8 by planar view by the several adhesive part 59 and a pair of adhesive part 60 exactly. As a result, there is a possibility that a short circuit is likely to occur between the plurality of wirings 5. On the contrary, when the average width of each adhesive part 60 exceeds the said upper limit, there exists a possibility that the plane area of the adhesive part 60 may become unnecessarily large.

As a minimum of the plane area per 20 wiring of each adhesive part 60, 6 mm < ² > is preferable and 8 mm < ² > is more preferable. On the other hand, as an upper limit of the plane area per 20 wirings of each adhesive part 60, 15 mm ² is preferable and 12 mm ² is more preferable. If the planar area of each pressure-sensitive adhesive part 60 is less than the lower limit, sufficient tackiness may not be obtained, and the temporary fixing function may be insufficient. Conversely, if the planar area of each pressure-sensitive adhesive part 60 exceeds the upper limit, the connection sheet 51 may become unnecessarily large.

  As a minimum of average thickness of a pair of adhesive parts 60, 20 micrometers is preferred and 50 micrometers is more preferred. On the other hand, as an upper limit of average thickness of a pair of adhesive part 60, 130 micrometers is preferable and 100 micrometers is more preferable. If the average thickness of the pair of pressure-sensitive adhesive parts 60 is less than the above lower limit, the temporary fixing function by the pressure-sensitive adhesive part 60 may not be sufficiently achieved. On the other hand, if the average thickness of the pair of pressure-sensitive adhesive parts 60 exceeds the above upper limit, the connection part may not be sufficiently thinned.

  The average thickness of the pair of pressure-sensitive adhesive portions 60 is preferably thicker than the average thickness of the plurality of conductive paste portions 8 and the plurality of adhesive portions 59. When the average thickness of the pair of adhesive portions 60 is thicker than the average thickness of the plurality of conductive paste portions 8 and the plurality of adhesive portions 59, the connection sheet 51 is exposed by the adhesive portion 60 to the exposed area of the flexible flat cable 1. Both are easy to thermocompression-bond in the state temporarily fixed to B. The lower limit of the difference between the average thickness of the pair of adhesive portions 60 and the average thickness of the plurality of conductive paste portions 8 and the plurality of adhesive portions 59 is preferably 10 μm, and more preferably 40 μm. On the other hand, the upper limit of the difference in average thickness is preferably 100 μm, and more preferably 70 μm. If the difference in the average thickness is less than the lower limit, the temporary fixing function by the pair of adhesive portions 60 may not be sufficiently achieved. On the other hand, when the difference in the average thickness exceeds the upper limit, the pair of pressure-sensitive adhesive portions 60 flows toward the plurality of conductive paste portions 8 and the plurality of adhesive portions 59 at the time of thermocompression bonding. May decrease.

  The adhesive 60 has a thermoplastic resin as a main component. The pressure-sensitive adhesive part 60 has tackiness and has adhesive strength at room temperature. That is, the adhesive part 60 is comprised with the pressure sensitive adhesive. Examples of the thermoplastic resin include acrylic resin, polyamide, polyolefin, fluororesin, polyester, and silicone resin. Among these, as the thermoplastic resin, a polyester excellent in moldability, insulation and the like is preferable.

  As a minimum of the softening temperature of the polymer which constitutes adhesive part 60, 20 ° C is preferred and 300 ° C is more preferred. If the softening temperature of the polymer constituting the pressure-sensitive adhesive part 60 is less than the above lower limit, the heat resistance may be insufficient. On the other hand, the upper limit of the softening temperature of the polymer constituting the pressure-sensitive adhesive part 60 is not particularly limited as long as it is a temperature that can be melted at the time of thermocompression bonding, and can be, for example, 60 ° C.

  As a minimum of the glass transition temperature of the polymer which constitutes adhesive part 60, -50 ° C is preferred and -40 ° C is more preferred. On the other hand, as an upper limit of the glass transition temperature of the polymer which comprises the adhesive part 60, 20 degreeC is preferable and 0 degreeC is more preferable. If the glass transition temperature of the polymer constituting the pressure-sensitive adhesive part 60 is less than the lower limit, the shape of the pressure-sensitive adhesive part 60 may be difficult to maintain. On the contrary, if the glass transition temperature of the polymer constituting the pressure-sensitive adhesive part 60 exceeds the above upper limit, the tackiness is insufficient and there is a possibility that the adhesive strength at room temperature cannot be obtained sufficiently.

  As a weight average molecular weight of the polymer which comprises the adhesive part 60, it can be more than 25,000 and 50,000 or less, for example.

  As a minimum of intrinsic viscosity of the polymer which constitutes adhesive part 60, 0.6 dl / g is preferred and 0.8 dl / g is more preferred. On the other hand, the upper limit of the intrinsic viscosity of the polymer constituting the pressure-sensitive adhesive part 60 is preferably 1.3 dl / g, more preferably 1.1 dl / g. If the intrinsic viscosity of the polymer constituting the pressure-sensitive adhesive part 60 is less than the above lower limit, the tackiness of the pressure-sensitive adhesive part 60 may be insufficient. On the other hand, when the intrinsic viscosity of the polymer constituting the pressure-sensitive adhesive part 60 exceeds the above upper limit, applicability may be reduced.

  As a minimum of the hydroxyl value of the polymer which constitutes adhesive part 60, 1 mgKOH / g is preferred and 3 mgKOH / g is more preferred. When the hydroxyl value of the polymer constituting the pressure-sensitive adhesive part 60 is equal to or higher than the above lower limit, the substrate bonded to the pressure-sensitive adhesive part 60 is a glass substrate or the like having a silanol group (—SiOH) on the surface. By forming (—Si—O—Si—), the adhesive strength can be improved. In addition, as an upper limit of the hydroxyl value of the polymer which comprises the adhesive part 60, it does not specifically limit, For example, it can be set to 30 mgKOH / g.

  Note that additives such as a curing agent, a thickener, a tackifier, and a rebilling agent can be added to the pressure-sensitive adhesive portion 60 within a range that does not impair the pressure-sensitive adhesive function of the pressure-sensitive adhesive portion 60. The pressure-sensitive adhesive part 60 has tackiness mainly by adjusting the planar area of the pressure-sensitive adhesive part 60 and the glass transition temperature of the polymer constituting the pressure-sensitive adhesive part 60, and therefore the pressure-sensitive adhesive part 60 has a tackifier. May not be added.

  The connection sheet 51 is formed by laminating a plurality of conductive paste portions 8 on the surface of the release film 22, and further laminating an adhesive portion 59 between the plurality of conductive paste portions 8. The adhesive part 59 is formed by laminating a pair of adhesive parts 60 on both ends in the longitudinal direction. As a method of laminating the conductive paste part 8, the adhesive part 59, and the adhesive part 60, the same printing or coating method as that for the connection sheet 21 in FIG.

<Advantages>
Since the connection sheet 51 includes the adhesive portion 60 disposed in the same layer as the conductive paste portion 8 and the adhesive portion 59, the connection sheet 51 and the exposed area B of the flexible flat cable are formed by the adhesive portion 60. Can be temporarily fixed. Thereby, the said connection sheet 51 carries out the position shift | offset | difference at the time of the thermocompression bonding of the said connection sheet 51 and the exposure area | region B by thermocompression-bonding the said connection sheet | seat 51 and the exposure area | region B of a flexible flat cable, for example in a temporarily fixed state. The connection sheet 51 and the exposed region B can be easily and reliably joined at a desired position. Moreover, according to the connection sheet 51, it is possible to save time and labor using a jig for positioning the connection sheet 51 and the exposed region B.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  For example, the connection sheet does not necessarily have a release film. Therefore, the flexible flat cable can be formed by, for example, laminating a conductive paste portion directly on one surface of a plurality of wirings and laminating an adhesive portion between the plurality of conductive paste portions to form a connection sheet. Good.

  The adhesive part need not necessarily surround the plurality of conductive paste parts in plan view. As a configuration in which the adhesive portion does not surround a plurality of conductive paste portions, for example, a configuration in which the adhesive portion is laminated only between a plurality of conductive paste portions arranged in a stripe shape, or a plurality of conductive paste portions The structure which does not have an adhesive part on both sides of the longitudinal direction of is mentioned.

  The average width of the conductive paste portion is not necessarily smaller than the average width of the wiring. In the flexible flat cable, even if the average width of the conductive paste portion is equal to or larger than the average width of the wiring, the adhesive portion is disposed between the conductive paste portions, thereby short-circuiting the conductive paste portions. Can be prevented.

  The conductive paste portion is not necessarily formed in a substantially rectangular shape in plan view, and may be, for example, a polygonal shape or an elliptical shape.

  Even if the connection sheet includes a pressure-sensitive adhesive portion disposed in the same layer as the conductive paste portion and the adhesive portion, the pressure-sensitive adhesive portion does not necessarily include a plurality of conductive paste portions and a plurality of adhesive portions. It is not necessary to be disposed on both ends in the longitudinal direction. In the connection sheet, for example, the adhesive portion is disposed only on one end side in the longitudinal direction of the plurality of conductive paste portions and the plurality of adhesive portions, and the adhesive portion is continuously provided on the other end side. Also good. Moreover, the said adhesive part may be arrange | positioned between several electroconductive paste parts.

  The flexible flat cable does not necessarily have a reinforcing sheet disposed on the other surface side of one end side of the flexible flat cable body. For example, the flexible flat cable peels only the insulating film and the adhesive layer disposed on one surface side of one end side of a plurality of wirings, and a plurality of conductive paste portions and the conductive paste portions are formed on the peeling surface. You may laminate | stack the adhesive part laminated | stacked between.

  The flexible flat cable is not necessarily connected to the electrode substrate, and can be connected to various conductive members.

  As described above, the connection sheet, the flexible flat cable, the connection structure of the flexible flat cable, and the connection method of the flexible flat cable according to the present invention can increase the electrical conductivity between the wirings to be connected and reduce the thickness of the connection portion. In addition, since space saving can be promoted, it is suitable for connection with, for example, an electrode substrate.

1, 31 Flexible flat cable 2 Flat cable body 3 Flexible flat cable connection sheet (connection sheet)
4 Reinforcing sheet 5 Wiring 6a, 6b Insulating film 7 Adhesive layer 8 Conductive paste part 9 Adhesive part 10 Insulating layer 11 Adhesive layer 21 Connection sheet 22 Release film 23 Conductive part 24 Thermoplastic adhesive part 41 Electrode substrate 42 Substrate 43 Wiring 51 Connection sheet 59 Adhesive part 60 Adhesive part B Exposed area

Claims (10)

A connection sheet used for electrical connection of a flexible flat cable having a plurality of wires,
A plurality of strip-shaped conductive paste portions disposed in parallel corresponding to the plurality of wirings in plan view, and including conductive particles and a binder thereof;
A connection sheet provided with at least an adhesive portion that is disposed between the plurality of conductive paste portions and has a thermoplastic resin as a main component.   The connection sheet according to claim 1, wherein the adhesive portion is disposed so as to surround the plurality of conductive paste portions in a plan view.   The connection sheet according to claim 1 or 2, wherein an average thickness of the conductive paste portion and an average thickness of the adhesive portion are the same.   The connection sheet according to claim 1, wherein the average width of the conductive paste portion is smaller than the average width of the wiring.   The connection sheet according to any one of claims 1 to 4, wherein a softening temperature of the polymer constituting the binder of the conductive paste part and the polymer constituting the adhesive part is 40 ° C or higher and 70 ° C or lower.   The connection sheet according to any one of claims 1 to 5, further comprising a pressure-sensitive adhesive portion disposed in the same layer as the conductive paste portion and the adhesive portion.   The connection sheet according to any one of claims 1 to 6, further comprising a release film laminated on one surface of the conductive paste portion and the adhesive portion. A flexible flat cable having a plurality of wires,
8. The device according to claim 1, wherein the plurality of wirings and the plurality of conductive paste portions match with each other in a plan view in a region where at least one surface side of the plurality of wirings is exposed. Flexible flat cable with connection sheet joined. A flexible flat cable connection structure having a plurality of wires,
A flexible flat cable in which at least one surface side of the plurality of wirings is exposed; and
The connection sheet according to any one of claims 1 to 6, wherein the plurality of wirings and the plurality of conductive paste portions are joined to an exposed region of the flexible flat cable in a plan view. ,
A connection structure for a flexible flat cable, comprising: a plurality of other wirings that are respectively bonded to a surface opposite to a bonding surface with the plurality of wirings of the plurality of conductive paste portions of the connection sheet. A method for connecting a flexible flat cable having a plurality of wires,
An exposing step of exposing at least one surface side of the plurality of wirings of the flexible flat cable;
8. The connection sheet according to claim 1, wherein the plurality of wirings and the plurality of conductive paste portions are overlapped with each other in an exposed area of the flexible flat cable in a plan view. One polymerization step;
A second polymerization step of superimposing a plurality of other wirings to be connected to a surface opposite to the overlapping surface with the plurality of wirings of the plurality of conductive paste portions;
A method of connecting a flexible flat cable, comprising: an exposed region of the above-described flexible flat cable, a connection sheet, and a crimping step of thermocompression bonding the plurality of other wirings.

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