TWI754611B - Conductive bonding sheet for fpc and fpc using the same - Google Patents

Abstract

A conductive adhesive sheet used for FPC is provided. When the conductive adhesive sheets used for FPC bonded to a metal reinforcing plate are stacked, blocking between the conductive adhesive layer and the metal reinforcing plate will not occur, and it has good peelability which means it can be easily peeled off. In addition, it can be firmly fixed to the FPC. The conductive adhesive sheet 5 used for FPC is provided. The conductive adhesive sheet 5 used for FPC is formed by coating an adhesive composition including a flame-retardant resin, a crosslinking agent 2, a conductive filler 3, and an antiblocking agent 4 onto one side of a support film 1, and stacking a conductive adhesive layers 13. When the sum volume Va of the non-volatile portion of the flame-retardant resin and the crosslinking agent is 100 (VOL%), the sum volume Vb of the conductive filler and the antiblocking agent is in a range of 15~70 (VOL%) preferably.

Description

Conductive adhesive sheet for FPC and FPC using the same

The present invention relates to a thermosetting conductive adhesive sheet for FPC, which is used on the surface of a flexible printed circuit board (hereinafter referred to as FPC), and an FPC using the same. Laminated metal reinforcement plate. In more detail, there is provided a conductive adhesive sheet for FPC which does not cause adhesion between the conductive adhesive layer and the metal reinforcement plate in a state where the conductive adhesive sheet for FPC attached to the metal reinforcement plate is laminated. It is attached (attached), has easy peelability that can be easily peeled off, and is firmly fixed to the FPC.

In portable electronic devices such as portable telephones and tablet terminals, in order to reduce the external size of the casing and facilitate portability, electronic components are integrated on the printed circuit board. Furthermore, in order to reduce the external size of the housing, the printed circuit board is divided into a plurality of pieces, and a flexible FPC is used for connecting lines between the divided printed circuit boards, thereby folding or sliding the printed circuit board. .

In addition, in recent years, in order to prevent malfunction caused by the noise of electromagnetic waves received from the outside of the electronic equipment or the noise of electromagnetic waves received by the electronic components arranged inside the electronic equipment, covering with an electromagnetic shielding material has been carried out. Important electronic parts or FPCs.

Conventionally, as an electromagnetic mask material for the purpose of the electromagnetic mask, a material in which an adhesive layer is provided on the surface of a metal foil such as rolled copper foil and soft aluminum foil has been used. A shielding object is covered with an electromagnetic shielding material composed of such a metal foil (for example, refer to Patent Document 1).

Specifically, in order to shield important electronic components from electromagnetic waves, metal foils or metal plates are used to cover them in an airtight box shape. In addition, in order to shield the bent FPC lines from electromagnetic waves, a material in which an adhesive layer is provided on one side of the metal foil is used, and it is bonded through the adhesive layer.

As described above, FPCs used in mobile phones and electromagnetic shielding materials for FPCs that cover the FPCs and shield electromagnetic waves are subjected to repeated bending operations at frequencies exceeding the common sense of conventional portable electronic devices. Therefore, the electromagnetic shielding material for FPC, which exhibits the electromagnetic wave shielding function of the FPC, is subjected to severe repeated stress. If the repeated stress cannot be tolerated, the support body and the mask material such as metal foil constituting the electromagnetic mask material for FPC will eventually be damaged, such as cracking or peeling. Worries about reduced or disappearance of function.

Therefore, electromagnetic mask materials corresponding to such repeated bending operations are known (for example, refer to Patent Document 2).

In addition, in recent years, portable telephones, tablet terminals, and the like have rapidly spread as portable electronic devices. In a portable telephone, it is preferable that the overall size is as small as possible when stored in a pocket, a bag, or the like when not in use, and the overall size can be enlarged during use. Here, reduction in size and thickness of the mobile phone is required, and improvement in operability is sought.

In addition, on the FPC assembled into the electronic equipment, on the FPC with the component mounted A reinforcing plate in which a plastic plate is attached to the surface opposite to one side or the terminal of an FPC connected by a connector, etc., but in recent years, in order to reduce the thickness, a metal reinforcement plate ( For example, refer to Patent Document 3).

[Prior Technology Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 61-222299

Patent Document 2: Japanese Patent Application Laid-Open No. 7-122883

Patent Document 3: Japanese Patent Laid-Open No. 2009-218443

In the electromagnetic mask material disclosed in the above-mentioned Patent Document 1 in which an adhesive layer is provided on the surface of metal foils such as rolled copper foil and soft aluminum foil, when the number of bending operations is small and the use time is short, the mask performance is not affected. influence.

However, in recent mobile phones, the thickness of the outer dimensions of the casing is reduced in units of 0.1 mm, and the thickness is required to be reduced as much as possible, so it cannot be applied.

In addition, the electromagnetic shielding material described in the examples of Patent Document 2 is a coating film of a conductive paint with a thickness of 0.5 μm and a conductive adhesive layer with a thickness of 30 μm laminated on a resin film with a thickness of 12 μm. The overall thickness of the cover material exceeds 40 μm.

As described above, in order to make the outer dimension of the casing of the mobile phone as thin as possible, the overall thickness of the electromagnetic shield material for FPC is required to be as thin as 30 μm or less. That is, there is a need for a strong electromagnetic shield material for FPC that is thinner in overall thickness and can withstand a more severe bending test than the conventional electromagnetic shield material for FPC.

In addition, in the flexible printed wiring board having the metal reinforcing plate described in Patent Document 3, the ground wire of the FPC and the metal reinforcing plate are adhered via a conductive adhesive. However, when a laminated body of a metal reinforcing plate cut into a predetermined size and an electroconductive adhesive is laminated, there is a phenomenon that blocking occurs, and there is a problem that it is difficult to peel off.

Therefore, there is a need for a conductive adhesive sheet for FPC, which does not cause adhesion between the conductive adhesive layer and the metal reinforcement plate in a state where the conductive adhesive sheet for FPC attached to the metal reinforcement plate is stacked. Easy peelability that can be easily peeled off and firmly fixed to the FPC.

In view of the above-mentioned situation, the technical problem of the present invention is to provide a conductive adhesive sheet for FPC which does not cause the conductive adhesive layer and the conductive adhesive sheet for FPC to be laminated in a state where the conductive adhesive sheet for FPC attached to a metal reinforcing plate is laminated The adhesion between the metal reinforcing plates is easy to peel off easily, and it is firmly fixed on the FPC.

The conductive adhesive sheet for FPC of the present invention does not cause adhesion between the conductive adhesive layer and the metal reinforcing plate, has easy peelability, and needs to have the opposite physical property of being able to be firmly fixed to the FPC.

Therefore, the technical idea of the present invention is to set the total volume of the conductive filler and the anti-blocking agent or the volume of the conductive filler relative to the total volume of the non-volatile components of the flame-retardant resin and the cross-linking agent. Within the predetermined range, the opposite physical properties can be taken into consideration.

In order to solve the technical problem, the present invention provides a conductive adhesive sheet for FPC, which is characterized in that the conductive adhesive sheet for FPC is used for FPC In one side of the support film, an adhesive composition containing a flame retardant resin, a crosslinking agent, and a conductive filler is applied, or an adhesive composition containing a flame retardant resin, a crosslinking agent, and a conductive filler is applied. , The adhesive composition of anti-blocking agent, which is formed by laminating conductive adhesive layers.

In addition, when the total volume VA of the non _- volatile components of the flame retardant resin and the crosslinking agent is taken as 100 (VOL%), the total volume _VB of the conductive filler and the anti-blocking agent The range of 15-70 (VOL%) is preferable.

In addition, the flame-retardant resin is preferably a phosphorus-containing polyurethane resin.

In addition, the conductive filler is dendritic metal particles, and the metal particles are one or more selected from the group consisting of silver particles, copper particles, and silver-coated copper particles. When the total volume VA of the non _- volatile components of the flame retardant resin and the crosslinking agent is 100 (VOL%), the volume _VC of the conductive filler is preferably 15 to 60 (VOL%). Scope.

In addition, the anti-blocking agent is hydrophobic silica powder, and when the total volume VA of the non _- volatile components of the flame retardant resin and the cross-linking agent is taken as 100 (VOL%), the anti-blocking agent The volume V _D of the continuous agent is preferably in the range of 0 to 15 (VOL%).

Furthermore, the present invention provides an FPC in which the conductive adhesive sheet for FPC is used for bonding a metal reinforcing plate on the surface of the FPC.

According to the conductive adhesive sheet for FPC of the present invention, an adhesive composition containing a flame retardant resin, a crosslinking agent, and a conductive filler is coated on one side of the support film, or a flame retardant Resin, crosslinking agent, conductive filler The adhesive composition of the adhesive and anti-blocking agent, and the conductive adhesive layer is laminated. As a result, the conductive adhesive sheet for FPC attached to the metal reinforcing plate does not cause adhesion between the conductive adhesive layer and the metal reinforcing plate in the state of being laminated, and has easy peelability and can be firmly peeled off. fixed on the FPC.

Therefore, after the conductive adhesive sheet for FPC of the present invention is laminated on the metal reinforcing plate via the conductive adhesive, it is cut into a predetermined size and used as the conductive adhesive sheet with the metal reinforcing plate, although the The state of the support film is stacked and stored, but the occurrence of blocking can be avoided, and it can be easily peeled off. Therefore, the conductive adhesive sheet for FPC of the present invention is expected to improve the efficiency of the work process for laminating the conductive adhesive sheet with the metal reinforcing plate (laminated body of the metal reinforcing plate and the conductive adhesive layer) on the FPC, It can contribute to the improvement of productivity, and has a large industrial value.

1‧‧‧Support film

2‧‧‧Flame retardant resin and crosslinking agent

3‧‧‧Conductive filler

4‧‧‧Anti-blocking agent

5‧‧‧Conductive adhesive sheet for FPC

6‧‧‧Metal reinforcement plate

7‧‧‧Installation

8‧‧‧Substrate film

9‧‧‧Ground circuit (copper foil)

10‧‧‧Insulating adhesive layer

11‧‧‧Insulating film

12‧‧‧Cover Film

13‧‧‧Conductive adhesive layer

14‧‧‧Through hole

20‧‧‧FPC

30‧‧‧Conductive adhesive sheet with metal reinforcement

Fig. 1 is a schematic cross-sectional view showing an example of the conductive adhesive sheet for FPC of the present invention; Fig. 2 is a schematic cross-sectional view showing an example of a reinforcing plate attached to the FPC via the conductive adhesive sheet for FPC of the present invention Figure 3; Figure 3 is a schematic cross-sectional view showing the conductive adhesive sheet with a metal reinforcing plate in which the conductive adhesive sheet for FPC of the present invention is laminated on a metal reinforcing plate through a conductive adhesive; Figure 4 ( a) is a schematic plan view of a simulated flexible substrate used in the evaluation method of electrical conductivity, and FIG. 4(b) is a cross-sectional view of FIG. 4(a) viewed from the direction of arrow AA; Fig. 5(a) is a schematic plan view of a test piece for evaluating conductivity used in the method for evaluating conductivity, and Fig. 5(b) is a cross-sectional view of Fig. 5(a) viewed from the direction of arrow B-B.

Preferred embodiments of the present invention will be described below.

The conductive adhesive sheet for FPC of the present invention is obtained by laminating one side of a conductive adhesive layer on a metal reinforcing plate or the like as an adherend, and removing the support film from the other side of the conductive adhesive layer When the conductive adhesive sheet with the adherend is stacked and stored, the other surface of the conductive adhesive layer does not cause adhesion to the outer surface of the adherend (metal reinforcement plate, etc.) The conductive adhesive sheet with the adherend is easily peeled off one by one, and the total volume of the conductive filler and anti-blocking agent is set relative to the total volume of the non-volatile components of the flame retardant resin and cross-linking agent Within the specified range, the conductive adhesive sheet with the adherend can be firmly adhered to the FPC.

Fig. 1 is a schematic cross-sectional view showing an example of the conductive adhesive sheet for FPC of the present invention.

The conductive adhesive sheet 5 for FPC of the present invention shown in FIG. 1 is formed by laminating the conductive adhesive layer 13 on the peeling-treated surface of the support film 1 that has undergone peeling treatment on one side. In addition, as shown in FIG. 3, after the conductive adhesive sheet 5 for FPC is laminated on the metal reinforcement plate 6 via the conductive adhesive layer 13, it is cut into a predetermined size, and is used as a conductive adhesive sheet with a metal reinforcement plate. The adhesive sheet 30 is stacked and stored in a state in which the support film 1 is removed. The conductive adhesive sheet 30 with a metal reinforcing plate is a laminate of the metal reinforcing plate 6 and the conductive adhesive layer 13 , and can be used as an electromagnetic shielding reinforcing plate for FPC as shown in FIG. 2 . In Figure 2, FPC 20 The substrate film 8 has the mount 7 and the ground circuit 9 in the following structure, and the ground circuit 9 is protected by the cover film 12 provided with the insulating adhesive layer 10 on the insulating film 11 . A through hole 14 is provided on the cover film 12, and the conductive adhesive layer 13 of the conductive adhesive sheet 30 with a metal reinforcing plate is in contact with the ground circuit 9 through the through hole 14, so that the metal reinforcing plate 6 acts as an electromagnetic shield. material to function.

(Support film)

Examples of the support film 1 used in the present invention include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; Polyolefin films such as propylene or polyethylene.

The support film 1 is, for example, polyethylene terephthalate or the like, and when the support film itself has a certain degree of releasability, a conductive adhesive may be directly laminated on the support film 1 without applying a peeling treatment. Layer 13. Moreover, you may apply the peeling process for peeling the electroconductive adhesive bond layer 13 from the support film 1 more easily to the surface of the support film 1.

In addition, when the resin film used as the above-mentioned support film 1 does not have peeling properties, a peeling treatment is performed by applying a peeling agent such as an aminoalkyd resin or a silicone resin, followed by heating and drying. Since the conductive adhesive sheet 5 for FPC of the present invention is bonded to the FPC, it is preferable not to use a silicone resin in the release agent. If a silicone resin is used as a release agent, part of the silicone resin is transferred on the surface of the conductive adhesive layer 13 in contact with the surface of the support film 1 , and some parts of the silicone resin pass through the inside of the conductive adhesive layer 13 . Possibility of transferring to the other side of the conductive adhesive layer 13 . The silicone resin transferred to the surface of the conductive adhesive layer 13 may weaken the adhesive force of the conductive adhesive layer 13 to the metal reinforcing plate 6 .

The thickness of the support film 1 used in the present invention is not particularly limited, but is usually about 12 to 150 μm, excluding the thickness of the conductive adhesive layer 13 when it is attached to the FPC and used.

(conductive adhesive layer)

In the conductive adhesive sheet 5 for FPC of the present invention, the conductive adhesive layer 13 is laminated on one side of the support film 1 . The conductive adhesive layer 13 is composed of an adhesive composition having conductivity by mixing a conductive filler with a resin component composed of a flame-retardant resin (flame-retardant adhesive) and a cross-linking agent. The resin (flame retardant adhesive) imparts resistance to the adhesive selected from the group of adhesives such as acrylic adhesives, urethane adhesives, epoxy adhesives, rubber adhesives, silicone adhesives, etc. A flammable flame-retardant resin, wherein the conductive filler is one or more conductive fillers selected from conductive fine particles such as silver, copper, and silver-coated copper. In the adhesive composition, one or more anti-blocking agents selected from inorganic fine particle powders such as silica and organic fillers composed of acrylic acid, styrene and the like can be further used, and are not particularly limited.

The conductive adhesive layer 13 is not an adhesive layer that exhibits pressure-sensitive adhesiveness at room temperature, but is preferably an adhesive layer that is heated and pressurized because heat resistance is not easily reduced.

The conductive adhesive layer 13 shown in FIGS. 1 to 3 contains a flame-retardant resin as a resin component, a crosslinking agent 2 , a conductive filler 3 , and an anti-blocking agent 4 . In Figures 1 to 3, the conductive filler 3 is described in the form of a dendritic shape because the particles are in contact with each other and exhibit conductivity. In addition, in order to distinguish it from the conductive filler 3, The anti-blocking agent 4 is spherical, but the particle shape is not particularly limited, and other shapes such as a columnar shape and a crushed shape may be used. The resin component of the conductive adhesive layer 13 may contain components (additives, etc.) other than the flame-retardant resin and the crosslinking agent.

The flame-retardant resin (flame-retardant adhesive) added to the conductive adhesive layer 13 is not particularly limited, and conventionally known flame-retardant resins are applicable. The flame-retardant resin may be a thermosetting resin or a thermoplastic resin. As additives to the resin, flame retardants such as phosphorus-based, halogen-based, antimony-based, and metal hydroxides can be added. In addition, the polymer resin itself may have, in the same molecule as the resin, a functional group constituting a flame retardant component, such as phosphorus-based and halogen-based functional groups.

Moreover, it is preferable that a flame-retardant resin is high in acid value, and it is easy to crosslink with a crosslinking agent. The acid value of the flame-retardant resin is preferably 5 or more, more preferably 10 or more. When the acid value of the flame-retardant resin is less than the aforementioned lower limit, for example, when it is less than 5, crosslinking may not proceed sufficiently, and sufficient heat resistance may not be obtained.

As a crosslinking agent to be added to the conductive adhesive layer 13, an epoxy resin having a bifunctional or more functional group is preferable. Among such epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolak type epoxy resins, glycidylamine type epoxy resins, and the like are mentioned. Among them, from the viewpoint of heat resistance, a polyfunctional epoxy resin is preferred. Examples of such polyfunctional epoxy resins include jER (registered trademark) 154, jER157, jER1031, jER1032 (Mitsubishi Chemical Corporation), EPICLON (registered trademark) N-740, EPICLON N-770 (DIC ( Co., Ltd.)), YDPN-638, YDCN-700, YH-434 (Nippon Steel & Sumitomo Metal Chemical Co., Ltd.), TETRAD (registered trademark)-X, TETRAD-C (Mitsubishi Gas Chemical Co., Ltd.), etc., However, there is no particular limitation.

In addition, the addition ratio of the flame retardant resin in the resin of the conductive adhesive layer 13 is determined by the concentration of the flame retardant component. The phosphorus concentration is preferably 1.0% by weight or more. When the phosphorus concentration in the entire resin component is less than 1.0% by weight, sufficient flame retardancy may not be obtained.

The conductive filler 3 added to the conductive adhesive layer 13 is not particularly limited, and conventionally known conductive fillers can be applied. For example, dendritic metal particles composed of metals such as carbon black, silver, nickel, copper, and aluminum, and composite metal particles in which other metals are coated on the surface of these metal particles can be cited, and one or both of them can be appropriately selected. Use above.

In addition, in the above-mentioned conductive adhesive sheet 5 for FPC, in order to obtain excellent conductivity, the conductive filler 3 is contained in a large amount so that the conductive filler particles can be brought into contact with each other and the conductive filler and the FPC as the adherend. The better the contact is, the lower the adhesive force of the conductive adhesive layer 13 is. On the other hand, if the content of the conductive filler 3 is decreased in order to improve the adhesive force, the contact between the conductive filler 3 and the FPC as the adherend becomes insufficient, and there is an opposite problem that the conductivity is lowered. Therefore, when the total volume VA of the non _- volatile components of the flame retardant resin and the crosslinking agent is taken as 100 (VOL%), the volume _VC of the conductive filler is preferably 15 to 60. The range of (VOL%) is more preferably the range of 20 to 30 (VOL%).

The anti-blocking agent 4 added to the conductive adhesive layer 13 is not particularly limited, and conventionally known anti-blocking agents can be applied. Examples include inorganic fillers such as silica and calcium carbonate, organic fillers composed of acrylic acid, styrene, and the like, and one or two or more of them can be appropriately selected and used.

Moreover, in the said electroconductive adhesive sheet 5 for FPCs, when a large amount of the anti-blocking agent 4 is contained in order to acquire blocking resistance, adhesive force will fall. On the other hand, if the content of the anti-blocking agent 4 is reduced in order to improve the adhesive force, the conductive adhesive sheet for FPC and the metal reinforcing plate are stuck, and there is a problem to the contrary that the workability is deteriorated. Therefore, when the addition amount of the anti-blocking agent takes the total volume VA of the non-volatile components of the flame retardant resin and the cross-linking agent as 100 (VOL%), the volume _{V D of} the anti-blocking agent is preferably 0~15 (VOL%) range. When the conductive adhesive layer 13 contains the anti _- blocking agent 4, when VA is set as 100 (VOL%), _VD is preferably 0.01 (VOL%) or more.

In addition, since the conductive filler 3 also has blocking resistance, the anti-blocking agent 4 may not be added to the conductive adhesive layer 13 . The addition amount of the conductive filler and the anti-blocking agent is when the total volume VA of the non _- volatile components of the flame retardant resin and the cross-linking agent is taken as 100 (VOL%), the conductive filler and the anti-blocking agent The total volume V _B is preferably in the range of 15-70 (VOL%).

The adhesive force of the conductive adhesive layer 13 is not particularly limited, and the measurement method is based on the test method described in Method A of 8.1.1 of JIS C6471. The adhesive force to the surface of the adherend is preferably in the range of 15 to 30 N/cm under the conditions of peeling at a peeling angle of 90° and peeling speed of 50 mm/min. When the adhesive force is less than 15 N/cm, for example, the electromagnetic mask material attached to the FPC may peel off and lift.

The conditions for the heat and pressure adhesion of the FPC conductive adhesive sheet for FPC are not particularly limited, but for example, the preferred temperature is 160° C., the pressure is 4.5 MPa, and the hot pressing is performed for 60 minutes.

(peeling film)

The conductive adhesive sheet 5 for FPC of the present invention shown in FIG. 1 is placed on a support A conductive adhesive layer 13 is laminated on one side of the film 1 . In addition, the conductive adhesive sheet 5 for FPC of the present invention may have a structure in which the conductive adhesive layer 13 is laminated on one side of the support film 1 and the release agent layer is laminated on one side of the base material. The film is bonded to the conductive adhesive layer 13 via the release agent layer.

Examples of the base material of the release film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyethylene terephthalate such as polypropylene and polyethylene. Olefin film. In these resin films, after applying a release agent such as an amino alkyd resin or a silicone resin, a release treatment is performed by heating and drying. Since the conductive adhesive sheet for FPC of the present invention is bonded to the FPC, it is preferable not to use a silicone resin in the release agent. This is because when silicone resin is used as a release agent, part of the silicone resin is transferred to the surface of the conductive adhesive layer in contact with the surface of the release film, and further there is a conductive Possibility of transferring the adhesive layer to the support film 1 . The silicone resin transferred to the surface of the conductive adhesive layer may weaken the adhesive force of the conductive adhesive layer. The thickness of the release film used in the present invention is not particularly limited, but is usually about 12 to 150 μm.

The conductive adhesive sheet for FPC of the present invention is a laminate of the metal reinforcing plate 6 and the conductive adhesive layer 13 cut to a predetermined size, and when the conductive adhesive sheet 30 with the metal reinforcing plate is laminated, The occurrence of sticking is avoided, the conductive adhesive sheet 30 with the metal reinforcing plate can be easily peeled off one by one, and it can be used in an automatic production line using a robotic arm or the like. Therefore, the conductive adhesive sheet for FPC of the present invention can be expected to improve the efficiency of the work process for bonding the conductive adhesive sheet with a metal reinforcing plate to the FPC, and can expect an improvement in productivity and industrial utility value. Big.

[Example]

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited by these examples at all.

(Example 1)

As the support film 1, a polyethylene terephthalate (PET) film having a thickness of 50 μm was subjected to peeling treatment on one side.

In addition, with respect to 250 parts by weight of the 40% solution (A-1) of the flame retardant resin (100 parts by weight of the resin component), 8.3 parts by weight of the 70% solution (B-1) of the crosslinking agent (5.8 parts by weight of the resin component) was added parts by weight), anti-blocking agent (hydrophobic silica with an average particle size of 16 nm) 11.2 parts by weight, silver-coated copper with an average particle size of 17 μm (manufactured by Toda Industry Co., Ltd., trade name: RM-D1) 167 parts by weight was diluted with methyl ethyl ketone and toluene, and stirred and kneaded to obtain a conductive adhesive solution.

In this conductive adhesive solution, with respect to the total amount of solid content in the 40% solution (A-1) of the flame retardant resin and the 70% solution (B-1) of the crosslinking agent (that is, the total resin content) 100VOL%, the volume ratio of the anti-blocking agent is 5.8VOL%. In addition, the amount of silver-coated copper was 143% by weight of the total solid content (117 parts by weight) of the resin and the anti-blocking agent.

On the peeling-treated surface of the above-mentioned support film 1, the obtained conductive adhesive solution was applied to a thickness of 40 μm after drying as measured by a dial gauge, and heated and dried at 150° C. for 3 minutes to make it After semi-curing, the conductive adhesive sheet for FPC of Example 1 was obtained.

(Examples 2 to 3)

The conductive adhesives for FPCs of Examples 2 to 3 were obtained in the same manner as in Example 1, except that the addition ratio of the conductive filler was changed according to Table 1. Sheet.

(Examples 4 to 5)

The conductive adhesive sheets for FPC of Examples 4 to 5 were obtained in the same manner as in Example 1, except that the addition ratio of the conductive filler was changed according to Table 1, and the anti-blocking agent was not added.

(Example 6)

A conductive adhesive sheet for FPC of Example 6 was obtained in the same manner as in Example 1, except that D-2 described later was used as a conductive filler and the addition ratio was changed according to Table 1.

(Comparative Examples 1 to 6)

Except having changed the amounts of the conductive filler and the anti-blocking agent according to Table 1, in the same manner as in Example 1, the conductive adhesive sheets for FPC of Comparative Examples 1 to 6 were obtained.

(Measuring method of adhesive force)

The side of the conductive adhesive layer 13 of the conductive adhesive sheet for FPC was overlapped with a metal reinforcing plate made of SUS foil (manufactured by Nisshin Steel Co., Ltd., material: SUS304) with a thickness of 30 μm, at 140° C., After thermal lamination under the condition of 1 m/min, the support film 1 was peeled off, and the conductive adhesive sheet for FPC was cut into a size of 50 mm×120 mm. A polyimide film (manufactured by Toray DuPont Co., Ltd., product number: 200H) with a thickness of 50 μm was superimposed on the conductive adhesive layer side of the cut conductive adhesive sheet with a metal reinforcing plate, and heated at 160° C., Hot pressing was performed at 2.5 MPa for 60 minutes to obtain a test piece. In accordance with the method A (peeling in the 90° direction) of 8.1.1 of JIS-C-6471 "Test methods for copper clad laminates for flexible printed wiring boards", one side of the SUS foil with a thickness of 30 μm is fixed to the support fittings ,from Then, the adhered polyimide film with a thickness of 50 μm was peeled off, and the peeling force (N/cm) was measured.

(Evaluation method of blocking resistance)

The conductive adhesive layer 13 side of the conductive adhesive sheet for FPC was relatively overlapped with a polyimide film with a thickness of 25 μm (manufactured by Toray DuPont Co., Ltd., product number: 100H), under the conditions of 140° C. and 1 m/min. After thermal lamination was performed, the support film 1 was peeled off and cut into a size of 90 mm×140 mm. The cut conductive adhesive sheet with a polyimide film was fixed to a SUS plate, a weight of 5 kg was placed, and it was left at room temperature for 1 hour to prepare a sample. In accordance with the method B (180° direction peeling) of 8.1.1 of JIS-C-6471 "Test methods for copper clad laminates for flexible printed wiring boards", peel off the polyimide film from the SUS board. For the conductive adhesive sheet, the peeling force (mN/50mm) was measured. A sample with a peeling force of less than 100 mN/50 mm was designated as ○, and a value greater than this value was designated as ×.

This evaluation method is to use a conductive adhesive sheet with a polyimide film instead of a conductive adhesive sheet with a metal For the conductive adhesive sheet of the reinforcing plate (on the side of the conductive adhesive layer), replace the other conductive adhesive sheet with the metal reinforcing plate (the side of the metal reinforcing plate) with a SUS plate.

(Evaluation method of conductivity)

The side of the conductive adhesive layer 13 of the conductive adhesive sheet 5 for FPC was overlapped with one side of the metal reinforcing plate 6 made of SUS foil (manufactured by Nisshin Steel Co., Ltd., material: SUS304) with a thickness of 30 μm. After thermal lamination under the conditions of 140° C. and 1 m/min, it was cut to a size of 15 mm in width×100 mm in length, and the support film 1 was peeled off to obtain a conductive adhesive sheet 30 with a metal reinforcing plate. Then, as shown in FIG. 4, on the substrate film 8 made of a polyimide film, a wide The strip-shaped copper foil sheets 9 of 5 mm×length 50 mm were arranged in a row at a pitch interval of 30 mm, and a plurality of copper foil sheets were arranged to prepare a simulated flexible substrate.

Then, as shown in FIG. 5 , a part of the strip-shaped copper foil sheet 9 of the simulated flexible substrate is covered with a cover film 12 having a through hole 14 having a diameter of 1.5 mm, and further, a conductive adhesive layer 13 is interposed therebetween. The conductive adhesive sheet 30 with a metal reinforcing plate was temporarily fixed so as to cover the through holes 14, and hot-pressed at 160° C. and 2.5 MPa for 60 minutes to obtain a test piece for evaluating the conductivity. Then, a digital multimeter (manufactured by TFF Keithley Instruments Co., Ltd., model: 2100/100) was used to measure the difference between the part of the copper foil sheet 9 exposing the simulated flexible substrate and the conductive adhesive sheet 30 with the metal reinforcing plate. For the resistivity between the metal reinforcing plates 6, a sample with a resistivity of less than 0.5Ω is marked as (○), a sample with a resistivity of 0.5Ω or more to less than 1.0Ω is marked as (△), and a sample with a resistivity of 1.0Ω or more is marked as is (×).

(test results)

With respect to Examples 1 to 6 and Comparative Examples 1 to 6, the adhesion test of the conductive paste layer was performed by the above-mentioned test method, and the obtained test results are shown in Tables 1 to 2. The abbreviations in Tables 1 to 2 are as follows.

‧40% solution of flame retardant resin (A-1): manufactured by Toyobo Co., Ltd., trade name "UR-3575" (flame retardant polyurethane resin, phosphorus concentration: 2.5%, acid value: 10KOHmg/g)

‧70% solution of crosslinking agent (B-1): Toyobo, trade name "HY-30"

‧Anti-blocking agent (C-1): Japan Aerosil (Co., Ltd.), trade name "R972" (hydrophobic fumed silica)

‧Conductive filler (D-1): manufactured by Toda Industry Co., Ltd., trade name "RM-D1" (10% silver mixed copper powder with an average particle size of 17 μm)

‧Conductive filler (D-2): manufactured by Futian Metal Foil Powder Industry Co., Ltd., trade name "FCC-TBX" (10% silver-coated copper powder with an average particle size of 8 μm)

In addition, in Tables 1 to 2, the numerical values shown in the columns of "A-1", "B-1", "C-1", "D-1", and "D-2" are as in Example 1 As described in the description, the parts by weight of each component (in the case of a solution, only solid content) are shown. In addition, the numerical values shown in ( ) in the columns "C-1", "D-1", and " _D -2" represent the respective values when the total volume VA of the nonvolatile components of the flame retardant resin and the crosslinking agent is 100. The volume ratio (VOL%) of the ingredients. "-" means that the ingredient is not contained.

In addition, the ratio of the volume V _D of the anti-blocking agent to the total volume VA of the non-volatile components of the flame retardant resin and the crosslinking agent ₍ V _D /V _A ×100%) and the volume VC of the conductive filler _The ratio of the total volume VA of the non-volatile components of the flame-retardant resin and the cross _- linking agent (V _C /VA × 100%), the density of the flame-retardant resin and the cross-linking agent is 1.2g/cm ³ , and the The density of the adhesive (hydrophobic silica) was 2.2 g/cm ³ , and the density of the conductive filler (10% silver-coated copper powder) was 9.1 g/cm ³ . Here, the density of the powder is the density (true density) of the substance itself which removes the voids of the powder from the volume. In addition, the column of "filler volume ratio" in Table 1 represents the total value of the volume ratio of the anti-blocking agent and the volume ratio of the conductive filler (V _B /V _A ×100%).

According to the test results in Tables 1 and 2, when the total volume VA of the non _- volatile components of the flame retardant resin and the crosslinking agent is 100 (VOL%), the total volume _VB of the conductive filler and the anti-blocking agent is In Examples 1 to 6 in the range of 15 to 70 (VOL%), it was possible to achieve both blocking resistance and adhesive force. However, as in Comparative Examples 1 to 2, when the amount of the conductive filler added was decreased, the blocking resistance was deteriorated. In addition, as in Comparative Examples 4 to 6, when the addition amount of the anti-blocking agent was increased, the blocking resistance was excellent, but the adhesive force decreased. Moreover, as in Comparative Examples 1-4, when the addition amount of the conductive filler was small, the electroconductive performance fell. Among them, although the adhesive force of Comparative Examples 1 and 2 was sufficient, the blocking resistance was poor, and the electrical conductivity was also lowered.

Therefore, by setting the total volume of the conductive filler and the anti-blocking agent in a predetermined range with respect to the total volume of the non-volatile components of the flame-retardant resin and the cross-linking agent, it is possible to obtain both blocking resistance and adhesive force. , Conductive conductive adhesive sheet for FPC with good operability.

[Industrial availability]

The conductive adhesive sheet for FPC of the present invention is expected to improve the adhesion of metal reinforcing plates and conductive adhesives to FPCs in the work process of FPCs used in various electronic devices such as mobile phones, notebook computers, and portable terminals. Efficiency of the work process of the laminated body of the layers.

1‧‧‧Support film

2‧‧‧Flame retardant resin and crosslinking agent

3‧‧‧Conductive filler

4‧‧‧Anti-blocking agent

5‧‧‧Conductive adhesive sheet for FPC

13‧‧‧Conductive adhesive layer

Claims (5)

A conductive adhesive sheet for FPC, the conductive adhesive sheet for FPC used in FPC, is characterized in that, on one side of a support film, a flame retardant resin, a crosslinking agent, a conductive adhesive are coated on one side. The adhesive composition of the conductive filler and the anti-blocking agent is formed by laminating the conductive adhesive layer; the anti-blocking agent is one or more selected from the group consisting of inorganic particulate powder and organic filler; When the total volume VA of the non _- volatile components of the flame retardant resin and the crosslinking agent is taken as 100 (VOL%), the total volume _VB of the conductive filler and the anti-blocking agent is 19.6 The range of ~70 (VOL%); one side of the conductive adhesive layer of the conductive adhesive sheet for FPC is attached to the metal reinforcing plate as the adherend, even if it is stored in an overlapping manner from the conductive adhesive The conductive adhesive sheet for FPC with a metal reinforcing plate in the state where the support film is removed from the other side of the agent layer does not cause the conductive adhesive sheet for FPC with the metal reinforcing plate. Adhesion of the other side of the conductive adhesive layer to the metal reinforcing plate of another conductive adhesive sheet for FPC with the metal reinforcing plate. The conductive adhesive sheet for FPC according to claim 1, wherein the flame-retardant resin is a phosphorus-containing urethane resin. The conductive adhesive sheet for FPC according to claim 1 or 2, wherein the conductive filler is dendritic metal particles, and the metal particles are selected from silver particles, copper particles, One or more of the group consisting of silver-coated copper particles, when the total volume VA of the non _- volatile components of the flame retardant resin and the crosslinking agent is taken as 100 (VOL%), the conductive filling The volume V _C of the agent is in the range of 15 to 60 (VOL%). The conductive adhesive sheet for FPC as described in claim 1 or 2, wherein the anti-blocking agent is hydrophobic silica powder, and the flame-retardant resin is cross-linked with the flame-retardant resin. When the total volume VA of the nonvolatile components of the agent is taken as 100 (VOL%), the volume _VD of the anti _- blocking agent is in the range of 0.01 to 15 (VOL%). An FPC that uses the conductive adhesive sheet for FPC as described in any one of claims 1 to 4 of the scope of the application for bonding a metal reinforcing plate on the surface of the FPC.

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