CN108300350B

CN108300350B - Film for flexible flat cable reinforcing plate

Info

Publication number: CN108300350B
Application number: CN201710901199.9A
Authority: CN
Inventors: 奥井雅一; 内山米
Original assignee: Du Pont Toray Co Ltd
Current assignee: Du Pont Toray Co Ltd
Priority date: 2016-09-29
Filing date: 2017-09-28
Publication date: 2022-02-18
Anticipated expiration: 2037-09-28
Also published as: KR20180035714A; TW201814733A; JP2018056018A; TWI751198B; JP6931278B2; KR102432656B1; CN108300350A

Abstract

The present invention relates to a film for a flexible flat cable reinforcing plate. The invention provides a reinforcing plate for a flexible flat cable, which can effectively inhibit or prevent wires from falling off even if exposed to high temperature. The reinforcing plate is made of at least a polyimide film and has a thickness of more than 100 μm. The reinforcing plate may be a laminate of a plurality of polyimide films, and the thickness ratio of the polyimide film to the entire thickness of the reinforcing plate may be 60% or more.

Description

Film for flexible flat cable reinforcing plate

Technical Field

The present invention relates to a reinforcing plate (or a film for a reinforcing plate) of a flat cable (flexible flat cable).

Background

Flexible flat cables are widely used in electrical equipment such as televisions, mobile phones, tablet computers, and hard disks of personal computers. The flat cable is manufactured as follows: conductors such as copper foils formed in a wiring pattern are arranged between substrates having an insulator layer and an adhesive layer (or may be simply referred to as "substrates for flat cables") and sandwiched between the adhesive layers of the substrates.

The end portion of the flexible flat cable thus manufactured is connected to a connector to form a wiring. In this case, the end portion of the flexible flat cable is reinforced by the reinforcing plate in order to secure the bondability with the connector and protect the wiring.

Further, a polyethylene terephthalate film (PET film) is generally used for the insulator layer and the reinforcing plate of such a flexible flat cable.

Among these, attempts are being made to form a flexible flat cable with a polyimide film. Patent document 1 describes a flexible flat cable in which a polyimide film having an adhesive is formed using a polyimide film as an insulating layer and an epoxy resin having a glass transition temperature and a curing temperature in specific ranges as an adhesive layer, and the longitudinal elastic modulus and the elongation of the polyimide film having an adhesive are set to specific ranges, and the 180 ° peel strength between the adhesive layer and a conductor is set to a specific range. This document does not describe a reinforcing plate.

Patent document 2 describes a highly heat-resistant flexible flat cable in which a polyimide film containing polyimide obtained by reacting an aromatic tetracarboxylic acid compound with an aromatic diamine compound as a main component and having a coefficient of linear expansion of 10ppm/° c or less is used as an insulator layer, and one or more adhesives selected from the group consisting of polyimides and polyamide imides having a 5% weight reduction temperature of 400 ℃ or higher are used as an adhesive layer. This document does not describe a reinforcing plate.

Patent document 3 describes that a polyimide film can be used as a synthetic resin film used for a reinforcing plate having a thermoplastic resin adhesive for a flexible flat cable. However, there is no description about a technique having a characteristic feature in the thermoplastic resin adhesive, as an example of actually using a polyimide film.

Patent document 4 describes that the connector base material of the flexible flat cable and the reinforcing plate are made of polyimide, and describes that the thickness of the reinforcing plate made of polyimide is, for example, 15 to 100 μm. However, as in patent document 3, there is no description of an example in which a polyimide film is actually used.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4292729

Patent document 2: japanese laid-open patent publication No. 2009-93817

Patent document 3: japanese patent laid-open No. 2005-97592 (claim 8, paragraphs [0044] and [0053])

Patent document 4: japanese patent laid-open No. 2008-262774 (claim 3, paragraph [0019])

Disclosure of Invention

Problems to be solved by the invention

The invention aims to provide a reinforcing plate (film for reinforcing plate) of a flat cable composed of a polyimide film.

Another object of the present invention is to provide a reinforcing plate for a flat cable, which can effectively suppress or prevent a wire from coming off even when exposed to a high temperature.

It is still another object of the present invention to provide a reinforcing plate for a flat cable, which can effectively suppress or prevent the lifting of the flat cable from a connector even when an external force is applied.

Means for solving the problems

As described above, no practical use of a polyimide film as a reinforcing plate of a flexible flat cable has been attempted in the present situation.

On the other hand, according to the studies of the present inventors, the conventional PET film may be exposed to a high temperature when used for a vehicle or the like, and the heat resistance of the PET film may be insufficient to cause the disconnection, or the PET film may be warped from the connector when an external force acts.

In the above circumstances, the present inventors have conceived that a reinforcing plate of a flat cable is actually formed using a polyimide film, but have found that, in the case of a flat cable formed using only a polyimide film, peeling of a wiring or lifting of a wiring due to an external force may occur in some cases due to insufficient heat resistance, despite the use of a polyimide film.

As a result of further intensive studies, the present inventors have found that a reinforcing plate which is composed of a polyimide film and has a specific thickness can be obtained which does not cause peeling of wiring even when exposed to high temperatures and which does not cause lifting of wiring even when an external force acts on the reinforcing plate, and that such an effect can be efficiently obtained particularly in combination with a flat cable in which a polyimide film is used as an insulating layer (further, a flat cable formed of a specific polyimide film having an adhesive).

The present invention has been completed based on these findings and further research has been advanced.

The present invention relates to the following reinforcing plate and the like.

[1] A reinforcing plate which is a reinforcing plate (film for reinforcing plate) for reinforcing a flat cable (flexible flat cable), wherein

The reinforcing plate is composed of at least a polyimide film and has a thickness greater than 100 μm.

[2] The reinforcing plate according to [1], wherein the reinforcing plate is a laminate of a plurality of polyimide films.

[3] The reinforcing plate according to [1] or [2], wherein the thickness of the reinforcing plate is 150 μm or more.

[4] The reinforcing plate according to any one of [1] to [3], wherein a ratio of a thickness of the polyimide film to an entire thickness of the reinforcing plate is 60% or more.

[5] The reinforcing plate according to any one of [1] to [4], wherein the thickness of the reinforcing plate is 170 μm or more, and the ratio of the thickness of the polyimide film to the entire thickness of the reinforcing plate is 70% or more.

[6] The reinforcing sheet according to any one of [1] to [5], wherein the reinforcing sheet has a loop stiffness (loop stiffness) value of 1000mN/cm or more measured under conditions of a loop length of 50mm and a compression distance of 10 mm.

[7] The reinforcing plate according to any one of [1] to [6], wherein the polyimide film has a thermal shrinkage of 0.15% or less after heating at 200 ℃ for 60 minutes.

[8] The reinforcing plate as recited in any one of [1] to [7], wherein the flat cable is composed of a conductor and a pair of polyimide films having an adhesive which sandwich the conductor.

[9] A flat cable having a reinforcing plate, wherein the reinforcing plate according to any one of [1] to [8] is provided at a portion of the flat cable to be reinforced.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention can provide a novel flat cable reinforcing plate (reinforcing plate film) made of a polyimide film. Such a reinforcing plate can effectively suppress or prevent the falling of the wiring even when exposed to high temperatures, and can be used particularly at high temperatures (for example, 180 ℃ or higher) at which a PET film cannot be used.

In addition, the reinforcing plate of the flat cable of the present invention can effectively suppress or prevent the lifting from the connector even when an external force acts.

In particular, the reinforcing plate of the present invention easily and efficiently exhibits excellent functions in combination with a flat cable having a polyimide film as an insulating layer. Such functions include, in addition to the above-described effect of suppressing or preventing the falling of the wiring (conductor) at high temperature or by an external force, functions of improving flame retardancy and dimensional stability, and reducing the generation of bubbles between conductors.

As described above, the reinforcing plate of the present invention has the above excellent characteristics, and particularly if used for a flat cable (reinforcing plate for a flat cable), a high-performance flat cable can be obtained.

The flat cable (flat cable having a reinforcing plate) is used for various electric devices (e.g., television, mobile phone, tablet pc, and personal computer), and is particularly suitable for use in applications in which high temperature is applied, such as in-vehicle applications.

Drawings

Fig. 1 is a graph showing measurement conditions of the ring stiffness values measured in examples.

Fig. 2 is a graph showing a bending test performed in the examples.

Detailed Description

The reinforcing plate (film for reinforcing plate) of the present invention is a reinforcing plate for reinforcing a flat cable (flexible flat cable).

In other words, the reinforcing plate is usually provided at a reinforced portion of the flat cable to reinforce the reinforced portion of the flat cable. The reinforced area may typically be the end of a flat cable. In addition, the reinforced portion may be formed with an opening (an opening generally located at an end).

Typically, a flat cable is composed of a conductor and two (a pair of) base material films sandwiching the conductor, and a portion (for example, an end portion of a connector portion or the like) thereof has a reinforced portion [ for example, a reinforced portion in which an opening (a portion where the conductor is not sandwiched between the two base material films) is formed ].

Then, a reinforcing plate for reinforcing the reinforced portion [ the opening (end portion) or the like ] is provided at the reinforced portion by bonding (laminating) or the like, whereby a flat cable (a flat cable having a reinforcing plate) can be obtained.

In other words, a part (end portion, connector portion) of the flat cable is reinforced by the reinforcing plate.

The present invention is characterized by at least a reinforcing plate constituting the flat cable (flat cable having a reinforcing plate).

The flat cable is explained in detail below.

[ conductor ]

The conductor is not particularly limited, and examples thereof include a flat foil or a round wire of a conductive metal, a rectangular conductor having a rectangular cross section, an organic conductor, and the like. The conductive metal is not particularly limited, and copper, silver, tin, indium, aluminum, molybdenum, an alloy thereof, or the like can be used. The width and thickness of the conductor are not particularly limited.

[ base film ]

The base film (base material) is not particularly limited as long as it can sandwich (cover) the conductor to form the flat cable, and is usually formed of an insulator layer (insulating film). The substrate film may directly sandwich the conductor, but usually sandwiches the conductor through an adhesive layer.

In such a case, the base material film is composed of an insulator layer and an adhesive layer (or an insulator layer having an adhesive and a base material film having an adhesive), and the conductors are sandwiched between the two base material films by the adhesive layers.

The flat cable can be manufactured, for example, as follows: the conductive film is produced by sandwiching a conductor array in which a plurality of conductors are arranged in the same plane between adhesive layers of a base film having an adhesive. When a conductor is sandwiched between base material films having an adhesive, heating, pressing, or the like may be performed.

The base film (or the insulator layer) is not particularly limited as long as it can function as an insulating layer, and may be made of various resins (for example, an aromatic polyester resin such as polyethylene terephthalate), and particularly may be a polyimide film.

In the present invention, the reinforcing sheet is composed of at least a polyimide film, and by combining such a reinforcing sheet of polyimide with a base film of polyimide film, excellent functions such as high temperature resistance can be easily and efficiently obtained.

(polyimide film)

The polyimide film may be a commercially available one or a manufactured one.

In order to obtain a polyimide film, first, an aromatic diamine component and an aromatic acid anhydride component are polymerized in an organic solvent to obtain a polyamic acid solution (hereinafter, also referred to as a polyamic acid solution).

The polyamic acid solution can be obtained by polymerizing a chemical substance mainly containing an aromatic diamine component and an aromatic acid anhydride component in an organic solvent.

Examples of the aromatic diamine component include: p-phenylenediamine, m-phenylenediamine, benzidine, p-xylylenediamine, 4' -diaminodiphenyl ether, 3,4' -diaminodiphenyl ether, 4' -diaminodiphenylmethane, 4' -diaminodiphenyl sulfone, 3' -dimethyl-4, 4' -diaminodiphenylmethane, 1, 5-diaminonaphthalene, 3' -dimethoxybenzidine, 1, 4-bis (3-methyl-5-aminophenyl) benzene, and amide-forming derivatives thereof. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The aromatic diamine component is preferably 1 or more selected from the group consisting of p-phenylenediamine, 4' -diaminodiphenyl ether, and 3,4' -diaminodiphenyl ether, and more preferably a combination of p-phenylenediamine and 4,4' -diaminodiphenyl ether, from the viewpoints of excellent heat resistance, excellent heat resistance when forming a flat cable, excellent dimensional stability by heat, and the like.

The raw material used for forming the polyamic acid solution may contain a diamine component other than the aromatic diamine component as long as the effect of the present invention is not inhibited.

Examples of the other diamine component include: 3,3' -diaminodiphenyl ether, 4' -diaminodiphenylpropane, 3' -diaminodiphenylpropane, 3,4' -diaminodiphenylmethane, 3' -diaminodiphenylmethane, 4' -diaminodiphenyl sulfide, 3' -diaminodiphenyl sulfide, 3,4' -diaminodiphenyl sulfone, 3' -diaminodiphenyl sulfone, 2, 6-diaminopyridine, bis (4-aminophenyl) diethylsilane, 3' -dichlorobenzidine, bis (4-aminophenyl) ethylphosphine oxide, bis (4-aminophenyl) phenylphosphine oxide, bis (4-aminophenyl) -N-phenylamine, bis (4-aminophenyl) diphenylsulfide, bis (3, 4' -diaminodiphenyl sulfide), bis (3, 3' -diaminodiphenyl sulfide), 3,4' -diaminodiphenyl sulfide), bis (4-aminophenyl) diphenylsulfone, 3' -diaminodiphenyl sulfide, 3,4' -diaminodiphenyl sulfide, 3' -diaminodiphenyl sulfide, bis (4 ' -diaminodiphenyl) N-aminophenyl) diphenylsulfide, bis (4-phenylphosphine, bis (2, bis (4-phenyl) N-phenylphosphine, bis (4-phenylphosphine, 2, bis (2, or one, 2, bis (4-aminophenyl) -N-methylamine, 1, 5-diaminonaphthalene, 3 '-dimethyl-4, 4' -diaminobiphenyl, 3,4 '-dimethyl-3', 4-diaminobiphenyl-3, 3 '-dimethoxybenzidine, 2, 4-bis (p- β -amino-t-butylphenyl) ether, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1, 1-dimethyl-5-aminopentyl) benzene, m-xylylenediamine, p-xylylenediamine, 1, 3-diaminoadamantane, 3' -diamino-1, 1 '-diaminoadamantane, 3' -diaminomethyl-1, 1' -diamantane, bis (p-aminocyclohexyl) methane, hexamethylenediamine, heptamethylenebisAmines, octamethylenediamine, nonamethylenediamine, decamethylenediamine, 3-methylheptamethylenediamine, 4' -dimethylheptamethylenediamine, 2, 11-diaminododecane, 1, 2-bis (3-aminopropoxy) ethane, 2-dimethylpropylenediamine, 3-methoxyhexaethylenediamine, 2, 5-dimethylhexamethylenediamine, 2, 5-dimethylheptamethylenediamine, 5-methylnonamethylenediamine, 1, 4-diaminocyclohexane, 1, 12-diaminooctadecane, 2, 5-diamino-1, 3,4-

Oxadiazole, 2-bis (4-aminophenyl) hexafluoropropane, N- (3-aminophenyl) -4-aminobenzamide, 4-aminophenyl-3-aminobenzoate, and the like. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

Specific examples of the aromatic acid anhydride component include: an acid anhydride component of an aromatic tetracarboxylic acid such as pyromellitic acid, 3',4,4' -biphenyltetracarboxylic acid, 2, 3', 3,4' -biphenyltetracarboxylic acid, 3',4,4' -benzophenonetetracarboxylic acid, 2,3,6, 7-naphthalenetetracarboxylic acid, 2-bis (3, 4-dicarboxyphenyl) ether, pyridine-2, 3,5, 6-tetracarboxylic acid, and amide-forming derivatives thereof. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The aromatic acid anhydride component is preferably pyromellitic dianhydride and/or 3,3',4,4' -biphenyltetracarboxylic dianhydride from the viewpoints of excellent heat resistance, excellent heat resistance when forming a flat cable, excellent dimensional stability by heat, and the like.

In the present invention, the raw material used for forming the polyamic acid solution may contain an acid anhydride component other than the aromatic acid anhydride component as long as the effect of the present invention is not inhibited.

Examples of other acid anhydride components include: 1,2,4, 5-naphthalene tetracarboxylic dianhydride, 1,4,5, 8-decahydronaphthalene tetracarboxylic dianhydride, 4, 8-dimethyl-1, 2,5, 6-hexahydronaphthalene tetracarboxylic dianhydride, 2, 6-dichloro-1, 4,5, 8-naphthalene tetracarboxylic dianhydride, 2, 7-dichloro-1, 4,5, 8-naphthalene tetracarboxylic dianhydride, 2,3,6, 7-tetrachloro-1, 4,5, 8-naphthalene tetracarboxylic dianhydride, 1,8,9, 10-phenanthrene tetracarboxylic dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, Bis (2, 3-dicarboxyphenyl) methane dianhydride, bis (3, 4-dicarboxyphenyl) sulfone dianhydride, benzene-1, 2,3, 4-tetracarboxylic dianhydride, 3,4,3',4' -benzophenone tetracarboxylic dianhydride, and the like. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The aromatic diamine component and/or the aromatic acid anhydride component may be a non-halogen component (a component containing no halogen).

In the present invention, the combination of the aromatic diamine component and the acid anhydride component is particularly preferably: a combination of 1 or more aromatic diamine components selected from the group consisting of p-phenylenediamine, 4,4 '-diaminodiphenyl ether and 3,4' -diaminodiphenyl ether, and an aromatic anhydride component selected from the group consisting of pyromellitic dianhydride and/or 3,3',4,4' -biphenyltetracarboxylic dianhydride.

When the aromatic diamine component comprises p-phenylenediamine and 4,4 '-diaminodiphenyl ether, the molar ratio of p-phenylenediamine to 4,4' -diaminodiphenyl ether is preferably 50/50 to 0/100, more preferably 40/60 to 0/100.

When the aromatic acid anhydride component includes pyromellitic dianhydride and 3,3',4,4' -biphenyltetracarboxylic dianhydride, the molar ratio of pyromellitic dianhydride to 3,3',4,4' -biphenyltetracarboxylic dianhydride is preferably 100/0 to 50/50, more preferably 100/0 to 60/40.

Specific examples of the organic solvent used for forming the polyamic acid solution include: sulfoxide solvents such as dimethylsulfoxide and diethylsulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, phenol solvents such as phenol, o-cresol, m-cresol and p-cresol, xylenol, halogenated phenol and catechol, and aprotic polar solvents such as hexamethylphosphoramide and γ -butyrolactone. These can be used alone or in combination of 2 or more, and can be used in combination with aromatic hydrocarbons such as xylene and toluene.

The polymerization method of the polyamic acid solution may be carried out by any known method, and examples thereof include:

(1) the method comprises the following steps: adding the total amount of aromatic diamine component into solvent, adding aromatic acid anhydride component equivalent to the total amount of aromatic diamine component, and polymerizing;

(2) the method comprises the following steps: adding the total amount of aromatic anhydride components into a solvent, adding an aromatic diamine component in an equivalent amount to the aromatic anhydride components, and polymerizing;

(3) the method comprises the following steps: adding one aromatic diamine component to a solvent, mixing the one aromatic anhydride component at a ratio of 95 to 105 mol% with respect to the reaction components for a time necessary for the reaction, adding the other aromatic diamine component, and then adding the other aromatic anhydride component so that the total amount of the aromatic diamine component and the total amount of the aromatic anhydride component are substantially equivalent to each other, and carrying out polymerization;

(4) the method comprises the following steps: adding one aromatic acid anhydride component to a solvent, mixing the one aromatic diamine component at a ratio of 95 to 105 mol% with respect to the reaction components for a time necessary for the reaction, adding the other aromatic acid anhydride component, and then adding the other aromatic diamine component so that the total amount of the aromatic diamine component and the total amount of the aromatic acid anhydride component are substantially equivalent to each other, and carrying out polymerization;

(5) the method comprises the following steps: the polyamic acid solution (a) is prepared by reacting one of the aromatic diamine component and the aromatic acid anhydride component in an excess amount in a solvent, and the other of the aromatic diamine component and the aromatic acid anhydride component in an excess amount in another solvent. The polyamic acid solutions (a) and (B) thus obtained were mixed to complete polymerization. In this case, when the aromatic diamine component is excessive in the production of the polyamic acid solution (a), the aromatic anhydride component is excessive in the polyamic acid solution (B), and when the aromatic anhydride component is excessive in the polyamic acid solution (a), the aromatic diamine component is excessive in the polyamic acid solution (B), and the polyamic acid solutions (a) and (B) are mixed and adjusted so that the total of the aromatic diamine component and the aromatic anhydride component used in these reactions is almost equivalent; and the like.

The polymerization method is not limited to these methods, and other known methods may be used.

In the present invention, the aromatic acid anhydride component and the aromatic diamine component constituting the polyamic acid are polymerized in such a ratio that the number of moles of each component is substantially equal to each other, and one of them may be blended in an excess amount of 10 mol%, preferably 5 mol%, relative to the other.

The polymerization reaction is preferably carried out in an organic solvent with stirring. The polymerization temperature is not particularly limited, and is usually carried out at an internal temperature of the reaction solution of 0 to 80 ℃. The polymerization time is not particularly limited, but is preferably continuously carried out for 10 minutes to 30 hours. For the polymerization, the polymerization may be carried out in batches, or the temperature may be raised or lowered, as required. The order of adding both reactants is not particularly limited, and it is preferable to add the aromatic acid anhydride to the solution of the aromatic diamine component. Vacuum degassing in the polymerization reaction is an effective method for producing an organic solvent solution of high-quality polyamic acid. Further, the polymerization reaction may be controlled by adding a small amount of an end-capping agent to the aromatic diamine before the polymerization reaction. The blocking agent is not particularly limited, and a known blocking agent can be used.

The polyamic acid solution thus obtained usually contains 5 to 40% by weight, preferably 10 to 30% by weight of solid content. The viscosity is measured by a Brookfield viscometer, but is not particularly limited, and is usually 10 to 2000 pas (100 to 20000 poise), and preferably 100 to 1000 pas (1000 to 10000 poise) for stable liquid transfer. The polyamic acid in the organic solvent solution may be partially imidized.

By heating the polyamic acid solution, a polyimide film can be produced.

Examples of the method for producing the polyimide film include: a method in which a polyamic acid solution is cast into a film form and subjected to thermal decyclization and desolvation to obtain a polyimide film; a method of mixing a cyclization catalyst and a dehydrating agent in a polyamic acid solution, followed by chemical decyclization to prepare a gel membrane, and heating the gel membrane to desolventize the gel membrane, and the latter method is preferred.

In the method of performing chemical decyclization, the foregoing polyamic acid solution is first prepared. The polyamic acid solution may contain a cyclization catalyst (imidization catalyst), a dehydrating agent, a gelation retarder, and the like.

Specific examples of the cyclization catalyst include: aliphatic tertiary amines such as trimethylamine and triethylenediamine, aromatic tertiary amines such as dimethylaniline, heterocyclic tertiary amines such as isoquinoline, pyridine and β -picoline, and the like, and these may be used singly or in combination of 2 or more. Among them, at least one heterocyclic tertiary amine is preferably used.

Specific examples of the dehydrating agent include: aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride, among which acetic anhydride and/or benzoic anhydride are preferred.

Examples of the method for producing a polyimide film from a polyamic acid solution include the following methods: a polyamic acid solution containing a cyclization catalyst and a dehydrating agent is cast from a slit metal port or the like onto a support to form a film, a gel film having self-supporting properties is formed by partial imidization on the support, and then the film is peeled from the support and subjected to heat treatment, thereby obtaining a polyimide film.

The polyamic acid solution is cast onto a heated support, and a ring-closure reaction is performed on the support to form a gel film having self-supporting properties and to be peeled off from the support.

The support is a metal drum or an endless belt, and the temperature of the support is controlled by a liquid or gas heat medium, or radiant heat from an electric heater or the like.

The gel film is generally heated to 30 to 200 ℃, preferably 40 to 150 ℃ by heat from a support and/or heat from a heat source such as hot air or an electric heater to perform a ring-closure reaction, and is dried to have a self-supporting property by a volatile component such as a free organic solvent, and is peeled off from the support.

The gel film peeled from the support is usually stretched in the moving direction while the moving speed is regulated by a rotating roller. The stretching is usually carried out at a temperature of 140 ℃ or lower by 1.01 to 1.90 times, preferably 1.05 to 1.60 times, and more preferably 1.10 to 1.50 times. The gel film stretched in the moving direction is introduced into a tenter device, and stretched in the width direction while both ends in the width direction are held by tenter clips and moved together with the tenter clips.

The gel film stretched as described above is usually heated with wind, an infrared heater, or the like for 15 seconds to 30 minutes. Then, heat treatment is performed by hot air, an electric heater, or the like, usually at a temperature of 250 to 500 ℃ for 15 seconds to 30 minutes.

In addition, the thickness of the polyimide film can be adjusted according to the moving speed. The thickness of the polyimide film may be appropriately selected in accordance with the target thickness of the laminate film, the number of polyimide films to be used, and the like.

The polyimide film thus obtained may be further subjected to an annealing treatment. The heat shrinkage ratio can be easily reduced efficiently by the annealing treatment (specifically, for example, the heat shrinkage ratio after heating at 200 ℃ for 60 minutes can be set to 0.15% or less). The method of annealing is not particularly limited, and a conventional method can be used. The temperature of the annealing treatment is not particularly limited, but is preferably 200 to 500 ℃, more preferably 200 to 370 ℃, and particularly preferably 210 to 350 ℃. Specifically, it is preferable to perform the annealing treatment by moving the film under low tension in a furnace heated to the above temperature range. The residence time of the film in the furnace is a treatment time, and is controlled by changing the moving speed, and a treatment time of 5 seconds to 5 minutes is preferable. The film tension during movement is preferably 10 to 50N/m, and more preferably 20 to 30N/m.

The polyimide film may contain a filler (e.g., inorganic particles, organic filler, etc.), and preferably contains inorganic particles.

The content of the filler in the polyimide film is not particularly limited, and may be: for example, the amount of the resin is about 0.03 to 1 wt%, preferably about 0.05 to 0.8 wt%, based on 1 wt% of the film resin.

The method for containing the filler in the polyimide film is not particularly limited, and the filler may be added to the polyamic acid solution. The filler may be added to the polyamic acid solution after polymerization in advance, or the polyamic acid solution may be polymerized in the presence of the filler.

The thermal shrinkage rate of the polyimide film after heating at 200 ℃ for 60 minutes is not particularly limited, and may be, for example, 0.15% or less (e.g., 0.005 to 0.15%), preferably 0.1% or less (e.g., 0.005 to 0.1%), and more preferably 0.07% or less (e.g., 0.005 to 0.06%). By using such a polyimide film, the heat shrinkage rate of the base film or the flat cable can be easily reduced with high efficiency.

The thermal shrinkage of the polyimide film after heating at 200 ℃ for 60 minutes can be calculated as follows: the film size (L1) after being left in a room adjusted to 25 ℃ and 60% RH for 2 hours or more was measured using a CNC image processing apparatus system NEXIV VM-250 (nikon), and after being heated at 200 ℃ for 60 minutes and then left in a room adjusted to 25 ℃ and 60% RH again for 1 day, the film size (L2) was measured using the CNC image processing apparatus system and calculated by the following equation.

Heat shrinkage (%) { (L2-L1)/L1} × 100

The average linear expansion coefficient of the polyimide film is not particularly limited, and may be, for example, 0 to 100 ppm/DEG C, preferably 0 to 50 ppm/DEG C, and more preferably 3 to 35 ppm/DEG C. The thermal expansion coefficient can be measured in the following temperature range using TMA-50 manufactured by Shimadzu corporation: 50-200 ℃ and temperature rise rate: the measurement was carried out at 10 ℃ per minute.

The surface roughness Rmax of the polyimide film may preferably be about 0.6 μm or more (e.g., about 0.6 to 2 μm) from the viewpoint of improving adhesiveness to the adhesive layer, adhesiveness to a reinforcing plate to be bonded to the opposite surface to the adhesive layer, and the like. The surface roughness Rz of the polyimide film may preferably be about 0.3 μm or more (e.g., about 0.3 to 1.2 μm) from the viewpoint of improving adhesiveness to the adhesive layer. The surface roughness of the polyimide film can be measured in accordance with JIS B0601 (2001).

The method for obtaining the polyimide film having the above surface roughness is not particularly limited, and for example, the polyimide film can be obtained by a known surface treatment (for example, wet blasting, sand-cushion treatment, resin-cushion (resin-resin マット) treatment, plasma treatment, or the like). The surface treatment may be performed on one side or both sides of the polyimide film.

The polyimide film may be a substantially non-halogen polyimide film (a polyimide film containing no halogen) or a polyimide film containing substantially no flame retardant (flame retardant auxiliary) as in the case of the adhesive layer described later.

(adhesive layer)

The base film may be a film (base film having an adhesive) in which an adhesive layer is provided on a base film (base film, particularly a polyimide film).

The adhesive is not particularly limited as long as it can form an adhesive layer, and generally contains an adhesive component.

Examples of the adhesive component include thermoplastic resins (e.g., polyamide resins, acrylic resins, etc.) and thermosetting resins (e.g., unsaturated polyester resins, epoxy resins, etc.), with thermosetting resins being preferred.

The adhesive layer may contain additives within a range not to impair adhesiveness. Examples of the additives include: flame retardants (or flame retardant aids), antioxidants, crosslinking agents, resins not included in the category of adhesive components { hereinafter also referred to simply as "other resins". For example, an elastomer (e.g., a styrene-based elastomer) and the like.

In particular, the adhesive layer may contain a flame retardant (including a flame retardant aid) or may contain substantially no flame retardant. In the present invention, even if the adhesive layer does not substantially contain a flame retardant, excellent flame retardancy can be achieved.

Examples of the flame retardant (including the flame retardant auxiliary) include: examples of the halogen-containing compound include, but are not limited to, a conventional component, for example, a metal hydrate [ for example, a metal hydroxide (for example, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, barium hydroxide, etc.), a tin oxide hydrate, basic magnesium carbonate, etc. ], a halogen-containing compound { for example, a halogen-containing low-molecular compound (for example, decabromodiphenyl ether, halogenated bisphenol a, etc.), a halogen-containing resin [ for example, an epoxy resin (for example, brominated epoxy resin, etc.) ], an antimony-containing compound (for example, antimony trioxide, etc.), a phosphorus-containing compound (for example, a phosphorus-containing oligomer, ammonium phosphate, aluminum tris (diphenyl) phosphinate, etc.), and the like.

The adhesive layer may contain a solvent (for example, an aromatic hydrocarbon solvent such as toluene or xylene, or a ketone solvent such as methyl ethyl ketone or dimethyl ketone).

In the adhesive layer, the amount of the additive (particularly, the additive other than the flame retardant) may be, for example, about 1.5 to 200 parts by weight (for example, about 2 to 170 parts by weight), preferably about 2 to 150 parts by weight (for example, about 3 to 140 parts by weight), and more preferably about 3 to 120 parts by weight (for example, about 5 to 100 parts by weight) based on 1 part by weight of the adhesive component.

In particular, the flame retardant is preferably contained at a level at which the adhesive layer contains substantially no flame retardant even when the adhesive layer contains the flame retardant, and the proportion of the flame retardant may be, for example, 20 wt% or less, preferably 10 wt% or less, more preferably 5 wt% or less, and particularly preferably 3 wt% or less with respect to the entire constituent components (solid components) of the adhesive layer.

In addition, the adhesive layer may be substantially halogen-free (halogen-free ).

(thickness of base film, etc.)

The thickness (average thickness) of the base film may be, for example, 1 to 500. mu.m, preferably 3 to 300. mu.m, and more preferably about 5 to 200. mu.m.

Particularly, when the base film has an adhesive layer, the thickness of the film (insulating film) as a base may be, for example, about 1 to 150 μm (e.g., about 3 to 125 μm), preferably about 5 to 120 μm (e.g., about 7 to 100 μm), and more preferably about 10 to 80 μm (e.g., about 15 to 50 μm).

In the substrate film having an adhesive (particularly, a polyimide film having an adhesive), the thickness (average thickness) of the adhesive layer is not particularly limited, and may be, for example, 300 μm or less (for example, 1 to 250 μm), preferably 200 μm or less (for example, 2 to 180 μm), more preferably 150 μm or less (for example, 3 to 120 μm), particularly 100 μm or less (for example, 5 to 80 μm), and usually 1 to 50 μm (for example, 3 to 40 μm, preferably 5 to 35 μm, more preferably 10 to 30 μm).

Particularly preferred are: the thickness (average thickness) of the adhesive layer is not excessively large relative to the entire thickness of the base film having the adhesive (particularly, the polyimide film having the adhesive), and may be selected, for example, from a range of 3 times or less (for example, 0.01 to 2.8 times) relative to the thickness (average thickness) of the base film (the base film not provided with the adhesive layer, particularly, the polyimide film), for example, 2.5 times or less (for example, 0.05 to 2.4 times), preferably 2.3 times or less (for example, 0.1 to 2.2 times), more preferably 2 times or less (for example, 0.15 to 1.8 times), particularly 1.5 times or less (for example, 0.2 to 1.2 times), and usually 0.25 to 2.3 times.

By adjusting the thickness of the adhesive layer as described above, a base film excellent in flame retardancy and the like can be easily obtained.

In consideration of the embedding property of the conductor, the thickness (average thickness) of the adhesive layer may be 1/2 or more of the thickness of the conductor. This is preferable from the viewpoint of sufficient embedding of the conductors and difficulty in generating voids between the conductors.

Such a base film (particularly, polyimide film) is excellent in flame retardancy.

For example, the oxygen index of the base film may be selected from the range of 25% or more (e.g., 27 to 90%), and for example, may be 30% or more (e.g., 32 to 80%), preferably 35% or more (e.g., 37 to 75%), more preferably 40% or more (e.g., 42 to 70%), and particularly 45% or more (e.g., 46 to 65%).

The oxygen index can be measured, for example, according to JIS K7201-2.

The amount of penetration in TMA needle penetration pattern measurement can be set to a specific range for the adhesive layer of the base film having an adhesive (particularly, a polyimide film having an adhesive).

For example, in the case of an adhesive layer of a base film having an adhesive (a polyimide film having an adhesive), the amount of penetration (penetration ratio) of needle penetration at 100 ℃ to the thickness of the adhesive layer in TMA penetration pattern measurement is 10% or less (e.g., 0 to 8%), preferably 7% or less (e.g., 0.1 to 6%), more preferably 6% or less (e.g., 0.3 to 5.5%), and particularly 5% or less (e.g., 0.5 to 5%).

The penetration amount (penetration ratio) of the needle relative to the thickness of the adhesive layer can be expressed by (B/a) × 100 (%) where a (μm) is the thickness of the adhesive layer and B (μm) is the penetration amount.

In addition, the amount of penetration (penetration ratio) of the base film having an adhesive (polyimide film having an adhesive) into the adhesive layer at 140 ℃ in TMA penetration pattern measurement with respect to the thickness of the adhesive layer may be selected from the range of 5% or more (for example, 7 to 90%), and may satisfy, for example, 10% or more (for example, 15 to 88%), preferably 20% or more (for example, 20 to 85%), and more preferably 25% or more (for example, 26 to 80%).

In the adhesive layer of the base film having an adhesive (polyimide film having an adhesive), the penetration amount (penetration ratio) of the needle at 180 ℃ to the thickness of the adhesive layer in TMA penetration pattern measurement may be selected from the range of 20% or more (for example, 22 to 95%), and may satisfy, for example, 25% or more (for example, 27 to 92%), preferably 30% or more (for example, 35 to 90%), more preferably 40% or more (for example, 42 to 88%), and particularly 45% or more (for example, 50 to 85%).

By adjusting the penetration of the needle at each temperature as described above, it is easy to efficiently adjust flame retardancy, heat resistance, dimensional stability, the amount of bubbles generated between conductors, and the like.

The penetration amount of the needle at each temperature (100 ℃, 140 ℃, 180 ℃) measured by the TMA penetration pattern can be determined as follows: the penetration depth (penetration amount, unit: μm) of the indenter was measured up to 200 ℃ at a temperature rise rate of 10 ℃/min by using a TMA measuring apparatus, and was measured by reading the penetration depth of the indenter up to each temperature (100 ℃, 140 ℃, 180 ℃), and determining the penetration depth of the indenter up to each temperature (100 ℃, 140 ℃, 180 ℃) from the ratio of the penetration depth of the indenter to the thickness of the adhesive layer. The TMA measuring apparatus used was a thermal analyzer (TMA-60) manufactured by Shimadzu corporation.

The base film having an adhesive (particularly, a polyimide film having an adhesive) can be obtained by, for example, coating an adhesive on one side or both sides of a base film (particularly, a polyimide film) and drying the coating. The coating and drying method is not particularly limited.

[ reinforcing plate and Flat Cable with reinforcing plate ]

The reinforcing plate (film for reinforcing plate) of the present invention contains at least a polyimide film.

Such a reinforcing plate may be composed of a single (one-sheet) polyimide film, or may be a laminate of a plurality of polyimide films. The reinforcing plate may be a laminate of a polyimide film and a non-polyimide film (for example, an aromatic polyester film such as a polyethylene terephthalate film), but in general, a laminate of only polyimide films is preferable even in the case of a laminate.

The polyimide film is not particularly limited, and the same polyimide film as exemplified in the above section of the base material film can be used. For example, the heat shrinkage of the polyimide film (or reinforcing plate) after heating at 200 ℃ for 60 minutes is in the same range as that of the polyimide film in the base film (for example, 0.15% or less).

In the laminate of polyimide films, a plurality of polyimide films may be directly laminated or may be laminated via an adhesive (adhesive layer). The method for obtaining the polyimide film laminate is not particularly limited, and may be selected depending on the form of the laminate, and there is a method of laminating through an adhesive layer; a method of performing heating and pressing or the like without using an adhesive; and the like. The adhesive agent to be used is an adhesive agent described later, and the coating and drying method is not particularly limited. When the polyimide film is heated and pressurized, the polyimide film is preferably bonded more firmly if the polyimide film is subjected to a surface treatment such as a plasma treatment.

The adhesive is not particularly limited, and for example, adhesive components exemplified in the section of the base film (for example, acrylic resin) can be used.

The adhesive layer may contain additives (the above exemplified components, etc.) within a range not to impair adhesiveness. When the additive is contained, the amount thereof may be, for example, about 1.5 to 200 parts by weight (for example, about 2 to 170 parts by weight), preferably about 2 to 150 parts by weight (for example, about 3 to 140 parts by weight), and more preferably about 3 to 120 parts by weight (for example, about 5 to 100 parts by weight) based on 1 part by weight of the adhesive component.

The thickness (average thickness) of the reinforcing plate is usually more than 100 μm (for example, 110 to 1000 μm), and may be, for example, 120 μm or more (for example, 130 to 700 μm), preferably 150 μm or more (for example, 160 to 500 μm), more preferably 170 μm or more (for example, 170 to 400 μm), and may be 180 μm or more (for example, 190 to 350 μm).

By providing such a thickness, the wires can be easily prevented or inhibited from falling off even when exposed to high temperatures. In addition, even when an external force acts, the warping from the connector can be easily and efficiently suppressed or prevented.

In the case where a plurality of polyimide films are laminated via an adhesive layer, the thickness of the reinforcing plate is the total thickness including the adhesive layer. As described later, the reinforcing plate is generally laminated (bonded) to the opening portion via an adhesive, and the thickness of the adhesive is not included in the thickness of the reinforcing plate.

When the reinforcing plate is composed of a plurality of polyimide films, the thickness of each polyimide film is not particularly limited as long as the thickness of the reinforcing plate is within the above range, and may be, for example, 5 to 250 μm, preferably 10 to 200 μm (for example, 20 to 180 μm), and more preferably about 30 to 150 μm.

The number of polyimide films (number of stacked layers) in the plurality of polyimide films is not particularly limited as long as the number of polyimide films is 2 or more, and may be, for example, 2 to 5, preferably 2 to 4, more preferably 2 to 3, and particularly 2.

The thickness ratio of one polyimide film a to the other polyimide film B different from the polyimide film a in the plurality of polyimide films may be, for example, about 0.01/1 to 100/1, preferably about 0.05/1 to 20/1, and more preferably about 0.1/1 to 10/1, based on the polyimide film a/polyimide film B (thickness ratio).

In the laminate of polyimide films, the thickness of the adhesive layer is not particularly limited as long as the thickness of the reinforcing plate is within the above range, and may be, for example, 1 to 100 μm, preferably 3 to 80 μm, and more preferably about 5 to 50 μm.

The reinforcing plate may contain a polyimide film or an adhesive layer as described above, and in order to obtain sufficient effects, it is preferable that: the polyimide film occupies a relatively high thickness in the entire thickness of the reinforcing plate.

The ratio of the thickness of the polyimide film to the total thickness of the reinforcing plate (in the case of a laminate of a plurality of polyimide films, the ratio of the total thickness of the plurality of polyimide films) is also related to the total thickness of the reinforcing plate, and may be selected from a range of 30% or more (e.g., 40% or more), for example, 50% or more (e.g., 55 to 100%), preferably 60% or more, more preferably 70% or more, particularly 75% or more, and particularly preferably 80% or more (e.g., 85% or more).

The reinforcing plate may have a ring stiffness value of, for example, 300mN/cm or more (e.g., 350 to 10000mN/cm), preferably 400mN/cm or more (e.g., 450 to 8000mN/cm or more), more preferably 500mN/cm or more (e.g., 500 to 5000mN/cm or more), particularly 1000mN/cm or more (e.g., 1500mN/cm or more, preferably 2000mN/cm or more) at a ring length of 50mm and a compression distance of 10 mm. When the ring stiffness value is within the above range, the connection between the flexible flat cable and the external terminal is strengthened, and the wiring connection failure can be easily and efficiently suppressed.

The ring stiffness value can be measured using, for example, a "ring stiffness tester DA" manufactured by the eastern seiko corporation. The base film may have the above-mentioned ring stiffness value (for example, 1000mN/cm or more).

As described above, the reinforcing plate is provided at a portion to be reinforced of the flat cable (for example, an end portion such as a conductor portion or a connector portion which is not sandwiched by the base material film). The method of providing the reinforcing plate to the reinforced region is not particularly limited, and the reinforcing plate may be generally bonded (laminated or coated) to the reinforced region with an adhesive interposed therebetween.

The adhesive used for the reinforced part is not particularly limited, and the adhesives exemplified above and the like can be used. The bonding may be performed under heating or under pressure. The thickness of the adhesive layer is not particularly limited, and may be, for example, 1 to 100 μm, preferably 3 to 80 μm, and more preferably about 5 to 50 μm.

Examples

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples, and those having ordinary knowledge in the art can make many modifications within the technical spirit of the present invention.

[ measurement of thickness ]

The thickness was measured by using a Litematic (Series318) thickness meter manufactured by Mitutoyo as follows. That is, 5 sites were arbitrarily selected from the entire surface of the film, the thicknesses of the 5 sites were measured, and the average value thereof was calculated as the thickness.

[ Ring rigidity value ]

The ring stiffness value was obtained by measurement using a ring stiffness tester DA manufactured by toyoyo seiki corporation under conditions of a ring length of 50mm and a compression distance of 10mm (see fig. 1).

[ Heat shrinkage of polyimide film ]

The heat shrinkage of the polyimide film after heating at 200 ℃ for 60 minutes was calculated as follows: the film size (L1) after being left in a room adjusted to 25 ℃ and 60% RH for 2 hours or more was measured using a CNC image processing apparatus system NEXIV VM-250 (nikon), and after being heated at 200 ℃ for 60 minutes and left in a room adjusted to 25 ℃ and 60% RH again for 1 day, the film size (L2) was measured using the CNC image processing apparatus system NEXIV VM-250 (nikon), and calculated by the following formula.

Heat shrinkage (%) { (L2-L1)/L1} × 100

[ Heat shrinkage Rate (dimensional Change Rate) of Flat Cable ]

The flat cable thus produced was heated at 180 ℃ for 10 minutes, and the dimension between conductors before heating (L3) and the dimension between conductors after heating (L4) were measured using a CNC image processing apparatus system NEXIV VM-250 (nikon), and calculated according to the following equation.

Heat shrinkage (%) { (L4-L3)/L3} × 100

[ penetration ratio of needle insertion ]

The polyimide film having the adhesive was cut into a size of 10mm × 10mm, and the penetration depth (penetration amount in μm) of the indenter was read at 200 ℃ to 100 ℃, 140 ℃ and 180 ℃ by measuring the penetration pattern with a constant load of 50gf at a heating rate of 10 ℃/min using a thermal analyzer (TMA-60) manufactured by Shimadzu corporation. Then, the ratio to the thickness of the adhesive layer is calculated from the read value.

The indenter used was a columnar indenter having a tip diameter of 0.5mm, and the adhesive surface was an indenter penetration surface.

[ measurement of oxygen index ]

Measured according to JIS K7201-2. The polyimide film with the adhesive was cut into a size of 150mm × 20mm, and was subjected to combustion using an oxygen index type flammability tester manufactured by Suga test co.

[ embeddability ]

The presence or absence of air bubbles between the flat cable conductors was visually checked, and the length of the portion where air bubbles were generated was measured. The ratio of the length of the bubble generation portion to the length of the flat cable is calculated and used as the bubble generation rate.

< example 1 >

[ polyimide film laminate ]

A polyimide film of 20cm square of "kapton" (200H, 50 μm thick, 0.03 (%) thermal shrinkage at 200 ℃ for 60 minutes) and 500H (125 μm thick, 0.03 (%) thermal shrinkage at 200 ℃ for 60 minutes) was prepared, and an adhesive of "Pyralux" LF0100(25 μm thick) was prepared. Next, an adhesive was sandwiched between 200H and 500H, and the mixture was pressed at a heating temperature of 180 ℃, a pressure of 2MPa, and a time of 60 minutes, to obtain a polyimide film laminate (reinforcing plate). The thickness of the polyimide film laminate was 200. mu.m, and the ring stiffness value was 2380 mN/cm.

[ Flexible Flat Cable ]

An adhesive was prepared by mixing 10 parts by weight of EPICLON HP-7200 (an epoxy resin containing a dicyclopentadiene skeleton, available from DIC Co., Ltd.), 100 parts by weight of Tuftec M1913 (available from Asahi Kasei Chemicals, maleic acid-modified styrene-ethylene block copolymer), 0.3 part by weight of Curezol C11-Z (available from Sikko Kasei Co., Ltd.) and 420 parts by weight of toluene, and applied to one surface of "kapton" 100EN (25 μ M thick, 0.06 (%) thermal shrinkage after heating at 200 ℃ for 60 minutes) available from Tokyo Dupont, and dried at 90 ℃ for 3 minutes to obtain a polyimide film having an adhesive. In the polyimide film with an adhesive, the thickness of the adhesive layer was 25 μm.

In the polyimide film having an adhesive, the penetration rate of the needle at each temperature measured by TMA needle penetration pattern was 0.5 μm (100 ℃ C.), 13 μm (140 ℃ C.) and 18 μm (180 ℃ C.). In the polyimide film with an adhesive, the oxygen index was 50%, the heat shrinkage of the flat cable was 0.08%, and the bubble generation rate was 1%.

Then, 2 sheets of the obtained polyimide film with an adhesive were prepared in a size of 20mm in width and 10cm in length. Of these, 1 sheet was provided with openings by forming holes 20mm in the film width direction and 5mm in the film length direction at the end portions. Next, 14 conductors having a width of 0.30mm and a thickness of 0.035mm were arranged on the adhesive layer side of the adhesive-free polyimide film having an adhesive with a conductor pitch of 0.50mm, and further another 1 polyimide film having an adhesive with an opening was superimposed on the adhesive layer side, and pressure was applied by a hot roll at 180 ℃ and 0.5MPa, thereby producing a flexible flat cable.

[ attachment of polyimide film laminate to Flexible Flat Cable ]

The polyimide film laminate was cut into a width of 2cm × a length of 3cm, and was attached to the opening of the flexible flat cable with an adhesive ("Pyralux" LF0100) having the same size as the laminate interposed therebetween. The attachment conditions were such that the pressing was performed at a heating temperature of 180 ℃ and a pressure of 2MPa for 60 minutes.

[ high temperature test ]

The opening of a flexible flat cable to which a polyimide film laminate as a reinforcing plate was attached was connected via a connector to a test wiring board which was arranged at intervals of 0.30mm and 0.50mm in width in the same arrangement as the conductors of the flexible flat cable, and the conductor of the opening after heating was observed to be in contact with the conductors of the test wiring board after heating at 105 ℃ for 3000 hours. The conductor of the flexible flat cable is firmly contacted with the conductor of the test wiring board without deformation of the reinforcing plate.

[ bending test ]

Similarly to the high temperature test, the opening of the flexible flat cable to which the polyimide film laminate as the reinforcing plate was attached was connected to the test wiring board via a connector, and then the flexible flat cable was bent in the shape shown in fig. 2 to apply an external force, and the contact between the opening conductor and the conductor of the test wiring board was observed. The conductors of the flexible flat cable are in firm contact with the conductors of the test wiring board even in a state where an external force is applied.

< example 2 >

A polyimide film laminate was obtained by following the same procedures as in example 1, except that 200H ("kapton" (50 μm thick), the thermal shrinkage rate of which was 0.03 (%) after heating at 200 ℃ for 60 minutes) and 400H ("100 μm thick", the thermal shrinkage rate of which was 0.03 (%) after heating at 200 ℃ for 60 minutes), manufactured by Toledu Pont were used. The thickness of the polyimide film laminate was 175. mu.m, and the ring stiffness value was 1630 mN/cm.

Various evaluations were made using this polyimide film laminate in the same manner as in example 1. There is no deformation of the reinforcing plate in the high temperature test, and the conductor of the flexible flat cable is firmly contacted with the conductor of the test wiring board. The conductor of the flexible flat cable and the conductor of the test wiring board are firmly contacted even in a state where an external force is applied in the bending test.

< example 3 >

A polyimide film laminate was obtained by following the same procedures as in example 1, except that 300H ("kapton" (75 μm thick, 0.03 (%) thermal shrinkage after heating at 200 ℃ for 60 minutes)) and 500H ("125 μm thick, 0.03 (%) thermal shrinkage after heating at 200 ℃ for 60 minutes)" manufactured by Toledu Pont were used. The thickness of the polyimide film laminate was 225 μm, and the ring stiffness value was 3550 mN/cm.

< example 4 >

A polyimide film laminate was obtained by the same procedure as in example 1, except that 2 sheets of "kapton" (50 μm thick) 200H (manufactured by tokdu pont) were used. The thickness of the polyimide film laminate was 125. mu.m, and the ring stiffness value was 510 mN/cm. Various evaluations were performed using the polyimide film laminate in the same manner as in example 1. There is no deformation of the reinforcing plate in the high temperature test, and the conductor of the flexible flat cable is firmly contacted with the conductor of the test wiring board.

< comparative example 1 >

Various evaluations were made in the same manner as in example 1, except that a PET film "Lumiror" S10#188(188 μm thick) manufactured by Toray corporation was used instead of the polyimide film laminate. In the high temperature test, the reinforcing plate is deformed by heating, whereby a contact failure between the conductor of the flexible flat cable and the conductor of the test wiring board occurs.

The results are summarized in Table 1. In table 1, "good" indicates a case of firm contact in each test, and "x" indicates deformation, and accompanying detachment of a conductor and poor contact in each test.

[ TABLE 1]

The polyimide film laminate of the example, when used as a flexible flat cable reinforcing plate, had no peeling of the wiring even when exposed to high temperatures. In addition, it was confirmed that the polyimide film laminates of examples 1 to 3 did not cause the wires to fall off even when an external force was applied.

On the other hand, in comparative example 1, the prepared film as the reinforcing plate was deformed at a high temperature, and the wirings were peeled off.

From the above results, it was confirmed that the wiring was not detached even when the film of the present invention was used as a reinforcing plate and exposed to high temperature or an external force was applied.

In addition, by combining the reinforcing plate of the present invention with a polyimide film having an adhesive, a flexible flat cable having a reinforcing plate with characteristics such as a small oxygen index (high flame retardancy), a small thermal shrinkage rate (dimensional change rate) at high temperatures, and a small generation of air bubbles between conductors can be efficiently obtained.

Industrial applicability

The reinforcing plate of the present invention can be suitably used as a reinforcing plate for a flexible flat cable.

Claims

1. A reinforcing plate for reinforcing a flat cable, wherein

The reinforcing plate is composed of at least a polyimide film and has a thickness of more than 100 μm,

the reinforcing plate is a laminate of a plurality of polyimide films, and the ratio of the thickness of the polyimide film to the overall thickness of the reinforcing plate is 60% or more.

2. The reinforced panel of claim 1, wherein

The thickness of the reinforcing plate is more than 150 mu m, and the thickness of each polyimide film is 30-250 mu m.

3. The reinforcing panel of claim 1 or 2, wherein

The thickness of the reinforcing plate is 170 [ mu ] m or more, and the ratio of the thickness of the polyimide film to the overall thickness of the reinforcing plate is 70% or more.

4. The reinforcing panel of claim 1 or 2, wherein

The reinforcement plate has a ring stiffness value of 1000mN/cm or more measured under the conditions that the ring length is 50mm and the compression distance is 10 mm.

5. The reinforcing plate of claim 1 or 2,

the polyimide film has a thermal shrinkage of 0.15% or less after heating at 200 ℃ for 60 minutes.

6. The reinforcing plate of claim 1 or 2,

the flat cable is composed of a conductor and a pair of polyimide films having an adhesive and sandwiching the conductor.

7. A flat cable having a reinforcing plate, wherein,

a reinforcing plate according to any one of claims 1 to 6 provided at a portion of a flat cable to be reinforced.