JP6437863B2 - Flame retardant biaxially oriented polyester film for flexible circuit board and flexible circuit board comprising the same - Google Patents

Description

  The present invention relates to a flame retardant polyester film for a flexible circuit board and a flexible circuit board comprising the same. More specifically, the present invention relates to a flame retardant biaxially oriented polyester film for a flexible circuit board excellent in flame retardancy and surface flatness, and a flexible circuit board comprising the same.

  With the technical progress of electronic devices such as mobile phones, the demand for flexible printed circuit (hereinafter sometimes abbreviated as FPC) substrates is growing rapidly. In recent years, with the enforcement of the Product Liability Act, there has been a demand for flame retarding of resins used for FPC in order to ensure safety against fire. Conventionally, a polyimide film laminated with a copper foil or a thin polyimide film has been used in this application. However, polyimide is poor in workability of thin film due to the nature of the material and is positioned as an expensive material.

  As flame retardant polyester films, films containing halogen-based flame retardants such as organic halogen compounds and halogen-containing organophosphorus compounds have been studied. Although these flame retardants have high flame retardant effects, Depending on the temperature, a small amount of halogen may be liberated and corrosive hydrogen halide gas may be generated to corrode molding and processing equipment, and a small amount of hydrogen halide gas may be generated during combustion such as a fire. It has been pointed out. Therefore, in recent years, there has been a demand for using a flame retardant containing no halogen in place of the halogen flame retardant.

  In addition, as one of the flame retardant methods for polyester resins, a method of copolymerizing a phosphorus compound with polyester has been studied. For example, Japanese Patent Application Laid-Open No. 2007-9111 (Patent Document 1) discloses a carboxyphosphinic acid component. Among them, it is disclosed that by using a specific carboxyphosphinic acid component, high flame retardancy can be imparted to polyethylene naphthalene dicarboxylate in a small amount without using another phosphorus compound in combination. However, a polyethylene naphthalene dicarboxylate film containing a carboxyphosphinic acid compound as in Patent Document 1 exhibits high flame retardancy in the state of the film, but flame retardancy after being processed for uses such as a flexible printed circuit. In some cases, the flame retardancy of the film itself was not reproduced.

  As other phosphorus flame retardants, for example, JP 2009-179037 A (Patent Document 2) and JP 2010-89334 A (Patent Document 3) include phosphoric acid derivatives of inorganic metals such as phosphinic acid metal salts. A laminated film in which a flame retardant layer containing a polyester film is laminated has been proposed. However, the proposed laminated film is a technology that provides a flame retardant layer using a flame retardant and a curing agent on the substrate film in view of the high flammability due to the void structure inside the film of the porous substrate film. there were. In addition, International Publication No. 2012/090732 (Patent Document 4) proposes a flame-retardant polyester film containing a phosphinate or diphosphinate, and a polyester film itself such as polyalkylene terephthalate or polyalkylene naphthalate. A flame retardant biaxially oriented polyester film in which a flame retardant is suppressed with a phosphorus-based flame retardant, and further a decrease in hydrolysis resistance due to these flame retardants has been proposed.

Japanese Patent Laid-Open No. 2007-9111 JP 2009-179037 A JP 2010-89334 A International Publication No. 2012/090732 Pamphlet

In the process of advancing the study of a polyester film using a phosphinate or diphosphinate as a flame retardant, the present inventors use a raw phosphinate as it is, and the film surface is rough, and the surface flatness is required to be flexible. It was found that the surface property is not suitable for use as a circuit board.
The object of the present invention is to solve such conventional problems and provide a flame-retardant biaxially oriented polyester film for a flexible circuit board that can be suitably used as an FPC circuit board excellent in flame retardancy and surface flatness, and a flexible circuit board comprising the same. There is to do.

  As a result of intensive studies to solve the above problems, the present inventors have found that phosphinates or diphosphinates are not compatible with polyester and exist as foreign substances such as particles in the film, Since the presence ratio of coarse particles is high, and voids tend to occur at the interface between these flame retardants and the polyester resin due to stretching, especially when the voids are formed around the coarse particles, the unevenness of the film surface becomes remarkable. It is found that the surface flatness is lowered due to the above factors, and the surface flatness is improved by controlling the frequency of coarse flame retardant particles together with the particle size of the flame retardant particles, thereby completing the present invention. It came to.

（式中、Ｒ^１、Ｒ^２は水素、炭素数１〜６のアルキル基および／またはアリール基であり、Ｍは金属、ｍはＭの価数をそれぞれ表す）

（式中、Ｒ^３、Ｒ^４は水素、炭素数１〜６のアルキル基および／またはアリール基、Ｒ^５は炭素数１〜６のアルキレン基または炭素数６〜１０のアリーレン基、アルキルアリーレン基もしくはアリールアルキレン基であり、Ｍは金属、ｎはＭの価数をそれぞれ表す）
該層Ａ中に含まれる最大長１０μｍ以上の粗大粒子の個数が１０個／ｍ^２以下であることを特徴とするフレキシブル回路基板用難燃性二軸配向ポリエステルフィルム（項１）によって達成される。 That is, an object of the present invention is that polyethylene naphthalene dicarboxylate is 70 wt% or more and 99.5 wt% or less, and an average particle size of 0.5 to 3.0 μm represented by the following formula (1) or (2): the flame retardant particles seen including a layer a containing less than 30% by weight 0.5% by weight, and a polyester film having a layer B on one side of the layer a,
The layer B contains 90% by weight to 100% by weight of polyethylene naphthalene dicarboxylate and 0% by weight to 10% by weight of the flame retardant particles based on the layer weight, and the layer A is more difficult than the layer B. Comprising a large amount of a flame retardant, wherein the layer thickness ratio of the layer A and the layer B is 2: 1 to 10: 1;

(Wherein R ¹ and R ² are hydrogen, an alkyl group having 1 to 6 carbon atoms and / or an aryl group, M is a metal, and m is a valence of M)

Wherein R ³ and R ⁴ are hydrogen, an alkyl group having 1 to 6 carbon atoms and / or an aryl group, R ⁵ is an alkylene group having 1 to 6 carbon atoms, an arylene group having 6 to 10 carbon atoms, and an alkylarylene group. Or an arylalkylene group, M represents a metal, and n represents a valence of M.)
Achieved by a flame-retardant biaxially oriented polyester film for flexible circuit boards (Item 1), wherein the number of coarse particles having a maximum length of 10 μm or more contained in the layer A is 10 / m ² or less. .

Moreover, the following aspects are also preferably included in the biaxially oriented polyester film of the present invention.
(Item 2) The flame retardant for flexible circuit board according to item 1, wherein the flame retardant biaxially oriented polyester film for flexible circuit board has a center line average roughness Ra of at least one surface of 0.1 μm or more and less than 2 μm. Biaxially oriented polyester film.
(Item 3 ) The flexible circuit according to Item 1 , wherein the center line average roughness Ra on the layer A side is 0.1 μm or more and less than 2 μm, and the center line average roughness Ra on the layer B side is 1 nm or more and less than 10 nm. Flame retardant biaxially oriented polyester film for substrates.
(Claim 4) or a flexible circuit board using a flexible circuit flame retardant biaxially oriented polyester film for the substrate described above are also encompassed in the present invention.

  The flame-retardant biaxially oriented polyester film of the present invention is excellent in surface flatness and has high flame retardancy without deteriorating the mechanical properties of polyester such as polyethylene naphthalene dicarboxylate. It can be suitably used for a substrate.

（式中、Ｒ^１、Ｒ^２は水素、炭素数１〜６のアルキル基および／またはアリール基であり、Ｍは金属、ｍはＭの価数をそれぞれ表す）

（式中、Ｒ^３、Ｒ^４は水素、炭素数１〜６のアルキル基および／またはアリール基、Ｒ^５は炭素数１〜６のアルキレン基または炭素数６〜１０のアリーレン基、アルキルアリーレン基もしくはアリールアルキレン基であり、Ｍは金属、ｎはＭの価数をそれぞれ表す）
かつ該層Ａ中に含まれる最大長１０μｍ以上の粗大粒子の個数が１０個／ｍ^２以下である、フレキシブル回路基板用の難燃性二軸配向ポリエステルフィルムである。 The present invention will be described in detail below.
<Flame retardant biaxially oriented polyester film>
The flame-retardant biaxially oriented polyester film of the present invention comprises polyethylene naphthalene dicarboxylate as a polymer component in an amount of 70% to 99.5% by weight and an average particle represented by the following formula (1) or (2) A polyester film comprising a layer A containing 0.5 to 30% by weight of flame retardant particles having a diameter of 0.5 to 3.0 μm,

(Wherein R ¹ and R ² are hydrogen, an alkyl group having 1 to 6 carbon atoms and / or an aryl group, M is a metal, and m is a valence of M)

Wherein R ³ and R ⁴ are hydrogen, an alkyl group having 1 to 6 carbon atoms and / or an aryl group, R ⁵ is an alkylene group having 1 to 6 carbon atoms, an arylene group having 6 to 10 carbon atoms, and an alkylarylene group. Or an arylalkylene group, M represents a metal, and n represents a valence of M.)
And it is a flame-retardant biaxially oriented polyester film for flexible circuit boards, wherein the number of coarse particles having a maximum length of 10 μm or more contained in the layer A is 10 particles / m ² or less.

(polyester)
In the flame-retardant biaxially oriented polyester film of the present invention, polyethylene naphthalene dicarboxylate is used as a polymer component, and preferably polyethylene-2,6-naphthalene dicarboxylate is used. The content of the polymer component is in the range of 70 wt% or more and 99.5 wt% or less based on the weight of the layer A for the layer A. The lower limit of the content of these polymer components is preferably 75% by weight, more preferably 78% by weight, further preferably 80% by weight, and particularly preferably 85% by weight.
Further, the upper limit of the content of these polymer components is preferably 99% by weight, more preferably 96% by weight, still more preferably 92% by weight, particularly preferably in relation to the content of the flame retardant component described later. Is 90% by weight.
If the content of these polymer components is less than the lower limit, the mechanical strength of the film is lowered. On the other hand, when the content of these polymer components exceeds the upper limit, the content of the flame retardant component is relatively small, and sufficient flame retardancy is not exhibited.

  Moreover, the flame-retardant biaxially oriented polyester film for flexible circuit boards of the present invention can further improve the surface flatness of one of the layers A in the present invention by laminating a layer B in the present invention to be described later. it can. In the case of such a laminated structure, the content of the polymer component (polyethylene naphthalene dicarboxylate) in the layer B is preferably 90% by weight or more and 100% by weight or less based on the weight of the layer B. The lower limit of the content of the polymer component in the layer B is preferably 91% by weight, more preferably 92% by weight, and still more preferably 93% by weight. Further, the upper limit value of the content of the polymer component in the layer B is preferably 99.5% by weight, more preferably 99% by weight, and still more preferably 98% by weight. If the content of the polymer component in the layer B is less than the lower limit, the further flattening effect by providing the layer B may not be sufficiently exhibited. It is preferable that the content of the polymer component in the layer B is larger in such a range from the viewpoint of further enhancing the planarization effect. On the other hand, since the amount of the flame retardant in the layer B is smaller than that in the layer A, if the thickness ratio of the layer B is increased, the flame retardancy may be reduced.

The polyethylene naphthalene dicarboxylate in the present invention is a polyester mainly composed of ethylene naphthalene dicarboxylate, preferably a polyester mainly composed of ethylene-2,6-naphthalene dicarboxylate.
In addition, when the polyethylene naphthalene dicarboxylate in the present invention is a copolymer having a component other than the main component (hereinafter sometimes referred to as a copolymer component), it contains a flame retardant component in the present invention and is more flat. It is preferable because excellent surface properties can be obtained.
When polyethylene naphthalene dicarboxylate is a copolymer, the copolymer component can be used in a range of less than 25 mol% based on the number of moles of all the repeating units of the polyester constituting each layer, more preferably 20 mol% or less, More preferably, it is 15 mol% or less, Most preferably, it is 10 mol% or less. Further, the lower limit of the copolymer component is preferably 1 mol% or more, more preferably 2 mol% or more, and further preferably 4 mol% or more.

When the flame-retardant biaxially oriented polyester film for flexible circuit board of the present invention has a laminated structure, the amount of copolymer components in layers A and B may be the same or different, and the amount of copolymer components in layer B is more When the amount is large, the surface on the layer B side becomes smoother, which is preferable.
Examples of the copolymer component include oxalic acid, adipic acid, phthalic acid, sebacic acid, dodecanedicarboxylic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, phenylindanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, tetralin dicarboxylic acid, decalin dicarboxylic acid, dicarboxylic acid such as diphenyl ether dicarboxylic acid, oxycarboxylic acid such as p-oxybenzoic acid, p-oxyethoxybenzoic acid, Or trimethylene glycol, tetramethylene glycol, hexamethylene glycol, cyclohexanedimethanol, neopentyl glycol, ethylene oxide adduct of bisphenol sulfone, ethylene oxide of bisphenol A Examples include diols such as mixed adducts, diethylene glycol, and polyethylene oxide glycol. Among these, components other than the main component can be preferably used. These copolymer components may be used alone or in combination of two or more.
These copolymer components may be copolymerized as monomer components, or may be copolymerized by transesterification with other polyesters.

Further, the flame-retardant biaxially oriented polyester film of the present invention may contain other polyester as a polymer component in addition to the polyethylene naphthalene dicarboxylate as long as the object of the present invention is not impaired. The thermoplastic resin may be contained. These other components can be used in place of polyethylene naphthalene dicarboxylate in a range of less than 10% by weight of the polymer component based on the weight of each layer, more preferably 5% by weight or less, and still more preferably 2% by weight. % Or less. Examples of thermoplastic resins other than polyester include polyolefin resins, polystyrene resins, polyimide resins, and the like.
The intrinsic viscosity of the polyethylene naphthalene dicarboxylate in the present invention is preferably 0.4 dl / g or more and 1.5 dl / g or less with an intrinsic viscosity measured at 25 ° C. using o-chlorophenol as a solvent, It is preferably 0.5 dl / g or more and 1.2 dl / g or less.

(Flame retardant component)
As a flame retardant component in the present invention, a phosphinate represented by the following formula (1) or a diphosphinate represented by the following formula (2) (hereinafter, these may be collectively referred to as phosphinates) Are used as flame retardant particles.

（式中、Ｒ^１、Ｒ^２は水素、炭素数１〜６のアルキル基および／またはアリール基であり、Ｍは金属、ｍはＭの価数をそれぞれ表す）

(Wherein R ¹ and R ² are hydrogen, an alkyl group having 1 to 6 carbon atoms and / or an aryl group, M is a metal, and m is a valence of M)

（式中、Ｒ^３、Ｒ^４は水素、炭素数１〜６のアルキル基および／またはアリール基、Ｒ^５は炭素数１〜６のアルキレン基または炭素数６〜１０のアリーレン基、アルキルアリーレン基もしくはアリールアルキレン基であり、Ｍは金属、ｎはＭの価数をそれぞれ表す）

Wherein R ³ and R ⁴ are hydrogen, an alkyl group having 1 to 6 carbon atoms and / or an aryl group, R ⁵ is an alkylene group having 1 to 6 carbon atoms, an arylene group having 6 to 10 carbon atoms, and an alkylarylene group. Or an arylalkylene group, M represents a metal, and n represents a valence of M.)

The phosphinic acid salt is a compound also referred to as a phosphinic acid metal salt. As R ¹ and R ² , hydrogen, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, Examples include a pentyl group, a hexyl group, a phenyl group, and a biphenyl group. Examples of M include aluminum, magnesium, and calcium, and the valence m is an integer of 2 to 4.

  Specific examples of the phosphinic acid salt represented by the formula (1) include calcium dimethylphosphinate, calcium methylethylphosphinate, calcium diethylphosphinate, calcium phenylphosphinate, calcium biphenylphosphinate, magnesium dimethylphosphinate, methylethyl Examples thereof include magnesium phosphinate, magnesium diethylphosphinate, magnesium phenylphosphinate, magnesium biphenylphosphinate, aluminum dimethylphosphinate, aluminum methylethylphosphinate, aluminum diethylphosphinate, aluminum phenylphosphinate, and aluminum biphenylphosphinate.

Among the diphosphinic acid salts, as R ³ and R ⁴ , hydrogen, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, pentyl group, hexyl group and phenyl group are Examples of R ⁵ include methylene group, ethylene group, propylene group, butylene group, pentylene group, hexylene group and phenylene group. Moreover, aluminum, magnesium, and calcium are illustrated as M, and the valence n is an integer of 2-4.
Examples of the diphosphinic acid salt represented by the formula (2) include alkanebis (phosphinic acid) calcium such as ethane-1,2-bis (phosphinic acid) calcium and alkanebis (alkyl alkyl such as ethane-1,2-bis (methylphosphinic acid) calcium. Phosphinic acid) calcium, alkane bisphosphinic acid magnesium, alkane bis (alkyl phosphinic acid) magnesium, alkane bis phosphinic acid aluminum, alkane bis (alkyl phosphinic acid) aluminum and the like.
Of these phosphinic acid salts, aluminum diethylphosphinate is particularly preferable.

The phosphinates used as flame retardant particles in the present invention are less affected by lowering of physical properties with respect to high-strength polyesters such as polyethylene naphthalene dicarboxylate compared to conventional phosphorus flame retardants. Thus, it is possible to add a flame retardant component up to a large amount that has been difficult to add.
Therefore, for example, when processed into a use that is laminated with a metal layer, the flame resistance of the metal laminate has been reduced compared to the flame retardant polyester film before laminating the metal layer. On the other hand, the metal laminate using the flame retardant particles of the present invention has a characteristic that high flame retardancy similar to that of the flame retardant polyester film itself can be obtained.

  The content of such phosphinic acid salts is 0.5 wt% or more and 30 wt% or less based on the weight of the layer A in the layer A. Further, the lower limit of the content of the phosphinates in the layer A is preferably 1% by weight, more preferably 4% by weight, still more preferably 8% by weight, and particularly preferably 10% by weight. Further, the upper limit of the content of the phosphinate is preferably 25% by weight, more preferably 22% by weight, still more preferably 20% by weight, and particularly preferably 15% by weight. If the content of the phosphinates in the layer A is less than the lower limit, the flame retardancy is not sufficient. On the other hand, if the content of the phosphinates in the layer A exceeds the upper limit, the film formability and the surface flatness are descend.

Furthermore, when providing the layer B in this invention, it is preferable that content of the phosphinic acid salt in the layer B is 0 to 10 weight% on the basis of the weight of the layer B. The lower limit of the content of the phosphinates in the layer B is preferably 0.5% by weight, more preferably 1% by weight, and still more preferably 2% by weight. Further, the upper limit of the content of the phosphinates in the layer B is preferably 9% by weight, more preferably 8% by weight, and still more preferably 7% by weight.
The layer B is further provided on one side of the layer A, and the layer A contains more flame retardant than the layer B, thereby exhibiting flame retardancy in the entire biaxially oriented polyester film and a flatter surface. Can be applied to one side.
If the content of phosphinates in layer B is less than the lower limit, flame retardancy may be reduced depending on the thickness ratio of layer B. On the other hand, if the content of the phosphinates in the layer B exceeds the upper limit value, the further flattening effect of the film surface by the layer B may not be sufficiently exhibited.

  Such phosphinates have a particle shape and are referred to as flame retardant particles in the present invention. The average particle size of the flame retardant particles of the present invention is 0.5 μm or more and 3.0 μm or less, and the lower limit of the average particle size is preferably 1.0 μm, more preferably 1.5 μm. The upper limit of the average particle diameter of the flame retardant particles is preferably 2.5 μm. If the average particle diameter is less than the lower limit, the dispersibility in the film is lowered, the particles are aggregated, and the flatness of the film surface is lowered. On the other hand, the average particle diameter exceeding the upper limit also leads to a decrease in the flatness of the film surface.

In the present invention, the number of coarse particles having a maximum length of 10 μm or more contained in the layer A needs to be 10 particles / m ² or less, and more preferably 5 particles / m ² or less. Further, when the layer B is further provided, the number of coarse particles having a maximum length of 10 μm or more contained in the layer B is preferably 10 / m ² or less, and more preferably 5 / m ² or less. Such flame retardant particles have a fairly wide particle size distribution, and these coarse particles affect the flatness of the film surface, making it difficult to use as a flexible circuit board. Therefore, a flame retardant biaxially oriented polyester film with improved flatness can be obtained by pre-treating the flame retardant particles in advance, such as pulverization and classification, and removing these coarse particles in advance.

Here, the average particle diameter of the flame retardant particles, as described in the measurement method column, sampled 20 particles at a magnification of 3500 times using Hilox Digital Microscope KH-3000 for the cross section of the polyester film, The maximum length of each particle diameter is measured, and the average value of 18 points excluding the minimum value and the maximum value out of 20 points is obtained.
The number of coarse particles having a maximum length of 10 μm or more can be obtained by measuring the maximum length of particles using a universal projector and enlarging 20 times with transmitted illumination.

(Phosphorus atom concentration)
The phosphorus atom concentration in the present invention is preferably 0.1% by weight or more and 7% by weight or less for the layer A based on the weight of the layer A. The lower limit of the phosphorus atom concentration is preferably 0.2% by weight, more preferably 0.9% by weight, still more preferably 1.8% by weight, and particularly preferably 2.3% by weight. The upper limit of the phosphorus atom concentration is preferably 5.8% by weight, more preferably 5.0% by weight, still more preferably 4.6% by weight, and particularly preferably 3.5% by weight.
In the present invention, when the layer B is further included, the phosphorus atom concentration of the layer B is preferably 0% by weight or more and 2.3% by weight or less based on the weight of the layer B, and more preferably about 0.1%. % By weight, more preferably 0.2% by weight, particularly preferably 0.5% by weight, and more preferably 2.1% by weight, more preferably 1.8% by weight, particularly preferably 1.6% by weight. It is.

The present invention uses conventional flame retardant particles of a specific size made of the phosphinic acid salts of the present invention for polyethylene naphthalene dicarboxylate having a high strength among polyesters, thereby adding a conventional additive-type phosphorus component or copolymer-type phosphorus. It is characterized in that it does not impair the mechanical properties of polyester compared to the system components.
On the other hand, if it is attempted to increase the phosphorus atom concentration to a concentration exceeding the upper limit value, the amount of phosphinic acid salts to be added is too large, resulting in poor flatness and film-forming property of the film. In addition, in the range close to the lower limit of the phosphorus atom concentration, that is, the range positioned in the content of the conventional phosphorus-based component, high flame retardancy is exhibited compared to other phosphorus-based components, and laminated with the metal layer. Even when processed to the intended use, it has the characteristic that high flame retardance similar to that of the flame retardant polyester film itself is reproduced. The reason why such an effect appears even in a range where the content of the phosphorus component is small is considered to be due to a radical trap effect by the metal component constituting the phosphinate.

(Other additives)
In order to improve the handleability of the film, inert particles and the like may be added to the flame-retardant biaxially oriented polyester film of the present invention within a range not impairing the effects of the invention. Examples of such inert particles include inorganic particles (for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, etc.) containing the elements of Periodic Tables IIA, IIB, IVA, and IVB, and crosslinked silicone resins. , Particles made of a polymer having high heat resistance such as crosslinked polystyrene and crosslinked acrylic resin particles.
When the inert particles are used, the average particle diameter of the inert particles is preferably in the range of 0.001 to 5 μm, and is preferably contained in the range of 0.01 to 10% by weight based on the weight of each layer. Preferably it is 0.05 to 5 weight%, Most preferably, it is 0.05 to 3 weight%.
The flame-retardant biaxially oriented polyester film of the present invention may further contain additives such as a heat stabilizer, an antioxidant, an ultraviolet absorber, a release agent, a colorant, and an antistatic agent as necessary. It can mix | blend in the range which does not impair.

(Film layer configuration)
As a layer constitution of the flame retardant biaxially oriented polyester film in the present invention, it has a layer A containing the flame retardant having a specific particle size and from which coarse particles are removed in a range of 0.5 wt% to 30 wt%. In order to further improve the surface smoothness of one of the layers, the layer A containing the flame retardant in the range of 0% by weight to 10% by weight on one side of the layer A preferable. When layer B is included, layer A preferably contains more flame retardant than layer B.

(Film thickness)
The thickness of the flame retardant biaxially oriented polyester film in the present invention is preferably 50 μm or more and 250 μm or less. Conventionally, adding a flame retardant to a polyester film to make it flame retardant causes a decrease in the mechanical properties and hydrolysis resistance of the polyester film. Rather than combusting, a method of laminating another layer containing a flame retardant on a polyester film has been the mainstream. In the present invention, since the above-mentioned problems due to the flame retardant component are solved, the phosphorous flame retardant is added to the biaxially oriented polyester film itself having various thicknesses as described above, for example, without restriction on the film thickness. be able to.
In addition, when the layer B is further provided in the present invention, the layer thickness ratio of the layer A and the layer B is 2: 1 to 10: 1 in order to further improve the surface flatness on the layer B side while maintaining flame retardancy. It is preferable that it is in the range of 4: 1 to 8: 1.

(Surface roughness)
In the flame-retardant biaxially oriented polyester film of the present invention, the surface roughness (centerline average roughness Ra) of the layer A is preferably 0.1 μm or more and less than 2 μm. The upper limit of the center line average roughness Ra of the layer A is more preferably less than 1.5 μm, further preferably less than 1.0 μm, and particularly preferably less than 0.5 μm. Further, the lower limit of the center line average roughness Ra may be 0.2 μm or more, and may be 0.3 μm or more. A more preferable range of the center line average roughness Ra is 0.1 μm or more and less than 1.5 μm, more preferably 0.1 μm or more and less than 1.0 μm, and particularly preferably 0.1 μm or more and less than 0.5 μm. Moreover, in the region where the content of the flame retardant component of the present invention is large, it may be 0.2 μm or more and less than 1.5 μm, 0.3 μm or more and less than 1.0 μm, or 0.3 μm or more and less than 0.5 μm.

Further, when the flame-retardant biaxially oriented polyester film of the present invention further has a layer B, the center line average roughness Ra on one surface is 0.1 μm or more and less than 2 μm, and the center line average roughness on the other surface is The thickness Ra is preferably 1 nm or more and less than 10 nm. Specifically, the center line average roughness Ra of the surface on the layer A side is 0.1 μm or more and less than 2 μm, and the center line average roughness Ra on the layer B side is It is preferably 1 nm or more and less than 10 nm.
The centerline average roughness Ra of the flatter surface is more preferably 2 nm or more and less than 9 nm, and further preferably 3 nm or more and less than 8 nm. The surface roughness of each surface is obtained by using flame retardant particles composed of phosphinates having the above-described average particle diameter and excluding coarse particles, and using a specific amount for each of layer A and layer B.

  In the flame-retardant biaxially oriented polyester film of the present invention, by having the above-mentioned surface characteristics for each surface, the layer A is formed from a rougher surface, which is formed while the film is wound in a roll shape. Transfer of particle traces to the layer B side can be prevented. Therefore, the surface flatness on the layer B side can be further improved, and a circuit with a thinner line width can be formed on the flat layer B side when used as a flexible circuit board. On the other hand, when the center line average roughness Ra on the layer A side exceeds the upper limit due to the presence of coarse particles, transfer to the layer B side occurs even if the layer B is present, and the surface flatness on the layer B side becomes poor. Sometimes.

<Film manufacturing method>
The flame-retardant biaxially oriented polyester film of the present invention can be manufactured using a known film forming method. For example, a polyester composition containing a phosphinate used for the layer A and a polyester composition containing a phosphinate used for the layer B are prepared. After sufficiently drying, each is melted in a separate extruder at a temperature of melting point to (melting point +70) ° C., laminated into two layers to form layer A / layer B using a feed block, and through a T-die Melt extrusion is performed, and the film-like melt is quenched on a cooling roll (casting drum) to form an unstretched film. Then, the unstretched film can be produced by a method of sequentially or simultaneously biaxially stretching and heat setting. When forming a film by sequential biaxial stretching, the unstretched film is stretched in the longitudinal direction at 80 to 190 ° C. in a range of 2.3 to 5.5 times, more preferably 2.5 to 5.0 times, and then a stenter. The film is stretched in the range of 2.3 to 5.0 times, more preferably 2.5 to 4.8 times at 90 to 190 ° C. in the transverse direction.
The heat setting is preferably heat setting at a temperature of 180 to 260 ° C., more preferably 190 to 240 ° C. under tension or limited shrinkage, and the heat setting time is preferably 1 to 1000 seconds. In the case of simultaneous biaxial stretching, the above stretching temperature, stretching ratio, heat setting temperature and the like can be applied. Moreover, you may perform a relaxation | loosening process after heat setting.

<Flame-retardant polyester film laminate>
The flame-retardant biaxially oriented polyester film of the present invention can be used as a flame-retardant polyester film laminate laminated with a metal layer. Here, the metal layer includes a layer formed on the film, a conductor, a certain pattern such as a circuit, etc., and a flexible printed circuit is formed.
Such a flame retardant polyester film laminate is suitably used for a flexible printed circuit board.

  A copper foil is illustrated as a metal layer used in this use. There are no particular restrictions on the means for joining and shape of the metal layer, for example, a so-called subtractive method in which a metal layer is laminated on a flame retardant biaxially oriented polyester film, and then the metal layer is subjected to pattern etching. An additive method of plating metal in a pattern on a biaxially oriented polyester film, a stamping foil for bonding a metal layer punched in a pattern to a flame retardant biaxially oriented polyester film, or the like can be used.

The flexible printed circuit board obtained using the flame retardant polyester film laminate of the present invention has a very high flame retardancy of the polyester film itself, and is processed into a flexible printed circuit board used by being laminated with a metal layer. The flame retardant biaxially oriented polyester film itself exhibits the same high flame retardancy, and at the same time, the flame retardant biaxially oriented polyester film of the present invention has high flame retardancy and also has a smooth surface. Since it is excellent, it is excellent in the formation of the circuit pattern of the metal layer. In particular, when it has a smooth surface with a center line average roughness Ra of 1 nm or more and less than 10 nm, the circuit pattern of the metal layer can be further refined, It is preferable because it can be densified.
Moreover, since the flame-retardant polyester film laminate of the present invention has sufficient mechanical strength and hydrolysis resistance, it is excellent in long-term durability as a flexible printed circuit board.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited only to these Examples. Each characteristic value was measured by the following method. Moreover, unless otherwise indicated, the part and% in an Example mean a weight part and weight%, respectively.

(1) Type and content of polyester component
^{By 1} H-NMR measurement and ¹³ C-NMR measurement, a polyester component, a copolymer component, and an amount of each component were specified.

(2) Type of phosphorus component The type of phosphorus component was specified using NMR and EPMA.

(3) Phosphorus atom concentration For the polyester film, the phosphorus atom concentration was calculated from the emission intensity of fluorescent X-rays.

(4) Average particle diameter of flame retardant particles About the cross section of the polyester film, using Hilox Digital Microscope KH-3000, 20 particles were sampled at a magnification of 3500 times, and the maximum length of each particle diameter The average particle diameter was determined from the average value of 18 points excluding the minimum value and the maximum value among the 20 points.

(5) Size and number of coarse particles A universal projector was used, and the number of particles having a maximum length of 10 μm or more was counted 20 times with transmitted illumination, and evaluated according to the following criteria. The measurement area was 1 m ² . If the area of one film sample is less than 1 m ² , adjust the total area of the plurality of film samples to 1 m ² , or based on the measurement results with a film sample smaller than 1 m ^2. it may be in terms of the number per 1m ^2.
○: The number of particles having a maximum length of 10 μm or more is 10 / m ² or less ×: The number of particles having a maximum length of 10 μm or more exceeds 10 / m ²

(6) Total film thickness, layer thickness A film sample is sandwiched between spindle detectors (K107C manufactured by Anritsu Electric Co., Ltd.) and the thickness is measured at different positions using a digital differential electronic micrometer (K351 manufactured by Anritsu Electric Co., Ltd.). Ten points were measured, and the average value was obtained as the film thickness.
Moreover, about the measurement of each layer thickness, the film was cut out to 2 mm of film longitudinal directions and 2 cm of width directions, and after embedding in an embedding capsule, it embedded with the epoxy resin (Refinetech Co., Ltd. Epomount). The embedded sample was cut perpendicularly in the width direction with a microtome (LETRAC ULCT UCT manufactured by LEICA) to form a thin film slice having a thickness of 5 nm. Using a transmission electron microscope (Hitachi S-4300), the film was observed and photographed at an acceleration voltage of 100 kV, and the thickness of each layer was measured from the photograph.

(7) Surface roughness: Centerline average roughness Ra
Using a stylus type surface roughness meter (SURFCORDER SE-30C) manufactured by Kosaka Laboratory Ltd., measurement was made on both sides of the polyester film under the following conditions, and the calculated center line average roughness Ra was measured. The average value measured four times for the surface was evaluated according to the following evaluation criteria.
<Measurement conditions>
Radius tip radius 2μm
Measurement length: 2.5mm
Cut-off: 0.25mm
Measurement environment: room temperature, in the air <Evaluation criteria: Ra>
5: 1 nm or more and less than 10 nm (0.001 μm or more and less than 0.01 μm)
4: 0.01 μm or more and less than 0.1 μm 3: 0.1 μm or more and less than 2 μm 2: 2 μm or more

(8) Film flammability Film samples were evaluated according to the UL-94 VTM method. The sample was cut into 20 cm × 5 cm and left in 23 ± 2 ° C. and 50 ± 5% RH for 48 hours, and then the lower end of the sample was held 10 mm above the burner and held vertically. The bottom end of the sample was indirectly heated for 3 seconds using a Bunsen burner having an inner diameter of 9.5 mm and a flame length of 19 mm as a heating source. Flame retardance was evaluated according to the evaluation standards of VTM-0, VTM-1, and VTM-2, and among the number of measurements of n = 5, the rank having the same number of ranks was set.

(9) Flammability in FPC configuration Create a single-sided FPC with a circuit formed on one side of the film,
Evaluation was performed according to the UL-94V method. In the case of the configuration in which the layer B is provided, a circuit is formed on the surface on the layer B side.
In conducting the flammability test, the FPC sample was cut into 13 mm × 125 mm and left in 50 ± 5% RH for 48 hours, and then the lower end of the test piece was separated from the burner by 10 mm and held vertically. The test piece was indirectly flamed for 10 seconds using a Bunsen burner having an inner diameter of 9.5 mm and a flame length of 19 mm as a heating source. The self-extinguishing property after flame release was evaluated and evaluated by V-0 and V-2.

[Example 1]
As the composition for layer A, polyethylene-2,6-naphthalenedicarboxylate having an intrinsic viscosity of 0.60 dl / g and a terminal carboxyl group concentration of 25 equivalents / ton (transesterification catalyst: manganese acetate tetrahydrate, polymerization catalyst: trioxide Antimony) and aluminum dimethylphosphinate (described in Table 1 as phosphorus compound C, average particle size 2 μm, coarse particles (maximum length 10 μm or more) are pulverized and removed by classification) 25 based on the weight of layer A A composition containing wt% was prepared, the same polyester as layer A was used as the composition for layer B, and a composition containing no phosphorus compound was prepared, and each was dried with a dryer at 170 ° C. for 3 hours, and then a separate extruder. And then melt-kneaded at a melting temperature of 300 ° C. and extruded from a die slit at 300 ° C., the thickness ratio of layer A and layer B in the feed block is An unstretched film was prepared by cooling and solidifying on a casting drum set at a surface temperature of 60 ° C. in a laminated state so as to be 87:13.

This unstretched film was led to a roll group heated to 140 ° C., stretched 3.2 times in the longitudinal direction (longitudinal direction), and cooled with a roll group at 40 ° C. Subsequently, both ends of the longitudinally stretched film were guided to a tenter while being held by clips, and stretched at a magnification of 3.6 times in the direction perpendicular to the longitudinal direction (lateral direction) in an atmosphere heated to 140 ° C. Thereafter, heat setting at 240 ° C. is performed in a tenter, relaxation is performed by 1% in the width direction at 200 ° C., and then uniformly cooled and cooled to room temperature. The thickness of layer A and layer B is 75 μm, respectively. Biaxially oriented films of 65 μm and 10 μm were obtained.
The characteristics of the obtained biaxially oriented film are shown in Table 1. The biaxially oriented film of this example was excellent in flame retardancy and surface flatness. The center line average roughness Ra was 0.3 μm on the layer A side and 8 nm on the layer B side, and a copper foil was laminated on the surface of the layer B, so that a highly delicate circuit pattern could be formed without distortion. Moreover, in obtaining the biaxially oriented film of the present Example, it was possible to form a film stably, and the film forming property was excellent.

[Example 2]
The flame retardant was changed to aluminum diethylphosphinate (indicated as phosphorus compound D in Table 1, average particle size 2 μm, coarse particles (maximum length 10 μm or more) was pulverized and removed by classification), and contained 25% by weight in layer A The biaxially oriented film having a thickness of 75 μm was obtained by performing the same operation as in Example 1 except that the composition was 5% by weight in layer B. The characteristics of the obtained biaxially oriented film are shown in Table 1. The biaxially oriented film of this example was excellent in flame retardancy, surface flatness, film-forming property, and high-definition circuit pattern formability.

[Example 3]
A biaxially oriented film having a thickness of 75 μm was obtained in the same manner as in Example 2 except that the flame retardant content was changed to 15% by weight for layer A and 10% by weight for layer B. The characteristics of the obtained biaxially oriented film are shown in Table 1. The biaxially oriented film of this example was excellent in flame retardancy, surface flatness, film-forming property, and high-definition circuit pattern formability.

[Example 4]
A biaxially oriented film having a thickness of 75 μm was obtained in the same manner as in Example 2 except that the flame retardant content was changed to 5% by weight for layer A and 3% by weight for layer B. The characteristics of the obtained biaxially oriented film are shown in Table 1. The biaxially oriented film of this example was excellent in flame retardancy, surface flatness, film-forming property, and high-definition circuit pattern formability.

[Example 5]
A biaxially oriented film having a thickness of 75 μm was obtained by performing the same operation as in Example 2 except that the layer thicknesses of the layers A and B were changed to 50 μm and 25 μm. The characteristics of the obtained biaxially oriented film are shown in Table 1. The biaxially oriented film of this example was excellent in flame retardancy, surface flatness, film-forming property, and high-definition circuit pattern formability.

[Example 6]
A biaxially oriented film having a thickness of 75 μm was obtained by performing the same operation as in Example 4 except that the layer thicknesses of the layers A and B were changed to 70 μm and 5 μm. The characteristics of the obtained biaxially oriented film are shown in Table 1. The biaxially oriented film of this example was excellent in flame retardancy, surface flatness, and film forming property. However, since the thickness of the layer B was thin, the surface flatness on the layer B side was lower than that in Example 4.

[Comparative Example 1]
A biaxially oriented film having a thickness of 75 μm was obtained by performing the same operation as in Example 1 except that the flame retardant was not added to the layer A, and only the layer A was a single layer. The characteristics of the obtained biaxially oriented film are shown in Table 1. Although the biaxially oriented film of this comparative example was excellent in film formability and surface flatness, the flame retardancy was not sufficient.

[Comparative Example 2]
A biaxially oriented film having a thickness of 75 μm was obtained in the same manner as in Example 2 except that the flame retardant content was changed to 40% by weight for layer A and 5% by weight for layer B. The characteristics of the obtained biaxially oriented film are shown in Table 1. Although the biaxially oriented film of this comparative example is excellent in film formability and flame retardancy, the surface flatness on the layer A side is not sufficient, and the surface shape of the layer A is transferred to the layer B, and the surface flatness of the layer B As compared with Example 2, it also decreased.

[Comparative Example 3]
The same operation as in Example 4 was performed except that aluminum diethyl diethylphosphinate from which coarse particles were not removed as a flame retardant (indicated in Table 1 as phosphorus compound D ′, average particle diameter of 2 μm) was used. An axially oriented film was obtained. The characteristics of the obtained biaxially oriented film are shown in Table 1. In this comparative example, the film forming property was not sufficient, and the obtained biaxially oriented film had a rough surface and the surface flatness was not sufficient.

  The flame-retardant biaxially oriented polyester film of the present invention is excellent in surface flatness and has high flame retardancy without deteriorating the mechanical properties of polyester such as polyethylene naphthalene dicarboxylate. It can be suitably used for a substrate.

Claims (4)

70 to 99.5% by weight of polyethylene naphthalene dicarboxylate and 0.5 to 3.0 μm of flame retardant particles having an average particle size of 0.5 to 3.0 μm represented by the following formula (1) or (2) look including a layer a containing wt% to 30 wt% or less, and a polyester film having a layer B on one side of the layer a,
The layer B contains 90% by weight to 100% by weight of polyethylene naphthalene dicarboxylate and 0% by weight to 10% by weight of the flame retardant particles based on the layer weight, and the layer A is more difficult than the layer B. Comprising a large amount of a flame retardant, wherein the layer thickness ratio of the layer A and the layer B is 2: 1 to 10: 1;

(Wherein R ¹ and R ² are hydrogen, an alkyl group having 1 to 6 carbon atoms and / or an aryl group, M is a metal, and m is a valence of M)

Wherein R ³ and R ⁴ are hydrogen, an alkyl group having 1 to 6 carbon atoms and / or an aryl group, R ⁵ is an alkylene group having 1 to 6 carbon atoms, an arylene group having 6 to 10 carbon atoms, and an alkylarylene group. Or an arylalkylene group, M represents a metal, and n represents a valence of M.)
The flame retardant biaxially oriented polyester film for flexible circuit boards, wherein the number of coarse particles having a maximum length of 10 μm or more contained in the layer A is 10 / m ² or less.   The flame-retardant biaxially oriented polyester film for flexible circuit boards according to claim 1, wherein the flame-retardant biaxially oriented polyester film for flexible circuit boards has a center line average roughness Ra of at least one surface of 0.1 µm or more and less than 2 µm. Oriented polyester film. The layer center line average roughness Ra of the A-side is less than 2μm above 0.1 [mu] m, the layer B-side flame flexible circuit board according to claim 1 center line average roughness Ra is less than 10nm or more 1nm of Flammable biaxially oriented polyester film. The flexible circuit board using the flame-retardant biaxially-oriented polyester film for flexible circuit boards in any one of Claims 1-3 .