SSPU 2021/015

Description

Composite films for mobile electronic device components Cross reference to related applications

This application claims priority from US Provisional patent application Nr 63/211638 filed on 17 June 2021 and from EP Patent Application Nr 21195292.4 filed on 7 September 2021 , the whole content of each of these applications being incorporated herein by reference for all purposes.

Technical field

[0001 ] The present disclosure relates to composite films comprising at least one Liquid Crystalline Polyester (LCP) and at least one fiber fabric (F), such composite films exhibiting low dielectric constant and dissipation factors, making them well-suited for mobile electronic device components, for example copper clad laminates (CCL) and flexible printed circuit boards (FPC).

Background

[0002] Due to their reduced weight and high mechanical performance, polymer compositions are widely used to manufacture mobile electronic device components. There is now a high demand from the market for polymer compositions to be used to manufacture mobile electronic device components having improved dielectric performances (i.e. low dielectric constants and dissipation factor).

[0003] In mobile electronic devices, the material forming the various components and housing can significantly degrade wireless radio signals (e.g. 1 MHz, 2.4 GHz and 5.0 GHz frequencies) transmitted and received by the mobile electronic device through one or more antennas. The dielectric performances of the material to be used in mobile electronic devices can be determined by measuring the dielectric constant and the dissipation factor as they represent the ability of the material to interact with the electromagnetic radiation and disrupt electromagnetic signals (e.g. radio signals) travelling through the material. Accordingly, the lower the dielectric constant of a material at a given SSPU 2021/015 frequency, the less the material disrupts the electromagnetic signal at that frequency.

[0004] Polymer films are employed in the domain of mobile electronic device. For example, aromatic polyimide films in the form of a continuous aromatic polyimide film/copper foil laminate structure have been described for manufacturing flexible printed circuit boards (FPC), carrier tapes for tape- automated-bonding (TAB), and tapes of lead-on-chip (LOC) structure. Such films are presented as showing good high temperature resistance, good chemical properties, high electrical insulating property, and high mechanical strength. However, polyimide films do not show the expected dielectric performances, especially the dissipation factor of polyimide films is too high to be used in applications at high frequency (> 20 GHz). In addition, the dissipation factor at high frequency of polyimide films gets even worse under humid environment, due to the moisture absorption.

[0005] An object of the present invention is to provide a composite film having improved dielectric performances. Such a composite film is made of a liquid crystalline polyester and a fiber fabric.

[0006] Summary

[0007] The present invention relates to a composite film comprising:

- at least one liquid crystalline polyester, [Polymer LCP], and

- at least one fiber fabric, [Fiber Fabric (F)].

[0008] The present invention also relates to methods for preparing such composite film.

[0009] Others objects of the present invention are as follows: articles, or components of articles, comprising at least one composite film of the present invention, use of at least one such composite film to prepare a mobile electronic device article or component thereof, for example a flexible printed circuit board (FPC). A further object is the use of a liquid crystalline polyester powder to prepare a composite film, which can for example have a thickness of less than 0.10 mm, said composite film further comprising at least one fiber fabric. SSPU 2021/015

Disclosure of the invention

[0010] In the present application :

- any description, even though described in relation to a specific embodiment, is applicable to and interchangeable with other embodiments of the present invention;

- where an element or component is said to be included in and/or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components; any element or component recited in a list of elements or components may be omitted from such list; and

- any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited ranges as well as the endpoints of the range and equivalents;

- the term “and/or” used in a phrase in the form of “A and/or B” means A alone, B alone, or A and B together.

[0011] Composite film

[0012] The present invention relates to a composite film comprising:

- at least one liquid crystalline polyester, [Polymer LCP], and

- at least one fiber fabric, [Fiber fabric (F)].

[0013] The composite film of the invention comprises at least on Polymer LCP. Liquid crystalline polymers are known polymers, and are sometimes described as "rigid-rod", "rod-like", or ordered polymers. These polymers are believed to have a fixed molecular shape, e. g. linear, or the like, due to the nature of the repeat units comprising the polymeric chain. The repeat units typically comprise rigid molecular elements. The rigid molecular elements (mesogens) are frequently rod-like or disk-like in shape and are typically aromatic. The rigid molecular elements may be present in either the main chain of the polymer or in the side chains. SSPU 2021/015

[0014] In some embodiments, Polymer LCP comprises 40.0 mol. % or more of repeat units derived from 6-hydroxy-2-naphthoic acid (HNA) or a derivative thereof, for instance an acetate ester. Polymer LCP may comprise 50.0 mol.% or more, even 60.0 mol.% or more of repeat units derived from 6-hydroxy-2-naphthoic acid, based on the total number of moles in Polymer LCP. According to the same embodiments, Polymer LCP comprises less than 99.0 mol. % of repeat units derived from 6-hydroxy-2-naphthoic acid (HNA) or a derivative thereof, for example less than 98.0 mol.% or less than 97.0 mol.%, based on the total number of moles in Polymer LCP.

[0015] Alternatively or additionally, Polymer LCP may comprise specific amounts of repeat units derived from 4,4’-bibenzoic acid (4,4’-BB) and/or 3,4’-bibenzoic acid (3,4’-BB).

[0016] Polymer LCP may comprise repeat units derived from 4,4’-bibenzoic acid (4,4’- BB) and/or 3,4’-bibenzoic acid (3,4’-BB) in combination with repeat units derived from 6-hydroxy-2-naphthoic acid (HNA), preferably in combination with 40.0 mol. % or more of repeat units derived from 6-hydroxy-2-naphthoic acid (HNA). This specific combination of components has been shown to provide good dielectric performances to the composite film comprising such Polymer LCP. Introduction of selected ratios of 4,4’-bibenzoic acid (4,4’-BB) and/or 3,4’- bibenzoic acid (3,4’-BB) may be advantageous in the sense that it enables the control of the melting temperature (Tm) and crystallization temperature (To) of Polymer LCP, while maintaining liquid crystallinity, which is desirable for various processing requirements.

[0017] Polymer LCP advantageously comprises:

- 40.0 mol. % or more of repeat units derived from 6-hydroxy-2-naphthoic acid (HNA), and

- 1.0 mol.% or more of repeat units derived from 4,4’-bibenzoic acid (4,4’-BB) and/or 3,4’-bibenzoic acid (3,4’-BB), for example more than 1.5 mol.%, or even more than 2.0 mol.%, based on the total number of moles in Polymer LCP.

[0018] Polymer LCP comprise: SSPU 2021/015

- less than 99.0 mol. % of repeat units derived from HNA,

- less than 23.0 mol.% of repeat units derived from 4,4’-bibenzoic acid (4,4’- BB) and/or 3,4’-bibenzoic acid (3,4’-BB), for example less than 22.0 mol.%, even less than 21.0 mol.%, based on the total number of moles in Polymer LCP.

[0019] In some embodiments, Polymer LCP comprises: a) from 40.0 to 98.0 mol.% of repeat units of formula (I):

(I), b) from 1 .0 to 30.0 mol.% of repeat units derived from at least one aromatic diol selected from the group consisting of the diols of formulae (I la) to (lid) (collectively referred to as “formula (II)”) below:

(lie), and/or SSPU 2021/015

(lid), and c) repeat units derived from aromatic compounds having two carboxyl groups as follows:

- either 1.0 to 23.0 mol.% of repeat units of formula (Ilia):

(Ilia), and/or from 1.0 to 13.0 mol.% of repeat units of formula (I I lb):

(I I lb).

[0020] Polymer LCP described herein may be a polymer consisting essentially in the above-mentioned repeat units or a polymer comprising such repeat units and optionally comprising additional repeat units as described below.

[0021] In some embodiments, when Polymer LCP comprises additional repeat units, these repeat units may be selected from the group consisting of those of formula:

(IV), SSPU 2021/015

(VII).

[0022] Each of the repeat units of formula (IV) and (V), may be present in Polymer LCP in a molar amount ranging from 0.1 to 15.0 mol.%, for example from 0.5 to 13.0 mol.%, from 1.0 to 11.0 mol.%, from 2.0 to 9.0 mol.% or from 3.0 to 8.0 mol.%, based on the total number of moles in Polymer LCP.

[0023] Each of repeat units of formula (VI) and (VII) may be present in Polymer LCP in a molar amount ranging from 0.1 and 25.0 mol.%, for example from 0.5 to 22.0 mol.%, from 1.0 to 21.0 mol.%, from 2.0 to 20.0 mol.% or from 3.0 to 18.0 mol.%, based on the total number of moles in Polymer LCP.

[0024] In some other embodiments, when Polymer LCP comprises additional repeat units, the additional repeat units may be selected from the group consisting of those of formulae: SSPU 2021/015

(XII).

[0025] Each of repeat units of formulae (VIII), (IX), (X), (XI) and (XII) may be present in Polymer LCP in a molar amount ranging from 0.1 to 20.0 mol.%, for example from 0.5 to 18.0 mol.%, from 1.0 to 15.0 mol.%, from 2.0 to 13.0 mol.% or from 3.0 to 10.0 mol.%, based on the total number of moles in Polymer LCP.

[0026] According to the present invention, when Polymer LCP used in the composite film of the present invention comprises additional repeat units, these additional repeat units may be selected from the group consisting of those of formula (IV), (V), (VI), (VII), (VIII), (IX), (X), (XI) and (XII). Polymer LCP may comprise one, two, three, four, five, six or seven of these repeat units. Each of these repeat units may be present in Polymer LCP in a molar amount ranging 0.1 and 15.0 mol.%, for example from 0.5 to 13.0 mol.%, from 1.0 to 11.0 mol.%, from 2.0 to 9.0 mol.% or from 3.0 to 8.0 mol.%, based on the total number of moles in Polymer LCP.

[0027] In some embodiments, Polymer LCP used in the composite film of the present invention comprises from 40.0 to 98.0 mol.% of repeat units of formula (I), preferably from 40.0 to 90.0 mol.%, more preferably from 50.0 to 85.0 mol.% or from 60.0 to 81.0 mol.% of repeat units of formula (I), based on the total number of moles in Polymer LCP. Polymer LCP may further comprise from 1.0 to 30.0 mol.% of repeat units derived from at least one aromatic diol, preferably repeat units selected from the group consisting of those of formula (I la), (lib), (lie) and (lid). Preferably, Polymer LCP comprises from 5.0 to 25.0 mol.% or SSPU 2021/015 from 10.0 to 22.0 mol.% of repeat units of formula (II), based on the total number of moles in Polymer LCP.

[0028] Polymer LCP may also comprise repeat units of formula (III). It may comprise repeat units of formula (Ilia), or repeat units of formula (lllb). Polymer LCP may comprise repeat units of formula (Ilia) and repeat units of formula (lllb).

[0029] When Polymer LCP comprises repeat units of formula (Ilia), the molar amount of these repeat units varies from 1.0 to 23.0 mol.%, preferably from 2.0 to 22.0 mol.% or from 3.0 to 21.0 mol.% or from 4.0 to 20.0 mol.%, based on the total number of moles in Polymer LCP.

[0030] When Polymer LCP comprises repeat units of formula (lllb), the molar amount of these repeat units varies from 1.0 to 13.0 mol.%, preferably from 2.0 to 12.0 mol.% or from 3.0 to 11.0 mol.% or from 4.0 to 10.0 mol.%, based on the total number of moles in Polymer LCP.

[0031] When Polymer LCP comprises repeat units of formula (Ilia) and of formula (lllb), the combined molar amount of the repeat units of formula (Ilia) and (lllb) may for example vary from 1.0 to 25.0 mol.%, preferably from 2.0 to 23.0 mol.% or from 3.0 to 21.0 mol.% or from 4.0 to 20.0 mol.%, based on the total number of moles in Polymer LCP. The molar ratio (llla)/(lllb) can vary from 1 :99 to 99:1 , preferably from 10:90 to 90:10, even more preferably from 20:80 to 80:20.

[0032] Polymer LCP may comprise repeat units derived from: 6-hydroxy-2-naphthoic acid (HNA), biphenol (BP), hydroquinone (HQ), and bibenzoicacid (BB). Esters of the monomers may be used in the preparation of Polymer LCP, such as 6- acetoxy-2-naphthoic acid (AcHNA), diacetoxybiphenyl (AcBP), diacetoxybenzene (AcHQ).

[0033] Various isomers of bibenzoic acid (BB) can be used to prepare Polymer LCP. Bibenzoic acid (BB) may be in the form of 4,4’-bibenzoic acid (4,4’-BB) and/or 3,4’-bibenzoic acid (3,4’-BB). Polymer LCP may comprise, even consist of, repeat units derived from hydroxy-2-naphthoic acid (HNA), biphenol (BP) and/or hydroquinone (HQ), and 4,4’-bibenzoic acid (4,4’-BB).

[0034] Polymer LCP may also comprise, even consist of, repeat units derived from hydroxy-2-naphthoicacid (HNA), biphenol (BP) and/or hydroquinone (HQ), and SSPU 2021/015

3,4’-bibenzoic acid (3,4’-BB). Polymer LCP may also comprise, even consist of, repeat units derived from a combination of 3,4’-BB and 4,4’-BB. For example Polymer LCP may comprise, even consist of, repeat units derived from hydroxy-2-naphthoic acid (HNA), biphenol (BP) and/or hydroquinone (HQ), 3,4’-bibenzoic acid (3,4’-BB) and 4,4’-bibenzoic acid (4,4’-BB). Polymer LCP may be made exclusively of these three, four or five monomers.

[0035] Various isomers of biphenol (BP) can be used to prepare Polymer LCP. Biphenol (BP) may be for example be in the form of 4,4’-biphenol (4,4’-BP), 3,4’-biphenol (3,4’-BP) or 3,3’-biphenol (3,3’-BP). One or several of these isomers can be used. Preferably, at least 4,4’-biphenol is used to prepare Polymer LCP. Various isomers of hydroquinone (HQ) can also be used in the context of the present invention.

[0036] Polymer LCP used in the composite film of the present invention may additionally comprises repeat units of formula (IV), (V), (VI) and/or (VII). In these embodiments, Polymer LCP may be made of repeat units deriving from the following monomers: hydroxybenzoic acid (HBA) (or derivative, for example acetoxybenzoic acid (AcHBA)), terephthalic acid (TPA), isophthalic acid (IPA). Various isomers of hydroxybenzoic acid (HBA) can be used to prepare Polymer LCP. Notably, HBA can be in the form of 4-hydroxybenzoicacid (4-HBA) and/or 3-hydroxy benzoic acid (3-HBA).

[0037] In some embodiments, Polymer LCP used in the composite film of the present invention comprises repeat units derived from terephthalic acid (TPA), in addition to hydroxy-2-naphthoic acid (HNA), biphenol (BP), and bibenzoic acid (BB).

[0038] In some preferred embodiments, Polymer LCP comprises, consists essentially of, or consists of:

- from 50.0 to 80.0 mol.% of repeat units of formula (I),

- from 9.0 to 25.0 mol.% of repeat units of formula (II), and - from 2.0 to 12.0 mol.% of repeat units of formula (I I lb).

[0039] In some other preferred embodiments, Polymer LCP used in the composite film of the present invention comprises, consists essentially of, or consists of: SSPU 2021/015

- from 50.0 to 80.0 mol.% of repeat units of formula (I),

- from 9.0 to 25.0 mol.% of repeat units of formula (II) and

- from 2.0 to 21.0 mol.% of repeat units of formula (Ilia).

[0040] In some other referred embodiments, Polymer LCP used in the composite film of the present invention comprises or consists essentially of:

- from 50.0 to 80.0 mol.% of repeat units of formula (I),

- from 9.0 to 25.0 mol.% of repeat units of formula (II),

- from 2.0 to 15.0 mol.% of repeat units of formula (Ilia), and

- from 2.0 to 11.0 mol.% of repeat units of formula (I I lb).

[0041 ] For the avoidance of doubt, repeat units of formula (II) are those selected from the group consisting of those of formulae (I la) to (lid).

[0042] Polymer LCP used in the composite film of the present invention may additionally comprises repeat units of formula (VIII), (IX), (Xa), (Xb) and/or (XI). In these embodiments, Polymer LCP may be made of the following monomers: cyclohexanedicarboxylic acid (CHDA), preferably 1 ,4-CHDA, 2,6-naphthalene dicarboxylic acid (NDA) (or derivative), resorcinol (RS) (or derivative) and/or catechol (CT) (or derivative). In these embodiments, Polymer LCP may comprise, even consist of, repeat units derived from: 6-hydroxy-2-naphthoic acid (HNA), biphenol (BP), terephthalic acid (TPA), as well as bibenzoic acids (BB). For example, Polymer LCP may be made exclusively of HNA, BP, TPA and BB.

[0043] Polymer LCP may also be made exclusively of HNA, BP, CHDA, HNA, TPA and BB. Polymer LCP may also be made exclusively of HNA, BP, HQ, and BB, for example 4,4’-BB, 3,4’-BB or a combination of both, preferably 3,4’-BB.

[0044] In some embodiments, Polymer LCP is such that the number of moles of repeat units is as follows:

-repeat units of formulas

(l)+(ll)+(lll)+(IV)+(V)+(VI)+(VII)+(VIII)+(IX)+(X)+(XI)+( XII) = 100 mol.%, wherein the number of moles of repeat units of formula (IV), (V), (VI), (VII), (VIII), (IX), (X), (XI) and/or (XII) > 0 mol.%, SSPU 2021/015

- repeat unit of formulas (l)+(ll)+(lll)+(IV)+(V)+(VI) = 100 mol.%, wherein the number of moles of repeat units of formula (IV), (V) and/or (VI) > 0 mol.%, and

- repeat unit of formulas (l)+(ll)+(lll)+(VII)+(VIII)+(IX)+(X)+(XI)+(XII) = 100 mol.%, wherein the number of moles of repeat units of formula (VII), (VIII),

(IX), (X), (XI) and/or (XII) > 0 mol.%.

[0045] In these embodiments, Polymer LCP may be made exclusively of the following monomers: 6-hydroxy-2-naphthoic acid (HNA), biphenol (BP), hydroquinone (HQ), bibenzoic acid (BB), hydroxybenzoic acid (HBA), for example 4- hydroxybenzoic acid (4-HBA) and/or 3-hydroxybenzoic acid (3-HBA), and bibenzoic acid (BB).

[0046] For example, Polymer LCP may be such that the number of moles of repeat units is as follows:

- repeat unit of formulas (l)+(ll)+(lll)= 100 mol.%, for example formulas (l)+(lla)+(llla)= 100 mol.%, or formulas (l)+(lla)+(lllb)= 100 mol.%

- repeat unit of formulas (l)+(ll)+(lll)+(VII) = 100 mol.%, for example formulas (l)+(lla)+(llla)+(VII)= 100 mol.%, or formulas (l)+(lla)+(lllb)+(VII)= 100 mol.%,

- repeat unit of formulas (l)+(ll)+(lll)+(IV) = 100 mol.%,

- repeat unit of formulas (l)+(ll)+(lll)+(V) = 100 mol.%,

- repeat unit of formulas (l)+(ll)+(lll)+(X) = 100 mol.%, or

- repeat unit of formulas (l)+(ll)+(lll)+(XI) = 100 mol.%.

[0047] Polymer LCP used in the composite film of the present invention is prepared from various entities, some of them being diols, dicarboxylic acids, hydroxycarboxylic acids, esters or diesters. The term “diol” refers to an organic compound having two hydroxyl groups, and preferably no other functional groups that can form ester linkages. The term “dicarboxylic acid” refers to an organic compound having two carboxyl groups, and preferably no other functional that can form ester linkages. The term “hydroxycarboxylic acid” refers to an organic compound having one hydroxyl group and one carboxyl group, and preferably no other functional groups which can form ester linkages. The terms “ester” or “diester” refer to organic compounds having one or two SSPU 2021/015 carboxyl groups (R ¹ C0 ₂ — , wherein R ¹ is alkyl or substituted alkyl) derived from carboxylic acids. In other words, Polymer LCP may be prepared from monomers having [-OH], [-OCOR ¹ ] and [-COOH] functional groups. In some embodiments, Polymer LCP is prepared from a molar ratio ([-OH]+[-OCOR ¹ ]) / [-COOH] ranging from 0.8 and 1.2, preferably from 0.9 and 1.1 , even more preferably from 0.95 and 1.05. As an example, according to these embodiments, the molar ratio of repeat units ([II]+[IX] ⁺ [XH]) / repeat units ([lll]+[VI]+[VII]+[VIII]+[X]+[XI]) equals to 1.00 ± 0.20, preferably 1.00 ± 0.10, more preferably 1.00 ± 0.05, even more preferably 1.00 ± 0.01.

[0048] According to an embodiment, Polymer LCP used in the composite film described herein has a melting temperature (Tm) above 255°C, for example ranging between 256 and 340°C, even between 260 and 335°C, or between 261 and 330°C. The melting temperature may be determined using differential scanning calorimetry (DSC) according to ASTM D3418 (2 ^nd heat, heating/cooling rate of 20°C/min).

[0049] According to an embodiment, Polymer LCP has a crystallization temperature (Tc) of less than 275°C, for example ranging between 150 and 275°C, for example ranging between 155 and 260°C, or between 160 and 255°C. The crystallization temperature may be determined using differential scanning calorimetry (DSC) according to ASTM D3418 (cool-down, heating/cooling rate of 20°C/min).

[0050] Polymer LCP described herein can be prepared by any conventional method adapted to the synthesis of polyesters, more precisely liquid crystalline polyesters.

[0051] According to the present invention, Fiber fabric (F) used in the composite film may be an aramid fabric, a glass fiber fabric, or a quartz fabric. Preferably, Fiber fabric (F) comprises glass fibers. Fiber fabric (F) may be a woven or non- woven fabric.

[0052] Preferably, Fiber fabric (F) comprises glass fibers. More preferably the glass fibers, and consequently the glass fiber fabric, are characterised by low dielectric constant and low dissipation factor. SSPU 2021/015

[0053] In an advantageous embodiment, the glass fiber fabric is made of fibers comprising at least 33.0 parts by mass to 48.0 parts by mass of silicon oxide; 1.0 parts by mass to 5.0 parts by mass of alumina; 5.0 parts by mass to 10.0 parts by mass of titanium oxide; 0.5 parts by mass to 4.0 parts by mass of zirconium oxide; and at least one of the following oxides holmium oxide, alkaline earth metal oxides, neodymium oxide, and iron oxide.

[0054] In certain embodiments, the glass fiber fabric is made of fibers having the following composition: silicon oxide, 35.0 parts by mass to 48.0 parts by mass; alumina, 1.0 parts by mass to 5.0 parts by mass; titanium oxide 5.5 parts by mass to 10.0 parts by mass; zirconium oxide, 0.5 parts by mass to 4.0 parts by mass; holmium oxide, less than or equal to 3.0 parts by mass; alkaline earth metal oxides, 32.0 parts by mass to 47.5 parts by mass, with respect to the total mass of the fiber. Alternatively, the glass fiber fabric is made of fibers having the following composition: silicon oxide, 33.0 parts by mass to 46.0 parts by mass; alumina, 1.5 parts by mass to 5.0 parts by mass; titanium oxide, 5.0 parts by mass to 10.0 parts by mass; zirconium oxide, 0.5 parts by mass to 4.0 parts by mass; neodymium oxide, less than or equal to 2.5 parts by mass; iron oxide, less than or equal to 1.2 parts by mass; alkaline earth metal oxide, 31.0 parts by mass to 53.0 parts by mass, with respect to the total mass of the fiber.

[0055] The glass fiber fabric may additionally or alternatively be characterized by a dielectric constant D _k at 1 GHz, measured using a transmission line method and a vector network analyzer, of less than 5.5 and a dissipation factor D _f at 1 GHz, measured using a transmission line method and a vector network analyzer, of less than 0.0030.

[0056] The glass fiber fabric preferably has a dielectric constant D _k at 1 GHz, measured using a transmission line method and a vector network analyzer, of less than 5.0. The dielectric constant D _k at 1 GHz, is generally not less than 3.0. The glass fiber fabric preferably has a dissipation factor D _f at 1 GHz, measured using a transmission line method and a vector network analyzer, of less than 0.0025, even less than 0.0020. The dissipation factor D _f at 1 GHz is generally not less than 0.0001. SSPU 2021/015

[0057] Glass fiber fabrics with the properties detailed above are available from Nittobo as well as from CTG Taishan Fiberglass.

[0058] Fiber fabric (F) may for example present an average thickness of about 200 pm or less, for example of 180 pm or less or of 160 pm or less. The fibers in Fiber fabric (F) may present an average diameter of about 25 pm or less, for example of about 23 pm or less or of 21 pm or less.

[0059] In some embodiments, Fiber fabric (F) is such that it has an average area weight (in grams per square meter or gsm) comprised between 10 gsm and 100 gsm, for example between 12 gsm and 90 gsm or between 15 gsm and 80 gsm.

[0060] In some embodiments, the Fiber fabric (F) is such that it has a thickness between 0.01 mm and 0.10 mm.

[0061] The use of such fiber fabric in the film of the invention is advantageous, as it brings additional stiffness or dimensional stability if required. These features can be advantageously optimized based on the choice of certain fabrics, in order to fit certain end-use requirements.

[0062] The composite film of the present invention may be a multi-layer composite film and may comprise several Fiber fabrics (F), each being identical or distinct. The fabrics may be of distinct thickness and/or of different composition. They may also be oriented in different direction. For example, the composite film may comprise a stack of 2, 3, 4, 5 and up to 10 fiber fabrics.

[0063] In the multi-layered film of the present invention, the same Polymer LCP described herein may be present between each fiber fabric, or distinct polymers, including different Polymer LCP may be used between each fiber fabric. Alternatively, chemically distinct polymers may be used to bond the layers together. Examples of such chemically distinct polymers are polyimide polymers.

[0064] According to the present invention, the composite film preferably comprises less than about 75 wt.% of Fiber fabric (F), preferably between 5 and 70 wt.% or between 10 and 60 wt.% of Fiber fabric (F) per unit area of the composite film. At such weight percentages, the composite film readily accommodates SSPU 2021/015 contraction of Polymer LCP as the composite film is cooled from elevated laminating temperatures.

[0065] According to the present invention, the composite film is preferably such that its volume fiber is between 20 and 60 vol.%, for example between 25 and 55 vol.%, or from 30 and 50 vol.%, wherein Vf is calculated according to the following equation:

Volume of fiber

Vf = Volume of fiber + Volume of polymer

[0066] The composite film of the invention may have a broad range of thicknesses. In one embodiment, the composite film has a thickness comprised between 0.100 mm and 0.005 mm, preferably between 0.090 and 0.010 mm, for example between 0.080 and 0.020, even between 0.070 and 0.030 mm.

[0067] In an alternative embodiment, it may present a higher thickness, for example comprised between 10.00 mm and 0.10 mm, preferably between 5.00 mm and 0.20 mm, for example between 3.00 mm and 0.40 or between 2.00 mm and 0.50 mm. The thickness of the composite film can be measured by any means; for example, it can be measured using a thickness gage.

[0068] The inventors have realized that a film with a thickness in the claimed range keeps its needed bendability for the application, while at the same time maintains its shape, thanks to the fiber fabric, which make such films well-fitted for use as mobile electronic device component, such as copper clad laminate (CCL) and flexible printed circuit boards (FPC). The composite film of the present invention are generally flexible in comparison to the films available on the market. Because of the chemical nature of the resin used to prepare the film, in combination with the fiber fabric, the films of the present invention not only present the appropriate flexibility for mobile electronic device components, but they do also present the right set of mechanical properties, including tensile strength and coefficient of thermal expansion.

[0069] The composite films of the invention are also advantageously characterised by excellent dielectric properties for use in mobile electronic device components. SSPU 2021/015

In particular, they are characterised by low dielectric constant and low dissipation factors even at high frequencies.

[0070] In some embodiments, the films have the following dielectric properties:

- a dielectric constant Dk at 5 GHz of less than 3.8, as measured by Split Post Dielectric Resonator (SPDR), IEC 61189-2-721 :2015 after drying 1h at 100°C, and/or

- a dissipation factor Df at 5 GHz of less than 0.0050, even less than 0.0025, as measured by Split Post Dielectric Resonator (SPDR), IEC 61189-2-

721 :2015 after drying 1 h at 100°C, and/or

- dielectric constant Dk at 20 GHz of less than 3.9, even less than 3.85 as measured by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after drying 1h at 100°C, and/or

- a dissipation factor Df at 20 GHz of less than 0.0100, even less than 0.0080, still less than 0.0050, as measured by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after drying 1h at 100°C, and/or

- a dielectric constant Dk at 5 GHz of less than 3.8, as measured by Split Post Dielectric Resonator (SPDR), IEC 61189-2-721 :2015 after immersion in water for 24 hours, and/or

- a dissipation factor Df at 5 GHz of less than 0.0050, even less than 0.0030, as measured by Split Post Dielectric Resonator (SPDR), IEC 61189-2- 721 :2015 after immersion in water for 24 hours, and/or

- dielectric constant Dk at 20 GHz of less than 3.8 as measured by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after immersion in water for 24 hours, and/or

- a dissipation factor Df at 20 GHz of less than 0.0100, even less than 0.0080, as measured by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after immersion in water for 24 hours.

[0071] In some embodiments, the film is such that it has a coefficient of thermal expansion (CTE) over a temperature range of 0°C to 300°C of less than about 50 x 10 ⁶ /°C, for example less than 40 x 10 ⁶ /°C or less than 30 x 10 6/°C. According to this embodiment, the film is such that it has a CTE of at SSPU 2021/015 least 1 x 10 ⁶ /°C or at least 4 x 10 ⁶ /°C. The coefficient of thermal expansion can be measured using a TMA equipment in tension mode according to ASTM D696.

[0072] Method for preparing the composite film

[0073] The composite film of the present invention may be prepared according to different methods.

[0074] Advantageous methods may start from a polymer powder comprising at least one Polymer LCP which is applied to at least one surface of Fiber fabric (F). According to a preferred embodiment, the powder comprising at least one Polymer LCP is applied to at least one surface of the Fiber fabric (F) is such that its average particle diameter d ₅₀ is comprised between 0.1 and 250.0 pm, between 0.1 and 100.0 pm, preferably between 1.0 and 90.0 pm or between 5.0 and 80.0 pm. As used herein, the term "d ₅₀ " refers to a diameter at with 50 % of the sample (on a volume basis, unless otherwise specified) is comprised of particles having a diameter less than said diameter value. The d ₅₀ of the powder comprising at least one Polymer LCP can be measured by laser scattering in isopropanol.

[0075] The polymer powder may include fillers and other additives well known in the art. Such fillers and additives may include, for example, organic or inorganic particles, plasticizers, light and weathering stabilizers, antistatic agents, ultraviolet absorbing agents, dyes, pigments, viscosity agents and lubricants.

[0076] According to an embodiment, the method for preparing a composite film of the invention comprises the steps of: a) applying a powder comprising at least one Polymer LCP to at least one surface of a Fiber fabric (F), wherein said powder is characterised by an average particle size d ₅₀ comprised between 0.1 and 250.0 pm, b) bonding the polymer powder to Fiber fabric (F) at a pressure P of at least

0.3 MPa and/or a temperature T such that T > Tm, wherein Tm is the melting temperature of the polymer powder (°C).

[0077] At the temperature and pressure referenced above, the polymer powder undergoes a melt-phase enabling it to bond securely to Fiber fabric (F). SSPU 2021/015

[0078] In some preferred embodiments, the powder comprising at least one Polymer LCP is applied to both surfaces of Fiber fabric (F). Protective films may be used to apply the powder comprising at least one Polymer LCP to both surfaces of Fiber fabric (F).

[0079] Preferably, step b) is performed at a pressure P of at least 0.4 MPa, at least 0.5 MPa or at least 0.5 MPa, and/or a temperature T such thatT > Tm, wherein Tm is the melting temperature of the polymer powder (°C). In some embodiments, T is such that T > Tm + 5°C. In some embodiments, T is such that 280°C < T < 400°C, for example 290°C < T < 390°C or 305°C < T < 380°C or 330°C < T < 360°C.

[0080] Step b) may for example consists in subjecting the fiber fabric with the polymer powder applied thereto to compression molding using a hot press.

[0081 ] If a molding press is used in the method of the present invention, a release film between the film and the platen of the press may be used, so that no sticking of the film to the platen occurs. Any release film, which does not interfere with or alter the characteristics of the composite film, is suitable. The release film can be a polyimide, or a release coated metal foil such as aluminum, for example.

[0082] This process can be a batch process, meaning that individual films can be formed one at a time with a stack press, in an autoclave or in a vacuum/oven. The process may alternatively be a continuous process, in which polymer powder is continuously laid over at least one fiber fabric, with or without one or more rolls of fiber fabric, and bonded thereto by means of high pressure and temperature with a double belt press, for example. The residence time in the press when the polymer powder is above its melting point is 0.5 to 1 ,000 sec. The typical double belt press may have a heating and cooling zone.

[0083] The amount of pressure and temperature applied to the film depends upon the type of polymer employed and upon the fiber fabric employed and the physical and dimensional properties of each, along with the operational, physical and dimensional properties of the press. The melt point of the polymer powder is an important feature along with the size of the polymer powder, the thickness SSPU 2021/015 of the fiber fabric as well as its ability to transfer heat, and of course how thick the composite film is (including multi-layered structures). Also, the heat transfer characteristics of the platen (of the press), its size and thickness, residence time of the film in the press, etc. are very important. For example, with a polymer powder comprising a Polymer LCP as described above, the temperature should be above approximately 280°C and a particularly preferred temperature range is 330°C to 380°C. While employing this particular polymer along with a fiber fabric having an average thickness of approximately 0.06 mm, the pressure to be applied to such a composite film should be in the range of from 0.3 MPa to 1.0 MPa.

[0084] One of the method of the present invention for preparing a composite film comprises the steps of: a) applying a polymer powder comprising at least one LCP Polymer to at least one surface of a Fiber fabric (F), said powder being characterised by an average particle size d ₅₀ comprised between 0.1 and 100 pm, b) sintering the polymer powder to the fiber fabric by means of an electromagnetic radiation, infrared or near-infrared radiation.

[0085] The polymer powder may be applied via electrostatic coating.

[0086] According to this method the polymer powder is sintered at the surface of the fiber fabric, using an electromagnetic radiation, infrared or near-infrared radiation, for example a high power laser source such as an electromagnetic beam source.

[0087] Others methods of the present invention for preparing a composite film start from a polymer material which is in the form of a slurry or a dispersion.

[0088] Others methods of the present invention for preparing a composite film start from a polymer in the form of a thin film, which can be made exclusively of Polymer LCP described herein or may comprise additional components or additives.

[0089] One of these methods for preparing a composite film comprises the steps of: a) applying a polymer film comprising at least one Polymer LCP to at least one surface of Fiber fabric (F), and SSPU 2021/015 b) bonding the polymer film to Fiber fabric (F) at a pressure P of at least 0.3 MPa and/or a temperature T such that T > Tm, wherein Tm is the melting temperature of the polymer film (°C).

[0090] The polymer film in step a) above preferably has a thickness of less than 0.10 mm.

[0091] Another method yet for preparing a composite film of the present invention comprises the steps of: a) applying a polymer film comprising at least one LCP Polymer to at least one surface of Fiber fabric (F), and b) sintering the polymer film to Fiber fabric (F), for example by means of an electromagnetic radiation, infrared or near-infrared radiation.

[0092] The polymer film in step a) above preferably has a thickness of less than 0.10 mm.

[0093] According to the present invention, several individual composite films may be stacked on each other to prepare a multilayer composite film. The composite films may for example be arranged in the same direction and/or they can be arranged in different directions. If necessary, the stacked multi-layer structure may be subjected to a new cycle (or several cycles) of compression molding using a hot press.

[0094] Alternatively, the multilayer composite film may be prepared by: a) applying a polymer powder comprising at least one LCP Polymer to at least one surface of at least two fiber fabrics, preferably Fiber fabrics (F), b) stacking the at least two fiber fabrics on each other, and c) bonding the polymer powder to the fiber fabrics at a pressure P of at least 0.3 MPa and/or a temperature T such that T > Tm, wherein Tm is the melting temperature of the polymer powder (°C).

[0095] Alternatively step c) may consists in sintering the polymer powder, as described above.

[0096] In some embodiments, the polymer powder is in the form of a slurry, for example a wet slurry. SSPU 2021/015

[0097] In some other embodiments, the polymer may be in the form of a thin film to be melted in order to bond with the fiber fabric. Preferably the film has a thickness of less than 0.09 mm.

[0098] Several of these options may be used to prepare one multi-layer composite film according to the invention.

[0099] End-use applications

[00100] While the composite film of the present invention may be characterized by a specific thickness, for example of less than 0.10 mm, the present invention also relates to assemblies of composite films according to the present invention, which can lead to a final assembly having a thickness above 0.10 mm.

[00101 ] The present invention also relates to an article or component article, comprising at least one composite film as described above, and optionally a metal layer, preferably a copper layer.

[00102] The present invention also relates to the use of at least one composite film to prepare a mobile electronic device article or component, for example a flexible printed circuit board (FPC).

[00103] The composite film of the present invention may notably be used to prepare flexible printed circuit boards (FPC), carrier tapes for tape-automated-bonding (TAB), and tapes of lead-on-chip (LOC) structure.

[00104] The present invention also relates to use of a powder comprising, even consisting of, at least one Polymer LCP to prepare a composite film said composite film further comprising at least one Fiber fabric (F). The composite film advantageously has a thickness of less than 0.10 mm.

[00105] The present invention also relates to the use of a comprising, even consisting of, at least one Polymer LCP to prepare a composite film said Polymer LCP comprising repeat units deriving from 4,4’-bibenzoic acid (4,4’-BB) and/or 3,4’- bibenzoic acid (3,4’-BB), in combination with aromatic monomers, including 6- hydroxy-2-naphthoicacid (HNA), said composite film further comprising at least one Fiber fabric (F). The composite film advantageously has a thickness of less than 0.10 mm. SSPU 2021/015

[00106] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[001071 EXAMPLES

[00108] The disclosure will be now described in more detail with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the disclosure.

[00109] Starting Materials

[00110] Glass Fabric GF-1 : Fiberglass® fabric 108, commercially available from BGF Industries, having 48 gsm and 0.06mm/2.4mils thickness and a fiber diameter of 5 pm

[00111] Glass fabric GF-2: Fabric LD1035-127, commercially available from CTG Taishan Fiberglass; Dielectric Constant Dk @ 1GHz of 4.3-4.5 and Dissipation factor Df @ 1 GHz of 0.0016, both Dk and Df measured using a transmission line method and a vector network analyzer.

[00112] LCP preparations

[00113] LCP#1 and LCP#2 were prepared as described below wherein:

- AcHNA is 6-acetoxy-2-naphthoic acid;

- Ac4,4’-BP is 4,4'-diacetoxybiphenyl

- 4,4’-BP is 4,4'-biphenol

- 4,4’-BB is 4,4’-bibenzoic acid

- NDA is 2,6-naphthalene dicarboxylic acid

- IPA is isophthalic acid [001141 LCP#1

[00115] Reactions were performed in a dried 500 ml_ round bottomed flask equipped with an overhead stirrer, nitrogen inlet, and distillation neck attached to a receiving flask. 128.17 g of AcHNA (70 mol.%), 32.24 g of 4,4’-BP (15 mol.%), 14.45 _g of 4,4’-BB (7.5 mol.%) and 12.90 g (7.5 mol.%) of NDA were added. Subsequent degassing with vacuum and N2 gas purging (3*) produced an SSPU 2021/015 oxygen-free environment. The initial temperature was 220°C or the temperature where all monomers formed a melt and this temperature was held and stirred for 0.5 h. The temperature was increased at 1.0°C/min from the starting temperature until 335°C, where it was held for 1 h. House vacuum was then applied to promote removal of acetic acid condensate for 0.5-1 h followed by application of high vacuum, reaching 0.1-2 mmHg. The reaction was held under high vacuum until no noticeable condensate was seen leaving the reaction and the polymer sample solidified around the stir blade. The sample was subsequently cooled and retrieved from the stir blade. The resulting polymer was dried at 100°C overnight before use. The polymer was obtained in the form of powder. Two samples were prepared having different average particle sizes as follows: LCP#1-A: d ₅₀ = 137.0 mhp; LCP#1-B: d50= 65.7 mίh.

G001161 LCP#2

[00117] This example follows the previous procedure with 129.53 g of AcHNA (70 mol.%), 32.59 g of Ac4,4’-BP (15 mol.%), 19.47 g of 4,4’-BB (10 mol.%) and 6.68 g of IPA (5 mol.%) as monomer charges. The polymer was obtained in the form of powder: LCP#2: d ₅₀ = 236.8 mhp

[00118] Film preparation method

[00119] The LCP polymer powder was dispersed on the fabric GF-1 or GF-2 in the following configuration: polymer/fabric/polymer. The resulting combination of components was then compression molded into a thin composite film using a hot press set up at a temperature of 330 °C and pressure of 1 MPa. The film was heated for approximately 10 minutes. The polymer powder melted and impregnated the fabric fibers. The film was immediately removed from the press and placed on a cool bench top and allowed to return to ambient temperature.

[00120] Test methods

[001211 Dielectric performances (Dk, Df)

The dielectric constant Dk and the dissipation factor Df were measured at 5 GHz by Split Post Dielectric Resonator (SPDR), IEC 61189-2-721 :2015 after drying 1h at 100°C and after immersion in water for 24 hours. SSPU 2021/015

The dielectric constant Dk and the dissipation factor Df were measured at 20 GHz by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after drying 1h at 100°C and after immersion in water for 24 hours.

[00122] Volume of fibers

Vf is calculated according to the following equation:

Volume of fiber

Vf = Volume of fiber + Volume of polymer

[00123] Results

Table 1 SSPU 2021/015

[00124] The data in Table 1 , show the excellent dielectric properties of the inventive composite film at high frequency (20 GHz) even after immersion in water. The dielectric properties appear further improved when the composite material is prepared from polymer powders having a low d ₅₀ .

Table 2

[00125] The data Table 2, show the excellent dielectric properties of the inventive composite film even at a frequency of 20 GHz.

Table 3 SSPU 2021/015

[00126] The data Table 3 show the good dielectric properties of the inventive composite film at a frequency of 20 GHz.