Composite films for mobile electronic device components

Abstract

The present disclosure relates to a composite film made of at least LCP and a fiber fabric, for example presenting a thickness of less than 0.10 mm, as well as articles comprising such composite films, exhibiting low dielectric constant and dissipation factors and being suitable for mobile electronic device components, for example flexible printed circuit board (FPC).

Claims

1. A composite film comprising: at least one Liquid Crystalline Polyester (LCP), and at least one fiber fabric (F), wherein the LCP comprises: a) repeat units of formula (IV): ##STR00011## b) repeat units of formula (V): ##STR00012## c) repeat units of formula (VI): ##STR00013## and d) repeat units of formula (VII): ##STR00014## wherein the proportions of these repeat units are the following: repeat units (IV): from 10.0 mol % to 25.0 mol %; repeat units (V): from 10.0 mol % to 30.0 mol %; repeat units (VI): from 30.0 mol % to 80.0 mol %; repeat units (VII): from 1.0 mol % to 10.0 mol %; these proportions in mol % being based on the total number of moles in the LCP.

2. The composite film of claim 1, wherein the total proportion of repeat units (IV) to (VII) is at least 95.0 mol %.

3. The composite film of claim 1, wherein the repeat units of the LCP consist essentially of the repeat units (IV)-(VII).

4. The composite film of claim 1, wherein the proportions of repeat units (IV)-(VII) are the following: repeat units (IV): from 10.0 mol % to 20.0 mol %; repeat units (V): from 15.0 mol % to 25.0 mol %; repeat units (VI): from 30.0 mol % to 80.0 mol %; repeat units (VII): from 1.0 mol % to 10.0 mol %.

5. The composite film of claim 1, wherein the proportions of repeat units (IV)-(VII) are the following: repeat units (IV): from 13.0 mol % to 17.0 mol %; repeat units (V): from 18.0 mol % to 22.0 mol %; repeat units (VI): from 58.0 mol % to 62.0 mol %; repeat units (VII): from 2.0 mol % to 7.0 mol %.

6. The composite film according to claim 1 wherein the molar ratio (VII)/[(VII)+(IV)] is lower than 0.45.

7. The composite film according to claim 1, wherein the LCP includes at least one additive blended with the LCP and selected from the group consisting of plasticizers, light and weathering stabilizers, antistatic agents, ultraviolet absorbing agents, dyes, pigments, viscosity agents and lubricants.

8. The composite film according to claim 1, wherein the LCP includes at least one filler blended with the LCP and selected from the group consisting of glass fibers, silica, alumina, aluminium borate, silicon carbide, mica, talc, clay, titanium oxide, zirconia, kaolin, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, magnesium hydroxide, quartz, graphite, carbon fibers, bentonite, and calcium phosphate.

9. The composite film of claim 1, wherein the fiber fabric (F) is an aramid fabric, a glass fiber fabric or a quartz fabric.

10. The composite film of claim 1, wherein the fiber fabric (F) is a woven fabric.

11. The composite film of claim 1, wherein the fiber fabric (F) is such that it has an average area weight comprised between 10 gsm and 100 gsm.

12. The composite film of claim 1, presenting a thickness of less than 0.10 mm.

13. The composite film of claim 1, wherein the fiber fabric (F) is impregnated with the Liquid Crystalline Polyester (LCP) on both faces of the fiber fabric.

14. The composite film of claim 1, wherein the volume fiber Vf is between 10.0 and 60.0 vol. %, Vf being calculated according to the following equation: $V_f=\frac{\mathrm{Volume}\mathrm{of}\mathrm{fiber}}{\mathrm{Volume}\mathrm{of}\mathrm{fiber}+\mathrm{Volume}\mathrm{of}\mathrm{polymer}}100.$

15. The composite film of claim 1, wherein the LCP exhibits a melting point Tm of: at least 305 C.; Tm being measured by Differential Scanning calorimetry (DSC).

16. The composite film of claim 1, wherein the film has: dielectric constant Dk at 20 GHz of less than 3.9, as measured by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after drying 1 h at 100 C., and/or a dissipation factor Df at 20 GHz of less than 0.002, as measured by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after drying 1 h at 100 C.

17. The composite film of claim 1, wherein the film has: dielectric constant Dk at 20 GHz of less than 3.7, 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 0.002, as measured by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after immersion in water for 24 hours.

18. The composite film according to claim 1, exhibiting a dissipation factor Df at 20 GHz which is less than 0.0020, as measured by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after drying 1 h at 100 C.

19. The composite film according to claim 1, exhibiting a dissipation factor Df at 20 GHz which is be less than 0.0020, as measured by Split Cylinder Resonator, IPC TM-650 2.5.5.13 after immersion in water for 24 hours.

20. An article or component article, comprising at least one composite film according to claim 1, and a metal layer, the composite film being in contact with the metal layer.

21. A method comprising preparing a mobile electronic device article or component with at least one composite film of claim 1.

Description

EXPERIMENTAL SECTION

(1) 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.

(2) Tm of the LCP was measured by DSC according to the method indicated before.

(3) Starting Materials

(4) Fabric LD1035-127, commercially available from CTG. This woven glass fiber fabric exhibits the following properties: a dielectric constant Dk @ 1 GHz of 4.3-4.5 and a dissipation factor Df @ 1 GHz of 0.0016, both Dk and Df measured using a transmission line method and a vector network analyzer.

(5) This glass fiber fabric exhibits the properties outlined in the table below:

(6) TABLE-US-00001 Thermal expansion coefficient 3.28 10.sup.6/K (ASTM D696) Refractive index (ASTM C1648) 1.49% Tensile strength (ASTM D2343) 2000 MPa Elastic modulus 67 GPa thickness 0.035 mm or 35 m average area weight 25.9 g/m.sup.2

(7) Fabric NTB 1017, commercially available from Nittobo. The glass fiber are made of a glass which has a lower contents of alkaline earth metals (such as CaO and MgO) than general-purpose E glass which is generally used for composite materials and a higher content of boric acid (B2O.sub.3). This specific composition ensures that the fibers exhibit a low dielectric constant and low dielectric dissipation factor.

(8) This glass fiber fabric exhibits the properties outlined in the table below:

(9) TABLE-US-00002 density 2.3 g/cm.sup.3 Thermal expansion coefficient 3.3 10.sup.6/K (ASTM D696) Tensile strength (ASTM D2343) 3100 MPa Elastic modulus 64 GPa Dielectric constant at 1 GHz 4.8 Dielectric dissipation factor at 1 GHz 0.0015

(10) LCP #1: a liquid crystal polymer was prepared from the following monomers: terephthalic acid; 2,6-napthalene dicarboxylic acid; 6-hydroxy-2-naphthoic acid; 4,4-biphenol.

(11) The following monomers: terephthalic acid (139.4 g, Flint Hills Resources; 0.84 mol), naphthalenedicarboxylic (52.7 g, BASF; 0.243 mol), 2-hydroxy-6-naphthoic acid (611.1 g, from Ueno Fine Chemicals; 3.24 mol), 4,4-biphenol (201.6 g, SI Group; 1.08 mol) and acetic anhydride (582.9 g, Aldrich) were charged into a 2-L glass reactor. Potassium acetate (0.06 g, Aldrich) and magnesium acetate (0.18 g, Aldrich) were used as catalysts. The mixture was heated to 165 C. and the acetylation reaction under reflux condition was allowed to proceed for 2 hrs. The heating then continued to 300 C. at the rate of 0.5 C. per minute while distilling off acetic acid from the reactor. The pre-polymer was discharged and allowed to cool down.

(12) The material was then ground into powder for solid-state polymerization. The resin was advanced in a rotatory oven using the following profile: 1 hr at 270 C., 1 hr at 280 C., 1 hr at 290 C., 2 hrs at 300 C. and 3-6 hrs at 310 C. under continuous nitrogen purging. The resulting high molecular resin had melt viscosity between 300-600 Pa-s at 340 C. The LCP as obtained was then ground in a grinder and the powder used for the preparation of the composite films exhibited a d.sub.50 of 56 m (laser scattering, isopropanol).

(13) Tm of LCP #1:325 C.

(14) LCP #2: a liquid crystal polymer was formed from the following monomers: terephthalic acid; 2,6-napthalene dicarboxylic acid; 6-hydroxy-2-naphthoic acid; 4,4-biphenol.

(15) The following monomers: terephthalic acid (61.6 g, INEOS; 0.369 mol), 2,6-naphthalenedicarboxylic (148.3 g, BASF; 0.686 mol), 6-hydroxy-2-naphthoic acid (595.5 g, from Ueno Fine Chemicals; 3.167 mol), 4,4-biphenol (201.5 g, SI Group; 1.082 mol) and acetic anhydride (574.1 g, Supelco) were charged into a 2-L glass reactor. Potassium acetate (0.062 g, Fisher) and magnesium acetate (0.186 g, Acros) were used as catalysts. The mixture was heated to 165 C. and the acetylation reaction under reflux condition was allowed to proceed for 2 hrs. The heating then continued to 300 C. at the rate of 0.5 C. per minute while distilling off acetic acid from the reactor. The pre-polymer was discharged and allowed to cool down. The material was then ground into powder for solid-state polymerization. The resin was advanced in a rotatory oven using the following profile: 1 hr at 200 C., 1 hr at 218 C., 1 hr at 240 C., 2 hr at 244 C., 2 hr at 266 C., 3 h at 270 C., 4 hr at 280 C. under continuous nitrogen purging.

(16) Tm of LCP #2:275 C. This LCP #2 exhibits a lower Tm than LCP #1.

(17) LCP #3: a liquid crystal polymer was formed from the following monomers: terephthalic acid; 2,6-napthalene dicarboxylic acid; 6-hydroxy-2-naphthoic acid; hydroquinone (instead of 4,4-biphenol).

(18) The following monomers: terephthalic acid (153.0 g, INEOS; 0.921 mol), 2,6-naphthalenedicarboxylic (57.6 g, BASF; 0.266 mol), 6-hydroxy-2-naphthoic acid (670.5 g, from Ueno Fine Chemicals; 3.563 mol), hydroquinone (134.3 g, Acros; 1.220 mol) and acetic anhydride (645.9 g, Supelco) were charged into a 2-L glass reactor. Potassium acetate (0.061 g, Fisher) and magnesium acetate (0.185 g, Acros) were used as catalysts. The mixture was heated to 165 C. and the acetylation reaction under reflux condition was allowed to proceed for 2 hrs. The heating then continued to 300 C. at the rate of 0.5 C. per minute while distilling off acetic acid from the reactor. The pre-polymer was discharged and allowed to cool down.

(19) Tm of LCP #3: <275 C. This LCP #3 exhibits a lower Tm than LCP #2, so a Tm even lower than LCP #1.

(20) Film Preparation Method

(21) The LCP polymer (LCP #1) in the powder form was dispersed on the fabric 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.

(22) Test Methods

(23) Dielectric Performances (Dk, Df)

(24) 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 1 h at 100 C. and after immersion in water for 24 hours.

(25) 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 1 h at 100 C. and after immersion in water for 24 hours.

(26) Coefficient of Thermal Expansion (CTE)

(27) CTE was measured using a TMA equipment in tension mode pursuant to ASTM D696.

(28) Tensile Strength

(29) Tensile test was measured using an Instron mechanical test machine according to ASTM D882.

(30) Volume of Fibers

(31) Vf is Calculated According to the Following Equation:

(32) $V_f=\frac{\mathrm{Volume}\mathrm{of}\mathrm{fiber}}{\mathrm{Volume}\mathrm{of}\mathrm{fiber}+\mathrm{Volume}\mathrm{of}\mathrm{polymer}}100$
Results

(33) TABLE-US-00003 Film #1 Components LD1035-127 LCP #1 Vf 15% Thickness (mm) 0.052 Dk 5 GHz after drying 1 h at 100 C. 3.3 Df 5 GHz after drying 1 h at 100 C. 0.0007 Dk 20 GHz after drying 1 h at 100 C. 3.6 Df 20 GHz after drying 1 h at 100 C. 0.0012 Dk 20 GHz after immersion in water for 24 h 3.6 Df 20 GHz after immersion in water for 24 h 0.0014 Film #2 Components LD1035-127 LCP #1 Vf 26% Thickness (mm) 0.037 Dk 5 GHz after drying 1 h at 100 C. 3.5 Df 5 GHz after drying 1 h at 100 C. 0.0007 Dk 20 GHz after drying 1 h at 100 C. 3.8 Df 20 GHz after drying 1 h at 100 C. 0.0015 Film #3 Components NTB 1017 LCP #1 Vf 10% Thickness (mm) 0.040 Dk 20 GHz after drying 1 h at 100 C. 3.5 Df 20 GHz after drying 1 h at 100 C. 0.0013 Dk 20 GHz after immersion in water for 24 h 3.4 Df 20 GHz after immersion in water for 24 h 0.0024