Liquid crystal polymer film and laminate comprising the same

Abstract

Provided are a liquid crystal polymer (LCP) film and a laminate comprising the same. The LCP film has a first surface and a second surface opposite each other, and a Kurtosis (Rku) of the first surface ranges from 3.0 to 60.0. With the Rku, the LCP film is able to improve the peel strength with a metal foil and ensure that a laminate comprising the same maintains the merit of low insertion loss.

Claims

1. A liquid crystal polymer film, comprising a first surface and a second surface opposite each other, wherein a Kurtosis (Rku) of the first surface is more than or equal to 3.0 and less than or equal to 60.0; wherein an Rku of the second surface is more than or equal to 3.0 and less than or equal to 60.0; wherein the liquid crystal polymer film is used for a laminate; wherein the Rku is defined according to JIS B 0601:2001.

2. The liquid crystal polymer film as claimed in claim 1, wherein the Rku of the first surface is more than or equal to 3.4 and less than or equal to 60.0.

3. The liquid crystal polymer film as claimed in claim 1, wherein an arithmetic average roughness of the first surface is less than or equal to 0.09 μm.

4. The liquid crystal polymer film as claimed in claim 3, wherein the arithmetic average roughness of the first surface is more than or equal to 0.02 μm and less than or equal to 0.09 μm.

5. The liquid crystal polymer film as claimed in claim 1, wherein a ten-point mean roughness of the first surface is less than or equal to 2.0 μm.

6. The liquid crystal polymer film as claimed in claim 5, wherein the ten-point mean roughness of the first surface is more than or equal to 0.1 μm and less than or equal to 2.0 μm.

7. The liquid crystal polymer film as claimed in claim 1, wherein an arithmetic average roughness of the second surface is less than or equal to 0.09 μm.

8. The liquid crystal polymer film as claimed in claim 3, wherein an arithmetic average roughness of the second surface is less than or equal to 0.09 μm.

9. The liquid crystal polymer film as claimed in claim 5, wherein an arithmetic average roughness of the second surface is less than or equal to 0.09 μm.

10. The liquid crystal polymer film as claimed in claim 1, wherein a ten-point mean roughness of the second surface is less than or equal to 2.0 μm.

11. The liquid crystal polymer film as claimed in claim 3, wherein a ten-point mean roughness of the second surface is less than or equal to 2.0 μm.

12. The liquid crystal polymer film as claimed in claim 5, wherein a ten-point mean roughness of the second surface is less than or equal to 2.0 μm.

13. A laminate, comprising a first metal foil and the liquid crystal polymer film as claimed in claim 1, the first metal foil disposed over the first surface of the liquid crystal polymer film.

14. The laminate as claimed in claim 13, wherein the laminate comprises a second metal foil, and the second metal foil is disposed over the second surface of the liquid crystal polymer film.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) Hereinafter, multiple preparation examples are provided to illustrate raw materials used to produce the LCP film of the present application. Multiple examples are further provided to illustrate the implementation of the LCP film and the laminate of the present application, while multiple comparative examples are provided as comparison. A person having ordinary skill in the art can easily realize the advantages and effects of the present application from the following examples and comparative examples. The descriptions proposed herein are just preferable embodiments for the purpose of illustrations only, not intended to limit the scope of the present application. Various modifications and variations could be made in order to practice or apply the present application without departing from the spirit and scope of the present application.

LCP Resin

Preparation Example 1: LCP Resin

(2) A mixture of 6-hydroxy-2-naphthalenecarboxylic acid (540 g), 4-hydroxybenzoic acid (1071 g), acetyl anhydride (1086 g), sodium phosphite (1.3 g), and 1-methylimidazole (0.3 g) was charged into a 3-liter autoclave and stirred for acetylation at 160° C. for about 2 hours under nitrogen atmosphere at normal pressure. Subsequently, the mixture was heated to 320° C. at a rate of 30° C. per hour, and then under this temperature condition, the pressure was reduced slowly from 760 torr to equal to or less than 3 torr or below, and the temperature was increased from 320° C. to 340° C. Afterwards, the stirring power and the pressure were increased, and steps of discharging polymers, drawing strands, and cutting strands into pellets were conducted to obtain an LCP resin having a melting point about 278° C. and a viscosity about 45 Pa.Math.s @300° C.

Preparation Example 2: LCP Resin

(3) A mixture of 6-hydroxy-2-naphthalenecarboxylic acid (440 g), 4-hydroxybenzoic acid (1145 g), acetyl anhydride (1085 g), and sodium phosphite (1.3 g) was charged into a 3-liter autoclave and stirred for acetylation at 160° C. for about 2 hours under nitrogen atmosphere at normal pressure. Subsequently, the mixture was heated to 320° C. at a rate of 30° C. per hour, and then under this temperature condition, the pressure was reduced slowly from 760 torr to 3 torr or below, and the temperature was increased from 320° C. to 340° C. Afterwards, the stirring power and the pressure were increased, and steps of discharging polymers, drawing strands, and cutting strands into pellets were conducted to obtain an LCP resin having a melting point about 305° C. and a viscosity about 40 Pa.Math.s @300° C.

LCP Film

Examples 1 to 12 and Comparative Examples 1 to 6: LCP Films

(4) The LCP resin obtained from Preparation Examples 1 and 2 (PE1 and PE2) was used as raw materials to prepare LCP films of Examples 1 to 12 (E1 to E12) and Comparative Examples 1 to 6 (C1 to C6) by the methods described below.

(5) First, the LCP resin was put into an extruder having a screw diameter of 27 millimeters (mm) (manufacturer: Leistritz, model: ZSE27) and heated to a temperature ranging from 300° C. to 320° C., and then extruded from a T-die of a width of 500 mm at a feeding speed ranging from 5.5 kilograms per hour (kg/hr) to 8.5 kg/hr. The LCP resin was then delivered to a space between two casting wheels, which were spaced from the T-die by about 5 mm to 20 mm and each had a temperature ranging from about 290° C. to 330° C. and a diameter ranging from about 35 centimeters (cm) to 45 cm, extruded with a force about 20 kilonewtons (kN) to 60 kN, and then transferred to a cooling wheel for cooling at room temperature, so as to obtain an LCP film having a thickness of 50 μm.

(6) The processes of Examples 1 to 12 differ from those of Comparative Examples 1 to 6 in the kind of the LCP resin, the distance from the T-die to the surfaces of the casting wheels, the feeding speed, and the extrusion temperature. The parameters of Examples 1 to 12 and Comparative Examples 1 to 6 are respectively listed in Table 1 below.

(7) TABLE-US-00001 TABLE 1 parameters of preparing LCP films of Examples 1 to 12 and Comparative Examples 1 to 6 Parameters Distance from Feeding Extrusion Sample LCP T-die to casting Speed Temp. No. Resin wheels (mm) (kg/hr) (° C.)  E1 PE1 20 5.5 300  E2 PE1 20 5.5 305  E3 PE1 20 5.5 310  E4 PE2 20 7.5 310  E5 PE2 20 7.5 315  E6 PE2 20 7.5 320  E7 PE1 20 6.5 300  E8 PE1 20 6.5 305  E9 PE1 20 6.5 310 E10 PE2 20 8.5 310 E11 PE2 20 8.5 315 E12 PE2 20 8.5 320 C1 PE1 10 6.0 290 C2 PE1  5 7.0 320 C3 PE1 10 5.5 290 C4 PE2 10 7.5 305 C5 PE1  5 6.5 320 C6 PE2  5 8.5 330

(8) The above-mentioned preparation method of LCP film is only used to exemplify implementation of the present application. A person having ordinary skill in the art may adopt conventional methods such as a laminate extension method and an inflation method to prepare an LCP film.

(9) In one of the embodiments, after the LCP resin was extruded from the T-die, the LCP resin might be delivered with two high-temperature resistant films to a space between two casting wheels to form a three-layered laminate based on needs by a person having ordinary skill in the art. The two high-temperature resistant films were detached from the LCP resin at room temperature to obtain the LCP film of the present application. The high-temperature resistant film may be selected from, but not limited to, poly(tetrafluoroethene) (PTFE) film, polyimide (PI) film, and poly(ether sulfone) (PES) film.

(10) In addition, post treatments for the obtained LCP film may be conducted based on different needs by a person having ordinary skill in the art. The post treatments may be, but are not limited to, polishing, ultraviolet irradiation, plasma, etc. For the plasma treatment, it may be applied with a plasma operated with a power of 1 kilowatt (kW) under nitrogen, oxygen, or air atmosphere at a reduced or normal pressure based on different needs, but is not limited thereto.

Test Example 1: Rku, Ra, and Rz of LCP Films

(11) In this test example, the LCP films of Examples 1 to 12 and Comparative Examples 1 to 6 were used as test samples. Rku of the surface of each test sample was measured according to JIS B 0601:2001, and Ra and Rz of the surface of each test sample were measured according to JIS B 0601:1994.

(12) In order to measure Rku, Ra, and Rz of the either surface of each test sample, the surface morphology images of the test samples were taken by using a laser confocal scanning microscope (manufacturer: Olympus, model: LEXT OLS5000-SAF, objective lens: MPLAPON-50xLEXT) with an objective lens having a magnification power of 50×, 1× optical zoom, and a 405 nanometers (nm) wavelength of light source at a temperature of 24±3° C. and a relative humidity of 63±3%. Rku of the test samples were measured with a selection of an evaluation length of 4 mm, a high-pass filter of cutoff value (λc) of 0.8 mm, a low-pass filter of cutoff value (λs) of 2.5 μm, a resolution of 1024 pixels×1024 pixels, and a mode of auto tilt removal. Ra and Rz of the test samples were measured with a selection of an evaluation length of 4 mm and a cutoff value of 0.8 mm.

(13) According to the foresaid method, the results of Rku, Ra, and Rz of either surface of each of the LCP films of Examples 1 to 12 and Comparative Examples 1 to 6 are listed in Table 2 below.

Examples 1A to 12A and Comparative Examples 1A to 6A: Laminates

(14) Laminates of Examples 1A to 12A (E1A to E12A) and Comparative Examples 1A to 6A (CIA to C6A) were respectively produced from the LCP films of Examples 1 to 12 and Comparative Examples 1 to 6 stacked to the commercially available copper foils. The product descriptions of the commercially available copper foils are provided as follows:

(15) Copper Foil 1: CF-T49A-HD2, purchased from FUKUDA METAL FOIL & POWDER CO., LTD., Rz: about 1.2 μm; and Copper Foil 2: CF-H9A-HD2, purchased from FUKUDA METAL FOIL & POWDER CO., LTD., Rz: about 1.0 μm.

(16) The kind of the LCP film and the kind of the copper foil used for each of the laminates of Examples 1A to 12A and Comparative Examples 1A to 6A were listed in Table 2, and each of the laminates was produced as follows.

(17) The LCP film having a thickness about 50 μm and two identical copper foils each having a thickness about 12 μm were each first cut to a size of 20 cm×20 cm. The LCP film was then sandwiched between the two commercially available copper foils to form a laminated structure. The laminated structure was subjected to a pressure of 5 kilograms per square centimeter (kg/cm.sup.2) for 60 seconds at 180° C., followed by a pressure of 20 kg/cm.sup.2 for 25 minutes (min) at 300° C., and then cooled to room temperature to obtain a laminate.

(18) Herein, the lamination method for the laminates is not particularly restricted. A person having ordinary skill in the art may use conventional techniques such as a wire lamination or a surface lamination to conduct the lamination process. A laminator applicable to the present application may be, but is not limited to, an intermittent hot-press machine, a roll-to-roll wheeling machine, a double belt press machine, etc. According to different needs, a person having ordinary skill in the art can also align the LCP film with the copper foils to form a laminated structure, which may then be processed with surface lamination comprising a heating step and a pressing step.

(19) In another embodiment, a metal foil, such as a copper foil, on an LCP film may be formed through sputtering, electroplating, chemical plating, evaporation deposition, etc. based on different needs by a person having ordinary skill in the art. Or, a connection layer, such as a glue layer, a nickel layer, a cobalt layer, a chromium layer, or an alloy layer thereof, may be formed between an LCP film and a metal foil based on different needs by a person having ordinary skill in the art.

Test Example 2: Peel Strength of Laminates

(20) The peel strength of the laminates was measured according to IPC-TM-650 No.: 2.4.9. The laminates of Examples 1A to 12A and Comparative Examples 1A to 6A were each cut to a size of a length about 228.6 mm and a width about 3.2 mm as etched specimens. Each etched specimen was placed at a temperature of 23±2° C. and a relative humidity of 50±5% for 24 hours to reach stabilization. Subsequently, each etched specimen was adhered to a clamp of a testing machine (manufacturer: Hung Ta Instrument Co., Ltd., model: HT-9102) with a double faced adhesive tape. Each etched specimen was then peeled from the clamp with a force at a peel speed of 50.8 mm/min, and the value of the force during the peeling process was continuously recorded. Herein, the force should be controlled within a range of 15% to 85% of the bearable force of the testing machine, the peeling distance from the clamp should be at least more than 57.2 mm, and the force for the initial distance of 6.4 mm was neglected and not recorded. The results are shown in Table 2.

Test Example 3: Insertion Loss of Laminates

(21) The laminates of Examples 1A to 12A and Comparative Examples 1A to 6A were each cut to a size of a length about 100 mm, a width about 140 mm, and a resistance about 50 Ohm (Ω) as strip line specimens. The insertion loss of the strip line specimens was measured under 10 GHz by a microwave network analyzer (manufacturer: Agilent Technologies, Ltd., model: 8722ES) including a probe (manufacturer: Cascade Microtech, model: ACP40-250). The results of the laminates are listed in Table 2 below.

(22) Table 2: the results of surface roughness of LCP films of Examples 1 to 12 and Comparative Examples 1 to 6 and the copper foils used for laminates as well as the peel strength and insertion loss of the laminates of Examples 1A to 12A and Comparative Examples 1A to 6A.

(23) TABLE-US-00002 LCP Film Laminate Copper Peel Sample Ra Rz Sample Foil Strength Insertion No. Rku (μm) (μm) No. No. (kN/m) Loss E1 34.507 0.051 0.856 E1A Copper 0.68 −3.0 Foil 1 E2 14.291 0.038 0.647 E2A Copper 0.60 −2.9 Foil 1 E3 3.449 0.033 0.302 E3A Copper 0.52 −2.9 Foil 1 E4 52.629 0.081 1.626 E4A Copper 0.72 −3.0 Foil 1 E5 21.020 0.054 0.734 E5A Copper 0.63 −2.9 Foil 1 E6 9.417 0.029 0.506 E6A Copper 0.60 −2.9 Foil 1 E7 31.534 0.057 0.864 E7A Copper 1.40 −2.9 Foil 2 E8 21.540 0.045 0.609 E8A Copper 1.38 −2.9 Foil 2 E9 8.689 0.037 0.391 E9A Copper 1.26 −2.9 Foil 2 E10 59.877 0.087 1.886 E10A Copper 1.44 −3.0 Foil 2 E11 21.330 0.056 0.735 E11A Copper 1.38 −2.9 Foil 2 E12 10.599 0.036 0.390 E12A Copper 1.30 −2.9 Foil 2 C1 74.526 0.128 2.568 C1A Copper 0.89 −3.1 Foil 1 C2 2.898 0.046 0.423 C2A Copper 0.43 −2.9 Foil 1 C3 69.860 0.113 2.362 C3A Copper 1.42 −3.1 Foil 2 C4 86.328 0.133 2.859 C4A Copper 1.43 −3.1 Foil 2 C5 2.569 0.038 0.386 C5A Copper 0.96 −2.9 Foil 2 C6 2.837 0.042 0.412 C6A Copper 1.02 −2.9 Foil 2

(24) Discussion on Test Results

(25) It should be understood for one having ordinary skill in the art that the results of the laminates would be compared with those of the laminates having the same type of copper foil to determine the influence of the LCP film on the performance of the laminates, so that the beneficial effects of the laminates are attributed to the LCP films and the LCP films being useful for optimizing the performance of the laminates can be confirmed.

(26) As shown in Table 2 above, the Rku of either surface of the LCP film of each of Examples 1 to 12 was controlled within the range of more than or equal to 3.0 and less than or equal to 60.0, so the laminates of Examples 1A to 12A, which were produced from such LCP films and various commercially available copper foils, all exhibited high peel strength and low insertion loss. In contrast, the Rku of either surface of the LCP film of each of Comparative Examples 1 to 6 was out of the foresaid range, so the laminates of Comparative Examples 1A to 6A failed to possess high peel strength as well as low insertion loss.

(27) The results of the multiple laminates having Copper Foil 1 were compared and analyzed. When the Rku of the LCP film, such as Comparative Example 1, was over 60.0, the produced laminate, such as Comparative Example 1A, yielded significant insertion loss; on the other hand, when the Rku of the LCP film, such as Comparative Example 2, was less than 3.0, the produced laminate, such as Comparative Example 2A, obviously had insufficient peel strength. In contrast, when the Rku of the LCP film, such as Examples 1 to 6, was controlled within the range of more than or equal to 3.0 and less than or equal to 60.0, the laminate, such as Examples 1A to 6A, not only exhibited improved peel strength between the LCP film and the metal foil but also had low insertion loss.

(28) Even if different copper foils were used, the LCP film of the present application still provided the laminate with improved peel strength and low insertion loss. Specifically, the results of the multiple laminates having Copper Foil 2 were compared and analyzed. In comparison with the results of the laminates without using the claimed LCP film, such as Comparatives 3A to 6A, the LCP film having the Rku within a range of 3.0 to 60.0, such as Examples 7 to 12, allowed the laminate, such as Examples 7A to 12A, to exhibit improved peel strength as well as low insertion loss.

(29) In summary, by controlling the Rku of the first surface of the LCP film to be more than or equal to 3.0 and less than or equal to 60.0, the laminate not only has improved peel strength between the LCP film and the metal foil but also exhibits low insertion loss. Therefore, the laminate of the present application is highly suitable for high-end 5G products.

(30) Even though numerous characteristics and advantages of the present application have been set forth in the foregoing description, together with details of the structure and features of the present application, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the present application to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.