Liquid crystal polymer film and laminate comprising the same

Abstract

The present application relates to a liquid crystal polymer film and a laminate comprising the same. The liquid crystal polymer film has opposite first and second surfaces, and the first surface has a kurtosis (Rku) of 3.0 to 60.0. The present application also provides a laminate comprising a first metal foil and the above-mentioned liquid crystal polymer film, wherein the first metal foil is disposed on the first surface of the liquid crystal polymer film. By controlling the Rku of the liquid crystal polymer film, the present application not only improves the peeling strength between the liquid crystal polymer film and the metal foil, but also ensures that the laminate comprising the same retains the advantage of low signal loss.

Description

Technical Field

[0001] This invention relates to a polymer film for use in laminates, and more particularly to a liquid crystal polymer film and a laminate containing the same. Background Technology

[0002] With the rapid development of mobile communication technology, the industry is actively developing fifth-generation mobile communication technology (5G). th Generation Mobile Networks (5G) are designed to optimize the performance of 4G communication technologies, including data transmission speed, response time, and system capacity.

[0003] Since 5G communication technology utilizes high-frequency bands for signal transmission, the higher the signal frequency, the greater the insertion loss. Therefore, existing technology knows to use a liquid crystal polymer film (LCP film) with low hygroscopicity and low dielectric properties to replace the polyimide film (PI film) with high dielectric properties, and to laminate the LCP film with metal foil to form a multilayer plate, in order to achieve signal transmission in the high-frequency band while reducing signal loss during high-frequency transmission.

[0004] However, the adhesion between the LCP film and the metal foil in multilayer laminates is often insufficient, which can easily lead to circuit detachment and serious deterioration of the subsequent processing of the multilayer laminate. Furthermore, with the advancement of high-tech industries, the signal loss of multilayer laminates needs to be further reduced. Therefore, it is still necessary to improve both the insufficient peel strength between the liquid crystal polymer film and the metal foil in multilayer laminates and the problem of excessive signal loss. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the purpose of the present invention is to improve the peel strength between the liquid crystal polymer film and the metal foil in the laminate, while ensuring that the laminate has the characteristic of low signal loss.

[0006] To achieve the above objectives, the present invention provides a liquid crystal polymer film having opposing first and second surfaces, wherein the kurtosis (Rku) of the first surface is 3.0 to 60.0.

[0007] By controlling the Rku of the first surface of the liquid crystal polymer film, not only can the adhesion of the liquid crystal polymer film to the metal foil be increased and the peel strength between the liquid crystal polymer film and the metal foil be improved, thereby avoiding problems such as circuit detachment in subsequent processing of the laminate, but also the laminate containing this liquid crystal polymer film can be ensured to have low signal loss characteristics.

[0008] In addition to the first surface of the liquid crystal polymer film, in one embodiment of the present invention, the Rku of the second surface of the liquid crystal polymer film of the present invention may also be 3.0 to 60.0; accordingly, the liquid crystal polymer film of the present invention can obtain good adhesion whether it is laminated with at least one metal foil through the first surface, the second surface or both, thereby improving the peel strength between the liquid crystal polymer film and at least one metal foil, and ensuring that the laminate has the characteristic of low signal loss.

[0009] In other words, when the liquid crystal polymer film of the present invention is applied to a laminate, the laminate is particularly suitable for high-end 5G products.

[0010] Preferably, the Rku of the first surface of the liquid crystal polymer film of the present invention is from 3.4 to 60.0. In one embodiment, the Rku of the first surface of the liquid crystal polymer film of the present invention is from 3.4 to 59.9. In one embodiment, the Rku of both the first surface and the Rku of the second surface of the liquid crystal polymer film of the present invention fall within the above range. Depending on the need, the Rku of the first surface and the Rku of the second surface of the liquid crystal polymer film of the present invention may be the same or different. In one embodiment, the Rku of the first surface and the Rku of the second surface of the liquid crystal polymer film of the present invention are not the same.

[0011] Preferably, the arithmetic average roughness (Ra) of the first surface of the liquid crystal polymer film of the present invention is less than or equal to 0.09 μm; thereby, the liquid crystal polymer film and the metal foil not only have high peel strength, but the application of the liquid crystal polymer film in a laminate can further reduce signal loss, making it more suitable for high-end 5G products. More preferably, the Ra of the first surface of the liquid crystal polymer film of the present invention is from 0.02 μm to 0.09 μm. Even more preferably, the Ra of the first surface of the liquid crystal polymer film of the present invention is greater than or equal to 0.020 μm and less than or equal to 0.088 μm. By reducing the Ra of the first surface of the liquid crystal polymer film, the signal loss of the laminate containing the liquid crystal polymer film can be further reduced, making it more suitable for high-end 5G products. In one embodiment, the Ra of the first surface of the liquid crystal polymer film of the present invention is greater than or equal to 0.04 μm and less than or equal to 0.09 μm. In one embodiment of the present invention, the Ra values ​​of both the first and second surfaces of the liquid crystal polymer film fall within the aforementioned range. Depending on the requirements, the Ra values ​​of the first and second surfaces of the liquid crystal polymer film may be the same or different. In another embodiment, the Ra values ​​of the first and second surfaces of the liquid crystal polymer film are not the same.

[0012] Preferably, the ten-point mean roughness (Rz) of the first surface of the liquid crystal polymer film is less than or equal to 2.0 micrometers (μm). More preferably, the Rz of the first surface of the liquid crystal polymer film of the present invention is less than or equal to 1.9 μm. In one embodiment, the Rz of the first surface of the liquid crystal polymer film of the present invention is greater than or equal to 0.1 μm and less than or equal to 2.0 μm; more preferably, the Rz of the first surface of the liquid crystal polymer film of the present invention is greater than or equal to 0.2 μm and less than or equal to 2.0 μm; more preferably, the Rz of the first surface of the liquid crystal polymer film of the present invention is greater than or equal to 0.3 μm and less than or equal to 2.0 μm; even more preferably, the Rz of the first surface of the liquid crystal polymer film of the present invention is greater than or equal to 0.3 μm and less than or equal to 1.9 μm. In one embodiment of the present invention, the Rz of both the first surface and the Rz of the second surface of the liquid crystal polymer film of the present invention fall within the above-mentioned ranges. Depending on the requirements, the Rz of the first surface and the Rz of the second surface of the liquid crystal polymer film of the present invention may be the same or different. In one embodiment, the Rz of the first surface and the Rz of the second surface of the liquid crystal polymer film of the present invention are not the same.

[0013] According to the present invention, the liquid crystal polymer film can be made from commercially available liquid crystal polymer resins or prepared using existing raw materials, and there are no particular limitations in the present invention. For example, aromatic or aliphatic hydroxyl compounds (e.g., hydroquinone, resorcinol, 2,6-naphthalenediol, ethylenediol, 1,4-butanediol, 1,6-hexanediol) can be used, as well as aromatic or aliphatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2-chloroterephthalic acid, adipic acid), and aromatic hydroxycarboxylic acids (e.g., 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 6-hydroxy-2-naphthalene carboxylic acid). Liquid crystal polymer resins are prepared using phenylenediamine (e.g., pphenylenediamine, 4,4ˊ-diaminobiphenyl, naphthalene-2,6-diamine, 4-aminophenol, 4-amino-3-methylphenol, 4-aminobenzoic acid) as raw materials, and the liquid crystal polymer film of the present invention is then prepared using this liquid crystal polymer resin. In one embodiment of the present invention, 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and acetyl anhydride can be selected to obtain the liquid crystal polymer resin used to prepare the liquid crystal polymer film of the present invention. In one embodiment, the melting point of the liquid crystal polymer resin is approximately 250°C to 360°C.

[0014] In one embodiment, those skilled in the art may add additives, such as lubricants, antioxidants, electrical insulators, or fillers, when preparing the liquid crystal polymer film of the present invention, depending on different needs, but are not limited to these. For example, additives that can be used include polycarbonate, polyamide, polyphenylene sulfide, or polyetheretherketone, but are not limited to these.

[0015] According to the present invention, the thickness of the liquid crystal polymer film is not particularly limited. For example, the thickness of the liquid crystal polymer film can be from 10 μm to 500 μm; preferably, the thickness of the liquid crystal polymer film of the present invention can be from 10 μm to 300 μm; more preferably, the thickness of the liquid crystal polymer film of the present invention can be from 15 μm to 250 μm; and even more preferably, the thickness of the liquid crystal polymer film of the present invention can be from 20 μm to 200 μm.

[0016] To achieve the above objectives, the present invention also provides a laminate comprising a first metal foil and the aforementioned liquid crystal polymer film, wherein the first metal foil is disposed on a first surface of the liquid crystal polymer film, that is, in the laminate of the present invention, the first metal foil is stacked on the first surface of the liquid crystal polymer film.

[0017] In one embodiment, the laminate of the present invention may further include a second metal foil disposed on the second surface of the liquid crystal polymer film. That is, in the laminate of the present invention, the first metal foil is laminated on the first surface of the liquid crystal polymer film, and the second metal foil is laminated on the second surface of the liquid crystal polymer film. In this embodiment, by simultaneously controlling the Rku characteristics of the first and second surfaces of the liquid crystal polymer film, not only can the adhesion of the liquid crystal polymer film laminated on the first and second metal foils be improved simultaneously, that is, the peel strength between the liquid crystal polymer film and the first and second metal foils be improved simultaneously, but the laminate can also be ensured to have low signal loss characteristics.

[0018] According to the present invention, "lamination" is not limited to direct contact, but also includes indirect contact. For example, in one embodiment of the present invention, the first metal foil in the laminate is in direct contact with the first surface of the liquid crystal polymer film. In another embodiment of the present invention, the first metal foil in the laminate is indirectly contacted with the first surface of the liquid crystal polymer film. Specifically, a connecting layer can be provided between the first metal foil and the first surface of the liquid crystal polymer film according to different needs, so that the first metal foil and the first surface of the liquid crystal polymer film are in contact through the connecting layer. The material of the connecting layer can be adjusted according to different needs; for example, the material of the connecting layer may include nickel, cobalt, chromium or alloys thereof to provide, for example, heat resistance, chemical resistance or electrical resistance. Similarly, the second metal foil in the laminate and the liquid crystal polymer film can also be laminated in either direct or indirect contact. In one embodiment, the lamination method of the liquid crystal polymer film and the first metal foil and the lamination method of the liquid crystal polymer film and the second metal foil are the same. In one embodiment, the stacking method of the liquid crystal polymer film and the first metal foil is different from the stacking method of the liquid crystal polymer film and the second metal foil.

[0019] According to the present invention, the first metal foil and / or the second metal foil may be copper foil, gold foil, silver foil, nickel foil, aluminum foil, or stainless steel foil, but are not limited thereto. In one embodiment, the first metal foil and the second metal foil are made of different materials. Preferably, the first metal foil and / or the second metal foil may be copper foil, which is laminated with a liquid crystal polymer film to form a copper clad laminate (CCL). Furthermore, the preparation method of the first metal foil and / or the second metal foil is not particularly limited, as long as it does not violate the inventive purpose of the present invention. For example, a rolling method or an electrolytic method may be used for preparation, but are not limited thereto.

[0020] According to the present invention, the thickness of the first metal foil and / or the second metal foil is not particularly limited, and those skilled in the art can make corresponding adjustments according to different needs. For example, in one embodiment, the thickness of the first metal foil and / or the second metal foil can each be independently from 1 μm to 200 μm; more preferably, the thickness of the first metal foil and / or the second metal foil can each be independently from 1 μm to 40 μm; more preferably, the thickness of the first metal foil and / or the second metal foil can each be independently from 1 μm to 20 μm; and even more preferably, the thickness of the first metal foil and / or the second metal foil can each be independently from 3 μm to 20 μm.

[0021] According to the present invention, those skilled in the art can perform surface treatment on the first metal foil and / or the second metal foil of the present invention according to different needs. For example, roughening treatment, acid and alkali treatment, heat treatment, degreasing treatment, ultraviolet irradiation treatment, corona discharge treatment, plasma treatment, primer coating treatment, etc. can be used, but are not limited to these.

[0022] According to the present invention, the roughness of the first metal foil and / or the second metal foil is not particularly limited, and those skilled in the art can make corresponding adjustments according to different needs. In one embodiment, the Rz of the first metal foil and / or the second metal foil can each be independently greater than or equal to 0.1 μm and less than or equal to 2.0 μm. Preferably, the Rz of the first metal foil and / or the second metal foil can each be independently greater than or equal to 0.1 μm and less than or equal to 1.5 μm. In one embodiment, the Rz of both the first metal foil and the second metal foil can fall within the above range. Depending on the need, the Rz of the first metal foil and the second metal foil can be the same or different. In one embodiment, the Rz of the first metal foil and the Rz of the second metal foil are not the same.

[0023] In one embodiment, those skilled in the art may additionally provide a third metal foil as needed. The third metal foil may be the same as or different from the first and / or second metal foils. In one embodiment, the Rz of the third metal foil may fall within the range of the Rz of the first and / or second metal foils. In one embodiment, the Rz of the first, second, and third metal foils are not the same.

[0024] Preferably, the first metal foil, the second metal foil and / or the third metal foil may be low-roughness metal foils, such as low-roughness copper foil.

[0025] In one embodiment, the laminate may comprise a plurality of liquid crystal polymer films. Without departing from the spirit of the invention, those skilled in the art can, depending on different needs, laminate multiple liquid crystal polymer films of the present invention with multiple metal foils (e.g., the aforementioned first metal foil, second metal foil, and / or third metal foil) to obtain a laminate having multiple liquid crystal polymer films and multiple metal foils.

[0026] In this specification, "kurtosis" is defined according to the standard method specified in JIS B 0601:2001, and "arithmetic mean roughness" and "ten-point mean roughness" are defined according to the standard method specified in JIS B 0601:1994. Detailed Implementation

[0027] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0028] The following examples illustrate the raw materials used to prepare the liquid crystal polymer film of the present invention, and several embodiments illustrate the implementation of the liquid crystal polymer film and laminate of the present invention. Several comparative examples are also provided for comparison. Those skilled in the art can easily understand the advantages and effects of the present invention through the following examples and comparative examples. It should be understood that the embodiments listed in this specification are merely illustrative of the implementation of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art can make various modifications and alterations based on their ordinary knowledge without departing from the spirit of the present invention to implement or apply the content of the present invention.

[0029] Liquid crystal polymer resin

[0030] Preparation Example 1: Liquid Crystal Polymer Resin

[0031] In a 3-liter autoclave, 540 g of 6-hydroxy-2-naphthoic acid, 1071 g of 4-hydroxybenzoic acid, 1086 g of acetic anhydride, 1.3 g of sodium phosphite, and 0.3 g of 1-methylimidazole were mixed and subjected to an acetylation reaction for about 2 hours under a nitrogen atmosphere, at 160°C and atmospheric pressure. Then, the temperature was increased to 320°C at a rate of 30°C per hour, and at this temperature, the pressure was slowly reduced from 760 torr to below 3 torr while the temperature was increased from 320°C to 340°C. Subsequently, the stirring power was increased, the pressure was increased, the material was discharged, stretched into strips, and pelletized to obtain a liquid crystal polymer resin with a melting point of about 278°C and a viscosity (@300°C) of about 45 Pa·s.

[0032] Preparation Example 2: Liquid Crystal Polymer Resin

[0033] In a 3-liter autoclave, 440 g of 6-hydroxy-2-naphthoic acid, 1145 g of 4-hydroxybenzoic acid, 1085 g of acetic anhydride, and 1.3 g of sodium phosphite were mixed and subjected to an acetylation reaction for about 2 hours under a nitrogen atmosphere, at 160°C and atmospheric pressure. Then, the temperature was increased to 320°C at a rate of 30°C per hour, and then the pressure was slowly reduced from 760 torr to below 3 torr while the temperature was increased from 320°C to 340°C. After that, the stirring power was increased, the pressure was increased, the material was discharged, stretched into strips, and pelletized to obtain a liquid crystal polymer resin with a melting point of about 305°C and a viscosity (@300°C) of about 40 Pa·s.

[0034] Liquid crystal polymer film

[0035] Examples 1 to 12, Comparative Examples 1 to 6: Liquid Crystal Polymer Films

[0036] Liquid crystal polymers obtained as described in Preparation Examples 1 and 2 above were used as raw materials, and liquid crystal polymer films of Examples 1 to 12 and Comparative Examples 1 to 6 were prepared by the following methods.

[0037] First, liquid crystal polymer resin is fed into an extruder with a screw diameter of 27 mm (instrument model: ZSE27, purchased from Leistritz) and heated to 300°C to 320°C. Then, the liquid crystal polymer resin is extruded from a T-die with a width of 500 mm at a feeding speed of 5.5 kg / hr to 8.5 kg / hr. Next, it is passed between two casting rollers with a diameter of about 35 cm to 45 cm and a temperature of about 290°C to 330°C, about 5 to 20 mm away from the T-die, and extruded with a force of about 20 kN to 60 kN. After being cooled to room temperature by a cooling roller, a liquid crystal polymer film with a thickness of about 50 micrometers (μm) is obtained.

[0038] The main differences in the preparation processes of the liquid crystal polymer films of Examples 1 to 12 and Comparative Examples 1 to 6 are: the type of liquid crystal polymer resin, the distance from the T-die to the die wheel surface, the feeding speed and the extruder temperature. The process parameters set for each example and comparative example are listed in Table 1 below.

[0039] Table 1: Process parameters for preparing liquid crystal polymer films of Examples 1 to 12 and Comparative Examples 1 to 6

[0040]

[0041]

[0042] The above-described method for preparing liquid crystal polymer films is only used to illustrate the embodiments of the present invention. Those skilled in the art can also use existing methods such as the laminate extension method and the blow-up method to prepare liquid crystal polymer films.

[0043] In one embodiment, after the liquid crystal polymer resin is extruded from the T-die, those skilled in the art can, as needed, pass the liquid crystal polymer resin and two high-temperature resistant films together between two casting rollers to further form a three-layer stacked structure. Then, at room temperature, the high-temperature resistant films are peeled off from the liquid crystal polymer resin to obtain the liquid crystal polymer film of the present invention. The high-temperature resistant film can be, for example, a polytetrafluoroethylene (PTFE) film, a polyimide (PI) film, or a polyether sulfone (PES) film, but is not limited to these.

[0044] Furthermore, those skilled in the art can perform post-processing on the prepared liquid crystal polymer film according to different needs, such as polishing, ultraviolet irradiation, plasma, etc., but are not limited to these. For example, for plasma post-processing, plasma post-processing can also be performed at 1 kilowatt in nitrogen, oxygen or air atmosphere, in a reduced pressure or normal pressure environment, depending on different needs, but are not limited to these.

[0045] Experimental Example 1: Surface Analysis of Rku, Ra and Rz of Liquid Crystal Polymer Films

[0046] In this test example, the liquid crystal polymer films prepared in Examples 1 to 12 and Comparative Examples 1 to 6 were used as test samples. The surface Rku of each test sample was analyzed according to the standard method specified in JIS B 0601:2001, and the surface Ra and Rz of each test sample were analyzed according to the standard method specified in JIS B0601:1994.

[0047] To obtain the Rku, Ra, and Rz of one surface of each sample, the surface morphology of each sample was first observed and its image was captured using a laser scanning conjugate microscope (model: LEXT OLS5000-SAF, purchased from Olympus Corporation, objective lens: MPLAPON-50xLEXT) at a temperature of 24±3℃ and a relative humidity of 63±3%, with a light source of 405 nm, an objective lens magnification of 50x, and an optical zoom of 1.0x. Next, the evaluation length was set to 4 mm, the high-pass filter cutoff value (λc) to 0.8 mm, the low-pass filter cutoff value (λs) to 2.5 μm, the mode was set to auto tilt removal, and the resolution was set to 1024 pixels × 1024 pixels to analyze the above images and obtain the Rku of each test sample. In addition, the evaluation length was set to 4 mm and the cutoff value was set to 0.8 mm to analyze the above images and obtain the Ra and Rz of each test sample.

[0048] Based on the above analytical method, the test results of Rku, Ra and Rz of one surface of the liquid crystal polymer film of Examples 1 to 12 and Comparative Examples 1 to 6 are consistent in Table 2 below.

[0049] Examples 1A to 12A: Laminated Plates

[0050] The liquid crystal polymer films of Examples 1 to 12 and Comparative Examples 1 to 6 were laminated with commercially available copper foil to prepare laminates as described in Examples 1A to 12A and Comparative Examples 1A to 6A, respectively. The product models and related descriptions of the commercially available copper foil are as follows:

[0051] Copper foil 1: CF-T49A-HD2, purchased from Fukuda Metal Foil Powder Industry Co., Ltd., with a radius (Rz) of approximately 1.2 μm; and

[0052] Copper foil 2: CF-H9A-HD2, purchased from Fukuda Metal Foil Powder Industry Co., Ltd., with an Rz of approximately 1.0 μm.

[0053] Select a liquid crystal polymer film with a thickness of approximately 50 μm and two commercially available copper foils with a thickness of approximately 12 μm. Cut the liquid crystal polymer film and the two commercially available copper foils into 20 cm × 20 cm pieces respectively. Then, stack the liquid crystal polymer film between the two commercially available copper foils. First, heat it at 180°C and 5 kg / cm². 2 The pressure was maintained for 60 seconds, followed by a temperature of 300℃ and a pressure of 20 kg / cm². 2The pressure was maintained for 25 minutes, and then cooled to room temperature to obtain a laminate. The sample numbers of the liquid crystal polymer film and two commercially available copper foils in each laminate are shown in Table 2 below.

[0054] Therefore, there are no particular limitations on the lamination method of the laminate. Those skilled in the art can use existing technologies such as line lamination or surface lamination to complete the lamination step. Applicable lamination machines for this invention include, but are not limited to, intermittent hot presses, roll-to-roll presses, and double-belt presses. Depending on different needs, those skilled in the art can also directly align the liquid crystal polymer film and copper foil and then perform heating and pressurization steps to complete the surface lamination step.

[0055] In other embodiments, those skilled in the art may also choose, depending on different needs, methods such as sputtering, electroplating, electroless plating, or vapor deposition to form a metal foil (e.g., copper foil) or an bonding layer (e.g., adhesive, nickel layer, cobalt layer, chromium layer, or alloy layer thereof) between the liquid crystal polymer film and the metal foil.

[0056] Experimental Example 2: Peel Strength Analysis of Laminated Laminates

[0057] In this test example, according to the test method of IPC-TM-650 No.:2.4.9, the laminated boards of Examples 1A to 12A and Comparative Examples 1A to 6A were made into etched specimens with a length of about 228.6 mm and a width of about 3.2 mm. Each etched specimen was then placed at a temperature of 23±2℃ and a relative humidity of 50±5% for 24 hours to allow it to stabilize. Next, each etched specimen was attached to the fixture of the test instrument (instrument model: HT-9102, purchased from Hung Ta Instrument Co., Ltd.) with double-sided tape. The etched specimens on the fixture were then peeled off at a peeling speed of 50.8 mm / min, and the peeling pull force during the peeling process was continuously recorded. Therefore, the peeling tensile force should be controlled within 15% to 85% of the range that the testing machine can withstand, the peeling length should be at least 57.2 mm, and the peeling tensile force of the initial 6.4 mm peeling should be ignored. The results are shown in Table 2 below.

[0058] Experimental Example 3: Signal Loss Analysis of Multilayer Laminates

[0059] In this test, the multilayer boards of Examples 1A to 12A and Comparative Examples 1A to 6A were fabricated into strip line specimens with a length of approximately 100 mm, a width of approximately 140 mm, and an impedance of approximately 50 ohms (Ω). The signal loss of each specimen at 10 GHz was measured using a microwave network analyzer (model: 8722ES, purchased from Agilent Technologies) and a probe (model: ACP40-250, purchased from Cascade Microtech). The test results for each multilayer board are listed in Table 2 below.

[0060] Table 2: Surface analysis results of liquid crystal polymer films of Examples 1 to 12 and Comparative Examples 1 to 6, and copper foil numbers and peel strength and signal loss test results used in the laminates of Examples 1A to 12A and Comparative Examples 1A to 6A.

[0061]

[0062] Discussion of Experimental Results

[0063] It should be understood that, in order to determine that the liquid crystal polymer film of the present invention can optimize the characteristics of the laminate, and in order to determine that the beneficial effects manifested on the laminate are attributable to the liquid crystal polymer film, those skilled in the art will compare the test results of multiple laminates containing the same copper foil when analyzing the above results, thereby determining the influence of the liquid crystal polymer film on the characteristics of the laminate.

[0064] As shown in Table 2 above, the Rku of one surface of the liquid crystal polymer film in Examples 1 to 12 is controlled between 3.0 and 60.0. Therefore, the laminates formed by laminating these liquid crystal polymer films with various commercially available copper foils (Examples 1A to 12A) can simultaneously possess the characteristics of high peel strength and low signal loss. Conversely, the Rku of one surface of the liquid crystal polymer film in Comparative Examples 1 to 6 exceeds the above range. Therefore, the laminates of Comparative Examples 1A to 6A cannot simultaneously obtain both high peel strength and low signal loss.

[0065] Specifically, comparing the test results of multiple laminates containing copper foil 1, it can be seen that when the Rku of the liquid crystal polymer film exceeds 60.0 (as in Comparative Example 1), the signal loss of the resulting laminate will be too high (as in Comparative Example 1A). However, if the Rku of the liquid crystal polymer film is lower than 3.0 (as in Comparative Example 2), the peel strength of the resulting laminate is significantly insufficient (as in Comparative Example 2A). Conversely, if the Rku of the liquid crystal polymer film is controlled between 3.0 and 60.0 (as in Examples 1 to 6), not only can a better peel strength be obtained between the liquid crystal polymer film and the metal foil, but the laminate also has the characteristic of low signal loss (as in Examples 1A to 6A).

[0066] In fact, even when using different copper foils to prepare the laminate, the liquid crystal polymer film of the present invention can provide a laminate with better peel strength and lower signal loss. Specifically, comparing the test results of multiple laminates containing copper foil 2, it can be seen that, as shown in Comparative Examples 3A to 6A, compared with liquid crystal polymer films with Rku not within the scope of the present invention (such as Comparative Examples 3 to 6), liquid crystal polymer films with Rku in the range of 3.0 to 60.0 (such as Examples 7 to 12) can provide laminates with better peel strength and lower signal loss (such as Examples 7A to 12A).

[0067] In summary, by controlling the Rku of the first surface of the liquid crystal polymer film to be between 3.0 and 60.0, the present invention can not only improve the peel strength between the liquid crystal polymer film and the metal foil, but also ensure that the laminate has low signal loss characteristics, thereby making the laminate containing this liquid crystal polymer film suitable for high-end 5G products.

Claims

1. A liquid crystal polymer film having opposing first and second surfaces, characterized in that, The kurtosis Rku of the first surface is 3.0 to 60.0, and the kurtosis Rku of the first surface is defined according to the standard method specified in JIS B 0601:2001; the ten-point average roughness of the first surface is 0.1 micrometer to 2.0 micrometer, and the ten-point average roughness of the first surface is defined according to the standard method specified in JIS B 0601:1994.

2. The liquid crystal polymer film as described in claim 1, characterized in that, The kurtosis Rku of the first surface ranges from 3.4 to 60.

0.

3. The liquid crystal polymer film as described in claim 1, characterized in that, The arithmetic mean roughness of the first surface is less than or equal to 0.09 micrometers, and the arithmetic mean roughness of the first surface is defined according to the standard method specified in JIS B 0601:1994.

4. The liquid crystal polymer film as described in claim 3, characterized in that, The arithmetic mean roughness of the first surface is between 0.02 micrometers and 0.09 micrometers.

5. The liquid crystal polymer film according to any one of claims 1 to 4, characterized in that, The kurtosis Rku of the second surface is between 3.0 and 60.0, and the kurtosis Rku of the second surface is defined according to the standard method specified in JIS B 0601:2001.

6. The liquid crystal polymer film as described in claim 5, characterized in that, The arithmetic mean roughness of the second surface is less than or equal to 0.09 micrometers, and the arithmetic mean roughness of the second surface is defined according to the standard method specified in JIS B 0601:1994.

7. The liquid crystal polymer film as described in claim 5, characterized in that, The ten-point average roughness of the second surface is less than or equal to 2.0 micrometers, and the ten-point average roughness of the second surface is defined according to the standard method specified in JIS B 0601:1994.

8. A laminated plate, characterized in that, The laminate includes a first metal foil and a liquid crystal polymer film as described in any one of claims 1 to 7, wherein the first metal foil is disposed on a first surface of the liquid crystal polymer film.

9. The laminated plate as claimed in claim 8, characterized in that, The laminate has a second metal foil disposed on the second surface of the liquid crystal polymer film.

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