A LCP film and preparation method thereof

Abstract

The present invention relates to the technical field of B29D7 / 00, and specifically to an LCP film and a preparation method thereof, comprising the following steps: subjecting LCP to melt extrusion and film blowing to obtain a film a, and then subjecting the film a to composite and heat treatment through a support to obtain an LCP film; the temperature of the heat treatment is from 150°C to the melting point of the LCP resin, and the treatment time is from 1 to 30 minutes. The LCP film provided by the present invention has high tear strength, which improves the processing stability of the LCP film during application. The LCP film provided by the present invention has excellent dimensional stability and good uniformity in thickness, which avoids the occurrence of bubbles in the LCP film during the application lamination process. The LCP film provided by the present invention has excellent dimensional stability and good bonding strength with copper foil, which avoids the phenomenon of separation of copper foil and LCP film when the LCP film is pressed with copper foil at high temperature.

Description

Technical Field

[0001] The invention relates to the technical field of B29D7 / 00, and in particular to an LCP film and a preparation method thereof. Background Art

[0002] LCP is a thermotropic liquid crystal polymer, which is a high-performance polymer material with excellent modulus, strength, barrier properties and other properties. Due to its low dielectric constant, its processed products will be used in the field of electronic communications. The molecular structure of LCP is a rigid segment, which is in a liquid crystal state in the molten state and has excellent fluidity, but it also has anisotropic defects and high requirements for processing technology. The LCP film obtained by stretching or extrusion blow molding has great rigidity, resulting in a low pass rate and low output of the LCP film. In addition, the bonding force between the formed LCP film and the metal foil is poor. There are also bubbles when it is pressed with the metal foil during application, and the copper foil and the LCP film will separate during high-temperature processing, which reduces the processing stability of the LCP film during application and further affects the bending resistance of the LCP film after being processed into electronic products. Due to the existence of the above problems, the LCP film is difficult to apply at the back end.

[0003] A Chinese patent with patent application number CN202011207859.1 discloses a method for preparing a tear-resistant, low-anisotropy liquid crystal polyester film. The temperature difference between the two rollers and the melting point of the liquid crystal polyester is used to make one side of the prepared liquid crystal polyester paper maintain high-order crystallization, thereby improving the tear strength of the liquid crystal polyester paper, while the other side retains the liquid crystal polyester paper with low anisotropy caused by the disordered liquid crystal polyester fibers in the liquid crystal polyester film, thereby obtaining a liquid crystal polyester film that meets both low anisotropy and high tear strength. The film can be directly used for circuit boards, reducing the manufacturing process of circuit boards; however, the patented technology does not provide solutions to the problems of reducing bubbles when the LCP film is pressed with metal foil during application, avoiding the separation of copper foil and LCP film during high-temperature processing, and improving the bending resistance of the LCP film after being processed into electronic products.

[0004] Therefore, the main technical problem that needs to be solved at present is to provide a treatment method that can solve the problems of poor bonding between LCP film and metal foil, reduce the appearance of bubbles when the LCP film is pressed with the metal foil during application, avoid the separation of copper foil and LCP film during high-temperature processing, and improve the bending resistance of LCP film after being processed into electronic products. Summary of the invention

[0005] In order to solve the above problems, the first aspect of the present invention provides a method for preparing an LCP film, comprising the following steps: subjecting the LCP to melt extrusion and film blowing to obtain a film a, and then subjecting the film a to composite with a support and heat treatment to obtain an LCP film; the heat treatment temperature is 150°C to the melting point of the LCP resin, and the treatment time is 1 to 30 minutes;

[0006] The ratio of the tensile strength of the LCP film in the MD direction to the TD direction (MD / TD) is 0.6 to 4;

[0007] The ratio of the elongation at break of the LCP film in the MD direction to that in the TD direction (MD / TD) is 0.4 to 2.5;

[0008] The dimensional stability of the LCP film in the MD direction is -0.1% to 0.1%, and the dimensional stability of the LCP film in the TD direction is -0.2% to 0.2%;

[0009] The thickness of the LCP film is ≥15 μm.

[0010] In one embodiment, the thickness of the film a is consistent with the thickness of the prepared LCP film.

[0011] The MD direction is the machine direction, length direction, and longitudinal direction of the film.

[0012] The TD direction is the width direction, or transverse direction, of the film.

[0013] In order to avoid the problem of LCP film being separated from copper foil at high temperature during application, the inventor creatively discovered during the experiment that the heat treatment of LCP film should not be too long. When the heating time exceeds 30 minutes, the tensile strength of the LCP film in the MD or TD direction will be reduced, and the dimensional stability of the LCP film will be reduced, which will further affect the bonding strength between the LCP film and the copper foil, causing the LCP film to be separated from the copper foil at high temperature during application. The possible reason is that as the heat treatment time increases, the arrangement time of the molecular chain segments in different directions in the LCP film will also increase, increasing the probability of unstable arrangement of the molecular chain segments, resulting in reduced tensile strength, tear strength and dimensional stability of the LCP film, and the problem of separation of the LCP film from the copper foil at high temperature.

[0014] In one embodiment, the melt viscosity of the LCP is ≥30 Pa·s.

[0015] In one embodiment, the melting point of the LCP is 270-330°C.

[0016] Further, the melting point of the LCP may be 270°C, 275°C, 280°C, 285°C, 290°C, 295°C, 300°C, 305°C, 310°C, 315°C, 320°C, 325°C, or 330°C.

[0017] The melting point is determined according to GB / T 19466.3-2004, specifically the secondary heating melting peak temperature.

[0018] The viscosity test standard is GB / T 25278-2010, using a die with an inner diameter of 0.5 mm, at 20°C above the melting temperature and for 1000 seconds. -1 The melt viscosity is measured by a capillary rheometer at a shear rate of .

[0019] In one embodiment, the melting point of the LCP is 280°C, 310°C, or 330°C.

[0020] In one embodiment, the melt viscosity of the LCP is 35-45 Pa·s, the melting point of the LCP is 330° C., and the manufacturer model of the LCP is Polyplastics C950RX from Japan.

[0021] In one embodiment, the melt viscosity of the LCP is 40-50 Pa·s, the melting point of the LCP is 280° C., and the manufacturer model of the LCP is Polyplastics A950RX from Japan.

[0022] In one embodiment, the melting point of the LCP is 310° C., and the manufacturer model of the LCP is A310 from Shanghai Pulite Composite Materials Co., Ltd.

[0023] In one embodiment, the step of compounding the film a through a support is to use a metal foil as a support to press the film a together to obtain a film a metal foil laminate.

[0024] In one embodiment, the film a is laminated with a metal foil by a double-sided lamination process or a single-sided lamination process to obtain a film a metal foil laminate, which is then heat treated.

[0025] The double-sided lamination process: film a is used as the middle layer, the upper and lower sides are covered with metal foil, and a heated roller calender is used for lamination.

[0026] The single-sided lamination process: one side of the film a is covered with a metal foil and is laminated using a heated roller calender.

[0027] In order to avoid the problem of bubbles appearing when the LCP film is pressed against the metal foil during the application process, the inventor creatively discovered during the experiment that the heat treatment temperature of the LCP film cannot be too high. When the heat treatment temperature exceeds the melting point of the LCP resin, the thickness uniformity of the LCP film will be reduced, resulting in bubbles appearing when the LCP film is pressed against the metal foil during the application process. The possible reason is that when the LCP film is heated at a higher temperature in a short period of time, the scale for adjusting the arrangement of molecular chain segments in different directions in the LCP film will become larger, resulting in various anisotropic differences in the density of the molecular chain segment arrangement, which will deteriorate the thickness uniformity of the LCP film at the microscopic level, resulting in bubbles appearing when the LCP film is pressed against the metal foil during the application process.

[0028] In one embodiment, the heat treatment is performed by heating in a gradient heating manner.

[0029] In one embodiment, the gradient temperature increase method includes increasing the temperature from 150° C. to the melting point of the LCP resin at a heating rate of 100° C. / min.

[0030] In one embodiment, the gradient heating method includes multi-stage heating; the multi-stage heating includes heating from 150°C to 240°C at a heating rate of 100°C / min, and then heating from 240°C to the melting point of the LCP resin at a heating rate of 5-30°C / min.

[0031] In order to improve the bonding property between the LCP film and the metal foil and enhance the bonding strength between the LCP film and the metal foil, the inventor creatively discovered during the experiment that when the heating temperature of the LCP film obtained by heat treatment is increased from 150°C to the melting point of the LCP resin and a gradient heating treatment method is adopted, the dimensional stability of the LCP film, the tear strength of the LCP film, and the bonding strength between the LCP film and the metal foil can be improved. The possible reason is that surface heat treatment of the LCP film, especially gradient heating treatment for a short time, can adjust the arrangement of molecular chain segments in different directions in the LCP film, so that the LCP film can maintain the stability of various anisotropic dimensions during the later application process. By adjusting the arrangement of molecular chain segments in different directions, the tear strength of the LCP film can be improved, and the bonding strength between the LCP film and the metal foil can be further improved. When the heating temperature of the LCP film is lower than 150°C, the arrangement of molecular chain segments in different directions in the LCP film cannot be effectively adjusted, and defects in the anisotropic direction will exist, which reduces the dimensional stability, elongation at break and tear strength of the LCP film, and further reduces the bonding strength between the LCP film and the metal foil.

[0032] In one embodiment, the LCP film has a thickness of 15 to 150 μm.

[0033] In one embodiment, the LCP film has a thickness of 25 μm.

[0034] In one embodiment, the method for preparing the LCP film comprises the following steps:

[0035] S1: The LCP is melt-extruded, and the melt passes through an annular die to obtain a film a by a film blowing method;

[0036] S2: Compounding the film by laminating: Using metal foil as a support, laminating the film a with the metal foil by double-sided lamination or single-sided lamination to obtain a film a metal foil laminate, the lamination temperature being 150-220°C;

[0037] S3: Heat treatment to obtain an LCP film: heat treatment is performed by a gradient temperature increase method, wherein the gradient temperature increase method is to increase the temperature from 150° C. to the melting point of the LCP resin at a heating rate of 100° C. / min.

[0038] In one embodiment, the method for preparing the LCP film comprises the following steps:

[0039] S1: The LCP is melt-extruded, and the melt passes through an annular die to obtain a film a by a film blowing method;

[0040] S2: Compounding the film by laminating: Using metal foil as a support, laminating the film a with the metal foil by double-sided lamination or single-sided lamination to obtain a film a metal foil laminate, the lamination temperature being 150-220°C;

[0041] S3: Heat treatment to obtain LCP film: heat treatment is performed by a gradient heating method, wherein the gradient heating method is to heat from 150°C to 240°C at a heating rate of 100°C / min, and then to heat from 240°C to the melting point of the LCP resin at a heating rate of 5-30°C / min.

[0042] In one embodiment, in S2, the films are laminated by a lamination process, and a lamination temperature of 200° C. is used.

[0043] In order to improve the excellent bending resistance of LCP film in back-end applications, the inventor creatively discovered during the experiment that the time for heat treatment of LCP film by gradient heating method is 1 to 30 minutes, and the heating temperature is increased from 150°C to the melting point of LCP resin to improve the excellent bending resistance of LCP film in back-end applications, but the treatment time cannot be too short. The possible reason is that when the treatment time is too short, it will affect the regularity of the molecular chain structure in the LCP film to adjust in a short time, increase the rigidity of the LCP film, reduce the tear strength of the LCP film, and also cause the elongation at break to decrease, further reducing the excellent bending resistance of the LCP film in back-end applications.

[0044] A second aspect of the present invention provides an LCP film, which is prepared by the above-mentioned method for preparing the LCP film.

[0045] In one embodiment, the peel strength between the LCP film and the copper foil is greater than 0.5 N / mm; the roughness of the copper foil is 0.5-20 μm, and the thickness of the copper foil is 9-35 μm.

[0046] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0047] 1. The LCP film provided by the present invention has good bonding strength with the copper foil during high-temperature processing, and further improves the stability of the LCP film during application.

[0048] 2. The LCP film provided by the present invention has high tear strength, which improves the processing stability of the LCP film during application.

[0049] 3. The LCP film provided by the present invention has excellent dimensional stability and good uniformity in thickness, thereby preventing bubbles from appearing in the LCP film during the lamination process of application.

[0050] 4. The LCP film provided by the present invention has excellent dimensional stability and good bonding strength with the copper foil, thereby avoiding the phenomenon of separation of the copper foil and the LCP film when the LCP film is pressed onto the copper foil at high temperature.

[0051] 5. The LCP film provided by the present invention has higher elongation at break and tear strength, which improves the bending resistance of the LCP film processed into flexible copper-clad laminates and flexible circuit board products. DETAILED DESCRIPTION

[0052] Example 1

[0053] A first aspect of the present embodiment provides a method for preparing an LCP film, comprising the following steps:

[0054] S1: The LCP is melt-extruded, and the melt passes through an annular die to obtain a film a by a film blowing method;

[0055] S2: Compounding the film by laminating: Using metal foil as a support, laminating the film a with the metal foil by a single-sided lamination process to obtain a film a metal foil laminate, the lamination temperature being 200°C;

[0056] S3: heat treatment to obtain the LCP film: heat treatment is performed by a gradient temperature increase method, wherein the gradient temperature increase method is to increase the temperature from 150° C. to 330° C. at a heating rate of 100° C. / min.

[0057] The melting point of the LCP is 330° C., and the manufacturer model of the LCP is Japan Polyplastics C950RX.

[0058] The thickness of the LCP film is 25 μm.

[0059] A second aspect of the present embodiment provides an LCP film, which is prepared by the above-mentioned method for preparing the LCP film.

[0060] Example 2

[0061] A first aspect of the present embodiment provides a method for preparing an LCP film, comprising the following steps:

[0062] S1: The LCP is melt-extruded, and the melt passes through an annular die to obtain a film a by a film blowing method;

[0063] S2: Compounding the film by laminating: Using metal foil as a support, laminating the film a with the metal foil by double-sided lamination process to obtain a film a metal foil laminate, the lamination temperature being 200°C;

[0064] S3: heat treatment to obtain the LCP film: heat treatment is performed by a gradient temperature increase method, wherein the gradient temperature increase method is to increase the temperature from 150° C. to 330° C. at a heating rate of 100° C. / min.

[0065] The melting point of the LCP is 330° C., and the manufacturer model of the LCP is Japan Polyplastics C950RX.

[0066] The thickness of the LCP film is 25 μm.

[0067] A second aspect of the present embodiment provides an LCP film, which is prepared by the above-mentioned method for preparing the LCP film.

[0068] Example 3

[0069] A first aspect of the present embodiment provides a method for preparing an LCP film, comprising the following steps:

[0070] S1: The LCP is melt-extruded, and the melt passes through an annular die to obtain a film a by a film blowing method;

[0071] S2: Compounding the film by laminating: Using metal foil as a support, laminating the film a with the metal foil by double-sided lamination process to obtain a film a metal foil laminate, the lamination temperature being 200°C;

[0072] S3: Heat treatment to obtain an LCP film: heat treatment is performed by a gradient heating method, wherein the gradient heating method is to increase the temperature from 150°C to 240°C at a heating rate of 100°C / min, and then to increase the temperature from 240°C to 330°C at a heating rate of 5°C / min.

[0073] The melting point of the LCP is 330° C., and the manufacturer model of the LCP is Japan Polyplastics C950RX.

[0074] The thickness of the LCP film is 25 μm.

[0075] A second aspect of the present embodiment provides an LCP film, which is prepared by the above-mentioned method for preparing the LCP film.

[0076] Example 4

[0077] A first aspect of the present embodiment provides a method for preparing an LCP film, comprising the following steps:

[0078] S1: The LCP is melt-extruded, and the melt passes through an annular die to obtain a film a by a film blowing method;

[0079] S2: Compounding the film by laminating: Using metal foil as a support, laminating the film a with the metal foil by double-sided lamination process to obtain a film a metal foil laminate, the lamination temperature being 200°C;

[0080] S3: Heat treatment to obtain an LCP film: heat treatment is performed using a gradient temperature increase method, wherein the gradient temperature increase method is to increase the temperature from 150°C to 240°C at a heating rate of 100°C / min, and then to increase the temperature from 240°C to 330°C at a heating rate of 30°C / min.

[0081] The melting point of the LCP is 330° C., and the manufacturer model of the LCP is Japan Polyplastics C950RX.

[0082] The thickness of the LCP film is 25 μm.

[0083] A second aspect of the present embodiment provides an LCP film, which is prepared by the above-mentioned method for preparing the LCP film.

[0084] Example 5

[0085] A first aspect of the present embodiment provides a method for preparing an LCP film, comprising the following steps:

[0086] S1: The LCP is melt-extruded, and the melt passes through an annular die to obtain a film a by a film blowing method;

[0087] S2: Compounding the film by laminating: Using metal foil as a support, laminating the film a with the metal foil by double-sided lamination process to obtain a film a metal foil laminate, the lamination temperature being 200°C;

[0088] S3: Heat treatment to obtain an LCP film: heat treatment is performed by a gradient heating method, wherein the gradient heating method is to increase the temperature from 150°C to 240°C at a heating rate of 100°C / min, and then to increase the temperature from 240°C to 330°C at a heating rate of 20°C / min.

[0089] The melting point of the LCP is 330° C., and the manufacturer model of the LCP is Japan Polyplastics C950RX.

[0090] The thickness of the LCP film is 25 μm.

[0091] A second aspect of the present embodiment provides an LCP film, which is prepared by the above-mentioned method for preparing the LCP film.

[0092] Example 6

[0093] A first aspect of the present embodiment provides a method for preparing an LCP film, comprising the following steps:

[0094] S1: The LCP is melt-extruded, and the melt passes through an annular die to obtain a film a by a film blowing method;

[0095] S2: Compounding the film by laminating: Using metal foil as a support, laminating the film a with the metal foil by double-sided lamination process to obtain a film a metal foil laminate, the lamination temperature being 200°C;

[0096] S3: Heat treatment to obtain an LCP film: heat treatment is performed by a gradient heating method, wherein the gradient heating method is to increase the temperature from 150°C to 240°C at a heating rate of 100°C / min, and then to increase the temperature from 240°C to 280°C at a heating rate of 20°C / min.

[0097] The melting point of the LCP is 280° C., and the manufacturer model of the LCP is Japan Polyplastics A950RX.

[0098] The thickness of the LCP film is 25 μm.

[0099] A second aspect of the present embodiment provides an LCP film, which is prepared by the above-mentioned method for preparing the LCP film.

[0100] Example 7

[0101] A first aspect of the present embodiment provides a method for preparing an LCP film, comprising the following steps:

[0102] S1: The LCP is melt-extruded, and the melt passes through an annular die to obtain a film a by a film blowing method;

[0103] S2: Compounding the film by laminating: Using metal foil as a support, laminating the film a with the metal foil by double-sided lamination process to obtain a film a metal foil laminate, the lamination temperature being 200°C;

[0104] S3: Heat treatment to obtain an LCP film: heat treatment is performed using a gradient temperature increase method, wherein the gradient temperature increase method is to increase the temperature from 150°C to 240°C at a temperature increase rate of 100°C / min, and then to increase the temperature from 240°C to 310°C at a temperature increase rate of 20°C / min.

[0105] The melting point of the LCP is 310° C., and the manufacturer model of the LCP is A310 from Shanghai Pulit Composite Materials Co., Ltd.

[0106] The thickness of the LCP film is 25 μm.

[0107] A second aspect of the present embodiment provides an LCP film, which is prepared by the above-mentioned method for preparing the LCP film.

[0108] Comparative Example 1

[0109] This comparative example provides a method for preparing an LCP film. The specific implementation method is the same as that of Example 5. The difference between this comparative example and Example 5 is as follows:

[0110] S3: heat treatment to obtain LCP film: the heat treatment adopts constant temperature heating treatment, the heating temperature is 140° C., and the treatment time is 2 min.

[0111] The thickness of the LCP film is 25 μm.

[0112] Comparative Example 2

[0113] This comparative example provides a method for preparing an LCP film. The specific implementation method is the same as that of Example 5. The difference between this comparative example and Example 5 is as follows:

[0114] S3: heat treatment to obtain an LCP film: the heat treatment adopts a constant temperature heating treatment, the heating temperature of the heat treatment is 330° C., and the treatment time is 10 s.

[0115] The thickness of the LCP film is 25 μm.

[0116] Comparative Example 3

[0117] This comparative example provides a method for preparing an LCP film. The specific implementation method is the same as that of Example 5. The difference between this comparative example and Example 5 is as follows:

[0118] S3: heat treatment to obtain an LCP film: the initial heating temperature of the heat treatment is 150° C., the final heating temperature is 330° C., and the temperature is increased at a heating rate of 200° C. / min.

[0119] The thickness of the LCP film is 25 μm.

[0120] Comparative Example 4

[0121] This comparative example provides a method for preparing an LCP film. The specific implementation method is the same as that of Example 5. The difference between this comparative example and Example 5 is as follows:

[0122] S3: Heat treatment to obtain an LCP film: heat treatment is performed by a gradient temperature increase method, wherein the gradient temperature increase method is to increase the temperature from 150°C to 240°C at a temperature increase rate of 100°C / min, and then to increase the temperature from 240°C to 330°C at a temperature increase rate of 2°C / min.

[0123] The thickness of the LCP film is 25 μm.

[0124] Comparative Example 5

[0125] This comparative example provides a method for preparing an LCP film. The specific implementation method is the same as that of Example 6. The difference between this comparative example and Example 6 is as follows:

[0126] S3: heat treatment to obtain the LCP film, wherein the heat treatment adopts constant temperature heating treatment, the heating temperature of the heat treatment is 140° C., and the treatment time is 1.5 min.

[0127] The thickness of the LCP film is 25 μm.

[0128] Comparative Example 6

[0129] This comparative example provides a method for preparing an LCP film. The specific implementation method is the same as that of Example 6. The difference between this comparative example and Example 6 is as follows:

[0130] S3: heat treatment to obtain an LCP film: the initial heating temperature of the heat treatment is 150° C., the final heating temperature is 285° C., and the temperature is increased at a heating rate of 200° C. / min.

[0131] The thickness of the LCP film is 25 μm.

[0132] Comparative Example 7

[0133] This comparative example provides a method for preparing an LCP film. The specific implementation method is the same as that of Example 7. The difference between this comparative example and Example 7 is as follows:

[0134] S3: heat treatment to obtain an LCP film: the initial heating temperature of the heat treatment is 150° C., the final heating temperature is 310° C., and the temperature is increased at a heating rate of 200° C. / min.

[0135] The thickness of the LCP film is 25 μm.

[0136] Comparative Example 8

[0137] This comparative example provides a method for preparing an LCP film. The specific implementation method is the same as that of Example 7. The difference between this comparative example and Example 7 is as follows:

[0138] S3: Heat treatment to obtain an LCP film: heat treatment is performed by a gradient temperature increase method, wherein the gradient temperature increase method is to increase the temperature from 150°C to 240°C at a temperature increase rate of 100°C / min, and then to increase the temperature from 240°C to 310°C at a temperature increase rate of 2°C / min.

[0139] The thickness of the LCP film is 25 μm.

[0140] The thickness of the LCP film in this application is measured by a thickness gauge according to the ASTM D645 method.

[0141] Performance Test:

[0142] 1Tensile strength, elongation at break:

[0143] The tensile strength and elongation at break were tested by a film tensile strength tester according to the GB / T 1040.3-2006 method. Ten test samples were taken for each embodiment, and the maximum and minimum test results were removed to take the average value of the test results. The test results are shown in Table 1.

[0144] 2. Peel strength and separation test of LCP film and copper foil:

[0145] The present invention heat-presses a liquid crystal polyester film and a copper foil to composite, and tests the maximum force required for the LCP film to peel off the copper foil, that is, the 90° peeling strength, to evaluate the bonding strength between the LCP film and the metal, and the test is performed with reference to the ASTM D3330 method; the hot pressing temperature is the melting point temperature of the LCP, the time is 2 minutes, and 10 test samples are taken for testing in each embodiment, and the maximum value and the minimum value of the test result are removed, and the average value of the test result is taken, and the test results are shown in Table 1; and whether the LCP film will separate from the copper foil during the hot pressing process is observed, and if 9-10 samples in the test results do not separate, the judgment result is A; if 6-8 samples in the test results do not separate, the judgment result is B; if 3-5 samples in the test results do not separate, the judgment result is C; if 0-2 samples in the test results do not separate, the judgment result is D; the test results are shown in Table 2.

[0146] The surface roughness of the copper foil is 5 μm, and the thickness of the copper foil is 12 μm.

[0147] 3. Dimensional stability

[0148] Test method: Refer to JIS C6471-1995 9.6 method for testing. Specifically, cut a 240*300mm film, mark 4 points according to the standard requirements and measure the distance between each point. Then place the film in a 150℃ oven for 30 minutes, measure the distance between the 4 points again and calculate the dimensional stability.

[0149] In each embodiment, 10 test samples were taken for testing, the maximum value and the minimum value of the test results were removed, and the average value of the test results was taken. The test results are shown in Table 1.

[0150] 4. Tear strength

[0151] Test method: The tear strength was tested according to the test method of 2.4.16 of the initial tear strength "Test Method Manual" Initial tear strength test method for flexible insulating materials IPC-TM-650 (03 / 14B version); 10 test samples were taken for testing in each embodiment, the maximum and minimum test results were removed, and the average test result was taken. The test results are shown in Table 1.

[0152] 5. Bubble test

[0153] (1) Observe whether bubbles appear when the LCP film is pressed with the metal foil (copper foil) during the application process. Ten test samples are taken for testing in each embodiment. If 9-10 samples do not have bubbles in the test results, the judgment result is A; if 6-8 samples do not have bubbles in the test results, the judgment result is B; if 3-5 samples do not have bubbles in the test results, the judgment result is C; if 0-2 samples do not have bubbles in the test results, the judgment result is D. The test results are shown in Table 2.

[0154] 6. Bending resistance test

[0155] In each embodiment, 10 test samples were taken for testing, the maximum value and the minimum value of the test result were removed, and the average value of the test result was taken to test the number of times the LCP film could be bent horizontally and vertically without being damaged. The test results are shown in Table 1.

[0156] Table 1

[0157]

[0158] Table 2

[0159] Example Bubble test Split Testing Bending resistance test Example 1 A A 255 Example 2 A A 258 Example 3 A A 257 Example 4 A A 254 Example 5 A A 256 Example 6 A A 254 Example 7 A A 256 Comparative Example 1 C D 174 Comparative Example 2 D D 169 Comparative Example 3 B C 137 Comparative Example 4 C D 168 Comparative Example 5 C D 184 Comparative Example 6 D D 164 Comparative Example 7 B C 143 Comparative Example 8 C D 167

Claims

1. A method for preparing an LCP film, characterized in that: The method comprises the following steps: subjecting LCP to melt extrusion and film blowing to obtain film a, and then subjecting film a to composite with a support and heat treatment to obtain an LCP film; the heat treatment temperature is from 150°C to the melting point of the LCP resin, and the treatment time is from 1 to 30 minutes; The ratio of the tensile strength of the LCP film in the MD direction to the TD direction (MD / TD) is 0.6-4; The ratio of the elongation at break of the LCP film in the MD direction to that in the TD direction (MD / TD) is 0.4-2.5; The dimensional stability of the LCP film in the MD direction is -0.1% to 0.1%, and the dimensional stability of the LCP film in the TD direction is -0.2% to 0.2%; The thickness of the LCP film is ≥15 μm; The heat treatment is performed by heating in a gradient heating manner; The gradient temperature increase includes increasing the temperature from 150° C. to 240° C. at a temperature increase rate of 100° C. / min, and then increasing the temperature from 240° C. to the melting point of the LCP resin at a temperature increase rate of 5-30° C. / min.

2. The method for preparing the LCP film according to claim 1, wherein: The melt viscosity of the LCP is ≥30 Pa·s.

3. The method for preparing the LCP film according to claim 1, characterized in that: The melting point of the LCP is 270-330°C.

4. The method for preparing the LCP film according to claim 1, characterized in that: The film a is laminated with a metal foil by a double-sided lamination process or a single-sided lamination process to obtain a film a metal foil laminate, which is then heat treated.

5. The method for preparing the LCP film according to claim 1, characterized in that: The thickness of the LCP film is 15-150 μm.

6. An LCP film, characterized in that: The LCP film is prepared by the method for preparing the LCP film according to any one of claims 1 to 5.

7. The LCP film according to claim 6, characterized in that The peel strength between the LCP film and the copper foil is greater than 0.5 N / mm.

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