TWI877793B - Polyimide and polyimide film - Google Patents

Abstract

A polyimide is provided. The polyimide comprises a repeating unit derived from dianhydrides and a repeating unit derived from diamines. The infrared absorption spectrum of the polyimide obtained via Fourier transform infrared spectroscopy (FTIR) with attenuated total reflectance (ATR) has a characteristic peak A from 1753 cm ^-1to 1803cm ^-1, a characteristic peak B from 1635 cm ^-1to 1752 cm ^-1, and a characteristic peak C from 1160 cm ^-1to 1170 cm ^-1, wherein the characteristic peak A has an characteristic peak area a, the characteristic peak B has an characteristic peak area b, the characteristic peak C has an characteristic peak area c, b/a is not larger than 25.00, and c/b is not less than 0.3000.

Description

Polyimide and polyimide film

The present invention relates to a polyimide, more particularly to a polyimide having specific Fourier transform infrared spectral characteristics. The present invention also relates to a polyimide film.

In order to meet the requirements of high-frequency and high-speed transmission, the insulating materials used to manufacture printed circuit boards must have a low dielectric constant (Dk) and a low dissipation factor (Df). Generally, the dielectric properties of insulating materials will deteriorate significantly due to the absorption of moisture. However, in the process of manufacturing printed circuit boards, the circuits will undergo processes such as blackening, water washing and drying. Therefore, the insulating materials of printed circuit boards must still have good dielectric properties after undergoing processes such as water absorption and drying to maintain the characteristics of the printed circuit boards. In addition, the insulating materials of printed circuit boards need to have a coefficient of thermal expansion (CTE) similar to that of metal foil (e.g., copper foil) to avoid peeling or board explosion during the manufacturing process of printed circuit boards.

It is known that polyimide can be used as an insulating material for preparing printed circuit boards. However, existing polyimide has technical problems such as poor dielectric properties, excessive water absorption, CTE incompatibility with metal foil, and obvious deterioration of dielectric properties after water absorption, and further improvement is still needed.

In view of this, the present invention provides a polyimide derived from dianhydride and diamine, which has excellent dielectric properties, low water absorption, and CTE suitable for metal foil, and the dielectric properties of the polyimide will not be significantly deteriorated after absorbing water, and is particularly suitable as an insulating material for printed circuit boards.

Therefore, one object of the present invention is to provide a polyimide comprising repeating units derived from a dianhydride and repeating units derived from a diamine, wherein the polyimide has an infrared absorption spectrum obtained by Fourier transform infrared spectroscopy (FTIR) with attenuated total reflectance (ATR) having a characteristic peak A at 1753 cm ^-1 to 1803 cm ^-1 , a characteristic peak B at 1635 cm ^-1 to 1752 cm ^-1 , and a characteristic peak C at 1160 cm ^-1 to 1170 cm -1. ^-1 , wherein the characteristic peak A has a characteristic peak area a, the characteristic peak B has a characteristic peak area b, the characteristic peak C has a characteristic peak area c, and b/a is not greater than 25.00, and c/b is not less than 0.3000.

In some implementations of the present invention, 10.00 ≤ b/a ≤ 25.00.

In some implementations of the present invention, 10.00 ≤ b/a ≤ 18.50.

In some implementations of the present invention, 0.32 ≤ c/b ≤ 0.54.

In some implementations of the present invention, 0.34 ≤ c/b ≤ 0.52.

In some embodiments of the present invention, FTIR is measured under the following conditions: ZnSe is used as the attenuated total reflection crystal, the scanning range is 650 cm ^-1 to 4000 cm ^-1 , and the scanning times are 8 times.

In some embodiments of the present invention, the repeating units derived from diamine include repeating units derived from aliphatic diamine.

In some embodiments of the present invention, the repeating units derived from diamine include repeating units derived from aliphatic diamine and repeating units derived from aromatic diamine.

In some embodiments of the present invention, the repeating units derived from a dianhydride include repeating units derived from an aromatic dianhydride.

In some embodiments of the present invention, the main polymer chain of the polyimide comprises an ester functional group.

In some embodiments of the present invention, based on the total number of all functional groups of the polyimide, the ratio of the number of ester functional groups to the number of imide functional groups is not less than 0.8.

Another object of the present invention is to provide a polyimide film, which is prepared from the polyimide as described above.

In order to make the above-mentioned objectives, technical features and advantages of the present invention more clearly understood, some specific implementation modes are described in detail below.

The following will specifically describe some specific implementation aspects of the present invention; however, the present invention can also be implemented in a variety of different forms, and the protection scope of the present invention should not be limited to the specific implementation aspects.

Unless otherwise specified, "a", "an", "the" and similar terms used in this specification and the scope of the patent application should be understood to include both singular and plural forms.

The advantages of the present invention over the prior art are that polyimide has excellent dielectric properties, low water absorption, and CTE that is compatible with metal foil (i.e., CTE that is close to that of metal foil), and has good dielectric properties after absorbing water. The following provides a detailed description of the polyimide of the present invention and its related applications.

1. Polyimide

1.1. Properties of polyimide

The polyimide of the present invention has a specific infrared absorption spectrum, which is obtained by Fourier transform infrared spectroscopy (FTIR) with attenuated total reflectance (ATR). The infrared absorption spectrum of the polyimide of the present invention has a characteristic peak A at 1753 cm ^-1 to 1803 cm ^-1 , a characteristic peak B at 1635 cm ^-1 to 1752 cm ^-1 , and a characteristic peak C at 1160 cm ^-1 to 1170 cm ^-1 , wherein the characteristic peak A has a characteristic peak area a, the characteristic peak B has a characteristic peak area b, and the characteristic peak C has a characteristic peak area c.

In the infrared absorption spectrum of the polyimide of the present invention, b/a is not greater than 25.00. For example, b/a may be 25.00, 24.75, 24.50, 24.25, 24.00, 23.75, 23.50, 23.25, 23.00, 22.75, 22.50, 22.25, 22.00, 21.75, 21.50, 21.25, 21.00, 20.75, 20.50, 20.25, 20.00, 19.75, 19.50, 19. .25, 19.00, 18.75, 18.50, 18.40, 18.25, 18.00, 17.75, 17.50, 17.25, 17.00, 16.75, 16.50 ,16.25,16.00,15.75,15.50,15.25,15.00,14.75,14.50,14.25,14.00,13.75,13.50,13. 25, 13.00, 12.75, 12.50, 12.25, 12.00, 11.75, 11.50, 11.25, 11.00, 10.75, 10.50, 10.25, 10.05, 10.00, 9.75, 9.50, 9.25, 9.00, 8.75, 8.50, 8.25, 8.00, 7.75, 7.50, 7.25, 7.00, 6.7 5, 6.50, 6.25, 6.00, 5.75, 5.50, 5.25, 5.00, 4.75, 4.50, 4.25, 4.00, 3.75, 3.50, 3.25, 3.00, 2.75, 2.50, 2.25, 2.00, 1.75, 1.50, 1.25, 1.00, 0.75, 0.50, or 0.25, or a range formed by any two of the foregoing values. In some embodiments of the present invention, 10.00 ≤ b/a ≤ 25.00, more specifically 10.00 ≤ b/a ≤ 18.50, and even more specifically 10.05 ≤ b/a ≤ 18.40. If the b/a value of polyimide falls outside the specified range, the CTE of polyimide cannot be adapted to the copper foil, and the dielectric properties deteriorate significantly after absorbing water.

In the infrared absorption spectrum of the polyimide of the present invention, c/b is not less than 0.3000. For example, c/b may be 0.3000, 0.3100, 0.3200, 0.3300, 0.3350, 0.3400, 0.3450, 0.3500, 0.3600, 0.3700, 0.3800, 0.3900, 0.4000, 0.4100, 0.4200, 0.4300, 0.4400, 0.4500. , 0.4600, 0.4700, 0.4800, 0.4900, 0.5000, 0.5100, 0.5200, 0.5300, 0.5400, 0.5 500, 0.5600, 0.5700, 0.5800, 0.5900, 0.6000, 0.6100, 0.6200, 0.6300, 0.6400, 0 .6500, 0.6600, 0.6700, 0.6800, 0.6900, 0.7000, 0.7100, 0.7200, 0.7300, 0.740 0, 0.7500, 0.7600, 0.7700, 0.7800, 0.7900, 0.8000, 0.8100, 0.8200, 0.8300, 0.8 400, 0.8500, 0.8600, 0.8700, 0.8800, 0.8900, 0.9000, 0.9100, 0.9200, 0.9300, 0.9400, 0.9500, 0.9600, 0.9700, 0.9800, 0.9900, or 1.0000, or a range formed by any two of the foregoing values. In some embodiments of the present invention, 0.32 ≤ c/b ≤ 0.54, more specifically 0.34 ≤ c/b ≤ 0.52, and even more specifically 0.345 ≤ c/b ≤ 0.52. If the c/b value in the infrared absorption spectrum of polyimide falls outside the specified range, the polyimide cannot have a CTE close to that of copper foil and the dielectric properties of the polyimide after absorbing water deteriorate significantly.

The FTIR measurement was performed under the following conditions: using ZnSe as the attenuated total reflection crystal, the scanning range was 650 cm ^-1 to 4000 cm ^-1 , the scanning times were 8 times, and the resolution was 1 cm ^-1 . The instrument used to implement FTIR is an infrared spectrometer purchased from Perkin Elmer (model: FTIR spectrometer spectrum two), the fixture is an ATR fixture purchased from PIKE Technologies (model: MIRacle ^TM Single Reflection ATR), and the software used to analyze the FTIR results is Perkin Elmer 10.5.3.738, in which the characteristic peak starting point, characteristic peak apex point and characteristic peak end point (the point selected is 0 after a first differentiation) are selected through the software, and then the area from the starting point to the apex to the end point is used as the integration range, and the characteristic peak area is calculated by the software.

1.2. Structure and preparation of polyimide

Generally speaking, the synthesis method of polyimide may include a two-stage condensation method and a one-stage condensation method. The two-stage condensation method is usually to form poly(amic acid) (PAA) by condensation polymerization of dianhydride and diamine, and then heat the poly(amic acid) to dehydrate and close the ring to form polyimide. The one-stage condensation method is usually to form polyimide by reacting dianhydride and diisocyanate at high temperature.

The preparation method of the polyimide of the present invention is not particularly limited. In some embodiments of the present invention, the polyimide is formed by polymerizing dianhydride and diamine using a two-stage condensation method, and thus comprises repeating units derived from dianhydride and repeating units derived from diamine. Specifically, the diamine is first placed in a flask under a nitrogen atmosphere, and a solvent is added to completely dissolve the diamine, and then the dianhydride is added, and the intermediate solution is stirred at room temperature for 12 hours to obtain a polyamide solution, and then the polyamide is subjected to a thermal ring closure reaction at a high temperature to obtain the polyimide. The preparation of the polyimide of the present invention is preferably carried out under the following conditions: (1) based on the total amount of diamines, the amount of long carbon chain aliphatic diamine is preferably not more than 20 mol%; and (2) based on the total number of all functional groups of the polyimide, the number ratio of ester functional groups to imide functional groups is 0.8 to 2.0.

The type of dianhydride that can be used to form the polyimide of the present invention is not particularly limited, and examples thereof include but are not limited to 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), pyromellitic dianhydride (PMDA), 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid-1,4-phenylene ester (TAHQ), 4,4'-bisphenol A dianhydride (4,4'-bisphenol A dianhydride), and 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid-1,4-phenylene ester (TAHQ). dianhydride (BPADA), 4,4'-oxydiphthalic anhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and hydroquinone diphthalic anhydride (HQDA). Each of the above-mentioned dianhydrides can be used alone or in combination. In some embodiments of the present invention, the repeating units derived from the dianhydride include repeating units derived from aromatic dianhydrides, and the aromatic dianhydrides can be selected from the following group: a-BPDA, s-BPDA, TAHQ, BTDA, ODPA, and combinations thereof.

There is no particular limitation on the type of diamine that can be used to form the polyimide of the present invention, and the diamine can be selected from aliphatic diamines and aromatic diamines. Examples of the aliphatic diamine include, but are not limited to, 1,2-ethylenediamine, 1,2-propylenediamine, 1,3-diaminopropane, 1,5-diaminopentane, 1,4-bis(aminomethyl)cyclohexane, 4,4'-methylenebis(2-methylcyclohexylamine), octamethylendiamine (OMDA), isophoronediamine (IPDA), 4,4'-diaminodicyclohexylmethane (4,4'-diaminodicyclohexylamine), 1,4'-diaminodicyclohexylamine (1,4'-diaminodicyclohexylamine), 1,4'-diaminodicyclohexylmethane ... methane), hexamethylenediamine (HMDA), octamethylenediamine (OMDA), 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, C36 dimer diamine (C36 DDA), C38 dimer diamine, and C40 dimer diamine. Examples of the dimer diamine include dimer diamines derived from oleic acid, linoleic acid, linolenic acid, palmitic acid, or elaidic acid, such as Priamine 1074 or Priamine 1075 available from Croda. The aforementioned aliphatic diamines may be used alone or in combination. Examples of the aromatic diamine include, but are not limited to, bis(4-aminophenyl)terephthalate (BPTP), 1,4-bis(4-aminobenzoyloxy) benzene (ABHQ), 4-aminophenyl-4-aminobenzoate (APAB), 4,4'-oxydianiline (ODA), p-phenylenediamine (PPD), bis(4-aminophenyl) deca-hydronaphthalene-2,6-dicarboxylate (ET-BDM), 2,7-bis(4-aminophenoxy) naphthalene (ET-BDM), bis(4-aminophenyl) terephthalate (BPTP), bis(4-aminophenyl) terephthalate (BPTP), bis(4-aminophenyl) terephthalate (BPTP), bis(4-aminophenyl) terephthalate (BPTP), bis(4-aminophenyl) terephthalate (BPTP), bis(4-aminophenoxy) terephthalate ( ABHQ ), bis(4-aminophenyl) terephthalate (APAB), bis(4-aminophenyl) terephthalate (APAB), bis(4-aminophenyl) terephthalate (ODA), bis(4-aminophenyl) terephthalate (PPD), bis(4-aminophenyl) terephthalate (ET-BDM), bis(4-aminophenoxy) terephthalate (ET-BDM), bis(4-aminophenoxy) terephthalate (ET-BDM), bis(4-aminophenyl ...phenyl) terephthalate (ET-BDM), bis(4-aminophenyl) terephthalate (ET-BDM), naphthalene, ET-2,7-Na), N,N'-(4,4'-(9H-fluorene-9,9-diyl)bis(4,1-phenylene))bis(4-aminobenzamide), FDA-ADA), 4,4'-(hexafluoroisopropylidene)dianiline, 6FPDA), 4,4'-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline, BAPHF), bis[4-(3-aminophenoxy)phenyl] bis[4-(3-aminophenoxy)phenyl]sulfone, BAPS; 4,4'-diaminobenzanilide, DABA; N1,N4-bis(4-aminophenyl)-terephthalamide, BPTPA; 4,4'-(4,4'-oxybis(4,1-phenylene)bis(oxy))bis(3-(trifluoromethyl)-aniline, p-6FAPE; and bis(4-aminophenyl)-cyclohexane-1,4-dicarboxylate. cyclohexane-1,4-dicarboxylate, ES-C). The aforementioned aromatic diamines may be used alone or in combination. In one embodiment of the present invention, the polyimide comprises repeating units derived from aliphatic diamines. In another embodiment of the present invention, the polyimide comprises repeating units derived from aliphatic diamines and repeating units derived from aromatic diamines. The aliphatic diamine is preferably a long carbon chain aliphatic diamine, and the aliphatic diamine and the aromatic diamine may be selected from the following group: PPD, ODA, C36 DDA, ABHQ, BPTP, and combinations thereof.

Examples of solvents that can be used to dissolve dianhydrides and diamines include, but are not limited to, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), acetonitrile, hexamethylphosphoric triamide (HMPA), and 1,3-dimethyl-2-imidazolidinone (DMI). The solvents can be used alone or in any combination.

In some embodiments of the present invention, the polyimide comprises an ester functional group ( ), the polyimide can be formed by polymerizing a dianhydride containing an ester functional group and a diamine, a dianhydride and a diamine containing an ester functional group, or a dianhydride containing an ester functional group and a diamine containing an ester functional group. Examples of the dianhydride containing an ester functional group include, but are not limited to, TAHQ, and examples of the diamine containing an ester functional group include, but are not limited to, ABHQ, APAB, and BPTP.

In a preferred embodiment of the present invention, the ratio of the number of ester functional groups to the number of imide functional groups based on the total number of all functional groups of the polyimide is not less than 0.8, preferably 0.8 to 2.0, for example, 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0, or a range consisting of any two of the above values. If the ratio of the number of ester functional groups to the number of imide functional groups of the polyimide is greater than 0.8, the dielectric properties of the polyimide and the dielectric properties after water absorption can be further improved.

2. Polyimide film

The polyimide of the present invention can be used to form a film product. Therefore, the present invention also relates to a polyimide film. The method of forming the polyimide film of the present invention is not particularly limited. The film can be formed by coating the polyimide by a coating method commonly used in the technical field to which the present invention belongs, or by coating a polyamide solution by a coating method commonly used in the technical field to which the present invention belongs to form a polyamide film, and then heating the polyamide film to thermally close the polyamide ring to form the polyimide film. Examples of the commonly used coating methods include, but are not limited to, roller coating, scraper coating, comma coating, die coating, slit coating, wire rod coating, and spray coating.

In some embodiments of the present invention, a polyimide film is prepared in the following manner. First, a polyamic acid solution is filtered to remove dust and impurities. Then, the polyamic acid solution is coated on a cleaned glass substrate using a scraper mold. Thereafter, the glass substrate coated with the polyamic acid solution is placed in a vacuum environment for 4 to 8 hours to slowly remove the solvent. Then, the glass substrate is placed in a high temperature and vacuum oven to allow the polyamic acid to undergo a thermal ring closure reaction to form polyimide, thereby obtaining a polyimide film. After that, the temperature is slowly lowered and then several stages of heat treatment are performed at a temperature of 100°C to 500°C to stabilize the properties of the polyimide membrane. Finally, the polyimide membrane is slowly cooled to room temperature to avoid membrane rupture.

The polyimide film of the present invention has excellent dielectric properties, low water absorption, and CTE close to that of metal foil, and the dielectric properties are still good after absorbing water, and is particularly suitable as an insulating material for printed circuit boards. The thickness of the polyimide film of the present invention is preferably 10 μm to 50 μm, for example, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, or 50 μm, or in a range consisting of any two of the above values.

3. Embodiment

3.1. Measurement method

The present invention is further illustrated by the following specific implementations, wherein the measuring instruments and methods used are as follows:

[FTIR analysis]

Prepare a polyimide film with a length of 5 cm, a width of 5 cm and a thickness of at least 10 μm as a specimen. Place the specimen in an infrared spectrometer (model: FTIR spectrometer spectrum two), use an ATR fixture (model: MIRacle ^TM Single Reflection ATR), and configure the analysis software Perkin Elmer 10.5.3.738, and perform FTIR analysis under the following conditions: use ZnSe as the attenuated total reflection crystal, scan range of 650 cm ^-1 to 4000 cm ^-1 , scan times of 8 times, and resolution of 1 cm ^-1 .

In the infrared absorption spectrum of the obtained polyimide, the software is used to select the point where the first differentiation is 0 as the starting point, the apex point and the end point of the characteristic peak, and then the area from the starting point to the apex point to the end point is used as the integration range, and the characteristic peak area is calculated by the software.

[Dielectric property measurement]

A polyimide film specimen with a length of 8 cm, a width of 8 cm and a thickness of at least 10 μm was vacuum dried at 100°C for 24 hours, and then the dielectric constant (Dk) and the dissipation factor (Df) of the dried specimen were measured to obtain the dielectric properties before water absorption. The measurement was performed using a vector network analyzer (model: R&S ^® ZVB, purchased from Rohde & Schwarz) at an analysis frequency of 10 GHz.

In addition, a polyimide film specimen with a length of 8 cm, a width of 8 cm and a thickness of at least 10 μm was immersed in water for 24 hours and then wiped dry, and the above-mentioned steps of measuring Dk and Df were performed to obtain the dielectric properties after water absorption.

[Water absorption test]

The water absorption of the polyimide film is measured in accordance with the specification of IPC-TM-650 2.6.2.1 and calculated by the following formula, where _W1 represents the weight of the polyimide film after drying in an oven at 105°C for 1 hour, _{and W2} represents the weight of the polyimide film after wiping off the water droplets on the film after soaking in water at 23°C for 24 hours. The test piece of the polyimide film has a length of 2 inches, a width of 2 inches, and a thickness of 25 microns.

[Measurement of coefficient of thermal expansion (CTE)]

The CTE of the polyimide film was measured using a thermomechanical analyzer (model: TMA Q400, purchased from TA Instruments). The measurement conditions were as follows: the polyimide film specimen used for measurement had a length of 10 mm, a width of 5 mm, and a thickness of 20 μm, the atmosphere was a dry nitrogen atmosphere, and the CTE test temperature range was 50°C to 300°C. The unit of CTE is ppm/K.

3.2. Preparation of polyamine solution

[Example 1]

First, 7.11 g (0.0204 mol) of ABHQ (purchased from Shifeng) and 1.21 g (0.0023 mol) of C36 DDA (model: Priamine 1074, purchased from Croda) were placed in a flask, and 85 ml of anhydrous DMAc was added and stirred at 80°C to dissolve to prepare an intermediate solution with a concentration of 15 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly added dropwise, and stirred for 10 minutes. Then, 6.68 g (0.0227 mol) of s-BPDA (purchased from UBE) was added to the intermediate solution and stirred at room temperature for 15 hours. Thereafter, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and the mixture was stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, thereby obtaining the polyamine solution of Example 1.

[Example 2]

First, 6.15 g (0.0177 mol) of ABHQ and 2.36 g (0.0044 mol) of C36 DDA were placed in a flask, and 85 ml of anhydrous DMAc was added and stirred at 80°C to dissolve to prepare an intermediate solution with a concentration of 15 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly dripped into it, and stirred for 10 minutes. Then, 6.49 g (0.0221 mol) of s-BPDA was added to the intermediate solution and stirred at room temperature for 15 hours. Then, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, and the polyamide solution of Example 2 was obtained.

[Example 3]

First, 6.15 g (0.0177 mol) of BPTP (purchased from Shifeng) and 2.36 g (0.0044 mol) of C36 DDA were placed in a flask, and 85 ml of anhydrous DMAc was added and stirred at 80°C to dissolve to prepare an intermediate solution with a concentration of 15 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly added dropwise, and stirred for 10 minutes. After that, 6.49 g (0.0221 mol) of s-BPDA was added to the intermediate solution and stirred at room temperature for 15 hours. Thereafter, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and the mixture was stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, thereby obtaining the polyamine solution of Example 3.

[Example 4]

First, 1.91 g (0.0177 mol) of PPD (purchased from Shifeng) and 1.52 g (0.0076 mol) of ODA (purchased from Liyongfa) were placed in a flask, and 85 ml of anhydrous DMAc was added and stirred at 80°C to dissolve to prepare an intermediate solution with a concentration of 10 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly added dropwise, and stirred for 10 minutes. Then, 11.57 g (0.0252 mol) of TAHQ (purchased from Shifeng) was added to the intermediate solution and stirred at room temperature for 15 hours. Thereafter, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and the mixture was stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, thereby obtaining the polyamine solution of Example 4.

[Example 5]

First, 5.8 g (0.0167 mol) of ABHQ and 0.99 g (0.0019 mol) of C36 DDA were placed in a flask, and 85 ml of anhydrous DMAc was added and stirred at 80°C to dissolve to prepare an intermediate solution with a concentration of 15 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly added, and stirred for 10 minutes. After that, 7.63 g (0.0167 mol) of TAHQ and 0.57 g (0.0019 mol) of ODPA (purchased from Yongfa Co., Ltd.) were added to the intermediate solution and stirred at room temperature for 15 hours. Thereafter, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and the mixture was stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, thereby obtaining the polyamine solution of Example 5.

[Comparison Example 1]

First, 8.13 g (0.0233 mol) of BPTP was placed in a flask, and 85 ml of anhydrous DMAc was added, and stirred at 80°C to dissolve, to prepare an intermediate solution with a concentration of 15 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly dripped, and stirred for 10 minutes. Then, 6.87 g (0.0233 mol) of s-BPDA was added to the intermediate solution, and stirred at room temperature for 15 hours. Then, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, and the polyamide solution of Comparative Example 1 was obtained.

[Comparison Example 2]

First, 8.13 g (0.0233 mol) of ABHQ was placed in a flask, and 85 ml of anhydrous DMAc was added, and stirred at 80°C to dissolve to prepare an intermediate solution with a concentration of 15 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly dripped, and stirred for 10 minutes. Then, 6.87 g (0.0233 mol) of s-BPDA was added to the intermediate solution, and stirred at room temperature for 15 hours. Then, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, and the polyamide solution of Comparative Example 2 was obtained.

[Comparison Example 3]

First, 6.48 g (0.0186 mol) of BPTP was placed in a flask, and 85 ml of anhydrous DMAc was added, and stirred at 80°C to dissolve, to prepare an intermediate solution with a concentration of 15 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly dripped, and stirred for 10 minutes. Then, 8.52 g (0.0186 mol) of TAHQ was added to the intermediate solution, and stirred at room temperature for 15 hours. Then, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, and the polyamide solution of Comparative Example 3 was obtained.

[Comparison Example 4]

First, 6.48 g (0.0186 mol) of ABHQ was placed in a flask, and 85 ml of anhydrous DMAc was added, and stirred at 80°C to dissolve to prepare an intermediate solution with a concentration of 15 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly dripped, and stirred for 10 minutes. Then, 8.52 g (0.0186 mol) of TAHQ was added to the intermediate solution, and stirred at room temperature for 15 hours. Then, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, and the polyamide solution of Comparative Example 4 was obtained.

[Comparison Example 5]

First, 6.07 g (0.0303 mol) of ODA was placed in a flask, and 85 ml of anhydrous DMAc was added, and stirred and dissolved at 80°C to prepare an intermediate solution with a concentration of 10 wt%. Then, the intermediate solution was placed in an ice water bath, 5.5 mmol of glacial acetic acid was slowly dripped, and stirred for 10 minutes. Then, 8.93 g (0.0303 mol) of s-BPDA was added to the intermediate solution, and stirred at room temperature for 15 hours. Then, 0.05 mmol of acetic anhydride was added as a ring-closing agent, and stirred for 30 minutes to confirm that the acetic anhydride was completely dissolved, and the polyamide solution of Comparative Example 5 was obtained.

3.3. Preparation of polyimide membrane

The polyimide film was prepared using the polyamide solutions of Examples 1 to 5 and Comparative Examples 1 to 5, respectively. First, the polyamide solution was filtered using a 0.45 μm filter to remove dust and impurities. Then, the polyamide solution was coated on a cleaned glass substrate (length 20 cm, width 20 cm, thickness 0.5 cm) using a 600 μm scraper mold. Afterwards, the glass substrate coated with the polyamide solution was placed in a vacuum environment for 6 hours to slowly remove the solvent. Next, the glass substrate coated with the polyamide solution was subjected to heat treatment at 100°C, 200°C, 300°C and 350°C for 1 hour respectively, so that the polyamide undergoes a thermal ring closure reaction to form a polyimide film and stabilize the properties of the polyimide film. Finally, in order to avoid film breakage, the temperature was slowly cooled to room temperature before being taken out, and the polyimide films of Examples 1 to 5 and Comparative Examples 1 to 5 were obtained.

3.4. Polyimide membrane FTIR , dielectric properties and CTE analyze

The properties of the polyimide films of Examples 1 to 5 and Comparative Examples 1 to 5 were measured according to the measurement methods described above, including FTIR analysis, Dk, Df, and CTE, and the results are recorded in Tables 1 to 4.

Table 1: FTIR analysis of polyimide membranes of Examples Embodiment 1 2 3 4 5 b/a 10.9 10.08 12.72 18.08 18.35 c/b 0.3483 0.3678 0.3974 0.4024 0.5195

Table 2: FTIR analysis of polyimide membrane of comparative example Comparison Example 1 2 3 4 5 b/a 14.62 10.25 33.43 28.06 8.12 c/b 0.101 0.2986 0.0743 0.4498 0

Table 3: CTE of polyimide films of the examples Embodiment 1 2 3 4 5 Dk @ 10 GHz 3.23 3.11 3.03 3.30 2.82 Df @ 10 GHz 0.0029 0.0022 0.0018 0.0030 0.0018 CTE (unit: ppm/°C) 10.3 27.4 36.1 23.3 twenty one

Table 4: Properties of the polyimide films of the comparative examples Comparison Example 1 2 3 4 5 Dk @ 10 GHz 3.30 3.32 2.94 2.99 3.40 Df @ 10 GHz 0.0049 0.0045 0.0023 0.0028 0.0038 CTE (unit: ppm/°C) 5.4 3.5 -17.1 4.6 71.1

Considering the CTE of metal foil (e.g., copper foil) and adhesive resin, the CTE value of the polyimide film used to prepare printed circuit boards is preferably close to the CTE value of the metal foil, generally falling between about 10 ppm/°C and 40 ppm/°C, preferably between about 20 ppm/°C and 40 ppm/°C, to avoid peeling or board explosion during the laminate processing process. As shown in Table 3, the polyimide film of the present invention not only has excellent Df and Dk values, but also has a CTE close to that of the metal foil. In contrast, as shown in Table 5, the polyimide film not belonging to the present invention cannot simultaneously have excellent Df, excellent Dk, and CTE suitable for metal foil. In particular, Comparative Examples 1 and 2 show that if the c/b value of polyimide is not within the specified range of the present invention, the polyimide film does not have excellent dielectric properties and does not have a CTE suitable for metal foil even if the b/a value is within the specified range of the present invention. Comparative Example 4 shows that if the b/a value of polyimide is not within the specified range of the present invention, the polyimide film does not have a CTE suitable for metal foil even if the c/b value is within the specified range of the present invention. Comparative Examples 3 and 5 show that if both the b/a value and the c/b value of the FTIR analysis of polyimide are not within the specified range of the present invention, the polyimide film does not have a CTE suitable for metal foil, and the CTE value of the polyimide film in Comparative Example 3 is even much lower than the CTE value of the metal foil.

3.4. Dielectric properties and water absorption rate of polyimide film after water absorption

According to the measurement method described above, the Dk after water absorption, the Df after water absorption, and the water absorption rate of the polyimide membranes of Examples 1 to 3 and 5 and Comparative Examples 1 to 2 and 4 to 5 were further measured, and the results are recorded in Tables 5 to 6.

Table 5: Dielectric properties and water absorption of the polyimide film of the embodiment after water absorption Embodiment 1 2 3 5 Dk after water absorption @ 10 GHz 3.27 3.12 3.05 2.93 Df after water absorption @ 10 GHz 0.0035 0.0025 0.0025 0.0024 Water absorption (unit: %) 0.4 0.3 0.3 0.5

Table 6: Dielectric properties and water absorption rate of polyimide films of comparative examples after water absorption Comparison Example 1 2 4 5 Dk after water absorption @ 10 GHz 3.35 3.37 3.01 3.50 Df after water absorption @ 10 GHz 0.0060 0.0053 0.0036 0.0120 Water absorption (unit: %) 0.6 0.5 0.5 1.1

As shown in Table 5, the polyimide film of the present invention has a low water absorption rate and still has good Df and Dk after absorbing water and drying, and is suitable as an insulating material for a printed circuit board. In contrast, as shown in Table 6, the polyimide film not belonging to the present invention cannot have good Df and Dk after absorbing water and drying, and is not suitable as an insulating material for a printed circuit board.

The above embodiments are only for illustrative purposes to illustrate the principle and efficacy of the present invention and to illustrate the technical features of the present invention, and are not intended to limit the scope of protection of the present invention. Any changes or arrangements that can be easily accomplished by anyone familiar with the present technology without violating the technical principle of the present invention are within the scope of the present invention. Therefore, the scope of protection of the present invention is as listed in the attached patent application scope.

without

without

Claims (9)

A polyimide comprises repeating units derived from dianhydride and repeating units derived from diamine, wherein the polyimide has a characteristic peak A at 1753 cm ^-1 to 1803 cm ^-1 , a characteristic peak B at 1635 cm -1 to 1752 cm -1 ^, and a characteristic peak C at 1160 cm ^-1 to 1170 ^{cm -1} , wherein the characteristic peak A has a characteristic peak area a, the characteristic peak B has a characteristic peak area b, the characteristic peak C has a characteristic peak area c, and 10.00

b/a

25.00, 0.32

c/b

0.54. The polyimide as described in claim 1, wherein 10.00

b/a

18.50. The polyimide as described in claim 2, wherein 0.34

c/b

0.52. The polyimide as claimed in any one of claims 1 to 3, wherein FTIR is measured under the following conditions: using ZnSe as a crystal of attenuated total reflection, the scanning range is 650 cm ^-1 to 4000 cm ^-1 , and the number of scanning times is 8 times. A polyimide as described in any one of claims 1 to 3, wherein the repeating units derived from diamines comprise repeating units derived from aliphatic diamines. The polyimide as described in claim 5, wherein the repeating units derived from diamine further include repeating units derived from aromatic diamine. A polyimide as described in any one of claims 1 to 3, wherein the repeating units derived from a dianhydride comprise repeating units derived from an aromatic dianhydride. A polyimide as described in any one of claims 1 to 3, wherein the polymer backbone of the polyimide contains an ester functional group. A polyimide membrane, which is made from the polyimide as described in any one of claims 1 to 8.