阅读说明：本技术 聚酰亚胺薄膜、包含其的柔性金属箔层压板及聚酰亚胺薄膜制备方法 (Polyimide film, flexible metal foil laminated plate comprising polyimide film and polyimide film preparation method ) 是由 金纪勋 李吉男 崔祯烈 白承烈 赵珉相 于 2019-10-23 设计创作，主要内容包括：本发明涉及具有低介电损失因子(Df)的聚酰亚胺薄膜、包含其的柔性金属箔层压板以及具有低介电损失因子(Df)的聚酰亚胺薄膜的制备方法,本发明的聚酰亚胺薄膜的特征在于,所述聚酰亚胺薄膜通过对包含第一聚酰亚胺酸的最终聚酰亚胺酸进行酰亚胺化来制备,所述第一聚酰亚胺酸包含衍生自均苯四酸二酐(PMDA)和间甲苯胺(m-tolidine)的第一嵌段,第一嵌段的平均分子量为20000g/mol以下。(The present invention relates to a polyimide film having a low dielectric loss factor (Df), a flexible metal foil laminate comprising the same, and a method for preparing a polyimide film having a low dielectric loss factor (Df), the polyimide film of the present invention being characterized in that the polyimide film is prepared by imidizing a final polyimide acid comprising a first block derived from pyromellitic dianhydride (PMDA) and m-toluidine (m-toluidine), the first block having an average molecular weight of 20000g/mol or less.)

1. A polyimide film characterized by comprising a polyimide film,

prepared by imidizing a final polyimide acid comprising a first block derived from pyromellitic dianhydride and m-toluidine,

the average molecular weight of the first block is 20000g/mol or less.

2. The polyimide film according to claim 1, wherein the number of repeating units of the first block is an integer of 5 to 55.

3. The polyimide film according to claim 1, wherein the molar ratio of pyromellitic dianhydride to m-toluidine is 0.86:1 to 0.98: 1.

4. The polyimide film according to claim 1,

the final polyimide acid also includes a second polyimide acid including a second block derived from m-toluidine and one or more dianhydrides selected from the group consisting of biphenyltetracarboxylic dianhydride, oxydiphthalic anhydride, and benzophenonetetracarboxylic dianhydride.

5. The polyimide film of claim 4 wherein the molar ratio of the sum of dianhydrides to m-toluidine in the final polyimide acid is from 0.96:1 to 0.98: 1.

6. The polyimide film of claim 1 wherein the final polyimide acid has a viscosity of 190000cP to 210000 cP.

7. The polyimide film of claim 4 wherein the first and second polyimide acids have a viscosity of 190000 to 210000 cP.

8. The polyimide film according to any one of claims 1 to 7, wherein a dielectric loss factor (Df) is 0.005 or less.

9. A flexible metal foil laminate comprising the polyimide film according to claim 8 and a conductive metal foil.

10. A method for preparing a polyimide film is characterized by comprising the following steps:

a step (a) of preparing a first polyimide acid comprising a first block derived by polymerizing pyromellitic dianhydride and m-toluidine in an organic solvent;

a step (b) of preparing a second polyimidic acid comprising a second block derived by polymerizing m-toluidine and one or more dianhydrides selected from the group consisting of biphenyltetracarboxylic dianhydride, oxydiphthalic anhydride and benzophenonetetracarboxylic dianhydride in an organic solvent; and

a step (c) of imidizing a final polyimide acid comprising the first polyimide acid and the second polyimide acid,

the average molecular weight of the first block is 20000g/mol or less.

11. The method of preparing a polyimide film according to claim 10, wherein in the step (a), the molar ratio of pyromellitic dianhydride to m-toluidine is 0.86:1 to 0.98: 1.

12. The method of preparing a polyimide film according to claim 10, wherein in the step (c), the molar ratio of the sum of dianhydrides in the final polyimide acid to m-toluidine is 0.96:1 to 0.98: 1.

Technical Field

The present invention relates to a polyimide film, and more particularly, to a polyimide film having a low dielectric loss factor (Df), a flexible metal foil laminate including the same, and a method of preparing a polyimide film having a low dielectric loss factor (Df).

Background

Generally, Polyimide (PI) is a polymer material having the highest levels of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance among organic materials based on a hard aromatic main chain and an imide ring having very excellent chemical stability. The polyimide film thus prepared has attracted attention as an insulating material for electronic components requiring the above-described characteristics, and in fact, a thin circuit board having high circuit integration and flexibility is widely used as an insulating film for a Flexible Metal Foil Laminate (Flexible Metal Foil Laminate) in a broader sense.

On the other hand, recently, electronic devices are required to have a fast calculation speed and a fast communication speed in accordance with various functions built in the electronic devices, and in order to meet the requirements, a thin circuit board capable of performing high-speed communication at a high frequency of 2GHz or more is being developed.

However, in the case of high-frequency communication at 2GHz or more, there is a problem that dielectric loss (dielectric dispersion) through the polyimide film inevitably occurs. More specifically, a dielectric loss factor (Df) refers to a degree of power consumption of a thin circuit board, and is closely associated with a signal transmission delay that determines a communication speed, and reducing the Df of a polyimide film as much as possible is an important factor that acts on the performance of the thin circuit board.

Therefore, it is a real situation that it is required to develop a polyimide film having a low dielectric loss factor (Df) while maintaining the existing mechanical properties and chemical resistance of the polyimide film to the maximum.

The matters described in the background above are intended to aid in understanding the background of the invention and may include technical matters not yet known to those of ordinary skill in the art.

Disclosure of Invention

Technical problem to be solved by the invention

Accordingly, in order to solve the above-mentioned problems, an object of the present invention is to provide a polyimide film having a low dielectric loss factor (Df), a flexible metal foil laminate comprising the same, and a method for preparing a polyimide film having a low dielectric loss factor (Df) by controlling a molecular weight.

Means for solving the problems

In order to achieve the above object, the polyimide film of the present invention is characterized by being prepared by imidizing a final polyimide acid comprising a first block derived from pyromellitic dianhydride (PMDA) and m-toluidine (m-tolidine), the first block having an average molecular weight of 20000g/mol or less.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention provides a flexible metal foil laminate which can be suitably used for an electrical transmission circuit capable of communicating at a high frequency of at least 2GHz or more, even 5G band, by providing a polyimide film having a low dielectric loss factor (Df) by controlling the molecular weight.

Detailed Description

The terms or words used herein and in the scope of the claimed invention should not be construed as being limited to general or dictionary meanings, but interpreted as meanings and concepts conforming to the technical spirit of the present invention on the basis of the principle that the inventor can appropriately define the concept of terms in order to explain his invention in the best way.

Therefore, it should be understood that the structure of the embodiment described herein is only one of the preferred embodiments of the present invention and does not represent all the technical spirit of the present invention, so that various equivalent substitutions and modifications can be made with respect to the present application.

As used herein, the singular forms "a", "an" and "the" include plural forms unless the context clearly dictates otherwise. It will be understood that, in this document, the terms "comprising", "including", "having" or "with", etc., are intended to specify the presence of stated features, steps, structural elements, or combinations thereof, and do not preclude the presence or addition of one or more other features or numbers, steps, structural elements, or combinations thereof.

"dianhydride" is intended herein to include precursors or derivatives thereof which may not technically be a dianhydride, but which will also react with a diamine to form a polyimide acid which can be reconverted to a polyimide.

When an amount, concentration, or other value or parameter is given herein as either a range, preferred range or an enumeration of upper preferable values and lower preferable values, regardless of whether ranges are separately disclosed, it is understood that all ranges formed from any upper limit value or preferred value in any pair, and any lower limit value or preferred value of ranges, are specifically disclosed.

When a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is intended that the scope of the invention not be limited to the particular values mentioned in defining the range.

The first mode is as follows: polyimide film

The present invention includes polyimide films. Hereinafter, the following description will be made more specifically.

The polyimide films of the present invention are prepared by imidizing a final polyimide acid comprising a first block derived from pyromellitic dianhydride (PMDA) and m-toluidine (m-tolidine).

Among them, the average molecular weight of the first block is 20000g/mol or less, more preferably 15000g/mol or less, further preferably 10000 g/mol.

This is because the polyimide film having a small average molecular weight is excellent in dielectric loss factor (Df), and therefore the polyimide film of the present invention having an average molecular weight of the first block of 20000g/mol or less satisfies a dielectric loss factor (Df) of 0.005 or less.

The number of repeating units (or the degree of polymerization) of the first block is an integer of 5 to 55, more preferably an integer of 5 to 40, and still more preferably an integer of 5 to 30.

As described above, the polyimide film having a small average molecular weight due to a small number of repeating units is excellent in dielectric loss factor (Df), and the polyimide film of the present invention in which the number of repeating units of the first block is an integer of 5 to 55 satisfies 0.005 or less in dielectric loss factor (Df).

On the other hand, when the average molecular weight of the first block and the number of repeating units are too small, it is preferable that the average molecular weight is at least 2000g/mol and the number of repeating units is 5 or more, because the exertion of excellent characteristics possessed by the polyimide may be limited in addition to the dielectric loss factor (Df).

In order to prepare the polyimide film of the present invention satisfying such conditions, the molar ratio of pyromellitic dianhydride (PMDA) to m-toluidine (m-tolidine) in the first polyimide acid satisfies 0.86:1 to 0.98:1, more preferably satisfies 0.86:1 to 0.975:1, and still more preferably satisfies 0.86:1 to 0.97: 1.

In another aspect, preferably the final polyimide acid further comprises a second polyimide acid comprising a second block derived from dianhydride and m-toluidine.

More specifically, it is preferable that the second block is derived from one or more dianhydrides selected from the group consisting of biphenyl tetracarboxylic dianhydride (BPDA), oxydiphthalic anhydride (ODPA), and benzophenone tetracarboxylic dianhydride (3,3',4,4' -benzophenone tetracarboxylic dianhydride, BTDA), but the kind of dianhydride is not limited thereto.

Preferably, the final polyimide acid consisting of a polyimide acid comprising a first polyimide acid and a second polyimide acid satisfies a molar ratio of the sum of a dianhydride of the first polyimide acid (PMDA) and a dianhydride of the second polyimide acid (BPDA) to m-toluidine of 0.96:1 to 0.98:1, more preferably, 0.97: 1. Then, the final molar ratio is set to 0.995-0.997: 1 using the PMDA protocol (solution).

Wherein the m-toluidine is m-toluidine comprising a first polyimide acid and a second polyimide acid.

Also, the viscosity of the final polyimide acid is preferably 190000 to 210000cP, more preferably 200000 cP. The viscosity of the first polyimide acid is preferably 190000 to 210000cP, more preferably 200000cP, as well as that of the second polyimide acid.

The polyimide film of the present invention described so far satisfies a dielectric loss factor (Df) of 0.005 or less, more preferably 0.0045 or less, and further preferably 0.004 or less.

The dielectric loss factor (Df) is generally used as an index indicating the ease of charge loss (dielectric loss), and the higher the dielectric loss factor (Df), the easier the charge loss, and conversely, the lower the dielectric loss factor (Df), the harder the charge loss. That is, the dielectric loss factor is a measure of power loss, and a lower dielectric loss factor can mitigate the signal propagation delay due to power loss and maintain a faster communication speed, which is a matter strongly required for a polyimide film as an insulating film.

Therefore, the polyimide film of the present invention satisfies a dielectric loss factor (Df) of 0.005 or less, more specifically 0.0045 or less, further specifically 0.004 or less at a high frequency of at least 2GHz or more, even 5G band, and therefore the polyimide film of the present invention can provide a flexible metal foil laminate suitable for an electrical transmission circuit capable of communicating at a high frequency of 5G band.

The second mode is as follows: preparation method of polyimide film

The invention includes a method for preparing a polyimide film. Hereinafter, the following description will be made more specifically.

The preparation method of the polyimide film comprises the following steps: a step (a) of preparing a first polyimide acid comprising a first block derived by polymerizing pyromellitic dianhydride (PMDA) and m-toluidine (m-tolidine) in an organic solvent; a step (b) of preparing a second polyimidic acid including a second block derived by polymerizing one or more dianhydrides selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic anhydride (ODPA), and Benzophenone Tetracarboxylic Dianhydride (BTDA) and m-toluidine in an organic solvent; and a step (c) of imidizing the final polyimide acid including the first and second polyimide acids.

In step (a), the molar ratio of pyromellitic dianhydride (PMDA) to m-toluidine (m-tolidine) satisfies 0.86:1 to 0.98:1, more preferably satisfies 0.86:1 to 0.975:1, and still more preferably satisfies 0.86:1 to 0.97: 1.

In step (c), the final polyimide acid comprising the first polyimide acid and the second polyimide acid is preferably a molar ratio of the sum of a dianhydride of the first polyimide acid (PMDA) and a dianhydride of the second polyimide acid (BPDA) to m-toluidine satisfying 0.96:1 to 0.98:1, more preferably satisfying 0.97: 1. Wherein the m-toluidine includes m-toluidine included in the first polyimide acid and the second polyimide acid.

In the steps (a) and (b), the first polyimide acid or the second polyimide acid may be prepared by any (random) polymerization manner or block (block) polymerization manner, but the polymerization manner is not limited thereto.

In the step (a) and the step (b), the organic solvent is preferably an organic polar solvent, more preferably an aprotic polar solvent, and particularly preferably one or more solvents selected from the group consisting of N, N-Dimethylformamide (DMF), N-dimethylacetamide, N-methyl-pyrrolidone (NMP), γ -butyrolactone (GBL), and Diglyme (Diglyme), but the kind of the solvent is not limited thereto.

On the other hand, in the step (a), the step (b) or the step (c), a filler may be additionally added for the purpose of improving various properties of the polyimide film such as slidability, thermal conductivity, corona resistance, coil hardness and the like. More specifically, one or more fillers selected from silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica may be added.

The average particle diameter of these fillers can be determined according to the properties of the polyimide film to be improved and the kind of the filler, and is preferably 0.05 to 100 μm, more preferably 0.1 to 75 μm, and further preferably 0.1 to 50 μm in consideration of the modification effect and the reduction of mechanical properties due to surface damage.

The amount of the filler to be added may be determined in accordance with the properties of the polyimide film to be improved and the kind of the filler, and is preferably 0.01 to 100 parts by weight, more preferably 0.015 to 90 parts by weight, and further preferably 0.02 to 80 parts by weight, based on 100 parts by weight of the polyimide film, in consideration of the reduction in the modification effect and the mechanical properties.

On the other hand, in the step (c), preferably, the final polyimide acid is prepared by polymerizing the first polyimide acid and the second polyimide acid in an organic solvent, and, preferably, after the final polyimide acid prepared in the above-described manner is formed into a film on a support, imidization is performed.

The final method of acid imidization of the polyimide may be a thermal imidization method or a chemical imidization method, or may be a method in which the thermal imidization method is performed in parallel with the chemical imidization method. Among them, the thermal imidization method is a method of initiating an imidization reaction by using hot air or an infrared dryer or the like as a heat source other than a chemical catalyst, and the chemical imidization method is a method of using a dehydrating agent and an imidizing agent.

When the thermal imidization method is used, the imidization reaction is preferably initiated at 100 to 600 ℃, more preferably 200 to 500 ℃, and further preferably 300 to 500 ℃.

A third mode: flexible metal foil laminate

The present invention includes the aforementioned flexible metal foil laminate comprising the polyimide film of the present invention and a conductive metal foil. The following describes the present invention more specifically.

The conductive metal foil is preferably composed of one or more metals selected from copper, stainless steel, nickel and aluminum or an alloy containing the same, and is most preferably a copper foil, but not limited thereto.

The surface of the metal foil may be coated with a rust-proof layer, a heat-resistant layer, or an adhesive layer, and the thickness of the metal foil may be a thickness that can sufficiently function according to the use.

The flexible metal foil laminate of the present invention may have a structure in which a metal foil is laminated on one surface of a polyimide film, or one surface of a polyimide film includes an adhesive layer containing thermoplastic polyimide, and the metal foil is attached and laminated.

Hereinafter, the action and effect of the invention will be further described by way of specific examples of the invention. However, such embodiments are merely provided as examples of the present invention, and do not limit the scope of the invention claimed herein.

Preparation example: preparation of polyimide film

In a 500ml reactor having a stirrer and a nitrogen injection discharge pipe, nitrogen was injected while NMP was added, and after the temperature of the reactor was set to 30 ℃, PMDA and m-tolidine were added to be completely dissolved. Then, the temperature of the reactor was heated to 40 ℃ under a nitrogen atmosphere while stirring for 120 minutes, thereby preparing a first polyimide acid having a viscosity of 500 to 2500cP at 23 ℃. The first polyimide acid so prepared comprises a first block resulting from the polymerization of PMDA and m-tolidine.

Thereafter, a second polyimide acid was prepared in the same manner as the previous first polyimide acid, but using BPDA instead of PMDA.

In preparing the second imidic acid, BPDA and m-tolidine are added in amounts such that the molar ratio of the sum of the dianhydrides of the final polyimide acid (PMDA and BPDA) to m-tolidine is 0.97: 1. Then, the final molar ratio is set to 0.995-0.997: 1 by utilizing PMDA (solution). The second imidic acid thus prepared comprises a second block resulting from the polymerization of BPDA and m-tolidine.

Next, after the first polyimide acid and the second polyimide acid prepared previously were mixed, the temperature of the reactor was heated to 40 ℃ under a nitrogen atmosphere while continuing the stirring for 120 minutes, thereby preparing a final polyimide acid having a final viscosity of 200000cP at 23 ℃. And (3) adjusting the viscosity and the molar ratio of dianhydride to m-toluidine by utilizing a PMDA scheme (solution) to ensure that the final molar ratio is 0.995-0.997: 1.

The final polyimide acid thus prepared was applied to a glass substrate by a spin coater after removing bubbles by high-speed rotation at 1500rpm or more. Thereafter, the gel film was dried at a temperature of 120 ℃ for 30 minutes under a nitrogen atmosphere to prepare a gel film, the temperature thereof was raised to 450 ℃ at a rate of 2 ℃/minute, and after a heat treatment was performed at 450 ℃ for 60 minutes, it was cooled again to 30 ℃ at a rate of 2 ℃/minute to obtain a final polyimide film, and immersed in (dipping) distilled water to be peeled from the glass substrate.

Examples and comparative examples

Prepared by the foregoing preparation examples, a first polyimide acid was prepared so that the average molecular weight of the first block had the values shown in table 1 below, thereby adjusting the molar ratio of PMDA to m-tolidine.

The molar ratio of PMDA to m-olide was calculated by taking into account the molecular weight of PMDA (about 218g/mol) and the molecular weight of m-olide (about 212g/mol), calculating the unit volume molecular weight of the first block (about 394.42g/mol) taking into account the molecular weight (about 36g/mol) at which two water molecules were detached due to dehydration during the polymerization reaction, dividing the target average molecular weight of the first block by the previously calculated unit volume molecular weight of the first block to find the number of repeating units (degree of polymerization), and applying it to Carothers' equalisation. Also, after preparing the polyimide films of practical examples 1 to 4 and comparative examples 1 to 4, it was confirmed whether or not the target average molecular weight of the first block was possessed.

TABLE 1

Distinction between	Average molecular weight of the first Block [ g/mol ]]	Molar ratio of PMDA to m-tolidine
			Example 1	3000	0.869:1
Example 2	5000	0.921:1
			Example 3	8000	0.951:1
Example 4	10000	0.961:1
			Comparative example 1	30000	0.987:1
Comparative example 2	40000	0.990:1
			Comparative example 3	50000	0.992:1
Comparative example 4	60000	0.993:1

Table 2 below shows dielectric loss factors (Df) of the polyimide films of examples 1 to 4 and comparative examples 1 to 4 previously prepared, and the dielectric loss factor (Df) was measured after a flexible metal foil laminate was prepared by roll-to-roll copper foil lamination on both sides of the polyimide film, using an ohmmeter (Agilent4294A), and was left to stand for 72 hours.

TABLE 2

Distinction between	Dielectric loss factor (Df)
		Example 1	0.0035
Example 2	0.0038
		Example 3	0.0042
Example 4	0.0045
		Comparative example 1	0.0055
Comparative example 2	0.0063
		Comparative example 3	0.0072
Comparative example 4	0.0083

As shown in table 2, the polyimide films of examples 1 to 4 satisfied a dielectric loss factor (Df) of 0.005 or less and were suitable for electronic transmission circuits for transmitting signals at high frequencies, while the polyimide films of comparative examples 1 to 4 had a relatively high dielectric loss factor (Df) and were expected to be hardly suitable for the same. The embodiments of the polyimide film, the flexible metal foil laminate including the same, and the method for preparing the polyimide film according to the present invention are only to enable those skilled in the art to easily implement the preferred embodiments of the present invention, and are not limited to the foregoing embodiments, so that the scope of the present invention is not limited thereto. Therefore, the true technical scope of the present invention should be determined according to the technical idea of the appended claims. It will be apparent to those skilled in the art that various substitutions, modifications and changes may be made without departing from the scope of the technical idea of the present invention, and it is apparent that a part which can be easily changed by those skilled in the art is also included in the scope of the invention claimed in the present invention.

Industrial applicability

The present invention provides a polyimide film having a low dielectric loss factor (Df) by controlling the molecular weight, thereby providing a flexible metal foil laminate that can be suitably used for an electrical transmission circuit capable of communicating at high frequencies of at least 2GHz or more, even 5G band.