TW201930471A - Black polyimide film comprising fluorine resin and method for preparing the same, coverlay comprising the same, and electronic device comprising the same - Google Patents

Abstract

The present invention provides a polyimide film comprising, on the basis of the total weight of the polyimide film, 75-95 wt% of a polyimide resin, 2-15 wt% of a fluororesin and 3-10 wt% of carbon black having an average diameter of 0.1-5 [mu]m, wherein the fluororesin contains oxygen (O) in the molecular structure thereof, has a thickness of 8.0 [mu]m or less and has an alkali resistance index, evaluated on the basis of the thickness of the polyimide film, of 70% or more.

Description

Black polyfluorene imide film including fluorine number lipid and preparation method thereof

The invention relates to a black polyfluorene imide film including a fluorine resin and a preparation method thereof.

Generally, polyimide (PI) resin refers to the solution polymerization of an aromatic dianhydride with an aromatic diamine or an aromatic diisocyanate to prepare a polyfluorinated acid derivative, and then dehydration at a high temperature to perform ring closure. High heat resistant resin prepared by amination.

The usual method is to polymerize aromatic dianhydrides such as pyromellitic dianhydride (PMDA) or biphenyltetracarboxylic dianhydride (BPDA) with 4,4'-oxydiphenylamine (ODA), 3,4 ' -Aromatic diphenylamine, p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), methylene diphenylamine (MDA), diaminophenylhexafluoropropane (HFDA) and other aromatic diamines Polyamine resin is prepared by using an amine component.

Polyimide resin is an insoluble and infusible ultra-high heat-resistant resin. It has excellent properties such as heat-resistant oxidation resistance, heat resistance, radiation resistance, low-temperature properties, and chemical resistance. Therefore, it is widely used in automotive materials and aviation. Materials, spacecraft materials, and other heat-resistant materials, insulating coatings, insulating films, semiconductors, and thin film transistors (TFT)-liquid crystal display (LCD) electrode protection films and other electronic materials.

Examples of the electronic material include a protective film that is attached to a circuit included in a portable electronic device and a communication device to provide insulation properties and protect the circuit from moisture, light, and impact. In a narrow sense, it will be protected as described above. The film of the circuit is called a coverlay.

On the other hand, circuits are becoming smaller and thinner and are being developed in a bendable form. Therefore, the cover film also needs to be thinner and more flexible. Recently, shielding properties of components mounted on circuits are also required.

Therefore, a black film containing a form of carbon black particles that can impart a black hue and a barrier property to a flexible polyimide film in a thin film form has attracted much attention.

However, the circuit manufacturing process may include a drilling process, a plating process, a desmear process, and a cleaning process. In the above process, the polyimide film is exposed to an alkaline solution.

At this time, when the polyimide film is slightly decomposed or modified by the alkaline solution, the carbon black particles contained in the polyimide film may also fall off in large amounts.

The black hue and shielding properties of the cover film are reduced for this reason, and the thickness is reduced due to the shedding of carbon black particles, so the function as a cover film is significantly reduced.

Therefore, the fact is that there is an urgent need for a technology that can fundamentally solve such problems.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a black polyimide film, and more specifically, to provide a polyimide resin comprising 75% to 95% by weight relative to the total weight of the polyimide film, 2% by weight To 15% by weight of a fluorine-based resin, and 3% to 10% by weight of carbon black having an average particle diameter of 0.1 μm to 5 μm, and the above-mentioned fluorine-based resin includes oxygen (O) in a molecular structure. Polyimide film with a thickness of 8 μm or less, excellent optical properties such as gloss and transmittance, mechanical stability, and alkali resistance.

[Means for solving problems]

In order to achieve such an object, the present invention provides a polyimide film comprising 75 to 95% by weight of a polyimide resin, and 2 to 15% by weight based on the total weight of the polyimide film. Fluororesin, and carbon black with an average particle size of 3 to 10% by weight, from 0.1 μm to 5 μm,
The above-mentioned fluorine-based resin includes oxygen (O) in the molecular structure,
The thickness is 8.0 μm or less, and the alkali resistance index evaluated based on the thickness of the polyimide film is 70% or more.

The polyimide film of the present invention has a thickness of 8 μm or less, and is excellent in optical physical properties such as gloss and transmittance, mechanical stability, and alkali resistance. Therefore, it can be used as a cover in portable electronic equipment and communication equipment. membrane.

Hereinafter, embodiments of the present invention will be described in more detail in the order of a "polyimide film" and a "method for producing a polyimide film" of the present invention.

Prior to this, the terms or words used in this specification and the scope of the patent application for inventions should not be construed as limited to ordinary meanings or meanings in the dictionary. In order for the inventor to explain his own invention in the best way, he should only base it on The principle of the concept of the term may be appropriately defined and interpreted as meanings and concepts conforming to the technical idea of the present invention.

Therefore, the structure of the embodiment described in this specification is only the best embodiment of the present invention, and does not represent all technical ideas of the present invention. Therefore, it should be understood that from the perspective of this application, there may be alternatives. Various equivalents and modifications of these embodiments.

In this specification, a singular expression includes a plural expression as long as it does not express otherwise in the text. In this specification, it should be understood that the terms "including," "having," or "having" indicate that there are implemented features, numbers, steps, constituent elements, or a combination thereof, and do not exclude one or more other features, numbers, Existence or additional possibility of steps, constituent elements, or a combination thereof.

Polyimide film

As described above, the polyimide film of the present invention is characterized in that it includes 75% to 95% by weight of polyimide resin, 2% to 15% by weight with respect to the total weight of the polyimide film. Fluororesin, and carbon black with an average particle size of 3 to 10% by weight of 0.1 μm to 5 μm,
The above-mentioned fluorine-based resin includes oxygen (O) in the molecular structure,
The thickness is 8.0 μm or less, and the alkali resistance index evaluated based on the thickness of the polyimide film is 70% or more.

At this time, when the particle size or content of the carbon black particles is less than the above range, it is difficult to ensure a desired degree of shielding properties, which is not preferable.

Conversely, when the particle size or content of the carbon black particles exceeds the above range, the dispersion degree will be lower when mixed with polyamic acid during the preparation process, and the filler will protrude from the surface of the film to cause poor appearance, so it is not good. .

On the other hand, as described above, polyimide is vulnerable to alkali components such as decomposition or modification when exposed to an alkaline environment.

Alkali resistance refers to the property that the polyimide film is not easily decomposed or modified even when exposed to an alkaline environment. When the polyimide film is decomposed or modified, the thickness of the polyimide decreases. Therefore, it can be based on the thickness reduction rate. Determine the "Alkali Resistance Index".

Specifically, as an index for evaluating alkali resistance, the following method can be used: After exposing the polyimide film to a NaOH solution and a detergent, the change in film thickness before and after the exposure can be measured.

The alkali resistance index evaluation method (evaluation method (a)) is as follows.

After corona treatment was performed on both sides of the polyimide film, the polyimide film, the bonding sheet (adhesive), and the copper foil were laminated in this order, and then applied at a temperature of 160 ° C. by a hot press at 50 ° C. Bonding was performed under a pressure of kgf for 30 minutes to produce a flexible circuit board sample.

Repeatedly, the flexible circuit board cut into 4 cm * 10 cm was exposed to a 10% NaOH solution for 3 minutes at 55 ° C and a decontamination solution (10% NaMnO ₄ + 4% NaOH) for 5 minutes at 55 ° C. After the cleaning process is performed, the thickness of the film is measured and compared with the thickness before exposure to the NaOH solution and the decontamination solution, and the degree of change in the thickness after exposure relative to the thickness before exposure is expressed as a percentage.

After the ordinary polyimide film is subjected to the above-mentioned evaluation method (a), the alkali resistance index may be approximately 70% or less. In particular, an ultra-thin polyimide film having a film thickness of 8 μm or less may be subjected to the above-mentioned method. After the evaluation method (a), the alkali resistance index can be expressed as approximately 60% or less.

In contrast, the polyimide film of the present invention includes a fluorine-based resin having excellent chemical resistance. As described below, the fluorine-based resin and carbon black particles are chemically bonded to form a matrix structure, thereby having the following excellent effects: The ultra-thin polyimide film prepared with a film thickness of 8 μm or less also showed an excellent alkali resistance index of more than 70%.

In a specific example, the fluorine-based resin may be a copolymer derived from a monomer composition including tetrafluoroethylene (TFE) and a compound represented by the following chemical formula (1).

CF ₂ = CF (OR ^f ) (1)

In the above chemical formula (1), R ^f is a C ₁ -C ₆ perfluoroalkyl group.

The compound represented by the chemical formula (1) may be, for example, perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), and perfluoropropyl vinyl ether (PPVE). Specifically, In the above-mentioned chemical formula (1), R ^f may be a C ₁ -C ₃ perfluoroalkyl group. More specifically, the compound represented by the above-mentioned chemical formula (1) may be PPVE.

For example, the above-mentioned fluorine-based resin can be obtained by polymerizing tetrafluoroethylene and a compound represented by the above-mentioned chemical formula (1).

At this time, the above-mentioned fluorine-based resin may have a tetrafluoroethylene: compound represented by the chemical formula (1) = a molar ratio of 96:10 to 97: 1, and in detail, may have a tetrafluoroethylene: represented by the chemical formula (1) Compound: Molar ratio from 96: 4 to 97: 3. More specifically, the above-mentioned fluorine-based resin may be a perfluoroalkoxy (PFA) resin.

On the other hand, the fluorine-based resin may be chemically bonded to the carbon black to form a matrix structure.

In detail, the above-mentioned fluorine-based resin may form a matrix structure by chemically bonding with the carbon black through interaction with a functional group including oxygen in a molecular structure.

At this time, the above-mentioned functional group including oxygen may be a perfluoroalkyl ether group.

That is, unlike ordinary fluorine-based resins which do not include oxygen in their molecular structure, such as fluorine-based resins such as polytetrafluoroethylene (PTFE) or fluorinated ethylene propylene (FEP), the polyfluorene of the present invention The perfluoroalkyl ether group in the imine film can be chemically bonded with carbon black to form a matrix structure.

Specifically, fluorine-based resins that include oxygen in their molecular structure, and specifically PFA have physical properties of particles, such as strength, elongation, and modulus that are more than 10% higher than PTFE. In the mixed organic solvent, PFA and carbon black chemically bond to form a matrix structure, so it can exert the effects of suppressing carbon black particle aggregation and improving dispersibility.

Therefore, when the polyimide film is slightly decomposed or modified due to the alkaline solution, the problem of a large amount of carbon black particles falling off can also be solved.

Preparation method of polyimide film

The invention provides a method for preparing a polyimide film, which comprises:
(A) a step of polymerizing polyamino acids from dianhydrides and diamines;
(B) a step of preparing a first composition including a fluorine-based resin and a first organic solvent;
(C) a step of preparing a second composition including carbon black having an average particle diameter of 0.1 μm to 5 μm and a second organic solvent;
(D) a step of preparing the third composition by mixing the first composition and the second composition; and (e) mixing the third composition with the polyamic acid, forming a film on a support, and performing heat treatment Here comes the imidization step.

In a specific example, the first composition may include 10% to 30% by weight of a fluororesin relative to the total weight of the first composition.

When the amount of the fluorine-based resin added is less than the above range, the absolute amount of the fluorine-based resin chemically bonded to each of the carbon black particles becomes insufficient, and the adhesion between the carbon black and the fluorine-based resin particles is insufficient, which is not satisfactory. .

On the contrary, when it exceeds the above range, the content of the fluorine-based resin included in the prepared polyimide film becomes too high and the physical properties of the polyimide film are lowered, which is not preferable.

On the other hand, in the step (d), the first composition and the second composition are mixed, whereby the fluorine-based resin and carbon black are chemically bonded to form a matrix structure.

That is, unlike the method that includes a step of simply preparing carbon black and a fluororesin in a polyamic acid to prepare a polyimide film, the production method of the present invention includes separately preparing a first composition and a second composition, and In the step of preparing the third composition by mixing the first composition and the second composition, the carbon black and the fluorine-based resin are chemically bonded to induce the formation of a matrix structure.

On the other hand, the polyimide film of the present invention can be obtained from a polyamidic acid solution that is a precursor of the polyimide.

Specifically, the polyamic acid solution may be derived from a dianhydride monomer and a diamine monomer. The dianhydride monomer includes pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3 , 3 ', 4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylene Pyromellitic dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxybisphthalate di Anhydride, bis (3,4-dicarboxyphenyl) fluorene dianhydride, p-phenylene bis (trimellitic acid monoester anhydride), ethylidene bis (trimellitic acid monoester anhydride), bisphenol A bis (Trimellitic acid monoester anhydride) and the like can be used alone or as a mixture obtained by mixing them at an arbitrary ratio.

The diamine monomer includes 4,4'-oxydiphenylamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, and diphenylmethane. Aniline, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylphosphonium, 4,4'-diaminodiphenylphosphonium , 4,4'-diaminodiphenyl ether (4,4'-oxydiphenylamine), 3,3'-diaminodiphenyl ether (3,3'-oxydiphenylamine), 3,4 '-Diaminodiphenyl ether (3,4'-oxydiphenylamine), 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'- Diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-aniline, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene and the like, which can be used alone or as any And use it as a mixture of mixed ratios.

On the other hand, a polyamidic acid solution is prepared by a method in which the aromatic diamine monomer and the aromatic dianhydride monomer are prepared in a substantially equal molar amount while stirring under a controlled temperature condition. The monomer compound is dissolved in a mixed solution obtained in an organic solvent until the polymerization of the aromatic dianhydride monomer and the aromatic diamine monomer is completed.

The polyamic acid solution is usually obtained at a concentration of 5 to 35% by weight, preferably 10 to 30% by weight, of the solid content.

When the concentration is in this range, the polyamic acid solution obtains an appropriate molecular weight and solution viscosity.

The solvent used to synthesize the polyamine solution is not particularly limited, and any solvent may be used as long as it is a solvent that dissolves the polyamino acid, but a amine-based solvent is preferred.

Specifically, the solvent may be an organic polar solvent, and in detail, it may be an aprotic polar solvent. For example, the solvent may be selected from the group consisting of N, N'-dimethylformamide (DMF), N , N'-dimethylacetamide (DMAc), N-methyl-pyrrolidone (NMP), γ-butyrolactone (GBL), diethylene glycol dimethyl ether (Diglyme) More than one type is used, but it is not limited thereto, and may be used alone or in combination of two or more types as necessary.

In one example, N, N-dimethylformamide and N, N-dimethylacetamide are particularly preferably used as the solvent.

On the other hand, the above-mentioned carbon black can be controlled by a bead mill, and this grinding process is used to properly mix and disperse fillers such as carbon black with a relatively small particle size dispersion with a polyamic acid solution to the whole. The light transmittance of the polyfluorene imide film thus prepared was maintained uniformly, thereby obtaining a result of further reducing the light transmittance.

In addition, in order to improve the dispersibility of the carbon black and stabilize the dispersion state, a dispersant, a thickener, etc. may be used together with the first organic solvent within a range that does not affect the physical properties of the film.

In this case, the first organic solvent is not particularly limited as long as it is a solvent capable of dispersing carbon black particles and dissolving polyamic acid.

The second organic solvent may be the same as or different from the first organic solvent.

Specifically, the first organic solvent and the second organic solvent may be organic polar solvents. More specifically, they may be aprotic polar solvents. For example, they may be selected from N, N'-dimethylformate. Methylformamide (DMF), N, N'-dimethylacetamide (DMAc), N-methyl-pyrrolidone (NMP), γ-butyrolactone (GBL), diethylene glycol dimethyl One or more of the groups consisting of ether (Diglyme) are not limited thereto, and may be used alone or in combination of two or more kinds as necessary.

On the other hand, the step of preparing the polyimide film may be applied to a support after further adding a catalyst to the polyacid solution and the third composition.

As the catalyst, a dehydration catalyst including an anhydrous acid such as acetic anhydride, and tertiary amines such as isoquinoline, β-methylpyridine, and pyridine can be used. The catalyst can be an anhydrous acid / amine mixture or an anhydrous acid / amine. / Solvent mixture.

The molar ratio of the o-carboxylic amide functional group in the polyamic acid solution can be used to calculate the amount of anhydrous acid input. 1.0 mol to 5.0 mol can be used, and the polyamino acid solution can be used. The molar ratio of the o-carboxamido group in the calculation of the tertiary amine input amount, specifically, 0.2 mol to 3.0 mol can be input.

In addition, in the step of subjecting the polyamidic acid solution applied to the support to gelation, the gelation temperature condition may be 100 ° C to 250 ° C.

As the support, glass plates, aluminum foil, circulating stainless steel belts, stainless steel drums, and the like can be used.

The processing time required for gelation can be from 5 minutes to 30 minutes, but it is not limited to this. It can be based on the gelation temperature, the type of support, the amount of the polyamic acid solution applied, and the catalyst. Changes in mixing conditions.

After the gelled membrane is separated from the support, it is subjected to a heat treatment to finish drying and fluorination.

The heat treatment temperature may be 100 ° C to 500 ° C, and the heat treatment time may be 1 minute to 30 minutes. When the gelled film is heat-treated, it can be fixed to a fixable bracket, such as a pin-type frame or a jig-type bracket, for heat treatment.

On the other hand, in the present invention, in order to realize an ultra-thin film having a thickness of 8 μm or less, it is necessary to control the process conditions such as the ejection amount, speed, and pressure when the polyamic acid is applied (ejected) to the support.

Specifically, it is necessary to minimize the sloshing at the time when the polyamic acid solution is ejected from the T-die to an endless belt and landed in the form of a film. Therefore, when forming the ejection film, The air may be supplied at a pressure lower than the pressure used when preparing a common polyimide film, such as a pressure of H ₂ O of 10 mm to 40 mm.

At this time, the amount ejected from the T-die and the speed of the endless belt can satisfy the following formula. For example, the amount ejected from the T-die can be 150 kg / hr to 300 kg / hr, and the speed of the endless belt can be 15 mpm to 25 mpm.

[Numerical formula]

Amount ejected from T-die / Time ejected from T-die = Specific gravity of film * (T-die cross-sectional area) * (Speed of endless belt)

At the laboratory level, the cast film thickness can be adjusted to obtain a polyimide film with an ultra-thin film thickness, but in a mass production process, when the above range is met, an ultra-thin film thickness of 8 μm or less can be achieved.

Specifically, the polyfluorene imide film of the present invention may have a thickness of 7.5 μm or less, specifically 3 μm to 7.5 μm, and more specifically 5 μm to 7.5 μm.

In addition, when heat treatment is performed by using a tenter dryer or the like after being fixed to the pin frame, in order to prevent the film from being broken during the heat treatment process, the maximum temperature of the heat treatment can be 50 when the yellow polyimide film of the same thickness is prepared The heat treatment is performed at a temperature as low as 150 ° C to 150 ° C.

In addition, the film whose fluorene imidization has been completed may be cooled at 20 ° C to 30 ° C to form a film.

In order to provide a light shielding function, the prepared polyfluoreneimide film may have a light transmittance of 10% or less or 9.7% or less, and the lower the light transmittance, the better.

The present invention may also provide a coverlay including the polyimide film, and may provide an electronic device including the coverlay film.

When the polyimide film is applied to cover films, insulating films, semiconductors, etc., it can not only make the product lighter and thinner, but also improve the aesthetic characteristics. It can block the internal shape and loading parts from the external field of view. Effective for confidentiality.

[Inventive effect]

As described above, the polyfluorene imide film of the present invention has low light transmittance in the visible light region.

In addition, the polyfluorene imide film is not only excellent in mechanical stability but also excellent in alkali resistance. Therefore, it can be effectively used for a cover film and an electronic device including the cover film.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples. The following examples are only used to describe the present invention more specifically, and the present invention is not limited to the following examples.

<Example 1>

Preparation Example 1: Polymerization of Polyamic Acid

As a polyamic acid solution polymerization process, 407.5 g of dimethylformamide (DMF) was put into a 500 mL reactor under a nitrogen atmosphere as a solvent.

After setting the temperature to 25 ° C, 35.90 g of 4,4'-oxydiphenylamine was added as the diamine monomer, and the mixture was stirred for about 30 minutes. After confirming that the monomer was dissolved, 35.90 g of pyromellitic dicarboxylic acid was added in batches. Anhydride is used as a dianhydride monomer, and the final amount is adjusted so that the viscosity becomes 250 million cP to 280 million cP.

After the completion of the addition, the polyamic acid solution having a final viscosity of 280,000,000 cP was polymerized by stirring for 1 hour while maintaining the temperature.

Preparation Example 2: Preparation of a composition including a fluorine-based resin and carbon black

30 g of a PFA resin as a fluorine-based resin was mixed with 70 g of DMF as a first organic solvent to prepare a first composition having a solid content of 30%.

After mixing 10 g of carbon black and 1 g of dispersant BYK-430 into 89 g of DMF as a second organic solvent, a second composition including carbon black having an average particle diameter of 0.5 μm was prepared using a mill.

A third composition was prepared by mixing 100 g of the first composition and 100 g of the second composition.

Preparation Example 3: Preparation of Polyfluorene Imide Film

5 g of the third composition prepared in Preparation Example 2 was mixed with 30 g of the polyamic acid solution prepared in Preparation Example 1. 4.76 g of isoquinoline (IQ) and 26.36 g of anhydrous acetic acid ( AA) and 18.87 g of DMF as catalysts, and then mixed uniformly, casted to a SUS plate (100SA, Sandvik) at 70 μm using a doctor blade, and dried at a temperature ranging from 100 ° C to 200 ° C.

After that, the film was peeled from the SUS board, fixed to a pin frame, and transferred to a high-temperature tenter.

After the film was heated to 200 ° C to 600 ° C in a high-temperature tenter, it was cooled at 25 ° C, and then separated from the pin frame to prepare 90% by weight of polyimide based on the total weight of the polyimide film. 7.5 μm thick polyimide film of amine resin, 5 wt% carbon black, and 5 wt% PFA resin.

<Example 2>

A 7.5 μm-thick polyimide film was prepared in the same manner as in Example 1 except that the contents of the polyimide resin, fluorine-based resin, and carbon black were changed as shown in Table 1.

<Example 3>

A 7.5 μm-thick polyimide film was prepared in the same manner as in Example 1 except that the contents of the polyimide resin, fluorine-based resin, and carbon black were changed as shown in Table 1.

<Example 4>

Except that the particle diameter of the carbon black was changed as in Table 1, a polyimide film having a thickness of 7.5 μm was prepared in the same manner as in Example 1.

<Example 5>

Except that the particle diameter of the carbon black was changed as in Table 1, a polyimide film having a thickness of 7.5 μm was prepared in the same manner as in Example 1.

〈Comparative example 1〉

In Preparation Example 2, except that the first composition was not mixed, and the contents of the polyfluorene imide resin and carbon black were changed as shown in Table 1, a 7.5 μm thick polyfluorene was prepared by the same method as in Example 1. Imine film.

〈Comparative example 2〉

A 7.5 μm-thick polyimide film was prepared in the same manner as in Example 1 except that the contents of the polyimide resin, fluorine-based resin, and carbon black were changed as shown in Table 1.

〈Comparative example 3〉

A 7.5 μm-thick polyimide film was prepared in the same manner as in Example 1 except that the contents of the polyimide resin, fluorine-based resin, and carbon black were changed as shown in Table 1.

〈Comparative example 4〉

Except that the particle diameter of the carbon black was changed as in Table 1, a polyimide film having a thickness of 7.5 μm was prepared in the same manner as in Example 1.

〈Comparative example 5〉

Except that the particle diameter of the carbon black was changed as in Table 1, a polyimide film having a thickness of 7.5 μm was prepared in the same manner as in Example 1.

〈Comparative example 6〉

A 7.5 μm-thick polyimide film was prepared in the same manner as in Example 1 except that the fluorine-based resin was changed as shown in Table 1.

〈Comparative example 7〉

A 7.5 μm-thick polyimide film was prepared in the same manner as in Example 1 except that the fluorine-based resin was changed as shown in Table 1.

〈Comparative example 8〉

Preparation Example 4: Preparation of Polyimide Film

1.5 g of carbon black with an average particle size of 0.5 μm and 1.5 g of PFA resin were mixed into 30 g of the polyamic acid solution prepared in Preparation Example 1. 4.76 g of isoquinoline (IQ) and 26.36 g Anhydrous acetic acid (AA) and 18.87 g of DMF were used as catalysts, and then uniformly mixed, casted to a SUS board (100SA, Sandvik) at 70 μm using a doctor blade, and dried at a temperature ranging from 100 ° C to 200 ° C.

After that, the film was peeled from the SUS board, fixed to a pin frame, and transferred to a high-temperature tenter.

After the film was heated to 200 ° C to 600 ° C in a high-temperature tenter, it was cooled at 25 ° C, and then separated from the pin frame to prepare 90% by weight of polyimide based on the total weight of the polyimide film. 7.5 μm thick polyimide film of amine resin, 5 wt% carbon black, and 5 wt% PFA resin.

[Table 1]

* Comparative Example 8 is a polyimide film prepared according to Preparation Example 1 and Preparation Example 4, but not Preparation Example 1 to Preparation Example 3.

Experimental Example 1: Evaluation of Alkali Resistance Index

After the corona treatment was performed on both sides of the polyimide film prepared in <Example 1> to <Example 5> and <Comparative Example 1> to <Comparative Example 8>, the polyimide film was sequentially laminated. , Bonding sheet (adhesive), and copper foil, and then a 50 kgf pressure was applied at a temperature of 160 ° C. for 30 minutes using a hot press to produce a sample.

Repeatedly, the sample cut into 4 cm * 10 cm was exposed to a 10% NaOH solution at 55 ° C for 5 minutes and a decontamination solution (10% NaMnO ₄ + 4% NaOH) at 55 ° C for 5 minutes. In the cleaning process, the thickness of the film is measured and compared with the thickness before exposure to the NaOH solution and the decontamination solution. The degree of change in the thickness after exposure is compared to the thickness before exposure. The results are shown in the following table. 2.

[Table 2]

Referring to Table 2, it can be confirmed that the polyimide films of Examples 1 to 5 include fluorine-based resins in a range of 3% to 15% by weight, and therefore have an alkali resistance index of 70% or more and are very excellent. On the contrary, compared with Examples 1 to 5, the content of the alkali resistance index of Comparative Example 1 excluding the fluorine-based resin and the content of the fluorine-based resin of the comparative example 2 which is less than the content range of the present invention is less than 70. %.

In addition, it was confirmed that the content of the fluorine-based resin exceeds the content range of the present invention. Comparative Example 3 has an alkali resistance index of 85% or more and is excellent in alkali resistance. However, the physical properties of Table 3 and Table 4 described below are shown. It was confirmed that the physical properties of the polyfluorene imine film of Comparative Example 3 were lower than those of Example 1.

Experimental example 2: Evaluation of light transmittance

The transmittance measurement equipment (model name: ColorQuesetXE, manufacturing company: HunterLab) was used in the visible light region by the American Society for Testing Materials (ASTM) D1003 method for <Example 1> to <Example 5 respectively. > And <Comparative Example 1> to <Comparative Example 8> The transmittance of the polyfluorene imide film was measured, and the results are shown in Table 3 below.

In addition, the polyimide films prepared in <Example 1> to <Example 5> and <Comparative Example 1> to <Comparative Example 8> were exposed to an alkaline environment as in Experimental Example 1 above, and were used. The transmittance measuring device (model name: ColorQuesetXE, manufacturing company: HunterLab) measures transmittance in the visible light region by the ASTM D1003 method, and the results are shown in Table 3 below.

[table 3]

Experimental example 3: Evaluation of tensile properties

The polyimide films prepared in <Example 1> to <Example 5> and <Comparative Example 1> to <Comparative Example 8> were measured for tensile properties, that is, tensile strength and elongation, according to ASTM D882. And elastic modulus, and the results are shown in Table 4 below.

In addition, after the polyimide films prepared in <Example 1> to <Example 5> and <Comparative Example 1> to <Comparative Example 8> were respectively exposed to an alkaline environment as in Experimental Example 1 above, according to According to ASTM D882, tensile properties, that is, tensile strength, elongation, and elastic modulus are measured. The results are shown in Table 4 below.

[Table 4]

With reference to Tables 3 and 4, it was confirmed that even the polyimide films of Examples 1 to 5 included PFA as a fluorine-based resin in a range of 3% to 15% by weight, light transmittance, tensile properties, and the like. The physical properties were also not lower than those of Comparative Example 1 excluding the fluorine-based resin, and it was confirmed that the above-mentioned physical properties of Comparative Example 3 in which the content of the fluorine-based resin exceeded the content range of the present invention were lower than those of Example 1.

In addition, it was confirmed that the particle size of carbon black in Comparative Example 3 which exceeds the range of the present invention and the particle size of carbon black in Comparative Example 4 which is less than the range of the present invention are in the physical properties such as gloss, transmittance, and tensile properties. More than at least one.

In particular, it was confirmed that the physical properties such as light transmittance and tensile properties of the polyfluorene imine films of Examples 1 to 5 after being exposed to an alkaline environment were better than those of the comparative examples. Polyimide films of Examples 1 to Comparative Example 8.

On the other hand, FIG. 1 is a SEM photograph showing an outer surface of a sample prepared by using the polyimide film of Comparative Example 1 after being exposed to an alkaline environment, and FIG. 2 is a photograph showing an enlarged part of the photograph of FIG. 1. 3 is a SEM photograph showing an outer surface of a sample prepared by using the polyfluorene imine film of Example 1 after being exposed to an alkaline environment, and FIG. 4 is a photograph showing an enlarged part of the photograph in FIG. 2.

With reference to these drawings, it was confirmed that in the case of the surface of the sample prepared according to Comparative Example 1, carbon black particles were peeled from the surface and the copper foil layer was exposed. On the contrary, it was confirmed that In the case of the surface of the sample having improved alkalinity, shedding of carbon black particles is minimized.

The above has been described with reference to the embodiments of the present invention. However, those skilled in the art to which the present invention pertains can perform various applications and modifications within the scope of the present invention based on the foregoing.

no

FIG. 1 is a scanning electron microscope (SEM) photograph of an external surface of a flexible circuit substrate prepared using the polyfluorene imide film of Comparative Example 1 after being exposed to an alkaline environment.

FIG. 2 is a photograph in which the photograph in FIG. 1 is enlarged.

FIG. 3 is a SEM photograph of an outer surface of a flexible circuit substrate prepared using the polyfluorene imide film of Example 1 after being exposed to an alkaline environment.

FIG. 4 is a photograph in which the photograph in FIG. 3 is enlarged.

Claims (16)

A polyimide film comprising 75% to 95% by weight of a polyimide resin, 2% to 15% by weight of a fluororesin, and 3% by weight to a total weight of the polyimide film. 10% by weight of carbon black with an average particle diameter of 0.1 μm to 5 μm, The fluorine-based resin includes oxygen in a molecular structure, The thickness is 8.0 μm or less, and the alkali resistance index evaluated based on the thickness of the polyimide film is 70% or more. The polyimide film according to item 1 of the scope of patent application has a thickness of 3 μm to 7.5 μm. The polyimide film according to item 1 of the scope of the patent application has a transmittance in the visible light region of 10% or less. The polyimide film according to item 1 of the scope of the patent application, wherein the fluorine-based resin is a copolymer derived from a monomer composition including tetrafluoroethylene and a compound represented by chemical formula (1): CF ₂ = CF (OR ^f ) (1) In the chemical formula (1), R ^f is a C ₁ -C ₆ perfluoroalkyl group. The polyfluorene imide film according to item 4 of the scope of the patent application, wherein in the chemical formula (1), R ^f is a C ₁ -C ₃ perfluoroalkyl group. The polyimide film according to item 4 of the scope of the patent application, wherein the fluorine-based resin is a perfluoroalkoxy resin. The polyfluoreneimide film according to item 4 of the scope of the patent application, wherein the fluorine-based resin has a molar ratio of tetrafluoroethylene: compound represented by the chemical formula (1) = 96: 4 to 97: 3. The polyimide film according to item 1 of the patent application scope, wherein the fluorine-based resin and the carbon black are chemically bonded to form a matrix structure. The polyimide film according to item 8 of the scope of the patent application, wherein the fluorine-based resin forms a matrix structure by chemically bonding with the carbon black through interaction with a functional group including oxygen in a molecular structure. The polyimide film according to item 9 of the scope of the patent application, wherein the functional group including oxygen is a perfluoroalkyl ether group. A method for preparing a polyfluoreneimide film, which is a method for preparing a polyfluoreneimide film according to item 1 of the scope of patent application, which comprises: (A) a step of polymerizing polyamino acids from dianhydrides and diamines; (B) a step of preparing a first composition including a fluorine-based resin and a first organic solvent; (C) a step of preparing a second composition including carbon black having an average particle diameter of 0.1 μm to 5 μm and a second organic solvent; (D) a step of preparing the third composition by mixing the first composition and the second composition; and (E) A step of mixing the third composition with the polyamic acid, forming a film on a support, and performing heat treatment to perform imidization. The method for preparing a polyfluoreneimide film according to item 11 of the scope of the patent application, wherein the polyfluoreneimide film includes 10% to 30% by weight of fluorine based on the total weight of the first composition. Resin. The method for preparing a polyimide film according to item 11 of the scope of the patent application, wherein in the step (d), by mixing the first composition and the second composition, a fluorine-based resin and carbon black Chemical bonding forms a matrix structure. The method for preparing a polyfluoreneimide film according to item 11 of the scope of the patent application, wherein the first organic solvent is the same as or different from the second organic solvent, and includes a material selected from the group consisting of N, N'-dimethylformamide, One or more members of the group consisting of N, N'-dimethylacetamide, N-methyl-pyrrolidone, γ-butyrolactone, and diethylene glycol dimethyl ether. A cover film comprising the polyimide film described in item 1 of the scope of patent application. An electronic device includes the cover film described in item 15 of the scope of patent application.