KR20200052178A - Polyamide-imide film and prepatartion methode thereof - Google Patents

Abstract

A polyamide-imide film according to the present invention has excellent mechanical properties and high elasticity, and has high dimensional stability to moisture, and thus is suitable for a display cover film.

Description

POLYAMIDE-IMIDE FILM AND PREPATARTION METHODE THEREOF}

The present invention relates to a polyamide-imide film, specifically having excellent mechanical properties and high elasticity, and having high dimensional stability against moisture, suitable for a polyimide-imide film and a manufacturing method thereof for a display cover film It is about.

Aromatic polyimide (PI) is a polymer material having excellent heat resistance, chemical stability, electrical properties, and dimensional stability, and is increasingly being used as a next-generation electric / electronic material that is increasingly miniaturized and integrated. However, due to the disadvantage that it has a dark brown color due to the charge transfer complex (CTC) of ð electrons present in the imide chain, there are many limitations in use. Introducing a strong electron attractor such as a trifluoromethyl (-CF ₃ ) group to limit the movement of ð electrons, or bending by introducing a sulfone (-SO _2- ) group, an ether (-O-) group, etc. into the main chain A colorless and transparent PI film can be prepared by reducing the CTC effect by making a structure, or by introducing an aliphatic ring compound to inhibit the resonance structure of electrons.

In addition, aromatic polyamide (PA) is a material having excellent heat resistance and high levels of tensile strength and tensile modulus. The high mechanical properties of PA are due to the amide functional groups periodically present in the polymer chain, and increase the crystallinity of the polymer to impart high strength and high elastic modulus, but at the same time, there is a disadvantage of deteriorating processability.

Poly (amide-imide) (PAI) multiblock copolymers are materials that emphasize the advantages of PI and PA, and are materials that can simultaneously have the advantages of PI as electrical / electronic materials and high mechanical properties of PA. imide) (PAI) The film was applied to the product, causing shrinkage when placed in humid conditions for a long time, or thermal deformation when placed in high temperature conditions for a long time, causing defects.

Accordingly, there is a need for a film having improved strain generation rate under high temperature and high humidity conditions while maintaining excellent mechanical properties of the PAI film.

The present invention is to provide a polyamide-imide film having excellent mechanical properties and high elasticity and high dimensional stability against moisture.

In addition, the present invention is to provide a method for producing the polyamide-imide film.

And, the present invention is to provide a display device comprising the polyamide-imide film.

According to the present invention, the aromatic imide-based first repeating unit; an amide-based second repeating unit containing meta-phenylene; And an amide-based third repeating unit containing para-biphenylene,

A polyamide-imide copolymer in which at least one of the first repeating unit, the second repeating unit and the third repeating unit is substituted with one or more fluorine-containing functional groups,

Provided is a polyamide-imide film having a coefficient of moisture expansion (CME) value of 25 ppm /% RH or less measured in a range of 20% RH to 80% RH.

Further, according to the present invention, a method for manufacturing the polyamide-imide film and a display device including the polyamide-imide film are provided.

Hereinafter, a polyamide-imide film according to embodiments of the present invention, a method of manufacturing the same, and a display device including the same will be described in detail.

Prior to that, the terminology is only for referring to a specific embodiment, and is not intended to limit the present invention, unless expressly stated in the specification.

Singular forms used herein include plural forms unless the phrases clearly indicate the opposite.

As used herein, the meaning of 'include' embodies a specific characteristic, region, integer, step, action, element, and / or component, and other specific characteristic, region, integer, step, action, element, component, and / or group. It does not exclude the existence or addition of.

In addition, in this specification, terms including an ordinal number such as 'first' and 'second' are used for the purpose of distinguishing one component from other components, and are not limited by the ordinal number. For example, within the scope of the present invention, the first component may also be referred to as the second component, and similarly, the second component may be referred to as the first component.

In this specification, the weight average molecular weight means the weight average molecular weight of polystyrene conversion measured by GPC method. In the process of measuring the weight average molecular weight in terms of polystyrene measured by the GPC method, detectors and analytical columns, such as a commonly known analytical device and a differential index detector, can be used, and the temperature is usually applied. Conditions, solvents, and flow rates can be applied. Specific examples of the measurement conditions include a temperature of 30 ° C, a chloroform solvent (Chloroform) and a flow rate of 1 mL / min.

Polyamide-imide film

According to an embodiment of the present invention, the aromatic imide-based first repeating unit; an amide-based second repeating unit containing meta-phenylene; And a amide-based third repeating unit comprising para-biphenylene, wherein at least one of the first repeating unit, the second repeating unit and the third repeating unit is substituted with one or more fluorine-containing functional groups, polyamide- A polyamide-imide film is provided, comprising an imide copolymer and having a Coefficient of Moisture Expansion (CME) value of 25 ppm /% RH or less measured in a 20% RH to 80% RH section.

Polyamide-imide copolymer is applied to various fields, it is required to satisfy several properties at the same time. As a result of continuous research by the present inventors, a film capable of satisfying high dimensional stability against moisture was invented by using a polyamide-imide copolymer having a specific structure. The film according to the present invention is easy to apply to industrial fields exposed to humid environments, etc., and has excellent mechanical properties, thermal stability, and high elasticity, which is a substrate for a display, a protective film for a display, a touch panel, flexible or foldable It can be usefully applied as a cover film of (foldable) devices.

More specifically, in the present invention, due to the structure containing a fluorine-containing functional group (for example, trifluoromethyl group (-CF ₃ )), ð electrons can be inhibited by charging the CTC (Charge Transfer Complex), thereby improving thermal stability. , The combination of the above-described effect of improving the flexibility according to the bonding structure of the meta position of the second repeating unit, and the effect of improving the mechanical properties resulting from the rigid property according to the bonding structure of the para position of the third repeating unit are combined to thermally copolymerize The properties, mechanical properties and optical properties can be improved simultaneously. In addition, a fluorine-containing functional group is included to effectively control an increase in dimensional change rate after exposure to moisture.

Particularly, in the transverse (TD) direction stretching process when manufacturing a film, the tensile elastic modulus can be improved by aligning the copolymer chains, and the induction of hydrogen bonds is advantageous due to packing of the polymer chains, thereby significantly improving water absorption. Can be.

The polyamide-imide film according to an embodiment of the present invention satisfies a value of 25 ppm or less of a coefficient of moisture expansion (CME) measured in a 20% RH to 80% RH section, and accordingly, a display It is easy to apply to the cover film and the like.

The water expansion coefficient may mean the slope of the graph with respect to the measured length for each relative humidity, and may be specifically measured according to the following general formula 1:

[Formula 1]

Water expansion coefficient (ppm /% RH) = (L1-L0) / (80% RH-20% RH)

The dimensional change rate of the general formula (1) is 50 µm thick, 0.5 cm wide and 1.5 cm long polyamide-imide film specimens are heated to 60 ° C. at 0.5 to 1 ° C./min, and the relative humidity increases up to 90% RH. While measuring the length change of the specimen,

80% RH, 20% RH means each relative humidity,

L0 is the length of the film specimen measured under the condition of 20% RH,

L1 is the length of the film specimen measured at 80% RH.

The polyamide-imide film according to an embodiment of the present invention may have a moisture expansion coefficient of 23 ppm /% RH or less or 20 ppm /% RH or less. When the water expansion coefficient exceeds 25ppm /% RH, it is difficult to apply to products exposed to humid environments, etc., and there is a possibility that mechanical properties are also deteriorated.

In the polyamide-imide film according to an embodiment of the present invention, the transverse (TD) direction elongation at 0.5 ° C and 300 mm / min satisfies 0.5% to 5%, so that the polyamide-imide copolymer has mechanical properties. While maintaining physical properties, it is possible to achieve thermal stability and high elasticity. In particular, when the transverse (TD) direction is stretched by the repeating unit structure, the tensile elastic modulus can be improved by aligning the copolymer chains, and the packing of the polymer chain is easy and the hydrogen bonding is advantageous, so that the expansion rate under humidification is remarkable. Can be reduced.

Preferably, the elongation in the transverse (TD) direction may be 1% to 4%, or 2.5% to 3.5%. When the elongation range of 0.5% to 5% is out of range, the alignment of the chain structures in the film is not sufficiently performed, and thus the tensile modulus may be reduced, and deformation by moisture may easily occur.

The polyamide-imide film according to an embodiment of the present invention is a film produced by applying a line speed of 250 ° C and 0.3 mm / min based on 50 ± 2 μm thickness according to the astm d 882 standard. Since the transverse (TD) direction elastic modulus satisfies 6.3 GPa or more, it is possible to realize thermal stability and high elasticity while maintaining the mechanical properties of the polyamide-imide copolymer. In particular, when the transverse (TD) direction is stretched by the repeating unit structure, the tensile modulus may be improved by aligning the copolymer chains.

The polyamide-imide film according to an embodiment of the present invention may have an elastic modulus in the TD direction of 6.5 GPa or more, or 6.7 GPa or more.

The thickness of the polyamide-imide resin film according to an embodiment of the present invention is not particularly limited, and may be selected within a range suitable for an applied product in consideration of optical properties, mechanical properties, and elastic modulus of the film. For example, it may be 0.1 to 1000 μm, preferably 1 to 500 μm or 10 to 100 μm.

The polyamide-imide resin film according to an embodiment of the present invention includes a polyamide-imide copolymer including an imide-based repeating unit and an amide-based repeating unit having a specific structure, and the copolymer is an amide repeating unit and imide repeating One or more fluorine-containing functional groups are substituted in the unit. Hereinafter, this will be described in more detail.

In the present invention, the polyamide-imide copolymer includes an aromatic imide-based first repeating unit, and may specifically include a structure represented by Formula 1 below.

(i) repeat unit derived from imide: first repeat unit

[Formula 1]

In Chemical Formula 1,

R ¹ is the same in each repeating unit or different from each other, and each independently a single bond, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) ₂ -, -Si (CH ₃ ) ₂ -,-(CH ₂ ) _p- (1≤p≤10),-(CF ₂ ) _q- (1≤q≤10), -C (CH ₃ ) ₂ -, -C (CF ₃ ) _2- , -C (= O) NH-, or a divalent aromatic organic group having 6 to 30 carbon atoms;

R ² is the same or different from each repeating unit, and each independently -H, -F, -Cl, -Br, -I, -CF ₃ , -CCl ₃ , -CBr ₃ , -CI ₃ , -NO ₂ , -CN, -COCH ₃ , -CO ₂ C ₂ H ₅ , a silyl group having three aliphatic organic groups having 1 to 10 carbon atoms, an aliphatic organic group having 1 to 10 carbon atoms, or an aromatic organic group having 6 to 20 carbon atoms ;

n1 and m1 are each independently an integer from 0 to 3;

Y ¹ is the same in each repeating unit or different from each other, and each independently includes a divalent aromatic organic group having 6 to 30 carbon atoms containing at least one trifluoromethyl group (-CF ₃ ); The aromatic organic group may be present alone; Two or more aromatic organic groups are bonded to each other to form a divalent condensed ring; Or two or more aromatic organic groups are a single bond, a fluorenylene group, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) _2- , -Si ( CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (here 1≤q≤10), -C (CH ₃ ) _2- , -C ( CF ₃ ) _2- , or -C (= O) NH-;

E ¹ is each independently a single bond or -NH-.

Here, the single bond means a case of chemically bonding to simply connect the groups R ¹ of the next amount in the formula (1).

R ² is the same or different from each repeating unit, and each independently -H, -F, -Cl, -Br, -I, -CF ₃ , -CCl ₃ , -CBr ₃ , -CI ₃ , -NO ₂ , -CN, -COCH ₃ , -CO ₂ C ₂ H ₅ , a silyl group having three aliphatic organic groups having 1 to 10 carbon atoms, an aliphatic organic group having 1 to 10 carbon atoms, or an aromatic organic group having 6 to 20 carbon atoms have.

n1 and m1 may be each independently an integer of 0 to 3.

Y ¹ is the same in each repeating unit or different from each other, and each independently may be an aliphatic organic group having 3 to 10 carbon atoms.

E ¹ may each independently be a single bond or -NH-.

Here, the single bond means a chemical bond in which the groups on each side of each substituent in the formula (1) are simply connected.

Preferably, the first repeating unit may include a repeating unit represented by Chemical Formula 1-1:

[Formula 1-1]

In Chemical Formula 1-1,

R ¹ , R ² , n1 and m1 are as defined in Chemical Formula 1.

In the present invention, the polyamide-imide copolymer includes an amide-based second repeating unit comprising meta-phenylene; And an amide-based third repeating unit including para-biphenylene, wherein the second repeating unit may include a structure represented by Formula 2, and the third repeating unit may be represented by Formula 3 below: Structure.

(ii) Amide origin  Repeat unit: 2nd repeat unit and 3rd repeat unit

[Formula 2]

[Formula 3]

In Formula 2 and Formula 3,

Y ² and Y ^{2 '} are the same or different in each repeating unit, and each independently is a divalent aromatic organic group having 6 to 30 carbon atoms containing at least one trifluoromethyl group (-CF ₃ ); The aromatic organic group may be present alone; Two or more aromatic organic groups are bonded to each other to form a divalent condensed ring; Or two or more aromatic organic groups are a single bond, a fluorenylene group, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) _2- , -Si ( CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (here 1≤q≤10), -C (CH ₃ ) _2- , -C ( CF ₃ ) _2- , or -C (= O) NH-;

E ² , E ^{2 '} , E ³ , E ^3' , E ⁴ and E ^{4 '} are each independently a single bond or -NH-.

)에 대하여 메타 위치에 위치하며, 제3 반복 단위에서 2개의 -C(=O)-는 A(

)에 대하여 파라 위치에 위치한다.The second repeating unit and the third repeating unit are amide-derived repeating units, and among the formulas 2 and 3, the divalent linking group of the form -C (= O) -AC (= O)-is diacyl halide, dicar It is derived from one or more compounds selected from the group consisting of carboxylic acids and dicarboxylates. In the second repeating unit, two -C (= O)-are A (

) In the meta position, and in the third repeating unit, two -C (= O)-are A (

) In the para position.

Preferably, the second repeating unit may include a repeating unit represented by Chemical Formula 2-1:

[Formula 2-1]

.

.

Preferably, the third repeating unit may include a repeating unit represented by Chemical Formula 3-1:

[Formula 3-1]

.

.

In the polyamide-imide copolymer according to the present invention, the molar ratio of the second repeating unit and the third repeating unit is 10:90 to 50:50, and by satisfying the molar ratio, thermal properties, mechanical properties, and humidification of the copolymer Under the conditions, dimensional stability can be simultaneously improved.

Specifically, the effect of improving the flexibility according to the bonding structure of the meta position of the second repeating unit and the effect of improving the mechanical properties resulting from the rigid property according to the bonding structure of the para position of the third repeating unit are combined to form a copolymer. It is possible to simultaneously improve dimensional stability under thermal, mechanical and humid conditions.

When the molar ratio of the second repeating unit and the third repeating unit is out of the above-described range, problems of deterioration in heat resistance, such as increased hazes or yellowing, may occur.

In the polyamide-imide copolymer according to the present invention, the molar ratio of the total sum of the second repeating unit and the third repeating unit derived from the amide is preferably 5: 5 to 2: 8 with respect to the first repeating unit derived from imide. (1: 1 to 1: 4), or 4.5: 5.5 to 3: 7 (about 1: 1.22 to 1: 2.33), or 4: 6 to 3: 7. By simultaneously satisfying the molar ratio and the molar ratio of the above-described second repeating unit and third repeating unit, it is possible to improve both mechanical properties, thermal properties and dimensional stability of the polyamideimide resin film to a high level.

In the polyamide-imide copolymer according to the present invention, the molar ratio of the total sum of the second repeating unit and the third repeating unit derived from amide is preferably 3: 7 to 6: 4 with respect to the first repeating unit derived from imide. It may be, by satisfying the molar ratio and the molar ratio conditions of the above-described second repeating unit and third repeating unit at the same time, it is possible to improve both the mechanical properties of the copolymer, dimensional stability under the humidifying conditions of the thermal properties to a high level.

Further, in the polyamideimide block copolymer, when the molar ratio between the sum of the first repeating unit: the second repeating unit and the third repeating unit is 3: 7 to 4: 6, the second repeating unit: third The molar ratio of the repeating unit may be 20:80 to 50:50, or 30:70 to 45:55, and more preferably 30:70. When satisfying the above range at the same time, it is possible to improve all of the mechanical properties, thermal properties and optical properties of the polyamideimide resin film to a high level.

Further, in the polyamideimide block copolymer, when the molar ratio of the total sum of the second repeating unit and the third repeating unit to the first repeating unit is 4.5: 5.5 to 4: 6, the second repeating unit: The molar ratio of the third repeating unit may be 20:80 to 40:60. When satisfying the above range at the same time, it is possible to improve all of the mechanical properties, thermal properties and optical properties of the polyamideimide resin film to a high level.

In one embodiment of the present invention, the polyamide-imide copolymer may further include a fourth repeating unit represented by the following Chemical Formula 4 in addition to the first repeating unit, second repeating unit and third repeating unit. :

[Formula 4]

In Chemical Formula 4,

R ^{1 '} is the same in each repeating unit or different from each other, and each independently includes a divalent aromatic organic group having 6 to 30 carbon atoms; The aromatic organic group may be present alone; Two or more aromatic organic groups are bonded to each other to form a divalent condensed ring; Or two or more aromatic organic groups are a single bond, a fluorenylene group, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) _2- , -Si ( CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (here 1≤q≤10), -C (CH ₃ ) _2- , -C ( CF ₃ ) _2- , or -C (= O) NH-.

R ^{2 '} is the same or different from each repeating unit, and each independently -H, -F, -Cl, -Br, -I, -CF ₃ , -CCl ₃ , -CBr ₃ , -CI ₃ ,- NO ₂ , -CN, -COCH ₃ , -CO ₂ C ₂ H ₅ , a silyl group having three aliphatic organic groups having 1 to 10 carbon atoms, an aliphatic organic group having 1 to 10 carbon atoms, or an aromatic organic group having 6 to 20 carbon atoms Can be.

n3 and m3 may each independently be an integer from 0 to 3.

Y ^{1 '} is the same or different in each repeating unit, and each independently is a divalent aromatic organic group having 6 to 30 carbon atoms containing at least one trifluoromethyl group (-CF ₃ ), and the aromatic organic group alone Exists; Two or more aromatic organic groups may be bonded to each other to form a divalent condensed ring; Or two or more aromatic organic groups are a single bond, a fluorenylene group, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) _2- , -Si ( CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (here 1≤q≤10), -C (CH ₃ ) _2- , -C ( CF ₃ ) _2- , or -C (= O) NH-.

E ^{1 '} may each independently be a single bond or -NH-.

As described above, the polyamide-imide block copolymer including both the first repeating unit, the second repeating unit, and the third repeating unit has a molar ratio of the second repeating unit and the third repeating unit described above, and the first imide derived therefrom. By satisfying the molar ratio of the repeating unit and the second repeating unit derived from the amide and the third repeating unit in a specific range, it is possible to simultaneously improve the dimensional stability in the mechanical properties, thermal properties and humidifying conditions of the copolymer.

In addition, the polyamide-imide copolymer according to an embodiment of the present invention may have a weight average molecular weight of 100,000 to 1,000,000 g / mol, preferably 150,000 to 800,000 g / mol. When the molecular weight is satisfied, mechanical properties, thermal properties, and dimensional stability desired by the present invention can be further improved.

II. Method for producing polyamide-imide film

According to another embodiment of the present invention, a method for manufacturing the above-described polyamide-imide film is provided.

The method for producing a polyamide-imide film according to an embodiment of the present invention includes a step of preparing a polyamide-imide copolymer, and specifically, an aromatic amine compound having an aromatic diamine compound in which one or more fluorine-containing functional groups are substituted. Or reacting with anhydride thereof to initiate a reaction; And synthesizing the polyamide-imide copolymer by reacting the resultant of the starting step with a mixture of isophthalic acid or a derivative thereof and bisphenyldicarboxylic acid or a derivative thereof and an aromatic diamine in which one or more fluorine-containing functional groups are substituted. Includes.

The aromatic diamine compound in which the fluorine-containing functional group is substituted by one or more is an aromatic carboxylic acid or anhydride thereof as a compound forming the above-described first repeating unit, and the reaction may be initiated by mixing them in an appropriate solvent.

Next, an aromatic diamine in which a mixture of isophthalic acid or a derivative thereof and a bisphenyldicarboxylic acid or derivative thereof, which is a compound forming the second repeating unit and the third repeating unit, is substituted with one or more fluorine-containing functional groups in the result of the starting step. And mixing to perform the reaction.

Finally, chemical imidization reaction is induced by adding compounds such as acetic anhydride and pyridine to the reaction mixture of the above step, or thermal imidization of amic acid by Azeotropic Distillation (azeotropic distillation) A polyamide-imide copolymer comprising a first repeating unit, a second repeating unit and a third repeating unit as described above is prepared by inducing a reaction.

The step of thermal imidization may be performed at a temperature of 100 ° C or higher, or a temperature of 100 ° C to 350 ° C, or a temperature of 150 ° C to 250 ° C.

In addition, as commonly known, low-temperature solution polymerization, interfacial polymerization, melt polymerization, solid phase polymerization, and the like may be used in the preparation of the polyamide-imide block copolymer.

A method for producing a polyamide-imide film according to an embodiment of the present invention includes: forming a preliminary film from the prepared polyamide-imide copolymer; And stretching the preliminary film under specific conditions to form a film.

The step of forming the preliminary film may be obtained by coating a solution containing the polyamideimide block copolymer on an arbitrary support to form a film, and evaporating a solvent from the film to dry it. The dryness temperature of the step of forming the preliminary film is not particularly limited, but may be selected, for example, within a range of 100 ° C to 200 ° C.

Next, the step of stretching the preliminary film so that the final elongation in the TD direction at a rate of 300mm / min at 250 ℃ to 0.5% to 5%. The specific method of the stretching, the device used, and the like are not particularly limited.

When the final elongation in the TD direction of the film satisfies 0.5% to 5% through the stretching process, thermal stability and high elasticity may be realized while maintaining excellent mechanical properties of the polyamide-imide film. In particular, it is preferable because it can realize high dimensional stability against moisture.

The elongation may preferably be 1% to 4%, or 2.5% to 3.5%.

The polyamide-imide film prepared according to the above production method has a coefficient of moisture expansion (CME) value measured in a range of 20% RH to 80% RH of 25ppm /% RH or less, and accordingly It is rarely used in various industries that are exposed to one environment. As for the contents of the water expansion coefficient, all of the above-described contents may be applied.

III. Display device

According to another embodiment of the present invention, a display device including the polyamide-imide film described above is provided.

As described above, the polyimide film comprising the polyamide-imide block copolymer of the present invention exhibits excellent mechanical properties, high elasticity and thermal stability, and has excellent dimensional stability due to moisture, and is exposed to various industrial groups exposed to humid environments, etc. Can be used for In particular, as a display device, it is usefully applicable as a display substrate, a protective film for a display, a touch panel, a cover film of a flexible or foldable device, or the like.

The polyamide-imide film according to the present invention has excellent mechanical properties and high elasticity, and has high dimensional stability against moisture.

Hereinafter, preferred embodiments are presented to help understanding of the invention. However, the following examples are only for illustrating the invention, and the invention is not limited thereto.

[Production Example]-Preparation of polyamide-imide copolymer

Manufacturing example  One

2,2'-bis (trifluoromethyl) benzidine (4,4 ') in a 500 mL round flask equipped with a dean-stark device and a condenser -(Hexafluoroisopropylidene) diphthalic anhydride and 3,3 ', 4,4,'-biphenyltetracarboxylic dianhydride (3, 3 ', 4,4,'-biphenylteteracarboxylic dianhydride) and dimethylacetamide were placed in a reactor and the reaction was started at room temperature. The reaction mixture was stirred at 0 ° C. for 4 hours using ice water under a nitrogen atmosphere.

After 4 hours, the reaction was taken out to room temperature, and thereafter, 2,2'-bis (trifluoromethyl) benzidine (2,2'-bis (trifluoromethyl) benzidine) and isophthaloyl dichloride (IPC) were added. , 4,4'-biphenyldicarbonyl chloride (4,4'-Biphenyldicarbonyl Chloride, BPC) and dimethylacetamide were added, and the reaction was initiated at room temperature in a nitrogen atmosphere (25 ° C ± 3 ° C). . After forming a polyamic acid polymer in a reaction for 4 hours, acetic anhydride and pyridine were added to the reaction mixture, followed by stirring for 15 hours in an oil bath at a temperature of 40 ° C. The chemical imidization reaction proceeded.

After completion of the reaction, water and ethanol (1: 1 (v / v)) precipitated to form a polyamide-imide block copolymer A-1 comprising a first repeating unit, a second repeating unit, and a third repeating unit having the following structure: Was obtained (weight average molecular weight about 500,000 g / mol). The obtained copolymer has a total sum of the 1st repeating unit and the 1-2 repeating unit (imide repeating unit): the molar ratio (①) to the total sum of the second repeating unit and the third repeating unit (amide repeating unit). The molar ratio is 35:65, and the second repeating unit: molar ratio (②) of the third repeating unit is 3: 7.

[Chapter 1-1 Repeat Unit]

[1-2 repeat units]

[2nd repeating unit]-Amide repeating unit (from IPC)

[Third repeating unit]-Amide repeating unit (derived from BPC)

.

.

Manufacturing example  2 : TPC  If only used

In Preparation Example 1, 4,4'-biphenyldicarbonyl chloride (4,4'-Biphenyldicarbonyl Chloride, BPC) instead of terephthaloyl dichloride (Terephthaloyl dichloride, TPC) was used instead of the third repeating unit. A copolymer comprising 2-2 repeat units of was prepared.

[2-2 repeat units]-Amide repeat units (TPC derived)

.

.

Example  And Comparative example

The polyamide-imide copolymer obtained in the preparation example was dissolved in a dimethylacetamide sample prepared in the preparation example to prepare a solution of about 10 wt%. The solution was cast on a glass plate through a bar coater equipment, and the drying temperature was sequentially controlled at 40 ° C and 120 ° C. As a result of the experiment, a preliminary film having a thickness of about 50 μm was prepared.

Next, the preliminary film was stretched in the TD direction at 250 ° C at 300 mm / min, and polyamide-imide films of Examples and Comparative Examples were prepared so that the final draw ratio satisfies the ratios shown in Table 1 (see Table 1).

Comparative Examples 1 and 2 (elongation 0%) mean that stretching was not performed.

division Copolymer
(Weight average molecular weight) Imide: Amide -① (mol%) Amide repeat unit ratio-② (mol%) Final elongation
(%) Kinds ratio Example 1 Preparation Example 1 35:65 IPC: BPC 30:70 3% Comparative Example 1 Preparation Example 1 35:65 IPC: BPC 30:70 0% Comparative Example 2 Preparation Example 2 35:65 TPC 100 0%

* Imide: Amide ① represents the molar ratio of the first repeating unit (or the sum of the 1-1 repeating unit and the 1-2 repeating unit): the second repeating unit + the third repeating unit.

* Amide repeating unit ratio ② indicates the molar ratio of the second repeating unit (or 2-2 repeating unit): third repeating unit (or 2-2 repeating unit).

Test example

The physical properties of the polyamide-imide film prepared in Examples and Comparative Examples were evaluated in the following manner, and the results are shown in Table 2 below.

1) Elastic Modulus  (Elastic Modulus, GPa )

For the polyamide-imide film samples (thickness 50 ± 2 μm) prepared in Examples and Comparative Examples, the strain rate was 12.5 mm / min using the Zwich / Roell z005 (1 kN) elastic modulus (Elastic Modulus). ) (GPa) was measured, and the results are shown in Table 2.

2) Coefficient of Moisture Expansion, CME )

The polyamide-imide film samples (thickness 50 ± 2 μm) prepared in Examples and Comparative Examples were heated to 60 ° C. at 0.5 to 1 ° C./min, and then changed in length while increasing the relative humidity up to 90% RH. Was measured, and specifically, the water expansion coefficient was measured according to the following general formula (1).

[Formula 1]

Water expansion coefficient (ppm /% RH) = (L1-L0) / (80% RH-20% RH)

The dimensional change rate of the general formula (1) is 50 µm thick, 0.5 cm wide and 1.5 cm long polyamide-imide film specimens are heated to 60 ° C. at 0.5 to 1 ° C./min, and the relative humidity increases up to 90% RH. While measuring the length change of the specimen,

80% RH, 20% RH means relative humidity

L0 is the length of the film specimen measured under the condition of 20% RH,

L1 is the length of the film specimen measured at 80% RH.

division CME (ppm /% RH) Elastic Modulus (GPa) Example 1 20.0 6.50 Comparative Example 1 28.6 6.13 Comparative Example 2 37.0 6.13

As can be seen from Table 1, it includes three types of repeating units having a specific structure according to the present invention. In particular, by having at least one fluorine-containing functional group substituted with at least one of these repeating units, excellent mechanical properties are obtained. While having, it was confirmed that the dimensional stability against moisture is large.

Claims (12)

Aromatic imide-based first repeating units; an amide-based second repeating unit containing meta-phenylene; And an amide-based third repeating unit containing para-biphenylene,
A polyamide-imide copolymer in which at least one of the first repeating unit, the second repeating unit and the third repeating unit is substituted with one or more fluorine-containing functional groups,
A polyamide-imide film having a Coefficient of Moisture Expansion (CME) value of 25 ppm /% RH or less measured in a 20% RH to 80% RH section.
According to claim 1,
The water expansion coefficient is measured according to the following general formula 1, polyamide-imide film:
[Formula 1]
Moisture expansion coefficient (ppm /% RH) = (L1-L0) / (80% RH-20% RH)
The water expansion coefficient of the general formula 1 is 50 µm thick, 0.5 cm wide and 1.5 cm long polyamide-imide film specimens are heated to 60 ° C. at 0.5 to 1 ° C./min, and the relative humidity is up to 90% RH. The length change of the specimen was measured while increasing.
L0 is the length of the film specimen measured under the condition of 20% RH,
L1 is the length of the film specimen measured at 80% RH.
According to claim 1,
A polyamide-imide film having an elongation in the transverse (TD) direction of 0.5% to 5% at 250 ° C and 300 mm / min.
According to claim 1,
The aromatic imide-based first repeating unit is represented by the following Chemical Formula 1, a polyamide-imide film:
[Formula 1]

In Chemical Formula 1,
R ¹ is the same in each repeating unit or different from each other, and each independently a single bond, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) ₂ -, -Si (CH ₃ ) ₂ -,-(CH ₂ ) _p- (here 1≤p≤10),-(CF ₂ ) _q- (here 1≤q≤10), -C (CH ₃ ) ₂ -, -C (CF ₃ ) _2- , -C (= O) NH-, or a divalent aromatic organic group having 6 to 30 carbon atoms;
R ² is the same or different in each repeating unit, and each independently -H, -F, -Cl, -Br, -I, -CF ₃ , -CCl ₃ , -CBr ₃ , -CI ₃ , -NO ₂ , -CN, -COCH ₃ , -CO ₂ C ₂ H ₅ , a silyl group having three aliphatic organic groups having 1 to 10 carbon atoms, an aliphatic organic group having 1 to 10 carbon atoms, or an aromatic organic group having 6 to 20 carbon atoms ;
n1 and m1 are each independently an integer from 0 to 3;
Y ¹ is the same or different in each repeating unit, and each independently includes a divalent aromatic organic group having 6 to 30 carbon atoms containing at least one trifluoromethyl group (-CF ₃ ); The aromatic organic group may be present alone; Two or more aromatic organic groups are bonded to each other to form a divalent condensed ring; Or two or more aromatic organic groups are a single bond, a fluorenylene group, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) _2- , -Si ( CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (here 1≤q≤10), -C (CH ₃ ) _2- , -C ( CF ₃ ) _2- , or -C (= O) NH-.
E ¹ is each independently a single bond or -NH-.
According to claim 1,
The second amide-based repeating unit containing meta-phenylene includes a repeating unit represented by the following Chemical Formula 2, a polyamide-imide film:
[Formula 2]

In Chemical Formula 2,
Y ² is the same or different from each repeating unit, and each is a divalent aromatic organic group having 6 to 30 carbon atoms, each independently containing at least one trifluoromethyl group (-CF ₃ ); The aromatic organic group may be present alone; Two or more aromatic organic groups are bonded to each other to form a divalent condensed ring; Or two or more aromatic organic groups are a single bond, a fluorenylene group, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) _2- , -Si ( CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (here 1≤q≤10), -C (CH ₃ ) _2- , -C ( CF ₃ ) _2- , or -C (= O) NH-;
E ² , E ³ and E ⁴ are each independently a single bond or -NH-.
According to claim 1,
The amide-based third repeating unit comprising para-biphenylene includes a repeating unit represented by Formula 3 below: Polyamide-imide film:
[Formula 3]

Y ^{2 '} is the same or different from each repeating unit, and is a divalent aromatic organic group having 6 to 30 carbon atoms, each independently containing at least one trifluoromethyl group (-CF ₃ ); The aromatic organic group may be present alone; Two or more aromatic organic groups are bonded to each other to form a divalent condensed ring; Or two or more aromatic organic groups are a single bond, a fluorenylene group, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) _2- , -Si ( CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (here 1≤q≤10), -C (CH ₃ ) _2- , -C ( CF ₃ ) _2- , or -C (= O) NH-;
E ^{2 '} , E ^3' and E ^{4 '} are each independently a single bond or -NH-.
According to claim 1,
The first repeating unit includes a repeating unit represented by the following Chemical Formula 1-1, a polyamide-imide film:
[Formula 1-1]

In Chemical Formula 1-1,
R ¹ , R ² , n1 and m1 are as defined in Chemical Formula 1.
According to claim 1,
The second repeating unit includes a repeating unit represented by the following Chemical Formula 2-1, a polyamide-imide film:
[Formula 2-1]

.
According to claim 1,
The third repeating unit, a polyamide-imide film comprising a repeating unit represented by Chemical Formula 3-1:
[Formula 3-1]

.
According to claim 1,
The polyamide-imide copolymer, a polyamide-imide film having a weight average molecular weight of 100,000 g / mol to 1,000,000 g / mol.
Reacting an aromatic diamine compound having one or more fluorine-containing functional groups substituted with an aromatic carboxylic acid or anhydride thereof to initiate a reaction;
Synthesizing the polyamide-imide copolymer by reacting the resultant of the starting step with a mixture of isophthalic acid or a derivative thereof and bisphenyldicarboxylic acid or a derivative thereof and an aromatic diamine in which one or more fluorine-containing functional groups are substituted;
Forming a preliminary film from the polyamide-imide copolymer; And
A method for producing a polyamide-imide film comprising stretching the preliminary film at 250 ° C. at a rate of 300 mm / min so that the final elongation is 0.5% to 5% in the TD direction.
A display device comprising the polyamide-imide film according to claim 1.