KR20220033036A - Polyimide-based polymer film, substrate for display device, and optical device using the same - Google Patents

Abstract

The present invention relates to a polyimide-based resin film which comprises a polyimide-based resin that comprises a polyimide repeating unit synthesized by the reaction of an acid anhydride compound having a specific structure and a diamine compound and has a glass transition temperature of 400℃ or higher and a retardation value of 150 nm or less in a thickness direction at a thickness of 10 μm.

Description

A polyimide-based resin film, a substrate for a display device using the same, and an optical device

The present invention relates to a polyimide-based resin film capable of having high heat resistance and realizing excellent optical properties and low retardation (Rth) in the thickness direction, a substrate for a display device using the same, and an optical device.

The display device market is rapidly changing mainly for flat panel displays (FPDs) that have a large area and can be thin and lightweight. Such flat panel displays include a liquid crystal display (LCD), an organic light emitting display (OLED), or an electrophoretic display (EPD).

In particular, in recent years, in order to further expand the applications and uses of the flat panel display, attention has been focused on so-called flexible display devices in which a flexible substrate is applied to the flat panel display. The application of such a flexible display device is being reviewed mainly for mobile devices such as smart phones, and the field of application thereof is gradually expanding.

In general, in manufacturing a flexible display device and a lighting device, a TFT device is manufactured by forming a multilayer inorganic film such as a buffer layer, an active layer, and a gate insulator on a cured polyimide.

However, when light is emitted to the polyimide layer (substrate layer), the emission efficiency may be reduced due to the difference between the refractive index of the upper layer of the inorganic film and the refractive index of the polyimide layer as described above.

In addition, when the polyimide material included in the polyimide layer (substrate layer) is cured at a high temperature of 400° C. or higher, optical properties may decrease due to deterioration of the polyimide.

Accordingly, there is a demand for the development of a new polyimide capable of satisfying high heat resistance and excellent optical properties.

The present invention relates to a polyimide-based resin film having high heat resistance, excellent optical properties, and low retardation (Rth) in the thickness direction.

Another object of the present invention is to provide a substrate for a display device using the polyimide-based resin film, and an optical device.

In order to solve the above problems, in the present specification, a polyimide-based resin including a polyimide repeating unit represented by the following Chemical Formula 1 is included, the glass transition temperature is 400° C. or higher, and the retardation value in the thickness direction at a thickness of 10 μm This 150 nm or less polyimide-type resin film is provided.

[Formula 1]

In Formula 1, X ₁ is a tetravalent functional group, and Y ₁ is an aromatic divalent functional group having 24 or more carbon atoms in which at least one electron withdrawing functional group is substituted.

In the present specification, there is also provided a substrate for a display device comprising the polyimide-based resin film.

In the present specification, an optical device including the polyimide-based resin film is also provided.

Hereinafter, a polyimide-based resin film, a substrate for a display device using the same, and an optical device according to specific embodiments of the present invention will be described in more detail.

Unless explicitly stated herein, terminology is for the purpose of referring to specific embodiments only, and is not intended to limit the present invention.

As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite.

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

And, in the present specification, terms including ordinal numbers 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, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

In the present specification, the (co)polymer is meant to include both polymers or copolymers, the polymer means a homopolymer consisting of a single repeating unit, and the copolymer means a composite polymer containing two or more kinds of repeating units.

In the present specification, examples of the substituent are described below, but is not limited thereto.

In the present specification, the term "substituted" means that other functional groups are bonded instead of hydrogen atoms in the compound, and the position to be substituted is not limited as long as the position at which the hydrogen atom is substituted, that is, the position where the substituent is substituted, is not limited, and when two or more substituted , two or more substituents may be the same as or different from each other.

As used herein, the term "substituted or unsubstituted" refers to deuterium; halogen group; cyano group; nitro group; hydroxyl group; carbonyl group; ester group; imid; amide group; primary amino group; carboxyl group; sulfonic acid group; sulfonamide group; a phosphine oxide group; alkoxy group; aryloxy group; alkyl thiooxy group; arylthioxy group; an alkyl sulfoxy group; arylsulfoxy group; silyl group; boron group; an alkyl group; cycloalkyl group; alkenyl group; aryl group; aralkyl group; aralkenyl group; an alkylaryl group; alkoxysilylalkyl group; an arylphosphine group; Or N, O, and S atom means that it is substituted or unsubstituted with one or more substituents selected from the group consisting of a heterocyclic group containing one or more, or substituted or unsubstituted, two or more of the above-exemplified substituents are linked. . For example, "a substituent in which two or more substituents are connected" may be a biphenyl group. That is, the biphenyl group may be an aryl group or may be interpreted as a substituent in which two phenyl groups are connected.

, 또는

는 다른 치환기에 연결되는 결합을 의미하고, 직접결합은 L 로 표시되는 부분에 별도의 원자가 존재하지 않은 경우를 의미한다. In this specification,

, or

denotes a bond connected to another substituent, and a direct bond denotes a case in which a separate atom does not exist in the portion represented by L .

In the present specification, aromatic is a characteristic that satisfies the Huckels Rule, and a case in which all of the following three conditions are satisfied according to the Huckels Rule may be defined as aromatic.

1) There must be 4n+2 electrons that are completely conjugated by empty p-orbitals, unsaturated bonds, unpaired electron pairs, etc.

2) 4n+2 electrons must form a planar isomer and form a ring structure.

3) All atoms of the ring must be able to participate in conjugation.

In the present specification, the alkyl group is a monovalent functional group derived from an alkane, and may be straight-chain or branched, and the number of carbon atoms in the straight-chain alkyl group is not particularly limited, but is preferably 1 to 20. In addition, the number of carbon atoms of the branched chain alkyl group is 3 to 20. Specific examples of the alkyl group include methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n -pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl , n-heptyl, 1-methylhexyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethyl- propyl, 1,1-dimethyl-propyl, isohexyl, 2-methylpentyl, 4-methylhexyl, 5-methylhexyl, 2,6-dimethylheptan-4-yl, and the like. The alkyl group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

In the present specification, the haloalkyl group refers to a functional group in which a halogen group is substituted with the aforementioned alkyl group, and examples of the halogen group include fluorine, chlorine, bromine or iodine. The haloalkyl group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

In the present specification, a multivalent functional group is a residue in a form in which a plurality of hydrogen atoms bonded to an arbitrary compound are removed, and may include, for example, a divalent functional group, a trivalent functional group, and a tetravalent functional group. For example, the tetravalent functional group derived from cyclobutane refers to a residue in which 4 hydrogen atoms bonded to cyclobutane are removed.

In the present specification, the electron withdrawing group (Electro-withdrawing group) may include at least one selected from the group consisting of a haloalkyl group, a halogen group, a cyano group, a nitro group, a sulfonic acid group, a carbonyl group and a sulfonyl group, preferably For example, it may be a haloalkyl group such as a trifluoromethyl group (-CF ₃ ).

In the present specification, a direct bond or a single bond means that no atom or group of atoms is present at the corresponding position, and thus is connected by a bonding line. Specifically, it refers to a case in which a separate atom does not exist in the portion represented by L ₁ and L ₂ in the formula.

In this specification, the weight average molecular weight means the weight average molecular weight in terms of polystyrene measured by the GPC method. In the process of measuring the weight average molecular weight in terms of polystyrene measured by the GPC method, a commonly known analyzer and a detector such as a differential refraction detector and a column for analysis may be used, and a temperature that is normally applied Conditions, solvents, and flow rates can be applied. As a specific example of the measurement conditions, the evaluation temperature is 160 ° C. using a Waters PL-GPC220 instrument using a Polymer Laboratories PLgel MIX-B 300 mm long column, and 1,2,4-trichlorobenzene is used as a solvent The flow rate was 1 mL/min, and the sample was prepared at a concentration of 10 mg/10 mL, and then supplied in an amount of 200 μL, and the value of Mw can be obtained using a calibration curve formed using a polystyrene standard. The molecular weight of the polystyrene standard was 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000.

Hereinafter, the present invention will be described in more detail.

1. Polyimide-based resin film

According to an embodiment of the present invention, it contains a polyimide-based resin including a polyimide repeating unit represented by Formula 1, a glass transition temperature of 400° C. or higher, and a retardation value in the thickness direction at a thickness of 10 μm is 150 nm The following polyimide-based resin films may be provided.

The present inventors, like the polyimide-based resin film of the embodiment, have a glass transition temperature of 400 ° C. or higher, and when the retardation value in the thickness direction at a thickness of 10 μm satisfies 150 nm or less, curing is carried out at a high temperature of 400 ° C. or higher Even in one polyimide resin film, optical isotropy is increased through colorless and transparent optical characteristics and low thickness direction retardation (Rth) characteristics, and excellent visibility can be realized by securing a display diagonal viewing angle to which the polyimide-based resin film is applied. It was confirmed through experiments and the invention was completed.

In particular, in the polyimide repeating unit represented by Formula ₁ , the polyimide-based resin has an aromaticity ( aromaticity), the ordering and orientation characteristics between the polyimide molecules are improved to ensure sufficient heat resistance even in the polyimide film obtained by high-temperature curing. It is possible to prevent the plastic substrate from being damaged by heat and realize excellent thermal stability without thermal decomposition even when applied to organic light emitting diode (OLED) devices using LTPS (low temperature polysilane) process close to 500 ° C. there is.

In addition, in the polyimide repeating unit represented by Formula ₁ , the polyimide-based resin has more aromatic ( aromaticity), as the difference between the average value of the plane refractive index value and the refractive index in the thickness direction decreases, a low retardation in the thickness direction (Rth) can be implemented.

In addition, by introducing an electron withdrawing functional group such as a trifluoromethyl group (-CF ₃ ) capable of imparting an electron withdrawing effect to the diamine monomer compound used for synthesizing the polyimide resin as a substituent, Pi- present in the imide chain By suppressing the formation of CTC (charge transfer complex) of electrons, transparency can be secured and excellent optical properties can be realized.

Specifically, the polyimide film according to the present invention can increase the refractive index and can be used as a substrate layer in a flexible display device to reduce the difference in refractive index with each layer constituting the device, and from this, By reducing the amount of light that is extinguished, it is possible to effectively increase the efficiency of the light emission (bottom emission).

The polyimide-based resin means that it includes all of polyimide, and polyamic acid and polyamic acid ester, which are precursor polymers thereof. That is, the polyimide-based polymer may include at least one selected from the group consisting of a polyamic acid repeating unit, a polyamic acid ester repeating unit, and a polyimide repeating unit. That is, the polyimide-based polymer may include one polyamic acid repeating unit, one polyamic acid ester repeating unit, one polyimide repeating unit, or a copolymer in which two or more repeating units thereof are mixed.

At least one repeating unit selected from the group consisting of the polyamic acid repeating unit, the polyamic acid ester repeating unit, and the polyimide repeating unit may form the main chain of the polyimide-based polymer.

In particular, the polyimide-based resin may include a polyimide repeating unit represented by Formula 1.

In Formula 1, X ₁ is an arbitrary tetravalent functional group, and X ₁ is a functional group derived from a tetracarboxylic dianhydride compound used for synthesizing a polyimide-based resin.

Specifically, the tetravalent functional group of X ₁ may include an aromatic tetravalent functional group containing multiple rings. When the aromatic tetravalent functional group containing the polycyclic group is included in X ₁ , a structure with increased steric hindrance by the polycyclic ring is introduced into the polyimide chain structure, thereby increasing the orientation in the thickness direction to induce isotropy, resulting in low thickness Excellent visibility can be realized by securing the display diagonal viewing angle through directional retardation (Rth) characteristics, heat resistance can be improved by alleviating heat deformation, and film shrinkage that occurs during the cooling process after the heating process is reduced. can alleviate

More specifically, the tetravalent functional group of X ₁ may include a functional group represented by Formula 3 below.

[Formula 3]

In Formula 3, Ar is a polycyclic aromatic divalent functional group. The polycyclic aromatic divalent functional group is a polycyclic aromatic hydrocarbon compound or a divalent functional group derived from a derivative compound thereof, and may include a fluorenylene group. The derivative compound includes all compounds in which one or more substituents are introduced or carbon atoms are replaced with heteroatoms.

More specifically, in Ar of Formula 3, the polycyclic aromatic divalent functional group may include a fused cyclic divalent functional group containing at least two or more aromatic ring compounds. That is, in the multicyclic aromatic divalent functional group, at least two or more aromatic ring compounds may be contained in the functional group structure, and the functional group may have a fused ring structure.

The aromatic ring compound may include an arene compound containing one or more benzene rings, or a hetero arene compound in which a carbon atom in the arene compound is replaced with a hetero atom.

The aromatic ring compound may be contained in at least two or more of the polycyclic aromatic divalent functional group, and each of the two or more aromatic ring compounds may form a directly fused ring or a fused ring through another ring structure. For example, when two benzene rings are each joined to a cycloalkyl ring structure, it can be defined that two benzene rings form a fused ring through the cycloalkyl ring.

The fused cyclic divalent functional group containing at least two or more aromatic ring compounds is a divalent functional group derived from a fused cyclic compound containing at least two or more aromatic ring compounds or a derivative compound thereof, wherein the derivative compound has one or more substituents introduced therein. or in which a carbon atom is replaced by a hetero atom.

Examples of the polycyclic aromatic divalent functional group are not particularly limited, but as an example, the tetravalent functional group represented by Formula 3 may include a functional group represented by Formula 3-1 below.

[Formula 3-1]

Meanwhile, in Formula 1, Y ₁ is an aromatic divalent functional group having 24 or more carbon atoms, or 24 or more 30 or less, or 24 or more and 28 or less carbon atoms substituted with at least one electron withdrawing functional group, and Y ₁ is polyamic acid, polyamic acid It may be an ester or a functional group derived from a diamine compound used in the synthesis of polyimide.

The aromatic divalent functional group having 24 or more carbon atoms in Y ₁ may include 4 or more aromatic ring compounds. As such, as four or more aromatic ring compounds are contained, the charge transfer complex (CTC) effect between polymer chains is strengthened, and the refractive index in the plane direction increases to induce anisotropy, and the ordering and orientation characteristics between molecules of the polyimide-based resin are improved. Therefore, it is possible to secure sufficient heat resistance and process efficiency even in a polyimide film obtained by high-temperature curing.

When the number of carbon atoms of the aromatic divalent functional group in Y ₁ is reduced to less than 24, the number of aromatic ring compounds is reduced to 3 or less and aromaticity is reduced, so that CTC (charge transfer complex) effect between polymer chains And, the ordering and orientation characteristics between the polyimide molecules are relatively weak, so that the heat resistance and process efficiency in the polyimide film obtained by high-temperature curing may be remarkably poor.

The aromatic divalent functional group having 24 or more carbon atoms may include at least one selected from the group consisting of a quaterphenylene group and a penterphenylene group. Specifically, the aromatic divalent functional group having 24 or more carbon atoms may be derived from an aromatic compound having a maximum light absorption wavelength of 280 nm or more and 300 nm or less.

For example, in the case of a biphenylene group having 12 carbon atoms, the maximum light absorption wavelength is 247 nm, and in the case of a terphenylene group having 18 carbon atoms, the maximum light absorption wavelength is 274 nm, whereas in the case of a quarterphenylene group having 24 carbon atoms , the maximum light absorption wavelength may represent 292 nm.

The maximum light absorption wavelength can be measured by using a CH ₂ Cl ₂ solvent, and by applying a conventionally known method and equipment for measuring the light absorption wavelength without limitation.

The electron withdrawing functional group may include at least one selected from the group consisting of a haloalkyl group, a halogen group, a cyano group, a nitro group, a sulfonic acid group, a carbonyl group, and a sulfonyl group.

As electron withdrawing substituents such as trifluoromethyl group (-CF ₃ ) with high electronegativity are substituted, the effect of inhibiting the formation of charge transfer complex (CTC) of Pi-electrons in the polyimide resin chain is increased. Accordingly, improved transparency can be secured. That is, it is possible to reduce the packing within the polyimide structure or between chains, and weaken the electrical interaction between the chromogenic sources due to steric hindrance and electrical effects, thereby making it possible to exhibit high transparency in the visible light region.

Specifically, the aromatic divalent functional group having 24 or more carbon atoms in which at least one electron withdrawing functional group of Y ₁ is substituted may include a functional group represented by Formula 2 below.

[Formula 2]

In Formula 2, Q ₁ to Q ₄ are the same as or different from each other, each independently an electron withdrawing group, q1 to q4 are the same or different from each other, each independently an integer of 0 to 4, and p is 1 to 10 , or an integer of 1 to 3.

More specifically, in Formula 1, Y ₁ may be substituted with 1 or more, or 3 or less, or 1 to 3, or 1 to 2 electron withdrawing functional groups.

Specifically, the aromatic divalent functional group having 24 or more carbon atoms in which at least one electron withdrawing functional group of Y ₁ is substituted may include a functional group represented by the following Chemical Formula 2-1.

[Formula 2-1]

In Formula 2-1, Q ₅ to Q ₆ are the same as or different from each other, each independently an electron withdrawing functional group, q5 to q6 are the same or different from each other, and each independently an integer of 0 or 1, (q5+ q6) is an integer of 1 or 2.

In Formula 1, when the number of electron withdrawing functional groups in Y ₁ is excessively increased to more than 2 or more than 3, the structure of the polyimide repeating unit represented by Formula 1 becomes relatively bulky, and due to the introduction of excessive electron withdrawing functional groups, As the electron density becomes insufficient due to this, a technical problem in which thermal properties (Tg, CTE) is deteriorated may occur.

For example, the aromatic divalent functional group having 24 or more carbon atoms in which at least one electron withdrawing functional group of Y ₁ is substituted may include a functional group represented by the following Chemical Formula 2-2.

[Formula 2-2]

The polyimide-based resin may include a combination of a tetracarboxylic dianhydride represented by the following Chemical Formula 4 and an aromatic diamine having 24 or more carbon atoms in which at least one electron withdrawing functional group is substituted.

[Formula 4]

In Formula 4, Ar ' is a polycyclic aromatic divalent functional group. The polycyclic aromatic divalent functional group is a divalent functional group derived from a polycyclic aromatic hydrocarbon compound, and is a divalent functional group derived from a fluorenylene group or a derivative compound thereof, and may include a fluorenylene group. . The derivative compound includes all compounds in which one or more substituents are introduced or carbon atoms are replaced with heteroatoms.

Specific examples of the tetracarboxylic dianhydride represented by Formula 4 include 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride (9,9-Bis (3,4-dicarboxyphenyl) fluorene Dianhydride, BPAF). can be heard

The aromatic diamine having 24 or more carbon atoms substituted with at least one electron withdrawing functional group is a compound in which an amino group (-NH ₂ ) is bonded to both terminals of the aromatic divalent functional group having 24 or more carbon atoms substituted with at least one or more electron withdrawing functional group, The description of the aromatic divalent functional group having 24 or more carbon atoms in which at least one electron withdrawing functional group is substituted is the same as described above.

Specific examples of the aromatic diamine having 24 or more carbon atoms in which at least one electron withdrawing functional group is substituted may include a diamine represented by the following formula (a).

[Formula a]

The diamine represented by Formula (a) is 95 mol% or more, or 96 mol% or more, or 97 mol% or more, or 98 mol% or more, or 99 mol% or more, or 100 mol% or less, or 95 mol% based on the total diamine. to 100 mol%, alternatively from 96 mol% to 100 mol%, alternatively from 97 mol% to 100 mol%, alternatively from 98 mol% to 100 mol%, or from 99 mol% to 100 mol%.

More specifically, the polyimide-based resin is a terminal anhydride group (-OC-O-CO-) of the tetracarboxylic acid dianhydride represented by Formula 4 and at least one electron withdrawing functional group substituted at the end of an aromatic diamine having 24 or more carbon atoms. A bond between the nitrogen atom of the amino group and the carbon atom of the anhydride group may be formed by the reaction of the amino group (—NH ₂ ).

In addition, the polyimide-based resin may further include a polyimide repeating unit represented by the following Chemical Formula 5 in addition to the polyimide repeating unit represented by Chemical Formula 1 above.

[Formula 5]

In Chemical Formula 5, X ₂ is a tetravalent functional group different from that of X ₁ , and Y ₂ is an aromatic divalent functional group having 24 or more carbon atoms in which at least one electron withdrawing functional group is substituted.

X ₂ may be one of the tetravalent functional groups represented by Formula 6 below.

[Formula 6]

In Formula 6, R ₁ to R ₆ are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms, and L ₃ is a single bond, -O-, -CO-, -COO-, -S-, -SO-, -SO ₂ -, -CR ₇ R ₈ -, -(CH ₂ ) _t -, -O(CH ₂ ) _t O-, -COO(CH ₂ ) _t OCO-, -CONH-, phenylene, or their Any one selected from the group consisting of combinations, wherein R ₇ and R ₈ are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, or a halo alkyl group having 1 to 10 carbon atoms, and t is an integer from 1 to 10 .

Specific examples of the functional group represented by Formula 6 include a functional group represented by the following Formula 6-1, a functional group represented by the following Formula 6-2, or a functional group represented by the following Formula 6-3.

[Formula 6-1]

[Formula 6-2]

[Formula 6-3]

That is, the polyimide-based polymer may include: a first repeating unit containing a repeating unit represented by Chemical Formula 1 in which the repeating unit derived from tetracarboxylic dianhydride is a functional group represented by Chemical Formula 3; and a second repeating unit containing a repeating unit represented by Formula 5, wherein the repeating unit derived from tetracarboxylic dianhydride is a functional group represented by Formula 6 above. The first repeating unit and the second repeating unit are randomly arranged in the polyimide-based polymer to form a random copolymer, or a block between the first repeating units and a block between the second repeating units to form a block copolymer can

The polyimide-based polymer including the repeating unit represented by Chemical Formula 1 and the repeating unit represented by Chemical Formula 5 may be prepared by reacting two or more different tetracarboxylic dianhydride compounds with a diamine compound. A random copolymer may be synthesized by simultaneously adding tetracarboxylic dianhydride, or a block copolymer may be synthesized by sequential addition.

The polyimide repeating unit represented by Chemical Formula 5 may be contained in an amount of 1 mol% or more and 99 mol% or less of the total repeating units contained in the polyimide-based resin.

The polyimide repeating unit represented by Formula 1 and the polyimide repeating unit represented by Formula 5 are 95 mol% or more, or 96 mol% or more, or 97 mol% or more, based on the total repeating units contained in the polyimide-based resin, or 98 mol % or more, or 99 mol % or more, or 100 mol % or less, or 95 mol % to 100 mol %, or 96 mol % to 100 mol %, or 97 mol % to 100 mol %, or 98 mol % to 100 mol % It may be contained in mol%, or 99 mol% to 100 mol%.

That is, the polyimide-based resin is composed of only the polyimide repeating unit represented by the formula (1) and the polyimide repeating unit represented by the formula (5), or most of the polyimide repeating unit represented by the formula (1) and the polyimide repeating unit represented by the formula (5) It may be formed of a polyimide repeating unit.

When the polyimide repeating unit represented by Formula 1 and the polyimide repeating unit represented by Formula 5 are contained in less than 95 mol% of the total repeating units contained in the polyimide-based resin, it is derived from a diamine structure having relatively high linearity. As the content of the polyimide repeating unit represented by Formula 1 and the polyimide repeating unit represented by Formula 5 decreased, and the polyimide repeating unit derived from other diamine structures having relatively low linearity increased, heat resistance (Tg, CTE) degradation may occur.

More specifically, in the polyimide-based resin, other diamines other than the diamine capable of inducing an aromatic divalent functional group having at least 24 carbon atoms in which at least one electron withdrawing functional group is substituted, or other diamines are not mixed, or can be mixed in a very small amount of less than 1 mol%. there is.

The weight average molecular weight (GPC measurement) of the polyimide-based resin is not particularly limited, but may be, for example, 1000 g/mol or more and 200000 g/mol or less, or 10000 g/mol or more and 200000 g/mol or less.

The polyimide-based resin according to the present invention can exhibit excellent colorless and transparent properties while maintaining properties such as heat resistance and mechanical strength due to a rigid structure, and can be used for device substrates, display cover substrates, and optical films. , IC (integrated circuit) package, electrodeposition film, multi-layer flexible printed circuit (FRC), tape, touch panel, protective film for optical disk, etc. there is.

Meanwhile, the polyimide-based resin film of the embodiment may include a cured product in which the polyimide-based resin is cured at a temperature of 400° C. or higher. The cured product refers to a material obtained through a curing process of the resin composition containing the polyimide-based resin, and the curing process may be performed at a temperature of 400°C or higher, or 400°C or higher and 500°C or lower.

More specifically, examples of the method for synthesizing the polyimide-based resin film are not particularly limited, for example, forming a coating film by applying a resin composition containing the polyimide-based resin to a substrate (step 1); drying the coating film (step 2); A method for producing a film, including the step of curing the dried coating film by heat treatment (step 3), may be used.

Step 1 is a step of forming a coating film by applying the resin composition containing the above-described polyimide-based resin to a substrate. A method of applying the resin composition containing the polyimide-based resin to the substrate is not particularly limited, and for example, a method such as screen printing, offset printing, flexographic printing, and inkjet printing may be used.

In addition, the resin composition containing the polyimide-based resin may be dissolved or dispersed in an organic solvent. When having such a form, for example, when polyimide-type resin is synthesize|combined in an organic solvent, the reaction solution itself obtained may be sufficient as the solution, and what diluted this reaction solution with another solvent may be sufficient. Moreover, when polyimide-type resin is obtained as powder, what was made to melt|dissolve this in an organic solvent, and was made into a solution may be sufficient.

Specific examples of the organic solvent include toluene, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethyl Pyrrolidone, N-vinylpyrrolidone, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylsulfoxide, gamma-butyrolactone, 3-methoxy-N,N-dimethylpropanamide, 3- Ethoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, 1,3-dimethyl-imidazolidinone, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoa Milk ketone, methyl isopropyl ketone, cyclohexanone, ethylene carbonate, propylene carbonate, diglyme, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether, ethylene glycol monopropyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether Acetate etc. are mentioned. These may be used alone or may be used in combination.

The resin composition containing the polyimide-based resin may contain a solid content in an amount to have an appropriate viscosity in consideration of fairness such as applicability during the film forming process. For example, the content of the composition may be adjusted so that the content of the total resin is 5 wt% or more and 25 wt% or less, or 5 wt% or more and 20 wt% or less, or 5 wt% or more and 15 wt% or less .

In addition, the resin composition containing the polyimide-based resin may further include other components in addition to the organic solvent. As a non-limiting example, when the resin composition containing the polyimide-based resin is applied, the film thickness uniformity or surface smoothness is improved, the adhesion to the substrate is improved, or the dielectric constant or the conductivity is changed. Or, an additive capable of increasing the compactness may be additionally included. Such additives may be exemplified by a surfactant, a silane-based compound, a dielectric or a crosslinking compound, and the like.

Step 2 is a step of drying the coating film formed by applying the resin composition containing the polyimide-based resin to the substrate.

The drying step of the coating film may be carried out by a heating means such as a hot plate, a hot air circulation furnace, an infrared furnace, and may be performed at a temperature of 50 °C or more and 150 °C or less, or 50 °C or more and 100 °C or less.

Step 3 is a step of curing the dried coating film by heat treatment. In this case, the heat treatment may be performed by a heating means such as a hot plate, a hot air circulation furnace, an infrared furnace, and may be performed at a temperature of 400 °C or higher, or 400 °C or higher and 500 °C or lower.

The thickness of the polyimide-based resin film is not particularly limited, but can be freely adjusted within, for example, 0.01 µm or more and 1000 µm or less. When the thickness of the polyimide-based resin film increases or decreases by a specific value, physical properties measured in the polyimide-based resin film may also change by a specific value.

The polyimide-based resin film may have a retardation value of 150 nm or less in the thickness direction at a thickness of 10 μm, or 0.1 nm or more and 150 nm or less, or 10 nm or more and 150 nm or less. As such, the optical isotropy is increased through the retardation (Rth) characteristic in the low thickness direction, and thus excellent visibility can be realized by securing a diagonal viewing angle of the display to which the polyimide-based resin film is applied.

In addition, when a transparent display is implemented, distortion is relatively reduced when light is transmitted in a structure in which polyimide is present on the top, so there is no need to additionally use a compensation film to correct the refraction of transmitted light. efficiency can be ensured.

The retardation in the thickness direction may be measured with respect to a wavelength of 550 nm, and examples of the measuring method and equipment are not specifically limited, and various methods conventionally used for measuring the retardation in the thickness direction may be applied without limitation.

Specifically, the thickness direction retardation R _th may be calculated through the following equation.

[Equation]

R _th (nm) = |[(n _x + n _y ) / 2] - n _z | ×d

(In the above formula, n _x is the largest refractive index among in-plane refractive indexes of the polyimide resin film measured with light having a wavelength of 550 nm; n _y is n _x among the in-plane refractive indexes of the polyimide resin film measured with light having a wavelength of 550 nm is the refractive index perpendicular to; n _z is the refractive index in the thickness direction of the polyimide resin film measured with light having a wavelength of 550 nm; d is the thickness of the polyimide film.)

That is, the thickness direction retardation R _th is a value obtained by multiplying the absolute value of the difference between the thickness direction refractive index value (n _z ) and the average value of the plane refractive index values [(n _x +n _y )/2] by the thickness direction, A smaller difference between the refractive index value (n _z ) and the average value [(n _x +n _y )/2] of the plane refractive index values may indicate a lower value.

As the polyimide-based resin film has a thickness direction retardation value of 150 nm or less at a thickness of 10 μm, the average value of the refractive index value in the thickness direction (n _z ) and the plane refractive index value on the display to which the polyimide-based resin film is applied As the difference of [(n _x +n _y )/2] decreases, excellent visibility may be realized.

When the retardation value in the thickness direction of the polyimide-based resin film at a thickness of 10 μm is excessively increased to more than 150 nm, a distortion phenomenon occurs when light is transmitted in a structure in which a polyimide is present on the upper portion when a transparent display is implemented, In order to correct the refraction of transmitted light, the process efficiency and economic efficiency of using an additional compensation film may be reduced.

Meanwhile, the polyimide-based resin film may have a glass transition temperature of 400°C or higher, or 400°C or higher and 500°C or lower. Accordingly, even when applied to an organic light emitting diode (OLED) device using a low temperature polysilane (LTPS) process close to 500° C., excellent thermal stability may be realized without thermal decomposition.

In addition, as the polyimide-based resin film has a glass transition temperature at a temperature of 400° C. or more, or 400° C. or more and 500° C. or less, sufficient heat resistance is ensured even in the polyimide film obtained by high-temperature curing, and when it is used as a plastic substrate , it is possible to prevent the plastic substrate from being damaged by heat when heat-treating the metal layer formed on the plastic substrate.

An example of the method of measuring the glass transition temperature is not particularly limited, but for example, using a thermomechanical analysis apparatus (TMA (Q400, TA)), the film pulling force is set to 0.02N, and the temperature is 100 to 350 ° C. After performing the first temperature increase process at a temperature increase rate of 5 °C/min in the range, cooling at a cooling rate of 4 °C/min in a temperature range of 350 to 100 °C, and then 5 °C in a temperature range of 100 to 450 °C The inflection point shown in the temperature increase section in the secondary temperature increase process can be obtained as Tg by performing the secondary temperature increase process at a temperature increase rate of /min.

When the glass transition temperature of the polyimide-based resin film is excessively reduced to less than 400° C., heat resistance is insufficient and dimensional stability is insufficient, and thus there is a limit that cannot be tolerated in the TFT process.

Specifically, the polyimide-based resin film may have a haze value of 1.5% or less, or 0.1% or more and 1.5% or less. In addition, the polyimide-based resin film may have a yellow index value of 15 or less, or 1 or more and 15 or less.

The haze may be measured from the polyimide film sample having a thickness of 10±2 μm. When the thickness of the polyimide film increases or decreases by a specific value, physical properties measured in the polyimide film may also change by a specific value.

In addition, the polyimide-based resin film may have an average transmittance of 60% or more, or 60% or more and 99% or less in a wavelength band of 380 nm or more and 780 nm or less. The transmittance may be measured from the polyimide film sample having a thickness of 10±2 μm. When the thickness of the polyimide film increases or decreases by a specific value, physical properties measured in the polyimide film may also change by a specific value.

2. Substrate for display device

Meanwhile, according to another embodiment of the present invention, a substrate for a display device including the polyimide-based resin film of the other embodiment may be provided. The content regarding the polyimide-based resin film may include all of the content described above in the embodiment.

A display device including the substrate may include a liquid crystal display device (LCD), an organic light emitting diode (OLED), a flexible display, or a rollable display or foldable display. ) and the like, but is not limited thereto.

The display device may have various structures depending on the field of application and specific form, for example, a structure including a cover plastic window, a touch panel, a polarizing plate, a barrier film, a light emitting device (OLED device, etc.), a transparent substrate, etc. there is.

The polyimide-based resin film of another embodiment described above may be used for various purposes such as a substrate, an external protective film, or a cover window in these various display devices, and more specifically, it may be applied as a substrate.

For example, the substrate for the display device may have a structure in which a device protection layer, a transparent electrode layer, a silicon oxide layer, a polyimide-based resin film, a silicon oxide layer, and a hard coating layer are sequentially stacked.

The transparent polyimide substrate may include a silicon oxide layer formed between the transparent polyimide-based resin film and the cured layer in terms of improving solvent resistance, moisture permeability, and optical properties, and the silicon oxide layer includes poly It may be produced by curing silazane.

Specifically, the silicon oxide layer is formed by curing the coated polysilazane after coating and drying a solution containing polysilazane before the step of forming a coating layer on at least one surface of the transparent polyimide-based resin film. it could be

The substrate for a display device according to the present invention can provide a transparent polyimide cover substrate having excellent warpage characteristics and impact resistance, and solvent resistance, optical characteristics, moisture permeability and scratch resistance by including the device protection layer described above. there is.

3. Optics

Meanwhile, according to another embodiment of the present invention, an optical device including the polyimide-based resin film of the other embodiment may be provided. The content regarding the polyimide-based resin film may include all of the content described above in the embodiment.

The optical device may include all kinds of devices using properties realized by light, for example, a display device. Specific examples of the display device include a liquid crystal display device (LCD), an organic light emitting diode (OLED), a flexible display, or a rollable display or foldable display. and the like, but is not limited thereto.

The optical device may have a variety of structures depending on the field of application and specific form, and for example, a structure including a cover plastic window, a touch panel, a polarizing plate, a barrier film, a light emitting device (OLED device, etc.), a transparent substrate, etc. there is.

The polyimide-based resin film of the other embodiments described above may be used for various purposes such as a substrate, an external protective film, or a cover window in these various optical devices, and more specifically, may be applied to a substrate.

Advantageous Effects of Invention According to the present invention, a polyimide-based resin film having high heat resistance, excellent optical properties and low retardation (Rth) in the thickness direction, a substrate for a display device using the same, and an optical device can be provided.

The invention is described in more detail in the following examples. However, the following examples only illustrate the present invention, and the content of the present invention is not limited by the following examples.

<Example: Preparation of polyimide film>

Example 1

(1) Preparation of polyimide precursor composition

After filling the organic solvent DEAc in a stirrer through which a nitrogen stream flows, 0.735 mol of the diamine represented by the following formula (a) was added and dissolved at the same temperature while the temperature of the reactor was maintained at 25 °C. 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride (9,9-Bis (3,4- 0.3675 mol of dicarboxyphenyl)fluorene Dianhydride, BPAF) and 0.3675 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride (3,3',4,4'-Biphenyltetracarboxylic dianhydride, BPDA) were added at the same temperature. A polyimide precursor composition was obtained by stirring for 24 hours.

[Formula a]

[Formula b]

(2) Preparation of polyimide film

The polyimide precursor composition was spin-coated on a glass substrate. The glass substrate coated with the polyimide precursor composition was placed in an oven and heated at a rate of 5 °C/min, and the curing process was carried out by maintaining at 80 °C for 30 minutes and at 400 °C for 30 minutes. Hardening

After completion of the process, the glass substrate was immersed in water to remove the film formed on the glass substrate and dried in an oven at 100° C. to prepare a polyimide film having a thickness of 10 μm.

Example 2

4,4'-(hexafluoroisopropylidene)dihydride instead of 3,3',4,4'-biphenyltetracarboxylic dianhydride (3,3',4,4'-Biphenyltetracarboxylic dianhydride, BPDA) as an acid dianhydride A polyimide film was prepared in the same manner as in Example 1, except that phthalic anhydride (4,4'-(Hexafluoroisopropylidene)diphthalic anhydride, 6-FDA) was used.

Example 3

As acid dianhydride, pyromellitic dianhydride (PMDA) was used instead of 3,3',4,4'-biphenyltetracarboxylic dianhydride (3,3',4,4'-Biphenyltetracarboxylic dianhydride, BPDA) Except that, a polyimide film was prepared in the same manner as in Example 1.

<Comparative Example: Preparation of polyimide film>

Comparative Example 1

A polyimide film was prepared in the same manner as in Example 1, except that p-phenylenediamine (p-PDA) was used as the diamine instead of the diamine represented by Formula (a).

Comparative Example 2

As the diamine, 2,2'-bis(trifluoromethyl)benzidine (2,2'-Bis(trifluoromethyl)benzidine, TFMB) represented by the following formula (c) was used instead of the diamine represented by the formula (a). A polyimide film was prepared in the same manner as in Example 1.

[Formula c]

Comparative Example 3

A polyimide film was prepared in the same manner as in Example 1, except that 4,4'-DDS (4,4'-diaminodiphenyl sulfone) represented by the following formula d was used instead of the diamine represented by the formula a as the diamine. did

[Formula d]

Comparative Example 4

(1) Preparation of polyimide precursor composition

After filling the organic solvent DEAc in a stirrer through which a nitrogen stream flows, 0.735 mol of the diamine represented by the following formula e was added and dissolved at the same temperature while the temperature of the reactor was maintained at 25 °C. 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (9,9-Bis(3, 0.3675 mol of 4-dicarboxyphenyl)fluorene Dianhydride (BPAF) and 0.3675 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride (3,3',4,4'-Biphenyltetracarboxylic dianhydride, BPDA) were mixed at the same temperature. The mixture was added and stirred for 24 hours to obtain a polyimide precursor composition.

[Formula e]

[Formula b]

(2) Preparation of polyimide film

The polyimide precursor composition was spin-coated on a glass substrate. The glass substrate coated with the polyimide precursor composition was placed in an oven and heated at a rate of 5 °C/min, and the curing process was carried out by maintaining at 80 °C for 30 minutes and at 400 °C for 30 minutes. Hardening

After completion of the process, the glass substrate was immersed in water to remove the film formed on the glass substrate and dried in an oven at 100° C. to prepare a polyimide film having a thickness of 10 μm.

Comparative Example 5

(1) Preparation of polyimide precursor composition

After filling the organic solvent DEAc in a stirrer through which a nitrogen stream flows, and maintaining the temperature of the reactor at 25 ° C., 0.6615 mol of diamine represented by the following formula (a), 4,4'-DDS represented by the following formula (d) (4,4 '-diaminodiphenyl sulfone) 0.0735 mol was added and dissolved at the same temperature. To a solution to which 0.6615 mol of a diamine represented by the following formula (a) and 0.0735 mol of 4,4'-DDS (4,4'-diaminodiphenyl sulfone) represented by the following formula (d) are added, 9,9 represented by the following formula (b) as an acid dianhydride -Bis (3,4-dicarboxyphenyl) fluorene dianhydride (9,9-Bis (3,4-dicarboxyphenyl) fluorene Dianhydride, BPAF) 0.3675 mol and 3,3',4,4'-biphenyltetracarboxylic acid 0.3675 mol of dianhydride (3,3',4,4'-Biphenyltetracarboxylic dianhydride, BPDA) was added at the same temperature and stirred for 24 hours to obtain a polyimide precursor composition.

[Formula a]

[Formula b]

[Formula d]

(2) Preparation of polyimide film

The polyimide precursor composition was spin-coated on a glass substrate. The glass substrate coated with the polyimide precursor composition was placed in an oven and heated at a rate of 5 °C/min, and the curing process was carried out by maintaining at 80 °C for 30 minutes and at 400 °C for 30 minutes. Hardening

After completion of the process, the glass substrate was immersed in water to remove the film formed on the glass substrate and dried in an oven at 100° C. to prepare a polyimide film having a thickness of 10 μm.

<Experimental Example: Measurement of physical properties of polyimide films obtained in Examples and Comparative Examples>

The physical properties of the polyimide films obtained in Examples and Comparative Examples were measured in the following manner, and the results are shown in Table 1.

1. Thickness direction retardation (R _th )

After inputting the values of the refractive index of the polyimide films prepared in Examples and Comparative Examples with respect to light at 550 nm using the brand name “AxoScan” manufactured by AXOMETRICS as a measuring device, temperature: 25 ° C., humidity: After measuring the retardation in the thickness direction using light with a wavelength of 550 nm under 40% conditions, the thickness of the film is 10 using the obtained retardation measurement value (measured value by automatic measurement of a measuring device) It calculated|required by conversion into the retardation value per micrometer, and evaluated under the following criteria.

Specifically, the thickness direction retardation R _th was calculated through the following equation.

[Equation]

R _th (nm) = |[(n _x + n _y ) / 2] - n _z | ×d

(In the above formula, n _x is the largest refractive index among in-plane refractive indexes of the polyimide resin film measured with light having a wavelength of 550 nm; n _y is n _x among the in-plane refractive indexes of the polyimide resin film measured with light having a wavelength of 550 nm is the refractive index perpendicular to; n _z is the refractive index in the thickness direction of the polyimide resin film measured with light having a wavelength of 550 nm; d is the thickness of the polyimide film.)

⊙: 150 nm or less

○: more than 150 nm and less than 200 nm

Χ: 200 nm or more

2. Glass transition temperature (Tg)

After preparing the polyimide films prepared in Examples and Comparative Examples in a size of 5 x 20 mm, the sample is loaded using an accessory. The length of the film actually measured was the same as 16 mm. After setting the film pulling force to 0.02N and performing the first temperature increase process at a temperature increase rate of 5 °C/min in a temperature range of 100 to 350 °C, a cooling rate of 4 °C/min in a temperature range of 350 to 100 °C After cooling, a second temperature increase process was performed in a temperature range of 100 to 450 °C at a temperature increase rate of 5 °C/min, and the change in thermal expansion was measured by TMA (Q400 manufactured by TA). At this time, the inflection point seen in the temperature increase section in the second temperature increase process was calculated as Tg, and evaluated under the following criteria.

⊙: 400℃ or higher

○: More than 350 ℃ and less than 400 ℃

Χ: 350 ℃ or less

3. Yellow index (YI)

The yellow index of the polyimide film was measured using a color meter (GRETAGMACBETH's Color-Eye 7000A) and evaluated under the following criteria.

⊙: 15 or less

○: more than 15 and less than 20

Χ: 20 or more

4. Haze

The haze value of the polyimide film was measured using a hazemeter (NDH-5000), and evaluation was performed under the following criteria.

⊙: 1.5% or less

○: More than 1.5% and less than 3%

Χ: 3% or more

5. Permeability

In accordance with JIS K 7105, the average transmittance in a wavelength band of 380 nm or more and 780 nm or less was measured with a transmittance meter (model name HR-100, manufactured by Murakami Color Research Laboratory), and evaluated under the following criteria.

⊙: 60% or more

○: More than 50% and less than 60%

Χ: 50% or less

Experimental Example Measurement Results of Examples and Comparative Examples division R _th Tg YI Haze (%) Transmittance (%)
@380~780 Example 1 ⊙ ⊙ ⊙ ⊙ ⊙ Example 2 ⊙ ⊙ ⊙ ⊙ ⊙ Example 3 ⊙ ⊙ ⊙ ⊙ ⊙ Comparative Example 1 Χ ⊙ Χ ⊙ Χ Comparative Example 2 ⊙ Χ ⊙ ⊙ ⊙ Comparative Example 3 ⊙ Χ ⊙ ⊙ ⊙ Comparative Example 4 ⊙ Χ ⊙ ⊙ ⊙ Comparative Example 5 ⊙ X ⊙ ⊙ ⊙

As shown in Table 1 above, the polyimide film obtained in Examples had a retardation R _th value of 150 nm or less, which was lower than Comparative Example 1 of 200 nm or more, thereby expressing visibility suitable for display in the retardation range in the thickness direction. In addition, it was confirmed that the glass transition temperature was as high as 400 °C or higher, and could have superior heat resistance compared to Comparative Examples 2, 3, 4, and 5 having a low glass transition temperature of 350 °C or less.

Claims (20)

Including a polyimide-based resin including a polyimide repeating unit represented by the following formula (1),
The glass transition temperature is more than 400 ℃,
A polyimide-based resin film having a retardation value of 150 nm or less in the thickness direction at a thickness of 10 μm:
[Formula 1]

In Formula 1,
X ₁ is a tetravalent functional group,
Y ₁ is an aromatic divalent functional group having 24 or more carbon atoms in which at least one electron withdrawing functional group is substituted.
According to claim 1,
A polyimide-based resin film having a haze value of 1.5% or less.
According to claim 1,
A polyimide-based resin film having a yellow index value of 15 or less.
According to claim 1,
A polyimide-based resin film having an average transmittance of 60% or more at a wavelength of 380 nm or more and 780 nm or less.
According to claim 1,
In Y ₁ , the aromatic divalent functional group having 24 or more carbon atoms includes 4 or more aromatic cyclic compounds, a polyimide-based resin film.
According to claim 1,
The polyimide-based resin film, wherein the aromatic divalent functional group having 24 or more carbon atoms is derived from an aromatic compound having a maximum light absorption wavelength of 280 nm or more and 300 nm or less.
According to claim 1,
In Formula 1, Y ₁ is 1 to 3 electron withdrawing functional groups are substituted, polyimide-based resin film.
According to claim 1,
A polyimide-based resin film, wherein the aromatic divalent functional group having 24 or more carbon atoms in which at least one electron withdrawing functional group of Y ₁ is substituted includes a functional group represented by the following formula (2):
[Formula 2]

In Formula 2,
Q ₁ To Q ₄ Are the same as or different from each other, and each independently an electron withdrawing functional group,
q1 to q4 are the same as or different from each other, and are each independently an integer of 0 to 4,
p is an integer from 1 to 10;
According to claim 1,
A polyimide-based resin film, wherein the aromatic divalent functional group having 24 or more carbon atoms substituted with at least one electron withdrawing functional group of Y ₁ includes a functional group represented by the following Chemical Formula 2-1:
[Formula 2-1]

In Formula 2-1, Q ₅ to Q ₆ are the same as or different from each other, each independently an electron withdrawing functional group, q5 to q6 are the same or different from each other, and each independently an integer of 0 or 1, (q5+ q6) is an integer of 1 or 2.
According to claim 1,
A polyimide-based resin film, wherein the aromatic divalent functional group having 24 or more carbon atoms substituted with at least one electron withdrawing functional group of Y ₁ includes a functional group represented by the following Chemical Formula 2-2:
[Formula 2-2]

.
According to claim 1,
Wherein X ₁ is a tetravalent functional group comprising an aromatic tetravalent functional group containing a multi-ring, polyimide-based resin film.
According to claim 1,
Wherein X ₁ is a tetravalent functional group comprising one of the tetravalent functional groups represented by the following Chemical Formula 3, a polyimide-based resin film:
[Formula 3]

In Formula 3, Ar is a polycyclic aromatic divalent functional group.
13. The method of claim 12,
In Ar of Formula 3, the polycyclic aromatic divalent functional group is
A polyimide-based resin film comprising a fused cyclic divalent functional group containing at least two or more aromatic ring compounds.
13. The method of claim 12,
The tetravalent functional group represented by Chemical Formula 3 includes a functional group represented by the following Chemical Formula 3-1, a polyimide-based resin film:
[Formula 3-1]

.
The method of claim 1,
The polyimide-based resin is a polyimide-based resin film comprising a combination of a tetracarboxylic dianhydride represented by the following Chemical Formula 4 and an aromatic diamine having 24 or more carbon atoms substituted with at least one electron withdrawing functional group:
[Formula 4]

In Formula 4, Ar ' is a polycyclic aromatic divalent functional group.
According to claim 1,
Wherein the polyimide-based resin further comprises a polyimide repeating unit represented by the following formula (5) in addition to the polyimide repeating unit represented by the formula (1), a polyimide-based resin film:
[Formula 5]

In Formula 5,
X ₂ is a tetravalent functional group different from that of X ₁ ,
Y ₂ is an aromatic divalent functional group having 24 or more carbon atoms in which at least one electron withdrawing functional group is substituted.
17. The method of claim 16,
Wherein X ₂ is one of the tetravalent functional groups represented by the following formula (6), a polyimide-based resin film:
[Formula 6]

In Formula 6, R ₁ to R ₆ are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms, and L ₃ is a single bond, -O-, -CO-, -COO-, -S-, -SO-, -SO ₂ -, -CR ₇ R ₈ -, -(CH ₂ ) _t -, -O(CH ₂ ) _t O-, -COO(CH ₂ ) _t OCO-, -CONH-, phenylene or a combination thereof It is any one selected from the group consisting of, wherein R ₇ and R ₈ are each independently one of hydrogen, an alkyl group having 1 to 10 carbon atoms, or a halo alkyl group having 1 to 10 carbon atoms, and t is an integer of 1 to 10.
17. The method of claim 16,
The polyimide repeating unit represented by Formula 1 and the polyimide repeating unit represented by Formula 5 are 95 mol% or more of the total repeating units contained in the polyimide-based resin, a polyimide-based resin film.
A substrate for a display device comprising the polyimide-based resin film of claim 1 .
An optical device comprising the polyimide-based resin film of claim 1 .