Polyimide-based resin films, substrates using them for display devices, and optical devices.

Abstract

This disclosure relates to polyimide-based resin films, substrates for display devices using the same, and optical devices thereof, the polyimide-based resin films comprising polyimide-based resins comprising polyimide repeating units represented by Chemical Formula 1 and polyimide repeating units represented by Chemical Formula 2.

Description

Technical Field

[0001] Cross-reference of related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0174999, filed with the Korean Intellectual Property Office on December 8, 2021, and Korean Patent Application No. 10-2022-0110024, filed with the Korean Intellectual Property Office on August 31, 2022, the entire contents of which are incorporated herein by reference.

[0003] This disclosure relates to polyimide-based resin films that can achieve excellent warp characteristics and low latency, substrates for display devices, and optical devices using the same. Background Technology

[0004] The display device market is rapidly evolving based on flat panel displays (FPDs), which are easy to manufacture in large areas and can reduce thickness and weight. Such flat panel displays include liquid crystal displays (LCDs), organic light-emitting displays (OLEDs), and electrophoretic displays (EPDs).

[0005] In light of recent efforts to further expand the applications and uses of flat panel displays, particular attention has been paid to so-called flexible display devices that utilize flexible substrates in flat panel displays. The applications of such flexible display devices have been specifically reviewed in relation to mobile devices such as smartphones, and their application areas are gradually expanding.

[0006] Typically, in the process of manufacturing flexible display devices and lighting devices, multiple inorganic films, such as buffer layers, active layers and gate insulators, are formed on cured polyimide to manufacture TFT devices.

[0007] However, conventionally used polyimide resins have a large refractive index in the planar direction, which differs significantly from its refractive index in the thickness direction. For this reason, polyimides exhibit anisotropic properties, thus limiting the occurrence of optical distortion, which greatly reduces visibility.

[0008] In addition, the polyimide material contained in the polyimide layer (base layer) has the following limitations: optical properties are reduced due to the deterioration of polyimide during curing at high temperatures of 400°C or higher, or flatness is difficult to ensure due to physical twisting and warping characteristics.

[0009] Therefore, there is a need to develop new polyimides that can satisfy excellent warpage characteristics while reducing the difference between the refractive index in the planar direction and the refractive index in the thickness direction to improve visibility. Summary of the Invention

[0010] Technical issues

[0011] One object of this disclosure is to provide polyimide-based resin films that can achieve excellent optical properties, warpage characteristics and low delay.

[0012] Another objective of this disclosure is to provide a substrate and optical device for a display device using a polyimide-based resin film.

[0013] Technical solution

[0014] To achieve the above objectives, this document provides a polyimide-based resin film comprising a polyimide-based resin, wherein the polyimide-based resin comprises polyimide repeating units represented by the following chemical formula 1 and polyimide repeating units represented by the following chemical formula 2:

[0015] [Chemical Formula 1]

[0016]

[0017] In chemical formula 1, X1 is a tetravalent aromatic functional group containing a monocyclic ring, and Y1 is a divalent aromatic functional group having 6 to 10 carbon atoms.

[0018] [Chemical Formula 2]

[0019]

[0020] In chemical formula 2, X2 is a tetravalent aromatic functional group containing multiple rings, and Y2 is a divalent aromatic functional group with 6 to 10 carbon atoms.

[0021] This article also provides substrates for display devices, including polyimide-based resin films.

[0022] This article further provides optical devices including polyimide-based resin films.

[0023] The following sections will describe in more detail the polyimide-based resin films and the substrates and optical devices using them for display devices.

[0024] Throughout this specification, unless otherwise stated, the technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of this disclosure.

[0025] Unless the context clearly indicates otherwise, the singular form used in this document is intended to include the plural form as well.

[0026] The terms “comprising” or “including” as used herein specify a particular feature, region, integer, step, action, element, and / or component, but do not exclude the presence or addition of different particular features, regions, integers, steps, actions, elements, components, and / or groups.

[0027] Terms including ordinal numbers such as "first," "second," etc., are used only for the purpose of distinguishing one component from another and are not limited by ordinal numbers. For example, without departing from the scope of this disclosure, the first component may be referred to as the second component, or similarly, the second component may be referred to as the first component.

[0028] In this disclosure, (copolymer) includes not only polymers but also copolymers, where polymer means homopolymer composed of a single repeating unit and copolymer means composite polymer containing two or more repeating units.

[0029] Examples of substituents are described below in this disclosure, but are not limited thereto.

[0030] As used herein, the term "substituted" means that a hydrogen atom in a compound is bonded to another functional group in place of the hydrogen atom, and there are no restrictions on the position of substitution, as long as it is a position where a hydrogen atom is substituted (i.e., a position that can be substituted by a substituent). When two or more substituents are substituted, the two or more substituents may be the same as or different from each other.

[0031] As used herein, the term "substituted or unsubstituted" means unsubstituted or substituted with one or more substituents selected from the following: deuterium; halogen group; cyano; nitro; hydroxyl; carbonyl; ester group; imide group; amide group; primary amino group; carboxyl group; sulfonic acid group; sulfonamide group; phosphine oxide group; alkoxy group; aryloxy group; alkyl thio group; aryl thio group; alkyl sulfonyl group; aryl sulfonyl group; silyl group; boron group; alkyl group; cycloalkyl group; alkenyl group; aryl group; aralkyl group; aryl-alkenyl group; alkyl aryl group; alkoxysilylalkyl group; arylphosphyl group; or a heterocyclic group containing at least one of N, O, and S atoms, or unsubstituted or substituted with two or more substituents linked together from the substituents exemplified above. For example, "substituents linked together with two or more substituents" can be biphenyl. That is, biphenyl can be aryl and can also be interpreted as substituents linked together with two phenyl groups.

[0032] As used in this article, symbols or A direct bond refers to a bond that is connected to another substituent; a direct bond means that there is no single atom in the part represented by L.

[0033] In this disclosure, aromatic is a property that satisfies Huckel's rule, which states that a compound is aromatic if it satisfies all three of the following conditions according to Huckel's rule.

[0034] 1) There must be 4n+2 electrons that are completely conjugated by empty p orbitals, unsaturated bonds, and unpaired electron pairs.

[0035] 2) The 4n+2 electrons must form a planar isomer and a ring structure.

[0036] 3) All atoms in the ring must be able to participate in conjugation.

[0037] In this disclosure, a multivalent functional group is a residue in which a plurality of hydrogen atoms bonded to any compound are removed; for example, it can be a divalent, trivalent, or tetravalent functional group. For example, a tetravalent functional group derived from cyclobutane means a residue in which any four hydrogen atoms bonded to cyclobutane are removed.

[0038] In this disclosure, the aryl group is a monovalent functional group derived from aromatic hydrocarbons and is not particularly limited, but its carbon number is preferably 6 to 20, and it can be a monocyclic aryl or a polycyclic aryl. As a monocyclic aryl, the aryl group can be phenyl, biphenyl, terphenyl, etc., but is not limited to these. Polycyclic aryl groups include naphthyl, anthraceneyl, phenanthryl, pyrene, etc. base, It includes, but is not limited to, methyl, fluorene, etc.

[0039] In this disclosure, a direct bond or single bond refers to a bond line connection where no atom or group of atoms is present at the corresponding position. Specifically, it refers to the absence of other atoms in the portions represented as L1 and L2 in the chemical formula.

[0040] In this disclosure, weight-average molecular weight refers to the weight-average molecular weight of polystyrene as measured by GPC. In determining the weight-average molecular weight of polystyrene as measured by GPC, known analytical apparatus, detectors such as refractive index detectors, and analytical columns can be used. Commonly applied temperature, solvent, and flow rate conditions can be used. Specific examples of measurement conditions are as follows: using a Waters PL-GPC220 instrument and a Polymer Laboratories PLgel MIX-B 300 mm column, an evaluation temperature of 160 °C, using 1,2,4-trichlorobenzene as solvent, a flow rate of 1 mL / min, preparing a sample at a concentration of 10 mg / 10 mL, and then supplying it in 200 μL increments, the Mw value can be obtained using a calibration curve formed using polystyrene standards. Nine polystyrene standards with molecular weights of 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000 were used.

[0041] The contents of this disclosure will now be described in more detail.

[0042] 1. Polyimide-based resin film

[0043] According to one embodiment of this disclosure, a polyimide-based resin film can be provided, the polyimide-based resin film comprising a polyimide-based resin comprising polyimide repeating units represented by the following chemical formula 1 and polyimide repeating units represented by the following chemical formula 2:

[0044] [Chemical Formula 1]

[0045]

[0046] In chemical formula 1, X1 is a tetravalent aromatic functional group containing a monocyclic ring, and Y1 is a divalent aromatic functional group having 6 to 10 carbon atoms.

[0047] [Chemical Formula 2]

[0048]

[0049] In chemical formula 2, X2 is a tetravalent aromatic functional group containing multiple rings, and Y2 is a divalent aromatic functional group with 6 to 10 carbon atoms.

[0050] Through experiments, the inventors discovered that when a polyimide-based resin film, as in one embodiment, simultaneously comprises polyimide repeating units represented by Chemical Formula 1 and polyimide repeating units represented by Chemical Formula 2, the polyimide resin film cured at 400°C or higher can minimize warping, exhibit high flatness and dimensional stability, and resolve defects caused by separation during panel processing. Furthermore, due to the increased refractive index in the thickness direction, the difference between the refractive index in the planar direction and the refractive index in the thickness direction decreases, and optical isotropy increases to achieve low delay. This ensures a good diagonal viewing angle for displays in which the polyimide-based resin film is applied and prevents visibility degradation due to optical distortion. This disclosure is based on these findings.

[0051] In particular, as in the structure represented by Formula 2, since the polyimide-based resin contains reaction products obtained through an imidization reaction of an aromatic tetracarboxylic dianhydride containing a polycyclic aromatic hydrocarbon and an aromatic diamine having 6 to 10 carbon atoms, high heat resistance can be ensured through the physical and chemical effects caused by the structure of the polycyclic aromatic tetracarboxylic dianhydride. This results in excellent flatness not only in films cured by heat treatment at 400°C or higher, but also during additional heat treatment of the cured film at 400°C or higher. Furthermore, the introduction of an asymmetric structure with increased steric hindrance due to polycyclicness into the polyimide chain structure reduces the difference between the refractive index in the planar direction and the refractive index in the thickness direction, thereby achieving low retardation.

[0052] Furthermore, low delay appears to be achieved by reducing the difference between the refractive index in the planar direction and the refractive index in the thickness direction due to the aromatic diamine with 6 to 10 carbon atoms having a curved asymmetric structure.

[0053] Furthermore, as in the structure represented by Formula 1, the polyimide-based resin contains a reaction product obtained by an imidization reaction comprising a monocyclic aromatic tetracarboxylic dianhydride and an aromatic diamine having 6 to 10 carbon atoms, thereby seemingly achieving low retardation by reducing the difference between the refractive index in the planar direction and the refractive index in the thickness direction due to the aromatic diamine having a curved asymmetric structure with 6 to 10 carbon atoms.

[0054] More specifically, in the case of polyimides with a planar linear main chain structure, since the polyimides are stacked and arranged side by side, the refractive index in the thickness direction is low. However, an asymmetric structure is introduced into the polyimide chain structure in a bent form, which can thus maintain the alignment in the thickness direction and reduce the difference between the refractive index in the planar direction and the refractive index in the thickness direction, thereby achieving low delay.

[0055] The polyimide-based resin film according to this disclosure can increase the refractive index and can be used as a base layer in a flexible display device to reduce the difference in refractive index between the layers constituting the device, thereby reducing the amount of light dissipated internally and effectively improving the efficiency of bottom light emission.

[0056] Specifically, the polyimide-based resin film may comprise a polyimide-based resin. A polyimide-based resin refers to a resin comprising all polyimide and polyamic acid or polyamic acid ester as a precursor polymer. That is, the polyimide-based resin may comprise at least one selected from polyamic acid repeating units, polyamic acid ester repeating units, and polyimide repeating units. Specifically, the polyimide-based resin may comprise one polyamic acid repeating unit, one polyamic acid ester repeating unit, one polyimide repeating unit, or a mixed copolymer of two or more repeating units thereof.

[0057] At least one repeating unit selected from polyamic acid repeating units, polyamic acid ester repeating units, and polyimide repeating units can form the main chain of a polyimide-based resin.

[0058] Polyimide-based resin films may contain cured products of polyimide-based resins. Cured products of polyimide-based resins refer to products obtained through a curing process of polyimide-based resins.

[0059] In particular, the polyimide-based resin may contain polyimide repeating units represented by the following chemical formula 1.

[0060] [Chemical Formula 1]

[0061]

[0062] In chemical formula 1, X1 is a tetravalent aromatic functional group containing a monocyclic ring, and Y1 is a divalent aromatic functional group having 6 to 10 carbon atoms.

[0063] In Formula 1, X1 is an aromatic tetravalent functional group containing a monocyclic ring, and X1 is a functional group derived from a tetracarboxylic dianhydride compound used to synthesize polyimide-based resins.

[0064] The monocyclic aromatic tetravalent functional group of X1 may include functional groups derived from pyromellitic dianhydride (PMDA) represented by the following chemical formula 5.

[0065] [Chemical Formula 5]

[0066]

[0067] When the functional group represented by chemical formula 5 is included as a monocyclic aromatic tetravalent functional group, the packing density of the polymer chain can be increased through a flat structure, thereby achieving high heat resistance and high mechanical properties.

[0068] Meanwhile, in chemical formula 1, Y1 is an aromatic divalent functional group having 6 to 10 carbon atoms, and Y1 can be a functional group derived from polyamic acid, polyamic acid ester or diamine compound used to synthesize polyimide.

[0069] Aromatic divalent functional groups having 6 to 10 carbon atoms may include phenylene. More specifically, aromatic divalent functional groups having 6 to 10 carbon atoms in Y1 may include functional groups represented by the following chemical formula 3.

[0070] [Chemical Formula 3]

[0071]

[0072] Specific examples of functional groups represented by chemical formula 3 may include functional groups derived from m-phenylenediamine (1,3-phenylenediamine, m-PDA) represented by the following chemical formula 3-1.

[0073] [Chemical Formula 3-1]

[0074]

[0075] When Y1 includes functional groups represented by chemical formula 3-1, an asymmetric structure is introduced into the polyimide chain structure in a bent form, which allows the alignment to be maintained in the thickness direction. This reduces the difference between the refractive index in the planar direction and the refractive index in the thickness direction, thereby achieving low delay.

[0076] Meanwhile, when Y1 includes functional groups derived from p-phenylenediamine (1,4-phenylenediamine, p-PDA) that do not possess a bending asymmetric structure, it is difficult to achieve the aforementioned bending asymmetric structure, resulting in the polyimide polymerizing in a planar linear direction, and the polymer growing only in the planar direction. Therefore, proper stacking of polymers reduces the refractive index in the thickness direction, which may cause an increase in the difference between the refractive index in the planar direction and the refractive index in the thickness direction.

[0077] In addition to the polyimide repeating unit represented by Chemical Formula 1, the polyimide-based resin may also contain the polyimide repeating unit represented by Chemical Formula 2. That is, the polyimide-based resin may contain both the polyimide repeating unit represented by Chemical Formula 1 and the polyimide repeating unit represented by Chemical Formula 2.

[0078] [Chemical Formula 2]

[0079]

[0080] In chemical formula 2, X2 is a tetravalent aromatic functional group containing multiple rings, and Y2 is a divalent aromatic functional group with 6 to 10 carbon atoms.

[0081] Y2 is the same as Y1 in chemical formula 1.

[0082] In chemical formula 2, X2 is a polycyclic aromatic tetravalent functional group, and X2 is a functional group derived from a tetracarboxylic dianhydride compound used to synthesize polyimide-based resins.

[0083] More specifically, the tetravalent functional groups of X2 may include tetravalent functional groups represented by the following chemical formula 4.

[0084] [Chemical Formula 4]

[0085]

[0086] In formula 4, Ar is a polycyclic aromatic divalent functional group. A polycyclic aromatic divalent functional group is a divalent functional group derived from polycyclic aromatic hydrocarbon compounds or their derivatives, wherein the derivative compounds include all compounds in which at least one substituent is introduced or where a carbon atom is replaced by a heteroatom.

[0087] More specifically, in Ar of Formula 4, the polycyclic aromatic divalent functional group may include a fused cyclic divalent functional group comprising at least two or more aromatic ring groups. That is, the polycyclic aromatic divalent functional group may contain at least two or more aromatic ring groups in its functional group structure, wherein the functional group may have a fused ring structure.

[0088] Aromatic ring groups may include aromatic groups containing at least one benzene ring, or heteroaromatic groups in which carbon atoms in the aromatic group are replaced by heteroatoms.

[0089] A polycyclic aromatic divalent functional group may contain at least two or more aromatic ring groups, each of which may directly form a fused ring or may form a fused ring via another ring structure. As an example, when two benzene rings are each fused with a cycloalkyl ring structure, it can be defined as the two benzene rings forming a fused ring via a cycloalkyl ring.

[0090] A fused cyclic divalent functional group containing at least two or more aromatic ring groups is a divalent functional group derived from a fused cyclic compound containing at least two or more aromatic ring groups or a derivative thereof, wherein the derivative compound includes all compounds in which at least one substituent is introduced or a carbon atom is replaced by a heteroatom.

[0091] In Ar of Formula 4, the polycyclic aromatic divalent functional group may include a fluorene group. Specific examples of functional groups represented by Formula 4 may include functional groups derived from 9,9-bis(3,4-dicarboxyphenyl)fluorene dihydric anhydride (BPAF) represented by the following Formula 4-1.

[0092] [Chemical Formula 4-1]

[0093]

[0094] When X2 includes a polycyclic aromatic tetravalent functional group, it not only introduces a symmetrical structure into the polyimide chain structure, which increases steric hindrance due to the polycyclic structure, thus reducing heat-induced deformation and improving heat resistance, but also introduces a large-volume structure into the polyimide chain structure, which increases steric hindrance in the thickness direction due to the polycyclic structure. This increases the refractive index in the thickness direction and reduces the difference between the refractive index in the planar direction and the refractive index in the thickness direction, thereby achieving low retardation and suppressing intermolecular stacking to achieve high transmittance.

[0095] Resins based on polyimide may include combinations of aromatic tetracarboxylic dianhydrides comprising a monocyclic aromatic tetracarboxylic dianhydride, aromatic tetracarboxylic dianhydrides comprising a polycyclic aromatic tetracarboxylic dianhydride, and aromatic diamines having 6 to 10 carbon atoms.

[0096] A monocyclic aromatic tetracarboxylic dianhydride is a compound in which an anhydride group (-OC-O-CO-) is introduced at both ends of the monocyclic aromatic tetravalent functional group. The details of the monocyclic aromatic tetravalent functional group are the same as those described above.

[0097] Specific examples of aromatic tetracarboxylic dianhydrides containing a monocyclic ring may include pyromellitic dianhydride (PMDA).

[0098] A polycyclic aromatic tetracarboxylic dianhydride is a compound in which an anhydride group (-OC-O-CO-) is introduced at both ends of the polycyclic aromatic tetravalent functional group. The details of the polycyclic aromatic tetravalent functional group are the same as those described above.

[0099] Specific examples of polycyclic aromatic tetracarboxylic dianhydrides may include 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF).

[0100] Aromatic diamines having 6 to 10 carbon atoms are compounds in which amino groups (-NH2) are introduced at both ends of the aromatic divalent functional groups having 6 to 10 carbon atoms. The details of the aromatic divalent functional groups having 6 to 10 carbon atoms are the same as described above. Specific examples of aromatic diamines having 6 to 10 carbon atoms may include m-phenylenediamine (1,3-phenylenediamine, m-PDA).

[0101] More specifically, polyimide-based resins can form bonds between the nitrogen atom of the amino group and the carbon atom of the anhydride group due to the reaction between the terminal anhydride group (-OC-O-CO-) of the aromatic tetracarboxylic dianhydride containing polycyclic aromatic tetracarboxylic dianhydride and the terminal amino group (-NH2) of the aromatic diamine having 6 to 10 carbon atoms.

[0102] Meanwhile, the polyimide-based polymer may comprise: a first repeating unit comprising repeating units represented by Chemical Formula 1, wherein the anhydride-derived repeating units are functional groups represented by Chemical Formula 5; and a second repeating unit comprising repeating units represented by Chemical Formula 2, wherein the anhydride-derived repeating units are functional groups represented by Chemical Formula 4. The first and second repeating units may be randomly arranged in the polyimide-based polymer to form a random copolymer, or blocks may be formed between the first repeating units and between the second repeating units to form a block copolymer.

[0103] Polyimide-based polymers comprising repeating units represented by Formula 1 and repeating units represented by Formula 2 can be prepared by reacting two or more distinct tetracarboxylic dianhydride compounds with a diamine compound. The two tetracarboxylic dianhydride compounds can be added simultaneously to synthesize a random copolymer, or they can be added sequentially to synthesize a block copolymer.

[0104] The molar ratio between the polyimide repeating unit represented by chemical formula 1 and the polyimide repeating unit represented by chemical formula 2 can be 85:15 to 15:85, or 80:20 to 20:80, or 75:25 to 25:75, or 60:40 to 40:60, or 60:40 to 70:30, or 70:30 to 85:15.

[0105] More specifically, the molar ratio of polyimide repeating units represented by chemical formula 2 to 1 mol of polyimide repeating units represented by chemical formula 1 can be 0.17 mol to 6 mol, or 0.25 mol to 4 mol, or 0.33 mol to 3 mol, or 0.6 mol to 1.5 mol, or 0.4 mol to 0.7 mol, or 0.17 mol to 0.5 mol.

[0106] It can achieve excellent warp characteristics and excellent colorless / transparent optical properties. Simultaneously, the refractive index increases in the thickness direction, thereby achieving optical isotropy through low retardation (Rt) in the thickness direction. th The increased properties ensure that the diagonal viewing angle of displays in which polyimide-based resin films are applied can be guaranteed, thereby preventing the degradation of visibility due to light distortion.

[0107] On the other hand, when the polyimide repeating unit represented by Formula 1 is included in too small a quantity, and therefore the molar ratio between the polyimide repeating unit represented by Formula 1 and the polyimide repeating unit represented by Formula 2 deviates from 15:85, the heat resistance decreases due to the decrease in glass transition temperature, and the occurrence of warpage in the polyimide resin film cured at 400°C or higher increases. This makes it difficult to stack elements on the film and also makes subsequent processes impossible.

[0108] Furthermore, when the polyimide repeating unit represented by Formula 2 is included in too small a quantity, and therefore the molar ratio between the polyimide repeating unit represented by Formula 1 and the polyimide repeating unit represented by Formula 2 deviates from 85:15, the following problem arises: a delay R in the thickness direction... th The increase in yellowness index leads to a deterioration in visibility due to optical distortion caused by the accompanying increase in delay. Furthermore, the increase in yellowness index may worsen transparency characteristics and reduce optical properties, such as a decrease in the refractive index in the thickness direction or the average refractive index.

[0109] Additionally, one embodiment of the polyimide-based resin film 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 product obtained by a curing step of a resin composition comprising a polyimide-based resin, wherein the curing step may be performed at a temperature of 400°C or higher, or 400°C or higher and 500°C or lower.

[0110] Relative to the total repeating units contained in the polyimide-based resin, the polyimide repeating units represented by Formula 1 and the polyimide repeating units represented by Formula 2 may be included in the following amounts: 70 mol% or greater, or 80 mol% or greater, or 90 mol% or greater, or 70 mol% or greater and 100 mol% or less, 80 mol% or greater and 100 mol% or less, 70 mol% or greater and 90 mol% or less, 70 mol% or greater and 99 mol% or less, 80 mol% or greater and 99 mol% or less, or 90 mol% or greater and 99 mol% or less.

[0111] That is, the polyimide-based resin may consist only of polyimide repeating units represented by chemical formula 1 and polyimide repeating units represented by chemical formula 2, or it may consist mostly of polyimide repeating units represented by chemical formula 1 and polyimide repeating units represented by chemical formula 2.

[0112] There are no particular limitations on the weight-average molecular weight (measured by GPC) of polyimide-based resins, but it can be, for example, 1000 g / mol or greater and 200000 g / mol or less, or 10000 g / mol or greater and 200000 g / mol or less.

[0113] The polyimide-based resin according to this disclosure can exhibit excellent colorless / transparent properties while retaining characteristics such as heat resistance and mechanical strength due to its rigid structure. Therefore, it can be used in various fields, such as substrates for devices, cover substrates for displays, optical films, integrated circuit (IC) packaging, adhesive films, multilayer FPCs (flexible printed circuits), tapes, touch panels, protective films for optical discs, etc., and in particular, it can be used as a cover substrate for displays.

[0114] More specifically, there are no particular limitations on the examples of methods for synthesizing polyimide-based resin films, but for example, a method for producing polymer films including the following steps can be used: coating a polymer composition containing a polyimide-based resin onto a substrate to form a coated film (step 1); drying the coated film (step 2); and heat-treating and curing the dried coated film (step 3).

[0115] Step 1 involves coating the polymer composition containing the aforementioned polyimide-based resin onto a substrate to form a coated film. There are no particular limitations on the method used to coat the polymer composition containing the polyimide-based resin onto the substrate, but methods such as screen printing, offset printing, flexographic printing, and inkjet printing can be used, for example.

[0116] Furthermore, polymer compositions comprising polyimide-based resins can be in the form of being dissolved or dispersed in an organic solvent. In these forms, for example, when the polyimide-based resin is synthesized in an organic solvent, the solution can be the reaction solution itself, or the reaction solution can be diluted with another solvent. Additionally, when the polyimide-based resin is obtained as a powder, it can be dissolved in an organic solvent to form a solution.

[0117] Specific examples of organic solvents include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethyl sulfoxide, tetramethylurea, pyridine, dimethyl sulfone, hexamethyl sulfoxide, γ-butyrolactone, 3-methoxy-N,N-dimethylpropionamide, 3-ethoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, 1,3- Dimethyl imidazolinone, ethylpentyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isopentyl ketone, methyl isopropyl ketone, cyclohexanone, ethylene carbonate, propylene carbonate, diethylene glycol dimethyl ether, 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. These can be used alone or in combination of two or more.

[0118] Considering processability during the film-forming process, such as coating characteristics, polymer compositions comprising polyimide-based resins can contain solid contents in an amount that gives the polymer composition an appropriate viscosity. For example, the content of the composition can be adjusted such that the total resin content is 5% by weight or more and 25% by weight or less, or alternatively, it can be adjusted to 5% by weight or more and 20% by weight or less, or 5% by weight or more and 15% by weight or less.

[0119] In addition to organic solvents, polymer compositions comprising polyimide-based resins may also contain other components. In a non-limiting example, when coating a polymer composition comprising a polyimide-based resin, compounds may also be included that can improve the uniformity of film thickness and surface smoothness, or improve the adhesion between the polymer composition and the substrate, or change the dielectric constant and conductivity, or increase density. Examples of such compounds may include surfactants, silane-based compounds, dielectrics, or crosslinking compounds, etc.

[0120] Step 2 is the step of drying the coating film formed by coating a polymer composition containing a polyimide-based resin onto a substrate.

[0121] The drying step of the coating film can be carried out by heating devices such as hot plates, hot air circulating ovens, infrared ovens, etc. The drying can be carried out at a temperature of 50°C or higher and 150°C or lower, or 50°C or higher and 100°C or lower.

[0122] Step 3 involves heat treatment and curing of the dried coating film. The heat treatment can be performed using heating devices such as hot plates, hot air circulating ovens, or infrared ovens. The heat treatment can be carried out at temperatures of 200°C or higher, or 200°C or higher and 300°C or lower, or 400°C or higher, or 400°C or higher and 500°C or lower.

[0123] There is no particular limitation on the thickness of the polyimide-based resin film, but it can be freely adjusted, for example, within a range of 0.01 μm or greater and 1000 μm or smaller. When the thickness of the polyimide-based resin film increases or decreases by a specific value, the physical properties measured by the polyimide-based resin film can also change by a specific value.

[0124] Meanwhile, the residual stress in the inorganic substrate of a polyimide-based resin film of one embodiment at a thickness of 10 μm can be 46 MPa or less, or 45 MPa or less, or 40 MPa or less, or 35 MPa or less, or 30 MPa or less, or 1 MPa or more, or 1 MPa to 46 MPa, or 10 MPa to 46 MPa, or 20 MPa to 46 MPa, or 1 MPa to 46 MPa, or 1 MPa to 40 MPa, or 1 MPa to 35 MPa, or 1 MPa to 30 MPa, or 10 MPa to 45 MPa, or 20 MPa to 45 MPa, or 28.7 MPa to 45 MPa. Because the residual stress in the inorganic substrate is reduced in this way, the polyimide-based resin film of one embodiment can reduce residual stress, thereby solving the defects caused by separation during panel processing.

[0125] There are no particular limitations on the methods and instruments used for measuring residual stress, and various methods commonly used for measuring residual stress can be applied without limitation. As an example, residual stress measuring devices can be used to measure the residual stress of polyimide-based resin films. Furthermore, examples of inorganic substrates can include wafer substrates.

[0126] Residual stress can be measured using a polyimide-based resin film sample with a thickness of 10 μm ± 1 μm. The physical properties of the polyimide-based resin film measured can also change by specific values ​​when the thickness of the polyimide-based resin film increases or decreases by a specific value.

[0127] When the residual stress in the inorganic substrate of a polyimide-based resin film with a thickness of 10 μm increases excessively to greater than 48 MPa, the polyimide resin film cured at a high temperature of 400°C or higher may warp, which may cause defects during panel processing due to separation.

[0128] Meanwhile, in one embodiment, the polyimide-based resin film has a thickness retardation value in the thickness direction of 300 nm or less, or 200 nm or less, or 100 nm or less, or 70 nm or less, or 30 nm or less, or 20 nm or less, or 1 nm or more, or 1 nm to 300 nm, or 1 nm to 200 nm, or 1 nm to 100 nm, or 1 nm to 70 nm, or 1 nm to 30 nm, or 1 nm to 20 nm. In this way, optical isotropic properties are achieved due to the low thickness direction retardation (Rt). th This property increases the diagonal viewing angle of displays in which polyimide-based resin films are applied, thereby achieving excellent visibility.

[0129] As described later, such low delay appears to be achieved by using m-phenylenediamine (m-PDA), a diamine with an asymmetric structure, as a monomer for producing polyimide-based resin films to reduce the difference between the refractive index in the planar direction and the refractive index in the thickness direction.

[0130] More specifically, in the case of polyimides with a planar linear main chain structure, the polyimides are stacked side by side, resulting in a low refractive index in the thickness direction. In contrast, polyimides with a curved main chain structure are poorly stacked between molecules, thus increasing the refractive index in the thickness direction.

[0131] The delay in the thickness direction can be measured at a wavelength of 532 nm. There are no particular limitations on the types of measurement methods and instruments used, and various methods commonly used to measure the delay in the thickness direction can be applied without limitation.

[0132] The delay in the thickness direction can be measured by a polyimide-based resin film sample with a thickness of 10 μm ± 1 μm. When the thickness of the polyimide-based resin film increases or decreases by a specific value, the physical properties measured by the polyimide-based resin film can also change by a specific value.

[0133] Specifically, the delay R in the thickness direction th It can be calculated according to the following equation 1.

[0134] [Equation 1]

[0135] R th (nm)=|[(n x +n y ) / 2]-n z |×d

[0136] In equation 1, n x The maximum refractive index among the in-plane refractive indices of the polyimide resin film measured by light with a wavelength of 532 nm; ny The in-plane refractive index of a polyimide resin film measured with light at a wavelength of 532 nm is related to n. x Vertical refractive index; n z d represents the refractive index of the polyimide resin film in the thickness direction, measured by light with a wavelength of 532 nm; and d represents the thickness of the polyimide-based resin film.

[0137] That is, the delay R in the thickness direction th To multiply the film thickness by the refractive index value in the thickness direction (n) z The average value of the plane refractive index [(n x +n y The value is obtained by taking the absolute value of the difference between [n] and [2]. This is due to the refractive index value in the thickness direction (n). z The average value of the plane refractive index [(n x +n y The difference between ) / 2] is small, so it can show a lower value.

[0138] Because polyimide-based resin films satisfy a thickness-direction retardation value of 100 nm or less at a thickness of 10 μm, the thickness-direction refractive index value (n) is reduced in displays in which polyimide-based resin films are used. z The average value of the plane refractive index [(n x +n y The difference of ) / 2] achieves excellent visibility.

[0139] When the retardation value in the thickness direction of a polyimide-based resin film increases excessively to more than 100 nm at a thickness of 10 μm, distortion occurs when the polyimide is present in the structure of the upper component during the realization of a transparent display. Therefore, there is a technical limitation that even as a compensation film with technical compensation up to 45 nm, the refraction of transmitted light cannot be calibrated.

[0140] The refractive index of a polyimide-based resin film with a thickness of 10 μm at a wavelength of 532 nm can be 1.71 or greater, or 1.7103 or greater, or 1.7120 or greater, or 1.7130 or greater, or 1.72 or less, or 1.71 to 1.72, or 1.7103 to 1.72, or 1.7120 to 1.72, or 1.7130 to 1.72, or 1.71 to 1.715, or 1.7102 to 1.7136. Furthermore, the planar refractive index of a polyimide-based resin film with a thickness of 10 μm at a wavelength of 532 nm can be 1.71 to 1.73.

[0141] There are no particular limitations on examples of methods and instruments used to measure the refractive index in the planar direction and the refractive index in the thickness direction, and various methods commonly used for measuring the refractive index can be applied without limitation. As an example, the refractive index in the planar direction and the refractive index in the thickness direction can be measured at a wavelength of 532 nm using a prism coupler.

[0142] The refractive index can be measured from a polyimide-based resin film sample with a thickness of 10 μm ± 1 μm. When the thickness of the polyimide-based resin film increases or decreases by a specific value, the physical properties measured from the polyimide-based resin film can also change by a specific value.

[0143] When the refractive index in the thickness direction is excessively reduced to less than 1.71 at a wavelength of 532 nm based on a thickness of 10 μm, the polyimide-based resin film has the following technical limitation: due to the increased difference between the refractive index in the planar direction and the refractive index in the thickness direction, the delay increases, resulting in distortion when transmitting light in the case of a transparent display, and poor visibility.

[0144] The average refractive index of a polyimide-based resin film with a thickness of 10 μm at a wavelength of 532 nm can be 1.7135 or greater, or 1.7140 or greater, or 1.7150 or greater, or 1.7180 or greater, or 1.72 or less, or 1.7135 to 1.72, or 1.7136 to 1.7182, or 1.7140 to 1.72, or 1.7150 to 1.72, or 1.7180 to 1.72. As an example of a method for measuring the average refractive index, the refractive index in the planar direction (TE) and the refractive index in the thickness direction (TM) at a wavelength of 532 nm are measured using a prism coupler, and the average refractive index is calculated according to the following Equation 2.

[0145] [Equation 2]

[0146] Average refractive index = (n x +n y +n z ) / 3

[0147] In equation 2, n x The maximum refractive index among the in-plane refractive indices of the polyimide polymer film measured by light with a wavelength of 532 nm; n y The in-plane refractive index of a polyimide polymer film measured by light with a wavelength of 532 nm is related to n. x The refractive index perpendicular to the direction; and n z The refractive index in the thickness direction of the polyimide polymer film is measured by light with a wavelength of 532 nm.

[0148] The average refractive index can be measured from a polyimide-based resin film sample with a thickness of 10 μm ± 1 μm. When the thickness of the polyimide-based resin film increases or decreases by a specific value, the physical properties of the polyimide-based resin film can also change by a specific value.

[0149] Meanwhile, the haze value of the polyimide-based resin film at a thickness of 10 μm can be less than 1.0%, or 0.1% or greater but less than 1.0%. Haze can be measured from a polyimide-based resin film sample with a thickness of 10 μm ± 1 μm. When the thickness of the polyimide-based resin film increases or decreases by a specific value, the measured physical properties of the polyimide-based resin film can also change by a specific value.

[0150] The Bow value of a polyimide-based resin film at a thickness of 10 μm can be 48 μm or less, or 45 μm or less, or 40 μm or less, or 35 μm or less, or 30 μm or less, or 1 μm or more, or 1 μm to 48 μm, or 1 μm to 45 μm, or 1 μm to 40 μm, or 1 μm to 35 μm, or 1 μm to 30 μm, or 10 μm to 48 μm, or 20 μm to 48 μm, or 28.35 μm to 45.62 μm. Bow, also known as bending or bending, is a type of surface flatness characteristic of a material. For its details, such as the specific measurement method, various methods known in the field of semiconductor wafer substrate manufacturing can be applied without limitation.

[0151] Specifically, Bow 3 can be defined as follows: Figure 1 The distance on the central axis 4 between the thickness center plane 1 and the reference plane 2 (the best-fit plane of the thickness center plane).

[0152] as follows Figure 1 As shown, the thickness center plane 1 refers to the plane connection point that is half (t / 2) of the thickness t of the object to be measured.

[0153] as follows Figure 1 As shown, reference plane 2 is the cross section of the straight line passing through the center point of the thickness at both ends of the object to be measured.

[0154] as follows Figure 1 As shown, the central axis 4 is a straight line perpendicular to the horizontal plane that passes through the center of gravity of the object to be measured.

[0155] As an example of a method for measuring Bow 3, a laser stress analyzer can be used. The stress analyzer measures the intensity of light reflected from the back surface of the sample being measured, and the Bow value can be automatically calculated and obtained through mathematical analysis.

[0156] Bow can be measured on a polyimide-based resin film sample with a thickness of 10 μm ± 1 μm in one embodiment.

[0157] Polyimide-based resin film samples used for Bow measurements include pure polyimide-based resin films; or laminates comprising a base film and a polyimide-based resin film coated on the base film. Examples of base films are not particularly limited, and glass substrates, wafer substrates, or mixtures thereof may be used without limitation.

[0158] When the polyimide-based resin film sample used for Bow measurements consists solely of a pure polyimide-based resin film, the Bow can be automatically measured using the results of analysis of the polyimide-based resin film sample with a laser stress analyzer. For example, a pure polyimide-based resin film can be ensured by peeling the base film from a laminate comprising a base film and a polyimide-based resin film coated on the base film.

[0159] When the Bow value of a polyimide-based resin film increases excessively to greater than 48 μm, the polyimide resin film cured at 400°C or higher may warp, which could cause defects during panel processing due to separation.

[0160] Meanwhile, the yellowness index of polyimide-based resin films at a thickness of 10 μm can be 25 or less, or 1 or greater, or 1 to 25, or 6.27 to 22.8. When the yellowness index of polyimide-based resin films at a thickness of 10 μm increases excessively to greater than 25, there is a limitation: the degree of yellowing of the polyimide-based resin film increases, making it difficult to produce colorless and transparent films.

[0161] There are no particular limitations on the examples of methods and instruments used to measure the yellowness index of a polyimide-based resin film in one embodiment, and various methods commonly used for YI measurement can be applied without limitation. In one example, it can be measured using a colorimeter (Color-Eye 7000A, available from GretagMacbeth).

[0162] The yellowness index can be measured from a polyimide-based resin film sample with a thickness of 10 μm ± 1 μm. When the thickness of the polyimide-based resin film increases or decreases by a specific value, the physical properties of the polyimide-based resin film can also change by a specific value.

[0163] 2. Base for display devices

[0164] Furthermore, according to another embodiment of this disclosure, a substrate for a display device, including a polyimide-based resin film, can be provided in other embodiments. Details of the polyimide-based resin film may include all those described above in one embodiment.

[0165] Display devices including a substrate may include, but are not limited to, liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), flexible displays, or rollable or foldable displays.

[0166] Depending on the application and specific shape, display devices can have various structures, such as covering plastic windows, touch panels, polarizing plates, blocking films, light-emitting devices (OLED devices, etc.), and transparent substrates.

[0167] The polyimide-based resin films of some of the other embodiments described above can be used in a variety of applications, such as substrates, external protective films or cover windows in these various display devices, and more specifically, they can be used as substrates.

[0168] For example, a substrate for a display device may have a structure in which a device protective layer, a transparent electrode layer, a silicon oxide layer, a polyimide-based resin film, a silicon oxide layer, and a hard coating are sequentially stacked.

[0169] In terms of further improving solvent resistance or water permeability and optical properties, the transparent polyimide substrate may include a silicon oxide layer formed between a transparent polyimide-based resin film and a cured layer, the silicon oxide layer being produced by curing polysilazane.

[0170] Specifically, the silicon oxide layer is formed by coating and drying a solution containing polysilazane before forming a coating layer on at least one surface of a transparent polyimide-based resin film, and then curing the coated polysilazane.

[0171] By including the aforementioned protective layer for the components, the substrate for a display device according to this disclosure can provide a transparent polyimide-coated substrate with excellent warp resistance, impact resistance, solvent resistance, optical properties, moisture permeability, and scratch resistance.

[0172] 3. Optical devices

[0173] Furthermore, according to yet another embodiment of this disclosure, optical devices comprising polyimide-based resin films can be provided in other embodiments. Details of the polyimide-based resin films may include all those described above in the other embodiments.

[0174] Optical devices may include various devices that utilize properties achieved through light, and may include, for example, display devices. Specific examples of display devices include, but are not limited to, liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), flexible displays, or rollable or foldable displays.

[0175] Optical devices can have various structures depending on their application and specific shape. For example, they can include structures such as plastic cover windows, touch panels, polarizers, blocking films, light-emitting elements (OLED elements, etc.), and transparent substrates.

[0176] The polyimide-based resin film of the other embodiment described above can be used in a variety of applications, such as substrates, external protective films or cover windows in various optical devices, and more specifically, it can be applied to substrates.

[0177] Beneficial effects

[0178] According to this disclosure, polyimide-based resin films that achieve excellent warp characteristics and low latency, substrates for display devices, and optical devices using the same can be provided. Attached Figure Description

[0179] Figure 1 This is a cross-sectional view of the Bow used to measure the polyimide-based resin film obtained in the examples and comparative examples. Detailed Implementation

[0180] The invention will be described in more detail below by way of examples. However, these examples are provided for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0181] <Examples and Comparative Examples: Preparation of Polyimide Precursor Compositions and Polyimide Films>

[0182] Examples 1 to 4

[0183] (1) Preparation of polyimide precursor composition

[0184] While maintaining the reactor temperature at 25°C, the organic solvent DMAc was filled into the reactor under a nitrogen atmosphere, and m-phenylenediamine (1,3-phenylenediamine, m-PDA) was added and dissolved at the same temperature. At the same temperature, pyromellitic dianhydride (PMDA) and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF) were added as acid dianhydrides to the solution containing m-phenylenediamine (1,3-phenylenediamine, m-PDA), and the mixture was stirred for 24 hours to prepare the polyimide precursor composition. The molar ratios of m-PDA, PMDA, and BPAF at this time are shown in Table 1 below.

[0185] (2) Preparation of polyimide film

[0186] The polyimide precursor composition was spin-coated onto 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, held at 80°C for 30 minutes, 250°C for 30 minutes, and 400°C for 30 minutes for curing. After curing, the glass substrate was immersed in water to peel off the film formed on the glass substrate, and then dried in an oven at 100°C to prepare a polyimide film with a thickness of 10 μm (including ±1 μm error).

[0187] Comparative Examples 1 to 5

[0188] The polyimide precursor composition and polyimide film were prepared in the same manner as in the examples above, except that the molar ratios of m-PDA, p-PDA (1,4-phenylenediamine), TFMB (2,2'-bis(trifluoromethyl)benzidine), PMDA and BPAF were changed as described in Table 2 below.

[0189] Refer to Examples 1 to 3

[0190] The polyimide precursor composition and polyimide film were prepared in the same manner as in the examples above, except that the molar ratios of m-PDA, PMDA and BPAF were changed as described in Table 3 below.

[0191] <Experimental Example: Measurement of the physical properties of the polyimide precursor compositions and polyimide films obtained in the Examples and Comparative Examples>

[0192] The physical properties of the polyimide precursor compositions and polyimide films obtained in the Examples and Comparative Examples were measured using the following methods, and the results are shown in Tables 1 to 3 below.

[0193] 1. Yellowness Index (YI)

[0194] The yellowness index of the polyimide films prepared in the examples and comparative examples was measured using a colorimeter (Color-Eye 7000A available from GretagMacbeth).

[0195] 2. Haze

[0196] The haze value of the polyimide film was measured using a haze meter (NDH-5000).

[0197] 3. Delay in the thickness direction (R) th )

[0198] The refractive index values ​​of the polyimide films produced in the examples and comparative examples were input using an "AxoScan" manufactured by AXOMETRICS as the measuring device. Then, under conditions of temperature: 25°C and humidity: 40%, the retardation in the thickness direction and the retardation in the planar direction were measured using light at a wavelength of 532 nm. The obtained retardation values ​​in the thickness direction (values ​​measured automatically by the measuring device) were converted into retardation values ​​per 10 μm film thickness, and the obtained values ​​are shown in Table 1 below.

[0199] Specifically, the delay R in the thickness direction is calculated according to the following Equation 1. th .

[0200] [Equation 1]

[0201] R th (nm)=|[(n x +n y ) / 2]-n z |×d

[0202] (In equation 1, n) x The maximum refractive index among the in-plane refractive indices of the polyimide resin film measured by light with a wavelength of 532 nm; n y The in-plane refractive index of a polyimide resin film measured with light at a wavelength of 532 nm is related to n. x Vertical refractive index; n z d represents the refractive index of the polyimide resin film in the thickness direction, measured using light with a wavelength of 532 nm; and d represents the thickness of the polyimide-based resin film.

[0203] 4. Residual stress and Bow

[0204] The polyimide precursor compositions prepared in the examples and comparative examples were coated onto 6-inch silicon wafers to a thickness of 525 μm using a spin coater, wherein the amount of wafer warpage was measured beforehand using a residual stress meter (FLX2320, available from TENCOR). The wafers were then thermally cured in a nitrogen atmosphere at 250°C for 30 minutes and then at 400°C for 30 minutes using an oven (available from Koyo Lindberg). After curing, silicon wafers with resin films were produced. The amount of warpage of the silicon wafers with attached resin films was measured using a residual stress meter, and the absolute value of the difference between the amount of warpage and the actual warpage was expressed as the actual Bow value beforehand. The residual stress generated between the silicon wafer and the resin film was also measured using a residual stress meter.

[0205] Bow 3 is defined as follows Figure 1The distance on the central axis between the thickness center plane and the reference plane (the best-fit plane of the thickness center plane) is shown. The bow of the sample was measured at room temperature using a stress analyzer (TENCOR FLX-2320).

[0206] 5. Refractive index

[0207] For the polyimide films produced in the examples and comparative examples, the refractive index in the planar direction (TE) and the refractive index in the thickness direction (TM) were measured at a wavelength of 532 nm using a prism coupler, and the average refractive index was calculated according to the following Equation 2.

[0208] [Equation 2]

[0209] Average refractive index = (n x +n y +n z ) / 3

[0210] (In equation 2, n) x The maximum refractive index among the in-plane refractive indices of the polyimide polymer film measured by light with a wavelength of 532 nm; n y The in-plane refractive index of a polyimide polymer film measured by light with a wavelength of 532 nm is related to n. x The refractive index perpendicular to the direction; and n z (This represents the refractive index along the thickness direction of the polyimide polymer film, measured using light with a wavelength of 532 nm.)

[0211] [Table 1]

[0212] Experimental measurement results of the embodiments

[0213]

[0214] As shown in Table 1, the polyimide films obtained in Examples 1 to 4 (based on a thickness of 10 μm) were determined to have a thickness directional retardation R of 13 nm to 100 nm. th Value, haze of 0.36% to 0.84%, YI of 6.27 to 22.8, residual stress of 28.7 MPa to 45 MPa, Bow of 28.35 μm to 45.62 μm, planar refractive index (nTE) of 1.7141 to 1.7222 at 532 nm, thickness refractive index (nTM) of 1.7102 to 1.7136, and average refractive index of 1.7136 to 1.7182 at 532 nm.

[0215] [Table 2]

[0216] Comparative example experimental results

[0217]

[0218] As shown in Table 2, the polyimide films (based on a thickness of 10 μm) obtained in Comparative Examples 1 to 5 were determined to have a thickness-direction refractive index (nTM) of 1.5773 to 1.7030 at 532 nm and an average refractive index of 1.6114 to 1.7130 at 532 nm, values ​​that are smaller than those of the Examples. In particular, the residual stress of the polyimide films (based on a thickness of 10 μm) obtained in Comparative Examples 1 to 3 was 49.1 MPa to 54.5 MPa, which is higher than the residual stress of the Examples, thus making flatness unattainable. Furthermore, the thickness-direction retardation R of the polyimide film (based on a thickness of 10 μm) obtained in Comparative Example 4 was determined to be... th The value is 319nm, which is a sharp increase relative to the example, so low latency cannot be achieved. In addition, YI increases to 27.42, so the transparency properties are reduced.

[0219] Furthermore, the thickness direction retardation R of the polyimide film (based on a thickness of 10 μm) obtained in Comparative Example 5 th The value is 508nm, which is a sharp increase compared to the example, thus making it impossible to achieve low latency.

[0220] [Table 3]

[0221] Measurement results of the experimental example (reference example)

[0222]

[0223] As shown in Table 3, the polyimide film obtained in Reference Example 1 (based on a thickness of 10 μm) was determined to have a thickness-direction refractive index (nTM) of 1.6903 at 532 nm and an average refractive index of 1.7100 at 532 nm, values ​​smaller than those of the examples. Furthermore, the thickness-direction retardation R of the polyimide film obtained in Reference Example 1 (based on a thickness of 10 μm) was determined to be... th The value is 307 nm, which is a sharp increase compared to the examples, thus making it impossible to achieve low latency. In addition, YI increases to 28.90, thus degrading the transparency properties. On the other hand, there is a problem that the polyimide films obtained in Examples 2 to 3 (based on a thickness of 10 μm) have a residual stress of 48 MPa to 48.5 MPa and a bow of 48.9 μm to 49.5 μm, which are increased compared to the examples, thus making it impossible to achieve a high level of flatness.

Claims

1. A polyimide-based resin film comprising a polyimide-based resin, said polyimide-based resin comprising polyimide repeating units represented by the following chemical formula 1 and polyimide repeating units represented by the following chemical formula 2: [Chemical Formula 1] in, In chemical formula 1, X1 is a tetravalent aromatic functional group containing a single ring, and Y1 is a functional group represented by the following chemical formula 3-1; [Chemical Formula 2] In chemical formula 2, X2 is a tetravalent aromatic functional group containing multiple rings, and Y2 is a functional group represented by the following chemical formula 3-1: [Chemical Formula 3-1] Wherein, the monocyclic aromatic tetravalent functional group of X1 includes a functional group represented by the following chemical formula 5: [Chemical Formula 5] Wherein, the polycyclic aromatic tetravalent functional group of X2 includes a functional group represented by the following chemical formula 4-1: [Chemical Formula 4-1] Furthermore, the molar ratio between the polyimide repeating unit represented by chemical formula 1 and the polyimide repeating unit represented by chemical formula 2 is 85:15 to 15:

85.

2. The polyimide-based resin film according to claim 1, wherein: The polyimide-based resin film has a residual stress of 46 MPa or less in an inorganic substrate at a thickness of 10 μm.

3. The polyimide-based resin film according to claim 1, wherein: The polyimide-based resin film exhibits a retardation R in the thickness direction at a thickness of 10 μm. th The value is 300 nm or smaller.

4. The polyimide-based resin film according to claim 1, wherein: The polyimide-based resin film has a thickness of 10 μm and a refractive index of 1.71 or greater in the thickness direction at a wavelength of 532 nm.

5. The polyimide-based resin film according to claim 1, wherein: The polyimide-based resin film has a haze value of less than 1.0% at a thickness of 10 μm.

6. The polyimide-based resin film according to claim 1, wherein: The polyimide-based resin film has a Bow value of 48 μm or less at a thickness of 10 μm.

7. The polyimide-based resin film according to claim 1, wherein: The polyimide-based resin film has a yellowness index of 25 or less at a thickness of 10 μm.

8. The polyimide-based resin film according to claim 1, wherein: The polyimide-based resin film, with a thickness of 10 μm, has an average refractive index of 1.7135 or greater at a wavelength of 532 nm.

9. The polyimide-based resin film according to claim 1, wherein: The polyimide-based resin film has a thickness of 10 μm and a refractive index of 1.71 to 1.73 in the planar direction at a wavelength of 532 nm.

10. A substrate for a display device, comprising a polyimide-based resin film according to claim 1.

11. An optical device comprising a polyimide-based resin film according to claim 1.

Images