Polyamide resin, method for manufacturing polyamide resin, polyamide film, and flexible display

Abstract

The objective is to provide a polyamide resin capable of producing a film with good mechanical properties while suppressing manufacturing costs, and the means for the solution is a polyamide resin comprising a structural unit represented by formula (1) and a structural unit represented by formula (2).

Description

Technology Field

[0001] The present invention relates to a polyamide resin, a method for manufacturing a polyamide resin, a polyamide film comprising a polyamide resin, and a flexible display having a polyamide film. Background Technology

[0002] Components for display devices, such as liquid crystal displays and organic EL displays, are widely used in various applications, such as mobile phones and tablets. Conventionally, glass has been used as the front panel for these display devices. However, while glass has high transparency and can exhibit high hardness depending on the type, it is very rigid and brittle, making it difficult to use as a front panel material for flexible displays that can be bent or folded.

[0003] For this reason, films utilizing polymer materials are being considered as alternative materials to glass. Since films containing polymer materials are easy to exhibit flexible properties, they are expected to be used in various applications such as flexible displays.

[0004] Conventionally, in flexible displays, pressure marks or bending marks may appear on the surface of the display when operated by finger touch or a stylus, or even when the display is kept in a folded state for a long time. Therefore, for such flexible displays, films are required to possess high mechanical strength (elasticity at break) in addition to high flexibility (elongation at break), that is, excellent mechanical properties, and additionally, excellent optical properties such as transparency are also required. In response to these requirements, films containing polyimide resins have been investigated and proposed.

[0005] For example, the following patent document 1 discloses a polyamide-imide resin having a constituent unit A derived from tetracarboxylic acid dianhydride, a constituent unit B derived from diamine, and a constituent unit C derived from aromatic dicarboxylic acid dichloride, with the aim of applying a polyamide-imide resin capable of forming a film having excellent mechanical properties (mechanical strength), heat resistance and transparency, and additionally achieving a reduction in residual stress.

[0006] In addition, the following patent document 2 aims to provide an aromatic polyamide having excellent transparency and resistance to solvents, having a structural unit represented by Formula (1) described below, and having a ratio of absorbance values ​​by ATR measurement of FT-IR of 1630 cm⁻¹ -1 / 1660cm -1 An aromatic polyamide film satisfying = 0.4 or more and 1.0 or less is disclosed. Prior art literature

[0007] International Publication No. 2019 / 216151 and Japanese Patent Publication No. 2019-1853 The problem to be solved

[0008] However, in the case of a resin film having an imide structural unit such as that of Patent Document 1, an imidization process is required, which makes the manufacturing process complicated and increases manufacturing costs. Therefore, there is a demand for a film that can be manufactured with a simple manufacturing process and has good properties, while reducing manufacturing costs.

[0009] In addition, in Patent Document 2, a polyamide resin is proposed, but while the said polyamide resin has excellent transparency, there was room for improvement regarding mechanical properties.

[0010] Therefore, the present invention aims to provide a polyamide resin capable of producing a film with good mechanical properties while solving the problems of the prior art and suppressing manufacturing costs.

[0011] In addition, the present invention has an additional objective of providing a method for manufacturing such a polyamide resin, a polyamide film comprising such a polyamide resin, and a flexible display having said polyamide film. means of solving the problem

[0012] The inventors have completed the present invention by discovering that the above problem can be solved by including a polyamide resin with a structural unit represented by formula (1) and a structural unit represented by formula (2) described below.

[0013] The gist of the present invention for solving the above problem is as follows.

[0014] [1] A polyamide resin comprising a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2).

[0015]

[0016]

[0017] [2] A polyamide resin described in [1] that includes a structural unit represented by the following formula (3).

[0018]

[0019] [3] A polyamide resin described in [2], wherein the ratio of the number of moles of the structural unit represented by the above formula (2) to the total number of moles of the structural unit represented by the above formula (3) is 10 to 90 mole%.

[0020] [4] A polyamide resin described in [2] or [3], wherein the ratio of the number of moles of the structural unit represented by the above formula (2) to the total number of moles of the structural unit represented by the above formula (3) is 30 to 90 mole%.

[0021] [5] A polyamide resin having a number average molecular weight of 5,000 or more and 200,000 or less, as described in any one of [1] to [4].

[0022] [6] A method for producing a polyamide resin as described in any one of [1] to [5], comprising reacting a diamine with a dicarboxylic acid dichloride,

[0023] The above diamine comprises an aromatic diamine represented by the following formula (1A), and

[0024] The above dicarboxylic acid dichloride comprises an aromatic dicarboxylic acid dichloride represented by the following formula (2A).

[0025] Method for manufacturing polyamide resin.

[0026]

[0027]

[0028] [7] A method for manufacturing a polyamide resin as described in [6], wherein the above dicarboxylic acid dichloride further comprises an aromatic dicarboxylic acid dichloride represented by the following formula (3A).

[0029]

[0030] [8] A polyamide film comprising a polyamide resin described in any one of [1] to [5].

[0031] [9] A flexible display having the film described in [8]. Effects of the invention

[0032] According to the present invention, a polyamide resin capable of producing a film having good mechanical properties while suppressing manufacturing costs, a method for producing said polyamide resin, a polyamide film comprising said polyamide resin, and a flexible display having said polyamide film can be provided. Specific details for implementing the invention

[0033] Hereinafter, the polyamide resin of the present invention, a method for manufacturing the polyamide resin, a polyamide film comprising the polyamide resin, and a flexible display having the polyamide film are described in detail based on embodiments thereof.

[0034] In this specification, the notation "a to b" in the description of numerical ranges indicates that it is greater than or equal to a and less than or equal to b, unless specifically stated otherwise.

[0035] Polyamide Resin

[0036] The polyamide resin of the present invention is characterized by comprising a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2).

[0037]

[0038]

[0039] In this specification, "polyamide resin" refers to a resin in which structural units derived from diamine compounds and structural units derived from dicarboxylic acid compounds are repeated, and the repeated structural units have an amide structure. Furthermore, the polyamide resin of the present invention differs from polyamideimide resin in that it does not contain an imide component (imide structure), and thus there is no need to perform cumbersome processes such as an imidization process during the manufacture of the resin, thereby allowing for the reduction of manufacturing costs. Additionally, when the polyamide resin of the present invention is used in a film, by having both the structural unit represented by Formula (1) and the structural unit represented by Formula (2), mechanical properties such as flexibility and mechanical strength can be improved. Having the structural unit of Formula (2) can also be advantageous in terms of the storage stability of a polyamide resin composition containing the polyamide resin of the present invention. It is preferable that the polyamide resin of the present invention has a bonding pattern between the repeated structural units that substantially includes only amide bonds.

[0040] (Structural unit represented by Equation (1))

[0041] The polyamide resin of the present invention comprises a structural unit derived from a diamine compound, represented by the above formula (1). It is inferred that by including the structural unit represented by the formula (1) (2,2'-bis(trifluoromethyl)biphenyl structural unit) in the polyamide resin, mechanical strength and colorless transparency can be imparted to the polyamide resin, such as having a structure with high rigidity containing an aromatic ring, having a large molecular volume, and having a high ionization potential of the structural unit represented by the formula (1) due to the trifluoromethyl group.

[0042] The structural unit represented by Formula (1) is preferably a structural unit derived from an aromatic diamine compound represented by Formula (1A) below. The aromatic diamine represented by Formula (1A) below is 2,2'-bis(trifluoromethyl)benzidine (TFMB).

[0043]

[0044] (Structural units based on other diamine compounds)

[0045] In the polyamide resin of the present invention, the structural unit based on the diamine compound may include a structural unit other than the structural unit represented by Formula (1) to the extent that it does not interfere with the effects of the present invention. In addition, the structural unit other than the structural unit represented by Formula (1) may be one or more of the same type.

[0046] The proportion of structural units represented by Formula (1) in structural units based on diamine compounds is preferably 70 mol% or more, more preferably 90 mol% or more, and 100 mol%, that is, it is particularly preferable that structural units based on diamine compounds substantially do not include structural units other than Formula (1) and substantially consist only of structural units represented by Formula (1).

[0047] A structural unit based on a diamine compound that provides a structural unit other than the structural unit represented by formula (1) may be a structural unit based on an aromatic diamine compound or a structural unit based on an aliphatic diamine compound.

[0048] In this specification, "aromatic diamine compound" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may include an aliphatic group or other substituents in part of its structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples include, but are not limited to, a benzene ring, a naphthalene ring, anthracene ring, and a fluorene ring. Among these, it is preferably a benzene ring.

[0049] Specific examples of aromatic diamine compounds include, but are not limited to, aromatic diamines having one aromatic ring, such as p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene; 4,4'-Diaminodiphenylmethane, 4,4'-Diaminodiphenylpropane, 4,4'-Diaminodiphenyl ether, 3,4'-Diaminodiphenyl ether, 3,3'-Diaminodiphenyl ether, 4,4'-Diaminodiphenylsulfone, 3,4'-Diaminodiphenylsulfone, 3,3'-Diaminodiphenylsulfone, 1,4-Bis(4-aminophenoxy)benzene, 1,3-Bis(4-aminophenoxy)benzene, Bis[4-(4-aminophenoxy)phenyl]sulfone, Bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-Bis[4-(4-aminophenoxy)phenyl]propane, 2,2-Bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-Dimethylbenzidine, Examples include aromatic diamines having two or more aromatic rings, such as 4,4'-bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene, 9,9-bis(4-amino-3-chlorophenyl)fluorene, and 9,9-bis(4-amino-3-fluorophenyl)fluorene. These may be used alone or in combination of two or more.

[0050] In this specification, "aliphatic diamine compound" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may include an aromatic ring or other substituents in part of its structure. Diamine compounds may be used alone or in combination of two or more types.

[0051] Specific examples of aliphatic diamine compounds include, but are not limited to, acyclic aliphatic diamines such as hexamethylenediamine; cyclic aliphatic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornandiamine, and 4,4'-diaminodicyclohexylmethane. These may be used individually or in combination of two or more.

[0052] (Structural unit represented by Equation (2))

[0053] A structural unit based on a dicarboxylic acid compound includes a structural unit represented by Formula (2). It is inferred that by including a structural unit based on a dicarboxylic acid compound represented by Formula (2), the flexibility and storage stability of the polyamide resin are improved while maintaining colorless transparency.

[0054] In this specification, "dicarboxylic acid compound" refers to a dicarboxylic acid or a dicarboxylic acid derivative. Examples of dicarboxylic acid derivatives include acid chlorides or esters of aromatic dicarboxylic acids.

[0055] The structural unit based on the dicarboxylic acid compound is preferably a structural unit based on a dicarboxylic acid derivative, and more preferably a structural unit based on a dicarboxylic acid dichloride.

[0056] The structural unit based on the dicarboxylic acid compound preferably further includes a structural unit represented by the following formula (3).

[0057]

[0058] If the polyamide resin of the present invention includes a structural unit represented by formula (3), mechanical strength such as tensile modulus is improved.

[0059] The structural unit represented by formula (2) is preferably a structural unit derived from an aromatic dicarboxylic acid dichloride represented by the following formula (2A). Additionally, the aromatic dicarboxylic acid dichloride represented by the following formula (2A) is oxybisbenzoyl chloride (DEDC).

[0060]

[0061] The structural unit represented by formula (3) is preferably a structural unit derived from the aromatic dicarboxylic acid dichloride represented by the following formula (3A). Additionally, the aromatic dicarboxylic acid dichloride represented by the following formula (3A) is terephthalic acid chloride (TPC).

[0062]

[0063] In the polyamide resin of the present invention, the structural unit based on the dicarboxylic acid compound may include a structural unit other than the structural unit represented by Formula (2) and Formula (3), to the extent that it does not interfere with the effects of the present invention. The structural unit other than the structural unit represented by Formula (2) and Formula (3) may be one or more of the same type.

[0064] The proportion of structural units represented by Formula (2) in a structural unit based on a dicarboxylic acid compound is preferably 70 mol% or more, more preferably 90 mol% or more, and 100 mol%, that is, when not including structural units represented by Formula (3), the structural unit based on the dicarboxylic acid compound substantially does not include structural units other than Formula (2), and the structural unit based on the dicarboxylic acid compound substantially consists only of structural units represented by Formula (2).

[0065] In addition, when the structural unit based on the dicarboxylic acid compound includes the structural unit represented by Formula (2) and the structural unit represented by Formula (3), the ratio of the total of the structural units represented by Formula (2) and Formula (3) in the structural unit based on the dicarboxylic acid compound is preferably 70 mol% or more, more preferably 90 mol% or more, and 100 mol%, that is, it is particularly preferable that the structural unit based on the dicarboxylic acid compound substantially does not include structural units other than Formula (2) and Formula (3), and the structural unit based on the dicarboxylic acid compound substantially consists only of the structural units represented by Formula (2) and Formula (3).

[0066] In the polyamide resin of the present invention, from the perspective of improving the flexibility of the film, it is preferable not to include the structural unit represented by Formula (3), and from the perspective of excellent balance between the mechanical strength and flexibility of the film, it is preferable to include the structural unit represented by Formulas (2) and (3). In the polyamide resin of the present invention, when the structural unit based on the dicarboxylic acid compound includes the structural unit represented by Formulas (2) and (3), from the perspective of the balance between the mechanical strength and flexibility of the film, it is preferable that the ratio of the moles of the structural unit represented by Formula (2) to the total moles of the structural unit represented by Formula (2) and the structural unit represented by Formula (3) is 10 to 90 mol%, more preferable that it is 30 to 90 mol%, and particularly preferable that it is 30 to 60 mol% from the perspective of the balance between the optical properties and mechanical strength of the film.

[0067] (Structural units based on other dicarboxylic acid compounds)

[0068] The structural unit based on a dicarboxylic acid compound that provides a structural unit other than that of formulas (2) and (3) may be a structural unit based on an aromatic dicarboxylic acid compound or a structural unit based on an aliphatic dicarboxylic acid compound.

[0069] Specific examples of aromatic dicarboxylic acid compounds include, but are not limited to, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,4-phenylenedioxydiacetic acid, 1,3-phenylenedioxydiacetic acid, dibenzoic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, etc., or derivatives thereof. These aromatic dicarboxylic acid compounds may be used individually or in combination of two or more types.

[0070] Specific examples of aliphatic dicarboxylic acid compounds include, but are not limited to, aliphatic dicarboxylic acids such as 1,3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid, or derivatives thereof. These may be used individually or in combination of two or more types.

[0071] (Polyamide resin)

[0072] The polyamide resin comprises the following structure (4) as a repeating unit. Additionally, it is preferable that 10 to 100 mole% of the total repeating unit of the polyamide resin is the following structure (4). Furthermore, it is preferable that the polyamide resin comprises the following structure (5) in addition to the following structure unit (4). When the polyamide resin comprises the following structures (4) and (5) as repeating units, it is more preferable that 10 to 100 mole% of the total repeating unit is the following structures (4) and (5). Additionally, it is particularly preferable that the total repeating unit substantially comprises the following structure (4) or substantially comprises the following structures (4) and (5).

[0073]

[0074] In order to improve mechanical properties, the polyamide resin of the present invention preferably has a number average molecular weight (Mn) of 5,000 or more and 200,000 or less, and more preferably 10,000 or more and 180,000 or less. Here, the number average molecular weight (Mn) refers to a value calculated by polystyrene conversion after measuring by GPC (gel permeation chromatography).

[0075] In order to improve mechanical properties, the polyamide resin of the present invention preferably has a weight average molecular weight (Mw) of 10,000 or more and 1,000,000 or less, more preferably 50,000 or more and 500,000 or less, and even more preferably 100,000 or more and 300,000 or less. Here, the weight average molecular weight (Mw) refers to a value calculated by polystyrene conversion after measuring by GPC (gel permeation chromatography).

[0076] The polyamide resin of the present invention preferably has a dispersion degree (Mw / Mn) of 1.0 or more and 20 or less, more preferably 1.0 or more and 15 or less, and even more preferably 1.0 or more and 4.0 or less.

[0077] The polyamide resin of the present invention has a wide range of applications, although not limited thereto, such as as a material for films, sheets, pipes, tubes, filaments, fibers, and containers. Among these, it is particularly suitable for use as a material for films.

[0078] Method for manufacturing polyamide resin

[0079] The polyamide resin of the present invention can be prepared by reacting a diamine compound with a dicarboxylic acid compound (a dicarboxylic acid or a dicarboxylic acid derivative). The diamine compound comprises a compound that provides a structural unit represented by Formula (1), and the dicarboxylic acid compound comprises a compound that provides a structural unit represented by Formula (2). Additionally, it is preferable that the dicarboxylic acid compound comprises a compound that provides a structural unit represented by Formula (3).

[0080] The method for manufacturing a polyamide resin of the present invention comprises reacting a diamine compound with a dicarboxylic acid dichloride, wherein the diamine compound comprises an aromatic diamine represented by Formula (1A), and the dicarboxylic acid dichloride may comprise an aromatic dicarboxylic acid dichloride represented by Formula (2A). It is preferable that the dicarboxylic acid dichloride further comprises an aromatic dicarboxylic acid dichloride represented by Formula (3A).

[0081] More preferably, the diamine compound is an aromatic diamine represented by formula (1A), and the dicarboxylic acid dichloride is an aromatic dicarboxylic acid dichloride represented by formula (2A), or an aromatic dicarboxylic acid dichloride represented by formula (2A) and an aromatic dicarboxylic acid dichloride represented by formula (3A).

[0082] Polyamide resins can be manufactured by methods known for manufacturing polyamides, such as solution polymerization, interfacial polymerization, melt polymerization, solid-state polymerization, etc. As a method for manufacturing the polyamide resin of the present invention, solution polymerization and interfacial polymerization are particularly preferred.

[0083] Specifically, a polyamide resin can be synthesized from a dicarboxylic acid chloride and a diamine compound by a solution polymerization method. In this case, the reaction can be carried out in a non-protonic organic polar solvent.

[0084] In this reaction, hydrogen chloride is produced as a byproduct, but when neutralizing it, inorganic neutralizing agents such as calcium hydroxide, calcium carbonate, and lithium carbonate; and organic neutralizing agents such as ethylene oxide, propylene oxide, 1,2-butylene oxide, ammonia, and pyridine are used.

[0085] When polymerizing using two or more types of diamine compounds, a stepwise reaction method is available in which one type of diamine compound is added, 10 to 99 mol% of dicarboxylic acid dichloride is added to the diamine compound to react, and then another diamine compound is added, and then additional dicarboxylic acid dichloride is added to react; and a method is available in which all diamine compounds are mixed and added, and then dicarboxylic acid dichloride is added to react. In addition, when using two or more types of dicarboxylic acid dichlorides, a stepwise method and a method of simultaneous addition can be used in the same way. The molar ratio of the total diamine compound to the total dicarboxylic acid dichloride (moles of total diamine compound:moles of total dicarboxylic acid dichloride) can be appropriately adjusted according to the desired molecular weight of the polyamide, but for example, by setting it to 49:51 to 51:49, a polyamide resin with a sufficiently high molecular weight and excellent mechanical properties can be obtained.

[0086] When a diamine compound and a dicarboxylic acid dichloride are used as raw materials, the amine terminal or the carboxylic acid terminal is formed according to the composition ratio of the raw materials. From the perspective of improving the colorless transparency of the film, it is desirable to perform terminal encapsulation using other amines, carboxylic acid chlorides, or carboxylic acid anhydrides.

[0087] Examples of compounds used for terminal encapsulation include benzoyl chloride, acetyl chloride, substituted benzoyl chloride, acetic anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride, 4-ethynylaniline, 4-phenylethynylphthalic anhydride, maleic anhydride, etc. Terminal encapsulation may not be performed, in which case the terminal group may be used as a crosslinking point, etc.

[0088] Examples of aprotic polar solvents used in the manufacture of polyamide resins include sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide-based solvents such as N,N-dimethylformamide and N,N-diethylformamide; acetamide-based solvents such as N,N-dimethylacetamide and N,N-diethylacetamide; pyrrolidone-based solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; or hexamethylphosphoramide and γ-butyrolactone. It is preferable to use these aprotic polar solvents alone or as a mixture, but furthermore, aromatic hydrocarbons such as xylene and toluene may also be used. Additionally, to promote the dissolution of the polymer, salts of alkali metals or alkaline earth metals may be added to the solvent in an amount of 50 mass% or less.

[0089] The reaction conditions for the synthesis of the polyamide resin can be set to 10 to 50°C for 10 minutes to 27 hours, and in order to maintain colorless transparency, it may be synthesized under a nitrogen atmosphere.

[0090] Polyamide Film

[0091] The present invention also relates to a polyamide film comprising the polyamide resin of the present invention. The polyamide film of the present invention has good mechanical properties.

[0092] The film thickness of the polyamide film is not particularly limited and can be appropriately set according to the application. The film thickness of the polyamide film is preferably 10㎛ or more and 150㎛ or less, and more preferably 20㎛ or more and 100㎛ or less.

[0093] The film thickness can be measured by a micrometer (manufactured by Mitutoyo Corporation) and is the average value of 5 measurements taken along the width direction of the film.

[0094] The polyamide film of the present invention preferably has an overall light transmittance of 80% or more, more preferably 85% or more, and even more preferably 88% or more.

[0095] The total light transmittance can be measured using a haze meter (manufactured by Japan Color Industry Co., Ltd., NDH 7000 II) in accordance with ASTM D1003.

[0096] The polyamide film of the present invention preferably has a haze of 10% or less. If the haze of the polyamide film is 10% or less, it is suitable as a film for displays, etc. because it has excellent transparency. Furthermore, the haze of the polyamide film is more preferably 5% or less, more preferably 2% or less, and particularly preferably 1% or less.

[0097] Haze can be measured using a haze meter (manufactured by Japan D1003, NDH 7000 II).

[0098] The polyamide film of the present invention preferably has a YI value (yellow index) of 0 or more and 20 or less, more preferably 0 or more and 10 or less, and even more preferably 0 or more and 5 or less.

[0099] The YI value (yellow index) can be measured using a spectrophotometer (manufactured by Konica Minolta Corporation, CM-5) in accordance with ASTM E313-73.

[0100] In terms of the mechanical strength of the film, the polyamide film of the present invention preferably has a tensile modulus of 2.5 GPa or higher, more preferably 3.0 GPa or higher, and even more preferably 3.5 GPa or higher. In addition, in terms of the balance between the mechanical strength and flexibility of the film, the tensile modulus may be 10.0 GPa or lower, or 8.0 GPa or lower.

[0101] In addition, regarding flexibility, the polyamide film preferably has a breaking elongation of 5% or more, more preferably 7% or more, and even more preferably 10% or more. In addition, regarding the balance between flexibility and mechanical strength, the breaking elongation may be 30% or less.

[0102] In addition, the polyamide film of the present invention preferably has a maximum strength of 100 MPa or more, and more preferably 120 MPa or more, in terms of the mechanical strength of the film. In addition, in terms of the balance between the mechanical strength and optical properties of the polyamide film, the maximum strength may be 250 MPa or less.

[0103] Tensile modulus, elongation at break, and maximum strength can be measured using EX-SX (manufactured by Shimadzu Corporation) under the following conditions. Additionally, the tensile modulus can be obtained from the slope of the obtained stress-strain curve at a strain of 0.2% to 0.5%.

[0104] [Test Conditions]

[0105] Sample size: 80mm × 10mm

[0106] Intercalation distance: 50mm

[0107] Speed: 5mm / min

[0108] Number of measurements: 3 times

[0109] The polyamide film of the present invention may include other components in addition to the polyamide resin, provided that the effects of the present invention are not impaired. Examples of other components include fillers, filler dispersants, crosslinking agents, bluening agents, UV absorbers, leveling agents, pH adjusters, lubricants, phosphorus compounds, surfactants, antioxidants, light stabilizers, plasticizers, waxes, pigments, dyes, foaming agents, defoaming agents, dehydrating agents, antistatic agents, antibacterial agents, antifungal agents, etc. When the polyamide film of the present invention includes a filler, the filler is preferably silica or alumina from the viewpoint of transparency and mechanical strength, and is particularly preferably a fibrous alumina filler. Here, "alumina" includes alumina and alumina hydrate, and examples of alumina hydrate include the boehmite type, pseudo-boehmite type, etc. Furthermore, "fibrous" refers to a shape in which the aspect ratio (filler length / filler diameter) is 5 or more.

[0110] A polyamide film can be produced by casting a solution containing polyamide resin onto a support and drying the resulting coating to form a film. A solution containing polyamide resin can be obtained by dissolving the polyamide resin in a solvent.

[0111] As for the solvent, it is not particularly limited as long as it can dissolve the polyamide resin, but from the perspective of the transparency of the film, a solvent having a functional group selected from the group consisting of ester groups, ether groups, ketone groups, hydroxyl groups, sulfonate groups, and sulfinyl groups is preferred. The organic solvent may be a single type or a combination of two or more types in any proportion.

[0112] Examples of solvents having ester groups include γ-butyrolactone (boiling point 204°C), ε-caprolactone (boiling point 230°C), γ-hexanolactone (boiling point 219°C), γ-valerolactone (boiling point 207°C), benzyl benzoate (boiling point 323°C), ethyl benzoate (boiling point 212°C), ethylene glycol monobutyl ether acetate (boiling point 191.5°C), ethylene glycol monoethyl ether acetate (boiling point 156.3°C), butyl lactate (boiling point 188°C), ethyl lactate (boiling point 154°C), 3-ethyl ethoxypropionate (boiling point 169°C), etc.

[0113] Examples of solvents having an ether group include 2-(2-butoxyethoxy)ethyl acetate (boiling point 245°C), 2-(2-ethoxyethoxy)ethyl acetate (boiling point 217°C), propyl cellosolve (boiling point 150°C), and triethylene glycol dimethyl ether (boiling point 216°C).

[0114] Examples of solvents having a ketone group include cyclohexanone (boiling point 156°C), 1-phenylethanone (boiling point 202°C), and benzaldehyde (boiling point 179°C).

[0115] Examples of solvents having hydroxyl groups include 2-methylphenol (boiling point 190°C), 3-methylphenol (boiling point 202°C), and octyl alcohol (boiling point 195°C).

[0116] Examples of solvents having a sulfonate group include methanesulfonic acid (boiling point 167°C), dimethylsulfone (boiling point 238°C), diethylsulfone (boiling point 238°C), sulfolane (boiling point 285°C), and dapsone (boiling point 177°C).

[0117] Examples of solvents having a sulfinyl group include dimethyl sulfoxide (boiling point 189°C).

[0118] As amide-based solvents, N-methyl-2-pyrrolidone (boiling point 202°C), N,N-dimethylformamide (boiling point 153°C), N,N-dimethylacetamide (boiling point 165°C), 3-butoxy-N,N-dimethylpropanamide (boiling point 252°C), etc. can be used.

[0119] Among these solvents, amide-based solvents are more preferable from the perspective of obtaining a film with a low YI value, and N,N-dimethylacetamide is particularly preferred.

[0120] In addition, the solution containing the polyamide resin may include any component other than the polyamide resin to the extent that it does not impair the purpose of the present invention. Examples of such components include other components that can be included in the aforementioned polyamide film.

[0121] The support is not particularly limited and may be a substrate or film such as glass, ceramic, metal (aluminum foil, etc.), resin film (polyester film such as PET or PEN, polyimide film, polyamideimide film, polypropylene film, thermoplastic film such as polystyrene film, etc.). These substrates or films may have circuits formed thereon using copper, etc.

[0122] The method of applying a solution containing polyamide resin to a support is not particularly limited, and examples include dip coating, flow coating, roll coating, bar coater, blade coater, screen printing, curtain coating, spray coating, etc.

[0123] In addition, the solvent is removed from the solution containing the polyamide resin by drying the coating film after application. Examples of drying methods include vacuum drying, heat drying, or a combination thereof. Furthermore, when drying at atmospheric pressure, drying can be performed at 30 to 350°C, and from the perspective of obtaining a colorless film with high transparency, it is preferable to dry at 60 to 250°C for 30 seconds to 180 minutes. In such drying methods, it is also possible to perform stepwise drying by gradually increasing the temperature from a low temperature within the above-mentioned range of temperature and time. Additionally, drying may be performed under a nitrogen atmosphere.

[0124] The polyamide film of the present invention can be used as a glass substitute material for cover films, base films, etc., of various components.

[0125] Specifically, the polyamide film of the present invention can be used as a component for displays (especially flexible displays), such as liquid crystal display devices and organic EL display devices.

[0126] In addition, the polyamide film of the present invention can also be used in components for touch panels, flexible printed circuit boards, components for solar cell panels, components for optical waveguides, and other semiconductor-related components.

[0127] Flexible Display

[0128] The present invention also relates to a flexible display having a polyamide film of the present invention. For example, a flexible display can be manufactured by using the polyamide film of the present invention as part of a layer of the flexible display, for example as a cover window, and bonding it to another layer (shock absorption layer, shatterproof layer, etc.).

[0129] These flexible displays can be used in flexible devices such as foldable mobile phones or tablets, and deformable solar panels.

[0130] Examples

[0131] The present invention will be described in more detail below with reference to examples, but the present invention is not at all limited to the following examples.

[0132] <Measurement Method>

[0133] The physical properties of the polyamide resin and polyamide film produced in the example were measured as follows.

[0134] (1) Film thickness

[0135] The film thickness of the produced film was measured using a micrometer (manufactured by Mitutoyo Corporation).

[0136] (2) Total light transmittance, haze

[0137] The total light transmittance and haze of the film were evaluated by cutting the film of each example into 30mm × 30mm pieces and measuring each evaluation sample using a haze meter (manufactured by Japan Color Industry Co., Ltd., NDH 7000 II) in accordance with ASTM D1003.

[0138] In addition, a higher value for total light transmittance indicates better transparency. Also, a lower value for haze indicates better transparency.

[0139] (3) YI value (Yellow Index)

[0140] The film of each example was cut to a size of 30 mm × 30 mm, and the YI value of each film was measured using a spectrophotometer (manufactured by Konica Minolta, CM-5) in accordance with ASTM E313-73.

[0141] In addition, the YI value (Yellow Index) indicates that the closer the value is to 0, the better the colorlessness.

[0142] (4) Tensile modulus, elongation at break, maximum strength

[0143] Tensile modulus, elongation at break, and maximum strength were measured using an EZ-SX (manufactured by Shimadzu Corporation) under the following conditions. In addition, the tensile modulus was determined from the slope of the obtained stress-strain curve at a strain of 0.2% to 0.5%.

[0144] [Test Conditions]

[0145] Sample size: 80mm × 10mm

[0146] Intercalation distance: 50mm

[0147] Speed: 5mm / min

[0148] Number of measurements: 3 times

[0149] Furthermore, higher values ​​for tensile modulus and maximum strength indicate superior mechanical strength. Additionally, higher values ​​for elongation at break indicate superior flexibility.

[0150] (5) Number average molecular weight (Mn), weight average molecular weight (Mw)

[0151] The number average molecular weight (Mn) and weight average molecular weight (Mw) of the polyamide resin were determined by gel permeation chromatography (GPC) measurement under the following conditions. In addition, the number average molecular weight (Mn) and weight average molecular weight (Mw) are polystyrene equivalents.

[0152] Device: GL7700 manufactured by GL Science

[0153] Column: TSKgelαM (Manufactured by Dososa)

[0154] Column internal temperature: 40℃

[0155] Eluent composition: NMP solution containing 100 mmol / L H3PO4 (using 85% aqueous H3PO4 solution as a raw material) and 10 mmol / L LiBr

[0156] Eluent flow rate: 0.7 mL / min

[0157] Calibration standard reagent: Polystyrene

[0158] Detector wavelengths: 260nm and 300nm

[0159] Detector temperature: Room temperature

[0160] Baseline range for interpretation: 15 to 40 minutes

[0161] Molecular weight calculation range during analysis: 20 to 35 minutes

[0162] Ingredients

[0163] The chemical structure of the compound used in the example is as follows.

[0164] [Aromatic diamine compounds]

[0165] As a compound providing a structural unit based on an aromatic diamine compound, 2,2'-bis(trifluoromethyl)benzidine (TFMB) represented by the following formula (1A) was used.

[0166]

[0167] [Aromatic dicarboxylic acid compounds]

[0168] As compounds that provide structural units based on aromatic dicarboxylic acid compounds, oxybisbenzoyl chloride (DEDC) represented by the following formula (2A) and terephthaloyl chloride (TPC) represented by the following formula (3A) were used.

[0169]

[0170]

[0171] <Example 1>

[0172] -Synthesis of Polyamide Resin-

[0173] 60.0 g of dimethylacetamide (DMAc) was charged into a 100 mL reactor, and 5.33 g (16.63 mmol) of TFMB and 2.64 g (36.59 mmol) of 1,2-butylene oxide were added. Next, 0.97 g (3.29 mmol) of DEDC and 2.67 g (13.17 mmol) of TPC were added to the TFMB solution, and the mixture was reacted by stirring at 30°C for 2 hours. Subsequently, 0.026 g (0.33 mmol) of acetyl chloride was added to the solution, and the mixture was reacted by stirring at 30°C for 30 minutes to obtain a solution containing a polymer having an amide structure. The weight-average molecular weight of polystyrene by GPC was 123522.

[0174] In addition, the ratio of the moles of DEDC to the total moles of DEDC and TPC is 20 mol% in Example 1.

[0175] -Production of Polyamide Films-

[0176] A resin composition for film manufacturing was prepared by adjusting the solid content concentration to 12.5 wt% using polyamide powder and a solvent (DMAc) with the mixing amounts shown in Table 1, and then dispersing and homogenizing them. Next, this resin composition was coated onto a glass plate using a table coater (AFA-standard manufactured by Kotech), dried at 120°C for 40 minutes and then at 220°C for 30 minutes using a precision incubator (Fine Oven DH612 manufactured by Yamato Kagaku), and then peeled off from the glass plate to form a film.

[0177] <Examples 2 to 4>

[0178] Polyamide resin, a solution containing polyamide resin, and a polyamide film were prepared in the same manner as in Example 1, except that the amounts (molar ratios) of TFMB, DEDC, and TPC added were set to the values ​​listed in Table 1.

[0179] In addition, the ratio of the moles of DEDC to the total moles of DEDC and TPC is 40 mol% in Example 2, 80 mol% in Example 3, and 100 mol% in Example 4.

[0180] <Comparative Example 1>

[0181] A polyamide resin, a solution containing the polyamide resin, and a polyamide film were prepared in the same manner as in Example 1, except that only TFMB and TPC were used and the addition amount (molar ratio) was 1:1.

[0182] The polyamide film of Comparative Example 1 was whitened throughout the entire film and was also very brittle, so it could not be peeled off from the glass plate. Therefore, it is thought that the transparency and mechanical properties are significantly inferior compared to the film of the Example. In addition, since a self-standing film could not be obtained from the film of Comparative Example 1, the evaluation of each physical property was not performed.

[0183]

[0184] From Table 1, it can be seen that a polyamide resin comprising a structural unit represented by Equation (1), a structural unit represented by Equation (2), or a structural unit represented by Equation (2) and a structural unit represented by Equation (3) has good mechanical properties when formed into a film. In addition, it can be seen that optical properties such as YI value and haze are better when the molar ratio of DEDC to TPC is set to a specific range. Industrial applicability

[0185] According to the present invention, a polyamide resin can be provided that can produce a film having good mechanical properties while suppressing manufacturing costs.

Claims

Claim 1 A polyamide resin comprising a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2). Claim 2 A polyamide resin according to claim 1, further comprising a structural unit represented by formula (3). Claim 3 A polyamide resin according to claim 2, wherein the ratio of the number of moles of the structural unit represented by formula (2) to the total number of moles of the structural unit represented by formula (3) is 10 to 90 mole%. Claim 4 A polyamide resin according to claim 3, wherein the ratio of the number of moles of the structural unit represented by formula (2) to the total number of moles of the structural unit represented by formula (3) is 30 to 90 mol%. Claim 5 A polyamide resin according to claim 1, having a number average molecular weight of 5,000 or more and 200,000 or less. Claim 6 A method for producing a polyamide resin according to any one of claims 1 to 5, comprising reacting a diamine with a dicarboxylic acid dichloride, wherein the diamine comprises an aromatic diamine represented by the following formula (1A), and the dicarboxylic acid dichloride comprises an aromatic dicarboxylic acid dichloride represented by the following formula (2A). Claim 7 A method for manufacturing a polyamide resin according to claim 6, wherein the dicarboxylic acid dichloride further comprises an aromatic dicarboxylic acid dichloride represented by the following formula (3A). Claim 8 A polyamide film comprising a polyamide resin described in any one of claims 1 to 5. Claim 9 A flexible display having the film described in paragraph 8.

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