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

Abstract

To provide a polyamide resin with which a film having good mechanical characteristics can be manufactured while reducing manufacturing costs.SOLUTION: A polyamide resin includes a structural unit represented by formula (1), and a structural unit represented by formula (2).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polyamide resin, a method for producing a polyamide resin, a polyamide film containing the polyamide resin, and a flexible display including the polyamide film.

Background Art

[0002] Members for display devices such as liquid crystal display devices and organic EL display devices are widely used in various applications such as mobile phones and tablets. Conventionally, glass has been used as the front panel of such display devices. However, although glass has high transparency and can exhibit high hardness depending on the type, it is very rigid and easily broken, so it is difficult to use as a front panel material for flexible displays that can be bent or folded. Therefore, films utilizing polymer materials as alternatives to glass have been studied. Since films containing polymer materials are likely to exhibit flexible characteristics, they are expected to be used in various applications such as flexible displays.

[0003] Conventionally, in flexible displays, when operating by finger touch or touch pen, or even when holding the display in a folded state for a long time, compression marks and bending marks may occur on the display surface. Therefore, as a film for such flexible displays, in addition to high flexibility (elongation at break), it is required to have high mechanical strength (elastic modulus and maximum strength), that is, excellent mechanical properties, and in addition, excellent optical properties such as transparency are also required. In response to such requirements, conventionally, films containing polyimide resins and the like have been studied and proposed.

[0004] For example, in Patent Document 1 below, for the purpose of applying a polyamide-imide resin capable of forming a film excellent in mechanical properties (mechanical strength), heat resistance, and transparency, and further achieving reduction of residual stress, a polyamide-imide resin having a structural unit A derived from a tetracarboxylic dianhydride, a structural unit B derived from a diamine, and a structural unit C derived from an aromatic dicarboxylic acid dichloride is disclosed.

[0005] Further, in Patent Document 2 below, for the purpose of providing an aromatic polyamide excellent in transparency and resistant to solvents, it has a structural unit represented by the following formula (1), and the ratio of the absorbance values by ATR measurement of FT-IR is 1630 cm -1 / 1660 cm -1 = 0.4 or more and 1.0 or less, and an aromatic polyamide film is disclosed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in a resin film having an imide structural unit as in Patent Document 1, since an imidization step is required, the manufacturing process becomes complicated and the manufacturing cost also increases. Therefore, there is a demand for a film that can reduce the manufacturing cost, can be manufactured by a simple manufacturing process, and has good properties. Further, in Patent Document 2, an aromatic polyamide resin is proposed. Although the aromatic polyamide resin is excellent in transparency, there is room for improvement in terms of mechanical properties.

[0008] Therefore, an object of the present invention is to provide a polyamide resin that can solve the above-mentioned problems of the prior art, suppress the manufacturing cost, and produce a film having good mechanical properties. Another object of the present invention is to provide a method for producing such a polyamide resin, a polyamide film containing such a polyamide resin, and a flexible display including the polyamide film.

Means for Solving the Problems

[0009] The inventors of the present invention have found that the above problems can be solved by a polyamide resin containing a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2), and have completed the present invention.

[0010] The gist configuration of the present invention for solving the above problems is as follows.

[0011] [1] A polyamide resin containing a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2).

Chemical Formula

Chemical Formula

[0012] [2] The polyamide resin according to [1], further containing a structural unit represented by the following formula (3).

Chemical Formula

[0013] [3] The polyamide resin according to [2], wherein the ratio of the number of moles of the structural unit represented by the formula (2) to the total number of moles of the structural unit represented by the formula (2) and the structural unit represented by the formula (3) is 10 to 90 mol%.

[0014] [4] The ratio of the number of moles of the structural unit represented by the formula (2) to the total number of moles of the structural unit represented by the formula (2) and the structural unit represented by the formula (3) is 30 to 90 mol%, the polyamide resin according to [2] or [3].

[0015] [5] The polyamide resin according to any one of [1] to [4], having a number average molecular weight of 5,000 or more and 200,000 or less.

[0016] [6] A method for producing a polyamide resin according to any one of [1] to [5], comprising reacting a diamine and a dicarboxylic acid dichloride, wherein the diamine contains an aromatic diamine represented by the following formula (1A), and the dicarboxylic acid dichloride contains an aromatic dicarboxylic acid dichloride represented by the following formula (2A). A method for producing a polyamide resin.

Chemical formula

Chemical formula

[0017] [7] The method for producing a polyamide resin according to [6], wherein the dicarboxylic acid dichloride further contains an aromatic dicarboxylic acid dichloride represented by the following formula (3A).

Chemical formula

[0018] [8] A polyamide film containing the polyamide resin according to any one of [1] to [5].

[0019] [9] A flexible display including the film according to [8].

Advantages of the Invention

[0020] According to the present invention, it is possible to provide a polyamide resin capable of manufacturing a film having good mechanical properties while suppressing manufacturing costs, a method for manufacturing the polyamide resin, a polyamide film containing the polyamide resin, and a flexible display including the polyamide film.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, the polyamide resin of the present invention, the method for manufacturing the polyamide resin, the polyamide film containing the polyamide resin, and the flexible display including the polyamide film will be described in detail based on their embodiments.

[0022] In this specification, the notation "a~b" in the description of a numerical range represents a or more and b or less, unless otherwise specified.

[0023] <Polyamide Resin> The polyamide resin of the present invention is characterized by containing a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2).

Chemical formula

Chemical formula

[0024] In this specification, the "polyamide resin" refers to a resin in which a structural unit derived from a diamine compound and a structural unit derived from a dicarboxylic acid compound are repeated, and the repeating structural unit is a unit having an amide structure. Further, unlike the polyamideimide resin, the polyamide resin of the present invention does not contain an imide component (imide structure), and there is no need to perform complicated steps such as an imidization step in the production of the resin, and the cost during production can be suppressed. Further, when the polyamide resin of the present invention is used for a film, by having both the structural unit represented by the above formula (1) and the structural unit represented by the above formula (2), mechanical properties such as flexibility and mechanical strength can be made good. Having the structural unit of the above formula (2) can also be advantageous from the viewpoint of the storage stability of the polyamide resin composition containing the polyamide resin of the present invention. The polyamide resin of the present invention preferably has a bonding mode between repeating structural units consisting essentially of only amide bonds.

[0025] (Structural unit represented by formula (1)) The polyamide resin of the present invention contains the structural unit represented by the above formula (1) as a structural unit derived from a diamine compound. By the polyamide resin containing the structural unit represented by formula (1) (2,2'-bis(trifluoromethyl)biphenyl structural unit), it is a highly rigid structure containing an aromatic ring, has a large molecular volume, and due to the trifluoromethyl group, the ionization potential of the structural unit represented by formula (1) becomes high. It is presumed that mechanical strength and colorless transparency can be imparted to the polyamide resin.

[0026] The structural unit represented by formula (1) is preferably a structural unit derived from an aromatic diamine compound represented by the following formula (1A). The aromatic diamine represented by the following formula (1A) is 2,2'-bis(trifluoromethyl)benzidine (TFMB). [Chemical formula]

[0027] (Structural units based on other diamine compounds) In the polyamide resin of the present invention, the structural unit based on the diamine compound may contain a structural unit other than the structural unit represented by the formula (1) as long as the effects of the present invention are not impaired. Further, the structural unit other than the structural unit represented by the formula (1) may be one kind or two or more kinds. The ratio of the structural unit represented by the formula (1) in the structural unit based on the diamine compound is preferably 70 mol% or more, more preferably 90 mol% or more, and particularly preferably 100 mol%, that is, the structural unit based on the diamine compound substantially does not contain a structural unit other than the formula (1) and is substantially only composed of the structural unit represented by the formula (1).

[0028] The structural unit based on the diamine compound that provides a structural unit other than the structural unit represented by the formula (1) may be a structural unit based on an aromatic diamine compound or a structural unit based on an aliphatic diamine compound.

[0029] In the present specification, the "aromatic diamine compound" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or other substituents in a part of its structure. This aromatic ring may be a monocyclic ring or a condensed ring, and examples include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited thereto. Among these, a benzene ring is preferred.

[0030] Specific examples of the aromatic diamine compound 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'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 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, 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, 9,9-bis(4-amino-3-fluorophenyl)fluorene, etc., which are aromatic diamines having two or more aromatic rings. These can be used alone or in combination of two or more kinds.

[0031] In this specification, the "aliphatic diamine compound" represents a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituents in a part of its structure. The diamine compound can be used alone or in combination of two or more kinds.

[0032] Specific examples of the aliphatic diamine compound include, but are not limited to, acyclic aliphatic diamines such as hexamethylenediamine; and cyclic aliphatic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, 4,4'-diaminodicyclohexylmethane, and the like. These can be used alone or in combination of two or more.

[0033] (Structural unit represented by formula (2)) The structural unit based on the dicarboxylic acid compound includes the structural unit represented by formula (2). By including the structural unit represented by formula (2) in the structural unit based on the dicarboxylic acid compound, it is presumed that the flexibility and storage stability are good while maintaining the colorless transparency of the polyamide resin.

[0034] In this specification, the "dicarboxylic acid compound" refers to a dicarboxylic acid or a dicarboxylic acid derivative. Examples of the dicarboxylic acid derivative include acid chlorides and esters of aromatic dicarboxylic acids.

[0035] 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.

[0036] The structural unit based on the dicarboxylic acid compound preferably further includes the structural unit represented by the following formula (3). [Chemical formula]

[0037] When the polyamide resin of the present invention contains the structural unit represented by formula (3), the mechanical strength such as the tensile modulus of elasticity is improved.

[0038] 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). The aromatic dicarboxylic acid dichloride represented by the following formula (2A) is oxybisbenzoyl chloride (DEDC). [Chemical formula]

[0039] The structural unit represented by formula (3) is preferably a structural unit derived from an aromatic dicarboxylic acid dichloride represented by the following formula (3A). The aromatic dicarboxylic acid dichloride represented by the following formula (3A) is terephthalic acid chloride (TPC). [Chemical formula]

[0040] In the polyamide resin of the present invention, the structural unit based on the dicarboxylic acid compound may contain a structural unit other than the structural units represented by formula (2) and formula (3) as long as the effects of the present invention are not impaired. The structural units other than the structural units represented by formula (2) and formula (3) may be one kind or two or more kinds.

[0041] When the structural unit represented by formula (2) in the structural unit based on the dicarboxylic acid compound does not contain the structural unit represented by formula (3), the ratio of the structural unit represented by formula (2) is preferably 70 mol% or more, more preferably 90 mol% or more, and particularly preferably 100 mol%, that is, the structural unit based on the dicarboxylic acid compound substantially does not contain a structural unit other than formula (2), and the structural unit based on the dicarboxylic acid compound is substantially only the structural unit represented by formula (2). In addition, when the structural unit based on the dicarboxylic acid compound contains the structural unit represented by the formula (2) and the structural unit represented by the formula (3), the total ratio of the structural units represented by the formula (2) and the 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 particularly preferably 100 mol%, that is, the structural unit based on the dicarboxylic acid compound substantially does not contain structural units other than the formula (2) and the formula (3), and the structural unit based on the dicarboxylic acid compound is substantially only the structural units represented by the formula (2) and the formula (3).

[0042] In the polyamide resin of the present invention, from the viewpoint of improving the flexibility of the film, it is preferable not to contain the structural unit represented by the formula (3), and from the viewpoint of excellent balance between the mechanical strength and flexibility of the film, it is preferable to contain the structural units represented by the formula (2) and the formula (3). In the polyamide resin of the present invention, when the structural unit based on the dicarboxylic acid compound contains the structural units represented by the formula (2) and the formula (3), from the viewpoint of the balance between the mechanical strength and flexibility of the film, the ratio of the number of moles of the structural unit represented by the formula (2) to the total number of moles of the structural units represented by the formula (2) and the formula (3) is preferably 10 to 90 mol%, more preferably 30 to 90 mol% from the viewpoint of the balance between the optical properties and mechanical strength of the film, and particularly preferably 30 to 60 mol%.

[0043] (Structural units based on other dicarboxylic acid compounds) The structural unit based on the dicarboxylic acid compound that provides a structural unit other than the formula (2) and the formula (3) may be a structural unit based on an aromatic dicarboxylic acid compound or a structural unit based on an aliphatic dicarboxylic acid compound.

[0044] Specific examples of the aromatic dicarboxylic acid compound 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 can be used alone or in combination of two or more.

[0045] Specific examples of the aliphatic dicarboxylic acid compound include, but are not limited to, aliphatic dicarboxylic acids such as 1,3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, etc., or derivatives thereof. These can be used alone or in combination of two or more.

[0046] (Polyamide resin) The polyamide resin contains the following structure (4) as a repeating unit. Also, it is preferable that 10 to 100 mol% of all the repeating units of the polyamide resin are the following structure (4). Further, it is preferable that the polyamide resin contains the following structure (5) in addition to the following structural unit (4). When the polyamide resin contains the following structures (4) and (5) as repeating units, it is more preferable that 10 to 100 mol% of all the repeating units are the following structures (4) and (5). Also, it is particularly preferable that all the repeating units consist essentially of the following structure (4) or consist essentially of the following structures (4) and (5). [Chemical formula]

[0047] From the viewpoint of improving 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, more preferably 10,000 or more and 180,000 or less. Here, the number average molecular weight (Mn) is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

[0048] From the viewpoint of improving 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) is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

[0049] The polyamide resin of the present invention preferably has a dispersity (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.

[0050] The uses of the polyamide resin of the present invention are not limited, and for example, it can be widely used as a material for films, sheets, pipes, tubes, filaments, fibers, containers, etc. Among these, it is particularly suitable for use as a material for films.

[0051] <Method for producing polyamide resin> The polyamide resin of the present invention can be produced by reacting a diamine compound with a dicarboxylic acid compound (dicarboxylic acid or dicarboxylic acid derivative). The diamine compound includes a compound that provides a structural unit represented by formula (1), and the dicarboxylic acid compound includes a compound that provides a structural unit represented by formula (2). Further, the dicarboxylic acid compound preferably includes a compound that provides a structural unit represented by formula (3).

[0052] The method for producing a polyamide resin of the present invention includes reacting a diamine compound with a dicarboxylic acid dichloride, wherein the diamine compound includes an aromatic diamine represented by formula (1A), and the dicarboxylic acid dichloride can include an aromatic dicarboxylic acid dichloride represented by formula (2A). It is preferable that the dicarboxylic acid dichloride further includes an aromatic dicarboxylic acid dichloride represented by formula (3A). 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).

[0053] The polyamide resin can be produced by a method known as a method for producing polyamide. For example, a solution polymerization method, an interfacial polymerization method, a melt polymerization method, a solid-phase polymerization method, etc. can be used. As the method for producing the polyamide resin of the present invention, in particular, a solution polymerization method and an interfacial polymerization method can be preferably used.

[0054] 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 an aprotic organic polar solvent.

[0055] In this reaction, hydrogen chloride is by-produced. When neutralizing this, 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.

[0056] When polymerization is carried out using two or more types of diamine compounds, the diamine compounds are added one by one, 10 to 99 mol% of dicarboxylic acid dichloride is added to the diamine compound and reacted, and then another diamine compound is added, and further dicarboxylic acid dichloride is added and reacted. A stepwise reaction method, and a method of mixing and adding all the diamine compounds and then adding dicarboxylic acid dichloride and reacting can be used. Also, when using two or more types of dicarboxylic acid dichloride, similarly, a stepwise method, a method of adding simultaneously, etc. can be used. The molar ratio of all diamine compounds to all dicarboxylic acid dichloride (the number of moles of all diamine compounds: the number of moles of all dicarboxylic acid dichloride) can be appropriately adjusted according to the molecular weight of the target polyamide. For example, by setting it to 49:51 to 51:49, a polyamide with a sufficiently large molecular weight and excellent mechanical properties can be obtained.

[0057] When a diamine compound and dicarboxylic acid dichloride are used as raw materials, it becomes an amine terminal or a carboxylic acid terminal depending on the composition ratio of the raw materials. From the viewpoint of improving the colorless transparency of the film, it is preferable to perform end capping with other amines, carboxylic acid chlorides, and carboxylic acid anhydrides.

[0058] Examples of the compound used for end capping include benzoyl chloride, acetyl chloride, substituted benzoyl chloride, acetic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, 4-ethynylaniline, 4-phenylethynylphthalic anhydride, maleic anhydride, etc. End capping may not be necessary. In this case, the end groups can also be used as crosslinking points, etc.

[0059] In the production of polyamide resin, examples of the aprotic polar solvent to be used include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N,N-dimethylformamide and N,N-diethylformamide, acetamide solvents such as N,N-dimethylacetamide and N,N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, or hexamethylphosphoramide, γ-butyrolactone, etc. It is desirable to use these alone or as a mixture. Furthermore, the use of aromatic hydrocarbons such as xylene and toluene is also possible. Further, for the purpose of promoting the dissolution of the polymer, a salt of an alkali metal or alkaline earth metal of 50% by mass or less can be added to the solvent.

[0060] The reaction conditions for the synthesis of polyamide resin can be 10 to 50 °C for 10 minutes to 27 hours, and from the viewpoint of maintaining colorless transparency, it may be synthesized under a nitrogen atmosphere.

[0061] <Polyamide film> The present invention also relates to a polyamide film containing the polyamide resin of the present invention. The polyamide film of the present invention has good mechanical properties.

[0062] 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 μm or more and 150 μm or less, and more preferably 20 μm or more and 100 μm or less. The film thickness can be measured with a micrometer (manufactured by Mitutoyo Corporation), and it is the average value measured at 5 points along the width direction of the film.

[0063] The total light transmittance of the polyamide film of the present invention is preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more. The total light transmittance can be measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH 7000 II) in accordance with ASTM D1003.

[0064] The polyamide film of the present invention preferably has a haze of 10% or less. When the haze of the polyamide film is 10% or less, it is excellent in transparency and thus suitable as a film for displays and the like. Further, the haze of the polyamide film is more preferably 5% or less, still more preferably 2% or less, and particularly preferably 1% or less. The haze can be measured in accordance with ASTM D1003 using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH 7000 II).

[0065] 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 still more preferably 0 or more and 5 or less. The YI value (yellow index) can be measured in accordance with ASTM E313-73 using a spectrophotometer (manufactured by Konica Minolta Inc., CM-5).

[0066] From the viewpoint of the mechanical strength of the film, the polyamide film of the present invention preferably has a tensile modulus of 2.5 GPa or more, more preferably 3.0 GPa or more, and still more preferably 3.5 GPa or more. Further, from the viewpoint of the balance between the mechanical strength and flexibility of the film, the tensile modulus may be 10.0 GPa or less, or may be 8.0 GPa or less. Further, from the viewpoint of flexibility, the polyamide film preferably has an elongation at break of 5% or more, more preferably 7% or more, and still more preferably 10% or more. Further, the elongation at break may be 30% or less from the viewpoint of the balance between flexibility and mechanical strength. Further, from the viewpoint of the mechanical strength of the film, the polyamide film of the present invention preferably has a maximum strength of 100 MPa or more, more preferably 120 MPa or more. Further, from the viewpoint of the balance between the mechanical strength and optical properties of the polyamide film, the maximum strength may be 250 MPa or less. The tensile elastic modulus, elongation at break, and maximum strength can be measured using an EX-SX (manufactured by Shimadzu Corporation) under the following conditions. The tensile elastic modulus can be determined from the slope of the stress-strain diagram obtained when the strain is between 0.2% and 0.5%. [Test Conditions] Sample size: 80 mm × 10 mm Distance between grips: 50 mm Speed: 5 mm / min Number of measurements: 3 times

[0067] In addition to the polyamide resin, the polyamide film of the present invention may contain other components as long as the effects of the present invention are not impaired. Examples of other components include fillers, filler dispersants, crosslinking agents, bluing agents, ultraviolet 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, fungicides, etc. When the polyamide film of the present invention contains a filler, the filler is preferably silica or alumina from the viewpoints of transparency and mechanical strength, and particularly preferably a fibrous alumina filler. Here, "alumina" includes alumina and alumina hydrates, and examples of alumina hydrates include boehmite form, pseudo-boehmite form, etc. Also, "fibrous" refers to a shape with an aspect ratio (filler length / filler diameter) of 5 or more.

[0068] The polyamide film can be produced by casting a solution containing a polyamide resin onto a support, drying the resulting coating film, and forming it into a film. The solution containing a polyamide resin can be obtained by dissolving a polyamide resin in a solvent. The solvent is not particularly limited as long as it can dissolve the polyamide resin, but from the viewpoint of the transparency of the film, etc., a solvent having a functional group selected from the group consisting of an ester group, an ether group, a ketone group, a hydroxyl group, a sulfone group, and a sulfinyl group is preferable. The organic solvent may be one kind or a combination of two or more kinds in any ratio. Solvents having an ester group 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), ethyl 3-ethoxypropionate (boiling point 169 °C), and the like.

[0069] 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), triethylene glycol dimethyl ether (boiling point 216 °C), and the like.

[0070] Solvents having a ketone group include cyclohexanone (boiling point 156 °C), 1-phenylethanone (boiling point 202 °C), benzaldehyde (boiling point 179 °C), and the like.

[0071] Solvents having a hydroxyl group include 2-methylphenol (boiling point 190 °C), 3-methylphenol (boiling point 202 °C), octyl alcohol (boiling point 195 °C), and the like.

[0072] Solvents having a sulfone group include methanesulfonic acid (boiling point 167 °C), dimethyl sulfone (boiling point 238 °C), diethyl sulfone (boiling point 238 °C), sulfolane (boiling point 285 °C), dapsone (boiling point 177 °C), and the like.

[0073] Solvents having a sulfinyl group include dimethyl sulfoxide (boiling point 189 °C), and the like.

[0074] As amide 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.

[0075] Among these solvents, from the viewpoint of obtaining a film with a low YI value, amide solvents are more preferable, and N,N-dimethylacetamide is particularly preferable.

[0076] In addition, the solution containing the polyamide resin can contain any component other than the polyamide resin as long as the object of the present invention is not impaired. Examples of the optional component include other components that can be contained in the aforementioned polyamide film.

[0077] The support is not particularly limited, and examples include substrates and films such as glass, ceramics, metals (such as aluminum foil), resin films (thermoplastic films such as polyester films such as PET and PEN, polyimide films, polyamideimide films, polypropylene films, polystyrene films, etc.). These substrates and films may have a circuit formed thereon with copper or the like.

[0078] The method for applying the solution containing the polyamide resin to the support is not particularly limited, and examples include dip coating method, flow coating method, roll coating method, bar coater method, blade coater method, screen printing method, curtain coating method, spray coating method, etc.

[0079] Also, after applying the solution containing the polyamide resin, the solvent is removed by drying the coating film. Examples of the drying method include vacuum drying, heat drying, or a combination of these methods. When drying at normal pressure, it can be dried at 30 to 350°C, and from the viewpoint of obtaining a highly colorless and transparent film, it is preferably dried at 60 to 250°C for about 30 seconds to 180 minutes. In such a drying method, stepwise drying such as gradually increasing the temperature from a low temperature can be performed within the above-mentioned temperature and time ranges. Also, drying may be performed under a nitrogen atmosphere.

[0080] The polyamide film of the present invention can be used as a glass substitute material for cover films, base films, etc. of various members. Specifically, the polyamide film of the present invention can be used as a member for displays such as liquid crystal display devices and organic EL display devices (particularly flexible displays). Also, the polyamide film of the present invention can be used in touch panel members, flexible printed circuit boards, solar cell panel members, optical waveguide members, and other semiconductor-related members.

[0081] <Flexible Display> The present invention also relates to a flexible display comprising the polyamide film of the present invention. For example, the polyamide film of the present invention can be used as a part of a layer of a flexible display, such as a cover window, and adhered to other layers (impact absorption layer, scattering prevention layer, etc.) to fabricate a flexible display. Such a flexible display can be used in flexible devices such as foldable mobile phones and tablets, and deformable solar cell panels.

Examples

[0082] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples at all.

[0083] <Measurement Method> The physical properties of the polyamide resin and polyamide film prepared in the examples were measured as follows. (1) Film Thickness The film thickness of the prepared film was measured using a micrometer (manufactured by Mitutoyo Corporation).

[0084] (2) Total Light Transmittance, Haze The total light transmittance and haze of the film were measured using a haze meter (NDH 7000 II, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with ASTM D1003. Evaluation samples were prepared by cutting the films of each example into a size of 30 mm × 30 mm. Note that the higher the total light transmittance value, the better the transparency. Also, the lower the haze value, the better the transparency.

[0085] (3) YI Value (Yellow Index) The films of each example were cut into a size of 30 mm × 30 mm, and the YI value of each film was measured using a spectrophotometer (CM-5, manufactured by Konica Minolta Inc.) in accordance with ASTM E313-73. Note that the closer the YI value (Yellow Index) is to 0, the better the colorlessness.

[0086] (4) Tensile Modulus, Elongation at Break, Maximum Strength The tensile modulus, elongation at break, and maximum strength were measured using EZ-SX (manufactured by Shimadzu Corporation) under the following conditions. The tensile modulus was determined from the slope of the stress-strain diagram obtained when the strain was between 0.2% and 0.5%. [Test Conditions] Sample Size: 80 mm × 10 mm Distance between Grips: 50 mm Speed: 5 mm / min Number of Measurements: 3 times Note that the higher the tensile modulus and maximum strength values, the better the mechanical strength. Also, the higher the elongation at break value, the better the flexibility.

[0087] (5) Number average molecular weight (Mn), weight average molecular weight (Mw) 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. The number average molecular weight (Mn) and weight average molecular weight (Mw) are in terms of polystyrene equivalent. Apparatus: GL7700 manufactured by GL Sciences Column: TSKgel αM (manufactured by Tosoh Corporation) Column internal temperature: 40 °C Eluent composition: 100 mmol / L of H 3 PO 4 (H 3 PO 4 85% aqueous solution was used as a raw material) and an NMP solution containing 10 mmol / L of LiBr Eluent flow rate: 0.7 mL / min Calibration standard reagent: Polystyrene Detector wavelength: 260 nm and 300 nm Detector temperature: Room temperature Baseline range during analysis: 15 minutes to 40 minutes Molecular weight calculation range during analysis: 20 to 35 minutes

[0088] <Raw material> The chemical structures of the compounds used in the examples are as follows. [Aromatic diamine compound] As a compound that gives a structural unit based on the aromatic diamine compound, 2,2'-bis(trifluoromethyl)benzidine (TFMB) represented by the following formula (1A) was used. [Chemical formula]

[0089] [Aromatic dicarboxylic acid compound] As compounds that give structural units based on the aromatic dicarboxylic acid compound, oxybisbenzoyl chloride (DEDC) represented by the following formula (2A) and terephthaloyl chloride (TPC) represented by the following formula (3A) were used. [Chemistry] [Chemistry]

[0090] [Example 1] -Synthesis of Polyamide Resin- A 100 mL reactor was charged with 60.0 g of dimethylacetamide (DMAc), and 5.33 g (16.63 mmol) of TFMB and 2.64 g (36.59 mmol) of 1,2-butylene oxide were added. Subsequently, 0.97 g (3.29 mmol) of DEDC and 2.67 g (13.17 mmol) of TPC were added to this solution of TFMB, and the mixture was stirred at 30 °C for 2 hours to react. Then, 0.026 g (0.33 mmol) of acetyl chloride was added to this solution, and the mixture was stirred at 30 °C for 30 minutes to react, obtaining a solution containing a polymer having an amide structure. The weight-average molecular weight in terms of polystyrene by GPC was 123522. Note that the ratio of the number of moles of DEDC to the total number of moles of DEDC and TPC is 20 mol% in Example 1.

[0091] -Preparation of Polyamide Film- Using the compounding amounts shown in Table 1, after adjusting the polyamide powder and the solvent (DMAc) to a solid content concentration of 12.5 wt%, the mixture was dispersed and homogenized to prepare a resin composition for film production. Subsequently, this resin composition was coated on a glass plate using a table coater (AFA-standard manufactured by Coatec), and dried at 120 °C for 40 minutes and then at 220 °C for 30 minutes in a precision thermostat (Fine Oven DH612 manufactured by Yamato Scientific Co., Ltd.), and a film was formed by peeling it from the glass plate.

[0092] [Examples 2 to 4] 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 the addition amounts (molar ratios) of TFMB, DEDC, and TPC were set to the values described in Table 1. Note that the ratio of the number of moles of DEDC to the total number of moles of DEDC and TPC is 40 mol% in Example 2, 80 mol% in Example 3, and 100 mol% in Example 4. <Comparative Example 1> 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 adjusted to 1:1. The polyamide film of Comparative Example 1 was whitened throughout the film, and the film was very brittle and could not be peeled off from the glass plate. Therefore, it is considered that the transparency and mechanical properties are significantly inferior to those of the films of the examples. Since a self-supporting film could not be obtained for the film of Comparative Example 1, the evaluation of each physical property was not performed.

[0093]

Table 1

[0094] From Table 1, it can be seen that a polyamide resin containing the structural unit represented by formula (1) and the structural unit represented by formula (2), or the structural unit represented by formula (2) and the structural unit represented by formula (3) has good mechanical properties when formed into a film. Also, it can be seen that by setting the molar ratio of DEDC and TPC within a specific range, optical properties such as the YI value and haze become more excellent.

Industrial Applicability

[0095] According to the present invention, it is possible to provide a polyamide resin capable of manufacturing a film having good mechanical properties while suppressing the manufacturing cost.

Claims

1. A polyamide resin containing a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2). 【Chemical 1】 【Chemical 2】

2. The polyamide resin according to claim 1, further containing a structural unit represented by formula (3). 【Chemical Formula 3】

3. The polyamide resin according to claim 2, wherein the ratio of the number of moles of the structural unit represented by the formula (2) to the total number of moles of the structural unit represented by the formula (2) and the structural unit represented by the formula (3) is 10 to 90 mol%.

4. The polyamide resin according to claim 3, wherein the ratio of the number of moles of the structural unit represented by the formula (2) to the total number of moles of the structural unit represented by the formula (2) and the structural unit represented by the formula (3) is 30 to 90 mol%.

5. The polyamide resin according to claim 1, having a number average molecular weight of 5,000 or more and 200,000 or less.

6. A method for producing a polyamide resin according to any one of claims 1 to 5, comprising reacting a diamine and a dicarboxylic acid dichloride, wherein the diamine contains an aromatic diamine represented by the following formula (1A), and the dicarboxylic acid dichloride contains an aromatic dicarboxylic acid dichloride represented by the following formula (2A). A method for producing a polyamide resin. [Chemical Formula 4] 【Chemical Formula 5】

7. The method for producing a polyamide resin according to claim 6, wherein the dicarboxylic acid dichloride further contains an aromatic dicarboxylic acid dichloride represented by the following formula (3A). [Chemical Formula 6]

8. A polyamide film containing the polyamide resin according to any one of claims 1 to 5.

9. A flexible display provided with the film according to claim 8.

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