Liquid crystal polymer film, laminate, and polarizing plate

Abstract

To provide a liquid crystal polymer film with high transparency, and applications thereof.SOLUTION: A liquid crystal polymer film and applications thereof are provided, the liquid crystal polymer film comprising a liquid crystal polymer having a polyester structure in a main chain, where the value obtained by subtracting the amount of heat of crystallization from the amount of heat of fusion is 1.5 J / g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a liquid crystal polymer film, a laminate, and a polarizing plate. [Background technology]

[0002] In recent years, polymer films have been applied to a variety of fields, and performance such as transparency is required depending on the application.

[0003] For example, Patent Document 1 describes a cholesteric liquid crystal polymer film having an acrylic structure in the main chain. Patent Document 2 describes a manufacturing method for producing a thermoplastic liquid crystal polymer film having a molecular orientation SOR of 0.8 to 1.4 and a moisture content of 300 ppm or less, which includes a preparation step of forming an optically anisotropic melt phase and preparing a thermoplastic liquid crystal polymer film having a molecular orientation SOR of 0.8 to 1.4, a first degassing step of heating the thermoplastic liquid crystal polymer film at a temperature in the range of 100°C to 200°C for a predetermined time to degas it, and a second degassing step of heating the thermoplastic liquid crystal polymer film at a vacuum level of 1500 Pa or less at a temperature in the range of 80°C to 200°C to further degas it for a predetermined time. Patent Document 3 describes a highly heat-resistant liquid crystal polymer film that is obtained by irradiating a raw liquid crystal polymer film with ionizing radiation of 2000 kGy or more, and is characterized in that, in a temperature-storage modulus curve graph in which temperature is plotted on the horizontal axis and measured storage modulus values ​​on the vertical axis, there is a point in the range of 300°C or more to 400°C or less where the storage modulus value changes from decreasing to increasing with increasing temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-514024 [Patent Document 2] Japanese Patent Application Publication No. 2019-135301 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-237769 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by one embodiment of the present invention is to provide a liquid crystal polymer film having high transparency. Another problem to be solved by another embodiment of the present invention is to provide a laminate and a polarizing plate using a highly transparent liquid crystal polymer film. [Means for solving the problem]

[0006] The means for solving the above problems include the following aspects. <1> The liquid crystal polymer contains a polyester structure in the main chain, A liquid crystal polymer film having a heat of fusion minus the heat of crystallization of 1.5 J / g or less. <2> Haze is 3% or less, <1> The liquid crystal polymer film according to claim 1. <3> The thickness is 10 μm or less, <1> or <2> The liquid crystal polymer film according to claim 1. <4> The content of liquid crystal polymer is the highest among all components contained in liquid crystal polymer film. <1> ~ <3> 10. The liquid crystal polymer film according to claim 9, wherein the liquid crystal polymer film is a liquid crystal polymer film having a thickness of 100 nm or less. <5> The retardation in the in-plane direction is 0 nm to 1000 nm. <1> ~ <4> 10. The liquid crystal polymer film according to claim 9, wherein the liquid crystal polymer film is a liquid crystal polymer film having a thickness of 100 nm or less. <6> The retardation in the thickness direction is 5 nm to 10,000 nm. <1> ~ <5> 10. The liquid crystal polymer film according to claim 9, wherein the liquid crystal polymer film is a liquid crystal polymer film having a thickness of 100 nm or less. <7> The liquid crystal polymer is soluble in N-methyl-2-pyrrolidone. <1> ~ <6> 10. The liquid crystal polymer film according to claim 9, wherein the liquid crystal polymer film is a liquid crystal polymer film having a thickness of 100 nm or less. <8> The liquid crystal polymer has a constitutional unit represented by any one of formulas (1) to (3). <1> ~ <7> 10. The liquid crystal polymer film according to claim 9, wherein the liquid crystal polymer film is a liquid crystal polymer film having a thickness of 100 nm or less. Formula (1) -O-Ar 1 -CO- Formula (2) -CO-Ar 2 -CO- Formula (3) -X-Ar 3 -Y- In formulas (1) to (3), Ar 1 represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar 2 and Ar 3 each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), X and Y each independently represent an oxygen atom or an imino group, Ar 1 ~Ar 3 At least one of the hydrogen atoms may be independently substituted with a halogen atom, an alkyl group, or an aryl group. Formula (4) -Ar 4 -Z-Ar 5 - In formula (4), Ar 4 and Ar 5 each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group. <9> a substrate and a film formed on the substrate; <1> ~ <8> and a liquid crystal polymer film according to any one of the above. <10> <1> ~ <8> or <9> 10. A polarizing plate comprising the laminate according to claim 1, and a polarizing film. [Effects of the Invention]

[0007] According to one embodiment of the present invention, a liquid crystal polymer film having high transparency is provided. According to another embodiment of the present invention, a laminate and a polarizing plate using a highly transparent liquid crystal polymer film can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. Furthermore, in the description of groups (atomic groups) in this specification, a description that does not specify whether it is substituted or unsubstituted includes both unsubstituted and substituted groups. For example, the term "alkyl group" includes not only alkyl groups that do not have a substituent (unsubstituted alkyl groups) but also alkyl groups that have a substituent (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used as a concept that includes both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept that includes both acryloyl and methacryloyl. Furthermore, the term "step" in this specification does not only refer to an independent step, but also includes a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Furthermore, in this disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Furthermore, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. Furthermore, unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in the present disclosure are molecular weights calculated using a gel permeation chromatography (GPC) analyzer with a TSKgel SuperHM-H (trade name of Tosoh Corporation) column, a solvent of PFP (pentafluorophenol) / chloroform = 1 / 2 (mass ratio), detection with a differential refractometer, and conversion using polystyrene as a standard substance.

[0009] [Liquid crystal polymer film] The liquid crystal polymer film (hereinafter also simply referred to as "film") according to the present disclosure contains a liquid crystal polymer having a polyester structure in the main chain, and has a heat of fusion minus heat of crystallization of 1.5 J / g or less.

[0010] The film according to the present disclosure has a high transparency because it contains a polyester structure in the main chain of the liquid crystal polymer and the value obtained by subtracting the heat of crystallization from the heat of fusion is 1.5 J / g or less.

[0011] On the other hand, the liquid crystal polymer film described in Patent Document 1 does not contain a polyester structure in the main chain of the liquid crystal polymer, and therefore has insufficient transparency.

[0012] Furthermore, the liquid crystal polymer films described in Patent Documents 2 and 3 were subjected to heat treatment after film formation, and therefore crystallization progressed, making them opaque.

[0013] None of Patent Documents 1 to 3 mentions any value obtained by subtracting the heat of crystallization from the heat of fusion.

[0014] <Liquid Crystal Polymer> The film according to the present disclosure includes a liquid crystal polymer having a polyester structure in the main chain, and since the main chain contains a polyester structure, the film has high transparency.

[0015] The main chain of a polymer refers to the relatively longest, backbone-forming bond among the chain-like portions of the polymer. Whether or not the main chain of a polymer contains a polyester structure can be determined by an appropriate combination of analytical methods such as NMR (nuclear magnetic resonance), IR (infrared spectroscopy), and GPC (gel permeation chromatography).

[0016] The liquid crystal polymer contained in the film according to the present disclosure may have a structure other than a polyester structure, such as an ether structure, a urethane structure, a carbonate structure, or an amide structure.

[0017] The liquid crystal polymer may be a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state, or a lyotropic liquid crystal polymer that exhibits liquid crystallinity in a solution state. In the case of a thermotropic liquid crystal, it is preferable that the polymer melts at a temperature of 450°C or less.

[0018] Examples of liquid crystal polymers having a polyester structure in the main chain include liquid crystal polyester, liquid crystal polyester amide in which an amide bond is introduced into liquid crystal polyester, liquid crystal polyester ether in which an ether bond is introduced into liquid crystal polyester, and liquid crystal polyester carbonate in which a carbonate bond is introduced into liquid crystal polyester.

[0019] From the viewpoint of liquid crystallinity, the liquid crystal polymer is preferably a polymer having an aromatic ring, and more preferably an aromatic polyester or an aromatic polyester amide.

[0020] Furthermore, the liquid crystal polymer may be a polymer in which an imide bond, a carbodiimide bond, or an isocyanate-derived bond such as an isocyanurate bond is introduced into an aromatic polyester or an aromatic polyester amide.

[0021] The liquid crystal polymer is preferably a wholly aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0022] Examples of liquid crystal polymers include the following: 1) A compound obtained by polycondensation of (i) an aromatic hydroxycarboxylic acid, (ii) an aromatic dicarboxylic acid, and (iii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 2) A compound obtained by polycondensation of multiple types of aromatic hydroxycarboxylic acids. 3) (i) A compound obtained by polycondensation of an aromatic dicarboxylic acid and (ii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 4) (i) Polyester such as polyethylene terephthalate and (ii) aromatic hydroxycarboxylic acid are polycondensed. Here, the aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol, aromatic hydroxyamine and aromatic diamine may each independently be replaced in part or in whole by a polycondensable derivative thereof.

[0023] Examples of polymerizable derivatives of compounds having a carboxy group, such as aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids, include those in which the carboxy group is converted to an alkoxycarbonyl group or an aryloxycarbonyl group (esters), those in which the carboxy group is converted to a haloformyl group (acid halides), and those in which the carboxy group is converted to an acyloxycarbonyl group (acid anhydrides).

[0024] Examples of polymerizable derivatives of compounds having a hydroxy group, such as aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines, include those obtained by acylation of the hydroxy group to convert it into an acyloxy group (acylated products).

[0025] Examples of polymerizable derivatives of compounds having an amino group, such as aromatic hydroxyamines and aromatic diamines, include those obtained by acylation of the amino group to convert it into an acylamino group (acylated product).

[0026] From the viewpoint of liquid crystallinity, the liquid crystal polymer preferably has a constitutional unit represented by any one of the following formulas (1) to (3) (hereinafter, a constitutional unit represented by formula (1) etc. may be referred to as unit (1) etc.), more preferably has a constitutional unit represented by formula (1) below, and particularly preferably has a constitutional unit represented by formula (1) below, a constitutional unit represented by formula (2) below, and a constitutional unit represented by formula (3) below. Formula (1) -O-Ar 1 -CO- Formula (2) -CO-Ar 2 -CO- Formula (3) -X-Ar 3 -Y- In formulas (1) to (3), Ar 1 represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar 2 and Ar 3 each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), X and Y each independently represent an oxygen atom or an imino group, Ar 1 ~Ar 3 At least one of the hydrogen atoms may be independently substituted with a halogen atom, an alkyl group, or an aryl group. Formula (4) -Ar 4 -Z-Ar 5 - In formula (4), Ar 4 and Ar 5 each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group.

[0027] The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, and an n-decyl group, and the number of carbon atoms thereof is preferably 1 to 10. Examples of the aryl group include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, and a 2-naphthyl group, and the number of carbon atoms therein is preferably 6 to 20. When the hydrogen atoms are substituted with these groups, the number of the groups is 1 , Ar 2 or Ar 3 The number of the groups represented by the formula (I) is preferably two or less, and more preferably one.

[0028] Examples of the alkylene group include a methylene group, a 1,1-ethanediyl group, a 1-methyl-1,1-ethanediyl group, a 1,1-butanediyl group, and a 2-ethyl-1,1-hexanediyl group, and the number of carbon atoms is preferably 1 to 10.

[0029] The unit (1) is a structural unit derived from an aromatic hydroxycarboxylic acid. Unit (1) is Ar 1 is a p-phenylene group (a structural unit derived from p-hydroxybenzoic acid), and Ar 1 is preferably a 2,6-naphthylene group (a structural unit derived from 6-hydroxy-2-naphthoic acid) or a 4,4'-biphenylylene group (a structural unit derived from 4'-hydroxy-4-biphenylcarboxylic acid).

[0030] The unit (2) is a structural unit derived from an aromatic dicarboxylic acid. Unit (2) is Ar 2 is a p-phenylene group (a structural unit derived from terephthalic acid), Ar 2 is an m-phenylene group (a structural unit derived from isophthalic acid), Ar 2 is a 2,6-naphthylene group (a structural unit derived from 2,6-naphthalenedicarboxylic acid), or Ar 2 is a diphenylether-4,4'-diyl group (a structural unit derived from diphenylether-4,4'-dicarboxylic acid) is preferred.

[0031] The unit (3) is a structural unit derived from an aromatic diol, an aromatic hydroxylamine, or an aromatic diamine. Unit (3) is Ar 3 is a p-phenylene group (structural unit derived from hydroquinone, p-aminophenol or p-phenylenediamine), Ar 3 is an m-phenylene group (a structural unit derived from isophthalic acid), or Ar 3 is a 4,4'-biphenylylene group (a structural unit derived from 4,4'-dihydroxybiphenyl, 4-amino-4'-hydroxybiphenyl or 4,4'-diaminobiphenyl).

[0032] The content of unit (1) is preferably 30 mol% or more, more preferably 30 mol% to 80 mol%, even more preferably 30 mol% to 60 mol%, and particularly preferably 30 mol% to 40 mol% of the total amount of all structural units (the value obtained by dividing the mass of each structural unit constituting the liquid crystal polymer by the formula weight of that unit to determine the substance equivalent (mol) of each unit, and then adding them up). The content of the unit (2) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all structural units. The content of the unit (3) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all structural units. The greater the content of the unit (1), the more likely it is that the heat resistance, strength and rigidity will improve, but if the content is too high, the solubility in solvents will tend to decrease.

[0033] The ratio of the content of units (2) to the content of units (3), expressed as [content of units (2)] / [content of units (3)] (mol / mol), is preferably 0.9 / 1 to 1 / 0.9, more preferably 0.95 / 1 to 1 / 0.95, and even more preferably 0.98 / 1 to 1 / 0.98.

[0034] The liquid crystal polymer may independently contain two or more types of units (1) to (3). The liquid crystal polymer may also contain other structural units in addition to units (1) to (3), but the content of such other structural units is preferably 10 mol % or less, more preferably 5 mol % or less, based on the total amount of all units.

[0035] The liquid crystal polymer preferably has, as the unit (3), one in which at least one of X and Y is an imino group, that is, one in which at least one of a structural unit derived from a specific aromatic hydroxylamine and a structural unit derived from an aromatic diamine, because this provides excellent solubility in a solvent. It is more preferable that the liquid crystal polymer has, as the unit (3), only one in which at least one of X and Y is an imino group.

[0036] The liquid crystal polymer is preferably produced by melt-polymerizing raw material monomers corresponding to the structural units constituting the liquid crystal polymer. The melt-polymerization may be carried out in the presence of a catalyst. Examples of the catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, and nitrogen-containing heterocyclic compounds such as 4-(dimethylamino)pyridine and 1-methylimidazole. Nitrogen-containing heterocyclic compounds are preferably used. The melt-polymerization may further be solid-phase polymerized as needed.

[0037] The flow initiation temperature of the liquid crystal polymer is preferably 250° C. or higher, more preferably 250° C. or higher and 350° C. or lower, and even more preferably 260° C. or higher and 330° C. or lower. When the flow initiation temperature of the liquid crystal polymer is within the above range, the polymer has excellent solubility, heat resistance, strength, and rigidity, and the viscosity of the solution is appropriate.

[0038] The flow initiation temperature is also called the flow temperature or flow temperature, and is measured using a capillary rheometer at 9.8 MPa (100 kg / cm 2When a liquid crystal polymer is melted and extruded through a nozzle with an inner diameter of 1 mm and a length of 10 mm while heating at a rate of 4°C / min under a load of 1000 kJ / s, the temperature at which the polymer shows a viscosity of 4,800 Pa·s (48,000 poise) is measured. This temperature is an indicator of the molecular weight of the liquid crystal polymer (see "Liquid Crystal Polymer - Synthesis, Molding, and Applications," edited by Naoyuki Koide, CMC Corporation, June 5, 1987, p. 95).

[0039] The weight-average molecular weight of the liquid crystal polymer is preferably 1,000,000 or less, more preferably 3,000 to 300,000, even more preferably 5,000 to 100,000, and particularly preferably 5,000 to 30,000. When the weight-average molecular weight of the liquid crystal polymer is within the above range, the polymer film has excellent thermal conductivity in the thickness direction, heat resistance, strength, and rigidity.

[0040] From the viewpoint of ease of film formation, the liquid crystal polymer is preferably soluble at 25°C in at least one solvent selected from the group consisting of N-methylpyrrolidone, N-ethylpyrrolidone, dichloromethane, dichloroethane, chloroform, N,N-dimethylacetamide, γ-butyrolactone, dimethylformamide, ethylene glycol monobutyl ether, and ethylene glycol monoethyl ether, and more preferably soluble in N-methyl-2-pyrrolidone.

[0041] The polymer soluble in N-methyl-2-pyrrolidone means a polymer that dissolves in an amount of 0.1 g or more in 100 g of N-methyl-2-pyrrolidone at 25° C. The liquid crystal polymer dissolves preferably in an amount of 0.1 g or more, more preferably in an amount of 0.5 g or more, in 100 g of N-methyl-2-pyrrolidone.

[0042] The content of the liquid crystal polymer is preferably 30% by mass to 100% by mass, and more preferably 50% by mass to 100% by mass, based on the total amount of the film.

[0043] The content of the liquid crystal polymer is preferably the highest among all components contained in the liquid crystal polymer film. That is, when the film contains two components, the content of the liquid crystal polymer is preferably more than 50% by mass of the total amount of the film. When the film contains three components, the content of the liquid crystal polymer is preferably 33.4% by mass or more of the total amount of the film.

[0044] <Surfactant> The film according to the present disclosure may contain a surfactant, which provides an excellent appearance.

[0045] The type of surfactant is not particularly limited, and examples thereof include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants. The surfactant may be a fluorine-based surfactant or a silicone-based surfactant. Among these, from the viewpoint of obtaining a film with good appearance, the surfactant is preferably a fluorine-based surfactant.

[0046] The films according to the present disclosure may also contain fillers.

[0047] The filler may be particulate or fibrous, and may be an inorganic filler or an organic filler.

[0048] As the inorganic filler, known inorganic fillers can be used. Examples of inorganic filler materials include BN, Al2O3, AlN, TiO2, SiO2, barium titanate, strontium titanate, aluminum hydroxide, calcium carbonate, and materials containing two or more of these.

[0049] Among these, as the inorganic filler, from the viewpoint of reducing the coefficient of friction, metal oxide particles or fibers are preferred, silica particles, titania particles or glass fibers are more preferred, and silica particles or glass fibers are particularly preferred.

[0050] As the organic filler, known organic fillers can be used. Examples of organic filler materials include polyethylene, polystyrene, urea-formalin filler, polyester, cellulose, acrylic resin, fluororesin, hardened epoxy resin, crosslinked benzoguanamine resin, crosslinked acrylic resin, and materials containing two or more of these. The organic filler may be in the form of fibers such as nanofibers, or may be hollow resin particles.

[0051] The film according to the present disclosure may contain other additives in addition to the liquid crystal polymer, surfactant, and filler.

[0052] As other additives, known additives can be used, such as leveling agents, antifoaming agents, antioxidants, ultraviolet absorbers, flame retardants, and colorants.

[0053] Furthermore, the film according to the present disclosure may contain, as other additives, resins other than the liquid crystal polymer. Examples of resins other than liquid crystal polymers include thermoplastic resins other than liquid crystal polyesters, such as polypropylene, polyamide, polyesters other than liquid crystal polyesters, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and modified products thereof, and polyether imide; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenolic resins, epoxy resins, polyimide resins, and cyanate resins.

[0054] <△Hm-△Hc> The film according to the present disclosure has a value of 1.5 J / g or less, obtained by subtracting the heat of crystallization (ΔHc) from the heat of fusion (ΔHm). The value of "ΔHm - ΔHc" is an index showing the amount of crystallinity in the film. The smaller the value of "ΔHm - ΔHc", the less crystallization has progressed. Therefore, the film according to the present disclosure has a value of "ΔHm - ΔHc" of 1.5 J / g or less, and therefore has excellent transparency. The value of "ΔHm - ΔHc" is preferably 1.0 J / g or less, more preferably 0.5 J / g or less, and most preferably 0.04 J / g or less.

[0055] ΔHm and ΔHc are measured by the following method. After conditioning the film for 24 hours at 25°C and 10% relative humidity, the film is sealed in a measurement pan. Using a differential scanning calorimeter, the temperature is raised from 25°C to 350°C at a rate of 20°C / min. The obtained thermogram is checked from the low-temperature side. The temperature at which the baseline begins to deviate is designated as Tg, the peak temperature at which an exothermic peak appears as Tc, and the temperature at which an endothermic peak appears as Tm. The peak calorific value at Tc is designated as ΔHc, and the peak calorific value at Tm is designated as ΔHm. If no exothermic or endothermic peak appears, these calorific values ​​are considered to be 0. The obtained ΔHc and ΔHm are used to calculate "ΔHm - ΔHc." A differential scanning calorimeter such as the "DSC6200" manufactured by Seiko Instruments Inc. can be used.

[0056] Methods for adjusting △Hm-△Hc to 1.5 J / g or less include, for example, a method of suppressing the heating temperature after forming the liquid crystal polymer into a film; a method of heating at a high temperature after reducing the amount of residual solvent; and a method of heating at a temperature from the appearance of the endothermic peak of Tm to the end of the peak, or at a temperature higher than Tm, followed by rapid cooling.

[0057] <Retardation> The retardation of the film according to the present disclosure is not particularly limited and may be appropriately adjusted depending on the application, but from the viewpoint of improving the viewing angle of an image display device, the in-plane retardation (Re) is preferably 0 nm to 1000 nm, more preferably 0 nm to 300 nm, and from the viewpoint of suppressing rainbow unevenness, it is preferably 5000 nm to 100,000 nm, more preferably 7000 nm to 30,000 nm.

[0058] Furthermore, from the viewpoint of improving the viewing angle of image display devices, the film according to the present disclosure preferably has a retardation in the thickness direction (Rth) of 5 nm to 10,000 nm, more preferably 10 nm to 1,000 nm.

[0059] Re and Rth are values ​​expressed by the following formulas. Re=(nx-ny)×d Rth={(nx+ny) / 2-nz}×d In the formula, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is the film thickness (unit: nm).

[0060] Re and Rth are measured using a retardation measurement device, for example, by irradiating the retardation measurement device with light having a wavelength of 590 nm. As the retardation measurement device, for example, a product name "KOBRA-21WR" manufactured by Oji Scientific Instruments Co., Ltd. can be used.

[0061] Specifically, the average value is calculated using the following method. A 5cm x 5cm sample was cut from the center and both ends of the film (5% inward from both ends). Each sample was attached to glass with adhesive, and the Re and Rth of each sample were measured and the average value was calculated.

[0062] <Haze, light transmittance> From the viewpoint of transparency, the film according to the present disclosure preferably has a haze of 3% or less, more preferably 1% or less. The lower limit of the haze is not particularly limited, and is, for example, 0.3%. From the viewpoint of transparency, the film according to the present disclosure preferably has a light transmittance of 85% or more, more preferably 88% or more, at a wavelength of 550 nm. The upper limit of the light transmittance is not particularly limited, and is, for example, 89%.

[0063] The haze and light transmittance are measured using a haze meter, for example, a haze meter (model number "HGM-2DP", manufactured by Suga Test Instruments Co., Ltd.).

[0064] Specifically, the average value is calculated using the following method. A 5cm x 5cm sample was cut from the center and both ends of the film (5% inward from both ends). Each sample was attached to glass with adhesive, and the haze of each sample was measured and the average value was calculated.

[0065] <Thickness> The thickness of the film according to the present disclosure is not particularly limited, but is preferably 10 μm or less, and more preferably 5 μm or less.

[0066] The thickness is measured at any five locations using an adhesive film thickness meter, and the average value of the measurements is used. The measurement can be performed using, for example, an electronic micrometer (product name "KG3001A" manufactured by Anritsu Corporation).

[0067] <Film manufacturing method> (Formation process) The method for producing the film according to the present disclosure is not particularly limited, and known methods can be used. The method for producing the film according to the present disclosure preferably includes a forming step of forming a film by applying a polymer composition containing a liquid crystal polymer and a solvent onto a substrate and drying the applied polymer composition. The polymer composition may contain the above-mentioned other additives.

[0068] The method for forming the film is not particularly limited, and known methods can be used. Suitable examples include casting, coating, and extrusion. Among these, the casting method is particularly preferred as the film-forming method. When the film has a multilayer structure, suitable examples include co-casting, multi-layer coating, and co-extrusion. Among these, the co-casting method is particularly preferred for forming a relatively thin film, and the co-extrusion method is particularly preferred for forming a thick film.

[0069] Examples of the solvent include halogenated hydrocarbons such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1-chlorobutane, chlorobenzene, and o-dichlorobenzene; halogenated phenols such as p-chlorophenol, pentachlorophenol, and pentafluorophenol; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketones such as acetone and cyclohexanone; esters such as ethyl acetate and γ-butyrolactone; and ethylene carbonate. nitriles such as acetonitrile and succinonitrile; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and urea compounds such as tetramethylurea; nitro compounds such as nitromethane and nitrobenzene; sulfur compounds such as dimethyl sulfoxide and sulfolane; and phosphorus compounds such as hexamethylphosphoramide and tri-n-butylphosphate, and two or more of these may be used.

[0070] As the solvent, a solvent mainly composed of an aprotic compound, particularly an aprotic compound having no halogen atoms, is preferred because it is less corrosive and easier to handle, and the proportion of the aprotic compound in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. Furthermore, as the aprotic compound, an amide such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, or an ester such as γ-butyrolactone is preferably used because it easily dissolves the liquid crystal polymer, and N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone are more preferred.

[0071] Furthermore, as the solvent, a solvent containing a compound having a dipole moment of 3 to 5 as a main component is preferred because it easily dissolves the liquid crystal polymer, and the proportion of the compound having a dipole moment of 3 to 5 in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. As the aprotic compound, a compound having a dipole moment of 3 to 5 is preferably used.

[0072] Furthermore, as the solvent, a solvent containing as its main component a compound having a boiling point of 220°C or less at 1 atmosphere is preferred because it is easy to remove, and the proportion of the compound having a boiling point of 220°C or less at 1 atmosphere in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. As the aprotic compound, it is preferable to use a compound having a boiling point of 220° C. or lower at 1 atmospheric pressure.

[0073] Examples of substrates used when applying the polymer composition include metal drums, metal bands, glass plates, resin films, and metal foils. Of these, resin films are preferred as the substrate.

[0074] Examples of resin films include polyimide (PI) films, and examples of commercially available products include U-Pirex S and U-Pirex R manufactured by Ube Industries, Ltd., Kapton manufactured by DuPont-Toray Co., Ltd., and IF30, IF70, and LV300 manufactured by SKC Kolon PI.

[0075] The substrate may have a surface treatment layer formed on its surface to facilitate peeling of the film, which may be made of hard chrome plating, fluororesin, or the like.

[0076] The average thickness of the substrate is not particularly limited, but is preferably 25 μm or more and 75 μm or less, and more preferably 50 μm or more and 75 μm or less.

[0077] The method for removing at least a part of the solvent from the cast or coated film-like composition (coating film) is not particularly limited, and any known drying method can be used.

[0078] (Stretching process) The method for producing a film according to the present disclosure preferably includes a stretching step of stretching the film after the forming step.

[0079] In the film manufacturing method according to the present disclosure, stretching can be appropriately combined to control the molecular orientation of the resulting film and adjust the linear expansion coefficient and mechanical properties. The stretching method is not particularly limited, and known methods can be used. It may be performed in a solvent-containing state or in a dry film state. Stretching in a solvent-containing state may be performed by gripping the film and stretching it, or by utilizing the self-shrinkage force of the web due to drying without stretching, or a combination thereof. Stretching is particularly effective for improving the breaking elongation or breaking strength when the film brittleness has decreased due to the addition of an inorganic filler or the like.

[0080] In the film manufacturing method according to the present disclosure, it is preferable not to carry out a heating step after the stretching step, since carrying out a heating step tends to promote crystallization of the polymer in the film and reduce the light transmittance of the film.

[0081] (peeling process) The method for producing a film according to the present disclosure preferably includes, after the forming step or the stretching step, a peeling step of peeling the substrate from a laminate comprising the substrate and the film. By peeling the substrate, the film alone can be used for other purposes.

[0082] <Other processes> The film manufacturing method according to the present disclosure may include other steps in addition to those described above. Other steps may include known steps.

[0083] <Application> The film according to the present disclosure can be used in a variety of applications, and among these, the film according to the present disclosure is suitably used as an optical film due to its high transparency.

[0084] [Laminate] The laminate according to the present disclosure may be any laminate including the film according to the present disclosure. The laminate according to the present disclosure preferably includes a substrate and the liquid crystal polymer film formed on the substrate.

[0085] The laminate according to the present disclosure may be a substrate obtained in the forming step of the film manufacturing method and a film formed on the substrate. Examples of the substrate include the substrate used in the forming step of the film manufacturing method.

[0086] Furthermore, the substrate in the laminate according to the present disclosure may be a substrate different from the substrate used in the forming step in the film manufacturing method. For example, in the film manufacturing method, the substrate used in the forming step is peeled off, and then another substrate is attached to the film to form a laminate.

[0087] [Polarizing plate] A polarizing plate according to the present disclosure includes the film or the laminate and a polarizing film.

[0088] The polarizing film can be produced by a known method, for example, by immersing a polyvinyl alcohol film in an iodine solution and stretching the film.

[0089] The film or laminate and the polarizing film are preferably bonded via an adhesive. Any known adhesive can be used as the adhesive. When the laminate and the polarizing film are bonded together, they are bonded so that the film side of the laminate comes into contact with the polarizing film.

[0090] The film according to the present disclosure has high transparency and is therefore suitable for use in polarizing plates. [Example]

[0091] The present disclosure will be described in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure is not limited to the specific examples shown below.

[0092] Details of the materials used in the examples and comparative examples are as follows.

[0093] <Liquid Crystal Polymer> LC-A: Liquid crystal polymer prepared according to the following manufacturing method

[0094] -Production of LC-A- A reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 940.9 g (5.0 mol) of 6-hydroxy-2-naphthoic acid, 272.8 g (2.5 mol) of 4-aminophenol, 415.3 g (2.5 mol) of isophthalic acid, and 1,123.0 g (11 mol) of acetic anhydride. The gas inside the reactor was replaced with nitrogen gas, and then the temperature was raised from room temperature (23°C; the same applies hereinafter) to 150°C over 15 minutes while stirring under a nitrogen gas stream, and the mixture was refluxed at 150°C for 3 hours. Next, while distilling off by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 150°C to 320°C over 3 hours, and when an increase in viscosity was observed, the contents were removed from the reactor and cooled to room temperature. The obtained solid was pulverized in a pulverizer to obtain a powdered liquid crystal polyester (B1).

[0095] The liquid crystal polyester (B1) obtained above was solid-phase polymerized by holding it at 250°C for 3 hours under a nitrogen atmosphere, and then cooled to obtain a powdered liquid crystal polyester (LC-A). The obtained LC-A was heated at 280°C for 3 hours under a nitrogen atmosphere, and the dielectric loss tangent of a sample was 0.01 or less.

[0096] <Filler> M-1: Silicon dioxide fine particles (product name "NX90S", manufactured by Nippon Aerosil Co., Ltd.)

[0097] <Surfactant> S-1: A polymer having the following structural units, with a mass ratio of 25:25:50:

[0098] [ka]

[0099] <Base material> B-1: Polyethylene naphthalate film (product name "Teonex Q83", film thickness 50 μm, manufactured by Toyobo Co., Ltd.)

[0100] Details of Examples 1 to 6 and Comparative Examples 1 to 3 are shown below.

[0101] Examples 1 to 6 -Preparation of polymer solution- LC-A was added to N-methylpyrrolidone and dissolved by heating and stirring at 120°C under a nitrogen atmosphere. Next, the additives listed in Table 1 were added and stirred, and the mixture was passed through a sintered fiber metal filter with an absolute filtration accuracy of 3 μm, and then passed through a sintered fiber metal filter with an absolute filtration accuracy of 1 μm to obtain a polymer solution. In Examples 5 and 6, the additives (filler, surfactant) listed in Table 1 were added in the mass ratios listed in Table 1. The solids concentration of each polymer solution was 8 mass%.

[0102] -Making laminates (multi-layer films)- A multilayer film was obtained by applying the polymer solution to a substrate B-1 (width 1340 mm) so that the coating width was 1320 mm. Specifically, the coating was performed using the die coating method using a slot die described in Example 1 of JP-A-2006-122889 so that the thickness after drying would be the value listed in Table 1, and the film was dried at 140°C for 5 minutes. The multilayer film was then wound into a roll. In Example 4, the tension in the conveying direction was increased in the drying process to increase Re.

[0103] -Preparation of polarizing plates- A polarizing plate was produced using the multilayer film, adhesive, polarizing film, and opposing film.

[0104] 1) Preparation of adhesive An adhesive composition was prepared by mixing a polymerizable compound, a polymerization initiator, and a sensitizer according to the method described below.

[0105] 2) Composition of adhesive composition 2-Ethylhexyl glycidyl ether (product name "Epiol EH-N", manufactured by NOF Corporation) ... 10.0 parts by mass 1,4-Cyclohexanedimethanol diglycidyl ether (product name: Rikaresin DME-100, manufactured by New Japan Chemical Co., Ltd.) ... 20.0 parts by mass 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (product name: Celloxide 2021P, manufactured by Daicel Corporation) ... 70.0 parts by mass Photocationic polymerization initiator (product name "CPI-100P", manufactured by San-Apro Co., Ltd.) ... 1.0 parts by mass Photocationic polymerization initiator (product name "IRGACURE290", manufactured by BASF) ... 4.0 parts by mass Sensitizer (product name "DarocurITX", manufactured by BASF) ... 0.5 parts by mass

[0106] 3) Preparation of the opposing film A polymethyl methacrylate film having a thickness of 60 μm was prepared as the opposing film according to Example 1 of JP 2015-227458 A.

[0107] 4) Surface treatment of multi-layer film and facing film The surface of the multilayer film prepared above opposite to the interface on the substrate side and the opposing film were subjected to a corona treatment.

[0108] 5) Preparation of polarizing film According to Example 1 of JP-A No. 2001-141926, a difference in peripheral speed was applied between two pairs of nip rolls, and the film was stretched in the longitudinal direction to prepare a polarizing film having a thickness of 15 μm.

[0109] 6) Lamination The surface-treated multilayer film, the polarizing film, and the surface-treated opposing film were laminated in this order to obtain a polarizing plate. The surface-treated surface was positioned facing the polarizing film, and the adhesive composition was used for adhesion. The films were laminated roll-to-roll so that the absorption axis of the polarizing film, the multilayer film, and the opposing film were parallel in their longitudinal directions. The adhesive composition was applied over a width of 1,300 mm. Subsequently, an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) was used to apply the adhesive composition at a dose of 300 mJ / cm. 2 The resulting polarizing plate was cut and the cross section was observed under an optical microscope, and it was confirmed that the thickness of the adhesive (adhesive layer) on both the multilayer film side and the opposing film side was 2.5 μm.

[0110] 7) Peeling of the substrate The substrate of the multilayer film was peeled off from the produced polarizing plate using a peeling device.

[0111] 8) Adhesive coating An acrylic adhesive containing an antistatic agent was applied to the surface of the polarizing plate from which the substrate had been peeled off, completing the processing of the polarizing plate.

[0112] The multilayer film thus prepared was used to measure the value obtained by subtracting the heat of crystallization from the heat of fusion (ΔHc - ΔHm), retardation (Re, Rth), light transmittance, and haze. The polarizing plate thus prepared was also used to measure the degree of polarization. The measurement methods are as follows:

[0113] [Retardation] The substrate was peeled off from the multilayer film to obtain a film. 5 cm x 5 cm samples were cut from the center and both ends of the film (positions 5% inward from both ends along the entire length). Each sample was attached to glass with an adhesive, and the in-plane retardation (Re) and thickness retardation (Rth) of each sample were measured and averaged. Re and Rth were measured using a phase difference measurement device (product name "KOBRA-21ADH", manufactured by Oji Scientific Instruments) with 590 nm wavelength light incident thereon.

[0114] [Light transmittance, haze] The substrate was peeled off from the multilayer film to obtain a film. 5 cm x 5 cm samples were cut out from the center and both ends of the film (positions 5% inward from both ends along the entire length). Each sample was attached to glass with an adhesive, and the light transmittance and haze of each sample were measured, and the average values ​​were calculated. The haze and light transmittance were measured using a haze meter (model number "HGM-2DP", manufactured by Suga Test Instruments Co., Ltd.).

[0115] [△Hc, △Hm] The substrate was peeled off from the multilayer film to obtain a film. The film was then conditioned for 24 hours at a temperature of 25°C and a relative humidity of 10%. The film was then sealed in a measurement pan, and the temperature was raised from 25°C to 350°C at a rate of 20°C / min using a differential scanning calorimeter (product name "DSC6200", manufactured by Seiko Instruments Inc.). The obtained thermogram was checked from the low temperature side, and the temperature at which the baseline began to deviate was defined as Tg, the peak temperature at which an exothermic peak appeared as Tc, and the temperature at which an endothermic peak appeared as Tm. The peak calorific value at Tc was defined as ΔHc, and the peak calorific value at Tm was defined as ΔHm. If Tc or Tm did not appear, the calorific values ​​were set to 0.

[0116] [Polarization degree] A 40 mm square sample was cut out from the polarizing plate. The transmittance (Tp) of two samples was measured when they were stacked with their absorption axes parallel, and the transmittance (Tc') was measured when they were stacked with their absorption axes perpendicular to each other. The polarization degree P was calculated using the following formula. Polarization degree P=((Tp-Tc') / (Tp+Tc')) 0.5

[0117] The measurement results are shown in Table 1.

[0118] [Table 1]

[0119] As shown in Table 1, the films of Examples 1 to 6 contain a liquid crystal polymer having a polyester structure in the main chain, and the value obtained by subtracting the heat of crystallization from the heat of fusion is 1.5 J / g or less, indicating that they are highly transparent.

[0120] Furthermore, in Examples 5 and 6, since a surfactant was contained, films with superior appearance compared to Examples 1 to 4 were obtained.

[0121] In Example 6, silicon dioxide fine particles were contained as a filler, and therefore it was easy to wind up into a roll.

[0122] (Comparative Example 1) A single-layer liquid crystal film was prepared according to Example 7 of JP-A-2009-514024. The obtained film did not contain a liquid crystal polymer having a polyester structure in the main chain, and its "ΔHm-ΔHc" was 0 J / g. Measurements were carried out in the same manner as in the example, and it was confirmed that the light transmittance was 89%, but the haze was high at 4%.

[0123] (Comparative Example 2) A film was produced according to Example 1 of JP 2019-135301 A. The obtained film was confirmed to have a "ΔHm-ΔHc" value of more than 1.5 J / g and to be opaque.

[0124] (Comparative Example 3) A film was produced according to Example 1 of JP 2014-237769 A. The obtained film was confirmed to have a "ΔHm-ΔHc" value of more than 1.5 J / g and to be opaque.

Claims

1. The liquid crystal polymer contains a polyester structure in the main chain, The value obtained by subtracting the heat of crystallization from the heat of fusion is 1.5 J / g or less, A liquid crystal polymer film having a retardation in the thickness direction of 5 nm to 10,000 nm.

2. 2. The liquid crystal polymer film according to claim 1, having a haze of 3% or less.

3. 3. The liquid crystal polymer film according to claim 1, having a thickness of 10 μm or less.

4. 4. The liquid crystal polymer film according to claim 1, wherein the content of the liquid crystal polymer is the highest among all components contained in the liquid crystal polymer film.

5. 5. The liquid crystal polymer film according to claim 1, wherein the retardation in the in-plane direction is 0 nm to 1000 nm.

6. 6. The liquid crystal polymer film according to claim 1, wherein the liquid crystal polymer is soluble in N-methyl-2-pyrrolidone.

7. 7. The liquid crystal polymer film according to claim 1, wherein the liquid crystal polymer has a constitutional unit represented by any one of formulas (1) to (3). Formula (1) -O-Ar １ -CO- Formula (2) -CO-Ar ２ -CO- Formula (3) -X-Ar ３ -Y- In formulas (1) to (3), Ar １ represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar ２ and Ar ３ each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), X and Y each independently represent an oxygen atom or an imino group, Ar １ ~Ar ３ At least one of the hydrogen atoms may be independently substituted with a halogen atom, an alkyl group, or an aryl group. Formula (4) -Ar ４ -Z-Ar ５ - In formula (4), Ar ４ and Ar ５ each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group.

8. A laminate comprising a substrate and the liquid crystal polymer film according to any one of claims 1 to 7 formed on the substrate.

9. A polarizing plate comprising the liquid crystal polymer film according to any one of claims 1 to 7 or the laminate according to claim 8, and a polarizing film.

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