CN111333885B

CN111333885B - Optical film, flexible display device, and resin composition

Info

Publication number: CN111333885B
Application number: CN201911292391.8A
Authority: CN
Inventors: 池内淳一; 片宝蓝; 有村孝; 吉川岳
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-12-19
Filing date: 2019-12-16
Publication date: 2023-08-25
Anticipated expiration: 2039-12-16
Also published as: KR102183172B1; TW202035537A; JP6595080B1; KR20200076637A; KR20200132820A; JP2020097710A; CN111333885A

Abstract

The invention relates to an optical film, a flexible display device and a resin composition. The invention aims to provide a resin film with high elastic modulus. The solution of the invention is the following optical film: an optical film comprising at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins, wherein the optical film has an ionic strength (I) of Na obtained by time-of-flight secondary ion mass spectrometry _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) Is 0.2 or more.

Description

Optical film, flexible display device, and resin composition

Technical Field

The invention relates to an optical film, a flexible display device and a resin composition.

Background

Image display devices such as liquid crystal display devices and organic EL display devices are widely used in various applications such as mobile phones and smart watches. Glass has been used as a front panel of such an image display device, but glass is very rigid and is easily broken, and thus it is difficult to use the glass as a front panel material of a flexible display device, for example. Therefore, as one of materials for replacing glass, effective use of a polymer material has been studied, and for example, an optical film using a polyimide resin has been studied (for example, patent document 1).

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2018-119132

Disclosure of Invention

Problems to be solved by the application

However, when an optical film using a polyimide resin, a polyamide resin, or the like is used in a flexible display device or the like, defects such as damage and wrinkles may occur in the optical film due to bending or contact with external factors. The present inventors have made various studies on means for improving the above-mentioned conditions, and have found that defects such as damage are less likely to occur in an optical film by increasing the elastic modulus of the optical film.

Accordingly, an object of the present application is to provide a resin film having a high elastic modulus.

Means for solving the problems

In order to solve the above problems, the present inventors have conducted intensive studies focusing on the types and amounts of components contained in a resin film. As a result, the ion strength (I _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) An optical film of 0.2 or more has surprisingly been found that it is easy to increase the elastic modulus, and the present application has been completed.

That is, the present application includes the following preferred modes.

[ 1 ] an optical film comprising at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins, wherein the optical film has an ionic strength (I) of Na obtained by time-of-flight secondary ion mass spectrometry _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) Is 0.2 or more.

The optical film according to [ 1 ] above, wherein the polyimide resin and the polyamide resin are aromatic resins.

The optical film according to [ 1 ] or [ 2 ], wherein the proportion of the structural units derived from the aromatic monomer in the polyimide resin and the polyamide resin is 80 mol% or more based on the total structural units.

The optical film according to any one of [ 1 ] to [ 3 ], wherein the thickness is 10 to 100. Mu.m, and the total light transmittance is 80% or more.

The optical film according to any one of [ 1 ] to [ 4 ], wherein the polyimide resin and the polyamide resin have a weight average molecular weight of 200,000 or more.

The optical film according to any one of [ 1 ] to [ 5 ], wherein the polyimide resin is a polyamideimide resin.

The optical film according to any one of [ 1 ] to [ 6 ], wherein the polyimide-based resin and the polyamide-based resin contain structural units derived from terephthalic acid.

The optical film according to any one of [ 1 ] to [ 7 ], which is a film for a front panel of a flexible display device.

A flexible display device comprising the optical film according to any one of [ 1 ] to [ 8 ].

The flexible display device according to [ 9 ] above, further comprising a touch sensor.

The flexible display device according to [ 9 ] or [ 10 ], which further comprises a polarizing plate.

[ 12 ] A resin composition comprising at least: at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins; at least one sodium-containing component selected from the group consisting of a sodium atom-containing compound, sodium, and sodium ions; and (3) a solvent.

ADVANTAGEOUS EFFECTS OF INVENTION

The optical film of the present invention has a high elastic modulus.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described herein, and various modifications may be made without departing from the spirit of the present invention.

The optical film of the present invention is an optical film comprising at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins, and has an ionic strength (I) of Na obtained by time-of-flight secondary ion mass spectrometry (TOF-SIMS) _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) Is 0.2 or more.

The optical device of the inventionIn the film, ionic strength of Na (I _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) Is calculated by the following method: determination of CH of optical film by Time-of-flight secondary ion mass spectrometry (Time-of-Flight Secondary Ion Mass Spectrometry: hereinafter also referred to as "TOF-SIMS") ₃ The ionic strength (I) _CH3 ) Ionic strength of Na (I) _Na ) And let I _Na Divided by I _CH3 . In the present specification, CH measured by time-of-flight type secondary ion mass spectrometry is referred to as CH ₃ The ionic strength (I) _CH3 ) Ionic strength of Na (I) _Na ) In the measurement data, the data are assigned to CH ₃ Integral value of peak of ion as CH ₃ The ionic strength (I) _CH3 ) The integrated value of the peak attributed to Na ion was taken as the ionic strength of Na (I _Na )。

TOF-SIMS is one type of mass spectrometry, and by TOF-SIMS, the element or molecular species present on the outermost surface of a sample can be obtained with extremely high detection sensitivity, and the distribution of the element or molecular species present on the outermost surface of the sample can be studied.

TOF-SIMS is a method of irradiating a sample with an ion beam (primary ion) in a high vacuum and mass-separating ions released from the surface by using the time difference of flight. When the primary ions are irradiated, ions (secondary ions) having positive or negative charges are released from the sample surface, and the lighter ions fly faster and the heavier ions fly slower, so that the mass of the generated secondary ions can be calculated by measuring the time (flight time) from the generation of the secondary ions until the detection of the secondary ions.

In TOF-SIMS based assays, CH ₃ Ions were detected near the mass of 15.02u, and Na ions were detected near the mass of 22.99 u. In addition, these ions are ions that can be detected in either positive (positive) ion analysis or negative (negative) ion analysis. In the present invention, the ionic strength of Na (I _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) The ratio detected in the positive ion analysis may be the ratio detected in the negative ion analysis, and from the viewpoint of obtaining higher detection sensitivity, it is preferable to use conditions for the positive ion analysis, and when at least one of the ratios is 0.2 or more, the ratio (I _Na /I _CH3 ) The number is 0.2 or more.

For TOF-SIMS based measurement, a time-of-flight type secondary ion mass spectrometry device can be used for an optical film, wherein the primary ion is Bi ³⁺⁺ The primary ion was accelerated at 25kV, the irradiation ion current was 0.23pA, and the measurement range was 200. Mu.m.times.200. Mu.m, and the measurement was performed by positive ion analysis or negative ion analysis. TOF-SIMS based assays can be performed, for example, as described in the examples. The above ratio (I) _Na /I _CH3 ) The composition inside the optical film may be within the above range, but it is presumed that the mechanical strength of the optical film is more easily affected, and therefore, it is preferable that the above ratio (I _Na /I _CH3 ) Within the above range.

Based on the ionic strength (I) of Na obtained by time-of-flight secondary ion mass spectrometry _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) The optical film of the present invention having a modulus of elasticity of 0.2 or more surprisingly can improve the elastic modulus of the optical film. Here, CH obtained by time-of-flight secondary ion mass spectrometry is used ₃ The ionic strength (I) _CH3 ) And the ionic strength of Na (I _Na ) Relatively indicates the amount of carbon atoms and/or carbon ions and the amount of sodium atoms and/or sodium ions present in the optical film. The above ratio is 0.2 or more: more than a certain amount of sodium atoms (Na) and/or total amount of sodium ions relative to the total amount of carbon atoms and/or carbon ions present in the optical film. Carbon atoms and carbon ions are represented by CH ₃ The reason why the form of the ion is detected is that: in the case of time-of-flight type secondary ion mass spectrometry, various secondary ions produced can also be represented as protonsThe form of the adduct is detected as a feature that CH is simultaneously generated as a proton adduct in the carbon atom ₃ Ions.

The reason why the elastic modulus of the optical film is improved by the presence of a certain amount of sodium atoms is not clear, but the elastic modulus is considered to be improved by, for example, the following mechanism, but the present invention is not limited to any of the mechanisms described below. It is considered that, when the optical film of the present invention is produced, a composition containing a polyimide-based resin and/or a polyamide-based resin contains a compound containing a sodium atom, sodium and/or sodium ions, and thus an imide bond and/or an amide bond (preferably an imide bond contained in a polyimide-based resin) contained in the resin causes some interaction (for example, electrostatic interaction between an imide bond, a carbonyl group of an amide bond, and sodium ions) with the compound containing a sodium atom, sodium and/or sodium ions. As a result, it is considered that the polyimide-based resin and/or the polyamide-based resin contained in the obtained optical film exist in the film in a state of interacting with the sodium atom-containing compound, sodium and/or sodium ions, or the orientation state of the resin changes due to the interaction of the sodium atom-containing compound, sodium and/or sodium ions with the polyimide-based resin and/or the polyamide-based resin, whereby the elastic modulus of the optical film is improved. The sodium-containing component contained in the optical film is preferably in an ionized state from the viewpoint of easy interaction with the imide bond and/or the amide bond of the polyimide-based resin and/or the polyamide-based resin. In the present specification, it is considered that the ion strength (I _Na ) The detected sodium atom-containing compound, sodium and/or sodium ions that may be contained in the optical film are also referred to as "sodium-containing components". The sodium atom-containing compound means a compound containing a sodium atom as a constituent atom of a molecule.

From the viewpoint of easy improvement of the elastic modulus of the optical film, the ionic strength (I _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) It is preferably at least 1 and preferably at least 1,more preferably 1.5 or more, still more preferably 3 or more, still more preferably 5 or more, still more preferably 10 or more, and particularly preferably 15 or more. Proportion (I) _Na /I _CH3 ) The upper limit of (2) is preferably 100 or less, more preferably 50 or less, further preferably 30 or less, further preferably 25 or less, and particularly preferably 20 or less.

The ratio (I) _Na /I _CH3 ) The method for adjusting the content within the above range is not particularly limited, and examples thereof include: a method for adjusting the content of a sodium-containing component (sodium atom-containing compound, sodium and/or sodium ion) in the optical film of the present invention comprising a polyimide-based resin and/or a polyamide-based resin; and a method for adjusting the content of the polyimide resin and/or the polyamide resin contained in the optical film. Specifically, when the content of the sodium-containing component in the optical film is increased, the ionic strength (I _Na ) And also becomes large. When the content of the polyimide-based resin and/or the polyamide-based resin contained in the optical film is increased, CH of the optical film obtained by TOF-SIMS ₃ The ionic strength (I) _CH3 ) And also increases. Therefore, if the content of the sodium-containing component in the optical film is increased, the ratio (I _Na /I _CH3 ) When the content of the polyimide-based resin and/or the polyamide-based resin contained in the optical film is increased, the ratio (I _Na /I _CH3 ) The value of (2) becomes smaller. By the above method, the ratio (I _Na /I _CH3 ) Adjusted to be within a desired range.

In the optical film of the present invention, CH obtained by TOF-SIMS ₃ The ionic strength (I) _CH3 ) Ionic strength of Na (I) _Na ) Is not particularly limited as long as the ratio (I _Na /I _CH3 ) The value of (2) may be within the above range, and the ion strength (I) of Na may be within the range from the viewpoint of ensuring sufficient quantitative performance in TOF-SIMS measurement _Na ) The measurement is preferably performed under conditions of preferably 100 or more, more preferably 300 or more, and still more preferably 500 or more.

Proportion (I) _Na /I _CH3 ) The invention is more than 0.2The optical film has a high elastic modulus. The elastic modulus of the optical film of the present invention is preferably 5.0MPa or more, more preferably 5.1MPa or more, and still more preferably 5.2MPa or more. The upper limit of the elastic modulus is not particularly limited, but is usually 100MPa or less. The elastic modulus may be measured by a tensile testing machine (for example, under conditions of 50mm distance between chucks and 10 mm/min stretching speed), and may be measured by the method described in examples.

The total light transmittance of the optical film of the present invention is preferably 80% or more, more preferably 85% or more, still more preferably 88% or more, still more preferably 90% or more, and particularly preferably 91% or more. When the total light transmittance is not less than the lower limit, visibility is easily improved when the optical film (particularly, the front panel) is mounted in an image display device. Since the optical film of the present invention generally exhibits high total light transmittance, the light emission intensity of a display element or the like required to obtain a constant luminance can be suppressed as compared with the case of using a film having a low transmittance, for example. Therefore, power consumption can be reduced. For example, when the optical film of the present invention is mounted in an image display device, bright display tends to be obtained even when the light amount of backlight is reduced, and energy saving can be contributed. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance may be, for example, in accordance with JIS K7361-1: 1997. the measurement was performed using a haze computer. The total light transmittance may be in a range of the thickness of the optical film described later.

The haze of the optical film of the present invention is preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.2% or less. When the haze of the optical film is equal to or less than the upper limit, visibility is easily improved when the optical film (particularly, as a front panel) is mounted in an image display device. The lower limit of haze is usually 0.01% or more. The haze may be in accordance with JIS K7136: 2000. the measurement was performed using a haze computer.

The optical film of the present invention preferably has a yellowness index (YI value) of 3.0 or less, more preferably 2.5 or less, and still more preferably 2.2 or less. When the yellow index of the optical film is equal to or less than the upper limit, the transparency becomes good, and the optical film can contribute to high visibility when used for a front panel of an image display device. The yellow index is usually-5 or more, preferably-2 or more. The yellow index (YI value) may be calculated by measuring the transmittance of light at 300 to 800nm using an ultraviolet-visible-near-infrared spectrophotometer, obtaining a tristimulus value (X, Y, Z), and based on the formula yi=100× (1.2769X-1.0592Z)/Y. In the present specification, the term "optical film is excellent in optical characteristics" means: high total light transmittance, low haze, and/or low YI (yellow index).

The thickness of the optical film of the present invention is preferably 10 μm or more, more preferably 20 μm or more, further preferably 25 μm or more, particularly preferably 30 μm or more, preferably 100 μm or less, more preferably 80 μm or less, further preferably 60 μm or less, and the upper limit and the lower limit thereof may be combined. When the thickness of the optical film is within the above range, the elastic modulus of the optical film is easily further improved. The thickness of the optical film may be measured by a micrometer, and may be measured by the method described in examples, for example.

The number of bending times (bending radius r=1mm) of the optical film of the present invention in the bending resistance test is preferably 150,000 times or more, more preferably 180,000 times or more, and still more preferably 200,000 times or more. When the number of bending is equal to or greater than the lower limit, the front panel material used as a flexible display device or the like has sufficient bending resistance. The number of bending times in the bending resistance test indicates: the optical film was repeatedly bent using a bending tester under the condition that the bending radius (radius of curvature) R was 1mm, and the number of times of bending was repeated until the point of time when the film was broken (1 round trip was regarded as 1 time).

Polyimide resin and Polyamide resin

The optical film of the present invention comprises a polyimide resin and/or a polyamide resin. In the present specification, the polyimide-based resin means at least one resin selected from the group consisting of a resin containing a repeating structural unit including an imide group (hereinafter, sometimes referred to as a polyimide resin) and a resin containing a repeating structural unit including both an imide group and an amide group (hereinafter, sometimes referred to as a polyamideimide resin). In other words, in the present specification, the polyimide-based resin means a polyimide resin and/or a polyamideimide resin. The polyamide resin means a resin containing a repeating structural unit including an amide group. The optical film of the present invention may contain 1 kind of polyimide resin or polyamide resin, or may contain 2 or more kinds of polyimide resin and/or polyamide resin in combination. The optical film of the present invention preferably contains a polyimide-based resin, and the polyimide-based resin is more preferably a polyamideimide resin, from the viewpoint of easy realization of both chemical stability and high elastic modulus of the optical film.

In a preferred embodiment of the present invention, the polyimide-based resin and the polyamide-based resin are preferably aromatic-based resins from the viewpoint of easiness of further improvement of the elastic modulus of the optical film. In the present specification, the aromatic resin means a polyimide resin and a resin in which a structural unit included in the polyamide resin is mainly an aromatic structural unit.

In one preferred embodiment, the proportion of the structural units derived from the aromatic monomer contained in the polyimide resin is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 85 mol% or more, with respect to the total structural units, from the viewpoint of easiness in further improving the elastic modulus of the optical film. Here, the structural unit derived from an aromatic monomer means a structural unit derived from a monomer having an aromatic structure (for example, an aromatic ring) in at least a part thereof and having an aromatic structure (for example, an aromatic ring) in at least a part thereof. Examples of the aromatic monomer include an aromatic tetracarboxylic acid compound, an aromatic diamine, and an aromatic dicarboxylic acid.

In a preferred embodiment of the present invention, the polyimide-based resin is preferably a polyimide resin having a structural unit represented by formula (1) or a polyamideimide resin having a structural unit represented by formula (1) and a structural unit represented by formula (2). The polyamide resin is preferably a polyamide resin having a structural unit represented by the formula (2). The following description will be given of the formulas (1) and (2), and the description of the formula (1) relates to both the polyimide resin and the polyamideimide resin, and the description of the formula (2) relates to both the polyamideimide resin and the polyamideimide resin.

[ chemical formula 1]

The structural unit represented by the formula (1) is a structural unit formed by reacting a tetracarboxylic acid compound with a diamine compound, and the structural unit represented by the formula (2) is a structural unit formed by reacting a dicarboxylic acid compound with a diamine compound.

In the formula (2), Z is a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms which may be substituted with a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms which may be substituted with fluorine, more preferably a divalent organic group having 4 to 40 carbon atoms which may be substituted with a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms which may be substituted with fluorine. Examples of the cyclic structure include alicyclic, aromatic and heterocyclic structures. Examples of the organic group of Z include: a group in which two non-adjacent bonds of the bonds between the groups represented by the following formulas (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29) are replaced with hydrogen atoms; a divalent chain hydrocarbon group having 6 or less carbon atoms; examples of the heterocyclic structure of Z may include a group having a thiophene ring skeleton. The groups represented by the formulas (20) to (27) and the group having a thiophene ring skeleton are preferable from the viewpoint of easy suppression of the yellowness index (lowering YI value) of the optical film.

In one embodiment of the present invention, the polyamide resin and the polyamideimide resin may contain a plurality of Z's, which may be the same or different from each other. In particular, from the viewpoint of easy improvement of the elastic modulus of the optical film of the present invention and easy improvement of optical characteristics, at least a part of Z is preferably represented by formula (3),

[ chemical formula 2]

In the formula (3) of the present invention,

R ¹ ～R ⁸ independently of one another, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R ¹ ～R ⁸ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other,

a independently of one another represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -S-, -CO-or-N (R) ⁹ )-，R ⁹ Represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom,

m is an integer of 0 to 4,

represents a bond.

In the formula (3), A independently represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -S-, -CO-or-N (R) ⁹ ) From the viewpoint of the bending resistance of the optical film, preferably represents-O-or-S-, more preferably-O-.

R ¹ 、R ² 、R ³ 、R ⁴ 、R ⁵ 、R ⁶ 、R ⁷ 、R ⁸ Independently of each other, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl and n-hexyl A base, etc. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, pentyloxy, hexyloxy, cyclohexyloxy and the like. Examples of the aryl group having 6 to 12 carbon atoms include phenyl, tolyl, xylyl, naphthyl, and biphenyl. From the viewpoint of surface hardness and flexibility of the optical film, R ¹ ～R ⁸ Independently of each other, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a hydrogen atom. Here, R is ¹ ～R ⁸ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other.

R ⁹ A monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, and n-decyl, and these may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

In the formula (3), m is an integer in the range of 0 to 4, and when m is in the range, the elastic modulus and bending resistance of the optical film are easily improved. From the viewpoint of easiness of further improving the elastic modulus and bending resistance of the optical film, m in the formula (3) is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, further preferably 0 or 1, and particularly preferably 0. The structural unit represented by the formula (3) in which m is 0 is a structural unit derived from terephthalic acid, and the structural unit is particularly preferably R in the formula (3) ⁵ ～R ⁸ A structural unit which is a hydrogen atom and m is 0. The resin may contain one or two or more structural units represented by formula (3) in Z. From the viewpoints of improving the elastic modulus and bending resistance of the optical film and reducing the yellowness index (YI value), the resin preferably contains two or more structural units having different values of m in the formula (3) in Z, and more preferably contains two or more structural units having different values of m in the formula (3) in ZA structural unit. In this case, from the viewpoint of easiness in improving the elastic modulus and bending resistance of the optical film and easiness in lowering the yellowness index (YI value) of the optical film, it is particularly preferable that the resin contains a structural unit represented by formula (3) in which m is 0 in Z and also contains a structural unit represented by formula (3) in which m is 1 in addition to the structural unit.

In a preferred embodiment of the present invention, the resin has m=0 and R ⁵ ～R ⁸ The structural unit which is a hydrogen atom is represented by the formula (3). In a more preferred embodiment of the present invention, the resin has m=0 and R ⁵ ～R ⁸ A structural unit represented by the formula (3') which is a hydrogen atom,

[ chemical formula 3]

In this case, the elastic modulus and bending resistance of the optical film are easily improved, and the yellow index is easily reduced.

In a preferred embodiment of the present invention in which the optical film comprises a polyamideimide resin, the proportion of the structural unit represented by the formula (3) is preferably 20 mol% or more, more preferably 30 mol% or more, still more preferably 40 mol% or more, particularly preferably 50 mol% or more, most preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, still more preferably 80 mol% or less, based on 100 mol% of the total of the structural units represented by the formula (1) and the structural unit represented by the formula (2) of the polyamideimide resin. When the proportion of the structural unit represented by the formula (3) is equal to or greater than the lower limit, the elastic modulus and bending resistance of the optical film are easily improved. When the proportion of the structural unit represented by the formula (3) is equal to or less than the upper limit, the increase in viscosity of the resin-containing varnish due to the inter-amide bond hydrogen bond derived from the formula (3) is easily suppressed, and the processability of the film is improved.

In addition, in the case where the polyamideimide resin has a structural unit represented by the formula (3) where m=1 to 4In the case where the total of the structural units represented by the formula (1) and the structural units represented by the formula (2) of the polyamideimide resin is 100 mol%, the ratio of the structural units represented by the formula (3) in which m is 1 to 4 is preferably 3 mol% or more, more preferably 5 mol% or more, still more preferably 7 mol% or more, particularly preferably 9 mol% or more, preferably 90 mol% or less, more preferably 70 mol% or less, still more preferably 50 mol% or less, and particularly preferably 30 mol% or less. When the ratio of the structural unit represented by the formula (3) in which m is 1 to 4 is equal to or more than the lower limit, the elastic modulus and bending resistance of the optical film are easily improved. When the proportion of the structural unit represented by the formula (3) in which m is 1 to 4 is equal to or less than the upper limit, the increase in viscosity of the resin-containing varnish due to the inter-amide bond hydrogen bond derived from the structural unit represented by the formula (3) is easily suppressed, and the processability of the film is improved. The proportion of the structural unit represented by the formula (1), the formula (2) or the formula (3) may be, for example ¹ The measurement is performed by H-NMR, or it may be calculated from the feed ratio of the raw materials.

In a preferred embodiment of the present invention, the structural unit represented by formula (3) in which m is 0 to 4 is preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, and particularly preferably 50 mol% or more of Z in the polyamide resin or the polyamideimide resin. When the lower limit or more of Z is a structural unit represented by the formula (3) in which m is 0 to 4, the elastic modulus and bending resistance of the optical film can be easily improved. In addition, 100 mol% or less of Z in the polyamide resin or the polyamideimide resin may be a structural unit represented by the formula (3) in which m is 0 to 4. The proportion of the structural unit represented by the formula (3) in the resin, in which m is 0 to 4, may be, for example ¹ The measurement is performed by H-NMR, or it may be calculated from the feed ratio of the raw materials.

In a preferred embodiment of the present invention, the polyamide resin or the polyamideimide resin is represented by formula (3) in which m is 1 to 4, preferably 5 mol% or more, more preferably 8 mol% or more, still more preferably 10 mol% or more, and particularly preferably 12 mol% or more of Z. Z of the polyamideimide resinWhen the lower limit or more of (2) is represented by the formula (3) in which m is 1 to 4, the elastic modulus and bending resistance of the optical film can be easily improved. Further, Z is preferably 90 mol% or less, more preferably 70 mol% or less, still more preferably 50 mol% or less, and particularly preferably 30 mol% or less, represented by formula (3) where m is 1 to 4. When the upper limit of Z is not more than the upper limit of m is represented by the formula (3) having m of 1 to 4, the increase in viscosity of the varnish containing the resin due to hydrogen bonding between amide bonds derived from the structural unit represented by the formula (3) having m of 1 to 4 is easily suppressed, and the processability of the film is improved. The proportion of the structural unit represented by the formula (3) in which m is 1 to 4 in the resin may be, for example ¹ The measurement is performed by H-NMR, or it may be calculated from the feed ratio of the raw materials.

In the formulas (1) and (2), X independently of each other represents a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms, more preferably a divalent organic group having 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic and heterocyclic structures. In the above-mentioned organic group, the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. In one embodiment of the present invention, the polyamide resin, polyimide resin, or polyamideimide resin may contain a plurality of X, which may be the same as or different from each other. Examples of the "X" may include groups represented by the formulae (10), (11), (12), (13), (14), (15), (16), (17) and (18); a group in which a hydrogen atom in the group represented by the formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

[ chemical formula 4]

In the formulas (10) to (18),

the term "connection" means a connection bond,

V ¹ 、V ² V (V) ³ Independently of one another, represents a single bond, -O-, -S-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -CO-or-N (Q) -. Here, Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include those represented by R ⁹ And the groups described hereinabove.

One example is: v (V) ¹ V (V) ³ Is a single bond, -O-or-S-, and V ² is-CH ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -or-SO ₂ -。V ¹ And V ² Bonding position with respect to each ring, and V ² And V ³ The bonding positions with respect to the respective rings are preferably meta or para with respect to the respective rings independently of each other, and more preferably para.

Among the groups represented by the formulae (10) to (18), the groups represented by the formulae (13), (14), (15), (16) and (17) are preferable, and the groups represented by the formulae (14), (15) and (16) are more preferable, from the viewpoint of easiness in improving the elastic modulus and bending resistance of the optical film. In addition, V from the viewpoint of easy improvement of the elastic modulus and flexibility of the optical film ¹ 、V ² V (V) ³ Preferably, each independently of the other, is a single bond, -O-or-S-, more preferably a single bond or-O-.

In a preferred embodiment of the present invention, at least a part of the plurality of X in the formulae (1) and (2) is a structural unit represented by the formula (4):

[ chemical formula 5]

In the formula (4) of the present invention,

R ¹⁰ ～R ¹⁷ independently of one another, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R ¹⁰ ～R ¹⁷ The hydrogen atoms contained in the ring may be substituted by halogen atoms independently of one another，

Represents a bond.

When at least a part of the plurality of X's in the formulas (1) and (2) is a group represented by the formula (4), the elastic modulus and transparency of the optical film can be easily improved.

In the formula (4), R ¹⁰ 、R ¹¹ 、R ¹² 、R ¹³ 、R ¹⁴ 、R ¹⁵ 、R ¹⁶ 、R ¹⁷ Independently of each other, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include those exemplified as the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms in the formula (3). R is R ¹⁰ ～R ¹⁷ Independently of each other, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, where R ¹⁰ ～R ¹⁷ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. From the viewpoints of elastic modulus, transparency and bending resistance of the optical film, R ¹⁰ ～R ¹⁷ Further preferred independently of one another are hydrogen, methyl, fluoro, chloro or trifluoromethyl, R being particularly preferred ¹⁰ 、R ¹² 、R ¹³ 、R ¹⁴ 、R ¹⁵ R is R ¹⁶ Is a hydrogen atom, and R ¹¹ R is R ¹⁷ Is a hydrogen atom, methyl, fluoro, chloro or trifluoromethyl group (R is particularly preferred ¹¹ R is R ¹⁷ Methyl or trifluoromethyl).

In a preferred embodiment of the present invention, the structural unit represented by formula (4) is a structural unit represented by formula (4'):

[ chemical formula 6]

That is, at least a part of the plurality of X's is a structural unit represented by formula (4'). In this case, the fluorine-containing skeleton improves the solubility of the polyimide-based resin or the polyamide-based resin in the solvent, and thus the storage stability of the varnish containing the resin can be easily improved, the viscosity of the varnish can be easily reduced, and the processability of the optical film can be easily improved. In addition, the skeleton containing fluorine element easily improves the optical properties of the optical film.

In a preferred embodiment of the present invention, the polyimide-based resin or the polyamide-based resin is represented by formula (4), in particular, formula (4'), and X is preferably 30 mol% or more, more preferably 50 mol% or more, and still more preferably 70 mol% or more. When X in the above range in the polyimide-based resin or the polyamide-based resin is represented by the formula (4), in particular, the obtained optical film has a skeleton containing a fluorine element, so that the solubility of the resin in a solvent is improved, the storage stability of a varnish containing the resin is easily improved, the viscosity of the varnish is easily reduced, and the processability of the optical film is easily improved. In addition, the optical properties of the optical film are also easily improved by the skeleton containing fluorine element. It is preferable that 100 mol% or less of X in the polyimide-based resin or the polyamide-based resin is represented by formula (4), particularly formula (4'). X in the above resin may be formula (4), especially formula (4'). The proportion of the structural unit represented by the formula (4) of X in the above resin may be, for example ¹ The measurement is performed by H-NMR, or it may be calculated from the feed ratio of the raw materials.

In the formula (1), Y represents a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms, more preferably a tetravalent organic group having 4 to 40 carbon atoms having a cyclic structure. The cyclic structure may be an alicyclic, aromatic or heterocyclic structure, and from the viewpoint of easy improvement of elastic modulus, the aromatic ring is preferable. The above-mentioned organic group is an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of types of Y, and the plurality of types of Y may be the same as or different from each other. As Y, there can be mentioned: a group represented by the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29); a group in which a hydrogen atom in the group represented by the formulas (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a 4-valent hydrocarbon group having 6 or less carbon atoms.

[ chemical formula 7]

In the formulae (20) to (29), W represents a bond ¹ Represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-Ar-、-SO ₂ -、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH ₂ -Ar-、-Ar-C(CH ₃ ) ₂ -Ar-or-Ar-SO ₂ Ar-. Ar represents an arylene group having 6 to 20 carbon atoms, the hydrogen atom of which may be substituted with a fluorine atom, and specific examples thereof include phenylene groups.

Among the groups represented by the formulae (20) to (29), the group represented by the formula (26), the formula (28) or the formula (29) is preferable, and the group represented by the formula (26) is more preferable, from the viewpoint of easiness in improving the elastic modulus and the bending resistance of the optical film. In addition, from the viewpoints of easy improvement of the elastic modulus and bending resistance of the optical film and easy reduction of the yellow index of the optical film, W ¹ Independently of one another, preferably a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -or-C (CF) ₃ ) ₂ -, more preferably a single bond, -O-, -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -or-C (CF) ₃ ) ₂ -, more preferably a single bond, -C (CH) ₃ ) ₂ -or-C (CF) ₃ ) ₂ -。

In a preferred embodiment of the present invention, at least a part of Y in the plurality of formulas (1) is a structural unit represented by formula (5):

[ chemical formula 8]

In the formula (5) of the above,

R ¹⁸ ～R ²⁵ independently of one another, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R ¹⁸ ～R ²⁵ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other,

represents a bond.

When at least a part of Y in the formula (1) is a group represented by the formula (5), the solubility of the polyimide resin in a solvent is improved, the viscosity of a varnish containing the polyimide resin is easily reduced, and the processability of the optical film is easily improved. In addition, the elastic modulus and optical characteristics of the optical film can be easily improved.

In the formula (5), R ¹⁸ 、R ¹⁹ 、R ²⁰ 、R ²¹ 、R ²² 、R ²³ 、R ²⁴ R is R ²⁵ Independently of each other, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include those exemplified above as the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms in the formula (3). R is R ¹⁸ ～R ²⁵ Independently of each other, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, where R ¹⁸ ～R ²⁵ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. R is R from the viewpoint of easily improving the elastic modulus and bending resistance of the optical film, and from the viewpoint of easily improving the transparency and easily maintaining the transparency ¹⁸ ～R ²⁵ Independent of each other, further preferablyHydrogen atom, methyl group, fluoro group, chloro group or trifluoromethyl group, and more preferably R ¹⁸ 、R ¹⁹ 、R ²⁰ 、R ²³ 、R ²⁴ R is R ²⁵ Is a hydrogen atom, R ²¹ R is R ²² Is a hydrogen atom, methyl, fluoro, chloro or trifluoromethyl group (R is particularly preferred ²¹ R is R ²² Methyl or trifluoromethyl).

In a preferred embodiment of the present invention, the structural unit represented by formula (5) is a group represented by formula (5'),

[ chemical formula 9]

That is, at least a part of the plurality of Y is a structural unit represented by the formula (5'). In this case, the fluorine-containing skeleton improves the solubility of the polyimide-based resin in a solvent, and thus the storage stability of the varnish containing the resin can be easily improved, and the viscosity of the varnish can be easily reduced, thereby improving the processability of the optical film. In addition, the skeleton containing fluorine element easily improves the optical properties of the optical film.

In a preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of Y in the polyimide-based resin is represented by formula (5), particularly formula (5'). When Y in the above range in the polyimide resin is represented by the formula (5), particularly the formula (5'), the fluorine-containing skeleton improves the solubility of the polyimide resin in a solvent, and thus the viscosity of a varnish containing the polyimide resin is easily reduced, and the processability of an optical film is easily improved. In addition, the skeleton containing fluorine element easily improves the optical properties of the optical film. It is preferable that 100 mol% or less of Y in the polyimide-based resin is represented by formula (5), particularly formula (5'). The polyimide resin may have the formula (5), particularly the formula (5'). The proportion of the structural unit represented by the formula (5) of Y in the polyimide-based resin may be, for example ¹ The measurement can be performed by H-NMR, or can be performed according toThe feed ratio of the raw materials was calculated.

The polyimide-based resin may contain a structural unit represented by the formula (30) and/or a structural unit represented by the formula (31) in addition to the structural units represented by the formula (1) and, if necessary, the formula (2).

[ chemical formula 10]

In the formula (30), Y ¹ The tetravalent organic group is preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine. As Y ¹ Examples thereof include: a group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29); a group in which a hydrogen atom in the group represented by the formulas (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a 4-valent hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of Y' s ¹ Multiple Y ¹ May be the same or different from each other.

In the formula (31), Y ² As the trivalent organic group, an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine is preferable. As Y ² Examples thereof include: a group in which any one of the bonds connecting the groups represented by the above-mentioned formulae (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29) is replaced with a hydrogen atom; and a 3-valent hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of Y' s ² Multiple Y ² May be the same or different from each other.

In the formula (30) and the formula (31), X ¹ X is X ² Are, independently of one another, divalent organic radicals, preferably organic radicals in which the hydrogen atoms in the organic radicals can be replaced by hydrocarbon radicals or fluorine-substituted hydrocarbon radicals. As X ¹ X is X ² Examples thereof include: the above formula (10), formula (11) and formula (12)) A group represented by formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); a group in which a hydrogen atom in the group represented by the formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In one embodiment of the present invention, the polyimide-based resin includes a structural unit represented by formula (1) and/or formula (2), and a structural unit represented by formula (30) and/or formula (31) which are optionally included. In the polyimide resin, the proportion of the structural units represented by the formula (1) and the formula (2) is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more, based on all the structural units represented by the formula (1) and the formula (2), and the formula (30) and the formula (31) which are contained in the polyimide resin, from the viewpoint of easiness in improving the optical characteristics, the elastic modulus, and the bending resistance of the optical film. In the polyimide resin, the proportion of the structural units represented by the formula (1) and the formula (2) is usually 100% or less based on the total structural units represented by the formula (1) and the formula (2) and, if necessary, the formula (30) and/or the formula (31). The above ratio may be, for example ¹ The measurement is performed by H-NMR, or it may be calculated from the feed ratio of the raw materials.

In one embodiment of the present invention, the content of the polyimide-based resin and/or the polyamide-based resin in the optical film is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, and still more preferably 95 parts by mass or less, based on 100 parts by mass of the optical film. When the content of the polyimide-based resin and/or the polyamide-based resin is within the above range, the optical properties and the elastic modulus of the optical film can be easily improved.

The weight average molecular weight (Mw) of the polyimide-based resin and the polyamide-based resin is preferably 200,000 or more, more preferably 230,000 or more, still more preferably 250,000 or more, still more preferably 270,000 or more, and particularly preferably 300,000 or more in terms of a standard polystyrene conversion, from the viewpoint of easiness in improving the elastic modulus and the bending resistance of the optical film. In addition, the weight average molecular weight of the polyimide resin and the polyamide resin is preferably 1,000,000 or less, more preferably 800,000 or less, still more preferably 700,000 or less, and particularly preferably 500,000 or less, from the viewpoint of easy improvement of the solubility of the resin in a solvent and easy improvement of the elongation and processability of the optical film. The weight average molecular weight can be obtained by GPC measurement and standard polystyrene conversion, and can be calculated by the method described in examples.

The content of the structural unit represented by the formula (2) in the polyamideimide resin is preferably 0.1 mol or more, more preferably 0.5 mol or more, further preferably 1.0 mol or more, particularly preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, further preferably 4.5 mol or less, based on 1 mol of the structural unit represented by the formula (1). When the content of the structural unit represented by the formula (2) is not less than the lower limit, the elastic modulus of the optical film is easily increased. In addition, when the content of the structural unit represented by the formula (2) is equal to or less than the upper limit, thickening due to hydrogen bonding between amide bonds in the formula (2) is easily suppressed, and thus the processability of the optical film is improved.

In a preferred embodiment of the present invention, the polyimide-based resin and/or the polyamide-based resin contained in the optical film may contain a halogen atom such as a fluorine atom which can be introduced through, for example, the fluorine-containing substituent or the like described above. When the polyimide-based resin and/or the polyamide-based resin contains a halogen atom, the elastic modulus of the optical film is easily increased and the yellowness index (YI value) is reduced. When the elastic modulus of the optical film is high, the occurrence of damage, wrinkles, and the like in the film is easily suppressed. In addition, when the yellow index of the optical film is low, the transparency and visibility of the film are easily improved. The halogen atom is preferably a fluorine atom. Examples of the fluorine-containing substituent that is preferable for the polyimide-based resin to contain a fluorine atom include a fluorine group and a trifluoromethyl group.

The content of halogen atoms in the polyimide-based resin and the polyamide-based resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and even more preferably 5 to 30% by mass, based on the mass of the polyimide-based resin and the polyamide-based resin, respectively. When the content of halogen atoms is not less than the lower limit, it is easy to further increase the elastic modulus of the optical film, reduce the water absorption, further reduce the yellow index, and further improve the transparency and visibility. When the content of halogen atoms is less than or equal to the upper limit, synthesis is easy.

The imidization ratio of the polyimide-based resin and the polyamideimide resin is preferably 90% or more, more preferably 93% or more, and even more preferably 96% or more. The imidization ratio is preferably not less than the lower limit described above from the viewpoint of easiness in improving the optical characteristics of the optical film. The upper limit of the imidization ratio is 100% or less. The imidization ratio represents a ratio of the molar amount of imide bonds in the polyimide resin to a value 2 times the molar amount of structural units derived from the tetracarboxylic acid compound in the polyimide resin. When the polyimide-based resin contains a tricarboxylic acid compound, the imidization rate represents a ratio of the molar amount of imide bonds in the polyimide-based resin to the sum of the molar amount of structural units derived from the tetracarboxylic acid compound and the molar amount of structural units derived from the tricarboxylic acid compound, which is 2 times the molar amount of structural units derived from the tetracarboxylic acid compound in the polyimide-based resin. The imidization rate can be obtained by IR method, NMR method, or the like.

As the polyimide resin and the polyamide resin, commercially available ones can be used. Examples of the commercially available polyimide resins include Neopulim (registered trademark) manufactured by Mitsubishi gas chemical corporation and KPI-MX300F manufactured by Hecun industries, ltd.

In the present invention, the optical film may contain a polyamide resin. The polyamide resin according to the present embodiment is a polymer mainly composed of a repeating structural unit represented by the formula (2). The preferable examples and specific examples of Z in the formula (2) of the polyamide-based resin are the same as those of Z of the polyimide-based resin. The polyamide resin may contain two or more kinds of repeating structural units represented by formula (2) in which Z is different.

(method for producing resin)

The polyimide resin can be produced using, for example, a tetracarboxylic acid compound and a diamine compound as main raw materials, the polyamide imide resin can be produced using, for example, a tetracarboxylic acid compound, a dicarboxylic acid compound and a diamine compound as main raw materials, and the polyamide resin can be produced using, for example, a diamine compound and a dicarboxylic acid compound as main raw materials. Here, the dicarboxylic acid compound preferably contains at least a compound represented by the formula (3 ").

[ chemical formula 11]

In the formula (3'),

a represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -S-, -CO-or-N (R) ⁹ )-，

R ⁹ Represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom,

m is an integer of 0 to 4,

R ³¹ r is R ³² Independently of one another, represents a hydroxyl group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group or a chlorine atom.]

In a preferred embodiment of the present invention, the dicarboxylic acid compound is a compound represented by formula (3') wherein m is 0. As the dicarboxylic acid compound, a compound represented by formula (3 ") in which a is an oxygen atom is more preferably used in addition to a compound represented by formula (3") in which m is 0. In addition, in another preferred embodiment, the dicarboxylic acid compound is represented by R ³¹ 、R ³² A compound represented by the formula (3') which is a chlorine atom. In addition, diamine compound can be replacedThe diisocyanate compound is used.

Examples of the diamine compound used for producing the resin include aliphatic diamine, aromatic diamine, and a mixture thereof. In the present embodiment, the term "aromatic diamine" means a diamine in which an amino group is directly bonded to an aromatic ring, and a part of the structure thereof may include an aliphatic group or other substituent. The aromatic ring may be a single ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited thereto. Among these, benzene rings are preferable. The term "aliphatic diamine" means a diamine in which an amino group is directly bonded to an aliphatic group, and a part of the structure may include an aromatic ring and other substituents.

Examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylenediamine and cyclic aliphatic diamines such as 1, 3-bis (aminomethyl) cyclohexane, 1, 4-bis (aminomethyl) cyclohexane, norbornanediamine, and 4,4' -diaminodicyclohexylmethane. They may be used singly or in combination of two or more.

Examples of the aromatic diamine include: aromatic diamines having one aromatic ring such as p-phenylenediamine, m-phenylenediamine, 2, 4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene, and 2, 6-diaminonaphthalene; 4,4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 3,4' -diaminodiphenylether 3,3 '-diaminodiphenyl ether, 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, and 2, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4,4 '-diaminobiphenyl (sometimes referred to as TFMB), 4' -bis (4-aminophenoxy) biphenyl, and aromatic diamines having two or more aromatic rings, such as 9, 9-bis (4-aminophenyl) fluorene, 9-bis (4-amino-3-methylphenyl) fluorene, 9-bis (4-amino-3-chlorophenyl) fluorene, and 9, 9-bis (4-amino-3-fluorophenyl) fluorene. They may be used singly or in combination of two or more.

The aromatic diamine is preferably 4,4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 3' -diaminodiphenylether, 4 '-diaminodiphenylsulfone, 3' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, and bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4,4 '-diaminobiphenyl (TFMB), 4' -bis (4-aminophenoxy) biphenyl, more preferably 4,4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 4' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, and 2, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4,4 '-diaminobiphenyl (TFMB), 4' -bis (4-aminophenoxy) biphenyl. They may be used singly or in combination of two or more.

Among the diamine compounds, one or more selected from the group consisting of aromatic diamines having a biphenyl structure are preferably used from the viewpoints of high elastic modulus, high transparency, high flexibility, high bending resistance, and low coloring of the optical film. More preferably, at least one selected from the group consisting of 2,2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) benzidine, 4 '-bis (4-aminophenoxy) biphenyl and 4,4' -diaminodiphenyl ether is used, and still more preferably, 2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl (TFMB) is used.

Examples of the tetracarboxylic acid compound used for the production of the resin include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic acid dianhydride, and the like. The tetracarboxylic acid compound may be used alone or in combination of two or more. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analogue such as an acid chloride compound, in addition to the dianhydride.

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydride, monocyclic aromatic tetracarboxylic dianhydride, and condensed polycyclic aromatic tetracarboxylic dianhydride. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride include 4,4 '-oxydiphthalic dianhydride, 3',4 '-benzophenone tetracarboxylic dianhydride, and 2,2',3,3 '-benzophenone tetracarboxylic dianhydride, 3',4 '-biphenyl tetracarboxylic dianhydride, 2',3 '-biphenyl tetracarboxylic dianhydride, 3',4,4 '-diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4' - (hexafluoroisopropylidene) diphthalic dianhydride (sometimes described as 6 FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4'- (terephthaloxy) diphthalic dianhydride, 4' - (isophthaloxy) diphthalic dianhydride. Examples of the monocyclic aromatic tetracarboxylic dianhydride include 1,2,4, 5-benzene tetracarboxylic dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic dianhydride include 2,3,6, 7-naphthalene tetracarboxylic dianhydride.

Among these, preferred examples include 4,4 '-oxybisphthalic anhydride, 3',4 '-benzophenone tetracarboxylic dianhydride, 2',3,3 '-benzophenone tetracarboxylic dianhydride, 3',4 '-biphenyl tetracarboxylic dianhydride, 2',3 '-biphenyl tetracarboxylic dianhydride, 3',4,4 '-diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4' - (hexafluoroisopropylidene) diphthalic dianhydride (6 FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4'- (terephthaloxy) diphthalic dianhydride, 4' - (isophthaloxy) diphthalic dianhydride, 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride bis (2, 3-dicarboxyphenyl) methane dianhydride, 4'- (terephthaloyl) diphthalic dianhydride, and 4,4' - (isophthaloyl) diphthalic dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride and 4,4' - (terephthaloyl) diphthalic dianhydride. They may be used singly or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include a cycloalkane tetracarboxylic dianhydride such as 1,2,4, 5-cyclohexane tetracarboxylic dianhydride, 1,2,3, 4-cyclobutane tetracarboxylic dianhydride, 1,2,3, 4-cyclopentane tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, dicyclohexyl-3, 3', 4' -tetracarboxylic dianhydride, and positional isomers thereof. They may be used singly or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3, 4-butanetetracarboxylic dianhydride, and 1,2,3, 4-pentanetetracarboxylic dianhydride, which may be used alone or in combination of two or more. In addition, cyclic aliphatic tetracarboxylic dianhydrides and acyclic aliphatic tetracarboxylic dianhydrides may be used in combination.

Among the above tetracarboxylic dianhydrides, from the viewpoints of high surface hardness, high transparency, high flexibility, high flex resistance, and low coloring of the optical film, preferably 4,4 '-oxybisphthalic dianhydride, 3',4 '-benzophenone tetracarboxylic dianhydride, 3',4,4 '-biphenyltetracarboxylic dianhydride, 2',3 '-biphenyltetracarboxylic dianhydride, 3',4,4 '-diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 4' - (hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof, more preferably 3,3', 4' -biphenyl tetracarboxylic dianhydride and 4,4'- (hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof, still more preferably 4,4' - (hexafluoroisopropylidene) diphthalic dianhydride (6 FDA).

As a means ofThe dicarboxylic acid compound used for the production of the resin is preferably terephthalic acid, 4' -oxybenzoic acid or an acid chloride compound thereof. In addition to terephthalic acid, 4' -oxybenzoic acid, or their acid chloride compounds, other dicarboxylic acid compounds may also be used. Examples of the other dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and acid chloride compounds and acid anhydrides which are analogues thereof, and two or more of these compounds may be used in combination. Specific examples thereof include isophthalic acid; naphthalene dicarboxylic acid; 4,4' -biphenyl dicarboxylic acid; 3,3' -biphenyl dicarboxylic acid; dicarboxylic acid compound of chain hydrocarbon having 8 or less carbon atoms and 2 benzoic acids each having a single bond, -CH ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -or phenylene linked compounds and their acid chloride compounds. Specifically, 4 '-oxybis (benzoyl chloride) and terephthaloyl chloride are preferable, and 4,4' -oxybis (benzoyl chloride) and terephthaloyl chloride are more preferable to be used in combination.

The polyimide resin may be one obtained by reacting a tetracarboxylic acid, a tricarboxylic acid, and anhydrides and derivatives thereof, in addition to the tetracarboxylic acid compound, within a range that does not impair the physical properties of the optical film.

Examples of the tetracarboxylic acid include water adducts of anhydrides of the above-mentioned tetracarboxylic acid compounds.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acid, aliphatic tricarboxylic acid, and acid chloride compounds and acid anhydrides which are analogues thereof, and two or more kinds of the tricarboxylic acid compounds and the acid anhydrides may be used in combination. Specific examples include: anhydrides of 1,2, 4-benzene tricarboxylic acid; 2,3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; phthalic anhydride and benzoic acid through single bond, -O-, -CH ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -or phenylene linked compounds.

In the production of the resin, the amount of the diamine compound, the tetracarboxylic acid compound and/or the dicarboxylic acid compound to be used may be appropriately selected depending on the desired ratio of each structural unit of the polyimide-based resin.

In the production of the resin, the reaction temperature of the diamine compound, the tetracarboxylic acid compound, and the dicarboxylic acid compound is not particularly limited, and is, for example, 5 to 350 ℃, preferably 20 to 200 ℃, and more preferably 25 to 100 ℃. The reaction time is also not particularly limited, and is, for example, about 30 minutes to 10 hours. The reaction may be carried out under an inert atmosphere or under reduced pressure, as required. In a preferred embodiment, the reaction is carried out under an atmosphere of normal pressure and/or inert gas while stirring. In addition, the reaction is preferably carried out in a solvent inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include alcohol solvents such as water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ -butyrolactone, γ -valerolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvents), and the like. Among these, an amide-based solvent can be preferably used from the viewpoint of solubility.

In the imidization step in the production of the polyimide-based resin, imidization may be performed in the presence of an imidization catalyst. Examples of the imidization catalyst include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; alicyclic amines (monocyclic) such as N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine and N-propylhexahydroazepine; alicyclic amines (polycyclic) such as azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane, and azabicyclo [3.2.2] nonane; and aromatic amines such as pyridine, 2-picoline (2-picoline), 3-picoline (3-picoline), 4-picoline (4-picoline), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-lutidine, 2,4, 6-trimethylpyridine, 3, 4-cyclopentenopyridine, 5,6,7, 8-tetrahydroisoquinoline, and isoquinoline. In addition, from the viewpoint of facilitating imidization, it is preferable to use an acid anhydride together with an imidization catalyst. The acid anhydride may be a conventional acid anhydride used in imidization reaction, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic acid anhydrides such as phthalic anhydride.

The polyimide-based resin and the polyamide-based resin can be separated (separated and purified) by a conventional method, for example, filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a separation method combining these, and preferably, a large amount of alcohol such as methanol is added to a reaction solution containing a transparent polyamide-imide resin to precipitate the resin, followed by concentration, filtration, drying, and the like.

< sodium-containing component >

The optical film of the present invention contains a sodium-containing component selected from the group consisting of a sodium atom-containing compound, sodium, and sodium ions. The content of the sodium-containing component in the optical film of the present invention is not limited as long as the ionic strength (I _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) The amount of the polyimide resin is not particularly limited as long as it is 0.2 or more, and the amount of the polyimide resin (I) is not particularly limited according to the type of the polyimide resin contained in the optical film _Na /I _CH3 ) The setting may be performed so as to fall within a predetermined range. For example, the content of the sodium-containing component in the varnish for producing the optical film of the present invention is preferably 0.002 mass% or more, more preferably 0.004 mass% or more, and further, from the viewpoint of easiness of improvement of the elastic modulus of the optical film, relative to the total amount of the polyimide-based resin and/or polyamide-based resin contained in the varnish The content is preferably 0.01 mass% or more, more preferably 0.02 mass% or more, still more preferably 0.03 mass% or more, and particularly preferably 0.04 mass% or more. The upper limit of the content of the sodium-containing component in the varnish for producing the optical film of the present invention is preferably 1 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, relative to the total amount of the polyimide-based resin and/or polyamide-based resin contained in the varnish, from the viewpoint of easy obtaining of a homogeneous film. In addition, the content of the sodium-containing component in the optical film of the present invention is preferably 0.002 mass% or more, more preferably 0.004 mass% or more, still more preferably 0.01 mass% or more, still more preferably 0.02 mass% or more, still more preferably 0.03 mass% or more, and particularly preferably 0.04 mass% or more, with respect to the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the optical film, from the viewpoint of easiness of improving the elastic modulus of the optical film. The upper limit of the content of the sodium-containing component in the optical film of the present invention is preferably 1 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, relative to the total amount of the polyimide-based resin and/or polyamide-based resin contained in the optical film, from the viewpoint of easy uniformity of the film. The content of the sodium-containing component relative to the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the optical film may be measured by an optical method such as infrared absorption spectroscopy, or the content of the varnish used in the production of the optical film may be used as the content of the optical film. In the case of using a compound containing a sodium atom as a sodium-containing component, the compound may be decomposed or the like during the production of the optical film within a range that does not impair the effects of the present invention.

The kind of the compound containing a sodium atom is not particularly limited. When an optical film is produced using a resin composition (also referred to as a "varnish") containing at least a polyimide resin and/or a polyamide resin and a solvent, the compound containing a sodium atom is preferably an organic sodium salt from the viewpoint of easy dissolution of the component in the solvent of the varnish and easy inclusion of the component in the optical film. Examples of the organic sodium salt include sodium alkoxides having 1 to 6 carbon atoms. The compound containing a sodium atom added to the resin composition is not necessarily contained in the optical film of the present invention in the form of, for example, an organic sodium salt, and may be formed into other salts in the final optical film by, for example, hydrolysis with moisture, alcohol, or the like that may be contained in the resin composition, ion exchange reaction with other salts, or the like, or may be contained in the form of sodium or sodium ions.

< additive >)

The optical film of the present invention may contain a filler. Examples of the filler include organic particles and inorganic particles, and preferably include inorganic particles. Examples of the inorganic particles include metal oxide particles such as silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium Tin Oxide (ITO), antimony oxide, and cerium oxide, and metal fluoride particles such as magnesium fluoride and sodium fluoride. The filler is preferably silica particles, zirconia particles or alumina particles, more preferably silica particles, from the viewpoint of easy improvement of the elastic modulus of the optical film and easy improvement of the impact resistance of the optical film. These fillers may be used singly or in combination of two or more.

The filler (preferably silica particles) has an average primary particle diameter of 1nm or more, preferably 5nm or more, more preferably 10nm or more, further preferably 15nm or more, particularly preferably 20nm or more, preferably 100nm or less, more preferably 90nm or less, further preferably 80nm or less, further preferably 70nm or less, particularly preferably 60nm or less, particularly preferably 50nm or less, and particularly preferably 40nm or less. When the average primary particle diameter of the silica particles is within the above range, aggregation of the silica particles is easily suppressed, and the optical properties of the obtained optical film are improved. The average primary particle diameter of the filler can be measured by the BET method. The primary particle diameter (average primary particle diameter) may be measured by image analysis using a Transmission Electron Microscope (TEM) or a Scanning Electron Microscope (SEM).

When the optical film of the present invention contains a filler (preferably silica particles), the content of the filler is usually 0.1 part by mass or more, preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, still more preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, preferably 60 parts by mass or less, relative to 100 parts by mass of the optical film. When the content of the filler is not less than the lower limit, the elastic modulus of the obtained optical film is easily increased. When the content of the filler is not more than the upper limit, the optical properties of the optical film can be easily improved.

The optical film of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber may be appropriately selected from substances commonly used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400nm or less. Examples of the ultraviolet absorber include at least one compound selected from the group consisting of benzophenone-based compounds, salicylate-based compounds, benzotriazole-based compounds, and triazine-based compounds. The ultraviolet absorber may be used alone or in combination of two or more. Since deterioration of the resin can be suppressed by incorporating the ultraviolet absorber into the optical film, visibility can be improved when the obtained optical film is applied to an image display device or the like. In the present specification, the term "compound" refers to a derivative of a compound to which the "compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a parent skeleton and a substituent bonded to the benzophenone.

When the optical film contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 3 parts by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, further preferably 6 parts by mass or less, relative to 100 parts by mass of the optical film. The appropriate content varies depending on the ultraviolet absorber used, and when the content of the ultraviolet absorber is adjusted so that the light transmittance at 400nm becomes about 20 to 60%, the light resistance of the optical film is improved and the transparency is easily improved.

The optical film of the present invention may further contain additives other than the filler and the ultraviolet absorber. Examples of the other additives include antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, leveling agents, and the like. When the other additive is contained, the content thereof may be preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and still more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the optical film.

(method for producing optical film)

The method for producing the optical film of the present invention is not particularly limited, and may be, for example, a method comprising the steps of:

(a) A step of preparing a resin composition (hereinafter, also referred to as a "varnish") containing at least one resin selected from the group consisting of the polyimide-based resin and the polyamide-based resin, a sodium atom-containing compound, sodium and/or sodium ions, and a solvent (varnish preparation step);

(b) A step of applying a varnish to a support material to form a coating film (coating step); and

(c) And a step of forming an optical film by drying the applied liquid (coating film) (optical film forming step).

The present invention also provides a resin composition suitable for producing the optical film of the present invention, the resin composition comprising at least: at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins; at least one sodium-containing component selected from the group consisting of a sodium atom-containing compound, sodium, and sodium ions; and (3) a solvent.

In the varnish preparation step, the polyimide-based resin and/or the polyamide-based resin and the sodium-containing component are dissolved in a solvent, and if necessary, the above-mentioned additives such as a filler and an ultraviolet absorber are added thereto, and the mixture is stirred and mixed to prepare a varnish. In the case of using silica particles as a filler, a silica sol obtained by replacing a dispersion of a silica sol containing silica particles with a solvent (for example, a solvent used in the preparation of a varnish described below) capable of dissolving the resin may be added to the resin.

The sodium-containing component is not particularly limited as long as it is a component capable of containing at least one selected from the group consisting of a compound containing a sodium atom, sodium and sodium ions in the optical film of the present invention, and is preferably a compound containing a sodium atom, more preferably an organic sodium salt, from the viewpoint of easy dissolution of the component in a solvent of a varnish and easy inclusion of the component in the optical film. Examples of the organic sodium salt include sodium alkoxides having 1 to 6 carbon atoms. The sodium-containing component contained in the varnish may be one component, or two or more components may be combined.

The content of the sodium-containing component contained in the resin composition is preferably 0.002 mass% or more, more preferably 0.004 mass% or more, still more preferably 0.01 mass% or more, still more preferably 0.02 mass% or more, particularly preferably 0.03 mass% or more, and particularly preferably 0.04 mass% or more, with respect to the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the resin composition, from the viewpoint of easiness of improving the elastic modulus of the optical film. The upper limit of the content of the sodium-containing component in the resin composition of the present invention is preferably 1.0 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, based on the total amount of the polyimide-based resin and/or polyamide-based resin contained in the resin composition, from the viewpoints of the adjustability of the varnish viscosity and film-forming property. When the content of the sodium-containing component is not more than the upper limit, the varnish viscosity is not excessively high, and the solid content of the resin in the varnish is easily increased, so that the film forming property is easily improved.

The solvent used in the preparation of the varnish is not particularly limited as long as it can dissolve the resin. Examples of the solvent include: amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; lactone solvents such as gamma-butyrolactone (GBL) and gamma-valerolactone; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvents). Among these, an amide-based solvent or a lactone-based solvent is preferable. These solvents may be used singly or in combination of two or more. The varnish may contain water, an alcohol-based solvent, a ketone-based solvent, an acyclic ester-based solvent, an ether-based solvent, or the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 15% by mass.

In the coating step, a varnish is applied to the support material by a known coating method to form a coating film. Examples of known coating methods include bar coating, reverse coating, roll coating such as gravure coating, die coating, comma coating, lip coating, spin coating, screen coating, spray coating, dip coating, spray coating, and cast molding.

In the film forming step, the coating film is dried and peeled off from the support material, whereby an optical film can be formed. After the peeling, a step of drying the optical film may be further provided. The drying of the coating film can be generally carried out at a temperature of 50 to 350 ℃. Drying of the coating film may be performed under an inert atmosphere or under reduced pressure, as required.

Examples of the support material include SUS plates when the support material is a metal type, and PET films, PEN films, polyamide resin films, other polyimide resin films, cyclic Olefin Polymer (COP) films, acrylic films, and the like when the support material is a resin type. Among them, PET films, COP films, and the like are preferable from the viewpoint of excellent smoothness and heat resistance, and PET films are more preferable from the viewpoint of adhesion to optical films and cost.

(functional layer)

More than 1 functional layer may be laminated on at least one surface of the optical film of the present invention. Examples of the functional layer include an ultraviolet absorbing layer, a hard coat layer, an undercoat layer, a gas barrier layer, an adhesive layer, a color tone adjusting layer, and a refractive index adjusting layer. The functional layer may be used alone or in combination of two or more. In the case where the optical film has the functional layer, measurement by TOF-SIMS is preferably performed on a cross section of the optical film.

The ultraviolet absorbing layer is a layer having an ultraviolet absorbing function, and is composed of a main material selected from the group consisting of an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, and an ultraviolet absorber dispersed in the main material.

The adhesive layer has an adhesive function and has a function of adhering the optical film to other members. As a material for forming the adhesive layer, a conventionally known material can be used. For example, a thermosetting resin composition or a photocurable resin composition may be used. In this case, the resin composition can be polymerized and cured by supplying energy afterwards.

The adhesive layer may be a layer called a pressure-sensitive adhesive (Pressure Sensitive Adhesive, PSA) that is bonded to the object by pressing. The pressure-sensitive adhesive may be an adhesive which is "a substance having adhesiveness at ordinary temperature and adhering to an adherend under light pressure" (JIS K6800), or may be a capsule-type adhesive which is "an adhesive capable of maintaining stability until the film is broken by an appropriate means (pressure, heat, etc.) (JIS K6800) in which a specific component is contained in a protective film (microcapsule).

The tone adjustment layer is a layer having a tone adjustment function, and is a layer capable of adjusting a laminate including an optical film to a target tone. The color tone adjusting layer is, for example, a layer containing a resin and a colorant. Examples of the colorant include inorganic pigments such as titanium oxide, zinc oxide, iron oxide red, titanium oxide-based calcined pigments, ultramarine blue, cobalt aluminate, and carbon black; organic pigments such as azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, perylene-based compounds, isoindolinone-based compounds, phthalocyanine-based compounds, quinophthalone-based compounds, petrolatum (threne) -based compounds, and diketopyrrolopyrrole-based compounds; a body pigment such as barium sulfate and calcium carbonate; basic dyes, acid dyes, mordant dyes, and the like.

The refractive index adjusting layer is a layer having a function of adjusting a refractive index, and is, for example, a layer having a refractive index different from that of the optical film and capable of imparting a predetermined refractive index to the optical laminate. The refractive index adjusting layer may be, for example, a resin layer containing a resin appropriately selected and optionally a pigment, or may be a metal thin film. Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The pigment may have an average primary particle diameter of 0.1 μm or less. By setting the average primary particle diameter of the pigment to 0.1 μm or less, diffuse reflection of light transmitted through the refractive index adjusting layer can be prevented, and a decrease in transparency can be prevented. Examples of the metal used for the refractive index adjusting layer include metal oxides or metal nitrides such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride.

The optical film of the present invention may be a single layer or a laminate, and for example, the optical film produced in the above manner may be used as it is or may be used in the form of a laminate with other films. Ion intensity (I) of Na obtained by time-of-flight secondary ion mass spectrometry _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) The optical film of the present invention having an elastic modulus of 0.2 or more has impact resistance, and is useful as an optical film in an image display device or the like.

In a preferred embodiment of the present invention, the optical film of the present invention is useful as a front panel of an image display device, particularly a front panel (window film) of a flexible display device. The flexible display device includes, for example, a flexible functional layer and an optical film that is laminated with the flexible functional layer and functions as a front panel. That is, the front panel of the flexible display device is arranged on the viewing side above the flexible functional layer. The front panel has a function of protecting the flexible functional layer.

Examples of the image display device include a television, a smart phone, a mobile phone, a car navigation system, a tablet computer, a portable game machine, electronic paper, an indicator, a bulletin board, a timepiece, and a wearable device such as a smart watch. As the flexible display device, all image display devices having flexible characteristics can be cited.

Flexible display device

The present invention also provides a flexible display device provided with the optical film of the present invention. The flexible display device includes a laminate for a flexible display device and an organic EL display panel, and the laminate for a flexible display device is disposed on the viewing side with respect to the organic EL display panel and is configured to be bendable. The laminate for a flexible display device may contain the optical film (window film), the circularly polarizing plate, and the touch sensor of the present invention, and the lamination order thereof is arbitrary, but it is preferable to laminate the window film, the circularly polarizing plate, and the touch sensor in this order, or the window film, the touch sensor, and the circularly polarizing plate in this order from the viewing side. When the circularly polarizing plate is present on the viewing side of the touch sensor, the pattern of the touch sensor is not easily recognized, and the visibility of the display image is improved, which is preferable. The components may be laminated using an adhesive, a binder, or the like. The touch panel may further include a light shielding pattern formed on at least one surface of any one of the window film, the circularly polarizing plate, and the touch sensor.

[ Window film ]

The window film is disposed on the viewing side of the flexible image display device and plays the following roles: other components are protected from external impact, environmental changes such as temperature and humidity. Conventionally, glass has been used as such a protective layer, but a window film in a flexible image display device is not as rigid and hard as glass, but has flexible characteristics. The optical film of the present invention may be used as a window film, or may include a flexible transparent substrate such as the film and a hard coat layer on at least one surface.

(transparent substrate)

The transmittance of the transparent substrate in the visible light region is usually 70% or more, preferably 80% or more. As the transparent substrate, an optical film containing a polyimide resin and/or a polyamide resin according to the present invention is preferably used. The optical film of the present invention may be dispersed with inorganic particles such as silica, organic fine particles, rubber particles, and the like. Further, the composition may contain a colorant such as a pigment or a dye, a fluorescent whitening agent, a dispersant, a plasticizer, a heat stabilizer, a light stabilizer, an infrared absorber, an ultraviolet absorber, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like. The thickness of the transparent substrate is usually 5 to 200. Mu.m, preferably 20 to 100. Mu.m.

(hard coat)

In the window film, a hard coat layer may be provided on at least one surface of the transparent substrate. The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100. Mu.m. When the thickness of the hard coat layer is within the above range, sufficient scratch resistance can be ensured, and further, bending resistance is not easily reduced, and a problem of occurrence of curling due to cure shrinkage tends not to occur.

The hard coat layer may be formed by curing a hard coat layer composition containing a reactive material capable of forming a crosslinked structure by irradiation with active energy rays or application of heat energy, and is preferably a layer based on irradiation with active energy rays. The active energy ray is defined as an energy ray capable of decomposing a compound that generates an active species to generate an active species, and includes visible light, ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays, electron rays, and the like, and preferably includes ultraviolet rays. The hard coat composition contains at least one polymer of a radical polymerizable compound and a cation polymerizable compound.

The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound may be a functional group capable of undergoing radical polymerization, and examples thereof include a group containing a carbon-carbon unsaturated double bond, specifically, a vinyl group, a (meth) acryl group, and the like. In the case where the radical polymerizable compound has 2 or more radical polymerizable groups, the radical polymerizable groups may be the same or different from each other. The number of radical polymerizable groups in 1 molecule of the radical polymerizable compound is preferably 2 or more from the viewpoint of improving the hardness of the hard coat layer. The radically polymerizable compound is preferably a compound having a (meth) acryloyl group, and specifically, a compound called a multifunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in 1 molecule, from the viewpoint of the high reactivity; the oligomer having a molecular weight of several (meth) acryloyl groups in a molecule, which is called epoxy (meth) acrylate, urethane (meth) acrylate, or polyester (meth) acrylate, is preferably one or more selected from the group consisting of epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate.

The cation polymerizable compound is a compound having a cation polymerizable group such as an epoxy group, an oxetanyl group, a vinyl ether group, or the like. The number of the cation polymerizable groups in 1 molecule of the cation polymerizable compound is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.

Among the above cationically polymerizable compounds, compounds having at least one of an epoxy group and an oxetane group as a cationically polymerizable group are preferable. From the viewpoint of small shrinkage accompanying the polymerization reaction, cyclic ether groups such as epoxy groups and oxetanyl groups are preferable. In addition, the compound having an epoxy group in a cyclic ether group has the following advantages: compounds of various structures are readily available; the durability of the obtained hard coating is not adversely affected; compatibility with the radical polymerizable compound is also easily controlled. In addition, the oxetanyl group in the cyclic ether group has the following advantages over the epoxy group: the polymerization degree is easy to increase; the toxicity is low; accelerating the network formation rate obtained from the cationically polymerizable compound of the obtained hard coat layer; even in the region where the radical polymerizable compound is mixed, an independent network is formed so that the unreacted monomer does not remain in the film; etc.

Examples of the cationically polymerizable compound having an epoxy group include: an alicyclic epoxy resin obtained by epoxidizing a polyglycidyl ether of a polyhydric alcohol having an alicyclic ring or a compound containing a cyclohexene ring or a cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or a peroxy acid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyols or alkylene oxide adducts, polyglycidyl esters of aliphatic long-chain polybasic acids, homopolymers and copolymers of glycidyl (meth) acrylates; glycidyl ethers produced by reacting bisphenol A, bisphenol F, hydrogenated bisphenol A or other phenols, or their alkylene oxide adducts, caprolactone adducts or other derivatives with epichlorohydrin, and bisphenol-derived glycidyl ether type epoxy resins such as Novolac epoxy resins, and the like.

The above hard coat composition may further comprise a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radical polymerization initiators, and cationic polymerization initiators, and may be appropriately selected and used. These polymerization initiators are decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, and undergo radical polymerization and cationic polymerization.

The radical polymerization initiator may be any initiator capable of releasing a substance that causes radical polymerization by at least either irradiation with active energy rays or heating. Examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, azo compounds such as azobisisobutyronitrile, and the like.

Examples of the active energy ray radical polymerization initiator include a Type1 radical polymerization initiator that generates radicals by decomposition of molecules and a Type2 radical polymerization initiator that generates radicals by hydrogen abstraction reaction in the presence of a tertiary amine, and these can be used alone or in combination.

The cationic polymerization initiator may be any substance capable of releasing a substance capable of initiating cationic polymerization by at least either irradiation with active energy rays or heating. As the cationic polymerization initiator, an aromatic iodonium salt, an aromatic sulfonium salt, a cyclopentadienyl iron (II) complex or the like can be used. The cationic polymerization initiator can initiate cationic polymerization by either or both of irradiation with active energy rays and heating depending on the structure.

The polymerization initiator may be contained in an amount of preferably 0.1 to 10 mass% relative to 100 mass% of the whole hard coat layer composition. When the content of the polymerization initiator is within the above range, the curing can be sufficiently performed, the mechanical properties and adhesion of the finally obtained coating film can be made to be within good ranges, and the adhesion failure, cracking phenomenon and curling phenomenon due to curing shrinkage tend to be less likely to occur.

The hard coat composition may further comprise one or more selected from the group consisting of solvents and additives.

The solvent may be any solvent which is known as a solvent for a hard coat composition in the art and which can dissolve or disperse the polymerizable compound and the polymerization initiator, and may be used within a range not to impair the effects of the present invention.

The above additives may further contain inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, and the like.

[ polarizing plate ]

The flexible display device provided with the optical film of the present invention may further comprise a polarizing plate. The circular polarizing plate is a functional layer having a function of transmitting only a right-handed or left-handed circularly polarized light component by laminating a λ/4 retardation plate on a linear polarizing plate. For example, can be used to: the external light is converted into right circularly polarized light, and the external light reflected by the organic EL panel into left circularly polarized light is blocked, and only the light-emitting component of the organic EL is transmitted, thereby suppressing the influence of the reflected light, and making it easy to view an image. In order to realize the circularly polarized light function, the absorption axis of the linear polarizing plate and the slow axis of the λ/4 retardation plate should be 45 ° in theory, but in practical application, 45±10°. The linear polarizing plate and the λ/4 retardation plate do not necessarily have to be stacked adjacently, as long as the relationship between the absorption axis and the slow axis satisfies the aforementioned range. It is preferable to achieve complete circularly polarized light at full wavelength, but this is not necessarily the case in practical applications, and thus circular polarizing plates in the present invention also include elliptical polarizing plates. It is also preferable to further laminate a lambda/4 phase difference film on the viewing side of the linear polarizing plate to convert the outgoing light into circularly polarized light, thereby improving visibility in a state where polarized sunglasses are worn.

The linear polarizing plate is a functional layer having the following functions: light vibrating in the transmission axis direction passes through but blocks polarized light of a vibrating component perpendicular thereto. The linear polarizing plate may be a single linear polarizer, or may have a structure including a linear polarizer and a protective film attached to at least one surface thereof. The thickness of the linear polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness is within the above range, flexibility tends to be less likely to decrease.

The linear polarizer may be a film type polarizer manufactured by dyeing and stretching a polyvinyl alcohol (PVA) based film. Polarizing performance can be exhibited by adsorbing a dichroic dye such as iodine to a PVA film oriented by stretching or by stretching the film in a state of being adsorbed to PVA to orient the dichroic dye. The film polarizer may be produced by swelling, crosslinking with boric acid, washing with an aqueous solution, drying, and the like. The stretching and dyeing steps may be performed as a PVA-based film alone or in a laminate with another film such as polyethylene terephthalate. The thickness of the PVA film used is preferably 10 to 100. Mu.m, and the stretching ratio is preferably 2 to 10 times.

In addition, as another example of the polarizer, a liquid crystal coated polarizer formed by coating a liquid crystal polarizing composition may be used. The liquid crystal polarizing composition may contain a liquid crystal compound and a dichroic dye compound. The liquid crystalline compound is preferable because it has a property of exhibiting a liquid crystal state, and particularly, it can exhibit a high polarizing performance when it has a high-order alignment state such as smectic state. In addition, it is also preferable that the liquid crystalline compound has a polymerizable functional group.

The dichroic dye is a dye which exhibits dichroism in conjunction with the alignment of the liquid crystal compound, and may have liquid crystallinity or may have a polymerizable functional group. Any one of the compounds in the liquid crystal polarizing composition has a polymerizable functional group.

The liquid crystal polarizing composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like.

The liquid crystal polarizing layer is manufactured by the following method: the liquid crystal polarizing composition is coated on the alignment film to form a liquid crystal polarizing layer.

The liquid crystal polarizing layer can be formed to a thin thickness as compared with the film type polarizer. The thickness of the liquid crystal polarizing layer may be preferably 0.5 to 10. Mu.m, more preferably 1 to 5. Mu.m.

The above-mentioned orientation film can be produced, for example, by the following means: the alignment film-forming composition is applied to a substrate, and alignment is imparted by rubbing, polarized light irradiation, or the like. The above-mentioned alignment film-forming composition may contain a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like in addition to the alignment agent. Examples of the orientation agent include polyvinyl alcohol, polyacrylate, polyamide acid, and polyimide. In the case of applying photo-alignment, an alignment agent containing a cinnamate group (cinnamate group) is preferably used. The weight average molecular weight of the polymer used as the alignment agent may be about 10,000 ～ 1,000,000. The thickness of the alignment film is preferably 5 to 10,000nm, more preferably 10 to 500nm, from the viewpoint of alignment control force. The liquid crystal polarizing layer may be laminated by being peeled from a substrate and transferred, or the substrate may be directly laminated. The above-mentioned substrate also preferably functions as a transparent substrate for a protective film, a retardation plate, and a window film.

The protective film may be a transparent polymer film, and specifically, the polymer film used may be a film of the following materials: polyolefins such as polyethylene, polypropylene, polymethylpentene, and cycloolefin derivatives having a monomer unit containing norbornene or cycloolefin; (modified) celluloses such as diacetyl cellulose, triacetyl cellulose, and propionyl cellulose; acrylic acids such as methyl methacrylate (co) polymers; polystyrene such as styrene (co) polymer; acrylonitrile-butadiene-styrene copolymers; acrylonitrile-styrene copolymers; ethylene-vinyl acetate copolymers; polyvinyl chloride; polyvinylidene chloride; polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyarylate; polyamides such as nylon; polyimides; polyamideimides; polyetherimides; polyethersulfones; polysulfones; polyvinyl alcohols; polyvinyl acetals; polyurethanes; epoxy resins and the like are preferable from the viewpoint of excellent transparency and heat resistance, and polyamide, polyamideimide, polyimide, polyester, olefin, acrylic or cellulose films are exemplified. These polymers may be used alone or in combination of two or more. These films may be used in an unstretched state or in the form of uniaxially or biaxially stretched films. Cellulose-based films, olefin-based films, acrylic-based films, and polyester-based films are preferable. The protective film may be a coated protective film obtained by coating and curing a cationic curing composition such as an epoxy resin or a radical curing composition such as an acrylate. If necessary, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, an optical brightening agent, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like can be contained. The thickness of the protective film may be 200 μm or less, and preferably 1 to 100 μm. When the thickness of the protective film is within the above range, the flexibility of the protective film is not easily reduced.

The λ/4 retardation plate is a film that imparts a phase difference of λ/4 in a direction (in-plane direction of the film) orthogonal to the traveling direction of the incident light. The lambda/4 retardation plate may be a stretched retardation plate produced by stretching a polymer film such as a cellulose film, an olefin film, or a polycarbonate film. Phase difference modifiers, plasticizers, ultraviolet absorbers, infrared absorbers, colorants (pigments, dyes, and the like), fluorescent brighteners, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants, lubricants, solvents, and the like may be contained as necessary. The thickness of the stretched phase difference plate may be 200 μm or less, and preferably 1 to 100 μm. When the thickness is within the above range, the flexibility of the film tends to be less likely to decrease.

In addition, another example of the λ/4 retardation plate may be a liquid crystal coated retardation plate formed by coating a liquid crystal composition. The liquid crystal composition contains a liquid crystalline compound having the following properties: showing a liquid crystal state of nematic, cholesteric, smectic, or the like. Any one of the compounds in the liquid crystal composition including the liquid crystalline compound has a polymerizable functional group. The liquid crystal coated retardation plate may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like. The liquid crystal coated retardation plate can be produced by: the liquid crystal composition was applied to the alignment film and cured as described in the liquid crystal polarizing layer, to form a liquid crystal retardation layer. The liquid crystal coating type retardation plate can be formed to have a smaller thickness than the stretching type retardation plate. The thickness of the liquid crystal polarizing layer may be generally 0.5 to 10. Mu.m, preferably 1 to 5. Mu.m. The liquid crystal coated retardation plate may be laminated by being peeled from a substrate and then transferred, or may be laminated directly on the substrate. The above-mentioned substrate also preferably functions as a transparent substrate for a protective film, a retardation plate, and a window film.

In general, the following materials are more: the shorter the wavelength, the greater the birefringence; the longer the wavelength, the smaller the birefringence is exhibited. In this case, since the phase difference of λ/4 cannot be achieved in the entire visible light region, the following is often designed: the in-plane retardation, which is lambda/4 around 560nm with high visibility, is 100 to 180nm (preferably 130 to 150 nm). When an inverse dispersion λ/4 retardation plate using a material having a wavelength dispersion characteristic of a birefringence opposite to that of the material is used, visibility can be improved, and thus it is preferable. As such a material, a material described in japanese patent application laid-open No. 2007-232873 and the like is preferably used in the case of a stretched phase difference plate, and a material described in japanese patent application laid-open No. 2010-30979 is also preferably used in the case of a liquid crystal coated phase difference plate.

In addition, as another method, a technique of obtaining a wide-band lambda/4 phase difference plate by combining it with a lambda/2 phase difference plate is known (Japanese patent application laid-open No. 10-90521). The lambda/2 phase difference plate is also manufactured by the same material method as the lambda/4 phase difference plate. The combination of the stretching type retardation plate and the liquid crystal coating type retardation plate is preferable because the thickness can be reduced when the liquid crystal coating type retardation plate is used.

In order to improve visibility in the oblique direction, a method of laminating a positive C plate is also known for the circularly polarizing plate (japanese patent application laid-open No. 2014-224837). The positive C plate may be a liquid crystal coated type retardation plate or a stretched type retardation plate. The phase difference in the thickness direction is-200 to-20 nm, preferably-140 to-40 nm.

[ touch sensor ]

The flexible display device including the optical film of the present invention may further include a touch sensor. The touch sensor is used as an input means. As the touch sensor, various methods such as a resistive film method, a surface elastic wave method, an infrared method, an electromagnetic induction method, and a capacitance method are proposed, and any method may be used. Among them, the electrostatic capacitance method is preferable. Capacitive touch sensors are classified into active regions and inactive regions located in the outer contour of the active regions. The active region is a region corresponding to a region (display portion) on the display panel where a screen is displayed, and the inactive region is a region corresponding to a region (non-display portion) in the display device where a screen is not displayed, in response to a touch by a user. The touch sensor may include: a substrate having a flexible characteristic; a sensing pattern formed in an active region of the substrate; and each sensing line formed in the inactive region of the substrate and connecting the sensing pattern to an external driving circuit via a pad (pad) portion. As the substrate having the flexible property, the same material as the polymer film can be used. In terms of suppressing cracking of the touch sensor, the toughness of the substrate of the touch sensor is preferably 2,000mpa% or more. More preferably, the toughness may be 2,000 to 30,000MPa%. Here, toughness is defined as: in a Stress-strain curve (Stress-strain) obtained by a stretching experiment of a polymer material, the area of the lower part of the curve up to the breaking point is measured.

The sensing pattern may include a 1 st pattern formed in a 1 st direction and a 2 nd pattern formed in a 2 nd direction. The 1 st pattern and the 2 nd pattern are arranged in different directions from each other. The 1 st pattern and the 2 nd pattern are formed in the same layer, and each pattern must be electrically connected in order to sense a touch location. The 1 st pattern is a form in which the respective cell patterns are connected to each other via a joint, but the 2 nd pattern is a structure in which the respective cell patterns are separated from each other in an island form, and thus, in order to electrically connect the 2 nd pattern, a separate bridge electrode is required. The sensing pattern may use a known transparent electrode material. For example, indium Tin Oxide (ITO), indium Zinc Oxide (IZO), zinc oxide (ZnO), indium Zinc Tin Oxide (IZTO), indium Gallium Zinc Oxide (IGZO), cadmium Tin Oxide (CTO), PEDOT (poly (3, 4-ethylenedioxythiophene)), carbon Nanotubes (CNT), graphene, metal wires, or the like may be used alone or in combination of two or more. ITO may be preferably used. The metal used for the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, chromium, and the like. These may be used alone or in combination of two or more.

The bridge electrode may be formed on the insulating layer above the sensing pattern via the insulating layer, and the bridge electrode may be formed on the substrate, on which the insulating layer and the sensing pattern may be formed. The bridge electrode may be formed of the same material as the sensing pattern, or may be formed of a metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of two or more thereof. Since the 1 st pattern and the 2 nd pattern must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridging electrode. The insulating layer may be formed only between the 1 st pattern tab and the bridge electrode, or may be formed to cover the layer of the sensing pattern. In the latter case, the bridge electrode may be connected to the 2 nd pattern via a contact hole formed in the insulating layer. In the touch sensor, as means for appropriately compensating for the difference in transmittance between the patterned region where the pattern is formed and the non-patterned region where the pattern is not formed (specifically, the difference in transmittance due to the difference in refractive index in these regions), an optical adjustment layer may be further included between the substrate and the electrode, and the optical adjustment layer may include an inorganic insulating material or an organic insulating material. The optical adjustment layer may be formed by applying a photocurable composition containing a photocurable organic binder and a solvent to a substrate. The above-mentioned photocurable composition may further comprise inorganic particles. The refractive index of the optical adjustment layer can be increased by the inorganic particles.

The photocurable organic binder may contain, for example, a copolymer of each monomer such as an acrylic monomer, a styrene monomer, and a carboxylic acid monomer. The photocurable organic binder may be a copolymer containing, for example, repeating units that are different from each other, such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.

The inorganic particles may include, for example, zirconia particles, titania particles, alumina particles, and the like. The photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing auxiliary agent.

[ adhesive layer ]

The layers (window film, circularly polarizing plate, touch sensor) forming the laminate for a flexible image display device may be bonded by an adhesive. As the adhesive, conventionally used adhesives such as an aqueous adhesive, an organic solvent adhesive, a solvent-free adhesive, a solid adhesive, a solvent-volatile adhesive, a moisture-curable adhesive, a heat-curable adhesive, an anaerobic-curable adhesive, an active energy ray-curable adhesive, a curing agent-mixed adhesive, a hot-melt adhesive, a pressure-sensitive adhesive (adhesive), and a rewet adhesive can be used. Among them, an aqueous solvent-volatile adhesive, an active energy ray-curable adhesive, and an adhesive are preferably used. The thickness of the adhesive layer may be appropriately adjusted depending on the required adhesive force or the like, and is, for example, 0.01 to 500. Mu.m, preferably 0.1 to 300. Mu.m. The laminate for a flexible image display device may have a plurality of adhesive layers, and the thicknesses of the adhesive layers and the types of adhesives used may be the same or different.

As the above-mentioned aqueous solvent-volatile adhesive, a polyvinyl alcohol polymer, a water-soluble polymer such as starch, a polymer in a water-dispersed state such as an ethylene-vinyl acetate emulsion or a styrene-butadiene emulsion can be used as a main polymer. In addition to water and the main agent polymer, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, and the like may be blended. In the case of bonding by using the above-mentioned aqueous solvent-volatile adhesive, the above-mentioned aqueous solvent-volatile adhesive is injected into the layer to be bonded, and the layer to be bonded is bonded and then dried, whereby the adhesiveness can be imparted. The thickness of the adhesive layer when the aqueous solvent-volatile adhesive is used may be 0.01 to 10. Mu.m, preferably 0.1 to 1. Mu.m. In the case of using the above aqueous solvent-volatile adhesive for forming the plurality of layers, the thickness of each layer and the kind of the adhesive may be the same or different.

The active energy ray-curable adhesive may be formed by curing an active energy ray-curable composition containing a reactive material capable of forming an adhesive layer by irradiation with active energy rays. The active energy ray-curable composition may contain at least one polymer selected from the group consisting of radical-polymerizable compounds and cation-polymerizable compounds similar to the hard coat composition. The radical polymerizable compound may be the same as the hard coat composition, and the same kind of compound as the hard coat composition may be used. The radical polymerizable compound used in the adhesive layer is preferably a compound having an acryl group. In order to reduce the viscosity as an adhesive composition, it is also preferable to contain a monofunctional compound.

The cation polymerizable compound may be the same as the hard coat composition, and the same kind of compound as the hard coat composition may be used. As the cationically polymerizable compound used in the active energy ray-curable composition, an epoxy compound is particularly preferable. In order to reduce the viscosity of the adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

The active energy ray composition may further contain a polymerization initiator. The polymerization initiator may be a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, or the like, and may be appropriately selected and used. These polymerization initiators are decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, and the radical polymerization and the cationic polymerization are performed. An initiator capable of initiating at least either radical polymerization or cationic polymerization by irradiation with active energy rays as in the description of the hard coat composition may be used.

The active energy ray-curable composition may further contain an ion scavenger, an antioxidant, a chain transfer agent, a blocking agent, a thermoplastic resin, a filler, a flow viscosity regulator, a plasticizer, an antifoaming agent, an additive, and a solvent. In the case of bonding by the active energy ray-curable adhesive, bonding can be performed as follows: the active energy ray-curable composition is applied to one or both of the adherend layers, and then bonded, and the adherend layers or both of the adherend layers are cured by irradiation with active energy rays. The thickness of the adhesive layer when the active energy ray-curable adhesive is used may be 0.01 to 20. Mu.m, preferably 0.1 to 10. Mu.m. When the active energy ray-curable adhesive is used for forming a plurality of layers, the thickness of each layer and the type of adhesive used may be the same or different.

The above-mentioned binders are classified into acrylic binders, urethane binders, rubber binders, silicone binders, and the like, depending on the main agent polymer, and may be used. The adhesive may contain, in addition to the main polymer, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, an adhesion imparting agent, a plasticizer, a dye, a pigment, an inorganic filler, and the like. The adhesive layer (adhesive layer) is formed by dissolving and dispersing the components constituting the adhesive in a solvent to obtain an adhesive composition, and applying the adhesive composition to a substrate and then drying the substrate. The adhesive layer may be formed directly or may be transferred to another substrate. In order to cover the adhesive surface before bonding, a release film is also preferably used. The thickness of the adhesive layer when the adhesive is used may be 1 to 500. Mu.m, preferably 2 to 300. Mu.m. In the case where the above adhesive is used for forming a plurality of layers, the thickness of each layer and the kind of the adhesive used may be the same or different.

[ shading Pattern ]

The light shielding pattern may be applied as at least a part of a frame (bezel) or a case of the flexible image display device. The wiring arranged at the edge of the flexible image display device is shielded by a light shielding pattern, so that the wiring is not easily recognized, thereby improving the visibility of the image. The light shielding pattern may be in the form of a single layer or a plurality of layers. The color of the light shielding pattern is not particularly limited, and may have various colors such as black, white, metallic color, and the like. The light shielding pattern may be formed of a pigment for color development, and a polymer such as an acrylic resin, an ester resin, an epoxy resin, polyurethane, or silicone. They may also be used singly or in the form of a mixture of two or more kinds. The light shielding pattern may be formed by various methods such as printing, photolithography, and ink-jet. The thickness of the light shielding pattern is usually 1 to 100. Mu.m, preferably 2 to 50. Mu.m. In addition, it is also preferable to impart a shape such as an inclination in the thickness direction of the light shielding pattern.

Examples

The present invention will be described in further detail with reference to examples. Unless otherwise specified, "%" and "parts" in examples refer to mass% and mass parts, respectively. First, a method for measuring physical property values will be described. The results shown in table 1 are measured according to the following measurement method.

(determination of weight average molecular weight (Mw))

The weight average molecular weight of the resin was measured using Gel Permeation Chromatography (GPC). The preparation method and measurement conditions of the measurement sample are as follows.

(1) Sample preparation method

20mg of the resin was weighed and 10mL of DMF (10 mM lithium bromide) was added to dissolve completely. The solution was filtered through a chromatographic disk (chromatodisk) (pore size 0.45 μm) to prepare a sample solution.

(2) Measurement conditions

The device comprises: HLC-8020GPC

Column: guard column+TSKgel. Alpha. -M (300 mm. Times.7.8 mm diameter). Times.2 roots+alpha. -2500 (300 mm. Times.7.8 mm diameter). Times.1 roots)

Eluent: DMF (10 mM lithium bromide added)

Flow rate: 1.0mL/min.

A detector: RI detector

Column temperature: 40 DEG C

Injection amount: 100 mu L

Molecular weight standard: standard polystyrene

(measurement of total light transmittance)

Full light transmittance of the optical film was measured in accordance with JIS K7105: 1981. the measurement was performed using a full-automatic direct-reading haze computer HGM-2DP manufactured by Suga Test Instruments co.

(measurement of elastic modulus)

The optical film was cut into 10mm×100mm long strips using a dumbbell cutter to obtain test samples. For the elastic modulus of this test sample, an S-S curve was measured using an automatic plotter AG-IS (Autograph AG-IS) manufactured by Shimadzu corporation under conditions of a distance between chucks of 50mm and a stretching speed of 10mm/min, and the elastic modulus (GPa) of the optical film was calculated from the slope in the range of 5 to 20 MPa.

(measurement of thickness)

The optical films obtained in examples and comparative examples were measured for thickness by using an ABS digital display meter (Digimatic Indicator) ("ID-C112 BS" manufactured by Mitsutoyo, inc.).

(determination of time-of-flight secondary ion Mass Spectrometry (TOF-SIMS))

A cross section of an optical film was produced using "Ultra Microtome EM UC6" manufactured by Leica Microsystems (Inc.).

The cross section of the resin film produced was analyzed by TOF-SIMS. The TOF-SIMS device and measurement conditions used in the analysis are as follows.

(1) The device comprises: "TOF.SIMS V" manufactured by ION-TOF Co., ltd,

(2) A first partSecondary ion: bi (Bi) ³⁺⁺

(3) Acceleration voltage of primary ions: 25kV (kV)

(4) Irradiation of ion current: 0.23pA

(5) Measurement conditions: determination of positive and negative ions using beam-focusing (high mass resolution) mode

(6) Measurement range: 200 μm by 200. Mu.m.

Data analysis for TOF-SIMS used SurfaceLab. Mass calibration of the measured data was performed for the assignment of Na ions and CH ₃ The peaks of the ions were each calculated as an integral value of the peak. The integrated value of the peak of Na ion was taken as the ionic strength I of Na _Na Will CH ₃ Integral value of peak of ion as CH ₃ Is the ionic strength I of (C) _CH3 Calculating the ratio I _Na /I _CH3 。

(measurement of viscosity)

The viscosity of the resin composition was measured under the following conditions.

Device name: LVDV-II+Pro (Brookfield Co., ltd.)

Measuring temperature: 25 DEG C

Spindle (spindle): CPE-52

Sample injection amount: 0.8mL

Rotor rotational speed: 3rpm

[ synthetic example: production of Polyamide-imide resin

The nitrogen gas was introduced into a sufficiently dried reaction vessel equipped with a stirrer and a thermometer, and the inside of the vessel was replaced with the nitrogen gas. To this reaction vessel were added 1907.2 parts by mass of dimethylacetamide (DMAc), 111.94 parts by mass of 2,2 '-bis (trifluoromethyl) benzidine (TFMB) and 46.84 parts by mass of 4,4' - (hexafluoroisopropylidene) diphthalic dianhydride (6 FDA) to react.

Then, 10.37 parts by mass of 4,4' -oxybis (benzoyl chloride) (OBBC) and 42.79 parts by mass of terephthaloyl chloride (TPC) were added to react them.

Subsequently, 37.66 parts by mass of acetic anhydride was added thereto, followed by stirring for 15 minutes, then 11.45 parts by mass of 4-methylpyridine was added thereto, and the reaction vessel was heated to 70℃and stirred for 3 hours to obtain a reaction solution.

The reaction solution was cooled, 3794.5 parts by mass of methanol was added thereto, and 1419.4 parts by mass of ion-exchanged water was then added dropwise thereto, whereby a white solid was precipitated. The precipitated white solid was captured by centrifugal filtration and washed with methanol, thereby obtaining a wet cake containing a polyamideimide resin. The wet cake obtained was dried at 78 ℃ under reduced pressure, whereby a powder of a polyamideimide resin was obtained. The weight average molecular weight of the obtained resin was 466,000.

[ production of GBL solution comprising sodium component ]

Sodium ethoxide ethanol solution (manufactured by Wako pure chemical industries, ltd.) containing 20 mass% of sodium ethoxide (NaOEt, sodium atom-containing compound) as a sodium-containing component was diluted with gamma-butyrolactone (GBL) to prepare a NaOEt solution containing sodium ethoxide at a concentration of 0.1 mass%.

[ production of Polyamide-imide resin composition (varnish) ]

The polyamide-imide resin obtained in the synthesis example, GBL, and the NaOEt solution produced as described above were mixed in such amounts that the content of the polyamide-imide resin and the content of NaOEt in each resin composition were as follows, to prepare a polyamide-imide resin composition (varnish) for film formation. The content of the polyamideimide resin in each resin composition was 6.3 mass% relative to the total amount of the polyamideimide resin compositions; the amount of NaOEt in each resin composition was 0 mass%, 0.005 mass%, 0.05 mass%, 0.1 mass%, or 1 mass%, respectively, with respect to the amount of the polyamideimide resin contained in each resin composition.

Examples 1 and 2 and comparative example 3: production of polyimide resin film

The polyamide-imide resin composition (resin composition having a NaOEt content of 0.05 mass%, 0.005 mass% or 0 mass%) produced in the above manner was applied to a smooth surface of a polyester substrate (trade name "A4100" manufactured by Toyobo Co., ltd.) so that the thickness of the self-supporting film became 55 μm using an applicator, dried at 50℃for 30 minutes, dried at 140℃for 15 minutes, and the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200℃for 40 minutes under the atmosphere to obtain a polyamideimide resin film having a thickness of 50. Mu.m. The results of measuring various physical properties of the film are shown in table 1.

TABLE 1

Example 3 and 4: viscosity measurement of polyimide resin composition

The viscosity of the polyamide-imide resin composition obtained in the above manner was measured according to the above measurement method, respectively, with respect to the ratio of the amount of NaOEt to the amount of the polyamide-imide resin of 0 mass%, 0.1 mass%, or 1 mass%. The results obtained are shown in Table 2.

TABLE 2

As shown in Table 1, the ratio (I) of the ionic strength obtained by TOF-SIMS with NaOEt added to the varnish _Na /I _CH3 ) The optical films of examples 1 and 2, which were 0.2 or more, were confirmed to have high elastic moduli. On the other hand, in the case of the optical film of comparative example 1 in which NaOEt was not added to the varnish, a sufficient elastic modulus was not obtained. As shown in table 2, it was confirmed that the viscosity of the resin composition tended to be high by adding the sodium-containing component to the resin composition. The reason why the viscosity of the resin composition is increased by adding the sodium-containing component is not clear, but it is presumed that some interaction occurs between the functional groups in the resin, for example, imide bonds and/or amide bonds, and the sodium-containing component (sodium atom-containing compound, sodium and/or sodium ion). It is considered that such interaction brings about an improvement in the elastic modulus of the obtained optical film, but the examination is not limited to the present invention.

Claims

1. An optical film comprising a polyamideimide resin, wherein the optical film has an ionic strength (I) of Na obtained by time-of-flight secondary ion mass spectrometry _Na ) Relative to CH ₃ The ionic strength (I) _CH3 ) Ratio (I) _Na /I _CH3 ) The elastic modulus of the optical film is more than 0.2, more than 5.0GPa, more than 80% of total light transmittance of the optical film and 20-100 μm of thickness.

2. The optical film according to claim 1, wherein the polyamideimide resin is an aromatic resin.

3. The optical film according to claim 1 or 2, wherein the proportion of structural units derived from an aromatic monomer in the polyamideimide resin is 60 mol% or more based on the total structural units.

4. The optical film according to claim 1 or 2, wherein the polyamideimide resin has a weight average molecular weight of 200,000 or more.

5. The optical film according to claim 1 or 2, wherein the polyamideimide resin comprises structural units derived from terephthalic acid.

6. The optical film according to claim 1 or 2, which is a film for a front panel of a flexible display device.

7. A flexible display device comprising the optical film according to any one of claims 1 to 6.

8. The flexible display device of claim 7, further comprising a touch sensor.

9. The flexible display device according to claim 7 or 8, further comprising a polarizing plate.