JP2020097710A - Optical film, flexible display device, and resin composition - Google Patents

Abstract

To provide a resin film having a high elastic modulus.SOLUTION: An optical film contains at least one resin selected from the group consisting of polyimide resin and polyamide resin. In the optical film, a ratio (I/I) of Na ionic strength (I) to CHionic strength (I), obtained by time-of-flight secondary ion mass spectrometry, is 0.2 or more.SELECTED DRAWING: None

Description

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

Currently, 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. Although glass has been used as the front plate of such an image display device, it is difficult to use it as a front plate material of a flexible display device, for example, because the glass is very rigid and easily broken. Therefore, utilization of a polymer material as one of the materials replacing the glass has been studied, and for example, an optical film using a polyimide resin has been studied (for example, Patent Document 1).

JP, 2018-119132, A

However, when an optical film using a polyimide resin and a polyamide resin is used in a flexible display device or the like, the optical film may have defects such as scratches and wrinkles due to bending and contact with external factors. It was The present inventor has studied various means for improving the above, and found that defects such as scratches are unlikely to occur in the optical film by increasing the elastic modulus of the optical film.
Therefore, an object of the present invention is to provide a resin film having a high elastic modulus.

In order to solve the above-mentioned problems, the present inventors have paid attention to the types and amounts of the components contained in the resin film, and have conducted earnest studies. As a result, the ratio (I _Na /I _CH3 ) of the ionic strength of _Na (I _Na ) to the ionic strength of CH ₃ (I _CH3 ) obtained by the time-of-flight secondary ion mass spectrometry in the optical film was 0.2. With respect to the above optical film, it was surprisingly found that the elastic modulus can be easily increased, and the present invention has been completed.

That is, the present invention includes the following preferred embodiments.
[1] An optical film containing at least one resin selected from the group consisting of a polyimide resin and a polyamide resin, wherein CH ₃ ions obtained by time-of-flight secondary ion mass spectrometry of the optical film the proportion of the intensity ionic strength of Na for _{(I CH3) (I Na)} (I Na / I CH3) is 0.2 or more, the optical film.
[2] The optical film as described in [1] above, wherein the polyimide resin and the polyamide resin are aromatic resins.
[3] The optical film as described in [1] or [2] above, wherein the ratio of the constituent units derived from the aromatic monomer to all constituent units in the polyimide resin and the polyamide resin is 80 mol% or more.
[4] The optical film as described in any one of [1] to [3] above, which has a thickness of 10 to 100 μm and a total light transmittance of 80% or more.
[5] The optical film as described in any of [1] to [4] above, wherein the weight average molecular weight of the polyimide resin and the polyamide resin is 200,000 or more.
[6] The optical film as described in any of [1] to [5] above, wherein the polyimide-based resin is a polyamide-imide resin.
[7] The optical film as described in any of [1] to [6] above, wherein the polyimide resin and the polyamide resin include a structural unit derived from terephthalic acid.
[8] The optical film as described in any of [1] to [7] above, which is a film for a front plate of a flexible display device.
[9] A flexible display device including the optical film according to any one of [1] to [8].
[10] The flexible display device according to [9], further including a touch sensor.
[11] The flexible display device according to [9] or [10], further including a polarizing plate.
[12] At least one resin selected from the group consisting of polyimide resins and polyamide resins, a compound containing a sodium atom, at least one sodium-containing component selected from the group consisting of sodium and sodium ions, and a solvent. A resin composition containing at least.

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

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

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

In the optical film of the present invention, the ratio of the ionic strength of _Na (I _Na ) to the ionic strength of CH ₃ (I _CH3 ) (I _Na /I _CH3 ) is the time-of-flight secondary ion mass spectrometry (Time-of-). The ionic strength of CH ₃ (I _CH3 ) and the ionic strength of _Na (I _Na ) of the optical film are measured by a Flight Secondary Ion Mass Spectrometry (hereinafter also referred to as “TOF-SIMS”), and I _Na is divided by I _CH3 . It is calculated by In the present specification, the ionic strength of CH ₃ (I _CH3 ) and the ionic strength of _Na (I _Na ) measured by time-of-flight secondary ion mass spectrometry are attributed to CH ₃ ions in the measurement data. The integrated value of a peak is CH ₃ ionic strength (I _CH3 ), and the integrated value of a peak attributed to Na ion is Na ionic strength (I _Na ).

TOF-SIMS is a kind of mass spectrometry. According to TOF-SIMS, an element or a molecular species existing on the outermost surface of a sample can be obtained with extremely high detection sensitivity, and also exists on the outermost surface of the sample. It is also possible to investigate the distribution of the element or molecular species to be used.

TOF-SIMS is a method of irradiating a sample with an ion beam (primary ion) in a high vacuum, and mass-separating ions emitted from the surface by using the time difference of flight. When irradiated with primary ions, positively or negatively charged ions (secondary ions) are emitted from the sample surface, but lighter ions fly faster and heavier ions fly slower, so after the secondary ions are generated. By measuring the time until detection (flight time), the mass of the generated secondary ions can be calculated.

In the measurement by TOF-SIMS, CH ₃ ions are detected at a mass of 15.02 u and Na ions are detected at a mass of 22.99 u. Further, these ions are ions detected in both the positive (negative) ion analysis and the negative (negative) ion analysis. In the present invention, the ratio (I _Na /I _CH3 ) of the ionic strength of _Na (I _Na ) to the ionic strength of CH ₃ (I _CH3 ) may be the ratio detected by positive ion analysis or negative ions. The ratio detected by analysis may be used, but from the viewpoint of obtaining higher detection sensitivity, conditions using positive ion analysis are preferable, and if at least one of the above ratios is 0.2 or more, the The requirement that the ratio (I _Na /I _CH3 ) in the invention is 0.2 or more is satisfied.

The measurement by TOF-SIMS was carried out on the optical film by using a time-of-flight secondary ion mass spectrometer, the primary ions were Bi ³⁺⁺ , the acceleration voltage of the primary ions was 25 kV, the irradiation ion current was 0.23 pA, and the measurement range was 200 μm. It can be carried out by positive ion analysis or negative ion analysis under the condition of ×200 μm. The measurement by TOF-SIMS can be performed, for example, according to the method described in Examples. The ratio (I _Na /I _CH3 ) measured on at least a part of the surface or the cross section of the optical film may be within the above range, but the composition inside the optical film is likely to be influenced by the mechanical strength of the optical film. From the assumption, it is preferable that the ratio (I _Na /I _CH3 ) measured on the cross section of the optical film is within the above range.

The optics of the present invention in which the ratio (I _Na /I _CH3 ) of the ionic strength of _Na (I _Na ) to the ionic strength of CH ₃ (I _CH3 ) obtained by time-of-flight secondary ion mass spectrometry is 0.2 or more. The film can surprisingly improve the elastic modulus of the optical film. Here, the ionic strength of CH ₃ (I _CH3 ) and the ionic strength of _Na (I _Na ) obtained by time-of-flight secondary ion mass spectrometry are the carbon atoms and/or carbon ions present in the optical film. The amount and the amount of sodium atom and/or sodium ion are shown relatively. That the above ratio is 0.2 or more means that the total amount of sodium atoms (Na) and/or sodium ions is a certain amount or more with respect to the total amount of carbon atoms and/or carbon ions present in the optical film. Represents. The reason why carbon atoms and carbon ions are detected as CH ₃ ions is that in the time-of-flight secondary ion mass spectrometry, various secondary ions generated are also detected in the form of proton adducts. This is because CH ₃ ions are simultaneously generated as a proton adduct at the carbon atom.

The presence of a certain amount of sodium atoms, it is not clear why the elastic modulus of the optical film is improved, the present invention is not limited to the mechanism described below, for example, it is considered that the elastic modulus is improved by the following mechanism. .. When producing the optical film of the present invention, a compound containing a sodium atom, a sodium atom and/or a sodium ion is contained in a composition containing a polyimide resin and/or a polyamide resin, so that an imide bond contained in the resin. And/or an amide bond, preferably an imide bond contained in the polyimide resin and a compound containing a sodium atom, sodium and/or a sodium ion, and some interaction (for example, a carbonyl group of an imide bond or an amide bond). Electrostatic interaction between sodium ions) is considered to occur. As a result, the polyimide-based resin and/or the polyamide-based resin contained in the obtained optical film is present in the film in a state of interacting with a compound containing a sodium atom, sodium and/or sodium ion, or, It is considered that the elastic modulus of the optical film is improved by changing the orientation state of the compound containing sodium atom, sodium and/or sodium ion and the polyimide-based resin and/or the polyamide-based resin due to the interaction between the resins. .. From the viewpoint of easily interacting with the imide bond and/or the amide bond of the polyimide resin and/or the polyamide resin, the sodium-containing component contained in the optical film is preferably in an ionized state. In the present specification, a compound containing a sodium atom that can be contained in the optical film, which is considered to be detected as the ionic strength (I _Na ) of _Na when the optical film is subjected to time-of-flight secondary ion mass spectrometry. , Sodium and/or sodium ions are also referred to as “sodium-containing components”. The compound containing a sodium atom is a compound containing a sodium atom as a constituent atom of a molecule.

The ratio (I _Na /I _CH3 ) of the ionic strength of Na (I _Na ) to the ionic strength of CH ₃ (I _CH3 ) is preferably 1 or more, and more preferably 1. from the viewpoint of easily increasing the elastic modulus of the optical film. It is 5 or more, more preferably 3 or more, further preferably 5 or more, more preferably 10 or more, and particularly preferably 15 or more. The upper limit of the ratio (I _Na /I _CH3 ) 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 method of adjusting the ratio (I _Na /I _CH3 ) to the above range is not particularly limited, but in the optical film of the present invention containing a polyimide resin and/or a polyamide resin, a sodium-containing component (a compound containing a sodium atom, Examples thereof include a method of adjusting the content of sodium and/or sodium ions, and a method of 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 of _Na (I _Na ) obtained by TOF-SIMS of the optical film also increases. When the content of the polyimide resin and/or the polyamide resin contained in the optical film is increased, the ionic strength of CH ₃ (I _CH3 ) obtained by TOF-SIMS of the optical film also increases. Therefore, when the content of the sodium-containing component in the optical film is increased, the value of the ratio (I _Na /I _CH3 ) is increased, and when the content of the polyimide resin and/or the polyamide resin contained in the optical film is increased, The value of the ratio (I _Na /I _CH3 ) becomes smaller. The ratio (I _Na /I _CH3 ) can be adjusted to a desired range by the above method.

In the optical film of the present invention, the ionic strength (I _CH3 ) of CH ₃ and the ionic strength (I _Na ) of _Na by TOF-SIMS are not particularly limited, and the value of the ratio (I _Na /I _CH3 ) is within the above range. However, the ionic strength of _Na (I _Na ) is preferably 100 or more, more preferably 300 or more, and still more preferably 500 or more, from the viewpoint of easily securing sufficient quantification of the measurement by TOF-SIMS. It is preferable to perform the measurement under the conditions.

The optical film of the present invention having a ratio (I _Na /I _CH3 ) of 0.2 or more has a high elastic modulus. The elastic modulus of the optical film of the present invention is preferably 5.0 MPa or more, more preferably 5.1 MPa or more, even more preferably 5.2 MPa or more. The upper limit of the elastic modulus is not particularly limited, but is usually 100 MPa or less. The elastic modulus can be measured by using a tensile tester (for example, a chuck distance of 50 mm and a tensile speed of 10 mm/min), and can be measured by, for example, the method described in the examples.

The total light transmittance of the optical film of the present invention is preferably 80% or more, more preferably 85% or more, even more preferably 88% or more, even more preferably 90% or more, and particularly preferably 91% or more. When the total light transmittance is not less than the above lower limit, it is easy to improve the visibility when the optical film is incorporated into an image display device, particularly as a front plate. Since the optical film of the present invention usually exhibits a high total light transmittance, for example, as compared with the case of using a film having a low transmittance, the emission intensity of a display element or the like required to obtain constant brightness is suppressed. It becomes possible. Therefore, power consumption can be reduced. For example, when the optical film of the present invention is incorporated into an image display device, bright display tends to be obtained even if the light amount of the backlight is reduced, which can contribute to energy saving. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance can be measured using a haze computer according to JIS K 7361-1:1997, for example. The total light transmittance may be the total light transmittance in the range of the thickness of the optical film described below.

The haze of the optical film of the present invention is preferably 1% or less, more preferably 0.5% or less, still more preferably 0.2% or less. When the haze of the optical film is not more than the above upper limit, the visibility is likely to be improved when the optical film is incorporated into an image display device, particularly as a front plate. The lower limit of haze is usually 0.01% or more. The haze can be measured using a haze computer according to JIS K 7136:2000.

The yellowness (YI value) of the optical film of the present invention is preferably 3.0 or less, more preferably 2.5 or less, still more preferably 2.2 or less. When the yellowness of the optical film is less than or equal to the above upper limit, the transparency becomes good, and when used for the front plate of the image display device, it is possible to contribute to high visibility. The yellowness is usually -5 or more, preferably -2 or more. Note that the yellowness (YI value) was measured for transmittance for light of 300 to 800 nm using an ultraviolet-visible near-infrared spectrophotometer to obtain tristimulus values (X, Y, Z), and YI=100×( It can be calculated based on the formula 1.2769X-1.0592Z)/Y. In the present specification, the optical film having excellent optical properties means that the total light transmittance is high, the haze is low, and/or the YI value is low (low yellowness).

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. It is below, and it may be a combination of these upper and lower limits. When the thickness of the optical film is within the above range, the elastic modulus of the optical film can be easily increased. The thickness of the optical film can be measured using a micrometer, for example, the method described in the examples.

The number of times of bending (bending radius R=1 mm) in the bending resistance test of the optical film of the present invention is preferably 150,000 times or more, more preferably 180,000 times or more, and further preferably 200,000 times or more. .. When the number of times of bending is not less than the above lower limit, it has sufficient bending resistance as a front plate material for flexible display devices and the like. In addition, the number of times of bending in the bending resistance test is performed by repeatedly bending the optical film using a bending tester under the condition that the bending radius (curvature radius) R is 1 mm, and making a reciprocating motion until the film is cracked. The number of times of bending (one reciprocation is once) is shown.

<Polyimide resin and polyamide resin>
The optical film of the present invention contains a polyimide resin and/or a polyamide resin. In the present specification, the polyimide-based resin is a resin containing a repeating structural unit containing an imide group (hereinafter sometimes referred to as a polyimide resin), and a resin containing a repeating structural unit containing both an imide group and an amide group. At least one resin selected from the group consisting of (hereinafter sometimes referred to as polyamideimide resin) is shown. That is, in the present specification, the polyimide-based resin is a polyimide resin and/or a polyamide-imide resin. The polyamide-based resin refers to a resin containing a repeating structural unit containing an amide group. The optical film of the present invention may contain one kind of polyimide resin or polyamide resin, or may contain two 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 more preferably the polyimide-based resin is a polyamide-imide resin, from the viewpoint of easily achieving both chemical stability and high elastic modulus of the optical film.

In a preferred embodiment of the present invention, the polyimide resin and the polyamide resin are preferably aromatic resins from the viewpoint of easily increasing the elastic modulus of the optical film. In the present specification, the aromatic resin means a resin in which the constituent units contained in the polyimide resin and the polyamide resin are mainly aromatic constituent units.

In the above preferred embodiment, from the viewpoint of easily increasing the elastic modulus of the optical film, the ratio of the structural unit derived from the aromatic monomer to all the structural units contained in the polyimide resin is preferably 60 mol% or more, It is more preferably 70 mol% or more, further preferably 80 mol% or more, and particularly preferably 85 mol% or more. Here, the structural unit derived from an aromatic monomer is derived from a monomer containing an aromatic structure (for example, an aromatic ring) in at least a part thereof, and at least a part of the aromatic structure (for example, an aromatic ring) is included. Is a structural unit included in. Examples of aromatic monomers include aromatic tetracarboxylic acid compounds, aromatic diamines, aromatic dicarboxylic acids, and the like.

In a preferred embodiment of the present invention, the polyimide resin is a polyimide resin having a constitutional unit represented by the formula (1), or a constitutional unit represented by the formula (1) and a formula (2). It is preferably a polyamide-imide resin having the structural unit shown. Further, the polyamide resin is preferably a polyamide resin having a constitutional unit represented by the formula (2). Formulas (1) and (2) will be described below. The formula (1) will be described with respect to both a polyimide resin and a polyamide-imide resin, and the formula (2) will be described with a polyamide resin and a polyamide-imide resin. For both.

The constitutional unit represented by the formula (1) is a constitutional unit formed by reacting a tetracarboxylic acid compound and a diamine compound, and the constitutional unit represented by the formula (2) is a dicarboxylic acid compound and a diamine compound. And are structural units formed by reaction.

In the formula (2), Z is a divalent organic group, preferably Z may be substituted with a hydrocarbon group having 1 to 8 carbon atoms or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms, A cyclic structure, which is a divalent organic group having 4 to 40 carbon atoms, and more preferably a hydrocarbon group having 1 to 8 carbon atoms or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms. Represents a divalent organic group having 4 to 40 carbon atoms. Examples of the cyclic structure include an alicyclic structure, an aromatic ring structure, and a heterocyclic structure. As the organic group of Z, formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula ( 28) and the group represented by the formula (29), a group in which two non-adjacent bonds are replaced by hydrogen atoms and a divalent chain hydrocarbon group having 6 or less carbon atoms are exemplified, and a heterocycle of Z Examples of the structure include groups having a thiophene ring skeleton. From the viewpoint of easily suppressing the yellowness of the optical film (reducing the YI value), groups represented by formulas (20) to (27) and groups having a thiophene ring skeleton are preferable.

［式（３）中、
Ｒ^１〜Ｒ^８は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基を表し、Ｒ^１〜Ｒ^８に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ａは、互いに独立に、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^９）−を表し、Ｒ^９は水素原子、ハロゲン原子で置換されていてもよい炭素数１〜１２の１価の炭化水素基を表し、
ｍは０〜４の整数であり、
＊は結合手を表す］
で表されることが好ましい。 In one embodiment of the present invention, the polyamide resin and the polyamide-imide resin may include a plurality of types of Z, and the plurality of types of Z may be the same or different from each other. Particularly, from the viewpoint of easily increasing the elastic modulus of the optical film of the present invention and easily improving the optical characteristics, at least a part of Z is represented by the formula (3):

[In Formula (3),
R ^{1 to} R ⁸ each independently represent 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, and each of R ^{1 to} R ⁸ is The contained hydrogen atoms may be independently substituted with a halogen atom,
A is, independently of one another, 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)} - represents, ^{R 9} is a hydrogen atom, monovalent 1-12 carbon atoms which may be substituted with a halogen atom Represents a hydrocarbon group,
m is an integer of 0 to 4,
* Represents a bond]
It is preferable that

In the formula (3), A is, independently of one another, 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)} - represents, from bending resistance of the point of view of the optical film, preferably -O- or -S Represents -, more preferably represents -O-.
R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, Alternatively, it represents an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl- group. A butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group and the like can be mentioned. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, propyloxy group, isopropyloxy group, butoxy group, isobutoxy group, tert-butoxy group, pentyloxy group, hexyloxy group and cyclohexyloxy group. Can be mentioned. Examples of the aryl group having 6 to 12 carbon atoms include phenyl group, tolyl group, xylyl group, naphthyl group and biphenyl group. From the viewpoint of the surface hardness and flexibility of the optical film, R ^{1 to} R ⁸ each independently represent preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom or 1 to 3 carbon atoms. Represents an alkyl group, more preferably represents a hydrogen atom. Here, the hydrogen atoms contained in R ^{1 to} R ⁸ may be independently substituted with a halogen atom.
R ⁹ represents a hydrogen atom or 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 group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group and the like. 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.

M in the formula (3) is an integer in the range of 0 to 4, and when m is in this range, the elastic modulus and bending resistance of the optical film are easily improved. 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, and further preferably from the viewpoint of easily improving the elastic modulus and the bending resistance of the optical film. 0 or 1, particularly preferably 0. The constitutional unit represented by the formula (3) in which m is 0 is a constitutional unit derived from terephthalic acid, and in the constitutional unit, R ^{5 to} R ⁸ in the formula (3) are hydrogen atoms, A structural unit in which m is 0 is preferable. The resin in Z may include one type or two or more types of the structural unit represented by the formula (3). From the viewpoint of improving the elastic modulus and bending resistance of the optical film and reducing the yellowness (YI value), the resin in Z may include two or more types of structural units having different values of m in formula (3). It is more preferable to include two types of structural units having different values of m in formula (3). In this case, from the viewpoint of easily increasing the elastic modulus and bending resistance of the optical film, and from the viewpoint of easily reducing the yellowness (YI value) of the optical film, in the formula (3) in which the resin is Z and m is 0, It is particularly preferable to contain the structural unit represented, and in addition to the structural unit, further contain a structural unit represented by the formula (3) in which m is 1.

で表される構成単位を有する。この場合、光学フィルムの弾性率及び耐屈曲性を向上させやすいと共に、黄色度を低減しやすい。 In a preferred embodiment of the present invention, the resin has a structural unit represented by the formula (3), in which m=0 and R ^{5 to} R ⁸ are hydrogen atoms. In a more preferred embodiment of the present invention, the resin has a constitutional unit represented by the formula (3), m=0, and R ^{5 to} R ⁸ are hydrogen atoms, and a formula (3′) ):

It has a structural unit represented by. In this case, the elastic modulus and bending resistance of the optical film are easily improved, and the yellowness is easily reduced.

In a preferred embodiment of the present invention in which the optical film contains a polyamide-imide resin, the proportion of the constitutional unit represented by the formula (3) is such that the constitutional unit represented by the formula (1) and the formula (2) of the polyamide-imide resin. When the total of the constitutional units represented by is 100 mol%, preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, particularly preferably 50 mol% or more, most preferably Is 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, and further preferably 80 mol% or less. When the proportion of the structural unit represented by the formula (3) is at least the above lower limit, the elastic modulus and bending resistance of the optical film can be easily increased. When the proportion of the constitutional unit represented by the formula (3) is at most the above upper limit, the viscosity increase of the resin-containing varnish due to the hydrogen bond between amide bonds derived from the formula (3) is suppressed, and the processability of the film is improved. Cheap.

Moreover, when the polyamide-imide resin has a structural unit represented by the formula (3) in which m=1 to 4, the proportion of the structural unit represented by the formula (3) in which m is 1 to 4 is polyamideimide. When the total of the constitutional unit represented by the formula (1) and the constitutional unit represented by the formula (2) of the resin is 100 mol %, preferably 3 mol% or more, more preferably 5 mol% or more, further It is preferably 7 mol% or more, particularly preferably 9 mol% or more, preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, particularly preferably 30 mol% or less. When the proportion of the structural unit represented by the formula (3) in which m is 1 to 4 is at least the above lower limit, the elastic modulus and bending resistance of the optical film can be easily increased. When the ratio of the constitutional unit represented by formula (3) in which m is 1 to 4 is equal to or less than the above upper limit, the resin-containing varnish due to the hydrogen bond between amide bonds derived from the constitutional unit represented by formula (3) It is easy to suppress the rise in viscosity and improve the processability of the film. The ratio of the constitutional units represented by the formula (1), the formula (2) or the formula (3) can be measured by using, for example, ¹ H-NMR, or can be calculated from the charging ratio of the raw materials. it can.

In a preferred embodiment of the present invention, Z in the polyamide resin or polyamide-imide resin is preferably 30 mol% or more, more preferably 40 mol% or more, further preferably 45 mol% or more, particularly preferably 50 mol%. The above is the constitutional unit represented by the formula (3) in which m is 0 to 4. When the above lower limit of Z is a constituent 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 increased. Further, 100 mol% or less of Z in the polyamide resin or the polyamide-imide 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 which m is 0 to 4 in the resin can be measured using, for example, ¹ H-NMR, or can be calculated from the charging ratio of raw materials. You can also

In a preferred embodiment of the present invention, Z in the polyamide resin or polyamide-imide resin is preferably 5 mol% or more, more preferably 8 mol% or more, further preferably 10 mol% or more, particularly preferably 12 mol%. The above is represented by the formula (3) in which m is 1 to 4. When the above-mentioned lower limit of Z of the polyamide-imide resin 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 increased. Further, Z is preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, particularly preferably 30 mol% or less, represented by the formula (3) in which m is 1 to 4. To be done. When the above upper limit of Z or less is represented by the formula (3) in which m is 1 to 4, it is due to inter-amide bond hydrogen bond derived from the structural unit represented by the formula (3) in which m is 1 to 4. It is possible to suppress the increase in viscosity of the resin-containing varnish and improve the processability of the film. The ratio of the structural unit represented by the formula (3) in which m is 1 to 4 in the resin can be measured using, for example, ¹ H-NMR, or can be calculated from the charging ratio of the raw materials. ..

In formulas (1) and (2), X's each independently represent a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms, and more preferably 4 carbon atoms having a cyclic structure. Represents a divalent organic group of ˜40. Examples of the cyclic structure include an alicyclic structure, an aromatic ring structure, and a heterocyclic structure. The organic group, the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case, the carbon number of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably Is 1-8. In one embodiment of the present invention, the polyamide resin, the polyimide resin, or the polyamideimide resin may include a plurality of types of X, and the plurality of types of X may be the same as or different from each other. X is represented by formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18). A group having a hydrogen atom in the group represented by the formula (10) to the formula (18) substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain having 6 or less carbon atoms A formula hydrocarbon group is illustrated.

In formula (10) to formula (18),
* Represents a bond,
V ^{1, V 2} and ^{V 3} independently of one another, 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) - represents a. 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 the groups described above for R ⁹ .
One example is a single bond ^{V 1} and ^{V 3,} -O- or -S-, and, ^{V 2} is _{-CH 2 -, - C (CH} 3) 2 -, - C (CF 3) 2 - or -SO ₂ - is. The bonding position of each of V ¹ and V ² with respect to each ring and the bonding position of each of V ² and V ³ with respect to each ring are independently of each other, preferably a meta position or a para position, and more preferably a para position. Rank.

Among the groups represented by the formulas (10) to (18), the formulas (13), (14), (15), and (16) are used from the viewpoint of easily increasing the elastic modulus and bending resistance of the optical film. ) And the group represented by Formula (17) are preferable, and the groups represented by Formula (14), Formula (15) and Formula (16) are more preferable. Further, V ¹ , V ² and V ³ are preferably a single bond, —O— or —S—, more preferably a single bond or −, independently of each other, from the viewpoint of easily increasing the elastic modulus and flexibility of the optical film. O-.

［式（４）中、
Ｒ^１０〜Ｒ^１７は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^１０〜Ｒ^１７に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
＊は結合手を表す］
で表される構成単位である。式（１）及び式（２）中の複数のＸの少なくとも一部が式（４）で表される基であると、光学フィルムの弾性率及び透明性を高めやすい。 In a preferred embodiment of the present invention, at least some of the plurality of Xs in formula (1) and formula (2) are represented by formula (4):

[In formula (4),
R ^{10 to} R ¹⁷ each independently represent 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, and included in R ^{10 to} R ¹⁷ . Hydrogen atoms which are independently of each other may be substituted with a halogen atom,
* Represents a bond]
Is a structural unit represented by. When at least a part of the plurality of Xs in the formulas (1) and (2) is a group represented by the formula (4), the elastic modulus and the transparency of the optical film can be easily increased.

In the formula (4), R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , and R ¹⁷ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a carbon number 1 Represents an alkoxy group having 6 to 6 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 an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms in the formula (3). The group illustrated as a group or a C6-C12 aryl group is mentioned. R ¹⁰ to R ¹⁷ independently of one another, preferably 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, ^{wherein, R 10} ~ The hydrogen atoms contained in R ¹⁷ may be independently substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. R ^{10 to} R ¹⁷ are, independently of each other, more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, from the viewpoint of the elastic modulus, transparency and bending resistance of the optical film, and Preferably R ¹⁰ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are hydrogen atoms, R ¹¹ and R ¹⁷ are hydrogen atoms, methyl groups, fluoro groups, chloro groups or trifluoromethyl groups, and particularly Preferably R ¹¹ and R ¹⁷ are methyl groups or trifluoromethyl groups.

で表される構成単位であり、すなわち、複数のＸの少なくとも一部は、式（４’）で表される構成単位である。この場合、フッ素元素を含有する骨格によりポリイミド系樹脂又はポリアミド系樹脂の溶媒への溶解性を高め、該樹脂を含有するワニスの保管安定性を向上しやすいと共に、該ワニスの粘度を低減しやすく、光学フィルムの加工性を向上しやすい。また、フッ素元素を含有する骨格により、光学フィルムの光学特性を向上しやすい。 In a preferred embodiment of the present invention, the structural unit represented by formula (4) is represented by formula (4′):

That is, at least a part of the plurality of X is a structural unit represented by the formula (4′). In this case, the solubility of the polyimide-based resin or the polyamide-based resin in the solvent by the skeleton containing the elemental fluorine is increased, the storage stability of the varnish containing the resin is easily improved, and the viscosity of the varnish is easily reduced. , Easy to improve the processability of the optical film. Further, the skeleton containing elemental fluorine easily improves the optical characteristics of the optical film.

In a preferred embodiment of the present invention, X in the polyimide-based resin or the polyamide-based resin is preferably 30 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more of the formula (4), Particularly, it is represented by the formula (4′). When X in the above range in the polyimide-based resin or the polyamide-based resin is represented by the formula (4), particularly the formula (4′), the obtained optical film has a skeleton containing an elemental fluorine, and thus the resin is dissolved in the solvent. The varnish containing the resin is easily improved in storage stability, the viscosity of the varnish is easily reduced, and the processability of the optical film is easily improved. Further, due to the skeleton containing elemental fluorine, the optical characteristics of the optical film are likely to be improved. Preferably, 100 mol% or less of X in the polyimide resin or polyamide resin is represented by the formula (4), especially the formula (4′). X in the resin may be formula (4), especially formula (4′). The proportion of the structural unit represented by the formula (4) of X in the resin can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of the raw materials.

In the formula (1), Y represents a tetravalent organic group, preferably a C4-40 tetravalent organic group, and more preferably a C4-40 tetravalent organic group having a cyclic structure. Represents a group. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure, and from the viewpoint of easily increasing the elastic modulus, an aromatic ring is preferable. The 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, in which case, a hydrocarbon group and a fluorine-substituted hydrocarbon group The carbon number is preferably 1-8. In one embodiment of the present invention, the polyimide-based resin may include 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, the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) And a group represented by the 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; Further, a chain hydrocarbon group having 4 or less carbon atoms and having 6 or less carbon atoms is exemplified.

In the formula (20) to (29), * represents a bond, ^{W 1} is 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) represents a 2 -Ar- or _-Ar-SO 2 -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be replaced by a fluorine atom, and a specific example thereof is a phenylene group.

Among the groups represented by formulas (20) to (29), represented by formula (26), formula (28) or formula (29) from the viewpoint of easily increasing the elastic modulus and flex resistance of the optical film. A group is preferable, and a group represented by formula (26) is more preferable. W ¹ is a single bond, —O—, —CH ₂ —, —CH independently of each other from the viewpoint of easily increasing the elastic modulus and bending resistance of the optical film and easily reducing the yellowness of the optical film. _{2 -CH 2 -, - CH (} CH 3) -, - C (CH 3) 2 - or -C _{(CF 3) 2} - is 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} It is more preferable that it is −.

［式（５）中、
Ｒ^１８〜Ｒ^２５は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^１８〜Ｒ^２５に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
＊は結合手を表す］
で表される構成単位である。複数の式（１）中のＹの少なくとも一部が式（５）で表される基であると、ポリイミド系樹脂の溶媒への溶解性を高め、ポリイミド系樹脂を含有するワニスの粘度を低減しやすく、光学フィルムの加工性を向上しやすい。また、光学フィルムの弾性率及び光学特性を向上しやすい。 In a preferred embodiment of the present invention, at least a part of Y in formulas (1) is represented by formula (5):

[In formula (5),
R ^{18 to} R ²⁵ each independently represent 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, and included in R ^{18 to} R ²⁵ . Hydrogen atoms which are independently of each other may be substituted with a halogen atom,
* Represents a bond]
Is a structural unit represented by. When at least a part of Y in the plurality of formulas (1) is a group represented by the formula (5), the solubility of the polyimide resin in the solvent is increased, and the viscosity of the varnish containing the polyimide resin is reduced. It is easy to improve the processability of the optical film. In addition, it is easy to improve the elastic modulus and the optical characteristics of the optical film.

In formula (5), R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ^24, and R ²⁵ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a carbon number 1 Represents an alkoxy group having 6 to 6 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 an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms in the formula (3). As the group or the aryl group having 6 to 12 carbon atoms, those exemplified above can be mentioned. R ¹⁸ to R ²⁵ are, independently of one another, preferably an alkyl group having 1 to 6 carbon hydrogen atom or atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, ^{wherein, R 18} ~ The hydrogen atoms contained in R ²⁵ may be independently substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. R ^{18 to} R ²⁵ are, independently of each other, more preferably a hydrogen atom, from the viewpoint of easily increasing the elastic modulus and bending resistance of the optical film, and from the viewpoint of easily increasing the transparency and maintaining the transparency. A methyl group, a fluoro group, a chloro group or a trifluoromethyl group, more preferably R ¹⁸ , R ¹⁹ , R ²⁰ , R ²³ , R ²⁴ and R ²⁵ are hydrogen atoms, and R ²¹ and R ²² are hydrogen atoms; It is a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and particularly preferably R ²¹ and R ²² are a methyl group or a trifluoromethyl group.

で表される基であり、すなわち、複数のＹの少なくとも一部は、式（５’）で表される構成単位である。この場合、フッ素元素を含有する骨格によりポリイミド系樹脂の溶媒への溶解性を高め、該樹脂を含有するワニスの保管安定性を向上しやすいと共に、該ワニスの粘度を低減しやすく、光学フィルムの加工性を向上しやすい。また、フッ素元素を含有する骨格により、光学フィルムの光学特性を向上しやすい。 In a preferred embodiment of the present invention, the structural unit represented by formula (5) has the formula (5′):

That is, at least a part of the plurality of Y's is a structural unit represented by the formula (5′). In this case, by increasing the solubility of the polyimide resin in the solvent by the skeleton containing the elemental fluorine, it is easy to improve the storage stability of the varnish containing the resin, it is easy to reduce the viscosity of the varnish, the optical film Easy to improve workability. Further, the skeleton containing elemental fluorine easily improves the optical characteristics of the optical film.

In a preferred embodiment of the present invention, Y in the polyimide resin is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more, represented by the formula (5), particularly the formula (5). '). When Y within the above range in the polyimide-based resin is represented by the formula (5), particularly the formula (5′), the skeleton containing the fluorine element enhances the solubility of the polyimide-based resin in the solvent and contains the resin. The viscosity of the varnish is easily reduced, and the processability of the optical film is easily improved. Further, the skeleton containing elemental fluorine easily improves the optical characteristics of the optical film. Preferably, 100 mol% or less of Y in the polyimide resin is represented by the formula (5), especially the formula (5′). Y in the polyimide-based resin may be the formula (5), particularly the formula (5′). The proportion of the structural unit represented by the formula (5) of Y in the polyimide resin can be measured by using, for example, ¹ H-NMR, or can be calculated from the charging ratio of the raw materials.

The polyimide-based resin includes a structural unit represented by formula (30) and/or a structural unit represented by formula (31) in addition to the structural unit represented by formula (2). Can be included.

In formula (30), Y ¹ is a tetravalent organic group, preferably 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. As Y ¹ , equation (20), equation (21), equation (22), equation (23), equation (24), equation (25), equation (26), equation (27), equation (28) and A group represented by the 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 Examples are tetravalent chain hydrocarbon groups having 6 or less carbon atoms. In an embodiment of the present invention, the polyimide-based resin may include a plurality of types of Y ¹ , and the plurality of types of Y ¹ may be the same as or different from each other.

In formula (31), Y ² is a trivalent organic group, preferably 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. As Y ² , the above formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) ) And a group represented by the formula (29) in which any one of the bonds is replaced by a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may include a plurality of types of Y ² , and the plurality of types of Y ² may be the same as or different from each other.

In formulas (30) and (31), X ¹ and X ² are each independently a divalent organic group, preferably a hydrocarbon group in which a hydrogen atom in the organic group is substituted or a fluorine-substituted hydrocarbon group. Is an organic group which may be substituted with. X ¹ and X ² are the above formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and A group represented by the 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 is exemplified.

In one embodiment of the present invention, the polyimide resin is a constitutional unit represented by the formula (1) and/or the formula (2), and optionally a constitutional unit represented by the formula (30) and/or the formula (31). It consists of units. Further, from the viewpoint of easily increasing the optical properties, elastic modulus and flex resistance of the optical film, the proportion of the constitutional units represented by the formulas (1) and (2) in the polyimide resin is represented by the formula (1) and Based on the formula (2) and optionally all the structural units represented by the formula (30) and the formula (31), preferably 80 mol% or more, more preferably 90 mol% or more, further preferably 95 mol% or more. Is. In the polyimide-based resin, the ratio of the constitutional units represented by the formula (1) and the formula (2) is the formula (1) and the formula (2), and in some cases, the formula (30) and/or the formula (31). It is usually 100% or less based on all the structural units represented by. The above ratio can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

In one embodiment of the present invention, the content of the polyimide resin and/or polyamide resin in the optical film is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, relative to 100 parts by mass of the optical film. It is more preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, and more preferably 95 parts by mass or less. When the content of the polyimide-based resin and/or the polyamide-based resin is within the above range, it is easy to improve the optical characteristics and elastic modulus of the optical film.

The weight average molecular weight (Mw) of the polyimide-based resin and the polyamide-based resin is, in terms of standard polystyrene, preferably 200,000 or more, more preferably 230,000 or more, from the viewpoint of easily increasing the elastic modulus and bending resistance of the optical film. , More preferably 250,000 or more, further preferably 270,000 or more, particularly preferably 300,000 or more. The weight average molecular weight of the polyimide-based resin and the polyamide-based resin is preferably 1,000,000 from the viewpoint of easily improving the solubility of the resin in a solvent and easily improving the stretchability and processability of the optical film. Or less, more preferably 800,000 or less, further preferably 700,000 or less, particularly preferably 500,000 or less. The weight average molecular weight can be determined by, for example, GPC measurement and standard polystyrene conversion, and may be calculated by the method described in Examples, for example.

In the polyamide-imide resin, the content of the structural unit represented by the formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol, based on 1 mol of the structural unit represented by the formula (1). Molar or more, more 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. .. When the content of the structural unit represented by the formula (2) is at least the above lower limit, the elastic modulus of the optical film can be easily increased. Further, when the content of the constituent unit represented by the formula (2) is at most the above upper limit, thickening due to hydrogen bonds between amide bonds in the formula (2) is suppressed, and the processability of the optical film is improved. Easy to make.

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 by, for example, the above-mentioned fluorine-containing substituent. .. When the polyimide resin and/or the polyamide resin contains a halogen atom, it is easy to improve the elastic modulus of the optical film and reduce the yellowness (YI value). When the elastic modulus of the optical film is high, it is easy to suppress generation of scratches and wrinkles in the film. Further, when the yellowness of the optical film is low, the transparency and the visibility of the film tend to be improved. The halogen atom is preferably a fluorine atom. Preferred examples of the fluorine-containing substituent for containing a fluorine atom in the polyimide resin include a fluoro 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 further preferably, based on the mass of the polyimide-based resin and the polyamide-based resin, respectively. It is 5 to 30 mass %. When the content of halogen atoms is at least the above lower limit, the elastic modulus of the optical film is further improved, the water absorption is lowered, the yellowness is further reduced, and the transparency and the visibility are easily improved. When the content of halogen atoms is at most the above upper limit, synthesis will be facilitated.

The imidization ratio of the polyimide-based resin and the polyamide-imide resin is preferably 90% or more, more preferably 93% or more, and further preferably 96% or more. From the viewpoint of easily improving the optical properties of the optical film, it is preferable that the imidization ratio be equal to or higher than the above lower limit. The upper limit of the imidization ratio is 100% or less. The imidization ratio indicates the ratio of the molar amount of imide bonds in the polyimide resin to the double value of the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin. When the polyimide-based resin contains a tricarboxylic acid compound, the value is twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide-based resin, and the molar amount of the structural unit derived from the tricarboxylic acid compound. And the ratio of the molar amount of imide bonds in the polyimide resin to the total of the above. The imidization ratio can be determined by IR method, NMR method, or the like.

Commercially available products may be used as the polyimide resin and the polyamide resin. Examples of commercially available polyimide resins include Neoprim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Inc. and KPI-MX300F manufactured by Kawamura Sangyo Co., Ltd.

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

［式（３”）中、
Ｒ^１〜Ｒ^８は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基を表し、Ｒ^１〜Ｒ^８に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ａは、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^９）−を表し、
Ｒ^９は水素原子、ハロゲン原子で置換されていてもよい炭素数１〜１２の１価の炭化水素基を表し、
ｍは０〜４の整数であり、
Ｒ^３１及びＲ^３２は、互いに独立に、ヒドロキシル基、メトキシ基、エトキシ基、ｎ−プロポキシ基、イソプロポキシ基、ｎ−ブトキシ基、ｓｅｃ−ブトキシ基、ｔｅｒｔ−ブトキシ基又は塩素原子を表す。］ (Resin manufacturing method)
Polyimide resin, for example, can be produced using a tetracarboxylic acid compound and a diamine compound as the main raw materials, polyamideimide resin, for example, a tetracarboxylic acid compound, a dicarboxylic acid compound and a diamine compound can be produced as the main raw material, the polyamide resin is For example, a diamine compound and a dicarboxylic acid compound can be used as main raw materials. Here, the dicarboxylic acid compound preferably contains at least a compound represented by the formula (3″).

[In the formula (3"),
R ^{1 to} R ⁸ each independently represent 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, and each of R ^{1 to} R ⁸ is The contained hydrogen atoms may be independently substituted with a halogen atom,
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)} - represents,
R ⁹ represents a hydrogen atom, 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 and R ³² each independently represent 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. The dicarboxylic acid compound is represented by formula (3″), wherein m is 0. In addition to the compound represented by the above, it is more preferable to use the compound represented by the formula (3″) in which A is an oxygen atom. In another preferred embodiment, the dicarboxylic acid compound is R ³¹ , A compound represented by the formula (3″), wherein R ³² is a chlorine atom. Moreover, you may use a diisocyanate compound instead of a diamine compound.

Examples of the diamine compound used for producing the resin include aliphatic diamines, aromatic diamines, and mixtures thereof. In addition, in this embodiment, the "aromatic diamine" represents a diamine in which an amino group is directly bonded to an aromatic ring, and may have an aliphatic group or another substituent in a part of its structure. The aromatic ring may be a monocyclic 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. Of these, a benzene ring is preferable. The "aliphatic diamine" represents a diamine in which an amino group is directly bonded to the aliphatic group, and may have an aromatic ring or other substituent in a part of its structure.

Examples of the aliphatic diamine include acyclic aliphatic diamine such as hexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine and 4,4′. Examples thereof include cycloaliphatic diamines such as diaminodicyclohexylmethane. These may be used alone or in combination of two or more.

As the aromatic diamine, for example, p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, etc. , An aromatic diamine having one aromatic ring, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′- Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4 -Aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl] Propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB and May be described), 4,4′-bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene , 9,9-bis(4-amino-3-chlorophenyl)fluorene, 9,9-bis(4-amino-3-fluorophenyl)fluorene and the like, and aromatic diamines having two or more aromatic rings. These may be used alone or in combination of two or more.

The aromatic diamine is preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone. ,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2 ,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2′-dimethylbenzidine, 2,2′-bis( Trifluoromethyl)-4,4′-diaminodiphenyl (TFMB) and 4,4′-bis(4-aminophenoxy)biphenyl, more preferably 4,4′-diaminodiphenylmethane and 4,4′-diaminodiphenyl. Propane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, 2,2- Bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB), 4,4'- It is bis(4-aminophenoxy)biphenyl. These may be used alone or in combination of two or more.

Among the above diamine compounds, one or more selected from the group consisting of aromatic diamines having a biphenyl structure is selected from the viewpoint of high elastic modulus, high transparency, high flexibility, high bending resistance and low colorability of the optical film. It is preferable to use. One selected from the group consisting of 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl and 4,4'-diaminodiphenyl ether It is more preferable to use the above, and it is further preferable to use 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenyl (TFMB).

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

Specific examples of the aromatic tetracarboxylic dianhydride include a non-condensed polycyclic aromatic tetracarboxylic dianhydride, a monocyclic aromatic tetracarboxylic dianhydride and a condensed polycyclic aromatic tetraanhydride. Examples include carboxylic acid dianhydride. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride include 4,4′-oxydiphthalic dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and 2,2 ',3,3'-Benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride ,3,3',4,4'-Diphenylsulfone tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-di) Carboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic acid dianhydride (described as 6FDA , 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,3) 4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3 -Dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diphthalic acid dianhydride and 4,4'-(m-phenylenedioxy)diphthalic acid dianhydride. Examples of monocyclic aromatic tetracarboxylic dianhydrides include 1,2,4,5-benzenetetracarboxylic dianhydride, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples thereof include 2,3,6,7-naphthalenetetracarboxylic dianhydride.

Among these, 4,4'-oxydiphthalic acid dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride and 2,2',3,3'-benzophenone tetracarboxylic acid dianhydride are preferable. Anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl Sulfonetetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2- Bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), 1,2-bis(2,3-dicarboxyphenyl) Ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3 ,4-Dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p- Examples thereof include phenylenedioxy)diphthalic acid dianhydride and 4,4′-(m-phenylenedioxy)diphthalic acid dianhydride, and more preferably 4,4′-oxydiphthalic acid dianhydride, 3,3′, 4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA) , Bis(3,4-dicarboxyphenyl)methane dianhydride and 4,4′-(p-phenylenedioxy)diphthalic acid dianhydride. These may be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic acid dianhydride include cyclic or acyclic aliphatic tetracarboxylic acid dianhydride. The cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride. , 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cycloalkanetetracarboxylic dianhydride such as 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo[2.2 .2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl 3,3′-4,4′-tetracarboxylic dianhydride and positional isomers thereof. .. These may be used alone 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. These may be used alone or in combination of two or more. Moreover, you may use combining cycloaliphatic tetracarboxylic dianhydride and acyclic aliphatic tetracarboxylic dianhydride.

Among the above tetracarboxylic dianhydrides, 4,4′-oxydiphthalic dianhydride, 3,4′-oxydiphthalic dianhydride, from the viewpoint of high surface hardness, high transparency, high flexibility, high bending resistance, and low colorability of the optical film. 3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride ,3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene ) Diphthalic acid dianhydride, and mixtures thereof are preferable, and 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 4,4′-(hexafluoroisopropylidene)diphthalic acid dianhydride, and These mixtures are more preferable, and 4,4′-(hexafluoroisopropylidene)diphthalic acid dianhydride (6FDA) is further preferable.

As the dicarboxylic acid compound used for producing the resin, terephthalic acid, 4,4′-oxybisbenzoic acid or their acid chloride compounds are preferably used. In addition to terephthalic acid, 4,4′-oxybisbenzoic acid or their acid chloride compounds, other dicarboxylic acid compounds may be used. Examples of the other dicarboxylic acid compounds include aromatic dicarboxylic acids, aliphatic dicarboxylic acids and their related acid chloride compounds, acid anhydrides, and the like, and two or more kinds may be used in combination. Specific examples include isophthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; dicarboxylic acid compounds of chain hydrocarbons having 8 or less carbon atoms and two benzoic acids. but a single _{bond, -CH 2 -, - C (} CH 3) 2 -, - C (CF 3) 2 -, - SO 2 - or a compound linked phenylene groups and their acid chlorides compounds. As a specific example, 4,4′-oxybis(benzoyl chloride) and terephthaloyl chloride are preferable, and it is more preferable to use 4,4′-oxybis(benzoyl chloride) and terephthaloyl chloride in combination.

The polyimide-based resin is obtained by further reacting tetracarboxylic acid and tricarboxylic acid and their anhydrides and derivatives, in addition to the tetracarboxylic acid compound, within a range that does not impair various physical properties of the optical film. Good.

Examples of the tetracarboxylic acid include a water adduct of an anhydride of the above tetracarboxylic acid compound.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and related acid chloride compounds, acid anhydrides, and the like, and two or more kinds may be used in combination. Specific examples thereof include 1,2,4-benzenetricarboxylic acid anhydride; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthalic anhydride and benzoic acid are single bonds, -O- _{, -CH 2 -, - C (} CH 3) 2 -, - C (CF 3) 2 -, - SO 2 - or a compound linked phenylene group.

In the production of the resin, the amount of the diamine compound, the tetracarboxylic acid compound and/or the dicarboxylic acid compound used can be appropriately selected according to the ratio of each constituent unit of the desired polyimide 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, but is, for example, 5 to 350°C, preferably 20 to 200°C, more preferably 25 to 100°C. Although the reaction time is not particularly limited, it is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be performed under an inert atmosphere or reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or an inert gas atmosphere with 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, for example, water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, Alcohol-based solvents such as 2-butoxyethanol and propylene glycol monomethyl ether; ester-based 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, methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; toluene, xylene Aromatic hydrocarbon solvent such as acetonitrile; Nitrile solvent such as acetonitrile; Ether solvent such as tetrahydrofuran and dimethoxyethane; Chlorine-containing solvent such as chloroform and chlorobenzene; Amide such as N,N-dimethylacetamide, N,N-dimethylformamide Examples thereof include system solvents; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvent). Among these, amide solvents can be preferably used from the viewpoint of solubility.

In the imidization step in the production of a polyimide resin, imidization can be performed in the presence of an imidization catalyst. Examples of the imidization catalyst include aliphatic amines such as tripropylamine, dibutylpropylamine and ethyldibutylamine; N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydro. Alicyclic amine (monocyclic) such as azepine; azabicyclo[2.2.1]heptane, azabicyclo[3.2.1]octane, azabicyclo[2.2.2]octane, and azabicyclo[3.2. 2] Alicyclic amine (polycyclic) such as nonane; and pyridine, 2-methylpyridine (2-picoline), 3-methylpyridine (3-picoline), 4-methylpyridine (4-picoline), 2- Ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and Aromatic amines such as isoquinoline. From the viewpoint of facilitating the imidization reaction, it is preferable to use an acid anhydride together with the imidization catalyst. Examples of the acid anhydride include conventional acid anhydrides used in imidization reaction, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and aromatics such as phthalic acid. Examples thereof include acid anhydrides.

Polyimide-based resin and polyamide-based resin are isolated (separated and purified) by a conventional method, for example, separation means such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a combination of these separation means. Alternatively, in a preferred embodiment, a large amount of alcohol such as methanol is added to a reaction solution containing a transparent polyamideimide resin to precipitate the resin, and the resin can be isolated 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 compound containing a sodium atom, sodium and sodium ion. The content of the sodium-containing component in the optical film of the present invention is the ratio (I _Na /I) of the ionic strength of _Na (I _Na ) to the ionic strength of CH ₃ (I _CH3 ) obtained by time-of-flight secondary ion mass spectrometry. _CH3 ) is not particularly limited as long as it is 0.2 or more, and the above ratio (I _Na /I _CH3 ) is within a predetermined range depending on the type of polyimide resin contained in the optical film. You can set it to. For example, the content of the sodium-containing component in the varnish for producing the optical film of the present invention, from the viewpoint of easily increasing the elastic modulus of the optical film, the total amount of the polyimide-based resin and / or polyamide-based resin contained in the varnish On the other hand, preferably 0.002% by mass or more, more preferably 0.004% by mass or more, further preferably 0.01% by mass or more, further preferably 0.02% by mass or more, further preferably 0.03% by mass. As described above, 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, from the viewpoint of easily obtaining a homogeneous film, with respect to the total amount of the polyimide resin and/or the polyamide resin contained in the varnish. , Preferably 1 mass% or less, more preferably 0.5 mass% or less, and further preferably 0.1 mass% or less. Further, the content of the sodium-containing component in the optical film of the present invention, from the viewpoint of easily increasing the elastic modulus of the optical film, with respect to the total amount of the polyimide-based resin and / or polyamide-based resin contained in the optical film, preferably 0.002% by mass or more, more preferably 0.004% by mass or more, further preferably 0.01% by mass or more, further preferably 0.02% by mass or more, further preferably 0.03% by mass or more, particularly preferably It is 0.04 mass% or more. The upper limit of the content of the sodium-containing component in the optical film of the present invention is preferably 1 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 easily obtaining a homogeneous film. The content is preferably not more than 0.5% by mass, more preferably not more than 0.5% by mass, further preferably not more than 0.1% by mass. The content of the sodium-containing component with respect to the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the optical film may be measured by a spectroscopic method such as infrared absorption spectrum, or when the optical film is produced. The content of the varnish used in Step 1 may be the content of the optical film. When a compound containing a sodium atom is used as the sodium-containing component, the compound may be decomposed in the process of producing an optical film, as long as the effect of the present invention is not impaired.

The type of compound containing a sodium atom is not particularly limited. In the case of producing an optical film using a resin composition containing at least a polyimide resin and/or a polyamide resin and a solvent (also referred to as “varnish”), the component is easily dissolved in the solvent of the varnish, From the viewpoint of easy inclusion in the optical film, the compound containing a sodium atom is preferably an organic sodium salt. Examples of the organic sodium salt include sodium alkoxide having 1 to 6 carbon atoms. The compound containing a sodium atom added to the resin composition does not need to be contained in the optical film of the present invention in the form of, for example, an organic sodium salt or the like, and for example, water that may be contained in the resin composition. Another salt may be formed in the final optical film by hydrolysis with a salt, alcohol or the like or an ion exchange reaction with another salt, or may be contained as sodium or sodium ion. ..

<Additive>
The optical film of the present invention may include a filler. Examples of the filler include organic particles and inorganic particles, and preferably inorganic particles. Examples of the inorganic particles include silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, metal oxide particles such as cerium oxide, magnesium fluoride, fluorine. Examples thereof include metal fluoride particles such as sodium fluoride. The filler is preferably silica particles, zirconia particles, or alumina particles, more preferably silica particles, from the viewpoint of easily increasing the elastic modulus of the optical film and improving the impact resistance of the optical film. These fillers can be used alone or in combination of two or more.

The average primary particle diameter of the filler, preferably silica particles, is 1 nm or more, preferably 5 nm or more, more preferably 10 nm or more, further preferably 15 nm or more, particularly preferably 20 nm or more, preferably 100 nm or less, more preferably 90 nm. Or less, more preferably 80 nm or less, still more preferably 70 nm or less, particularly preferably 60 nm or less, particularly preferably 50 nm or less, particularly preferably 40 nm or less. When the average primary particle diameter of the silica particles is within the above range, aggregation of the silica particles is suppressed and the optical properties of the obtained optical film are easily improved. The average primary particle diameter of the filler can be measured by the BET method. The primary particle size (average primary particle size) may be measured by image analysis with 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, and more preferably 100 parts by mass of the optical film. It is 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 60 parts by mass or less. When the content of the filler is at least the above lower limit, the elastic modulus of the obtained optical film can be easily improved. Moreover, when the content of the filler is not more than the above upper limit, the optical characteristics of the optical film are likely to be improved.

The optical film of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber can be appropriately selected from those usually used as an ultraviolet absorber in the field of resin materials. The ultraviolet absorber may include a compound that absorbs light having a wavelength of 400 nm or less. Examples of the ultraviolet absorber include at least one compound selected from the group consisting of benzophenone compounds, salicylate compounds, benzotriazole compounds, and triazine compounds. The ultraviolet absorbers can be used alone or in combination of two or more kinds. Since the optical film contains the ultraviolet absorber, deterioration of the resin is suppressed, and thus the visibility can be improved when the obtained optical film is applied to an image display device or the like. In the present specification, the “system compound” refers to a derivative of the compound to which the “system compound” is attached. For example, “benzophenone-based compound” refers to a compound having benzophenone as a base skeleton and a substituent bonded to 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, and further preferably 3 parts by mass or more with respect to 100 parts by mass of the optical film. And preferably 10 parts by mass or less, more preferably 8 parts by mass or less, still more preferably 6 parts by mass or less. The suitable content varies depending on the ultraviolet absorber used, but if the content of the ultraviolet absorber is adjusted so that the light transmittance at 400 nm is about 20 to 60%, the light resistance of the optical film is increased and the transparency is improved. It is easy to raise.

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

(Method of manufacturing optical film)
The method for producing the optical film of the present invention is not particularly limited, but for example, the following steps:
(A) at least one resin selected from the group consisting of the polyimide-based resin and the polyamide-based resin, a compound containing a sodium atom, sodium and/or sodium ions, and a resin composition containing at least a solvent (hereinafter, (Also referred to as "varnish") step (varnish preparation step),
(B) a step of applying a varnish to a support material to form a coating film (application step), and (c) a step of drying the applied liquid (coating film) to form an optical film (optical film forming step) )
It may be a manufacturing method including. The present invention comprises at least one resin selected from the group consisting of polyimide resins and polyamide resins suitable for producing the optical film of the present invention, a compound containing a sodium atom, a group consisting of sodium and sodium ions. There is also provided a resin composition containing at least one selected sodium-containing component and at least a solvent.

In the varnish preparation step, the varnish is prepared by dissolving the polyimide-based resin and/or the polyamide-based resin and the sodium-containing component in a solvent, and if necessary, adding the filler, an additive such as an ultraviolet absorber, and stirring and mixing. To prepare. When silica particles are used as a filler, a dispersion of a silica sol containing silica particles may be added to the resin with a solvent capable of dissolving the resin, for example, a silica sol obtained by substituting with a solvent used for preparing a varnish described below. ..

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 ion in the optical film of the present invention. From the viewpoint of being easily dissolved in the solvent of the varnish and easily containing the component in the optical film, a compound containing a sodium atom is preferable, and an organic sodium salt is more preferable. Examples of the organic sodium salt include sodium alkoxide having 1 to 6 carbon atoms. The sodium-containing component contained in the varnish may be one type of component or a combination of two or more types of components.

The content of the sodium-containing component contained in the resin composition is preferably 0. 0 based on the total amount of the polyimide resin and/or the polyamide resin contained in the resin composition from the viewpoint of easily increasing the elastic modulus of the optical film. 002 mass% or more, more preferably 0.004 mass% or more, further preferably 0.01 mass% or more, even more preferably 0.02 mass% or more, particularly preferably 0.03 mass% or more, particularly preferably 0. It is 0.04 mass% or more. The upper limit of the content of the sodium-containing component in the resin composition of the present invention, from the viewpoint of the varnish viscosity adjusting property and the film forming property, with respect to the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the resin composition. It is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less. When the content of the sodium-containing component is less than or equal to the above upper limit, the viscosity of the varnish does not increase too much, and the resin solid content in the varnish is easily increased, so that the film formability is easily improved.

The solvent used for preparing 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 γ-butyrolactone (GBL) and γ-valerolactone; dimethyl sulfone, dimethyl sulfoxide, sulfolane and the like. And a carbonate-based solvent such as ethylene carbonate and propylene carbonate; and a combination thereof (mixed solvent). Among these, amide solvents or lactone solvents are preferable. These solvents can be used alone or in combination of two or more. Further, the varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether 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 further preferably 5 to 15% by mass.

In the coating step, a varnish is coated on the support material to form a coating film by a known coating method. As a known coating method, for example, wire bar coating method, reverse coating, roll coating method such as gravure coating, die coating method, comma coating method, lip coating method, spin coating method, screen coating method, fountain coating method, dipping method, A spray method, a spout molding method and the like can be mentioned.

In the film forming process, the optical film can be formed by drying the coating film and peeling it from the support material. You may provide the process of drying an optical film further after peeling. The coating film can be dried usually at a temperature of 50 to 350°C. If necessary, the coating film may be dried under an inert atmosphere or a reduced pressure condition.

Examples of the support material include SUS plate if it is metal-based, PET film, PEN film if it is resin-based, polyamide resin film, other polyimide resin film, cycloolefin polymer (COP) film, acrylic resin. A film etc. are mentioned. Among them, a PET film, a COP film and the like are preferable from the viewpoint of excellent smoothness and heat resistance, and further, a PET film is more preferable from the viewpoint of adhesion to an optical film and cost.

(Functional layer)
One or more functional layers 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, a primer layer, a gas barrier layer, an adhesive layer, a hue adjusting layer and a refractive index adjusting layer. The functional layer may be used alone or in combination of two or more kinds. When the optical film has the functional layer, it is preferable to measure the cross section of the optical film by TOF-SIMS.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays, and for example, a main material selected from a transparent resin of an ultraviolet curable type, a transparent resin of an electron beam curable type, and a transparent resin of a thermosetting type, and the main material It is composed of dispersed ultraviolet absorbers.

The adhesive layer is a layer having an adhesive function and has a function of adhering the optical film to another member. A commonly known material can be used as the material for forming the adhesive layer. For example, a thermosetting resin composition or a photocurable resin composition can be used. In this case, the resin composition can be polymerized and cured by supplying energy afterwards.

The pressure-sensitive adhesive layer may be a layer called pressure sensitive adhesive (Pressure Sensitive Adhesive, PSA) that is attached to an object by pressing. The pressure-sensitive adhesive may be an adhesive that is "a substance that has tackiness at room temperature and that adheres to an adherend with a light pressure" (JIS K6800), "a protective film (microcapsule) for a specific component". The capsule-type adhesive which is "adhesive capable of maintaining stability until the coating is broken by an appropriate means (pressure, heat, etc.)" (JIS K6800).

The hue adjusting layer is a layer having a hue adjusting function, and is a layer capable of adjusting a laminate including the optical film to a desired hue. The hue adjustment layer is, for example, a layer containing a resin and a colorant. Examples of the colorant include titanium oxide, zinc oxide, rouge, titanium oxide-based calcined pigment, ultramarine blue, cobalt aluminate, and inorganic pigments such as carbon black; azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, Organic pigments such as perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, slene compounds, and diketopyrrolopyrrole compounds; extender pigments such as barium sulfate and calcium carbonate; and basic dyes, Examples include acid dyes and mordant dyes.

The refractive index adjusting layer is a layer having a function of adjusting the refractive index, and has a refractive index different from that of the optical film, for example, and is a layer capable of imparting a predetermined refractive index to the optical laminate. The refractive index adjusting layer may be, for example, a resin layer containing an appropriately selected resin and optionally a pigment, or 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 average primary particle diameter of the pigment may be 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 passing 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 metals 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. An oxide or a metal nitride is mentioned.

The optical film of the present invention may be a single layer or a laminate, for example, the optical film produced as described above may be used as it is, or a laminate with another film. May be used as. The optical film of the present invention having a ratio (I _Na /I _CH3 ) of _Na ionic strength (I _Na ) to CH ₃ ionic strength (I _CH3 ) obtained by time-of-flight secondary ion mass spectrometry of 0.2 or more. Is a film having excellent impact resistance due to its excellent elastic modulus, and is useful as an optical film in image display devices and the like.

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

Examples of the image display device include TVs, smartphones, mobile phones, car navigations, tablet PCs, portable game machines, electronic paper, indicators, bulletin boards, watches, and wearable devices such as smart watches. Examples of the flexible display device include all image display devices having flexible characteristics.

[Flexible display device]
The present invention also provides a flexible display device including the optical film of the present invention. The flexible display device includes a flexible display device laminate and an organic EL display panel. The flexible display device laminate is arranged on the viewing side of 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) of the present invention, a circularly polarizing plate, and a touch sensor, and the order of laminating them is arbitrary, but the window film, the circularly polarized light from the viewing side may be included. It is preferable that the plate, the touch sensor or the window film, the touch sensor, and the circularly polarizing plate are laminated in this order. The presence of the circularly polarizing plate on the viewing side of the touch sensor is preferable because the pattern of the touch sensor is less visible and the visibility of the display image is improved. Each member can be laminated using an adhesive, a pressure-sensitive adhesive or the like. In addition, a light-shielding pattern formed on at least one surface of any one of a window film, a circularly polarizing plate, and a touch sensor can be provided.

[Window film]
The window film is arranged on the viewing side of the flexible image display device and plays a role of protecting the other components from external impacts or environmental changes such as temperature and humidity. Conventionally, glass has been used as such a protective layer, but the window film in a flexible image display device is not rigid and rigid like glass, but has flexible characteristics. The optical film of the present invention may be used as the window film, and it may be made of a flexible transparent substrate such as the film and may include a hard coat layer on at least one surface.

(Transparent substrate)
The transmittance of the transparent substrate in the visible region is usually 70% or higher, preferably 80% or higher. As the transparent substrate, it is preferable to use an optical film containing the polyimide resin and/or the polyamide resin of the present invention. Inorganic particles such as silica, organic particles, rubber particles and the like may be dispersed in the optical film of the present invention. Furthermore, colorants such as pigments and dyes, optical brighteners, dispersants, plasticizers, heat stabilizers, light stabilizers, infrared absorbers, ultraviolet absorbers, antistatic agents, antioxidants, lubricants, solvents, etc. You may include the compounding agent of. The thickness of the transparent substrate is usually 5 to 200 μm, preferably 20 to 100 μm.

(Hard coat)
The window film may be provided with a hard coat layer 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 μm. When the thickness of the hard coat layer is within the above range, sufficient scratch resistance can be ensured, bending resistance is unlikely to decrease, and a problem of curling due to curing shrinkage tends not to occur. ..
The hard coat layer can be formed by curing a hard coat composition containing a reactive material capable of forming a crosslinked structure by irradiation with active energy rays or application of heat energy, and irradiation with active energy rays is preferable. Active energy rays are defined as energy rays capable of decomposing compounds that generate active species to generate active species, such as visible light, ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays and electron rays. And the like, and preferably ultraviolet rays. The hard coat composition contains at least one polymer of a radically polymerizable compound and a cationically polymerizable compound.

The radically polymerizable compound is a compound having a radically polymerizable group. The radical polymerizable group contained in the radical polymerizable compound may be any functional group capable of causing a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond, and specifically, a vinyl group. And (meth)acryloyl group. When the radical-polymerizable compound has two or more radical-polymerizable groups, these radical-polymerizable groups may be the same or different. The number of radically polymerizable groups contained in one molecule of the radically polymerizable compound is preferably 2 or more from the viewpoint of improving the hardness of the hard coat layer. From the viewpoint of high reactivity, the radical-polymerizable compound is preferably a compound having a (meth)acryloyl group. Specifically, 2 to 6 (meth)acryloyl groups are included in one molecule. A compound called a polyfunctional acrylate monomer, an epoxy (meth)acrylate, a urethane (meth)acrylate, or a polyester (meth)acrylate, which has several (meth)acryloyl groups in the molecule, has a molecular weight of from several hundred. Thousands of oligomers may be mentioned, preferably one or more selected from epoxy (meth)acrylate, urethane (meth)acrylate and polyester (meth)acrylate.

The cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetanyl group and a vinyl ether group. The number of cationically polymerizable groups contained in one molecule of the cationically polymerizable compound is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.
In addition, as the cationically polymerizable compound, among others, a compound having at least one of an epoxy group and an oxetanyl group as a cationically polymerizable group is preferable. A cyclic ether group such as an epoxy group or an oxetanyl group is preferable from the viewpoint that the shrinkage accompanying the polymerization reaction is small. In addition, compounds having an epoxy group among cyclic ether groups are easily available as compounds having various structures, do not adversely affect the durability of the obtained hard coat layer, and easily control the compatibility with the radically polymerizable compound. There is an advantage that. Further, among the cyclic ether groups, the oxetanyl group is more likely to have a higher degree of polymerization than the epoxy group and has low toxicity, and accelerates the network formation rate obtained from the cationically polymerizable compound of the obtained hard coat layer, and radicals. Even in a region mixed with a polymerizable compound, there is an advantage that an unreacted monomer is not left in the film and an independent network is formed.
As the cationically polymerizable compound having an epoxy group, for example, a polyglycidyl ether of a polyhydric alcohol having an alicyclic ring or a cyclohexene ring, a cyclopentene ring-containing compound, hydrogen peroxide, with a suitable oxidizing agent such as peracid Alicyclic epoxy resin obtained by epoxidation; polyglycidyl ether of aliphatic polyhydric alcohol or alkylene oxide adduct thereof, polyglycidyl ester of aliphatic long-chain polybasic acid, homopolymer of glycidyl (meth)acrylate, Aliphatic epoxy resins such as copolymers; glycidyl ethers produced by the reaction of bisphenol A, bisphenol F, bisphenols such as hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts and caprolactone adducts with epichlorohydrin, And glycidyl ether type epoxy resins derived from bisphenols, such as novolac epoxy resins.

The hard coat composition may further include a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, etc., which are 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, thereby promoting radical polymerization and cation polymerization.
The radical polymerization initiator may be any one that can release a substance that initiates radical polymerization by at least one of irradiation with active energy rays and heating. Examples of thermal radical polymerization initiators include hydrogen peroxide, organic peroxides such as perbenzoic acid, and azo compounds such as azobisbutyronitrile.
As the active energy ray radical polymerization initiator, a Type 1 type radical polymerization initiator that produces a radical by decomposition of a molecule and a Type 2 type radical polymerization initiator that produces a radical by a hydrogen abstraction type reaction coexisting with a tertiary amine Yes, they are used alone or in combination.
Any cationic polymerization initiator may be used as long as it can release a substance that initiates cationic polymerization by irradiation with active energy rays and/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. These can initiate cationic polymerization either by irradiation with active energy rays or by heating, or both, depending on the difference in structure.

The polymerization initiator may be included in an amount of preferably 0.1 to 10% by mass based on 100% by mass of the entire hard coat composition. When the content of the polymerization initiator is in the above range, curing can be sufficiently advanced, and the mechanical properties and adhesion of the finally obtained coating film can be set in a good range, and Poor adhesion due to curing shrinkage, cracking and curling tend to occur less easily.

The hard coat composition may further include one or more selected from the group consisting of a solvent and an additive.
The solvent is a solvent that can dissolve or disperse the polymerizable compound and the polymerization initiator, if the solvent is known as a solvent of the hard coat composition of the present technical field, does not impair the effects of the present invention Can be used in a range.
The additive may further include inorganic particles, a leveling agent, a stabilizer, a surfactant, an antistatic agent, a lubricant, an antifouling agent, and the like.

[Polarizer]
The flexible display device including the optical film of the present invention may further include a polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only the right or left circularly polarized light component by laminating a λ/4 retardation plate on a linearly polarizing plate. For example, by converting the external light into right circularly polarized light and blocking the external light reflected by the organic EL panel to become left circularly polarized light, and transmitting only the luminescent component of the organic EL, the influence of reflected light is suppressed and the image is displayed. It is used to make it easier to see. In order to achieve the circular polarization function, the absorption axis of the linear polarizing plate and the slow axis of the λ/4 retardation plate are theoretically required to be 45°, but they are practically 45±10°. The linearly polarizing plate and the λ/4 retardation plate are not necessarily required to be laminated adjacent to each other as long as the relationship between the absorption axis and the slow axis satisfies the above range. It is preferable to achieve perfect circularly polarized light at all wavelengths, but this is not necessary in practice, so the circularly polarizing plate in the present invention also includes an elliptically polarizing plate. It is also preferable to further laminate a λ/4 retardation film on the visible side of the linearly polarizing plate to make the emitted light circularly polarized light to improve the visibility in the state of wearing polarized sunglasses.

The linearly polarizing plate is a functional layer having a function of transmitting light oscillating in the transmission axis direction but blocking polarized light of an oscillating component perpendicular thereto. The linear polarizing plate may be configured to include a linear polarizer alone or 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 in the above range, the flexibility tends to be difficult to decrease.
The linear polarizer may be a film-type polarizer manufactured by dyeing and stretching a polyvinyl alcohol (PVA) film. A dichroic dye such as iodine is adsorbed on a PVA-based film oriented by stretching or is stretched in a state of being adsorbed on PVA, whereby the dichroic dye is oriented and exhibits polarization performance. The production of the film-type polarizer may further include steps such as swelling, crosslinking with boric acid, washing with an aqueous solution, and drying. The stretching and dyeing steps may be performed on the PVA film alone, or may be performed in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA-based film used is preferably 10 to 100 μm, and the stretching ratio is preferably 2 to 10 times.
Further, as another example of the polarizer, a liquid crystal coating type polarizer formed by coating a liquid crystal polarizing composition may be used. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic dye compound. The liquid crystalline compound is only required to have a property of exhibiting a liquid crystal state, and particularly preferably has a higher order alignment state such as a smectic phase because high polarization performance can be exhibited. It is also preferable that the liquid crystal compound has a polymerizable functional group.

The dichroic dye is a dye that is aligned with the liquid crystal compound and exhibits dichroism, and the dichroic dye itself may have liquid crystallinity or has a polymerizable functional group. You can also Any 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 cross-linking agent, a silane coupling agent and the like.
The liquid crystal polarizing layer is manufactured by applying a liquid crystal polarizing composition on the alignment film to form a liquid crystal polarizing layer.
The liquid crystal polarizing layer can be formed thinner than a film type polarizer. The thickness of the liquid crystal polarizing layer may be preferably 0.5 to 10 μm, more preferably 1 to 5 μm.
The alignment film can be produced, for example, by applying the composition for forming an alignment film on a substrate and imparting the alignment property by rubbing, irradiation of polarized light, or the like. The composition for forming an alignment film may contain a solvent, a cross-linking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent and the like in addition to the alignment agent. As the alignment agent, for example, polyvinyl alcohols, polyacrylates, polyamic acids, and polyimides can be used. When photo-alignment is applied, it is preferable to use an aligning agent containing a cinnamate group. The weight average molecular weight of the polymer used as the aligning agent may be about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000 nm, more preferably 10 to 500 nm from the viewpoint of the alignment control force. The liquid crystal polarizing layer can be peeled from the base material and transferred to be laminated, or the base material can be laminated as it is. It is also preferable that the base material plays a role as a transparent base material of 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 has a monomer unit containing polyethylene, polypropylene, polymethylpentene, norbornene or cycloolefin. Polyolefins such as cycloolefin derivatives, (modified)celluloses such as diacetylcellulose, triacetylcellulose, propionylcellulose, acrylics such as methylmethacrylate (co)polymers, polystyrenes such as styrene (co)polymers, acrylonitrile -Butadiene-styrene copolymers, acrylonitrile-styrene copolymers, ethylene-vinyl acetate copolymers, polyvinyl chlorides, polyvinylidene chlorides, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, poly Films such as polyesters such as arylate, polyamides such as nylon, polyimides, polyamideimides, polyetherimides, polyethersulfones, polysulfones, polyvinyl alcohols, polyvinyl acetals, polyurethanes, epoxy resins, etc. Of these, polyamide, polyamide-imide, polyimide, polyester, olefin, acrylic or cellulose-based films are preferable in terms of excellent transparency and heat resistance. These polymers can be used alone or in admixture of two or more. These films are used as unstretched films or as uniaxially or biaxially stretched films. Cellulose type films, olefin type films, acrylic films and polyester type films are preferable. It may be a coating type protective film obtained by applying and curing a cationically curable composition such as an epoxy resin or a radical curable composition such as an acrylate. If necessary, plasticizers, ultraviolet absorbers, infrared absorbers, colorants such as pigments and dyes, optical brighteners, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants, lubricants, solvents, etc. May be included. 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 does not easily deteriorate.

The λ/4 retardation plate is a film that gives a λ/4 retardation in a direction orthogonal to the traveling direction of incident light (in-plane direction of the film). The λ/4 retardation plate may be a stretchable retardation plate produced by stretching a polymer film such as a cellulose-based film, an olefin-based film, or a polycarbonate-based film. If necessary, retarder, plasticizer, ultraviolet absorber, infrared absorber, colorant such as pigment or dye, fluorescent brightening agent, dispersant, heat stabilizer, light stabilizer, antistatic agent, antioxidant. , A lubricant, a solvent, etc. may be contained. The thickness of the stretchable retardation plate may be 200 μm or less, and preferably 1 to 100 μm. When the thickness is in the above range, the flexibility of the film tends to be less likely to decrease.
Further, another example of the λ/4 retardation plate may be a liquid crystal coating type retardation plate formed by applying a liquid crystal composition. The liquid crystal composition contains a liquid crystal compound having a property of exhibiting a liquid crystal state such as nematic, cholesteric, or smectic. Any compound in the liquid crystal composition, including the liquid crystal compound, has a polymerizable functional group. The liquid crystal coated retardation plate may further contain an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a cross-linking agent, a silane coupling agent and the like. The liquid crystal coating type retardation plate can be manufactured by coating and curing the liquid crystal composition on the alignment film to form the liquid crystal retardation layer as in the case of the liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed thinner than the stretched type retardation plate. The liquid crystal polarizing layer may have a thickness of usually 0.5 to 10 μm, preferably 1 to 5 μm. The liquid crystal coating type retardation plate can be peeled from the base material and transferred to be laminated, or the base material can be laminated as it is. It is also preferable that the base material plays a role as a transparent base material of a protective film, a retardation plate and a window film.

In general, many materials exhibit large birefringence at shorter wavelengths and smaller birefringence at longer wavelengths. In this case, since a phase difference of λ/4 cannot be achieved in the entire visible light region, an in-plane phase difference of 100 to 180 nm, preferably 130, which is λ/4 near 560 nm where the visibility is high. Often designed to be ~150 nm. It is preferable to use an inverse dispersion λ/4 retardation plate using a material having a birefringence wavelength dispersion characteristic opposite to the usual one because the visibility can be improved. As such a material, those described in JP-A-2007-232873 in the case of a stretched phase difference plate and those disclosed in JP-A-2010-30979 in the case of a liquid crystal coating type phase difference plate may be used. preferable.
As another method, there is also known a technique for obtaining a broadband λ/4 retardation plate by combining it with a λ/2 retardation plate (Japanese Patent Laid-Open No. 10-90521). The λ/2 retardation plate is also manufactured by the same material method as that of the λ/4 retardation plate. The combination of the stretched retardation plate and the liquid crystal coating type retardation plate is arbitrary, but it is preferable to use the liquid crystal coating type retardation plate for both because the thickness can be reduced.
There is also known a method of laminating a positive C plate on the circularly polarizing plate in order to enhance visibility in an oblique direction (Japanese Patent Laid-Open No. 2014-224837). The positive C plate may be a liquid crystal coating type retardation plate or a stretching type retardation plate. The retardation 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 types such as a resistance film type, a surface acoustic wave type, an infrared type, an electromagnetic induction type, and a capacitance type have been proposed, and any type may be used. Of these, the capacitance method is preferable. The capacitive touch sensor is divided into an active region and a non-active region located outside the active region. The active region is a region corresponding to a region where the screen is displayed on the display panel (display unit), and is a region where the user's touch is sensed, and the inactive region is a region where the screen is not displayed on the display device (non-display region). It is an area corresponding to the display part). The touch sensor includes a substrate having flexible characteristics; a sensing pattern formed in an active region of the substrate; formed in an inactive region of the substrate and connected to an external driving circuit through the sensing pattern and a pad unit. Each sensing line can be included. As the substrate having flexible characteristics, the same material as the polymer film can be used. The toughness of the substrate of the touch sensor is preferably 2,000 MPa% or more from the viewpoint of suppressing cracks in the touch sensor. More preferably, the toughness may be 2,000 to 30,000 MPa%. Here, the toughness is defined as the area under the curve to the breaking point in a stress (MPa)-strain (%) curve (Stress-strain curve) obtained through a tensile test of a polymer material.

The sensing pattern may include a first pattern formed in the first direction and a second pattern formed in the second direction. The first pattern and the second pattern are arranged in different directions. The first pattern and the second pattern are formed on the same layer, and the respective patterns must be electrically connected in order to detect a touched point. The first pattern has a structure in which the unit patterns are connected to each other through a joint, but the second pattern has a structure in which the unit patterns are separated from each other in an island shape. A separate bridge electrode is required to make the connection. A known transparent electrode material can be applied to the sensing pattern. 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 nanotube (CNT), graphene, metal wire, and the like, and these may be used alone or in combination of two or more. Preferably ITO can be used. The metal used for the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, terrenium, and chromium. These may be used alone or in combination of two or more.

The bridge electrode may be formed on the sensing layer via an insulating layer, and the bridge electrode may be formed on the substrate, and the insulating layer and the sensing pattern may be formed on the bridge electrode. The bridge electrode may be formed of the same material as the sensing pattern, and 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 of these. You can also do it. Since the first pattern and the second pattern must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the joint of the first pattern and the bridge electrode, or may be formed in the structure of the layer covering the sensing pattern. In the latter case, the bridge electrode can connect the second pattern through a contact hole formed in the insulating layer. The touch sensor has a difference in transmittance between a pattern area where a pattern is formed and a non-pattern area where a pattern is not formed, specifically, a light transmittance which is induced by a difference in refractive index in these areas. An optical adjustment layer may be further included between the substrate and the electrode as a means for appropriately compensating the difference, and the optical adjustment layer may include an inorganic insulating material or an organic insulating material. The optical adjustment layer may be formed by coating a photocurable composition containing a photocurable organic binder and a solvent on a substrate. The photocurable composition may further include inorganic particles. The inorganic particles can increase the refractive index of the optical adjustment layer.
The photocurable organic binder may include, for example, a copolymer of each monomer such as an acrylate-based monomer, a styrene-based monomer, and a carboxylic acid-based monomer. The photocurable organic binder may be, for example, a copolymer containing different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.
The inorganic particles can include, for example, zirconia particles, titania particles, alumina particles, and the like. The photocurable composition may further include various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

[Adhesive layer]
Each layer (window film, circularly polarizing plate, touch sensor) forming the laminate for a flexible image display device and film members (linear polarizing plate, λ/4 retardation plate, etc.) forming each layer are bonded with an adhesive. You can As the adhesive, a water-based adhesive, an organic solvent-based adhesive, a solvent-free adhesive, a solid adhesive, a solvent volatilization adhesive, a moisture-curable adhesive, a heat-curable adhesive, an anaerobic-curable adhesive, active General-purpose adhesives such as energy ray-curable adhesives, curing agent-mixed adhesives, hot-melt adhesives, pressure-sensitive adhesives (adhesives), and rewet adhesives can be used. Of these, water-based solvent volatilizing adhesives, active energy ray-curing adhesives, and pressure-sensitive adhesives are often used. The thickness of the adhesive layer can be appropriately adjusted according to the required adhesive strength and the like, and is, for example, 0.01 to 500 μm, preferably 0.1 to 300 μm. A plurality of adhesive layers may be present in the laminate for a flexible image display device, but the thickness of each and the type of adhesive used may be the same or different.

As the water-based water-based solvent volatilizing adhesive, polyvinyl alcohol-based polymers, water-soluble polymers such as starch, and water-dispersed polymers such as ethylene-vinyl acetate emulsions and styrene-butadiene-based emulsions can be used as the main polymer. In addition to water and the base polymer, a cross-linking agent, a silane compound, an ionic compound, a cross-linking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent and the like may be added. In the case of bonding with the water-based solvent volatilization type adhesive, the water-based water-based solvent volatilization type adhesive may be injected between the adhered layers to bond the adhered layers and then dried to impart adhesiveness. When the water-based water-based solvent volatilizing adhesive is used, the thickness of the adhesive layer may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the former aqueous solvent volatilization type adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive may be the same or different.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material that is irradiated with an active energy ray to form an adhesive layer. The active energy ray-curable composition can contain at least one polymer of a radically polymerizable compound and a cationically polymerizable compound similar to the hard coat composition. The radical-polymerizable compound is the same as the hard coat composition, and the same kind as the hard coat composition can be used. As the radically polymerizable compound used in the adhesive layer, a compound having an acryloyl group is preferable. It is also preferable to include a monofunctional compound in order to reduce the viscosity of the adhesive composition.

The cationically polymerizable compound is the same as that used in the hard coat composition, and the same kind as the hard coat composition can be used. An epoxy compound is particularly preferable as the cationically polymerizable compound used in the active energy ray-curable composition. It is also preferable to include a monofunctional compound as a reactive diluent to reduce the viscosity of the adhesive composition.
The active energy ray composition may further contain a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, etc., which can 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, thereby promoting radical polymerization and cation polymerization. In the description of the hard coat composition, an initiator capable of initiating radical polymerization and/or cationic polymerization by irradiation with active energy rays can be used.

The active energy ray-curable composition is further an ion scavenger, an antioxidant, a chain transfer agent, an adhesion promoter, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, a defoaming agent solvent, an additive, a solvent. Can be included. In the case of adhering with the active energy ray-curable adhesive, the active energy ray-curable composition is applied to either or both of the adherend layers and then laminated, and activated through either adherent layer or both adherent layers. It can be adhered by irradiating it with an energy ray and curing it. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer may be 0.01 to 20 μm, preferably 0.1 to 10 μm. 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 pressure-sensitive adhesive may be classified into an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, etc. depending on the base polymer, and any of these may be used. In addition to the base polymer, the adhesive may contain a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a tackifier, a plasticizer, a dye, a pigment, an inorganic filler, and the like. A pressure-sensitive adhesive layer (adhesive layer) is formed by dissolving and dispersing each component constituting the pressure-sensitive adhesive in a solvent to obtain a pressure-sensitive adhesive composition, applying the pressure-sensitive adhesive composition on a substrate, and then drying it. To be done. The adhesive layer may be directly formed, or may be separately formed on a substrate and transferred. It is also preferable to use a release film to cover the adhesive surface before adhesion. When the pressure-sensitive adhesive is used, the thickness of the adhesive layer may be 1 to 500 μm, preferably 2 to 300 μm. When the pressure sensitive adhesive is used to form a plurality of layers, the thickness of each layer and the type of pressure sensitive adhesive used may be the same or different.

[Shading pattern]
The light shielding pattern may be applied as at least a part of a bezel or a housing of the flexible image display device. The light-shielding pattern hides the wiring arranged at the peripheral portion of the flexible image display device to make it difficult to be visually recognized, thereby improving the visibility of the image. The light-shielding pattern may be in the form of a single layer or multiple layers. The color of the light-shielding pattern is not particularly limited, and may have various colors such as black, white and metallic colors. The light-shielding pattern can be formed of a pigment for realizing color and a polymer such as acrylic resin, ester resin, epoxy resin, polyurethane, or silicone. These may be used alone or as a mixture of two or more kinds. The light-shielding pattern can be formed by various methods such as printing, lithography and inkjet. The thickness of the light-shielding pattern is usually 1 to 100 μm, preferably 2 to 50 μm. Further, it is also preferable to provide a shape such as an inclination in the thickness direction of the light shielding pattern.

Hereinafter, the present invention will be described in more detail with reference to Examples. Unless otherwise specified, "%" and "parts" in the examples mean% by mass and parts by mass, respectively. First, a method for measuring physical property values will be described. The results shown in Table 1 are the results measured according to the following measuring method.

(Measurement of weight average molecular weight (Mw))
The weight average molecular weight of the resin was measured using gel permeation chromatography (GPC). The method for preparing the measurement sample and the measurement conditions are as follows.
(1) Sample preparation method 20 mg of resin was weighed and 10 mL of DMF (10 mM lithium bromide) was added to completely dissolve the resin. This solution was filtered through a chromatodisc (pore size 0.45 μm) to give a sample solution.
(2) Measurement condition device: HLC-8020GPC
Column: Guard column + TSKgel α-M (300 mm × 7.8 mm diameter) × 2 + α-2500 (300 mm × 7.8 mm diameter) × 1 Eluent: DMF (10 mM lithium bromide added)
Flow rate: 1.0 mL/min.
Detector: RI detector Column temperature: 40°C
Injection volume: 100 μL
Molecular weight standard: Standard polystyrene

(Measurement of total light transmittance)
The total light transmittance of the optical film was measured by a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. according to JIS K 7105:1981.

(Measurement of elastic modulus)
The optical film was cut into a strip of 10 mm×100 mm using a dumbbell cutter to obtain a test sample. The elastic modulus of this test sample was measured using an Autograph AG-IS manufactured by Shimadzu Corporation under the conditions of a chuck distance of 50 mm and a pulling speed of 10 mm/min, and an optical curve was obtained from the inclination of 5 to 20 MPa. The elastic modulus (GPa) of the film was calculated.

(Measurement of thickness)
With respect to the optical films obtained in Examples and Comparative Examples, the thickness of the optical film was measured using an ABS Digimatic Indicator (“ID-C112BS” manufactured by Mitutoyo Corporation).

(Time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurement)
A cross section of the optical film was prepared using "Ultra Microtome EM UC6" manufactured by Leica Micro Systems.

The cross section of the produced resin film was analyzed by TOF-SIMS. The TOF-SIMS device used for the analysis and the measurement conditions are as follows.
(1) Device: "TOF.SIMS V" manufactured by ION-TOF,
(2) Primary ion: Bi ³⁺⁺
(3) Accelerating voltage of primary ion: 25 kV
(4) Irradiation ion current: 0.23 pA
(5) Measurement conditions: Positive ions and negative ions are measured in bunching (high mass resolution) mode. (6) Measurement range: 200 μm×200 μm.

SurfaceLab was used for TOF-SIMS data analysis. The measurement data was subjected to mass calibration, and the integrated value of the peak was calculated for each of the peaks attributed to Na ions and CH ₃ ions. The ratio I _Na /I _CH3 was calculated with the integrated value of the Na ion peak as the Na ion intensity I _Na and the integrated value of the CH ₃ ion peak as the CH ₃ ion intensity I _CH3 .

(Measurement of viscosity)
The viscosity of the resin composition was measured under the following conditions.
Device name: LVDV-II+Pro (manufactured by Brookfield)
Measurement temperature: 25℃
Spindle: CPE-52
Sample volume: 0.8mL
Rotor rotation speed: 3 rpm

[Synthesis example: manufacture of polyamide-imide resin]
Nitrogen was introduced into a sufficiently dried reaction vessel equipped with a stirrer and a thermometer, and the inside of the vessel was replaced with nitrogen. Into the reaction vessel, 1907.2 parts by mass of dimethylacetamide (DMAc) was put, and 111.94 parts by mass of 2,2′-bis(trifluoromethyl)benzidine (TFMB) and 4,4′-(hexafluoroisopropylidene). 46.84 parts by mass of diphthalic dianhydride (6FDA) was added and reacted.
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 and reacted.
Next, after adding 37.66 parts by mass of acetic anhydride and stirring for 15 minutes, 11.45 parts by mass of 4-picoline was added, the temperature of the reaction vessel was raised to 70° C., and stirring was further performed for 3 hours to obtain a reaction liquid. ..
The reaction liquid was cooled, 3794.5 parts by mass of methanol was added, and then 1419.4 parts by mass of ion-exchanged water was added dropwise to deposit a white solid. The precipitated white solid was collected by centrifugal filtration and washed with methanol to obtain a wet cake containing a polyamideimide resin. The obtained wet cake was dried at 78° C. under reduced pressure to obtain a polyamideimide resin powder. The weight average molecular weight of the obtained resin was 466,000.

[Production of GBL solution containing sodium-containing component]
As a sodium-containing component, a sodium ethoxide ethanol solution (manufactured by Wako Pure Chemical Industries, Ltd.) containing 20% by mass of sodium ethoxide (NaOEt, a compound containing a sodium atom) was diluted with γ-butyrolactone (GBL) to obtain sodium. A NaOEt solution containing ethoxide at a concentration of 0.1 mass% was prepared.

[Production of Polyamideimide Resin Composition (Varnish)]
The polyamide-imide resin obtained in the above synthesis example, GBL, and the NaOEt solution produced as described above are mixed in an amount such that the content rate of the polyamide-imide resin and the content rate of NaOEt in each resin composition are the following values. Then, a polyamide-imide resin composition (varnish) for film formation was prepared. The content of the polyamideimide resin in each resin composition is 6.3% by mass with respect to the total amount of the polyamideimide resin composition, and the content of NaOEt in each resin composition is included in each resin composition. It was 0% by mass, 0.005% by mass, 0.05% by mass, 0.1% by mass, or 1% by mass with respect to the amount of the polyamide-imide resin, respectively.

[Examples 1 and 2 and Comparative Example 3: Production of polyimide resin film]
The polyamide-imide resin composition produced as described above (resin composition having a NaOEt content of 0.05% by mass, 0.005% by mass or 0% by mass) was used as a polyester substrate (manufactured by Toyobo Co., Ltd.). , The product name "A4100") was applied on a smooth surface using an applicator so that the thickness of the self-supporting film was 55 μm, dried at 50° C. for 30 minutes, and then at 140° C. for 15 minutes, and the obtained coating film was obtained. Was peeled from the polyester base material to obtain a self-supporting film. The self-supporting film was fixed to a metal frame and further dried at 200° C. for 40 minutes in the air to obtain a polyamideimide resin film having a thickness of 50 μm. Table 1 shows the results of measuring various physical properties of the film.

[Examples 3 and 4: Viscosity measurement of polyimide resin composition]
For each of the polyamideimide resin compositions obtained as described above, the ratio of the amount of NaOEt to the amount of polyamideimide resin is 0% by mass, 0.1% by mass, or 1% by mass. The viscosity was measured according to. The obtained results are shown in Table 2.

As shown in Table 1, the optical films of Examples 1 and 2 in which the ratio of ionic strength by TOF-SIMS (I _Na /I _CH3 ) obtained by adding NaOEt to the varnish is 0.2 or more has a high elastic modulus. It was confirmed to have. 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 could not be obtained. Further, as shown in Table 2, it was confirmed that the viscosity of the resin composition tends to increase by adding the sodium-containing component to the resin composition. By adding the sodium-containing component, the cause of increasing the viscosity of the resin composition is not clear, but a functional group in the resin, such as an imide bond and / or amide bond, and a sodium-containing component (compound containing a sodium atom, Some interaction is expected to occur with sodium and/or sodium ions. It is considered that such an interaction brings about an improvement in the elastic modulus of the obtained optical film, but the consideration does not limit the present invention in any way.

The optical film of the present invention having a ratio (I _Na /I _CH3 ) of 0.2 or more has a high elastic modulus. Modulus of the optical film of the present invention is preferably 5.0 G Pa or more, more preferably 5.1 G Pa or more, more preferably 5.2 G Pa or more. The upper limit of the elastic modulus is not particularly limited, but is usually 100 G Pa or less. The elastic modulus can be measured by using a tensile tester (for example, a chuck distance of 50 mm and a tensile speed of 10 mm/min), and can be measured by, for example, the method described in the examples.

Claims (12)

An optical film containing at least one resin selected from the group consisting of a polyimide resin and a polyamide resin, the ionic strength (I) of CH ₃ obtained by time-of-flight secondary ion mass spectrometry of the optical film. _An optical film having a ratio (I _Na /I _CH3 ) of Na ionic strength (I _Na ) to _CH3 ) of 0.2 or more. The optical film according to claim 1, wherein the polyimide resin and the polyamide resin are aromatic resins. The optical film according to claim 1, wherein the ratio of the structural unit derived from the aromatic monomer to all the structural units in the polyimide resin and the polyamide resin is 60 mol% or more. The optical film according to claim 1, having a thickness of 10 to 100 μm and a total light transmittance of 80% or more. The optical film according to claim 1, wherein the polyimide-based resin and the polyamide-based resin have a weight average molecular weight of 200,000 or more. The optical film according to claim 1, wherein the polyimide resin is a polyamide-imide resin. The optical film according to claim 1, wherein the polyimide-based resin and the polyamide-based resin include a structural unit derived from terephthalic acid. The optical film according to claim 1, which is a film for a front plate of a flexible display device. A flexible display device comprising the optical film according to claim 1. The flexible display device according to claim 9, further comprising a touch sensor. The flexible display device according to claim 9, further comprising a polarizing plate. At least one resin selected from the group consisting of polyimide resins and polyamide resins, a compound containing a sodium atom, at least one sodium-containing component selected from the group consisting of sodium and sodium ions, and at least a solvent. , Resin composition.