CN112143227A

CN112143227A - Optical film, flexible display device, and method for manufacturing optical film

Info

Publication number: CN112143227A
Application number: CN202010593954.3A
Authority: CN
Inventors: 西冈宏司; 杉山纮子; 有村孝
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2019-06-27
Filing date: 2020-06-24
Publication date: 2020-12-29
Also published as: KR20210002016A

Abstract

The invention relates to an optical film, a flexible display device, and a method for manufacturing the optical film. The object of the present invention is to provide a rubber composition having high impact resistanceAnd (3) a flexible resin film. The solution of the present invention is the following optical film: an optical film comprising at least one resin selected from the group consisting of polyimide resins and polyamide resins, wherein the optical film has a Na ion intensity (I) obtained by a time-of-flight secondary ion mass spectrometry_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) 0.2 or more, and K has an ionic strength (I)_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) Is 0.2 or more.

Description

Optical film, flexible display device, and method for manufacturing optical film

Technical Field

The invention relates to an optical film, a flexible display device and a method for manufacturing the optical film.

Background

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 smartwatches. Glass has been used as a front panel of such an image display device, but it is very rigid and easily broken, and thus it is difficult to use the glass as a front panel material of a flexible display device, for example. Therefore, effective use of polymer materials has been studied as one of materials replacing glass, and for example, an optical film using a polyimide resin has been studied (for example, patent document 1).

Documents of the prior art

Patent document

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

Disclosure of Invention

Problems to be solved by the invention

However, according to the studies of the inventors of the present application, it has been found that an optical film used as a front panel material of such a flexible display device is directly touched by a user or collides with a surrounding object, and therefore, when the contact and collision are repeated, a scratch such as a dent may be generated on the surface, and optical characteristics and visibility may be degraded.

Accordingly, an object of the present invention is to provide an optical film having excellent impact resistance, which can suppress deterioration of optical characteristics and visibility due to repeated collision of an object, and a flexible display device including the optical film.

Means for solving the problems

In order to solve the above problem, the inventors of the present application have paid attention to the kind and amount of components contained in the resin film and made intensive studies. As a result, the ionic strength (I) of Na in the optical film obtained by the time-of-flight type secondary ion mass spectrometry_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) 0.2 or more and an ionic strength (I) of K_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) 0.2 or more, it has been surprisingly found that the impact resistance of the optical film is easily improved, and the present invention has been completed.

That is, the present invention includes the following preferred embodiments.

[ 1] an optical film comprising at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins, the optical film having Na ion intensity (I) obtained by time-of-flight secondary ion mass spectrometry_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) 0.2 or more, and K has an ionic strength (I)_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) Is 0.2 or more.

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

The optical film according to the above [ 1] or [ 2], wherein the ratio of the structural unit derived from the aromatic monomer in the polyimide-based resin and the polyamide-based resin to the total structural units is 60 mol% or more.

The optical film according to 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.

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

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

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

[ 8] the optical film according to any one of [ 1] to [ 7] above, wherein a brightness L of the optical film^*Is 90 or more.

The optical film according to any one of [ 1] to [ 8] above, which is a film for a front panel of a flexible display device.

A flexible display device comprising the optical film according to any one of [ 1] to [ 9] above.

The flexible display device according to [ 11] above [ 10], further comprising a touch sensor.

The flexible display device according to [ 10] or [ 11] above, further comprising a polarizing plate.

The method for producing an optical film according to any one of [ 1] to [ 9] above, comprising at least the steps of:

a step (a) for preparing a resin composition containing at least one resin selected from the group consisting of a polyimide-based resin and a polyamide-based resin, at least one sodium-containing component selected from the group consisting of a sodium atom-containing compound, sodium and sodium ions, at least one potassium-containing component selected from the group consisting of a potassium atom-containing compound, potassium and potassium ions, and a solvent;

a step (b) of applying the resin composition to a support material to form a coating film; and

and (c) drying the coating film to form an optical film.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, an optical film having excellent impact resistance can be provided.

Detailed Description

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

The optical film of the present invention comprises a resin selected from the group consisting of polyimide-based resins and polyamide-based resinsAn optical film of at least one resin of the group consisting of lipids, and Na ion intensity (I) of the optical film obtained by time-of-flight secondary ion mass spectrometry (TOF-SIMS)_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) 0.2 or more, and K has an ionic strength (I)_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) Is 0.2 or more.

In the optical film of the present invention, Na ion intensity (I)_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) And the ionic strength (I) of K_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) Is calculated by the following method: the CH of the optical film was measured by Time-of-Flight Secondary Ion Mass Spectrometry (also referred to as "TOF-SIMS" in the present specification)₃Ionic strength (I) of_CH3) Na ion Strength (I)_Na) And the ionic strength (I) of K_K) And respectively make I_NaAnd I_KIs divided by I_CH3. In the present specification, the term "CH" measured by time-of-flight secondary ion mass spectrometry₃Ionic strength (I) of_CH3) Is assumed to belong to CH in the measurement data₃Integral value of ion peak, so-called Na ion intensity (I)_Na) The integral value of the peak ascribed to Na ion in the measurement data, i.e., the ion intensity of K (I)_K) The integral value of the peak ascribed to the K ion in the measurement data is set.

TOF-SIMS is one type of mass spectrometry, and TOF-SIMS can obtain an element or a molecular species present in the outermost surface of a sample with extremely high detection sensitivity and also can study the distribution of the element or the molecular species present in the outermost surface of the sample.

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

In TOF-SIMS based assays, CH₃Ions were detected in the vicinity of mass 15.02u, Na ions in the vicinity of mass 22.99u, and K ions in the vicinity of mass 38.96 u. In addition, these ions are ions that can be detected in either of positive (positive) ion analysis and negative (negative) ion analysis. In the present invention, the ionic strength (I) of Na_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) And the ionic strength (I) of K_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) The ratio detected in the positive ion analysis may be the ratio detected in the negative ion analysis. Regarding the ratio (I) in the present invention_Na/I_CH3) When the ratio of at least one of the ratio detected in the positive ion analysis and the ratio detected in the negative ion analysis is 0.2 or more, the ratio (I) in the present invention is satisfied_Na/I_CH3) The requirement is 0.2 or more. In addition, the ratio (I) in the present invention_K/I_CH3) When the ratio of at least one of the ratio detected in the positive ion analysis and the ratio detected in the negative ion analysis is 0.2 or more, the ratio (I) in the present invention is satisfied_K/I_CH3) The requirement is 0.2 or more. From the viewpoint of obtaining higher detection sensitivity, the condition using positive ion analysis is preferable.

For the measurement by TOF-SIMS, a time-of-flight type secondary ion mass spectrometer can be used for the optical film, and Bi can be used as the primary ion³⁺⁺The acceleration voltage of the primary ions was 25kV, the irradiation ion current was 0.23pA, and the measurement range was 200. mu. m.times.200. mu.m, and the analysis was carried out by positive ion analysis or negative ion analysis. The measurement by TOF-SIMS can be carried out, for example, as described in examplesThe method is carried out. The above ratio (I) measured for at least a part of the surface or cross section of the optical film_Na/I_CH3) And the ratio (I)_K/I_CH3) Within the above range, it is presumed that the composition inside the optical film more easily affects the mechanical strength of the optical film, and therefore, the ratio (I) measured with respect to the cross section of the optical film is preferable_Na/I_CH3) And the ratio (I)_K/I_CH3) Within the above range.

According to the Na ion intensity (I) obtained by time-of-flight type secondary ion mass spectrometry_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) 0.2 or more and an ionic strength (I) of K_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) The optical film of the present invention having an average particle size of 0.2 or more surprisingly improves the impact resistance of the optical film. Here, CH obtained by time-of-flight secondary ion mass spectrometry₃Ionic strength (I) of_CH3) Na ion Strength (I)_Na) And the ionic strength (I) of K_K) The amounts of carbon atoms and/or carbon ions, sodium atoms and/or sodium ions, and potassium atoms and/or potassium ions present in the optical film are indicated relatively. The above ratio (I)_Na/I_CH3) Is more than 0.2 and represents that: the optical film includes a plurality of optical layers, each of which includes a plurality of optical layers, and each of the optical layers includes a carbon atom (Na) and a sodium ion (Na). The above ratio (I)_K/I_CH3) Is more than 0.2 and represents that: the potassium atom (K) and/or potassium ion is present in an amount of at least a certain amount relative to the total amount of carbon atoms and/or carbon ions present in the optical film. The carbon atom and the carbon ion are each CH₃The reason why the form of the ion is detected is that: in the time-of-flight secondary ion mass spectrometry, there is a feature that various secondary ions generated can also be detected as a proton adduct, and CH is simultaneously generated as a proton adduct in a carbon atom₃Ions.

By the presence of a certain amount or more of sodium atoms and/or sodium ions, and potassium atoms and/orThe reason why the potassium ion improves the impact resistance of the optical film is not clear, and it is considered that the impact resistance is improved by the following mechanism, for example, but the present invention is not limited to the mechanism described below. In the present specification, the ion intensity (I) of Na is considered to be obtained when the optical film is subjected to the time-of-flight secondary ion mass spectrometry_Na) The detected sodium atom-containing compound, sodium and/or sodium ions that may be contained in the optical film are also referred to as "sodium-containing components". The sodium atom-containing compound is a compound containing a sodium atom as a constituent atom of a molecule. Further, the ion intensity (I) considered as K when the optical film is subjected to the time-of-flight type secondary ion mass spectrometry_K) The detected potassium atom-containing compound, potassium and/or potassium ions that may be contained in the optical film are also referred to as "potassium-containing components". The potassium atom-containing compound is a compound containing a potassium atom as a constituent atom of a molecule.

It is considered that when the composition containing the polyimide-based resin and/or the polyamide-based resin contains the sodium-containing component (the sodium atom-containing compound, sodium and/or sodium ions) and the potassium-containing component (the potassium atom-containing compound, potassium and/or potassium ions) in the production of the optical film of the present invention, the imide bond and/or the amide bond (preferably, the imide bond contained in the polyimide-based resin) contained in the resin and the sodium-containing component and the potassium-containing component cause some interaction (for example, electrostatic interaction between the carbonyl group of the imide bond, the sodium ion of the amide bond, and the carbonyl group of the imide bond or the amide bond and the potassium ion). As a result, it is considered that the polyimide-based resin and/or the polyamide-based resin contained in the obtained optical film exist in the film in a state where the polyimide-based resin and/or the polyamide-based resin interact with the sodium-containing component and the potassium-containing component, or the orientation state of the resin is changed by the interaction between the sodium-containing component and the potassium-containing component and the polyimide-based resin and/or the polyamide-based resin, whereby the impact resistance of the optical film is improved. In addition, it is also considered that when both the sodium-containing component and the potassium-containing component are present, the sodium-containing component and the potassium-containing component having different atomic radii, ionic radii, and/or molecular sizes coexist in the optical film, and as a result, stacking (packing) of the polyimide-based resin and/or the polyamide-based resin included in the optical film is enhanced, and the impact resistance of the optical film is improved, as compared with the case where only either the sodium-containing component or the potassium-containing component is present in the optical film. It should be noted that the above examination does not limit the present invention in any way. The sodium-containing component and the potassium-containing component contained in the optical film are preferably in an ionized state from the viewpoint of being considered to be likely to interact with an imide bond and/or an amide bond of the polyimide-based resin and/or the polyamide-based resin.

Na ion Strength (I) from the viewpoint of easily improving impact resistance of the optical film_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) Preferably 0.95 or more, more preferably 1.0 or more, further preferably 1.2 or more, further preferably 1.4 or more, particularly preferably 1.5 or more, particularly preferably 3 or more, particularly preferably 5 or more, particularly preferably 7 or more, particularly preferably 10 or more, and most preferably 12 or more. The ratio (I) is a ratio that facilitates improvement in film-forming properties of a varnish containing a polyimide resin and/or a polyamide resin and uniformity of an optical film_Na/I_CH3) The upper limit of (b) 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.

Ion Strength (I) of K from the viewpoint of easily improving impact resistance of the optical film_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) Preferably 0.95 or more, more preferably 1.0 or more, further preferably 1.2 or more, further preferably 1.4 or more, particularly preferably 1.5 or more, particularly preferably 3 or more, particularly preferably 5 or more, particularly preferably 10 or more, and most preferably 12 or more. The ratio (I) is a ratio that facilitates improvement in film-forming properties of a varnish containing a polyimide resin and/or a polyamide resin and uniformity of an optical film_K/I_CH3) The upper limit of (A) is preferably 100 or less, more preferably 50 or less, furtherOne step is preferably 30 or less, more preferably 25 or less, and particularly preferably 20 or less.

The ratio (I) is from the viewpoint of easily improving the impact resistance of the optical film_Na/I_CH3) To ratio (I)_K/I_CH3) The total value of (a) is preferably 0.5 or more, more preferably 1.0 or more, further preferably 1.5 or more, further preferably 2 or more, particularly preferably 4 or more, particularly preferably 5 or more, particularly preferably 10 or more, particularly preferably 15 or more, and most preferably 20 or more. The ratio (I) is a ratio that facilitates improvement in film-forming properties of a varnish containing a polyimide resin and/or a polyamide resin and uniformity of an optical film_K/I_CH3) The upper limit of (b) is preferably 200 or less, more preferably 100 or less, further preferably 50 or less, further preferably 30 or less, and particularly preferably 25 or less.

Will be proportional to (I)_Na/I_CH3) And the ratio (I)_K/I_CH3) The method for adjusting the content within the above range is not particularly limited, and examples thereof include: a method for adjusting the content of a sodium-containing component (a sodium atom-containing compound, sodium and/or sodium ions) and a potassium-containing component (a potassium atom-containing compound, potassium and/or potassium ions) in the optical film of the present invention comprising a polyimide-based resin and/or a polyamide-based resin; and a method for adjusting the content of the polyimide resin and/or the polyamide resin contained in the optical film. Specifically, when the content of the sodium-containing component in the optical film is increased, the ion strength (I) of Na obtained by TOF-SIMS of the optical film is increased_Na) And also becomes larger. Further, when the content of the potassium-containing component in the optical film is increased, the ion intensity (I) of K obtained by TOF-SIMS of the optical film is increased_K) And also becomes larger. When the content of the polyimide resin and/or the polyamide resin contained in the optical film is increased, the CH obtained by TOF-SIMS of the optical film₃Ionic strength (I) of_CH3) And also becomes larger. Therefore, if the content of the sodium-containing component in the optical film is increased, the ratio (I)_Na/I_CH3) The ratio (I) is increased when the content of the potassium-containing component in the optical film is increased_K/I_CH3) The ratio (I) is increased when the content of the polyimide-based resin and/or the polyamide-based resin contained in the optical film is increased_Na/I_CH3) And the ratio (I)_K/I_CH3) The value of (c) becomes small. By the above method, the ratio (I) can be adjusted_Na/I_CH3) And the ratio (I)_K/I_CH3) Adjusted to within the desired range.

In the optical film of the present invention, CH derived from TOF-SIMS₃Ionic strength (I) of_CH3) Na ion Strength (I)_Na) And the ionic strength (I) of K_K) Is not particularly limited as long as the ratio (I)_Na/I_CH3) And the ratio (I)_K/I_CH3) The value of (A) is within the above range, and the Na ion strength (I) is determined from the viewpoint of easily ensuring the accuracy of the measurement by TOF-SIMS_Na) And the ionic strength (I) of K_K) It is preferable that the measurement is performed under conditions of preferably 100 or more, more preferably 300 or more, and still more preferably 500 or more, of each.

Ratio (I)_Na/I_CH3) Is 0.2 or more and the ratio (I)_K/I_CH3) The optical film of the present invention having an impact resistance of 0.2 or more has high impact resistance. In the present specification, the impact resistance means: even if a peripheral object collides with the surface of the optical film, damage such as a dent is not easily generated and/or left on the optical film. When the optical film has high impact resistance, damage such as a dent is less likely to occur and/or remain on the surface of the optical film, and thus deterioration in optical characteristics and visibility of the optical film is more likely to be suppressed. In addition, the optical film of the present invention can improve impact resistance particularly when subjected to a concentrated load, and can suppress the occurrence of fine depressions as starting points of deterioration of the optical film properties. The impact resistance of the optical film can be measured by, for example, an impact resistance test in which the amount of dishing in the impact resistance test described in examples is measured. In the optical film of the present invention, the depth of the depression in the above-mentioned impact resistance test is preferably 29 μm or less, more preferably 27 μm or less, still more preferably 26 μm or less, still more preferably 25 μm or less, and particularly preferably 24 μm or less.

Ratio (I)_Na/I_CH3) Is 0.2 or more and the ratio (I)_K/I_CH3) The elastic modulus of the optical film of the present invention which is 0.2 or more is preferably 5.0GPa or more, more preferably 5.1GPa or more, further preferably 5.2GPa or more, and usually 100GPa or less. The modulus of elasticity can be measured using a tensile tester (for example, conditions in which the distance between chucks is 50mm and the tensile speed is 10 mm/min). When the elastic modulus of the optical film is merely increased, the following may occur: the toughness of the optical film is low, and sufficient impact resistance cannot be obtained. However, the optical film of the present invention has high impact resistance. In addition, according to the optical film of the present invention, even when the weight average molecular weight of the resin contained in the optical film is low, the impact resistance of the optical film can be improved.

The optical film of the present invention has a total light transmittance of preferably 80% or more, more preferably 85% or more, further preferably 88% or more, further preferably 89% or more, particularly preferably 90% or more, and particularly preferably 91% or more. When the total light transmittance is not lower than the above lower limit, visibility is easily improved when the optical film (particularly, the front panel) is mounted on an image display device. Since the optical film of the present invention generally exhibits a high total light transmittance, the emission intensity of a display element or the like required to obtain a certain luminance can be suppressed as compared with the case of using a film having a low transmittance, for example. Therefore, power consumption can be reduced. For example, when the optical film of the present invention is mounted on an image display device, bright display tends to be obtained even if the amount of backlight light is reduced, and this contributes to energy saving. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance can be determined, for example, according to JIS K7105: 1981 or JIS K7361-1: 1997. the haze was determined using a haze computer. The total light transmittance may be a total light transmittance within a range of a thickness of an optical film to be described later.

The haze of the optical film of the present invention is preferably 1% or less, more preferably 0.5% or less, further preferably 0.2% or less, further preferably 0.15% or less, particularly preferably 0.14% or less, particularly preferably 0.1% or less, and usually 0.01% or more. When the haze of the optical film is not more than the above upper limit, the visibility is easily improved when the optical film (particularly, as a front panel) is mounted on an image display device. The haze may be measured according to JIS K7105: 1981 or JIS K7136: 2000. the haze was determined using a haze computer.

The yellow index (hereinafter, also referred to as YI value) of the optical film of the present invention is preferably 3.0 or less, more preferably 2.5 or less, further preferably 2.2 or less, and is preferably-5 or more, more preferably-2 or more. When the YI value of the optical film is not more than the above upper limit, the transparency becomes good, and when the optical film is used for a front panel of an image display device, high visibility can be achieved. The YI value can be calculated based on the formula of YI × (1.2769X-1.0592Z)/Y by measuring the transmittance to light of 300 to 800nm using an ultraviolet-visible near-infrared spectrophotometer to obtain the tristimulus value (X, Y, Z).

The optical film of the present invention has a luminance L from the viewpoint of easily improving the transparency and visibility of the optical film^*The value is preferably 90 or more, more preferably 93 or more, and further preferably 95 or more. L is^*The upper limit of the value is not particularly limited, and may be 100 or less. The above-mentioned luminance L^*The value can be measured using a spectrophotometer, and can be measured, for example, by the method described in examples.

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, further preferably 30 μm or more, preferably 100 μm or less, more preferably 80 μm or less, further preferably 60 μm or less, and may be a combination of the upper limit and the lower limit thereof. When the thickness of the optical film is within the above range, the impact resistance of the optical film is easily further improved. The thickness of the optical film can be measured using a micrometer, and can be measured, for example, by the method described in examples.

The optical film of the present invention is preferably bent 150,000 times or more (bend radius R ═ 1mm) in a bending resistance test, more preferably 180,000 times or more, and still more preferably 200,000 times or more. When the number of times of bending is not less than the above lower limit, the front panel material of a flexible display device or the like has sufficient bending resistance. The number of bending times in the bending resistance test is represented by: the optical film was repeatedly bent using a bending tester under a condition that the bending radius (curvature radius) R was 1mm, and the number of times of bending was repeated until the point of time when a crack occurred in the film (1 time of repeated bending was defined as 1 time).

< polyimide-based resin and polyamide-based resin >

The optical film of the present invention comprises a polyimide-based resin and/or a polyamide-based resin. In the present specification, the polyimide-based resin means at least one resin selected from the group consisting of a polyimide resin, a polyamideimide resin, a polyimide precursor resin, and a polyamideimide precursor resin. The polyimide resin is a resin containing a repeating structural unit containing an imide group, and the polyamideimide resin is a resin containing a repeating structural unit containing both an imide group and an amide group. The polyimide precursor resin and the polyamideimide precursor resin are each a precursor before imidization, which provides the polyimide resin and the polyamideimide resin by imidization, and are also referred to as polyamic acid resins. In the present specification, the polyamide resin is a resin containing a repeating structural unit containing an amide group. The optical film of the present invention may contain 1 kind of polyimide-based resin or polyamide-based resin, or may contain two or more kinds of polyimide-based resins and/or polyamide-based resins in combination. From the viewpoint of easily achieving both chemical stability and impact resistance of the optical film, the optical film of the present invention preferably contains a polyimide-based resin, preferably a polyimide resin or a polyamideimide resin, more preferably a polyamideimide resin.

In a preferred embodiment of the present invention, the polyimide-based resin and the polyamide-based resin are preferably aromatic resins from the viewpoint of facilitating further improvement in the impact resistance of the optical film. In the present specification, the aromatic resin means a resin in which the structural units contained in the polyimide-based resin and the polyamide-based resin are mainly aromatic structural units.

In the above-described preferred embodiment, the proportion of the structural unit derived from the aromatic monomer contained in the polyimide-based resin and the polyamide-based resin to the total structural units is preferably 60 mol% or more, more preferably 70 mol% or more, further preferably 80 mol% or more, and particularly preferably 85 mol% or more, from the viewpoint of facilitating further improvement in the impact resistance of the optical film. Here, the structural unit derived from an aromatic monomer means a structural unit derived from a monomer at least a part of which contains an aromatic structure (for example, an aromatic ring) and at least a part of which contains an aromatic structure (for example, an aromatic ring). Examples of the aromatic monomer include an aromatic tetracarboxylic acid compound, an aromatic diamine, and an aromatic dicarboxylic acid.

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

[ chemical formula 1]

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

In the formula (2), Z is a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms which may be substituted by a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms and substituted by fluorine, an alkoxy group having 1 to 6 carbon atoms or a alkoxy group having 1 to 6 carbon atoms and substituted by fluorine, more preferably a divalent organic group having 4 to 40 carbon atoms which may be substituted by a hydrocarbon group having 1 to 8 carbon atoms, a hydrocarbon group having 1 to 8 carbon atoms and substituted by fluorine, an alkoxy group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms and substituted by fluorine and has a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. Examples of the organic group of Z include: groups in which two non-adjacent bonds among the bonds of the groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28), and formula (29) described later are replaced with hydrogen atoms; and a divalent chain hydrocarbon group having 6 or less carbon atoms; examples of the heterocyclic structure of Z include a group having a thiophene ring skeleton. From the viewpoint of easily suppressing the yellowness index (lowering the YI value) of the optical film, the groups represented by formulae (20) to (29) and the group having a thiophene ring skeleton are preferable. In one embodiment of the present invention, the polyamide resin and the polyamideimide resin may contain 1 kind of organic group as Z, or may contain two or more kinds of organic groups as Z.

More preferred as the organic group of Z is a divalent organic group represented by formula (20 '), formula (21'), formula (22 '), formula (23'), formula (24 '), formula (25'), formula (26 '), formula (27'), formula (28 ') and formula (29'):

[ chemical formula 2]

In [ formulae (20 ') to (29'), W¹And as defined in formulas (20) to (29)]。

The hydrogen atoms on the ring in the formulae (20) to (29) and (20 ') to (29') may be substituted by a hydrocarbon group having 1 to 8 carbon atoms, a hydrocarbon group having 1 to 8 carbon atoms substituted with fluorine, an alkoxy group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms substituted with fluorine.

When the polyamide resin or polyamideimide resin has a structural unit wherein Z in formula (2) is represented by any one of formulae (20 ') to (29'), it is preferable that the polyamide resin or polyamideimide resin has a structural unit derived from a carboxylic acid represented by the following formula (d1) in addition to the structural unit, from the viewpoint of easily improving the film-forming property of the varnish and easily obtaining the uniformity of the obtained optical film:

[ chemical formula 3]

[ in the formula (d1), R²⁴Independently represents a hydrogen atom, a halogen 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, R²⁵Represents R²⁴or-C (═ O) -, denotes a bond]。

R²⁴In the formula (3), examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include R¹～R⁸The radicals illustrated. Specific examples of the structural unit (d1) include R²⁴And R²⁵Structural units each of which is a hydrogen atom (structural units derived from a dicarboxylic acid compound), R²⁴Are each a hydrogen atom, R²⁵A structural unit (structural unit derived from a tricarboxylic acid compound) representing — C (═ O) -, and the like.

In one embodiment of the present invention, the polyamide resin and the polyamideimide resin may contain a plurality of kinds of Z, and the plurality of kinds of Z may be the same as or different from each other. In particular, from the viewpoint of easily improving the impact resistance and the optical characteristics of the optical film of the present invention, it is preferable that at least a part of Z is represented by formula (3a),

[ chemical formula 4]

[ in the formula (3a), R^gAnd R^hIndependently represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R^gAnd R^hWherein the hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other, A, m and the same as A, m and u in the formula (3), and t and u are integers of 0 to 4 independently of each other]。

More preferably represented by the formula (3),

[ chemical formula 5]

[ in the formula (3),

R¹～R⁸independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R¹～R⁸The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

a independently of one another represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹)-，R⁹Represents 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,

it represents a bond.

In the formulae (3) and (3a), A independently represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹) From the viewpoint of the bending resistance of the optical film, the compound preferably represents-O-or-S-, and more preferably represents-O-.

R¹、R²、R³、R⁴、R⁵、R⁶、R⁷And R⁸Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a carbon atomAn alkoxy group having a sub-number of 1 to 6 or an aryl group having 6 to 12 carbon atoms. R^gAnd R^hIndependently represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 2-ethylpropyl group, and an n-hexyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a cyclohexyloxy group and the like. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. From the viewpoint of surface hardness and flexibility of the optical film, R¹～R⁸Independently of each other, the alkyl group preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a hydrogen atom. Here, R¹～R⁸、R^gAnd R^hThe hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other.

R⁹Represents a hydrogen atom, 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 a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 2-ethylpropyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a tert-octyl group, an n-nonyl group, an n-decyl group, and the like, which may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

T and u in formula (3a) are each independently an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0.

When m in the formulae (3) and (3a) is an integer in the range of 0 to 4, and m is within this range, the impact resistance, elastic modulus, and bending resistance of the optical film are easily improved. The impact resistance, elastic modulus and bending resistance of the optical film can be easily further improvedFrom the viewpoint of the above, m in the formulae (3) and (3a) is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, still more preferably 0 or 1, and still more preferably 0. The structural unit represented by the formula (3) or the formula (3a) wherein m is 0 is a structural unit derived from terephthalic acid or isophthalic acid, and the structural unit is particularly preferably R in the formula (3)⁵～R⁸A structural unit in which m is 0 and a structural unit in which u is 0 and m is 0 in the formula (3 a). The polyimide-based resin and the polyamide-based resin preferably contain a structural unit derived from terephthalic acid, from the viewpoint of easily improving the impact resistance, elastic modulus, and bending resistance of the optical film. The polyimide-based resin and the polyamide-based resin may contain one or more structural units represented by formula (3) in Z. From the viewpoint of improving impact resistance, elastic modulus, and bending resistance of the optical film and reducing the yellow index (YI value), it is preferable that the resin contains two or more kinds of structural units different in the value of m in formula (3) or formula (3a) in Z, and more preferable that the resin contains two or three kinds of structural units different in the value of m in formula (3) or formula (3a) in Z. In this case, from the viewpoint of easily improving the impact resistance, elastic modulus, and bending resistance of the optical film, and from the viewpoint of easily lowering the yellow index (YI value) of the optical film, it is particularly preferable that the resin contains a structural unit represented by formula (3) in which m is 0 in Z, and contains a structural unit represented by formula (3) in which m is 1 in addition to the structural unit. It is also preferable that the structural element represented by the above formula (d1) is contained in addition to the structural element represented by the formula (2) (which includes Z represented by the formula (3) in which m is 0).

In a preferred embodiment of the present invention, the resin has m ═ 0 and R⁵～R⁸The structural unit which is a hydrogen atom is a structural unit represented by formula (3). In a more preferred embodiment of the present invention, the resin has m ═ 0 and R⁵～R⁸A structural unit which is a hydrogen atom and a structural unit represented by formula (3') as a structural unit represented by formula (3),

[ chemical formula 6]

In this case, the impact resistance, elastic modulus, and bending resistance of the optical film are easily improved, and the YI value is easily reduced.

In one preferred embodiment of the present invention in which the optical film comprises a polyamideimide resin, the proportion of the structural unit represented by formula (3) or formula (3a) is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, still more preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, and still more preferably 80 mol% or less, where the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) of the polyamideimide resin is 100 mol%. When the proportion of the structural unit represented by formula (3) or formula (3a) is not less than the above lower limit, the impact resistance, elastic modulus and bending resistance of the optical film are easily improved. When the proportion of the structural unit represented by formula (3) or formula (3a) is not more than the above upper limit, the viscosity of the varnish containing the resin is easily inhibited from increasing due to hydrogen bonding between amide bonds derived from formula (3) or formula (3a), and the processability of the film is improved.

In the case where the polyamideimide resin has a structural unit represented by formula (3) or formula (3a) in which m is 1 to 4, the proportion of the structural unit represented by formula (3) or formula (3a) in which m is 1 to 4 is preferably 3 mol% or more, more preferably 5 mol% or more, further 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, and particularly preferably 30 mol% or less, where the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) in the polyamideimide resin is 100 mol%. When the ratio of the structural unit represented by the formula (3) or the formula (3a) in which m is 1 to 4 is not less than the above lower limit, the impact resistance, elastic modulus and bending resistance of the optical film are easily improved. When the proportion of the structural unit represented by formula (3) or formula (3a) in which m is 1 to 4 is not more than the upper limit, the inclusion of a dendron due to hydrogen bonds between amide bonds derived from the structural unit represented by formula (3) or formula (3a) is easily suppressedThe viscosity of the varnish of the grease increases, thereby improving the processability of the film. The proportion of the structural unit represented by formula (1), formula (2), formula (3) or formula (3a) may be, for example, the same as that of the structural unit represented by formula (1), formula (2), formula (3) or formula (3a)¹H-NMR was measured, or it was calculated from the feed ratio of the raw materials.

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 40 mol% or more, further preferably 45 mol% or more, and particularly preferably 50 mol% or more of Z in the polyamide resin or polyamideimide resin is a structural unit represented by formula (3) or formula (3a) wherein m is 0 to 4. When the lower limit of Z is a structural unit represented by formula (3) or formula (3a) where m is 0 to 4, the impact resistance, elastic modulus and bending resistance of the optical film are easily improved. In addition, the polyamide resin or the polyamide-imide resin may contain a structural unit represented by formula (3) or formula (3a) in which m is 0 to 4, in an amount of 100 mol% or less of Z. The proportion of the structural unit represented by the formula (3) or the formula (3a) wherein m is 0 to 4 in the resin can be, for example, used¹H-NMR was measured, or it was calculated from the feed ratio of the raw materials.

In a preferred embodiment of the present invention, preferably 5 mol% or more, more preferably 8 mol% or more, still more preferably 10 mol% or more, and particularly preferably 12 mol% or more of Z in the polyamide resin or polyamideimide resin is represented by formula (3) or formula (3a) wherein m is 1 to 4. When the lower limit of Z of the polyamideimide resin is represented by formula (3) or formula (3a) wherein m is 1 to 4, the impact resistance, elastic modulus and bending resistance of the optical film are easily improved. In addition, preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, and particularly preferably 30 mol% or less of Z is represented by formula (3) or formula (3a) in which m is 1 to 4. When the upper limit of Z is less than or equal to the upper limit of Z and is represented by formula (3) or formula (3a) in which m is 1 to 4, the viscosity of the resin-containing varnish is easily prevented from increasing due to hydrogen bonding between amide bonds derived from the structural unit represented by formula (3) or formula (3a) in which m is 1 to 4, and the film processability is improved. In addition, the resin with m is 1 ~ 4 formula (3) or formula (3a) representation of the structural unit ratio can use the exampleSuch as¹H-NMR was measured, or it was calculated from the feed ratio of the raw materials.

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

[ chemical formula 7]

In the formulae (10) to (18),

it represents a connecting bond,

V¹、V²and V³Independently of one another, represents a single bond, -O-, -S-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -CO-or-N (Q) -. Wherein Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include those for R⁹But the groups described hereinbefore.

An example is: v¹And V³Is a single bond, -O-or-S-, and V²is-CH₂-、-C(CH₃)₂-、-C(CF₃)₂-or-SO₂-。V¹And V²Bonding position with respect to each ring, and V²And V³The bonding positions to each ring are independently preferably meta or para to each ring, more preferably para.

Among the groups represented by formulae (10) to (18), from the viewpoint of easily improving the impact resistance, elastic modulus and bending resistance of the optical film, the groups represented by formulae (13), (14), (15), (16) and (17) are preferable, and the groups represented by formulae (14), (15) and (16) are more preferable. In addition, from the viewpoint of easily improving the impact resistance, elastic modulus and flexibility of the optical film, V¹、V²And V³Independently of one another, are preferably single bonds, -O-or-S-, more preferably single bonds or-O-.

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

[ chemical formula 8]

[ in the formula (4),

R¹⁰～R¹⁷independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R¹⁰～R¹⁷The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

it represents a bond.

When at least a part of the plurality of xs in the formulae (1) and (2) is a group represented by the formula (4), the impact resistance, elastic modulus, and transparency of the optical film are easily improved.

In the formula (4), R¹⁰、R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R¹⁶And R¹⁷Independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. As the number of carbon atomsExamples 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 the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms in the formula (3). R¹⁰～R¹⁷Independently of each other, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R¹⁰～R¹⁷The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R is R from the viewpoint of impact resistance, elastic modulus, transparency and bending resistance of the optical film¹⁰～R¹⁷Independently of one another, further preferably represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and further preferably R¹⁰、R¹²、R¹³、R¹⁴、R¹⁵And R¹⁶Represents a hydrogen atom, and R¹¹And R¹⁷Represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group (particularly preferably R)¹¹And R¹⁷Represents a methyl group or a trifluoromethyl group).

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

[ chemical formula 9]

That is, at least a part of X among the structural units represented by formulas (1) and (2) is a structural unit represented by formula (4'). In this case, the fluorine element-containing skeleton improves the solubility of the polyimide-based resin or the polyamide-based resin in a solvent, and the varnish containing the resin is likely to have improved storage stability, and the varnish is likely to have reduced viscosity, and thus the optical film is likely to have improved processability. Further, the optical properties of the optical film are easily improved by the skeleton containing the fluorine element.

In a preferred embodiment of the present invention, the polyimide-based material is a polyimidePreferably 30 mol% or more, more preferably 50 mol% or more, and still more preferably 70 mol% or more of X in the resin or polyamide resin is represented by formula (4), particularly formula (4'). When X in the above range in the polyimide-based resin or polyamide-based resin is represented by formula (4), particularly formula (4'), the solubility of the resin in a solvent is improved by the fluorine element-containing skeleton of the obtained optical film, the storage stability of a varnish containing the resin is easily improved, the viscosity of the varnish is easily reduced, and the processability of the optical film is easily improved. In addition, the optical properties of the optical film are also easily improved by the skeleton containing the fluorine element. Preferably, 100 mol% or less of X in the polyimide-based resin or the polyamide-based resin is represented by formula (4), particularly formula (4'). X in the above resin may be formula (4), particularly formula (4'). The proportion of the structural unit represented by formula (4) of X in the above resin can be used, for example¹H-NMR was measured, or it was calculated from the feed ratio of the raw materials.

In the formula (1), Y represents a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms, and more preferably a tetravalent organic group having 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure, and preferred examples thereof include an aromatic ring from the viewpoint of easily improving impact resistance and elastic modulus. 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, and in this case, the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of kinds of Y, and the plurality of kinds of Y may be the same as or different from each other. Examples of Y include: a group represented by the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29); a group represented by the formulae (20) to (29) wherein a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having a valence of 4 and a carbon number of 6 or less.

[ chemical formula 10]

In the formulae (20) to (29), W represents a connecting bond¹Represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-Ar-、-SO₂-、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂-Ar-、-Ar-C(CH₃)₂-Ar-or-Ar-SO₂-Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and specific examples thereof include phenylene groups.

Among the groups represented by formulae (20) to (29), the group represented by formula (26), formula (28) or formula (29) is preferable, and the group represented by formula (26) is more preferable, from the viewpoint of easily improving the impact resistance, elastic modulus and bending resistance of the optical film. In addition, W is considered to easily improve the impact resistance, elastic modulus and bending resistance of the optical film and easily reduce the YI value of the optical film¹Independently of one another, are preferably single bonds, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-, more preferably a single bond, -O-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-is more preferably a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-, particularly preferably a single bond or-C (CF)₃)₂-。

In a preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of Y in the polyimide-based resin is represented by formula (26). Y in the above range in the polyimide resin is represented by the formula (26), preferably W¹Is a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-formula (26), more preferably W¹Is a single bond or-C (CF)₃)₂When represented by the formula (26), the optical film tends to have improved impact resistance,Elastic modulus and bending resistance, and easily decrease the YI value of the optical film. The proportion of the structural unit represented by the formula (26) in Y in the polyimide-based resin can be used, for example¹H-NMR was measured, or it was calculated from the feed ratio of the raw materials.

In a preferred embodiment of the present invention, at least a part of Y in the plurality of formulas (1) is represented by formula (5) and/or formula (9):

[ chemical formula 11]

[ in the formula (5), R¹⁸～R²⁵Independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R¹⁸～R²⁵The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

denotes a bond

[ chemical formula 12]

[ formula (9) wherein R³⁵～R⁴⁰Independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R³⁵～R⁴⁰The hydrogen atoms contained in (A) may be substituted independently of each other by halogen atoms, representing a bond]。

When at least a part of Y in the plurality of formulae (1) is represented by formula (5) and/or formula (9), the impact resistance, elastic modulus, and optical characteristics of the optical film are easily improved.

In the formula (5), R¹⁸、R¹⁹、R²⁰、R²¹、R²²、R²³、R²⁴And R²⁵Independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Alkyl group having 1 to 6 carbon atoms, C1 to EExamples of the alkoxy group having 6 or the aryl group having 6 to 12 carbon atoms include those exemplified above as the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms in the formula (3). R¹⁸～R²⁵Independently of each other, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R¹⁸～R²⁵The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. R is a group of R which is easy to improve the impact resistance, elastic modulus and bending resistance of the optical film and is easy to improve the transparency and maintain the transparency¹⁸～R²⁵Independently of one another, further preferably represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and further preferably R¹⁸、R¹⁹、R²⁰、R²³、R²⁴And R²⁵Represents a hydrogen atom, and R²¹And R²²Represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group (particularly preferably R)²¹And R²²Represents a methyl group or a trifluoromethyl group).

In the formula (9), R is R from the viewpoint of easily improving the impact resistance, elastic modulus and bending resistance of the optical film, and from the viewpoint of easily improving the transparency and easily maintaining the transparency³⁵～R⁴⁰Preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a hydrogen atom. Here, R³⁵～R⁴⁰The hydrogen atoms contained in (a) may be independently substituted with a halogen atom, and examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. As R³⁵～R⁴⁰In the above-mentioned (C1-C6) alkyl group and (C6-C12) aryl group, the groups exemplified above are mentioned.

In a preferred embodiment of the present invention, formula (5) is represented by formula (5 '), formula (9) is represented by formula (9'):

[ chemical formula 13]

That is, at least a part of the plurality of Y is represented by formula (5 ') and/or formula (9'). In this case, the impact resistance, elastic modulus, and bending resistance of the optical film are easily improved. When the formula (5) is represented by the formula (5'), the solubility of the polyimide-based resin in a solvent is improved by the skeleton containing a fluorine element, the storage stability of the varnish containing the resin is easily improved, the viscosity of the varnish is easily reduced, and the processability of the optical film is easily improved. Further, the optical properties of the optical film are easily improved by the skeleton containing the fluorine element.

In a preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of Y in the polyimide-based resin is represented by formula (5), particularly formula (5'). When Y in the above range in the polyimide-based resin is represented by formula (5), particularly formula (5'), the solubility of the polyimide-based resin in a solvent is improved by the fluorine element-containing skeleton, the viscosity of a varnish containing the resin is easily reduced, and the processability of an optical film is easily improved. Further, the optical properties of the optical film are easily improved by the skeleton containing the fluorine element. Preferably, 100 mol% or less of Y in the polyimide-based resin is represented by formula (5), particularly formula (5'). Y in the polyimide-based resin may be formula (5), particularly formula (5'). The proportion of the structural unit represented by formula (5) or formula (5') of Y in the polyimide-based resin can be used, for example¹H-NMR was measured, or it was calculated from the feed ratio of the raw materials.

In a preferred embodiment of the present invention, the plurality of structural units represented by formula (1) preferably include a structural unit represented by formula (9) in addition to the structural unit represented by formula (5). When the structural unit represented by formula (9) Y is further contained, the impact resistance and the elastic modulus of the optical film can be easily further improved.

The polyimide-based resin may contain a structural unit represented by formula (30) and/or a structural unit represented by formula (31), or may contain 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 (1) and, optionally, the structural unit represented by formula (2).

[ chemical formula 14]

In the formula (30), Y¹Is 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 Y¹Examples thereof include: a group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29); a group represented by the formulae (20) to (29) wherein a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having a valence of 4 and a carbon number of 6 or less. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of kinds of Y¹Plural kinds of Y¹May be the same as or different from each other.

In the formula (31), Y²Is 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 hydrocarbon group substituted with fluorine. As Y²Examples thereof include: a group in which any one of the connecting bonds of the groups represented by the above-mentioned formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29) is replaced with a hydrogen atom; and a chain hydrocarbon group having 3-valent carbon atoms of 6 or less. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of kinds of Y²Plural kinds of Y²May be the same as or different from each other.

In the formulae (30) and (31), X¹And X²Independently of one another, are divalent organic groups, preferably organic groups in which the hydrogen atoms of the organic group may be replaced by hydrocarbon groups or fluorine-substituted hydrocarbon groups. As X¹And X²Examples thereof include: the above-mentioned formula (10), formula (11), formula (12), formula (13), formula(14) A group represented by formula (15), formula (16), formula (17) or formula (18); a group represented by the formulae (10) to (18) wherein a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In one embodiment of the present invention, the polyimide-based resin includes a structural unit represented by formula (1) and/or formula (2), and a structural unit represented by formula (30) and/or formula (31) which is contained as the case may be. In addition, from the viewpoint of easily improving the optical properties, impact resistance, elastic modulus, and bending resistance of the optical film, the proportion of the structural unit represented by formula (1) and formula (2) in the polyimide-based resin is preferably 80 mol% or more, more preferably 90 mol% or more, further preferably 95 mol% or more, and usually 100% or less, based on the total structural units represented by formula (1) and formula (2) and, if necessary, formula (30) and/or formula (31). The above ratio can be used, for example¹H-NMR was measured, or it was calculated from the feed ratio of the raw materials.

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

The weight average molecular weight of the polyimide-based resin and the polyamide-based resin is preferably 200,000 or more, more preferably 230,000 or more, further preferably 250,000 or more, further preferably 270,000 or more, and particularly preferably 280,000 or more, in terms of standard polystyrene, from the viewpoint of easily improving the impact resistance, elastic modulus, and bending resistance of the optical film. The weight average molecular weights of the polyimide-based resin and the polyamide-based resin are preferably 1,000,000 or less, more preferably 800,000 or less, even more preferably 700,000 or less, and particularly preferably 500,000 or less, from the viewpoint of easily improving the solubility of the resins in a solvent and easily improving the stretchability and processability of the optical film. The weight average molecular weight can be determined by GPC measurement, for example, in terms of standard polystyrene, and can be calculated by the method described in examples, for example.

In the polyamide-imide resin, the content of the structural unit represented by formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol or more, further preferably 1.0 mol or more, particularly preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, and further preferably 4.5 mol or less, relative to 1 mol of the structural unit represented by formula (1). When the content of the structural unit represented by formula (2) is not less than the above lower limit, the impact resistance and elastic modulus of the optical film are easily improved. When the content of the structural unit represented by formula (2) is not more than the upper limit, the thickening due to the hydrogen bond between the amide bonds in formula (2) is easily suppressed, and the processability of the optical film is improved.

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

The content of the halogen atom 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 still more preferably 5 to 30% by mass, based on the mass of the polyimide-based resin and the polyamide-based resin. When the content of the halogen atom is not less than the above lower limit, the elastic modulus of the optical film is further increased, the water absorption is reduced, the YI value is further reduced, and the transparency and the visibility are further improved. When the content of the halogen atom is not more than the above upper limit, the synthesis is easy.

The imidization ratio of the polyimide-based resin and the polyamideimide resin is preferably 90% or more, more preferably 93% or more, further preferably 96% or more, and usually 100% or less. The imidization ratio is preferably not less than the above-described lower limit from the viewpoint of easily improving the optical properties of the optical film. The imidization ratio indicates a ratio of a molar amount of imide bonds in the polyimide-based resin to a value 2 times a molar amount of structural units derived from a tetracarboxylic acid compound in the polyimide-based resin. When the polyimide resin contains a tricarboxylic acid compound, the imidization degree indicates a ratio of a value of a molar amount of imide bonds in the polyimide resin to a total of a value 2 times a molar amount of structural units derived from a tetracarboxylic acid compound in the polyimide resin and a molar amount of structural units derived from a tricarboxylic acid compound. The imidization ratio can be determined by an IR method, an NMR method, or the like.

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

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

(method for producing resin)

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

[ chemical formula 15]

[ in the formula (3'),

a represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹)-，

R⁹Represents 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,

R³¹and R³²Independently of one another, represents a hydroxyl group, a methoxy group, an ethoxy group, a n-propoxy group, an isopropoxy group, a n-butoxy group, a sec-butoxy group, a tert-butoxy group or a chlorine atom.]

In a preferred embodiment of the present invention, the dicarboxylic acid compound is a compound represented by formula (3 ") wherein m is 0. As the dicarboxylic acid compound, it is more preferable to use a compound represented by the formula (3 ") in which a is an oxygen atom in addition to the compound represented by the formula (3") in which m is 0. In another preferred embodiment, the dicarboxylic acid compound is represented by R³¹And R³²A compound represented by the formula (3') which is a chlorine atom. In addition, a diisocyanate compound may be used instead of the diamine compound.

Examples of the diamine compound used for producing the resin include aliphatic diamines, aromatic diamines, and mixtures thereof. In the present embodiment, the "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may include an aliphatic group or other substituent in a part of the structure. The aromatic ring may be a monocyclic ring or a fused ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited thereto. Among these, benzene rings are preferred. The "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituent in a part of the structure.

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

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

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

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

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

Specific examples of the aromatic tetracarboxylic acid dianhydride include non-condensed polycyclic aromatic tetracarboxylic acid dianhydride, monocyclic aromatic tetracarboxylic acid dianhydride, and condensed polycyclic aromatic tetracarboxylic acid dianhydride. Examples of the non-condensed polycyclic aromatic tetracarboxylic acid dianhydride include 4,4 '-oxydiphthalic dianhydride, 3, 3', 4,4 '-benzophenonetetracarboxylic acid dianhydride, 2', 3,3 '-benzophenonetetracarboxylic acid dianhydride, 3, 3', 4,4 '-biphenyltetracarboxylic acid dianhydride, 2', 3,3 '-biphenyltetracarboxylic acid dianhydride, 3, 3', 4,4 '-diphenylsulfonetetracarboxylic acid dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4, 4' - (hexafluoroisopropylidene) diphthalic acid dianhydride (hereinafter, sometimes referred to as "6 FDA"), (a diamine having a double bond with two or more carbon atoms), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4 '- (p-phenylenedioxy) diphthalic dianhydride, 4' - (m-phenylenedioxy) diphthalic dianhydride. Examples of the monocyclic aromatic tetracarboxylic acid dianhydride include 1,2,4, 5-benzenetetracarboxylic acid dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic acid dianhydride include 2,3,6, 7-naphthalenetetracarboxylic acid dianhydride.

Among these, preferred examples include 4,4 '-oxydiphthalic dianhydride, 3, 3', 4,4 '-benzophenonetetracarboxylic dianhydride, 2', 3,3 '-benzophenonetetracarboxylic dianhydride, 3, 3', 4,4 '-biphenyltetracarboxylic dianhydride, 2', 3,3 '-biphenyltetracarboxylic dianhydride, 3, 3', 4,4 '-diphenylsulfonetetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 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-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4,4 '- (terephthalic acid) diphthalic dianhydride and 4, 4' - (isophthalic acid) diphthalic dianhydride, more preferably 4,4 '-oxybisphthalic acid dianhydride, 3, 3', 4,4 '-biphenyltetracarboxylic acid dianhydride, 2', 3,3 '-biphenyltetracarboxylic acid dianhydride, 4, 4' - (hexafluoroisopropylidene) diphthalic acid dianhydride (6FDA), bis (3, 4-dicarboxyphenyl) methane dianhydride and 4, 4' - (p-phenylenedioxy) diphthalic dianhydride. These may be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic and acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkanetetracarboxylic dianhydrides such as 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, 1,2,3, 4-cyclobutanetetracarboxylic dianhydride and 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 acid dianhydride include 1,2,3, 4-butanetetracarboxylic acid dianhydride, and 1,2,3, 4-pentanedicarboxylic acid dianhydride, and these can be used alone or in combination of two or more. In addition, a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

Among the above tetracarboxylic dianhydrides, from the viewpoint of high impact resistance, high elastic modulus, high surface hardness, high transparency, high flexibility, high bending resistance, and low coloring property of the optical film, 4,4 ' -oxydiphthalic dianhydride, 3,3 ', 4,4 ' -benzophenone tetracarboxylic dianhydride, 3,3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride, 2 ', 3,3 ' -biphenyl tetracarboxylic dianhydride, 3,3 ', 4,4 ' -diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 4,4 ' - (hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof are preferable, and 3,3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride and 4,4 ' - (hexafluoroisopropylidene) diphthalic dianhydride, are more preferable, And mixtures thereof, and more preferably 4,4 ' - (hexafluoroisopropylidene) diphthalic dianhydride (6FDA) and 3,3 ', 4,4 ' -biphenyltetracarboxylic dianhydride (hereinafter, sometimes referred to as BPDA).

Dicarboxylic acids used in the production of resinsAs the compound, terephthalic acid, 4' -oxybenzoic acid or an acid chloride compound thereof is preferably used. In addition to terephthalic acid, 4' -oxybis-benzoic acid or their acid chloride compounds, other dicarboxylic acid compounds may also be used. Examples of the other dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and acid chloride compounds and acid anhydrides which are analogues thereof, and two or more of them may be used in combination. Specific examples thereof include isophthalic acid; naphthalenedicarboxylic acid; 4, 4' -biphenyldicarboxylic acid; 3, 3' -biphenyldicarboxylic acid; a dicarboxylic acid compound of chain hydrocarbon having 8 or less carbon atoms and 2 benzoic acids via a single bond, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene group-linked compounds and their acid chloride compounds. Specifically, 4 '-oxybis (benzoyl chloride) and terephthaloyl chloride are preferable, and a combination of 4, 4' -oxybis (benzoyl chloride) and terephthaloyl chloride is more preferable.

The polyimide resin may be obtained by reacting tetracarboxylic acid, tricarboxylic acid, and their anhydrides and derivatives in addition to the tetracarboxylic acid compound, as long as the properties of the optical film are not impaired.

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

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and acid chloride compounds and acid anhydrides which are analogues thereof, and two or more of them may be used in combination. Specific examples thereof include: anhydride of 1,2, 4-benzenetricarboxylic acid; 2,3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; phthalic anhydride and benzoic acid through single bond, -O-, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene groups.

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

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

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

The polyimide-based resin and the polyamide-based resin can be separated by separation and purification by a conventional method, for example, separation means such as filtration, concentration, extraction, crystallization, recrystallization and column chromatography, or separation means combining these, and in a preferred embodiment, the resin can be separated by precipitating a large amount of an alcohol such as methanol into a reaction solution containing the transparent polyamide-imide resin, and then concentrating, filtering and drying the resin.

< ingredient containing sodium >

The optical film of the present invention contains a sodium-containing component selected from the group consisting of a sodium atom-containing compound, sodium, and sodium ions. The content of the sodium-containing component in the optical film of the present invention is determined by the ionic strength (I) of Na obtained by time-of-flight secondary ion mass spectrometry_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) The amount of the polyimide resin is not particularly limited, and may be 0.2 or more, and the ratio (I) is not particularly limited, depending on the kind of the polyimide resin contained in the optical film_Na/I_CH3) The setting may be performed so as to fall within a predetermined range. For example, the content of the sodium-containing component in the varnish used for producing the optical film of the present invention is preferably 0.002 mass% or more, more preferably 0.004 mass% or more, even more preferably 0.01 mass% or more, and even more preferably 0.01 mass% or more, based on the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the varnish, from the viewpoint of easily improving the impact resistance of the optical filmIs 0.02 mass% or more, particularly preferably 0.03 mass% or more, and particularly preferably 0.04 mass% or more. The upper limit of the content of the sodium-containing component in the varnish used for producing the optical film of the present invention is preferably 1 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, based on the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the varnish, from the viewpoint of easily obtaining a homogeneous film. The content of the sodium-containing component in the optical film of the present invention is preferably 0.002 mass% or more, more preferably 0.004 mass% or more, further preferably 0.01 mass% or more, further preferably 0.02 mass% or more, particularly preferably 0.03 mass% or more, and particularly preferably 0.04 mass% or more, with respect to the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the optical film, from the viewpoint of easily improving the impact resistance of the optical film. The upper limit of the content of the sodium-containing component in the optical film of the present invention is preferably 1 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, 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 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 an optical method such as infrared absorption spectroscopy, or the content of the varnish used in the production of the optical film may be the content in the optical film. In the case of using a sodium atom-containing compound as the sodium-containing component, the compound may be decomposed or the like in the process of producing the optical film within a range not to impair the effects of the present invention.

The kind of the compound containing a sodium atom is not particularly limited. In the case of producing an optical film using a resin composition (also referred to as a "varnish") containing at least a polyimide-based resin and/or a polyamide-based resin and a solvent, the sodium atom-containing compound is preferably an organic sodium salt from the viewpoint of easily dissolving the component in the solvent of the varnish and easily allowing the component to be contained in the optical film. Examples of the organic sodium salt include sodium alkoxides having 1 to 6 carbon atoms. From the viewpoint of improving the solubility of the sodium atom-containing compound and easily obtaining a resin composition containing a polyimide-based resin and/or a polyamide-based resin having excellent film-forming properties, it is preferable to use an aprotic polar solvent as the solvent for the varnish. When an aprotic polar solvent is used, it is considered that even when a salt such as sodium hydroxide or sodium chloride is used as the sodium atom-containing compound, the salt is easily dissolved in the varnish, and the interaction between the polyimide-based resin and/or the polyamide-based resin and the sodium atom-containing compound in the varnish is easily improved. The sodium atom-containing compound added to the resin composition may be contained in the form of sodium or sodium ions, or may be contained in the form of, for example, an organic sodium salt, or the like, without being directly contained in the optical film of the present invention, and may be formed into another salt in the final optical film by hydrolysis with water, alcohol, or the like contained in the resin composition, an ion exchange reaction with another salt, or the like. Here, the polyimide-based resin and/or the polyamide-based resin contained in the optical film is a resin that is likely to absorb moisture, and the resin composition and the optical film containing these resins usually contain moisture. Further, as described above, since hydrolysis is considered to occur by reaction with moisture in the resin composition, it is considered that at least a part of the sodium-containing component added to the resin composition in the form of, for example, an organic sodium salt such as sodium alkoxide is present as sodium hydroxide or the like as a salt in the final optical film, and the sodium hydroxide or the like is present as ionized partially and interacts with a carbonyl group.

< composition containing Potassium >

The optical film of the present invention contains a potassium-containing component selected from the group consisting of a potassium atom-containing compound, potassium, and potassium ions. The content of the potassium-containing component in the optical film of the present invention is determined by the ion intensity (I) of K obtained by time-of-flight secondary ion mass spectrometry_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) The amount of the optical film is not particularly limited, and may be 0.2 or more, depending on the optical film contained thereinThe kind of the polyimide resin (I) and the above ratio_K/I_CH3) The setting may be performed so as to fall within a predetermined range. For example, the content of the potassium-containing component in the varnish used for producing the optical film of the present invention is preferably 0.002 mass% or more, more preferably 0.005 mass% or more, further preferably 0.015 mass% or more, further preferably 0.03 mass% or more, particularly preferably 0.05 mass% or more, and particularly preferably 0.08 mass% or more, based on the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the varnish, from the viewpoint of easily improving the impact resistance of the optical film. The upper limit of the content of the potassium-containing component in the varnish used for producing the optical film of the present invention is preferably 1 mass% or less, more preferably 0.5 mass% or less, even more preferably 0.3 mass% or less, and particularly preferably 0.2 mass% or less, based on the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the varnish, from the viewpoint of easily obtaining a homogeneous film. The content of the potassium-containing component in the optical film of the present invention is preferably 0.002 mass% or more, more preferably 0.005 mass% or more, further preferably 0.015 mass% or more, further preferably 0.03 mass% or more, particularly preferably 0.05 mass% or more, and particularly preferably 0.08 mass% or more, based on the total amount of the polyimide-based resin and/or the polyamide-based resin contained in the optical film, from the viewpoint of easily improving the impact resistance of the optical film. The upper limit of the content of the potassium-containing component in the optical film of the present invention is preferably 1 mass% or less, more preferably 0.5 mass% or less, further preferably 0.3 mass% or less, and particularly preferably 0.2 mass% or less, 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 of the potassium-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 spectroscopy, or the content of the varnish used in the production of the optical film may be the content in the optical film. In addition, in the use of potassium atomsWhen the compound of (3) is used as a potassium-containing component, the compound may be decomposed or the like in the process of producing an optical film within a range not to impair the effects of the present invention.

The kind of the compound containing a potassium atom is not particularly limited. In the case of producing an optical film using a varnish containing at least a polyimide-based resin and/or a polyamide-based resin and a solvent, the compound containing a potassium atom is preferably an organic potassium salt from the viewpoint of easily dissolving the component in the solvent of the varnish and easily allowing the component to be contained in the optical film. Examples of the organic potassium salt include potassium alkoxides having 1 to 6 carbon atoms. From the viewpoint of improving the solubility of the potassium atom-containing compound and easily obtaining a resin composition containing a polyimide-based resin and/or a polyamide-based resin having excellent film-forming properties, it is preferable to use an aprotic polar solvent as the solvent for the varnish. When an aprotic polar solvent is used, it is considered that even when a salt such as potassium hydroxide or potassium chloride is used as the potassium atom-containing compound, the salt is easily dissolved in the varnish, and the interaction between the polyimide-based resin and/or the polyamide-based resin and the potassium atom-containing compound in the varnish is easily improved. The compound containing a potassium atom added to the resin composition may be contained in the optical film of the present invention, for example, in the form of an organic potassium salt or the like, without being directly contained in the optical film, or may be contained in the form of potassium or potassium ions, for example, by hydrolysis with water, alcohol or the like contained in the resin composition, ion exchange reaction with another salt, or the like to form another salt in the final optical film. Here, the polyimide-based resin and/or the polyamide-based resin contained in the optical film is a resin that is likely to absorb moisture, and the resin composition and the optical film containing these resins usually contain moisture. Further, as described above, it is considered that hydrolysis occurs by reaction with water in the resin composition, and therefore, it is considered that a potassium-containing component added to the resin composition in the form of, for example, an organic potassium salt such as potassium alkoxide is present as potassium hydroxide or the like as a salt at least in part in the final optical film, and the potassium hydroxide or the like is present as ionized in part and interacts with a carbonyl group.

< additive >

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

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

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

The optical film of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber can be appropriately selected from those commonly used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400nm or less. Examples of the ultraviolet absorber include at least one compound selected from the group consisting of benzophenone-based compounds, salicylate-based compounds, benzotriazole-based compounds, and triazine-based compounds. The ultraviolet absorber may be used alone or in combination of two or more. Since the optical film contains the ultraviolet absorber, deterioration of the resin can be 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 term "related compound" refers to a derivative of a compound to which the "related compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a matrix 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, further preferably 3 parts by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 6 parts by mass or less, per 100 parts by mass of the optical film. The appropriate content varies depending on the ultraviolet absorber used, and when the content of the ultraviolet absorber is adjusted so that the light transmittance at 400nm is about 20 to 60%, the light resistance of the optical film is improved, and the transparency is easily improved.

The optical film of the present invention may further contain other additives besides the filler and the ultraviolet absorber. Examples of the other additives include an antioxidant, a mold release agent, a stabilizer, a bluing agent, a flame retardant, a pH adjuster, a silica dispersant, a lubricant, a thickener, and a leveling agent. When other additives are contained, the content thereof is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and still more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the optical film.

(method for producing optical film)

The method for producing the optical film of the present invention is not particularly limited, and for example, a production method including at least the following steps:

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

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

(c) and a step of drying the coating film to form an optical film (optical film forming step).

The present invention also provides the above-mentioned production method using a resin composition suitable for producing the optical film of the present invention, the resin composition containing at least one resin selected from the group consisting of a polyimide-based resin and a polyamide-based resin, at least one sodium-containing component, at least one potassium-containing component, and a solvent.

In the varnish preparation step, a varnish is prepared by dissolving at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins, at least one sodium-containing component, and at least one potassium-containing component in a solvent, and adding the above-mentioned additives such as a filler and an ultraviolet absorber as needed, followed by stirring and mixing. When silica particles are used as the filler, a silica sol obtained by replacing a dispersion of a silica sol containing silica particles with a solvent capable of dissolving the resin (for example, a solvent used in the preparation of a varnish described below) may be added to the resin.

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

The content of the sodium-containing component contained in the resin composition is preferably 0.002 mass% or more, more preferably 0.004 mass% or more, further preferably 0.01 mass% or more, further preferably 0.02 mass% or more, particularly preferably 0.03 mass% or more, and particularly preferably 0.04 mass% or more, with respect to the total amount of at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins contained in the resin composition, from the viewpoint of easily improving the impact resistance and elastic modulus of the optical film. The upper limit of the content of the sodium-containing component in the resin composition of the present invention is preferably 1.0 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, with respect to the total amount of at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins contained in the resin composition, from the viewpoint of varnish viscosity controllability and film-forming properties. When the content of the sodium-containing component is not more than the above upper limit, the viscosity of the varnish is not excessively high, and the film-forming property is easily improved because the resin solid content in the varnish is easily increased.

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

The content of the potassium-containing component in the resin composition is preferably 0.002 mass% or more, more preferably 0.005 mass% or more, further preferably 0.015 mass% or more, further more preferably 0.03 mass% or more, particularly preferably 0.05 mass% or more, and particularly preferably 0.08 mass% or more, with respect to the total amount of at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins contained in the resin composition, from the viewpoint of easily improving the impact resistance and elastic modulus of the optical film. The upper limit of the content of the potassium-containing component in the resin composition of the present invention is preferably 1.0 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, with respect to the total amount of at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins contained in the resin composition, from the viewpoint of varnish viscosity controllability and film-forming properties. When the content of the potassium-containing component is not more than the above upper limit, the viscosity of the varnish is not excessively high, and the solid resin component in the varnish is easily increased, so that the film-forming property is easily improved.

The solvent used for the preparation of the varnish is not particularly limited as long as it can dissolve the resin. Examples of the solvent include amide solvents such as N, N-dimethylacetamide (hereinafter, sometimes referred to as DMAc) and N, N-dimethylformamide (hereinafter, sometimes referred to as DMF); lactone solvents such as γ -butyrolactone (hereinafter, sometimes referred to as GBL) and γ -valerolactone; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, an amide solvent or a lactone solvent is preferable. These solvents may be used alone or in combination of two or more. The varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The solid content concentration of the varnish is preferably 1 to 25 mass%, more preferably 5 to 20 mass%, and still more preferably 5 to 15 mass%. Here, in view of easily improving the interaction between the polyimide-based resin and/or the polyamide-based resin and the sodium-containing component and/or the potassium-containing component, a solvent capable of dissolving them is preferably used in the preparation of the varnish. For example, the above-mentioned solvent is preferable from the viewpoint of the solubility of the resin, and the aprotic polar solvent is preferable from the viewpoint of the solubility of the sodium-containing component and/or the potassium-containing component, and the aprotic polar solvent selected from the group consisting of an amide-based solvent and a lactone-based solvent is more preferable. Since the solvent described above is likely to absorb moisture in the atmosphere, it is considered that water is often contained in the varnish even if water is not intentionally added to the varnish. Further, it is considered that when a part of the sodium-containing component and/or the potassium-containing component which becomes sodium ions and/or potassium ions in the varnish interacts with the resin, the equilibrium progresses in the direction of ionizing the sodium-containing component and/or the potassium-containing component. Therefore, even if the sodium-containing component and/or the potassium-containing component is a compound such as a salt that is hardly soluble in the solvent used for the preparation of the varnish, the polyimide-based resin and/or the polyamide-based resin is contained in the varnish, so that the above-mentioned component can be dissolved in the varnish. Further, the interaction between the resin and the sodium-containing component and/or the potassium-containing component may be promoted by leaving the resin in the varnish state for a certain period of time.

It was confirmed that: the viscosity of the resin composition comprising the resin, the sodium-containing component, the potassium-containing component, and the solvent is higher than the viscosity of the composition prior to the addition of the sodium-containing component and the potassium-containing component. Such a viscosity rise is thought to be due to: by adding the sodium-containing component and the potassium-containing component, the resin interacts with the sodium-containing component and the potassium-containing component. Specifically, when the viscosity of the resin composition was measured using a viscometer under the conditions described in examples, for example, it was confirmed that: the viscosity is increased by the addition of the sodium-containing component and/or the addition of the potassium-containing component. It is presumed that stacking between resins is further enhanced by coexistence of a sodium-containing component and a potassium-containing component having such an interaction and differing in atomic radius, ionic radius, or molecular size in the resins.

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

In the film forming step, the coating film is dried and peeled from the support material, whereby an optical film can be formed. After the peeling, a step of drying the optical film may be further provided. The drying of the coating film may be carried out at a temperature of 50 to 350 ℃. If necessary, the coating film may be dried in an inert atmosphere or under reduced pressure. In the optical film obtained, a part of the solvent contained in the varnish may be slightly left. The amount of the solvent contained in the optical film is preferably 1.5% or less, more preferably 1.2% or less, further preferably 1.1% or less, and further preferably 1.0% or less, with respect to the mass of the optical film. The lower limit of the amount of the solvent is preferably 0% or more, more preferably 0.02% or more, still more preferably 0.1% or more, and still more preferably 0.3% or more. When the amount of the residual solvent in the optical film is within the above range, the impact resistance of the optical film can be improved and the YI value can be reduced. The amount of the residual solvent in the optical film can be adjusted by the drying conditions of the coating film.

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

(functional layer)

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

A hard coat layer may be provided on at least one side of the optical film of the present invention. 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, the impact resistance can be further improved, the bending resistance is less likely to be lowered, and the problem of occurrence of curling due to curing shrinkage tends to be less likely to occur. The hard coat layer may be formed by curing a hard coat layer composition containing a reactive material capable of forming a cross-linked structure by irradiation with active energy rays or application of thermal energy, and is preferably a layer based on irradiation with active energy rays. The active energy ray is defined as an energy ray that can decompose a compound that generates an active species to generate an active species, and examples thereof include visible light, ultraviolet ray, infrared ray, X-ray, α -ray, β -ray, γ -ray, and electron ray, and preferable examples thereof include ultraviolet ray. The hard coat composition contains at least one polymer selected from a radical polymerizable compound and a cation polymerizable compound.

The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound may be a functional group capable of undergoing a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond, specifically, a vinyl group and a (meth) acryloyl group. When the radical polymerizable compound has 2 or more radical polymerizable groups, the radical polymerizable groups may be the same or different. The number of the radical polymerizable groups contained in 1 molecule of the radical polymerizable compound is preferably 2 or more in terms of increasing the hardness of the hard coat layer. The radical polymerizable compound is preferably a compound having a (meth) acryloyl group in view of high reactivity, and specifically, a compound called a multifunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in 1 molecule; oligomers having a molecular weight of several hundred to several thousand and having several (meth) acryloyl groups in the molecule, which are called epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate, preferably include 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 oxetane group, or a vinyl ether group. The number of the cationically polymerizable groups contained in 1 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.

Among the above cationically polymerizable compounds, preferred are compounds having at least one of an epoxy group and an oxetane group as a cationically polymerizable group. From the viewpoint of reducing shrinkage accompanying the polymerization reaction, a cyclic ether group such as an epoxy group or an oxetane group is preferable. In addition, the compound having an epoxy group in a cyclic ether group has the following advantages: compounds with various structures are easily obtained; the durability of the obtained hard coating is not adversely affected; the compatibility with the radical polymerizable compound can be easily controlled. In addition, the oxetanyl group in the cyclic ether group has the following advantages as compared with the epoxy group: the polymerization degree is easy to be improved; the toxicity is low; accelerating the network formation rate obtained from the cationic polymerizable compound of the obtained hard coat layer; forming an independent network so that an unreacted monomer does not remain in the film even in a region where the radical polymerizable compound is present in a mixed state; and so on.

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

The above hard coating composition may further comprise a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and they 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, and radical polymerization and cationic polymerization are performed.

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

The active energy ray radical polymerization initiator includes a Type1 radical polymerization initiator which generates radicals by decomposition of molecules and a Type2 radical polymerization initiator which generates radicals by hydrogen abstraction reaction in the coexistence of a tertiary amine, and they can be used alone or in combination.

The cationic polymerization initiator may be a substance capable of releasing cationic polymerization initiated by at least one of irradiation with active energy rays and heating. As the cationic polymerization initiator, aromatic iodonium salts, aromatic sulfonium salts, cyclopentadienyl iron (II) complexes, and the like can be used. In the case of these cationic polymerization initiators, cationic polymerization can be initiated by either or both of irradiation with active energy rays or heating, depending on the structure.

The polymerization initiator may be contained 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 within the above range, the curing can be sufficiently performed, the mechanical properties and the adhesion of the finally obtained coating film can be in a favorable range, and poor adhesion, a crack phenomenon, and a curl phenomenon due to curing shrinkage tend to be less likely to occur.

The hard coating composition may further include one or more selected from the group consisting of a solvent and an additive.

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

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

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

The pressure-sensitive adhesive layer is a layer having a pressure-sensitive adhesive function and has a function of bonding the optical film to another member. As a material for forming the adhesive layer, a generally known material can be used. For example, a thermosetting resin composition or a photocurable resin composition may be used. In this case, the resin composition can be polymerized and cured by supplying energy afterwards.

The Pressure-Sensitive Adhesive layer may be a layer called a Pressure-Sensitive Adhesive (PSA) that is pressed and attached to an object. The pressure-sensitive adhesive may be a capsule adhesive as "a substance having adhesiveness at normal temperature and adhering to an adherend under light pressure" (JIS K6800), or as "an adhesive which contains a specific component in a protective film (microcapsule) and can maintain stability until the film is broken by an appropriate means (pressure, heat, etc.)" (JIS K6800).

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

The refractive index adjustment layer is a layer having a function of adjusting the refractive index, and is, for example, a layer having a refractive index different from that of the optical film and capable of providing 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, in some cases, a pigment, or may be a metal thin film. Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The 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 transmitted through the refractive index adjustment layer can be prevented, and a decrease in transparency can be prevented. Examples of the metal used for the refractive index adjustment layer include metal oxides and metal nitrides such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride.

The optical film of the present invention may be a single layer or a laminate, and for example, the optical film produced as described above may be used as it is, or may be used in the form of a laminate with another film. Na ion intensity (I) obtained by time-of-flight type secondary ion mass spectrometry_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) 0.2 or more and an ionic strength (I) of K_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) The optical film of the present invention having an impact resistance of 0.2 or more has high impact resistance, and is useful as an optical film in an image display device or the like.

In a preferred embodiment of the present invention, the optical film of the present invention is useful as a front panel of an image display device, particularly a front panel (window film) of a flexible display device, and particularly a front panel of a rollable display or a foldable display which is sometimes bent or restored to flat. The flexible display device includes, for example, a flexible functional layer and an optical film that functions as a front panel by being laminated with the flexible functional layer. That is, the front panel of the flexible display device is arranged on the viewing side above the flexible functional layer. The front panel has a function of protecting a flexible functional layer, for example, an image display element in a flexible display.

Examples of the image display device include wearable devices such as televisions, smart phones, mobile phones, car navigation systems, tablet computers, portable game machines, electronic papers, indicators, bulletin boards, clocks, and smartwatches. As the flexible display device, all image display devices having a flexible characteristic can be cited.

[ Flexible display device ]

The present invention also provides a flexible display device provided with the optical film of the present invention. The optical film of the present invention is preferably used as a front panel in a flexible display device, which is sometimes referred to as a window film. The flexible display device includes a laminate for flexible display device and an organic EL display panel, and the laminate for flexible display device is disposed 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), circularly polarizing plate, and touch sensor of the present invention in any order of lamination, but it is preferable to laminate the window film, circularly polarizing plate, and touch sensor in this order, or the window film, touch sensor, and circularly polarizing plate in this order from the viewing side. When the circularly polarizing plate is present on the viewing side of the touch sensor, the pattern of the touch sensor is not easily recognized, and visibility of the display image is improved, which is preferable. The members may be laminated using an adhesive, a bonding agent, or the like. The touch panel may further include a light-shielding pattern formed on at least one surface of any one of the window film, the circularly polarizing plate, and the touch sensor.

[ polarizing plate ]

The flexible display device of the present invention may further include a polarizing plate, preferably a circular polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only a right-handed circularly polarized light component or a left-handed circularly polarized light component by laminating a λ/4 phase difference plate on a linearly polarizing plate. For example, can be used for: the external light is converted into right-handed circularly polarized light, the external light which is reflected by the organic EL panel and becomes left-handed circularly polarized light is blocked, and only the light emitting component of the organic EL is transmitted, thereby suppressing the influence of the reflected light and making it easy to view an image. In order to realize the circularly polarized light function, the absorption axis of the linear polarizer and the slow axis of the λ/4 phase difference plate must be 45 ° in theory, but in practical use, 45 ± 10 °. The linear polarizing plate and the λ/4 phase difference plate do not necessarily have to be stacked adjacent to each other, and the relationship between the absorption axis and the slow axis may be satisfied in the above range. It is preferable to realize completely circularly polarized light at the full wavelength, but this is not necessarily required in practical use, and thus 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 viewing side of the linear polarizing plate to convert the emitted light into circularly polarized light, thereby improving visibility in a state where the polarized sunglasses are worn.

The linear polarizing plate is a functional layer having the following functions: light vibrating in the direction of the transmission axis passes through but polarized light of the vibration component perpendicular thereto is blocked. The linear polarizing plate may be a single linear polarizer or a linear polarizer and a protective film attached to at least one surface of the linear polarizer. The thickness of the linearly polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness is within the above range, the flexibility tends not to be easily lowered.

The linear polarizer may be a film type polarizer manufactured by dyeing and stretching a polyvinyl alcohol (PVA) film. The polarizing performance can be exhibited by adsorbing a dichroic dye such as iodine onto a PVA-based film that has been stretched and oriented, or by stretching the film in a state where the dichroic dye is adsorbed onto PVA to orient the dichroic dye. The film-type polarizer may be produced by steps such as swelling, crosslinking with boric acid, washing with an aqueous solution, and drying. The stretching and dyeing step may be performed by a 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 film to be used is preferably 10 to 100 μm, and the stretch ratio is preferably 2 to 10 times.

In addition, 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 pigment compound. The liquid crystalline compound is preferably used as long as it has a property of exhibiting a liquid crystal state, and particularly, it can exhibit high polarizing performance when it has a high-order alignment state such as smectic state. Further, it is also preferable that the liquid crystalline compound has a polymerizable functional group.

The dichroic pigment is a pigment which exhibits dichroism by being aligned with the liquid crystal compound, and the dichroic pigment itself may have liquid crystallinity or may have a polymerizable functional group. 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 crosslinking agent, a silane coupling agent, and the like.

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

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

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

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

The λ/4 phase difference plate is a film that imparts a phase difference of λ/4 in a direction orthogonal to the traveling direction of incident light (in other words, in the in-plane direction of the film). The λ/4 retardation plate may be a stretched retardation plate produced by stretching a polymer film such as a cellulose film, an olefin film, or a polycarbonate film. If necessary, a retardation adjuster, a plasticizer, an ultraviolet absorber, an infrared absorber, a colorant (such as a pigment or a dye), a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, or the like may be contained. The thickness of the stretched retardation film may be 200 μm or less, preferably 1 to 100 μm. When the thickness is within the above range, the flexibility of the film tends not to be easily reduced.

Further, another example of the λ/4 retardation plate may be a liquid crystal coating type retardation plate formed by coating a liquid crystal composition. The liquid crystal composition comprises a liquid crystalline compound having the following properties: showing nematic, cholesteric, smectic, and the like liquid crystal states. Any compound including a liquid crystalline compound in the liquid crystal composition has a polymerizable functional group. The liquid crystal coating type retardation plate may further contain an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like. The liquid crystal coating type retardation plate can be produced by: similarly to the above-mentioned liquid crystal polarizing layer, a liquid crystal composition is applied onto an alignment film and cured to form a liquid crystal retardation layer. The liquid crystal coating type retardation plate can be formed to a smaller thickness than the stretching type retardation plate. The thickness of the liquid crystal polarizing layer may be usually 0.5 to 10 μm, preferably 1 to 5 μm. The liquid crystal-coated retardation plate may be peeled from the substrate and transferred to be laminated, or the substrate may be directly laminated. The substrate preferably functions as a transparent substrate for a protective film, a retardation plate, and a window film.

Generally, the following materials are more: the shorter the wavelength, the greater the birefringence; the longer the wavelength, the less birefringence is exhibited. In this case, since a phase difference of λ/4 cannot be realized in all visible light regions, it is often designed as follows: the in-plane retardation is 100 to 180nm (preferably 130 to 150nm) such as λ/4 in the vicinity of 560nm, which is high in visibility. The use of an inverse dispersion λ/4 phase difference plate using a material having a birefringence wavelength dispersion characteristic opposite to that of the usual one is preferable because it can improve visibility. As such a material, the material described in japanese patent application laid-open No. 2007-232873 and the like is preferably used also in the case of a stretched phase difference plate, and the material described in japanese patent application laid-open No. 2010-30979 is preferably used also in the case of a liquid crystal coated phase difference plate.

As another method, a technique is also known in which a broadband λ/4 phase difference plate is obtained by combining a λ/2 phase difference plate (japanese patent application laid-open No. h 10-90521). The λ/2 phase difference plate is also manufactured by the same material and method as the λ/4 phase difference plate. The combination of the stretching type retardation plate and the liquid crystal coating type retardation plate is arbitrary, and the use of the liquid crystal coating type retardation plate is preferable because the thickness can be reduced.

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

[ touch sensor ]

The flexible display device of the present invention may further include a touch sensor. The touch sensor serves as an input means. As the touch sensor, various types such as a resistive film type, a surface acoustic wave type, an infrared ray type, an electromagnetic induction type, and a capacitance type have been proposed, and any type may be used. Among them, the electrostatic capacitance system is preferable. The capacitive touch sensor is divided into an active region and an inactive region located at an outer peripheral portion of the active region. The active region is a region corresponding to a display unit, which is a region on the display panel where a screen is displayed, and is a region where a user's touch is sensed, and the inactive region is a region corresponding to a non-display unit, which is a region on the display device where a screen is not displayed. The touch sensor may include: a substrate having flexible properties; a sensing pattern formed in an active region of the substrate; and each sensing line formed in the inactive region of the substrate and used for connecting the sensing pattern with an external driving circuit through a pad (pad) part. As the substrate having a flexible property, the same material as the polymer film can be used. The substrate of the touch sensor preferably has a toughness of 2,000 MPa% or more in terms of suppressing cracks in the touch sensor. The toughness may be more preferably 2,000 to 30,000 MPa%. Here, toughness is defined as: in a Stress (MPa) -strain (%) curve (Stress-strain curve) obtained by a tensile test of a polymer material, the area of the lower portion of the curve up to the failure point is determined.

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

The bridge electrode may be formed on the insulating layer with an insulating layer interposed therebetween on the sensing pattern, and the bridge electrode may be formed on the substrate, on which the insulating layer and the sensing pattern may be formed. The bridge electrode may be formed of the same material as the sensor pattern, or may be formed of a metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of two or more of these metals. Since the 1 st pattern and the 2 nd pattern must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the contact of the 1 st pattern and the bridge electrode, or may be formed in a structure of a layer covering the sensing pattern. In the latter case, the bridge electrode may be connected with the 2 nd pattern via a contact hole formed in the insulating layer. In the touch sensor, as means for appropriately compensating for a difference in transmittance between a pattern region where a pattern is formed and a non-pattern region where no pattern is formed (specifically, a difference in transmittance due to a difference in refractive index in these regions), an optical adjustment layer may be further included between the substrate and the electrode, and the optical adjustment layer may include an inorganic insulating substance or an organic insulating substance. The optical adjustment layer can be formed by applying a photocurable composition containing a photocurable organic binder and a solvent onto a substrate. The above-mentioned photocurable composition may further comprise inorganic particles. The refractive index of the optical adjustment layer can be increased by the inorganic particles.

The photocurable organic binder may include a copolymer of monomers such as an acrylate monomer, a styrene monomer, and a carboxylic acid monomer. The photocurable organic binder may be 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 may include, for example, zirconia particles, titania particles, alumina particles, and the like. The photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing assistant.

[ adhesive layer ]

Each layer (a window film, a polarizing plate, a touch sensor, and the like) and a film member (a linear polarizing plate, a λ/4 retardation plate, and the like) constituting each layer forming the laminate for a flexible display device may be bonded with an adhesive. As the adhesive, a commonly used adhesive such as an aqueous adhesive, an organic solvent adhesive, a solventless adhesive, a solid adhesive, a solvent volatile adhesive, a moisture curable adhesive, a heat curable adhesive, an anaerobic curable adhesive, an aqueous solvent volatile adhesive, an active energy ray curable adhesive, a curing agent hybrid adhesive, a hot melt adhesive, a pressure sensitive adhesive, and a rewetting adhesive can be used. Among them, an aqueous solvent-volatile adhesive, an active energy ray-curable adhesive, and a pressure-sensitive adhesive are preferably used. The thickness of the adhesive layer can be adjusted as appropriate according to the required adhesive strength, and is, for example, 0.01 to 500. mu.m, preferably 0.1 to 300. mu.m. The laminate for a flexible image display device may have a plurality of adhesive layers, and the thickness of each adhesive layer and the type of adhesive used may be the same or different.

The aqueous solvent-volatile adhesive may be a polyvinyl alcohol polymer, a water-soluble polymer such as starch, or a water-dispersed polymer such as an ethylene-vinyl acetate emulsion or a styrene-butadiene emulsion. In addition to water and the main agent polymer, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, and the like may be added. In the case of bonding with the aqueous solvent volatile adhesive, adhesiveness can be provided by injecting the aqueous solvent volatile adhesive between the layers to be bonded, bonding the layers to be bonded, and then drying the layers. The thickness of the adhesive layer when the aqueous solvent-volatile adhesive is used may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the aqueous solvent volatile 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 capable of forming an adhesive layer by irradiation with an active energy ray. The active energy ray-curable composition may contain at least one polymer selected from the group consisting of a radically polymerizable compound and a cationically polymerizable compound, as in the case of the hard coat composition. The radical polymerizable compound may be the same kind of compound as the hard coat composition, as the hard coat composition. The radical polymerizable compound used in the adhesive layer is preferably a compound having an acryloyl group. In order to reduce the viscosity of the adhesive composition, it is also preferable to include a monofunctional compound.

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

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

The active energy ray-curable composition may further contain an ion scavenger, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, an antifoaming agent, an additive, and a solvent. When the bonding is performed by the active energy ray-curable adhesive, the bonding may be performed by: the active energy ray-curable composition is applied to either or both of the adhesive layers, and then the adhesive layers are bonded to each other, and either or both of the adhesive layers are cured by irradiation with active energy rays. The thickness of the adhesive layer when the active energy ray-curable adhesive is used may be usually 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 the adhesive used may be the same or different.

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

[ light-shielding pattern ]

The light shielding pattern may be applied to at least a part of a frame (bezel) or a housing of the flexible image display device. The wiring disposed at the edge of the flexible image display device is shielded by the light shielding pattern and is not easily recognized, thereby improving visibility of the image. The light-shielding pattern may be in the form of a single layer or a plurality of layers. The color of the light-shielding pattern is not particularly limited, and may have various colors such as black, white, metallic color, and the like. The light-shielding pattern may be formed of a pigment for color development, and a polymer such as an acrylic resin, an ester resin, an epoxy resin, polyurethane, or silicone. They may also be used alone or in the form of a mixture of two or more. The light-shielding pattern can be formed by various methods such as printing, photolithography, 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.

Examples

The present invention will be described in further detail below with reference to examples. Unless otherwise specified, "%" and "part" in the examples mean mass% and part by mass, respectively. First, a method for measuring physical property values will be described.

< determination of weight average molecular weight >

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

(1) Sample preparation method

20mg of the resin was weighed out and 10mL of DMF (10mmol/L lithium bromide) was added to dissolve it completely. The solution was filtered using a chromatography plate (chromatodisk) with a pore size of 0.45 μm to prepare a sample solution.

(2) Measurement conditions

The device comprises the following steps: HLC-8020GPC

Column: guard column + TSKgel alpha-M (300 mm. times.7.8 mm diameter). times.2 pieces + alpha-2500 (300 mm. times.7.8 mm diameter). times.1 pieces

Eluent: DMF (with addition of 10mmol/L lithium bromide)

Flow rate: 1.0 mL/min

A detector: RI detector

Column temperature: 40 deg.C

Injection amount: 100 μ L

Molecular weight standard: standard polystyrene

< measurement of Total light transmittance >

The total light transmittance of the optical film was measured in accordance with JIS K7105: 1981, using a fully automated direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd.

< determination of haze >

Haze of optical film according to JIS K7105: 1981, using a fully automated direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd.

< luminance (L)^*Value) >

Brightness L of optical film^*The value was measured using a spectrophotometer ("V-670" manufactured by Nippon Kabushiki Kaisha). After background measurement in the absence of a sample, an optical film was placed on a sample holder, and the transmittance with respect to light having a wavelength of 300 to 800nm was measured to determine L^*The value is obtained.

< measurement of thickness >

The thickness of the optical film obtained in examples and comparative examples was measured using an ABS digital Indicator ("ID-C112 BS" manufactured by Mitsutoyo corporation).

< method for measuring residual solvent >

The polyamideimide resin films obtained in example 1 and comparative example 1 were heated from 30 ℃ to 120 ℃ for 5 minutes using TG-DTA (EXSTAR 6000 TG/DTA6300 manufactured by SII Co., Ltd.), and then heated to 400 ℃ at a heating rate of 5 ℃/minute. The ratio of the mass loss of the optical film from 120 ℃ to 250 ℃ to the mass of the resin film at 120 ℃ was calculated as the content of the solvent contained in the resin film (referred to as the residual solvent amount). The amount of the residual solvent in the resin film represents a ratio of the solvent contained in the resin film with respect to the mass of the resin film.

< measurement of time-of-flight type Secondary ion Mass Spectrometry (TOF-SIMS) >

An optical film was formed on a cross section using "Ultra Microtome EM UC 6" manufactured by Leica Microsystems.

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

(1) The device comprises the following steps: SIMS V manufactured by ION-TOF Inc "

(2) Primary ion: bi³⁺⁺

(3) Acceleration voltage of primary ions: 25kV

(4) Irradiation of ion current: 0.23pA

(5) The measurement conditions were as follows: measurement of Positive and negative ions Using a Beam bunching (high Mass resolution) mode

(6) Measurement range: 200 μm × 200 μm

Data analysis by TOF-SIMS was performed using Surface Lab. Mass calibration of assay data for Na ions, K ions and CH₃The integrated values of the peaks were calculated for the peaks of the ions. The integral value of the peak of Na ion was defined as Na ion intensity I_NaThe integral value of the peak of the K ion is defined as the ion intensity I of K_KIs prepared from CH₃Integral value of peak of ion as CH₃Ionic strength of (I)_CH3Calculating a ratio I_Na/I_CH3And the ratio I_K/I_CH3。

< impact resistance test >

(preparation of sample for impact resistance evaluation)

97.0 parts by mass of n-butyl acrylate, 1.0 part by mass of acrylic acid, 0.5 part by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate, and 0.08 part by mass of 2, 2' -azobisisobutyronitrile were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen gas inlet tube, and the atmosphere in the reaction vessel was replaced with nitrogen gas. The reaction solution was heated to 60 ℃ with stirring under a nitrogen atmosphere, allowed to react for 6 hours, and then cooled to room temperature. The weight average molecular weight of a part of the obtained solution was measured, and it was confirmed that a (meth) acrylate ester polymer of 1,800,000 was produced.

100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth) acrylate polymer obtained in the above step, 0.30 parts by mass of trimethylolpropane-modified tolylene diisocyanate (trade name "Coronate (registered trademark) L", manufactured by Tosoh corporation) as an isocyanate-based crosslinking agent, and 0.30 parts by mass of 3-glycidoxypropyltrimethoxysilane (trade name "KBM 403", manufactured by shin-Etsu chemical industry corporation) as a silane coupling agent were mixed, sufficiently stirred, and diluted with ethyl acetate to obtain a coating solution of the pressure-sensitive adhesive composition.

The coating solution was applied to a release-treated surface (release layer surface) of a separator (SP-PLR 382190, manufactured by Lintec corporation) using an applicator so that the thickness after drying became 25 μm, and then dried at 100 ℃ for 1 minute, and another separator (SP-PLR 381031, manufactured by Lintec corporation) was bonded to the surface of the adhesive layer opposite to the surface to which the separator was bonded, to obtain an adhesive layer having a separator on both surfaces.

The optical films obtained in examples and comparative examples were bonded to the pressure-sensitive adhesive layer formed by transferring the pressure-sensitive adhesive layer from the pressure-sensitive adhesive layer having a separator on both sides to glass, to obtain a laminate (sample for impact resistance evaluation) in which glass, the pressure-sensitive adhesive layer, and the optical film were laminated in this order.

(evaluation of impact resistance)

Impact resistance was evaluated. Specifically, a weight was dropped from a height of 10cm onto the optical film surface of the laminate (sample for impact resistance evaluation), thereby forming a depression. The weight had a mass of 4.6g, and the portion of the weight that collided with the optical film surface was spherical and made of stainless steel with a diameter of 0.75 mm. Next, the shape of the above-mentioned depressions on the surface of the optical film was observed using an optical interference film thickness meter (product of Ryoka Systems inc., Micromap (MM557N-M100 type)), and the depth of the point of maximum depression (the shortest distance from the surface of the film in the state of no depression before the test to the point of maximum depression) was measured with reference to the surface of the film in the state of no depression before the test. The measurement was repeated 3 times, and the average value of the dent depth was defined as the dent amount in the impact resistance test.

< measurement of viscosity >

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

Device name: brookfield viscometer (DV2THBCJ0)

Measuring temperature: 25 deg.C

A main shaft: CPA-52Z

Sample introduction amount: 0.5mL

Rotor speed: 3rpm

< Synthesis example 1: production of Polyamide-imide resin (1)

A reaction vessel equipped with a stirrer and a thermometer, which had been sufficiently dried, was purged with nitrogen, and the inside of the vessel was replaced with nitrogen. To the reaction vessel, 1907.2 parts by mass of dimethylacetamide (DMAc) and 111.94 parts by mass of 2,2 '-bis (trifluoromethyl) benzidine (TFMB) and 46.84 parts by mass of 4, 4' - (hexafluoroisopropylidene) diphthalic dianhydride (6FDA) were added and reacted.

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

The reaction solution was cooled, and 3794.5 parts by mass of methanol was added, followed by dropwise addition of 1419.4 parts by mass of ion-exchanged water, to precipitate a white solid. The precipitated white solid was captured by centrifugal filtration and washed with methanol to obtain a wet cake containing a polyamideimide resin. The obtained wet cake was dried at 78 ℃ under reduced pressure, thereby obtaining a powder of a polyamideimide resin. The weight average molecular weight of the obtained polyamideimide resin (1) was 466,000.

< Synthesis example 2: production of Polyamide-imide resin (2)

A reaction vessel equipped with a stirrer and a thermometer, which had been sufficiently dried, was purged with nitrogen, and the inside of the vessel was replaced with nitrogen. Into the reaction vessel were added 529.0 parts by mass of DMAc and 14.64 parts by mass (45.72mmol) of TFMB, and the TFMB was dissolved in DMAc while stirring at room temperature. Subsequently, 6.15 parts by mass (13.85mmol) of FDA and 1.36 parts by mass (4.62mmol) of 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride (BPDA) were added thereto, and the mixture was stirred at room temperature for 16 hours. Subsequently, 2.53 parts by mass (12.47mmol) of TPC was added thereto, and the mixture was stirred for 10 minutes, and then 2.58 parts by mass (12.47mmol) of TPC was further added thereto, and the mixture was stirred for 20 minutes. 0.56 part by mass (2.77mmol) of TPC was further added thereto, and the mixture was stirred at room temperature for 2 hours.

Subsequently, 2.58 parts by mass (27.70mmol) of 4-methylpyridine and 13.21 parts by mass (129.40mmol) of acetic anhydride were added to the flask, and the mixture was stirred at room temperature for 30 minutes, and then the temperature of the reaction vessel was raised to 70 ℃ and further stirred for 3 hours to obtain a reaction solution.

The reaction solution was cooled to 40 ℃ or lower, and then methanol 954 parts by mass was added thereto, followed by dropwise addition of ion-exchanged water 360 parts by mass to precipitate a white solid. The precipitated white solid was collected by filtration under reduced pressure and washed with methanol to obtain a wet cake containing a polyamideimide resin. The obtained wet cake was dried at room temperature under reduced pressure, thereby obtaining a powder of a polyamideimide resin. The weight average molecular weight of the obtained polyamideimide resin (2) was 260,000.

Production of a solution containing a sodium-containing component

A sodium ethoxide ethanol solution (manufactured by FUJIFILM Wako Pure Chemical Corporation) containing 20 mass% of sodium ethoxide (hereinafter, also referred to as "NaOEt", a sodium atom-containing compound) as a sodium-containing component was diluted with DMAc to prepare a solution containing sodium ethoxide at a concentration of 0.1 mass% (hereinafter, also referred to as "NaOEt solution").

Production of a solution containing a Potassium-containing component

A THF solution of t-BuOK (manufactured by FUJIFILM Wako Pure Chemical Corporation) containing 1 mol% of potassium t-butoxide (hereinafter, also referred to as "t-BuOK", a compound containing a potassium atom) as a potassium-containing component was diluted with DMAc to prepare a solution containing t-BuOK at a concentration of 0.2 mass% (hereinafter, also referred to as "t-BuOK solution").

< example 1 >

The polyamideimide resin (1) obtained in synthesis example 1 and DMAc were mixed in an amount such that the content ratio of the polyamideimide resin in the resin composition became 9.0 mass%. To these, the NaOEt solution and t-BuOK solution prepared in the above-described manner were added so as to obtain peak intensities of TOF-SIMS shown in Table 1, thereby preparing a polyamide-imide resin composition (varnish for film formation). The obtained resin composition was applied to a smooth surface of a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") using an applicator so that the thickness of the self-supporting film became 55 μm, dried at 50 ℃ for 30 minutes, and then dried at 140 ℃ for 15 minutes, and the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 40 minutes under the atmosphere to obtain a polyamideimide resin film (1) having a thickness of 50 μm. The amount of the residual solvent in the polyamideimide resin film (1) was 0.7%.

< example 2 >

The polyamideimide resin (1) obtained in synthesis example 1 and DMAc were mixed in an amount such that the content ratio of the polyamideimide resin in the resin composition became 9.0 mass%. To these, the NaOEt solution and t-BuOK solution prepared in the above-described manner were added so as to obtain peak intensities of TOF-SIMS shown in Table 1, thereby preparing a polyamide-imide resin composition (varnish for film formation). A polyamideimide resin film (2) having a thickness of 50 μm was obtained in the same manner as in example 1 except that the resin composition obtained in the above-mentioned manner was used.

< example 3 >

The polyamideimide resin (2) obtained in synthesis example 2 and DMAc were mixed in an amount such that the content ratio of the polyamideimide resin in the resin composition became 11.0 mass%. To these, the NaOEt solution and t-BuOK solution prepared in the above-described manner were added so as to obtain peak intensities of TOF-SIMS shown in Table 1, thereby preparing a polyamide-imide resin composition (varnish for film formation). A polyamideimide resin film (3) having a thickness of 50 μm was obtained in the same manner as in example 1 except that the resin composition obtained in the above-mentioned manner was used.

< comparative example 1 >

The polyamideimide resin (1) obtained in synthesis example 1 and DMAc were mixed in an amount such that the content ratio of the polyamideimide resin in the resin composition became 9.0 mass%. A polyamideimide resin film (4) having a thickness of 50 μm was obtained in the same manner as in example 1 except that the resin composition obtained in the above-mentioned manner was used. The amount of the residual solvent in the polyamideimide resin film (4) was 0.7%.

< comparative example 2 >

The polyamideimide resin (1) obtained in synthesis example 1 and DMAc were mixed in an amount such that the content ratio of the polyamideimide resin in the resin composition became 9.0 mass%. To this, the NaOEt solution prepared in the above manner was added so as to obtain the peak intensity of TOF-SIMS shown in table 1, thereby preparing a polyamide-imide resin composition (varnish for film formation). A polyamideimide resin film (5) having a thickness of 50 μm was obtained in the same manner as in example 1 except that the resin composition obtained in the above-mentioned manner was used.

< comparative example 3 >

The polyamideimide resin (1) obtained in synthesis example 1 and DMAc were mixed in an amount such that the content ratio of the polyamideimide resin in the resin composition became 9.0 mass%. To this, the t-BuOK solution prepared in the above-described manner was added so as to obtain the peak intensity of TOF-SIMS shown in Table 1, thereby preparing a polyamideimide resin composition (varnish for film formation). A polyamideimide resin film (6) having a thickness of 50 μm was obtained in the same manner as in example 1 except that the resin composition obtained in the above-mentioned manner was used.

< comparative example 4 >

The polyamideimide resin (2) obtained in synthesis example 2 and DMAc were mixed in an amount such that the content ratio of the polyamideimide resin in the resin composition became 11.0 mass%. A polyamideimide resin film (7) having a thickness of 50 μm was obtained in the same manner as in example 1 except that the resin composition obtained in the above-mentioned manner was used.

The results of measuring various physical properties of the polyamideimide resin films (1) to (7) obtained in examples 1 to 3 and comparative examples 1 to 4 are shown in tables 1 and 2.

[ Table 1]

[ Table 2]

< example 4 >

The polyamideimide resin (1) obtained in synthesis example 1 and DMAc were mixed in an amount such that the content ratio of the polyamideimide resin in the resin composition became 9.0 mass%. To this, sodium chloride (manufactured by FUJIFILM Wako Pure Chemical Corporation) was mixed in an amount having a content ratio of 0.05 mass%, and potassium chloride (manufactured by FUJIFILM Wako Pure Chemical Corporation) was mixed in an amount having a content ratio of 0.06 mass%, to prepare a polyamideimide resin composition.

< reference example >

The polyamideimide resin (1) obtained in synthesis example 1 and DMAc were mixed in an amount such that the content ratio of the polyamideimide resin in the resin composition became 9.0 mass%. To this, potassium chloride (manufactured by FUJIFILM Wako Pure Chemical Corporation) was mixed in an amount to give a content ratio of 0.12 mass%, to prepare a polyamideimide resin composition.

The viscosity of the polyamide-imide resin compositions obtained in examples 2 to 4, comparative examples 1 and 4, and reference example was measured by the above-described measurement method. The obtained results are shown in table 3.

[ Table 3]

As shown in tables 1 and 2, the ratio (I) of the ionic strength by TOF-SIMS of the varnish to which NaOEt and t-BuOK were added_Na/I_CH3) Is 0.2 or more and the ratio (I)_K/I_CH3) The optical films of examples 1 to 3 having a value of 0.2 or more were found to have a small amount of dishing in the impact resistance test and high impact resistance. On the other hand, in the case of the optical films of comparative examples 1 and 4 in which neither NaOEt nor t-BuOK was added to the varnish, and comparative examples 2 and 3 in which only either NaOEt or t-BuOK was added but the other was not added, the sag based on the impact resistance test was large, and sufficient impact resistance was not obtained. The reason why the impact resistance of the optical film containing a certain amount of NaOEt and t-BuOK is improved is notSpecifically, it is presumed that stacking between resins is further enhanced by allowing a sodium-containing component and a potassium-containing component different in atomic radius, ionic radius, or molecular size to coexist in the resins. Such an effect is considered to improve the impact resistance of the optical film obtained, but the present invention is not limited to this.

Claims

1. An optical film comprising at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins, the optical film having an Na ion intensity (I) obtained by a time-of-flight secondary ion mass spectrometry_Na) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_Na/I_CH3) 0.2 or more, and K has an ionic strength (I)_K) Relative to CH₃Ionic strength (I) of_CH3) Ratio of (I)_K/I_CH3) Is 0.2 or more.

2. The optical film according to claim 1, wherein the polyimide-based resin and the polyamide-based resin are aromatic resins.

3. The optical film according to claim 1 or 2, wherein the ratio of the structural unit derived from the aromatic monomer in the polyimide-based resin and the polyamide-based resin to the total structural unit is 60 mol% or more.

4. The optical film according to any one of claims 1 to 3, which has a thickness of 10 to 100 μm and a total light transmittance of 80% or more.

5. The optical film according to any one of claims 1 to 4, wherein the weight average molecular weight of the polyimide-based resin and the polyamide-based resin is 200,000 or more.

6. The optical film according to any one of claims 1 to 5, wherein the polyimide-based resin is a polyamideimide resin.

7. The optical film according to any one of claims 1 to 6, wherein the polyimide-based resin and the polyamide-based resin contain a structural unit derived from terephthalic acid.

8. The optical film according to any one of claims 1 to 7, wherein the optical film has a brightness L^*Is 90 or more.

9. An optical film according to any one of claims 1 to 8, which is a film for a front panel of a flexible display device.

10. A flexible display device comprising the optical film according to any one of claims 1 to 9.

11. The flexible display device of claim 10, further provided with a touch sensor.

12. The flexible display device according to claim 10 or 11, further comprising a polarizing plate.

13. The method for producing an optical film according to any one of claims 1 to 9, comprising at least the steps of:

and (c) drying the coating film to form an optical film.