TW201817780A - Optical film and manufacturing method thereof - Google Patents

Abstract

The present invention is to provide an optical film in which cracks are unlikely to occur at the end even if it is stored in a high temperature and high humidity environment in a deformed state. The optical film of the present invention comprises a polyimide-based polymer containing a fluorine atom in its molecule, wherein, the atomic ratio of fluorine atoms to carbon atoms (F/C) measured by X-ray photoelectron spectroscopy at an end face of the optical film is larger than the atomic ratio of fluorine atoms to carbon atoms (F/C) measured by X-ray photoelectron spectroscopy at a cross section which is obtained by cutting an inner side of 1 mm from the end face of the optical film.

Description

 Optical film and method of manufacturing same  

The present invention relates to an optical film, a method of manufacturing the same, and a flexible device.

Conventionally, glass has been used as a material for a transparent member such as a base material of various display members such as a solar cell or a display, and a front panel. However, the glass has the disadvantage of being easily broken and heavy. In addition, there is no sufficient material for the requirements for thinness, weight reduction, and flexibility of displays in recent years. Therefore, various films (optical films) are being studied as transparent members of flexible devices that replace glass.

For example, Patent Document 1 discloses a polyimide film having excellent transparency, flexibility, and folding resistance formed by using a polyimide composition.

 [Previous Technical Literature]    [Patent Literature]  

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-215412

When the optical film is used for a display having a curved surface, a foldable device, a rollable display, or the like, it may be stored in a state of being curled (rolled in a roll shape) or bent. However, when the polyimide film of the prior art is stored in a high-temperature and high-humidity environment in a state of being wound into a roll and being bent, and the like, there is a problem that cracks are likely to occur at the ends.

The present invention has been made in view of the above problems in the prior art, and it is an object of the invention to provide an optical film which is less likely to be cracked at the end portion even when stored in a high-temperature and high-humidity environment in a deformed state. The present invention further provides a method for producing the optical film described above, and a front panel and a flexible device for a flexible device using the optical film.

In order to achieve the above object, the present invention provides an optical film comprising a polyimine-based polymer containing a fluorine atom in a molecule, wherein a fluorine atom pair measured by X-ray photoelectron spectroscopy on an end surface of the optical film The atomic ratio (F/C) of the carbon atom is larger than the atomic ratio (F/C) of the fluorine atom to the carbon atom measured by X-ray photoelectron spectroscopy on the cross section obtained by cutting the inner side of the optical film from the end surface of 1 mm.

According to the above optical film, by making the above atomic ratio (F/C) at the end face larger than the above atomic ratio (F/C) in the cross section obtained by cutting the inner side of the end face by 1 mm, even when the optical film is When the state in which the end surface is deformed by being wound into a roll shape, a bend, or the like is stored in a high-temperature, high-humidity (for example, 85 ° C, 85% RH) environment, the occurrence of cracks from the end faces can be suppressed. When it is stored in a high-temperature and high-humidity environment in a deformed state, in addition to deformation due to winding or bending, cracks may occur due to thermal expansion and moisture swelling to generate complex stress at the periphery of the end portion. However, the fluorine atom of the salt-bearing end face is relatively larger than the film system inside the film to suppress the complex stress.

The atomic ratio of fluorine atoms to carbon atoms (F _E /C _E ) measured by X-ray photoelectron spectroscopy on the end surface of the optical film, and the inner side of the optical film cut by 1 mm from the end surface of the optical film The ratio of the atomic ratio of fluorine atoms to carbon atoms (F _C /C _C ) measured by X-ray photoelectron spectroscopy (F _E /C _E ) / (F _C /C _C ) may be 1.1 to 10.

The present invention further provides an optical film comprising a polyfluorene-based polymer having fluorine atoms in a molecule, wherein an atomic ratio of a fluorine atom to an oxygen atom measured by X-ray photoelectron spectroscopy on an end surface of the optical film (F/O) is larger than the atomic ratio (F/O) of a fluorine atom to an oxygen atom measured by X-ray photoelectron spectroscopy on a cross section obtained by cutting the inside of 1 mm from the end surface of the optical film.

According to the above optical film, by making the above atomic ratio (F/O) at the end face larger than the above atomic ratio (F/O) in the cross section obtained by cutting the inner side of the end face by 1 mm, even when the optical film is When the state in which the end surface is deformed by being wound into a roll shape, a bend, or the like is stored in a high-temperature, high-humidity (for example, 85 ° C, 85% RH) environment, the occurrence of cracks from the end faces can be suppressed. When it is stored in a high-temperature and high-humidity environment in a deformed state, in addition to deformation due to winding or bending, cracks may occur due to thermal expansion and moisture swelling to generate complex stress at the periphery of the end portion. However, the fluorine atom of the salt-bearing end face is relatively larger than the film system inside the film to suppress the complex stress.

The atomic ratio of fluorine atom to oxygen atom (F _E /O _E ) measured by X-ray photoelectron spectroscopy on the end surface of the optical film, and the inner side of the optical film cut by 1 mm from the end surface of the optical film The ratio of the atomic ratio of fluorine atoms to oxygen atoms (F _C /O _C ) measured by X-ray photoelectron spectroscopy (F _E /O _E ) / (F _C /O _C ) may be 1.1 to 10.

The above optical film may further contain cerium oxide particles.

The present invention further provides a method for producing an optical film comprising a polyfluorene-based polymer having fluorine atoms in a molecule, the method comprising the steps of: oxidizing the end face to cause the optical The atomic ratio (F/C) of the fluorine atom to the carbon atom measured by the X-ray photoelectron spectroscopy of the end surface of the film is larger than the cross section obtained by cutting the inner side of the end surface of the optical film by 1 mm by X-ray photoelectron spectroscopy. The atomic ratio of fluorine atoms to carbon atoms (F/C) was determined.

According to the above production method, it is possible to produce an optical film which is less likely to be cracked at the end portion even when it is stored in a high-temperature and high-humidity environment in a deformed state.

The present invention further provides a method for producing an optical film comprising a polyimine-based polymer having fluorine atoms in a molecule, the method comprising the steps of: cutting a germ film by laser irradiation to form the above An end surface of the optical film, whereby an atomic ratio of fluorine atoms to carbon atoms (F/C) measured by X-ray photoelectron spectroscopy on the end surface of the optical film is larger than 1 mm inside the end surface of the optical film The resulting cross section is determined by X-ray photoelectron spectroscopy as the atomic ratio of fluorine atoms to carbon atoms (F/C).

According to the above production method, it is possible to produce an optical film which is less likely to be cracked at the end portion even when it is stored in a high-temperature and high-humidity environment in a deformed state.

The present invention further provides a method for producing an optical film comprising a polyfluorene-based polymer having fluorine atoms in a molecule, the method comprising the steps of: oxidizing the end face to cause the optical The atomic ratio (F/O) of the fluorine atom to the oxygen atom measured by the X-ray photoelectron spectroscopy of the end surface of the film is larger than the cross section obtained by cutting the inner side of the end surface of the optical film by 1 mm by X-ray photoelectron spectroscopy. The atomic ratio (F/O) of the fluorine atom to the oxygen atom was measured.

According to the above production method, it is possible to produce an optical film which is less likely to be cracked at the end portion even when it is stored in a high-temperature and high-humidity environment in a deformed state.

The present invention further provides a method for producing an optical film comprising a polyimine-based polymer having fluorine atoms in a molecule, the method comprising the steps of: cutting a germ film by laser irradiation to form the above An end surface of the optical film, whereby an atomic ratio (F/O) of a fluorine atom to an oxygen atom measured by X-ray photoelectron spectroscopy on the end surface of the optical film is larger than 1 mm inside the end surface of the optical film The obtained cross section is an atomic ratio (F/O) of a fluorine atom to an oxygen atom measured by X-ray photoelectron spectroscopy.

According to the above production method, it is possible to produce an optical film which is less likely to be cracked at the end portion even when it is stored in a high-temperature and high-humidity environment in a deformed state.

The present invention further provides a front panel for a flexible device having the above-described optical film of the present invention.

The present invention further provides a flexible device having a flexible functional layer and the above-described optical film of the present invention.

According to the present invention, it is possible to provide an optical film which is less likely to be cracked at the end portion even when stored in a high-temperature and high-humidity environment in a deformed state, a method for producing the same, and a front panel for a flexible device using the optical film. And flexible devices.

10‧‧‧Optical film

100‧‧‧Flexible display

110‧‧‧ front panel

120‧‧‧Polar plate

120A‧‧‧ polarizer

120B‧‧‧ polarizer protective film

130‧‧‧Touch sensing film

140‧‧‧Organic EL element layer

150‧‧‧TFT substrate

190‧‧‧Flexible functional layer

C1, C2, C3, C4‧‧‧ profiles

E1, E2, E3, E4‧‧‧ end faces

Fig. 1 is a perspective view showing an example of an optical film according to an embodiment of the present invention.

Fig. 2 is a perspective view showing an example of a flexible display according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and the description thereof will be omitted. Further, the dimensional ratio of the drawings is not limited to the ratio shown in the drawings.

The optical film of the present embodiment contains a polyimine-based polymer containing a fluorine atom in the molecule, and one or both of the following conditions (1) or (2) are satisfied.

Condition (1): an atomic ratio (F/C) of a fluorine atom to a carbon atom measured by X-ray photoelectron spectroscopy on an end surface of the optical film is larger than a section obtained by cutting inside from the end surface of the optical film by 1 mm. The atomic ratio of fluorine atoms to carbon atoms (F/C) as determined by X-ray photoelectron spectroscopy.

Condition (2): an atomic ratio (F/O) of a fluorine atom to an oxygen atom measured by X-ray photoelectron spectroscopy on an end surface of the optical film is larger than a section obtained by cutting inside from the end surface of the optical film by 1 mm. The atomic ratio (F/O) of a fluorine atom to an oxygen atom as determined by X-ray photoelectron spectroscopy.

Fig. 1 is a perspective view showing an example of an optical film of the embodiment. The optical film 10 shown in Fig. 1 has a rectangular (rectangular) planar shape and has end faces E1 and E2 which are opposite to each other in the short direction (two long sides which are parallel to each other) and The end faces E3 and E4 of the two sides facing each other in the long direction (the two short sides parallel to each other are formed). In the optical film 10, when the cut surfaces obtained by cutting the inside of 1 mm from the end faces E1, E2, E3, and E4 are the cross-sections C1, C2, C3, and C4, respectively, the end faces E1 to E4 and the above-described cross-sections C1 to C4. The atomic ratio of fluorine atom to carbon atom (F/C) determined by X-ray photoelectron spectroscopy (XPS) is F _E /C _E greater than F _C /C _C in all or part of the end face, and/or The atomic ratio of fluorine atom to oxygen atom (F/O) measured by X-ray photoelectron spectroscopy (XPS) in the above-mentioned end faces E1 to E4 and the above-mentioned cross sections C1 to C4 is F _E / in the whole or a part of the end face. O _{E is} greater than F _C /O _C . Further, the atomic ratio of the fluorine atom to the carbon atom measured by XPS on the end face is F _E /C _E , and the atomic ratio of the fluorine atom to the carbon atom measured by XPS in the cross section is F _C /C _C . The atomic ratio of the fluorine atom to the oxygen atom measured by XPS on the end face was F _E /O _E , and the atomic ratio of the fluorine atom to the oxygen atom measured by XPS in the cross section was F _C /O _C . An optical film suitable for a foldable device having a quadrangular display preferably satisfies any of the following conditions (I) and (II), and more preferably satisfies both.

(I) In the end faces E1, E2, F _E /C _{E is} greater than F _C /C _C , and/or F _E /O _{E is} greater than F _C /O _C .

(II) In the end faces E3, E4, F _E /C _{E is} greater than F _C /C _C , and/or F _E /O _{E is} greater than F _C /O _C .

By making the optical film 10 satisfy the above conditions, that is, F _E /C _{E is} larger than F _C /C _C in the end face, and/or F _E /O _{E is} larger than F _C /O _C even if the optical film 10 is deformed. The state is stored in a high-temperature and high-humidity environment, and the occurrence of cracks from the end face can also be suppressed. The optical film 10 preferably satisfies both of the conditions (I) and (II) above from the viewpoint of suppressing the occurrence of cracks from all the end faces.

The crack easily occurs from the end face where the deformation occurs, so from the viewpoint of effectively preventing such cracking, F _E /C _E can be larger than F _C /C _C , and/or F _E /O _{E is} larger than F _C / The end face of O _C is a surface which is deformed by bending or the like when the optical film is bent (for example, during storage or use). For example, when an optical film having a rectangular planar shape is bent or wound into a roll shape with the short direction of the optical film as an axis, the end faces that face each other in the short direction (for example, in FIG. 1 In the case of the optical film 10 shown, the end faces E1 and E2) are deformed by bending. In such a case, it is preferred that the fluorine atoms are present at a higher concentration than the inside of the film, at least on the end faces of the optical film opposite to each other.

When an optical film is used as a member of the flexible display, the end portion where the film is deformed inside the display becomes F _E /C _E greater than F _C /C _C , and/or F _E /O _{E is} greater than F _C / The end face of O _C suppresses deterioration due to cracking from the end portion, and higher reliability can be obtained. For example, when a display having a curved surface has an end portion having a curvature such that an F _E /C _{E is} larger than F _C /C _C and/or an F _E /O _{E is} larger than F _C /O _C , the present invention is easily obtained. The tendency of the effect. Further, in the case of the foldable device, when the end portion bent on the side bent by folding is F _E /C _E larger than F _C /C _C and/or F _E /O _{E is} larger than the end face of F _C /O _C , There is a tendency to easily obtain the effects of the present invention. In the case of a rollable display, it is easy to obtain an end portion having a curvature due to curling when F _E /C _{E is} larger than F _C /C _C , and/or F _E /O _{E is} larger than F _C /O _C end face. The tendency of the effect of the present invention.

The XPS measurement of the end surface and the cross section of the optical film can be carried out under the following conditions. Further, the XPS measurement can be carried out by irradiating X-rays from the vertical direction with respect to the end surface or the cross section of the optical film, and detecting photoelectrons from the 45° direction.

<XPS measurement conditions>

Device: Quantera SXM (manufactured by ULVAC PHI)

X-ray: AlKα line (1486.6eV)

X-ray spot diameter: 50μm

Neutralization conditions: Neutralization electron (1eV), low-speed Ar ion (10eV)

The atomic ratio of fluorine atom to carbon atom (F/C) and/or the atomic ratio of fluorine atom to oxygen atom (F/O) measured by XPS can be obtained from the peak areas of C1s, O1s and F1s of XPS spectrum. .

When the cross section of the XPS measurement (the cross sections C1 to C4 in the optical film 10) is formed, the cutting of the optical film is performed without changing the atomic composition of the cut surface and causing no strain on the cut surface. The cutting system can be performed, for example, using a razor.

In the end face of the optical film 10 according to an embodiment of the present invention, the value of (F _E /C _E )/(F _C /C _C ) must be greater than 1, but preferably 1.1 to 10, and 1.5 to 8 is better, and 2 to 5 is even better. When the value is 1.1 or more, the concentration of fluorine atoms in the end face of the film is sufficiently higher than the concentration of fluorine atoms in the film cross section (inside the film), and the tendency of cracking from the end face can be more sufficiently suppressed.

In the optical film 10, the value of F _E /C _{E in} the end face having a value of (F _E /C _E )/(F _C /C _C ) of more than 1 is preferably 0.03 or more, more preferably 0.04 or more, More than 0.05 is even better. When the value of F _E /C _E of the end face is 0.03 or more, the tendency of cracking from the end face can be more sufficiently suppressed.

An end face having a value of (F _E /C _E )/(F _C /C _C ) greater than 1 can be formed by laser cutting. The value of the end face system (F _E /C _E )/(F _C /C _C ) formed by the above method tends to be more than 1, and the tendency of cracking from the end face can be more sufficiently suppressed.

In the end face of the optical film 10 of another embodiment of the present invention, the value of (F _E /O _E )/(F _C /O _C ) must be greater than 1, but preferably 1.1 to 10, 1.3 to 8 is better, and 1.5 to 5 is even better. When the value is 1.1 or more, the concentration of fluorine atoms in the end face of the film is sufficiently higher than the concentration of fluorine atoms in the cross section of the film (inside the film), and the tendency of cracking from the end face can be more sufficiently suppressed.

In the optical film 10, the value of F _E /O _E of the end face having a value of (F _E /O _E )/(F _C /O _C ) of more than 1 is preferably 0.2 or more. When the value of F _E /O _E of the end face is 0.2 or more, the tendency of cracking from the end face can be more sufficiently suppressed.

An end face having a value of (F _E /O _E )/(F _C /O _C ) greater than 1 can be formed by laser cutting. The value of the end face system (F _E /O _E )/(F _C /O _C ) formed by the above method tends to be more than 1, and the tendency of cracking from the end face can be more sufficiently suppressed.

The refractive index of the above optical film 10 is usually from 1.45 to 1.70, preferably from 1.50 to 1.66.

The thickness of the optical film 10 can be appropriately adjusted depending on the kind of the flexible device or the like, but is usually 10 to 500 μm, preferably 15 to 200 μm, and more preferably 20 to 100 μm.

Optical film 10 is typically transparent. The total light transmittance of the optical film 10 in accordance with JIS K 7105:1981 is usually 85% or more, preferably 90% or more.

The haze value of the optical film 10 in accordance with JIS K 7105:1981 may be 1 or less, or may be 0.9 or less.

Further, the refractive index, total light transmittance, and haze value are values measured in the thickness direction of the optical film.

The size of the optical film 10 can be appropriately adjusted in accordance with the size of the flexible device to be used. The planar shape of the optical film 10 is usually rectangular or square, but may be other quadrangles such as a trapezoidal shape or a parallelogram. Further, the planar shape of the optical film 10 may be a chamfered quadrangle.

(material of film)

(transparent resin)

The optical film includes a transparent resin such as a polyimine-based polymer containing a fluorine atom in a molecule.

(polyimine-based polymer)

In the present specification, the polyimine is a polymer containing a repeating structural unit containing a quinone imine group, and the polyamine is a polymer containing a repeating structural unit containing a guanamine group. The polyimine-based polymer is a polymer of a polyimine and a repeating structural unit containing both a quinone imine group and a guanamine group.

The polyimine-based polymer of the present embodiment can be produced by using a tetracarboxylic acid compound and a diamine compound which will be described later as a main raw material, and has a repeating structural unit represented by the formula (10). Here, G is a tetravalent organic group, and A is a divalent organic group. Two or more structures represented by the formula (10) different in G and/or A may be contained.

In addition, the polyimine-based polymer of the present embodiment may contain any of the formulas (11) to (13) in the range of various physical properties of the obtained polyimide-based polymer film. Construction.

G and G ¹ are a tetravalent organic group, preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group, and may be exemplified by the formula (20), the formula (21), the formula (22), and the formula (23). a group represented by the formula (24), the formula (25), the formula (26), the formula (27), the formula (28) or the formula (29), and a tetravalent hydrocarbon group having 6 or less carbon atoms. In the formula, * represents a bond, and Z represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -Ar-, -SO ₂ -, -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar- C(CH ₃ ) ₂ -Ar- or -Ar-SO ₂ -Ar-. The Ar system represents an extended aryl group having 6 to 20 carbon atoms which may be substituted by a fluorine atom, and a specific example is a phenyl group. The resulting yellow of the film due to the easily suppressed, and so any of which G (20) to (27) shown in the group as G ¹ in formula is selected from the preferred.

G ² is a trivalent organic group, preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group, and may be exemplified by the formula (20), the formula (21), the formula (22), the formula (23), and the formula. (24) Any one of the bonding bonds of the group represented by the formula (25), the formula (26), the formula (27), the formula (28) or the formula (29) is substituted with a hydrogen atom group and a trivalent group A chain hydrocarbon group having 6 or less carbon atoms.

G ³ is a divalent organic group, preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group, and may be exemplified by the formula (20), the formula (21), the formula (22), the formula (23), and the formula. (24) Two of the bonding bonds of the group represented by the formula (25), the formula (26), the formula (27), the formula (28) or the formula (29) are substituted with a hydrogen atom. a base and a chain hydrocarbon group having 6 or less carbon atoms.

Any one of A, A ¹ to A ³ is a divalent organic group, preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group, and may be exemplified by the formula (30), the formula (31), and the formula. (32), a group represented by formula (33), formula (34), formula (35), formula (36), formula (37) or formula (38); these are methyl, fluoro, chloro or A trifluoromethyl-substituted group and a chain hydrocarbon group having 6 or less carbon atoms. Wherein * represents a bond, and Z ¹ , Z ² and Z ³ each independently represent a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ ) -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or -CO-. One of the examples Z ¹ and Z ³ is -O-, and Z ² is -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ - or -SO ₂ -. Z ¹ and Z ² , and Z ² and Z ^{3 are} preferably each a meta or para position relative to each ring.

The above optical film may contain polyamine. The polyamine of the present embodiment is a polymer mainly composed of a repeating structural unit represented by the formula (13). Preferred examples and specific examples are the same as G ³ and A ³ in the polyimine-based polymer. It is also possible to contain a structure represented by the formula (13) in which two or more kinds of G ³ and/or A ^{3 are} different. The polyimine-based polymer can be obtained, for example, by polycondensation of a diamine and a tetracarboxylic acid compound (tetracarboxylic dianhydride or the like), and can be obtained, for example, according to JP-A-2006-199945 or JP-A-2008- It is synthesized by the method described in 163107. Commercially available products of polyimine are, for example, Neopulim manufactured by Mitsubishi GAS Chemical Co., Ltd., KPI-MX300F manufactured by Kawamura Industry Co., Ltd., and the like.

The tetracarboxylic acid compound used for the synthesis of the polyimine-based polymer may, for example, be an aromatic tetracarboxylic acid compound such as an aromatic tetracarboxylic dianhydride or an aliphatic tetracarboxylic acid compound such as an aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compound may be used singly or in combination of two or more. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as a ruthenium chloride compound in addition to the dianhydride.

Specific examples of the aromatic tetracarboxylic dianhydride include, for example, 4,4'-oxydicarboxylic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride , 3,3',4,4'-diphenylphosphonium tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3- Dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene) dicarboxylic acid dianhydride, 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis (3,4- Dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, double (2,3 -dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diphthalic acid dianhydride, 4,4'-(meta-phenylenedioxy)diphthalic acid dianhydride The 2,3,6,7-naphthalenetetracarboxylic dianhydride is preferably, for example, 4,4'-oxydiphthalic acid dianhydride or 3,3',4,4'-benzophenone tetracarboxylic acid Anhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyl Carboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylphosphonium tetracarboxylic dianhydride, 2,2-bis (3 , 4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane Dihydride, 4,4'-(hexafluoroisopropylidene) dicarboxylic acid dianhydride, 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-double (2, 3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane Anhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diruthenate Anhydride and 4,4'-(meta-phenylenedioxy)dicarboxylic acid dianhydride. These may be used alone or in combination of two or more.

The aliphatic tetracarboxylic dianhydride may, for example, be a cyclic or acyclic aliphatic tetracarboxylic dianhydride. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 1,2. a cycloalkane tetracarboxylic dianhydride such as 3,4-cyclobutanetetracarboxylic dianhydride or 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 the positional isomers thereof. These may be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride, and the like. These may be used alone or in combination of two or more.

Among the above tetracarboxylic dianhydrides, from the viewpoint of high transparency and low coloring property, 1,2,4,5-cyclohexanetetracarboxylic dianhydride and bicyclo [2.2.2] octane are preferred. 7-ene-2,3,5,6-tetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene)dicarboxylic acid dianhydride.

In addition, the polyimine-based polymer of the present embodiment does not impair the various physical properties of the obtained polyamidene-based polymer film, except for the anhydride of the tetracarboxylic acid used in the synthesis of the above polyimine. In addition, the tetracarboxylic acid, the tricarboxylic acid, the dicarboxylic acid, and the anhydrides and derivatives may be further reacted.

The tricarboxylic acid compound may, for example, be an aromatic tricarboxylic acid, an aliphatic tricarboxylic acid, or a chlorophyll compound or an acid anhydride of the above-mentioned analogs, and may be used in combination of two or more kinds. Specific examples include, for example, an anhydride of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthalic anhydride and benzoic acid as a single bond, -CH ₂ -, - A compound in which C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or a phenyl group is bonded.

The dicarboxylic acid compound may, for example, be an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid or a ruthenium chloride compound or an acid anhydride of the above analogs, and may be used in combination of two or more kinds. Specific examples thereof include tannic acid; isophthalic acid; naphthalene dicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; and chain hydrocarbons having 8 or less carbon atoms; A carboxylic acid compound and a compound in which two benzoic acid are bonded by a single bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or a phenylene group.

The diamine used in the synthesis of the polyimine-based polymer may be an aliphatic diamine, an aromatic diamine or a mixture thereof. In the present embodiment, the "aromatic diamine" means a diamine in which an amine group is directly bonded to an aromatic ring, and an aliphatic group or another substituent may be contained in a part of the structure. The aromatic ring may be a single ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and an anthracene ring, but are not limited thereto. Among these, a benzene ring is preferred. Further, the "aliphatic diamine" means a diamine in which an amine group is directly bonded to an aliphatic group, and an aromatic ring or other substituent may be contained in a part of the structure.

The aliphatic diamine may, for example, be an acyclic aliphatic diamine such as hexamethylenediamine or a 1,3-bis(aminomethyl)cyclohexane or a 1,4-bis(aminomethyl)cyclohexane. A cycloaliphatic diamine such as an alkane, a norbornanediamine or a 4,4'-diaminodicyclohexylmethane may be used alone or in combination of two or more.

Examples of the aromatic diamine include p-phenylenediamine, meta-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, An aromatic diamine having an aromatic ring such as 2,6-diaminonaphthalene; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'- Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl hydrazine, 3,4 '-Diaminodiphenylphosphonium, 3,3'-diaminodiphenylphosphonium, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminobenzene) Oxy)benzene, 4,4'-diaminodiphenylphosphonium, bis[4-(4-aminophenoxy)phenyl]anthracene, bis[4-(3-aminophenoxy)benzene碸, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2, 2'-Dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-diamino Diphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 9,9-bis(4-aminophenyl)anthracene, 9,9- Bis(4-amino-3-methylphenyl)indole, 9,9-bis (4- An aromatic diamine having two or more aromatic rings, such as benzyl-3-chlorophenyl)anthracene or 9,9-bis(4-amino-3-fluorophenyl)anthracene, which may be used alone or in combination of two Use above.

Among the above-mentioned diamines, one or more selected from the group consisting of aromatic diamines having a biphenyl structure are preferred from the viewpoint of high transparency and low coloring. To use, selected from 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl and 4, More preferably, one part or more of the group consisting of 4'-diaminodiphenyl ether is more preferably 2,2'-bis(trifluoromethyl)benzidine.

A polyimide-based polymer and a polyamine which are polymers containing at least one of the repeating structural units represented by any one of the formulas (10) to (13), wherein the diamine and the tetracarboxylic acid compound are used. (a tetracarboxylic acid compound analog such as a ruthenium chloride compound or a tetracarboxylic dianhydride), a tricarboxylic acid compound (a tricarboxylic acid compound analog such as a ruthenium chloride compound or a tricarboxylic acid anhydride), and a dicarboxylic acid compound (a ruthenium chloride compound or the like) A condensed polymer of a polycondensation product of at least one compound contained in a group consisting of a carboxylic acid compound analog). In addition to these, a dicarboxylic acid compound (containing a ruthenium chloride compound or the like) may be further used in addition to these. The repeating structural unit represented by the formula (11) is usually derived from a diamine and a tetracarboxylic acid compound. The repeating structural unit represented by the formula (12) is usually derived from a diamine and a tricarboxylic acid compound. The repeating structural unit represented by the formula (13) is usually derived from a diamine and a dicarboxylic acid compound. Specific examples of the diamine and tetracarboxylic acid compounds are as described above.

The polystyrene-based polymer of the present embodiment and polyamine have a standard polystyrene-equivalent weight average molecular weight of usually 10,000 to 500,000, preferably 50,000 to 500,000, more preferably 100,000 to 400,000. The larger the weight average molecular weight of the polyimine-based polymer and the polyamine, the higher the tendency to exhibit high bending resistance when the film is formed, but if the weight average molecular weight of the polyimine-based polymer is too large, there is The viscosity of the varnish becomes high and the workability tends to decrease.

The polyimine-based polymer and the polyamine contain a fluorine-containing substituent, and the modulus of elasticity at the time of film formation is improved, and the YI value is lowered, and the transparency tends to be improved. If the film has a high modulus of elasticity, there is a tendency to suppress damage and wrinkles. Further, the polyimide-based polymer containing a fluorine atom in the molecule has a value of (F _E /C _E )/(F _C /C _C ) described above, and/or (F _E /O _E ) The end face having a value of /(F _C /O _C ) of more than 1 can sufficiently suppress the occurrence of cracks from the end portion even if it is stored in a high-temperature and high-humidity environment in a deformed state. Specific examples of the fluorine-containing substituent include a fluorine group and a trifluoromethyl group.

(Polyimide-based polymer containing fluorine atoms in the molecule)

The polyimine-based polymer containing a fluorine atom in the molecule is at least one of G, G ¹ to G ³ , A, A ¹ to A ³ and Ar in the molecular structure of the polyimide-based polymer. , having a fluorine-substituted group. The content of the fluorine atom in the polyimine-based polymer containing a fluorine atom in the molecule is preferably 1% by mass or more and 40% by mass or less based on the mass of the polyfluorene-based polymer, and more preferably 5 The mass% is 40% by mass or less. When the content of the fluorine atom is 1% by mass or more, the modulus of elasticity at the time of film formation is further increased, the YI value is further lowered, and the transparency is further improved. When the content of the fluorine atom is 40% by mass or less, there is a tendency that the reactivity at the time of synthesis becomes favorable.

In the optical film of the present embodiment, the content of the polyimine-based polymer is usually 30% by mass or more, preferably 40% by mass or more, and more preferably 50% by mass or more based on the total mass of the optical film. When the content of the polyimine-based polymer is 30% by mass or more, the bending resistance of the film tends to be favorable.

(inorganic particles)

The optical film of the present embodiment may further contain an inorganic material such as inorganic particles in addition to the above polyimine-based polymer.

The inorganic material is preferably a ruthenium compound such as a cerium oxide particle or a tetradecyl sulfonate such as TEOS, and it is preferable to use cerium oxide particles from the viewpoint of varnish stability. .

The average primary particle diameter of the cerium oxide particles is preferably from 10 to 100 nm, more preferably from 20 to 80 nm. When the average primary particle diameter of the cerium oxide particles is 100 nm or less, the transparency tends to be improved. When the average primary particle diameter of the cerium oxide particles is 10 nm or more, since the cohesive force of the cerium oxide particles is weak, handling tends to be easy.

The cerium oxide microparticles of the present embodiment may be a cerium oxide sol obtained by dispersing cerium oxide particles in an organic solvent or the like, and a cerium oxide fine particle powder produced by a vapor phase method may be used, but the operation is easy. Therefore, a cerium oxide sol is preferred.

The (average) primary particle diameter of the cerium oxide particles in the optical film can be obtained by observation by a transmission electron microscope (TEM). The particle size distribution of the cerium oxide particles before the formation of the optical film can be determined by a commercially available laser diffraction type particle size distribution meter.

In the optical film of the present embodiment, the content of the inorganic material is usually 0% by mass or more and 70% by mass or less, preferably 0% by mass or more and 60% by mass or less, based on the total mass of the optical film. 0% by mass or more and 50% by mass or less. When the content of the inorganic material (ruthenium material) is within the above range, it tends to have both transparency and mechanical strength of the optical film.

The optical film of the present embodiment may further contain an additive in addition to the components described above. The above additives may, for example, be pH adjusters, cerium oxide dispersants, ultraviolet absorbers, antioxidants, release agents, stabilizers, blueing agents, colorants, flame retardants, slip agents and leveling agents. .

The content of the components other than the resin component and the inorganic material is preferably 0% by mass or more and 20% by mass or less, more preferably 0% by mass or less and 10% by mass or less based on the total mass of the optical film.

(Method of manufacturing optical film)

Next, an example of a method for producing an optical film of the present embodiment will be described.

The varnish used in the production of the optical film of the present embodiment, for example, a reaction liquid or a solvent of a polyimine-based polymer obtained by selecting and reacting the tetracarboxylic acid compound, the diamine, and the other raw materials described above And the above-mentioned additives used as needed are mixed and stirred to prepare. A reaction solution such as a polyimine-based polymer or the like may be used, and a solution such as a commercially available polyimine-based polymer or a solution of a commercially available solid polyimide-based polymer may be used.

The solvent contained in the varnish may be any one that dissolves the polyimine-based polymer. As the solvent, for example, a guanamine solvent such as N,N-dimethylformamide or N,N-dimethylacetamide; a lactone solvent such as γ-butyrolactone or γ-valerolactone; A sulfur-containing solvent such as hydrazine, dimethyl hydrazine or cyclobutyl hydrazine; a carbonate-based solvent such as ethyl carbonate or propyl carbonate. Among these solvents, a guanamine solvent or a lactone solvent is preferred. Further, these solvents may be used singly or in combination of two or more.

Then, the varnish described above is applied onto a resin substrate, a stainless steel belt or a glass substrate by a known roll to reel or batch method to form a coating film, and the coating film is dried and peeled off from the substrate. A film containing a polyimine-based polymer is obtained. After the peeling, the film can be further dried.

The drying of the coating film is carried out by evaporating the solvent at a temperature of 50 to 350 °C. Drying can be carried out under atmospheric conditions, in an inert environment or under reduced pressure.

Examples of the resin substrate include, for example, PET, PEN, polyimide, polyamidimide, and the like. Among them, a resin excellent in heat resistance is preferred. In particular, a PET substrate is preferred from the viewpoint of adhesion to a film and cost.

Then, for the end face of the film, the atomic ratio of fluorine atoms to carbon atoms (F _E /C _E ) measured by XPS for the end face, and/or the atomic ratio of fluorine atoms to oxygen atoms (F _E /O) _E ) is larger than the atomic ratio of fluorine atom to carbon atom (F _C /C _C ) and/or the atomic ratio of fluorine atom to oxygen atom measured by XPS for the cross section cut from the inner side of the end face by 1 mm ( The method of F _E /O _E ) is applied.

Moreover, the present invention includes a method of oxidizing an end surface of an optical film containing a polyimine-based polymer, and a method of irradiating a laser. According to these methods, a film containing a polyimine-based polymer which is less likely to be cracked at the end portion even in a state of being deformed in a high-temperature and high-humidity environment can be obtained.

The laser system for laser irradiation can be made without any particular limitation, and any laser can be used. Specific examples of the laser that can be used include gas lasers such as CO ₂ lasers and excimer lasers; solid lasers such as YAG lasers; and semiconductor lasers. A suitable laser CO ₂ laser for laser illumination can be used. Specifically, the polyimine-based polymer embryo membrane is cut into a desired size by a CO ₂ laser, and can be easily obtained even in a deformed state in a high-temperature and high-humidity environment at the end. It is also difficult to produce a film containing a polyimine-based polymer which is cracked. Oxidation of the end faces can also be carried out by laser irradiation.

From the atomic ratio (F _E /C _E ) of the end face of the film to be easily and sufficiently higher than the atomic ratio (F _C /C _C ) inside the film, and/or to make the atomic ratio (F _E /O _E ) of the end face of the film easy From the viewpoint of sufficiently higher than the atomic ratio (F _C /O _C ) inside the film, laser irradiation is preferably carried out under the following conditions. That is, the laser system is preferably a CO ₂ laser, and more preferably a wavelength of 10 μm or less. The output system is preferably a condition in which the film can be cut, since the amount of fluorine in the end portion can be increased simultaneously with the cutting. The output is preferably 10 W or more, and more preferably 12 W or more. The processing speed by laser is preferably 50 mm/sec or more, and more preferably 100 mm/sec or more. It is also possible to illuminate the ends with a plurality of lasers.

When the obtained optical film is used, for example, in a display having a curved surface, a foldable device, a rollable display, or the like, it may be deformed in a state of being curled (rolled into a roll shape) or bent. storage. At this time, the end faces of the optical film are in a state of being deformed. Further, the optical film in a deformed state may be placed in a high-temperature and high-humidity environment during storage. When the optical film is stored in a high-temperature and high-humidity environment in a deformed state, the conventional optical film has a problem that cracks are likely to occur at the ends. However, according to the optical film of the present embodiment, the end face F _E / C _{E is} higher than F _C /C _C , and / or F _E /O _{E is} higher than F _C /O _C to suppress cracking at the ends.

(use)

Such an optical film can be suitably used as a front panel of a flexible device. The flexible device of the present embodiment includes the flexible functional layer and the optical film that is superposed on the flexible functional layer and functions as a front panel. That is, the front panel of the flexible device is disposed on the identification side above the flexible functional layer. The front panel has the function of protecting the flexible functional layer.

Examples of the flexible device include an image display device (flexible display, electronic paper, etc.), a solar battery, and the like. For example, the display function layer and the solar cell functional layer become a flexible functional layer.

An example of a flexible display is shown in Fig. 2. The flexible display 100 has a front panel 110 / a polarizing plate protective film 120B / a polarizing plate 120A / a polarizing plate protective film 120B / a touch sensing film 130 / an organic EL element layer from the surface side (viewing side). The structure of the 140/TFT substrate 150. The layer other than the front panel 110 in the flexible display 100 is the flexible function layer 190. The polarizing plate protective film 120B/polarizing plate 120A/polarizing plate protective film 120B constitutes the polarizing plate 120. A hard coat layer, an adhesive layer, an adhesive layer, a retardation layer, or the like may be contained on the surface of each layer and between the layers. The optical film 10 described above can be used for the front panel 110. Such a flexible display can be used as an image display unit such as a tablet computer, a smart phone, or a mobile game machine.

According to the flexible device of the embodiment, the optical film 10 described above is used as the front panel 110. Since the optical film 10 suppresses the occurrence of cracks from the end faces, reliability can be improved.

Further, a laminate of various functional layers such as an ultraviolet absorbing layer, a hard coat layer, an adhesive layer, a hue adjustment layer, and a refractive index adjusting layer may be added to the surface of the optical film.

 [Examples]  

Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

(Example 1)

"Neopulim C6A20" (γ-butyrolactone solvent, 22% by mass) manufactured by Mitsubishi GAS Chemical Co., Ltd., which is a polyimine-based polymer, and a oxidized solid concentration of 30% by mass in γ-butyrolactone A solution of cerium particles, a solution of an alkoxy decane having an amino group, and a solution of dimethyl acetamide, and water were mixed and stirred for 30 minutes. Here, the mass ratio of cerium oxide to polyimine is 30:70, and the amount of the alkoxy decane having an amine group is 1.67 parts by mass based on 100 parts by mass of the total of cerium oxide and polyimine. The water is 10 parts by mass based on 100 parts by mass of the total of cerium oxide and polyimide.

The obtained mixed solution was applied onto a glass substrate, heated at 50 ° C for 30 minutes, and heated at 140 ° C for 10 minutes to dry the solvent. Thereafter, the film was peeled off from the glass substrate, and a metal frame was attached and heated at 210 ° C for 1 hour to obtain a transparent polyimide film having a thickness of 50 μm. The refractive index of the embryonic membrane is 1.57.

The cutting of the film and the modification of the end portion were carried out by performing CO ₂ laser irradiation under the following conditions.

Device: ML-Z9510T manufactured by Keyence

Wavelength: 9.3μm

Output: 80%

Processing speed: 150mm / sec

Processing size: 5cm × 5cm

(Comparative Example 1)

A polyimine-based polymer embryo membrane was obtained in the same manner as in Example 1. An optical film was obtained by cutting out a rectangular (5 cm × 5 cm) region from the obtained embryonic membrane with a shearing knife.

<XPS measurement>

The end portions of the optical films obtained in the examples and the comparative examples were subjected to X-ray photoelectron spectroscopy (XPS) measurement in the following steps 1 and 2. The XPS measurement conditions are as follows.

Device: Quantera SXM (manufactured by ULVAC PHI)

X-ray: AlKα line (1486.6eV)

X-ray spot diameter: 50μm

Neutralization conditions: Neutralization electron (1eV), low-speed Ar ion (10eV)

(step 1)

The optical film was attached to the metal block, and the film end face was fixed upward, and the film end surface was irradiated with X-rays from above (vertical direction), and photoelectrons were detected from the 45° direction to evaluate the film end faces. F/C was calculated from the C1s and F1s peak areas of the obtained XPS spectrum. The F/C was calculated by measuring the three points of the equidistant distance on the end face of one side of the film, and the average value of these is the F/C of the end face. Further, in the same manner, F/O is obtained.

(Step 2)

Next, the razor (manufactured by PERSONNA, Single Edge, stainless steel, 3-Facet. 009)/.23 mm) was cut and cut from the end face of the film at a distance of 1 mm from the inside of the film. The XPS measurement was carried out under the same conditions as the F/C of the film cross section (inside the film). Further, F/O was obtained in the same manner.

The XPS measurement described above was first performed on the opposite ends (each referred to as a first end portion and a second end portion) of the optical film obtained in the examples and the comparative examples. The results are shown in Table 1. Further, the optical films obtained in the examples and the comparative examples were subjected to XPS measurement results equivalent to the first end portion and the second end portion on all four sides.

<Evaluation of crack resistance>

The 5 cm × 5 cm optical film obtained in the examples and the comparative examples was attached to a SUS rod having a diameter of 5 mm, and stored in an environment of 85 ° C and 85% RH for 15 hours. The winding attachment is performed in a direction in which the first end portion and the second end portion are wound perpendicularly to the SUS rod. The first end portion and the second end portion of the optical film after storage were observed, and the generated crack was confirmed by an optical microscope. The number of cracks exceeding the length of 100 μm per 5 cm width of the first end portion and the second end portion was calculated, and the average value of the number of cracks at both end portions was determined. The results are shown in Table 1.

From the results shown in Table 1, it was found that the film end face of Example 1 was increased in oxygen and oxidized. Further, from the results shown in Table 1, it was confirmed that the optical film of Example 1 having a larger F/C value than the inside of the film was stored in a high-temperature and high-humidity environment in a deformed state. It is difficult to produce cracks at the ends. Further, it was confirmed that the optical film of Example 1 having a large F/O value of the end surface in comparison with the inside of the film was difficult to be cracked at the end portion even when it was stored in a high-temperature and high-humidity environment in a deformed state.

Claims (11)

 An optical film comprising a polyfluorene-based polymer containing fluorine atoms in a molecule, wherein an atomic ratio of a fluorine atom to a carbon atom measured by X-ray photoelectron spectroscopy on an end surface of the optical film (F/C) The atomic ratio of fluorine atoms to carbon atoms (F/C) measured by X-ray photoelectron spectroscopy is larger than the cross section obtained by cutting the inner side of 1 mm from the end surface of the optical film.   The optical film according to claim 1, wherein an atomic ratio of fluorine atoms to carbon atoms (F _E /C _E ) measured by X-ray photoelectron spectroscopy on an end surface of the optical film, and The ratio of the atomic ratio of fluorine atom to carbon atom (F _C /C _C ) measured by X-ray photoelectron spectroscopy (F _E /C _E )/(F _C ) of the cross section of the optical film cut by 1 mm inside. /C _C ) is 1.1 to 10.  An optical film comprising a polyfluorene-based polymer having fluorine atoms in a molecule, wherein an atomic ratio of a fluorine atom to an oxygen atom measured by X-ray photoelectron spectroscopy on an end surface of the optical film (F/O) The ratio of the atomic ratio of fluorine atoms to oxygen atoms (F/O) measured by X-ray photoelectron spectroscopy is larger than the cross section obtained by cutting the inner side of 1 mm from the end surface of the optical film.   The optical film according to claim 3, wherein an atomic ratio of fluorine atoms to oxygen atoms (F _E /O _E ) measured by X-ray photoelectron spectroscopy on an end surface of the optical film, and The ratio of the atomic ratio of fluorine atoms to oxygen atoms (F _C /O _C ) measured by X-ray photoelectron spectroscopy (F _E /O _E )/(F _C ) of the cross section of the optical film cut by 1 mm inside. /O _C ) is 1.1 to 10.  The optical film according to any one of claims 1 to 4, further comprising cerium oxide particles.    A method for producing an optical film comprising a polyfluorene-based polymer having fluorine atoms in a molecule, the method comprising the steps of: oxidizing an end surface to cause the end surface of the optical film to be The atomic ratio (F/C) of the fluorine atom to the carbon atom measured by X-ray photoelectron spectroscopy is larger than the fluorine atom pair measured by X-ray photoelectron spectroscopy on the cross section obtained by cutting the inner side of the optical film from the end face by 1 mm. The atomic ratio of carbon atoms (F/C).    A method for producing an optical film comprising a polyfluorene-based polymer having fluorine atoms in a molecule, the method comprising the steps of: cutting an end surface of the optical film by laser irradiation to form an end surface of the optical film; Thereby, the atomic ratio (F/C) of the fluorine atom to the carbon atom measured by the X-ray photoelectron spectroscopy on the end surface of the optical film is larger than the cross section obtained by cutting the inside from the end surface of the optical film by 1 mm. The atomic ratio of fluorine atoms to carbon atoms (F/C) as determined by X-ray photoelectron spectroscopy.    A method for producing an optical film comprising a polyfluorene-based polymer having fluorine atoms in a molecule, the method comprising the steps of: oxidizing an end surface to cause the end surface of the optical film to be The atomic ratio (F/O) of the fluorine atom to the oxygen atom measured by X-ray photoelectron spectroscopy is larger than the fluorine atom pair measured by X-ray photoelectron spectroscopy on the profile obtained by cutting the inner side of the optical film from the end face by 1 mm. The atomic ratio of oxygen atoms (F/O).    A method for producing an optical film comprising a polyfluorene-based polymer having fluorine atoms in a molecule, the method comprising the steps of: cutting an end surface of the optical film by laser irradiation to form an end surface of the optical film; Thereby, the atomic ratio (F/O) of the fluorine atom to the oxygen atom measured by the X-ray photoelectron spectroscopy on the end surface of the optical film is larger than the cross section obtained by cutting the inside from the end surface of the optical film by 1 mm. The atomic ratio (F/O) of a fluorine atom to an oxygen atom as determined by X-ray photoelectron spectroscopy.    A front panel for a flexible device, comprising the optical film according to any one of claims 1 to 5.    A flexible device comprising a flexible functional layer, and the optical film according to any one of claims 1 to 5.