KR20180045891A - Optical film and manufacturing method thereof - Google Patents

Abstract

Provided is an optical film in which cracks are unlikely to be generated at the ends even when stored under a high temperature and high humidity environment in a deformed state.
An optical film containing a polyimide-based polymer containing a fluorine atom in a molecule, wherein the atomic ratio (F / C) of the fluorine atom to the carbon atom measured by X-ray photoelectron spectroscopy on the cross section of the optical film is (F / C) with respect to carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on a cut face cut inside 1 mm from the end face of the optical film.

Description

Optical film and manufacturing method thereof

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

BACKGROUND ART Conventionally, glass has been used as a material for a transparent member such as a base material and a front plate of various display members such as a solar cell and a display. However, the glass was fragile and heavy. In addition, in recent years, there has not been a sufficient material for the demands for thinning, lightening, and flexibility of displays. For this reason, various films (optical films) have been studied as transparent members of flexible devices replacing glass.

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

Japanese Patent Application Laid-Open No. 2009-215412

When the optical film is used in a display having a curved surface, a foldable device, or a display capable of being rounded, the optical film may be stored in a deformed state such as a rolled state (rolled state) or a bent state. However, the conventional polyimide-based film has a problem that cracks tend to occur at the end portions when the film is stored under a high temperature and high humidity environment in a deformed state such as a rolled state or a bent state.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide an optical film which is less susceptible to cracking at its ends even when stored under a high temperature and high humidity environment in a deformed state. It is another object of the present invention to provide a method for producing the optical film, and a front panel and a flexible device for the flexible device using the optical film.

In order to achieve the above object, the present invention provides an optical film comprising a polyimide-based polymer containing a fluorine atom in a molecule, wherein the optical film has a fluorine atom (s) measured by X-ray photoelectron spectroscopy (F / C) with respect to the carbon atom of the fluorine atom is not more than a circle for a carbon atom of a fluorine atom measured by X-ray photoelectron spectroscopy in a cut face cut inside 1 mm from the end face of the optical film (F / C). ≪ / RTI >

According to the above optical film, since the atomic ratio (F / C) on the cross section is larger than the atomic ratio (F / C) on the cut face cut inside 1 mm from the cross section, (For example, 85 占 폚, 85% RH) in a state in which the above-mentioned section is deformed by winding or bending it into a shape have. When stored under a high temperature and high humidity environment in a deformed state, in addition to deformation caused by winding or bending, a complicated stress is generated around the end portion due to thermal expansion and hygroscopic expansion, It is believed that a film having a fluorine atom relative to the inside of the film can suppress the complicated stress.

Wherein the optical film has an atomic ratio (F _E / C _E ) with respect to carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the optical film, (F _E / C _E ) / (F _C / C _C ) of the fluorine atom to the atomic ratio (F _C / C _C ) of the fluorine atom measured on the one cut face by the X- .

The present invention also provides an optical film containing a polyimide-based polymer containing a fluorine atom in a molecule, wherein the atomic ratio (F / R) of the fluorine atom to the oxygen atom measured by X-ray photoelectron spectroscopy on the cross- O) of the optical film is larger than an atomic ratio (F / O) of oxygen atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on a cut face obtained by cutting 1 mm inward from the end face of the optical film do.

According to the above optical film, since the atomic ratio (F / O) on the cross section is larger than the atomic ratio (F / O) on the cut face cut inside 1 mm from the cross section, (For example, 85 占 폚, 85% RH) in a state in which the above-mentioned section is deformed by winding or bending it into a shape have. When stored under a high temperature and high humidity environment in a deformed state, in addition to deformation caused by winding or bending, a complicated stress is generated around the end portion due to thermal expansion and hygroscopic expansion, It is believed that a film having a fluorine atom relative to the inside of the film can suppress the complicated stress.

Wherein the optical film has an atomic ratio (F _E / O _E ) of oxygen atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the optical film, and an atomic ratio (F _E / O _E ) / (F _C / O _C ) of the fluorine atom to the atomic ratio (F _C / O _C ) of the fluorine atom to the oxygen atom measured by X-ray photoelectron spectroscopy on one cut face is 1.1 to 10 .

The optical film may further contain silica particles.

The present invention also provides a method of producing an optical film containing a polyimide-based polymer containing a fluorine atom in a molecule, the method comprising the steps of: irradiating the optical film with a fluorine atom (F / C) relative to the carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cut surface obtained by cutting the inside of the optical film by 1 mm from the end face of the optical film, C) of the optical film is increased.

According to the above production method, it is possible to produce an optical film which is less susceptible to cracking at its ends even when stored under a high temperature and high humidity environment in a deformed state.

The present invention also provides a method for producing an optical film containing a polyimide-based polymer containing a fluorine atom in a molecule, wherein a cross section of the optical film is formed by cutting a film original by laser irradiation (F / C) with respect to carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the optical film in a cut face obtained by cutting the inside of the optical film by 1 mm from the end face (F / C) relative to carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy. The present invention also provides a method for producing an optical film.

According to the above production method, it is possible to produce an optical film which is less susceptible to cracking at its ends even when stored under a high temperature and high humidity environment in a deformed state.

The present invention also provides a method of producing an optical film containing a polyimide-based polymer containing a fluorine atom in a molecule, the method comprising the steps of: irradiating the optical film with a fluorine atom (F / O) with respect to an oxygen atom of a fluorine atom measured by X-ray photoelectron spectroscopy on a cut face obtained by cutting the inside of the optical film by 1 mm from the end face, O) of the optical film is increased.

According to the above production method, it is possible to produce an optical film which is less susceptible to cracking at its ends even when stored under a high temperature and high humidity environment in a deformed state.

The present invention also provides a method for producing an optical film containing a polyimide-based polymer containing a fluorine atom in a molecule, wherein a cross section of the optical film is formed by cutting a film original by laser irradiation, (F / O) with respect to oxygen atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the optical film was measured by X-ray photoelectron spectroscopy (F / O) of the fluorine atom to the oxygen atom measured by the fluorine atom.

According to the above production method, it is possible to produce an optical film which is less susceptible to cracking at its ends even when stored under a high temperature and high humidity environment in a deformed state.

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

The present invention also provides a flexible functional layer and a flexible device having the optical film of the present invention.

According to the present invention, it is possible to provide an optical film in which cracks are unlikely to be generated at the ends even when stored under a high temperature and high humidity environment in a deformed state, a method for producing the optical film, and a front plate and a flexible device for a flexible device using the optical film.

Can be obtained.

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

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and a duplicate description will be omitted. Note that the dimensional ratios in the drawings are not limited to the ratios shown in the drawings.

The optical film of the present embodiment contains a polyimide-based polymer containing fluorine atoms in the molecule and satisfies one or both of the following conditions (1) and (2).

Condition (1): The ratio of the atomic ratio (F / C) of the fluorine atom to the carbon atom measured by X-ray photoelectron spectroscopy on the cross section of the optical film is cut by 1 mm from the end face of the optical film (F / C) to the carbon atom of the fluorine atom measured by X-ray photoelectron spectroscopy.

Condition (2): The ratio of the atomic ratio (F / O) of the fluorine atom to the oxygen atom measured by X-ray photoelectron spectroscopy on the cross section of the optical film is cut by 1 mm from the end face of the optical film (F / O) of the fluorine atom to the oxygen atom measured by X-ray photoelectron spectroscopy.

1 is a perspective view showing an example of an optical film according to the present embodiment. The optical film 10 shown in Fig. 1 has a rectangular (rectangular) plane shape, and has two sides (two long sides parallel to each other forming a rectangle) E1 and E2), and two end faces E3 and E4 facing each other in the longitudinal direction (two short sides parallel to each other forming a rectangle). The optical film 10 is a film obtained by cutting the inside of 1 mm from the cross sections E1, E2, E3 and E4 into cut faces C1, C2, C3 and C4, the atomic ratio (F / C) to carbon atoms of the fluorine atom as measured by X ray photoelectron spectrometer (XPS) in each of the cut surfaces (C1~C4), in the whole or a part of cross-section, F _E / C _E is greater than F _C / C or _C, and / or, of the cross section (E1~E4) and fluorine atom, measured by X-ray photoelectron spectroscopy (XPS) in each of the cut surfaces (C1~C4) The atomic ratio (F / O) to the oxygen atom is greater than F _C / O _C in all or part of the cross section, F _E / O _E. In addition, the atomic ratio of the atomic ratio to the carbon atom of a fluorine atom, measured by XPS in a cross section to a carbon atom of a fluorine atom, measured by XPS in the surface as F _E / C _E, and cut F _C / C _C , the atomic ratio of the fluorine atom to the oxygen atom measured by XPS on the cross section is F _E / O _E , and the atomic ratio of the fluorine atom to the oxygen atom measured by XPS on the cut surface is F _C / O _C. The optical film for a foldable device having a quadrangular display preferably satisfies any one of the following conditions (I) and (II), and more preferably satisfies both of them.

F _E / C _E is greater than F _C / C _C and / or F _E / O _E is greater than F _C / O _{C in} cross section (I) cross section (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 in the} cross section (II) cross section (E3, E4)

It is preferable that the optical film 10 satisfies the above condition, that is, F _E / C _E is larger than F _C / C _C and / or F _E / O _E is larger than F _C / O _C It is possible to suppress the occurrence of cracks from the end face even when the optical film 10 is stored under a high temperature and high humidity environment while being deformed. It is preferable that the optical film 10 satisfies both of the conditions (I) and (II) above from the viewpoint of suppressing the generation of cracks from all the end faces.

Since cracks are liable to occur from the end surface which occurs is deformed, with a view to effectively prevent such a crack, F _E / C _E is F _C / C is greater than _C, or, and / or, F _E / O _E a F _C If the winding cross-section than the large / O _C, the resulting optical film may be a surface deformation such as bending (e. g., storage or when in use, and so on) may occur. For example, when an optical film having a rectangular planar shape is bent or stored in a roll shape in the direction of the shorter side of the optical film as an axis, a cross section of two sides opposite to each other in the shorter direction , The optical films 10 shown in Fig. 1 are deformed by bending in the cross-sections E1 and E2). In such a case, it is preferable that fluorine atoms are present at a higher concentration than in the inside of the film, at least on two cross-sections of mutually opposing sides in the short direction of the optical film.

When using the optical film as the flexible display member, of the part to be loaded with variations in the interior of the display ends, F _E / C _E is F _C / C is greater than _C, or, and / or, F _E / O _E is F By having a section larger than _C / O _C , deterioration due to cracks from the ends is suppressed, and higher reliability can be obtained. For example, in the case of a display having a curved surface, the end portion having a curvature, F _E / C _E is greater than F _C / C _C, or, and / or, F _E / O _E is greater than F _C / O _C The effect of the present invention tends to be easily obtained. In the case of devices that can be folded, a side of the end portion is bent by being folded, F _E / C _E is greater than F _C / C _C, or, and / or, F _E / O _E is more F _C / O _C If the cross section is large, the effect of the present invention tends to be easily obtained. In the case of a display which can be rounded, the rounded end by curvature may have a cross section with F _E / C _E greater than F _C / C _C and / or F _E / O _E greater than F _C / O _C The effect of the present invention tends to be easily obtained.

The XPS measurement of the cross section and the cut face of the optical film can be performed under the following conditions. XPS measurement can be performed by irradiating an X-ray from a perpendicular direction to a cross-section or a cut face of the optical film, and detecting photoelectrons from the 45 占 direction.

≪ XPS measurement condition >

Apparatus: Quantera SXM (manufactured by ULVAC PHI)

X-ray: AlK ray (1486.6 eV)

X-ray spot diameter: 50 탆

Neutralization condition: neutralization electron (1 eV), low-rate Ar ion (10 eV)

The atomic ratio (F / C) of the fluorine atom to the carbon atom and / or the atomic ratio (F / O) to the oxygen atom of the fluorine atom, as measured by XPS, satisfy the relationship of C1s, Can be obtained from the area.

The cutting of the optical film at the time of forming the cut face (cut face (C1 to C4) in the optical film (10)) to be subjected to the XPS measurement is performed by a method in which the atomic composition of the cut face is not changed, . The cutting can be performed, for example, using a razor.

In the cross section of the optical film 10 according to the embodiment of the present invention, the value of (F _E / C _E ) / (F _C / C _C ) needs to be larger than 1, More preferably from 1.5 to 8, and even more preferably from 2 to 5. When the value is 1.1 or more, the fluorine atom concentration in the film cross section is sufficiently higher than the concentration of fluorine atoms in the film-cut surface (inside of the film), and the occurrence of cracks from the cross section can be sufficiently suppressed .

In the optical film 10, the value of F _E / C _{E in} a cross section in which the value of (F _E / C _E ) / (F _C / C _C ) is larger than 1 is preferably 0.03 or more, More preferably 0.05 or more. When the value of F _E / C _E of the cross section is 0.03 or more, occurrence of cracks from the cross section tends to be sufficiently suppressed.

The cross section having a value of (F _E / C _E ) / (F _C / C _C ) greater than 1 can be formed by laser cutting. The cross section formed by the above method tends to have a value of (F _E / C _E ) / (F _C / C _C ) larger than 1, and can more sufficiently suppress the occurrence of cracks from the cross section.

In the cross section of the optical film 10 according to another embodiment of the present invention, the value of (F _E / O _E ) / (F _C / O _C ) More preferably from 1.3 to 8, and further preferably from 1.5 to 5. When the value is 1.1 or more, the fluorine atom concentration in the film cross section is sufficiently higher than the concentration of fluorine atoms in the film-cut surface (inside of the film), and the occurrence of cracks from the cross section can be sufficiently suppressed .

In the optical film 10, the value of F _E / O _{E in} a cross section where (F _E / O _E ) / (F _C / O _C ) is larger than 1 is preferably 0.2 or more. When the value of F _E / O _E of the cross section is 0.2 or more, the generation of cracks from the cross section tends to be more sufficiently suppressed.

(F _E / O _E ) / (F _C / O _C ) greater than 1 can be formed by laser cutting. The cross section formed by the above method tends to have a value of (F _E / O _E ) / (F _C / O _C ) greater than 1, and can more sufficiently suppress the occurrence of cracks from the cross section.

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

The thickness of the optical film 10 is appropriately adjusted according to the type of the flexible device and the like, but is usually 10 to 500 占 퐉, preferably 15 to 200 占 퐉, and more preferably 20 to 100 占 퐉.

The optical film 10 is usually transparent. The optical film 10 has a total light transmittance generally in accordance with JIS K 7105: 1981 of 85% or more, and preferably 90% or more.

The optical film 10 may have haze of not more than 1 and not more than 0.9 according to JIS K 7105: 1981.

The refractive index, total light transmittance and haze 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 used. The plane shape of the optical film 10 is generally rectangular or square, but other squares such as a trapezoid, a parallelogram, and the like may be used. In addition, the optical film 10 may have a rectangular shape with rounded corners.

(Material of film)

(Transparent resin)

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

(Polyimide-based polymer)

In the present specification, the polyimide is a polymer containing a repeating structural unit containing an imide group, and the polyamide is a polymer containing a repeating structural unit containing an amide group. The polyimide-based polymer refers to a polymer containing repeating structural units including both polyimide and imide groups and amide groups.

The polyimide-based polymer according to the present embodiment can be produced as a main raw material of a tetracarboxylic acid compound and a diamine compound described later, 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. G, and / or A may contain two or more kinds of structures represented by formula (10).

The polyimide-based polymer according to the present embodiment may include a structure represented by any one of the formulas (11) to (13) within a range that does not impair various physical properties of the resulting polyimide-based polymer film.

(21), (22), (23), and (23), G and G ¹ are each a tetravalent organic group and are preferably organic groups which may be substituted by a hydrocarbon group or a fluorine- Examples of the group represented by the formula (24), the formula (25), the formula (26), the formula (27), the formula (28) or the formula (29) and the quadrivalent cyclic hydrocarbon group having 6 or less carbon atoms are exemplified. 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-. Ar represents an arylene group having 6 to 20 carbon atoms which may be substituted by a fluorine atom, and specific examples thereof include a phenylene group. It is preferable that G and G ¹ are any groups selected from the groups represented by formulas (20) to (27) since the degree of yellowness of the resulting film is easily suppressed.

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 is an organic group represented by Formula (20), Formula (21), Formula (22) Any one of the groups bonded to each other represented by the formulas (24), (25), (26), (27), (28) or (29) Of the chain hydrocarbon group are exemplified.

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 is an organic group represented by Formula (20), Formula (21), Formula (22) Of the groups bonded to each other represented by formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) The following chain hydrocarbon groups are exemplified.

(30), (31), (32), (32), and (32), A and A ^{1 to} A ³ are all bivalent organic groups and preferably may be substituted by a hydrocarbon group or a fluorine- A group represented by formulas (33), (34), (35), (36), (37) or (38); A group substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a chain hydrocarbon group having 6 or less carbon atoms. 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 - or denotes a -CO- -, -SO _2. One example is where Z ¹ and Z ³ are -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 each preferably a meta position or a para position with respect to each ring.

The optical film may contain a polyamide. The polyamide according to the present embodiment is a polymer mainly comprising a repeating structural unit represented by formula (13). Preferred examples and specific examples are the same as G ³ and A ³ in the polyimide-based polymer. G ³ and / or A ³ may contain two or more kinds of structures represented by formula (13).

The polyimide-based polymer is obtained, for example, by polycondensation of a diamine with a tetracarboxylic acid compound (tetracarboxylic acid dianhydride or the like). For example, JP-A-2006-199945 or JP- Can be synthesized according to the method described in JP-A-2008-163107. Examples of commercially available products of polyimide include Neopurim, manufactured by Mitsubishi Gas Chemical Co., Ltd. and KPI-MX300F manufactured by Kawamura Industry Co., Ltd.

Examples of the tetracarboxylic acid compound used in the synthesis of the polyimide-based polymer include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydrides and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydrides. 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 derivative such as an acid chloride compound in addition to dianhydrides.

Specific examples of the aromatic tetracarboxylic acid dianhydride include 4,4'-oxydiphthalic 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 (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2- Bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 '- (hexafluoroisopropylidene) diphthalic dianhydride, 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 '- (p- Oxy) diphthalic dianhydride, 4,4 '- (m-phenylenedioxy) diphthalic dianhydride and 2,3,6,7-naphthalenetetracarboxylic dianhydride, preferably 4,4' 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, Biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 2'- Bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) Propane dianhydride, 4,4'- (hexafluoroisopropylidene) diphthalic dianhydride, 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1- Bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1- Dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 '- (p-phenylenedioxy) diphthalic dianhydride and 4,4' - ) Diphthalic acid dianhydride. These may be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic acid dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic acid dianhydride is tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclo Butane tetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride and the like, cycloalkanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5 , 6-tetracarboxylic dianhydride, dicyclohexyl 3,3'-4,4'-tetracarboxylic dianhydride, and their positional isomers. These may be used alone or in combination of two or more. Specific examples of the non-cyclic aliphatic tetracarboxylic acid dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride, etc., Two or more species may be used in combination.

Among the tetracarboxylic dianhydrides, from the viewpoint of high transparency and low coloring property, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo [2.2.2] oct- 5,6-tetracarboxylic dianhydride and 4,4 '- (hexafluoroisopropylidene) diphthalic dianhydride are preferable.

In addition to the anhydride of the tetracarboxylic acid used in the polyimide synthesis, the polyimide-based polymer according to the present embodiment may contain tetracarboxylic acid, Tricarboxylic acid, dicarboxylic acid and anhydrides and derivatives thereof may be further reacted.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids and their acid chloride compounds and acid anhydrides, and two or more of them may be used in combination. Specific examples include anhydrides of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; Compounds in which phthalic anhydride and benzoic acid are linked by a single bond, -CH ₂ -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ -, -SO ₂ - or phenylene group.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids and their flexible acid chloride compounds and acid anhydrides, and two or more of them may be used in combination. Specific examples include terephthalic acid; Isophthalic acid; Naphthalene dicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; A dicarboxylic acid compound of a cyclic hydrocarbon having 8 or less carbon atoms and two benzoic acids are bonded to a single bond, -CH ₂ -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ -, -SO ₂ - And the like.

The diamine used for synthesis of the polyimide-based polymer may be an aliphatic diamine, an aromatic diamine, or a mixture thereof. In the present embodiment, the term "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and a part of the structure may contain an aliphatic group or other substituent. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring and a fluorene ring, but are not limited thereto. Of these, benzene rings are preferable. The term " aliphatic diamine " means a diamine in which an amino group is bonded directly to an aliphatic group, and an aromatic ring or other substituent may be contained in a part of the structure.

Examples of the aliphatic diamines include alicyclic diamines such as hexamethylene diamine and the like; alicyclic diamines such as 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornanediamine, -Diaminodicyclohexylmethane, and the like, and they may be used alone or in combination of two or more.

Examples of the aromatic diamine include aromatic diamines such as p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylenediamine, p-xylenediamine, 1,5-diaminonaphthalene, Naphthalene, aromatic diamines having one aromatic ring, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4 ' - diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone , 4,4'-diaminodiphenylsulfone, bis [4- (4-aminophenoxy) benzene, Bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- Bis (4-aminophenoxy) phenyl] propane, 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, - Aminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 9,9-bis (4-aminophenyl) fluorene, 9,9- Phenyl) fluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene and 9,9-bis Or an aromatic diamine having two or more aromatic diamines. These diamines may be used alone or in combination of two or more.

Among the above diamines, from the viewpoints of high transparency and low coloring property, it is preferable to use at least one selected from the group consisting of aromatic diamines having a biphenyl structure. (4-aminophenoxy) biphenyl and 4,4'-diaminodiphenyl ether, which is composed of 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, , More preferably at least one selected from the group consisting of 2,2'-bis (trifluoromethyl) benzidine, and still more preferably 2,2'-bis (trifluoromethyl) benzidine.

Polyimide-based polymers and polyamides, which are polymers containing at least one repeating structural unit represented by any one of formulas (10) to (13), are obtained by reacting a diamine with a tetracarboxylic acid compound (acid chloride compound, tetracarboxylic acid 2 (A derivative of a tetracarboxylic acid compound such as an anhydride), a tricarboxylic acid compound (an acid chloride compound, a tricarboxylic acid compound such as a tricarboxylic acid anhydride) and a dicarboxylic acid compound ) And at least one kind of compound contained in the group consisting of the compound represented by the general formula (1). As the starting material, there may be used a dicarboxylic acid compound (including a derivative such as an acid chloride compound) in addition to these. The repeating structural unit represented by the formula (11) is usually derived from diamines and tetracarboxylic acid compounds. 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 compound are as described above.

The weight average molecular weight of the polyimide-based polymer and the polyamide according to the present embodiment in terms of standard polystyrene standards is generally 10,000 to 500,000, preferably 50,000 to 500,000, and more preferably 100,000 to 400,000. The larger the weight average molecular weight of the polyimide-based polymer and the polyamide tends to exhibit high flex resistance when formed into a film, but when the weight average molecular weight of the polyimide-based polymer is too large, the viscosity of the varnish increases and the workability decreases There is a tendency.

When the polyimide-based polymer and the polyamide contain a fluorine-substituted substituent, the YI value is reduced and the transparency tends to be improved as well as the modulus of elasticity when the film is made into a film. If the elastic modulus of the film is high, the occurrence of scratches and wrinkles tends to be suppressed. In addition, the value of a polyimide-based polymer containing the fluorine atom, the above-described _{(F E / C E) /} (F C / C C) in the molecule and / or (F _E / O _E) / (F _C / O _C ) is larger than 1, even when stored under a high temperature and high humidity environment in a deformed state, occurrence of cracks from the end portion can be sufficiently suppressed. Specific examples of fluorine-substituted groups include a fluoro group and a trifluoromethyl group.

(A polyimide-based polymer containing a fluorine atom in a molecule)

The polyimide-based polymer containing a fluorine atom in the molecule has a fluorine-substituted group in 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. The content of fluorine atoms in the polyimide-based polymer containing fluorine atoms in the molecule is preferably 1% by mass or more and 40% by mass or less based on the mass of the polyimide-based polymer, more preferably 5% % Or more and 40 mass% or less. When the fluorine atom content is 1% by mass or more, the elastic modulus at the time of film formation is further improved, the YI value is further reduced, and the transparency tends to be further improved. When the content of fluorine atoms is 40 mass% or less, the cost and the reactivity at the time of synthesis tend to be favorable.

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

(Inorganic particles)

The optical film according to this embodiment may further contain an inorganic material such as inorganic particles in addition to the above-mentioned polyimide-based polymer.

The inorganic material is preferably a silicon compound such as silica particles or quaternary alkoxysilane such as tetraethylorthosilicate (TEOS), and from the viewpoint of the varnish stability, silica particles are preferable.

The average primary particle size of the silica particles is preferably 10 to 100 nm, more preferably 20 to 80 nm. When the average primary particle diameter of the silica particles is 100 nm or less, the transparency tends to be improved. When the average primary particle diameter of the silica particles is 10 nm or more, the cohesive force of the silica particles is weakened, and therefore, the silica particles tend to be easy to handle.

The silica fine particles according to the present embodiment may be silica sol in which silica particles are dispersed in an organic solvent or the like, and silica fine particle powders produced by a vapor phase method may be used, but silica sol is preferable because handling is easy.

The (average) primary particle size of the silica particles in the optical film can be obtained by observation with a transmission electron microscope (TEM). The particle size distribution of the silica particles before forming the optical film can be obtained by a commercially available laser diffraction particle size distribution meter.

In the optical film related to the present embodiment, the content of the inorganic material is usually 0 mass% or more and 70 mass% or less, preferably 0 mass% or more and 60 mass% or less based on the total mass of the optical film, And preferably 0 mass% or more and 50 mass% or less. When the content of the inorganic material (silicon material) is within the above range, the transparency and the mechanical strength of the optical film tends to be compatible with each other.

The optical film according to the present embodiment may further contain an additive in addition to the above-described components. Examples of the additives include pH adjusters, silica dispersants, ultraviolet absorbers, antioxidants, releasing agents, stabilizers, coloring agents such as bluing agents, flame retardants, lubricants and leveling agents.

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

(Production method of optical film)

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

The varnish used in the production of the optical film according to the present embodiment can be obtained, for example, by reacting a reaction solution of a polyimide-based polymer obtained by selecting from the tetracarboxylic acid compound, the diamine and the above- Can be prepared by mixing and stirring the above-mentioned additive to be used in accordance with the present invention. Instead of the reaction liquid such as the polyimide-based polymer, a solution of the purchased polyimide-based polymer or the like or a solution of the purchased solid polyimide-based polymer may be used.

The solvent contained in the varnish may be any solvent capable of dissolving the polyimide-based polymer. Examples of the solvent include amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide, lactone solvents such as? -Butyrolactone and? -Valerolactone, dimethylsulfone, , Sulfur-containing solvents such as sulfolane, carbonate solvents such as ethylene carbonate and propylene carbonate can be used. Of these solvents, amide solvents or lactone solvents are preferred. These solvents may be used alone or in combination of two or more.

Subsequently, the above-mentioned varnish is applied onto a resin substrate, a stainless steel belt, or a glass substrate by a known roll-to-roll method or a batch method to form a coated film. The coated film is dried and peeled off from the substrate, To obtain a film containing the polymer. After the peeling, the film may be further dried.

The coating film is dried by evaporating the solvent at a temperature of 50 to 350 캜. The drying may be carried out under atmospheric pressure, in an inert atmosphere, or under a reduced pressure.

Examples of the resin substrate include PET, PEN, polyimide, and polyamideimide. Above all, a resin having excellent heat resistance is preferable. In particular, the PET substrate is preferable from the viewpoint of adhesion with the film and cost.

Next, the atomic ratio of the oxygen atoms of the atomic ratio (F _E / C _E) and / or fluorine atoms with respect to the end face of the film, a carbon atom such as fluorine atom, measured by XPS in respect of the cross-section (F _E / O _E ) of the fluorine atom to the cut surface cut by a razor within 1 mm from the cross section, the atomic ratio (F _C / C _C ) to the carbon atom of the fluorine atom measured by XPS and / (F _E / O _E ).

The present invention also includes a method of oxidizing a cross section of an optical film comprising a polyimide-based polymer, and a method of irradiating a laser. By these methods, it is possible to obtain a film containing a polyimide-based polymer which is less susceptible to cracking at its ends even when stored under a high-temperature and high-humidity environment in a deformed state.

The laser usable for laser irradiation is not particularly limited, and any laser can be used. Specific examples of usable lasers include gas lasers such as CO ₂ lasers and excimer lasers; Solid state lasers such as YAG lasers; Semiconductor lasers, and the like. A suitable laser for laser irradiation is a CO ₂ laser. Specifically, by cutting the original polyimide-based polymer film with a CO ₂ laser in a desired size, it is possible to easily produce a film containing a polyimide-based polymer in which cracks are unlikely to be generated at the ends even when stored under a high temperature and high humidity environment in a deformed state Can be obtained. The cross-section may be oxidized by laser irradiation.

Laser irradiation, and an atomic ratio of a section of the film (F _E / C _E) to facilitate than the atomic ratio of the inner film (F _C / C _C) also sufficiently high, and / or, and an atomic ratio of a section of the film (F _E / O _E ) of the film is preferably made higher than the atomic ratio (F _C / O _C ) inside the film easily and sufficiently. That is, the laser is preferably a CO ₂ laser, and more preferably 10 탆 or less. The output is preferable because the amount of fluorine at the end portion can be increased at the same time as the cutting is performed if the film is cutable. The output is preferably 10 W or more, and more preferably 12 W or more. The processing speed by the laser is preferably 50 mm / sec or more, more preferably 100 mm / sec or more. The end portion may be irradiated with a laser a plurality of times.

The resulting optical film is stored in a deformed state such as a rolled state (rolled state) or a bent state when it is used, for example, in a display having a curved surface, a foldable device, or a display capable of being rolled There is a case. At this time, the cross section of the optical film becomes deformed. The optical film in a deformed state may be placed under a high temperature and high humidity environment during storage. If the storage under high temperature and humidity environment, in a state in which deformation of the optical film as described above, in the conventional optical film, but a problem is liable to crack at the ends, according to the optical film of the present embodiment, in the cross-section F _E / C _{When E} is higher than F _C / C _C and / or F _E / O _E is higher than F _C / O _C , generation of cracks at the ends can be suppressed.

(Usage)

Such an optical film can be suitably used as a front plate of a flexible device. The flexible device according to the present embodiment has a flexible functional layer and the above optical film which overlaps the flexible functional layer and functions as a front plate. That is, the front panel of the flexible device is disposed on the visible side on the flexible functional layer. This front plate has a function of protecting the flexible functional layer.

Examples of the flexible device include an image display device (such as a flexible display and an electronic paper), a solar cell, and the like. For example, the display functional layer and the solar cell functional layer are flexible functional layers.

An example of the flexible display is shown in Fig. The flexible display 100 includes a front plate 110, a polarizer protective film 120B, a polarizer 120A, a polarizer protective film 120B, a touch sensor film 130, an organic EL The element layer 140 / the TFT substrate 150. [ The flexible functional layer 190 is a layer other than the front plate 110 in the flexible display 100. [ The polarizing plate protective film 120B / polarizer 120A / polarizing plate protective film 120B constitute the polarizing plate 120. A hard coating layer, an adhesive layer, an adhesive layer, a retardation layer, and the like may be included between the surface of each layer and each layer. As the front plate 110, the above optical film 10 can be used. Such a flexible display can be used as an image display unit of a tablet PC, a smart phone, a portable game machine, or the like.

According to the flexible device according to the present embodiment, the above optical film 10 is used as the front plate 110. Since the occurrence of cracks from the end face of the optical film 10 is suppressed, reliability can be improved.

It is also possible to form a laminate in which various functional layers such as an ultraviolet absorbing layer, a hard coat layer, an adhesive layer, a color adjusting layer, and a refractive index adjusting layer are added to the surface of the optical film.

[Example]

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

(Example 1)

A solution prepared by dispersing silica particles having a solid content concentration of 30 mass% in? -Butyrolactone, a neopurine C6A20 (? -Butyrolactone solvent, 22 mass%) manufactured by Mitsubishi Gas Chemical Company, Silane in dimethylacetamide, and water were mixed and stirred for 30 minutes. Here, the mass ratio of the silica and the polyimide was 30:70, the amount of the alkoxysilane having the amino group was 1.67 parts by mass based on 100 parts by mass of the total of the silica and the polyimide, and 10 parts by mass of water was added to 100 parts by mass of the total amount of the silica and the polyimide Mass part.

The obtained mixed solution was applied to a glass substrate and heated at 50 占 폚 for 30 minutes and at 140 占 폚 for 10 minutes to dry the solvent. Thereafter, the film was peeled off from the glass substrate, and a metal frame was mounted thereon and heated at 210 DEG C for 1 hour to obtain a transparent polyimide film original having a thickness of 50 mu m. The refractive index of the original disc was 1.57.

CO ₂ laser irradiation was performed under the following conditions to cut off the film and modify the end portions.

Apparatus: ML-Z9510T manufactured by KEYENCE CORPORATION

Wavelength: 9.3 탆

Output: 80%

Processing speed: 150 mm / sec

Processing Size: 5 cm × 5 cm

(Comparative Example 1)

An original disc of a polyimide-based polymer film was obtained in the same manner as in Example 1. An area of a rectangle (5 cm x 5 cm) was cut out from the obtained master disc by a shear blade to obtain an optical film.

<XPS measurement>

X-ray photoelectron spectroscopy (XPS) measurements were performed on the ends of the optical films obtained in the examples and comparative examples by the following steps 1 and 2. XPS measurement conditions are as follows.

Apparatus: Quantera SXM (manufactured by ULVAC PHI)

X-ray: AlK ray (1486.6 eV)

X-ray spot diameter: 50 탆

Neutralization condition: neutralization electron (1 eV), low-rate Ar ion (10 eV)

(Step 1)

The optical film was attached to the metal block, and the film was fixed in a state that the end face thereof faced upward. X-ray was irradiated from the upper side (vertical direction) to the end face of the film and photoelectrons were detected from the direction of 45 degrees. F / C was calculated from the area of C1s and F1s peaks of the obtained XPS spectrum. Three points spaced apart at regular intervals were measured on the cross section of one side of the film to calculate F / C, and the average value of the F / C was determined as the F / C of the cross section. In the same manner, F / O was obtained.

(Step 2)

Next, a portion spaced 1 mm inward from the end face of the film was cut and cut with a razor blade (PERSONNA, Single Edge, stainless steel, 3-Facet. 009 "/. 23 mm). , XPS measurement was carried out under the same conditions as in step 1, and F / C was determined on the cut surface (film inside) of the film.

The XPS measurement was performed on the opposite ends of the optical film obtained in Examples and Comparative Examples (referred to as the first end and the second end, respectively). The results are shown in Table 1. The optical films obtained in Examples and Comparative Examples were XPS measurement results equivalent to those of the first and second ends in all four sides.

&Lt; Evaluation of resistance against cracking >

The optical film of 5 cm x 5 cm obtained in Examples and Comparative Examples was wound on a SUS bar having a diameter of 5 mm and stored for 15 hours under the conditions of 85 ° C and 85% RH. The winding was performed in such a direction that the two ends of the first end and the second end were moved vertically to the SUS rod. The first end and the second end of the optical film after storage were observed, and the generated crack was confirmed by an optical microscope. The number of cracks having a length of more than 100 mu m per 5 cm width of the first end portion and the second end portion was counted to obtain an average value of the number of cracks at both ends. The results are shown in Table 1.

From the results shown in Table 1, it can be seen that the cross-section of the film of Example 1 is oxidized due to an increase in oxygen atoms. As is clear from the results shown in Table 1, according to the optical film of Example 1 having a larger F / C value at the end face than at the inside of the film, cracks were generated at the end portions even if they were stored under a high temperature and high humidity environment in a deformed state It was confirmed that it was difficult. Further, according to the optical film of Example 1 in which the value of F / O is larger in the section than in the inside of the film, it was confirmed that cracks are unlikely to occur at the ends even when stored under a high temperature and high humidity environment in a deformed state.

10: Optical film, 100: Flexible display

Claims (11)

An optical film containing a polyimide-based polymer containing a fluorine atom in a molecule,
Wherein an atomic ratio (F / C) of carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the optical film is 1 / (F / C) relative to the carbon atom of the fluorine atom measured by photoelectron spectroscopy. The method according to claim 1,
(F _E / C _E ) with respect to carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the above optical film and a ratio of an atomic ratio (F _E / C _E ) Wherein the ratio (F _E / C _E ) / (F _C / C _C ) of the atomic ratio (F _C / C _C ) to the carbon atom of the fluorine atom measured by X-ray photoelectron spectroscopy is 1.1 to 10. An optical film containing a polyimide-based polymer containing a fluorine atom in a molecule,
Wherein an atomic ratio (F / O) of oxygen atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the optical film is larger than an atomic ratio (F / (F / O) of oxygen atoms of fluorine atoms measured by photoelectron spectroscopy. The method of claim 3,
(F _E / O _E ) with respect to oxygen atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the optical film and a ratio of an atomic ratio (F _E / O _E ) Wherein the ratio (F _E / O _E ) / (F _C / O _C ) of the atomic ratio (F _C / O _C ) of the fluorine atom to the oxygen atom measured by X-ray photoelectron spectroscopy is 1.1 to 10. 5. The method according to any one of claims 1 to 4,
An optical film further comprising silica particles. A method for producing an optical film containing a polyimide-based polymer containing a fluorine atom in a molecule,
(F / C) with respect to carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the optical film by oxidizing a cross section of the optical film by 1 mm inside from the end face of the optical film (F / C) relative to carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cut face of the optical film. A method for producing an optical film containing a polyimide-based polymer containing a fluorine atom in a molecule,
The cross section of the optical film is formed by cutting the original film by laser irradiation so that the atomic ratio (F / C) of the fluorine atom to the carbon atom of the fluorine atom measured by the X-ray photoelectron spectroscopy on the cross section of the optical film (F / C) with respect to carbon atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on a cut face cut inside 1 mm from the end face of the optical film, &Lt; / RTI &gt; A method for producing an optical film containing a polyimide-based polymer containing a fluorine atom in a molecule,
(F / O) of oxygen atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cross section of the optical film by oxidizing the cross section by 1 mm inside the cross section of the optical film (F / O) with respect to oxygen atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on the cut face of the optical film. A method for producing an optical film containing a polyimide-based polymer containing a fluorine atom in a molecule,
The cross section of the optical film is formed by cutting the original film by laser irradiation so that the atomic ratio (F / O) of the fluorine atom to the oxygen atom measured by the X-ray photoelectron spectroscopy on the cross section of the optical film (F / O) with respect to oxygen atoms of fluorine atoms measured by X-ray photoelectron spectroscopy on a cut surface cut by 1 mm inward from the end face of the optical film, &Lt; / RTI &gt; A front panel for a flexible device comprising the optical film according to any one of claims 1 to 5. A flexible device having the flexible functional layer and the optical film according to any one of claims 1 to 5.

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