JP7021887B2 - Optical film manufacturing method - Google Patents

Description

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

Conventionally, glass has been used as a material for a base material of various display members such as solar cells and displays and a transparent member such as a front plate. However, glass has drawbacks such as being fragile and heavy. In addition, it did not have sufficient materials to meet the recent demands for thinner and lighter displays and more flexible displays. Therefore, various films (optical films) are being studied as transparent members for flexible devices instead of glass.

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

Japanese Unexamined Patent Publication No. 2009-2154412

When used for displays with curved surfaces, foldable devices, rollable displays, etc., the optical film is stored in a deformed state such as a rolled state (rolled state) or a bent state. May be done. However, the conventional polyimide-based film has a problem that cracks are likely to occur at the end when it is stored in a high-temperature and high-humidity environment in a deformed state such as a rolled state or a bent state.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an optical film in which cracks are less likely to occur at the edges even when stored in a deformed state in a high temperature and high humidity environment. And. It is also an object of the present invention to provide a method for manufacturing an optical film, and a front plate for a flexible device and a flexible device using the optical film.

In order to achieve the above object, the present invention is an optical film containing a polyimide-based polymer containing a fluorine atom in the molecule, and the fluorine atom measured by X-ray photoelectron spectroscopy on the end face of the optical film. The atomic ratio (F / C) to carbon atoms is higher than the atomic ratio (F / C) of fluorine atoms to carbon atoms measured by X-ray photoelectron spectroscopy in a cross section cut 1 mm inside from the end face of the optical film. Provides a large, optical film.

According to the optical film, the optical film is rolled into a roll because the atomic ratio (F / C) on the end face is larger than the atomic ratio (F / C) on the cross section cut 1 mm inside from the end face. Even when the end face is deformed by bending or bending and stored in a high temperature and high humidity (for example, 85 ° C., 85% RH) environment, the generation of cracks from the end face can be suppressed. .. When stored in a high-temperature and high-humidity environment in a deformed state, it is thought that cracks will occur due to complex stress around the edges due to thermal expansion and hygroscopic expansion, in addition to deformation due to winding and bending. However, in a film in which the number of fluorine atoms on the end face is relatively larger than that inside the film, it is considered that the complicated stress can be suppressed.

The optical film has an atomic ratio ( _FE / _CE ) of a fluorine atom to a carbon atom measured by X-ray photoelectron spectroscopy on the end face of the optical film, and a cross section cut 1 mm inside from the end face of the optical film. The ratio ( _FE / _CE ) / ( _FC / _CC ) of the fluorine atom to the _carbon atom of the fluorine atom measured by X _- ray photoelectron spectroscopy is 1.1 to 10. There may be.

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

According to the optical film, the optical film is rolled into a roll because the atomic ratio (F / O) on the end face is larger than the atomic ratio (F / O) on the cross section cut 1 mm inside from the end face. Even when the end face is deformed by bending or bending and stored in a high temperature and high humidity (for example, 85 ° C., 85% RH) environment, the generation of cracks from the end face can be suppressed. .. When stored in a high-temperature and high-humidity environment in a deformed state, it is thought that cracks will occur due to complex stress around the edges due to thermal expansion and hygroscopic expansion, in addition to deformation due to winding and bending. However, in a film in which the number of fluorine atoms on the end face is relatively larger than that inside the film, it is considered that the complicated stress can be suppressed.

The optical film has an atomic ratio ( _FE / _OE ) of a fluorine atom to an oxygen atom measured by X-ray photoelectron spectroscopy on the end face of the optical film, and a cross section cut 1 mm inside from the end face of the optical film. The ratio ( _FE / _OE ) / ( _FC / _{OC )} of the fluorine atom to the oxygen atom measured by X _- ray photoelectron spectroscopy is 1.1 to 10. There may be.

The optical film may further contain silica particles.

The present invention is also a method for producing an optical film containing a polyimide-based polymer containing a fluorine atom in the molecule, which is measured by X-ray photoelectron spectroscopy on the end face of the optical film by oxidizing the end face. The atomic ratio (F / C) of a fluorine atom to a carbon atom is measured by X-ray photoelectron spectroscopy in a cross section cut 1 mm inside from the end face of the optical film (F / C). C) Provided is a method for manufacturing an optical film, which has a step of making it larger than C).

By the above manufacturing method, it is possible to manufacture an optical film in which cracks are less likely to occur at the edges even when the film is stored in a high temperature and high humidity environment in a deformed state.

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

By the above manufacturing method, it is possible to manufacture an optical film in which cracks are less likely to occur at the edges even when the film is stored in a high temperature and high humidity environment in a deformed state.

The present invention is also a method for producing an optical film containing a polyimide-based polymer containing a fluorine atom in the molecule, which is measured by X-ray photoelectron spectroscopy on the end face of the optical film by oxidizing the end face. The atomic ratio (F / O) of a fluorine atom to an oxygen atom is measured by X-ray photoelectron spectroscopy in a cross section cut 1 mm inside from the end face of the optical film (F / O). O) Provided is a method for manufacturing an optical film, which has a step of making it larger than O).

By the above manufacturing method, it is possible to manufacture an optical film in which cracks are less likely to occur at the edges even when the film is stored in a high temperature and high humidity environment in a deformed state.

The present invention is also a method for producing an optical film containing a polyimide-based polymer containing a fluorine atom in the molecule, wherein the end face of the optical film is formed by cutting the original fabric of the film by laser irradiation. The atomic ratio (F / O) of a fluorine atom to an oxygen atom measured by X-ray photoelectron spectroscopy on the end face of the optical film is measured by X-ray photoelectron spectroscopy in a cross section cut 1 mm inside from the end face of the optical film. Provided is a method for producing an optical film, which comprises a step of increasing the atomic ratio (F / O) of a fluorine atom to an oxygen atom measured by a method.

By the above manufacturing method, it is possible to manufacture an optical film in which cracks are less likely to occur at the edges even when the film is stored in a high temperature and high humidity environment in a deformed state.

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

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

According to the present invention, an optical film in which cracks are less likely to occur at the edges even when stored in a deformed state in a high temperature and high humidity environment, a method for manufacturing the same, and a front plate and a flexible device for a flexible device using the above optical film. Devices can be provided.
Can be obtained.

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 as the case may be.
In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted. Further, 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 a fluorine atom in the molecule, and satisfies one or both of the following conditions (1) and (2).
Condition (1): The atomic ratio (F / C) of the fluorine atom to the carbon atom measured by X-ray photoelectron spectroscopy on the end face of the optical film is X in the cross section cut 1 mm inside from the end face of the optical film. It is larger than the atomic ratio (F / C) of the fluorine atom to the carbon atom measured by photoelectron spectroscopy.
Condition (2): The atomic ratio (F / O) of the fluorine atom to the oxygen atom measured by X-ray photoelectron spectroscopy on the end face of the optical film is X in the cross section cut 1 mm inside from the end face of the optical film. It is larger than the atomic ratio (F / O) of the fluorine atom to the oxygen atom measured by photoelectron spectroscopy.

FIG. 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) planar shape, and has end faces E1 and E2 of two sides facing each other (two long sides parallel to each other forming a rectangle) in the lateral direction. , And the end faces E3 and E4 of two sides facing each other in the longitudinal direction (two short sides parallel to each other forming a rectangle). In the optical film 10, when the cut surfaces cut 1 mm inside from the end faces E1, E2, E3 and E4 are the cross sections C1, C2, C3 and C4, respectively, X in the end faces E1 to E4 and the cross sections C1 to C4, respectively. The atomic ratio ( _F / _C ) of fluorine atoms to carbon atoms measured by X-ray photoelectron spectroscopy (XPS) is greater than FC / CC in _FE / _CE on all or part of the end face, and / Or, the atomic ratio (F / O) of the fluorine atom to the oxygen atom measured by X-ray photoelectron spectroscopy (XPS) in each of the end faces E1 to E4 and the cross sections C1 to C4 is the whole or a part of the end face. In, _FE / _OE is larger than _FC / _OC . The atomic ratio of the fluorine atom measured by XPS to the _carbon atom on the end face is set to _FE / _CE , and the atomic ratio of the fluorine atom measured by XPS to the carbon atom on the cross section is set to FC / _CC . Let _FE / OE be the atomic ratio of the fluorine atom to the oxygen atom measured by XPS, and let _FC / _OC be the atomic ratio of the fluorine atom to the oxygen atom measured by _XPS in the cross section. As an optical film for a foldable device having a rectangular display, it is preferable that any one of the following conditions (I) and (II) is satisfied, and it is more preferable that both conditions are satisfied.
(I) In the end faces E1 and _E2 , _FE / _CE is larger than FC / CC and / or _FE / _OE is _larger than _FC / _OC .
(II) At the end faces E3 and E4, _FE / _CE is larger than FC / _CC and / or _FE / _OE is _larger than _FC / _OC .

The optical film 10 satisfies the above conditions, that is, _FE / _CE is larger than _FC / _CC and / or _FE / _OE is larger than _FC / _OC at the end face. Even if the optical film 10 is stored in a high-temperature and high-humidity environment in a deformed state, the generation of cracks from the end face can be suppressed. From the viewpoint of suppressing the generation of cracks from all the end faces, it is preferable that the optical film 10 satisfies both the above conditions (I) and (II).

Since cracks are likely to occur from the deformed end face, _{FE / CE is larger than FC / CC and / or FE / OE is F from the} viewpoint of efficiently preventing such cracks. An end surface larger than _C / _OC can be a surface that undergoes deformation such as bending 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 around the lateral direction of the optical film or rolled into a roll and stored, the end faces of two sides facing each other in the lateral 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 preferable that fluorine atoms are present at a higher concentration than inside the film, at least on the end faces of the two sides facing each other in the lateral direction of the optical film.

When an optical film is used as a member of a flexible display, the edge of the part where the film is deformed inside the display has _FE / _CE larger than _FC / _CC and / or _FE / _OE . Since the end face is larger than the _FC / _OC , deterioration due to cracks from the end portion is suppressed, and higher reliability can be obtained. For example, in the case of a curved display, the edges with curvature have _FE / CE greater than _FC / _CC and / or _FE / _{OE greater} than _FC / _OC . If the end face is large, the effect of the present invention tends to be easily obtained. Also, in the case of a foldable device, the end on the side bent by folding is _FE / _CE larger than FC / _CC and / or _FE / _OE is _greater than _FC / _OC . If the end face is large, the effect of the present invention tends to be easily obtained. In the case of a _rollable display, the edges that have a curvature by rolling are _FE / _CE greater than _FC / CC and / or _FE / _OE is _FC / O. If the end face is larger than _C , the effect of the present invention tends to be easily obtained.

XPS measurement of the end face and the cross section of the optical film can be performed under the following conditions. Further, the XPS measurement can be performed by irradiating X-rays from the direction perpendicular to the end face or the cross section of the optical film and detecting photoelectrons from the direction of 45 °.

<XPS measurement conditions>
Equipment: Quantera SXM (manufactured by ULVAC-PHI)
X-ray: AlKα ray (1486.6 eV)
X-ray spot diameter: 50 μm
Neutralization conditions: Neutralizing electron (1eV), slow Ar ion (10eV)

The atomic ratio of a fluorine atom to a carbon atom (F / C) and / or the atomic ratio of a fluorine atom to an oxygen atom (F / O) measured by XPS is determined from the area of C1s, O1s and F1s peaks in the XPS spectrum. Can be asked.

The optical film is cut when forming a cross section (cross sections C1 to C4 in the optical film 10) for XPS measurement by a method in which the atomic composition of the cut surface does not change and the cut surface is not distorted. Cutting can be done, for example, using a razor.

In the end face of the optical film 10 according to the embodiment of the present invention, the value of ( _FE / _CE ) / ( _FC / _CC ) needs to be larger than 1, but 1.1. It is preferably from 10 to 10, more preferably 1.5 to 8, and even more preferably 2 to 5. When this value is 1.1 or more, the concentration of fluorine atoms on the end face of the film is sufficiently higher than the concentration of fluorine atoms on the cross section of the film (inside the film), and the generation of cracks from the end face is more sufficiently suppressed. Tend to be able to.

In the optical film 10, the value of _FE / _CE at the end face where the value of ( _FE / _CE ) / ( _FC / _CC ) is larger than 1 is preferably 0.03 or more, preferably 0.04. The above is more preferable, and 0.05 or more is further preferable. When the _FE / _CE value of the end face is 0.03 or more, the generation of cracks from the end face tends to be more sufficiently suppressed.

End faces with a value of ( _FE / _CE ) / ( _FC / _CC ) greater than 1 can be formed by laser cutting. The end face formed by the above method tends to have a value of ( _FE / _CE ) / ( _FC / _CC ) larger than 1, and the generation of cracks from the end face can be more sufficiently suppressed. Tend.

In the end face of the optical film 10 according to another embodiment of the present invention, the value of ( _FE / _OE ) / ( _FC / _OC ) needs to be larger than 1, but 1 It is preferably 1 to 10, more preferably 1.3 to 8, and even more preferably 1.5 to 5. When this value is 1.1 or more, the concentration of fluorine atoms on the end face of the film is sufficiently higher than the concentration of fluorine atoms on the cross section of the film (inside the film), and the generation of cracks from the end face is more sufficiently suppressed. Tend to be able to.

In the optical film 10, the _FE / _OE value of the end face having a value of ( _FE / _OE ) / ( _FC / _OC ) larger than 1 is preferably 0.2 or more. When the _FE / _OE value of the end face is 0.2 or more, the generation of cracks from the end face tends to be more sufficiently suppressed.

End faces with a value of ( _FE / O _E ) / ( _FC / _OC ) greater than 1 can be formed by laser cutting. The end face formed by the above method tends to have a value of ( _FE / O _E ) / ( _FC / _OC ) larger than 1, and the generation of cracks from the end face can be more sufficiently suppressed. Tend.

The optical film 10 has a refractive index of usually 1.45 to 1.70, preferably 1.50 to 1.66.

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

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

The optical film 10 can have a Haze according to JIS K 7105: 1981 of 1 or less, and can also be 0.9 or less.

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 according to the size of the flexible device used. The planar shape of the optical film 10 is usually a rectangle or a square, but it may be another quadrangle such as a trapezoid or a parallelogram. Further, the planar shape of the optical film 10 may be a quadrangle with rounded corners.

(Film material)
(Transparent resin)
The optical film contains a transparent resin such as a polyimide polymer containing a fluorine atom in the molecule.

(Polyimide-based polymer)
As used herein, polyimide is a polymer containing a repeating structural unit containing an imide group, and polyamide is a polymer containing a repeating structural unit containing an amide group. The polyimide-based polymer refers to a polymer containing a polyimide and a repeating structural unit containing both an imide group and an amide group.

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

Further, the polyimide-based polymer according to the present embodiment includes a structure represented by any of the formulas (11) to (13) as long as the various physical properties of the obtained polyimide-based polymer film are not impaired. May be good.

G and G ¹ are tetravalent organic groups, preferably organic groups which may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine, and are represented by the formulas (20) to (29). Examples thereof include a tetravalent group having 6 or less carbon atoms and a chain hydrocarbon group having 4 or less carbon atoms. * In the formula represents a bond, Z is a single bond, -O-, -CH _{2-, -CH 2 -} CH _2- , -CH (CH ₃ )-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -Ar-, -SO _2- , -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar- Represents 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 with a fluorine atom, and specific examples thereof include a phenylene group. G and G ¹ are preferably groups represented by the formulas (20) to (27) because the yellowness of the obtained film can be easily suppressed.

G ² is a trivalent organic group, preferably an organic group that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and is a group represented by the formulas (20) to (29). Examples thereof include a group in which any one of the bonds of the above is replaced with a hydrogen atom, and a chain hydrocarbon group having a trivalent carbon number of 6 or less.

G ³ is a divalent organic group, preferably an organic group optionally substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and is a group represented by the formulas (20) to (29). Examples thereof include a group in which two non-adjacent bonds are replaced with hydrogen atoms and a chain hydrocarbon group having 6 or less carbon atoms.

A and A ¹ to A ³ are all divalent organic groups, preferably an organic group optionally substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and formulas (30) to (30). 38); Examples thereof include a group in which they are substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a chain hydrocarbon group having 6 or less carbon atoms. * In the formula represents a bond, and Z ¹ , Z ² and Z ³ are independent, 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 example is that Z ¹ and Z ³ are -O- and Z ² is -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- or -SO _2- . be. It is preferable that Z ¹ and Z ² and Z ² and Z ³ are in the meta-position or the para-position for each ring, respectively.

The optical film may contain polyamide. The polyamide according to this 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 ^G3 and A3 in the polyimide ^- based polymer. It may contain two or more kinds of structures represented by the formula (13) in which G ³ and / or A ³ are different.

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

Examples of the tetracarboxylic acid compound used for synthesizing a polyimide polymer include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic acid dianhydride and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic acid dianhydride. Can be mentioned. The tetracarboxylic acid compound may be used alone or in combination of two or more. The tetracarboxylic acid compound may be an analog of a tetracarboxylic acid compound such as an acid chloride compound in addition to dianhydride.

Specific examples of the aromatic tetracarboxylic acid dianhydride include 4,4'-oxydiphthalic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,. 3'-Benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetracarboxylic acid dianhydride, 3,3 ', 4,4'-Diphenylsulfone tetracarboxylic acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane Dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic 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, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 ''-(P-Phenylenidooxy) diphthalic acid dianhydride, 4,4'-(m-Phenylenidooxy) diphthalic acid dianhydride and 2,3,6,7-naphthalenetetracarboxylic acid dianhydride. , Preferably 4,4'-oxydiphthalic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride. , 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-diphenylsulfone tetra Carboxydic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis ( 3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic 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) Phenyl) ethane dianhydride , Bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4'-(p-phenylenedioxy) diphthalic acid dianhydride and 4 , 4'-(m-phenylenedioxy) diphthalic acid dianhydride. These can be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydride. The cyclic aliphatic tetracarboxylic acid dianhydride is a tetracarboxylic acid dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride. , 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, cycloalkhantetracarboxylic acid dianhydride such as 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, Bicyclo [2.2] .2] Oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, dicyclohexyl3,3'-4,4'-tetracarboxylic acid dianhydride and their positional isomers can be mentioned. .. These can 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 can be used alone or in combination of two or more.

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

The polyimide-based polymer according to the present embodiment includes tetracarboxylic acid, in addition to the tetracarboxylic acid anhydride used in the above-mentioned polyimide synthesis, as long as the various physical properties of the obtained polyimide-based polymer film are not impaired. It may be a reaction of a tricarboxylic acid and a dicarboxylic acid and their anhydrides and derivatives.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, acid chloride compounds related thereto, acid anhydrides, and the like, and two or more thereof may be used in combination.
Specific examples include anhydrate of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalentricarboxylic acid-2,3-anhydride; a single bond between phthalic anhydride and benzoic acid, -CH ₂ . -, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- or a compound linked with a phenylene group can be mentioned.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, acid chloride compounds related thereto, acid anhydrides, and the like, and two or more of them may be used in combination. Specific examples include a dicarboxylic acid compound of terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; a chain hydrocarbon having 8 or less carbon atoms, and 2 Examples thereof include compounds in which one benzoic acid is linked by a single bond, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- or a phenylene group.

The diamine used for synthesizing the polyimide polymer may be an aliphatic diamine, an aromatic diamine, or a mixture thereof. In addition, in this embodiment, "aromatic diamine" represents a diamine in which an amino group is directly bonded to an aromatic ring, and an aliphatic group or another substituent may be contained in a part of the structure thereof. 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 the aromatic ring is not limited thereto. Among these, a benzene ring is preferable. Further, the "aliphatic diamine" represents a diamine in which an amino group is directly bonded to an aliphatic group, and an aromatic ring or other substituent may be contained as a part of the structure thereof.

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

Examples of the aromatic diamine include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylene diamine, p-xylylene diamine, 1,5-diaminonaphthalene and 2,6-diaminonaphthalene. Aromatic diamine having one aromatic ring, such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'. -Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis ( 4-Aminophenoxy) benzene, 4,4'-diaminodiphenyl sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [ 4- (4-Aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine , 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 9,9-bis (4-aminophenyl) Fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9,9-bis (4-amino-3-fluorophenyl) Examples thereof include aromatic diamines having two or more aromatic rings, such as fluorene, which can be used alone or in combination of two or more.

Among the above diamines, from the viewpoint of high transparency and low coloring property, it is preferable to use one or more selected from the group consisting of aromatic diamines having a biphenyl structure. One selected from the group consisting of 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, 4,4'-bis (4-aminophenoxy) biphenyl and 4,4'-diaminodiphenyl ether. It is more preferable to use the above, and it is even more preferable to contain 2,2'-bis (trifluoromethyl) benzidine.

The polyimide-based polymer and polyamide, which are polymers containing at least one repeating structural unit represented by any of the formulas (10) to (13), include diamine and a tetracarboxylic acid compound (acid chloride compound, tetracarboxylic). Tetracarboxylic acid compound analogs such as acid dianhydride), tricarboxylic acid compounds (tricarboxylic acid compound analogs such as acid chloride compounds and tricarboxylic acid anhydrides) and dicarboxylic acid compounds (dicarboxylic acid compound analogs such as acid chloride compounds) It is a condensation type polymer which is a polycondensation product with at least one kind of compound contained in the group consisting of. In addition to these, a dicarboxylic acid compound (including an analog such as an acid chloride compound) may be used as a starting material. 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 the tetracarboxylic acid compound are as described above.

The standard polystyrene-equivalent weight average molecular weight of the polyimide-based polymer and the polyamide according to the present embodiment is usually 10,000 to 500,000, preferably 50,000 to 500,000, and more preferably 100,000. ~ 400,000. The larger the weight average molecular weight of the polyimide polymer and the polyamide, the more likely it is to develop high bending resistance when filmed. However, if the weight average molecular weight of the polyimide polymer is too large, the viscosity of the varnish becomes high. , Workability tends to decrease.

By containing a fluorine-containing substituent, the polyimide-based polymer and the polyamide tend to improve the elastic modulus when formed into a film, reduce the YI value, and improve the transparency.
When the elastic modulus of the film is high, the occurrence of scratches and wrinkles tends to be suppressed. Further, the polyimide-based polymer containing a fluorine atom in the molecule has the above _- mentioned ( _FE / _CE ) / (FC / _CC ) values and / or ( _FE / _OE ) / ( _FC ). By having an end face having a value of / _OC ) greater than 1, it is possible to sufficiently suppress the generation of cracks from the end portion even when stored in a high temperature and high humidity environment in a deformed state. Specific examples of the fluorine-containing substituent include a fluoro group and a trifluoromethyl group.

(Polyimide-based polymer containing a fluorine atom in the molecule)
The polyimide polymer containing a fluorine atom in the molecule is substituted with fluorine by at least ^one of G ^, G1 to G3, ^{A ,} A1 to A3 and Ar in the molecular structure of the polyimide polymer. Has a matrix. The content of fluorine atoms in the polyimide polymer containing fluorine atoms in the molecule is preferably 1% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 40, based on the mass of the polyimide polymer. It is less than mass%. When the content of the fluorine atom is 1% by mass or more, the elastic modulus at the time of film formation tends to be further improved, the YI value can be further reduced, and the transparency can be further improved. When the content of the fluorine atom is 40% by mass or less, the cost and the reactivity at the time of synthesis tend to be advantageous.

In the optical film according 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, based on the total mass of the optical film. % Or more. When the content of the polyimide-based polymer is 30% by 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.

Preferred examples of the inorganic material include silica particles and silicon compounds such as quaternary alkoxysilane such as tetraethyl orthosilicate (TEOS), and silica particles are preferable from the viewpoint of varnish stability.

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, so that the silica particles tend to be easy to handle.

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

The (average) primary particle size of the silica particles in the optical film can be determined 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 type particle size distribution meter.

In the optical film according to 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. More preferably, it is 0% by mass or more and 50% by mass or less. When the content of the inorganic material (silicon material) is within the above range, it tends to be easy to achieve both transparency and mechanical strength of the optical film.

The optical film according to the present embodiment may further contain an additive in addition to the components described above. Examples of the additive include pH adjusters, silica dispersants, ultraviolet absorbers, antioxidants, mold release agents, stabilizers, colorants 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% by mass or more and 20% by mass or less, and more preferably more than 0% by mass and 10% by mass or less, based on the total mass of the optical film.

(Manufacturing method of optical film)
Next, an example of the method for manufacturing the optical film of the present embodiment will be described.

The varnish used for producing the optical film according to the present embodiment is, for example, a reaction solution of a polyimide polymer, a solvent, and a reaction solution of a polyimide polymer obtained by selecting and reacting with the above tetracarboxylic acid compound, the above diamine, and the above other raw materials. It can be prepared by mixing and stirring the above-mentioned additives used as needed. Instead of the reaction solution of the polyimide-based polymer or the like, a purchased solution of the polyimide-based polymer or the like or a solution of the purchased solid polyimide-based polymer or the like may be used.

The solvent contained in the varnish may be any as long as it can dissolve the polyimide polymer. Examples of the solvent include amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide, lactone solvents such as γ-butyrolactone and γ-valerolactone, and sulfur-containing solvents such as dimethyl sulfoxide, dimethyl sulfoxide and sulfolane. A carbonate solvent such as a system solvent, ethylene carbonate, or propylene carbonate can be used. Among these solvents, an amide solvent or a lactone solvent is preferable. Further, these solvents may be used alone or in combination of two or more.

Next, the above varnish is applied onto a resin substrate, a stainless steel belt, or a glass substrate to form a coating film by a known roll-to-roll or batch method, and the coating film is dried. By peeling from the substrate, a film containing a polyimide-based polymer is obtained. After peeling, the film may be further dried.

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

Examples of the resin base material include PET, PEN, polyimide, polyamide-imide and the like. Of these, a resin having excellent heat resistance is preferable. In particular, the PET base material is preferable from the viewpoint of adhesion to the film and cost.

Subsequently, with respect to the end face of the film, the atomic ratio of the fluorine atom to the carbon atom ( _FE / _CE ) measured by XPS for the end face and / or the atomic ratio of the fluorine atom to the oxygen atom ( _FE / O). _E ) is the atomic ratio of the fluorine atom to the _carbon atom (FC / CC) and / or the atomic ratio of the fluorine atom to the oxygen atom (FC / _CC ) measured by XPS for the cross section cut 1 mm inside from the end face with a sword. Process so that it is larger than _FE / _OE ).

The present invention also includes a method of oxidizing the end face of an optical film containing 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 in which cracks are less likely to occur at the edges even when the film is stored in a deformed state in a high temperature and high humidity environment.

The laser that can be used for laser irradiation is not particularly limited, and any laser can be used. Specific examples of the lasers that can be used include gas lasers such as CO ₂ lasers and excimer lasers; solid-state lasers such as YAG lasers; and semiconductor lasers. A suitable laser that can be used for laser irradiation is a CO ₂ laser. Specifically, by cutting the raw fabric of the polyimide-based polymer film to the desired size with a CO ₂ laser, cracks are less likely to occur at the edges even if it is stored in a high-temperature and high-humidity environment in a deformed state. A film containing a polyimide-based polymer can be easily obtained. Oxidation of the end face may be performed by laser irradiation.

Laser irradiation makes the atomic ratio (FE / _CE ) of the end face of the film easier and sufficiently higher than the atomic ratio ( _FC / _CC ) inside the film, and / or the atomic ratio of the end face of the film ( _F ). From the viewpoint of making _E / O _E ) easier and sufficiently higher than the atomic ratio ( _FC / _OC ) inside the film, it is preferable to carry out under the following conditions. That is, the laser is preferably a CO ₂ laser, and more preferably a wavelength of 10 μm or less. If the output is a condition that can cut the film, the amount of fluorine at the end can be increased at the same time as cutting, which is preferable. 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, and more preferably 100 mm / sec or more. The end may be irradiated with the laser multiple times.

When the obtained optical film is used for, for example, a display having a curved surface, a foldable device, a rollable display, or the like, the obtained optical film is deformed in a rolled state (rolled state) or in a bent state. It may be stored in a closed state. At this time, the end face of the optical film is in a deformed state. In addition, the deformed optical film 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 such a deformed state, there is a problem that cracks are likely to occur at the edges of the conventional optical film, but according to the optical film of the present embodiment, there is a problem. Suppressing cracks at the ends by having _{FE / C E higher than FC} / _{C C} and / or _FE / _OE higher than FC / OC at the end face. Can be done.

(Use)
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-mentioned optical film which is superposed on the flexible functional layer and functions as a front plate. That is, the front plate of the flexible device is arranged on the visible side above the flexible functional layer. This front plate has a function of protecting the flexible functional layer.

Examples of flexible devices include image display devices (flexible displays, electronic paper, etc.), solar cells, and the like. For example, the display functional layer and the solar cell functional layer are flexible functional layers.

An example of a flexible display is shown in FIG. The flexible display 100 is referred to as a front plate 110 / polarizing plate protective film 120B / polarizing element 120A / polarizing plate protective film 120B / touch sensor film 130 / organic EL element layer 140 / TFT substrate 150 in order from the front surface side (visual recognition side). Has a configuration. The layer other than the front plate 110 in the flexible display 100 is the flexible functional layer 190. The polarizing plate protective film 120B / polarizing element 120A / polarizing plate protective film 120B constitutes the polarizing plate 120. A hard coat layer, an adhesive layer, an adhesive layer, a retardation layer, and the like may be included on the surface of each layer and between each layer. The above optical film 10 can be used as the front plate 110. Such a flexible display can be used as an image display unit of a tablet PC, a smartphone, a portable game machine, or the like.

According to the flexible device according to the present embodiment, the above-mentioned optical film 10 is used as the front plate 110. Since the optical film 10 suppresses the generation of cracks from the end face, it is possible to improve the reliability.

It should be noted that the surface of this optical film may be laminated with various functional layers such as an ultraviolet absorbing layer, a hard coat layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Example 1)
"Neoprim C6A20" (γ-butyrolactone solvent, 22% by mass) manufactured by Mitsubishi Gas Chemicals, a polyimide-based polymer, a solution in which silica particles having a solid content concentration of 30% by mass are dispersed in γ-butyrolactone, an alkoxysilane having an amino group. The dimethylacetamide solution and water were mixed and stirred for 30 minutes. Here, the mass ratio of silica to polyimide is 30:70, the amount of alkoxysilane having an amino group is 1.67 parts by mass with respect to the total of 100 parts by mass of silica and polyimide, and the total mass of water is 100 parts by mass of silica and polyimide. It was set to 10 parts by mass.

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

By performing CO ₂ laser irradiation under the following conditions, the film was cut and the edges were modified.
Equipment: ML-Z9510T manufactured by KEYENCE
Wavelength: 9.3 μm
Output: 80%
Processing speed: 150 mm / sec Processing size: 5 cm x 5 cm

(Comparative Example 1)
A polyimide polymer film raw fabric 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 film raw fabric with a shear blade.

<XPS measurement>
X-ray photoelectron spectroscopy (XPS) measurements were performed on the edges of the optical films obtained in Examples and Comparative Examples in steps 1 and 2 below. The XPS measurement conditions are as follows.
Equipment: Quantera SXM (manufactured by ULVAC-PHI)
X-ray: AlKα ray (1486.6 eV)
X-ray spot diameter: 50 μm
Neutralization conditions: Neutralizing electron (1eV), slow Ar ion (10eV)

(Step 1)
The optical film is attached to a metal block, fixed with the film end face facing up, the film end face is irradiated with X-rays from above (vertical direction), and photoelectrons are detected from the 45 ° direction to evaluate the film end face. did. F / C was calculated from the areas of C1s and F1s peaks in the obtained XPS spectrum. The F / C was calculated by measuring three points at equal intervals on the end faces of one side of the film, and the average value thereof was taken as the F / C of the end faces. Further, the F / O was obtained in the same manner.

(Step 2)
Next, a portion 1 mm inward from the end face of the film was cut by pushing it off with a razor (Single Edge, stainless steel, 3-Facet .009 "/. 23 mm manufactured by PERSONNA". The cut surface with the razor was stepped. XPS measurement was performed under the same conditions as in No. 1, and the F / C of the film cross section (inside the film) was used. In the same manner, the F / O was determined.

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

<Evaluation of crack resistance>
The 5 cm × 5 cm optical films obtained in Examples and Comparative Examples were wrapped around a 5 mm diameter SUS rod and stored at 85 ° C. in an 85% RH environment for 15 hours. The winding was performed in a direction in which the two sides of the first end and the second end were wound perpendicularly to the SUS rod. The first end and the second end of the optical film after storage were observed, and the generated cracks were confirmed with an optical microscope. The number of cracks having a length exceeding 100 μm per width of 5 cm at the first end and the second end was counted, and the average value of the cracks at both ends was obtained. The results are shown in Table 1.

From the results shown in Table 1, it can be seen that the end face of the film of Example 1 is oxidized due to an increase in oxygen atoms. Further, as is clear from the results shown in Table 1, according to the optical film of Example 1 in which the end face has a larger F / C value than the inside of the film, the film is in a deformed state under a high temperature and high humidity environment. It was confirmed that cracks are unlikely to occur at the edges even when stored. Further, according to the optical film of Example 1, in which the end face has a larger F / O value than the inside of the film, cracks are less likely to occur at the end even if the film is stored in a deformed state in a high temperature and high humidity environment. It was confirmed that.

10 ... Optical film, 100 ... Flexible display.

Claims (4)

A method for manufacturing an optical film for a front plate of a flexible device, which contains a polyimide polymer containing a fluorine atom in the molecule.
By CO ₂ laser irradiation , the atomic ratio (F / C) of the fluorine atom to the carbon atom measured by X-ray photoelectron spectroscopy on the end face of the optical film for the front plate of the flexible device is determined for the front plate of the flexible device. Optics for the front plate of a flexible device, comprising a step of increasing the atomic ratio (F / C) of a fluorine atom to a carbon atom measured by X-ray photoelectron spectroscopy in a cross section cut 1 mm inside from the end face of the optical film. How to make a film. A method for manufacturing an optical film for a front plate of a flexible device, which contains a polyimide polymer containing a fluorine atom in the molecule.
The end face of the optical film for the front plate of the flexible device is formed by cutting the original fabric of the film by laser irradiation with a CO ₂ laser having a wavelength of 10 μm or less , and X is formed on the end face of the optical film for the front plate of the flexible device. The atomic ratio (F / C) of a fluorine atom to a carbon atom measured by photoelectron spectroscopy is measured by X-ray photoelectron spectroscopy in a cross section cut 1 mm inside from the end face of the optical film for the front plate of the flexible device. A method for manufacturing an optical film for a front plate of a flexible device, which comprises a step of increasing the atomic ratio (F / C) of the fluorine atom to the carbon atom. A method for manufacturing an optical film for a front plate of a flexible device, which contains a polyimide polymer containing a fluorine atom in the molecule.
By CO ₂ laser irradiation , the atomic ratio (F / O) of the fluorine atom to the oxygen atom measured by X-ray photoelectron spectroscopy on the end face of the optical film for the front plate of the flexible device is determined for the front plate of the flexible device. Optics for the front plate of a flexible device, comprising a step of increasing the atomic ratio (F / O) of a fluorine atom to an oxygen atom measured by X-ray photoelectron spectroscopy in a cross section cut 1 mm inside from the end face of the optical film. How to make a film. A method for manufacturing an optical film for a front plate of a flexible device, which contains a polyimide polymer containing a fluorine atom in the molecule.
The end face of the optical film for the front plate of the flexible device is formed by cutting the original fabric of the film by laser irradiation with a CO ₂ laser having a wavelength of 10 μm or less , and X is formed on the end face of the optical film for the front plate of the flexible device. The atomic ratio (F / O) of a fluorine atom to an oxygen atom measured by line-of-sight electron spectroscopy is measured by X-ray photoelectron spectroscopy in a cross section cut 1 mm inside from the end face of the optical film for the front plate of the flexible device. A method for manufacturing an optical film for a front plate of a flexible device, which comprises a step of increasing the atomic ratio (F / O) of the fluorine atom to the oxygen atom.

Images