JP7112838B2 - OPTICAL FILM, LAMINATED FILM USING THE SAME, AND OPTICAL FILM MANUFACTURING METHOD - Google Patents

Description

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

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

For example, Patent Document 1 discloses a polyimide film excellent in transparency, flexibility, folding resistance, etc., which is formed using a polyimide resin composition.

JP 2009-215412 A

However, conventional polyimide films have the problem that defects such as crease marks and scratches are likely to occur during handling. Therefore, during the process of picking up and moving the film independently, such as the process of stacking the cut films so that they overlap in the same direction, and the process of removing one film from the stacked film one by one and using it for the next processing Defects tend to occur and yields tend to decrease.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an optical film and a laminated film that are less prone to defects such as creases and scratches during handling. Another object of the present invention is to provide a front panel for a flexible device and a flexible device using the optical film. A further object of the present invention is to provide a method for producing the above optical film.

In order to achieve the above object, the present invention provides an optical film containing a polyimide polymer, wherein an end surface of the optical film is inclined at an angle of 5° or more and 75° or less with respect to the surface of the optical film. Provided is an optical film having a slanted surface.

As a result of extensive studies, the inventors of the present invention have found that when the conventional polyimide film is dragged during handling, the edges of the film are caught and irregularly bent or broken, resulting in folding on the film surface. It was found that defects such as marks and scratches are likely to occur. These defects occur not only at the edges of the film, but also over the entire film surface, including near the center of the film. In contrast to such a conventional polyimide film, according to the optical film of the present invention, since the end face is a slanted surface slanted at the above-mentioned predetermined angle, the end portion is caught during handling of the optical film. It is possible to suppress regular bending and folding, and to suppress the occurrence of defects such as creases and scratches on the film surface.

［式（Ａ）中、ＬはＲａの算出範囲の長さを表し、Ｍ（ｘ）は測定位置ｘにおけるＤＭＴ弾性率の測定値を表す。］ The optical film has a variation in DMT elastic modulus (Ra) defined by the following formula (A), which is measured in a region 10 to 20 μm inside from the end face of the cross section obtained by cutting the end face of the optical film perpendicularly. may be 500 MPa or less.

[In formula (A), L represents the length of the Ra calculation range, and M(x) represents the measured value of the DMT elastic modulus at the measurement position x. ]

In the optical film, the inclined surface may be a laser-cut surface. In other words, in the optical film, the inclined surface may be a cut surface by laser irradiation.

［式（Ａ）中、ＬはＲａの算出範囲の長さを表し、Ｍ（ｘ）は測定位置ｘにおけるＤＭＴ弾性率の測定値を表す。］ The present invention also provides an optical film containing a polyimide-based polymer, wherein the following formula (A) is measured in a region 10 to 20 μm inside from the end face of the cross section obtained by cutting the end face of the optical film perpendicularly. Provided is an optical film having a DMT elastic modulus variation (Ra) value of 500 MPa or less.

[In formula (A), L represents the length of the Ra calculation range, and M(x) represents the measured value of the DMT elastic modulus at the measurement position x. ]

According to the optical film of the present invention, the value of the dispersion (Ra) of the DMT elastic modulus measured by the above method on the end face is within the above range, so that residual strain is suppressed in the vicinity of the end. As a result, it is possible to suppress irregular bending or folding due to catching of the ends of the optical film during handling, and it is possible to suppress the occurrence of defects such as crease marks and scratches on the film surface.

The optical film may further contain silica particles.

In the optical film, the polyimide polymer may contain fluorine atoms in an amount of 5% by mass or more based on the total mass of the polyimide polymer.

The optical film may have a thickness of 20 μm or more and 100 μm or less.

The present invention also includes the optical film of the present invention and a functional layer laminated on at least one surface of the optical film, wherein the end surface of the optical film and the end surface of the functional layer are connected. provides laminated films.

According to the laminated film, the end surface of the optical film constituting the laminated film is an inclined surface inclined at the predetermined angle, or the DMT elastic modulus measured by the above method for the end surface of the optical film is When the value of the variation (Ra) is within the above range, it is possible to suppress irregular bending or folding due to the edges being caught during handling of the laminated film, resulting in defects such as creases and scratches on the film surface. can be suppressed.

In the laminated film, the end surface of the functional layer is an inclined surface inclined at an angle of 5° or more and 75° or less with respect to the surface of the functional layer, and the inclined surface of the optical film and the inclined surface of the functional layer. The surfaces may be continuously connected. In this case, it is possible to further prevent the laminated film from being caught at the edges and irregularly bent or broken, and to further prevent defects such as creases and scratches on the film surface.

In the laminated film, the functional layer may be a hard coat layer.

The present invention also provides a method for producing an optical film containing a polyimide-based polymer, which comprises a step of cutting the edges by laser irradiation.

In the method for producing an optical film, the end surface of the optical film formed by the cutting process may be an inclined surface inclined at an angle of 5° or more and 75° or less with respect to the surface of the optical film.

［式（Ａ）中、ＬはＲａの算出範囲の長さを表し、Ｍ（ｘ）は測定位置ｘにおけるＤＭＴ弾性率の測定値を表す。］ In the method for producing an optical film, the cross section of the optical film formed by the cutting process is defined by the following formula (A) measured in a region 10 to 20 μm inward from the end face of the cross section obtained by cutting the end face perpendicularly. The DMT elastic modulus variation (Ra) value may be 500 MPa or less.

[In formula (A), L represents the length of the Ra calculation range, and M(x) represents the measured value of the DMT elastic modulus at the measurement position x. ]

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

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

According to the present invention, it is possible to provide an optical film and a laminated film that are less prone to defects such as crease marks and scratches during handling. Further, according to the present invention, it is possible to provide a flexible device front panel and a flexible device using the optical film. Furthermore, according to the present invention, it is possible to provide a method for producing the above optical film.

FIG. 1 is a perspective view showing one example of an optical film according to an embodiment of the invention. FIG. 2 is a II-II cross-sectional view of the optical film shown in FIG. FIG. 3 is a perspective view showing one example of the laminated film according to the embodiment of the invention. FIG. 4(a) is a sectional view taken along line IV-IV of the laminated film shown in FIG. 3, and FIGS. 4(b) and 4(c) are sectional views showing other forms of the laminated film. FIG. 5 is a perspective view showing one example of a flexible display according to an embodiment of the invention. 6 is a cross-sectional photograph of the laminated film of Example 4. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will now be described in detail with reference to the drawings as the case may be.
In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are not limited to the illustrated ratios. Further, the positional relationships such as top, bottom, left, and right when describing the embodiments with reference to the drawings are based on the positional relationships shown in the drawings unless otherwise specified.

［式（Ａ）中、ＬはＲａの算出範囲の長さを表し、Ｍ（ｘ）は測定位置ｘにおけるＤＭＴ弾性率の測定値を表す。］
以下、条件（１）を満たす光学フィルムの実施形態を説明するが、本発明は以下の実施形態に限定されず、条件（１）を満たさず、条件（２）のみを満たすものであってもよい。なお、条件（１）及び（２）の両方を満たす光学フィルムが特に好ましい。 [Optical film]
The optical film of this embodiment is an optical film containing a polyimide-based polymer, and the end surface of the optical film satisfies one or both of the following conditions (1) and (2).
Condition (1): The end surface of the optical film is an inclined surface inclined at an angle of 5° or more and 75° or less with respect to the surface of the optical film.
Condition (2): The dispersion (Ra) of the DMT elastic modulus defined by the following formula (A), which is measured in a region 10 to 20 μm inside from the end face of the cross section obtained by cutting the end face of the optical film perpendicularly. value is 500 MPa or less.

[In formula (A), L represents the length of the Ra calculation range, and M(x) represents the measured value of the DMT elastic modulus at the measurement position x. ]
Hereinafter, an embodiment of an optical film that satisfies the condition (1) will be described, but the present invention is not limited to the following embodiments. good. An optical film that satisfies both conditions (1) and (2) is particularly preferable.

FIG. 1 is a perspective view showing an example of the optical film according to this embodiment. The optical film 10 shown in FIG. 1 has a rectangular (rectangular) planar shape, and end faces E1 and E2 of two sides (two parallel long sides forming a rectangle) facing each other in the short direction. , and end faces E3 and E4 of two sides (two parallel short sides forming a rectangle) facing each other in the longitudinal direction. The optical film 10 has an end surface that is inclined at an angle of 5° or more and 75° or less with respect to the surface of the optical film 10 . From the viewpoint of sufficiently suppressing the occurrence of defects during handling, it is preferable that the end surfaces of the two opposing sides (end surfaces E1 and E2, or end surfaces E3 and E4) are the inclined surfaces. It is more preferable that all the end surfaces are the inclined surfaces. In the optical film 10 of the present embodiment shown in FIG. 1, all of the end surfaces E1, E2, E3 and E4 are the inclined surfaces, but the present invention is not limited to this.

FIG. 2 is a II-II cross-sectional view of the optical film shown in FIG. In the optical film 10 of this embodiment, the inclination angles θ of the end faces E1 and E2 with respect to the surface of the optical film 10 are both 5° or more and 75° or less. Similarly, in the optical film 10 of the present embodiment, the inclination angles θ of the end faces E3 and E4 with respect to the surface of the optical film 10 are both 5° or more and 75° or less. The inclination angles θ at the end faces E1, E2, E3 and E4 may be the same or different.

In this specification, the tilt angle θ means an average angle in a film thickness range of 20% or more and 80% or less of the film thickness. This average angle is obtained by measuring the inclination angles of the end faces at positions of 20%, 30%, 40%, 50%, 60%, 70% and 80% of the film thickness and calculating the average value. . Further, in this specification, the tilt angle θ is obtained from the average angle obtained from the angle formed by one surface of the optical film 10 and the end surface, and the angle formed by the other surface of the optical film 10 and the end surface. It means the smaller average angle among the above average angles. In the vicinity of the film surface in the film thickness range of less than 20% or more than 80% of the film thickness, the end face may have a curvature or may have a raised portion with an increased film thickness. Although it is preferable that the inclination angle is substantially constant within one end face, it may vary. Here, the difference in inclination angle (the difference between the maximum value and the minimum value) is preferably 30° or less, more preferably 20° or less, still more preferably 10° or less, and particularly preferably 5° or less. , and the case of 30° or less is assumed to be substantially constant.

The inclination angle θ is preferably 5° or more and 75° or less, more preferably 10° or more and 73° or less, and still more preferably 20° from the viewpoint of sufficiently suppressing the occurrence of defects during film handling. 70° or less, particularly preferably 25° or more and 70° or less. If the angle of inclination θ is less than 5°, the strength of the edges may be lowered, and defects at the edges are likely to occur during handling of the film. If the angle of inclination θ exceeds 75°, defects such as creases and scratches are likely to occur during handling of the film. The tilt angle θ can be measured by observing the end face or cross section of the optical film 10 with an optical microscope.

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

The thickness of the optical film 10 is adjusted appropriately according to the type of flexible device and the like, but is usually 10 to 500 μm. If the film is thin, it is likely to fold during handling after cutting, which may cause defects. Also, if the film is thick, it tends to be difficult to perform uniform cutting.

Optical film 10 is generally transparent. The optical film 10 generally has a total light transmittance of 85% or more, preferably 90% or more, according to JIS K 7105:1981.

The optical film 10 may have a Haze of 1 or less, or 0.9 or less, 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 according to the size of the flexible device used. The planar shape of the optical film 10 is generally rectangular or square, but may be other quadrilaterals such as trapezoids and parallelograms. Further, the planar shape of the optical film 10 may be a square with rounded corners.

(Material of optical film)
(transparent resin)
The optical film contains a transparent resin such as a polyimide polymer.

(polyimide polymer)
As used herein, polyimide is a polymer containing repeating structural units containing imide groups, and polyamide is a polymer containing repeating structural units containing amide groups. Polyimide-based polymers refer to polyimides and polymers containing repeating structural units containing both imide and amide groups.

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 formula (10). Here, G is a tetravalent organic group and A is a divalent organic group. Two or more types of structures represented by formula (10) in which G and/or A are different may be included. In addition, the polyimide polymer according to the present embodiment contains a structure represented by any one of formulas (11) to (13) within a range that does not impair various physical properties of the obtained polyimide polymer film. good too.

G and G ¹ are a tetravalent organic group, preferably an organic group optionally substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, represented by formulas (20) to (29) and a tetravalent chain hydrocarbon group having 6 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 include a phenylene group. G and G ¹ are preferably groups represented by formulas (20) to (27) because they tend to suppress the yellowness of the resulting film.

G ² is a trivalent organic group, preferably an organic group optionally substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, represented by formulas (20) to (29) is substituted with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms.

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

Each of A and A ¹ to A ³ is a divalent organic group, preferably a hydrocarbon group or an organic group optionally substituted with a fluorine-substituted hydrocarbon group, represented by formulas (30) to ( 38); groups substituted with a methyl group, fluoro group, chloro group or trifluoromethyl group, and chain hydrocarbon groups having 6 or less carbon atoms. * in the formula represents a bond, and Z ¹ , Z ² and Z ³ each independently represent a single bond, —O—, —CH ₂ —, —CH ₂ —CH ₂ —, —CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or -CO-. One example is when 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. Z ¹ and Z ² and Z ² and Z ³ are each preferably meta or para to each ring.

The optical film may contain polyamide. The polyamide according to this embodiment is a polymer mainly composed of repeating structural units represented by formula (13). Preferred examples and specific examples ^are the same as ^G3 and A3 in the polyimide polymer. Two or more types of structures represented by formula (13) in which G ³ and/or A ³ are different may be included.

Polyimide-based polymers, for example, are obtained by polycondensation of a diamine and a tetracarboxylic acid compound (tetracarboxylic dianhydride, etc.), for example, described in JP-A-2006-199945 or JP-A-2008-163107. can be synthesized according to the method Commercial products of polyimide include Neoprim manufactured by Mitsubishi Gas Chemical Co., Ltd., KPI-MX300F manufactured by Kawamura Sangyo Co., Ltd., and the like.

Examples of the tetracarboxylic acid compound used for polyimide synthesis include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydrides and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydrides. A tetracarboxylic acid compound may be used independently and may use 2 or more types together. The tetracarboxylic acid compound may be a dianhydride or a tetracarboxylic acid compound analog such as an acid chloride compound.

Specific examples of aromatic tetracarboxylic dianhydrides include 4,4′-oxydiphthalic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 2,2′,3, 3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3 ',4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, 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-phenylenedioxy)diphthalic dianhydride, 4,4'-(m-phenylenedioxy)diphthalic dianhydride and 2,3,6,7-naphthalenetetracarboxylic dianhydride. preferably 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride , 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,2′,3,3′-biphenyltetracarboxylic dianhydride, 3,3′,4,4′-diphenylsulfonetetra Carboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis ( 3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4′-(hexafluoroisopropylidene)diphthalic dianhydride, 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-dicarboxy Phenyl)ethane dianhydride , bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4′-(p-phenylenedioxy)diphthalic dianhydride and 4 , 4′-(m-phenylenedioxy)diphthalic dianhydride. These can be used individually or in combination of 2 or more types.

Aliphatic tetracarboxylic dianhydrides include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride. 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cycloalkanetetracarboxylic dianhydride such as 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo[2.2 .2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl 3,3′-4,4′-tetracarboxylic dianhydride and positional isomers thereof . These can be used individually or in combination of 2 or more types. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,3,4-pentanetetracarboxylic dianhydride. and 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]oct-7-ene, from the viewpoint of high transparency and low coloring -2,3,5,6-tetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride are preferred.

The polyimide-based polymer according to the present embodiment contains, in addition to the anhydride of tetracarboxylic acid used in the polyimide synthesis, tetracarboxylic acid, Further reaction of tricarboxylic acids and dicarboxylic acids and their anhydrides and derivatives may also be used.

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

Examples of dicarboxylic acid compounds include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, their analogous acid chloride compounds, acid anhydrides, and the like, and two or more of them may be used in combination. Specific examples include terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4,4′-biphenyldicarboxylic acid; 3,3′-biphenyldicarboxylic acid; Examples include compounds in which two benzoic acids are linked via a single bond, —CH ₂ —, —C(CH ₃ ) ₂ —, —C(CF ₃ ) ₂ —, —SO ₂ — or a phenylene group.

Aliphatic diamines, aromatic diamines, or mixtures thereof may be used as the diamines used in polyimide synthesis. In this embodiment, the term "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and part of its structure may contain an aliphatic group or other substituents. The aromatic ring may be a single ring or a condensed ring, and examples include, but are not limited to, benzene ring, naphthalene ring, anthracene ring and fluorene ring. Among these, a benzene ring is preferred. The term "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and part of its structure may contain an aromatic ring or other substituents.

Aliphatic diamines include, for example, acyclic aliphatic diamines such as hexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, 4,4'- Cycloaliphatic diamines such as diaminodicyclohexylmethane and the like can be mentioned, and these can be used alone or in combination of two or more.

Examples of aromatic diamines include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene and 2,6-diaminonaphthalene. 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'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis( 4-aminophenoxy)benzene, 4,4'-diaminodiphenylsulfone, 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, and these can be used alone or in combination of two or more.

Among the above diamines, it is preferable to use one or more selected from the group consisting of aromatic diamines having a biphenyl structure from the viewpoint of high transparency and low coloration. 1 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 More preferably, the above is used, and even more preferably 2,2'-bis(trifluoromethyl)benzidine is included.

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 composed of a diamine and a tetracarboxylic acid compound (acid chloride compound, tetracarboxylic acid tetracarboxylic acid compound analogues such as acid dianhydrides), tricarboxylic acid compounds (acid chloride compounds, tricarboxylic acid compound analogues such as tricarboxylic anhydride) and dicarboxylic acid compounds (dicarboxylic acid compound analogues such as acid chloride compounds) It is a condensation-type polymer that is a polycondensation product with at least one compound included in the group consisting of In addition to these, dicarboxylic acid compounds (including analogues such as acid chloride compounds) may also be used as starting materials. The repeating structural unit represented by formula (11) is usually derived from diamines and tetracarboxylic acid compounds. A repeating structural unit represented by formula (12) is usually derived from a diamine and a tricarboxylic acid compound. A repeating structural unit represented by formula (13) is usually derived from a diamine and a dicarboxylic acid compound. Specific examples of diamines and tetracarboxylic acid compounds are as described above.

The standard polystyrene equivalent weight average molecular weight of the polyimide polymer and polyamide according to the present embodiment is usually 10,000 to 500,000, preferably 50,000 to 500,000, more preferably 100,000. ~400,000. The higher the weight-average molecular weight of the polyimide-based polymer and the polyamide, the higher the flexibility tends to be when formed into a film. It tends to be high and workability tends to decrease.

Polyimide-based polymers and polyamides tend to improve the elastic modulus and reduce the YI value when formed into a film by containing fluorine-containing substituents. When the elastic modulus of the film is high, the occurrence of scratches and wrinkles tends to be suppressed. From the viewpoint of film transparency, the polyimide polymer and the polyamide preferably have a fluorine-containing substituent. Specific examples of fluorine-containing substituents include a fluoro group and a trifluoromethyl group.

The content of fluorine atoms in the polyimide polymer and polyamide is preferably 1% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 40% by mass or less, based on the mass of the polyimide polymer or polyamide. is. When the content of fluorine atoms is 1% by mass or more, there is a tendency that the elastic modulus when formed into a film can be further improved, the water absorption rate can be lowered, the YI value can be further reduced, and the transparency can be further improved. . On the other hand, if the fluorine atom content is 1% by mass or more, static electricity is generated when the film is made into a film, which tends to cause irregular folding during handling. According to the present invention, it is possible to provide an optical film that does not easily cause defects such as crease marks and scratches during handling. If the content of fluorine atoms exceeds 40% by mass, synthesis tends to become difficult.

In the optical film according to this embodiment, the content of the polyimide polymer may be 40% by mass or more, preferably 50% by mass or more, more preferably 70% by mass, based on the total mass of the optical film. % by mass or more. When the content of the polyimide-based polymer is 40% by mass or more, there is a tendency that good flexibility is likely to be obtained.

(Inorganic particles)
The optical film according to this embodiment may further contain an inorganic material such as inorganic particles in addition to the polyimide polymer and/or polyamide.

Preferred inorganic materials include silicon compounds such as silica particles and quaternary alkoxysilanes such as tetraethyl orthosilicate (TEOS), and silica particles are preferred from the viewpoint of varnish stability.

The silica particles preferably have an average primary particle size of 10 to 100 nm, more preferably 20 to 80 nm. When the average primary particle size of the silica particles is 100 nm or less, the transparency tends to be improved. When the average primary particle size of the silica particles is 10 nm or more, the cohesive force of the silica particles is weakened, which tends to facilitate handling.

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 may be a silica fine particle powder produced by a gas phase method. Preferably.

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 silica particles before forming the optical film can be determined by a commercially available laser diffraction particle size distribution meter.

In the optical film according to the present embodiment, the content of the inorganic material may be 0% by mass or more and 90% 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 0% by mass or more and 40% 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 this embodiment may further contain additives in addition to the components described above. Examples of the additives include pH adjusters, silica dispersants, ultraviolet absorbers, antioxidants, release agents, stabilizers, colorants such as bluing agents, flame retardants, lubricants and leveling agents.

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

［式（Ａ）中、ＬはＲａの算出範囲の長さを表し、Ｍ（ｘ）は測定位置ｘにおけるＤＭＴ弾性率の測定値を表す。］ Further, the optical film according to the present embodiment has a DMT elastic modulus defined by the formula (A), which is measured in a region 10 to 20 μm inside from the end face of the cross section obtained by cutting the end face of the optical film perpendicularly. is preferably 500 MPa or less, more preferably 400 MPa or less, and even more preferably 350 MPa or less.

[In formula (A), L represents the length of the Ra calculation range, and M(x) represents the measured value of the DMT elastic modulus at the measurement position x. ]

Here, the elastic modulus distribution in the vicinity of the film end surface can be confirmed by DMT (Derjaguin-Muller-Toporov) Modulus Image measurement of SPM (Scanning Probe Microscope). In the case of cutting using a general shear blade, irregular stress is generated near the end portion and strain remains, so the distribution of the elastic modulus tends to increase. tend to be more effective.

(SPM measurement method)
The optical film is cut with a knife such as a razor in a direction perpendicular to one side of the optical film. When cut with a blade, strain may remain, so an ultramicrotome is used to cool the cut test piece to −60° C., and a glass knife is used to cut a cross section of 10 μm or more. Set the cut test piece in the SPM. A cantilever having a spring constant of 10 to 60 N/m is selected, and DMT Modulus Image is measured using QNM (Quantitative Nanomechanical Mapping) mode. Here, the DMT modulus is the modulus (elastic modulus) obtained by fitting using the DMT model. The DMT model is the Derjaquin, Muller, Toropov model. An image near the edge of the film is measured, and a Line Profile is created from the image. The Line Profile is created inward from the film end surface, and the position of the film end surface is set to 0 μm. Ra is obtained from the distribution of the DMT elastic modulus of 10 to 20 μm. Image is measured at 3 points at 90% to 70%, 60% to 40%, and 30% to 10% of the thickness of the film, a line profile is created from each image, Ra at N=3 is calculated, Find the average value.

[Laminated film]
The laminated film of this embodiment includes the optical film of this embodiment described above and a functional layer laminated on at least one surface of the optical film. In the laminated film of the present embodiment, it is preferable that the end face of the optical film and the end face of the functional layer are continuously connected.

FIG. 3 is a perspective view showing one example of the laminated film according to this embodiment. The laminated film 30 shown in FIG. 3 has a rectangular planar shape. The functional layer 20 constituting the laminated film 30 has end faces E11 and E12 of two sides (two long sides parallel to each other forming a rectangle) facing each other in the short direction, and two sides facing each other in the longitudinal direction ( It has end faces E13 and E14 with two short sides parallel to each other forming a rectangle. The functional layer 20 only needs to have a portion where the end faces are inclined at an angle of 5° or more and 75° or less with respect to the surface of the functional layer 20, and at least the end faces of the two opposite sides (end faces It is more preferable that E11 and E12, or end faces E13 and E14) be inclined with respect to the surface of the functional layer 20 at an angle of 5° or more and 75° or less. The inclined surface of the functional layer 20 is preferably connected continuously with the inclined surface of the optical film 10 . From the viewpoint of more sufficiently suppressing the occurrence of defects during handling, it is particularly preferable that all the end surfaces of the functional layer 20 are the inclined surfaces. In the laminated film 30 of this embodiment shown in FIG. 3, all of the end faces E11, E12, E13 and E14 of the functional layer 20 are the inclined faces, but the present invention is not limited to this.

FIG. 4(a) is a cross-sectional view of the laminated film shown in FIG. 3 taken along line IV-IV. In the functional layer 20 of the laminated film 30 of the present embodiment, the inclination angles θ′ of the end faces E11 and E12 with respect to the surface of the functional layer 20 are both preferably 5° or more and 75° or less. Similarly, in the functional layer 20 of the laminated film 30 of the present embodiment, the inclination angles θ′ of the end faces E13 and E14 with respect to the surface of the functional layer 20 are both preferably 5° or more and 75° or less. The inclination angles θ' of the end faces E11, E12, E13 and E14 may be the same or different. Further, it is preferable that the inclination angle θ′ is substantially constant within one end face, but it may vary within the range of 5° or more and 75° or less. When the tilt angle θ' fluctuates within one end surface, the difference between the maximum and minimum values of the tilt angle θ' is 30° or less from the viewpoint of sufficiently suppressing the occurrence of defects during film handling. is preferable, and 20° or less is more preferable. In the laminated film 30 shown in FIG. 4A, the tilt angle θ of the optical film 10 is set such that the tilt angle θ of the laminated surface of the optical film 10 and the functional layer 20 is 0°.

FIG. 4(b) is a cross-sectional view showing another form of the laminated film 30 of this embodiment. In the laminated film 30 shown in FIG. 4B, the tilt angle θ of the optical film 10 is 0° on the side opposite to the side of the optical film 10 laminated with the functional layer 20 .
In the laminated film 30 shown in FIG. 4B, the tilt angle θ′ of the functional layer 20 is such that the tilt angle θ′=0° of the laminated surface of the optical film 10 and the functional layer 20 . Note that the orientation of the laminated film 30 in FIGS. 4A and 4B may be upside down.

FIG. 4(c) is a cross-sectional view showing another form of the laminated film 30 of this embodiment. As shown in (c) of FIG. 4, in the laminated film 30, one end surfaces E1 and E11 of the optical film 10 and the functional layer 20 are inclined surfaces, and the opposite end surfaces E2 and E12 are the optical film 10 and the functional layer 20. It may be a vertical plane perpendicular to the surface of the functional layer 20 . The other end surfaces E3 and E4 of the optical film 10 and the other end surfaces E13 and E14 of the functional layer 20 may be inclined surfaces or vertical surfaces. In the laminated film 30 shown in FIG. 4C, the tilt angle θ of the optical film 10 is such that the tilt angle θ of the surface of the optical film 10 laminated with the functional layer 20 is 0°. In addition, in the laminated film 30 shown in FIG. 4C, the tilt angle θ′ of the functional layer 20 is such that the surface of the optical film 10 opposite to the laminated surface with the functional layer 20 is tilted at an angle of θ′=0°. and

The laminated film 30 shown in (c) of FIG. 4 has an inverted trapezoidal cross-sectional shape in which the lower base is shorter than the upper base like the laminated film 30 shown in (b) of FIG. The laminated film 30 may have a cross-sectional shape in which the end faces taper from the surface on the optical film 10 side toward the surface on the functional layer 20 side. The positions of the tilt angle θ of the optical film 10 and the tilt angle θ′ of the functional layer 20 in this case are the same as in FIG. 4B. Furthermore, the orientation of the laminated film 30 in FIG. 4(c) may be upside down.

In this specification, the inclination angle θ of the end surface of the optical film 10 in the laminated film 30 is the average angle obtained from the angle formed by one surface of the optical film 10 and the end surface, and the other surface of the optical film 10. It means the smaller average angle among the average angles obtained from the angles formed with the end faces. Similarly, the inclination angle θ of the end surface of the functional layer 20 in the laminated film 30 is the average angle obtained from the angle formed by one surface of the functional layer 20 and the end surface, and the angle between the other surface of the functional layer 20 and the end surface. means the smaller average angle among the above average angles obtained from the angles formed by . The surfaces of the optical film 10 and the functional layer 20 referred to here include the laminated surfaces of the optical film 10 and the functional layer 20 .

The inclination angle θ′ is 5° or more and 75° or less, but from the viewpoint of sufficiently suppressing the occurrence of defects during film handling, it is more preferably 10° or more and 73° or less, and 20° or more and 70°. or less, and particularly preferably 25° or more and 70° or less. If the angle of inclination θ′ is less than 5°, the strength of the edges tends to be low and defects tend to occur at the edges when the film is handled. If the angle of inclination θ′ exceeds 75°, defects such as creases and scratches tend to occur during handling of the film. Note that the tilt angle θ′ can be measured by observing the end face or cross section of the laminated film 30 with an optical microscope.

When the end surface of the optical film 10 and the end surface of the functional layer 20 continuously form an inclined surface, the inclination angle θ of the end surface of the optical film 10 and the inclination angle θ′ of the end surface of the functional layer 20 are the same. may also be different. The difference between the tilt angle θ and the tilt angle θ′ is 20° or less because the occurrence of defects such as crease marks and scratches can be further suppressed when the film is handled, and the optical film 10 and the functional layer 20 are more difficult to peel off. is preferably 10° or less, and it is particularly preferable that the inclination angle θ and the inclination angle θ′ are substantially the same.

Examples of the functional layer 20 include layers having various functions such as an ultraviolet absorbing layer, a hard coat layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer. Note that the laminated film 30 may include a plurality of functional layers having different functions, or may include two or more of the functional layers described above. Functional layer 20 preferably includes a hard coat layer.

(functional layer)
The hard coat layer as a functional layer is a layer having a function of expressing high hardness on the surface, for example, a layer that provides the laminated film with a surface having a higher pencil hardness than the pencil hardness of the surface of the optical film. The surface of the hard coat layer may have a pencil hardness of, for example, 2H or more.
The hard coat layer is not particularly limited, but known hard coats such as acrylic, epoxy, urethane, benzyl chloride, and vinyl can be used. Acrylic hard coats include UV-curing, electron beam-curing, or heat-curing resins typified by poly(meth)acrylates. The hard coat layer may contain a photopolymerization initiator and an organic solvent, and may contain inorganic oxides such as silica, alumina, and polyorganosiloxane.

The ultraviolet absorption layer as a functional layer is a layer having a function of absorbing ultraviolet rays, and includes, for example, a main material selected from an ultraviolet-curing transparent resin, an electron beam-curing transparent resin, and a heat-curing transparent resin, It is composed of an ultraviolet absorber dispersed in this main material. By providing an ultraviolet absorption layer as a functional layer, it is possible to easily suppress a change in yellowness due to light irradiation.

The adhesive layer as a functional layer is a layer having an adhesive function, and has a function of adhering the optical film to another member. Commonly known materials can be used as the material for forming the adhesive layer. For example, a thermosetting resin composition or a photocurable resin composition can be used.

The adhesive layer may be composed of a resin composition containing a component having a polymerizable functional group. In this case, strong adhesion can be achieved by further polymerizing the resin composition forming the adhesive layer after the optical film is adhered to another member. The adhesive strength between the optical film and the adhesive layer may be 0.1 N/cm or more, or 0.5 N/cm or more.

The adhesive layer may contain a thermosetting resin composition or a photocurable resin composition as a material. In this case, the resin composition can be polymerized and cured by supplying energy afterward.

The adhesive layer may be a layer that adheres to an object by pressing, which is called a pressure sensitive adhesive (PSA). The pressure-sensitive adhesive may be a pressure-sensitive adhesive that is "a substance that has adhesiveness at room temperature and adheres to the adherend with light pressure" (JIS K6800), and "a specific component is a protective coating (microcapsule) It may be a capsule-type adhesive that is "adhesive that can maintain stability until the coating is destroyed by appropriate means (pressure, heat, etc.)" (JIS K6800).

The hue-adjusting layer as a functional layer is a layer having a hue-adjusting function and capable of adjusting the hue of the optical film to a desired hue. A hue adjustment layer is a layer containing resin and a coloring agent, for example. Examples of the coloring agent include inorganic pigments such as titanium oxide, zinc oxide, red iron oxide, titanium oxide-based calcined pigments, ultramarine blue, cobalt aluminate, and carbon black; azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, Organic pigments such as perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, threne compounds and diketopyrrolopyrrole compounds; extender pigments such as barium sulfate and calcium carbonate; basic dyes, acid dyes and Dyes such as mordant dyes can be mentioned.

The refractive index adjusting layer as a functional layer is a layer having a refractive index adjusting function, has a refractive index different from that of the optical film, and can impart a predetermined refractive index to the laminated film.
The refractive index adjusting layer may be, for example, a resin layer containing an appropriately selected resin and optionally a pigment, or may be a metal thin film.

Pigments that adjust the refractive index include, for example, silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average particle size of the pigment may be 0.1 μm or less. By setting the average particle size of the pigment to 0.1 μm or less, it is possible to prevent diffused reflection of light passing through the refractive index adjusting layer and prevent deterioration of transparency.

Examples of metals used for the refractive index adjusting layer include metals such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride. Oxides or metal nitrides may be mentioned.

The functional layer appropriately has the above functions depending on the use of the optical film. The functional layer may be a single layer or multiple layers. Each layer may have one function or more than one function.

The thickness of the functional layer is appropriately adjusted according to the application such as a flexible device to which the optical film is applied.

[Method for producing optical film]
Next, an example of the method for manufacturing the optical film of this embodiment will be described.

The varnish (varnish for optical film) used for producing the optical film according to the present embodiment is, for example, a polyimide-based polymer obtained by selecting and reacting the above tetracarboxylic acid compound, the above diamine, and the above other raw materials. And/or it can be prepared by mixing and stirring the reaction solution of the polyamide, the solvent, and the additives used as necessary. A solution of a purchased polyimide polymer or the like, or a solution of a purchased solid polyimide polymer or the like may be used instead of the reaction liquid of the polyimide polymer or the like.

The solvent contained in the varnish may be any solvent as long as it can dissolve the polyimide polymer. Examples of solvents include amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide, lactone solvents such as γ-butyrolactone and γ-valerolactone, sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane. Carbonate-based solvents such as ethylene carbonate and propylene carbonate can be used. Among these solvents, amide solvents or lactone solvents are preferred. Moreover, these solvents may be used alone or in combination of two or more.

Next, by a known roll-to-roll or batch method, the above varnish is applied to a resin substrate, stainless steel belt, or glass substrate to form a coating film, and the coating film is dried, A film containing a polyimide-based polymer is obtained by peeling from the substrate. 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. under air, inert atmosphere or reduced pressure.

Examples of resin substrates include PET, PEN, polyimide, and polyamideimide. Among them, a resin having excellent heat resistance is preferable. In particular, a PET base material is preferable from the viewpoint of adhesion to the film and cost.

Subsequently, the end surface of the optical film is processed so as to form an inclined surface inclined at an angle of 5° or more and 75° or less with respect to the surface of the optical film.

Examples of the processing method include a method of cutting or shaving the end face so as to have the inclination angle. Examples of the method of cutting or scraping the end face include a method of irradiating a laser and a method of using a cutting blade such as a shear blade at an angle. Among them, the method of irradiating with a laser is preferable because it is easy to form a smooth inclined surface with little variation in inclination angle. That is, it is preferable that the end surface formed by the above treatment be a laser-cut surface.

The laser is not particularly limited, and any laser capable of forming the inclined surface can be used. Specific examples of usable lasers include gas lasers such as _CO2 lasers and excimer lasers; solid lasers such as YAG lasers; and semiconductor lasers. A preferred laser is a _CO2 laser. Specifically, by cutting the original film into a desired size with a CO ₂ laser, the end face having the above-described inclination angle can be easily formed.

Laser irradiation is preferably performed under the following conditions from the viewpoint of easily forming the end face having the above-described inclination angle. Preferably, the laser has a wavelength of 10 μm or less. The output is preferably 10 W or more, more preferably 12 W or more. The tilt angle tends to decrease as the output increases, and the tilt angle tends to increase as the output decreases. The laser processing speed is preferably 50 mm/sec or higher, more preferably 100 mm/sec or higher. The edge may be irradiated with the laser multiple times. In order to form a cut surface having the above tilt angle, the laser can be irradiated obliquely so that the central axis of the laser is tilted with respect to the surface of the optical film. In addition, while irradiating the surface of the optical film with a laser in a direction perpendicular to the surface of the optical film, by shifting the focal position of the laser (for example, by setting the focal position above the surface of the optical film), the cut surface having the above inclination angle can be obtained. may be formed.

[Method for producing laminated film]
In the production of the laminated film according to the present embodiment, the varnish used for forming the functional layer (varnish for functional layer) can be prepared by blending the materials according to the type of the functional layer described above.

In the method for producing a laminated film according to the present embodiment, first, the varnish for optical films is applied onto a resin substrate, a stainless steel belt, or a glass substrate by a known roll-to-roll or batch method. A coating film is formed, the coating film is dried, and peeled off from the substrate to obtain an optical film. Then, the functional layer varnish is applied on the optical film to form a coating film, thereby obtaining a laminated film in which the optical film and the functional layer are laminated. The order of forming the optical film and the coating film of the functional layer may be reversed, and after the coating film of the functional layer is formed on the substrate, the coating film of the optical film may be formed on the coating film. Alternatively, the optical film may be attached using a known adhesive or pressure-sensitive adhesive.

The coating film of the optical film and the functional layer is dried by evaporating the solvent at a temperature of 50 to 350°C. Drying may be performed under air, inert atmosphere, or under reduced pressure.

Subsequently, the end face of the laminated film is treated so as to form an inclined surface inclined at an angle of 5° or more and 75° or less with respect to the laminated film surface. The processing method is the same as the method described in the method for producing the optical film. Such treatments are usually applied simultaneously to both the optical film and the functional layer. In this case, the optical film and the functional layer form a continuous inclined surface, which is preferable.

[Flexible device]
Such an optical film and laminated film can be suitably used as a front plate of a flexible device. A flexible device according to the present embodiment has a flexible functional layer and the above optical film or laminated film that is overlaid on the flexible functional layer and functions as a front plate. That is, the front panel of the flexible device is positioned on the viewing side above the flexible functional layer. This front plate has the 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, a display functional layer and a solar cell functional layer are flexible functional layers.

An example of a flexible display is shown in FIG. This flexible display 100 is composed of front plate 110/polarizing plate protective film 120B/polarizer 120A/polarizing plate protective film 120B/touch sensor film 130/organic EL element layer 140/TFT substrate 150 in this order from the surface side (visible side). have a configuration. A layer other than the front plate 110 in the flexible display 100 is the flexible functional layer 190 . Polarizing plate protective film 120B/polarizer 120A/polarizing plate protective film 120B constitute polarizing plate 120. FIG. 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 the layers. The front panel 110 is composed of an optical film 110A and a hard coat layer 110B. As the front plate 110, a laminated film 30 comprising the optical film 10 and a hard coat layer as the functional layer 20 can be used. The hard coat layer 110B may be replaced with a layer having other functions, and depending on the function, it may be arranged inside the optical film 110A (between the optical film 110A and the flexible functional layer 190). Such a flexible display can be used as an image display unit for tablet PCs, smart phones, portable game machines, and the like.

According to the flexible device according to this embodiment, the laminated film 30 described above is used as the front plate 110 . Since the laminated film 30 is less likely to cause defects such as creases and scratches during handling, defects are less likely to occur during flexible device fabrication, and defect-free flexible devices with excellent visibility can be obtained at a high yield.

EXAMPLES The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

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

(film formation)
Varnish 1 prepared by the above method was cast on a base material to obtain a polyimide polymer film material having a thickness of 50 μm. The refractive index of the original film was 1.57. After that, a rectangular area (10 cm×5 cm) was cut out from the original film with a CO ₂ laser to obtain an optical film. Processing was performed under the following conditions.
Device: ML-Z9510T manufactured by Keyence Corporation
Wavelength: 9.3 μm
Output: 80%
Machining speed: 150mm/sec

(Example 2)
A raw polyimide polymer film was produced in the same manner as in Example 1. Thereafter, a rectangular region was cut out from the original film by a CO ₂ laser in the same manner as in Example 1, except that the processing speed was 300 mm/sec, to obtain an optical film.

(Comparative example 1)
A raw polyimide polymer film was produced in the same manner as in Example 1. Thereafter, a rectangular region (10 cm×5 cm) was cut out from the raw film with a shear blade to obtain an optical film.

(Example 3)
A polyimide polymer (“KPI-MX300F (100)” manufactured by Kawamura Sangyo Co., Ltd.) was dissolved in γ-butyrolactone to obtain a polymer solution (varnish 2) having a polyimide polymer concentration of 16% by mass. The resulting varnish 2 was cast on a base material to obtain a polyimide polymer film raw material having a thickness of 50 μm and a refractive index of 1.56. An optical film was obtained by CO ₂ laser processing under the same conditions as in Example 1.

(Comparative example 2)
A raw polyimide polymer film was produced in the same manner as in Example 3. After that, a rectangular region was cut out from the original film with a shear blade to obtain an optical film.

(Example 4)
A 30 μm-thick epoxy hard coat layer was cast on a 30 μm-thick polyimide film cast from the varnish 1 of Example 1, and a 30 μm-thick optical film and a 30 μm-thick hard coat layer were formed. A laminated film raw material was obtained. After that, CO ₂ laser processing was performed from the original film under the same conditions as in Example 1, and a rectangular region (10 cm×5 cm) was cut out to obtain a laminated film. When cutting out, a laser was irradiated from the optical film side of the laminated film.

(Comparative Example 3)
A laminated film raw fabric was produced in the same manner as in Example 4. After that, a rectangular region (10 cm×5 cm) was cut out from the original film with a shear blade to obtain a laminated film. When cutting out, the blade was inserted from the optical film side of the laminated film.

(Example 5)
A raw polyimide film was obtained in the same manner as in Example 3, except that the film thickness was 80 μm.
After that, CO ₂ laser processing was performed on the original film under the following conditions. During processing, the laser was fixed and the film was moved. A rectangular shape (10 cm×5 cm) was irradiated with a laser three times and the edges were cut to obtain an optical film.
Device: E400iCL manufactured by COHERENT
Wavelength: 9.4 μm
Output: 13W
Machining speed: 400 mm/sec Frequency: 60 kHz

(Comparative Example 4)
A raw polyimide film was produced in the same manner as in Example 5. Thereafter, a rectangular region (10 cm×5 cm) was cut out from the raw film with a shear blade to obtain an optical film.

<Measurement of elastic modulus variation (Ra)>
For the films obtained in Example 5 and Comparative Example 4, the variation (Ra) of the DMT elastic modulus in the region 10 to 20 μm from the end face was measured under the following conditions.
First, a section was cut perpendicular to one side of the film using a razor to prepare a section, and then the section was treated under the following conditions.
Apparatus: Microtome EMFC6 manufactured by LEICA
Cutting conditions: −60° C. Dry knife: glass knife cutting: cutting of 10 μm or more After that, a DMT Modulus Image was obtained for the obtained cross section using SPM under the following conditions.
Device: Dimension ICOM (manufactured by Bruker)
Cantilever: RTESP
The measured deflection error sensitivity: 63.59nm/V
Calculated spring constant: 20.8727N/m
Resonance frequency: 320.192kHz
Tip radius: 10nm
Sample Poisson's ratio: 0.42
Feedback gain: 10-20
Peak Force setpoint: 70nN
Scan size: 2μm×40μm
Scan ratio: 0.1Hz
Points/Line: 256
A line profile is created from the obtained DMT Modulus Image, and the line profile is 90 to 70%, 60 to 40%, 30 to 70%, 60 to 40%, and 30 to Ra was calculated at each 10% position, and an average value was calculated. The Ra measurement result of the film obtained in Example 5 was 345 MPa, and the Ra measurement result of the film obtained in Comparative Example 4 was 1026 MPa.

<Measurement of tilt angle>
The cross sections of the optical films or laminated films obtained in Examples and Comparative Examples were observed with an optical microscope to measure the tilt angles of the film end surfaces. The tilt angles of the film end surfaces were substantially the same values for all four end surfaces. Table 1 shows the results. Moreover, the cross-sectional photograph of the laminated|multilayer film obtained in Example 4 is shown in FIG. As shown in FIG. 6, the edge surface of the optical film 10 obtained in Example 4 was slightly rough depending on the measurement position, but the average angle was approximately 45°. In addition, in the laminated film obtained in Example 4, the end face of the optical film 10 and the end face of the hard coat layer (functional layer 20) were continuously connected at the same inclination angle. On the other hand, in the laminated film obtained in Comparative Example 3, the end face of the optical film 10 was rough, and the angle of the end face varied greatly in the thickness direction from about 10 to 170°, averaging 80°. rice field. Moreover, in the laminated film obtained in Comparative Example 3, the end face of the optical film 10 and the end face of the hard coat layer (functional layer 20) were not continuous. The films obtained in Comparative Examples 2 and 4 also had a portion with an obtuse angle, and the inclination greatly fluctuated in the thickness direction.

<Evaluation of presence/absence of defects during handling>
A skeleton cutting mat "EKM-L" manufactured by ECOLE is laid on a laboratory bench, the optical films or laminated films obtained in Examples and Comparative Examples are placed on the mat, and the following (1) to (5) are applied to the film. ) was repeated 10 times. The film is tapered so that the end face tapers toward the side that contacts the mat (that is, the cross section of the film on the mat is an inverted trapezoid in which the upper base on the opposite side of the mat is longer than the lower base that contacts the mat). ) was installed. In the case of the laminated film, the surface of the functional layer was placed in contact with the mat.
(1) Rubber A and rubber B with a diameter of 1 cm are pressed against two locations on the film that are 8 cm apart in the longitudinal direction of the film.
(2) Fix the rubber A and bring it closer to the rubber A by 5 cm while pressing the rubber B against the mat. At this time, the film is dragged by the rubber B, and the film between the rubbers A and B is lifted.
(3) Separate rubber A and rubber B from the mat and lift upward by 5 cm. The film is sandwiched between rubber A and rubber B and lifted.
(4) Hold in that state for 3 seconds. In the meantime the film may fall onto the mat.
(5) Widen the gap between rubber A and rubber B to 8 cm. The film falls onto the mat.
After the above operation, the film as a whole was examined for defects (fold marks and scratches), and the film was rated as "A" if no defects were found, and as "B" if defects were found. Table 1 shows the results.

<Evaluation of bending resistance>
The laminated films obtained in Example 4 and Comparative Example 3 were evaluated for bending resistance by the following method. The laminated film was subjected to a repeated bending test using a bending tester DLDM111LH manufactured by Yuasa under the conditions of R=2 mm and 1 Hz. The number of times of bending was measured until the laminated film cracked or the optical film and the hard coat layer peeled off. The laminated film of Example 4 did not crack or peel even after being flexed 30,000 times. Since the laminated film of Comparative Example 3 had fine scratches at the edges, cracks occurred in the hard coat layer after bending 20,000 times or less, whereas the laminated film of Example 4 had smooth edges without cracks. It is thought that the end portion of the fiber endured 30,000 times of flexing without triggering a crack because it had a portion all over. Such fine cracks at the edges of the film are caused not only when the film is cut, but also when the edges are rubbed or bumped during transportation and handling. In addition, if there is a defect such as a crease or a scratch on the film, the film cracks or peels from that defect, so the present invention also has the effect of improving the bending resistance.

As is clear from the results shown in Table 1, it was confirmed that the optical films and the laminated films obtained in the examples are less likely to cause defects such as creases and scratches during handling. On the other hand, both the optical films and laminated films obtained in the comparative examples had defects such as creases and scratches during handling. It is believed that this is because when the film is dragged during handling, the edges tend to get caught on the mat and bend or fold irregularly.

A film containing silica particles and a laminated film having a hard coat layer are particularly susceptible to creases, but it was confirmed in the examples that the occurrence of defects such as creases could be suppressed in any case. In addition, the optical films and laminated films of Examples and Comparative Examples were in a state where static electricity was generated due to their low water absorption, and they easily stuck to the mat and were difficult to lift. Therefore, in the optical film and laminated film of the comparative example, when the film was lifted, stress was applied locally and creases were formed, but it was confirmed that defects such as creases could be suppressed in the examples. As described above, the optical film and laminated film of the present invention can be used to prevent defects even when defects are likely to occur during handling, such as when silica particles are included, when the hard coat layer is provided, and when static electricity is likely to occur. The occurrence can be suppressed.

DESCRIPTION OF SYMBOLS 10... Optical film, 20... Functional layer, 30... Laminated film, 100... Flexible display.

Claims (10)

An optical film for an image display device containing a polyimide polymer,
an end surface of the optical film for an image display device is an inclined surface inclined at an angle of 5° or more and 75° or less with respect to the surface of the optical film for an image display device;
Variation (Ra) of DMT elastic modulus defined by the following formula (A), which is measured in a region 10 to 20 μm inside from the end face of the cross section obtained by cutting the end face of the optical film for an image display device perpendicularly. value is 500 MPa or less,
The variation (Ra) of the DMT elastic modulus is the average value of the measurement results at positions of 90 to 70%, 60 to 40%, and 30 to 10% of the thickness of the film in the region 10 to 20 μm inside from the end face. , an optical film for an image display device.

[In formula (A), L represents the length of the Ra calculation range, and M(x) represents the measured value of the DMT elastic modulus at the measurement position x. ] The optical film for an image display device according to claim 1, wherein the inclined surface is a laser-cut surface. 3. The optical film for an image display device according to claim 1, wherein the polyimide polymer contains 5% by mass or more of fluorine atoms based on the total mass of the polyimide polymer. 4. The optical film for an image display device according to claim 1, further comprising silica particles. 5. The optical film for an image display device according to claim 1, having a thickness of 20 μm or more and 100 μm or less. The optical film for an image display device according to any one of claims 1 to 5, and a functional layer laminated on at least one surface of the optical film for an image display device,
A laminated film in which an end face of the optical film for an image display device and an end face of the functional layer are connected. 7. The laminated film according to claim 6, wherein said functional layer is a hard coat layer. A method for producing an optical film for an image display device containing a polyimide-based polymer, comprising a step of cutting edges by laser irradiation,
The wavelength of the laser is 10 μm or less,
an end surface of the optical film for an image display device formed by the cutting process is an inclined surface inclined at an angle of 5° or more and 75° or less with respect to the surface of the optical film for an image display device;
DMT elastic modulus defined by the following formula (A), which is measured in a region 10 to 20 μm inside from the end face of the cross section obtained by cutting the end face of the optical film for an image display device formed by the cutting process. The value of the variation (Ra) is 500 MPa or less,
The variation (Ra) of the DMT elastic modulus is the average value of the measurement results at positions of 90 to 70%, 60 to 40%, and 30 to 10% of the thickness of the film in the region 10 to 20 μm inside from the end face. and a method for producing an optical film for an image display device.

[In formula (A), L represents the length of the Ra calculation range, and M(x) represents the measured value of the DMT elastic modulus at the measurement position x. ] A front plate for a flexible device comprising the optical film for an image display device according to any one of claims 1 to 5. A flexible device comprising a flexible functional layer and the optical film for an image display device according to any one of claims 1 to 5.

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