JP2020055953A - Optical film, flexible display device and method for manufacturing optical film - Google Patents

Abstract

To provide an optical film having excellent homogeneity, a flexible image display device including the optical film, and a method for manufacturing an optical film.SOLUTION: An optical film contains a polyimide-based resin and/or polyamide-based resin having a weight average molecular weight of 230,000 or more and a filler having an average primary particle size of 5-35 nm, in which when line profiles in mutually perpendicular directions in a film reverse space image obtained by Fourier transformation of a projection image by a projection method using the optical film are represented by h and v, line profiles in mutually perpendicular directions in a background reverse space image are represented by h' and v', the maximum strength of the line profile (h-h') is represented by Y, a frequency indicating the maximum strength Yis represented by X, the maximum strength of the line profile (v-v') is represented by Y, and a frequency indicating the maximum strength Yis represented by X, both Yand Yare 30 or less, the following relationship is satisfied.SELECTED DRAWING: None

Description

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

  An optical film used in an image display device such as a liquid crystal display device and an organic EL display device has a very high optical homogeneity because a user can directly view the displayed image through the optical film. Required.

  As a method for producing such an optical film, a method is used in which a solution containing a volatile solvent and a resin constituting the optical film is applied to a substrate, dried, and then peeled off (for example, Patent Document 1). 1). In a manufacturing method involving such coating and drying, thickness unevenness and orientation unevenness may occur depending on coating conditions and drying conditions. Even when the film has a level of unevenness that cannot be visually confirmed, when finally incorporated as an optical film in an image display device, the optical uniformity is impaired due to such unevenness, and the image May be visually recognized. Therefore, a film used as an optical film in an image display device is required to have a very high level of homogeneity with a level that is difficult to confirm visually. Therefore, there is still a need for further improvement in the optical homogeneity of the film.

  As an optical film in which unevenness of the film is suppressed, for example, in Patent Document 1, in a rectangular area cut out from a projected image of a polyimide-based optical film, a standard deviation σ of gray scale and a black part in a binarized image of the rectangular area are described. A polyimide-based optical film whose area is adjusted within a predetermined range is described. Patent Literature 2 describes an optical transparent film in which the variation in the luminance of transmitted light in the film plane is within 15% of the average luminance in standard deviation. Patent Document 3 discloses that a grid plate is irradiated with light from a light source unit, light transmitted through the grid plate is projected as a grid image, and the grid image is photographed. A shape measurement method by a fringe projection method for digitizing a system shape is described.

International Publication No. 2016/152449 JP-A-9-48866 JP 2011-226871 A

However, any of the methods described in the above-mentioned patent documents are extremely high in accuracy required for an optical film as used in an image display device, and a method sufficient to evaluate the optical homogeneity of the film. I can't say. Since the method described in Patent Document 1 is an evaluation in an analysis area of 1 cm × 5 cm, it is not a method that can sufficiently evaluate a decrease in optical homogeneity due to unevenness generated in a vertical direction. The method described in Patent Literature 2 is not a method that can accurately evaluate a decrease in optical homogeneity due to a light and shade unevenness having a small difference in transmitted light luminance.
Since the method described in Patent Document 3 is a method for detecting a shape, it is impossible to evaluate a decrease in optical homogeneity due to uneven refractive index. Therefore, none of the films evaluated by these methods have sufficient optical homogeneity.

  Furthermore, in addition to being optically homogeneous, the optical film is required to be uniform in physical properties. However, when manufacturing an optical film continuously while transporting the film by, for example, a roll-to-roll method, it may be difficult to achieve uniform optical and physical properties in the MD and TD directions. is there.

  The present invention has been made in view of the problems of the above prior art, and is preferably used as an optical film in an image display device, an optical film having high homogeneity, a flexible display device including the optical film, and It is an object to provide a method for producing the film.

  The present inventors have intensively studied an evaluation method capable of evaluating the homogeneity of an optical film with high accuracy, and a method of increasing the homogeneity of an optical film, in order to solve the above problems. As a result, the inventors focused on an inverse aerial image obtained by Fourier transform from an image projected by a film projection method, and found that an optical film satisfying specific requirements has excellent homogeneity, thereby completing the present invention.

を満たす、光学フィルム。
〔２〕フィルムのＭＤ方向の引裂き強度をＥ_ＭＤ（Ｎ／ｍｍ）とし、ＴＤ方向の引裂き強度をＥ_ＴＤ（Ｎ／ｍｍ）とすると、Ｅ_ＴＤに対するＥ_ＭＤの割合（Ｅ_ＭＤ／Ｅ_ＴＤ）は０．９３以上である、前記〔１〕に記載の光学フィルム。
〔３〕フィルムの黄色度は３以下である、前記〔１〕又は〔２〕に記載の光学フィルム。
〔４〕フィラーはシリカ粒子である、前記〔１〕〜〔３〕のいずれかに記載の光学フィルム。
〔５〕フィラーの含有量は、光学フィルムの質量に対して５〜６０質量％である、前記〔１〕〜〔４〕のいずれかに記載の光学フィルム。
〔６〕フレキシブル表示装置の前面板用のフィルムである、前記〔１〕〜〔５〕のいずれかに記載の光学フィルム。
〔７〕前記〔１〕〜〔６〕のいずれかに記載の光学フィルムを備えるフレキシブル表示装置。
〔８〕タッチセンサをさらに備える、前記〔７〕に記載のフレキシブル表示装置。
〔９〕偏光板をさらに備える、前記〔７〕又は〔８〕に記載のフレキシブル表示装置。
〔１０〕（ａ）重量平均分子量が２３万以上であるポリイミド系樹脂及び／又はポリアミド系樹脂、平均一次粒子径が５〜３５ｎｍのフィラー、ならびに溶媒を少なくとも含有するワニスを支持体上に塗布し、乾燥させ、塗膜を形成させる工程、
（ｂ）支持体から塗膜を剥離する工程、及び
（ｃ）剥離した塗膜を加熱し、フィルムを得る工程
を少なくとも含む、前記〔１〕〜〔６〕のいずれかに記載の光学フィルムの製造方法。 That is, the present invention includes the following preferred embodiments.
[1] An optical film containing a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more, and a filler having an average primary particle diameter of 5 to 35 nm, and a projection method using the optical film. In the film inverse aerial image obtained by Fourier transforming the obtained projected image, the line profiles in the directions h and v perpendicular to each other are set to line profile h and line profile v, respectively, and obtained without using the optical film in the projection method. In the background inverse aerial image obtained by performing the Fourier transform on the background image, the line profiles in the directions h ′ and v ′ orthogonal to each other are defined as line profiles h ′ and v ′, respectively. Line profile obtained by drawing (hh ') The maximum intensity and _{Y mh,} the frequency showing the maximum intensity _{Y mh} and _{X mh,} the maximum intensity of the 'line profile obtained by subtracting the (v-v' line profile v from the line profile v) and _{Y mv,} the maximum intensity _Assuming that the frequency indicating Y _mv is X _mv , both Y _mh and Y _mv are 30 or less, and Y _mh , Y _mv , X _mh and X _mv have the following relationship:

Meet the optical film.
[2] The MD direction tear strength of the film and _E MD (N / mm), when the tear strength in the TD direction _E TD (N / _mm), the ratio of _{E MD} for _{E TD (E MD / E TD} ) Is the optical film according to the above [1], which is 0.93 or more.
[3] The optical film according to [1] or [2], wherein the yellowness of the film is 3 or less.
[4] The optical film according to any of [1] to [3], wherein the filler is silica particles.
[5] The optical film according to any of [1] to [4], wherein the content of the filler is 5 to 60% by mass based on the mass of the optical film.
[6] The optical film according to any one of [1] to [5], which is a film for a front panel of a flexible display device.
[7] A flexible display device comprising the optical film according to any one of [1] to [6].
[8] The flexible display device according to [7], further including a touch sensor.
[9] The flexible display device according to [7] or [8], further including a polarizing plate.
[10] (a) A varnish containing at least a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more, a filler having an average primary particle diameter of 5 to 35 nm, and a solvent is coated on a support. Drying, forming a coating film,
(B) the optical film according to any of (1) to (6), which comprises at least a step of peeling the coating film from the support, and (c) a step of heating the peeled coating film to obtain a film. Production method.

  According to the present invention, it is possible to provide an optical film having excellent homogeneity, a flexible image display device including the optical film, and a method for manufacturing the optical film.

It is the schematic which shows the example of arrangement | positioning in the process of obtaining a projection image. It is the schematic for demonstrating the arrangement | positioning in the process of obtaining a projection image in an Example and a comparative example. It is a figure for explaining Y _max , X _max, and X _cen in a line profile. FIG. 4 is a diagram illustrating a line profile before standardization obtained from a projection image according to the first embodiment. FIG. 4 is a diagram illustrating a normalized line profile obtained from a projection image according to the first embodiment. FIG. 7 is a diagram illustrating a normalized line profile obtained from a background image according to the first embodiment. FIG. 7 is a diagram illustrating a line profile obtained by subtracting a normalized line profile obtained from a background image of the first embodiment from a normalized line profile obtained from a projection image of the first embodiment. FIG. 9 is a diagram showing a line profile obtained by smoothing a line profile obtained by subtracting the normalized line profile obtained from the background image of the first embodiment from the normalized line profile obtained from the projection image of the first embodiment. It is.

  Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiment described here, and various changes can be made without departing from the spirit of the present invention.

を満たす光学フィルムである。ここで、方向ｈ及び方向ｈ’は互いに対応する方向であり、方向ｖ及び方向ｖ’は互いに対応する方向である。これら方向が対応するとは、方位角が同じであることを意味する。上記特徴を満たす本発明の光学フィルムは、優れた均質性を有し、特に画像表示装置における光学フィルムとして好ましく使用される。ここで、光学フィルムの光学的均質性は、フィルムの面状ムラ、厚みムラ、配向ムラなどと密接に関係し、これらのムラが生じると光学的均質性が低下する。そのため、優れた光学的均質性を有する本発明の光学フィルムは、面状ムラ、厚みムラ、配向ムラ等のムラが低減されたフィルムであるといえる。また、光学フィルムの物理的性質の均質性も、フィルムの厚みムラ及び配向ムラと密接に関係し、これらのムラが生じると物理的性質の均質性が低下する。光学フィルムの物理的性質としては、弾性率、表面硬度、引裂き強度等である。上記特徴を有する本発明の光学フィルムは、これらの物理的性質の同一フィルム内でのばらつきが低減されたフィルムであるといる。なお、本明細書において、光学的均質性と物理的性質の均質性を併せて単に「均質性」とも称する。また、本発明の光学フィルムを単に「フィルム」とも称する。 The optical film of the present invention is a polyimide-based resin and / or a polyamide-based resin having a weight average molecular weight of 230,000 or more, and an optical film including a filler having an average primary particle diameter of 5 to 35 nm. In the film inverse aerial image obtained by Fourier transform of the projection image obtained by the projection method, the line profiles in the directions h and v perpendicular to each other are set to line profiles h and v, respectively, without using the optical film in the projection method. In the background inverse aerial image obtained by Fourier transforming the obtained background image, the line profiles in the directions h ′ and v ′ orthogonal to each other are defined as line profiles h ′ and v ′, respectively, and the line profile h ′ is subtracted from the line profile h. The maximum intensity of the line profile ( _hh ′) obtained by The frequency indicating the maximum intensity Y _mh is _defined as X _mh , the maximum intensity of the line profile (v−v ′) obtained by subtracting the line profile v ′ from the line profile v is _defined as Y _mv, and the frequency indicating the maximum intensity Y _mv Is defined as X _mv , Y _mh and Y _mv are both 30 or less, and Y _mh , Y _mv , X _mh and X _mv have the following relationship:

It is an optical film that satisfies the following. Here, the directions h and h 'are directions corresponding to each other, and the directions v and v' are directions corresponding to each other. The correspondence of these directions means that the azimuth angles are the same. The optical film of the present invention which satisfies the above characteristics has excellent homogeneity, and is particularly preferably used as an optical film in an image display device. Here, the optical homogeneity of the optical film is closely related to the surface unevenness, thickness unevenness, alignment unevenness, and the like of the film, and the occurrence of these unevenness lowers the optical uniformity. Therefore, it can be said that the optical film of the present invention having excellent optical homogeneity is a film in which unevenness such as surface unevenness, thickness unevenness, and alignment unevenness is reduced. The homogeneity of the physical properties of the optical film is also closely related to the thickness unevenness and the orientation unevenness of the film, and when these unevennesses occur, the uniformity of the physical properties decreases. Physical properties of the optical film include an elastic modulus, a surface hardness, and a tear strength. The optical film of the present invention having the above characteristics is said to be a film in which variations in these physical properties within the same film are reduced. In this specification, optical homogeneity and physical property homogeneity are also simply referred to as “homogeneity”. Further, the optical film of the present invention is also simply referred to as “film”.

A film inverse aerial image obtained by performing a Fourier transform on a projection image obtained by the projection method using the optical film of the present invention, and a background image obtained without using the film in the projection method was obtained by performing a Fourier transform. The background inverse aerial image is not particularly limited as long as it is obtained by Fourier transform from the projected image and the background image, respectively.
(1) a step of irradiating a film with light from a light source and obtaining a projection image by a projection method of projecting light transmitted through the film onto a projection surface;
(2) a step of projecting light from a light source onto a projection surface without using a film in the projection method of step (1) to obtain a background image;
as well as,
(3) The projection image obtained in the step (1) and the background image obtained in the step (2) are respectively converted into numerical values by gray scale conversion, and the numerically converted image data is subjected to Fourier transform to obtain an inverse aerial image (film inverse aerial image) And a background inverse aerial image). By evaluating the surface quality of the optical film using the inverse aerial image, it is possible to analyze the shading and period of the unevenness.

  A method for obtaining an inverse aerial image by Fourier transform from an image projected by a film projection method is not particularly limited. For example, a method described later for an evaluation step may be used.

Next, (4) the line profiles in the two directions orthogonal to each other in the inverse aerial image of the background image are subtracted from the line profiles in the two directions orthogonal to each other in the inverse aerial image of the projection image, and the blank-corrected line profiles are obtained. And (5) the maximum intensity Y _max (Y _mh and Y _mv , respectively) of the blank-corrected line profile obtained in step (4), and the maximum intensity Y _max (Y _mh and Y _mh in each line profile). A frequency X _max (X _mh and X _mv ) indicative of Y _mv ) is measured. For example, a case will be described below in which line profiles are created in each of a horizontal direction (h1 direction) and a vertical direction (v1 direction) passing through the center of the inverse aerial image. The line profile is shown as a graph showing frequency on the X axis and intensity on the Y axis, for example, as shown in FIG. The maximum intensity Y _max in the horizontal (h1 direction) line profile is _defined as Y _mh1, and a value X _max obtained by subtracting the median value X _cen of all frequencies in the blank-corrected line profile from the frequency indicating the maximum intensity Y _mh1 is obtained. X _mh1 . The maximum intensity Y _max in the line profile in the vertical direction (v1 direction) is _defined as Y _mv1, and a value X _max obtained by subtracting the median value X _cen of all frequencies in the blank-corrected line profile from the frequency indicating the maximum intensity Y _mv1 is obtained. X _mv1 . In the above example, the horizontal direction (h1 direction) and the vertical direction (v1 direction) passing through the center of the aerial image are selected as two orthogonal directions, but the two directions (h direction and v direction) are orthogonal to each other. The direction is not particularly limited as long as the direction does not pass through the center, and may not be the horizontal direction and the vertical direction. In this specification, the “blank-corrected line profile” refers to each line in the two directions orthogonal to each other in the inverse aerial image of the background image from the line profiles in two directions orthogonal to the inverse aerial image of the projection image. It means a line profile obtained by drawing each profile. With the above operation, the baseline of the line profile in the inverse aerial image of the projection image can be corrected.

In the optical film of the present invention, the _{Y mh} and _{Y mv} are both 30 or less. When Y _mh or Y _mv exceeds 30, the homogeneity of the optical film cannot be said to be sufficient. In particular, the optical homogeneity of the film cannot be said to be sufficient for use as an optical film in an image display device, and image distortion and the like cannot be sufficiently reduced. Y _mh and Y _mv are preferably 28 or less, more preferably 26 or less, from the viewpoint of easily increasing the optical homogeneity of the optical film and improving the visibility of an image in an image display device. The smaller the values of Y _mh and Y _mv are, the better. The lower limit is not particularly limited, and may be 0 or more, and is usually 1 or more.

を満たす。（Ｙ_ｍｈ＋Ｙ_ｍｖ）／（Ｘ_ｍｈ＋Ｘ_ｍｖ）^１／２の値が３０を超えると、光学的均質性が十分でないために画面の歪み等が生じる。また、物理的均質性が十分でないために、例えば光学フィルムをフレキシブル表示装置において使用する場合、十分な耐屈曲性又は強度が得られない場合がある。（Ｙ_ｍｈ＋Ｙ_ｍｖ）／（Ｘ_ｍｈ＋Ｘ_ｍｖ）^１／２の値の上限は、フィルムの均質性をより高める観点から、好ましくは２５以下、より好ましくは２２以下、さらに好ましくは２０以下、さらに好ましくは１９．５以下、さらに好ましくは１９以下、さらに好ましくは１８以下、さらに好ましくは１７以下、さらに好ましくは１６以下、さらに好ましくは１３以下、特に好ましくは９以下である。（Ｙ_ｍｈ＋Ｙ_ｍｖ）／（Ｘ_ｍｈ＋Ｘ_ｍｖ）^１／２の値は小さければ小さいほどよく、その下限値は特に限定されず０以上であればよく、通常は０．５以上である。 In the optical film of the present invention, Y _mh , Y _mv , X _mh and X _mv obtained as described above have the following relationship:

Meet. If the value of (Y _mh + Y _mv ) / (X _mh + X _mv ) ^1/2 exceeds 30, screen distortion or the like occurs due to insufficient optical homogeneity. In addition, due to insufficient physical homogeneity, for example, when an optical film is used in a flexible display device, sufficient bending resistance or strength may not be obtained. The upper limit of the value of (Y _mh + Y _mv ) / (X _mh + X _mv ) ^1/2 is preferably 25 or less, more preferably 22 or less, further preferably 20 or less, from the viewpoint of further improving the homogeneity of the film. It is preferably 19.5 or less, more preferably 19 or less, further preferably 18 or less, more preferably 17 or less, further preferably 16 or less, further preferably 13 or less, and particularly preferably 9 or less. _{(Y mh + Y mv) /} (X mh + X mv) 1/2 value may smaller, the lower limit may be any particularly limited not less than 0, typically 0.5 or more.

を満たすことが好ましい。なお、上記の式中、Ｘ_ｍはＸ_ｍｈ又はＸ_ｍｖを表し、Ｘ_ｍｈ及びＸ_ｍｖのいずれもが上記式を満たすことが好ましい。｜Ｘ_ｍ−Ｘ_ｃｅｎ｜の下限は、より好ましくは０．５ｃｍ^−１以上、さらに好ましくは１．０ｃｍ^−１以上である。また、｜Ｘ_ｍ−Ｘ_ｃｅｎ｜の上限は、より好ましくは８．０ｃｍ^−１以下、さらに好ましくは６．０ｃｍ^−１以下である。ムラとして視認されない光学的均質性を備えることと、生産性とを考慮すると、Ｘ_ｍｈ及びＸ_ｍｖが上記関係を満たすフィルムであることが好ましい。 In the optical film of the present invention, the median value of all frequencies in the blank-corrected line profile obtained as described above is defined as X _cen . For example, in the line profile shown in FIG. 3, the total frequency is 90 cm ⁻¹ , and the median value of 45 cm ⁻¹ is X _cen . Here, X _cen and X _mh and X _mv obtained as described above have the following relationship:

It is preferable to satisfy the following. Incidentally, in the above formula, _{X m} represents the _{X mh} or _{X mv,} none of _{X mh} and _{X mv} preferably satisfies the above formula. The lower limit of | X _m -X _cen | is more preferably 0.5 cm ^-1 or more, and further preferably 1.0 cm ^-1 or more. The upper limit of | X _m -X _cen | is more preferably 8.0 cm ^-1 or less, and still more preferably 6.0 cm ^-1 or less. In consideration of providing optical homogeneity that is not visually recognized as unevenness and productivity, it is preferable that X _mh and X _mv satisfy the above relationship.

The optical film of the present invention having the above characteristics regarding _{Ymh and the} like has high homogeneity and also has high homogeneity in physical properties. Therefore, in the optical film of the present invention, when the tear strength in the MD direction of the film is E _MD (N / mm) and the tear strength in the TD direction is E _TD (N / mm), the ratio of E _{MD to} E _TD ( _EMD / _ETD ) is preferably 0.93 or more, more preferably 0.95 or more. As the value of E _{MD /} E _TD approaches 1, indicates that there is no difference in the values of the MD direction tear strength and TD direction of the tear strength of the film, the film of the present invention is the high homogeneity also in physical properties Indicates that it has. Note that the MD direction is the direction of flow of the resin substrate when manufacturing the optical film of the present invention, and the TD direction is a direction perpendicular to the direction of flow of the resin substrate. The tear strength is measured according to the trouser test method in accordance with JIS K 7128-1. Details of the measurement conditions are as described in Examples.

In the optical film of the present invention, when there is no MD direction and no TD direction, or when the MD direction and the TD direction are not determined, two directions orthogonal to each other are defined as A direction and B direction, and the tear strength of the optical film in the A direction is defined. the _E and a (N / mm), the tear strength of the B direction and _E B (N / mm). In that case, the ratio of _{E A} for _{E B (E A / E B} ) is preferably 0.93 or more, more preferably 0.95 or more. Note that, of the two orthogonal directions, a direction having a lower tear strength is defined as an A direction, and a direction having a higher tear strength is defined as a B direction. The proportion of the plurality of set the B direction orthogonal to the A direction and the A direction to the direction, a plurality of directions (preferably 10 or more directions) E _A for E _B obtained for the plane of the optical film ( It is preferred that all of E _A / E _B ) be equal to or more than the above lower limit.

The tear strength of the optical film of the present invention is preferably 0.5 N / mm or more, more preferably 0.7 N / mm or more, and still more preferably 0.1 N / mm or more, from the viewpoint of increasing the strength of the optical film and easily improving the durability. 9 N / mm or more. The upper limit of the tear strength of the optical film of the present invention is not particularly limited, but is preferably 10 N / mm or less, more preferably 8 N / mm or less, and still more preferably 5 N / mm or less from the viewpoint of flexibility. From the same viewpoint as above, preferably 15N / mm ² or more, more preferably 17N / mm ² or more, further preferably 20 N / mm ² or more, preferably 100 N / mm ² or less, more preferably 70N / mm ^2, more preferably not more than 50 N / mm ^2. It is preferable that the optical film has the above tear strength in the TD direction and the MD direction. The measurement of the tear strength is measured according to the trouser test method in accordance with JIS K 7128-1. Details of the measurement conditions are as described in Examples.

  The optical film of the present invention contains a filler having an average primary particle diameter of 5 to 35 nm. Such an optical film has high tensile modulus in addition to high homogeneity and transparency. The tensile elastic modulus of the optical film is preferably at least 4,000 MPa, more preferably at least 5,000 MPa, further preferably at least 5,500 MPa, particularly preferably at least 6,000 MPa. When the tensile elastic modulus is equal to or more than the lower limit, defects such as dents are less likely to occur in the optical film, and the strength of the optical film is easily increased, and the durability is easily improved. The tensile modulus is preferably 10,000 MPa or less, more preferably 9,000 MPa or less. When the tensile modulus is equal to or less than the above upper limit, the bending resistance of the optical film is easily improved. The tensile modulus of the optical film can be measured at room temperature using a tensile tester in accordance with JIS K 7127, for example, by the method described in Examples.

  The yellowness (YI value) of the optical film of the present invention is preferably 3 or less, more preferably 3.0 or less, further preferably 2.5 or less, and particularly preferably 2 or less. When the yellowness of the optical film is equal to or less than the above upper limit, the transparency is easily improved. Yellowness is usually -5 or more, preferably -2 or more, more preferably 0 or more, further preferably 0.3 or more, further preferably 0.5 or more, and particularly preferably 0.7 or more. The yellowness (YI) is measured based on JIS K 7373: 2006 by using an ultraviolet-visible-near-infrared spectrophotometer to measure the transmittance of light having a wavelength of 300 to 800 nm, and tristimulus values (X, Y, Z) And YI = 100 × (1.2769X−1.0592Z) / Y.

  The total light transmittance of the optical film of the present invention is preferably 80% or more, more preferably 85% or more, further preferably 90% or more, and particularly preferably 92% or more. When the total light transmittance is equal to or more than the lower limit, visibility is easily increased when the optical film is incorporated in an image display device. Since the optical film of the present invention has a high optical homogeneity and a high transmittance, for example, compared to the case of using a film having a low transmittance, light emission of a display element or the like necessary to obtain a constant brightness is obtained. Strength can be reduced. Therefore, power consumption can be reduced. For example, when the optical film of the present invention is incorporated in a display device, a bright display tends to be obtained even when the amount of light of the backlight is reduced, which can contribute to energy saving. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance can be measured using a haze computer in accordance with, for example, JIS K7361-1: 1997. The total light transmittance may be the total light transmittance in the range of the thickness of the optical film described later.

  The haze of the optical film of the present invention is preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, further preferably 0.5% or less, and particularly preferably 0.3% or less. % Or less. When the haze of the optical film is equal to or less than the above-mentioned upper limit, transparency becomes good. For example, when the optical film is used for a front plate of an image display device, the visibility of an image is easily increased. The lower limit of the haze is usually at least 0.01%. The haze can be measured using a haze computer according to JIS K7136: 2000.

  The thickness of the optical film of the present invention may be appropriately adjusted depending on the application, but is preferably 25 μm or more, more preferably 27 μm or more, still more preferably 30 μm or more, preferably 100 μm or less, more preferably 90 μm or less. And more preferably 85 μm or less. The film thickness of the optical film can be measured by a film thickness meter or the like, for example, by the method described in Examples.

The optical film of the present invention is an optical film containing a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more, and a filler having an average primary particle diameter of 5 to 35 nm. The optical film of the present invention is preferably a cast film from the viewpoint of easily producing a highly homogeneous optical film having the above characteristics regarding Y _{mh and the} like. In the present specification, the cast film refers to, for example, a solution, dispersion, or melt containing the resin and the filler, which is cast on a suitable support, coated or the like, and heated, cooled, dried, or the like to form a coating film. And a film obtained by peeling the coating film from the support, if necessary. The film thus obtained contains at least a polyimide-based resin and / or a polyamide-based resin and a filler having an average primary particle diameter of 5 to 35 nm, and optionally contains a trace amount of a solvent.

  The optical film of the present invention contains a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more, and a filler having an average primary particle diameter of 5 to 35 nm. The optical film of the present invention may contain one kind of polyimide resin or polyamide resin, or may contain two or more kinds of polyimide resin and / or polyamide resin. Further, the optical film of the present invention may contain one kind of filler having an average primary particle diameter of 5 to 35 nm, or may contain two or more kinds of fillers having an average primary particle diameter of 5 to 35 nm.

<Polyimide resin and polyamide resin>
The optical film of the present invention contains a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more. The polyimide resin is a resin containing a repeating structural unit containing an imide group (hereinafter sometimes referred to as a polyimide resin), and a resin containing a repeating structural unit containing both an imide group and an amide group (hereinafter, a polyamideimide). At least one resin selected from the group consisting of: Further, the polyamide-based resin refers to a resin containing a repeating structural unit containing an amide group.

In a preferred embodiment of the present invention, the polyimide-based resin is a polyimide resin having a structural unit represented by the formula (1) or a structural unit represented by the formula (1) and a resin represented by the formula (2). It is preferably a polyamide-imide resin having the structural unit represented. Further, the polyamide resin is preferably a polyamide resin having a structural unit represented by the formula (2). The formula (1) and the formula (2) will be described below. The description of the formula (1) relates to both the polyimide resin and the polyamideimide resin, and the description of the formula (2) refers to the polyamide resin and the polyamideimide resin. Regarding both.

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

  In the formula (2), Zs are each independently a divalent organic group, preferably substituted with a hydrocarbon group having 1 to 8 carbon atoms or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms. A cyclic group which may be an organic group having 4 to 40 carbon atoms, and more preferably may be substituted with a hydrocarbon group having 1 to 8 carbon atoms or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms. Represents a divalent organic group having 4 to 40 carbon atoms having a structure. Examples of the cyclic structure include an alicyclic, aromatic, and heterocyclic structure. As the organic group of Z, the following formulas (20), (21), (22), (23), (24), (25), (26), (27), and ( 28) and the bond of the group represented by the formula (29), a group in which two non-adjacent atoms are replaced by a hydrogen atom and a divalent chain hydrocarbon group having 6 or less carbon atoms are exemplified. Examples of the structure include a group having a thiophene ring skeleton. From the viewpoint of easily suppressing the yellowness (reducing the YI value) of the obtained optical film, groups represented by the formulas (20) to (27) and a group having a thiophene ring skeleton are preferable.

［式（３）中、Ｒ^１〜Ｒ^８は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基を表し、Ｒ^１〜Ｒ^８に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ａは、互いに独立に、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^９）−を表し、Ｒ^９は水素原子、ハロゲン原子で置換されていてもよい炭素数１〜１２の１価の炭化水素基を表し、
ｍは０〜４の整数であり、
＊は結合手を表す］
で表されることが好ましい。 In one embodiment of the present invention, the polyamide resin and the polyamideimide resin may include a plurality of types of Z, and the plurality of types of Z may be the same or different from each other. Particularly, from the viewpoint of easily exhibiting high surface hardness and excellent optical characteristics of the optical film, at least a part of Z is represented by the formula (3).

[In formula (3), R ^{1 to} R ⁸ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. , R ^{1 to} R ⁸ may be each independently substituted with a halogen atom,
A is, independently of one another, a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) _{2 -, - SO 2 -,} - S -, - CO- or -N ^{(R 9)} - represents, ^{R 9} is a hydrogen atom, monovalent 1-12 carbon atoms which may be substituted with a halogen atom Represents a hydrocarbon group,
m is an integer of 0 to 4,
* Represents a bond]
Is preferably represented by

In the formula (3), A is, independently of one another, a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, —C (CF ₃ ) ₂ —, —SO ₂ —, —S—, —CO— or —N (R ⁹ ) —, and preferably —O— or —S from the viewpoint of the bending resistance of the optical film. -, More preferably -O-.
R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, Alternatively, it represents an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, and 2-methyl-. Butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl and the like. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, and a cyclohexyloxy group. No. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. From the viewpoint of the surface hardness and flexibility of the optical film, R ^{1 to} R ⁸ independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom or 1 to 3 carbon atoms. And more preferably a hydrogen atom. Here, the hydrogen atoms contained in R ^{1 to} R ⁸ may be independently substituted with halogen atoms.
R ⁹ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group and the like. And these may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

  In the formula (3), m is an integer in the range of 0 to 4, and when m is within this range, the bending resistance and the elastic modulus of the optical film tend to be good. In the formula (3), m is preferably an integer in the range of 0 to 3, more preferably 0 to 2, further preferably 0 or 1, and particularly preferably 0. When m is within this range, the bending resistance and the elastic modulus of the optical film can be easily improved. In addition, Z may include one or more types of the structural unit represented by the formula (3), and from the viewpoint of improving the elastic modulus and bending resistance of the optical film and reducing the yellowness (YI value). In particular, it may include two or more types of structural units having different values of m, preferably two types of structural units having different values of m. In this case, the resin contains a structural unit represented by the formula (3) in which m is 0 in Z, from the viewpoint of easily exhibiting a high elastic modulus, bending resistance, and low yellowness (YI value) of the optical film. It is more preferable to further include a structural unit represented by the formula (3) in which m is 1 in addition to the structural unit.

で表される構成単位を有する。この場合、光学フィルムの表面硬度及び耐屈曲性を向上させやすく、黄色度を低減しやすい。 In a preferred embodiment of the present invention, the resin has, as a structural unit represented by the formula (3), a structural unit in which m = 0 and R ^{5 to} R ⁸ are hydrogen atoms. In a more preferred embodiment of the present invention, the resin includes, as a structural unit represented by the formula (3), a structural unit in which m = 0 and R ^{5 to} R ⁸ are a hydrogen atom; ):

Having a structural unit represented by In this case, the surface hardness and bending resistance of the optical film are easily improved, and the yellowness is easily reduced.

  In a preferred embodiment of the present invention in which the optical film contains a polyamide-imide resin, the ratio of the structural unit represented by the formula (3) is determined by the ratio of the structural unit represented by the formula (1) and the formula (2) of the polyamide-imide resin. 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, particularly preferably 50 mol% or more, and most preferably 60 mol% or more, based on the total of the structural units represented by , Preferably 90 mol% or less, more preferably 85 mol% or less, and still more preferably 80 mol% or less. When the proportion of the structural unit represented by the formula (3) is equal to or more than the above lower limit, the surface hardness of the optical film is easily increased, and the bending resistance and the elastic modulus are easily increased. When the proportion of the structural unit represented by the formula (3) is equal to or less than the above upper limit, the increase in the viscosity of the resin-containing varnish due to the hydrogen bond between the amide bonds derived from the formula (3) is suppressed, and the processability of the film is improved. Cheap.

Further, when the polyamide-imide resin has the structural unit of the formula (3) in which m = 1 to 4, the ratio of the structural unit in the formula (3) in which m is 1 to 4 is determined according to the formula (1) of the polyamide-imide resin. Is preferably at least 3 mol%, more preferably at least 5 mol%, further preferably at least 7 mol%, particularly preferably at least 9 mol%, based on the total of the constitutional unit represented by the formula (2) and the constitutional unit represented by the formula (2). Mol% or more, preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, particularly preferably 30 mol% or less. When the ratio of the structural unit of the formula (3) in which m is 1 to 4 is equal to or more than the above lower limit, the surface hardness and the bending resistance of the optical film are easily increased. When the proportion of the structural unit of the formula (3) in which m is 1 to 4 is equal to or less than the above upper limit, an increase in the viscosity of the resin-containing varnish due to the hydrogen bond between the amide bonds derived from the formula (3) is suppressed, and the film is processed. It is easy to improve the performance. In addition, the content of the structural unit represented by the formula (1), the formula (2) or the formula (3) can be measured, for example, using ¹ H-NMR, or calculated from the charging ratio of the raw materials. Can also.

In a preferred embodiment of the present invention, the content of Z in the polyamide resin or the polyamideimide resin is preferably at least 30 mol%, more preferably at least 40 mol%, still more preferably at least 45 mol%, particularly preferably at least 50 mol%. The above is the structural unit represented by Formula (3) in which m is 0 to 4. When the above-mentioned lower limit of Z is a structural unit represented by the formula (3) in which m is 0 to 4, the surface hardness of the optical film is easily increased, and the bending resistance and the elastic modulus are also easily increased. Further, 100 mol% or less of Z in the polyamide resin or polyamideimide resin may be a structural unit represented by the formula (3) in which m is 0 to 4. In addition, the ratio of the structural unit represented by the formula (3) in which m is 0 to 4 in the resin can be measured, for example, using ¹ H-NMR, or calculated from the charging ratio of the raw materials. Can also.

In a preferred embodiment of the present invention, the content of Z in the polyamide resin or polyamideimide resin is preferably 5 mol% or more, more preferably 8 mol% or more, further preferably 10 mol% or more, particularly preferably 12 mol%. The above is represented by Expression (3) in which m is 1 to 4. When the above-mentioned lower limit of Z of the polyamideimide resin is represented by the formula (3) in which m is 1 to 4, the surface hardness of the optical film is easily increased, and the bending resistance and the elastic modulus are easily increased. Further, Z is preferably 90 mol% or less, more preferably 70 mol% or less, still more preferably 50 mol% or less, and particularly preferably 30 mol% or less. Is preferably performed. When the above-described upper limit of Z is represented by the formula (3) in which m is 1 to 4, the viscosity increase of the resin-containing varnish due to the hydrogen bond between the amide bonds derived from the formula (3) in which m is 1 to 4 And it is easy to improve the processability of the film. The ratio of the structural unit represented by the formula (3) in which m is 1 to 4 in the resin can be measured, for example, using ¹ H-NMR, or can be calculated from the charge ratio of the raw materials. .

  In the formulas (1) and (2), X independently represents a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms, more preferably 4 carbon atoms having a cyclic structure. Represents a divalent organic group of ４０40. Examples of the cyclic structure include an alicyclic, aromatic, and heterocyclic structure. The organic group, a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case the carbon number of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably Is 1 to 8. In one embodiment of the present invention, the polyimide resin or the polyamide-imide resin may include a plurality of types of X, and the plurality of types of X may be the same as or different from each other. X is represented by Expression (10), Expression (11), Expression (12), Expression (13), Expression (14), Expression (15), Expression (16), Expression (17), and Expression (18). A group in which a hydrogen atom in those groups represented by the formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a group having 6 or less carbon atoms A chain hydrocarbon group is exemplified.

In the formulas (10) to (18), * represents a bond,
V ^{1, V 2} and ^{V 3} independently of one another, a single _{bond, -O -, - S -,} - CH 2 -, - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH _{3) 2 -, - C (} CF 3) 2 -, - SO 2 -, - CO- or -N (Q) - represents a. Here, Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include the groups described above for R ⁹ .
One example is a single bond ^{V 1} and ^{V 3,} -O- or -S-, and, ^{V 2} is _{-CH 2 -, - C (CH} 3) 2 -, - C (CF 3) 2 — Or —SO ₂ —. The bonding position of V ¹ and V ² to each ring and the bonding position of V ² and V ³ to each ring are independently of each other, preferably meta or para to each ring, more preferably Is in para position.

Among the groups represented by the formulas (10) to (18), from the viewpoint of easily increasing the surface hardness and the bending resistance of the optical film, the formulas (13), (14), (15), and (16) are preferable. ) And a group represented by the formula (17) are preferable, and groups represented by the formulas (14), (15) and (16) are more preferable. In addition, V ¹ , V ² and V ³ are preferably each independently a single bond, —O— or —S— from the viewpoint of easily increasing the surface hardness and flexibility of the optical film, and a single bond or − More preferably, it is O-.

［式（４）中、Ｒ^１０〜Ｒ^１７は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^１０〜Ｒ^１７に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、＊は結合手を表す］
で表される構成単位である。式（１）及び式（２）中の複数のＸの少なくとも一部が式（４）で表される基であると、光学フィルムの表面硬度及び透明性を高めやすい。 In a preferred embodiment of the present invention, at least a part of the plurality of Xs in the formulas (1) and (2) is represented by the formula (4):

[In formula (4), R ^{10 to} R ¹⁷ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms; The hydrogen atoms contained in R ^{10 to} R ¹⁷ may be independently substituted with a halogen atom, and * represents a bond.
Is a structural unit represented by When at least a part of the plurality of Xs in the formulas (1) and (2) is a group represented by the formula (4), the surface hardness and the transparency of the optical film are easily increased.

In the formula (4), R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , and R ¹⁷ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and 1 carbon atom. Represents an alkoxy group having 6 to 6 or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms in the formula (3). Examples of the group or the aryl group having 6 to 12 carbon atoms are given. R ¹⁰ to R ¹⁷ independently of one another, preferably hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, ^{wherein, R 10} ~ The hydrogen atoms contained in R ¹⁷ may be independently substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. R ^{10 to} R ¹⁷ are, independently of each other, more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group from the viewpoint of the surface hardness, transparency and bending resistance of the optical film, Preferably, R ¹⁰ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , and R ¹⁶ are a hydrogen atom, and R ¹¹ and R ¹⁷ are a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group. Preferably, R ¹¹ and R ¹⁷ are a methyl group or a trifluoromethyl group.

で表される構成単位であり、すなわち、複数のＸの少なくとも一部は、式（４’）で表される構成単位である。この場合、フッ素元素を含有する骨格によりポリイミド系樹脂又はポリアミド系樹脂の溶媒への溶解性を高め、該樹脂を含有するワニスの保管安定性を向上しやすいと共に、該ワニスの粘度を低減しやすく、光学フィルムの加工性を向上しやすい。また、フッ素元素を含有する骨格により、光学フィルムの光学特性を向上しやすい。 In a preferred embodiment of the present invention, the structural unit represented by the formula (4) is represented by the formula (4 ′):

In other words, at least a part of the plurality of Xs is a structural unit represented by the formula (4 ′). In this case, the solubility of the polyimide-based resin or the polyamide-based resin in the solvent is enhanced by the skeleton containing the fluorine element, and the storage stability of the varnish containing the resin is easily improved, and the viscosity of the varnish is easily reduced. It is easy to improve the workability of the optical film. Moreover, the optical characteristics of the optical film are easily improved by the skeleton containing the fluorine element.

In a preferred embodiment of the present invention, X in the polyimide-based or polyamide-based resin is preferably at least 30 mol%, more preferably at least 50 mol%, even more preferably at least 70 mol%, of the formula (4): In particular, it is represented by equation (4 ′). When X in the above range in the polyimide-based resin or the polyamide-based resin is represented by the formula (4), particularly the formula (4 ′), the obtained optical film dissolves in a solvent of the resin due to a skeleton containing a fluorine element. The varnish containing the resin is easily improved in storage stability, the viscosity of the varnish is easily reduced, and the processability of the optical film is easily improved. Moreover, the optical characteristics of the optical film are easily improved by the skeleton containing the elemental fluorine. Preferably, 100 mol% or less of X in the polyimide resin or the polyamide resin is represented by the formula (4), particularly the formula (4 ′). X in the polyamideimide resin may be represented by the formula (4), particularly the formula (4 ′). The ratio of the structural unit represented by the formula (4) of X in the resin can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of the raw materials.

  In the formula (1), Y represents a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms, and more preferably a tetravalent organic group having 4 to 40 carbon atoms having a cyclic structure. Represents Examples of the cyclic structure include an alicyclic, aromatic, and heterocyclic structure. The organic group is an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case, the hydrocarbon group and the fluorine-substituted hydrocarbon group may be substituted. The number of carbon atoms is preferably 1 to 8. In one embodiment of the present invention, the polyimide-based resin may include a plurality of types of Y, and the plurality of types of Y may be the same as or different from each other. As Y, the following Expression (20), Expression (21), Expression (22), Expression (23), Expression (24), Expression (25), Expression (26), Expression (27), Expression (28) And a group represented by the formula (29); a group in which a hydrogen atom in the group represented by the formulas (20) to (29) is substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group And a tetravalent chain hydrocarbon group having 6 or less carbon atoms.

In Equations (20) to (29),
* Represents a bond,
W ¹ represents a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) 2 -, _{-Ar -, - SO 2 -,} - CO -, - O-Ar-O -, - Ar-O-Ar -, - Ar-CH 2 -Ar -, - Ar-C (CH 3) 2 -Ar- or an _-Ar-SO 2 -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted by a fluorine atom, and specific examples include a phenylene group.

Among the groups represented by the formulas (20) to (29), the groups represented by the formulas (26), (28) and (29) are preferable from the viewpoint of the surface hardness and the bending resistance of the optical film. Preferably, a group represented by the formula (26) is more preferable. Further, ^{W 1} it is easy to increase the surface hardness and flexibility of the optical film, from the viewpoint of easily decreased yellowness, independently of one another, a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 _{-, - CH (CH 3)} -, - C (CH 3) 2 - or -C _{(CF 3) 2} - is preferably a single _{bond, -O -, - CH 2 -} , - CH (CH 3 _{) -, - C (CH 3} ) 2 - or -C _{(CF 3) 2} -, more preferably a single bond, -C _{(CH 3) 2} - or -C _{(CF 3) 2} - and that Is more preferred.

［式（５）中、Ｒ^１８〜Ｒ^２５は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^１８〜Ｒ^２５に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
＊は結合手を表す］
で表される構成単位である。式（１）中の複数のＹの少なくとも一部が式（５）で表される基であると、ポリイミド系樹脂の溶媒への溶解性を高め、ポリイミド系樹脂を含有するワニスの粘度を低減しやすく、光学フィルムの加工性を向上しやすい。また、光学フィルムの光学特性を向上しやすい。 In a preferred embodiment of the present invention, at least a part of the plurality of Ys in the formula (1) is represented by the formula (5):

[In the formula (5), R ^{18 to} R ²⁵ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, The hydrogen atoms contained in R ^{18 to} R ²⁵ may be independently substituted with a halogen atom,
* Represents a bond]
Is a structural unit represented by When at least a part of the plurality of Ys in the formula (1) is a group represented by the formula (5), the solubility of the polyimide resin in the solvent is increased, and the viscosity of the varnish containing the polyimide resin is reduced. It is easy to improve the workability of the optical film. Further, it is easy to improve the optical characteristics of the optical film.

In the formula (5), R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ , and R ²⁵ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and 1 carbon atom. Represents an alkoxy group having 6 to 6 or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms in the formula (3). Examples of the group or the aryl group having 6 to 12 carbon atoms include those described above. R ¹⁸ to R ²⁵ are, independently of one another, preferably an alkyl group having 1 to 6 carbon hydrogen atom or atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, ^{wherein, R 18} ~ The hydrogen atoms contained in R ²⁵ may be independently substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R ^{18 to} R ²⁵ are each independently preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, from the viewpoint of easily improving the surface hardness, flex resistance and transparency of the optical film. And even more preferably, R ¹⁸ , R ¹⁹ , R ²⁰ , R ²³ , R ²⁴ , and R ²⁵ are hydrogen atoms, and R ²¹ and R ²² are hydrogen atoms, methyl, fluoro, chloro, or trifluoromethyl groups And particularly preferably, R ²¹ and R ²² are a methyl group or a trifluoromethyl group.

で表される基であり、すなわち、複数のＹの少なくとも一部は、式（５’）で表される構成単位である。この場合、フッ素元素を含有する骨格によりポリイミド系樹脂の溶媒への溶解性を高め、該樹脂を含有するワニスの保管安定性を向上しやすいと共に、該ワニスの粘度を低減しやすく、光学フィルムの加工性を向上しやすい。また、フッ素元素を含有する骨格により、光学フィルムの光学特性を向上しやすい。 In a preferred embodiment of the present invention, the structural unit represented by the formula (5) is a compound represented by the formula (5 ′):

In other words, at least a part of the plurality of Ys is a structural unit represented by the formula (5 ′). In this case, the solubility of the polyimide-based resin in the solvent is enhanced by the skeleton containing the fluorine element, and the storage stability of the varnish containing the resin is easily improved, and the viscosity of the varnish is easily reduced, and the optical film has Easy to improve workability. Moreover, the optical characteristics of the optical film are easily improved by the skeleton containing the fluorine element.

In one preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of Y in the polyimide resin is represented by the formula (5), particularly the formula (5) '). When Y in the above range in the polyimide-based resin is represented by the formula (5), particularly the formula (5 ′), the solubility of the polyimide-based resin in a solvent is increased by a skeleton containing a fluorine element, and the content of the polyimide-based resin is increased. The viscosity of the varnish is easily reduced, and the processability of the optical film is easily improved. Moreover, the optical characteristics of the optical film are easily improved by the skeleton containing the fluorine element. Preferably, 100 mol% or less of Y in the polyimide resin is represented by the formula (5), particularly the formula (5 ′). Y in the polyimide resin may be the formula (5), particularly the formula (5 ′). The proportion of the structural unit represented by the formula (5) of Y in the polyimide-based resin can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of the raw materials.

The polyimide-based resin or the polyamide-based resin has a structural unit represented by the formula (30) and / or a structural unit represented by the formula (31), in addition to the structural units represented by the formulas (1) and (2). Units can be included.

In the formula (30), Y ¹ is a tetravalent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y ¹ , Expression (20), Expression (21), Expression (22), Expression (23), Expression (24), Expression (25), Expression (26), Expression (27), Expression (28), and A group represented by the formula (29), a group in which a hydrogen atom in the group represented by the formulas (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; In addition, a tetravalent chain hydrocarbon group having 6 or less carbon atoms is exemplified. In one embodiment of the present invention, the polyimide-based resin or the polyamide-based resin may include a plurality of types of Y ¹ , and the plurality of types of Y ¹ may be the same as or different from each other.

In the formula (31), Y ² is a trivalent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y ² , the above equations (20), (21), (22), (23), (24), (25), (26), (27), and (28) ) And the group represented by the formula (29), in which one of the bonding hands is replaced by a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin or the polyamide-based resin may include a plurality of types of Y ² , and the plurality of types of Y ² may be the same as or different from each other.

In the formulas (30) and (31), X ¹ and X ² are each independently a divalent organic group, and preferably, a hydrogen atom in the organic group is a hydrocarbon group or a hydrocarbon group in which fluorine is substituted. Is an organic group which may be substituted. As X ¹ and X ² , the above equations (10), (11), (12), (13), (14), (15), (16), (17), And a group represented by the formula (18); a group in which a hydrogen atom in the groups represented by the formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; And a chain hydrocarbon group having 6 or less carbon atoms.

In one embodiment of the present invention, the polyimide resin or the polyamide resin is a structural unit represented by the formula (1) and / or the formula (2) and optionally represented by the formula (30) and / or the formula (31). Consists of the structural units represented. In addition, from the viewpoint of the optical properties, surface hardness and bending resistance of the optical film, the structural units represented by the formulas (1) and (2) in the polyimide resin or the polyamide resin are represented by the formulas (1) and (2). Based on the formula (2) and, if necessary, all the structural units represented by the formulas (30) and (31), preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more. It is. In the polyimide resin or the polyamide resin, the structural units represented by the formulas (1) and (2) are represented by the formulas (1) and (2), and optionally the formulas (30) and / or ( 31% or less based on all constituent units represented by 31). The above ratio is, for example, can also be calculated from ^{1 H-NMR} can be measured using, or the material feed ratio.

  The weight average molecular weight (Mw) of the polyimide resin or the polyamide resin is 230,000 or more in terms of standard polystyrene. When the weight average molecular weight is lower than 230,000, sufficient bending resistance of the optical film cannot be obtained. From the viewpoint of easily increasing the surface hardness and the bending resistance of the optical film, the weight average molecular weight of the polyimide resin or the polyamide resin is preferably 230,000 or more, more preferably 250,000 or more, and further preferably 270,000 or more. And particularly preferably 300,000 or more. Further, the weight average molecular weight of the resin is preferably 1,000,000 from the viewpoint that the solubility of the polyamide resin or the polyimide resin in the solvent is easily improved, and the stretchability and processability of the optical film are easily improved. Or less, more preferably 800,000 or less, further preferably 700,000 or less, particularly preferably 500,000 or less. The weight average molecular weight can be determined, for example, by performing GPC measurement and converting it into standard polystyrene, and may be calculated, for example, by the method described in Examples.

  In the polyamideimide resin, the content of the structural unit represented by the formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol, per 1 mol of the structural unit represented by the formula (1). Mol or more, more preferably 1.0 mol or more, particularly preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, and still more preferably 4.5 mol or less. . When the content of the structural unit represented by the formula (2) is equal to or more than the above lower limit, the surface hardness of the optical film is easily increased. Further, when the content of the structural unit represented by the formula (2) is equal to or less than the above upper limit, the viscosity increase due to the hydrogen bond between the amide bonds in the formula (2) is suppressed, and the processability of the optical film is improved. Easy to make.

  In a preferred embodiment of the present invention, the polyimide resin or the polyamide resin contained in the optical film of the present invention can be introduced by, for example, the above-mentioned fluorinated substituent or the like, and contains a halogen atom such as a fluorine atom. Good. When the polyimide resin or the polyamide resin contains a halogen atom, it is easy to improve the elasticity of the optical film and to reduce the yellowness (YI value). When the elastic modulus of the optical film is high, generation of scratches and wrinkles in the film is easily suppressed, and when the yellowness of the optical film is low, the transparency and visibility of the film are easily improved. The halogen atom is preferably a fluorine atom. Preferred fluorine-containing substituents for containing a fluorine atom in the polyimide resin or the polyamide resin include, for example, a fluoro group and a trifluoromethyl group.

  The content of halogen atoms in the polyimide resin or the polyamide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and still more preferably 5 to 40% by mass, based on the mass of the polyimide resin or the polyamide resin. 30% by mass. When the content of the halogen atom is equal to or more than the above lower limit, the elasticity of the optical film is further improved, the water absorption is reduced, the yellowness is further reduced, and the transparency and visibility are more easily improved. When the content of the halogen atom is equal to or less than the above upper limit, synthesis becomes easy.

  The imidation ratio of the polyimide resin and the polyamideimide resin is preferably 90% or more, more preferably 93% or more, and further preferably 96% or more. From the viewpoint of easily increasing the optical homogeneity of the optical film, the imidization ratio is preferably equal to or more than the above lower limit. The upper limit of the imidation ratio is 100% or less. The imidation ratio indicates the ratio of the molar amount of imide bonds in the polyimide resin and the polyamideimide resin to twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin or the polyamideimide resin. In addition, when the polyimide resin and the polyamideimide resin contain a tricarboxylic acid compound, the value of twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin and the polyamideimide resin, and the value derived from the tricarboxylic acid compound It shows the ratio of the molar amount of the imide bond in the polyimide resin and the polyamideimide resin to the total molar amount of the constituent units. The imidation ratio can be determined by an IR method, an NMR method, or the like. For example, in the NMR method, the imidation ratio can be measured by the method described in Examples.

  Commercial products may be used as the polyimide resin and the polyamide resin. Commercially available polyimide resins include, for example, Neoprim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Ltd., and KPI-MX300F manufactured by Kawamura Sangyo Co., Ltd.

［式（３”）中、Ｒ^１〜Ｒ^８は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基を表し、Ｒ^１〜Ｒ^８に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ａは、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^９）−を表し、
Ｒ^９は水素原子、ハロゲン原子で置換されていてもよい炭素数１〜１２の１価の炭化水素基を表し、
ｍは０〜４の整数であり、
Ｒ^３１及びＲ^３２は、互いに独立に、ヒドロキシル基、メトキシ基、エトキシ基、ｎ−プロポキシ基、イソプロポキシ基、ｎ−ブトキシ基、ｓｅｃ−ブトキシ基、ｔｅｒｔ−ブトキシ基又は塩素原子を表す。］ <Resin manufacturing method>
Polyimide resin, for example, can be produced using a tetracarboxylic acid compound and a diamine compound as a main raw material, polyamide imide resin, for example, a tetracarboxylic acid compound, a dicarboxylic acid compound and a diamine compound can be produced as a main raw material, polyamide resin is For example, a dicarboxylic acid compound and a diamine compound can be produced as main raw materials. Here, the dicarboxylic acid compound preferably contains at least a compound represented by the formula (3 ″).

[In the formula (3 ″), R ^{1 to} R ⁸ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. And the hydrogen atoms contained in R ^{1 to} R ⁸ may be independently substituted with a halogen atom,
A represents a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) 2 -, - Represents SO ₂ —, —S—, —CO— or —N (R ⁹ ) —;
R ⁹ represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom,
m is an integer of 0 to 4,
R ³¹ and R ³² independently represent a hydroxyl group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group or a chlorine atom. ]

In a preferred embodiment of the present invention, the dicarboxylic acid compound is a compound represented by the formula (3 ″) wherein m is 0. As the dicarboxylic acid compound, a compound represented by the formula (3 ″) wherein m is 0 It is more preferable to use a compound represented by the formula (3 ″) wherein A is an oxygen atom, in addition to the compound represented by the formula (1): In another preferable embodiment, the dicarboxylic acid compound is represented by R ³¹ , A compound represented by the formula (3 ″), wherein R ³² is a chlorine atom. Further, a diisocyanate compound may be used instead of the diamine compound.

  Examples of the diamine compound used in the production of the resin include an aliphatic diamine, an aromatic diamine, and a mixture thereof. In the present embodiment, the “aromatic diamine” refers to a diamine in which an amino group is directly bonded to an aromatic ring, and a part of the structure may include an aliphatic group or another substituent. The aromatic ring may be a single ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring and a fluorene ring, but are not limited thereto. Among these, a benzene ring is preferred. The “aliphatic diamine” refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may have an aromatic ring or another substituent in a part of its structure.

  Examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylene diamine, and 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornanediamine, and 4,4 ′. And cycloaliphatic diamines such as diaminodicyclohexylmethane. These 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-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, and 2,6-diaminonaphthalene. Aromatic diamine 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, bis [4- (4-aminophen Xy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-amino Phenoxy) phenyl] propane, 2,2′-dimethylbenzidine, 2,2′-bis (trifluoromethyl) -4,4′-diaminodiphenyl (sometimes referred to as TFMB), 4,4′-bis ( 4-aminophenoxy) biphenyl, 9,9-bis (4-aminophenyl) fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene, 9,9-bis (4-amino-3-chlorophenyl) ) Aromatic diamines having two or more aromatic rings, such as fluorene and 9,9-bis (4-amino-3-fluorophenyl) fluorene. These can be used alone or in combination of two or more.

  The aromatic diamine is preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylether, 3,3'-diaminodiphenylether, 4,4'-diaminodiphenylsulfone, , 3'-Diaminodiphenyl sulfone, 1,4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, , 2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2′-dimethylbenzidine, 2,2′-bis ( (Trifluoromethyl) -4,4′-diaminodiphenyl (TFMB), 4,4′-bis (4-amido) Phenoxy) biphenyl, more preferably 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, 1,4-bis (4 -Aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2′-dimethylbenzidine, 2,2 ′ -Bis (trifluoromethyl) -4,4'-diaminodiphenyl (TFMB) and 4,4'-bis (4-aminophenoxy) biphenyl. These can be used alone or in combination of two or more.

  Among the above diamine compounds, from the viewpoint of high surface hardness, high transparency, high flexibility, high bending resistance and low coloring property of the optical film, at least one selected from the group consisting of aromatic diamines having a biphenyl structure is used. Preferably, it is used. 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 use 2,2′-bis (trifluoromethyl) -4,4′-diaminodiphenyl (TFMB).

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

  Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides and condensed polycyclic aromatic tetracarboxylic acids. Carboxylic dianhydrides are mentioned. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride 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-di (Carboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (described as 6FDA) ), 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis ( 3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2 , 3-dicarboxyphenyl) methane dianhydride, 4,4 '-(p-phenylenedioxy) diphthalic dianhydride, and 4,4'-(m-phenylenedioxy) diphthalic dianhydride . Examples of the monocyclic aromatic tetracarboxylic dianhydride include 1,2,4,5-benzenetetracarboxylic dianhydride, and a condensed polycyclic aromatic tetracarboxylic dianhydride. Examples thereof include 2,3,6,7-naphthalenetetracarboxylic dianhydride.

  Of these, 4,4'-oxydiphthalic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, and 2,2', 3,3'-benzophenonetetracarboxylic dianhydride are preferred. Anhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-diphenyl Sulfonetetracarboxylic 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 (6FDA), 1,2-bis (2,3-dicarboxyphenyl) Nyl) 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 and 4,4 ′-(m-phenylenedioxy) diphthalic dianhydride; more preferably 4,4′-oxydiphthalic dianhydride; 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride ( 6FDA , Bis (3,4-carboxyphenyl) methane dianhydride, and 4, 4 '- (p-phenylene-oxy) diphthalic acid dianhydride. These can be used alone or in combination of two or more.

  Examples of the aliphatic tetracarboxylic dianhydride include cyclic and acyclic aliphatic tetracarboxylic dianhydrides. The cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride. , Cycloalkanetetracarboxylic dianhydride such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 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 alone or in combination of two or more. 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. Further, a combination of a cycloaliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used.

  Among the above tetracarboxylic dianhydrides, from the viewpoint of high surface hardness, high transparency, high flexibility, high bending resistance, and low coloring property of the optical film, 4,4′-oxydiphthalic dianhydride, 3, 3 ', 4,4'-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, 4,4'-(hexafluoroisopropylidene ) Diphthalic dianhydride and mixtures thereof are preferred, and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride are preferred. Objects, and more preferably mixtures thereof, 4,4 '- (hexafluoro isopropylidene) diphthalic anhydride (6FDA) is more preferred.

As the dicarboxylic acid compound used for the production of the resin, terephthalic acid, 4,4′-oxybisbenzoic acid or an acid chloride compound thereof is preferably used. In addition to terephthalic acid, 4,4'-oxybisbenzoic acid, or their acid chloride compounds, other dicarboxylic acid compounds may be used. Examples of other dicarboxylic acid compounds include aromatic dicarboxylic acids, aliphatic dicarboxylic acids and their related acid chloride compounds, acid anhydrides, and the like, and two or more kinds may be used in combination. Specific examples include a dicarboxylic acid compound of isophthalic acid; naphthalenedicarboxylic acid; 4,4′-biphenyldicarboxylic acid; 3,3′-biphenyldicarboxylic acid; a chain hydrocarbon having 8 or less carbon atoms, and two benzoic acids but a single _{bond, -CH 2 -, - C (} CH 3) 2 -, - C (CF 3) 2 -, - SO 2 - or a compound linked phenylene groups and their acid chlorides compounds. As specific examples, 4,4′-oxybis (benzoyl chloride) and terephthaloyl chloride are preferable, and it is more preferable to use 4,4′-oxybis (benzoyl chloride) and terephthaloyl chloride in combination.

  In addition, the polyimide-based resin, in addition to the tetracarboxylic acid compound, in a range that does not impair the various physical properties of the optical film, is obtained by further reacting tetracarboxylic acid and tricarboxylic acid and anhydrides and derivatives thereof. Is also good.

  Examples of the tetracarboxylic acid include a water adduct of an anhydride of the above tetracarboxylic acid compound.

Examples of the tricarboxylic acid compound include an aromatic tricarboxylic acid, an aliphatic tricarboxylic acid, an acid chloride compound and an acid anhydride related thereto, and a combination of two or more thereof may be used. Specific examples include anhydrides of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; a single bond of phthalic anhydride and benzoic acid; _{, -CH 2 -, - C (} CH 3) 2 -, - C (CF 3) 2 -, - SO 2 - or a compound linked phenylene group.

  In the production of the resin, the amount of the diamine compound, the tetracarboxylic acid compound and / or the dicarboxylic acid compound to be used can be appropriately selected according to the desired ratio of each constituent unit of the polyimide resin and the polyamide resin.

  In the production of the resin, the reaction temperature of the diamine compound, the tetracarboxylic acid compound and the dicarboxylic acid compound is not particularly limited, but is, for example, 20 to 200 ° C, preferably 25 to 100 ° C. Although the reaction time is not particularly limited, it is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out under an inert atmosphere or under reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and / or an inert gas atmosphere with stirring. The reaction is preferably performed in a solvent inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, for example, water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, Alcohol solvents such as 2-butoxyethanol and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, γ-valerolactone, propylene glycol methyl ether acetate, and ethyl lactate; Ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl isobutyl ketone; pentane, hexane Hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chloroform And chlorinated solvents such as chlorobenzene; amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide and sulfolane; carbonates such as ethylene carbonate and propylene carbonate. Solvents; and combinations thereof (mixed solvents). Among them, amide solvents can be preferably used from the viewpoint of solubility.

  In the imidization step in the production of the polyimide resin, the imidization can be performed in the presence of an imidation catalyst. Examples of the imidization catalyst include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydro. Alicyclic amines (monocyclic) such as azepine; azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane, and azabicyclo [3.2. 2] alicyclic amines such as nonane (polycyclic); and pyridine, 2-methylpyridine (2-picoline), 3-methylpyridine (3-picoline), 4-methylpyridine (4-picoline), 2- Ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4,6-trimethyl Pyridine, 3,4-cyclopentenopyridine pyridine, 5,6,7,8-tetrahydroisoquinoline, and aromatic amines isoquinoline. From the viewpoint of facilitating the imidization reaction, it is preferable to use an acid anhydride together with the imidization catalyst. Examples of the acid anhydride include a conventional acid anhydride used in an imidization reaction. Specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic acids such as phthalic acid. Acid anhydride and the like.

  The polyimide resin and the polyamide resin are isolated (separated and purified) by a conventional method, for example, separation means such as filtration, concentration, extraction, crystallization, recrystallization, and column chromatography, or a separation means combining these. In a preferred embodiment, the reaction solution containing the transparent polyamide-imide resin can be isolated by adding a large amount of alcohol such as methanol to precipitate the resin, followed by concentration, filtration, drying and the like.

<Filler>
The optical film of the present invention contains a filler having an average primary particle diameter of 5 to 35 nm. The optical film of the present invention containing a filler having an average primary particle diameter of 5 to 35 nm is an optical film having both transparency and optical homogeneity and high elastic modulus and strength, and is used in a flexible display device or the like. Particularly suitable for. If the average primary particle diameter of the filler is smaller than 5 nm, the filler particles are likely to aggregate, and it is difficult to obtain an optical film in which the filler is uniformly dispersed. As a result, the optical homogeneity and physical property homogeneity of the optical film are likely to be impaired, and the transparency, elastic modulus, and strength of the optical film are likely to be reduced. When the average primary particle diameter of the filler is larger than 35 nm, the optical properties of the filler itself affect the optical properties of the optical film, and the transparency of the optical film cannot be sufficiently increased. From the viewpoint of easily increasing the homogeneity, transparency, elastic modulus and strength of the optical film, the average primary particle diameter of the filler is preferably 10 nm or more, more preferably 15 nm or more, and further preferably 20 nm or more. In addition, from the viewpoint of easily increasing the transparency of the optical film, the average primary particle diameter of the filler is preferably 30 nm or less.

The average primary particle diameter of the filler can be measured by the BET method. Specifically, it can be calculated by converting the specific surface area (BET specific surface area) measured by the BET method (nitrogen adsorption BET method) into an average primary particle diameter. Here, assuming that the average primary particle diameter is d (nm), the density of the filler is ρ (g / cm ³ ), and the BET specific surface area is S (m ² / g), d = 6000 between them. / (S × ρ) holds. For example, when the filler is silica, the average primary particle diameter can be calculated from the BET specific surface area from the equation of d = 2070 / S. The primary particle diameter (average primary particle diameter) may be measured by image analysis using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). The average primary particle diameter of the filler contained in the optical film may be the average primary particle diameter of the filler used as a raw material, or may be the average primary particle diameter measured from the optical film. When measuring the average primary particle diameter of the filler from the optical film, the average primary particle diameter of the filler in the optical film may be measured by image analysis of a transmission electron microscope or a scanning electron microscope using the film as a measurement sample. If necessary, the film is crushed, and the crushed film is dissolved in a solvent capable of dissolving the resin in the film (eg, γ-butyrolactone), and the dispersed particles are subjected to transmission electron microscopy (TEM) or The measurement may be performed by observing with a scanning electron microscope (SEM), or the filler may be taken out from the film, dried, and the average primary particle diameter may be calculated from the BET specific surface area in the same manner as described above. When the average primary particle diameter is measured by, for example, image analysis with an electron microscope, the average value of the primary particle diameter measured for each of 100 particles present in a certain area may be used as the average primary particle diameter.

  Examples of the filler include organic particles and inorganic particles, and preferably include inorganic particles. Examples of the inorganic particles include metal oxide particles such as silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide, magnesium fluoride, and fluorine. Metal fluoride particles such as sodium fluoride and the like. Among them, silica particles, zirconia particles, and the like, from the viewpoint of increasing the elastic modulus and / or tear strength of the obtained optical film and easily improving impact resistance, Alumina particles are preferred, and silica particles are more preferred. These fillers can be used alone or in combination of two or more.

  The content of the filler having an average primary particle diameter of 5 to 35 nm is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and still more preferably 20% by mass or more, based on the mass of the optical film. % By mass, more preferably at least 25% by mass, particularly preferably at least 30% by mass. When the content of the filler is equal to or more than the above lower limit, the impact resistance and durability of the optical film can be easily improved. The content of the filler having an average primary particle diameter of 5 to 35 nm is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 45% by mass or less, based on the mass of the optical film. When the content of the filler is equal to or less than the above upper limit, haze and yellowness of the optical film are easily reduced, and transparency and optical characteristics are easily improved, and bending resistance is easily improved.

<Ultraviolet absorber>
The optical film of the present invention may contain at least one ultraviolet absorber. The ultraviolet absorber can be appropriately selected from those commonly used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may include a compound that absorbs light having a wavelength of 400 nm or less. Examples of the ultraviolet absorber include at least one compound selected from the group consisting of a benzophenone-based compound, a salicylate-based compound, a benzotriazole-based compound, and a triazine-based compound. The ultraviolet absorbers can be used alone or in combination of two or more. Since the deterioration of the resin is suppressed when the optical film contains the ultraviolet absorber, the visibility can be improved when the optical film of the present invention is applied to an image display device or the like. In this specification, the “system compound” refers to a derivative of the compound to which the “system compound” is attached. For example, “benzophenone-based compound” refers to a compound having benzophenone as a parent skeleton and a substituent bonded to benzophenone.

  When the optical film of the present invention contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 0.01 to 10 parts by mass, more preferably 1 to 8 parts by mass, based on the mass of the resin contained in the optical film. Parts by mass, more preferably 2 to 7 parts by mass. When the content of the ultraviolet absorber is equal to or more than the above lower limit, the ultraviolet absorption is easily improved. When the content of the ultraviolet absorber is equal to or less than the above upper limit, the decomposition of the ultraviolet absorber due to heat during the production of the base material can be suppressed, and the optical characteristics can be easily improved, for example, the haze can be easily reduced.

<Other additives>
The optical film of the present invention may further contain other additives other than the filler and the ultraviolet absorber. Other additives include, for example, antioxidants, release agents, stabilizers, coloring agents such as bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, and leveling agents. No. When other additives are contained, the content is preferably 0.005 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and still more preferably 0.1 to 15 parts by mass, based on the mass of the optical film. It may be 10 parts by mass.

<Production method of optical film>
The method for producing the optical film of the present invention having the above characteristics is not particularly limited. For example, the following steps:
(A) A varnish containing at least a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more, a filler having an average primary particle diameter of 5 to 35 nm, and a solvent is coated on a support and dried. , Forming a coating film,
It can be produced by a production method including at least a step of (b) peeling a coating film from a support, and (c) a step of heating the peeled coating film to obtain a film. The present invention also provides a method for producing an optical film, which includes at least the above steps.

After the step (c), the method for producing an optical film of the present invention comprises:
(D) Line profiles in directions h and v orthogonal to each other in a film inverse aerial image obtained by Fourier transforming a projection image obtained by a projection method using the obtained film are defined as a line profile h and a line profile v, respectively. In the projection method, a line profile in a direction h ′ and a direction v ′ orthogonal to each other in a background inverse aerial image obtained by Fourier transforming a background image obtained without using the film are line profiles h ′ and line profiles v, respectively. , The maximum intensity of the line profile (h−h ′) obtained by subtracting the line profile h ′ from the line profile h is Y _mh , the frequency indicating the maximum intensity Y _mh is X _mh , and the line profile v Line profile (vv ') obtained by subtracting v' The maximum intensity and _{Y mv,} the frequency showing the maximum intensity _{Y mv} when the _{X mv,} the value of _{Y mh} and _{Y mv, and,} Y _mh, is calculated from Y _{mv, X mh} and _{X mv (Y mh} + Y _mv ) / (X _mh + X _mv ) ^1/2 may further include a step of evaluating the film based on the value of ^1/2 .

を満たすことが好ましい。 The varnish used in the above step (a) contains at least a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more, a filler having an average primary particle diameter of 5 to 35 nm, and a solvent. Here, the viscosity (cps) of the varnish and the solid content concentration (% by mass) of the varnish are in the following relationship:

It is preferable to satisfy the following.

  First, the step (a) of applying a varnish on a support, drying the varnish, and forming a coating film will be described. Examples of the resin and filler contained in the varnish include the resins and fillers described above as the resin and filler contained in the optical film of the present invention. Further, the varnish may contain the above-mentioned ultraviolet absorbent and other additives.

  The solvent contained in the varnish is not particularly limited as long as it can dissolve the resin. Examples of such a solvent include amide solvents such as N, N-dimethylacetamide (DMAc) and N, N-dimethylformamide; lactone solvents such as γ-butyrolactone (GBL) and γ-valerolactone; dimethyl sulfone, dimethyl sulfoxide , Sulfolane and the like; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvents). Among these, an amide-based solvent or a lactone-based solvent is preferable from the viewpoint of easily improving the homogeneity of the optical film, particularly the optical homogeneity. These solvents can be used alone or in combination of two or more. Further, the varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 20% by mass.

  The varnish can be prepared by mixing and stirring the above resin, filler, solvent, and if necessary, an ultraviolet absorber and other additives. For example, a reaction solution of a polyimide-based resin or a polyamide-based resin obtained by reacting the above dicarboxylic acid compound, tetracarboxylic acid compound, and / or diamine compound, and the other raw materials described above, with a solvent and optionally another The varnish may be prepared by mixing and stirring with the additives. A varnish may be prepared by isolating the polyimide-based resin or the polyamide-based resin from the reaction solution and mixing with a solvent or the like, or purchasing a solution or a solid of the polyimide-based resin or the polyamide-based resin, as necessary. The varnish may be prepared by mixing with a solvent or the like. When silica is used as the filler, a varnish may be prepared by using a silica sol in which a dispersion of a silica sol containing silica is replaced with a solvent in which the resin can be dissolved, for example, a solvent used for preparing a varnish described below. .

を満たすことが好ましい。ここで、ワニスの粘度（ｃｐｓ）は、ＪＩＳ Ｋ８８０３：２０１１に従い、Ｅ型粘度計を用いて、２５℃で測定される。また、ワニスの固形分濃度は、ワニスに含有される樹脂、フィラー及び添加剤等の濃度（質量％）を表し、ワニスの全質量に基づくワニスに含有される固形分の質量から算出される。上記式で表されるワニスの粘度とワニスの固形分濃度との積は、フィルムの光学的均質性を高めやすい観点から、好ましくは３，０００以上、より好ましくは３，５００以上である。上記式で表されるワニスの粘度とワニスの固形分濃度との積の上限は特に限定されないが、ワニスのハンドリングの観点からは、好ましくは１０，０００以下、より好ましくは７，０００以下である。 The viscosity (cps) of the varnish prepared as described above and the solid content concentration (% by mass) of the varnish are not particularly limited, but from the viewpoint of easily obtaining the film of the present invention having excellent homogeneity, these are the following. connection of:

It is preferable to satisfy the following. Here, the viscosity (cps) of the varnish is measured at 25 ° C. using an E-type viscometer according to JIS K8803: 2011. In addition, the solid content concentration of the varnish represents the concentration (% by mass) of the resin, filler, additive, and the like contained in the varnish, and is calculated from the mass of the solid content contained in the varnish based on the total mass of the varnish. The product of the viscosity of the varnish represented by the above formula and the solid content concentration of the varnish is preferably 3,000 or more, more preferably 3,500 or more, from the viewpoint of easily increasing the optical homogeneity of the film. The upper limit of the product of the viscosity of the varnish represented by the above formula and the solid content concentration of the varnish is not particularly limited, but from the viewpoint of varnish handling, is preferably 10,000 or less, more preferably 7,000 or less. .

  The viscosity of the varnish is preferably 5,000 to 60,000 cps, more preferably 10,000 to 50,000 cps, and still more preferably 15,000 to 45,000 cps. When the viscosity of the varnish is not less than the above lower limit, the effects of the present invention can be easily obtained, and it is preferable that the viscosity is not more than the above upper limit from the viewpoint of easy handling of the varnish.

  The solid content concentration of the varnish is preferably 5 to 25% by mass, more preferably 7 to 23% by mass, and still more preferably 9 to 20% by mass. It is preferable from the viewpoint of obtaining a thick film thickness that the solid content concentration of the varnish is equal to or higher than the above lower limit, and is preferably equal to or lower than the above upper limit from the viewpoint of easy handling of the varnish.

  Examples of the support include a resin substrate, a stainless steel belt, and a glass substrate. It is preferable to use a resin film substrate as the support. Examples of the resin film substrate include a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a cycloolefin (COP) film, an acrylic film, a polyimide film, and a polyamideimide film. Above all, a PET film, a COP film and the like are preferable from the viewpoint of excellent smoothness and heat resistance, and a PET film is more preferable from the viewpoint of adhesion to an optical film and cost.

  The thickness of the support is not particularly limited, but is preferably 50 to 250 μm, more preferably 100 to 200 μm, and still more preferably 150 to 200 μm. It is preferable that the thickness of the support is equal to or less than the above upper limit because the production cost of the film can be easily reduced. Further, it is preferable that the film thickness of the support is equal to or more than the above lower limit, since curling of the film which may occur in the step of removing at least a part of the solvent is easily suppressed. Here, the thickness of the support is measured by a contact-type thickness gauge or the like. From the viewpoint of improving the surface quality of the film and easily manufacturing the optical film of the present invention, the thickness distribution of the support is preferably ± 3 μm or less, more preferably ± 2.5 μm or less, and still more preferably ± 2 μm or less. is there. According to the thickness measurement method described above, the thickness of the support is measured at least at 20 locations of the film, the average thickness at the 20 locations is calculated, and the difference between the thickness at each location and the average thickness is determined. Is calculated from

  When applying the varnish to the support, the varnish may be applied to the support by a known coating method. Known coating methods include, for example, wire bar coating, reverse coating, roll coating such as gravure coating, die coating, comma coating, lip coating, spin coating, screen coating, fountain coating, dipping, A spray method, a salivation molding method and the like can be mentioned.

Next, the coating film can be formed by drying the coating film of the varnish applied on the support. Drying is performed by removing at least a part of the solvent from the varnish coating film, and the drying method is not particularly limited. For example, drying may be performed by heating a varnish coating film applied on the support. Hereinafter, the drying in the step (a) is also referred to as “first drying”, and the coating film formed on the support after drying is also referred to as “dry coating film”. The dried coating film may be a coating film in which the solvent contained in the varnish is completely dried, or may be a coating film in a semi-dry state in which a part of the solvent is dried. The first drying may be performed under an inert atmosphere or under reduced pressure, if necessary. The first drying is preferably performed at a relatively low temperature over a long period of time. When the first drying is performed at a relatively low temperature for a long time, the values of Y _mh and Y _mv in the above equation are easily reduced, and the value of (Y _mh + Y _mv ) / (X _mh + X _mv ) ^1/2 is reduced. It is easy to decrease and it is easy to increase the optical homogeneity of the optical film. When drying by heating, the heating temperature in the first drying is preferably 50 to 150 ° C, more preferably 60 to 130 ° C, and further preferably 70 to 120 ° C. The time for the first drying is preferably 5 to 60 minutes, more preferably 10 to 40 minutes. The first drying may be performed under one-step or multi-step conditions. When drying is carried out under multi-stage conditions, preferably, in each stage, drying can be carried out under the same or different temperature conditions and / or drying times, for example, 2 to 10 stages, preferably 3 to 8 stages Drying may be performed under the following conditions. When the first drying is performed in a multi-stage condition, it is easy to increase the optical homogeneity of the optical film. In a preferred embodiment of the present invention in which the first drying is performed under three or more stages of multi-stage conditions, it is preferable that the temperature profile of the first drying includes a temperature increase and a temperature decrease. As an example of such a temperature profile, in the case of four stages, the first drying temperature is 70 to 90 ° C. (first temperature), 90 to 120 ° C. (second temperature), and 80 to 120 ° C. ° C (third temperature) and 80 to 100 ° C (fourth temperature). In this example, the first drying temperature increases from the first temperature to the second temperature, then decreases from the second temperature to the third temperature, and further decreases from the third temperature to the fourth temperature. Cool down. Here, the first drying time is, for example, 5 to 15 minutes in each stage. The first drying is preferably performed so that the residual amount of the solvent in the dried coating film is preferably 5 to 15% by mass, more preferably 6 to 12% by mass, based on the mass of the dried coating film. Lowering the solvent remaining amount is within the above range, tends to reduce the value of _{Y mh} and _{Y mv} in the above formula of the optical _film, the value of _{(Y mh + Y mv) /} (X mh + X mv) 1/2 Easy to make. Further, in the subsequent step (b), it is easy to enhance the releasability when the coating film is peeled from the support. As a result, it is easy to increase the homogeneity of the optical film. The residual amount of the solvent is reduced by increasing the drying temperature in each step and increasing the drying time. Therefore, the drying temperature and the drying time are adjusted so that the amount of the remaining solvent is within a desired range, and the homogeneity of the optical film can be improved.

  Next, in the step (b), the dried coating film is peeled from the support. The peeling method is not particularly limited, and the peeling may be performed by moving the coating in a state where the support is fixed, or the peeling may be performed by moving the support in a state where the coating is fixed. The peeling may be performed by moving both the coating film and the support.

Next, in the step (c), the film of the present invention can be obtained by heating the coating film peeled off in the step (b). The heating step in the step (c) is hereinafter also referred to as “second drying” or “post-baking”, and the coating film peeled in the step (b) is hereinafter also referred to as “peeling coating film”. In the step (c), it is preferable to perform post-baking in a state where the release coating is stretched in the in-plane direction. The heating temperature at the time of the second drying is preferably 150 to 300 ° C, more preferably 180 to 250 ° C, and still more preferably 180 to 230 ° C. The heating time in the second drying is preferably 10 to 60 minutes, more preferably 30 to 50 minutes. When the post-baking treatment is performed in a state where the dried coating film is uniformly stretched in the in-plane direction, the values of Y _mh and Y _mv in the above formula of the optical film are easily reduced, and (Y _mh + Y _mv ) / (X _mh + _Xmv ) ^1/2 is easily reduced.

When heating the coating film in the step (3), it is preferable to apply the tension to the coating film and perform the heating in a state where the coating film is stretched in the in-plane direction. By heating while applying tension, tends to suppress a decrease in the optical homogeneity of the optical film obtained by shrinkage of the coating film by drying, so that the value of Y _mh and Y _mv in the above formula of the optical film tends to _{lower, (Y mh + Y mv)} / (X mh + X mv) tends to reduce the ^half value, the homogeneity of the optical film, particularly susceptible enhance optical homogeneity.

  In one embodiment of the present invention, when producing an optical film by a roll-to-roll method, the release coating may be dried while being stretched in the transport direction. When the optical film is manufactured in a single-wafer manner, the optical film may be dried while being uniformly stretched in the in-plane direction. The transport speed in the roll-to-roll system is preferably from 0.1 to 5 m / min, more preferably from 0.5 to 3 m / min, from the viewpoint of easily improving the homogeneity of the obtained optical film, particularly the optical homogeneity. And more preferably 0.7 to 1.5 m / min.

  For example, when an optical film is manufactured by a roll-to-roll method, the optical film of the present invention can be obtained by heating a long strip-shaped coating film having a predetermined width while transporting the coating film. Here, when heating is performed while applying tension to the coating film, the method is not limited at all, for example, gripping both ends of a long strip-shaped film to be transported, and gripping while transporting the gripped film. The heat treatment is performed while, for example, the inside of the dryer is conveyed with the width of the applied film being a predetermined distance. At this time, the ratio of the width of the film after the heat treatment (but not including the grip portion) to the width of the film before the heat treatment (however, the grip portion is not included in the width) is 1.1 or less, and The step (3) is preferably performed by releasing the holding of the resin film coming out of the dryer.

  The ratio of the width of the film after the heat treatment (however, not including the gripping portion) to the width of the film before the heat treatment (however, not including the gripping portion) (hereinafter, sometimes referred to as a draw ratio) is preferable. Is 0.70 to 1.10, more preferably 0.8 to 1.05, and still more preferably 0.80 to 1.00.

The holding of the film is performed, for example, by using a plurality of clips.
The plurality of clips can be fixed to an endless chain of a predetermined length depending on the size of the transport device, and the chain moves at the same speed as the film, and the clips are placed at appropriate positions on the chain. It is installed and grips the transparent resin film before entering the dryer, and the grip is released when it leaves the dryer.

  The plurality of clips installed at one end of the film are installed such that the space between adjacent clips is, for example, 1 to 50 mm, preferably 3 to 25 mm, and more preferably 5 to 10 mm.

  Also, when a straight line perpendicular to the film transport axis is aligned with the center of the grip portion of an arbitrary clip at one end of the film, the intersection of the straight line and the other end of the film and the center of the grip portion of the clip closest to the intersection point. Is preferably 3 mm or less, more preferably 2 mm or less, and still more preferably 1 mm or less. When the distance is within the above range, the homogeneity of the optical film, particularly on the left and right sides, can be easily increased.

  When the ratio of the width of the film after heat treatment to the width of the film before heat treatment is in the above range, the appearance of the film tends to be good.

The amount of the solvent in the film after the heat treatment is preferably 0.001 to 3% by mass, more preferably 0.001 to 2% by mass, and still more preferably 0.001 to 1.5% by mass, based on the mass of the film. And particularly preferably 0.001 to 1.3% by mass. When the amount of the solvent in the film after the heat treatment is in the above range, the appearance of the optical film tends to be good.
When the heat treatment is over and the film comes out of the dryer, the grip of the film is released and, preferably, immediately the film edge is slit. By performing the slit, by removing the cracks that are likely to occur between the gripping portion and the portion that was not gripped from the film at the edge of the film, the film is transported thereafter, and the temperature of the film decreases due to the temperature drop. The spread of cracks can be prevented in advance.

When the film exits the dryer, the film is quenched and shrinks, which can cause cracking. Therefore, it is preferable that there is a step of relaxing a certain percentage of the film from the outlet of the dryer to the position where the gripping of the film is released. The ratio is preferably the width (W) of the film coming out of the dryer (however, excluding the gripped width) (W) and the distance (F) at which the grip is relaxed until the film is opened from the dryer outlet. 1.7 ≦ F / W × 100 ≦ 6.9, more preferably 1.8 ≦ F / W × 100 ≦ 6.8, even more preferably 1.9 ≦ F / W × 100 ≦ 6. 7, even more preferably 2.0 ≦ F / W × 100 ≦ 6.7.
The relaxed distance at one end with respect to the transport direction of the film is Fa, the relaxed distance at the other end is Fb, and the combined relaxed distance is F.
The distance from the dryer outlet to the release of the grip of the film is preferably 200 to 1,000 mm, more preferably 300 to 900 mm, and still more preferably 300 to 800 mm. When the distance is in the above range, the film is less likely to crack and poor appearance such as dripping tends to be less likely to occur.

In the production method of the present invention, from the viewpoint of easily producing an optical film having the above characteristics, after the coating film is peeled from the support in the step (b), the peeled coating film is heated in the step (c). By doing so, films are manufactured. However, the optical film of the present invention may be a film produced by any production method as long as it has the above-mentioned features relating to Y _{mh and the} like. For example, it may be manufactured by post-baking the coating film before peeling the coating film from the support, and peeling the post-baked film from the support.

The production method of the present invention may further include a step (d) of evaluating a film described later, after the steps (a) to (c). In the step (d), a line profile in a direction h and a line profile v in a direction v orthogonal to each other in a film inverse aerial image obtained by performing a Fourier transform on a projection image obtained by a projection method using the obtained film are respectively a line profile h and a line As the profile v, the line profiles in the directions h ′ and v ′ orthogonal to each other in the background inverse aerial image obtained by Fourier transforming the background image obtained without using the film in the projection method are line profiles h ′ and h, respectively. The line profile v ′, the maximum intensity of the line profile (h−h ′) obtained by subtracting the line profile h ′ from the line profile h is Y _mh , the frequency indicating the maximum intensity Y _mh is X _mh , and the line profile v From the line profile (v The maximum intensity of the -v ') and _{Y mv,} calculates the frequency showing the maximum intensity _{Y mv} when the _{X mv,} the value of _{Y mh} and _{Y mv, and,} from the Y _mh, Y mv, _{X mh} and _{X mv} This is a step of evaluating the film based on the (Y _mh + Y _mv ) / (X _mh + X _mv ) ^1/2 value obtained.

In step (d), the homogeneity of the film, especially the optical homogeneity, is evaluated based on the values of Y _mh and Y _{mv and} the value of (Y _mh + Y _mv ) / (X _mh + X _mv ) ^1/2. be able to. For example, a predetermined value is set according to the required homogeneity, and the value is compared with the result obtained for the film to judge the quality of the film. By separating the film, Y _mh and Y _{mv are determined.} And the value of (Y _mh + Y _mv ) / (X _mh + X _mv ) ^1/2 are equal to or less than a predetermined value, and an optical film having excellent homogeneity can be produced. In addition, while evaluating the above values, the drying conditions and the like are adjusted, and the film of the present invention having the above characteristics can be produced.

In assessing the film (d), based on the maximum intensity Y _mh and Y _mv measured by the evaluation method of the present invention, to evaluate the homogeneity of the films, it is possible to determine the quality of the quality of the film, It is preferable from the viewpoint that a film having excellent homogeneity can be efficiently produced. The criterion for determining the quality of the film may be appropriately set according to the use of the manufactured film and the optical homogeneity required for the film, and is not particularly limited. Preferably used in optical films and the like, when determining the quality of the film for the purpose of obtaining a film having excellent homogeneity, whether the film of the present invention has the properties described above or not It is preferable to judge the quality of the film on the basis of.

According to the above evaluation step, it is possible to evaluate the homogeneity of the film, particularly the optical homogeneity, with higher accuracy than the conventional evaluation method. More specifically, according to the evaluation process, the optical characteristics caused by unevenness in both the TD direction and the MD direction and unevenness in width, which cannot be evaluated with sufficient accuracy by the conventional evaluation method, It is possible to evaluate variations in physical properties and / or physical properties, and it is possible to accurately evaluate the uniformity of a film regardless of the type of unevenness. In addition, the homogeneity of the film can be quantified by the evaluation step. Specifically, the evaluation step in the step (d) includes the following steps (1) to (5):
(1) a step of irradiating a film with light from a light source and obtaining a projection image by a projection method of projecting light transmitted through the film onto a projection surface;
(2) a step of projecting light from a light source onto a projection surface without using a film in the projection method of step (1) to obtain a background image;
(3) The projection image obtained in the step (1) and the background image obtained in the step (2) are respectively converted into numerical values by gray scale conversion, and the numerically converted image data is subjected to Fourier transform to obtain an inverse aerial image (film inverse aerial image) And a background inverse aerial image).
(4) a step of obtaining a blank-corrected line profile by subtracting the line profiles in the two directions orthogonal to each other in the inverse space image of the background image from the line profiles in the two directions orthogonal to each other in the inverse space image of the projection image. ,
as well as,
(5) At least a step of measuring the maximum intensity (Y _mh and Y _mv ) of the blank-corrected line profile obtained in the step (4).

  In step (1), a film is irradiated with light from a light source, and the light transmitted through the film is projected on a projection surface to obtain a projected image. In the step (1), for example, a film, a projection surface, and the like may be arranged as shown in FIG. Specifically, the light source 1, the film 2, and the projection surface 3 are arranged, and a projection image 4 projected on the projection surface 3 is photographed by the camera 6 to obtain a projection image. The light 5 output from the light source 1 passes through the film 2, and the transmitted light is projected on the projection surface 3 as a projection image 4. When the light 5 transmits through the film 2, if the film 2 is homogeneous, the light 5 uniformly transmits through the film 2 and reaches the projection surface 3, but the film 2 is not uniform and has uneven surface, uneven thickness, and orientation. When there is unevenness or the like, the light 5 undergoes reflection and / or refraction when transmitted through the film 2, and the light that is distorted as compared with the state output from the light source reaches the projection surface 3. By evaluating the projection image 4 thus obtained by a method described later, the optical homogeneity of the film can be evaluated or quantified with high accuracy. From the viewpoint of easily obtaining a clear projected image, it is preferable to shoot only a light from a light source through a film in a dark room. The type of the light source is not particularly limited, and for example, an LED light source or a halogen lamp may be used. A light source close to a point light source is preferable, and the light emitting portion preferably has a diameter of 1 cm or less. Since the projected image tends to be unclear when passing through a filter or a lens, light that does not pass through the filter or the lens is preferable. The projection surface is not particularly limited as long as the projected image of the film is visually recognized. For example, an acrylic plate, a vinyl chloride plate, a polyethylene plate, a movie screen, or the like may be used. The method of photographing the image projected on the projection surface is not particularly limited. For example, as shown in FIG. 1, the projection surface 3, the film 2, and the light source 1 are arranged on a straight line, and the projection projected on the projection surface 3 is performed. The camera 6 may be fixed at a position where the image 4 is photographed obliquely and photographed. The shooting mode may be appropriately set, for example, a setting as described in the embodiment may be used. Thus, a projection image is obtained.

  In step (2), light from a light source is projected onto a projection surface without using a film in the projection method of step (1) to obtain a projected image. Specifically, for example, in FIG. 1, shooting is performed with only the film 2 removed, and a background image is obtained.

  In the step (3), the projection image obtained in the step (1) and the background image obtained in the step (2) are respectively converted into numerical values by gray scale conversion, and the numerically converted image data is subjected to Fourier transform to obtain an inverse space image. . The gray scale can be converted into, for example, 8-bit gray scale using image analysis software (for example, “Image-J” manufactured by the National Institutes of Health, USA). By the gray scale, the projection image and the background image can be digitized. Next, Fourier transform is performed on the digitized image data to obtain an inverse aerial image (film inverse aerial image and background inverse aerial image). By performing the Fourier transform on the digitized image data, it is possible to obtain the period and amplitude of the density of the image. As a Fourier transform method, for example, a Fourier transform function of image analysis software (Image-J) is used.

  In the step (4), the line profiles in the two directions orthogonal to each other in the inverse aerial image of the background image are subtracted from the line profiles in the two directions orthogonal to the inverse aerial image of the projection image, respectively. Get.

In step (5), the maximum intensity Y _max (Y _mh and Y _mv , respectively) of the blank-corrected line profile obtained in step (4) is measured. The method for measuring Y _mh and Y _mv is as described above for the film of the present invention. For example, for each of the horizontal direction (h1 direction) and the vertical direction (v1 direction) passing through the center of the inverse aerial image. When a line profile is created, for example, as shown in FIG. 3, the graph is shown as a graph representing frequency on the X axis and intensity on the Y axis. The maximum intensity Y _max in the line profile in the horizontal direction (h1 direction) is _defined as Y _mh1, and X is a value obtained by subtracting the median value X _cen of all frequencies in the blank-corrected line profile from the frequency indicating the maximum intensity Y _mh1. Let _max be X _mh1 . Further, the maximum intensity Y _max in the line profile in the vertical direction (v1 direction) is _defined as Y _mv1, and the value X is a value obtained by subtracting the median value X _cen of all the frequencies in the blank-corrected line profile from the frequency indicating the maximum intensity Y _mv1. Let _max be X _mv1 . The two directions are not particularly limited as long as they are orthogonal to each other, and may be two directions that do not pass through the center, and may not be the horizontal and vertical directions.

By measuring the Y _mh and Y _mv, it is possible to evaluate the homogeneity in two-dimensional direction of the film. The surface unevenness that contributes to lowering the optical homogeneity of the film includes, for example, unevenness of a type that cannot be sufficiently detected by one-dimensional evaluation, such as striped unevenness. According to the evaluation method of the present invention, since the optical homogeneity can be evaluated in the two-dimensional direction, the evaluation can be performed with high accuracy regardless of the type of film unevenness. Further, by measuring the above Y _mh and Y _mv and obtaining the values, it is possible to quantify the homogeneity of the film.

Furthermore, in addition to the maximum intensity Y _mh and Y _mv, using the X _mh and X _mv is a value obtained by subtracting the median value X _cen all frequencies in the blank-corrected line profile from the frequency showing these maximum intensity By performing the evaluation, it is also possible to detect a cycle in which the surface unevenness which contributes to the optical homogeneity of the film occurs.

  In the case where the optical film of the present invention has a multilayer structure, the production method of the present invention may be arranged such that the film obtained in the step (c) includes at least one functional layer or the like between the steps (c) and (d). May be included, or after the step (d), a step of laminating at least one type of functional layer or the like on the film may be included.

<Layer configuration>
The optical film of the present invention and the optical film manufactured by the manufacturing method of the present invention include a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more, and a filler having an average primary particle diameter of 5 to 35 nm. As long as it includes, it may be a single layer or a multilayer laminate. When the optical film of the present invention is a multilayer laminate, the laminate has at least one layer containing both the resin and the filler. The optical film of the present invention is a single layer containing both the resin and the filler, and has a value of Y _mh and Y _{mv and} a value of (Y _mh + Y _mv ) / (X _mh + X _mv ) ^1/2 . The value may be within the above-mentioned predetermined range, or a laminate having at least one layer containing both the resin and the filler and having at least one functional layer laminated on the layer. in the state of the _body, the value of _{Y mh} and _{Y mv,} and _{(Y mh + Y mv) /} (X mh + X mv) 1/2 values may be in the range of the predetermined. Hereinafter, the optical film of the present invention having a multilayer structure in which another layer such as at least one functional layer is laminated on the optical film of the present invention is also referred to as an “optical laminate”.

<Optical laminate>
The optical film of the present invention is an optical laminate having a multilayer structure in which at least one layer containing both the resin and the filler is included, and at least one surface of the layer is laminated with at least one functional layer. Is also good. Examples of the functional layer include an ultraviolet absorbing layer, a hard coat layer, an adhesive layer, a hue adjusting layer, a refractive index adjusting layer, a primer layer, and a gas barrier layer. The functional layers can be used alone or in combination of two or more. When measuring various physical properties, it is preferable to measure the optical film of the present invention alone (in a single layer state) rather than the optical laminate.

  The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet light, for example, a main material selected from an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, and And a dispersed ultraviolet absorber.

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

  The pressure-sensitive adhesive layer may be a layer called a pressure-sensitive adhesive (Pressure Sensitive Adhesive, PSA), which is attached to an object by pressing. The pressure-sensitive adhesive may be a pressure-sensitive adhesive that is “a substance that is tacky at room temperature and adheres to an adherend with light pressure” (JIS K6800), and “a protective film (microcapsule) containing a specific component”. And an adhesive capable of maintaining stability until the film is broken by an appropriate means (pressure, heat, etc.) (JIS K6800).

  The hue adjustment layer is a layer having a hue adjustment function, and is a layer that can adjust the optical laminate to a target hue. The hue adjustment layer is, for example, a layer containing a resin and a colorant. As the coloring agent, for example, titanium oxide, zinc oxide, red iron oxide, titanium oxide-based baked pigment, ultramarine, cobalt aluminate, inorganic pigments such as carbon black; azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, Organic pigments such as perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, sulene compounds, and diketopyrrolopyrrole compounds; extender pigments such as barium sulfate and calcium carbonate; and basic dyes; Dyes such as acid dyes and mordant dyes can be mentioned.

  The refractive index adjustment layer is a layer having a function of adjusting the refractive index, for example, has a different refractive index from the layer containing both the resin and the filler, it is possible to impart a predetermined refractive index to the optical laminate Layer. The refractive index adjustment layer may be, for example, a resin layer containing an appropriately selected resin and optionally a pigment, or may be a metal thin film. Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle size of the pigment may be 0.1 μm or less. When the average primary particle diameter of the pigment is 0.1 μm or less, irregular reflection of light passing through the refractive index adjusting layer can be prevented, and a decrease in transparency can be prevented. Examples of the metal used for the refractive index adjustment 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 are mentioned.

  In a preferred embodiment of the present invention, the optical film has a hard coat layer on at least one surface (one or both surfaces) of the layer containing the resin and the filler. When a hard coat layer is provided on both sides, the two hard coat layers may contain the same or different components.

  Examples of the hard coat layer include known hard coat layers such as acrylic, epoxy, urethane, benzyl chloride, and vinyl. Among these, from the viewpoint of suppressing a decrease in visibility in the wide angle direction of the optical film and improving the bending resistance, a hard coat layer of an acrylic type, a urethane type, or a combination thereof can be preferably used. The hard coat layer is preferably a cured product of a curable composition containing a curable compound, and is formed by polymerizing the curable compound by irradiation with active energy rays. Examples of the curable compound include a polyfunctional (meth) acrylate compound. The polyfunctional (meth) acrylate-based compound is a compound having at least two (meth) acryloyl groups in a molecule.

  Examples of the polyfunctional (meth) acrylate compound include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, Methylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaglycerol tri (meth) acrylate, pentaerythritol tri (meth) acrylate Pentaerythritol tetra (meth) acrylate, glycerin tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol Tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tris ((meth) acryloyloxyethyl) isocyanurate; (meth) acryloyl group introduced into phosphazene ring of phosphazene compound Phosphazene-based (meth) acrylate compound; urethane (meth) acrylate obtained by reacting a polyisocyanate having at least two isocyanate groups in a molecule with a polyol compound having at least one (meth) acryloyl group and a hydroxyl group Compounds: polyester (meth) amines obtained by reacting at least two carboxylic acid halides in the molecule with at least one polyol compound having a (meth) acryloyl group and a hydroxyl group. Relate compound; and dimer of each compound, and the like oligomers, such as trimers. These compounds are used alone or in combination of two or more.

  The curable compound may include a monofunctional (meth) acrylate compound in addition to the above polyfunctional (meth) acrylate compound. Examples of the monofunctional (meth) acrylate compound include hydroxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and 2-hydroxy-3. -Phenoxypropyl (meth) acrylate, glycidyl (meth) acrylate and the like. These compounds are used alone or in combination of two or more. The content of the monofunctional (meth) acrylate compound is preferably 10% by mass or less, when the solid content of the compound contained in the curable composition is 100% by mass. In addition, in this specification, a solid content means all components except the solvent contained in a curable composition.

  Further, the curable compound may contain a polymerizable oligomer. By including the polymerizable oligomer, the hardness of the hard coat layer can be adjusted. As the polymerizable oligomer, terminal (meth) acrylate polymethyl methacrylate, terminal styryl poly (meth) acrylate, terminal (meth) acrylate polystyrene, terminal (meth) acrylate polyethylene glycol, terminal (meth) acrylate acrylonitrile-styrene copolymer, terminal Macromonomers such as (meth) acrylate styrene-methyl (meth) acrylate copolymer can be exemplified. The content of the polymerizable oligomer is preferably 5 to 50% by mass when the solid content of the compound contained in the curable composition is 100% by mass.

  The curable composition for forming the hard coat layer may contain an additive in addition to the polyfunctional (meth) acrylate compound and the polymerizable oligomer. Examples of the additive include a polymerization initiator, silica, a leveling agent, a solvent, and the like. Examples of the solvent include methyl ethyl ketone and polypropylene glycol monomethyl ether.

  The thickness of the hard coat layer is preferably 3 to 30 μm, more preferably 5 to 25 μm, and still more preferably 5 to 20 μm, from the viewpoint of improving the hardness, bending resistance and visibility of the optical film.

<Protective film>
A protective film may be laminated on the optical film of the present invention. The protective film may be laminated on one side or both sides of the optical film. When the optical film of the present invention has a functional layer on one side of the layer containing both the resin and the filler, the protective film is provided on the surface on the layer side or the functional layer side containing both the resin and the filler. They may be laminated, or may be laminated on both surfaces. When the optical film has functional layers on both sides of the layer containing both the resin and the filler, the protective film may be laminated on one functional layer side surface, and both functional layer side surfaces May be laminated. The protective film is a film for temporarily protecting the surface of the optical film or the functional layer, and is not particularly limited as long as it is a peelable film that can protect the surface of the optical film or the functional layer. Examples of the protective film include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resin films such as polyethylene and polypropylene films, and acrylic resin films. Polyolefin resin films, polyethylene It is preferably selected from the group consisting of a terephthalate resin film and an acrylic resin film. When two protective films are laminated on the optical film of the present invention, each protective film may be the same or different.

  The thickness of the protective film is not particularly limited, but is usually 10 to 120 µm, preferably 15 to 110 µm, more preferably 20 to 100 µm. When two protective films are laminated on the optical film of the present invention, the thickness of each protective film may be the same or different.

<Flexible display device>
The present invention also provides a flexible display device including the optical film. The optical film of the present invention is preferably used as a front plate in a flexible display device, and the front plate may be referred to as a window film. The flexible display device includes a laminate for a flexible display device and an organic EL display panel. The laminate for a flexible display device is arranged on the viewing side with respect to the organic EL display panel, and is configured to be bendable. The laminate for a flexible display device may further contain a polarizing plate, preferably a circularly polarizing plate, and a touch sensor, and the order of stacking them is arbitrary. Alternatively, a window film, a touch sensor, and a polarizing plate are preferably stacked in this order. The presence of the polarizing plate on the viewing side relative to the touch sensor is preferable because the pattern of the touch sensor is hardly viewed and the visibility of the displayed image is improved. Each member can be laminated using an adhesive, a pressure-sensitive adhesive or the like. Further, it may include a light-shielding pattern formed on at least one surface of any of the layers of the window film, the polarizing plate, and the touch sensor.

<Circularly polarizing plate>
As described above, the flexible display device of the present invention preferably includes a polarizing plate, especially a circular polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only right or left circularly polarized light components by laminating a λ / 4 retardation plate on a linearly polarizing plate. For example, by converting external light into right-handed circularly polarized light, the external light reflected by the organic EL panel and turned into left-handed circularly polarized light is blocked, and only the luminescent component of the organic EL is transmitted, thereby suppressing the influence of the reflected light to reduce the image. Used to make it easier to see. In order to achieve the circular polarization function, the absorption axis of the linear polarizing plate and the slow axis of the λ / 4 retardation plate need to be 45 ° theoretically, but practically 45 ± 10 °. The linear polarizing plate and the λ / 4 retardation plate do not necessarily have to be stacked adjacent to each other, as long as the relationship between the absorption axis and the slow axis satisfies the above range. It is preferable to achieve perfect circularly polarized light at all wavelengths, but this is not always necessary in practical use. Therefore, the circularly polarizing plate in the present invention includes an elliptically polarizing plate. It is also preferable to further laminate a λ / 4 retardation film on the viewing side of the linear polarizing plate and to make the outgoing light circularly polarized so as to improve the visibility in a state where polarized sunglasses are worn.

  The linear polarizing plate is a functional layer having a function of transmitting light vibrating in the transmission axis direction, but blocking polarization of a vibration component perpendicular to the light. The linear polarizing plate may have a configuration including a linear polarizer alone or a linear polarizer and a protective film attached to at least one surface thereof. The thickness of the linear polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness of the linearly polarizing plate is in the above range, the flexibility of the linearly polarizing plate tends to hardly decrease.

The linear polarizer may be a film-type polarizer manufactured by dyeing and stretching a polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) film. A dichroic dye such as iodine is adsorbed on a PVA-based film oriented by stretching or stretched in a state of being adsorbed on PVA, whereby the dichroic dye is oriented and exhibits polarizing performance. In the production of the film-type polarizer, other steps such as swelling, crosslinking with boric acid, washing with an aqueous solution, and drying may be included. The stretching and dyeing steps may be performed on the PVA-based film alone, or may be performed on a laminate with another film such as polyethylene terephthalate. The thickness of the PVA-based film used is preferably 10 to 100 μm, and the stretching ratio is preferably 2 to 10 times.
Another example of the polarizer is a liquid crystal-coated polarizer formed by applying a liquid crystal polarizing composition. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic dye compound. The liquid crystal compound only needs to have a property of exhibiting a liquid crystal state, and particularly preferably has a higher order alignment state such as a smectic phase because high polarization performance can be exhibited. Further, the liquid crystal compound preferably has a polymerizable functional group.
The dichroic dye compound is a dye that exhibits dichroism when aligned with the liquid crystal compound, and may have a polymerizable functional group, and the dichroic dye itself has liquid crystallinity. May be.
Any of the compounds contained in the liquid crystal polarizing composition has a polymerizable functional group. The liquid crystal polarizing composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like.
The liquid crystal polarizing layer is manufactured by applying a liquid crystal polarizing composition on an alignment film to form a liquid crystal polarizing layer. The liquid crystal polarizing layer can be formed to be thinner than the film type polarizer, and the thickness is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.

The alignment film is manufactured by, for example, applying an alignment film forming composition on a substrate and imparting the alignment by rubbing, polarized light irradiation, or the like. The composition for forming an alignment film includes an alignment agent, and may further include a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like. Examples of the aligning agent include polyvinyl alcohols, polyacrylates, polyamic acids, and polyimides. When using an aligning agent that imparts orientation by polarized light irradiation, it is preferable to use an aligning agent containing a cinnamate group. The weight average molecular weight of the polymer used as the alignment agent is, for example, about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000 nm, and more preferably 10 to 500 nm from the viewpoint that the alignment regulating force is sufficiently exhibited.
The liquid crystal polarizing layer can be peeled off from the substrate and transferred and laminated, or the substrate can be laminated as it is. It is also preferable that the base material plays a role as a transparent base material for a protective film, a retardation plate, or a window film.

  The protective film may be any transparent polymer film, and the same materials and additives as those used for the transparent substrate of the window film can be used. Further, a coating type protective film obtained by applying and curing a cationically curable composition such as an epoxy resin or a radically curable composition such as an acrylate may be used. The protective film may be, if necessary, a plasticizer, an ultraviolet absorber, an infrared absorber, a coloring agent such as a pigment or a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, and an antioxidant. , A lubricant, a solvent, and the like. The thickness of the protective film is preferably 200 μm or less, more preferably 1 to 100 μm. When the thickness of the protective film is in the above range, the flexibility of the film tends to hardly decrease.

The λ / 4 phase difference plate is a film that gives a λ / 4 phase difference in a direction (in-plane direction of the film) perpendicular to the traveling direction of the incident light. The λ / 4 retardation plate may be a stretched retardation plate manufactured by stretching a polymer film such as a cellulose film, an olefin film, and a polycarbonate film. The λ / 4 retardation plate may include a retardation adjuster, a plasticizer, an ultraviolet absorber, an infrared absorber, a colorant such as a pigment or a dye, a fluorescent brightener, a dispersant, a heat stabilizer, and a light stabilizer, if necessary. Agents, antistatic agents, antioxidants, lubricants, solvents and the like.
The thickness of the stretch type retardation plate is preferably 200 μm or less, more preferably 1 to 100 μm. When the thickness of the stretched retardation film is in the above range, the flexibility of the stretched retardation film tends to be hardly reduced.
Another example of the λ / 4 retardation plate is a liquid crystal-coated retardation plate formed by applying a liquid crystal composition.
The liquid crystal composition contains a liquid crystal compound exhibiting a liquid crystal state such as nematic, cholesteric, or smectic. The liquid crystal compound has a polymerizable functional group.
The liquid crystal composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like.
The liquid crystal coating type retardation plate can be manufactured by applying and curing a liquid crystal composition on a base to form a liquid crystal retardation layer, similarly to the liquid crystal polarizing layer. The liquid crystal coating type retarder can be formed to be thinner than the stretch type retarder. The thickness of the liquid crystal polarizing layer is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.
The liquid crystal-coated retardation plate can be peeled off from the substrate and transferred to be laminated, or the substrate can be laminated as it is. It is also preferable that the base material plays a role as a transparent base material for a protective film, a retardation plate, or a window film.

In general, there are many materials exhibiting a large birefringence at a short wavelength and a small birefringence at a long wavelength. In this case, since a phase difference of λ / 4 cannot be achieved in the entire visible light region, the in-plane phase difference is preferably from 100 to λ / 4 near 560 nm where visibility is high. It is designed to be 180 nm, more preferably 130 to 150 nm. An inverse dispersion λ / 4 retardation plate using a material having a wavelength dispersion characteristic of a birefringence opposite to that of a normal one is preferable in that visibility is improved. As such a material, for example, a stretching type retarder described in JP-A-2007-232873 and a liquid crystal coating type retarder described in JP-A-2010-30979 can be used. .
As another method, a technique of obtaining a broadband λ / 4 phase difference plate by combining with a λ / 2 phase difference plate is also known (for example, Japanese Patent Application Laid-Open No. 10-90521). The λ / 2 retardation plate is also manufactured by the same material method as the λ / 4 retardation plate. The combination of the stretching type retardation plate and the liquid crystal coating type retardation plate is optional, but both can be reduced in thickness by using the liquid crystal coating type retardation plate.
There is known a method of laminating a positive C plate on the circularly polarizing plate in order to increase the visibility in an oblique direction (for example, Japanese Patent Application Laid-Open No. 2014-224837). The positive C plate may be a liquid crystal coating type retardation plate or a stretch type retardation plate. The retardation in the thickness direction of the retardation plate is preferably -200 to -20 nm, more preferably -140 to -40 nm.

<Touch sensor>
As described above, the flexible display device of the present invention preferably includes a touch sensor. The touch sensor is used as an input unit. Examples of the touch sensor include various types such as a resistive film type, a surface acoustic wave type, an infrared type, an electromagnetic induction type, and a capacitance type, and preferably a capacitance type.
The capacitive touch sensor is divided into an active area and a non-active area located outside the active area. The active area is an area corresponding to an area (display unit) where a screen is displayed on the display panel, and is an area where a user's touch is sensed, and the inactive area is an area where the screen is not displayed on the display device (non-display area). Display area). The touch sensor is formed on a substrate having flexible characteristics, a sensing pattern formed on an active region of the substrate, and an inactive region of the substrate, and is connected to an external driving circuit through the sensing pattern and a pad unit. For each sensing line. The same material as the transparent substrate of the window film can be used as the substrate having flexible characteristics.

The sensing pattern may include a first pattern formed in a first direction and a second pattern formed in a second direction. The first pattern and the second pattern are arranged in directions different from each other. The first pattern and the second pattern are formed on the same layer, and must be electrically connected to each other in order to detect a touched point. The first pattern is a form in which a plurality of unit patterns are connected to each other via a joint, while the second pattern has a structure in which a plurality of unit patterns are separated from each other in an island form. A separate bridge electrode is required to make the connection. A well-known transparent electrode can be applied to the electrode for the connection of the second pattern. As a material of the transparent electrode, for example, indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium zinc tin oxide (IZTO), indium gallium zinc oxide (IGZO) , Cadmium tin oxide (CTO), PEDOT (poly (3,4-ethylenedioxythiophene)), carbon nanotube (CNT), graphene, metal wire, and the like, and preferably ITO. These can be used alone or in combination of two or more. The metal used for the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, terenium, and chromium. These may be used alone or in combination of two or more. Can be.
The bridge electrode may be formed on the insulating layer above the sensing pattern via an insulating layer. The bridge electrode is formed on the substrate, and the insulating layer and the sensing pattern may be formed thereon. The bridge electrode may be formed of the same material as the sensing pattern, and may be formed of molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium or an alloy of two or more of these. it can.
Since the first and second patterns must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the joint of the first pattern and the bridge electrode, or may be formed as a layer covering the entire sensing pattern. In the case of a layer that covers the entire sensing pattern, the bridge electrode can connect the second pattern through a contact hole formed in the insulating layer.

The touch sensor is induced by a difference in transmittance between a pattern region where a sensing pattern is formed and a non-pattern region where a sensing pattern is not formed, specifically, a difference in refractive index in these regions. As a means for appropriately compensating for the difference in light transmittance, an optical adjustment layer may be further included between the substrate and the electrode. The optical control layer may include an inorganic insulating material or an organic insulating material. The optical control layer can be formed by coating a photocurable composition containing a photocurable organic binder and a solvent on a substrate. The photocurable composition may further include inorganic particles. The refractive index of the optical control layer can be increased by the inorganic particles.
The photocurable organic binder includes, for example, a copolymer of each monomer such as an acrylate-based monomer, a styrene-based monomer, and a carboxylic acid-based monomer as long as the effects of the present invention are not impaired. be able to. The photocurable organic binder may be, for example, a copolymer containing different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.
Examples of the inorganic particles include zirconia particles, titania particles, and alumina particles.
The photocurable composition may further include additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

<Adhesive layer>
Each layer (window film, circular polarizer, touch sensor) forming the laminate for the flexible image display device and a film member (linear polarizer, λ / 4 retardation plate, etc.) forming each layer are bonded by an adhesive. Can be. Examples of the adhesive include a water-based adhesive, an organic solvent-based adhesive, a solvent-free adhesive, a solid adhesive, a solvent volatile adhesive, a moisture-curable adhesive, a heat-curable adhesive, an anaerobic-curable adhesive, and an active energy ray-curable adhesive. Commonly used adhesives such as a mold adhesive, a curing agent-mixed adhesive, a hot-melt adhesive, a pressure-sensitive adhesive (adhesive), a rewetting adhesive, and the like can be used, and preferably an aqueous solvent is volatilized. Adhesives, active energy ray-curable adhesives and pressure-sensitive adhesives can be used. The thickness of the adhesive layer can be appropriately adjusted according to the required adhesive strength and the like, and is preferably 0.01 to 500 μm, and more preferably 0.1 to 300 μm. A plurality of adhesive layers are present in the laminate for a flexible image display device, and the thickness and type of each may be the same or different.

  As the aqueous-based solvent-evaporating adhesive, a water-soluble polymer such as a polyvinyl alcohol-based polymer, a starch, an ethylene-vinyl acetate-based emulsion, or a styrene-butadiene-based emulsion can be used as a main polymer. . In addition to the main polymer and water, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, and the like may be blended. When bonding with the aqueous water-based solvent-evaporating adhesive, after injecting the water-based aqueous solvent-evaporation-type adhesive between the layers to be bonded and laminating the adhesion layer, it is possible to impart adhesiveness by drying. . When the water-based water-based solvent-evaporating adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.1 to 1 μm. When the water-based water-based solvent-evaporating adhesive is used for a plurality of layers, the thickness and type of each layer may be the same or different.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material that forms an adhesive layer upon irradiation with an active energy ray. The active energy ray-curable composition can contain at least one polymer of the same radical polymerizable compound and cationic polymerizable compound as those contained in the hard coat composition. As the radical polymerizable compound, the same compound as the radical polymerizable compound in the hard coat composition can be used.
As the cationic polymerizable compound, the same compound as the cationic polymerizable compound in the hard coat composition can be used.
As the cationically polymerizable compound used in the active energy ray-curable composition, an epoxy compound is particularly preferred. It is also preferable to include a monofunctional compound as a reactive diluent in order to reduce the viscosity of the adhesive composition.

The active energy ray composition may include a monofunctional compound in order to reduce the viscosity. Examples of the monofunctional compound include an acrylate monomer having one (meth) acryloyl group in one molecule and a compound having one epoxy group or oxetanyl group in one molecule, for example, glycidyl (meth) A) acrylate and the like.
The active energy ray composition can further include a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and a cationic polymerization initiator, and the like, which are appropriately selected and used. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate radicals or cations, thereby promoting radical polymerization and cationic polymerization. In the description of the hard coat composition, an initiator capable of initiating at least one of radical polymerization and cationic polymerization by irradiation with active energy rays can be used.
The active energy ray-curable composition further comprises an ion scavenger, an antioxidant, a chain transfer agent, an adhesion promoter, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, a defoamer solvent, an additive, and a solvent. Can be included. When the two adhesive layers are bonded by the active energy ray-curable adhesive, the active energy ray-curable composition is applied to one or both of the adhesive layers, and then bonded, and any one of the adhesive layers is bonded. Alternatively, both the layers to be bonded can be bonded by irradiating active energy rays to cure the layers. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of adhesive layers, the thickness and type of each layer may be the same or different.

  The pressure-sensitive adhesive is classified into an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive and the like depending on the main polymer, and any of them can be used. The adhesive may contain a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a tackifier, a plasticizer, a dye, a pigment, an inorganic filler, and the like, in addition to the base polymer. The components constituting the pressure-sensitive adhesive are dissolved and dispersed in a solvent to obtain a pressure-sensitive adhesive composition, and the pressure-sensitive adhesive composition is dried after being coated on a substrate, thereby forming a pressure-sensitive adhesive layer adhesive layer. You. The pressure-sensitive adhesive layer may be directly formed, or a layer separately formed on a substrate may be transferred. It is also preferable to use a release film to cover the adhesive surface before bonding. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.1 to 500 μm, more preferably 1 to 300 μm. When the pressure-sensitive adhesive is used in a plurality of layers, the thickness of each layer may be the same or different.

<Shading pattern>
The light-shielding pattern can be applied as at least a part of a bezel or a housing of the flexible image display device. The visibility of the image is improved by concealing the wiring arranged on the peripheral portion of the flexible image display device by the light-shielding pattern so that the wiring is difficult to see. The light-shielding pattern may be in the form of a single layer or multiple layers. The color of the light-shielding pattern is not particularly limited, and may be various colors such as black, white, and metal. The light-shielding pattern can be formed of a pigment for realizing a color and a polymer such as an acrylic resin, an ester resin, an epoxy resin, polyurethane, or silicone. These can be used alone or in a mixture of two or more. The light-shielding pattern can be formed by various methods such as printing, lithography, and inkjet. The thickness of the light-shielding pattern is preferably 1 to 100 μm, more preferably 2 to 50 μm. It is also preferable to provide a shape such as inclination in the thickness direction of the light-shielding pattern.

  Hereinafter, the present invention will be described in more detail with reference to examples. "%" And "parts" in the examples mean% by mass and parts by mass unless otherwise specified. First, a method of measuring physical properties will be described.

<Weight average molecular weight>
Gel Permeation Chromatography (GPC) Measurement (1) Pretreatment Method A sample was dissolved in γ-butyrolactone (GBL) to make a 20% by mass solution, and then diluted 100-fold with a DMF eluent, and a 0.45 μm membrane filter was used. The filtrate was used as a measurement solution.
(2) Measurement condition column: TSKgel SuperAWM-H × 2 + SuperAW2500 × 1 (6.0 mm ID × 150 mm × 3)
Eluent: DMF (10 mM lithium bromide added)
Flow rate: 0.6 mL / min.
Detector: RI detector Column temperature: 40 ° C
Injection volume: 20 μL
Molecular weight standard: Standard polystyrene

上記式において、αはポリアミド酸（イミド化率０％）の場合におけるアミドプロトン１個に対するベンゼンプロトンＡの個数割合である。 <Imidation ratio>
The imidation ratio was determined by ¹ H-NMR measurement as follows.
(1) a material obtained by a 2 wt% solution dissolved was measured solution pretreatment method samples a deuterated dimethyl sulfoxide (DMSO-d _6).
(2) Measuring conditions Measuring apparatus: JEOL 400 MHz NMR apparatus JNM-ECZ400S / L1
_Standard: DMSO-d 6 (2.5ppm)
Sample temperature: room temperature integration frequency: 256 times Relaxation time: 5 seconds (3) Method for analyzing imidation rate In the obtained ¹ H-NMR spectrum, benzene protons are observed at 7.0 to 9.0 ppm, of which imidization is observed. The integral ratio of benzene proton A derived from the structure that does not change before and after was defined as Int _A. Moreover, the amide protons of the amic acid structure remaining in the polyimide was observed at 10.5～11.5Ppm, the integral ratio was Int _B. From these integral ratios, the imidation ratio was determined by the following equation.

In the above formula, α is the number ratio of benzene protons A to one amide proton in the case of polyamic acid (imidation ratio 0%).

<Average primary particle size>
The specific surface area of the powder obtained by drying the silica sol at 300 ° C. was measured using a specific surface area measuring device Monosorb MS-16 manufactured by Yuasa Iokunis Co., Ltd., and the measured specific surface area S (m ² / g) was used. The average primary particle diameter was calculated by the formula of D (nm) = 2720 / S.

<Varnish viscosity>
Based on JIS K8803: 2011, it was measured using Brookfield E-type viscometer DV-II + Pro. The measurement temperature was 25 ° C.

<Film thickness and film thickness distribution of support>
Using ID-C112XBS manufactured by Mitutoyo Corporation, the film thickness at 20 points or more in the width direction of the support was measured, and the difference between the average value and each data was calculated to obtain a film thickness distribution.

<Film thickness>
Ten or more film thicknesses were measured using ID-C112XBS manufactured by Mitutoyo Corporation, and the average value was calculated.

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

<Yellowness of film>
The yellowness (Yellow Index: YI value) of the optical film was measured using an ultraviolet-visible-near-infrared spectrophotometer “V-670” manufactured by JASCO Corporation. After the background measurement was performed in the absence of the sample, the optical film was set on the sample holder, the transmittance was measured for light of 300 to 800 nm, and the tristimulus values (X, Y, Z) were obtained. The YI value was calculated based on.
YI = 100 × (1.2767X−1.0592Z) / Y

<Bending resistance of film>
In accordance with JIS P8115, the number of times until fracture was measured using an MIT bending fatigue tester D type (Toyo Seiki Seisaku-sho, Ltd.). The curvature radius R was measured at 1.

<Tear strength of film>
The tear strength of the film was measured according to the trouser test method under the following conditions in accordance with JIS K 7128-1. The strength per unit length obtained by dividing the strength obtained by setting the tear direction as the MD direction by the length of the sample was defined as the tear strength E _MD (N / mm). The tearing direction was defined as the TD direction, and the strength obtained in the same manner was defined as E _TD (N / mm). Further, the strength per unit cross-sectional area obtained by dividing the strength obtained by setting the tear direction in the MD direction by the cross-sectional area of the sample was defined as the tear strength F _MD (N / mm ² ). The tearing direction was defined as the TD direction, and the strength obtained in the same manner was defined as F _TD (N / mm ² ).
(Measurement condition)
Sample size: L150mm × W50mm, central cut 75mm
Test conditions: test speed; 200 mm / min
Number of measurements; n = 5
Test environment: 25 ° C ± 2 ° C, 50% RH ± 10% RH
Measuring device: Universal material testing machine 5982 (Instron)

<Film tensile modulus>
The film was cut out into a 100 × 10 mm dumbbell shape, and subjected to a tensile test at a test speed of 5 m / min and a load cell of 5 kN using an electromechanical universal testing machine (manufactured by Instron) in accordance with JIS K7127. Was measured for tensile modulus.

<Evaluation method of optical homogeneity of film>
1. Photographing of Projection Image and Background Image As shown in FIG. 2, a light source 1, a film 2, a projection surface 3 and a camera 6 were arranged in a dark room, and a projection image 4 was photographed. The distance between the light source 1 and the film 2 is 250 cm, the distance between the film 2 and the projection surface 3 is 30 cm, the film 2 and the projection surface 3 are arranged in parallel, and the camera 6 is operated from the light source 1 to the screen. It is installed directly below the line, the distance between the camera 6 and the projection surface 3 (screen) is 30 cm, and the camera angle 7 (from a state where the camera is oriented perpendicular to the screen, is tilted upward. Angle) was 25 °. The shooting of the background image was performed in the same manner as the shooting of the projection image except that the film 2 was removed in FIG. Details of the measurement conditions and imaging conditions are shown below.
Light source: LED light source (“LA-HDF15T” manufactured by Hayashi Watch Industry Co., Ltd.)
Film: The film produced in the following Examples and Comparative Examples was cut into a 200 mm x 300 mm film to be used as a measurement sample.
Projection surface: White commercially available movie viewing screen (“BTP600FHD-SH1000” manufactured by Theater House Co., Ltd.)
Camera: “COOLPIX (registered trademark) P600” manufactured by Nikon Corporation
Detailed camera settings: Shooting mode Manual shooting
Image size 2M
Focus Manual focus (distance 0.3m)
Shutter speed 1/2 second
Aperture value (F value) 4.2
Flash off

2. Fourier Transform In this embodiment, since the camera is installed at the position of the camera angle, the projected image is inclined. Therefore, in order to correct the inclination of the projection image, the inclination correction conditions were determined.
If there is no distortion in the projected image, no correction is necessary.
(Determination of tilt correction conditions)
A square of 10 cm × 10 cm was written on a transparent film, and a reference projected image was taken under the above condition 1. The obtained reference projection image is read by Photoshop (registered trademark) CS4 manufactured by Adobe Systems, and the camera and the screen are corrected using a lens correction distortion correction function so as to correspond to 90 °, and the TIFF format is used. Saved in. The condition at this time was defined as a tilt correction condition. From the reference projection image after the inclination correction, the length of each pixel in the vertical and horizontal directions was calculated (vertical: 816 pixels = 10 cm, horizontal: 906 pixels = 10 cm).
(Fourier transform)
The projected images obtained as described above for the films of Examples and Comparative Examples were corrected under the tilt correction conditions determined as described above, and the corrected images were stored in TIFF format. The projection image obtained after the inclination correction was converted into an 8-bit gray scale by using image analysis software “Image-J, ver. 1.48” and quantified. Note that the length per pixel in each of the vertical and horizontal directions obtained from the reference projection image after the inclination correction was used as Set Scale. A rectangular area having a size of 10.2 cm × 11.2 cm (length × width) in the gray scale image is selected, and the image in the selected area is subjected to Fourier transform using Image-J to obtain an inverse space image. Was. With respect to the inverse aerial image after the Fourier transform, correct values (horizontal direction: ¹ pixel = 11.3 cm ^-1 , vertical direction: ¹ pixel = 12.55 cm ^-1 ) were input to Set Scale.

図４に示される実施例１で得たラインプロファイル（データＹ）について、上記補正を行うことにより、図５に示されるようなラインプロファイルＡ（データＹ’）が得られる。
次に、１で得た背景画像についても同様の操作を行い、背景画像のラインプロファイルを得た。具体的には、図６に示されるようなラインプロファイルＢが得られた。
次いで、上記のプロファイルＡから、バックグラウンドのプロファイルＢをＥｘｃｅｌにより引いて、ブランク補正を行った。実施例１では、図５に示されるラインプロファイルＡのデータＹ’から、図６に示されるようなラインプロファイルＢのデータを引いて、図７に示されるようなブランク補正されたラインプロファイルＡ−Ｂを得た。
このようにして得たラインプロファイルをスムージングして、Ｙ”のプロファイルを得、これをラインプロファイルの最大強度（Ｙ_ｍｈ１及びＹ_ｍｖ１）の測定に使用した。グラフのスムージングは、次の式に従い、２１個のデータの平均値であるｙ_ｉを算出して行った。

3. Measurement of maximum intensity (Y _mh1 and Y _mv1 ) of blank-corrected line profile In the inverse aerial image obtained as described above, the horizontal direction (h1 direction) and the vertical direction (v1 direction) passing through the center of the inverse aerial image Line profiles were created for each direction.
The line width was 10 pixels. The obtained line profile was saved in a text format. Next, the data in the text format is read by Microsoft Excel (ver. 14.0), and the line profile is standardized as follows, and each of the data in the horizontal direction (h1 direction) and the vertical direction (v1 direction) is read. In the direction of, a line profile of Y ″ is obtained, the maximum intensity Y _{max is set} to Y _mh1 and Y _mv1 in each line profile, and all the frequencies in the line profile blank-corrected from the frequency indicating the maximum intensity Y _mh1 and Y _mv1 X _max , which is a value obtained by subtracting the median value X _cen , is defined as X _mh1 and X _mv1 , respectively.The normalization method will be described using a horizontal (h1 direction) line profile obtained in the first embodiment as an example.
(Standardization method)
The frequency at which the value of Y is the maximum is defined as the center of X (X _cen ), and the value of Y at that time is defined as Y _cen . _Then, around the _{X cen,} for the area of a total of 100 pixels each at both ends 50 pixels minutes, an average value of Y, is the average value and the baseline _{(Y base).} Then, the data Y is corrected according to the following equation so that Y _cen = 100 and Y _base = 0, and Y ′ is obtained.

By performing the above correction on the line profile (data Y) obtained in the first embodiment shown in FIG. 4, a line profile A (data Y ') as shown in FIG. 5 is obtained.
Next, the same operation was performed on the background image obtained in step 1 to obtain a line profile of the background image. Specifically, a line profile B as shown in FIG. 6 was obtained.
Next, the background profile B was subtracted from the profile A by Excel to perform blank correction. In the first embodiment, the data of the line profile B shown in FIG. 6 is subtracted from the data Y ′ of the line profile A shown in FIG. 5, and the blank-corrected line profile A− shown in FIG. B was obtained.
The line profile thus obtained was smoothed to obtain a profile of Y ″, which was used for measuring the maximum intensity of the line profile (Y _mh1 and Y _mv1 ). The smoothing of the graph was performed according to the following equation. The calculation was performed by calculating y _i , which is the average value of 21 data.

(Sensory evaluation of visibility)
The produced film was visually inspected from an angle of elevation of 80 ° in an indoor environment adjusted to 50 to 100 lux, and the visibility was evaluated based on the distortion of the reflected background. Table 2 shows the results. The evaluation criteria for visibility are as follows.
A: No distortion is observed in the background.
〇: Very slight distortion in the background, but no problem.
×: Clear distortion is confirmed in the background.

<Remaining solvent amount>
Using TG-DTA (EXSTAR6000 TG / DTA6300 manufactured by SII Corporation), the transparent resin films obtained in Examples 1 and 2 and Comparative Examples and 2 were heated from 30 ° C. to 120 ° C., and heated at 120 ° C. for 5 hours. Then, the temperature was raised to 400 ° C. at a rate of 5 ° C./min. The ratio of the weight loss of the film from 120 ° C. to 250 ° C. with respect to the weight of the film at 120 ° C. was calculated as the content of the solvent (referred to as the residual solvent amount).

Abbreviations used in the following Production Examples and Examples are as follows.
TFMB: 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl 6FDA: 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride TPC: terephthaloyl chloride OBBC: 4,4 '-Oxybis (benzoyl chloride)
DMAc: N, N-dimethylacetamide GBL: γ-butyrolactone PET: polyethylene terephthalate

<Production example>
Production Example 1 Production of Polyamideimide Resin 1 Under a nitrogen gas atmosphere, a reaction vessel equipped with a stirring blade in a separable flask and an oil bath were prepared. 45 parts of TFMB and 768.55 parts of DMAc were charged into a reaction vessel installed in an oil bath. TFMB was dissolved in DMAc while stirring the contents in the reaction vessel at room temperature. Next, 19.01 parts of 6FDA was further charged into the reaction vessel, and the contents in the reaction vessel were stirred at room temperature for 3 hours. Thereafter, 4.21 parts of OBBC and then 17.30 parts of TPC were charged into the reaction vessel, and the contents in the reaction vessel were stirred at room temperature for 1 hour. Next, 4.63 parts of 4-methylpyridine and 13.04 parts of acetic anhydride were further charged into the reaction vessel, and the contents in the reaction vessel were stirred at room temperature for 30 minutes. After stirring, the temperature in the vessel was increased to 70 ° C. using an oil bath, and the temperature was maintained at 70 ° C., and the mixture was further stirred for 3 hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature and poured into a large amount of methanol in a thread form to precipitate a precipitate. The deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin 1. The weight average molecular weight of the obtained polyamideimide resin 1 was 370,000, and the imidation ratio was 98.9%.

Production Example 2: Production of polyamide-imide resin 2 Under a nitrogen gas atmosphere, 50 parts of TFMB and 642.07 parts of DMAc were added to a separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 20.84 parts of 6FDA was added to the flask, and the mixture was stirred at room temperature for 3 hours. Thereafter, 9.23 parts of OBBC and 15.87 parts of TPC were added to the flask, and the mixture was stirred at room temperature for 1 hour. Next, 9.89 parts of 4-methylpyridine and 14.37 parts of acetic anhydride were added to the flask, and the mixture was stirred at room temperature for 30 minutes, heated to 70 ° C. using an oil bath, and further stirred for 3 hours. I got The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, and the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamide-imide resin 2. The weight average molecular weight of the obtained polyamideimide resin 2 was 420,000, and the imidation ratio was 99.0%.

Production Example 3: Production of polyimide resin A separable flask was equipped with a silica gel tube, a reactor equipped with a stirrer and a thermometer, and an oil bath. 75.52 parts of 6FDA and 54.44 parts of TFMB were charged into the flask. While stirring at 400 rpm, 519.84 parts of DMAc was added, and stirring was continued until the contents of the flask became a uniform solution. Subsequently, stirring was continued for another 20 hours while adjusting the temperature in the container to be in the range of 20 to 30 ° C. using an oil bath, and the mixture was reacted to generate a polyamic acid. After 30 minutes, the stirring speed was changed to 100 rpm. After stirring for 20 hours, the temperature of the reaction system was returned to room temperature, and 649.8 parts of DMAc was added to adjust the polymer concentration to 10% by mass. Further, 32.27 parts of pyridine and 41.65 parts of acetic anhydride were added, and the mixture was stirred at room temperature for 10 hours to perform imidization. The polyimide varnish was taken out of the reaction vessel. The obtained polyimide varnish was dropped into methanol to perform reprecipitation, and the obtained powder was dried by heating to remove the solvent, thereby obtaining a polyimide resin as a solid content. The weight average molecular weight of the obtained polyimide resin was 360,000, and the imidation ratio was 98.9%.

Production Example 4: Preparation of silica sol 1 Amorphous silica sol having an average primary particle diameter of 27 nm (average primary particle diameter measured by the BET method) prepared by a sol-gel method was used as a raw material, and a GBL-substituted silica sol was prepared by solvent substitution. . The obtained sol was filtered with a membrane filter having an opening of 10 μm to obtain GBL-substituted silica sol 1. In the obtained GBL-substituted silica sol 1, the content of the silica particles was 30 to 32% by mass.

Production Example 5: Preparation of silica sol 2 Using an amorphous silica sol having an average primary particle diameter of 25 nm produced by a sol-gel method as a raw material, a GBL-substituted silica sol was prepared by solvent replacement. The obtained sol was filtered with a membrane filter having an opening of 10 μm to obtain GBL-substituted silica sol 2. In the obtained GBL-substituted silica sol 2, the content of the silica particles was 30 to 32% by mass.

Production Example 6: Preparation of Varnish (1) Using the polyamideimide resin 1 obtained in Production Example 1 and the silica sol 1 obtained in Production Example 4, the composition ratio of the polyamideimide resin and silica particles was 60:40 in the GBL solvent. And mixed. To the obtained mixture, Sumisorb 340 (UVA absorber) and Sumiplast Violet B (BA, bluing agent) were added in amounts of 5.7 phr and 35 ppm, respectively, based on the total mass of the polymer and silica, The mixture was stirred until it became uniform to obtain varnish (1). The varnish (1) had a solids content of 11.0% by mass and a viscosity at 25 ° C. of 38,500 cps.

Production Example 7: Preparation of Varnish (2) Except for using the polyamideimide resin 2 obtained in Production Example 2, in the same manner as in Production Example 6, the solid content is 9.9% by mass, and the viscosity at 25 ° C is 38,000 cps. Varnish (2)

Production Example 8: Preparation of varnish (3) Except that the polyimide resin obtained in Production Example 3 was used, the solid content was 18.0% by mass, and the viscosity at 25 ° C was 35,000 cps. Varnish (3) was obtained.

Example 1
The varnish (1) was applied on a PET film (Cosmoshine (registered trademark) A4100, Toyobo Co., Ltd., film thickness 188 μm, film thickness distribution ± 2 μm), and was drool-molded to form a varnish coating film. At this time, the linear velocity was 0.3 m / min. The coating film of the varnish is heated at 80 ° C. for 10 minutes, then heated at 100 ° C. for 10 minutes, then heated at 90 ° C. for 10 minutes, and finally dried at 80 ° C. for 10 minutes. A film was formed. Thereafter, the coating film was peeled off from the PET film to obtain a raw material film 1 having a thickness of 58 μm and a width of 700 mm. The residual solvent amount in the raw material film 1 was 9.7% by mass. Next, the raw material film 1 was heated at 200 ° C. for 25 minutes at a stretching ratio of 0.98 times with a film transverse stretching apparatus (tenter) to obtain a polyamideimide film 1 having a thickness of 50 μm. The residual solvent amount in the polyamideimide film 1 was 0.8% by mass.

Example 2
Example 1 was repeated except that the drying conditions were changed to heating at 80 ° C. for 10 minutes, heating at 100 ° C. for 10 minutes, heating at 90 ° C. for 10 minutes, and finally heating at 85 ° C. for 10 minutes. Similarly, a raw material film 2 having a thickness of 58 μm and a width of 700 mm was obtained. The residual solvent amount in the raw material film 2 was 9.8% by mass. Next, a polyamide-imide film 2 having a thickness of 50 μm was obtained in the same manner as in Example 1, except that the raw material film 2 was used instead of the raw material film 1. The residual solvent amount in the polyamideimide film 2 was 0.7% by mass.

Example 3
The varnish (3) was applied on a PET film (Toyobo Co., Ltd. “Cosmoshine (registered trademark) A4100”, film thickness 188 μm, film thickness distribution ± 2 μm), and was drool-molded to form a varnish coating film. At this time, the linear velocity was 0.8 m / min. The varnish coating is heated at 100 ° C. for 3.5 minutes, then at 120 ° C. for 3.5 minutes, then at 90 ° C. for 3.5 minutes, and finally at 80 ° C. for 3.5 minutes. Drying was performed under drying conditions to form a dried coating film. Thereafter, the coating film was peeled off from the PET film to obtain a raw material film 3 having a thickness of 58 μm and a width of 700 mm. The residual solvent amount in the raw material film 3 was 9.5% by mass. Next, a polyimide film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the raw material film 3 was used instead of the raw material film 1. The amount of residual solvent in the polyimide film was 1.0% by mass.

Comparative Example 1
Using varnish (2), the drying conditions were changed to heating at 70 ° C. for 10 minutes, heating at 80 ° C. for 10 minutes, heating at 100 ° C. for 10 minutes, and finally heating at 100 ° C. for 10 minutes. Except for this, the raw material film 4 having a thickness of 58 μm and a width of 700 mm was obtained in the same manner as in Example 1. The residual solvent amount in the raw material film 4 was 9.7% by mass. Next, a polyamide-imide film 3 having a thickness of 50 μm was obtained in the same manner as in Example 1, except that the raw material film 3 was used instead of the raw material film 1. The residual solvent amount in the obtained polyamideimide film 3 was 0.7% by mass.

Reference Example 1
Polyamideimide resin 3 was obtained in the same manner as in Production Example 1, except that the amount of DMAc charged was changed to 1650 parts. The weight average molecular weight of the obtained polyamideimide resin 3 was 180,000. A varnish was prepared in the same manner as in Production Example 6 except that the polyamideimide resin 3 was used instead of the polyamideimide resin 1, and a 50 μm-thick film for reference was prepared using the varnish in the same manner as in Example 1. did.

Table 1 shows the physical property values of the varnishes used for producing the films of the examples and the comparative examples, and the conditions of the first drying. Tables 2 to 4 show the results obtained by measuring various physical property values of the films obtained in Examples and Comparative Examples according to the above-described measurement methods. Table 3 shows the results of the bending resistance test performed on the film shown in Reference Example 1.

In the optical films of Examples 1 to 3, Y _mh and Y _mv were less than 30, A / B was less than 30, and the visibility was evaluated as ◎ or も. In contrast, the optical film of Comparative Example 1 had an A / B of 30 or more, and the visibility evaluation result was x. Further, the film of Reference Example 1 containing a resin having a weight average molecular weight of less than 230,000 did not have sufficient bending resistance.

Reference Signs List 1 light source 2 film 3 projection surface 4 projection image 5 light 6 camera 7 camera angle

Claims (10)

An optical film containing a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more, and a filler having an average primary particle diameter of 5 to 35 nm, obtained by a projection method using the optical film. A background image obtained without using the optical film in the projection method, wherein line profiles in directions h and v orthogonal to each other in a film inverse aerial image obtained by performing a Fourier transform on the image are line profiles h and v, respectively. Are obtained by subtracting the line profile h 'from the line profile h in the background inverse aerial image obtained by performing Fourier transform on the line profile h' and the line profile v 'in the direction h' and the direction v 'orthogonal to each other. Line profile (hh ') maximum The degrees and _{Y mh,} the frequency showing the maximum intensity _{Y mh} and _{X mh,} the maximum intensity of the 'line profile obtained by subtracting the (v-v' line profile v from the line profile v) and _{Y mv,} maximum intensity Y If the frequency indicating the _mv and _{X mv, Y mh} and _{Y mv} is any even 30 or _less, Y _mh, Y _{mv, X mh} and _{X mv} is the following relationship:

Meet the optical film. The MD direction tear strength of the film and _E MD (N / mm), when the tear strength in the TD direction _E TD (N / _mm), the ratio of _{E MD} for _{E TD (E MD / E TD} ) is 0. The optical film according to claim 1, wherein the number is 93 or more.   The optical film according to claim 1, wherein the yellowness of the film is 3 or less.   The optical film according to claim 1, wherein the filler is a silica particle.   The optical film according to any one of claims 1 to 4, wherein the content of the filler is 5 to 60% by mass based on the mass of the optical film.   The optical film according to any one of claims 1 to 5, which is a film for a front panel of a flexible display device.   A flexible display device comprising the optical film according to claim 1.   The flexible display device according to claim 7, further comprising a touch sensor.   The flexible display device according to claim 7, further comprising a polarizing plate. (A) A varnish containing at least a polyimide resin and / or a polyamide resin having a weight average molecular weight of 230,000 or more, a filler having an average primary particle diameter of 5 to 35 nm, and a solvent is coated on a support and dried. , Forming a coating film,
(B) a step of peeling the coating film from the support, and (c) a step of heating the peeled coating film to obtain a film;
The method for producing an optical film according to claim 1, comprising at least:

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