JP2018119133A - Optical film and production method for optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film that includes a polyamide-imide resin that is particularly suitable as a front surface plate of a flexible display or the like and can increase the surface hardness even under relatively low-temperature heating conditions.SOLUTION: The present invention provides an optical film that: includes a polyamide-imide resin that has a tanδ peak value, as measured by DMA, within the range of 300°C-370°C; and has a YI value of no greater than 3.SELECTED DRAWING: None

Description

  The present invention relates to an optical film containing a polyamideimide resin and a method for producing the optical film.

  Currently, image display devices such as liquid crystal display devices and organic EL display devices are widely used not only for televisions but also for various applications such as mobile phones and smart watches. With the expansion of such applications, an image display device (flexible display) having flexible characteristics is required. The image display apparatus includes a display element such as a liquid crystal display element or an organic EL display element, and other constituent members such as a polarizing plate, a retardation plate, and a front plate. In order to achieve a flexible display, all these components need to be flexible.

  Until now, glass has been used as the front plate. Glass is highly transparent and can exhibit high hardness depending on the type of glass, but it is very rigid and easily broken, making it difficult to use as a front plate material for flexible displays.

  Therefore, the use of a polymer material as a material to replace glass is being studied. Since the front plate made of a polymer material is easy to exhibit flexible characteristics, it can be expected to be used for various applications. Various resins can be used as the flexible resin, and one of them is a polyamideimide resin. Polyamideimide resins are used in various applications from the viewpoints of transparency and heat resistance.

  For example, Patent Document 1 describes a copolymerized polyamideimide resin having a specific logarithmic viscosity and elongation at break, in which a polyoxyalkylene group-containing compound is copolymerized. Patent Document 2 describes a polyamideimide resin obtained by polymerizing specific monomers (a), (b1) and (b2). Patent Document 3 describes a polyamideimide resin having a predetermined number average molecular weight, which is produced using a trivalent carboxylic acid component having an acid anhydride group and an isocyanate or diamine.

JP-A-9-328550 JP 2008-285660 A JP 2009-286826 A

  Conventionally, when a film containing a polyamideimide resin is used as a front plate, a process of heating the film under a high temperature condition has been performed for the purpose of increasing the surface hardness. However, when the film is yellowed by heating under high temperature conditions or the film contains an additive (for example, an ultraviolet absorber) in addition to the polyamideimide resin, the additive may be decomposed. As a result, the quality of the film is impaired.

  Therefore, an object of the present invention is to provide an optical film containing a polyamide-imide resin that can be suitably used as a front plate for a flexible display or the like and can increase the surface hardness even under relatively low-temperature heating conditions.

  In order to solve the above-mentioned problems, the present inventors have intensively studied various characteristics of the polyamide-imide resin by paying attention to the heating temperature and the surface hardness. As a result, it has been found that if a polyamideimide resin satisfying specific requirements is used, the surface hardness can be increased under relatively low-temperature heating conditions, and the present invention has been completed.

［式（１）中、Ｒ^１〜Ｒ^８は、それぞれ独立に、水素原子、炭素数１〜６のアルキル基または炭素数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、それぞれ独立に、ハロゲン原子で置換されていてもよく、
Ａは、それぞれ独立に、−Ｏ−、−Ｓ−、−ＣＯ−または−ＮＲ^９−を表し、Ｒ^９はハロゲン原子で置換されていてもよい炭素数１〜１２の炭化水素基を表し、
ｍは１〜４の整数であり、
＊は結合手を表す］
で表される構成単位を少なくとも有する、前記［１］〜［５］のいずれかに記載の光学フィルム。
［７］ポリアミドイミド樹脂は、ジカルボン酸に由来する構成単位を少なくとも有する、前記［１］〜［６］のいずれかに記載の光学フィルム。
［８］ポリアミドイミド樹脂は、フッ素原子含有ジアミンおよび／またはフッ素原子含有テトラカルボン酸二無水物に由来する構成単位を少なくとも有する、前記［１］〜［７］のいずれかに記載の光学フィルム。
［９］３０μｍ以上の厚みを有する、前記［１］〜［８］のいずれかに記載の光学フィルム。
［１０］（１）ポリアミドイミド樹脂および溶剤を少なくとも含む樹脂組成物を支持体に塗付する工程、ならびに、
（２−１）該樹脂組成物の塗膜を２４０℃以下の温度で乾燥後に支持体から剥離する工程、または、
（２−２）該樹脂組成物の塗膜を２４０℃以下の温度で乾燥後に支持体から剥離する工程、および、剥離したフィルムを２４０℃以下の温度で加熱する工程
を少なくとも含む、光学フィルムの製造方法。
［１１］樹脂組成物は光吸収機能を有する添加剤をさらに含む、前記［１０］に記載の製造方法。
［１２］溶剤はジメチルアセトアミドを含む、前記［１０］または［１１］に記載の製造方法。 That is, the present invention includes the following preferred embodiments.
[1] An optical film comprising a polyamideimide resin having a peak value of tan δ as measured by DMA measurement in the range of 300 to 370 ° C. and having a YI value of 3 or less.
[2] The optical film according to [1], which has a pencil hardness of 3B or more as measured according to ASTM D 3363 under an illumination condition of 4000 lux.
[3] The optical film according to any one of [1] or [2], further including an additive having a light absorption function.
[4] The optical film according to any one of [1] to [3], wherein the additive having a light absorbing function is selected from the group consisting of an ultraviolet absorber and a bluing agent.
[5] The optical film according to any one of [1] to [4], wherein the polyamideimide resin contains a fluorine atom.
[6] Polyamideimide resin has the formula (1):

[In Formula (1), R ^{1 to} R ⁸ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and hydrogen contained in R ^{1 to} R ^8. Each atom may be independently substituted with a halogen atom,
Each A independently represents —O—, —S—, —CO— or —NR ⁹ —, wherein R ⁹ represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom;
m is an integer of 1 to 4,
* Represents a bond]
The optical film in any one of said [1]-[5] which has at least the structural unit represented by these.
[7] The optical film according to any one of [1] to [6], wherein the polyamideimide resin has at least a structural unit derived from dicarboxylic acid.
[8] The optical film according to any one of [1] to [7], wherein the polyamideimide resin has at least a structural unit derived from a fluorine atom-containing diamine and / or a fluorine atom-containing tetracarboxylic dianhydride.
[9] The optical film according to any one of [1] to [8], which has a thickness of 30 μm or more.
[10] (1) A step of applying a resin composition containing at least a polyamideimide resin and a solvent to a support, and
(2-1) A step of peeling the coating film of the resin composition from the support after drying at a temperature of 240 ° C. or lower, or
(2-2) An optical film comprising at least a step of peeling the coating film of the resin composition from the support after drying at a temperature of 240 ° C. or lower, and a step of heating the peeled film at a temperature of 240 ° C. or lower. Production method.
[11] The production method according to [10], wherein the resin composition further includes an additive having a light absorption function.
[12] The production method according to [10] or [11], wherein the solvent includes dimethylacetamide.

  The optical film of the present invention can increase surface hardness under relatively low-temperature heating conditions. Therefore, the optical film of the present invention has sufficient surface hardness, high transparency, and low yellowness.

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

The optical film of the present invention contains a polyamide-imide resin having a peak value of tan δ by DMA measurement within a range of 300 to 370 ° C. Hereinafter, the temperature at which the polyamideimide resin has a peak value of tan δ as measured by DMA is also referred to as “tan δ peak temperature”.
The tan δ peak temperature of the resin is a temperature also called the glass transition temperature of the resin. The said range is a lower range compared with the tan-delta peak temperature which the conventional polyamideimide resin usually has. The optical film of the present invention containing a polyamideimide resin having a peak value of tan δ at a temperature in the predetermined range can achieve a sufficiently high surface hardness under relatively low temperature heating conditions. This is thought to be because the free volume of the resin decreases under relatively low temperature heating conditions. In addition, the said mechanism does not limit this invention at all. Since the optical film of the present invention can achieve a sufficiently high surface hardness under relatively low temperature heating conditions, heat resistance such as yellowing of the film by heating and additives having a light absorption function included in some cases The decomposition of the additive with a low content is suppressed, and the quality of the film can be improved. When the tan δ peak temperature of the polyamideimide resin contained in the optical film of the present invention is lower than 300 ° C., the elastic modulus of the resin is lowered, so that high surface hardness tends to be hardly exhibited. On the other hand, when the tan δ peak temperature exceeds 370 ° C., heat treatment at a high temperature is required for high surface hardness, and the optical characteristics of the resin may be deteriorated. The tan δ peak temperature of the polyamideimide resin contained in the optical film of the present invention is preferably 305 to 365 ° C., more preferably. In an embodiment, the tan δ peak temperature of the polyamideimide resin contained in the optical film of the present invention is preferably 305 to 365 ° C, more preferably 320 to 365 ° C, and further preferably 340 to 365 ° C.

  The method for adjusting the tan δ peak temperature of the polyamideimide resin to the above range is not particularly limited. For example, a method for adjusting the amount of a structural unit represented by the formula (1) described later contained in the polyamideimide resin, polyamide A method for adjusting the imidization ratio in the imide resin is exemplified. Note that tan δ tends to decrease when the amount of the structural unit represented by the formula (1) described later is increased or the imidization ratio of the polyamide-imide resin is increased, so that these values become desired values. Can be adjusted.

  The tan δ peak temperature is measured by DMA measurement. Specifically, it can be evaluated according to the example of the present specification using a DMA measuring device (DMA Q800 manufactured by TA Instrument).

The YI value of the optical film of the present invention is 3 or less. When the YI value exceeds 3, the yellowness of the optical film becomes too high, so that sufficient visibility cannot be obtained. The YI value of the optical film of the present invention is preferably 3.0 or less, more preferably 2.5 or less, and still more preferably 2.0 or less. When the YI value is not more than the above upper limit, the visibility of the optical film can be further increased. Note that the lower limit of the YI value is not particularly limited, and may be usually 0 or more. The YI value represents the yellowness of the film (Yellow Index: YI value). According to JIS K 7373: 2006, a spectrophotometer (UV-Vis near-infrared spectrophotometer V-670 manufactured by JASCO Corporation). ). Specifically, it is calculated based on the following formula from tristimulus values (X, Y, Z) obtained by measuring transmittance with respect to light of 300 to 800 nm.

  The pencil hardness (surface hardness) of the optical film of the present invention is preferably 3B or more, more preferably 2B or more, still more preferably B or more, and particularly preferably HB or more, as measured according to ASTM D 3363 under an illumination condition of 4000 lux. , Very preferably H or more, most preferably 2H or more. When the optical film of the present invention has a pencil hardness equal to or higher than the above lower limit, when used as a front plate (window film) of an image display device, it is easy to suppress scratches on the surface of the image display device, and the optical film shrinks. And it is preferable because it is easy to prevent expansion. The upper limit of the pencil hardness of the optical film of the present invention is not particularly limited. The pencil hardness is measured according to JIS K5600-5-4: 1999. Specifically, measurement is performed at a load of 100 g and a scanning speed of 60 mm / min, and evaluation is performed under an illuminance condition of a light amount of 4000 lux. In addition, when evaluating pencil hardness, a result may change with the illumination intensity conditions to be used. Specifically, compared with the pencil hardness measured and evaluated under the illuminance condition of 4000 lux, the pencil hardness measured and measured under the lower illuminance condition is As a result of making the scratches on the film difficult to see, it is likely that results higher than actual results will be obtained. Therefore, the pencil hardness in the present specification is a value obtained by evaluating under an illuminance condition of a light amount of 4000 lux.

  The thickness of the optical film of the present invention is preferably 20 μm or more, more preferably 30 μm or more, and still more preferably 40 μm or more, from the viewpoint that the pencil hardness also affects the film thickness. The thickness of the optical film of the present invention is preferably 300 μm or less, more preferably 200 μm or less, and still more preferably 100 μm or less from the viewpoint of bending resistance. The thickness is measured using a contact-type digimatic indicator.

  The total light transmittance (Tt) of the optical film of the present invention is preferably 70% or more, more preferably 80% or more, still more preferably 85% or more, particularly preferably, as measured according to JIS K 7105: 1981. 90% or more. When the total light transmittance is at least the above lower limit, it is easy to improve the visibility when the optical film of the present invention is incorporated in an image display device. In addition, the upper limit of the total light transmittance of the optical film of the present invention is usually 100% or less. The total light transmittance is measured using, for example, a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. in accordance with JIS K 7105: 1981.

  The elastic modulus of the optical film of the present invention is preferably 5.9 GPa or less, more preferably 5.5 GPa or less, still more preferably 5.2 GPa or less, particularly preferably 5.0 GPa or less, most preferably from the viewpoint of film flexibility. Preferably it is 4.5 GPa or less. When the elastic modulus is not more than the above upper limit, it is easy to suppress damage to other members due to the optical film when the flexible display is bent. In addition, although the minimum of the elasticity modulus of the optical film of this invention is not specifically limited, Usually, it is 2.0 GPa or more. For example, using an autograph AG-IS manufactured by Shimadzu Corporation, a modulus of elasticity is measured by measuring an SS curve on a 10 mm wide test piece under conditions of a distance between chucks of 500 mm and a tensile speed of 20 mm / min. Can be measured.

  The number of reciprocal folds of the optical film of the present invention is measured from the viewpoint of bending resistance of the film until the film breaks under the conditions of R = 1 mm, 135 °, load 0.75 kgf, speed 175 cpm, preferably 10,000. More than 20,000 times, more preferably 20,000 times or more, still more preferably 30,000 times or more, particularly preferably 40,000 times or more, most preferably 50,000 times or more. When the number of reciprocal folding of the optical film of the present invention is equal to or more than the above lower limit, weaving that may occur when the optical film is bent is easily suppressed. The upper limit of the number of reciprocal folds of the optical film is not particularly limited, but it is sufficiently practical if it can be bent usually about 1,000,000 times or less. The number of reciprocal bendings can be obtained, for example, using a test piece cut from an optical film having a thickness of 50 μm and a width of 10 mm using a MIT folding fatigue tester (model 0530) manufactured by Toyo Seiki Seisakusho.

  The weight average molecular weight (Mw) of the polyamideimide resin contained in the optical film of the present invention is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 50,000 or more, and particularly preferably 70,000 or more. More preferably, it is 100,000 or more, preferably 800,000 or less, more preferably 600,000 or less, further preferably 500,000 or less, and particularly preferably 450,000 or less. When the weight average molecular weight (Mw) of the polyamideimide resin is not less than the above lower limit, the bending resistance of the optical film of the present invention can be easily increased. When the weight average molecular weight (Mw) of the polyamideimide resin is not more than the above upper limit, the solubility of the polyamideimide resin in the solvent is improved, and the viscosity of the polyamideimide varnish used when producing the optical film of the present invention is reduced. Since it can suppress low, it becomes easy to manufacture the optical film of this invention. In addition, since the optical film can be easily stretched, the processability is good. The weight average molecular weight (Mw) can be determined by, for example, GPC measurement and standard polystyrene conversion, and can be specifically determined by the method described in the examples.

The imidization ratio of the polyamideimide resin contained in the optical film of the present invention is preferably 90% or more, more preferably 95% or more. When the imidization ratio is not less than the above lower limit, high surface hardness is easily exhibited. The upper limit of the imidization ratio of the polyamideimide resin is not particularly limited, and may be 100% or less. The imidization ratio represents the ratio of the number of moles of imide bonds in the polyamide-imide resin to the value twice the number of moles of structural units derived from the tetracarboxylic dianhydride in the polyamide-imide resin. Is measured by two-dimensional NMR.
Details of the two-dimensional NMR measurement conditions are as shown in the Examples.

［式（１）中、Ｒ^１〜Ｒ^８は、それぞれ独立に、水素原子、炭素数１〜６のアルキル基または炭素数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、それぞれ独立に、ハロゲン原子で置換されていてもよく、
Ａは、それぞれ独立に、−Ｏ−、−Ｓ−、−ＣＯ−または−ＮＲ^９−を表し、Ｒ^９はハロゲン原子で置換されていてもよい炭素数１〜１２の炭化水素基を表し、
ｍは１〜４の整数であり、
＊は結合手を表す。］
ポリアミドイミド樹脂が式（１）で表される構成単位を有する場合、ポリアミドイミド樹脂の主鎖に上記式中の−Ａ−で表される、フィルムとした場合に高い屈曲性を付与し得る構造が含まれることとなる。ポリアミドイミド樹脂が高い屈曲性を付与し得る構造を適度に有することにより、ポリアミドイミド樹脂のｔａｎδピーク温度を適度に低下させることができ、その結果、該ポリアミドイミド樹脂を含むフィルムの表面硬度を、比較的低温の加熱条件で高めることができる。 The polyamideimide resin contained in the optical film of the present invention preferably has at least a structural unit represented by the formula (1).

[In Formula (1), R ^{1 to} R ⁸ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and hydrogen contained in R ^{1 to} R ^8. Each atom may be independently substituted with a halogen atom,
Each A independently represents —O—, —S—, —CO— or —NR ⁹ —, wherein R ⁹ represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom;
m is an integer of 1 to 4,
* Represents a bond. ]
When the polyamide-imide resin has a structural unit represented by the formula (1), the structure represented by -A- in the above formula on the main chain of the polyamide-imide resin can give a high flexibility when used as a film. Will be included. By having a structure capable of imparting high flexibility to the polyamide-imide resin, the tan δ peak temperature of the polyamide-imide resin can be appropriately reduced. As a result, the surface hardness of the film containing the polyamide-imide resin is It can be increased under relatively low temperature heating conditions.

The symbols in formula (1) will be described below.
Each A independently represents —O—, —S—, —CO— or —NR ⁹ —, wherein R ⁹ is a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Represents. From the viewpoint of the flexibility of the optical film of the present invention, A preferably independently represents —O— or —S—, and more preferably represents —O—.
R ^{1 to} R ⁸ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. From the viewpoints of flexibility and surface hardness of the optical film of the present invention, R ^{1 to} R ⁸ each independently preferably represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or carbon. Represents an alkyl group of 1 to 3, more preferably a hydrogen atom. Here, the hydrogen atoms contained in R ^{1 to} R ⁸ may be each independently substituted with a halogen atom.
m is an integer in the range of 1 to 4, and is preferably an integer in the range of 1 to 3, more preferably 1 or 2, and even more preferably 1 from the viewpoint of availability of raw materials. When m is within the above range, the availability of the raw materials is good, and the flexibility of the optical film of the present invention is easily increased.

In a preferred embodiment of the present invention, the formula (1) is a structural unit represented by the formula (1 ′). In this case, the optical film of the present invention exhibits high surface hardness, and at the same time has a low elastic modulus and tends to have high flexibility.

In a preferred embodiment in which the polyamideimide resin contained in the optical film of the present invention has a structural unit represented by the formula (1) or the formula (1 ′), the amount of the structural unit is the total amount contained in the polyamideimide resin. Based on the structural unit, it is preferably at least 3 mol%, more preferably at least 5 mol%, even more preferably at least 10 mol%, particularly preferably at least 20 mol%. When the amount of the structural unit represented by the formula (1) or the formula (1 ′) is not less than the above lower limit, a polyamideimide resin having a tan δ peak value in a temperature range of 370 ° C. or less can be easily obtained.
Further, the amount of the structural unit represented by the formula (1) or the formula (1 ′) is preferably 45 mol% or less, more preferably 40 mol% or less, based on all the structural units contained in the polyamideimide resin. More preferably, it is 30 mol% or less. When the amount of the structural unit represented by the formula (1) or the formula (1 ′) is not more than the above upper limit, it is easy to obtain a polyamideimide resin having a tan δ peak value in a temperature range of 300 ° C. or higher.

  The polyamideimide resin contained in the optical film of the present invention can be produced using, for example, dicarboxylic acid, diamine and tetracarboxylic acid as main raw materials, and preferably has at least a structural unit derived therefrom. Here, the structural unit represented by the formula (1) or the formula (1 ′) is preferably a structural unit derived from a dicarboxylic acid.

  The polyamideimide resin contained in the optical film of the present invention preferably has at least a structural unit derived from dicarboxylic acid from the viewpoints of pencil hardness and elastic modulus. The structural unit derived from dicarboxylic acid is preferably a structural unit derived from dicarboxylic acid dichloride.

［式（２）中、Ｚは２価の有機基を表し、Ｂ^１およびＢ^２は、それぞれ独立して、ＯＨまたはハロゲン原子、好ましくは塩素原子を表す。］ Examples of the dicarboxylic acid include a compound represented by the formula (2). The polyamideimide resin may have a structural unit derived from one type of dicarboxylic acid, or may have a structural unit derived from two or more types of dicarboxylic acid.

[In the formula (2), Z represents a divalent organic group, and B ¹ and B ² each independently represent OH or a halogen atom, preferably a chlorine atom. ]

  In a preferred embodiment in which the polyamideimide resin contained in the optical film of the present invention has a constitutional unit derived from the dicarboxylic acid represented by the formula (2), the amount of the constitutional unit is the total constitution contained in the polyamideimide resin. Based on the unit, it is preferably 5 mol% or more, more preferably 15 mol% or more, and further preferably 20 mol% or more. When the amount of the structural unit derived from the dicarboxylic acid represented by the formula (2) is not less than the above lower limit, high surface hardness is likely to be exhibited. The amount of the structural unit derived from the dicarboxylic acid represented by the formula (2) is preferably 45 mol% or less, more preferably 40 mol% or less, based on the total structural units contained in the polyamideimide resin. Preferably it is 30 mol% or less. When the amount of the structural unit derived from the dicarboxylic acid represented by the formula (2) is not more than the above upper limit, it is easy to obtain a polyamideimide resin having a tan δ peak value in a temperature range of 370 ° C. or less.

Z in the formula (2) represents a divalent organic group, and preferably represents 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. Examples of the divalent organic group include groups represented by formulas (2a) and (2b); a hydrogen atom in the groups represented by formulas (2a) and (2b) is a methyl group, a fluoro group, or a chloro group Or a group substituted with a trifluoromethyl group; and a divalent chain hydrocarbon group having 6 or less carbon atoms.

[In Formula (2a) and Formula (2b),
* Represents a bond,
U 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 with a fluorine atom, and specific examples thereof include a phenylene group. ]

Specific examples of the dicarboxylic acid represented by the formula (2) include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and related acid chloride compounds, acid anhydrides, and the like. May be. Specific examples include terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4,4′-biphenyldicarboxylic acid; 3,3′-biphenyldicarboxylic acid; dicarboxylic acid compounds of chain hydrocarbons having 8 or less carbon atoms and 2 A compound in which two benzoic acids are linked by a single bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —SO ₂ — or a phenylene group, and their acid chloride compounds Can be mentioned. The dicarboxylic acid represented by the above formula (2) preferably contains 4,4′-oxybisbenzoic acid and / or an acid chloride compound thereof. Specifically, it is preferable to contain 4,4′-oxybis (benzoyl chloride), and the combined use of 4,4′-oxybis (benzoyl chloride) and terephthaloyl chloride is more preferable.

In a preferred embodiment of the present invention in which the polyamideimide resin has a structural unit derived from dicarboxylic acid, from the viewpoint of easily increasing the surface hardness, elastic modulus and flexibility of the optical film of the present invention, the polyamideimide resin is represented by the formula (2 Z) preferably has at least a structural unit derived from the dicarboxylic acid represented by the formula (1). When the polyamideimide resin has a structural unit derived from two or more kinds of dicarboxylic acids, the amount of the structural unit derived from the dicarboxylic acid in which Z in formula (2) is represented by formula (1) is the surface of the optical film. From the viewpoint of hardness, elastic modulus and flexibility, it is preferably 5 mol% or more, more preferably 7 mol% or more, and even more preferably 9 mol%, based on the entire structural unit derived from dicarboxylic acid contained in the polyamideimide resin. Above, especially preferably 11 mol% or more. The upper limit of the amount of the structural unit derived from the dicarboxylic acid in which Z in the formula (2) is represented by the formula (1) is not particularly limited, and is based on the entire structural unit derived from the dicarboxylic acid contained in the polyamideimide resin. What is necessary is just 100 mol% or less. The ratio of the structural units derived from the dicarboxylic acid in which Z in formula (2) is represented by formula (1) can be measured, for example, using ¹ H-NMR, or calculated from the raw material charge ratio. You can also.

  The polyamide-imide resin contained in the optical film of the present invention preferably has at least a structural unit derived from diamine from the viewpoints of transparency, low hygroscopicity, and solubility in a solvent.

［式（３）中、Ｘは２価の有機基を表す。］
ポリアミドイミド樹脂は、１種類のジアミンに由来する構成単位を有していてもよいし、２種以上のジアミンに由来する構成単位を有していてもよい。 Examples of the diamine include a compound represented by the formula (3).

[In formula (3), X represents a divalent organic group. ]
The polyamideimide resin may have a structural unit derived from one kind of diamine, or may have a structural unit derived from two or more kinds of diamines.

  In a preferred embodiment in which the polyamideimide resin contained in the optical film of the present invention has a constitutional unit derived from the diamine represented by the formula (3), the amount of the constitutional unit is the total constitutional unit contained in the polyamideimide resin. Is preferably 47.5 mol% or more, more preferably 49.0 mol% or more, and further preferably 49.5 mol% or more. When the amount of the structural unit derived from the diamine represented by the formula (3) is not less than the above lower limit, it is easy to obtain a high molecular weight polyamideimide resin and easily develop high surface hardness. Further, the amount of the structural unit derived from the diamine represented by the formula (3) is preferably 50.5 mol% or less, more preferably 50.0 mol%, based on all the structural units contained in the polyamideimide resin. Hereinafter, it is more preferably 49.99 mol% or less. When the amount of the structural unit derived from the diamine represented by the formula (3) is not more than the above upper limit, high transparency and low yellowness are likely to be exhibited.

X in the formula (3) represents a divalent organic group, and preferably represents 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. Examples of the divalent organic group include formula (3a), formula (3b), formula (3c), formula (3d), formula (3e), formula (3f), formula (3g), formula (3h), and formula ( A group represented by 3i); a group in which hydrogen atoms in the groups represented by these formulas are substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a divalent chain having 6 or less carbon atoms Illustrative are hydrocarbon radicals.

[In Formula (3a), Formula (3b), Formula (3c), Formula (3d), Formula (3e), Formula (3f), Formula (3g), Formula (3h) and Formula (3i),
* Represents a bond,
V ¹ ~V ³ are each independently a single _{bond, -O -, - S -,} - CH 2 -, - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) _{2 -, - C (CF 3} ) 2 -, - representing the or -CO- - SO _2. ]
In one example, V ¹ and V ³ are a single bond, —O— or —S—, and V ² is —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) _2. - or -SO ₂ - is. The bonding position of each of V ¹ and V ² with respect to each ring and the bonding position of each of V ² and V ³ with respect to each ring is preferably in the meta position or the para position with respect to each ring. More preferably.

Formula (3a), Formula (3b), Formula (3c), Formula (3d), Formula (3e), Formula (3f), Formula (3g), Formula (3h) and Formula (3i) Among these, from the viewpoint of the surface hardness and flexibility of the optical film of the present invention, a group represented by the formula (3d), the formula (3e), the formula (3f), the formula (3g), or the formula (3h) is preferable. The group represented by (3e), formula (3f) or formula (3g) is more preferred. V ^{1 to} V ³ are each independently preferably a single bond, —O— or —S— from the viewpoint of the surface hardness and flexibility of the optical film of the present invention, and are preferably a single bond or —O—. -Is more preferable.

  Specific examples of the diamine represented by the formula (3) include aliphatic diamines, aromatic diamines, and mixtures thereof. In the present embodiment, the “aromatic diamine” represents a diamine in which an amino group is directly bonded to an aromatic ring, and an aliphatic group or other substituent may be included in a part of the structure. The aromatic ring may be a single ring or a condensed ring, and examples thereof include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferable. The “aliphatic diamine” refers to a diamine in which an amino group is directly bonded to an aliphatic group, and an aromatic ring or other substituent may be included in a part of the structure.

  Examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylene diamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornane diamine, and 4,4 ′. -Cyclic aliphatic 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-diamino. An aromatic diamine having one aromatic ring, such as naphthalene; 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3 '-Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-Aminophenoxy) benzene, 4,4'-diamino Phenylsulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2 , 2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2′-dimethylbenzidine, 2,2′-bis (trifluoromethyl) benzidine (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) Having two or more aromatic rings such as -3-chlorophenyl) fluorene and 9,9-bis (4-amino-3-fluorophenyl) fluorene. Aromatic diamine and the like. These can be used alone or in combination of two or more.

  As the aromatic diamine, preferably 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenylsulfone, 1,4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2′-dimethylbenzidine, 2,2′-bis (Trifluoromethyl) -4,4′-diaminodiphenyl, 4,4′-bis (4-aminophen Xyl) 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, 4,4'-bis (4-aminophenoxy) biphenyl. These can be used alone or in combination of two or more.

  Among the diamine compounds, from the viewpoint of surface hardness, flexibility, bending resistance, transparency and yellowness of the optical film of the present invention, at least one selected from the group consisting of aromatic diamines having a biphenyl structure should be used. Preferably 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 one or more of these, and it is even more preferable to use 2,2′-bis (trifluoromethyl) benzidine.

［式（３ｅ’）中、Ｒ^１０〜Ｒ^１７は、それぞれ独立に、水素原子、炭素数１〜６のアルキル基または炭素数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、それぞれ独立に、ハロゲン原子で置換されていてもよく、
＊は結合手を表す。］ In a preferred embodiment of the present invention in which the polyamideimide resin has a structural unit derived from diamine, from the viewpoint of easily increasing the surface hardness and transparency of the optical film of the present invention, the polyamideimide resin is represented by X in the formula (3). Preferably has at least a structural unit derived from a diamine represented by the formula (3e ′).

[In Formula (3e ′), R ^{10 to} R ¹⁷ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and are included in R ^{10 to} R ^17. Each hydrogen atom may be independently substituted with a halogen atom,
* Represents a bond. ]

In the formula (3e ′), R ^{10 to} R ¹⁷ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, preferably a hydrogen atom or 1 to 1 carbon atom. 6 represents an alkyl group, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein the hydrogen atoms contained in R ^{10 to} R ¹⁷ are each independently substituted with a halogen atom. Also good. From the viewpoint of the surface hardness, flexibility and transparency of the optical film of the present invention, R ^{10 to} R ¹⁷ are each independently more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group. And particularly preferably a hydrogen atom or a trifluoromethyl group.

［式（３ｅ”）中、＊は結合手を表す］
この場合、本発明の光学フィルムが高い透明性を有すると同時に、ポリアミドイミド樹脂がフッ素元素を含有する骨格を有することにより、ポリアミドイミド樹脂の溶剤への溶解性が向上し、本発明の光学フィルムを作製する際に使用するポリアミドイミドワニスの粘度を低く抑制することができるため、本発明の光学フィルムを製造しやすくなる。 In the preferable embodiment, the polyamideimide resin preferably includes at least a structural unit derived from a diamine in which X in the formula (3) is represented by the formula (3e ″).

[In formula (3e ″), * represents a bond]
In this case, the optical film of the present invention has high transparency, and at the same time, the polyamideimide resin has a skeleton containing elemental fluorine, so that the solubility of the polyamideimide resin in the solvent is improved, and the optical film of the present invention Since the viscosity of the polyamidoimide varnish used for producing can be suppressed low, the optical film of the present invention can be easily produced.

When the polyamideimide resin has a structural unit derived from two or more diamines, X in the formula (3) is a structural unit derived from the diamine represented by the formula (3e ′), preferably the formula (3e ″). The amount is preferably 30 mol% or more, more preferably 50 mol%, based on the entire structural unit derived from the diamine contained in the polyamideimide resin, from the viewpoint of improving the transparency of the optical film and ease of production. More preferably, it is 70 mol% or more The upper limit of the amount of the structural unit derived from the diamine in which X in the formula (3) is represented by the formula (3e ′), preferably the formula (3e ″) is particularly limited. However, 100 mol% or less should just be based on the whole structural unit derived from the diamine contained in a polyamideimide resin. The ratio of the structural unit derived from the diamine in which X in Formula (3) is represented by Formula (3e ′) or Formula (3e ″) can be measured using, for example, ¹ H-NMR, It can also be calculated from the charging ratio.

  The polyamideimide resin contained in the optical film of the present invention preferably has at least a structural unit derived from tetracarboxylic dianhydride from the viewpoints of transparency, hygroscopic properties and solubility in a solvent.

［式（４）中、Ｙは、４価の有機基を表す］ Examples of the tetracarboxylic dianhydride include compounds represented by the formula (4). The polyamideimide resin may have a structural unit derived from one type of tetracarboxylic dianhydride, or may have a structural unit derived from two or more types of tetracarboxylic dianhydride. .

[In formula (4), Y represents a tetravalent organic group]

  In a preferred embodiment in which the polyamideimide resin contained in the optical film of the present invention has a structural unit derived from the tetracarboxylic dianhydride represented by the formula (4), the amount of the structural unit is the amount of the polyamideimide resin. Based on all the structural units contained, it is preferably 5 mol% or more, more preferably 10 mol% or more, and still more preferably 20 mol% or more. When the amount of the structural unit derived from the tetracarboxylic dianhydride represented by the formula (4) is not less than the above lower limit, the proportion of the structural unit derived from the dicarboxylic acid can be suppressed, and the temperature is 370 ° C. or lower. It is easy to obtain a polyamideimide resin having a peak value of tan δ in the range. The amount of the structural unit derived from the tetracarboxylic dianhydride represented by the formula (4) is preferably 45 mol% or less, more preferably 40 mol, based on the total structural units contained in the polyamideimide resin. % Or less, more preferably 30 mol% or less. When the amount of the structural unit derived from the tetracarboxylic dianhydride represented by the formula (4) is not more than the above upper limit, the proportion of the structural unit derived from the dicarboxylic acid can be increased, and high surface hardness is expressed. Cheap.

Y in Formula (4) represents a tetravalent organic group, and preferably represents 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. Examples of the tetravalent organic group include formula (4a), formula (4b), formula (4c), formula (4d), formula (4e), formula (4f), formula (4g), formula (4h), formula ( Groups represented by 4i) and formula (4j); a group in which a hydrogen atom in the groups represented by these formulas is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and 6 or less carbon atoms And a tetravalent chain hydrocarbon group.

[Formula (4a), Formula (4b), Formula (4c), Formula (4d), Formula (4e), Formula (4f), Formula (4g), Formula (4h), Formula (4i), and Formula (4j) During,
* 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 with a fluorine atom, and specific examples thereof include a phenylene group. ]

Formula (4a), Formula (4b), Formula (4c), Formula (4d), Formula (4e), Formula (4f), Formula (4g), Formula (4h), Formula (4i), and Formula (4j) Among the groups represented, from the viewpoint of the surface hardness and flexibility of the optical film of the present invention, a group represented by the formula (4g), the formula (4i) or the formula (4j) is preferable, and represented by the formula (4g). More preferred are the groups Further, ^{W 1,} from the viewpoint of surface hardness and flexibility of the optical film of the present invention, a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH ₃ ) ₂ — or —C (CF ₃ ) ₂ — is preferable, and a single bond, —O—, —CH ₂ —, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ — is preferable. Or —C (CF ₃ ) ₂ —, more preferably a single bond, —O—, —C (CH ₃ ) ₂ — or —C (CF ₃ ) ₂ —, and —O—. or -C _{(CF 3) 2} - is deliberately preferably.

  Examples of the tetracarboxylic dianhydride represented by the formula (4) include aromatic tetracarboxylic dianhydrides and aliphatic tetracarboxylic dianhydrides. One type of tetracarboxylic dianhydride may be used, or two or more types may be used in combination.

  Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydride, monocyclic aromatic tetracarboxylic dianhydride, and condensed polycyclic aromatic tetra Carboxylic dianhydrides are mentioned. Specific examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride include 4,4′-oxydiphthalic dianhydride (may be described as OPDA), 3,3 ′, 4,4′- Benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3 , 3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 '-(hexafluoroisopropylidene) Phthalic dianhydride (may be described as 6FDA), 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane Anhydride, 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. In addition, 1,2,4,5-benzenetetracarboxylic dianhydride is used as the monocyclic aromatic tetracarboxylic dianhydride, and 1,4,5-benzenetetracarboxylic dianhydride is used as the condensed polycyclic aromatic tetracarboxylic dianhydride. 2,4,5-benzenetetracarboxylic dianhydride, and condensed polycyclic aromatic tetracarboxylic dianhydride includes 2,3,6,7-naphthalenetetracarboxylic dianhydride, respectively. . These can be used alone or in combination of two or more.

  Among these, 4,4′-oxydiphthalic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfonetetra Carboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis ( 3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride, 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxy) Phenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 ′-(p-phenylenedioxy) diphthal Acid dianhydride and 4,4 ′-(m-phenylenedioxy) diphthalic dianhydride are preferable, 4,4′-oxydiphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid More preferred are dianhydrides and 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride.

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

  Among the tetracarboxylic dianhydrides, 4,4′-oxydiphthalic dianhydride, from the viewpoint of easily increasing the surface hardness, flexibility, bending resistance and transparency of the optical film and easily reducing the yellowness, 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, 4,4'-oxydiphthalic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 4,4' -(Hexafluoroisopropylidene) diphthalic dianhydride and mixtures thereof are more preferred, and 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride is more preferred.

［式（４ｇ’）中、Ｒ^１８〜Ｒ^２５は、それぞれ独立に、水素原子、炭素数１〜６のアルキル基または炭素数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、それぞれ独立に、ハロゲン原子で置換されていてもよく、
＊は結合手を表す］
この場合、本発明の光学フィルムが高い透明性を有すると同時に、ポリアミドイミド樹脂の高い屈曲性骨格を有することにより、ポリアミドイミド樹脂の溶剤への溶解性が向上し、本発明の光学フィルムを作製する際に使用するポリアミドイミドワニスの粘度を低く抑制することができるため、本発明の光学フィルムを製造しやすくなる。 In a preferred embodiment of the present invention in which the polyamideimide resin has a structural unit derived from tetracarboxylic dianhydride, the polyamideimide resin has a tetracarboxylic acid in which Y in the formula (4) is represented by the formula (4g ′). It is preferable to have at least a structural unit derived from an acid dianhydride.

[In Formula (4g ′), R ^{18 to} R ²⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and are included in R ^{18 to} R ^25. Each hydrogen atom may be independently substituted with a halogen atom,
* Represents a bond]
In this case, the optical film of the present invention has high transparency and at the same time has a high flexibility skeleton of the polyamideimide resin, so that the solubility of the polyamideimide resin in the solvent is improved and the optical film of the present invention is produced. Since the viscosity of the polyamide-imide varnish used in the process can be suppressed low, the optical film of the present invention can be easily produced.

In the formula (4g ′), R ^{18 to} R ²⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, preferably a hydrogen atom or 1 to 3 carbon atoms. 6 represents an alkyl group, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein the hydrogen atoms contained in R ^{18 to} R ²⁵ are each independently substituted with a halogen atom. Also good. From the viewpoint of the surface hardness and flexibility of the optical film of the present invention, R ^{18 to} R ²⁵ are each independently more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group. A hydrogen atom or a trifluoromethyl group is preferred.

［式（４ｇ”）中、＊は結合手を表す］
この場合、本発明の光学フィルムが高い透明性を有すると同時に、ポリアミドイミド樹脂がフッ素元素を含有する骨格を有することにより、ポリアミドイミド樹脂の溶剤への溶解性が向上し、本発明の光学フィルムを作製する際に使用するポリアミドイミドワニスの粘度を低く抑制することができるため、本発明の光学フィルムを製造しやすくなる。 In one preferable embodiment described above, the polyamideimide resin preferably has at least a structural unit derived from tetracarboxylic dianhydride in which Y in Formula (4) is represented by Formula (4g ″).

[In formula (4g "), * represents a bond]
In this case, the optical film of the present invention has high transparency, and at the same time, the polyamideimide resin has a skeleton containing elemental fluorine, so that the solubility of the polyamideimide resin in the solvent is improved, and the optical film of the present invention Since the viscosity of the polyamidoimide varnish used for producing can be suppressed low, the optical film of the present invention can be easily produced.

When the polyamideimide resin has a structural unit derived from two or more kinds of tetracarboxylic dianhydrides, Y in the formula (4) is a tetracarboxylic acid represented by the formula (4g ′), preferably the formula (4g ″). The amount of the structural unit derived from the acid dianhydride is based on the entire structural unit derived from the tetracarboxylic dianhydride contained in the polyamideimide resin from the viewpoint of improving the transparency of the optical film and the ease of production. In the formula (4), Y in the formula (4g ′), preferably the formula (4g ″) is preferably 50 mol% or more, more preferably 60 mol% or more, and further preferably 70 mol% or more. The upper limit of the amount of the structural unit derived from the tetracarboxylic dianhydride is not particularly limited, and is 100% based on the entire structural unit derived from the tetracarboxylic dianhydride contained in the polyamideimide resin. % May be any less. The ratio of the structural unit derived from the diamine in which X in Formula (4) is represented by Formula (4g ′) or Formula (4g ″) can be measured using, for example, ¹ H-NMR, It can also be calculated from the charging ratio.

The polyamideimide resin contained in the optical film of the present invention may further have a structural unit derived from tricarboxylic acid. Examples of the tricarboxylic acid include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and acid chloride compounds, acid anhydrides and the like that are analogs thereof. One type of tricarboxylic acid may be used, or two or more types may be used in combination.
Specific examples include 1,2,4-benzenetricarboxylic acid anhydride; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthalic anhydride and benzoic acid are a single bond, -O- , —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —SO ₂ —, or a compound connected by a phenylene group.

［式（５）および式（６）中、Ｘ、ＹおよびＺは前記と同義である］
式（５）および式（６）中のＸ、ＹおよびＺは、それぞれ、式（３）中のＸ、式（４）中のＹおよび式（２）中のＺと同義であり、式（２）〜式（４）中のＸ、ＹおよびＺに関して上記に述べた好ましい記載が、式（５）および式（６）中のＸ、ＹおよびＺについても同様にあてはまる。式（５）で表される構成単位は、通常、ジアミンおよびテトラカルボン酸に由来する構成単位であり、式（６）で表される構成単位は、通常、ジアミンおよびジカルボン酸に由来する構成単位である。 In a preferred embodiment of the present invention, the polyamideimide resin having a tan δ peak value measured by DMA in the range of 300 to 370 ° C. contained in the optical film of the present invention is dicarboxylic acid (dicarboxylic acid analog such as acid chloride). ), Diamine and tetracarboxylic acid (tetracarboxylic acid analogs such as acid chloride and tetracarboxylic dianhydride), and in some cases tricarboxylic acid (acid chloride compounds and tricarboxylic acid analogs such as tricarboxylic acid anhydride) ) And a condensation polymer that is a polycondensation product. In this embodiment, the polyamideimide resin has a structural unit represented by the formula (5) and a structural unit represented by the formula (6).

[In Formula (5) and Formula (6), X, Y, and Z are as defined above]
X, Y and Z in the formula (5) and the formula (6) are respectively synonymous with X in the formula (3), Y in the formula (4) and Z in the formula (2). The preferable description described above regarding X, Y, and Z in 2) to formula (4) applies to X, Y, and Z in formula (5) and formula (6) as well. The structural unit represented by the formula (5) is usually a structural unit derived from diamine and tetracarboxylic acid, and the structural unit represented by the formula (6) is usually structural unit derived from diamine and dicarboxylic acid. It is.

［式（７）中、Ｘ^１は２価の有機基を表し、Ｙ^１は４価の有機基を表し、
式（８）中、Ｘ^２は２価の有機基を表し、Ｙ^２は３価の有機基を表す］ In a preferred embodiment of the present invention, the polyamideimide resin having a peak value of tan δ as measured by DMA in the range of 300 to 370 ° C. contained in the optical film of the present invention is further represented by the formula (7): You may have a unit and / or the structural unit represented by Formula (8).

[In Formula (7), X ¹ represents a divalent organic group, Y ¹ represents a tetravalent organic group,
In formula (8), X ² represents a divalent organic group, and Y ² represents a trivalent organic group.]

In Formula (7), each Y ¹ is independently a tetravalent organic group, and preferably a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Organic group. The Y ^1, equation (4a), formula (4b), wherein (4c), the formula (4d), the formula (4e), Equation (4f), the formula (4g), formula (4h), Formula (4i) and Examples are a group represented by the formula (4j) and a tetravalent chain hydrocarbon group having 6 or less carbon atoms. The polyamide-imide resin may have a structural unit represented by one type of formula (7), or a structure represented by two or more types of formula (7) that are different from each other in Y ¹ and / or X ¹ . You may have a unit.

In Formula (8), each Y ² is independently a trivalent organic group, and preferably a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Organic group. The Y ^2, formula (4a), formula (4b), wherein (4c), the formula (4d), the formula (4e), Equation (4f), the formula (4g), formula (4h), Formula (4i) or Examples thereof include a group in which any one of the bonds of the group represented by formula (4j) is replaced with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. The polyamideimide resin may have one type of structural unit represented by Formula (8), or may be represented by two or more types of Formula (8) that are different from each other in Y ² and / or X ² . You may have a unit.

In the formula (7) and the formula (8), X ¹ and X ² are each independently a divalent organic group, preferably a hydrocarbon group or a fluorine-substituted hydrocarbon in which a hydrogen atom in the organic group is substituted An organic group which may be substituted with a group. X ¹ and X ² include formula (3a), formula (3b), formula (3c), formula (3d), formula (3e), formula (3f), formula (3g), formula (3h), and formula ( A group represented by 3i); a group in which a hydrogen atom in the group represented by the formula is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon having 6 or less carbon atoms Examples are groups.

In a preferred embodiment of the present invention, the polyamideimide resin contained in the optical film of the present invention comprises a structural unit represented by formula (5) and formula (6), and optionally formula (7) and / or formula ( 8). In this embodiment, from the viewpoint of easily increasing the flexibility and surface hardness of the optical film, the amount of the structural unit represented by the formula (5) and the structural unit represented by the formula (6) contained in the polyamide-imide resin Based on (5) and formula (6), and optionally the sum of the structural units represented by formula (7) and / or formula (8), preferably 80% or more, more preferably 90% or more, Preferably it is 95% or more. In addition, the upper limit of the amount of the structural unit represented by the formula (5) and the formula (6) contained in the polyamideimide resin is the formula (5) or the formula (6), or the formula (7) or the formula in some cases. Based on the total of the structural units represented by (8), it is usually 100% or less. The above ratio is, for example, may ^{be 1 H-NMR} can be measured using, or calculated from the charge ratio of the raw materials.

  The polyamideimide resin contained in the optical film of the present invention preferably contains a halogen atom, and more preferably contains a fluorine atom. Specific examples of the fluorine-containing substituent include a fluoro group and a trifluoromethyl group. When the polyamideimide resin contains a halogen atom, it is easy to reduce the yellowness (YI value) of the optical film of the present invention, and it is easy to achieve both high flexibility and bending resistance. From the viewpoints of reduction in yellowness, reduction in water absorption, and bending resistance of the optical film of the present invention, the halogen atom is preferably a fluorine atom. From the above viewpoint, the polyamideimide resin preferably has at least a structural unit derived from a fluorine atom-containing diamine and / or a fluorine atom-containing tetracarboxylic dianhydride.

  The content of the halogen atom in the polyamide-imide resin is the mass of the polyamide-imide resin contained in the optical film of the present invention from the viewpoints of reducing yellowness (improving transparency), reducing water absorption, and suppressing deformation of the optical film. Is preferably 1 to 40% by mass, more preferably 3 to 35% by mass, and still more preferably 5 to 32% by mass.

  Next, a method for producing the polyamideimide resin contained in the optical film of the present invention will be described. The polyamide-imide resin can be produced, for example, by using the above-mentioned dicarboxylic acid, diamine and tetracarboxylic acid as main raw materials, and optionally polycondensing these together with the tricarboxylic acid described above.

  Although the reaction temperature of the said polycondensation reaction is not specifically limited, For example, it is 50-350 degreeC. Although reaction time is not specifically limited, For example, it is about 30 minutes-10 hours. If necessary, the reaction may be carried out under an inert atmosphere or under reduced pressure. Further, the reaction may be carried out in a solvent, and examples of the solvent include a solvent described later used for preparing a polyamideimide varnish.

  In the polycondensation reaction, an imidization catalyst may be used. Examples of imidation catalysts include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydro Alicyclic amines such as azepine (monocyclic); azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane, and azabicyclo [3.2. 2] Alicyclic amines (polycyclic) such as nonane; and pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine 5,6,7,8-tetrahydroisoquinoline, and include aromatic amines isoquinoline.

  From the viewpoint of improving the visibility and quality of the optical film of the present invention, the optical film of the present invention preferably further contains an additive having a light absorption function in addition to the polyamideimide resin. Examples of the additive having a light absorbing function include an ultraviolet absorber and a bluing agent. The additive having a light absorbing function is preferably selected from the group consisting of an ultraviolet absorber and a bluing agent because the visibility and quality of the optical film of the present invention are easily improved. The optical film of the present invention may contain one type of additive having a light absorption function, or may contain two or more types of additives having a light absorption function. Here, when an additive having a light absorbing function such as an ultraviolet absorber and a bluing agent is added to a film containing a conventional polyamideimide resin, since these additives have low heat resistance, a polyamideimide resin is used. In the process of heating the containing film under high-temperature conditions, there was a problem that degradation or the like occurred and the quality of the film deteriorated. For this reason, for example, it is necessary to add such an additive to a layer different from the layer containing the polyamide-imide resin and to bond it to the polyamide film. According to the optical film of the present invention including a polyamideimide resin having a peak value of tan δ within a predetermined temperature range, a sufficiently high surface hardness can be achieved under relatively low temperature heating conditions. Even when an additive having a light-absorbing function is added to the same layer as the layer, degradation of these additives can be suppressed, and deterioration of film quality can be suppressed.

  The ultraviolet absorber may be appropriately selected from those usually used as an ultraviolet absorber in the field of resin materials. The ultraviolet absorber may contain 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 benzophenone compounds, salicylate compounds, benzotriazole compounds, and triazine compounds. When the optical film of the present invention contains an ultraviolet absorber, the degradation of the polyamideimide resin is suppressed, so that the visibility of the optical film can be enhanced. In the present specification, “system compound” refers to a derivative of a compound to which the “system compound” is attached. For example, a “benzophenone compound” refers to a compound having benzophenone as a host skeleton and a substituent bonded to benzophenone.

  When the optical film contains an ultraviolet absorber, the addition amount of the ultraviolet absorber may be appropriately selected depending on the type of the ultraviolet absorber to be used. As a guideline, it is preferably 1% by mass based on the total mass of the optical film. More preferably, it is 2% by mass or more, more preferably 3% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less. The preferred addition amount varies depending on the ultraviolet absorber to be used, but adjusting the addition amount so that the light transmittance at 400 nm is about 20 to 60% is easy to improve the light resistance of the optical film of the present invention and is transparent. Since it is easy to obtain an optical film with high property, it is preferable.

  The bluing agent may be appropriately selected from those normally used as a bluing agent in the field of resin materials. The bluing agent is an additive (dye, pigment) that adjusts the hue by absorbing light in a wavelength region such as orange to yellow in the visible light region. For example, ultramarine, bitumen, cobalt blue, etc. And inorganic dyes and pigments such as organic dyes and pigments such as phthalocyanine blueing agents and condensed polycyclic blueing agents. The bluing agent is not particularly limited, but from the viewpoint of heat resistance, light resistance, and solubility, a condensed polycyclic bluing agent is preferable, and an anthraquinone bluing agent is more preferable. From the viewpoint of heat resistance, the bluing agent preferably has a thermal decomposition temperature of 200 ° C. or higher, preferably 240 ° C. or higher. Examples of the condensed polycyclic bluing agent include anthraquinone bluing agents, indigo bluing agents, and phthalocyanine bluing agents.

  When the optical film contains a bluing agent, the amount of bluing agent added may be appropriately selected depending on the type of bluing agent used, but as a guideline, it is preferably 0.01 based on the total mass of the optical film. % By mass or more, more preferably 0.02% by mass or more, further preferably 0.03% by mass or more, preferably 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.8% by mass. 2% by mass or less.

  The optical film of the present invention may further contain an inorganic material such as inorganic particles in addition to the polyamideimide resin. Examples of the inorganic material include inorganic particles such as titania particles, alumina particles, zirconia particles, and silica particles, and silicon compounds such as quaternary alkoxysilanes such as tetraethyl orthosilicate. From the viewpoint of the stability of the polyamideimide varnish, the inorganic material is preferably inorganic particles, particularly silica particles. The inorganic particles may be bonded by a molecule having a siloxane bond (that is, -SiOSi-).

  The average primary particle diameter of the inorganic particles is preferably 10 to 100 nm, more preferably 20 to 80 nm, from the viewpoints of transparency of the optical film, mechanical properties, and aggregation suppression of the inorganic particles. In the present invention, the average primary particle diameter can be determined by measuring a 10-point average value of the unidirectional diameter by a transmission electron microscope.

  The optical film of the present invention may contain an inorganic material. The content of the inorganic material in the optical film is preferably 0 to 90% by mass, more preferably 0.01 to 60% by mass, and further preferably 5 to 40% by mass based on the total mass of the optical film. When the content of the inorganic material is within the above range, the transparency and mechanical properties of the optical film tend to be compatible.

  The optical film of the present invention may contain other additives. Examples of other additives include an antioxidant, a mold release agent, a stabilizer, a flame retardant, a pH adjuster, a silica dispersant, a lubricant, a thickener, and a leveling agent. The content of other additives is preferably 0% by mass or more and 20% by mass or less, more preferably 0.01% by mass or more and 10% by mass or less, based on the mass of the optical film of the present invention.

(Layer structure)
The layer structure of the optical film of the present invention is not particularly limited, and may be a single layer or a multilayer of two or more layers. When the optical film of the present invention further contains an additive such as an additive having a light absorption function, from the viewpoint of thinning of the image display device and economy, the additive and the polyamideimide resin are combined into one layer. It is preferable to contain. In this case, the optical film of the present invention is more preferably a single layer containing the additive and the polyamideimide resin, or a laminate having at least a layer containing the additive and the polyamideimide resin. From the viewpoint of impact resistance characteristics, the optical film of the present invention preferably has a multilayer structure of two or more layers including at least a layer containing a polyamideimide resin. When the optical film of the present invention further contains an additive such as an additive having a light absorption function, the optical film is a laminate having at least a layer containing the additive and a polyamideimide resin, or a layer containing the additive And a laminate having at least a layer containing a polyamideimide resin.

  The optical film of the present invention may be a polyamideimide laminate in which one or more functional layers are further laminated on the above layer. Examples of the functional layer include layers having various functions such as a hard coat layer, an ultraviolet absorbing layer, an adhesive layer, a refractive index adjusting layer, and a primer layer. The optical film of the present invention may include one or more functional layers. One functional layer may have a plurality of functions. For example, an optical film having a multilayer structure may be obtained by forming the functional layer on a film containing a polyamideimide resin.

The optical film of the present invention is, for example,
(1) A step of applying a resin composition containing at least a polyamideimide resin and a solvent to a support, and
(2-1) A step of peeling the coating film of the resin composition from the support after drying at a temperature of 240 ° C. or lower, or
(2-2) Manufactured by a production method including at least a step of peeling a coating film of the resin composition from a support after drying at a temperature of 240 ° C. or less, and a step of heating the peeled film at a temperature of 240 ° C. or less. can do. The present invention also provides a method for producing the optical film.

  In order to produce a resin composition containing at least a polyamideimide resin and a solvent (also referred to as “polyamideimide varnish” in the present specification) used in step (1), the dicarboxylic acid, diamine, and tetracarboxylic acid described above are used. If necessary, other components (a tertiary amine that acts as an imidization catalyst, a dehydrating agent, etc.) are mixed and reacted to produce a polyamideimide resin mixture. Examples of the tertiary amine include the aromatic amines and aliphatic amines described above. Examples of the dehydrating agent include acetic anhydride, propionic anhydride, isobutyric anhydride, pivalic anhydride, butyric anhydride, isovaleric anhydride, and the like. A resin composition containing at least the polyamideimide resin and the solvent is produced by adding the solvent and, if necessary, the above-described additive to the polyamideimide resin mixed solution and stirring the mixture. Even if a poor solvent is added to the above-mentioned polyamideimide mixed liquid, a polyamideimide resin is precipitated by a reprecipitation method, dried and taken out as a precipitate, and the polyamideimide resin precipitate taken out is dissolved in a solvent to obtain a polyamideimide mixed liquid. Good. Further, instead of the polyamide-imide resin mixed solution, a purchased polyamide-imide resin solution or a purchased solid polyamide-imide resin may be dissolved in a solvent and used as a solution.

  The solvent used for manufacturing the polyamideimide varnish is not particularly limited as long as the polyamideimide resin can be dissolved. Examples of such solvents include amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; lactone solvents such as γ-butyrolactone and γ-valerolactone; sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane. Examples thereof include carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvents). Among these solvents, an amide solvent or a lactone solvent is preferable, and a solvent containing dimethylacetamide is more preferable. The polyamideimide varnish may contain water, alcohol solvents, ketone solvents, acyclic ester solvents, ether solvents and the like.

  Next, a polyamide-imide varnish coating is applied by coating the polyamide-imide varnish on a support such as a resin substrate, a SUS belt, or a glass substrate, for example, by a known roll-to-roll or batch method. Can be formed. Examples of the support include PET film, PEN film, polyimide film, and polyamideimide film. Among these, from the viewpoint of excellent heat resistance, a PET film, a PEN film, a polyimide film, and other polyamideimide films are preferable. From the viewpoint of adhesion to the optical film of the present invention and cost, a PET film is more preferable.

  Next, in the step (2-1) or the step (2-2), the polyamide-imide varnish coating film is dried at a temperature of 240 ° C. or lower, and is peeled off from the support after drying. The coating film can be dried preferably at a temperature of 50 to 240 ° C. If necessary, the coating film may be dried under an inert atmosphere or under reduced pressure. The optical film of the present invention can be obtained by peeling the coating film from the support after drying. In addition, as described in the step (2-2), the production method of the present invention is performed by removing the peeled optical film at 240 ° C. for the purpose of further increasing the surface hardness (for example, pencil hardness) of the optical film of the present invention. A step of heating at the following temperature may be further included.

You may perform the surface treatment process which surface-treats to the at least one surface of the optical film manufactured as mentioned above. Examples of the surface treatment include UV ozone treatment, plasma treatment, and corona discharge treatment.
When heating is performed in the step performed after the step (2-1) or the step (2-2), the temperature is preferably 280 ° C. or lower, more preferably 240 ° C. or lower.

  In a preferred embodiment of the present invention in which the optical film of the present invention contains an additive such as an additive having a light absorption function, the optical film of the present invention contains a polyamideimide resin and the additive in the same layer. Such a layer can be produced in the same manner as described above by using a polyamideimide varnish obtained by further adding the additive to a resin composition containing at least the polyamideimide resin and a solvent. In a preferred embodiment of the present invention in which an additive such as an additive having a light absorption function and a polyamide-imide resin are contained in one layer, an additive having a thermal decomposition temperature of at least 200 ° C. or more, preferably 240 ° C. or more. Is preferably used.

  The optical film of the present invention may further include a functional layer. Examples of the functional layer include layers having various functions such as a hard coat layer, an ultraviolet absorbing layer, an adhesive layer, a refractive index adjusting layer, and a primer layer. The optical film of the present invention may include one or more functional layers. One functional layer may have a plurality of functions.

  The hard coat layer is preferably disposed on the viewing side surface of the optical film. The hard coat layer may have a single layer structure or a multilayer structure. The hard coat layer includes a hard coat layer resin, and examples of the hard coat layer resin include acrylic resins, epoxy resins, urethane resins, benzyl chloride resins, vinyl resins, silicone resins, and mixtures thereof. Examples of the resin include ultraviolet curable resins, electron beam curable resins, and thermosetting resins. In particular, the hard coat layer preferably comprises an acrylic resin from the viewpoint of mechanical properties such as surface hardness and from an industrial viewpoint. In one preferred embodiment of the present invention, since the optical film of the present invention has a high surface hardness, the optical film has a sufficient surface hardness for use in an image display device or the like without a hard coat layer. For this reason, when the optical film of the present invention further has a hard coat layer, the surface hardness of the optical film can be further increased.

  The ultraviolet absorbing layer is a layer having an ultraviolet absorbing function. For example, a main material selected from an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, It is composed of dispersed UV absorbers. By providing the ultraviolet absorbing layer as the functional layer, a change in yellowness due to light irradiation can be easily suppressed.

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

  The adhesion layer may be comprised from the resin composition containing the component which has a polymerizable functional group. In this case, strong adhesion can be realized by further polymerizing the resin composition constituting the adhesive layer after the optical film is closely attached to another member. The adhesive strength between the optical film of the present invention and the pressure-sensitive adhesive layer may be 0.1 N / cm or more, or 0.5 N / cm or more.

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

  The pressure-sensitive adhesive layer may be a layer composed of an adhesive called a pressure-sensitive adhesive (PSA) that is attached to an object by pressing. The pressure-sensitive adhesive may be a pressure-sensitive adhesive that is “a substance that is sticky at room temperature and adheres to an adherend with light pressure” (JIS K6800). And an adhesive that can maintain stability until the coating is broken by appropriate means (pressure, heat, etc.) (JIS K6800).

  The hue adjustment layer is a layer having a hue adjustment function, and is a layer capable of adjusting the optical film of the present invention to a target hue. A hue adjustment layer is a layer containing resin and a coloring agent, for example. Examples of the colorant include inorganic pigments such as titanium oxide, zinc oxide, dial, titanium oxide-based fired pigment, ultramarine blue, cobalt aluminate, and carbon black; azo compounds, quinacridone compounds, anthraquinone compounds, Organic pigments such as perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, selenium compounds, and diketopyrrolopyrrole compounds; extender pigments such as barium sulfate and calcium carbonate; and basic dyes, Examples include acid dyes and mordant dyes.

  The refractive index adjusting layer is a layer having a function of adjusting the refractive index, has a refractive index different from that of the layer containing the polyamideimide resin in the optical film of the present invention, and gives a predetermined refractive index to the optical film of the present invention. It is a layer that can be. The refractive index adjusting layer may be, for example, an appropriately selected resin, and optionally a resin layer further containing 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 diameter of the pigment may be 0.1 μm or less. By setting the average primary particle diameter of the pigment to 0.1 μm or less, irregular reflection of light transmitted 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 may be mentioned.

  The optical film of the present invention is useful as a front plate of an image display device, particularly as a front plate (that is, a window film) of a flexible display. The optical film of this invention can be arrange | positioned as a front plate on the visual recognition side surface of an image display apparatus, especially a flexible display. The front plate has a function of protecting the image display element in the flexible display.

  Examples of the image display device include wearable devices such as a television, a smartphone, a mobile phone, a car navigation system, a tablet PC, a portable game machine, electronic paper, an indicator, a bulletin board, a clock, and a smart watch. Examples of the flexible display include the above-described image display device having flexible characteristics.

  Hereinafter, the present invention will be described in more detail with reference to examples. Unless otherwise specified, “%” and “parts” in the examples mean mass% and parts by mass. First, the evaluation method will be described.

<Measurement of weight average molecular weight (Mw)>
The weight average molecular weight (Mw) of the polyamideimide resin was determined by standard polystyrene conversion by gel permeation chromatography (GPC) measurement. Specific measurement conditions were as follows.
(1) Pretreatment method A DMF eluent (10 mM lithium bromide solution) is added to the polyamideimide resin so as to have a concentration of 2 mg / mL, heated at 80 ° C. with stirring for 30 minutes, cooled, and then cooled to a 0.45 μm membrane. A solution obtained by filtering was used as a measurement solution.
(2) Measurement condition column: TSKgel SuperAWM-H × 2 + SuperAW2500 × 1 (6.0 mm ID × 150 mm × 3) (all manufactured by Tosoh Corporation)
Eluent: DMF (10 mM lithium bromide added)
Flow rate: 1.0 mL / min.
Detector: RI detector Column temperature: 40 ° C
Injection volume: 100 μL
Molecular weight standard: Standard polystyrene

<Measurement of tan δ and tan δ peak temperature>
Using TA Instrument DMA Q800, measurement was performed under the following samples and conditions to obtain a tan δ curve, which is the ratio between the loss modulus and the storage modulus. From the top of the peak of the tan δ curve, the tan δ peak temperature of the polyamideimide resin was calculated.
Sample: 5-15mm long, 5mm wide
Experimental mode: DMA Multi-Frequency-Strain
Detailed experimental mode conditions:
(1) Clamp: Tension: Film
(2) Amplitude: 5 μm
(3) Frequency: 10 Hz (no fluctuation in all temperature sections)
(4) Preload Force: 0.01N
(5) Force Track: 125N
Temperature conditions: (1) Temperature rise range: normal temperature to 400 ° C, (2) Temperature rise rate: 5 ° C / min Main data collected: (1) Storage modulus (E '), (2) Loss modulus (Loss modulus, E "), (3) tan δ (E" / E ')

（前処理方法）
試料を重水素化ジメチルスルホキシド（ＤＭＳＯ−ｄ６）に溶解させて２質量％溶液としたものを測定試料とした。
（測定条件）
測定装置：Ｂｒｕｋｅｒ社製６００ＭＨｚＮＭＲ装置ＡＶＡＮＣＥ６００
試料温度：３０３Ｋ
測定手法：^１Ｈ−ＮＭＲ，ＨＳＱＣ
（ポリイミド樹脂のイミド化率の算出方法）
ポリイミド樹脂を含む溶液を測定試料として得られた^１Ｈ−ＮＭＲスペクトルにおいて、式（ＸＸＸ）中のプロトン（Ａ）に由来するシグナルの積分値をＩｎｔ_Ａ、プロトン（Ｂ）に由来するシグナルの積分値をＩｎｔ_Ｂとした。これらの値から、式（ＮＭＲ−１）によりイミド化率（％）を求めた。

（ポリアミドイミド樹脂のイミド化率の算出方法）
ポリイミド樹脂を含む溶液を測定試料として得られたＨＳＱＣスペクトルにおいて、式（ＸＸＸ）中のプロトン（Ｃ）に由来するシグナルの積分値をＩｎｔ_Ｃ、プロトン（Ｄ）およびプロトン（Ｅ）に由来するシグナルの積分値の平均値をＩｎｔ_ＤＥとした。これらの値から、式（ＮＭＲ−２）によりβ値を求めた。

次に、複数のポリイミド樹脂について、式（ＮＭＲ−２）によるβ値および式（ＮＭＲ−１）によるイミド化率（％）を求め、この結果から相関式（ＮＭＲ−３）を得た。

そして、ポリアミドイミド樹脂を含む溶液を測定試料として得られたＨＳＱＣスペクトルにおいて、上記と同様にして式（ＮＭＲ−２）によりβ値を求めた。このβ値を上記の相関式（ＮＭＲ−３）へ代入することにより、ポリアミドイミド樹脂のイミド化率（％）を得た。 <Measurement of imidization ratio>
The imidation ratios of the polyimide resin and the polyamideimide resin used in Examples and Comparative Examples were measured by NMR and using signals derived from protons in the partial structures (A) to (E) shown in Formula (XXX). Calculated. The method for calculating the imidization ratio from the measurement conditions and the obtained results is as follows.

(Pre-processing method)
A sample prepared by dissolving the sample in deuterated dimethyl sulfoxide (DMSO-d6) to give a 2% by mass solution was used as a measurement sample.
(Measurement condition)
Measuring apparatus: 600 MHz NMR apparatus AVANCE600 manufactured by Bruker
Sample temperature: 303K
Measurement method: ¹ H-NMR, HSQC
(Calculation method of imidization ratio of polyimide resin)
In the ¹ H-NMR spectrum obtained using a solution containing a polyimide resin as a measurement sample, the integral value of the signal derived from the proton (A) in formula (XXX) is represented by Int _A and the integral of the signal derived from the proton (B). The value was Int _B. From these values, the imidization ratio (%) was determined by the formula (NMR-1).

(Calculation method of imidization ratio of polyamide-imide resin)
In the HSQC spectrum obtained using a solution containing a polyimide resin as a measurement sample, the integral value of the signal derived from proton (C) in formula (XXX) is the signal derived from Int _C , proton (D), and proton (E). The average value of the integrated values of was defined as Int _DE . From these values, the β value was determined by the formula (NMR-2).

Next, for a plurality of polyimide resins, the β value according to the formula (NMR-2) and the imidization ratio (%) according to the formula (NMR-1) were obtained, and the correlation formula (NMR-3) was obtained from the results.

Then, in the HSQC spectrum obtained using the solution containing the polyamideimide resin as a measurement sample, the β value was determined by the formula (NMR-2) in the same manner as described above. By substituting this β value into the above correlation equation (NMR-3), the imidization ratio (%) of the polyamideimide resin was obtained.

<Measurement of total light transmittance (Tt)>
The total light transmittance Tt of the sample was measured by a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. according to JIS K7105: 1981.

<Measurement of yellowness (YI value)>
The yellowness (Yellow Index: YI value) of the sample was measured using an ultraviolet-visible near-infrared spectrophotometer V-670 manufactured by JASCO Corporation based on JIS K 7373: 2006. After measuring the background in the absence of the sample, the sample was set in a sample holder, the transmittance for light of 300 to 800 nm was measured, and tristimulus values (X, Y, Z) were obtained. The YI value was calculated based on the following formula.

<Measurement of surface hardness>
As the sample surface hardness, the pencil hardness of the sample surface was measured in accordance with JIS K5600-5-4: 1999. Measurement was performed under the conditions of a load of 100 g and a scanning speed of 60 mm / min, and under the illuminance condition of a light amount of 4000 lux, the presence or absence of scratches was evaluated, and the pencil hardness was determined.

<Measurement of elastic modulus>
The elastic modulus of the sample was measured using Autograph AG-IS manufactured by Shimadzu Corporation. A sample cut into a width of 10 mm was used as a test piece, an SS curve was measured under conditions of a distance between chucks of 500 mm and a tensile speed of 20 mm / min, and an elastic modulus was calculated from the inclination.

<Measurement of bending resistance>
As the bending resistance of the sample, the number of reciprocal bendings was measured using an MIT folding fatigue tester (model 0530) manufactured by Toyo Seiki Seisakusho. A sample cut into a thickness of 50 μm and a width of 10 mm was used as a test piece, and the number of reciprocal bendings until the film was broken under the conditions of R = 1 mm, 135 °, load 0.75 kgf, and speed 175 cpm was measured.

[Production Example 1: Preparation of polyamideimide resin (1)]
In a 1 L separable flask equipped with a stirring blade under a nitrogen gas atmosphere, 52 g (162.38 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and 734.10 g of N, N-dimethylacetamide (DMAc) were added. TFMB was dissolved in DMAc with stirring at room temperature. Next, 28.90 g (65.05 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was added to the flask and stirred at room temperature for 3 hours. Thereafter, 28.80 g (97.57 mmol) of 4,4′-oxybis (benzoyl chloride) (OBBC) was added to the flask and stirred at room temperature for 1 hour.
Next, 7.49 g (94.65 mmol) of pyridine and 26.56 g (260.20 mmol) of acetic anhydride were added to the flask, stirred for 30 minutes at room temperature, then heated to 70 ° C. using an oil bath, Stir for hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, 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). When the weight average molecular weight (Mw), tan δ peak temperature and imidization rate of the polyamideimide resin (1) were measured according to the above measurement method, the Mw was 200,000, the tan δ peak temperature was 345 ° C., and the imidization rate was 96%. there were.

[Example 1: Formation of polyamideimide film (1)]
DMAc was added to the polyamideimide resin (1) obtained in Production Example 1 so as to have a concentration of 15% by mass to prepare a polyamideimide varnish (1). The obtained polyamideimide varnish (1) was applied on a smooth surface of a polyester base material (trade name “A4100”, manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the self-supporting film became 55 μm, and 50 ° C. 30 After drying for 15 minutes at 140 ° C. for 15 minutes, the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film.
The self-supporting film was fixed to a metal frame, and further dried at 230 ° C. for 30 minutes in the air to obtain a polyamideimide film (1) having a thickness of 50 μm.

[Example 2: Formation of polyamideimide film (2)]
DMAc was added to the polyamideimide resin (1) obtained in Production Example 1 so as to have a concentration of 15% by mass, and an ultraviolet absorber (manufactured by Sumika Chemtex Co., Ltd., product name “Sumisorb340”) was added to the polyamideimide. 4 parts by mass of 100 parts by mass of the resin (1) was mixed to prepare a polyamideimide varnish (2). A polyamideimide film (2) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyamideimide varnish (2) was used instead of the polyamideimide varnish (1).

[Example 3: Film-forming of polyamideimide film (3)]
DMAc was added to the polyamideimide resin (1) obtained in Production Example 1 so that the concentration was 15% by mass, and a bluing agent (product name “Violet B” manufactured by Chemiplast Co., Ltd.) was added to the polyamideimide resin (1 ) 0.05 parts by mass with respect to 100 parts by mass to prepare a polyamideimide varnish (3). A polyamideimide film (3) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyamideimide varnish (3) was used instead of the polyamideimide varnish (1).

[Production Example 2: Preparation of polyamideimide resin (2)]
Under a nitrogen gas atmosphere, 52 g (162.38 mmol) of TFMB and 705.94 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 25.28 g (56.92 mmol) of 6FDA was added to the flask and stirred at room temperature for 3 hours. Thereafter, 21.60 g (73.18 mmol) of OBBC and then 6.60 g (32.52 mmol) of terephthaloyl chloride (TPC) were added to the flask and stirred at room temperature for 1 hour. Next, 8.11 g (102.53 mmol) of pyridine and 23.24 g (227.67 mmol) of acetic anhydride were added to the flask. After stirring for 30 minutes at room temperature, the temperature was raised to 70 ° C. using an oil bath, and further for 3 hours. Stir to obtain a reaction solution.
The resulting reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, 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 (2). When the weight average molecular weight (Mw), tan δ peak temperature and imidization rate of the polyamideimide resin (2) were measured according to the above measurement method, the Mw was 180,000, the tan δ peak temperature was 340 ° C., and the imidization rate was 99%. there were.

[Example 4: Film formation of polyamideimide film (4)]
DMAc was added to the polyamideimide resin (2) obtained in Production Example 2 so as to have a concentration of 15% by mass to prepare a polyamideimide varnish (4). A polyamideimide film (4) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyamideimide varnish (4) was used instead of the polyamideimide varnish (1).

[Example 5: Formation of polyamideimide film (5)]
DMAc was added to the polyamide-imide resin (2) obtained in Production Example 2 to a concentration of 15% by mass, and an ultraviolet absorber (manufactured by Sumika Chemtex Co., Ltd., product name “Sumisorb 340”) was added to the polyamide-imide resin. (2) 4 parts by mass was mixed with 100 parts by mass to prepare a polyamideimide varnish (5). A polyamideimide film (5) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyamideimide varnish (5) was used instead of the polyamideimide varnish (1).

[Example 6: Formation of polyamideimide film (6)]
DMAc was added to the polyamideimide resin (2) obtained in Production Example 2 so that the concentration was 15% by mass, and a bluing agent (product name “Violet B” manufactured by Sumiplast) was added to the polyamideimide resin (2 ) 0.05 parts by mass with respect to 100 parts by mass to prepare a polyamideimide varnish (6). A polyamideimide film (6) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyamideimide varnish (6) was used instead of the polyamideimide varnish (1).

[Production Example 3: Preparation of polyamideimide resin (3)]
Under a nitrogen gas atmosphere, 52 g (162.38 mmol) of TFMB and 698.10 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 25.28 g (56.92 mmol) of 6FDA was added to the flask and stirred at room temperature for 3 hours. Thereafter, 20.43 g (73.18 mmol) of BPDOC and then 6.60 g (32.52 mmol) of terephthaloyl chloride (TPC) were added to the flask and stirred at room temperature for 1 hour. Next, 8.11 g (102.53 mmol) of pyridine and 23.24 g (227.67 mmol) of acetic anhydride were added to the flask. After stirring for 30 minutes at room temperature, the temperature was raised to 70 ° C. using an oil bath, and further for 3 hours. Stir to obtain a reaction solution.
The resulting reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, 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 (3). When the weight average molecular weight (Mw), tan δ peak temperature and imidization rate of the polyamideimide resin (3) were measured according to the above measurement method, the Mw was 200,000, the tan δ peak temperature was 380 ° C., and the imidization rate was 99%. there were.

[Comparative Example 1: Film formation of polyamideimide film (7)]
DMAc was added to the polyamideimide resin (3) obtained in Production Example 3 so as to have a concentration of 15% by mass to prepare a polyamideimide varnish (7). Instead of using the polyamideimide varnish (1) instead of the polyamideimide varnish (1), the self-supporting film fixed to the metal frame was dried at 230 ° C for 30 minutes in the air, and the self-supporting film was 300 ° C in the air at 30 ° C. A polyamideimide film (7) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that it was dried for a minute.

[Comparative Example 2: Film formation of polyamideimide film (8)]
A polyamideimide film (8) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyamideimide varnish (7) obtained in Comparative Example 1 was used instead of the polyamideimide varnish (1). .

[Production Example 4: Preparation of polyamideimide resin (4)]
Under a nitrogen gas atmosphere, 52 g (162.38 mmol) of TFMB and 655.58 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 23.84 g (53.67 mmol) of 6FDA was added to the flask and stirred at room temperature for 3 hours. Thereafter, 22.12 g (108.96 mmol) of terephthaloyl chloride (TPC) was added to the flask and stirred at room temperature for 1 hour. Next, 8.36 g (105.69 mmol) of pyridine and 21.91 g (214.66 mmol) of acetic anhydride were added to the flask, stirred at room temperature for 30 minutes, then heated to 70 ° C. using an oil bath, and further 3 hours Stir to obtain a reaction solution.
The resulting reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, 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 (4). When the weight average molecular weight (Mw), tan δ peak temperature and imidization rate of the polyamide-imide resin (4) were measured according to the above measurement method, the Mw was 200,000, the tan δ peak temperature was 379 ° C., and the imidization rate was 96%. there were.

[Comparative Example 3: Film Formation of Polyamideimide Film (9)]
DMAc was added to the polyamideimide resin (4) obtained in Production Example 4 so as to have a concentration of 15% by mass to prepare a polyamideimide varnish (8). Instead of using the polyamideimide varnish (1) instead of the polyamideimide varnish (1), the self-supporting film fixed to the metal frame was dried at 230 ° C for 30 minutes in the atmosphere, and the self-supporting film was 300 ° C in the atmosphere at 30 ° C. A polyamideimide film (9) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that it was dried for a minute.

[Comparative Example 4: Film Formation of Polyamideimide Film (10)]
A polyamideimide film (10) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyamideimide varnish (8) obtained in Comparative Example 3 was used instead of the polyamideimide varnish (1). .

[Comparative Example 5: Formation of polyamideimide film (11)]
A thickness of 50 μm was obtained in the same manner as in Example 1 except that the self-supporting film fixed to the metal frame was dried at 230 ° C. for 30 minutes in the air, and the self-supporting film was dried at 300 ° C. for 30 minutes in the air. A polyamideimide film (11) having

[Comparative Example 6: Polyamideimide film (12) film formation]
A thickness of 50 μm was obtained in the same manner as in Example 2 except that the self-supporting film fixed to the metal frame was dried at 230 ° C. for 30 minutes in the air, and the self-supporting film was dried at 300 ° C. for 30 minutes in the air. A polyamideimide film (12) having

[Comparative Example 7: Formation of polyamideimide film (13)]
A thickness of 50 μm was obtained in the same manner as in Example 4 except that the self-supporting film fixed to the metal frame was dried at 230 ° C. for 30 minutes in the air, and the self-supporting film was dried at 300 ° C. for 30 minutes in the air. A polyamideimide film (13) having

[Comparative Example 8: Formation of polyamideimide film (14)]
A thickness of 50 μm was obtained in the same manner as in Example 5 except that the self-supporting film fixed to the metal frame was dried at 230 ° C. for 30 minutes in the air, and the self-supporting film was dried at 300 ° C. for 30 minutes in the air. A polyamideimide film (14) having

[Production Example 5: Preparation of polyimide resin (5)]
Under a nitrogen gas atmosphere, 52 g (162.38 mmol) of TFMB and 831.46 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 72.24 g (16.262 mmol) of 6FDA was added to the flask and stirred at room temperature for 5 hours. Next, 9.65 g (121.97 mmol) of pyridine and 66.41 g (650.49 mmol) of acetic anhydride were added to the flask, stirred at room temperature for 30 minutes, then heated to 70 ° C. using an oil bath, and further 3 hours Stir to obtain a reaction solution.
The resulting reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, 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 polyimide resin (5). When the weight average molecular weight (Mw), tan δ peak temperature and imidization rate of the polyimide resin (5) were measured according to the above measurement method, the Mw was 220,000, the tan δ peak temperature was 350 ° C., and the imidization rate was 99%. It was.

[Comparative Example 9: Formation of polyimide film (15)]
DMAc was added to the obtained polyimide resin (5) so as to have a concentration of 15% by mass to prepare a polyimide varnish (9). A polyimide film (15) having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyimide varnish (9) was used instead of the polyamideimide varnish (1).

[Production Example 6: Preparation of polyamideimide resin (6)]
Under a nitrogen gas atmosphere, 14.67 g (45.8 mmol) of TFMB and 233.3 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 4.283 g (13.8 mmol) of 4,4′-oxydiphthalic dianhydride (OPDA) was added to the flask and stirred at room temperature for 16.5 hours. Thereafter, 1.359 g (4.61 mmol) of OBBC and 5.609 g (27.6 mmol) of TPC were added to the flask and stirred at room temperature for 1 hour. Next, 4.937 g (48.35 mmol) of acetic anhydride and 1.501 g (16.12 mmol) of 4-picoline were added to the flask, stirred at room temperature for 30 minutes, heated to 70 ° C. using an oil bath, The mixture was stirred for 3 hours to obtain a reaction solution.
After cooling the obtained reaction liquid to room temperature, 360 g of methanol and 170 g of ion-exchanged water were added to obtain a polyamideimide precipitate. It was immersed in methanol for 12 hours, recovered by filtration and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin (6). When the weight average molecular weight (Mw), tan δ peak temperature, and imidization ratio of the polyamideimide resin (6) were measured according to the above measurement method, Mw was 259,000 and tan δ peak temperature was 362 ° C.

[Example 7: Formation of polyamideimide film (16)]
GBL was added to the polyamideimide resin (6) obtained in Production Example 6 so as to have a concentration of 12% by mass to prepare a polyamideimide varnish (16). 50 μm in the same manner as in Example 1 except that the polyamideimide varnish (1) was used instead of the polyamideimide varnish (1), that the self-supporting film was fixed to a metal frame and dried at 200 ° C. for 30 minutes. A polyamideimide film (16) having a thickness was obtained.

About the polyamideimide films (1) to (14) and (16) and the polyimide film (15) obtained in the above examples and comparative examples, the total light transmittance (Tt), yellowness (YI value) according to the above measurement method ), Pencil hardness, elastic modulus and bending resistance (number of reciprocating bendings). The obtained results are shown in Table 1. Table 1 also shows the numbers of the polyamideimide resin or polyimide resin contained in these films.

Claims (12)

  An optical film comprising a polyamideimide resin having a peak value of tan δ as measured by DMA within a range of 300 to 370 ° C. and having a YI value of 3 or less.   The optical film of claim 1 having a pencil hardness of 3B or greater as measured according to ASTM D 3363 under an illuminance condition of 4000 lux.   The optical film according to claim 1, further comprising an additive having a light absorption function.   The optical film according to any one of claims 1 to 3, wherein the additive having a light absorbing function is selected from the group consisting of an ultraviolet absorber and a bluing agent.   The optical film according to claim 1, wherein the polyamideimide resin contains a fluorine atom. Polyamideimide resin has the formula (1):

[In Formula (1), R ^{1 to} R ⁸ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and hydrogen contained in R ^{1 to} R ^8. Each atom may be independently substituted with a halogen atom,
Each A independently represents —O—, —S—, —CO— or —NR ⁹ —, wherein R ⁹ represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom;
m is an integer of 1 to 4,
* Represents a bond]
The optical film in any one of Claims 1-5 which has at least the structural unit represented by these.   The optical film according to claim 1, wherein the polyamideimide resin has at least a structural unit derived from dicarboxylic acid.   8. The optical film according to claim 1, wherein the polyamideimide resin has at least a structural unit derived from a fluorine atom-containing diamine and / or a fluorine atom-containing tetracarboxylic dianhydride.   The optical film in any one of Claims 1-8 which has a thickness of 20 micrometers or more. (1) A step of applying a resin composition containing at least a polyamideimide resin and a solvent to a support, and
(2-1) A step of peeling the coating film of the resin composition from the support after drying at a temperature of 240 ° C. or lower, or
(2-2) An optical film comprising at least a step of peeling the coating film of the resin composition from the support after drying at a temperature of 240 ° C. or lower, and a step of heating the peeled film at a temperature of 240 ° C. or lower. Production method.   The manufacturing method of Claim 10 with which the resin composition further contains the additive which has a light absorption function.   The method according to claim 10 or 11, wherein the solvent comprises dimethylacetamide.