TW202122463A - Optical film - Google Patents

Abstract

Provided is an optical film that has excellent transparency and folding resistance. The optical film includes a polyimide resin. The polyimide resin: includes a structural unit represented by formula (1); includes, as Y in formula (1), a structure represented by formula (3); and has a weight-average molecular weight of at least 160,000.

Description

Optical film

The present invention relates to an optical film and polyimide-based resin used in the material of a flexible display device, and a flexible display device provided with the optical film.

Display devices such as liquid crystal display devices or organic EL display devices are widely used in various applications such as mobile phones and smart watches. Previously, glass has been used as the front panel of such a display device, but the glass is very rigid and easy to break, so it is difficult to be used as a material for the front panel of a flexible display device. As a material to replace glass, the use of polyimide-based resins and other polymers for optical films with high heat resistance, etc. are being studied. Patent Document 1 discloses a polyimide resin having an ester type tetracarboxylic dianhydride formed by esterification of biphenyl-4,4' diols and two trimellitic acids as monomer components, and A polyimide film formed from the polyimide resin. The polyimide film formed from this polyimide resin is advantageous in terms of high heat resistance and low linear thermal expansion coefficient. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2014/046180

[The problem to be solved by the invention]

As the material of the flexible display device, the film for the front panel also plays a role of protecting the internal components of the flexible display device. In order to alleviate the impact from the outside, it is required to increase its thickness. However, it is known that the polyimide resin of Patent Document 1 contains a rigid structure derived from ester-type tetracarboxylic dianhydride, and therefore the transparency of the obtained polyimide film is insufficient, especially if the thickness becomes large. The haze is significantly increased and the transmittance is significantly reduced, and it is impossible to ensure the transparency required by the materials of the flexible display device. In addition, optical films used in materials such as flexible display devices also require excellent folding resistance.

Therefore, the object of the present invention is to provide an optical film and polyimide-based resin excellent in transparency and folding resistance, and a flexible display device provided with the optical film. [Technical means to solve the problem]

In order to solve the above-mentioned problems, the inventors have made intensive research and found that if an optical film containing a polyimide-based resin, as Y in formula (1), the structure represented by formula (3) is included, and the polyimide resin is adjusted The weight average molecular weight of the imine-based resin can solve the above-mentioned problems, and the present invention has been completed. That is, the present invention includes the following suitable forms.

[式(1)中，X表示二價有機基， Y表示四價有機基， *表示鍵結鍵]， 作為式(1)中之Y，包含式(3)所表示之結構： [化2]

[式(3)中，R¹ 相互獨立地表示鹵素原子、可具有鹵素原子之烷基、烷氧基、芳基或芳氧基， R² ～R⁵ 相互獨立地表示氫原子或可具有鹵素原子之一價烴基， m相互獨立地表示0～3之整數， n表示1～4之整數， *表示鍵結鍵，其中，於具有R² ～R⁵ 之至少1個苯環中，R² ～R⁵ 中之至少1個為可具有鹵素原子之一價烴基]， 且上述聚醯亞胺系樹脂之重量平均分子量為160,000以上。 [2]如[1]所記載之光學膜，其中作為式(1)中之X，包含二價芳香族基、二價脂環族基及二價脂肪族基之至少1種。 [3]如[1]或[2]所記載之光學膜，其中作為式(1)中之X，包含式(4)所表示之結構： [化3]

[式(4)中，A表示單鍵、-O-、二苯基亞甲基、可具有鹵素原子之二價烴基、-SO₂ -、-S-、-CO-、-PO-、-PO₂ -、-N(R^A1 )-或-Si(R^A2 )₂ -， R^A1 及R^A2 相互獨立地表示氫原子或可具有鹵素原子之烷基，R⁶ 相互獨立地表示鹵素原子、可具有鹵素原子之烷基、烷氧基、芳基或芳氧基， s相互獨立地表示0～4之整數， *表示鍵結鍵]。 [4]如[1]至[3]中任一項所記載之光學膜，其厚度為35 μm以上。 [5]如[1]至[4]中任一項所記載之光學膜，其全光線透過率為85%以上。 [6]如[1]至[5]中任一項所記載之光學膜，其黃度為3.0以下。 [7]如[1]至[6]中任一項所記載之光學膜，其彈性模數為3.5 GPa以上。 [8]如[1]至[7]中任一項所記載之光學膜，其係可撓性顯示裝置之前面板用膜。 [9]一種可撓性顯示裝置，其具備如[1]至[8]中任一項所記載之光學膜。 [10]如[9]所記載之可撓性顯示裝置，其進而具備觸控感測器。 [11]如[9]或[10]所記載之可撓性顯示裝置，其進而具備偏光板。 [12]一種聚醯亞胺系樹脂，其包含式(1)所表示之結構單元： [化4]

[式(1)中，X表示二價有機基， Y表示四價有機基， *表示鍵結鍵]， 且作為式(1)中之Y，包含式(3)所表示之結構： [化5]

[式(3)中，R¹ 相互獨立地表示鹵素原子、可具有鹵素原子之烷基、烷氧基、芳基或芳氧基， R² ～R⁵ 相互獨立地表示氫原子或可具有鹵素原子之一價烴基， m相互獨立地表示0～3之整數， n表示1～4之整數， *表示鍵結鍵，其中，於具有R² ～R⁵ 之至少1個苯環中，R² ～R⁵ 中之至少1個為可具有鹵素原子之一價烴基]， 且上述聚醯亞胺系樹脂之重量平均分子量為160,000以上。 [發明之效果][1] An optical film comprising a polyimide-based resin, and the polyimide-based resin includes a structural unit represented by formula (1): [化1]

[In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, * represents a bonding bond], as Y in the formula (1), it includes the structure represented by the formula (3): [化2] ]

[In formula (3), R ¹ independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, and R ² to R ⁵ independently represent a hydrogen atom or may have a halogen Atomic monovalent hydrocarbon group, m independently represents an integer of 0 to 3, n represents an integer of 1 to 4, * represents a bonding bond, wherein, in at least one benzene ring ^{having R 2} to R ^{5 , R 2} At least one of -R ⁵ is a monovalent hydrocarbon group which may have a halogen atom], and the weight average molecular weight of the polyimide resin is 160,000 or more. [2] The optical film as described in [1], wherein X in the formula (1) includes at least one of a divalent aromatic group, a divalent alicyclic group, and a divalent aliphatic group. [3] The optical film as described in [1] or [2], wherein X in the formula (1) includes the structure represented by the formula (4): [化3]

[In formula (4), A represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group that may have a halogen atom, -SO ₂ -, -S-, -CO-, -PO-,- PO ₂ -, -N(R ^A1 )- or -Si(R ^A2 ) ₂ -, R ^A1 and R ^A2 independently represent a hydrogen atom or an alkyl group which may have a halogen atom, and R ⁶ independently represent a halogen atom, An alkyl group, an alkoxy group, an aryl group or an aryloxy group which may have a halogen atom, s independently represents an integer of 0 to 4, and * represents a bonding bond]. [4] The optical film as described in any one of [1] to [3], which has a thickness of 35 μm or more. [5] The optical film as described in any one of [1] to [4], which has a total light transmittance of 85% or more. [6] The optical film as described in any one of [1] to [5], which has a yellowness of 3.0 or less. [7] The optical film as described in any one of [1] to [6], which has an elastic modulus of 3.5 GPa or more. [8] The optical film as described in any one of [1] to [7], which is a film for a front panel of a flexible display device. [9] A flexible display device including the optical film as described in any one of [1] to [8]. [10] The flexible display device as described in [9], which further includes a touch sensor. [11] The flexible display device as described in [9] or [10], which further includes a polarizing plate. [12] A polyimide-based resin comprising the structural unit represented by formula (1): [化4]

[In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, and * represents a bonding bond], and as Y in formula (1), it includes the structure represented by formula (3): [化] 5]

[In formula (3), R ¹ independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, and R ² to R ⁵ independently represent a hydrogen atom or may have a halogen Atomic monovalent hydrocarbon group, m independently represents an integer of 0 to 3, n represents an integer of 1 to 4, * represents a bonding bond, wherein, in at least one benzene ring ^{having R 2} to R ^{5 , R 2} At least one of -R ⁵ is a monovalent hydrocarbon group which may have a halogen atom], and the weight average molecular weight of the polyimide resin is 160,000 or more. [Effects of Invention]

The optical film of the present invention is excellent in transparency and folding resistance. Therefore, it is suitable for materials and the like for flexible display devices.

[式(1)中，X表示二價有機基， Y表示四價有機基， *表示鍵結鍵]。[Optical film] The optical film of the present invention contains a polyimide-based resin. <Polyimide resin> The polyimide resin contained in the optical film of the present invention contains the structural unit represented by formula (1): [化6]

[In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, and * represents a bonding bond].

In formula (1), Y independently represents a tetravalent organic group, preferably a tetravalent organic group with 4 to 80 carbons, and more preferably a tetravalent organic group with 4 to 60 carbons having a cyclic structure base. Examples of the cyclic structure include alicyclic, aromatic, and heterocyclic structures. The above-mentioned organic group is an organic group in which the hydrogen atom in the organic group may be substituted with a substituent. The substituent is preferably a halogen atom, a hydrocarbon group (such as an alkyl group, an aryl group, etc.) that may have a halogen atom, an alkoxy group or an aryloxy group. In this case, the hydrocarbon group, alkoxy group or aryloxy group which may have a halogen atom preferably has a carbon number of 1-8. The polyimide-based resin as one embodiment of the present invention may contain a plurality of Y types, and the plurality of types Y may be the same or different from each other.

[式(3)中，R¹ 相互獨立地表示鹵素原子、可具有鹵素原子之烷基、烷氧基、芳基或芳氧基， R² ～R⁵ 相互獨立地表示氫原子或可具有鹵素原子之一價烴基， m相互獨立地表示0～3之整數， n表示1～4之整數， *表示鍵結鍵，其中，於具有R² ～R⁵ 之至少1個苯環中，R² ～R⁵ 中之至少1個為可具有鹵素原子之一價烴基]， 且上述聚醯亞胺系樹脂之重量平均分子量為160,000以上。The characteristic of the polyimide resin in the present invention is that as Y in the formula (1), it includes the structure represented by the formula (3): [化7]

[In formula (3), R ¹ independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, and R ² to R ⁵ independently represent a hydrogen atom or may have a halogen Atomic monovalent hydrocarbon group, m independently represents an integer of 0 to 3, n represents an integer of 1 to 4, * represents a bonding bond, wherein, in at least one benzene ring ^{having R 2} to R ^{5 , R 2} At least one of -R ⁵ is a monovalent hydrocarbon group which may have a halogen atom], and the weight average molecular weight of the polyimide resin is 160,000 or more.

According to the present inventors, it is known that in the polyimide-based resin in which Y in the formula (1) described in Patent Document 1 contains the structure represented by the formula (3), especially if the thickness of the obtained optical film changes Large, the transparency of the film is insufficient. Furthermore, it is also known that the viscosity of the reaction solution for polymerizing the polyimide resin having such a structure is relatively high, and the polymerization is difficult to proceed, and therefore it is difficult to increase the molecular weight of the polyimide resin. By optimizing the production conditions of the resin, the inventors succeeded in increasing the weight average molecular weight of the polyimide resin to more than 160,000. As a result, it was unexpectedly found that the optical film containing the polyimide resin has obvious transparency Promote. Furthermore, it was also found that the folding endurance of the optical film was improved.

Therefore, the optical film containing the polyimide-based resin of the present invention can have excellent transparency and folding resistance. On the other hand, if the weight average molecular weight of the polyimide resin contained in the optical film is less than 160,000, there is a tendency that an optical film with sufficient transparency and folding resistance cannot be obtained.

The weight average molecular weight (hereinafter, sometimes referred to as Mw) of the polyimide resin in the present invention is 160,000 or more, preferably 180,000 or more, more preferably 200,000 or more, still more preferably 250,000 or more, and still more preferably 300,000 or more, particularly preferably 350,000 or more, and preferably 1,000,000 or less, more preferably 800,000 or less, still more preferably 700,000 or less, and particularly preferably 600,000 or less. If the Mw of the polyimide-based resin is more than the above lower limit, it is easy to further improve the transparency, elastic modulus and folding resistance of the obtained optical film. If the Mw is below the above upper limit, it is easy to inhibit the gelation of the resin varnish It is easy to improve the optical properties of the obtained optical film. In addition, the weight average molecular weight can be measured by, for example, gel permeation chromatography (hereinafter, sometimes referred to as GPC) and can be obtained by standard polystyrene conversion, for example, can be obtained by the method described in the examples.

In the formula (3), R ¹ independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom. As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned, for example. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, second butyl, tertiary butyl, n-pentyl, and 2-methylbutyl , 3-methylbutyl, 2-ethylpropyl, n-hexyl, etc. Examples of alkoxy groups include methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, second butoxy, tertiary butoxy, and pentoxy. Group, hexyloxy, cyclohexyloxy, etc. As an aryl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a biphenyl group etc. are mentioned, for example. As an aryloxy group, a phenoxy group, a naphthyloxy group, a biphenoxy group, etc. are mentioned, for example. R ¹ independently of each other preferably represents a halogen atom, an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, an aryl group with 6 to 12 carbons, or 6 to 12 carbons which may have a halogen atom的aryloxy. From the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, R ¹ is preferably an alkyl group or an alkoxy group that may have a halogen atom, and more preferably a carbon that may have a halogen atom. An alkyl group having 1 to 6 or an alkoxy group having 1 to 6 carbons.

In formula (3), from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, m independently represents an integer of 0 to 3, preferably an integer of 0 to 2, more preferably It is 0 or 1, more preferably 0.

In formula (3), R ² , R ³ , R ⁴ and R ⁵ independently represent a hydrogen atom or a monovalent hydrocarbon group which may have a halogen atom. In at least one benzene ring ^{having R 2} to R ^{5, R At least one of 2} to R ⁵ is a monovalent hydrocarbon group which may have a halogen atom. Examples of the hydrocarbon group include aromatic hydrocarbon groups, alicyclic hydrocarbon groups, and aliphatic hydrocarbon groups. As an aromatic hydrocarbon group, aryl groups, such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a biphenyl group, etc. are mentioned, for example. As an alicyclic hydrocarbon group, cycloalkyl groups, such as a cyclopentyl group and a cyclohexyl group, etc. are mentioned. Examples of the aliphatic hydrocarbon group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, second butyl, tertiary butyl, n-pentyl, 2-methylbutyl Alkyl, 3-methylbutyl, 2-ethylpropyl, n-hexyl, n-heptyl, n-octyl, tertiary octyl, n-nonyl, n-decyl, etc. Examples of the halogen atom include those described above. R ² to R ⁵ each independently preferably represent a hydrogen atom, or an aryl group having 6 to 12 carbons, a cycloalkyl group having 4 to 8 carbons, or an alkyl group having 1 to 6 carbons which may have a halogen atom. From the standpoint of easily improving the solubility of the resin in solvents and the transparency, elastic modulus, and folding resistance of the optical film, R ² to R ⁵ are each independently preferably a hydrogen atom or an alkyl group that may have a halogen atom, More preferably, it is a hydrogen atom or an alkyl group of 1 to 6 which may have a halogen atom, and still more preferably a hydrogen atom or an alkyl group of 1 to 3 which may have a halogen atom. In addition, from the viewpoint of easily improving the solubility of the resin in solvents and the transparency, elastic modulus, and folding resistance of the optical film, in at least one benzene ring ^{having R 2} to R ^{5 , R 2 is preferred} ~ R ⁵ in the at least two monovalent hydrocarbon group which may have one of a halogen atom, more preferably R ² ~ R ⁵ are at least three of a halogen atom which may have one monovalent hydrocarbon group.

In formula (3), n represents an integer of 1 to 4. From the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, n is preferably an integer of 1 to 3, more preferably 2 Or 3, more preferably 2. Furthermore, the structural unit represented by the formula (1) may include one or more of the structures represented by the formula (3) as Y.

[式(3')中，*表示鍵結鍵] 即，式(1)中之複數個Y之至少一部分由式(3')表示。若為此種形態，則容易提高光學膜之透明性、彈性模數及耐折性。In a preferred embodiment of the present invention, formula (3) is represented by formula (3'). [化8]

[In the formula (3'), * represents a bonding bond] That is, at least a part of the plural Y in the formula (1) is represented by the formula (3'). If it is in this form, it is easy to improve the transparency, elastic modulus, and folding resistance of the optical film.

In one embodiment of the present invention, with respect to the total molar amount (100 mol%) of the structural unit represented by formula (1), Y in the structural unit represented by formula (1) is represented by formula (3) The ratio of the structural unit is preferably 30 mol% or more, more preferably 50 mol% or more, and still more preferably 70 mol% or more. If the ratio of the structural unit represented by the formula (3) of Y is more than the above lower limit, it is easy to improve the transparency, elastic modulus, and folding resistance of the optical film. The upper limit of the ratio of Y structural units represented by formula (3) is 100 mol% or less. The ratio of the structural unit represented by the formula (3) of Y can ^{be measured using 1} H-NMR, for example, or can be calculated from the addition ratio of the raw materials.

In the polyimide resin of the present invention, as Y in formula (1), it may further include formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28), and formula (29). [化9]

In formulas (20) to (29), * represents a bonding bond, and W ¹ represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group that may have a halogen atom, such as -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -Ar-, -SO ₂ -, -S-, -CO- , -PO-, -PO ₂ -, -N(R ^W1 )-or -Si(R ^W2 ) ₂ -, -O-Ar-O-, -Ar-O-Ar-, -Ar _{-CH 2 -Ar} -, -Ar-C(CH ₃ ) ₂ -Ar- or Ar-SO ₂ -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms which may have a fluorine atom, and a specific example includes a phenylene group. R ^W1 and R ^W2 independently represent a hydrogen atom or an alkyl group which may have a halogen atom. Furthermore, it may be a group in which the hydrogen atom in the group represented by formula (20) to formula (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and four of the groups with 6 or less carbon atoms Valence chain hydrocarbon group. Furthermore, the hydrogen atoms on the rings in formulas (20) to (29) may be substituted with alkyl groups having 1 to 6 carbons, alkoxy groups having 1 to 6 carbons, or aryl groups having 6 to 12 carbons. Examples of the alkyl group having 1 to 6 carbons, the alkoxy group having 1 to 6 carbons, and the aryl group having 6 to 12 carbons include those exemplified above as R ^{1 of} the formula (3).

In the base represented by formulas (20) to (29), from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, formulas (26), (28), or The group represented by the formula (29) is more preferably the group represented by the formula (26). In addition, from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, W ¹ preferably represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -,- CH(CH ₃ )-, -C(CH ₃ ) ₂ -or C(CF ₃ ) ₂ -, more preferably represents a single bond, -O-, -CH ₂ -, -CH(CH ₃ )-, -C (CH ₃ ) ₂ -or C(CF ₃ ) ₂ -, more preferably represents a single bond, -C(CH ₃ ) ₂ -or C(CF ₃ ) ₂ -, more preferably represents a single bond or C(CF ₃ ) ₂ -, it is best to represent -C(CF ₃ ) ₂ -.

[式(5)中，B表示單鍵、-O-、二苯基亞甲基、可具有鹵素原子之二價烴基、-SO₂ -、-S-、-CO-、-COO-、-PO-、-PO₂ -、-N(R^B1 )-或-Si(R^B2 )₂ -， R^B1 及R^B2 相互獨立地表示氫原子或可具有鹵素原子之烷基， R⁷ 相互獨立地表示鹵素原子、可具有鹵素原子之烷基、烷氧基、芳基或芳氧基， t相互獨立地表示0～3之整數， *表示鍵結鍵] 若聚醯亞胺系樹脂中，作為式(1)中之Y，進而包含式(5)所表示之結構，則容易提高樹脂對溶劑之溶解性、以及光學膜之透明性、彈性模數及耐折性。In a preferred embodiment of the present invention, formula (26) is represented by formula (5). [化10]

[In formula (5), B represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group that may have a halogen atom, -SO ₂ -, -S-, -CO-, -COO-,- PO-, -PO ₂ -, -N(R ^B1 )- or -Si(R ^B2 ) ₂ -, R ^B1 and R ^B2 independently represent a hydrogen atom or an alkyl group which may have a halogen atom, and R ⁷ are independently of each other It represents a halogen atom, an alkyl group, an alkoxy group, an aryl group or an aryloxy group which may have a halogen atom, t independently represents an integer of 0 to 3, * represents a bonding bond] If in the polyimide resin, as The Y in the formula (1), and further including the structure represented by the formula (5), can easily improve the solubility of the resin to the solvent, as well as the transparency, elastic modulus and folding resistance of the optical film.

In formula (5), R ⁷ independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom. As a halogen atom, an alkyl group, an alkoxy group, an aryl group, and an aryloxy group which may have a halogen atom, the ones exemplified as ^{R 1 of the formula (3) above can be cited, respectively.} From the viewpoints of the transparency, elastic modulus and folding resistance of the optical film, R ⁷ independently of each other preferably represents an alkyl group having 1 to 6 carbon atoms that may have a halogen atom, and more preferably represents that it may have a halogen atom. The C1-C3 alkyl group.

In formula (5), t represents an integer of 0 to 3. From the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, it is preferably an integer of 0 to 2, more preferably 0 or 1, more preferably 0.

B in formula (5) independently represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group that may have a halogen atom, -SO ₂ -, -S-, -CO-, -COO- , -PO-, -PO ₂ -, -N(R ^B1 )- or -Si(R ^B2 ) ₂ -, ^RB1 and ^RB2 independently represent a hydrogen atom or an alkyl group which may have a halogen atom.

Examples of the divalent hydrocarbon group that may have a halogen atom include a divalent group obtained by removing one hydrogen atom from a monovalent hydrocarbon group that may have a halogen atom among ^{R 2} to R ^{5 in the formula (3).} The divalent hydrocarbon group which may have a halogen atom can replace two hydrogen atoms of the hydrogen atoms contained in the group to form a ring, that is, the two hydrogen atoms can be replaced by a bonding bond, and the two bonding bonds can be connected to form a ring. A ring is formed, and examples of the ring include a cycloalkane ring having 3 to 12 carbon atoms. In addition, as the alkyl group that may have a halogen atom in R ^B1 and R ^{B2 in -N(R B1} )- and -Si(R ^B2 ) ₂ -included in B in formula (5), the above mentioned as The alkyl group which may have a halogen atom ^{in R 1} in formula (3) is exemplified.

As B in formula (5), from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, a single bond or a divalent hydrocarbon group that may have a halogen atom is preferred, and a single bond is more preferred. Bond, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, more preferably a single bond, -C (CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, more preferably a single bond or -C(CF ₃ ) ₂ -, particularly _{preferably -C(CF 3} ) ₂ -.

[式(5')中，*表示鍵結鍵] 即，式(1)中之複數個Y之至少一部分由式(5')表示。若為此種形態，則容易提昇光學膜之透明性、彈性模數及耐折性。In a preferred embodiment of the present invention, formula (5) is represented by formula (5'). [化11]

[In the formula (5'), * represents a bonding bond] That is, at least a part of the plural Y in the formula (1) is represented by the formula (5'). If it is in this form, it is easy to improve the transparency, elastic modulus, and folding resistance of the optical film.

In one embodiment of the present invention, when Y in formula (1) includes the structure represented by formula (5), with respect to the total molar amount of the structural unit represented by formula (1), Y The ratio of the structural unit represented by the formula (5) is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 15 mol% or more, and still more preferably 20 mol% or more, especially It is preferably 25 mol% or more, particularly more preferably 30 mol%, and more preferably 80 mol% or less, more preferably 70 mol% or less, and still more preferably 60 mol% or less. If the ratio of the structural unit represented by the formula (5) of Y is within the above range, it is easy to improve the transparency, elastic modulus, and folding resistance of the optical film. In addition, the ratio of the structural unit represented by the formula (5) of Y can ^{be measured using 1} H-NMR, for example, or can be calculated from the addition ratio of the raw materials.

In one embodiment of the present invention, when Y in formula (1) includes the structure represented by formula (5), with respect to the total molar amount of the structural unit represented by formula (1), Y The total ratio of the structural unit represented by the formula (3) and the structural unit represented by the formula (5) of Y is preferably 50 mol% or more, more preferably 70 mol% or more, and still more preferably 90 mol% or more , And preferably 100 mol% or less. If the total ratio is within the above range, it is easy to improve the transparency, elastic modulus, and folding resistance of the optical film. In addition, this total ratio can ^{be measured using 1} H-NMR, for example, or it can also be calculated based on the addition ratio of raw materials.

In the formula (1), X represents a divalent organic group, and preferably represents a divalent organic group having 4 to 40 carbon atoms.

In the polyimide resin of the present invention, from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, as X in the formula (1), it is preferable to include a divalent aromatic At least one of a divalent alicyclic group, a divalent alicyclic group, and a divalent aliphatic group, and more preferably includes a divalent aromatic group. As the divalent aromatic group, for example, the aromatic hydrocarbon group exemplified as R ² to R ⁵ in the formula (3) above has a hydrogen atom in which one hydrogen atom is substituted with a bonding bond. divalent aromatic hydrocarbon group; the divalent aromatic hydrocarbon group is at least one or more linking group by, for example, the following groups V ¹ and the like for connecting together the bonding group. As the divalent alicyclic group, for example, one of the hydrogen atoms in the alicyclic hydrocarbon group exemplified as ^{R 2} to R ^{5 in the formula (3) above is replaced by a bonding bond.} divalent alicyclic hydrocarbon group; the divalent alicyclic hydrocarbon group of at least one or more linking group by, for example, the following groups V ¹ and the like for connecting together the bonding group. As the divalent aliphatic group, for example, the aliphatic hydrocarbon group exemplified as R ² to R ⁵ in the formula (3) above has a hydrogen atom in which one hydrogen atom is substituted with a bonding bond. divalent aliphatic hydrocarbon group; the divalent aliphatic hydrocarbon group of at least one or more linking group by, for example, the following groups V ¹ and the like for connecting together the bonding group.

X in the formula (1) preferably represents a divalent organic group having 4 to 40 carbon atoms with a cyclic structure such as alicyclic, aromatic ring, and heterocyclic structure, and more preferably represents a divalent aromatic group having 4 to 40 carbon atoms The group group and the divalent alicyclic group having 4 to 40 carbon atoms are more preferably a divalent aromatic group having 4 to 40. Regarding the organic group, the hydrogen atom in the organic group may be substituted with a hydrocarbyl group or a hydrocarbyl group substituted with fluorine. In this case, the carbon number of the hydrocarbyl group and the hydrocarbyl group substituted with fluorine is preferably 1-8. In one embodiment of the present invention, the polyimide-based resin of the present invention may include a plurality of types of X, and the plurality of types of X may be the same or different from each other. Examples of X include: formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17), and formula (18) The group represented; the hydrogen atom in the group represented by the formula (10) to the formula (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a carbon number of 6 or less The chain hydrocarbon group.

[化12]

In formulas (10) to (18), * represents a bonding bond, and V ¹ , V ² and V ³ independently represent a single bond, -O-, -S-, -CH ₂ -, -CH _2- CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -CO- or -N(Q)-. Here, Q represents a C1-C12 monovalent hydrocarbon group which may have a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms that may have a halogen atom include those exemplified above as the monovalent hydrocarbon group of R ² to R ⁵ in the formula (3) that may have a halogen atom. An example is that V ¹ and V ³ are single bonds, -O- or -S-, and V ² is -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -or -SO _2- . The bonding position of V ¹ and V ² in each ring, and the bonding position of V ² and V ³ in each ring are independently relative to each ring, preferably meta-position or para-position, more preferably para-position. Furthermore, the hydrogen atom on the ring in formula (10) to formula (18) can be substituted with an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons or an aryl group with 6 to 12 carbons . Examples of the alkyl group having 1 to 6 carbons, the alkoxy group having 1 to 6 carbons, and the aryl group having 6 to 12 carbons include those exemplified above as R ^{1 of} the formula (3).

[式(4)中，A表示單鍵、-O-、二苯基亞甲基、可具有鹵素原子之二價烴基、-SO₂ -、-S-、-CO-、-PO-、-PO₂ -、-N(R^A1 )-或-Si(R^A2 )₂ -， R^A1 及R^A2 相互獨立地表示氫原子或可具有鹵素原子之烷基， R⁶ 相互獨立地表示鹵素原子、可具有鹵素原子之烷基、烷氧基、芳基或芳氧基， s相互獨立地表示0～4之整數， *表示鍵結鍵] 若為此種形態，則容易提昇光學膜之透明性、彈性模數及耐折性。又，式(1)所表示之結構單元可包含一種或複數種式(4)所表示之結構作為X。In a preferred embodiment of the present invention, the polyimide resin in the present invention, as X in the formula (1), may further include the structure represented by the formula (4). [化13]

[In formula (4), A represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group that may have a halogen atom, -SO ₂ -, -S-, -CO-, -PO-,- PO ₂ -, -N(R ^A1 )- or -Si(R ^A2 ) ₂ -, R ^A1 and R ^A2 independently represent a hydrogen atom or an alkyl group which may have a halogen atom, and R ⁶ independently represent a halogen atom, Alkyl group, alkoxy group, aryl group or aryloxy group which may have a halogen atom, s represents an integer of 0-4 independently of each other, * represents a bonding bond] In this form, the transparency of the optical film is easily improved , Elastic modulus and folding resistance. In addition, the structural unit represented by formula (1) may include one or more of the structures represented by formula (4) as X.

R ⁶ independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom. As a halogen atom, an alkyl group, an alkoxy group, an aryl group, and an aryloxy group which may have a halogen atom, the ones exemplified as ^{R 1 of the formula (3) above can be cited, respectively.}

Among them, from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, R ^{6 is} independently preferably an alkyl group having 1 to 6 carbons or a haloalkyl group having 1 to 6 carbons, and more It is preferably an alkyl group having 1 to 6 carbons or a fluoroalkyl group having 1 to 6 carbons, and more preferably a perfluoroalkyl group. In suitable forms, R ⁶ are independently methyl, chloro or trifluoromethyl. s represents an integer of 0-4 independently of each other. From the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, it is preferably an integer of 1 to 3, and more preferably 1 or 2. More preferably, it is 1. In a preferred embodiment of the present invention, it is preferable that in each benzene ring, s is 1, R ⁶ is substituted at the ortho position on the basis of -A-, and R ⁶ is methyl, fluoro, or chloro基 or trifluoromethyl.

In formula (4), from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, the position of the bonding bond is based on -A-, and is preferably meta or paired independently of each other. Position, more preferably counterpoint.

A in formula (4) independently represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group that may have a halogen atom, -SO ₂ -, -S-, -CO-, -PO- , -PO ₂ -, -N(R ^A1 )- or -Si(R ^A2 ) ₂ -, R ^A1 and R ^A2 independently represent a hydrogen atom or an alkyl group which may have a halogen atom. Examples of the divalent hydrocarbon group that may have a halogen atom include a divalent group obtained by removing one hydrogen atom from the monovalent hydrocarbon group that may have a halogen atom among ^{R 2} to R ^{5 in the formula (3).} The divalent hydrocarbon group which may have a halogen atom can replace two hydrogen atoms in the hydrogen atoms contained in the group to form a ring, that is, the two hydrogen atoms can be replaced by a bonding bond, and the two bonding bonds can be connected to form a ring As the ring, examples of the ring include a cycloalkane ring having 3 to 12 carbon atoms. In addition, as the alkyl groups that may have halogen atoms in R ^A1 and R ^{A2 of -N(R A1} )- and -Si(R ^A2 ) ₂ -included in A in formula (4), the above mentioned as The alkyl group which may have a halogen atom ^{in R 1} in the formula (3) is exemplified.

From the viewpoint of easily improving the transparency, elastic modulus and folding resistance of the optical film, A in formula (3) is preferably a single bond, -CH ₂ -, -CH ₂ -CH ₂ -, -CH( CH ₃ )-, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, more preferably a single bond, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, more preferably It is a single bond or -C(CF ₃ ) ₂ -, and is particularly preferably a single bond.

In a suitable embodiment of the present invention, from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, in formula (4), R ⁶ independently represents a halogenated alkyl having 1 to 6 carbons. Group, s represents 1 or 2, and A represents a single bond, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -.

即，式(1)中之複數個X之至少一部分由式(4')表示。若為此種形態，則容易提高光學膜之透明性、彈性模數及耐折性。再者，式(1)所表示之結構單元中，作為X，可包含一種或複數種式(4')所表示之結構。In a suitable form of the present invention, the formula (4) is represented by the formula (4'). [化14]

That is, at least a part of the plural X in the formula (1) is represented by the formula (4'). If it is in this form, it is easy to improve the transparency, elastic modulus, and folding resistance of the optical film. Furthermore, in the structural unit represented by formula (1), as X, one or more types of structures represented by formula (4') may be included.

In one embodiment of the present invention, when X in the formula (1) includes the structure represented by the formula (4), relative to the total molar amount of the structural unit represented by the formula (1), X The ratio of the structural unit represented by the formula (4) is preferably 30 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more, and preferably 100 mol% or less. If the ratio of the structural unit represented by the formula (4) of X is within the above range, it is easy to improve the transparency, elastic modulus, and folding resistance of the optical film. The ratio of the structural unit represented by X by the formula (4) can ^{be measured using 1} H-NMR, for example, or can be calculated from the addition ratio of the raw materials.

In addition to the structural unit represented by the formula (1), the polyimide-based resin in the present invention may also include the structural unit represented by the formula (30) and/or the structural unit represented by the formula (31). [化15]

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

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

In formula (30) and formula (31), X ¹ and X ² are independently a divalent organic group, preferably an organic group in which a hydrogen atom in the organic group can be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Examples of X ¹ and X ² include the above-mentioned formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), and formula (17) And the group represented by the formula (18); the hydrogen atom in the group represented by the formula (10) to the formula (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a carbon number of 6 The following chain hydrocarbon groups.

In one embodiment of the present invention, the polyimide-based resin comprises a structural unit represented by formula (1), and a structural unit represented by formula (30) and a structural unit represented by formula (31) which are optionally included At least one structural unit of the structural unit. In addition, from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, in the above-mentioned polyimide-based resin, relative to all the structural units contained in the polyimide-based resin, for example, the formula (1) The structural unit represented, and the total molar amount of at least one structural unit selected from the structural unit represented by formula (30) and the structural unit represented by formula (31), which are optionally included, formula (1 The ratio of the structural unit represented by) is preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more. Furthermore, the upper limit of the ratio of the structural unit represented by formula (1) in the polyimide-based resin is 100 mol% or less. In addition, the above-mentioned ratio can ^{be measured using 1} H-NMR, for example, or it can also be calculated based on the addition ratio of raw materials. In addition, from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film, the polyimide resin in the present invention is preferably a polyimide resin.

In a preferred embodiment of the present invention, the polyimide-based resin of the present invention may include, for example, a halogen atom such as a fluorine atom, and the halogen atom may be introduced by the above-mentioned fluorine-containing substituent or the like. When the polyimide-based resin contains halogen atoms, it is easy to reduce the yellowness of the optical film (hereinafter, sometimes referred to as the YI value), and it is easy to increase the elastic modulus and folding resistance. In addition, if the elastic modulus of the optical film is high, it is easy to suppress the occurrence of damage and wrinkles. In addition, if the YI value of the optical film is low, the transparency and visibility of the film can be easily improved. The halogen atom is preferably a fluorine atom. As a fluorine-containing substituent which is preferable to make a polyimide resin contain a fluorine atom, a fluorine group and a trifluoromethyl group are mentioned, for example.

Based on the quality of the polyimide resin, the content of the halogen atom in the polyimide resin is preferably 1-40% by mass, more preferably 5-40% by mass, and still more preferably 5-30 quality%. If the content of the halogen atom is more than the above lower limit, the YI value of the optical film is easily reduced, and the elastic modulus and folding resistance are easily improved. If the content of halogen atoms is less than the above upper limit, synthesis is easy.

The imidization rate of the polyimide resin is preferably 90% or more, more preferably 93% or more, and still more preferably 96% or more. From the viewpoint of easy improvement of the optical properties of the optical film, the imidization rate is preferably at least the above lower limit. In addition, the upper limit of the imidization rate is 100% or less. The imidization rate represents the value of the molar amount of the amide bond in the polyimine resin relative to the molar amount of the tetracarboxylic acid compound-derived structural unit in the polyimine resin. The ratio. Furthermore, when the polyimide-based resin contains a tricarboxylic acid compound, the imidization rate means the molar amount of the imine bond in the polyimide-based resin relative to that in the polyimide-based resin The ratio of the value of twice the molar amount of the structural unit derived from the tetracarboxylic acid compound to the total molar amount of the structural unit derived from the tricarboxylic acid compound. In addition, the imidization rate can be determined by an IR (Infra-red Ray) method, an NMR (nuclear magnetic resonance) method, or the like.

In one embodiment of the present invention, relative to 100% by mass of the optical film, the polyimide resin contained in the optical film is preferably 40% by mass or more, more preferably 50% by mass or more, and still more preferably 60% by mass, more preferably 80% by mass or more, and more preferably 100% by mass or less.

<Manufacturing method of polyimide resin> The manufacturing method of the polyimide resin contained in the optical film of this invention is not specifically limited. In one embodiment of the present invention, the polyimide-based resin containing the structural unit represented by formula (1) can be produced by a method including the steps of reacting a diamine compound with a tetracarboxylic acid compound to obtain The step of polyamide acid; and the step of imidizing the polyamide acid. Furthermore, in addition to the tetracarboxylic acid compound, it can also react with a tricarboxylic acid compound.

[式(X)中，R¹ ～R⁵ 、n及m分別與式(3)中之R¹ ～R⁵ 、n及m相同] 又，式(X)中之R¹ ～R⁵ 、n及m之適宜形態亦與式(3)中之R¹ ～R⁵ 、n及m相同。The tetracarboxylic acid compound used for producing the polyimide resin preferably contains at least the compound represented by formula (X). [化16]

[In the formula (X), R ¹ ~ R ^5, n and m in the formula (3) is the same as R ¹ ~ R ^5, n and m] in general formula (X), the R ¹ ~ R ^5, n Suitable forms of and m are also the same as R ¹ to R ⁵ , n and m in formula (3).

The compound represented by the formula (X) can be obtained by a conventional method, for example, by reacting trimellitic anhydride or a derivative thereof with an aromatic diol, and a commercially available product can also be used.

The structural units represented by formula (1) and formula (30) are usually derived from diamine compounds and tetracarboxylic acid compounds. The structural unit represented by the formula (31) is usually derived from a diamine compound and a tricarboxylic acid compound.

Examples of tetracarboxylic acid compounds used in the synthesis of polyimide resins include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride, etc. . The tetracarboxylic acid compound may be used alone or in combination of two or more kinds. In addition to the dianhydride, the tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as a chlorine compound.

Specific examples of aromatic tetracarboxylic dianhydrides include: non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides . Examples of non-condensed polycyclic aromatic tetracarboxylic dianhydrides include: trimellitic anhydride and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol Esterified product (hereinafter, sometimes referred to as TAHMBP), esterified product of trimellitic anhydride and 2,2',3,3'-tetramethyl-4,4'-biphenol, trimellitic anhydride and 3,3 ',5,5'-Tetramethyl-4,4'-biphenol ester, 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone Tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter, sometimes referred to as BPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl tetracarboxylic 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 (hereinafter, sometimes referred to as 6FDA), 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride , 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4 -Dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(terephthalene) Oxy)diphthalic dianhydride, 4,4'-(isophthalic)diphthalic dianhydride. In addition, as the monocyclic aromatic tetracarboxylic dianhydride, for example, 1,2,4,5-benzenetetracarboxylic dianhydride (also denoted as pyromellitic dianhydride, sometimes referred to as PMDA) As the condensed polycyclic aromatic tetracarboxylic dianhydride, for example, 2,3,6,7-naphthalenetetracarboxylic dianhydride can be cited. Among them, preferred examples include: trimellitic anhydride and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol ester, trimellitic anhydride and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol ester, trimellitic anhydride and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol 2',3,3'-Tetramethyl-4,4'-biphenol ester, trimellitic anhydride and 3,3',5,5'-tetramethyl-4,4'-biphenol Ester, PMDA, 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-di Benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-Diphenyl tetracarboxylic 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, 6FDA; 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1 -Bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxybenzene) Base) ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy) two Phthalic acid dianhydride and 4,4'-(isophthalic acid) diphthalic dianhydride, more preferably include: trimellitic anhydride and 2,2',3,3',5, 5'-hexamethyl-4,4'-biphenol ester, trimellitic anhydride and 2,2',3,3'-tetramethyl-4,4'-biphenol ester, benzene Tricarboxylic anhydride and 3,3',5,5'-tetramethyl-4,4'-biphenol ester, 4,4'-oxydiphthalic dianhydride, BPDA, 2,2',3 ,3'-Biphenyltetracarboxylic dianhydride, 6FDA, bis(3,4-dicarboxyphenyl)methane dianhydride and 4,4'-(terephthalic acid dianhydride). These etc. can be used individually or in combination of 2 or more types.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydride. Cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure. Specific examples thereof include: 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1, Cycloalkane tetracarboxylic dianhydride such as 2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride; bicyclo[2.2.2]oct-7- En-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride; and its positional isomers. These etc. can be used individually or in combination of 2 or more types. Specific examples of acyclic aliphatic tetracarboxylic dianhydride include: 1,2,3,4-butane tetracarboxylic dianhydride, 1,2,3,4-pentane tetracarboxylic dianhydride, etc. , These can be used alone or in combination of two or more kinds. Moreover, cycloaliphatic tetracarboxylic dianhydride and acyclic aliphatic tetracarboxylic dianhydride can also be used in combination.

Among the above-mentioned tetracarboxylic dianhydrides, in terms of easily improving the transparency, elastic modulus, and folding resistance of the optical film, trimellitic anhydride and 2,2',3,3',5, 5'-hexamethyl-4,4'-biphenol ester, trimellitic anhydride and 2,2',3,3'-tetramethyl-4,4'-biphenol ester, benzene Tricarboxylic anhydride and 3,3',5,5'-tetramethyl-4,4'-biphenol ester, PMDA, 4,4'-oxydiphthalic dianhydride, 3,3',4 ,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl) propane dianhydride, 6FDA and their mixtures, more preferably partial Trimellitic anhydride and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol ester, trimellitic anhydride and 2,2',3,3'-tetra Methyl-4,4'-biphenol ester, trimellitic anhydride and 3,3',5,5'-tetramethyl-4,4'-biphenol ester, 6FDA and their mixture , More preferably an ester of trimellitic anhydride and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol, trimellitic anhydride and 2,2', The esterified product of 3,3'-tetramethyl-4,4'-biphenol, the esterified product of trimellitic anhydride and 3,3',5,5'-tetramethyl-4,4'-biphenol.

Examples of the diamine compound used for synthesizing the polyimide resin include aliphatic diamines, aromatic diamines, and mixtures thereof. Furthermore, in this embodiment, "aromatic diamine" means a diamine in which an amine group is directly bonded to an aromatic ring, and a part of its structure may include an aliphatic group or other substituents. The aromatic ring may be a single ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a sulphur ring, but are not limited to them. Among them, a benzene ring is preferred. In addition, "aliphatic diamine" means a diamine in which an amine group and an aliphatic group are directly bonded, and a part of its structure may include an aromatic ring or other substituents.

As aliphatic diamines, for example, acyclic aliphatic diamines such as hexamethylene diamine; and 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl) Group) Cycloaliphatic diamines such as cyclohexane, noralkanediamine and 4,4'-diaminodicyclohexylmethane, etc. These etc. can be used individually or in combination of 2 or more types.

Examples of aromatic diamines include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2 ,6-Diaminonaphthalene and other aromatic diamines with one aromatic ring; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'- Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,4'-di Amino diphenyl benzene, 3,3'-diamino diphenyl benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy) Benzene, bis[4-(4-aminophenoxy)phenyl] ash, bis[4-(3-aminophenoxy)phenyl] ash, 2,2-bis[4-(4-amine Phenyloxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis( Trifluoromethyl)-4,4'-diaminobiphenyl (hereinafter, sometimes referred to as TFMB), 4,4'-(hexafluoropropylene) diphenylamine (hereinafter, sometimes referred to as 6FDAM), 4,4'-bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)pyridium, 9,9-bis(4-amino-3-methylphenyl) ) Tungsten, 9,9-bis(4-amino-3-chlorophenyl) Tungsten, 9,9-bis(4-Amino-3-fluorophenyl) Tungsten, etc. with more than 2 aromatic rings Group diamine. These etc. can be used individually or in combination of 2 or more types.

The aromatic diamine is preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3 '-Diaminodiphenyl ether, 4,4'-Diaminodiphenyl sulfide, 3,3'-Diaminodiphenyl sulfide, 1,4-bis(4-aminophenoxy)benzene , Bis[4-(4-aminophenoxy)phenyl] ash, bis[4-(3-aminophenoxy)phenyl] ash, 2,2-bis[4-(4-amino) Phenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, TFMB, 4,4'-bis (4-aminophenoxy) biphenyl, more preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl Phenyl ether, 4,4'-diaminodiphenyl sulfide, 1,4-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl] sulfide, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, TFMB, 6FDAM, 4,4'-bis(4-aminophenoxy) Base) Biphenyl. These etc. can be used individually or in combination of 2 or more types.

Among the above-mentioned diamine compounds, it is more preferable to use 2,2'-dimethylbenzidine, TFMB, 4,4 from the viewpoint of easily improving the transparency, elastic modulus, and folding resistance of the optical film. One or more of the group consisting of'-bis(4-aminophenoxy)biphenyl, 6FDAM, and 4,4'-diaminodiphenyl ether, and it is more preferable to use TFMB and/or 6FDAM.

Furthermore, the above-mentioned polyimide-based resin can also be used in a range that does not impair the various physical properties of the optical film. In addition to the tetracarboxylic acid compound used in the synthesis of the above-mentioned resin, it can be combined with other tetracarboxylic acid, tricarboxylic acid, and others. The reaction of anhydride and derivatives.

Examples of other tetracarboxylic acids include water adducts of the anhydrides of the above-mentioned tetracarboxylic acid compounds.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and similar chlorinated compounds, acid anhydrides, and the like, and two or more of them can 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 have a single bond,- O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -or phenylene-linked compound.

When manufacturing the polyimide resin, the usage amount of the diamine compound and the tetracarboxylic acid compound can be appropriately selected according to the required ratio of each structural unit of the resin. In a suitable embodiment of the present invention, relative to 1 mol of the tetracarboxylic acid compound, the usage amount of the diamine compound is preferably 0.94 mol or more, more preferably 0.96 mol or more, and still more preferably 0.98 mol or more, It is particularly preferably 0.99 mol or more, preferably 1.20 mol or less, more preferably 1.10 mol or less, still more preferably 1.05 mol or less, and particularly preferably 1.02 mol or less. If the usage amount of the diamine compound relative to the tetracarboxylic acid compound is within the above range, it is easy to adjust the weight average molecular weight of the polyimide-based resin to 160,000 or more.

The reaction temperature of the diamine compound and the tetracarboxylic acid compound is not particularly limited, and may be, for example, 5 to 200°C, and the reaction time is also not particularly limited, and may be, for example, about 30 minutes to 72 hours. In a suitable embodiment of the present invention, the reaction temperature is preferably 5 to 50°C, more preferably 5 to 40°C, from the viewpoint of easy adjustment of the weight average molecular weight of the polyimide-based resin to 160,000 or more It is preferably 5 to 25°C, and the reaction time is preferably 3 to 24 hours, more preferably 5 to 20 hours.

The reaction of the diamine compound and the tetracarboxylic acid compound is preferably carried out in a solvent. The solvent is not particularly limited as long as it does not affect the reaction. Examples include water, methanol, ethanol, ethylene glycol, isopropanol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1- Alcohol solvents such as methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, γ- Ester solvents such as valerolactone, propylene glycol methyl ether acetate and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl isobutyl ketone, etc. ; Aliphatic hydrocarbon solvents such as pentane, hexane and heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; tetrahydrofuran and dimethoxyethane Ether solvents such as alkane; chlorine-containing solvents such as chloroform and chlorobenzene; N,N-dimethylacetamide (hereinafter, sometimes referred to as DMAc), N,N-dimethylformamide (hereinafter, sometimes Described as DMF) and other amide solvents; sulfur-containing solvents such as dimethyl sulfide, dimethyl sulfide, and cyclobutyl sulfide; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof Wait. Among them, from the viewpoint of solubility, an amide-based solvent can be suitably used. In a suitable embodiment of the present invention, from the viewpoint that the weight average molecular weight of the polyimide-based resin can be easily adjusted to 160,000 or more, the solvent used for the reaction is preferably a solvent that is strictly dehydrated to a moisture content of 700 ppm or less. .

The reaction between the diamine compound and the tetracarboxylic acid compound can be carried out in an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere, or under reduced pressure conditions, and the weight average molecular weight of the polyimide-based resin can be easily adjusted to 160,000 or more. In general, it is preferably carried out by stirring in a strictly controlled dehydration solvent under the above-mentioned inert atmosphere.

Examples of the imidization catalyst used in the imidization step include: aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidine, N-propylpiper Alicyclic amines (monocyclic) such as pyridine, N-butylpyrrolidine, N-butylpiperidine and N-propylhexahydroazepine (monocyclic); azabicyclo[2.2.1]heptane, azabicyclo[ 3.2.1] Octane, azabicyclo[2.2.2]octane and azabicyclo[3.2.2]nonane and other alicyclic amines (polycyclic); and pyridine, 2-methylpyridine (2- (Methylpyridine), 3-methylpyridine (3-methylpyridine), 4-methylpyridine (4-methylpyridine), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2 Aromatic amines such as ,4-lutidine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline and isoquinoline . In addition, from the viewpoint of facilitating the promotion of the imidization reaction, it is preferable to use an acid anhydride together with the imidization catalyst. Examples of the acid anhydride include conventional acid anhydrides used in the imidization reaction, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic acid anhydride, and butyric acid anhydride; aromatic acid anhydrides such as phthalic acid and the like.

In a suitable embodiment of the present invention, it is preferable to perform the imidization step step by step, and raise the temperature to the optimal reaction temperature. By stepwise imidization, it is easy to suppress the decomposition of the resin, and the weight average molecular weight of the obtained polyimide-based resin is adjusted to 160,000 or more. The reaction temperature for raising the temperature in the stepwise imidization step is preferably 40 to 85°C, more preferably 45 to 80°C. If the reaction temperature is within the above range, there is a tendency for the amide reaction to proceed sufficiently, and in addition, there is a tendency that the molecular weight is not easy to decrease in the imidization of the amide acid in the imidization step. The reaction time is preferably 30 minutes to 10 hours, more preferably 30 minutes to 5 hours. If the reaction time is within the above-mentioned range, there is a tendency that the resin will not decompose to reduce the molecular weight, and the imidization rate will not be lowered, and the molecular weight will be lowered in the subsequent steps. In this way, in addition to the above synthesis conditions, the imidization step is also controlled, thereby obtaining a resin with a larger weight average molecular weight.

Polyimide-based resins can be separated and purified by conventional methods, such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography and other separation methods, or a combination of separation methods such as separation and purification. In a preferred form, the resin can be separated by adding a large amount of alcohol such as methanol to the reaction solution containing the resin, and then concentrating, filtering, drying, etc.

＜Additives＞ The optical film of the present invention may include at least one type of filler in addition to the polyimide-based resin. Examples of the filler include organic particles and inorganic particles, and preferably inorganic particles. Examples of inorganic particles include metal oxide particles such as silicon dioxide, zirconium oxide, aluminum oxide, titanium oxide, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide. ; Metal fluoride particles such as magnesium fluoride, sodium fluoride, etc., among them, from the viewpoint of easy to have both the elastic modulus and transparency of the optical film, preferably, silicon dioxide particles, zirconium oxide particles, oxide The aluminum particles are more preferably silicon dioxide particles. These fillers can be used alone or in combination of two or more kinds.

The average primary particle size of the filler, preferably silica particles, is usually 1 nm or more, preferably 5 nm or more, more preferably 10 nm or more, still more preferably 15 nm or more, particularly preferably 20 nm or more, and It is preferably 100 nm or less, more preferably 90 nm or less, still more preferably 80 nm or less, still more preferably 70 nm or less, particularly preferably 60 nm or less, most preferably 50 nm or less, and most preferably 40 nm or less . If the average primary particle size of the filler, preferably silica particles is within the above range, it is easy to have both the elastic modulus and transparency of the optical film. In addition, it is easy to inhibit the aggregation of fillers, preferably silica particles, and improve the transparency of the obtained optical film. The average primary particle size of the filler can be measured by the BET method. Furthermore, the average primary particle size can also be measured by image analysis of a transmission electron microscope or a scanning electron microscope.

When the optical film of the present invention contains a filler, preferably silica particles, the content of the filler is usually 0.1% by mass or more, preferably 1% by mass or more, and more preferably 5% by mass relative to the mass of the optical film % Or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, particularly preferably 30% by mass or more, and preferably 60% by mass or less. If the content of the filler is more than the above lower limit, it is easy to have both the elastic modulus and transparency of the obtained optical film. Moreover, if the content of the filler is less than or equal to the above upper limit, the optical properties of the optical film are easily improved.

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

When the optical film contains an ultraviolet absorber, relative to the quality of the optical film, the content of the ultraviolet absorber is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 3% by mass or more, and more It is preferably 10% by mass or less, more preferably 8% by mass or less, and still more preferably 6% by mass or less. Depending on the UV absorber used, the appropriate content is different. If the content of the UV absorber is adjusted so that the light transmittance of 400 nm becomes about 20-60%, the light resistance of the optical film is easily improved, and the transparency is easily improved.

The optical film of the present invention may further contain other additives other than fillers and ultraviolet absorbers. Examples of other additives include antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, and levelers. When other additives are contained, relative to the mass of the optical film, its content is preferably 0.001-20% by mass, more preferably 0.01-15% by mass, and still more preferably 0.1-10% by mass .

＜Optical film＞ In the optical film of the present invention, as Y in the formula (1), the structure represented by the formula (3) is included, and the weight average molecular weight of the polyimide resin is adjusted to 160,000 or more, so it can have excellent transparency Performance and excellent folding resistance. Furthermore, the elastic modulus of the optical film of the present invention is also excellent. Therefore, the optical film of the present invention can be suitably used as a material for flexible display devices. Furthermore, in this specification, transparency can be evaluated by total light transmittance and haze, etc. An increase or improvement in transparency means that the total light transmittance becomes higher and the haze becomes lower.

In a suitable embodiment of the present invention, the total light transmittance of the optical film of the present invention, preferably at a thickness of 50 μm, is preferably 85% or more, more preferably 88% or more, and more preferably 89% or more, more preferably 90% or more, most preferably 91% or more. If the total light transmittance is above the above lower limit, the transparency of the optical film can be improved. For example, when it is used in the front panel of a display device, it can exhibit higher visibility. The upper limit of total light transmittance is usually below 100%. In addition, the total light transmittance can be measured using a haze meter in accordance with JIS K 7105:1981, for example, it can be measured by the method described in the examples. In addition, in this specification, the total light transmittance can also be set as the total light transmittance within the thickness range of the optical film of the present invention.

In a suitable embodiment of the present invention, the haze of the optical film of the present invention, preferably at a thickness of 50 μm, is preferably 2.0% or less, more preferably 1.5% or less, and still more preferably 1.0% or less, Furthermore, it is more preferably 0.8% or less, particularly preferably 0.5% or less, and most preferably 0.3% or less. If the haze of the optical film is below the above upper limit, the transparency of the optical film can be improved. For example, when it is used in the front panel of a display device, it can exhibit higher visibility. In addition, the lower limit of the haze of the optical film is usually 0% or more. In addition, the haze can be measured using a haze meter or the like in accordance with JIS K 7136:2000, and can be measured, for example, by the method described in the examples. In addition, in this specification, the haze can also be set as the haze within the thickness range of the optical film of the present invention.

In a suitable embodiment of the present invention, the YI value of the optical film of the present invention is preferably 3.0 or less, more preferably 2.8 or less, still more preferably 2.5 or less, and is usually -5 or more, preferably -2 or more. If the YI value of the optical film is less than the above upper limit, the transparency of the optical film can be improved, and when it is used in the front panel of a display device, it can exhibit higher visibility. In addition, the YI value can be measured with a UV-visible-near-infrared spectrophotometer to measure the transmittance of light from 300 to 800 nm to obtain the tristimulus value (X, Y, Z), based on YI=100×(1.2769X-1.0592 Z)/Y is calculated. For example, it can be calculated by the method described in the examples.

In a suitable embodiment of the present invention, the optical film of the present invention is excellent in transparency and folding resistance, and also excellent in elastic modulus. The elastic modulus of the optical film of the present invention is preferably 3.5 GPa or more, more preferably 4.0 GPa or more, and still more preferably 4.5 GPa or more. If the modulus of elasticity is more than the above lower limit, the deformation of the optical film is easily suppressed, and durability is easily improved. In addition, the upper limit of the elastic modulus is not particularly limited, but it is usually 15 GPa or less. The modulus of elasticity can be measured using a tensile testing machine. In more detail, the elastic modulus can be measured with a tensile testing machine under the conditions of a distance between the chucks of 50 mm and a tensile speed of 10 mm/min, and set the slope of the stress-strain curve (SS curve), for example, The measurement was performed by the method described in the examples. Furthermore, the modulus of elasticity is the value at 25°C.

In a preferred embodiment of the present invention, the optical film of the present invention has excellent folding resistance. The optical film of the present invention has preferably 350,000 or more folds, more preferably 400,000 or more, and even more preferably 450,000 or more in the MIT flex fatigue test conducted in accordance with ASTM standard D2176-16. If the number of folds is more than the above lower limit, the occurrence of cracks, cracks, etc. can be effectively suppressed even with repeated bending. In addition, the MIT flexural fatigue test can be measured using an MIT flexural fatigue tester, for example, it can be measured by the method described in the examples.

The total light transmittance and haze change according to the thickness of the optical film. The greater the thickness, the lower the total light transmittance and the higher the haze. That is, it is difficult to produce an optical film with a higher total light transmittance and a lower haze in a film with a larger thickness. On the other hand, the optical film of the present invention has a high level of transparency, so even if the thickness is relatively large, it can exhibit high total light transmittance and low haze. Therefore, the thickness of the optical film of the present invention can be preferably 35 μm or more, more preferably 40 μm or more, and still more preferably 45 μm or more. In addition, the upper limit of the thickness of the optical film of the present invention is preferably 100 μm or less, more preferably 80 μm or less, and still more preferably 60 μm or less. The thickness of an optical film can be measured by a film thickness meter etc., for example, can be measured by the method described in an Example.

The use of the optical film of the present invention is not particularly limited, and it can be used for various purposes. As described above, the optical film of the present invention may be a single layer or a laminate, and the optical film of the present invention may be used as it is, or may be further laminated with other films for use. Furthermore, when the optical film is a laminated body, all layers laminated on one or both sides of the optical film are collectively referred to as an optical film.

When the optical film of the present invention is a laminate, it is preferable that at least one surface of the optical film has one or more functional layers. As the functional layer, for example, a hard coat layer, an undercoat layer, a gas barrier layer, an ultraviolet absorbing layer, an adhesive layer, a hue adjustment layer, a refractive index adjustment layer, etc. may be mentioned. The functional layer can be used alone or in combination of two or more.

The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100 μm. If the thickness of the hard coat layer is within the above range, there is a tendency that the impact resistance can be improved, the folding resistance is not easily reduced, and the problem of curling due to hardening shrinkage is less likely to occur. The hard coat layer can be formed by curing a hard coat composition containing a reactive material capable of forming a cross-linked structure by active energy ray irradiation or application of thermal energy, and is preferably formed by active energy ray irradiation. Active energy rays are defined as energy rays that can decompose compounds that produce active species to produce active species. Examples include visible light, ultraviolet rays, infrared rays, X-rays, α-rays, β-rays, γ-rays, and electron beams. Enumerate ultraviolet light. The above-mentioned hard coating composition contains at least one polymer of a radical polymerizable compound and a cation polymerizable compound.

The above-mentioned radically polymerizable compound is a compound having a radically polymerizable group. The radical polymerizable group possessed by the above radical polymerizable compound may be a functional group capable of generating a radical polymerization reaction, and includes a group containing a carbon-carbon unsaturated double bond. Specifically, : Vinyl, (meth)acryloyl, etc. In addition, when the above-mentioned radically polymerizable compound has two or more radically polymerizable groups, the radically polymerizable groups may be the same or different. In terms of increasing the hardness of the hard coat layer, the number of radical polymerizable groups contained in one molecule of the radical polymerizable compound is preferably 2 or more. As the above-mentioned radically polymerizable compound, in terms of high reactivity, a compound having a (meth)acryloyl group is preferable. Specifically, there are 2 to 6 ( (Meth)acrylic acid group, a compound called multifunctional acrylate monomer; or called epoxy (meth)acrylate, (meth)acrylate urethane, (meth)acrylate polyester The oligomers having several (meth)acrylic acid groups in the molecule and having a molecular weight of several hundred to several thousand, preferably selected from epoxy (meth)acrylate, (meth)acrylic urethane One or more of acid ester and (meth)acrylic polyester.

The above-mentioned cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetanyl group, and a vinyloxy group. In terms of increasing the hardness of the hard coat layer, the number of cationically polymerizable groups contained in one molecule of the above-mentioned cationically polymerizable compound is preferably 2 or more, more preferably 3 or more. In addition, as the above-mentioned cationically polymerizable compound, a compound having at least one of an epoxy group and an oxetanyl group as a cationically polymerizable group is preferred. Cyclic ether groups such as epoxy groups and oxetanyl groups are preferred in terms of less shrinkage accompanying the polymerization reaction. In addition, the compound having the epoxy group in the cyclic ether group has the following advantages: it is easy to obtain a compound of diversified structure, does not adversely affect the durability of the obtained hard coat, and is easy to control and free radical polymerizability. Compatibility of the compound. In addition, the oxetanyl group in the cyclic ether group has the following advantages compared with the epoxy group: the degree of polymerization is easily increased, the toxicity is lower, and the network obtained from the cationically polymerizable compound of the hard coat layer is accelerated. The formation speed, even in the region where the radical polymerizable compound is mixed, will not leave unreacted monomer in the film, forming an independent network, etc. Examples of cationic polymerizable compounds having epoxy groups include: polyglycidyl ethers of polyhydric alcohols having an alicyclic ring by using appropriate oxidizing agents such as hydrogen peroxide and peracid, or polyglycidyl ethers containing cyclohexene ring and ring Alicyclic epoxy resin obtained by epoxidation of compound of pentene ring; polyglycidyl ether of aliphatic polyol or its alkylene oxide adduct, polyglycidyl ester of aliphatic long-chain polybasic acid, (methyl) ) Aliphatic epoxy resins such as homopolymers and copolymers of glycidyl acrylate; by bisphenols such as bisphenol A, bisphenol F or hydrogenated bisphenol A, or their alkylene oxide adducts, Glycidyl ether produced by the reaction of derivatives such as lactone adducts and epichlorohydrin, and glycidyl ether type epoxy resins derived from bisphenols such as novolac epoxy resins.

The above-mentioned hard coat composition may further contain a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, and the like, which can be appropriately selected and used. The polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate free radicals or cations for radical polymerization and cationic polymerization. The radical polymerization initiator only needs to release a substance that initiates radical polymerization by at least one of active energy ray irradiation and heating. For example, as a thermal radical polymerization initiator, organic peroxides, such as hydrogen peroxide and perbenzoic acid; azo compounds, such as azobisbutyronitrile, etc. are mentioned. As active energy ray radical polymerization initiators, there are Type1 radical polymerization initiators that generate free radicals by the decomposition of molecules; and those that coexist with tertiary amines to generate free radicals by hydrogen abstraction reaction Type 2 radical polymerization initiators can be used alone or in combination. The cationic polymerization initiator should just release a substance that starts cationic polymerization by at least any one of active energy ray irradiation and heating. As the cationic polymerization initiator, aromatic sulfonium, aromatic sulfonium, cyclopentadienyl iron (II) complex, and the like can be used. Depending on the structure, the cationic polymerization can be started by either or both of active energy ray irradiation or heating.

The polymerization initiator may preferably be contained in an amount of 0.1 to 10% by mass relative to 100% by mass of the entire hard coating composition. If the content of the above-mentioned polymerization initiator is within the above-mentioned range, there is a tendency that the curing can be carried out sufficiently, the mechanical properties or adhesion of the finally obtained coating film can be in a good range, and the shrinkage caused by curing will not easily occur. Caused by poor adhesion or cracking phenomenon and curling phenomenon.

The above-mentioned hard coating composition may further contain one or more members selected from the group consisting of solvents and additives. The solvent can be used as long as it can dissolve or disperse the polymerizable compound and the polymerization initiator, and is widely known as a solvent for the hard coating composition in the technical field, and can be used within a range that does not hinder the effects of the present invention. The above-mentioned additives may further include inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, and the like.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays, and includes, for example, a main material selected from ultraviolet curable transparent resin, electron beam curable transparent resin, and thermosetting transparent resin; and an ultraviolet absorber dispersed in the main material.

The adhesive layer is a layer with the function of adhesion, and has the function of bonding the optical film to other components. As the forming material of the adhesive layer, generally known ones can be used. For example, a thermosetting resin composition or a photocuring resin composition can be used. In this case, by supplying energy afterwards, the molecular weight of the thermosetting resin composition or the photocuring resin composition can be increased and cured.

The adhesive layer may be a layer that is called a pressure sensitive adhesive (PSA) that is attached to an object by pressing. The pressure-sensitive adhesive can be an adhesive that is "adhesive at room temperature and adheres to the material to be bonded with a lighter pressure" (JIS K 6800). It can also be a capsule adhesive. The capsule type adhesive is an "adhesive that allows the protective coating (microcapsule) to contain specific ingredients and maintains stability before the coating is destroyed by appropriate methods (pressure, heat, etc.)" (JIS K 6800).

The hue adjustment layer is a layer that has the function of adjusting the hue, and is a layer that can adjust the optical film to the target hue. The hue adjusting layer is, for example, a layer containing resin and coloring agent. Examples of the coloring agent include inorganic pigments such as titanium oxide, zinc oxide, red lead, titanyl calcined pigments, ultramarine blue, cobalt aluminate, and carbon black; azo compounds, quinacridone compounds, and anthraquinone Organic pigments such as series compounds, perylene series compounds, isoindolinone series compounds, phthalocyanine series compounds, quinophthalone series compounds, anthracene series compounds and diketopyrrolopyrrole series compounds; extender pigments such as barium sulfate and calcium carbonate; And dyes such as basic dyes, acid dyes and mordant dyes.

The refractive index adjustment layer is a layer having the function of adjusting the refractive index, for example, a layer that has a refractive index different from that of a single-layer optical film and can impart a specific refractive index to the optical film. The refractive index adjustment layer may be, for example, a resin layer containing appropriately selected resin, and optionally a pigment, or a metal thin film. Examples of pigments for adjusting refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle size of the pigment may be 0.1 μm or less. By setting the average primary particle diameter of the pigment to 0.1 μm or less, the diffuse reflection of light passing through the refractive index adjustment layer can be prevented, and the decrease in transparency can be prevented. Examples of metals used in the refractive index adjustment layer include titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride Such as metal oxides or metal nitrides.

In one embodiment of the present invention, the optical film may have a protective film on at least one side, that is, one side or both sides. For example, when the optical film has a functional layer on one side, the protective film may be laminated on the surface on the optical film side or on the functional layer side, or on both sides of the optical film side and the functional layer side. When there are functional layers on both sides of the optical film, the protective film can be laminated on the surface on one side of the functional layer, or on both sides of the functional layer. The protective film is a film for temporarily protecting the surface of the optical film or the functional layer, and it is not particularly limited as long as it is a peelable film that can protect the surface of the optical film or the functional layer. Examples of protective films include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resin films such as polyethylene and polypropylene films. Resin film; acrylic resin film, etc., preferably selected from the group consisting of polyolefin resin film, polyethylene terephthalate resin film, and acrylic resin film. When the optical film has two protective films, each protective film may be the same or different.

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

[Method of manufacturing optical film] The optical film of the present invention is not particularly limited. For example, it can be manufactured by a method including the following steps: (a) A step of preparing a liquid (sometimes called a resin varnish) containing the above-mentioned polyimide-based resin (a varnish preparation step); (b) The step of applying the resin varnish to the substrate to form a coating film (coating step); and (c) The step of drying the applied liquid (coating film) to form an optical film (optical film forming step).

In the varnish preparation step, the polyimide-based resin is dissolved in a solvent, and the additives are added as necessary, followed by stirring and mixing, thereby preparing a resin varnish.

The solvent used to prepare the resin varnish is not particularly limited as long as it can dissolve the above-mentioned resin. Examples of the solvent include: amide-based solvents such as DMAc and DMF; lactone-based solvents such as γ-butyrolactone (hereinafter, sometimes referred to as GBL) and γ-valerolactone; Sulfur-containing solvents such as sulfite and cyclobutyl; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among them, an amide-based solvent or a lactone-based solvent is preferred. These solvents can be used alone or in combination of two or more. In addition, the resin varnish may contain water, alcohol-based solvents, ketone-based solvents, acyclic ester-based solvents, ether-based solvents, and the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 15% by mass. Furthermore, in this specification, the solid content of the varnish means the total amount of the components after the solvent is removed from the varnish.

In the coating step, the varnish is coated on the substrate by a well-known coating method to form a coating film. As well-known coating methods, for example, roll coating methods such as wire bar coating, reverse coating, and gravure coating, die nozzle coating methods, comma coating methods, and die lip coating methods can be cited. Cloth method, spin coating method, screen coating method, spray coating method, dipping method, spray method, flow casting method, etc.

In the optical film forming step, the optical film can be formed by drying the coating film and peeling it from the substrate. After peeling, a drying step of drying the optical film can be further performed. The drying of the coating film can be carried out at a temperature of usually 50 to 350°C, preferably 50 to 230°C. In a suitable embodiment of the present invention, drying is preferably carried out in stages. There are situations where the viscosity of varnishes containing high molecular weight resins tends to increase, and it is generally difficult to obtain a uniform film, and it is impossible to obtain a film with excellent transparency. Therefore, by stepwise drying, the varnish containing high molecular weight resin can be dried uniformly, and the transparency can be improved. The coating film can be dried under inert atmosphere as needed. In addition, if the optical film is dried under vacuum conditions, fine bubbles may be generated and remain in the film, resulting in a decrease in transparency. Therefore, it is preferably performed under atmospheric pressure.

Examples of substrates include: PET (polyethylene terephthalate, polyethylene terephthalate) film, PEN (polyethylene naphthalate, polyethylene naphthalate) film, other polyimide resins or polyamides Amine resin film, etc. Among them, from the viewpoint of excellent heat resistance, a PET film, a PEN film, etc. are preferable, and further, from the viewpoint of adhesion to an optical film and cost, a PET film is more preferable.

The optical film of the present invention is suitable for use as a display device, especially a front panel of a flexible display device (sometimes called a window film), especially a front panel of a roll display or a foldable display. That is, the optical film of the present invention is preferably a film for a front panel of a flexible display device. The front panel has the function of protecting the display elements of the flexible display device. Furthermore, the flexible display device is a display device that is used in conjunction with operations such as repeatedly bending and repeatedly rolling up the image display device. The front panel of such a flexible display device used with repeated bending operations and the like requires high folding resistance. In addition, the front panel also requires high visibility. Compared with the film for the substrate of the image display device used inside the image display device, the front panel of the image display device, especially the film for the front panel of the flexible display device, requires high visibility and high folding resistance. . For example, regarding the film of the present invention, it is preferable to have the above-mentioned total light transmittance, haze and/or YI from the viewpoint of easily improving the visibility when used in the front panel of a flexible display device. Moreover, from the viewpoint that it is easy to improve the folding endurance when used as a front panel of a flexible display device, it is preferable to satisfy the above-mentioned folding endurance test in the endurance fatigue test.

Examples of display devices include televisions, smart phones, mobile phones, car navigation, tablet PCs (personal computers), portable game consoles, electronic paper, indicators, bulletin boards, clocks, smart watches, etc. Wearable devices, etc. Examples of flexible displays include display devices with flexible characteristics, such as televisions, smart phones, mobile phones, smart watches, and the like. As the flexible display device, all image display devices having flexibility characteristics can be cited, for example, the roll display or the foldable display as described above can be cited. The scroll display is an image display device that rolls the image display part including the front panel into a roll shape, pulls out the image display part, and uses it in a flat or curved state, and the scroll display is used every time Operations such as roll-like winding are performed at all times. In addition, the foldable display is an image display device in which the image display portion including the front panel is bent, the image display portion is opened, and used in a flat or curved state, and the foldable display is used every time Perform operations such as bending. This kind of image display device that repeatedly performs operations such as winding and bending is called a flexible display device.

[Flexible display device] The present invention includes a flexible display device provided with the optical film of the present invention. The optical film of the present invention is preferably used as a front panel in a flexible display device, and the front panel is sometimes called a window film. The flexible display device includes a laminate for a flexible display device and an organic EL display panel. The laminate for a flexible display device is arranged on the visible side of the organic EL display panel and is configured to be flexible. As a laminate for a flexible display device, it may further include a polarizing plate and a touch sensor. The order of the layers is arbitrary, and it is preferable to laminate the window film, the polarizing plate, and the touch sensor in order from the viewing side Mirror or window film, touch sensor, polarizing plate. If the polarizing plate is more on the viewing side than the touch sensor, the pattern of the touch sensor is not easily recognized, and the visibility of the displayed image becomes better, which is better. Each member can be laminated using adhesives, adhesives, etc. In addition, it may be provided with a light-shielding pattern formed on at least one surface of any layer of the above-mentioned window film, polarizing plate, and touch sensor.

[Polarizer] As described above, the flexible display device of the present invention preferably further includes a polarizing plate, especially a circular polarizing plate. The circular polarizing plate is a functional layer that has a function of transmitting only right-handed or left-handed circularly polarized light components by laminating a λ/4 retardation plate on the linear polarizing plate. For example, it is used to block the external light that is converted into right-handed circularly polarized light and then reflected on the organic EL panel to become left-handed circularly polarized light. Like easy to see. In order to achieve the circularly polarized light function, the absorption axis of the linear polarizer and the late axis of the λ/4 retardation plate must theoretically be 45°, but in practice it is 45±10°. The linear polarizing plate and the λ/4 retardation plate do not necessarily have to be laminated adjacently, as long as the relationship between the absorption axis and the slow phase axis satisfies the above range. It is preferable to achieve complete circularly polarized light at the full wavelength, but this is not necessary in practice. Therefore, the circular polarizing plate in the present invention also includes an elliptical polarizing plate. It is also preferable to laminate a λ/4 retardation film on the visual recognition side of the linear polarizer to make the emitted light circularly polarized light, thereby improving the visual recognition in the state of wearing polarized sunglasses.

The linear polarizer is a functional layer that has the function of passing light that vibrates in the direction of the transmission axis, but blocking the polarization of the vibration component perpendicular to it. The above-mentioned linear polarizing plate may be a structure including a linear polarizing element alone or a linear polarizing element and a protective film attached to at least one surface thereof. The thickness of the linear polarizer may be 200 μm or less, preferably 0.5-100 μm. If the thickness of the linear polarizing plate is within the above range, the flexibility of the linear polarizing plate tends not to decrease easily.

The linear polarizing element described above may be a film-type polarizing element manufactured by dyeing and stretching a polyvinyl alcohol (hereinafter, abbreviated as PVA) film. The dichroic dye such as iodine is adsorbed on the PVA-based film aligned by stretching or stretched while being adsorbed on the PVA, thereby aligning the dichroic dye to exhibit polarization performance. In the production of the above-mentioned film-type polarizing element, in addition to the above, steps such as swelling, cross-linking with boric acid, washing with an aqueous solution, and drying may be included. The stretching or dyeing step can be performed in a PVA-based film alone, or in a state where the PVA-based film and other films such as polyethylene terephthalate are laminated. The thickness of the PVA-based film used is preferably 10-100 μm, and the above-mentioned stretching ratio is preferably 2-10 times. Furthermore, as another example of the above-mentioned polarizing element, a liquid crystal coating type polarizing element formed by applying a liquid crystal polarizing composition can be cited. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic dye compound. The above-mentioned liquid crystalline compound only needs to have the property of displaying a liquid crystal state, and especially if it has an alignment state of the same order as the smectic sequence, it can exhibit higher polarization performance, so it is preferred. Moreover, it is preferable that the liquid crystal compound has a polymerizable functional group. The dichroic dye compound is a dye that is aligned together with the liquid crystal compound to exhibit dichroism, and may have a polymerizable functional group, and the dichroic dye itself may also have liquid crystallinity. Any of the compounds contained in the liquid crystal polarizing composition has a polymerizable functional group. The above-mentioned liquid crystal polarizing composition may further include a starter, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like. The above-mentioned liquid crystal polarizing layer is manufactured by coating a liquid crystal polarizing composition on an alignment film to form a liquid crystal polarizing layer. The liquid crystal polarizing layer can be formed into a thinner thickness than the film-type polarizing element, and the thickness is preferably 0.5-10 μm, more preferably 1-5 μm.

The above-mentioned alignment film is produced, for example, by coating an alignment film forming composition on a substrate, and imparting alignment properties by rubbing, polarized light irradiation, or the like. The aforementioned alignment film forming composition includes an alignment agent, and may further include a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like. Examples of the alignment agent include polyvinyl alcohols, polyacrylates, polyamides, and polyimines. In the case of using an alignment agent that imparts alignment properties by polarized light irradiation, it is preferable to use an alignment agent containing a cinnamate group. The weight average molecular weight of the polymer used as the above-mentioned alignment agent is, for example, about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000 nm, and more preferably 10 to 500 nm in terms of sufficiently exhibiting the alignment restriction force. The liquid crystal polarizing layer may be peeled from the base material and then transferred and laminated, or the base material may be directly laminated. It is also preferable that the above-mentioned base material functions as a transparent base material of a protective film, a phase difference plate, and a window film.

The protective film may be a transparent polymer film, and the same materials or additives as those used for the transparent substrate of the window film may be used. In addition, it may be a coating type protective film obtained by applying and curing a cationic curing composition such as epoxy resin or a radical curing composition such as acrylate. The protective film may also contain plasticizers, ultraviolet absorbers, infrared absorbers, pigments or dyes, fluorescent whitening agents, dispersants, heat stabilizers, light stabilizers, antistatic agents, antistatic agents, etc., if necessary. Oxidizers, lubricants, solvents, etc. The thickness of the protective film is preferably 200 μm or less, more preferably 1-100 μm. If the thickness of the protective film is within the above range, there is a tendency that the flexibility of the film is not easily reduced.

The above-mentioned λ/4 retardation plate is a film that gives a λ/4 retardation in the direction orthogonal to the traveling direction of the incident light, that is, the in-plane direction of the film. The above-mentioned λ/4 retardation plate may be a stretched retardation plate manufactured by stretching a polymer film such as a cellulose-based film, an olefin-based film, or a polycarbonate-based film. The above-mentioned λ/4 retardation plate may also contain retardation modifiers, plasticizers, ultraviolet absorbers, infrared absorbers, coloring agents such as pigments or dyes, fluorescent whitening agents, dispersants, heat stabilizers, Light stabilizers, antistatic agents, antioxidants, lubricants, solvents, etc. The thickness of the above-mentioned extended phase difference plate is preferably 200 μm or less, more preferably 1-100 μm. If the thickness of the extended phase difference plate is within the above range, the flexibility of the extended phase difference plate tends to be less likely to decrease. Furthermore, as another example of the above-mentioned λ/4 retardation plate, a liquid crystal coating type retardation plate formed by applying a liquid crystal composition can be cited. The above-mentioned liquid crystal composition contains a liquid crystal compound showing a liquid crystal state such as nematic, cholesteric, smectic, and the like. The above-mentioned liquid crystal compound has a polymerizable functional group. The above-mentioned liquid crystal composition may further include a starter, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like. The liquid crystal coating type retardation plate can be manufactured by applying a liquid crystal composition on a base and curing the liquid crystal composition to form a liquid crystal retardation layer in the same manner as the liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed into a thinner thickness than the extension type retardation plate. The thickness of the above-mentioned liquid crystal polarizing layer is preferably 0.5 to 10 μm, more preferably 1 to 5 μm. The liquid crystal coating type retardation plate may be peeled from the base material and then transferred and laminated, or the base material may be directly laminated. It is also preferable that the above-mentioned base material functions as a transparent base material of a protective film, a phase difference plate, and a window film.

Generally speaking, most materials show a tendency that the shorter the wavelength, the greater the birefringence, and the longer the wavelength, the smaller the birefringence. In this case, the phase difference of λ/4 cannot be achieved in the full visible light region. Therefore, the in-plane phase difference is designed to be preferably 100-180 nm, more preferably 130-150 nm, so that The high sensitivity near 560 nm becomes λ/4. A reverse dispersion λ/4 retardation plate using a material having a birefringence wavelength dispersion characteristic opposite to the usual one is preferable in terms of good visibility. As such a material, for example, the extension type retardation plate can be described in Japanese Patent Laid-Open No. 2007-232873, and the liquid crystal coating type retardation plate can be used as described in the Japanese Patent Laid-Open No. 2010-30979. In addition, as another method, a technique of obtaining a wide-band λ/4 retardation plate by combining with a λ/2 retardation plate is also known (for example, Japanese Patent Laid-Open No. 10-90521, etc.). The λ/2 retardation plate is also manufactured by the same material method as the λ/4 retardation plate. The combination of the extension type retardation plate and the liquid crystal coating type retardation plate is arbitrary, and the thickness can be reduced by using the liquid crystal coating type retardation plate. A method of laminating a positive C plate on the above-mentioned circular polarizing plate to improve the visibility in the oblique direction is known (for example, Japanese Patent Laid-Open No. 2014-224837, etc.). The positive C plate can be a liquid crystal coating type retardation plate or an extended type retardation plate. The retardation in the thickness direction of the retardation plate is preferably -200 to -20 nm, more preferably -140 to -40 nm.

[Touch Sensor] As described above, the flexible display device of the present invention preferably further includes a touch sensor. The touch sensor is used as an input mechanism. As the touch sensor, various types can be cited, such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and an electrostatic capacitance method, and an electrostatic capacitance method is preferable. The capacitive touch sensor is divided into an active area and an inactive area located outside the active area. The active area corresponds to the area of the display panel as the display part of the display screen and the area that perceives the user's touch, and the inactive area corresponds to the area of the display device as the area of the display part that does not display the picture. The touch sensor may include: a substrate with flexible characteristics; a sensing pattern formed on the active area of the substrate; and an inactive area formed on the substrate for communicating with an external drive circuit via the sensing pattern and pad Connect each sensing line. Regarding the substrate with flexible properties, the same material as the transparent substrate of the above-mentioned window film can be used.

The aforementioned sensing pattern may include a first pattern formed in the first direction and a second pattern formed in the second direction. The first pattern and the second pattern are arranged in mutually different directions. The first pattern and the second pattern are formed on the same layer. In order to sense the touch position, each pattern must be electrically connected. The first pattern is a form in which a plurality of unit patterns are connected to each other via a joint, but the second pattern is a structure in which a plurality of unit patterns are separated from each other into an island shape. Therefore, in order to electrically connect the second pattern, an additional bridge electrode is necessary. As the electrode for connecting the second pattern, a well-known transparent electrode can be used. As the material of the transparent electrode, for example, indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium zinc tin oxide (IZTO), indium gallium zinc oxide (IGZO) ), cadmium tin oxide (CTO), PEDOT (poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)), carbon nanotube (CNT), graphene and metal wire, etc. Preferably, ITO can be cited. These etc. can be used individually or in mixture of 2 or more types. The metal used for the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, and chromium. These can be used alone or in combination of two or more. The bridge electrode can be formed on the upper part of the insulating layer through the insulating layer located on the upper part of the sensing pattern, and the bridge electrode is formed on the substrate, and the insulating layer and the sensing pattern can be formed thereon. The above-mentioned bridge electrode may be formed of the same material as the sensing pattern, or may be formed of two or more alloys of molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or the like. The first pattern and the second pattern must be electrically insulated, so an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the joints of the first pattern and the bridging electrodes, or may be formed as a layer covering the entire sensing pattern. In the case of covering the whole layer of the sensing pattern, the bridge electrode may be connected to the second pattern through the contact hole formed in the insulating layer.

The above-mentioned touch sensor may further include an optical adjustment layer between the substrate and the electrode to appropriately compensate for the difference in transmittance between the pattern area where the sensing pattern is formed and the non-pattern area where the sensing pattern is not formed. Specifically, it is the mechanism of the difference in light transmittance caused by the difference in refractive index of these regions. The optical adjustment layer may include an inorganic insulating material or an organic insulating material. The optical adjustment layer can be formed by coating a photo-curing composition containing a photo-curing organic adhesive and a solvent on a substrate. The above-mentioned photocurable composition may further contain inorganic particles. The above-mentioned inorganic particles can increase the refractive index of the optical adjustment layer. The above-mentioned photocurable organic adhesive may be within a range that does not impair the effects of the present invention, and for example, a copolymer containing various monomers such as acrylate monomers, styrene monomers, and carboxylic acid monomers. The above-mentioned photocurable organic binder may be, for example, a copolymer containing different repeating units such as epoxy group-containing repeating units, acrylate repeating units, and carboxylic acid repeating units. Examples of the above-mentioned inorganic particles include zirconium oxide particles, titanium oxide particles, and aluminum oxide particles. The above-mentioned photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

[Next layer] The window film, circular polarizing plate, touch sensor and other layers forming the laminated body for the flexible display device, and the film members such as the linear polarizing plate and λ/4 phase difference plate constituting each layer can be joined by an adhesive. As the adhesive, commonly used adhesives and the like can be used, namely, water-based adhesives, organic solvent-based, solvent-free adhesives, solid adhesives, solvent-sublimation adhesives, water-based solvent-sublimation adhesives, and moisture-curing adhesives. Adhesive, heat curing type adhesive, anaerobic curing type, active energy ray curing type adhesive, curing agent mixed type adhesive, hot melt type adhesive, pressure sensitive adhesive, pressure sensitive adhesive, rewetting type As an adhesive etc., it is preferable to use an aqueous solvent sublimation type adhesive, an active energy ray hardening type adhesive, and an adhesive agent. The thickness of the adhesive layer can be appropriately adjusted according to the required adhesive force, etc., preferably 0.01-500 μm, more preferably 0.1-300 μm. There are a plurality of adhesive layers in the above-mentioned laminate for flexible display devices, and the thickness and type of each layer may be the same or different.

Regarding the above-mentioned water-based solvent sublimation adhesive, water-dispersed polymers such as polyvinyl alcohol-based polymers, starch and other water-soluble polymers, ethylene-vinyl acetate-based emulsions, styrene-butadiene-based emulsions, and other water-dispersed polymers can be used as the main Agent polymer. In addition to the above-mentioned main agent polymer and water, crosslinking agents, silane-based compounds, ionic compounds, crosslinking catalysts, antioxidants, dyes, pigments, inorganic fillers, organic solvents, etc. can also be formulated. In the case of bonding by the above-mentioned water-based solvent sublimation adhesive, the above-mentioned water-based solvent sublimation adhesive can be injected between the layers to be bonded and the bonded layers are bonded, and then dried to impart adhesiveness. When the above-mentioned water-based solvent sublimation adhesive is used, the thickness of the adhesive layer is preferably 0.01-10 μm, more preferably 0.1-1 μm. When multiple layers of the above-mentioned aqueous solvent sublimation adhesive are used, the thickness and type of each layer may be the same or different.

The active energy ray curable adhesive can be formed by curing an active energy ray curable composition containing a reactive material that forms an adhesive layer by irradiating active energy rays. The active energy ray hardening composition may contain at least one polymer of the same radical polymerizable compound and cation polymerizable compound as those contained in the hard coat composition. The radical polymerizable compound can be the same compound as the radical polymerizable compound in the hard coat composition. As the above-mentioned cationically polymerizable compound, the same compound as the cationically polymerizable compound in the hard coat composition can be used. The cationic polymerizable compound used in the active energy ray hardening composition is particularly preferably an epoxy compound. In order to reduce the viscosity of the adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

The active energy ray composition may include a monofunctional compound to reduce viscosity. Examples of the monofunctional compound include: an acrylate monomer having one (meth)acrylic acid group in one molecule; or a compound having one epoxy group or oxetanyl group in one molecule, for example ( Glycidyl meth)acrylate and the like. The active energy ray composition may further include a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, and the like, and these can be appropriately selected and used. The polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate free radicals or cations, and carry out free radical polymerization and cationic polymerization. In the description of the hard coating composition, an initiator that can start at least any one of radical polymerization or cationic polymerization by active energy ray irradiation can be used. The active energy ray hardening composition may further include an ion scavenger, an antioxidant, a chain transfer agent, an adhesion imparting agent, a thermoplastic resin, a filler, a fluid viscosity adjuster, a plasticizer, a solvent-based defoamer, an additive, and a solvent. In the case where two adhesive layers are bonded by the above-mentioned active energy ray-curing adhesive, the bonding can be performed by applying the above-mentioned active energy ray-curing composition to either one of the adhesive layers or both After the bonded layer is bonded, either the bonded layer or the two bonded layers are irradiated with active energy rays for curing. In the case of using the active energy ray-curable adhesive, the thickness of the adhesive layer is preferably 0.01-20 μm, more preferably 0.1-10 μm. In the case of using the above-mentioned active energy ray hardening adhesive to form a plurality of adhesive layers, the thickness and type of each layer may be the same or different.

The above-mentioned adhesives are classified into acrylic adhesives, urethane-based adhesives, rubber-based adhesives, silicone-based adhesives, etc. according to the main agent polymer, and any of them can be used. In the adhesive, in addition to the main agent polymer, crosslinking agents, silane compounds, ionic compounds, crosslinking catalysts, antioxidants, adhesion imparting agents, plasticizers, dyes, pigments, inorganic fillers, etc. can also be blended . Each component constituting the adhesive is dissolved and dispersed in a solvent to obtain an adhesive composition, and the adhesive composition is coated on a substrate and dried to form an adhesive layer adhesive layer. The adhesive layer can be formed directly, or it can be formed on the substrate by transfer printing. In order to cover the adhesive surface before bonding, it is also preferable to use a release film. In the case of using the above-mentioned active energy ray-curable adhesive, the thickness of the adhesive layer is preferably 0.1 to 500 μm, more preferably 1 to 300 μm. In the case of using multiple layers of the above-mentioned adhesive, the thickness and type of each layer may be the same or different.

[Shading Pattern] The light-shielding pattern can be used as at least a part of the frame or housing of the flexible display device. The wiring arranged at the edge of the flexible display device is shielded by the light-shielding pattern and is not easy to be recognized, so that the visibility of the image is improved. The above-mentioned light-shielding pattern may be in the form of a single layer or a multiple layer. The color of the shading pattern is not particularly limited, and can be a variety of colors such as black, white, and metallic. The light-shielding pattern can be formed by pigments used to realize colors, and polymers such as acrylic resins, ester resins, epoxy resins, polyurethanes, and silicones. These etc. can also be used individually or in mixture of 2 or more types. The above-mentioned light-shielding pattern can be formed by various methods such as printing, photolithography, and inkjet. The thickness of the light-shielding pattern is preferably 1-100 μm, more preferably 2-50 μm. Moreover, it is also preferable to give a shape such as an inclination in the thickness direction of the light-shielding pattern.

[Polyimide resin] The present invention includes a polyimide-based resin comprising a structural unit represented by formula (1), as Y in formula (1), including a structure represented by formula (3), and the above-mentioned polyimide-based resin The weight average molecular weight is above 160,000. In the polyimide resin of the present invention, Y in the formula (1) includes the structure represented by the formula (3), and the weight average molecular weight of the polyimine resin is 160,000 or more, so the polyimide resin is included The optical film of the imide resin is excellent in transparency and folding resistance. Furthermore, the optical film containing the polyimide-based resin of the present invention can have an excellent elastic modulus. Therefore, the optical film containing the polyimide-based resin of the present invention can be suitably used as a material for flexible display devices and the like. The polyimide-based resin of the present invention is preferably the same as the polyimide-based resin described in the section of the above-mentioned <Polyimide-based resin>. [Example]

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

＜Total light transmittance＞ According to JIS K 7105:1981, the total light transmittance (Tt) of the optical film obtained in the examples and comparative examples was measured by the automatic direct reading haze meter HGM-2DP manufactured by Suga Testing Machine Co., Ltd.

＜Haze (Haze)＞ According to JIS K 7136: 2000, the optical films obtained in the examples and comparative examples were cut into a size of 30 mm×30 mm, and the haze was measured using a haze meter (manufactured by Suga Testing Machine Co., Ltd., "HGM-2DP") degree(%).

＜YI value＞ For the optical films obtained in the examples and comparative examples, use an ultraviolet-visible-near-infrared spectrophotometer (V-670 manufactured by JASCO Corporation) to obtain the tristimulus values (X, Y, Z), and substitute them as follows The calculation formula is used to calculate the YI value. YI=100×(1.2769X－1.0592Z)/Y

＜Evaluation of folding endurance＞ According to ASTM standard D2176-16, the number of bending of the optical films in the examples and comparative examples was calculated as follows. Using a dumbbell cutter, cut the optical film into short strips of 15 mm×100 mm. Install the cut optical film on the main body of the MIT flexural fatigue testing machine ("Model 0530", manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a test speed of 175 cpm, a bending angle of 135°, a load of 0.75 kgf, and the radius of the bending clamp R =1 mm, measure the number of reciprocating bending in the front and back directions until the optical film breaks, and set it as the number of bending (also referred to as the number of fold resistance).

＜Elastic modulus＞ Using "Autograph AG-IS" manufactured by Shimadzu Corporation, the elastic modulus of the optical films obtained in the Examples and Comparative Examples was measured. A film with a length of 10 mm is produced, and the stress-strain curve (S-S curve) is measured under the conditions of a distance between the chucks of 50 mm and a stretching speed of 10 mm/min, and the elastic modulus is calculated based on the slope.

＜Determination of weight average molecular weight＞ GPC determination (1) Pretreatment method The DMF lysate (solution with 10 mmol/L lithium bromide added) was added to the polyimide resin obtained in the examples and comparative examples at a concentration of 2 mg/mL, while stirring at 80°C for 30 It is heated for a minute, and after cooling, it is filtered through a 0.45 μm membrane filter, and the resultant is used as the measurement solution. (2) Measurement conditions Tubular column: TSKgel α-2500 ((7) diameter 7.8 mm×300 mm) × 1 piece, α-M ((13) diameter 7.8 mm×300 mm) × 2 pieces manufactured by Tosoh Co., Ltd. Eluent: DMF (with 10 mmol/L lithium bromide) Flow rate: 1.0 mL/min Detector: RI (Refractive Index, refractive index) detector Column temperature: 40℃ Injection volume: 100 μL Molecular weight standard: standard polystyrene

＜Thickness of optical film＞ Using an ABS digital dial indicator (manufactured by Mitutoyo Co., Ltd., "ID-C112BS"), the thickness of the optical film obtained in the examples and comparative examples was measured.

<Example 1> [Preparation of polyimide resin (1)] Under a nitrogen atmosphere, add TFMB and DMAc whose water content is strictly dehydrated to 700 ppm or less so that the solid content of TFMB becomes 7.81% by mass into a separable flask equipped with a stirring blade, while stirring at room temperature Dissolve TFMB in DMAc. Next, TAHMBP was added to the flask so that it might become 101.01 mol% with respect to TFMB, and it stirred at room temperature for 16 hours. Then, 60.61 mol% of 4-picoline was added to TFMB, and 707.07 mol% of acetic anhydride was added to TFMB. After stirring for 30 minutes, the internal temperature was increased to 50°C in 20 minutes, and the temperature was increased in 20 minutes. It took 20 minutes to raise the temperature to 70°C to 60°C, and then stir for 3 hours to obtain a reaction liquid. The obtained reaction liquid was cooled to room temperature, linearly poured into a large amount of methanol, and the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60°C to obtain polyimide resin (1). The weight average molecular weight is 484,000.

[Manufacturing of Optical Film (1)] DMAc was added to the obtained polyimide resin (1) so that the solid content concentration became 10 mass %, and the polyimide varnish (1) was produced. Use an applicator to apply the polyimide varnish (1) obtained to a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") to smooth the thickness of the self-supporting film to 55 μm. The surface was dried at 50°C for 30 minutes, and then at 140°C for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and then dried at 200° C. for 60 minutes to obtain an optical film (1) with a thickness of 50 μm.

<Comparative example 1> [Preparation of polyimide resin (2)] In a nitrogen atmosphere, TFMB and DMAc whose water content is strictly dehydrated to 700 ppm or less are added to a separable flask with a stirring blade so that the solid content of TFMB becomes 9.43% by mass, while stirring at room temperature Dissolve TFMB in DMAc. Next, 6FDA was added to the flask so that it might become 101.01 mol% with respect to TFMB, and it stirred at room temperature for 16 hours. Then, 60.61 mol% of 4-picoline was added to TFMB, and 707.07 mol% of acetic anhydride was added to TFMB. After stirring for 30 minutes, the internal temperature was increased to 70° C. and further stirred for 3 hours to obtain a reaction liquid. The obtained reaction liquid was cooled to room temperature, linearly poured into a large amount of methanol, and the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60°C to obtain polyimide resin (2). The weight average molecular weight is 255,000.

[Manufacturing of Optical Film (2)] DMAc was added to the obtained polyimide resin (2) so that the solid content concentration became 10 mass %, and the polyimide varnish (2) was produced. The thickness of the self-supporting film becomes 55 μm, and the obtained polyimide varnish (2) is applied to a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") to smooth it using an applicator. The surface was dried at 50°C for 30 minutes, and then at 140°C for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and then dried at 200° C. for 60 minutes to obtain an optical film (2) with a thickness of 50 μm.

＜Comparative example 2＞ [Preparation of polyimide resin (3)] Under nitrogen atmosphere, add TFMB and DMAc whose water content is strictly dehydrated to 700 ppm or less so that the solid content of TFMB becomes 11.48% by mass into a separable flask equipped with a stirring blade, while stirring at room temperature Dissolve TFMB in DMAc. Next, BPDA was added to the flask at 101.01 mol% relative to TFMB, and stirring was performed at room temperature. However, as time passed, the viscosity increased, and it became a solid state after 16 hours, and the stirring was poor, so the preparation was abandoned.

＜Comparative example 3＞ [Preparation of polyimide resin (4)] Under nitrogen atmosphere, add TFMB and DMAc whose water content is strictly dehydrated to 700 ppm or less so that the solid content of TFMB becomes 8.52% by mass into a separable flask equipped with a stirring blade, while stirring at room temperature Dissolve TFMB in DMAc. Next, the esterified product of trimellitic anhydride and 4,4'-biphenol was added to the flask so that it became 101.01 mol% relative to TFMB, and stirring was performed at room temperature. However, as time passed, the viscosity increased. It became a solid state after 16 hours, and the stirring was poor, so the preparation was abandoned.

For the optical films obtained in Example 1 and Comparative Example 1, the total light transmittance, haze, YI value, and elastic modulus were measured, and the folding resistance was evaluated. The obtained results are shown in Table 1. Furthermore, regarding Comparative Examples 2 and 3, as described above, the polyimide resin was not kept in a solution state during the synthesis of the polyimide resin, and the polyimide resin could not be taken out, so the evaluation of the optical film could not be performed.

[Table 1] Total light transmittance (%) Haze (%) YI Modulus of Elasticity (GPa) Folding times (times) Example 1 91.4 0.2 2.42 4.98 463,130 Comparative example 1 92.7 0.1 1.66 3.44 319,956

As shown in Table 1, it can be seen that the optical film of Example 1 has a higher folding endurance, a higher total light transmittance and a lower haze. Therefore, it can be seen that the optical film of the present invention is excellent in transparency and folding resistance.

Claims (12)

An optical film comprising a polyimide resin, and the polyimide resin includes a structural unit represented by formula (1): [化1]

[In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, * represents a bonding bond], as Y in the formula (1), it includes the structure represented by the formula (3): [化2] ]

[In formula (3), R ¹ independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, and R ² to R ⁵ independently represent a hydrogen atom or may have a halogen Atomic monovalent hydrocarbon group, m independently represents an integer of 0 to 3, n represents an integer of 1 to 4, * represents a bonding bond, wherein, in at least one benzene ring ^{having R 2} to R ^{5 , R 2} At least one of -R ⁵ is a monovalent hydrocarbon group which may have a halogen atom], and the weight average molecular weight of the polyimide resin is 160,000 or more. The optical film of claim 1, wherein X in formula (1) includes at least one of a divalent aromatic group, a divalent alicyclic group, and a divalent aliphatic group. Such as the optical film of claim 1 or 2, where X in formula (1) includes the structure represented by formula (4): [化3]

[In formula (4), A represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group that may have a halogen atom, -SO ₂ -, -S-, -CO-, -PO-,- PO ₂ -, -N(R ^A1 )- or -Si(R ^A2 ) ₂ -, R ^A1 and R ^A2 independently represent a hydrogen atom or an alkyl group which may have a halogen atom, and R ⁶ independently represent a halogen atom, An alkyl group, an alkoxy group, an aryl group or an aryloxy group which may have a halogen atom, s independently represents an integer of 0 to 4, and * represents a bonding bond]. The optical film of any one of claims 1 to 3, which has a thickness of 35 μm or more. For example, the optical film of any one of claims 1 to 4 has a total light transmittance of 85% or more. The optical film of any one of claims 1 to 5 has a yellowness of 3.0 or less. Such as the optical film of any one of claims 1 to 6, the elastic modulus of which is 3.5 GPa or more. The optical film of any one of claims 1 to 7, which is a film for a front panel of a flexible display device. A flexible display device provided with the optical film as claimed in any one of claims 1 to 8. For example, the flexible display device of claim 9 further includes a touch sensor. For example, the flexible display device of claim 9 or 10 is further provided with a polarizing plate. A polyimide resin comprising the structural unit represented by formula (1): [化4]

[In the formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, * represents a bonding bond], as Y in the formula (1), includes the formula (3): [化5]

[In formula (3), R ¹ independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, and R ² to R ⁵ independently represent a hydrogen atom or may have a halogen Atomic monovalent hydrocarbon group, m independently represents an integer of 0 to 3, n represents an integer of 1 to 4, * represents a bonding bond, wherein, in at least one benzene ring ^{having R 2} to R ^{5 , R 2} At least one of -R ⁵ is a monovalent hydrocarbon group which may have a halogen atom], and the weight average molecular weight of the polyimide resin is 160,000 or more.