CN114667466A

CN114667466A - Optical laminate and flexible display device

Info

Publication number: CN114667466A
Application number: CN202080075557.5A
Authority: CN
Inventors: 大松一喜; 中小路崇; 铃木宏昌
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2019-10-31
Filing date: 2020-10-27
Publication date: 2022-06-24
Also published as: KR20220086685A; JP2021075052A; TW202122259A

Abstract

The invention provides an optical laminate which comprises a base material and a hard coat layer laminated on at least one surface of the base material and has excellent bending resistance. The optical laminate of the present invention comprises at least a base layer comprising a polyamide resin and a hard coat layer laminated on at least one surface of the base layer, wherein an intermediate layer having a thickness of 0.3 [ mu ] m or more and a thickness variation of 25% or less is provided between the base layer and the hard coat layer, and the optical laminate is formed so that the cross section in the thickness direction thereof isThe indentation hardness of the intermediate layer measured by a nanoindenter was AN/mm²The press-in hardness of the base material layer is BN/mm²In the case, the ratio of A to B (A/B) is 0.96 or less.

Description

Optical laminate and flexible display device

Technical Field

The present invention relates to an optical laminate having at least a base material layer containing a polyamide resin and a hard coat layer laminated on at least one surface of the base material layer, and a flexible electronic device containing the optical laminate.

Background

Image display devices such as liquid crystal display devices and organic EL display devices are widely used for various applications such as mobile phones and smartwatches. Glass has been used as a front panel of such an image display device in the past, but glass is very rigid and easily broken, and thus it is difficult to use as a front panel material of, for example, a flexible display or the like. As an optical film that replaces glass, a plastic film having a substrate and a hard coat layer laminated on at least one surface of the substrate has been studied (for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-125063

Disclosure of Invention

Problems to be solved by the invention

According to the studies by the present inventors, it has been found that when an optical laminate having a base material and a hard coat layer laminated on at least one surface of the base material is used in a flexible electronic device such as a flexible display, even if the base material has high bending resistance, the bending resistance as a laminate may be reduced by laminating the hard coat layer. Further, it is found that the optical characteristics may be deteriorated by repeated bending because of low bending resistance. Accordingly, an object of the present invention is to provide an optical laminate having a substrate and a hard coat layer laminated on at least one surface of the substrate, and having excellent bending resistance.

Means for solving the problems

As a result of intensive studies to solve the above problems, the present inventors have found that a reduction in the bending resistance of an optical laminate is easily prevented and a reduction in the optical characteristics is easily suppressed by providing an intermediate layer that is softer and has a uniform thickness than the base material layer and the hard coat layer at the interface between the base material layer and the hard coat layer, and have completed the present invention. That is, the present invention includes the following embodiments.

[1]AN optical laminate comprising at least a base layer comprising a polyamide resin and a hard coat layer laminated on at least one surface of the base layer, wherein AN interlayer having a thickness of 0.3 [ mu ] m or more and a variation in thickness (Japanese: ばらつき with thickness さ) of 25% or less is provided between the base layer and the hard coat layer, and the indentation hardness of the interlayer measured by a nanoindenter on a cross section in the thickness direction of the optical laminate is AN/mm²The press-in hardness of the base material layer is BN/mm²In the case, the ratio of A to B (A/B) is 0.96 or less.

[2]According to [1] above]The optical laminate according to (1), wherein the interlayer has an indentation hardness A of 700N/mm²The following.

[3]According to said [1]Or [ 2]]The optical laminate according to (1), wherein the substrate layer has an indentation hardness B of 350 to 800N/mm²。

[4] The optical laminate according to any one of the above [1] to [3], wherein a pencil hardness of a surface of the hard coat layer laminated on at least one surface of the base material layer is H or more.

[5] The optical laminate according to any one of the above [1] to [4], wherein the hard coat layer contains a cured product of a (meth) acrylate monomer.

[6] The optical laminate according to any one of the above [1] to [5], which is a film for a front panel of a flexible display device.

[7] A flexible display device comprising the optical laminate according to any one of [1] to [6 ].

[8] The flexible display device according to [7], further comprising a touch sensor.

[9] The flexible display device according to the above [7] or [8], further comprising a polarizing plate.

Effects of the invention

According to the present invention, there can be provided an optical laminate having a substrate and a hard coat layer laminated on at least one surface of the substrate, which is excellent in bending resistance and has high optical characteristics even after repeated bending.

Detailed Description

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

< optical laminate >

The optical laminate of the present invention has at least a base layer comprising a polyamide resin and a hard coat layer laminated on at least one surface of the base layer, and has an intermediate layer having a thickness of 0.3 [ mu ] m or more and a thickness variation of 25% or less between the base layer and the hard coat layer. The intermediate layer is a layer formed between the base layer and the hard coat layer by laminating the hard coat layer on the base layer under a specific condition, and is considered to be a layer in which a component constituting the base layer and a component constituting the hard coat layer are in a mixed state. Thus, the intermediate layer is a layer comprising a mixture of at least a part of the components constituting the hard coat layer and at least a part of the components constituting the base layer.

The thickness of the intermediate layer of the optical laminate of the present invention is 0.3 μm or more. When the thickness of the intermediate layer is less than 0.3 μm, the bending resistance of the optical laminate of the present invention cannot be sufficiently improved. From the viewpoint of facilitating improvement of the bending resistance of the optical laminate, the thickness of the intermediate layer is preferably 0.5 μm or more, more preferably 0.7 μm or more, still more preferably 0.9 μm or more, still more preferably 1.1 μm or more, and particularly preferably 1.3 μm or more. In addition, the thickness of the intermediate layer is preferably 10 μm or less, more preferably 7 μm or less, and still more preferably 5 μm or less, from the viewpoint of facilitating improvement of the mechanical strength and optical characteristics of the optical laminate. When the thickness of the intermediate layer is equal to or less than the upper limit, it is considered that the decrease in the optical properties of the optical laminate (for example, local whitening of the optical laminate) which may occur due to repeated bending is easily suppressed. When the thickness of the intermediate layer is equal to or greater than the lower limit described above, it is considered that the bending resistance of the optical laminate is easily improved while the mechanical strength (e.g., pencil hardness) of the optical laminate is maintained.

The fluctuation (uniformity) in the thickness of the intermediate layer of the optical laminate of the present invention is 25% or less. The thickness variation of the intermediate layer may be based on a maximum value (tmax) and a minimum value (tmin) of thicknesses t (μm) of the intermediate layer measured at arbitrary plural points in the cross-sectional direction of the optical laminate, according to the formula: { (tmax-tmin)/(tmax + tmin) } × 100 (%). From the viewpoint of sufficiently improving the bending resistance of the optical laminate of the present invention and easily suppressing the decrease in optical properties of the optical laminate after repeated bending, for example, local whitening of the optical laminate, an increase in haze, and the like, the fluctuation in the thickness of the intermediate layer is preferably 23% or less, more preferably 18% or less, further preferably 15% or less, and still further preferably 12% or less.

As described above, the intermediate layer of the optical laminate of the present invention is considered to be a layer in which a component constituting the base layer and a component constituting the hard coat layer are mixed. Therefore, as a method for measuring the thickness of the intermediate layer, for example, there can be mentioned a method I in which a cross section in the thickness direction of the optical laminate of the present invention is observed with an electron microscope, and the thickness of the intermediate layer is measured by using a mixed portion of the layers located between the intermediate layer and the hard coat layer as the intermediate layer, and a method II in which a portion having a composition between the composition of the hard coat layer and the composition of the base material layer and having a change in composition is determined as the intermediate layer by performing raman spectroscopy, microscopic IR measurement, TOF-SIMS measurement or the like at a plurality of positions in the thickness direction from a certain position on the surface on the hard coat layer side of the optical laminate of the present invention to a certain position in the base material layer, and the thickness of the intermediate layer is measured. From the viewpoint of facilitating accurate measurement of the thickness of the intermediate layer, it is preferable to measure the thickness of the intermediate layer by the method II described above.

For example, when the intermediate layer is identified using a confocal raman microscope, it is preferable to identify the intermediate layer by focusing on raman peaks that are detected in the components constituting the hard coat layer but not in the components constituting the base material layer. From noise, base line based on measurementFrom the viewpoint of reliability of data such as increase and decrease of (a) and (b), the intermediate layer is determined by comparison with a reference peak (for example, peak intensity ratio or peak area ratio). Specifically, the optical laminate of the present invention is focused on the surface on the hard coat layer side by a confocal raman microscope, and then the intensity of a peak unique to a component constituting the hard coat layer is measured at regular intervals in the thickness direction. Then, the peak intensity in the hard coat layer can be set to I_HFrom the position where the peak intensity starts to decrease to reach I_HThe distance in the thickness direction from the position of × 0.1 strength was defined as the thickness of the intermediate layer. Alternatively, instead of the peak intensity, the peak area may be determined, and the thickness of the intermediate layer may be determined using the same reference. As described in examples, a raman spectrum may be obtained at regular intervals in the thickness direction from the hard coat layer side to the substrate side, the peak intensity ratio or the peak area ratio of a peak which appears particularly strongly in the hard coat layer to an arbitrary peak in the spectrum may be obtained, and the thickness of the intermediate layer may be obtained from the relationship between the peak intensity ratio and the peak area ratio from the hard coat layer to the substrate side.

In the optical laminate of the present invention, press-in hardness of the intermediate layer and the base material layer is measured by a nanoindenter on a cross section in the thickness direction of the optical laminate, and the press-in hardness of the intermediate layer is AN/mm²The press-in hardness of the base material layer is BN/mm²In the case, the ratio of A to B (A/B) is 0.96 or less.

In the optical laminate of the present invention, the ratio (a/B) is preferably 0.94 or less, more preferably 0.93 or less, even more preferably 0.92 or less, and particularly preferably 0.91 or less, from the viewpoint of facilitating improvement of the bending resistance of the optical laminate of the present invention. In addition, the ratio (a/B) is preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 0.8 or more, from the viewpoint of facilitating improvement of mechanical strength and optical characteristics of the optical laminate of the present invention.

Here, the indentation hardness of each layer of the optical laminate of the present invention was measured by indentation each layer in a cross section in the thickness direction of the optical laminate with a nanoindenter indentation measurement jig. Specifically, for example, a cross section in the thickness direction of the optical laminate is obtained by the method described in the examples. Thereafter, in this cross section, the press-in hardness can be measured at a plurality of points from a point on the hard coat layer side to a point on the base layer side, and the press-in hardness of each layer can be measured in accordance with the position of the intermediate layer or the like determined by the above-described method.

Here, the case where the thickness of the intermediate layer is 0.3 μm or more, the fluctuation of the thickness is 25% or less, and the ratio (a/B) is 0.96 or less means that the intermediate layer softer than the base material layer is present in a uniform thickness at a predetermined thickness or more in the optical laminate of the present invention. The reason why the optical laminate of the present invention having the above-described characteristics is excellent in the bending resistance and the optical properties after repeated bending is not clear, but it is considered that the optical laminate can be improved in flexibility while maintaining the optical properties, mechanical strength, and the like of the optical laminate by uniformly providing a layer having a specific softness between the hard coat layer and the base material layer in a specific thickness. The press-in hardness of the hard coat layer is higher than those of the base material layer and the intermediate layer.

The method for forming the intermediate layer satisfying the thickness, the thickness fluctuation, and the ratio (a/B) of the intermediate layer as described above is not particularly limited as long as the optical laminate having the above-described characteristics can be obtained, and examples thereof include a method in which a component for providing a hard coat layer is dissolved in a solvent having solubility in a resin constituting a base layer, the obtained hard coat layer-forming composition is applied onto the base layer, and the resultant composition is allowed to stand at a predetermined holding temperature or less for a predetermined holding time. The holding temperature is preferably a temperature lower than 25 ℃, more preferably 20 ℃ or lower, further preferably 15 ℃ or lower, and further preferably 10 ℃ or lower, and the holding time is preferably 20 minutes to 5 hours, more preferably 25 minutes to 3 hours, and further preferably 0.5 hours to 1 hour. After leaving at a predetermined holding temperature or lower for a predetermined holding time, a drying step is performed, and then the hard coat layer-forming composition is dried and cured to form a hard coat layer. Further, by adjusting the thickness of the base material layer, the composition of the hard coat layer, the solvent of the hard coat layer-forming composition, the concentration of the monomer in the hard coat layer-forming composition, and the like, the intermediate layer satisfying the thickness, the fluctuation in thickness, and the ratio (a/B) as described above can be formed.

In the optical laminate of the present invention, the press-fitting hardness a of the intermediate layer is preferably 700N/mm from the viewpoint of more easily improving the bending resistance of the optical laminate²Hereinafter, more preferably 600N/mm²Hereinafter, 570N/mm is more preferable²The following. In addition, from the viewpoint of more easily improving the mechanical strength and optical characteristics of the optical laminate, the press-fitting hardness a is preferably 300N/mm²Above, more preferably 350N/mm²Above, it is more preferably 400N/mm²The above.

The total light transmittance of the optical laminate of the present invention is preferably 80% or more, more preferably 83% or more, further preferably 85% or more, further preferably 88% or more, particularly preferably 89% or more, and particularly preferably 90% or more. When the total light transmittance is not less than the lower limit, the optical laminate is likely to have improved visibility when incorporated into a display device, particularly as a front panel. The optical laminate of the present invention generally exhibits a high total light transmittance, and therefore can suppress the emission intensity of a display element or the like necessary to obtain a certain luminance, for example, as compared with the case of using a film having a low transmittance. Therefore, power consumption can be reduced. For example, when the optical laminate of the present invention is incorporated in a display device, bright display tends to be obtained even when the amount of backlight light is reduced, which contributes to energy saving. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance may be, for example, in accordance with JIS K7361-1: 1997 using a turbidity computer. The total light transmittance may be a total light transmittance in a range of a thickness of an optical laminate described later. In the present specification, the optical laminate having excellent optical properties means high total light transmittance, low haze and/or low YI.

The haze of the optical laminate of the present invention is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2.5% or less, particularly preferably 2% or less, particularly preferably 1% or less, and particularly preferably 0.5% or less. When the haze of the optical laminate is not more than the upper limit, the visibility is easily improved when the optical laminate, particularly a front panel, is incorporated into a display device. The lower limit of the haze is usually 0.01% or more. The turbidity may be measured according to JIS K7136: 2000 was measured using a turbidity computer.

The amount of change in haze before and after repeated bending, i.e., Δ Hz, of the optical laminate of the present invention is preferably less than 0.5%, more preferably 0.4% or less, even more preferably 0.3% or less, and even more preferably 0.1% or less. When the Δ Hz of the optical laminate is not more than the upper limit, the optical laminate is likely to have improved durability and visibility when used as a front panel of a flexible display device, particularly a front panel of a rollable display or a foldable display. Bending can be preferably performed 5 ten thousand times using a U-shaped stretching tester, and Δ Hz can be calculated from the change amount of the turbidity before and after the test.

The optical laminate of the present invention has excellent bending resistance. The number of times of bending resistance in the U-shaped expansion and contraction test of the optical laminate of the present invention is preferably 50000 or more, more preferably 60000 or more, and further preferably 70000 or more. When the number of times of bending resistance is not less than the above lower limit, damage due to bending and the like when used as a front panel material of a flexible display or the like can be easily prevented, and deterioration of optical characteristics due to bending can be easily prevented. The U-shaped expansion test can be measured using a U-shaped expansion tester, and can be measured, for example, by the method described in examples.

The optical laminate of the present invention has a yellowness (YI value) of preferably 3.5 or less, more preferably 3.0 or less, still more preferably 2.5 or less, and particularly preferably 2.0 or less. When the yellowness index of the optical laminate is not more than the above upper limit, the transparency is good, and the optical laminate can contribute to high visibility when used for a front panel of a display device. The yellowness index is usually-5 or more, preferably-2 or more. The yellowness (YI value) can be calculated by measuring the transmittance of light of 300 to 800nm using an ultraviolet-visible near-infrared spectrophotometer to obtain a 3-stimulus value (X, Y, Z) and calculating the YI value based on the formula of 100 × (1.2769X-1.0592Z)/Y.

The thickness of the optical laminate of the present invention is preferably 10 μm or more, more preferably 20 μm or more, further preferably 25 μm or more, particularly preferably 30 μm or more, preferably 200 μm or less, more preferably 120 μm or less, further preferably 110 μm or less, particularly preferably 100 μm or less, and may be a combination of these upper and lower limits. When the thickness of the optical laminate is within the above range, the bending resistance of the optical laminate is more easily improved, and the elastic modulus is more easily improved. The thickness of the optical laminate can be measured using a micrometer, for example, by the method described in examples.

The pencil hardness of the surface on the hard coating layer side of the optical layered body of the present invention is preferably HB or more, more preferably F or more, further preferably H or more, and particularly preferably 2H or more. When the pencil hardness of the surface of the optical layered body on the hard coating layer side is equal to or higher than the above hardness, damage or the like to the surface of the optical layered body can be easily prevented. The pencil hardness may be measured in accordance with JIS K5600-5-4: 1999.

< substrate layer >

The optical laminate of the present invention has a base layer containing a polyamide resin. The base layer may contain 1 kind of polyamide resin, or may contain 2 or more kinds of polyamide resins. The base material layer may be a single layer or a multilayer. The thickness of the base layer is not particularly limited as long as the optical laminate having the above-described characteristics can be obtained, but is preferably 100 μm or less, more preferably 90 μm or less, further preferably 80 μm or less, further preferably 60 μm or less, particularly preferably less than 50 μm, and particularly preferably 49.5 μm or less, from the viewpoint of easily adjusting the thickness, the fluctuation in thickness, and the ratio (a/B) of the intermediate layer to desired ranges and easily improving the flexibility of the optical laminate. When the thickness of the base material layer is within the above range, it is considered that the thickness of the intermediate layer, the fluctuation in thickness, and the ratio (a/B) can be easily adjusted to desired ranges in accordance with the relationship between the evaporation of the residual solvent in the base material layer and the penetration of the composition for forming a hard coat layer into the base material layer. As described above, the optical laminate of the present invention includes at least a base material layer and a hard coat layer laminated on at least one surface of the base material layer, and an intermediate layer is formed between the base material layer and the hard coat layer. Therefore, the thickness of the base material layer of the optical laminate of the present invention is generally considered to be slightly smaller than the thickness of the base material film constituting the base material layer used in the production of the optical laminate of the present invention.

From the viewpoint of facilitating the improvement in pencil hardness and light transmittance, the thickness of the base layer is preferably 150 μm or less, more preferably 110 μm or less, and still more preferably 75 μm or less. From the viewpoint of facilitating formation of an intermediate layer satisfying the thickness, the fluctuation in thickness, and the ratio (a/B) as described above, the thickness is preferably 10 μm or more, more preferably 20 μm or more, further preferably 25 μm or more, and particularly preferably 30 μm or more.

(Polyamide resin)

The base layer contains a polyamide resin. The polyamide resin contained in the base layer is not particularly limited as long as it contains at least a repeating structural unit containing an amide group, and may be at least 1 polymer selected from a polymer containing a repeating structural unit containing an amide group (hereinafter also referred to as a polyamide resin) and a polymer containing both a repeating structural unit containing an amide group and a repeating structural unit containing an imide group (hereinafter also referred to as a polyamideimide resin), for example. The base layer may contain 1 kind of polyamide resin, or may contain 2 or more kinds of polyamide resins. The polyamide resin contained in the base material layer is preferably a polyamideimide resin from the viewpoint of film formability.

In one embodiment of the present invention, the polyamide resin is a polyamide resin having a constituent unit represented by formula (2) or a polyamideimide resin having a constituent unit represented by formula (1) and a constituent unit represented by formula (2):

[ solution 1]

[ in the formula (2), Z and X independently represent an organic group having a valence of 2, and represent a bonding end ]

[ solution 2]

In the formula (1), Y represents an organic group having a valence of 4, X represents an organic group having a valence of 2, and a bonding end. The polyamide resin is preferably a polyamide-imide resin having a constituent unit represented by formula (1) and a constituent unit represented by formula (2) from the viewpoint of film formability, transparency, and bending resistance. The following describes formulae (1) and (2), but the description of formula (2) refers to both polyamide resins and polyamideimide resins (polyamide resins), and the description of formula (1) refers to polyamideimide resins.

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

In the formula (2), Z represents an organic group having a valence of 2, preferably an organic group having a valence of 2 having 4 to 40, which may be substituted by an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, the hydrogen atom of which may be substituted by a halogen atom (preferably a fluorine atom), and more preferably an organic group having a valence of 2 having 4 to 40, which may be substituted by an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, the hydrogen atom of which may be substituted by a halogen atom (preferably a fluorine atom), and has a cyclic structure. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, or the aryl group having 6 to 12 carbon atoms include R in the formula (3) described later^3aAnd R^3bThe same applies to the illustrations of (1). Examples of the cyclic structure include alicyclic ring, aromatic ring, and heterocyclic ringAnd (5) structure. Examples of the organic group of Z include a group having 2 valence of 6 or less and 2 groups substituted with hydrogen atoms out of the bonding ends of the groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29), and examples of the heterocyclic structure of Z include a group having a thiophene ring skeleton. From the viewpoint of easily suppressing the yellowness (lowering the YI value) of the optical layered body, the groups represented by formulae (20) to (29) and the group having a thiophene ring skeleton are preferable, and the groups represented by formulae (26), (28), and (29) are more preferable:

[ solution 3]

[ formula (20) to formula (29),

W¹represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-Ar-、-SO₂-、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂-Ar-、-Ar-C(CH₃)₂-Ar-or-Ar-SO₂Ar-wherein Ar independently represents an arylene group having 6 to 20 carbon atoms (e.g., phenylene group) in which hydrogen atoms may be substituted with fluorine atoms, and Ar represents a bonding terminal]。

As the organic group of Z, more preferred are 2-valent organic groups represented by formula (20 '), formula (21'), formula (22 '), formula (23'), formula (24 '), formula (25'), formula (26 '), formula (27'), formula (28 ') and formula (29'):

[ solution 4]

In [ formulae (20 ') to (29'), W¹And as defined in formulae (20) to (29)]。

The hydrogen atom on the ring in the formulae (20) to (29) and (20 ') to (29') may be substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, the hydrogen atom in these groups may be substituted with a halogen atom (preferably, a fluorine atom).

In the case where the polyamide resin has a constituent unit represented by any one of the above-described formulae (20 ') to (29') in which Z in formula (2) is represented by formula (3 '), particularly in the case where Z in formula (2) is represented by formula (3'), it is preferable that the polyamide resin has a constituent unit derived from a carboxylic acid represented by the following formula (d1) in addition to the constituent unit, from the viewpoint of easily improving the film-forming property of the varnish and easily improving the uniformity of the optical film:

[ solution 5]

[ formula (d1), R²⁴Is R in the following formula (3)^3aA defined group or a hydrogen atom, R²⁵Represents R²⁴or-C (═ O) -, represents a bonding end]。

Specific examples of the structural unit (d1) include R²⁴And R²⁵Constituent units (constituent units derived from dicarboxylic acid compound) R, both of which are hydrogen atoms²⁴Are each a hydrogen atom, R²⁵A constituent unit (a constituent unit derived from a tricarboxylic acid compound) that represents-C (═ O) -, and the like.

The polyamide resin may contain a plurality of types of Z as Z in formula (2), and the plurality of types of Z may be the same as or different from each other. In particular, from the viewpoint of easily improving the bending resistance and impact resistance of the optical laminate of the present invention and easily improving the optical characteristics, Z in formula (2) preferably has at least a constituent unit represented by formula (3), more preferably represented by formula (3'):

[ solution 6]

[ in the formula (3), R^3aAnd R^3bIndependently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R^3aAnd R^3bWherein the hydrogen atoms contained in (A) may be independently substituted by halogen atoms, and W independently represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹)-，R⁹A C1-12 hydrocarbon group which may be substituted with a halogen atom, s is an integer of 0 to 4, t is an integer of 0 to 4, u is an integer of 0 to 4, and represents a bonding end]

[ solution 7]

[ formula (3') wherein R^3a、R^3bS, t, u, W and x are as defined in formula (3)]。

In the present specification, the structural unit in which Z in the formula (2) in the polyamide resin is represented by the formula (3) and the structural unit in which Z in the formula (2) in the polyamide resin is represented by the formula (3) have the same meaning, and Z in the structural unit representing at least a part of the plurality of structural units represented by the formula (2) contained in the polyamide resin is represented by the formula (3). This description is also applicable to other similar descriptions.

In the formulae (3) and (3'), W independently represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹) From the viewpoint of the bending resistance of the optical laminate, the compound preferably represents-O-or-S-, and more preferably represents-O-.

R^3aAnd R^3bIndependently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, and,Isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl and the like. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, pentyloxy, hexyloxy, cyclohexyloxy and the like. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. R is the amount of the functional group represented by the formula R^3aAnd R^3bPreferably independently represent an alkyl group having 1 to 6 carbon atoms, and more preferably represent an alkyl group having 1 to 3 carbon atoms. Here, R^3aAnd R^3bThe hydrogen atoms contained in (a) may be independently substituted with halogen atoms.

R⁹Represents a hydrogen atom, or a C1-12 hydrocarbon group which may be substituted with a halogen atom. Examples of the 1-valent hydrocarbon group having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group, and the like, which may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

T and u in the formulae (3) and (3') are each independently an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0.

S in the formula (3) and the formula (3') is an integer in the range of 0 to 4, and if s is in this range, the impact resistance, elastic modulus and bending resistance of the optical laminate are easily improved. From the viewpoint of more easily improving the impact resistance, elastic modulus, and bending resistance of the optical laminate, s in the formulae (3) and (3') is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, further preferably 0 or 1, and still further preferably 0. The constituent unit in which Z in formula (2) includes a structure represented by formula (3) or formula (3 ') in which s is 0 is, for example, a constituent unit derived from terephthalic acid or isophthalic acid, and the constituent unit is particularly preferably a constituent unit including a structure in which s in formula (3) or formula (3') is 0 and u is 0. The polyamide resin preferably contains a constituent unit derived from terephthalic acid, from the viewpoint of facilitating improvement in impact resistance, elastic modulus, and bending resistance of the optical laminate. The polyamide resin may contain 1 or 2 or more kinds of constituent units represented by formula (3) or formula (3'). From the viewpoint of improving the impact resistance, elastic modulus, and bending resistance of the optical laminate, and reducing the yellowness (YI value), the polyamide resin preferably includes 2 or more structures having different values of s in the formula (3) or the formula (3 ') as Z in the formula (2), and more preferably includes 2 or 3 structures having different values of s in the formula (3) or the formula (3'). In this case, from the viewpoint of easily improving the impact resistance, elastic modulus, and bending resistance of the optical laminate, and from the viewpoint of easily reducing the yellowness (YI value) of the optical laminate, it is more preferable that Z in the polyamide resin as the constituent unit represented by formula (2) contains a structure represented by formula (3) in which s is 0, and that the polyamide resin further contains a constituent unit including a structure represented by formula (3) in which s is 1 in addition to the constituent unit including the structure. It is also preferable that the composition further contains a constituent unit represented by the above formula (d1) in addition to a constituent unit represented by the formula (2) having Z represented by the formula (3) in which s is 0.

In a preferred embodiment of the present invention, the polyamide resin has a structure in which s is 0 and u is 0 as the structure (group having a valence of 2) represented by formula (3) or formula (3'). In a more preferred embodiment of the present invention, the polyamide resin has a structure in which s is 0 and u is 0 and a structure represented by formula (3 ″):

[ solution 8]

In this case, the impact resistance, elastic modulus, and bending resistance of the optical laminate are easily improved, and the yellowness is easily reduced.

When the polyamide resin has a constituent unit represented by formula (3) or formula (3') wherein Z in formula (2) is represented by formula (3), the proportion thereof is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, still more preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, and further preferably 80 mol% or less, assuming that the total of the constituent unit represented by formula (1) and the constituent unit represented by formula (2) of the polyamide resin is 100 mol%. When the proportion of the constituent unit represented by formula (3) or formula (3') in Z in formula (2) is not less than the above-described lower limit, the impact resistance, elastic modulus, and bending resistance of the optical laminate are easily improved. When the proportion of the constituent unit represented by formula (3) or formula (3') in Z in formula (2) is not more than the above upper limit, the increase in viscosity of the resin-containing varnish due to hydrogen bonding between amide bonds derived from formula (3) is easily suppressed, and the processability of the film is easily improved.

In the case where Z in formula (2) in the polyamide resin has a structure represented by formula (3) or formula (3 ') in which s is 1 to 4, the proportion of the constituent unit represented by formula (2) having Z in formula (3) or formula (3') in which s is 1 to 4 is preferably 3 mol% or more, more preferably 5 mol% or more, still more preferably 7 mol% or more, yet more preferably 9 mol% or more, preferably 90 mol% or less, more preferably 70 mol% or less, still more preferably 50 mol% or less, and yet more preferably 30 mol% or less, when the total of the constituent unit represented by formula (1) and the constituent unit represented by formula (2) in the polyamide resin is 100 mol%. When the proportion of the constituent unit represented by formula (2) having Z represented by formula (3) or formula (3') in which s is 1 to 4 is not less than the above lower limit, the impact resistance, elastic modulus, and bending resistance of the optical laminate can be easily improved. When the proportion of the constituent unit represented by formula (2) having Z represented by formula (3) or formula (3 ') in which s is 1 to 4 is not more than the above upper limit, the increase in viscosity of the resin-containing varnish due to hydrogen bonding between amide bonds derived from the structure represented by formula (3) or formula (3') is easily suppressed, and the processability of the film is easily improved. The ratio of the constituent unit represented by formula (1), the ratio of the constituent unit represented by formula (2), and the ratio in formula (2)The ratio of the constituent unit represented by formula (3) or formula (3') Z can be used, for example¹H-NMR measurement or calculation from the charge ratio of the raw materials.

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, and still more preferably 50 mol% or more of Z in the polyamide resin is represented by formula (3) or formula (3') with s being 0 to 4. When the above lower limit or more of Z is represented by formula (3) or formula (3') where s is 0 to 4, the impact resistance, elastic modulus, and bending resistance of the optical laminate are easily improved. In addition, the polyamide resin can be represented by formula (3) or formula (3') wherein s is 0 to 4, wherein 100 mol% or less of Z is represented by. The proportion of the constituent unit represented by formula (2) having Z represented by formula (3) or formula (3') wherein s is 0 to 4 in the resin can be used, for example¹H-NMR measurement or calculation from the charge ratio of the raw materials.

In a preferred embodiment of the present invention, preferably 5 mol% or more, more preferably 8 mol% or more, still more preferably 10 mol% or more, and still more preferably 12 mol% or more of Z in the polyamide resin is represented by formula (3) or formula (3') with s being 1 to 4. When the lower limit or more of Z of the polyamide resin is represented by formula (3) or formula (3') where s is 1 to 4, the impact resistance, elastic modulus, and bending resistance of the optical laminate are easily improved. In addition, preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, and further preferably 30 mol% or less of Z is represented by formula (3) or formula (3') with s of 1 to 4. When Z is represented by formula (3) or formula (3 ') wherein s is 1 to 4 or less than the above upper limit, it is easy to suppress an increase in viscosity of the varnish containing the resin due to hydrogen bonds between amide bonds derived from the structure represented by formula (3) or formula (3') wherein s is 1 to 4, and to improve film processability. The proportion of the constituent unit represented by formula (2) having Z represented by formula (3) or formula (3') wherein s is 1 to 4 in the resin can be used, for example, as¹H-NMR measurement or calculation from the charge ratio of the raw materials.

In the formulas (1) and (2), X independently represents a 2-valent organic group, preferably a 2-valent organic group having 4 to 40 carbon atoms, and more preferably a 2-valent organic group having 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. In the organic group, a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the carbon number of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. In one embodiment of the present invention, the polyamide resin of the present invention may contain a plurality of types of X, and the plurality of types of X may be the same or different. Examples of X include groups represented by formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17), and formula (18); a group in which a hydrogen atom in the group represented by the formulae (10) to (18) is substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

[ solution 9]

[ formula (10) to formula (18),

it represents a bonding terminal of a silicon atom,

V¹、V²and V³Independently of each other, represents a single bond, -O-, -S-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -CO-or-N (Q) -. Wherein Q represents a C1-12 hydrocarbon group having a valence of 1 to 12 which may be substituted with a halogen atom.]

Examples of the C1-12 hydrocarbon group having a valence of 1 include p-R⁹The groups recited hereinbefore.

1 example is V¹And V³Is a single bond, -O-or-S-, and V²is-CH₂-、-C(CH₃)2-、-C(CF₃)₂-or-SO₂-。V¹And V²Bonding position to each ring and V²And V³The bonding position to each ring is preferably, independently of one another, with respect to each ringMeta-or para-position, more preferably para-position.

Among the groups represented by formulae (10) to (18), the groups represented by formulae (13), (14), (15), (16) and (17) are preferable, and the groups represented by formulae (14), (15) and (16) are more preferable, from the viewpoint of facilitating improvement in impact resistance, elastic modulus and bending resistance of the optical laminate. In addition, from the viewpoint of easily improving the impact resistance, elastic modulus and flexibility of the optical laminate, V¹、V²And V³Preferably, independently of one another, a single bond, -O-or-S-, more preferably a single bond or-O-.

In a preferred embodiment of the present invention, the polyamide resin contains a structure represented by formula (4) as X in formula (1) or X in formula (2):

[ solution 10]

[ in the formula (4), R¹⁰～R¹⁷Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R¹⁰～R¹⁷Wherein the hydrogen atoms contained in the above-mentioned groups may be independently substituted by halogen atoms, and represent bonding terminals]。

When at least a part of X in the plurality of constituent units represented by formulas (1) and (2) is represented by formula (4), the impact resistance, elastic modulus, and transparency of the optical laminate can be easily improved.

In the formula (4), R¹⁰、R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R¹⁶And R¹⁷Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, or the aryl group having 6 to 12 carbon atoms include alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, or aryl groups having 6 to 12 carbon atoms in the formula (3). Preferably R¹⁰～R¹⁷Independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R represents¹⁰～R¹⁷The hydrogen atoms contained in (a) may be independently substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. From the viewpoint of impact resistance, elastic modulus, transparency, and bending resistance of the optical laminate, R is more preferable¹⁰～R¹⁷Independently of one another, a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, more preferably R¹⁰、R¹²、R¹³、R¹⁴、R¹⁵And R¹⁶Represents a hydrogen atom, R¹¹And R¹⁷Represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and R is particularly preferred¹¹And R¹⁷Represents a methyl group or a trifluoromethyl group.

In a preferred embodiment of the present invention, the constituent unit represented by formula (4) is a constituent unit represented by formula (4'):

[ solution 11]

That is, at least a part of X in the plurality of constituent units represented by formulas (1) and (2) is a constituent unit represented by formula (4'). In this case, the fluorine element-containing skeleton can easily improve the solubility of the polyamide resin in the solvent, the storage stability of the varnish containing the resin can easily be improved, the viscosity of the varnish can easily be reduced, and the processability of the optical laminate can easily be improved. Further, the optical characteristics of the optical laminate can be easily improved by the fluorine element-containing skeleton.

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 50 mol% or more, and still more preferably 70 mol% or more of X in the polyamide resin is represented by formula (4), particularly formula (4'). In the case where X in the polyamide resin within the above range is represented by formula (4), particularly formula (4'), the solubility of the resin in a solvent can be easily improved by the fluorine element-containing skeleton in the obtained optical film, and the optical film can be easily obtainedThe storage stability of a varnish containing the resin is improved, the viscosity of the varnish is easily reduced, and the processability of an optical film is easily improved. Further, the optical characteristics of the optical laminate can be easily improved by the fluorine element-containing skeleton. Preferably, 100 mol% or less of X in the polyamide resin is represented by formula (4), particularly formula (4'). X in the resin may be represented by formula (4), particularly formula (4'). The proportion of the constituent unit represented by the formula (4) in X in the resin can be used, for example¹H-NMR measurement or calculation from the charge ratio of the raw materials.

In the formula (1), Y represents a 4-valent organic group, preferably a 4-valent organic group having 4 to 40 carbon atoms, and more preferably a 4-valent organic group having 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure, and preferred examples thereof include an aromatic ring from the viewpoint of facilitating improvement of impact resistance and elastic modulus. The organic group is an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the carbon number of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. In one embodiment of the present invention, the polyamide resin is a polyamideimide resin, and the polyamideimide resin may contain a plurality of kinds of Y, and the plurality of kinds of Y may be the same as or different from each other. Examples of Y include groups represented by the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28), and formula (29); a group in which a hydrogen atom in the group represented by the formula (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 4-valent carbon atoms of 6 or less.

[ solution 12]

In the formulae (20) to (29), W represents a bonding end¹Represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-Ar-、-SO₂-、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂-Ar-、-Ar-C(CH₃)₂-Ar-or-Ar-SO₂-Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and specific examples thereof include phenylene groups.

Among the groups represented by formulae (20) to (29), the group represented by formula (26), formula (28), or formula (29) is preferable, and the group represented by formula (26) is more preferable, from the viewpoint of facilitating improvement in impact resistance, elastic modulus, and bending resistance of the optical laminate. In addition, W is a material for easily improving the impact resistance, elastic modulus, and bending resistance of the optical laminate, and easily reducing the yellowness index of the optical laminate¹Preferably independently of one another, a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-, more preferably a single bond, -O-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-is more preferably a single bond, -C (CH)₃)₂-or-C (CF)₃)2-, still more preferably a single bond or-C (CF)₃)₂-。

In a preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of Y in the polyamideimide resin is represented by formula (26). When Y in the above range in the polyamideimide resin is represented by the formula (26), preferably W¹Is a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-formula (26), more preferably W¹Is a single bond or-C (CF)₃)₂The formula (26) above is advantageous in that the impact resistance, elastic modulus and bending resistance of the optical laminate are improved, and the yellowness of the optical laminate is reduced. The proportion of the constituent unit represented by the formula (26) for Y in the polyamideimide resin can be used, for example¹H-NMR measurement or calculation from the charge ratio of the raw materials.

In a preferred embodiment of the present invention, at least a part of Y in the plurality of formulas (1) is represented by formula (5) and/or formula (9):

[ solution 13]

[ in the formula (5), R¹⁸～R²⁵Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R¹⁸～R²⁵Wherein the hydrogen atoms contained in the above-mentioned groups may be independently substituted by halogen atoms, and represent bonding terminals]

[ solution 14]

[ formula (9) wherein R³⁵～R⁴⁰Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R³⁵～R⁴⁰Wherein the hydrogen atoms contained in the above-mentioned groups may be independently substituted by halogen atoms, and represent bonding terminals]。

When at least a part of Y in the plurality of formulae (1) is represented by formulae (5) and/or (9), the impact resistance, elastic modulus, and optical properties of the optical laminate are easily improved.

In the formula (5), R¹⁸、R¹⁹、R²⁰、R²¹、R²²、R²³、R²⁴And R²⁵Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include those exemplified above as the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms in the formula (3). R¹⁸～R²⁵Preferably independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R represents¹⁸～R²⁵The hydrogen atoms contained in (a) may be independently substituted by halogen atoms. Examples of the halogen atom includeFluorine atom, chlorine atom, bromine atom and iodine atom. From the viewpoint of easily improving the impact resistance, elastic modulus and bending resistance of the optical laminate, and from the viewpoint of easily improving the transparency and easily maintaining the transparency, R is more preferable¹⁸～R²⁵Independently of each other, a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and more preferably R¹⁸、R¹⁹、R²⁰、R²³、R²⁴And R²⁵Represents a hydrogen atom, R²¹And R²²Represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and R is particularly preferred²¹And R²²Represents a methyl group or a trifluoromethyl group.

In the formula (9), R is from the viewpoint of easily improving chemical stability, impact resistance, elastic modulus and bending resistance of the optical laminate, and from the viewpoint of easily improving transparency and easily maintaining the transparency³⁵～R⁴⁰Preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a hydrogen atom. Here, R³⁵～R⁴⁰The hydrogen atoms in (b) may be independently substituted by a halogen atom, and examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. As R³⁵～R⁴⁰In the above formula, examples of the alkyl group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include those exemplified above.

In a preferred embodiment of the present invention, formula (5) is represented by formula (5 '), formula (9) is represented by formula (9'):

[ solution 15]

That is, at least a part of the plurality of Y is represented by formula (5 ') and/or formula (9'). In this case, the impact resistance, elastic modulus, and bending resistance of the optical laminate are easily improved. In the case where the formula (5) is represented by the formula (5'), the solubility of the polyimide-based resin in a solvent can be easily improved by the fluorine element-containing skeleton, the storage stability of the varnish containing the resin can be easily improved, the viscosity of the varnish can be easily reduced, and the processability of the optical film can be easily improved. Further, the optical characteristics of the optical laminate can be easily improved by the fluorine element-containing skeleton.

In a preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of Y in the polyamideimide resin is represented by formula (5), particularly formula (5'). When Y in the above range in the polyamideimide resin is represented by formula (5), particularly formula (5'), it is easy to improve the solubility of the polyamide resin in a solvent by the fluorine element-containing skeleton, to reduce the viscosity of a varnish containing the resin, and to improve the processability of an optical film. Further, the optical properties of the optical laminate can be easily improved by the fluorine element-containing skeleton. Preferably, 100 mol% or less of Y in the polyamideimide resin is represented by formula (5), particularly formula (5'). Y in the polyamideimide resin may be formula (5), particularly formula (5'). The proportion of the constituent unit represented by the formula (5) for Y in the polyamideimide resin can be used, for example¹H-NMR measurement or calculation from the charge ratio of the raw materials.

In a preferred embodiment of the present invention, the plurality of constituent units represented by formula (1) preferably further include a constituent unit represented by formula (9) in addition to the constituent unit represented by formula (5). When the optical laminate further includes a constituent unit represented by formula (9) Y, the impact resistance and the elastic modulus of the optical laminate can be further improved.

The polyamideimide resin may contain a constituent unit represented by formula (30) and/or a constituent unit represented by formula (31), or may contain a constituent unit represented by formula (30) and/or a constituent unit represented by formula (31) in addition to the constituent unit represented by formula (1) and, optionally, the constituent unit represented by formula (2).

[ solution 16]

In formula (30), Y¹Represents a 4-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine. As Y¹Examples of the group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29), a group in which a 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 a chain hydrocarbon group having 4 valences and 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of kinds of Y¹Plural kinds of Y¹May be the same as or different from each other.

In formula (31), Y²Represents a 3-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted by a hydrocarbon group or a hydrocarbon group substituted by fluorine. As Y²Examples thereof include a group in which any 1 of the bonding ends of the groups represented by the above formulae (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29) is replaced by a hydrogen atom, and a chain hydrocarbon group having 3 valences and 6 or less carbon atoms. In one embodiment of the present invention, the polyamideimide resin may include a plurality of Y' s²Plural kinds of Y²May be the same or different from each other.

In the formulae (30) and (31), X¹And X²Independently of each other, represents a 2-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted by a hydrocarbon group or a hydrocarbon group substituted with fluorine. As X¹And X²Examples thereof include groups represented by the above-mentioned formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); a group in which a hydrogen atom in the group represented by the formulae (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In one embodiment of the present invention, the polyamide resin contains a constituent unit represented by formula (1) and/or formula (2) and a constituent unit represented by formula (30) and/or formula (31) used in some casesAnd (5) Yuan. In the polyamide resin, the proportion of the constituent unit represented by formula (1) or (2) is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more based on the total constituent units represented by formula (1) or (2) and, if used, formula (30) or (31), from the viewpoint of facilitating improvement in optical properties, impact resistance, elastic modulus, and bending resistance of the optical laminate. In the polyamide resin, the proportion of the constituent units represented by the formulae (1) and (2) is usually 100% or less based on all the constituent units represented by the formulae (1) and (2) and, if necessary, the formulae (30) and/or (31). The above ratio can be used, for example¹H-NMR measurement or calculation from the charge ratio of the raw materials.

In one embodiment of the present invention, the content of the polyamide resin in the base material layer contained in the optical laminate is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, further preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, and more preferably 95 parts by mass or less, with respect to 100 parts by mass of the base material layer constituting the optical laminate. When the content of the polyamide resin is within the above range, the thickness of the intermediate layer of the optical laminate, the variation in thickness, and the ratio (a/B) can be easily adjusted to the above ranges, the bending resistance can be easily improved, and the optical characteristics, the impact resistance, and the elastic modulus of the optical laminate can be easily improved.

From the viewpoint of making it easy to adjust the thickness, the variation in thickness, and the ratio (a/B) of the intermediate layer of the optical laminate to the above-described ranges, and from the viewpoint of making it easy to improve the impact resistance, the elastic modulus, and the bending resistance, the weight average molecular weight of the polyamide resin is preferably 200000 or more, more preferably 230000 or more, further preferably 250000 or more, further preferably 270000 or more, and particularly preferably 280000 or more, in terms of standard polystyrene. The weight average molecular weight of the polyamide resin is preferably 1000000 or less, more preferably 800000 or less, still more preferably 700000 or less, and still more preferably 500000 or less, from the viewpoint of easily adjusting the thickness, the fluctuation in thickness, and the ratio (a/B) of the intermediate layers of the optical laminate to the above-described ranges, and from the viewpoint of easily improving the solubility of the resin in a solvent, and easily improving the stretchability and processability of the optical film. The weight average molecular weight can be determined, for example, by gel permeation chromatography (GPC in some cases) and converted to standard polystyrene, and can be calculated, for example, by the method described in examples.

In a preferred embodiment of the present invention, when the polyamide resin is a polyamideimide resin, the content of the constituent unit represented by the formula (2) in the polyamideimide resin is preferably 0.1 mol or more, more preferably 0.5 mol or more, further preferably 1.0 mol or more, further preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, and further preferably 4.5 mol or less, relative to 1 mol of the constituent unit represented by the formula (1). When the content of the constituent unit represented by formula (2) is not less than the above lower limit, the impact resistance and the elastic modulus of the optical laminate are easily improved. When the content of the constituent unit represented by formula (2) is not more than the above upper limit, the increase in viscosity due to hydrogen bonds between amide bonds in formula (2) is easily suppressed, and the processability of the optical film is easily improved.

In a preferred embodiment of the present invention, the polyamide resin may contain a halogen atom such as a fluorine atom which can be introduced by the above-mentioned fluorine-containing substituent or the like. When the polyamide resin contains a halogen atom, the elastic modulus of the optical laminate is easily increased, and the yellowness (YI value) is easily reduced. When the elastic modulus of the optical laminate is high, the occurrence of scratches, wrinkles, and the like can be easily suppressed. Further, when the yellowness of the optical laminate is low, the transparency and visibility of the film are easily improved. The halogen atom is preferably a fluorine atom. Examples of the fluorine-containing substituent preferably used for the fluorine atom-containing polyamide resin include a fluorine group and a trifluoromethyl group.

The content of the halogen atom in the polyamide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and still more preferably 5 to 30% by mass, based on the mass of the polyamide resin. When the content of the halogen atom is not less than the lower limit, the elastic modulus of the optical laminate is likely to be further increased, the water absorption rate is likely to be reduced, the yellowness is likely to be further reduced, and the transparency and the visibility are likely to be further improved. If the content of the halogen atom is not more than the above upper limit, the synthesis is easy.

The imidization ratio of the polyamide-imide resin is preferably 90% or more, more preferably 93% or more, and further preferably 96% or more. The imidization ratio is preferably not less than the above-described lower limit from the viewpoint of easily improving the optical characteristics of the optical laminate. The upper limit of the imidization ratio is 100% or less. The imidization ratio represents a ratio of a molar amount of imide bonds in the polyamideimide resin to a value 2 times the molar amount of constituent units derived from the tetracarboxylic acid compound. When the polyamideimide resin contains a tricarboxylic acid compound, the molar amount of imide bonds in the polyamideimide resin is expressed as a ratio of a value 2 times the molar amount of constituent units derived from a tetracarboxylic acid compound in the polyamideimide resin to the total molar amount of constituent units derived from a tricarboxylic acid compound. The imidization ratio can be determined by an IR method, an NMR method, or the like.

(method for producing resin)

The polyamide resin can be produced, for example, from a diamine compound and a dicarboxylic acid compound as main raw materials. The polyamideimide resin and the polyamideimide precursor resin can be produced, for example, from tetracarboxylic acid compounds, dicarboxylic acid compounds and diamine compounds as main raw materials. Here, the dicarboxylic acid compound preferably contains at least a compound represented by the formula (3 ").

[ solution 17]

In the formula (3'),

R¹～R⁸independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R¹～R⁸The hydrogen atoms contained in (a) may be independently substituted by halogen atoms,

a represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹)-，

R⁹Represents a hydrogen atom, a C1-12 hydrocarbon group which may be substituted with a halogen atom, m is an integer of 0 to 4,

R³¹and R³²Independently of one another, represents a hydroxyl group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group or a chlorine atom.]

In a preferred embodiment of the present invention, the dicarboxylic acid compound is a compound represented by the formula (3 ") wherein m is 0. More preferably, the dicarboxylic acid compound is a compound represented by the formula (3 ") wherein m is 0, and a compound represented by the formula (3") wherein a is an oxygen atom. In addition, in another preferred embodiment, the dicarboxylic acid compound is R³¹And R³²A compound represented by the formula (3') which is a chlorine atom. In addition, a diisocyanate compound may be used instead of the diamine compound.

Examples of the diamine compound used for producing the resin include aliphatic diamines, aromatic diamines, and mixtures thereof. In the present embodiment, the "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or another substituent in a part of the structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but not necessarily limited thereto. Among them, benzene ring is preferable. The "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituent in a part of the structure.

Examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylenediamine and cyclic aliphatic diamines such as 1, 3-bis (aminomethyl) cyclohexane, 1, 4-bis (aminomethyl) cyclohexane, norbornanediamine and 4, 4' -diaminodicyclohexylmethane. These may be used alone or in combination of 2 or more.

Examples of the aromatic diamine include aromatic diamines having 1 aromatic ring such as p-phenylenediamine, m-phenylenediamine, 2, 4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene, and 2, 6-diaminonaphthalene, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 3' -diaminodiphenylether, 4 '-diaminodiphenylsulfone, 3' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, and the like, Bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 ' -dimethylbenzidine, 2 ' -bis (trifluoromethyl) -4, 4 ' -diaminobiphenyl (sometimes referred to as TFMB), aromatic diamines having 2 or more aromatic rings, such as 4, 4' -bis (4-aminophenoxy) biphenyl, 9-bis (4-aminophenyl) fluorene, 9-bis (4-amino-3-methylphenyl) fluorene, 9-bis (4-amino-3-chlorophenyl) fluorene, and 9, 9-bis (4-amino-3-fluorophenyl) fluorene. These may be used alone or in combination of 2 or more.

Preferred examples of the aromatic diamine include 4, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 3' -diaminodiphenylether, 4 '-diaminodiphenylsulfone, 3' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, TFMB, 4' -bis (4-aminophenoxy) biphenyl, more preferred examples thereof include 4, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 4' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, TFMB, and 4, 4' -bis (4-aminophenoxy) biphenyl. These may be used alone or in combination of 2 or more.

Among the diamine compounds, 1 or more selected from aromatic diamines having a biphenyl structure are preferably used from the viewpoint of high elastic modulus, high transparency, high flexibility, high bending resistance, and low coloring properties of the optical laminate. More preferably, 1 or more selected from 2, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) benzidine, 4 '-bis (4-aminophenoxy) biphenyl, and 4, 4' -diaminodiphenyl ether is used, and further more preferably, TFMB is used.

Examples of the tetracarboxylic acid compound used for producing the resin include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compound may be used alone or in combination of 2 or more. The tetracarboxylic acid compound may be a dianhydride, or may be a tetracarboxylic acid compound analog such as an acid chloride compound.

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride include 4, 4 '-oxydiphthalic anhydride, 3, 3', 4, 4 '-benzophenonetetracarboxylic dianhydride, 2', 3, 3 '-benzophenonetetracarboxylic dianhydride, 3, 3', 4, 4 '-biphenyltetracarboxylic dianhydride (sometimes referred to as BPDA), 2', 3, 3 '-biphenyltetracarboxylic dianhydride, 3, 3', 4, 4 '-diphenylsulfonetetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4, 4' - (hexafluoroisopropylidene) bisphthalic anhydride (sometimes referred to as 6) and the like, 1, 2-bis (2, 3-dicarboxyphenyl) acetic dianhydride, 1-bis (2, 3-dicarboxyphenyl) acetic dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) acetic dianhydride, 1-bis (3, 4-dicarboxyphenyl) acetic dianhydride, bis (3, 4-dicarboxyphenyl) formic dianhydride, bis (2, 3-dicarboxyphenyl) formic dianhydride, 4 '- (p-phenylene) diphthalic anhydride, 4' - (m-phenylene) diphthalic anhydride. Examples of the monocyclic aromatic tetracarboxylic acid dianhydride include 1, 2, 4, 5-benzenetetracarboxylic acid dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic acid dianhydride include 2, 3, 6, 7-naphthalenetetracarboxylic acid dianhydride.

Among them, preferred are 4, 4 ' -oxydiphthalic anhydride, 3, 3 ', 4, 4 ' -benzophenonetetracarboxylic dianhydride, 2 ', 3, 3 ' -benzophenonetetracarboxylic dianhydride, BPDA, 2 ', 3, 3 ' -biphenyltetracarboxylic dianhydride, 3, 3 ', 4, 4 ' -diphenylsulfonetetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 6FDA, 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 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 '- (p-phenylenedioxy) bis phthalic anhydride and 4, 4' - (m-phenylenedioxy) bis phthalic anhydride, more preferably 4, 4 '-oxydiphthalic anhydride, BPDA, 2', 3, 3 '-biphenyltetracarboxylic dianhydride, 6FDA, bis (3, 4-dicarboxyphenyl) methane dianhydride and 4, 4' - (p-phenylenedioxy) bis phthalic anhydride. These may be used alone or in combination of 2 or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic and acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkanetetracarboxylic dianhydrides such as 1, 2, 4, 5-cyclohexanetetracarboxylic dianhydride, 1, 2, 3, 4-cyclobutanetetracarboxylic dianhydride and 1, 2, 3, 4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3, 5, 6-tetracarboxylic dianhydride, dicyclohexyl-3, 3 ', 4, 4' -tetracarboxylic dianhydride and positional isomers thereof. These may be used alone or in combination of 2 or more. Specific examples of the acyclic aliphatic tetracarboxylic acid dianhydride include 1, 2, 3, 4-butanetetracarboxylic acid dianhydride, and 1, 2, 3, 4-pentanedicarboxylic acid dianhydride, and these can be used alone or in combination of 2 or more. In addition, a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

Among the tetracarboxylic dianhydrides, from the viewpoint of high impact resistance, high elastic modulus, high surface hardness, high transparency, high flexibility, high bending resistance, and low coloring properties of the optical laminate, 4, 4 ' -oxydiphthalic anhydride, 3, 3 ', 4, 4 ' -benzophenone tetracarboxylic dianhydride, BPDA, 2 ', 3, 3 ' -biphenyl tetracarboxylic dianhydride, 3, 3 ', 4, 4 ' -diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 6FDA and a mixture thereof are more preferable, BPDA and 6FDA and a mixture thereof are further preferable, and 6FDA and BPDA are particularly preferable.

As the dicarboxylic acid compound used for producing the resin, terephthalic acid, isophthalic acid, 4' -oxybis benzoic acid, or an acid chloride compound thereof is preferably used. Other dicarboxylic acid compounds may be used in addition to terephthalic acid, isophthalic acid, 4' -oxybis-benzoic acid, or their acid chloride compounds. Examples of the other dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their analogous acid chloride compounds and acid anhydrides, and 2 or more of them may be used in combination. Specific examples thereof include isophthalic acid; naphthalenedicarboxylic acid; 4, 4' -biphenyldicarboxylic acid; 3, 3' -biphenyldicarboxylic acid; dicarboxylic acid compound of chain hydrocarbon with carbon number of 8 or less and 2 benzoic acids formed by single bond, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene-linked compounds and their acid chloride compounds. Specific examples thereof include 4, 4' -oxybis (benzoyl chloride) (sometimes referred to as OBBC), terephthaloyl chloride (sometimes referred to as TPC) and isophthaloyl chloride, and OBBC and TPC are more preferably used in combination.

The polyimide resin may be prepared by reacting the tetracarboxylic acid compound with tetracarboxylic acid and tricarboxylic acid, and anhydrides and derivatives thereof, in addition to the tetracarboxylic acid compound, in a range that does not impair various physical properties of the optical laminate.

Examples of the tetracarboxylic acid include water adducts of acid anhydrides of the above tetracarboxylic acid compounds.

Examples of the tricarboxylic acid compound include an aromatic tricarboxylic acid, an aliphatic tricarboxylic acid, and an acid chloride compound and an acid anhydride similar thereto, and 2 or more species may be used in combination. Specific examples thereof include acid anhydrides of 1, 2, 4-benzenetricarboxylic acid; anhydrides of 1, 3, 5-benzenetricarboxylic acid; 2, 3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; phthalic anhydride with benzoic acid by single bond, -O-, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene linkage.

In the production of the resin, the amount of the diamine compound, the tetracarboxylic acid compound and/or the dicarboxylic acid compound to be used may be appropriately selected depending on the ratio of each constituent unit of the desired polyimide-based resin.

In the production of the resin, the reaction temperature of the diamine compound, the tetracarboxylic acid compound and the dicarboxylic acid compound is not particularly limited, but is, for example, 5 to 350 ℃, preferably 20 to 200 ℃, and more preferably 25 to 100 ℃. The reaction time is also not particularly limited, but is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out in an inert atmosphere or under reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or in an inert gas atmosphere while stirring. In addition, the reaction is preferably carried out in a solvent inactive to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include alcohol solvents such as water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ -butyrolactone (sometimes referred to as GBL), γ -valerolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl isobutyl ketone; 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; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as N, N-dimethylacetamide (sometimes referred to as DMAc) and N, N-dimethylformamide (sometimes referred to as DMF); sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide (sometimes referred to as DMSO), and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof, and the like. Among them, an amide solvent can be suitably used from the viewpoint of solubility.

In the imidization step in the production of the polyimide-based resin, imidization may be performed in the presence of an imidization catalyst. Examples of the imidization catalyst include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; alicyclic amines (monocyclic amines) such as N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepine; alicyclic amines (polycyclic type) such as azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane and azabicyclo [3.2.2] nonane; and aromatic amines such as pyridine, 2-methylpyridine (2-picoline), 3-methylpyridine (3-picoline), 4-methylpyridine (4-picoline), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-dimethylpyridine, 2, 4, 6-trimethylpyridine, 3, 4-cyclopentenopyridine, 5, 6, 7, 8-tetrahydroisoquinoline, and isoquinoline. In addition, from the viewpoint of facilitating the imidization reaction, it is preferable to use an acid anhydride together with an imidization catalyst. The acid anhydride may be a conventional acid anhydride used in the imidization reaction, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic acid anhydrides such as phthalic acid.

The polyamide resin can be isolated by separation and purification by a conventional method, for example, a separation method such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a separation method combining these methods, and in a preferred embodiment, isolation can be performed by adding a large amount of an alcohol such as methanol to a reaction solution containing a transparent polyamide resin to precipitate the resin, followed by concentration, filtration, drying, or the like.

The substrate layer of the optical laminate of the present invention may further contain at least 1 type of filler in addition to the polyamide resin. Examples of the filler include organic particles and inorganic particles, and inorganic particles are preferably used. The inorganic particles include silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, Indium Tin Oxide (ITO), metal oxide particles such as antimony oxide and cerium oxide, and metal fluoride particles such as magnesium fluoride and sodium fluoride, among which silica particles, zirconia particles and alumina particles are preferable, and silica particles are more preferable, from the viewpoint of facilitating improvement of the elastic modulus and/or tear strength of the optical layered body and the improvement of the impact resistance. These fillers may be used alone or in combination of 2 or more.

The average primary particle diameter of the filler, preferably the silica particles, is usually 1nm or more, preferably 5nm or more, more preferably 10nm or more, further preferably 15nm or more, particularly preferably 20nm or more, preferably 100nm or less, more preferably 90nm or less, further preferably 80nm or less, further preferably 70nm or less, particularly preferably 60nm or less, particularly preferably 50nm or less, and particularly preferably 40nm or less. When the average primary particle diameter of the filler, preferably silica particles, is within the above range, aggregation of the filler, preferably silica particles, is easily suppressed, and the optical characteristics of the optical laminate obtained are easily improved. The average primary particle diameter of the filler can be determined by the BET method. The average primary particle diameter may be measured by image analysis using a transmission electron microscope or a scanning electron microscope.

In the optical laminate of the present invention, when the base material layer contains a filler, preferably silica particles, the content of the filler is usually 0.1 part by mass or more, preferably 1 part by mass or more, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, further preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 60 parts by mass or less with respect to 100 parts by mass of the film constituting the base material layer. When the content of the filler is not less than the above lower limit, the elastic modulus of the optical laminate to be obtained can be easily increased. When the content of the filler is not more than the above upper limit, the optical properties of the optical laminate are easily improved.

The optical laminate of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber may be contained in the base material layer, may be contained in the hard coat layer, and may be contained in another layer of the optical laminate of the present invention. The ultraviolet absorber can be appropriately selected from those generally used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400nm or less. Examples of the ultraviolet absorber include at least 1 compound selected from benzophenone-based compounds, salicylate-based compounds, benzotriazole-based compounds, and triazine-based compounds. The ultraviolet absorbers may be used alone or in combination of two or more. Since the optical laminate contains the ultraviolet absorber, deterioration of the resin can be suppressed, and thus, the visibility can be improved when the optical laminate obtained is applied to an image display device or the like. In the present specification, the term "related compound" refers to a derivative of a compound to which the "related compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a matrix skeleton and a substituent bonded to benzophenone.

When the optical laminate contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 3 parts by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 6 parts by mass or less, per 100 parts by mass of the optical laminate. The appropriate content varies depending on the ultraviolet absorber used, but when the content of the ultraviolet absorber is adjusted so that the 400nm light transmittance is about 20 to 60%, the light resistance of the optical laminate is improved and the transparency is easily improved.

The optical laminate of the present invention may further contain other additives besides the filler and the ultraviolet absorber. Examples of the other additives include an antioxidant, a release agent, a stabilizer, a bluing agent, a flame retardant, a pH adjuster, a silica dispersant, a lubricant, a thickener, and a leveling agent. When other additives are contained, the content thereof may be preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and still more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the optical laminate.

From the viewpoint of easily preventing wrinkles, scratches, and the like of the optical laminate, the elastic modulus of the base layer constituting the optical laminate of the present invention is preferably 4.5GPa or more, more preferably 4.8GPa or more, further preferably 5.0GPa or more, further preferably 5.1GPa or more, and particularly preferably 5.2GPa or more. The upper limit of the elastic modulus is not particularly limited, but is usually 100GPa or less. The elastic modulus can be measured using a tensile tester under conditions such as a chuck-to-chuck distance of 50mm and a tensile speed of 10 mm/min.

< hard coating >

The hard coat layer is a layer having a function of protecting the optical laminate by imparting scratch resistance, chemical resistance, and the like to the surface of the optical laminate. As the hard coat layer, a known hard coat layer can be suitably used, and examples thereof include a known hard coat layer of acrylic, epoxy, urethane, benzyl chloride, vinyl, or the like. Among them, acrylic, urethane, epoxy, and a combination thereof hard coat layers are preferable from the viewpoint of suppressing a decrease in visibility in the wide angle direction of the optical laminate and improving the bending resistance. The pencil hardness of the hard coat layer is measured in a state of being laminated on the optical film in the optical laminate of the present invention, and is preferably HB or more, more preferably F or more, further preferably H or more, and particularly preferably 2H or more. The pencil hardness may be measured in accordance with JIS K5600-5-4: 1999.

The hard coat layer may be, for example, a cured product of a composition containing an active energy ray-curable compound. The active energy ray-curable compound is a compound having a property of being cured by irradiation with an active energy ray such as an electron beam or ultraviolet ray. Examples of such an active energy ray-curable compound include an electron beam-curable compound that is cured by irradiation with an electron beam, and an ultraviolet-curable compound that is cured by irradiation with ultraviolet light. These compounds are the same compounds as the main component of the hard coat agent used for forming a normal hard coat layer, and include, for example, at least 1 compound of a radical polymerizable compound and a cation polymerizable compound.

The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound may be any functional group that can cause a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond, specifically, a vinyl group and a (meth) acryloyl group. When the radical polymerizable compound has 2 or more radical polymerizable groups, the radical polymerizable groups may be the same or different from each other. The number of radical polymerizable groups contained in 1 molecule of the radical polymerizable compound is preferably 2 or more in order to increase the hardness of the hard coat layer. The radical polymerizable compound is preferably a compound having a (meth) acryloyl group in view of high reactivity, and specifically includes a compound called a multifunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in 1 molecule, an oligomer called an epoxy (meth) acrylate, a urethane (meth) acrylate, or a polyester (meth) acrylate having several (meth) acryloyl groups in a molecule and having a molecular weight of several hundred to several thousand, and preferably 1 or more selected from the group consisting of an epoxy (meth) acrylate, a urethane (meth) acrylate, and a polyester (meth) acrylate. Among them, a (meth) acrylic resin is preferable, and a resin containing a polyfunctional (meth) acrylate compound as a main component is more preferable. In the present specification, the term (meth) acrylic means acrylic and/or methacrylic, and the term (meth) acrylate means acrylate and/or methacrylate.

The polyfunctional (meth) acrylate compound is a compound having at least 2 acryloyloxy groups and/or methacryloyloxy groups in the molecule, and specific examples thereof include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaglycerol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, and mixtures thereof, Dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tris ((meth) acryloyloxyethyl) isocyanurate, phosphazene acrylate compound or phosphazene methacrylate compound in which a (meth) acryloyloxy group is introduced into the phosphazene ring of the phosphazene compound, urethane (meth) acrylate compounds obtained by the reaction of a polyisocyanate having at least 2 isocyanate groups in the molecule with a polyol compound having at least 1 (meth) acryloyloxy group and a hydroxyl group, polyester (meth) acrylate compounds obtained by the reaction of a halogenated carboxylic acid compound having at least 2 carboxylic acid groups in the molecule with a polyol compound having at least 1 (meth) acryloyloxy group and a hydroxyl group, and oligomers such as dimers, trimers, and the like of the above compounds.

These compounds may be used alone or in combination of 2 or more. In addition to the above-mentioned polyfunctional (meth) acrylate compound, at least 1 type of monofunctional (meth) acrylate may be used. Examples of the monofunctional (meth) acrylate include hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and glycidyl (meth) acrylate. These compounds may be used alone or in combination of 2 or more. The content of the monofunctional (meth) acrylate compound is preferably 10 mass% or less with respect to the solid content of the compound contained in the functional layer forming composition (hard coat coating material). In the present specification, the solid component refers to all components excluding the solvent contained in the curable composition.

In the hard coat layer, for example, a polymerizable oligomer may be added for the purpose of adjusting hardness. Examples of such oligomers include macromonomers such as terminal (meth) acrylate polymethyl methacrylate, terminal styrene-based poly (meth) acrylate, terminal (meth) acrylate polystyrene, terminal (meth) acrylate polyethylene glycol, terminal (meth) acrylate acrylonitrile-styrene copolymer, and terminal (meth) acrylate styrene-methyl (meth) acrylate copolymer. When the polymerizable oligomer is added, the content thereof is preferably 5 to 50% by mass relative to the solid content of the hard coat layer-forming composition.

The active energy ray-curable compound may be used in the form of a solution mixed with a solvent. The active energy ray-curable compound and the solution thereof may be those commercially available as a hard coating agent. Specific examples of commercially available Hard coating agents include "NK Hard M101" (manufactured by Ningzhou chemical Co., Ltd., urethane acrylate compound), "NK Ester A-TMM-3L" (manufactured by Ningzhou chemical Co., Ltd., tetramethylolmethane triacrylate), "NK Ester A-9530" (manufactured by Ningzhou chemical Co., Ltd., dipentaerythritol hexaacrylate), "KAYARAD (registered trademark) DPCA series" (manufactured by Nippon chemical Co., Ltd., derivative of dipentaerythritol hexaacrylate compound), "ARONIX (registered trademark) M-8560" (manufactured by Toyata synthetic Co., Ltd., polyester acrylate compound), "New Fronti (Japanese: ニューフロンティア) (registered trademark) TEICA" (manufactured by first Industrial pharmaceutical Co., Ltd., tris (acryloyloxyethyl) isocyanurate), "PPZ" (manufactured by Co., Ltd., Japan, and, Phosphazene methacrylate compounds), and the like.

The cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetane group, or a vinyl ether group. The number of the cationically polymerizable groups contained in 1 molecule of the cationically polymerizable compound is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer. Among the above cationically polymerizable compounds, preferred are compounds having at least 1 kind of an epoxy group and an oxetanyl group as a cationically polymerizable group. From the viewpoint of reducing shrinkage accompanying the polymerization reaction, a cyclic ether group such as an epoxy group or an oxetane group is preferable. Further, the compound having an epoxy group in a cyclic ether group has advantages that it is easy to obtain a compound having various structures, does not adversely affect the durability of the obtained hard coat layer, and is easy to control the compatibility with a radical polymerizable compound. The oxetanyl group in the cyclic ether group is easily higher in polymerization degree than the epoxy group, and has advantages that the network formation rate of the cationic polymerizable compound in the obtained hard coat layer is increased, and an independent network is formed in a region where the cationic polymerizable compound is mixed with the radical polymerizable compound without leaving an unreacted monomer in the film.

Examples of the cationically polymerizable compound having an epoxy group include polyglycidyl ethers of polyhydric alcohols having an alicyclic ring, and alicyclic epoxy resins obtained by epoxidizing compounds having a cyclohexene ring or a cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or a peracid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, polyglycidyl esters of aliphatic long-chain polybasic acids, and homopolymers and copolymers of glycidyl (meth) acrylate; glycidyl ethers produced by the reaction of epichlorohydrin with bisphenols such as bisphenol a, bisphenol F, and hydrogenated bisphenol a, or derivatives such as alkylene oxide adducts and caprolactone adducts thereof, and glycidyl ether type epoxy resins derived from bisphenols, and the like.

The thickness of the hard coat layer is not particularly limited, and may be appropriately set, for example, 2 to 100 μm, but is preferably 30 μm or less, more preferably 20 μm or less, further preferably 15 μm or less, further preferably 10 μm, and particularly preferably 8 μm or less, from the viewpoint of easily improving the bending resistance and the surface hardness of the optical laminate.

As a method of laminating a hard coat layer on at least one surface of an optical film, for example, a composition for forming a hard coat layer containing an active energy ray-curable compound such as an active energy ray-curable resin may be applied to the surface of an optical film as a substrate, and irradiated with an active energy ray. Such a composition can be obtained by mixing an active energy ray-curable compound with additives and the like as needed. A cured product of the composition for forming a hard coat layer constitutes a hard coat layer.

The composition for forming a hard coat layer preferably contains a solvent, and in the composition for forming a hard coat layer, the active energy ray-curable compound is preferably diluted with the solvent. In this case, the composition may be produced by mixing the active energy ray-curable compound with various additives for imparting surface smoothness or the like, for example, silicone oil or the like, and then diluting the obtained mixture with a solvent, or may be produced by diluting the active energy ray-curable compound with a solvent and then mixing the additives, or may be produced by mixing the active energy ray-curable compound with an additive diluted with a solvent in advance, or may be produced by mixing the active energy ray-curable compound diluted with a solvent in advance with an additive diluted with a solvent in advance. The mixed composition may be further stirred.

From the viewpoint of ease of application, it is also preferable that the composition for forming a hard coat layer contains an appropriate solvent. Examples of the solvent include aliphatic hydrocarbons such as hexane and octane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as dichloromethane and dichloroethane, alcohols such as ethanol, 1-propanol, isopropanol, 1-butanol and cyclohexanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 2-heptanone and 3-heptanone, esters such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl glycol acetate and propylene glycol monomethyl ether acetate, ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether and polyethylene glycol monomethyl ether, cellosolve, sulfoxides such as DMSO, amides such as dimethylformamide and dimethylacetamide, and these can be appropriately selected and used. These organic solvents may be used in combination as needed. The solvent contained in the composition for forming a hard coat layer is preferably a solvent having an appropriate solubility in the polyimide resin, from the viewpoint of facilitating formation of an intermediate layer satisfying the thickness, the thickness variation, and the ratio (a/B) described above. From the above-mentioned viewpoint, the solvent preferably includes methyl ethyl ketone, methyl isobutyl ketone, and propylene glycol monomethyl ether, and more preferably methyl ethyl ketone and propylene glycol monomethyl ether. In addition, the boiling point of the solvent is preferably in the range of 70 to 200 ℃ from the viewpoint of facilitating evaporation of the organic solvent finally after application of the composition for forming a hard coat layer. The kind and amount of the solvent may be appropriately selected depending on the kind and amount of the active energy ray-curable compound to be used, the material and shape of the substrate (optical film), the coating method, the thickness of the target hard coat layer, and the like.

From the viewpoint of facilitating formation of an intermediate layer satisfying the thickness, thickness variation, and ratio (a/B) as described above, it is preferable that the intermediate layer is left at or below a predetermined holding temperature for a predetermined holding time after application of the hard coat layer-forming composition. The holding temperature is preferably a temperature lower than 25 ℃, more preferably 20 ℃ or lower, further preferably 15 ℃ or lower, and further preferably 10 ℃ or lower, and the holding time is preferably 20 minutes to 5 hours, more preferably 25 minutes to 3 hours, and further preferably 0.5 hours to 1 hour. It is considered that by bringing the composition for forming a hard coat layer into contact with the substrate at the above-mentioned holding temperature and holding time, volatilization of the solvent contained in the composition for forming a hard coat layer can be suppressed, and the solvent or monomer in the composition for forming a hard coat layer can be gradually permeated into the surface of the substrate, whereby the intermediate layer having a thickness and uniformity of thickness equal to or greater than the predetermined value can be easily formed. In addition, it is preferable to provide a drying step at a predetermined drying temperature and for a predetermined drying time from the viewpoint of facilitating formation of an intermediate layer satisfying the above-described thickness and thickness fluctuation after holding under the above-described conditions. When the boiling point of the solvent contained in the composition for forming a hard coat layer is X ℃, the drying temperature is preferably X-55 ℃ or higher, more preferably X-50 ℃ or higher, further preferably X-45 ℃ or higher, preferably X +20 ℃ or lower, more preferably X ℃ or lower, and further preferably X-20 ℃ or lower. When the composition for forming a hard coat layer contains 2 or more solvents, it is preferable to set the boiling point of the mixed solvent contained in the composition to X ℃ and adjust the drying temperature to the above range. The drying time is preferably 1 minute to 30 minutes, more preferably 2 minutes to 20 minutes, and further preferably 5 minutes to 12 minutes. It is considered that by setting the drying step at the above-mentioned drying temperature and drying time, uniform diffusion of the solvent and the monomer, particularly the monomer, in the composition for forming a hard coat layer is easily caused, and an intermediate layer having a thickness within a predetermined range and having small variations in thickness is easily formed.

The solid content of the composition for forming a hard coat layer is preferably 5 to 60% by mass, more preferably 10 to 55% by mass, even more preferably 20 to 50% by mass, and particularly preferably 25 to 50% by mass. When the solid content is in the above range, the film thickness to be applied is not excessively large, and the value of formula 1 is not excessively large, so that the visibility tends to be good, and the smoothness of the surface of the hard coat layer tends to be good.

The composition for forming a hard coat layer may contain a polymerization initiator. When ultraviolet rays or visible rays are used as the active energy rays, a photopolymerization initiator is generally used as the polymerization initiator.

Examples of the photopolymerization initiator include acetophenone, acetophenone benzil ketal, anthraquinone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, carbazole, xanthone, 4-chlorobenzophenone, 4 '-diaminobenzophenone, 1-dimethoxydeoxybenzoin, 3' -dimethyl-4-methoxybenzophenone, thioxanthone, 2-dimethoxy-2-phenylacetophenone, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropan-1-one, and the like, Triphenylamine, 2, 4, 6-trimethylbenzoyldiphenylphosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, fluorenone, fluorene, benzaldehyde, benzoin ethyl ether, benzoin propyl ether (Japanese: ベンゾイソプロピルエーテル), benzophenone, michigan ketone, 3-methylacetophenone, 3 ', 4, 4 ' -tetra-tert-butylperoxycarbonylbenzophenone (BTTB), 2- (dimethylamino) -1- [4- (morpholinyl) phenyl ] -2-phenylmethyl) -1-butanone, 4-benzoyl-4 ' -methylbenzene sulfide, benzil and the like. In addition, the photopolymerization initiator may be used in combination with a pigment sensitizer. Examples of the dye sensitizer include xanthene, thioxanthene, coumarin, and coumarin ketone. Examples of the combination of the photopolymerization initiator and the dye sensitizer include a combination of BTTB and xanthene, a combination of BTTB and thioxanthene, a combination of BTTB and coumarin, and a combination of BTTB and coumarin.

When a photopolymerization initiator is used, the amount thereof to be used is preferably 0.1 part by mass or more per 100 parts by mass of the active energy ray-curable compound. When the amount of the curing agent is within the above range, a sufficient curing rate tends to be easily obtained. The amount of the photopolymerization initiator used is preferably 10 parts by mass or less per 100 parts by mass of the active energy ray-curable compound.

Further, examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical polymerization initiator, and a cationic polymerization initiator. These polymerization initiators are substances which decompose by at least one of irradiation with active energy rays and heating, generate radicals or cations, and advance radical polymerization and cationic polymerization.

The radical polymerization initiator may be any one that can release a substance that initiates radical polymerization by at least one of irradiation with active energy rays and heating. Examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, and azo compounds such as azobisbutyronitrile.

The active energy ray radical polymerization initiator includes a Type1 radical polymerization initiator which generates radicals by decomposition of molecules and a Type2 radical polymerization initiator which generates radicals by hydrogen abstraction reaction in the presence of a tertiary amine, and they may be used alone or in combination.

The cationic polymerization initiator may be any initiator that can release a substance that initiates cationic polymerization by at least one of irradiation with active energy rays and heating. As the cationic polymerization initiator, aromatic iodonium salts, aromatic sulfonium salts, cyclopentadienyl iron (II) complexes, and the like can be used. They are capable of initiating cationic polymerization by some or any of irradiation with active energy rays or heating depending on the difference in structure.

The radical polymerization initiator and the cationic polymerization initiator may be contained in an amount of preferably 0.1 to 10% by mass based on 100% by mass of the entire hard coat layer-forming composition. When the content of the polymerization initiator is in the above range, curing can be sufficiently advanced, mechanical properties and adhesion of a finally obtained coating film can be set to a favorable range, and poor adhesion, a crack phenomenon, and a curl phenomenon due to curing shrinkage tend to be less likely to occur.

The composition for forming a hard coat layer may contain an antistatic agent in addition to the active energy ray-curable compound. By adding an antistatic agent to the composition, an antistatic function can be imparted to the hard coat layer. Examples of the antistatic agent include a surfactant, a conductive polymer, conductive particles, an alkali metal salt and/or an organic cation-anion salt. These antistatic agents may be used in 1 kind or in combination of 2 or more kinds.

Examples of the surfactant include hydrocarbon surfactants, fluorine surfactants, and silicone surfactants.

Examples of the conductive polymer include polyaniline, polypyrrole, polyacetylene, and polythiophene.

Examples of the conductive particles include particles of indium-tin composite oxide (ITO), antimony-doped tin oxide, and the like.

Examples of the alkali metal salt include organic and inorganic salts of an alkali metal. Examples of the alkali metal ion constituting the cation portion of the alkali metal salt include lithium, sodium, and potassium ions. Among these alkali metal ions, lithium ions are preferable.

The anion portion of the alkali metal salt may be composed of an organic substance or an inorganic substance. As the anion portion constituting the organic salt, for example, CH can be used₃COO^-、CF₃COO^-、CH₃SO₃ ^-、CF₃SO₃ ^-、(CF₃SO₂)₃C^-、C₄F₉SO₃ ^-、C₃F₇COO^-、(CF₃SO₂)(CF₃CO)N^-、(FSO₂)₂N^-、^-O₃S(CF₂)₃SO₃ ^-、CO₃ ^2-And anion units represented by formulae (A1) to (A4).

(A1)：(C_nF_2n+1SO₂)₂N^-(n represents an integer of 1 to 10),

(A2)：CF₂(C_mF_2mSO₂)₂N^-(m represents an integer of 1 to 10),

(A3)：^-O₃S(CF₂)_lSO₃ ^-(l represents an integer of 1 to 10),

(A4)：(C_pF_2p+1SO₂)N^-(C_qF_2q+1SO₂) (wherein p and q independently represent an integer of 1 to 10.)

Among them, it is preferable to use an anion portion containing a fluorine atom, from the viewpoint that an ionic compound having good ion dissociation property can be obtained. As the anion portion constituting the inorganic salt, Cl may be used^-、Br^-、I^-、AlCl₄ ^-、Al₂Cl₇ ^-、BF₄ ^-、PF₆ ^-、ClO₄ ^-、NO₃ ^-、AsF₆ ^-、SbF₆ ^-、NbF₆ ^-、TaF₆ ^-、(CN)₂N^-And the like. As the anion portion, (FSO) is preferable₂)₂N^-、(CF₃O₂)₂N^-、(C₂F₅SO₂)₂N^-More preferably (FSO)₂)₂N^-、(CF₃SO₂)₂N^-。

The organic cation-anion salt is an organic salt which is formed of a cation portion and an anion portion, and the cation portion is organic. The anion portion may be an organic or inorganic substance. The "organic cation-anion salt" may be a substance called an ionic liquid or an ionic solid.

Specific examples of the cation component include a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline skeleton, a cation having a pyrrole skeleton, an imidazolium cation, a tetrahydropyrimidinium cation, a dihydropyrimidinium cation, a pyrazolium cation, a pyrazolinium cation, a tetraalkylammonium cation, a trialkylsulfonium cation, and a tetraalkylphosphonium cation. Examples of the anionic component include the same anionic portion as that of the alkali metal salt. Among these, it is preferable to use an anionic component containing a fluorine atom, from the viewpoint that an ionic compound having good ion dissociation property can be obtained.

The composition for forming a hard coat layer may contain fine particles of an organic compound containing a bromine atom, a fluorine atom, a sulfur atom, a benzene ring, or the like, for example, an inorganic oxide such as tin oxide, antimony oxide, titanium oxide, zirconium oxide, zinc oxide, silicon oxide, or the like. In this case, the refractive index of the obtained hard coat layer can be adjusted, and optical functions such as a low reflection function and an antireflection function can be provided to the hard coat layer.

The layer containing the active energy ray-curable compound can be formed by applying the composition for forming a hard coat layer containing the active energy ray-curable compound onto an optical film and then drying the composition. The coating can be performed by a general method such as a microgravure coating method, a roll coating method, a dip coating method, a spin coating method, a die coating method, a casting transfer method, a flow coating method, and a spray coating method. From the viewpoint of facilitating improvement of optical characteristics of the optical laminate, it is preferable to laminate the composition for forming a hard coat layer by a microgravure coating method or a die coating method.

Thereafter, the active energy ray-curable compound applied to the surface of the optical film is cured by irradiation with an active energy ray, thereby obtaining a target hard coat layer. Examples of the active energy ray include an electron beam, ultraviolet rays, and visible rays, and can be appropriately selected according to the type of the active energy ray-curable compound used. The active energy ray may be irradiated in the same manner as in the formation of a general hard coat layer. The intensity, irradiation time, and the like of the active energy ray to be irradiated can be appropriately selected depending on the kind of the curable compound to be used, the thickness of the layer containing the curable compound, and the like. The active energy ray may be irradiated in an inert gas atmosphere. When the active energy ray is irradiated in a nitrogen atmosphere, for example, the active energy ray may be irradiated in an inert gas in a sealed container, and nitrogen, argon, or the like may be used as the inert gas.

It is also useful to further laminate another layer described later on the surface of the hard coat layer. The other layers in this case may be laminated in a single layer on the surface of the hard coat layer, or in multiple layers.

< other layer >

The optical laminate of the present invention may further include other layers such as an antireflection layer, a low reflection layer, an antistatic layer, an antiglare layer, an ultraviolet absorbing layer, an adhesive layer, and a color tone adjusting layer, in addition to the base layer and the hard coat layer. The hard coat layer contained in the optical laminate of the present invention may have a hard coat function and an antireflection function.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays, and is formed of a main material selected from ultraviolet curing type transparent resins, electron beam curing type transparent resins, and thermosetting type transparent resins, and an ultraviolet absorber dispersed in the main material, for example.

The pressure-sensitive adhesive layer is a layer having a pressure-sensitive adhesive function, and has a function of bonding the optical laminate to another member. As a material for forming the adhesive layer, a generally known material can be used. For example, a thermosetting resin composition or a photocurable resin composition may be used. In this case, the resin composition can be polymerized and cured by supplying energy after the polymerization.

The Pressure-Sensitive Adhesive layer may be a layer called a Pressure-Sensitive Adhesive (PSA) that is pressed and attached to an object. The pressure-sensitive adhesive may be a capsule adhesive as "a substance having adhesiveness at normal temperature and adhering to an adherend under light pressure" (JIS K6800), or as "an adhesive capable of holding a specific component in a protective film (microcapsule) and maintaining stability before the film is broken by an appropriate method (pressure, heat, etc.)" (JIS K6800).

The color tone adjusting layer is a layer having a function of adjusting color tones, and is a layer capable of adjusting the color tone of the optical layered body to a target color tone. The color tone adjusting layer is, for example, a layer containing a resin and a colorant. Examples of the colorant include inorganic pigments such as titanium oxide, zinc oxide, red iron oxide, titanium dioxide (titanium oxide) -based firing pigments, ultramarine blue, cobalt aluminate, and carbon black; organic pigments such as azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, perylene-based compounds, isoindolinone-based compounds, phthalocyanine-based compounds, quinophthalone-based compounds, threne-based compounds, and diketopyrrolopyrrole-based compounds; bulk pigments such as barium sulfate and calcium carbonate; and basic dyes, acid dyes, mordant dyes, and the like.

The refractive index adjustment layer is a layer having a function of adjusting the refractive index, and may be, for example, a layer having a refractive index different from that of the optical film constituting the base layer and capable of providing a predetermined refractive index to the optical laminate. The refractive index adjustment layer may be a resin layer containing a suitably selected resin and, in some cases, a pigment, or may be a metal thin film. Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle diameter of the pigment may be 0.1 μm or less. By setting the average primary particle diameter of the pigment to 0.1 μm or less, diffuse reflection of light transmitted through the refractive index adjustment layer can be prevented, and a decrease in transparency can be prevented. Examples of the metal used for the refractive index adjustment layer include metal oxides and metal nitrides such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride.

(method for producing optical film constituting substrate layer)

The method for producing the optical film constituting the base layer included in the optical laminate of the present invention is not particularly limited, and for example, a production method including at least the following steps may be used:

(a) a step of preparing a resin composition (hereinafter also referred to as "varnish") containing at least the polyamide resin and a solvent (varnish preparation step),

(b) A step of applying a varnish to a support material to form a coating film (coating step), and

(c) and a step of drying the coating film to form an optical film (optical film forming step).

In the varnish preparation step, a polyamide resin is dissolved in a solvent, and if necessary, the filler, the ultraviolet absorber, and other additives are added and mixed with stirring to prepare a resin varnish. When silica particles are used as the filler, a dispersion of a silica sol containing silica particles may be replaced with a solvent capable of dissolving the resin, for example, a solvent used in the preparation of a varnish described below, and the obtained silica sol may be added to the resin.

The solvent used in the preparation of the varnish is not particularly limited as long as it can dissolve the resin. Examples of the solvent include amide solvents such as DMAc and DMF; lactone solvents such as GBL and gamma valerolactone; sulfur-containing solvents such as dimethyl sulfone, DMSO, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among them, an amide solvent or a lactone solvent is preferable. These solvents may be used alone or in combination of two or more. The varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, and still more preferably 5 to 15% by mass.

In the coating step, a varnish is applied to the support material by a known coating method to form a coating film. Examples of known coating methods include roll coating methods such as wire bar coating, reverse coating, and gravure coating, die coating methods, comma knife coating methods, lip coating methods, spin coating methods, screen coating methods, jet coating methods, dipping methods, spraying methods, and cast molding methods.

In the film forming step, the coating film is dried and peeled from the support material, whereby an optical film can be formed. After the peeling, a step of drying the optical film may be further provided. The drying of the coating film may be carried out at a temperature of 50 to 350 ℃. If necessary, the coating film may be dried in an inert atmosphere or under reduced pressure.

Examples of the support material include a SUS plate in the case of a metal, and a PET film, a PEN film, a polyamide resin film, another polyimide resin film, a cycloolefin polymer (COP in some cases), and an acrylic film in the case of a resin. Among them, from the viewpoint of excellent smoothness and heat resistance, a PET film, a COP film, and the like are preferable, and from the viewpoint of adhesion to an optical film and cost, a PET film is more preferable.

< method for producing optical layered body >

The optical laminate of the present invention can be produced by laminating a hard coat layer on the obtained optical film by, for example, the method described above.

The use of the optical laminate of the present invention is not particularly limited, and the optical laminate can be used for various applications. In a preferred embodiment of the present invention, the optical laminate of the present invention is very useful as a front panel of an image display device, particularly as a front panel (window film) of a flexible display device, particularly as a front panel of a rollable display, a foldable display. The flexible display device includes, for example, a flexible functional layer and an optical laminate that is stacked on the flexible functional layer and functions as a front panel. That is, the front panel of the flexible display device is disposed on the visible side of the flexible functional layer. The front panel has the function of protecting a flexible functional layer, such as an image display element within a flexible display. The flexible display device is a display device used in association with operations such as repeated bending and repeated curling of an image display device. A front panel of a flexible display device used in association with such repeated bending operations is required to have high bending resistance. In addition, high visibility is also required for the front panel. In comparison with a film for a substrate of an image display device used inside an image display device, a film for a front panel of an image display device, particularly a front panel of a flexible display device, is required to have higher visibility and higher bending resistance. For example, the film of the present invention preferably has the total light transmittance, haze and/or YI value as described above from the viewpoint of easily improving the visibility when used for a front panel of a flexible display device, and preferably satisfies the number of times of bending resistance in the U-shaped stretching test as described above from the viewpoint of easily improving the bending resistance when used as a front panel of a flexible display device.

Examples of the image display device include wearable devices such as a television, a smartphone, a mobile phone, a car navigation system, a tablet PC, a portable game machine, electronic paper, a pointer, a notice board, a clock, and a smart watch. As the flexible display device, all image display devices having a flexible property can be cited, and for example, the rollable display and the foldable display as described above can be cited. A rollable display is an image display device in which an image display portion including a front panel is rolled up in a roll shape and is used in a state where the image display portion is pulled out and formed into a flat or curved surface, and is an image display device which performs an operation such as rolling up in a roll shape every time it is used. The foldable display is an image display device in which an image display portion including a front panel is folded and the image display portion is opened and used in a state of being formed into a flat surface or a curved surface, and is an image display device in which an operation such as folding is performed every time the image display device is used. Such an image display device that repeats operations such as winding and bending is referred to as a flexible image display device.

[ Flexible display device ]

The present invention also provides a flexible display device including the optical laminate of the present invention. The optical laminate of the present invention is preferably used as a front panel in a flexible display device, and the front panel is sometimes referred to as a window film. The flexible display device is formed of a laminate for flexible display device and an organic EL display panel, and the laminate for flexible display device is arranged on the visible side of the organic EL display panel and can be bent. The laminate for a flexible display device may contain a window film, a polarizing plate, and a touch sensor as the optical laminate of the present invention, and the order of lamination is optional, but it is preferable to laminate the window film, the polarizing plate, the touch sensor or the window film, the touch sensor, and the circularly polarizing plate in this order from the visible side. If the circularly polarizing plate is present on the visible side of the touch sensor, the pattern of the touch sensor is less likely to be observed, and the visibility of the displayed image is improved, which is preferable. The respective members may be laminated using an adhesive, or the like. The liquid crystal display device may further include a light-shielding pattern formed on at least one surface of any one of the window film, the polarizing plate, and the touch sensor.

[ polarizing plate ]

The flexible display device of the present invention may further include a polarizing plate, and preferably further includes a circularly polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only a right-handed circularly polarized light component or a left-handed circularly polarized light component by laminating a λ/4 phase difference plate on a linear polarizing plate. For example, can be used for: the external light is blocked, converted into right-handed circularly polarized light, reflected by the organic EL panel, and converted into left-handed circularly polarized light, and only the light emitting component of the organic EL panel is transmitted, thereby suppressing the influence of the reflected light and facilitating the observation of an image. In order to realize the circular polarization function, the absorption axis of the linear polarization plate and the slow axis of the λ/4 phase difference plate need to be 45 ° in theory, but are 45 ± 10 ° in practice. The linearly polarizing plate and the λ/4 phase difference plate are not necessarily stacked adjacent to each other, and the relationship between the absorption axis and the slow axis may satisfy the above range. It is preferable to achieve complete circular polarization at all wavelengths, but this is not necessary for practical use, and thus the circular polarizing plate of the present invention also includes an elliptical polarizing plate. It is also preferable to further laminate a λ/4 phase difference film on the viewing side of the linear polarizing plate to make the emitted light circularly polarized light, thereby improving the visibility when the polarized sunglasses are worn.

The linear polarizing plate is a functional layer having a function of passing light vibrating in the transmission axis direction and blocking polarized light of vibration components perpendicular thereto. The linearly polarizing plate may be provided with a single linearly polarizing plate or with a linearly polarizing plate and a protective film attached to at least one surface thereof. The thickness of the linear polarizer may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness of the linear polarizer is in the above range, the flexibility tends not to be easily lowered.

The linear polarizer may be a film-type polarizer produced by dyeing and stretching a polyvinyl alcohol (hereinafter, abbreviated as PVA) film. The polarizing film exhibits polarization performance by allowing a dichroic dye such as iodine to adsorb to a PVA-based film oriented by stretching or by stretching the PVA-adsorbed film while the dichroic dye is oriented. The production of the film-type polarizing plate may further include steps of swelling, crosslinking with boric acid, washing with an aqueous solution, drying, and the like. The stretching and dyeing step may be performed on the PVA-based film alone or in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA film is preferably 10 to 100 μm, and the stretch ratio is preferably 2 to 10 times.

Another example of the polarizing plate is a liquid crystal coating type polarizing plate formed by coating a liquid crystal polarizing composition. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic dye compound. The liquid crystalline compound is preferable because it has a property of exhibiting a liquid crystal state, and particularly, it has a high-order alignment state such as a smectic state, since it can exhibit high polarization performance. Further, it is also preferable that the liquid crystalline compound has a polymerizable functional group.

The dichroic dye compound is a dye that exhibits dichroism by being aligned together with the liquid crystal compound, and may have liquid crystal properties and a polymerizable functional group. Any of the compounds in the liquid crystal polarizing composition has a polymerizable functional group.

The liquid crystal polarizing composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like.

The liquid crystal polarizing layer may be manufactured by coating a liquid crystal polarizing composition on an alignment film and forming a liquid crystal polarizing layer.

The liquid crystal polarizing layer can be formed to have a reduced thickness compared to the film-type polarizing plate. The thickness of the liquid crystal polarization layer is preferably 0.5-10 μm, and more preferably 1-5 μm.

The alignment film can be produced, for example, by applying an alignment film-forming composition to a base material and imparting alignment properties by rubbing, polarized light irradiation, or the like. The alignment film forming composition may further contain a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like in addition to the alignment agent. Examples of the orientation agent include polyvinyl alcohols, polyacrylates, polyamide acids, and polyimides. In case photo-alignment is applied, it is preferred to use an alignment agent comprising cinnamate groups. The weight average molecular weight of the polymer used as the orientation agent may be 10000 to 1000000. The thickness of the alignment film is preferably 5 to 10000nm, more preferably 10 to 500nm, from the viewpoint of alignment regulating force. The liquid crystal polarizing layer may be laminated by being peeled off from the substrate and then transferred, or the substrate may be directly laminated. The substrate preferably functions as a transparent substrate for a protective film, a retardation plate, and a window film.

The protective film may be a transparent polymer film, and specific examples of the polymer film to be used include polyolefins such as polyethylene, polypropylene, polymethylpentene, cycloolefin derivatives of cycloolefin having a unit containing a norbornene or cycloolefin monomer, (modified) celluloses such as diacetylcellulose, triacetylcellulose and propionylcellulose, acrylics such as methyl methacrylate (co) polymers, polystyrenes such as styrene (co) polymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, ethylene-vinyl acetate copolymers, polyvinyl chlorides, polyvinylidene chlorides, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonates, aryl ester polyesters such as polyarylate, and the like, Films of polyamides such as nylon, polyimides, polyamideimides, polyetherimides, polyethersulfones, polysulfones, polyvinyl alcohols, polyvinyl acetals, polyurethanes, epoxy resins, and the like are preferably films of polyamides, polyamideimides, polyimides, polyesters, olefins, acrylic resins, or cellulose resins, from the viewpoint of excellent transparency and heat resistance. These polymers may be used alone or in combination of 2 or more. These films may be used as they are in the form of unstretched films or in the form of uniaxially or biaxially stretched films. Cellulose film, olefin film, acrylic film, and polyester film are preferred. The protective film may be a coating type protective film obtained by applying a cationically curable composition such as an epoxy resin or a radically curable composition such as an acrylate and curing the composition. If necessary, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, or the like may be contained. The thickness of the protective film may be 200 μm or less, preferably 1 to 100 μm. If the thickness of the protective film is within the above range, the flexibility of the protective film is not easily reduced.

The λ/4 phase difference plate is a film that imparts a phase difference of λ/4 in a direction orthogonal to the traveling direction of incident light, in other words, in the in-plane direction of the film. The λ/4 retardation plate may be a stretched retardation plate produced by stretching a polymer film such as a cellulose film, an olefin film, or a polycarbonate film. If necessary, a phase difference adjusting agent, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like may be included. The thickness of the tension type phase difference plate can be less than 200 μm, and is preferably 1-100 μm. When the thickness is within the above range, the flexibility of the film tends not to be easily lowered.

Another example of the λ/4 retardation plate is a liquid crystal coating type retardation plate formed by coating a liquid crystal composition. The liquid crystal composition contains a liquid crystalline compound having a property of exhibiting a liquid crystal state such as a nematic state, a cholesteric state, or a smectic state. Any of the compounds including the liquid crystalline compound in the liquid crystal composition has a polymerizable functional group. The liquid crystal coating type phase difference plate may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like. The liquid crystal coated retardation plate can be produced by coating a liquid crystal composition on an alignment film and curing the coating to form a liquid crystal retardation layer, as described in the liquid crystal polarizing layer. The liquid crystal coated retardation plate can be formed thinner than the stretched retardation plate. The thickness of the liquid crystal polarizing layer is usually 0.5 to 10 μm, preferably 1 to 5 μm. The liquid crystal-coated phase difference plate may be peeled from a substrate and then transferred to be laminated, or the substrate may be directly laminated. The substrate preferably functions as a transparent substrate for a protective film, a retardation plate, and a window film.

In general, there are many materials that exhibit large birefringence at shorter wavelengths and small birefringence at longer wavelengths. In this case, since a retardation of λ/4 cannot be realized in all visible light regions, an in-plane retardation of λ/4, that is, an in-plane retardation of 100 to 180nm, preferably 130 to 150nm, is usually designed for a region around 560nm, which has high visibility. From the viewpoint of satisfactory visibility, it is preferable to use an inverse dispersion λ/4 phase difference plate using a material having a wavelength dispersion characteristic of birefringence opposite to that of the conventional material. As such a material, the material described in jp 2007-30873 a and the like is preferably used also in the case of a stretched type retardation plate, and the material described in jp 2010-30979 a is preferably used also in the case of a liquid crystal coated type retardation plate.

As another method, a technique of obtaining a wide-band λ/4 phase difference plate by combining with a λ/2 phase difference plate is also known (japanese patent application laid-open No. 10-90521). The λ/2 phase difference plate can be manufactured by the same material and method as the λ/4 phase difference plate. The combination of the stretching type retardation plate and the liquid crystal coating type retardation plate is optional, but in any case, the liquid crystal coating type retardation plate is preferably used in view of the possibility of reduction in thickness.

In order to improve visibility in an oblique direction, a method of laminating a front C-plate on the circularly polarizing plate is also known (japanese patent application laid-open No. 2014-224837). The positive C plate may be a liquid crystal coated retardation plate or a stretched retardation plate. The phase difference in the thickness direction is preferably from-200 to-20 nm, more preferably from-140 to-40 nm.

[ touch sensor ]

The flexible display device of the present invention may further include a touch sensor. Touch sensors are used as input tools. As the touch sensor, various types such as a resistive film type, a surface acoustic wave type, an infrared ray type, an electromagnetic induction type, and an electrostatic capacitance type have been proposed, and any type may be used. The electrostatic capacitance system is particularly preferable. The capacitive touch sensor is divided into an active region and an inactive region located in an outer region of the active region. The active area is an area corresponding to a display unit, which is an area of the display panel where a screen is displayed, and is an area where a user's touch is sensed, and the inactive area is an area corresponding to a non-display unit, which is an area of the display device where a screen is not displayed. The touch sensor may include: a substrate having flexible characteristics; a sensing pattern formed in an active region of the substrate; and each sensing line formed in the inactive region of the substrate and used for connecting the sensing pattern with an external driving circuit through a pad portion. As the substrate having a flexible property, the same material as the polymer film can be used. The substrate of the touch sensor preferably has a toughness of 2000 MPa% or more in order to suppress cracking of the touch sensor. The toughness may be more preferably 2000 to 30000 MPa%. Here, the toughness is defined as the area of the lower part of a Stress (MPa) -strain (%) curve (Stress-strain curve) of a polymer material obtained by a tensile test, the area being defined as the area up to the breaking point.

The sensing pattern may include a1 st pattern formed along a1 st direction and a 2 nd pattern formed along a 2 nd direction. The 1 st pattern and the 2 nd pattern are arranged in mutually different directions. The 1 st pattern and the 2 nd pattern are formed on the same layer, and the patterns must be electrically connected in order to sense a touched point. The 1 st pattern is a form in which the unit patterns are connected to each other via a tab, and the 2 nd pattern is a structure in which the unit patterns are separated from each other in an island form, and thus, in order to electrically connect the 2 nd pattern, an additional bridge electrode is required. The sensing pattern may employ a known transparent electrode material. Examples thereof include Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), zinc oxide (ZnO), Indium Zinc Tin Oxide (IZTO), Indium Gallium Zinc Oxide (IGZO), Cadmium Tin Oxide (CTO), PEDOT (poly (3, 4-ethylenedioxythiophene)), Carbon Nanotubes (CNT), graphene, and a metal wire, and 2 or more of them may be used alone or in combination. ITO may be preferably used. 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 may be used alone or in combination of 2 or more.

The bridge electrode may be formed on the insulating layer with the insulating layer interposed therebetween on the sensing pattern, and the bridge electrode may be formed on the substrate, and the insulating layer and the sensing pattern may be formed thereon. The bridge electrode may be formed of the same material as the sensing pattern, or may be formed of a metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of 2 or more of these metals. Since the 1 st pattern and the 2 nd pattern must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the contact of the 1 st pattern and the bridge electrode, or may be formed in a structure of a layer covering the sensing pattern. In the latter case, the bridge electrode may connect the 2 nd pattern via a contact hole formed in the insulating layer. In the touch sensor, an optical adjustment layer, which is a difference in transmittance between a patterned region where a pattern is formed and a non-patterned region where no pattern is formed, specifically, a difference in transmittance induced by a difference in refractive index of these regions, may be further included between the substrate and the electrode as a means for appropriately compensating for a difference in transmittance, which may include an inorganic insulating substance or an organic insulating substance. The optical adjustment layer may be formed by applying a photocurable composition including a photocurable organic binder and a solvent onto a substrate. The photocurable composition may further include inorganic particles. The inorganic particles may be used to raise the refractive index of the optical adjustment layer.

The photocurable organic binder may include a copolymer of monomers such as an acrylate monomer, a styrene monomer, and a carboxylic acid monomer. The photocurable organic binder may be, for example, a copolymer containing repeating units different from each other, such as repeating units containing an epoxy group, repeating units of an acrylate ester, and repeating units of a carboxylic acid.

The inorganic particles may include, for example, zirconia particles, titania particles, alumina particles, and the like. The photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing assistant.

[ adhesive layer ]

Each layer of the laminate for a flexible display device, such as a window film, a polarizing plate, and a touch sensor, and a film member constituting each layer, such as a linear polarizing plate and a λ/4 retardation plate, may be bonded with an adhesive. As the adhesive, widely used adhesives such as an aqueous adhesive, an organic solvent adhesive, a solventless adhesive, a solid adhesive, a solvent-volatile adhesive, a moisture-curable adhesive, a heat-curable adhesive, an anaerobic curable adhesive, an aqueous solvent-volatile adhesive, an active energy ray-curable adhesive, a curing agent-mixed adhesive, a hot-melt adhesive, a pressure-sensitive adhesive, and a remoistenable adhesive can be used. Among them, an aqueous solvent-volatile adhesive, an active energy ray-curable adhesive, and a pressure-sensitive adhesive are often used. The thickness of the adhesive layer can be suitably adjusted according to the required adhesive strength, and is, for example, 0.01 to 500. mu.m, preferably 0.1 to 300. mu.m. In the laminate for a flexible image display device, a plurality of adhesive layers may be present, and the thickness and the type of the adhesive used may be the same or different.

As the aqueous solvent-volatile adhesive, a polyvinyl alcohol polymer, a water-soluble polymer such as starch, or a water-dispersed polymer such as an ethylene-vinyl acetate emulsion or a styrene-butadiene emulsion can be used as a main polymer. In addition to water and the main agent polymer, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, and the like may be added. In the case of bonding with the aqueous solvent volatile adhesive, the adhesive layer is bonded by pouring the aqueous solvent volatile adhesive between the adhesive layers, and then drying the adhesive layers, whereby adhesiveness can be provided. The thickness of the adhesive layer when the aqueous solvent volatile adhesive is used may be 0.01 to 10 μm, and preferably 0.1 to 1 μm. When the aqueous solvent-volatile adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive may be the same or different.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material that forms an adhesive layer upon irradiation with an active energy ray. The active energy ray-curable composition may contain at least 1 polymer of the radical polymerizable compound and the cationic polymerizable compound similar to those of the hard coat composition. The radical polymerizable compound may be the same kind of compound as the hard coat composition, as the hard coat composition. The radical polymerizable compound used in the adhesive layer is preferably a compound having an acryloyl group. In order to reduce the viscosity of the adhesive composition, it is also preferable to include a monofunctional compound.

The cationic polymerizable compound may be the same kind of compound as used in the hard coat composition, as used in the hard coat composition. The cationic polymerizable compound used in the active energy ray-curable composition is more preferably an epoxy compound. 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 further contain a polymerization initiator. The polymerization initiator may be a radical polymerization initiator, a cationic polymerization initiator, a radical or cationic polymerization initiator, and the like, and may be appropriately selected and used. These polymerization initiators are decomposed by at least one of irradiation with active energy rays and heating, and generate radicals or cations to advance radical polymerization and cationic polymerization. An initiator capable of initiating at least either of radical polymerization and cationic polymerization by irradiation with active energy rays described in the description of the hard coating composition can be used.

The active energy ray-curable composition may further contain an ion scavenger, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, a defoaming agent solvent, an additive, and a solvent. In the case of bonding with the active energy ray-curable adhesive, the active energy ray-curable composition is applied to one or both of the adhesive layers, and then the adhesive layers are bonded to each other, and active energy rays are irradiated through one or both of the adhesive layers to cure the adhesive layers, whereby the adhesive layers can be bonded to each other. The thickness of the adhesive layer when the active energy ray-curable adhesive is used may be usually 0.01 to 20 μm, and preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive used may be the same or different.

The pressure-sensitive adhesive is classified into an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, and the like according to the base polymer, and any of them can be used. The adhesive may contain a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a tackifier, a plasticizer, a dye, a pigment, an inorganic filler, and the like in addition to the main polymer. The adhesive layer is formed by dissolving and dispersing the components constituting the adhesive in a solvent to obtain an adhesive composition, applying the adhesive composition to a substrate, and then drying the adhesive composition. The adhesive layer may be formed directly or may be transferred to an adhesive layer separately formed on the substrate. It is also preferable to use a release film for covering the pressure-sensitive adhesive surface before bonding. The thickness of the adhesive layer when the adhesive is used may be usually 1 to 500. mu.m, preferably 2 to 300. mu.m. When the adhesive is used for forming a plurality of layers, the thickness of each layer and the kind of the adhesive used may be the same or different.

[ light-shielding pattern ]

The light blocking pattern may be applied as at least a part of a bezel or a housing of the flexible image display device. The wiring disposed at the edge portion of the flexible image display device is hidden by the light-shielding pattern and is not easily viewed, thereby improving the visibility of an image. The light blocking pattern may be in the form of a single layer or a plurality of layers. The color of the light-shielding pattern is not particularly limited, and various colors such as black, white, and metallic colors may be used. The light-shielding pattern can be formed using a pigment for expressing color, and a polymer such as acrylic resin, ester resin, epoxy resin, polyurethane, or silicone. They may be used alone or in a mixture of 2 or more. The light shielding pattern may be formed by various methods such as printing, photolithography (photolithography), and inkjet. The thickness of the light-shielding pattern is usually 1 to 100 μm, preferably 2 to 50 μm. Further, it is also preferable to provide a shape such as an inclination in the thickness direction of the light-shielding pattern.

Examples

The present invention will be described in further detail below with reference to examples. In the examples, "%" and "part(s)" are% by mass and part(s) by mass unless otherwise specified. First, the evaluation method will be explained.

< thickness of film >

The optical films of the optical laminates obtained in examples and comparative examples and the substrate layers constituting the optical laminates were measured for film thickness using an ABS digimato table ("ID-C112 BS", manufactured by Mitsutoyo corporation).

Thickness of hard coating layer

The thickness of the hard coat layer was measured using a F20 bench-type film thickness system manufactured by Filmetrics.

< flexibility resistance >

The optical layered body was cut into a size of 10mm × 150mm using a dumbbell cutter. The cut laminate (film) was placed in a stretching test jig for a planar unloaded U-shape stretching test ("DLDMLH-FS" manufactured by YUASA SYSTYM machine, ltd.) so that the hard coat layer was positioned inside during bending and the bending radius was 1mm, and a bending test for repeating horizontal and U-shaped bending was performed by moving the working part left and right at a test speed of 60rpm, to measure the number of times of bending resistance of each film (the number of times of bending without generating cracks (japanese: ヒビ) or whitening at the bent portion).

Measurement of haze Change amount (. DELTA.Hz) before and after bending test of < 5 million times

The optical layered bodies obtained in examples and comparative examples were cut into a size of 10mm × 150mm using a dumbbell cutter, and the haze Hz2 (%) of the optical layered body before the bending test was measured at the center portion in the longitudinal direction thereof using a haze computer (manufactured by Suga testing machine, "HGM-2 DP"). Thereafter, the optical laminate was bent 5 ten thousand times at the center portion in the longitudinal direction of the optical laminate by the same method as the above-described bending resistance test, and thereafter, Hz1 (%) was measured at the bent portion of the optical laminate. From the measurement results, Δ Hz (Hz 1-Hz2) was calculated as Δ Hz before and after 5 ten thousand bending tests.

[ measurement of Raman Spectroscopy (measurement of thickness of intermediate layer) ]

(preparation of measurement sample)

The optical layered bodies obtained in examples and comparative examples were cut into a size of 2mm × 5mm using a dicing saw. At this time, the optical laminate is cut so that the TD direction of the optical film constituting the base layer is the long side. The cut optical laminate was disposed so that the cut cross section was disposed on the surface, and subjected to embedding treatment using epoxy-based room temperature curing resin 53 type (manufactured by Acura (japanese アキュラ)). The optical laminate was processed on the cross-sectional side with an ultra thin microtome EM UC7 (manufactured by Leica) to prepare a cross-sectional surface.

(measurement by Raman spectroscopy)

Raman spectroscopy of the cross sections of the laminates of examples and comparative examples was performed using ramandouch manufactured by Nanophoton corporation, and data processing was performed by irradiating a cross section in the longitudinal direction with raman light from the hard coat layer side in the thickness direction under the following conditions in a linear manner crossing the base material layer to obtain raman spectra at intervals of 0.2 μm. Determine 1600cm at each point^-1、3000cm^-1Peak area of (a). Here, the above 1600cm^-1The peak of (2) is a peak derived from a carbonyl group contained in the substrate layer or the hard coat layer, and is considered to be 3000cm^-1The peak of (A) is considered to be derived from CH contained in the hard coat layer₂Peak of the radical. 3000cm^-1The peak of (2) shows the maximum peak intensity at the hard coat layer portion, and the peak intensity decreases as the measurement position approaches the base material layer, and becomes 0 at the portion corresponding to the base material layer. In addition, 1600cm^-1The peak intensity increases as the measurement position approaches the substrate layer. Calculate 3000cm^-1Peak area of (2) relative to 1600cm^-1The range from the position where the peak intensity ratio starts to decrease, that is, less than 1 to 1/10 or more which is an average value, that is, the inclined portion is defined as the intermediate layer.

(measurement conditions)

Exposure time: 30 seconds

Excitation wavelength: 531.90nm

Slit width: 50 μm

Grating: 300gr/mm

An objective lens: TU Plan Fluor 100 ×/0.90N.A.

Laser irradiation method: and (4) irradiating the line.

[ Raman Spectroscopy (measurement of fluctuation of thickness of intermediate layer) ]

The thickness of the intermediate layer was determined by the above-described method at any 5 points of the cross section of the laminate in examples and comparative examples. Using the following equation based on the values of the maximum value (tmax) and the minimum value (tmin) of the plurality of thicknesses: { (tmax-tmin)/(tmax + tmin) } × 100 (%), the fluctuation in the thickness of the intermediate layer of each film was calculated.

Hardness at indentation

(preparation of measurement sample)

A measurement sample was prepared in the same manner as the measurement sample of the raman spectroscopic measurement.

(measurement method Using nanoindenter)

The indentation hardness of the cross section of the laminate of examples and comparative examples was measured using an ultra-fine indentation hardness tester (ENT-2100, product of Elionix corporation) under the following conditions.

Pressure head: berkovich indenter

Loading load mode: electromagnetic mode

Surface detection: inclination mode setting value 2.0

Loading a curve: reach 0.5mN in 15 seconds (Linear)

Creep deformation: 0.5mN at 1 second

Unloading curve: reach 0mN in 15 seconds (Linear)

Measuring temperature: at 26 ℃.

The measurement was performed at intervals of 1.5 μm from the hard coat layer toward the base material layer. The measurement results of the vicinity of the interface where the indentation hardness is the lowest and the measurement results of the center of the base material layer (average value of 5 points near the center in the thickness direction) are shown in the table. In the optical layered body of the example, the point of the interface showing the lowest indentation hardness corresponds to the position of the intermediate layer determined in the raman spectroscopic measurement described above.

< determination of Pencil hardness >

According to JIS K5600-5-4: 1999, the pencil hardness on the hard coat layer side of the laminates obtained in examples and comparative examples was measured. The load during the measurement was 750g, and the measurement speed was 4.5 mm/sec.

< determination of weight average molecular weight >

The weight average molecular weight of the resin was determined using GPC. The preparation method and the measurement conditions of the measurement sample are as follows.

(1) Sample preparation method

20mg of the resin was weighed out, and 10mL of DMF (10 mmol/L solution of lithium bromide in DMF) was added to dissolve it completely. The solution was filtered through a chromatography plate (pore size: 0.45 μm) to prepare a sample solution.

(2) Measurement conditions

The device comprises the following steps: HLC-8020GPC

A chromatographic column: guard column + TSKgel alpha-M (300 mm. times.7.8 mm diameter). times.2 pieces + alpha-2500 (300 mm. times.7.8 mm diameter). times.1 pieces

Eluent: DMF (with addition of 10mmol/L lithium bromide)

Flow rate: 1.0 mL/min

A detector: RI detector

Column temperature: 40 deg.C

Injection amount: 100 μ L

Molecular weight standard: standard polystyrene.

< preparation of silica Sol >

A1000 mL flask was charged with 442.6g of methanol-dispersed silica sol (primary particle diameter: 27nm, silica particle solid content: 30.5%) and 301.6g of GBL, and methanol was evaporated by a vacuum evaporator at 400hPa and 250hPa for 1 hour in a hot water bath at 45 ℃. Then, the temperature was raised to 70 ℃ at 250hPa and the mixture was heated for 30 minutes to obtain GBL dispersed silica sol 1. The solid content concentration of the GBL-dispersed silica sol 1 thus obtained was 29.1%.

< Synthesis example 1: production of Polyamide-imide resin (1)

A reaction vessel having a sufficiently dried stirrer and a thermometer was purged with nitrogen gas, and the inside of the vessel was replaced with nitrogen gas. 1907.2 parts by mass of DMAc was charged into the reaction vessel, and 111.94 parts by mass of TFMB and 46.84 parts by mass of 6FDA were added thereto to carry out a reaction.

Then, 10.37 parts by mass of OBBC and 42.79 parts by mass of TPC were added and reacted. Then, 37.66 parts by mass of acetic anhydride was added, and after stirring for 15 minutes, 11.45 parts by mass of 4-methylpyridine was added, the temperature of the reaction vessel was raised to 70 ℃, and further stirring was carried out for 3 hours, thereby obtaining a reaction solution.

The reaction solution was cooled, 3794.5 parts by mass of methanol was added, and 1419.4 parts by mass of ion-exchanged water was added dropwise thereto, to precipitate a white solid. The precipitated white solid was collected by centrifugal filtration and washed with methanol to obtain a wet cake containing a polyamideimide resin. The obtained wet cake was dried at 78 ℃ under reduced pressure, thereby obtaining a powder of a polyamideimide resin. The weight average molecular weight of the resulting polyamideimide resin (1) was 466000.

Production example 1: production of resin film constituting substrate layer (before HC lamination) >

(production of resin composition 1)

The GBL dispersion surface-modified silica sol 1 was added to a GBL solvent at room temperature, sufficiently stirred and mixed, and sumiosorb 340[2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, Sumika ChemteX (manufactured by ltd.) ] and Sumiplast Violet B (bluing agent, Sumika ChemteX (manufactured by ltd.)) were added thereto and mixed so that the amount of the sumiosorb 340 and the amount of the Sumiplast Violet B per 100 parts by mass of the total amount of the resin and the silica particles were 5.7 parts by mass and 35ppm, respectively. Thereafter, the polyamideimide resin (1) was added and mixed so that the composition ratio of the resin to the silica particles was 60: 40, the mixture was stirred until uniform, to obtain a resin composition 1 (hereinafter, may be referred to as a resin varnish 1) having a solid content of 10 mass%.

(production of resin film 1)

The resin varnish 1 thus obtained was cast onto a PET (polyethylene terephthalate) film ("Cosmoshine (registered trademark) A4100", thickness 188 μm, thickness distribution. + -. 2 μm manufactured by Toyobo Co., Ltd.) to form a coating film. At this time, the linear velocity was 0.3 m/min. Further, the coating film was dried under such conditions that the coating film was heated at 80 ℃ for 10 minutes, then at 100 ℃ for 10 minutes, then at 90 ℃ for 10 minutes, and finally at 80 ℃ for 10 minutes. Thereafter, the coating film was peeled from the PET film to obtain a raw material film 1 having a thickness of 58 μm and a width of 700 mm.

A raw material film 1 having a width of 700mm was heated by using a tenter type dryer having 1 to 6 chambers equipped with a gripper as a holder, and the solvent was removed to obtain a resin film 1 having a thickness of 49.5. mu.m. At this time, the preparation was carried out under conditions in the drying furnace such that the temperature in the drying furnace was 200 ℃, the holding width of the nip was 25mm, the film transport speed was 0.9 m/min, the ratio of the film width at the outlet of the drying furnace to the film width at the inlet of the drying furnace, that is, the distance between the nips was 0.98, and the air speed in each chamber of the tenter type dryer was adjusted to 13.5 m/sec in chamber 1, 13 m/sec in chamber 2, and 11 m/sec in chambers 3 to 6. Hot air is blown from above and below the film.

Production example 2: production of resin film constituting substrate layer (before hard coating lamination) >

(production of resin composition 2)

The polyamideimide resin (1) was added to the GBL solvent at room temperature, and sufficiently stirred and mixed, and Sumiporb 340[2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, manufactured by Sumika ChemteX, Inc. ] and Sumiplast Violet B (bluing agent, manufactured by Sumika ChemteX, Inc.) were added thereto and mixed so as to be 5.7 parts by mass and 35ppm by mass, respectively, with respect to 100 parts by mass of the total amount of the resins. The mixture was stirred until uniform, to obtain a resin composition 2 (hereinafter, also referred to as a resin varnish 2) having a solid content of 15 mass%.

(production of resin film 2)

Resin film 2 having a thickness of 49.5 μm was obtained in the same manner as in example 1, except that resin varnish 2 was used as the resin varnish.

< preparation of curable composition >

(curable resin composition 1)

Trimethylolpropane triacrylate (a-TMPT, a product of shinkanmura chemical corporation, a-TMPT)28.4 parts by mass, pentaerythritol tetraacrylate (a-TMMT, a product of shinkanmura chemical corporation, a-TMPT)28.4 parts by mass, 1-hydroxycyclohexyl phenyl ketone (a product of BASF, Irgacure (registered trademark) 184)1.8 parts by mass, a leveling agent (a product of BYK Chemie Japan, BYK (registered trademark) -307)0.1 part by mass, and propylene glycol 1-monomethyl ether (a product of tokyo chemical industry, a product of shin-ko chemical industries, respectively) 39 parts by mass were stirred and mixed to obtain photocurable resin composition 1.

(curable resin composition 2)

Trimethylolpropane triacrylate (a-TMPT, manufactured by Ninghamura chemical Co., Ltd.) 28.4 parts by mass, pentaerythritol tetraacrylate (a-TMMT, manufactured by Ninghamura chemical Co., Ltd.) 28.4 parts by mass, 1-hydroxycyclohexyl phenyl ketone (BASF, manufactured by BASF Co., Ltd.) 184)1.8 parts by mass as a photopolymerization initiator, a leveling agent (BYK Chemie, manufactured by BYK (registered trademark) -307)0.1 part by mass, and methanol (Fuji film, manufactured by Wako pure chemical Co., Ltd.) 39 parts by mass were stirred and mixed to obtain photocurable resin composition 2.

< example 1: production of optical laminate

A film of 300 mm. times.200 mm was cut out from the resin film 1, and the curable composition 1 was applied to one surface of the film by a bar coater and left at a temperature of 5 ℃ for 1 hour. Thereafter, the mixture was dried at 80 ℃ for 3 minutes and then heated under a nitrogen atmosphere using a high pressure mercury lamp at 500mJ/cm²、200mW/cm²The laminate 1 was irradiated under the conditions of (1) and cured to form a hard coat layer, thereby obtaining a hard coat layer having a thickness of 10 μm.

< example 2: production of optical laminate

A laminate 2 was obtained in the same manner as in example 1, except that the resin film 2 was used instead of the resin film 1.

< comparative example 1: production of optical laminate

A laminate 3 was obtained in the same manner as in example 1, except that the curable resin composition 2 was used in place of the curable resin composition 1 and the standing time after application was set to 5 minutes.

< example 3: production of optical laminate

A laminate 4 was obtained in the same manner as in example 2, except that the drying time at 80 ℃ was changed to 10 minutes.

< comparative example 2: production of optical laminate

A laminate 5 was obtained in the same manner as in example 1, except that the curable resin composition 1 was allowed to stand at a temperature of 25 ℃ for 20 minutes after application.

The press-in hardness A (N/mm) of the intermediate layer was measured for the obtained laminates 1 to 5²) And press-in hardness B (N/mm) of the base material layer²) Then, a ratio (A/B) was calculated. In addition, the first and second substrates are,the thickness of the interlayer, the fluctuation in thickness, the number of times of bending resistance of the optical laminate, and Δ Hz before and after 5 ten thousand bending tests were measured. The obtained results are shown in table 1. The pencil hardness of the surface of the hard coat layer of the laminate was 2H or more in each of examples 1 to 3, and was lower than 2B in comparative example 1.

[ Table 1]

Claims

1. An optical laminate comprising at least a substrate layer comprising a polyamide resin and a hard coat layer laminated on at least one surface of the substrate layer,

an intermediate layer having a thickness of 0.3 [ mu ] m or more and a thickness variation of 25% or less is provided between the base material layer and the hard coat layer,

the indentation hardness of the intermediate layer measured by a nanoindenter on a cross section in the thickness direction of the optical laminate is AN/mm²Setting the press-in hardness of the base material layer to BN/mm²In the case, the ratio of A to B, namely, A/B, is 0.96 or less.

2. The optical stack of claim 1,

the indentation hardness A of the intermediate layer is 700N/mm²The following.

3. The optical stack of claim 1 or 2,

the press-in hardness B of the base material layer is 350N/mm²～800N/mm²。

4. The optical stack according to any one of claims 1 to 3,

the pencil hardness of the surface of the hard coat layer laminated on at least one surface of the base material layer is HB or more.

5. The optical stack according to any one of claims 1 to 4,

the hard coat layer contains a cured product of a (meth) acrylate monomer.

6. The optical laminate according to any one of claims 1 to 5, which is a film for a front panel of a flexible display device.

7. A flexible display device comprising the optical laminate according to any one of claims 1 to 6.

8. The flexible display device of claim 6, further provided with a touch sensor.

9. The flexible display device according to claim 6 or 7, further provided with a polarizing plate.