CN116731514A

CN116731514A - Film, laminate, and flexible display device each comprising polyimide resin

Info

Publication number: CN116731514A
Application number: CN202310217337.7A
Authority: CN
Inventors: 中谷昭彦; 片宝蓝; 大松一喜; 平城慎也
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2022-03-11
Filing date: 2023-03-08
Publication date: 2023-09-12

Abstract

The present invention relates to a film, a laminate, and a flexible display device each including a polyimide resin. A film comprising a polyimide resin, wherein any one of the directions in the surface of the film is taken as the X axis, and the surface of the film perpendicular to the X axisWhen the inner direction is the Y axis and the thickness direction of the film perpendicular to the X axis is the Z axis, the light absorption coefficient k obtained by the polarization ATR method using infrared rays is based on _X 、k _Y K _Z And < cos > calculated from the formulas (a) - (c) ² (yX)>、〈cos ² (yY)>Cos ² (yZ)>Satisfies the formula (d) and (e). |<cos ² (yX)>‑<cos ² (yY)>|＜0.09 (d)0≤<cos ² (yZ)>＜0.25 (e)。

Description

Film, laminate, and flexible display device each comprising polyimide resin

Technical Field

The present invention relates to a film containing a polyimide resin, and a laminate and a flexible display device each including the film.

Background

Currently, image display devices such as liquid crystal display devices and organic EL display devices are widely and effectively used not only for televisions but also for various applications such as mobile phones and smart watches. With such expansion of applications, there is a need for an image display device having a flexible characteristic, which is also called a flexible display. The image display device is composed of components such as a polarizing plate, a phase difference plate, and a front plate in addition to display elements such as a liquid crystal display element and an organic EL display element. In order to manufacture an image display device having flexibility characteristics, all the constituent members described above are required to have flexibility.

Heretofore, glass has been used as the front panel. Glass has high transparency and can exhibit high hardness depending on the type of glass, but on the other hand, is very rigid and is easily broken, and thus is difficult to be used as a front panel material for flexible displays. Accordingly, as one of materials for replacing glass, polyimide-based resins have been studied, and optical films using the polyimide-based resins have been studied (for example, japanese patent application laid-open publication No. 2018-123319 and international publication No. 2018/147618).

Disclosure of Invention

In recent years, the size of image display devices has been increased, and the desire to use input devices such as touch pens has been increasing. In such a technical background, a material used for an image display device such as a flexible display is required to be less likely to cause a depression due to an external factor (for example, contact between an input device such as a touch pen and a surface, etc.), and to be able to restore the generated depression.

Accordingly, the present application aims to improve dent resistance in polyimide resin films.

The present inventors have conducted intensive studies with a view to solving the above problems, and as a result, have found that the above problems can be solved by a polyimide resin film having specific alignment characteristics, and have completed the present application. That is, the present application includes the following modes.

The polyimide resin film 1 has an absorbance k in each of the X, Y and Z directions obtained by a polarized light ATR method using infrared rays, in which any one of the directions in the plane of the film is taken as the X axis, the direction in the plane of the film perpendicular to the X axis is taken as the Y axis, and the thickness direction of the film perpendicular to the X axis is taken as the Z axis _X 、k _Y K _z And are calculated from the formulas (a) - (c)<cos ² (yX)>、〈cos ² (yY)>A kind of electronic device with high-pressure air-conditioning system<cos ² (yZ)>Satisfies the formula (d) and (e).

|<cos ² (yX)>-<cos ² (yY)>|＜0.09 (d)

0≤<cos ² (yZ)>＜0.25 (e)

The film according to [ 2 ], which also satisfies the formulas (f) and (g).

0.3≤<cos ² (yX)>≤1.0 (f)

0.3≤<cos ² (yY)>≤1.0 (g)

The film of [ 1 ] or [ 2 ], wherein the film satisfies the formulas (h) to (j) when the heat shrinkage ratio before and after heating at 400℃for 2 hours of the film in the X-axis direction is Sx and the heat shrinkage ratio at 400℃for 2 hours of the film in the Y-axis direction is Sy.

10％≤Sx≤25％ (h)

10％≤Sy≤25％ (i)

|Sx-Sy|≤5％ (j)

The film of any one of [ 1 ] to [ 3 ], wherein the yellowness of the film is 2.0 or less.

The film according to any one of [ 1 ] to [ 4 ], wherein the film has a thickness of 45 μm or more.

The film of any one of [ 1 ] to [ 5 ], which is a film for a front panel of a flexible display device.

A laminate comprising the film of any one of [ 1] to [ 6 ], and a functional layer laminated on at least one surface of the film.

The flexible display device of [ 8 ], which comprises the film of any one of [ 1] to [ 6 ], and/or the laminate of [ 7 ].

The flexible display device according to [ 8 ], which further comprises a touch sensor.

The flexible display device according to [ 8 ] or [ 9 ], which further comprises a polarizing plate.

According to the present invention, a polyimide resin film having improved dent resistance can be provided.

Drawings

FIG. 1 is a schematic view showing the respective directions when absorbance is measured.

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 spirit of the present invention. In the case where a plurality of upper limit values and lower limit values are described for specific parameters, any one of the upper limit values and lower limit values may be combined with the lower limit value to form a preferable numerical range.

[ polyimide resin film ]

The film of the present invention is a film comprising a polyimide resin. In this specification, a film containing a polyimide resin is also referred to as a polyimide resin film. In the film of the present invention, when any one of the directions in the plane of the film is taken as the X-axis, the direction in the plane of the film perpendicular to the X-axis is taken as the Y-axis, and the thickness direction of the film perpendicular to the X-axis is taken as the Z-axis, the absorption coefficient k in each axis direction obtained by the polarized ATR method using infrared rays is used _X 、k _Y K _Z And are calculated from the formulas (a) - (c)<cos ² (yX)>、<cos ² (yY)>A kind of electronic device with high-pressure air-conditioning system<cos ² (yZ)>Satisfies the formula (d) and (e).

|<cos ² (yX)>-<cos ² (yY)>|＜0.09 (d)

0≤<cos ² (yZ)>＜0.25 (e)

For example, the MD direction in the polyimide resin film may be defined as the X axis.

Here the number of the elements is the number,<cos ² (yX)>is above 0The value of 1 or less, (yX) represents the angle between the main axis (y axis) of the molecular chain of the polyimide resin contained in the film and the X axis.<cos ² (yX)>The closer to 1 the value of (c) means that the closer to 0 the angle of the y-axis to the X-axis.<cos ² (yY)>Similarly, (yY) represents the principal axis (Y axis) of the molecular chain of the polyimide resin contained in the film and the angle with the Y axis.<cos ² (yY)>The closer to 1 the value of (c) means that the closer to 90 the angle of the y-axis to the X-axis. It should be noted that the number of the substrates,<cos ² (yX)>the mean square value of the component in the X axis direction, which is an orientation vector formed by the molecular chain main axes, corresponds to the average distribution of the molecular chain main axes of 0 to 90 ° when the angle parallel to the X axis is 0 °.

The expression (d)<cos ² (yX)>-<cos ² (yY)>The closer the value of i is to 0, the closer the angle formed by the main axis (Y axis) of the molecular chain of the polyimide-based resin and the X axis is to the angle formed by the main axis (Y axis) of the molecular chain of the polyimide-based resin and the Y axis, which means that the orientation of the molecular chain of the polyimide-based resin in the X axis direction is not different from the orientation in the Y axis direction. In the film of the invention, | <cos ² (yX)>-<cos ² (yY)>Since the value of l is smaller than 0.09, the difference between the orientation in the X-axis direction and the orientation in the Y-axis direction is small, and the dent resistance in the polyimide resin film can be sufficiently improved. From the viewpoint of easy improvement of dent resistance in polyimide resin film |<cos ² (yX)〉-〈cos ² The value of (yY) is preferably 0.07 or less, more preferably 0.05 or less, and further preferably 0.03 or less.

Cos in the film of the invention ² As described in formula (e), the value of (yZ) is 0 or more and less than 0.25. The term (yZ) denotes an angle between a main axis (y axis) of a molecular chain of the polyimide resin contained in the film and a Z axis (thickness direction of the film). Cos ² The closer the value of (yZ) is to 0, the closer the angle between the principal axis (y-axis) of the molecular chain and the Z-axis is to 90 °. In the film of the invention, < cos ² (yZ) > is 0 or more and less than 0.25. If < cos ² (yZ) > less than 0.25, the polyimide resinThe orientation of the main axes of the molecular chains in the thickness direction does not excessively increase, and thus dent resistance in the polyimide resin film can be sufficiently improved. From the viewpoint of easily improving dent resistance in polyimide resin films, < cos- ² The value of (yZ) is preferably 0.24 or less, more preferably 0.23 or less.

In the film of the present invention, the absorption coefficient k can be calculated by applying a polarized ATR method using infrared rays _X 、k _Y K _Z . Specifically, the method described in S.Matsuda et al, journal of Polymer Science, part B, polymer Physics (journal of Polymer science, part B, polymer Physics), vol.41,418-428 (2003) can be used, and the method can be calculated as follows. The two incident lights of the infrared light (s-polarized light) in the s-polarized light state vibrating perpendicular to the incident surface and the infrared light (p-polarized light) in the p-polarized light state vibrating parallel to the incident surface were respectively incident at an incident angle of 30 ° so that the in-plane traveling direction was along the X-axis (or Y-axis), and were obtained as 1370cm ^-1 A of the absorbance of the peak of (C) _s,X 、A _s,Y 、A _p,X And A _p,Y . In the subscript, s and p refer to the direction of polarized light, and X, Y refers to the direction along which the incident surface travels. The obtained 4 IR absorbances were substituted into the following equation (p) to obtain X, Y of the film and the absorbance coefficient (k) in the Z-axis direction _X 、k _Y K _Z ). The values of α, β, and γ in equation (p) are obtained by substituting the refractive index and the incident angle into equation (q) in which α, β, and γ are coefficients indicating the contribution ratios of the light absorption coefficients in the respective axial directions in the polarization ATR.

※n ₁ : refractive index of sample (assumed to be 1.5), n ₂ : folding of GeEmissivity (4), θ=30°

In the film of the present invention, the formulae (d) and (e) may be satisfied by measuring at least 1 surface, in other words, the formulae (d) and (e) may be satisfied by measuring one surface or both surfaces. As for other characteristics described later, it is sufficient to measure one or both surfaces of the film of the present invention and to satisfy the characteristics.

The reason why the dent resistance can be improved in the polyimide resin film satisfying the formulas (d) and (e) is not clear, but it is considered that the molecular chains of the polyimide resin are oriented to the same extent in the X-axis direction and the Y-axis direction by satisfying the formula (e) in which the proportion of the molecular chains of the polyimide resin to be oriented in the in-plane direction is large compared with the thickness direction, and the molecular chains of the polyimide resin are considered to be oriented to the same extent in the X-axis direction and the Y-axis direction by satisfying the formula (d). In the polyimide resin film having such an alignment state, the proportion of the molecular chains which are two-dimensionally aligned in the in-plane direction of the film is considered to be large, and the proportion of the molecular chains of the polyimide resin which are aligned in a network or lattice form in the in-plane direction is considered to be large. When an input device such as a stylus pen contacts the surface of a film having such a structure, it is considered that the molecular chains of the polyimide resin exist in a network-like or lattice-like orientation in the plane, and thus deformation of the film surface is easily prevented, and in particular, even if the surface of the film is depressed by the stylus pen or the like, the surface has a high restoring force. Therefore, it is considered that the dent resistance of the film is easily improved in the film satisfying the above-mentioned formulas (d) and (e). It should be noted that the present invention is not limited to any of the above mechanisms.

Here, dent resistance in the present invention means the following characteristics: it is not easy to generate depressions (which are also called permanent depressions, plastic deformation) on the surface of the film that have not been restored due to external major factors such as the input device such as a stylus touching the film. Dent resistance can be evaluated by, for example, the methods described in examples.

As described above, < cos ² (yX)〉、〈cos ² (yY) cos ² (yZ) represents a polyimide resin film containing a polyimide with respect to each axial directionOrientation of the main axis of the molecular chain of the amine resin. Therefore, the orientation of the polyimide resin can be adjusted to satisfy the formulas (d) and (e) ² (yX)〉、〈cos ² (yY) cos ² (yZ). Preferably, the film is produced by the production methods (1) to (3) described later, whereby < cos ² (yX)〉、〈cos ² (yY) cos ² (yZ) > is adjusted to be within a desired range.

Cos in the film of the invention ² (yX) > preferably satisfies the formula (f).

0.3≤<cos ² (yX)>≤1.0 (f)

From the viewpoint of easily improving dent resistance of the film, < cos- ² (yX) > is preferably 0.3 or more, more preferably 0.35 or more, still more preferably 0.36 or more, and still more preferably 0.37 or more. In addition, < cos ² The ratio of (yX) is 1 or less, but is preferably 0.9 or less, more preferably 0.8 or less, still more preferably 0.7 or less, still more preferably 0.6 or less, and particularly preferably 0.5 or less, from the viewpoint of easiness in improving mechanical properties such as fracture strain.

Cos in the film of the invention ² (yY) > preferably satisfies the formula (g).

0.3≤<cos ² (yY)>≤1.0 (g)

From the viewpoint of easily improving dent resistance of the film, < cos- ² (yY) > is preferably 0.3 or more, more preferably 0.30 or more, further preferably 0.35 or more, further more preferably 0.36 or more, and particularly preferably 0.37 or more. In addition, < cos ² The ratio of (yY) is 1 or less, but is preferably 0.9 or less, more preferably 0.8 or less, still more preferably 0.7 or less, still more preferably 0.6 or less, and particularly preferably 0.5 or less, from the viewpoint of easiness in improving mechanical properties such as fracture strain.

In the film of the present invention, it is preferable that the formula (h) to formula (j) be satisfied when the heat shrinkage ratio before and after heating at 400 ℃ for 2 hours of the film in the X-axis direction is Sx and the heat shrinkage ratio at 400 ℃ for 2 hours of the film in the Y-axis direction is Sy.

10％≤Sx≤25％ (h)

10％≤Sy≤25％ (i)

|Sx-Sy|≤5％ (j)

In the case where the films satisfying the above-mentioned formulae (d) and (e) further satisfy the above-mentioned formulae (h) to (j), the film is preferable because it has not only high orientation but also reduced heat shrinkage and excellent dimensional stability.

The heat shrinkage (Sx) of the film in the X-axis direction before and after heating at 400 ℃ for 2 hours indicates how much the film shrinks in the X-axis direction before and after heating when the film is heated at 400 ℃ for 2 hours, and can be calculated by the following equation.

Heat shrinkage ratio (Sx) [% ] = { (length of film in X-axis direction before heating-length of film in X-axis direction after heating)/(length of film in X-axis direction before heating) } ×100

The heat shrinkage (Sx) preferably satisfies the formula (k).

10％≤Sx≤25％ (k)

From the viewpoint of easiness in improving the dent resistance of the film, sx is preferably 10% or more, more preferably 12% or more, further preferably 15% or more, and from the viewpoint of easiness in suppressing the occurrence of curling at the time of use, sx is preferably 24% or less, more preferably 23% or less, further preferably 22% or less.

The heat shrinkage (Sy) of the film in the Y-axis direction before and after heating at 400 ℃ for 2 hours indicates how much the film shrinks in the Y-axis direction before and after heating when the film is heated at 400 ℃ for 2 hours, and can be calculated by the following equation.

Heat shrinkage rate (Sy) [% ] = { (length of film in Y-axis direction before heating-length of film in Y-axis direction after heating)/(length of film in Y-axis direction before heating) } ×100

The heat shrinkage (Sy) preferably satisfies the formula (l).

10％≤Sy≤25％ (l)

From the viewpoint of easiness in improving the dent resistance of the film, sy is preferably 10% or more, more preferably 12% or more, further preferably 15% or more, and from the viewpoint of easiness in suppressing the occurrence of curling at the time of use, sy is preferably 24% or less, more preferably 23% or less, further preferably 22% or less.

From the viewpoint of improving the dent resistance of the film, sx and Sy calculated from the above formula preferably satisfy formula (m).

|Sx-Sy|≤5％ (m)

The value of Sx-Sy is preferably 5% or less, more preferably 4% or less, and still more preferably 3.5% or less.

The thickness of the film of the present invention may be suitably adjusted depending on the application, etc., and is usually 10 to 1,000. Mu.m, preferably 15 to 500. Mu.m, more preferably 20 to 400. Mu.m, still more preferably 30 to 200. Mu.m, still more preferably 40 to 200. Mu.m, particularly preferably 40 to 150. Mu.m, and even more preferably 45 to 100. Mu.m, from the viewpoint of easiness of further improvement of dent resistance. In the present invention, the thickness may be measured by a touch digital display meter.

The total light transmittance Tt of the film of the present invention is preferably 70% or more, more preferably 80% or more, still more preferably 85% or more, still more preferably 89% or more, and particularly preferably 90% or more. If the total light transmittance Tt of the film is equal to or greater than the lower limit, sufficient visibility is easily ensured when the film is incorporated into an image display device. The upper limit value of the total light transmittance Tt of the film is usually 100% or less. The film of the present invention is easy to exhibit high total light transmittance, and for example, can suppress the light emission intensity of a display element or the like required to obtain a constant luminance as compared with the case of using a film having low transmittance. Therefore, power consumption can be reduced. For example, when the film of the present invention is incorporated into an image display device, bright display tends to be obtained even when the light quantity of a backlight is reduced, and energy saving can be contributed.

The haze of the film is preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, further more preferably 0.8% or less, particularly preferably 0.5% or less, and even more preferably 0.3% or less. When the haze of the film is equal to or less than the upper limit, sufficient visibility is easily ensured when the film is incorporated into a flexible electronic device such as an image display device. The lower limit of the haze is not particularly limited, and may be 0% or more. The total light transmittance and haze may be determined in accordance with JIS K7105: 19811 or JIS K7361-1: 1997, using a haze computer.

The YI value of the film of the present invention is preferably 5 or less, more preferably 3 or less, further preferably 2.5 or less, further more preferably 2.3 or less, particularly preferably 2.0 or less, particularly preferably 1.9 or less, and most preferably 1.8 or less. When the YI value of the film is equal to or less than the upper limit, the transparency becomes good, and for example, when the film is used for a front panel of an image display device, the film can contribute to high visibility. The YI value is usually-5 or more, preferably-2 or more. The YI value may be calculated by measuring the transmittance of light of 300 to 800nm using an ultraviolet-visible near-infrared spectrophotometer, obtaining a tristimulus value (X, Y, Z), and based on the formula yi=100× (1.2769X-1.0592Z)/Y.

The film of the present invention is not particularly limited as long as it has an improved dent resistance as compared with a film that does not satisfy the features of the present invention, but has a dent resistance pencil hardness of preferably 2B or more, more preferably B or more, and still more preferably HB or more, from the viewpoint of easily imparting more excellent dent resistance. The dent-resistant pencil hardness can be determined by judging whether or not the dent generated on the film surface is recovered after a pencil of a specific hardness is reciprocated on the film at a pencil speed of 300 mm/min while applying a load (300 g) using a pencil hardness tester, and the highest pencil hardness before permanent dent is generated is taken as the dent-resistant pencil hardness. The details of the dent resistance test are as described in examples.

The film of the present invention preferably has excellent bending resistance. The number of bending resistance at room temperature of the film of the present invention is preferably 20 ten thousand times or more, more preferably 25 ten thousand times or more, and even more preferably 30 ten thousand times or more, measured at room temperature and humidity of 50% at r=1.5 mm. When the number of bending resistance is equal to or greater than the lower limit, the occurrence of cracks, breaks, creases, and the like can be effectively suppressed even if the bending is repeated. The number of bending resistance can be measured using a folding tester.

[ polyimide resin ]

The polyimide-based resin contained in the film of the present invention is a polyimide resin, a polyamideimide resin, or a polyamic acid resin that is a precursor of a polyimide resin and a polyamideimide resin. The film of the present invention may contain 1 kind of polyimide resin or 2 or more kinds of polyimide resins. From the viewpoint of film formability, the polyimide-based resin is preferably a polyimide resin or a polyamideimide resin, more preferably a polyamideimide resin.

The weight average molecular weight of the polyimide resin contained in the film of the present invention in terms of polystyrene is preferably 100,000 or more, more preferably 130,000 or more, still more preferably 150,000 or more, still more preferably 200,000 or more, from the viewpoints of improving dent resistance, suppressing yellowing with time, and improving bending resistance of the film. The weight average molecular weight of the polyimide resin in terms of polystyrene is preferably 800,000 or less, more preferably 600,000 or less, further preferably 500,000 or less, further more preferably 450,000 or less, from the viewpoints of ease of production of varnish and film forming property in producing a polymer material. The weight average molecular weight can be measured by Gel Permeation Chromatography (GPC). As the measurement conditions, the conditions described in examples can be used.

In one embodiment of the present invention, the polyimide-based resin is preferably a polyimide resin containing a structural unit represented by formula (1), or a polyamideimide resin containing a structural unit represented by formula (1) and a structural unit represented by formula (2).

[ in formula (1), X represents a 2-valent organic group, Y represents a 4-valent organic group, and X represents a bond ]

[ in formula (2), X and Z independently of each other represent a 2-valent organic group, and X represents a bond ]

The polyimide-based resin is more preferably a polyamide-imide resin having a structural unit represented by the formula (1) and a structural unit represented by the formula (2) from the viewpoints of improvement in dent resistance, transparency, and bendability of the film, and suppression of yellowing of the film. The following description of the formulas (1) and (2) relates to both polyimide resins and polyamideimide resins, and the description of the formula (2) relates to polyamideimide resins.

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

In one embodiment of the present invention, the polyimide-based resin is a polyimide resin having a structural unit represented by the formula (1), or a polyamideimide resin having a structural unit represented by the formula (1) and a structural unit represented by the formula (2), Y in the formula (1) independently represents a 4-valent organic group, preferably a 4-valent organic group having 4 to 40 carbon atoms. 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 number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. The polyimide resin according to an embodiment of the present invention may include a plurality of Y, and the plurality of Y may be the same or different from each other. Examples of Y include groups 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 the above formulae (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a 4-valent hydrocarbon group having 6 or less carbon atoms.

[ formula (20) to formula (29) ], represents a bond,

W ¹ represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-Ar-、-SO ₂ -、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH ₂ -Ar-、-Ar-C(CH ₃ ) ₂ -Ar-、-Ar-SO ₂ Ar-or-CO-O Ar-O-CO-. Ar represents an arylene group having 6 to 20 carbon atoms, the hydrogen atom of which may be substituted with a fluorine atom, and specific examples thereof include phenylene and biphenylene.]

Among the groups represented by the formulas (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29), the group represented by the formula (26), (28) or (29) is preferable, and the group represented by the formula (26) is more preferable from the viewpoint of improvement of dent resistance, surface hardness and flexibility of the film comprising the polyimide resin. In addition, from the viewpoints of improvement of dent resistance, surface hardness and flexibility of a film comprising the polyimide resin, W ¹ Independently of one another, preferably a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -or-C (CF) ₃ ) ₂ -, more preferably a single bond, -O-, -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -or-C (CF) ₃ ) ₂ -, more preferably a single bond, -O-, -C (CH) ₃ ) ₂ -or-C (CF) ₃ ) 2-, particularly preferably-O-or-C (CF) ₃ ) ₂ -。

In the above aspect, at least a part of the plurality of Y in the formula (1) is preferably a structural unit represented by the formula (5). If at least a part of Y in the formula (1) is a group represented by the formula (5), the resulting film tends to exhibit high dent resistance and high transparency. In addition, the high flexibility of the skeleton can improve the solubility of the polyimide resin in a solvent, suppress the viscosity of a varnish containing the polyimide resin to a low level, facilitate the processing of the film, and easily improve the optical properties of the obtained film.

[ in formula (5), R ¹⁸ ～R ²⁵ Independently of one another, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R ¹⁸ ～R ²⁵ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other,

and represents a connecting bond. ]

In the formula (5), R ¹⁸ 、R ¹⁹ 、R ²⁰ 、R ²¹ 、R ²² 、R ²³ 、R ²⁴ 、R ²⁵ Independently of each other, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include 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 in the formula (3), which are described later. Here, R is ¹⁸ ～R ²⁵ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other. From the viewpoint of surface hardness and flexibility of a film comprising the polyimide resin, R ¹⁸ ～R ²⁵ Further preferred independently of one another are hydrogen atoms, methyl groups, fluoro groups, chloro groups or trifluoromethyl groups, particularly preferred are hydrogen atoms or trifluoromethyl groups.

In a preferred embodiment of the present invention, the structural unit represented by formula (5) is a group represented by formula (5 '), i.e., at least a part of the plurality of Y's is a structural unit represented by formula (5 ').

In this case, the film containing the polyimide resin can have high transparency.

[ in formula (5'), the symbol represents a bond ]

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 polyimide-based resin is represented by formula (5), particularly formula (5'). When Y in the above range in the polyimide resin is represented by the formula (5), particularly the formula (5'), a film containing the polyimide resin can have high transparency, and the solubility of the polyimide resin in a solvent can be improved by a skeleton containing a fluorine element, so that the viscosity of a varnish containing the polyimide resin can be suppressed to a low level, and the film can be easily produced. It is preferable that 100 mol% or less of Y in the polyimide-based resin is represented by formula (5), particularly formula (5'). The polyimide resin may have the formula (5), particularly the formula (5'). The content of the structural unit represented by the formula (5) of Y in the polyimide-based resin may be, for example ¹ The measurement may be performed by H-NMR, or may be calculated from the ratio of the raw materials charged.

In one embodiment of the present invention in which the polyimide-based resin is a polyamideimide resin having a structural unit represented by formula (1) and a structural unit represented by formula (2), Z in formula (2) independently represents a 2-valent organic group. In one embodiment of the present invention, the polyamideimide resin may contain a plurality of Z's, which may be the same or different from each other. The 2-valent organic group preferably represents a 2-valent organic group having 4 to 40 carbon atoms. The aforementioned organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. Examples of the organic group of Z include a group in which 2 non-adjacent bonds in the bond between 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) are replaced with a hydrogen atom, and a 2-valent chain hydrocarbon group having 6 or less carbon atoms. From the viewpoint of improving the optical properties of the film, for example, lowering the YI value, the group represented by the non-adjacent 2 groups among the bonds between the groups represented by the formulas (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29) is preferably replaced with a hydrogen atom. In one embodiment of the present invention, the polyamideimide resin may contain 1 kind of organic group as Z, or may contain 2 or more kinds of organic groups as Z.

The organic group of Z is more preferably a 2-valent organic group represented by the formula (20 '), the formula (21'), the formula (22 '), the formula (23'), the formula (24 '), the formula (25'), the formula (26 '), the formula (27'), the formula (28 ') and the formula (29').

[ formula (20 ') -formula (29') ] ¹ And 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 a hydrocarbon group having 1 to 8 carbon atoms, a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a fluorine-substituted alkoxy group having 1 to 6 carbon atoms.

In the case where the polyamideimide resin has a structural unit represented by any one of the above-mentioned formulae (20 ') to (29') in the formula (2), the polyamideimide resin preferably has a structural unit derived from a carboxylic acid represented by the following formula (d 1) in addition to the structural unit, from the viewpoints of easiness in reducing the viscosity of the varnish, easiness in improving the film forming property of the varnish, and easiness in improving the uniformity of the obtained film.

[ in formula (d 1), R ²⁴ Independently of one another, represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R ²⁵ R represents ²⁴ or-C (= O) -, where represents a bond]

R ²⁴ Wherein R in formula (3) described below is each 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 ¹ ～R ⁸ And the exemplified groups. As the structural unit (d 1), specifically, R is exemplified ²⁴ R is R ²⁵ Structural units each of which is a hydrogen atom (structural units derived from a dicarboxylic acid compound), R ²⁴ Are all hydrogen atoms and R ²⁵ Structural units (structural units derived from tricarboxylic acid compounds) representing-C (=O) -, and the like.

In one embodiment of the present invention, the polyamideimide resin may contain a plurality of Z's, which may be the same or different from each other. In particular, from the viewpoint of easily improving the surface hardness and optical characteristics of the obtained film, at least a part of Z is preferably represented by formula (3 a), more preferably by formula (3).

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[ in formula (3 a), R ^g R is R ^h Independently of one another, represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R ^g R is R ^h The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other, A, m and (b) are the same as A, m and (b) in formula (3), and t and u are independently an integer of 0 to 4 ]

[ in formula (3), R ¹ ～R ⁸ Independently of one another, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R ¹ ～R ⁸ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other,

a independently of one another represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -S-, -CO-or-N (R) ⁹ )-，R ⁹ Represents a hydrogen atom, a 1-valent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom,

m is an integer of 0 to 4,

indicating a connection key

In the formula (3) and the formula (3 a), A independently represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -S-, -CO-or-N (R) ⁹ ) From the viewpoint of the bending resistance of the film obtained, preferably represents-O-or-S-, more preferably-O-.

R ¹ 、R ² 、R ³ 、R ⁴ 、R ⁵ 、R ⁶ 、R ⁷ R is R ⁸ Independently of each other, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. R is R ^g R is R ^h Independently of each other, a halogen 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 include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, and n-hexyl. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy, ethoxy, propyloxy, isopropyloxy, butoxy, isobutoxy, t-butoxy, pentyloxy, hexyloxy, cyclohexyloxy and the like. Examples of the aryl group having 6 to 12 carbon atoms include phenyl, tolyl, xylyl, naphthyl, and biphenyl. From the viewpoint of the surface hardness and flexibility of the film obtained from the varnish, R ¹ ～R ⁸ Independently of each other, preferably 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, R is ¹ ～R ⁸ 、R ^g R is R ^h The hydrogen atoms contained in the mixture can be halogenated independently of one anotherAnd (3) substitution of a prime atom.

R ⁹ A 1-valent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the 1-valent hydrocarbon group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, and n-decyl groups, which may be substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The polyimide-based resin may contain a plurality of kinds a, and the plurality of kinds a may be the same or different from each other.

T and u in the formula (3 a) are each independently an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

In the formulae (3) and (3 a), m is an integer in the range of 0 to 4, and if m is in the range, the stability of the varnish, and the flex resistance and elastic modulus of the film obtained from the varnish are easily improved. In the formulae (3) and (3 a), m is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, still more preferably 0 or 1, and still more preferably 0. When m is within this range, the film is easily improved in bending resistance and elastic modulus. In addition, Z may include 1 or 2 or more structural units represented by formula (3) or (3 a), and may include especially 2 or more structural units having different values of m, preferably 2 or 3 structural units having different values of m, from the viewpoints of improving the elastic modulus and bending resistance of the film, reducing YI value, and suppressing yellowing of the film. In this case, from the viewpoint that the film obtained from the varnish easily exhibits a high elastic modulus, bending resistance, and low YI value, it is preferable that the resin contains a structural unit represented by formula (3) or formula (3 a) in which m is 0 in Z, and more preferably contains a structural unit represented by formula (3) or formula (3 a) in which m is 1 in addition to the structural unit. It is also preferable that the composition further contains a structural unit represented by the above formula (d 1) in addition to the structural unit represented by the formula (2) having Z represented by the formula (3) where m is 0.

In a preferred embodiment of the invention, the treeFat has m=0 and R ⁵ ～R ⁸ Structural units which are independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms are represented by the formula (3).

In a more preferred embodiment of the present invention, the resin has m of 0 and R ⁵ ～R ⁸ Structural units which are independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms are represented by the formula (3). In this case, the dent resistance of the film of the present invention is easily further improved.

In another preferred embodiment of the present invention, the polyimide-based resin may have m=0 and R ⁵ ～R ⁸ The structural unit represented by the formula (3) is a structural unit represented by a hydrogen atom. In this case, the surface hardness and bending resistance of the film are easily improved, and the YI value is easily reduced.

In a preferred embodiment of the present invention, the proportion of the structural unit represented by the formula (3) or the formula (3 a) is preferably 20 mol% or more, more preferably 30 mol% or more, still more 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, still more preferably 80 mol% or less, and still more preferably 75 mol% or less, based on 100 mol% of the total of the structural units represented by the formula (1) and the structural unit represented by the formula (2) of the polyamideimide resin. When the ratio of the structural units represented by the formula (3) or (3 a) is equal to or greater than the lower limit, the surface hardness of the film obtained from the varnish is easily increased, and the bending resistance and the elastic modulus are easily improved. When the proportion of the structural unit represented by the formula (3) or the formula (3 a) is equal to or less than the upper limit, the increase in viscosity of the varnish containing the resin due to the inter-amide bond hydrogen bond derived from the formula (3) or the formula (3 a) is easily suppressed, and the processability of the film is improved.

In the case where the polyamideimide resin has a structural unit of formula (3) or (3 a) in which m=1 to 4, the ratio of the structural unit of formula (3) or (3 a) in which m is 1 to 4 is preferably 2 mol% or more, more preferably 4 mol% or more, still more preferably 6 mol% or more, still more preferably 8 mol% or more, preferably 70 mol% or less, still more preferably 50 mol% or less, still more preferably 30 mol% or less, still more preferably 15 mol% or less, and particularly preferably 12 mol% or less, based on 100 mol% of the total of the structural units of formula (1) and (2) of the polyamideimide resin. If the ratio of the structural units of formula (3) or formula (3 a) in which m is 1 to 4 is equal to or greater than the lower limit, the surface hardness and bending resistance of the film obtained from the varnish can be easily improved. If the ratio of the structural units of formula (3) or formula (3 a) in which m is 1 to 4 is equal to or less than the upper limit, the increase in viscosity of the resin-containing varnish due to the inter-amide bond hydrogen bond derived from formula (3) or formula (3 a) is easily suppressed, and the processability of the film is improved. The content of the structural unit represented by the formula (1), the formula (2), the formula (3) or the formula (3 a) may be, for example ¹ The measurement may be performed by H-NMR, or may be calculated from the ratio of the raw materials charged.

In a preferred embodiment of the present invention, the structural unit represented by formula (3) or (3 a) in which m is 0 to 4 is preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, still more preferably 50 mol% or more, and particularly preferably 70 mol% or more of Z in the polyamide-imide resin. When the lower limit or more of Z is a structural unit represented by formula (3) or formula (3 a) in which m is 0 to 4, the surface hardness of a film obtained from the varnish is easily improved, and bending resistance and elastic modulus are also easily improved. In addition, 100 mol% or less of Z in the polyamideimide resin may be a structural unit represented by formula (3) or formula (3 a) in which m is 0 to 4. The proportion of the structural unit represented by the formula (3) or the formula (3 a) in the resin, in which m is 0 to 4, may be, for example ¹ The measurement may be performed by H-NMR, or may be calculated from the ratio of the raw materials charged.

In a preferred embodiment of the present inventionThe formula (3) or (3 a) in which m is 1 to 4 is 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-imide resin. If the lower limit or more of Z of the polyamideimide resin is represented by the formula (3) or (3 a) in which m is 1 to 4, the surface hardness of the film obtained from the varnish is easily improved, and the bending resistance and the elastic modulus are easily improved. Further, it is preferable that Z is preferably 90 mol% or less, more preferably 70 mol% or less, still more preferably 50 mol% or less, still more preferably 30 mol% or less, represented by formula (3) or formula (3 a) in which m is 1 to 4. If the upper limit of Z is represented by the formula (3) or the formula (3 a) in which m is 1 to 4, the increase in viscosity of the varnish containing the resin due to the inter-amide bond hydrogen bond of the formula (3) or the formula (3 a) in which m is 1 to 4 is easily suppressed, and the processability of the film is improved. The proportion of the structural unit represented by the formula (3) or the formula (3 a) in the resin, in which m is 1 to 4, may be, for example ¹ The measurement may be performed by H-NMR, or may be calculated from the ratio of the raw materials charged.

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 and heterocyclic structures. In the organic group, the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. In one embodiment of the present invention, the polyimide resin or the polyamideimide resin may contain a plurality of X, which may be the same or different from each other. 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 groups represented by the above formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In the formulae (10) to (18), the "represents a bond,

V ¹ 、V ² v (V) ³ Independently of one another, represents a single bond, -O-, -S-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -CO-or-N (Q) -. Here, Q represents a 1-valent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the 1-valent hydrocarbon group having 1 to 12 carbon atoms include R ⁹ And the groups described hereinabove.

One example is: v (V) ¹ V (V) ³ Is a single bond, -O-or-S-, and V ² is-CH ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -or-SO ₂ -。V ¹ And V ² Bonding position with respect to each ring, and V ² And V ³ The bonding positions with respect to the respective rings are preferably meta or para with respect to the respective rings independently of each other, and more preferably para.

Among the groups represented by the formulas (10) to (18), the groups represented by the formulas (13), (14), (15), (16) and (17) are preferable, and the groups represented by the formulas (14), (15) and (16) are more preferable from the viewpoint of easily improving the surface hardness and bending resistance of the film obtained from the varnish. In addition, V from the viewpoint of easily improving the surface hardness and flexibility of the film obtained from the varnish of the present invention ¹ 、V ² V (V) ³ Preferably, each independently of the other, is a single bond, -O-or-S-, more preferably a single bond or-O-.

In a preferred embodiment of the present invention, at least a part of the plurality of X in the formulae (1) and (2) is a structural unit represented by the formula (4). If at least a part of the plurality of X in the formulas (1) and (2) is a group represented by the formula (4), the surface hardness and transparency of the film obtained from the varnish can be easily improved.

[ in formula (4), R ¹⁰ ～R ¹⁷ Independently of one another, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R ¹⁰ ～R ¹⁷ The hydrogen atoms contained in (a) independently of each other may be substituted by halogen atoms, and (b) represents a bond]

In the formula (4), R ¹⁰ 、R ¹¹ 、R ¹² 、R ¹³ 、R ¹⁴ 、R ¹⁵ 、R ¹⁶ R is R ¹⁷ Independently of each other, represents 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, and aryl groups having 6 to 12 carbon atoms in the formula (3). R is R ¹⁰ ～R ¹⁷ Independently of each other, preferably 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, where R ¹⁰ ～R ¹⁷ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. From the viewpoint of surface hardness, transparency and bending resistance of the film, R ¹⁰ ～R ¹⁷ Further preferably independently of one another, represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and still more preferably R ¹⁰ 、R ¹² 、R ¹³ 、R ¹⁴ 、R ¹⁵ R is R ¹⁶ Represents a hydrogen atom and R ¹¹ R is R ¹⁷ Represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, R being particularly preferred ¹¹ R is R ¹⁷ Represents methyl or trifluoromethyl.

In a preferred embodiment of the present invention, the structural unit represented by formula (4) is a structural unit represented by formula (4 '), that is, at least a part of the plurality of X's in the plurality of structural units represented by formulas (1) and (2) is a structural unit represented by formula (4 '). In this case, the fluorine-containing skeleton makes it easy to improve the solubility of the polyimide resin in a solvent. In addition, the viscosity of the varnish is easily reduced, and the processability of the film is easily improved. In addition, the skeleton containing fluorine element can easily improve the optical properties of the film obtained from the varnish.

/>

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 polyimide-based resin is represented by formula (4), particularly formula (4'). When X in the above range in the polyimide resin is represented by formula (4), particularly formula (4'), the solubility of the polyimide resin in a solvent can be easily improved by the skeleton containing fluorine element. In addition, the viscosity of the varnish is easily reduced, and the processability of a film obtained from the varnish is easily improved. In addition, the optical properties of the film obtained from the varnish can be easily improved by the skeleton containing fluorine element. It is preferable that 100 mol% or less of X in the polyimide-based resin is represented by formula (4), particularly formula (4'). X in the polyamide-imide resin may be formula (4), particularly formula (4'). The proportion of the structural unit represented by the formula (4) of X in the above resin may be, for example ¹ The measurement may be performed by H-NMR, or may be calculated from the ratio of the raw materials charged.

The polyimide-based resin may contain the structural unit represented by the formula (30) and/or the structural unit represented by the formula (31), or may contain the structural unit represented by the formula (30) and/or the structural unit represented by the formula (31) in addition to the structural units represented by the formulas (1) and (2).

In the formula (30), Y ¹ Independently of one another, are 4-valent organic groups, preferably organic groups in which the hydrogen atoms in the organic groups can be replaced by hydrocarbon groups or fluorine-substituted hydrocarbon groups. As Y ¹ Can exemplify [ ]20 A group represented by 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 formula (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a 4-valent hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of Y' s ¹ Multiple Y ¹ May be the same as or different from each other.

In the formula (31), Y ² For the 3-valent organic group, 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 is preferable. As Y ² Examples of the chain hydrocarbon group include a group in which any one of the bonds between the groups represented by the above-mentioned formulae (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29) is replaced with a hydrogen atom, and a 3-valent chain hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of Y' s ² Multiple Y ² May be the same as or different from each other.

In the formula (30) and the formula (31), X ¹ X is X ² Independently of one another, are 2-valent organic groups, preferably organic groups in which the hydrogen atoms in the organic groups can be replaced by hydrocarbon groups or fluorine-substituted hydrocarbon groups. As X ¹ X is X ² Examples of the above-mentioned formulae (10), (11), (12), (13), (14), (15), (16), (17) and (18) are as follows

A group represented; a group in which a hydrogen atom in the groups represented by the above formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In one embodiment of the present invention, the polyimide-based resin includes a structural unit represented by formula (1) and/or formula (2), and a structural unit represented by formula (30) and/or formula (31) which are optionally included. From the viewpoints of the optical properties, surface hardness, and bending resistance of the film obtained from the varnish, the polyimide-based resin is based on all the structural units represented by the formulas (1) and (2) and, if necessary, the formulas (30) and (31) The structural units represented by the formulas (1) and (2) are preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more. In the polyimide resin, the structural units represented by the formulae (1) and (2) are usually 100% or less based on the total structural units represented by the formulae (1) and (2) and, if necessary, the formulae (30) and/or (31). The above ratio may be, for example ¹ The measurement may be performed by H-NMR, or may be calculated from the ratio of the raw materials charged. From the same viewpoint, when the polyimide-based resin is a polyimide resin, the structural unit represented by the formula (1) is preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more, based on the total structural units contained in the polyimide resin. In the case where the polyimide-based resin is a polyamide-imide resin, the structural units represented by the formulas (1) and (2) are preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more, based on the total structural units contained in the polyimide resin.

In one embodiment of the present invention, the content of the polyimide-based resin contained in the film of the present invention is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, and still more preferably 95 parts by mass or less, based on 100 parts by mass of the film. When the content of the polyimide resin is within the above range, the dent resistance of the film is easily improved, and the optical characteristics and the elastic modulus are easily improved.

The content of the structural unit represented by the formula (2) in the polyamideimide resin is preferably 0.1 mol or more, more preferably 0.5 mol or more, still more preferably 1.0 mol or more, still more preferably 1.5 mol or more, preferably 6.0 mol or less, still more preferably 5.0 mol or less, and still more preferably 4.5 mol or less, based on 1 mol of the structural unit represented by the formula (1). When the content of the structural unit represented by the formula (2) is not less than the lower limit, the surface hardness of the film obtained from the varnish is easily increased. In addition, when the content of the structural unit represented by the formula (2) is equal to or less than the upper limit, thickening due to hydrogen bonding between amide bonds in the formula (2) is easily suppressed, and thus the processability of the film is improved.

In a preferred embodiment of the present invention, the polyimide-based resin may contain a halogen atom such as a fluorine atom which can be introduced through the fluorine-containing substituent or the like described above. When the polyimide resin contains a halogen atom, the elastic modulus of a film containing the polyimide resin is easily increased, and the YI value is reduced. When the elastic modulus of the film is high, the film is easy to suppress the occurrence of damage, wrinkles, and the like in the film when the film is used in, for example, a flexible display device. In addition, if the YI value of the film is low, the transparency and visibility of the film can be easily improved. The halogen atom is preferably a fluorine atom. Examples of the fluorine-containing substituent that is preferable for the polyimide-based resin to contain a fluorine atom include a fluorine group and a trifluoromethyl group.

The content of the halogen atom in the polyimide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and even more preferably 5 to 30% by mass, based on the mass of the polyimide resin. If the content of halogen atoms is not less than the lower limit, the elastic modulus of the film containing the polyimide resin is easily further improved, the water absorption is reduced, the YI value is further reduced, and the transparency and visibility are further improved. If the content of halogen atoms is not more than the upper limit, the resin can be easily synthesized.

The imidization ratio of the polyimide resin is preferably 90% or more, more preferably 93% or more, and even more preferably 96% or more. The imidization ratio is preferably not less than the lower limit described above, from the viewpoint of easily improving the dent resistance of the film containing the polyimide resin and easily improving the optical characteristics. The upper limit of the imidization ratio is 100% or less. The imidization ratio represents a ratio of the molar amount of imide bonds in the polyimide resin to a value 2 times the molar amount of structural units derived from the tetracarboxylic acid compound in the polyimide resin. When the polyimide-based resin contains a tricarboxylic acid compound, the imidization ratio represents a ratio of the molar amount of imide bonds in the polyimide resin and the polyamideimide resin to the sum of the molar amount of structural units derived from the tetracarboxylic acid compound and the molar amount of structural units derived from the tricarboxylic acid compound in the polyimide-based resin, which is 2 times the molar amount of the structural units derived from the tetracarboxylic acid compound. The imidization rate can be determined by IR method, NMR method, or the like, and for example, in the NMR method, the imidization rate can be determined by the method described in examples.

The polyimide resin may be commercially available. Examples of the commercially available polyimide resins include Neopulim (registered trademark) manufactured by Mitsubishi gas chemical corporation and KPI-MX300F manufactured by Hecun industries, ltd.

< method for producing polyimide-based resin >

The polyimide resin can be produced using, for example, a tetracarboxylic acid compound and a diamine compound as main raw materials, and the polyamide-imide resin can be produced using, for example, a tetracarboxylic acid compound, a dicarboxylic acid compound and a diamine compound as main raw materials. The dicarboxylic acid compound preferably contains at least a compound represented by the formula (3 ").

[ in formula (3) ], R ¹ ～R ⁸ Independently of one another, represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R ¹ ～R ⁸ The hydrogen atoms contained in (a) may be substituted with halogen atoms independently of each other,

a represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ )2-、-C(CF ₃ ) ₂ -、-SO ₂ -, -S-, -CO-or-N (R) ⁹ )-，

R ⁹ Represents a hydrogen atom, a 1-valent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom,

m is an integer of 0 to 4,

R ³¹ r is R ³² Independently of each other, represents hydroxy, methoxy, ethoxyA radical, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy or a chlorine atom. ]

In the case of using a dicarboxylic acid compound in the production of a polyimide resin, it is preferable to sufficiently purify the polyimide resin so that the polyimide resin does not contain an unreacted dicarboxylic acid compound. By using a polyimide resin having high purity, the content of dicarboxylic acid in a varnish containing the polyimide resin can be easily adjusted to 10ppm or less.

In a preferred embodiment of the present invention, the dicarboxylic acid compound is a compound represented by formula (3') wherein m is 0. As the dicarboxylic acid compound, a compound represented by formula (3 ") in which a is an oxygen atom may be used in addition to a compound represented by formula (3") in which m is 0. In another preferred embodiment, the dicarboxylic acid compound is represented by R ³¹ R is R ³² A 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 diamine, aromatic diamine, and a mixture thereof. In the present embodiment, the term "aromatic diamine" means a diamine in which an amino group is directly bonded to an aromatic ring, and a part of the structure thereof may include an aliphatic group or other substituent. The aromatic ring may be a single ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited thereto. Among them, benzene rings are preferable. The term "aliphatic diamine" means a diamine in which an amino group is directly bonded to an aliphatic group, and a part of the structure may include an aromatic ring and other substituents.

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. They may be used alone or in combination of 2 or more.

As the aromatic diamine, there is used, examples thereof 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, and 4,4' -diaminodiphenyl ether, 3' -diaminodiphenyl ether, 4' -diaminodiphenyl sulfone, 3' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene 4,4' -diaminodiphenyl ether, 3' -diaminodiphenyl ether, 4' -diaminodiphenyl sulfone 3,4' -diaminodiphenyl sulfone, 3' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, aromatic diamines having 2 or more aromatic rings such as 9, 9-bis (4-amino-3-fluorophenyl) fluorene. They may be used alone or in combination of 2 or more.

The aromatic diamine is preferably 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, and 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 (TFMB), 4' -bis (4-aminophenoxy) biphenyl, more preferably 4,4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 4' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, and 2, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4,4 '-diaminobiphenyl (TFMB), 4' -bis (4-aminophenoxy) biphenyl. They may be used alone or in combination of 2 or more.

Among the diamine compounds, 1 or more selected from the group consisting of aromatic diamines having a biphenyl structure is preferably used from the viewpoints of high surface hardness, high transparency, high flexibility, high bending resistance, and low coloring of the film. More preferably, 1 or more selected from the group consisting of 2,2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) benzidine, 4 '-bis (4-aminophenoxy) biphenyl and 4,4' -diaminodiphenyl ether is used, and still more preferably, 2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl (TFMB) is used.

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

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride include 4,4 '-oxydiphthalic dianhydride, 3',4 '-benzophenone tetracarboxylic dianhydride, and 2,2',3,3 '-benzophenone tetracarboxylic dianhydride, 3',4 '-biphenyl tetracarboxylic dianhydride, 2',3 '-biphenyl tetracarboxylic dianhydride, 3',4,4 '-diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4' - (hexafluoroisopropylidene) diphthalic dianhydride (sometimes described as 6 FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4'- (terephthaloxy) diphthalic dianhydride, 4' - (isophthaloxy) diphthalic dianhydride. Examples of the monocyclic aromatic tetracarboxylic dianhydride include 1,2,4, 5-benzene tetracarboxylic dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic dianhydride include 2,3,6, 7-naphthalene tetracarboxylic dianhydride.

Among them, preferred examples include 4,4 '-oxybisphthalic anhydride, 3',4 '-benzophenone tetracarboxylic dianhydride, 2',3,3 '-benzophenone tetracarboxylic dianhydride, 3',4 '-biphenyl tetracarboxylic dianhydride, 2',3 '-biphenyl tetracarboxylic dianhydride, 3',4,4 '-diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4' - (hexafluoroisopropylidene) diphthalic dianhydride (6 FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4'- (terephthaloxy) diphthalic dianhydride, 4' - (isophthaloxy) diphthalic dianhydride, 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride bis (2, 3-dicarboxyphenyl) methane dianhydride, 4'- (terephthaloyl) diphthalic dianhydride, and 4,4' - (isophthaloyl) diphthalic dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride and 4,4' - (terephthaloyl) diphthalic dianhydride. They may be used alone or in combination of 2 or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include a cycloalkane tetracarboxylic dianhydride such as 1,2,4, 5-cyclohexane tetracarboxylic dianhydride, 1,2,3, 4-cyclobutane tetracarboxylic dianhydride, 1,2,3, 4-cyclopentane tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, dicyclohexyl-3, 3', 4' -tetracarboxylic dianhydride, and positional isomers thereof. They may be used alone or in combination of 2 or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3, 4-butanetetracarboxylic dianhydride, and 1,2,3, 4-pentanetetracarboxylic dianhydride, which may be used alone or in combination of 2 or more. In addition, cyclic aliphatic tetracarboxylic dianhydrides and acyclic aliphatic tetracarboxylic dianhydrides may be used in combination.

Among the above tetracarboxylic dianhydrides, from the viewpoints of high surface hardness, high transparency, high flexibility, high bending resistance, and low colorability of the film, preferably 4,4 '-oxybisphthalic dianhydride, 3',4 '-benzophenone tetracarboxylic dianhydride, 3',4,4 '-biphenyltetracarboxylic dianhydride, 2',3 '-biphenyltetracarboxylic dianhydride, 3',4,4 '-diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 4' - (hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof, more preferably 3,3', 4' -biphenyl tetracarboxylic dianhydride and 4,4'- (hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof, still more preferably 4,4' - (hexafluoroisopropylidene) diphthalic dianhydride (6 FDA).

Examples of the dicarboxylic acid compound used for producing the resin include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and similar acid chloride compounds and acid anhydrides thereof, and 2 or more kinds of the dicarboxylic acid compounds may be used in combination. Specific examples thereof include terephthalic acid; 2, 5-bis (trifluoromethyl) terephthalic acid; isophthalic acid; 2, 5-dimethylterephthalic acid; 2, 5-dimethoxy terephthalic acid; naphthalene dicarboxylic acid; 4,4' -biphenyl dicarboxylic acid; 3,3' -biphenyl dicarboxylic acid; 2,2 '-bis (trifluoromethyl) -4,4' -biphenyl dicarboxylic acid; dicarboxylic acid compound of chain hydrocarbon having 8 or less carbon atoms and 2 benzoic acids each having a single bond, -CH ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -or phenylene linked compounds, and acid chloride compounds thereof. Among these dicarboxylic acid compounds, 4' -oxybisbenzoic acid, terephthalic acid, isophthalic acid, 2-methoxy terephthaloyl chloride, 2, 5-dimethylterephthalic acid, 2, 5-dimethoxy terephthalic acid, 2, 5-bis (trifluoromethyl) terephthalic acid, 2' -bis (trifluoromethyl) -4,4' -biphenyl dicarboxylic acid and their are preferable from the viewpoint of easiness of improvement of dent resistance, hardness, YS and optical characteristics of the filmMore preferably 2-methoxy terephthaloyl chloride (hereinafter sometimes referred to as OMTPC), 4' -oxybis (benzoyl chloride) (hereinafter sometimes referred to as OBBC), 2, 5-dimethyl terephthaloyl chloride, 2, 5-dimethoxy terephthaloyl chloride, 2, 5-bis (trifluoromethyl) terephthaloyl chloride, terephthaloyl dichloride (hereinafter sometimes referred to as TPC), isophthaloyl dichloride (hereinafter sometimes referred to as IPC), and still more preferably OBBC, TPC, IPC, 2-methoxy terephthaloyl chloride, 2, 5-dimethyl terephthaloyl chloride, and 2, 5-dimethoxy terephthaloyl chloride.

The polyimide resin may be one obtained by reacting a tetracarboxylic acid, a tricarboxylic acid, and an anhydride and a derivative thereof in addition to the tetracarboxylic acid compound, within a range that does not impair various physical properties of the film.

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

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acid, aliphatic tricarboxylic acid, and similar acid chloride compounds and acid anhydrides thereof, and 2 or more kinds of the tricarboxylic acid compounds may be used in combination. Specific examples thereof include anhydrides of 1,2, 4-benzenetricarboxylic acid; acyl chloride compounds of 1,3, 5-benzene tricarboxylic acid; 2,3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; phthalic anhydride and benzoic acid through single bond, -O-, -CH ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -or phenylene linked compounds.

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 desired ratio of each structural unit of the 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, and is, for example, 5 to 350 ℃, preferably 20 to 200 ℃, and more preferably 25 to 100 ℃. The reaction time is also not particularly limited, and is, for example, about 30 minutes to 10 hours. The reaction may be carried out under an inert atmosphere or under reduced pressure, as required. In a preferred embodiment, the reaction is carried out under an atmosphere of normal pressure and/or inert gas while stirring. 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, GBL, gamma-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 DMAc and DMF; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof, and the like. Among them, from the viewpoint of solubility, an amide-based solvent can be preferably used.

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) such as N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine and N-propylhexahydroazepine; alicyclic amines (polycyclic) 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-picoline (2-picoline), 3-picoline (3-picoline), 4-picoline (4-picoline), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-lutidine, 2,4, 6-trimethylpyridine, 3, 4-cyclopentenopyridine, 5,6,7, 8-tetrahydroisoquinoline, and isoquinoline. In addition, from the viewpoint of facilitating imidization, it is preferable to use an acid anhydride together with an imidization catalyst. The acid anhydride may be a general acid anhydride used in imidization, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic acid anhydrides such as phthalic anhydride.

The polyimide resin can be separated (separated and purified) by a common method such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a separation means combining these, and preferably, a large amount of an alcohol such as methanol is added to a reaction solution containing the transparent imide resin to precipitate the resin, followed by concentration, filtration, drying, and the like.

(Filler)

The film of the present invention may contain at least 1 filler in addition to the polyimide-based resin. Examples of the filler include organic particles and inorganic particles, and preferably include inorganic particles. Examples of the inorganic particles include metal oxide particles such as silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (sometimes referred to as ITO), antimony oxide, and cerium oxide, metal fluoride particles such as magnesium fluoride and sodium fluoride, and among them, silica particles, zirconia particles, and alumina particles are preferable, and silica particles are more preferable. These fillers may be used alone or in combination of 2 or more.

The average primary particle diameter of the filler (preferably 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 more 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 obtained optical laminate are improved. The average primary particle diameter of the filler can be measured 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.

When the film of the present invention contains a filler (preferably silica particles), the content of the filler (preferably silica particles) is usually 0.1 mass% or more, preferably 1 mass% or more, more preferably 5 mass% or more, still more preferably 10 mass% or more, still more preferably 20 mass% or more, particularly preferably 30 mass% or more, and preferably 60 mass% or less, relative to the total amount of the film. If the content of the filler is not less than the lower limit, the elastic modulus of the obtained film is easily increased. In addition, when the content of the filler is not more than the upper limit, the storage stability of the varnish can be improved, and the optical properties of the obtained film can be easily improved.

(ultraviolet absorber)

The film of the present invention may contain 1 or 2 or more ultraviolet absorbers. The ultraviolet absorber may be appropriately selected from those commonly 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 the group consisting of benzophenone-based compounds, salicylate-based compounds, benzotriazole-based compounds, and triazine-based compounds. By incorporating the ultraviolet absorber in the film of the present invention, deterioration of the polyimide resin can be suppressed, and thus visibility of the film can be improved.

In the present specification, the term "compound" refers to a derivative of a compound to which the "compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a parent skeleton and a substituent bonded to the benzophenone.

When the film of the present invention contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 1 mass% or more, more preferably 2 mass% or more, further preferably 3 mass% or more, preferably 10 mass% or less, more preferably 8 mass% or less, further preferably 6 mass% or less, relative to the total amount of the film. The appropriate content varies depending on the ultraviolet absorber used, and when the content of the ultraviolet absorber is adjusted so that the light transmittance at 400nm becomes about 20 to 60%, the light resistance of the film is improved, and a film having high transparency can be obtained.

(other additives)

The film of the present invention may further contain additives other than the filler and the ultraviolet absorber. Examples of the other additives include antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, leveling agents, and the like. When the other additive is 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.

[ method for producing film of the present invention ]

The method for producing a film of the present invention is not particularly limited as long as a film satisfying the above characteristics can be obtained, and examples thereof include the following production methods (1) to (3):

the manufacturing method (1) at least comprises the following steps:

(a) A varnish preparation step of preparing a resin composition comprising at least the polyimide resin and a solvent,

(b) A coating step of coating a varnish on a substrate to form a coating film,

(c1) A step of obtaining a film by predrying and drying the coating film, and

(d) A step of biaxially stretching the obtained film to obtain a film of the present invention;

the manufacturing method (2) comprises at least the following steps:

(b) A coating step of coating a varnish on a substrate to form a coating film,

(c 2-1) a step of peeling off the film after predrying the coating film, and

(c 2-2) a step of subjecting the peeled film to biaxial stretching and final drying to obtain the film of the present invention; and

the manufacturing method (3) comprises at least the following steps:

(b) Coating step of forming a coating film by applying varnish to a substrate

(c 3-1) a step of subjecting the coating film to preliminary drying and final drying on a substrate to obtain a film formed on the substrate, and

(e) And a step of peeling the film from the substrate to obtain the film of the present invention.

In the varnish preparation step (a) in the production methods (1) to (3), the polyimide resin is dissolved in a solvent, and if necessary, the filler, an additive such as an ultraviolet absorber, and the like are added thereto, followed by stirring and mixing, to prepare a varnish. In the case of using silica particles as the filler, a silica sol obtained by replacing a dispersion of a silica sol containing silica particles with a solvent in which the resin is soluble, for example, a solvent used in the preparation of a varnish described below, may be added to the resin.

The solvent used in the preparation of the varnish is not particularly limited as long as the resin can be dissolved. 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, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among them, an amide-based solvent or a lactone-based solvent is preferable. These solvents may be used singly or in combination of two or more. The varnish may contain water, an alcohol-based solvent, a ketone-based solvent, an acyclic ester-based solvent, an ether-based solvent, or the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 15% by mass.

In the coating step (b) in the production methods (1) to (3), a varnish is applied to the substrate by a known coating method to form a coating film. Examples of known coating methods include roll coating methods such as bar coating, reverse coating, and gravure coating, die coating, comma coating, lip coating, spin coating, screen coating, spray coating, dipping, spraying, and casting.

Examples of the substrate include a metal-based material such as SUS plate, and a resin-based material such as PET film, PEN film, polyamide resin film, other polyimide resin film, other polyamide-imide resin film, cyclic olefin polymer film, acrylic film, or glass. Among them, glass, PET film, SUS plate, and the like are preferable from the viewpoint of excellent smoothness and heat resistance, and glass and PET film are more preferable from the viewpoints of adhesion to the film of the present invention and cost and easiness in producing a film excellent in dent resistance.

In the case of the production method (3), since the preliminary drying and the main drying are performed in a state where the coating film is formed on the substrate in the subsequent step (c 3-1), a substrate having high heat resistance, which does not cause softening, deformation, or the like even when heated to the temperature of the main drying, is used. Examples of such a substrate include inorganic substrates such as glass plates, metal substrates such as SUS plates, and highly heat-resistant resin films such as polyimide films.

In the case of the production method (1), in the step (c 1), the coating film formed in the step (b) is subjected to preliminary drying and main drying to obtain a film. The film can be formed by drying the obtained coating film and peeling it from the support material, but from the viewpoint of heat resistance and peeling easiness of the base material, the following steps are generally carried out: the film is peeled from the substrate in a state of containing a certain degree of solvent after the pre-drying, and the peeled film is further subjected to main drying. The drying of the coating film may be carried out at a temperature of 50 to 350℃in general, and for example, it may be carried out at a temperature of about 50 to 200℃and then the film may be peeled off from the substrate and finally dried at a temperature of about 150 to 300 ℃. Drying of the coating film may be performed under an inert atmosphere or under reduced pressure, as required. In the film finally obtained, a part of the solvent contained in the varnish may remain in a small amount. The amount of the solvent contained in the film is preferably 1.5% or less, more preferably 1.2% or less, further preferably 1.1% or less, further more preferably 1.0% or less, based on the mass of the film. The lower limit of the amount of the solvent is preferably 0% or more, more preferably 0.02% or more, still more preferably 0.1% or more, and still more preferably 0.3% or more.

In the case of the production method (1), in the step (d), the film after the main drying is simultaneously biaxially stretched or sequentially biaxially stretched, preferably simultaneously biaxially stretched, whereby the film of the present invention satisfying the above-mentioned formulas (d) and (e) can be produced. The heating temperature at the time of simultaneous biaxial stretching or sequential biaxial stretching is preferably 220 ℃ or higher, more preferably 230 ℃ or higher, still more preferably 240 ℃ or higher, still more preferably 250 ℃ or higher, and particularly preferably 260 ℃ or higher, from the viewpoint of easy production of the film of the present invention satisfying the formulae (d) and (e). In addition, from the viewpoint of easily preventing the modification of the polyimide-based resin contained in the film and easily preventing the orientation of the polyimide-based resin contained in the film in the thickness direction, the temperature is preferably lower than 340 ℃, more preferably 320 ℃ or lower, still more preferably 300 ℃ or lower, and still more preferably 290 ℃ or lower. The heating temperature may be adjusted according to the relationship with the tension applied to the film when biaxially stretching the film to obtain a film satisfying the above-mentioned formulas (d) and (e). For example, when the tension is large, even if the heating temperature is high, the polyimide resin main chain is easily prevented from being oriented in the thickness direction. From the viewpoint of reducing the load on the biaxial stretching apparatus and easily preventing the film from breaking, it is preferable to heat at the above temperature and simultaneously biaxially stretch, and it is considered that it is easy to efficiently produce the film of the present invention satisfying the formulae (d) and (e).

The conditions for biaxial stretching are not particularly limited as long as the film of the present invention satisfying the above-mentioned formulae (d) and (e) can be produced, but from the viewpoint of easy incorporation of < cos ] ² (yX)〉、〈cos ² (yY) cos ² From the standpoint of adjusting (yZ) to a predetermined relationship, biaxial stretching is preferably performed by the following method. The film produced through the steps (a), (b) and (c 1) is often in the form of a film roll. The film is drawn from the film roll, and cut into a shape that can be stretched by a biaxial stretching machine, for example, a quadrangle of a predetermined size. Then, holding devices are attached to the four edges of the film at regular intervals, and stretching is performed in both directions under a heating environment. As the gripping device, a gripping device commonly used in a film manufacturing apparatus such as a pin holder, a jig, and a film chuck can be used.

The stretching ratio in the biaxial stretching may be preferably 1.05 to 1.25 times, more preferably 1.1 to 1.20 times, in each of 2 directions orthogonal to each other of the film. The stretching ratio was obtained as a ratio of the width of the stretched film (excluding the portion to be gripped) to the width of the film excluding the portion to be gripped. The stretching ratios in two orthogonal directions (for example, MD direction and TD direction) are preferably the same. For example, the stretching ratio in both directions perpendicular to each other may be preferably 1.05 to 1.25 times, and more preferably 1.1 to 1.20 times.

As the apparatus for biaxially stretching a film, a biaxial stretching apparatus having a holding apparatus for holding, for example, 4 sheets of film is preferably used. Here, in the biaxial stretching method in which a film is stretched in the TD direction while being stretched in the MD direction by a plurality of rolls having different rotational speeds, it is considered that it is difficult to obtain the film of the present invention satisfying the above-mentioned formulas (d) and (e) based on the following estimation. That is, in such biaxial stretching, the film is usually stretched in the MD direction by passing the film through a plurality of rollers having different rotational speeds, but the polyimide-based resin film is not easily stretched, and therefore it is difficult to achieve stretching in the MD direction sufficient to obtain the film of the present invention by using a force of a degree such that the film passes through a plurality of rollers having different rotational speeds. Therefore, even if the above operation is performed, it is considered that it is difficult to sufficiently affect the orientation of the polyimide resin contained in the film. It is to be noted that, when the film obtained by such biaxial stretching satisfies the specific formula of the present invention, the film is certainly included in the scope of the present invention.

In the case of the production method (2), in the step (c 2-1), the coating film formed in the step (b) is pre-dried, and then the film is peeled off, and in the step (c 2-2), the peeled film is subjected to main drying while being biaxially stretched, thereby obtaining the film of the present invention. For example, the film may be peeled from the substrate after predrying at a temperature of about 50 to 200 ℃, and the peeled film may be subjected to primary drying at a temperature higher than 200 ℃, for example, about 210 to 340 ℃, preferably about 210 to 340 ℃ and lower than 340 ℃ under conditions including at least a step of simultaneous biaxial stretching or sequential biaxial stretching at a temperature of preferably 220 ℃ or higher, more preferably 230 ℃ or higher, still more preferably 240 ℃ or higher.

In the steps (c 2-1) and (c 2-2), for example, the film after the preliminary drying may be taken out in the form of a film roll, and the film may be taken out from the film roll, cut into a shape that can be stretched by a biaxial stretching machine, for example, a quadrangle of a predetermined size, and stretched in the biaxial direction while performing the main drying. As the conditions for biaxial stretching, the same conditions as those of the production method (1) can be used.

In the case of the production method (3), in the step (c 3-1), the coating film applied to the substrate through the steps (a) and (b) is subjected to preliminary drying and main drying on the substrate. From the viewpoint of easy production of the film of the present invention satisfying the above expression, this step is performed directly in a state where the coating film is applied to the substrate. By performing the preliminary drying and the main drying so as not to peel the coating film from the substrate, a large strain is not easily generated in the coating film, and the main chain of the polyimide resin is easily oriented in the in-plane direction, so that a film satisfying the formula of the present invention can be easily produced.

In the case of the production method (3), in the pre-drying step, the resin varnish applied to the substrate is dried at a temperature of 50 ℃ or higher below the boiling point of the solvent in the resin varnish, for example, to form a resin coating film on the substrate. In one embodiment of the present invention, at least 50 mass% of the solvent contained in the resin varnish applied to the substrate may be removed by pre-drying, and the concentration of the solid content of the resin coating film after the pre-drying step is not particularly limited, but is preferably 50 to 95 mass%, more preferably 55 to 90 mass%. For example, the preliminary drying is preferably performed until the amount of the residual solvent becomes preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 20% by mass or less. Next, in the main drying step, the resin coating film formed on the substrate after the pre-drying step is further dried at a temperature of at least 10 ℃, for example, at least 150 ℃, which is lower than the boiling point of the solvent contained in the resin varnish, thereby forming a resin coating film on the substrate. The solid content concentration of the resin coating film after the main drying step is not particularly limited, but is preferably 80 to 100% by mass, more preferably 90 to 99.9% by mass, still more preferably 95 to 99.9% by mass, still more preferably 97 to 99.9% by mass, and particularly preferably 98 to 99.9% by mass.

In the case of the production methods (1) and (2), the preliminary drying and the main drying may be performed by placing the coating film applied to the substrate or the film peeled off from the substrate after the preliminary drying in a heating apparatus such as a full-air oven heated to a predetermined temperature, or by heating the coating film and the substrate or the peeled film on a heating plate. In the case of the production method (3), it is particularly preferable to perform the pre-drying step with a large solvent content in an environment which is not easily affected by the air flow during drying, from the viewpoint of ease of producing a film satisfying the above formula. From this viewpoint, in the case of the production method (3), it is preferable to perform the pre-drying step by heating the substrate coated with the coating film at least on a heating plate such as a hot plate.

In the production methods (1) to (3), the pre-drying temperature is preferably 50 ℃ or higher, more preferably 80 ℃ or higher, still more preferably 100 ℃ or higher, preferably 200 ℃ or lower, more preferably 150 ℃ or lower, from the viewpoint of maintaining the quality of the film surface. The pre-drying time is appropriately selected depending on the type of solvent contained in the resin varnish, the pre-drying temperature, and the like, and is preferably 5 to 150 minutes, more preferably 10 to 120 minutes, and even more preferably 20 to 60 minutes. The pre-drying may be performed under an inert atmosphere or under reduced pressure, as required.

In the production methods (1) to (3), the total drying temperature is preferably 150 ℃ or higher, more preferably 180 ℃ or higher, further preferably 200 ℃ or higher, from the viewpoint of removing the solvent in the film, and is preferably 300 ℃ or lower, more preferably 250 ℃ or lower, further preferably 220 ℃ or lower, from the viewpoint of preventing the film from being colored. The main drying temperature is a temperature higher than the pre-drying temperature, preferably 30 ℃ or higher than the pre-drying temperature, more preferably 40 ℃ or higher than the pre-drying temperature, and even more preferably 50 ℃ or higher than the pre-drying temperature. The main drying time is appropriately selected depending on the solid content concentration of the resin coating film after the preliminary drying, and is preferably 1 to 120 minutes, more preferably 5 to 80 minutes, and still more preferably 10 to 40 minutes. The drying may be carried out under an inert atmosphere or under reduced pressure, as required.

[ film of the present invention and laminate comprising the same ]

The use of the film of the present invention is not particularly limited, and can be used for various purposes. In addition, at least 1 functional layer may be laminated on one or both sides of the film of the present invention. The present invention also provides a laminate comprising the film of the present invention and a functional layer laminated on at least one side of the film.

The laminate of the present invention has at least 1 functional layer on at least one surface of the film of the present invention. Examples of the functional layer include a hard coat layer, an undercoat layer, a gas barrier layer, an ultraviolet absorbing layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer. The functional layer may be used alone or in combination of two or more.

The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100. Mu.m. If the thickness of the hard coat layer is within the above range, the following tends to occur: the impact resistance can be improved, and the bending resistance is not easily reduced, and the problem of curling caused by curing shrinkage is not easily generated. The hard coat layer may be formed by curing a hard coat layer composition containing a reactive material capable of forming a crosslinked structure by irradiation with active energy rays or application of heat energy, and is preferably a layer formed by irradiation with active energy rays. The active energy ray is defined as an energy ray capable of decomposing a compound that generates an active species to generate an active species, and includes visible light, ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays, electron rays, and the like, and preferably includes ultraviolet rays. The hard coat composition contains at least 1 polymer 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 a functional group capable of undergoing radical polymerization, and examples thereof include a group containing a carbon-carbon unsaturated double bond, specifically, a vinyl group, a (meth) acryl group, and the like. In the case where 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 in 1 molecule of the radical polymerizable compound is preferably 2 or more from the viewpoint of improving the hardness of the hard coat layer. The radically polymerizable compound is preferably a compound having a (meth) acryloyl group, more specifically, a compound called a polyfunctional 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 a molecular weight of several (meth) acryloyl groups in a molecule 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, from the viewpoint of high reactivity.

The cation polymerizable compound is a compound having a cation polymerizable group such as an epoxy group, an oxetanyl group, a vinyl ether group, or the like. The number of the cation polymerizable groups in 1 molecule of the cation polymerizable compound is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.

Among the cationically polymerizable compounds, compounds having at least 1 of an epoxy group and an oxetane group as the cationically polymerizable group are preferable. From the viewpoint of small shrinkage accompanying the polymerization reaction, cyclic ether groups such as epoxy groups and oxetanyl groups are preferable. In addition, the compound having an epoxy group in a cyclic ether group has the following advantages: compounds of various structures are readily available; the durability of the obtained hard coating is not adversely affected; compatibility with the radical polymerizable compound is also easily controlled. In addition, the oxetanyl group in the cyclic ether group has the following advantages over the epoxy group: the polymerization degree is easily increased; accelerating the network formation rate obtained from the cationically polymerizable compound of the obtained hard coat layer; even in the region where the radical polymerizable compound is mixed, an independent network is formed so that the unreacted monomer does not remain in the film; etc.

Examples of the cationic polymerizable compound having an epoxy group include alicyclic epoxy resins obtained by epoxidizing polyglycidyl ethers of polyhydric alcohols having an alicyclic ring or compounds containing a cyclohexene ring or a cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or a peroxy acid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyols or alkylene oxide adducts, polyglycidyl esters of aliphatic long-chain polybasic acids, homopolymers and copolymers of glycidyl (meth) acrylates; glycidyl ethers produced by reacting bisphenol such as bisphenol a, bisphenol F, and hydrogenated bisphenol a, or an alkylene oxide adduct or a derivative thereof such as caprolactone adduct with epichlorohydrin, and glycidyl ether type epoxy resins derived from bisphenol such as Novolac epoxy resins; etc.

The aforementioned hard coat composition may further comprise a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radical polymerization initiators, and cationic polymerization initiators, and may be appropriately selected and used. These polymerization initiators are decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, and undergo radical polymerization and cationic polymerization.

The radical polymerization initiator may be any initiator capable of releasing a substance that initiates radical polymerization by at least either irradiation with active energy rays or heating. Examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, azo compounds such as azobisisobutyronitrile, and the like.

Examples of the active energy ray radical polymerization initiator include a Type1 radical polymerization initiator that generates radicals by decomposition of molecules and a Type2 radical polymerization initiator that generates radicals by hydrogen abstraction reaction in the presence of a tertiary amine, and these can be used alone or in combination.

The cationic polymerization initiator may be any one capable of releasing a substance that initiates cationic polymerization by at least either irradiation with active energy rays or heating. As the cationic polymerization initiator, an aromatic iodonium salt, an aromatic sulfonium salt, a cyclopentadienyl iron (II) complex or the like can be used. The cationic polymerization initiator can initiate cationic polymerization by either or both of irradiation with active energy rays and heating depending on the structure.

The polymerization initiator may be contained in an amount of preferably 0.1 to 10 mass% relative to 100 mass% of the whole hard coat layer composition. When the content of the polymerization initiator is within the above range, the curing can be sufficiently performed, and the mechanical properties and adhesion of the finally obtained coating film can be made to be within good ranges, and further, adhesion failure, cracking phenomenon and curling phenomenon due to curing shrinkage tend to be less likely to occur.

The hard coat composition may further comprise one or more selected from the group consisting of solvents and additives.

The solvent may be any solvent which is known as a solvent for a hard coat composition in the art and which can dissolve or disperse the polymerizable compound and the polymerization initiator, and may be used within a range not to impair the effects of the present invention.

The aforementioned additives may further contain inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, and the like.

The ultraviolet absorbing layer is a layer having an ultraviolet absorbing function, and is composed of a main material selected from the group consisting of an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, and an ultraviolet absorber dispersed in the main material.

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

The adhesive layer may be a layer called a pressure-sensitive adhesive (Pressure Sensitive Adhesive, PSA) that is bonded to the object by pressing. The pressure-sensitive adhesive may be an adhesive which is "a substance having adhesiveness at ordinary temperature and adhering to an adherend under light pressure" (JIS K6800), or may be a capsule-type adhesive which is "an adhesive capable of maintaining stability until the film is broken by an appropriate means (pressure, heat, etc.) (JIS K6800) in which a specific component is contained in a protective film (microcapsule).

The hue control layer is a layer having a function of controlling hue, and is a layer capable of controlling a film to a target hue. The hue control 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, iron oxide red, titanium oxide-based calcined 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, petrolatum (threne) -based compounds, and diketopyrrolopyrrole-based compounds; such pigments as barium sulfate and calcium carbonate; and dyes such as basic dyes, acid dyes, and mordant dyes.

The refractive index adjusting layer is a layer having a function of adjusting a refractive index, and is, for example, a layer having a refractive index different from that of a single layer of the film of the present invention, and capable of imparting a predetermined refractive index to a laminate including the film. The refractive index adjusting layer may be, for example, a resin layer containing a resin appropriately selected and a pigment further used according to circumstances, 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 pigment may have an average primary particle diameter of 0.1 μm or less. By making the average primary particle diameter of the pigment 0.1 μm or less, diffuse reflection of light transmitted through the refractive index adjusting layer can be prevented, thereby preventing a decrease in transparency. Examples of the metal used for the refractive index adjusting layer include metal oxides or 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.

In one embodiment of the present invention, the film of the present invention and/or the laminate of the present invention may have a protective film on at least one side (one side or both sides). For example, in the case of the laminate of the present invention having a functional layer on one side of the film of the present invention, the protective film may be laminated on the surface of the film side of the present invention or the surface of the functional layer side, or may be laminated on both the film side and the functional layer side of the present invention. In the case of a laminate having functional layers on both surfaces of the film of the present invention, the protective film may be laminated on one functional layer side surface or on both functional layer side surfaces. The protective film is not particularly limited as long as it is a film that temporarily protects the surface of the film or functional layer of the present invention and is a releasable film that can protect the surface of the film or functional layer. Examples of the protective film include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; the polyolefin resin film such as polyethylene and polypropylene film, the acrylic resin film, and the like are preferably selected from the group consisting of polyolefin resin film, polyethylene terephthalate resin film, and acrylic resin film. In the case where the film and/or the laminate of the present invention has 2 protective films, the protective films may be the same or different.

The thickness of the protective film is not particularly limited, but is usually 10 to 120. Mu.m, preferably 15 to 110. Mu.m, more preferably 20 to 100. Mu.m. In the case where the film of the present invention and/or the laminate of the present invention has 2 protective films, the thicknesses of the respective protective films may be the same or different.

The film of the present invention and/or the laminate of the present invention can be suitably used as a front panel (sometimes referred to as a window film) of a display device, particularly a flexible display device, particularly a front panel of a rollable display or a foldable display. That is, the film of the present invention and/or the laminate of the present invention is preferably an optical film or an optical laminate, more preferably a film or a laminate for a front panel of a display device, and even more preferably a film or a laminate for a front panel of a flexible display device. The front panel has a function of protecting a display element of the flexible display device. The flexible display device is a display device that is used in association with operations such as repeatedly bending and repeatedly winding the image display device. Such a front panel of a flexible display device used in conjunction with repeated bending operations and the like is required to have high bending resistance, in particular, high folding resistance. In addition, the front panel is required to have high visibility. Films and laminates for front panels of image display devices, particularly front panels of flexible display devices, are required to have high visibility and high bending resistance as compared with films for substrates of image display devices used in the interior of image display devices. For example, the film of the present invention or the laminate of the present invention preferably has the total light transmittance, haze and/or YI value as described above from the viewpoint of easy improvement of visibility in use for a front panel of a flexible display device, and the number of bending resistance times as described above is preferably satisfied from the viewpoint of easy improvement of bending resistance, particularly folding resistance in use for a front panel of a flexible display device. Examples of the display device include a television, a smart phone, a mobile phone, a car navigation system, a tablet computer, a portable game machine, electronic paper, an indicator, a bulletin board, a timepiece, and a wearable device such as a smart watch. As the flexible display, a display device having a flexible characteristic, for example, a television, a smart phone, a mobile phone, a smart watch, or the like can be given. Examples of the flexible display device include all image display devices having flexible characteristics, such as a rollable display and a foldable display as described above. The rollable display is an image display device in which an image display portion including a front panel is rolled up, and the image display portion is usable in a state where the image display portion is pulled out to be flat or curved, and is rolled up or the like 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 is usable in a state in which the image display portion is unfolded to be flat or curved, and is operated such that folding is performed every time the display is used. Such an image display device in which the operations such as winding and bending are repeatedly performed is called a flexible image display device.

[ Flexible display device ]

The present invention also provides a flexible display device comprising the film of the present invention and/or the laminate of the present invention. The film of the present invention and/or the laminate of the present invention is preferably used as a front panel, sometimes referred to as a window film, in a flexible display device. The flexible display device is formed of a laminate for a flexible display device and an organic EL display panel, and the laminate for a flexible display device is disposed on the viewing side with respect to the organic EL display panel and is configured to be bendable. The laminate for a flexible display device may further include a polarizing plate and a touch sensor, and the lamination order thereof is arbitrary, but it is preferable that the window film, the polarizing plate, and the touch sensor are laminated in this order or the window film, the touch sensor, and the polarizing plate are laminated in this order from the viewing side. If the polarizing plate is present on the viewing side of the touch sensor, the pattern of the touch sensor is less likely to be visually recognized, and visibility of the display image is improved, which is preferable. The components may be laminated using an adhesive, a binder, or the like. The touch panel 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 >

As described above, the flexible display device of the present invention preferably further includes a polarizing plate, particularly a circularly polarizing plate. The circular 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 retardation plate on a linear polarizing plate. For example, can be used to: the external light is converted into right circularly polarized light, and the external light reflected by the organic EL panel into left circularly polarized light is blocked, and only the light emitting component of the organic EL is transmitted, thereby suppressing the influence of the reflected light, and making it easy to view an image. In order to achieve the circularly polarized light function, the absorption axis of the linear polarizing plate and the slow axis of the λ/4 retardation plate are theoretically required to be 45 °, but in practical applications, 45±10°. The linear polarizing plate and the λ/4 retardation plate are not necessarily stacked adjacently, and the relationship between the absorption axis and the slow axis may satisfy the above-described range. It is preferable to achieve complete circularly polarized light at all wavelengths, but this is not necessary in practice, and thus circular polarizers in the present invention also include elliptical polarizers. It is also preferable to further laminate a lambda/4 phase difference film on the viewing side of the linear polarizing plate to convert the outgoing light into circularly polarized light, thereby improving visibility in a state where the polarized sunglasses are worn.

The linear polarizing plate is a functional layer having a function of blocking polarized light of a vibration component perpendicular thereto by passing light vibrating in the transmission axis direction. The linear polarizing plate may be a linear polarizer alone or a linear polarizer and a protective film attached to at least one surface thereof. The thickness of the linear polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness of the linear polarizing plate is within the above range, the flexibility of the linear polarizing plate tends to be less likely to be lowered.

The linear polarizer may be a film type polarizer produced by dyeing and stretching a polyvinyl alcohol (hereinafter, may be abbreviated as PVA) film. The polarizing performance is exhibited by aligning the dichroic dye by adsorbing the dichroic dye such as iodine to the PVA film aligned by stretching or stretching the PVA film in a state of being adsorbed to the PVA film. In the production of the film polarizer, the film polarizer may further include swelling, crosslinking with boric acid, washing with an aqueous solution, drying, and the like. The stretching and dyeing steps may be performed as a PVA-based film alone or in a laminate with another film such as polyethylene terephthalate. The thickness of the PVA film used is preferably 10 to 100. Mu.m, and the stretching ratio is preferably 2 to 10 times.

Further, as another example of the polarizer, a liquid crystal coated polarizer formed by coating a liquid crystal polarizing composition may be mentioned. The liquid crystal polarizing composition may contain 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 can exhibit a high polarization performance when it has an alignment state of a high order such as smectic. The liquid crystalline compound preferably has a polymerizable functional group.

The dichroic dye compound is a dye which is aligned with the liquid crystal compound and exhibits dichroism, and may have a polymerizable functional group, or the dichroic dye itself may have liquid crystallinity.

Any compound contained in the liquid crystal polarizing composition has a polymerizable functional group. The liquid crystal polarizing composition may further contain 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 can be produced by coating a liquid crystal polarizing composition on an alignment film to form a liquid crystal polarizing layer. The liquid crystal polarizing layer may be formed to have a smaller thickness than the film polarizer, and the thickness thereof is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.

The alignment film can be produced, for example, by: the composition for forming an alignment film is applied to a substrate, and alignment is imparted by rubbing, polarized light irradiation, or the like. The composition for forming an alignment film may contain an alignment agent, a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like. Examples of the orientation agent include polyvinyl alcohols, polyacrylates, polyamide acids, and polyimides. When an alignment agent having an alignment property by irradiation with polarized light is used, an alignment agent containing a cinnamate group is preferably used. The Mw of the polymer used as the alignment agent is, for example, about 10,000 ～ 1,000,000. The thickness of the alignment film is preferably 5 to 10,000nm, and more preferably 10 to 500nm in terms of sufficiently exhibiting an alignment controlling force.

The liquid crystal polarizing layer may be laminated by being peeled from the substrate and transferred, or the substrate may be directly laminated. The substrate preferably functions as a transparent substrate for a protective film, a retardation film, and a window film.

The protective film may be a transparent polymer film, and the same materials and additives as those used for the transparent substrate of the window film may be used. The protective film may be a coated protective film obtained by applying and curing a cationic curing composition such as an epoxy resin or a radical curing composition such as an acrylic acid ester. The protective film may contain a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, an optical brightening agent, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like, as necessary. The thickness of the protective film is preferably 200 μm or less, more preferably 1 to 100 μm. When the thickness of the protective film is within the above range, the flexibility of the film tends to be less likely to be lowered.

The λ/4 retardation plate is a film that imparts a phase difference of λ/4 in a direction (in-plane direction of the film) orthogonal to the traveling direction of the incident light. The lambda/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. The lambda/4 phase difference plate may contain a phase difference regulator, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, an optical brightening agent, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like, as required.

The thickness of the stretched phase difference plate is preferably 200 μm or less, more preferably 1 to 100 μm. When the thickness of the stretched phase difference plate is within the above range, the flexibility of the stretched phase difference plate tends to be less likely to be lowered.

Further, another example of the λ/4 retardation plate is a liquid crystal coated retardation plate formed by coating a liquid crystal composition.

The liquid crystal composition contains a liquid crystalline compound exhibiting a liquid crystalline state such as nematic, cholesteric, smectic, or the like. The liquid crystalline compound has a polymerizable functional group.

The liquid crystal composition may further contain 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 a substrate and curing the composition to form a liquid crystal retardation layer, similarly to the liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed with a smaller thickness than the stretching type retardation plate. The thickness of the liquid crystal polarizing layer is preferably 0.5 to 10. Mu.m, more preferably 1 to 5. Mu.m.

The liquid crystal coated retardation plate may be laminated by peeling it from a substrate and then transferring it, or the substrate may be directly laminated. The substrate preferably functions as a transparent substrate for a protective film, a retardation film, and a window film.

In addition, as another method, a technique of obtaining a wide-band λ/4 phase difference plate by combining it with a λ/2 phase difference plate is also known (for example, japanese patent application laid-open No. 10-90521, etc.). The lambda/2 phase difference plate can also be manufactured by using the same materials and methods as the lambda/4 phase difference plate. The combination of the stretching type retardation plate and the liquid crystal coating type retardation plate is arbitrary, but the thickness can be made thin by using the liquid crystal coating type retardation plate in each case.

For the circularly polarizing plate, a method of laminating a positive C plate is known in order to improve visibility in an oblique direction (for example, japanese patent application laid-open No. 2014-224837 and the like). The positive C plate may be a liquid crystal coated type retardation plate or a stretched type retardation plate. The retardation in the thickness direction of the retardation plate is preferably-200 to-20 nm, more preferably-140 to-40 nm.

[ touch sensor ]

As described above, the flexible display device of the present invention preferably further includes a touch sensor. The touch sensor is used as an input means. The touch sensor may be of various types such as a resistive film type, a surface elastic wave type, an infrared type, an electromagnetic induction type, and a capacitance type, and preferably of a capacitance type.

The capacitive touch sensor may be divided into an active region and an inactive region located at a peripheral portion of the active region. The active region is a region corresponding to a region (display portion) on the display panel where a screen is displayed, and is a region where a touch by a user is sensed, and the inactive region is a region corresponding to a region (non-display portion) in the display device where a screen is not displayed. The touch sensor may include: a substrate having a flexible characteristic; a sensing pattern formed in an active region of the substrate; and each sensing line formed in the inactive region of the substrate and connecting the sensing pattern to an external driving circuit via a pad portion. As the substrate having the flexible characteristic, the same material as the transparent substrate of the window film can be used.

[ adhesive layer ]

The layers (window film, circularly polarizing plate, touch sensor) forming the laminate for a flexible display device may be bonded by an adhesive. As the adhesive, a conventionally used adhesive such as an aqueous adhesive, an organic solvent-based adhesive, a solvent-free adhesive, a solid adhesive, a solvent-volatile adhesive, a water-based solvent-volatile adhesive, a moisture-curable adhesive, a heat-curable adhesive, an anaerobic-curable, an active energy ray-curable adhesive, a curing agent-mixed adhesive, a hot-melt adhesive, a pressure-sensitive adhesive (adhesive), a rewet adhesive, and the like can be used, and an aqueous solvent-volatile adhesive, an active energy ray-curable adhesive, and an adhesive can be preferably used. The thickness of the adhesive layer can be appropriately adjusted depending on the required adhesive force or the like, and is preferably 0.01 to 500. Mu.m, more preferably 0.1 to 300. Mu.m. In the laminate for a flexible display device, a plurality of adhesive layers are present, and the thickness and the type of each adhesive layer may be the same or different.

As the aqueous solvent-volatile adhesive, a polyvinyl alcohol polymer, a water-soluble polymer such as starch, a polymer in a water-dispersed state such as an ethylene-vinyl acetate emulsion or a styrene-butadiene emulsion can be used as a main polymer. In addition to the above-mentioned main agent polymer and water, a crosslinking agent, a silane-based compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, and the like may be blended. In the case of bonding with the aqueous solvent-volatile adhesive, the aqueous solvent-volatile adhesive may be injected between the layers to be bonded, and the layers to be bonded may be bonded and then dried, thereby imparting adhesiveness thereto. When the aqueous solvent-volatile adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 10. Mu.m, more preferably 0.1 to 1. Mu.m. When the aqueous solvent-volatile adhesive is used in a plurality of layers, the thickness and type of each layer may be the same or different.

The active energy ray-curable adhesive may be formed by curing an active energy ray-curable composition containing a reactive material capable of forming an adhesive layer by irradiation with active energy rays. The active energy ray-curable composition may contain at least 1 polymer of a radical polymerizable compound and a cation polymerizable compound similar to those contained in the hard coat composition. The radical polymerizable compound may be the same as the radical polymerizable compound in the hard coat composition.

The cation polymerizable compound may be the same as that in the hard coat composition.

The cationically polymerizable compound used in the active energy ray-curable composition is preferably an epoxy compound. In order to reduce the viscosity as an adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 20. Mu.m, more preferably 0.1 to 10. Mu.m. When the active energy ray-curable adhesive is used to form a plurality of adhesive layers, the thickness and type of each layer may be the same or different.

The binder may be classified into an acrylic binder, a urethane binder, a rubber binder, a silicone binder, and the like, depending on the base polymer. The adhesive may contain, in addition to the main polymer, 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. The adhesive composition is obtained by dissolving and dispersing the components constituting the adhesive in a solvent, and is applied to a substrate and then dried, thereby forming an adhesive layer. The adhesive layer may be formed directly or an adhesive layer formed separately on the substrate may be transferred. In order to cover the adhesive surface before bonding, a release film is also preferably used. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.1 to 500. Mu.m, more preferably 1 to 300. Mu.m. In the case of using the above adhesive in plural layers, the thickness and the kind of each layer may be the same or different.

Examples (example)

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples. Unless otherwise specified, "%" and "parts" in examples and comparative examples refer to "% by mass" and "parts by mass", respectively.

< determination of weight average molecular weight >

Gel Permeation Chromatography (GPC) measurement

(1) Pretreatment method

The following eluent was added to the polyimide resin film so that the concentration of the polyimide resin became 2mg/mL, the mixture was heated at 80℃for 30 minutes with stirring, cooled, and then filtered through a 0.45 μm membrane filter, and the resulting solution was used as a measurement solution.

(2) Measurement conditions

Column: TSKgel. Alpha. -2500 ((7) 7.8mm diameter. Times.300 mm). Times.1 root,. Alpha. -M ((13) 7.8mm diameter. Times.300 mm). Times.2 root) manufactured by TOSOH Co., ltd

Eluent: dimethylformamide DMF (containing 10mmol/L lithium bromide)

Flow rate: 1.0 mL/min

A detector: RI detector

Column temperature: 40 DEG C

Injection amount: 100 mu L

Molecular weight standard: standard polystyrene

< measurement of imidization Rate >

By passing through ¹ The imidization ratio was determined by H-NMR measurement as follows.

(1) Pretreatment method

A film containing a polyimide resin was dissolved in deuterated dimethyl sulfoxide (DMSO-d 6) to prepare a polyimide resin concentration solution of 2 mass%, and the obtained solution was used as a measurement sample.

(2) Measurement conditions

Measurement device: JEOL 400MHz NMR apparatus JNM-ECZ400S/L1

Standard substance: DMSO-d ₆ (2.5ppm)

Sample temperature: room temperature

Cumulative number of times: 256 times

Relaxation time: 5 seconds

(3) Imidization rate analysis method

(imidization Rate of polyimide resin)

Obtained by using a measurement sample containing polyimide resin ¹ In the H-NMR spectrum, the integral value of benzene proton A from the structure which does not change before and after imidization among the observed benzene protons was set as Int _A . The integral value of the amide proton derived from the amic acid structure remaining in the polyimide resin was set to Int _B . From these integrated values, the imidization ratio of the polyimide resin was determined based on the following formula.

Imidization ratio (%) =100× (1-Int) _B /Int _A )

(imidization Rate of Polyamide imide resin)

Obtained from a measurement sample containing a polyamideimide resin ¹ In the H-NMR spectrum, the integral value of benzene proton C derived from the structure which does not change before and after imidization and is not affected by the structure derived from the amic acid structure remaining in the polyamideimide resin in the observed benzene proton was set as Int _C . Further, the integral value of benzene proton D, which is derived from the structure that does not change before and after imidization and is affected by the structure derived from the amic acid structure remaining in the polyamideimide resin, among the observed benzene protons is set as Int _D . Based on the obtained Int _C Int _D The beta value was obtained by the following equation.

β＝Int _D /Int _C

Next, the β value of the above formula and the imidization rate of the polyimide resin of the above formula were obtained for a plurality of polyamide-imide resins, and the following relational expression was obtained from these results.

Imidization ratio (%) =k×β+100

In the above-described correlation equation, k is a constant.

Substituting β into the correlation formula gives the imidization ratio (%) of the polyamideimide resin.

< measurement of viscosity of varnish >

According to JIS K8803: 2011, using a Brookfield company model E viscometer DV-II+Pro. The measurement temperature was set at 25 ℃.

< measurement of film thickness >

The film thickness was measured using an ABS digital display scale (manufactured by Mitutoyo, "ID-C112 BS").

< measurement of residual solvent amount of film >

As a measurement device for TG-DTA, hitachi High-Tech Science Corporation TG/DTA6300 was used. About 20mg of a sample was obtained from the produced transparent resin film. The sample was warmed up from room temperature to 120℃at a warming rate of 10℃per minute, and after holding at 120℃for 5 minutes, the sample was warmed up (heated) to 400℃at a warming rate of 10℃per minute, and the mass change of the sample was measured.

Based on the TG-DTA measurement result, the mass reduction rate S (% by mass) from 120℃to 250℃was calculated according to the following formula.

S (mass%) =100- (W1/W0) ×100

[ in the formula, W0 is the mass of the sample after 5 minutes at 120 ℃, and W1 is the mass of the sample at 250 ℃.

The calculated mass reduction rate S was used as the residual solvent amount S (mass%) in the transparent resin film. When a protective film is laminated on the surface of the transparent resin film opposite to the support, the protective film is peeled off, and then the amount of residual solvent is measured.

< YI value >

According to JIS K7373: 2006, YI value (Yellow Index) of the film was measured using an ultraviolet visible near infrared spectrophotometer "V-670" manufactured by Japan Spectrophotometer (Inc.). After background measurement in a state without a sample, a film was set on a sample holder, and transmittance was measured for light of 300 to 800nm, tristimulus values (X, Y, Z) were obtained, and YI values were calculated based on the following formula.

YI＝100×(1.2769X-1.0592Z)/Y

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

In a 1L separable flask equipped with stirring blades, 313.57g of DMAc was charged under a nitrogen atmosphere, and a necessary amount of ion-exchanged water was charged so that the water content became 700 ppm. Subsequently, 18.53g (57.86 mmol) of TFMB was added thereto, and the mixture was stirred at room temperature to dissolve TFMB in DMAc. Next, 6FDA 7.64g (17.19 mmol) was added to the flask, cooled to 10℃and stirred for 16 hours. Next, 1.69g (5.73 mmol) of OBBC and 6.28g (30.93 mmol) of TPC were added to the flask, and the mixture was stirred at 10℃for 30 minutes. Subsequently, 313.57g of DMAC having a water content adjusted to 700ppm was added, followed by stirring for 10 minutes, 0.70g (3.45 mm. Mu.l) of TPC was further added to the flask, followed by stirring at 10℃for 30 minutes, and then 0.0367g (0.115 mm. Mu.l) of TFMB was further added, followed by stirring for 2 hours. Next, 5.18g (40.11) of diisopropylethylamine, 3.74g (40.11 mmol) of 4-methylpyridine and 12.29g (120.30 mmol) of acetic anhydride were added to the flask, and the mixture was stirred at 10℃for 30 minutes. Then, the reaction mixture was stirred while maintaining the temperature at 70℃for 3 hours by using an oil bath for 30 minutes from 10℃to 50℃and 10 minutes from 50℃to 60℃and 10 minutes from 60℃to 65℃and then stepwise from 65℃to 70℃and 10 minutes from 70℃to 75℃respectively, thereby obtaining a reaction mixture. The reaction solution obtained was cooled to room temperature, poured into a large excess of methanol in a linear manner, the precipitate was filtered, and the precipitate was taken out as a solid and immersed in methanol for 6 hours. Then, after the solid was filtered again, it was washed with a large excess of methanol. Then, the solid material was dried under reduced pressure at 80℃for 24 hours to obtain a polyamideimide resin (1). The obtained polyamideimide resin (1) had a Mw weight-average molecular weight of 295,000 and an imidization ratio of 98.1%.

< production example 2: preparation of varnish (1)

The polyamide-imide resin (1) was added to GBL, stirred at room temperature for 24 hours to completely dissolve it, and sumisuorb 340 (UVA absorber) and Sumiplast Violet B (BA, bluing agent) were added to the obtained mixed solution in amounts of 5.7phr and 15ppm, respectively, relative to the polyamide-imide resin, to obtain a varnish (1) having a viscosity of 40,000cps and a solid content of 8.5%.

< manufacturing example 3: preparation of varnish (2)

The polyamideimide resin (1) was added to GBL and stirred at room temperature for 24 hours to completely dissolve, thereby obtaining a varnish (2) having a viscosity of 39,000cps and a solid content of 9.0%.

< production example 4: preparation of Polyamide-imide resin (2)

313.6g of DMAc was charged into a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere, and 17.43g (54.43 mmol) of TFMB was added while stirring at room temperature to dissolve the DMAc. Next, 6FDA 2.493g (5.610 mmol) and 6.942g (11.22 mmol) of tetracarboxylic dianhydride (TMPBP-TME) represented by the following formula (A) were added to the flask, and the mixture was stirred at room temperature for 16 hours.

Then, 7.975g (39.28 mmol) of TPC and 313.6g of DMAc were charged into the flask, and stirred at room temperature for 2 hours. Next, 5.077g (39.28 mmol) of N, N-diisopropylethylamine and 12.03g (117.84 mmol) of acetic anhydride, and 3.658g (39.28 mmol) of 4-methylpyridine were added to the flask, and after stirring at room temperature for 30 minutes, the temperature was raised to 70℃using an oil bath, and further stirring was performed for 3 hours, to obtain a reaction solution. The obtained reaction solution was cooled to room temperature, stirred, and then methanol 1.385 times the mass of the reaction solution was slowly added thereto, and then water 0.6924 times the mass of the reaction solution was slowly added thereto. The precipitate was taken out and washed with methanol. Next, the precipitate was dried under reduced pressure at 80 ℃ to obtain a polyamideimide resin (2). The Mw of the polyamide-imide resin (2) was 330,000, and the imidization rate was 99.0%.

< production example 5: preparation of varnish (3)

DMAc was added to the polyamideimide resin (2) and stirred at room temperature for 24 hours to completely dissolve it, thereby obtaining a varnish (3) having a viscosity of 37,000cps and a solid content of 9.0%.

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

A polyethylene terephthalate film substrate (Cosmo Shine (registered trademark) A4100, hereinafter referred to simply as PET substrate, manufactured by Toyobo Co., ltd.) having a thickness of 188 μm was unwound, and a varnish (1) contained in a pot was cast from a nozzle at a width of 500mm while being fed at a line speed of 0.30 m/min, and applied to the PET substrate. Then, the varnish thus applied was dried by heating at 120℃for 20 minutes, at 95℃for 10 minutes, and at 85℃for 10 minutes by a dryer while being conveyed at the same linear speed, to obtain a laminate of the raw material film (1) and the PET substrate. Next, a protective film (Sun a Kaken co., ltd.; NSA-33T) was unwound from the roll, and after being attached to the surface opposite to the surface of the raw material film (1) that was in contact with the PET substrate, the PET substrate was peeled off from the raw material film (1) and wound into a PET substrate roll, and a laminate of the remaining raw material film (1) and the protective film was obtained in the form of a laminate roll (1) having a length of 100 m. Next, from the obtained laminate roll (1), the laminate film was unwound at a conveying speed of 0.5 m/sec, the protective film was peeled off from the laminate film, and the remaining raw material film (1) was dried in a tenter dryer under the following conditions to obtain a raw material film (2). The interior of the tenter dryer was divided into 1 st to 6 th chambers in this order from the inlet side of the film. The raw material film (2) was further subjected to simultaneous biaxial stretching using a simultaneous biaxial stretching machine at a temperature set in a furnace of 260 ℃, and after setting the sample, it was allowed to stand for 5 minutes, and then subjected to simultaneous biaxial stretching at a stretching ratio of 1.1 times in length and width to obtain a polyamide-imide resin film (1). The thickness of the polyamide-imide resin film (1) was 50. Mu.m, and the amount of residual solvent was 0.3%.

(drying conditions in a tenter dryer in example 1)

Clip holding width (distance from one end of the film to the corresponding clip holding portion): 25mm of

Ratio of the distance between clamps at the dryer exit relative to the distance between clamps at the two ends of the film at the dryer entrance: 0.98

Temperature in the dryer: 200 DEG C

< example 2: production of Polyamide-imide resin film (2)

A polyamide-imide resin film (2) was obtained in the same manner as in example 1, except that the temperature of simultaneous biaxial stretching was changed to 280 ℃. The thickness of the polyamide-imide resin film (2) was 50. Mu.m, and the amount of residual solvent was 0.2%.

< example 3: production of Polyamide-imide resin film (3)

Varnish (1) was applied by casting using a small-sized automatic film applicator on Corning (registered trademark) EAGLE XG (registered trademark) slide (hereinafter abbreviated as Glass) as a Glass plate having a thickness of 0.5mm and a size of 300mm×200 mm. The Glass coated with the varnish was placed on a hot plate set to 120℃and dried until the amount of the residual solvent became 15%, to obtain a laminate of raw material film (1)/Glass.

Next, the raw material film (1)/Glass laminate was put into a full-air oven set to 210 ℃ and heated and dried for 30 minutes. Then, the polyamideimide resin film (3) was peeled off from Glass. The thickness of the obtained polyamideimide resin film (3) was 50 μm, and the residual solvent content was 0.5%.

Comparative example 1: production of Polyamide-imide resin film (4)

A polyamide-imide resin film (4) was obtained in the same manner as in example 1, except that the temperature of simultaneous biaxial stretching was changed to 340 ℃. The thickness of the polyamide-imide resin film (4) was 50. Mu.m, and the amount of residual solvent was 0.1%.

Comparative example 2: production of Polyamide-imide resin film (5)

From a laminate roll (1) produced in the same manner as in example 1, a laminate film was unwound at a conveying speed of 1.5 m/sec, a protective film was peeled off from the laminate film, and the remaining raw material film (1) was dried in a tenter dryer under the following conditions to obtain a raw material film (3). The obtained raw material film (3) was used as a polyamide-imide resin film (5). The thickness of the polyamide-imide resin film (5) was 58. Mu.m, and the amount of residual solvent was 0.8%.

(drying conditions in a tenter type dryer in comparative example 2)

Clip holding width (distance from one end of the film to the corresponding clip holding portion): 10mm of

Ratio of the distance between clamps at the dryer exit relative to the distance between clamps at the two ends of the film at the dryer entrance: 1.00

Temperature in the dryer: 280 DEG C

Comparative example 3: production of Polyamide-imide resin film (6)

A raw material film (4) was obtained by drying in a tenter dryer in the same manner as in comparative example 2 except that the raw material film (1) was subjected to main drying at 200 ℃. The raw material film (4) was uniaxially stretched at room temperature at a stretching ratio of 1.2 times to obtain a polyamideimide resin film (6). The thickness of the obtained polyamideimide resin film (6) was 50 μm, and the residual solvent content was 0.5%.

Comparative example 4: production of Polyamide-imide resin film (7)

Varnish (1) was applied by casting using a small-sized automatic film applicator on Corning (registered trademark) EAGLE XG (registered trademark) slide (hereinafter abbreviated as Glass) as a Glass plate having a thickness of 0.5mm and a size of 300mm×200 mm. The Glass coated with the varnish was put into an oven set to 120 ℃ and dried until the amount of the residual solvent became 15%, to obtain a laminate of raw material film (5)/Glass. Next, the raw material film (5) was peeled from the raw material film (5)/Glass laminate, the peeled raw material film (5) was sandwiched between metal frames, and the resultant was put into a full-air oven set at 210 ℃ for 30 minutes and heated and dried to obtain a polyamide-imide resin film (7). The thickness of the obtained polyamideimide resin film (7) was 50 μm, and the residual solvent content was 0.5%.

< example 4: production of Polyamide-imide resin film (8)

A polyamide-imide resin film (8) was obtained in the same manner as in example 2, except that the varnish was changed to varnish (2). The thickness of the polyamide-imide resin film (8) was 50. Mu.m, and the amount of residual solvent was 0.3%.

< example 5: production of Polyamide-imide resin film (9)

A polyamide-imide resin film (9) was obtained in the same manner as in example 2, except that the varnish was changed to varnish (3). The thickness of the polyamide-imide resin film (9) was 49. Mu.m, and the amount of residual solvent was 0.3%.

Will be as described aboveThe polyamide-imide resin films (1) to (9) produced as described above were used as measurement samples, and k was measured as follows _X 、k _Y K _Z 。

The film surface was measured by attenuated total reflectance spectrum (ATR: attenuated total reflection) using infrared light as the measuring light under the following conditions, and 1370cm of the absorbance spectrum was measured ^-1 Absorbance of the peak of (A) _s,X 、A _s,Y 、A _p,X And A _p,Y ) The X, Y and Z-axis absorption coefficient (k) of the film were calculated from the following formulas (p) and (q) _X 、k _Y K _Z ). In this measurement, the X axis is set to MD and the Y axis is set to TD.

(apparatus)

The device comprises: agilent Technologies 670-IR

Polarized ATR unit: seagull manufactured by Harrick Scientific Co

The measuring method comprises the following steps: ATR (reflection method)

ATR crystal: ge (gallium nitride)

Incidence angle: at 30 DEG relative to the film surface

A detector: MCT detector

Wavenumber range: 4000-400 cm ^-1

Resolution ratio: 4cm ^-1

Isotropic sample: resin obtained by UV curing acrylic monomer

(measurement)

1. The geometric axis is set as follows. An X axis and a Y axis are provided in the film surface, and a Z axis is provided in the film thickness direction. The x-axis is placed in the in-plane travel direction of the incident light of the infrared light (see fig. 1).

2. The polarized infrared light (measurement light) to be incident is polarized light (s-polarized light) that vibrates perpendicularly to the incident plane, and absorbance is obtained under the condition that the X-axis and the X-axis are parallel to each other, and the X-axis and the Y-axis are parallel to each other. The absorbance obtained was used as A in this order _s,X A is a _s,Y . In the case of a uniaxially stretched product (or a sample having anisotropy in the plane), the stretching direction (or the direction having the highest in-plane orientation) is set to be equal to the X-axis directionSo that.

3. The polarized infrared light (measurement light) to be incident is polarized light (p-polarized light) vibrating parallel to the incident surface, and absorbance is obtained under the condition that the X-axis is parallel to the X-axis and the Y-axis, respectively. The absorbance obtained was used as A in this order _p,X A is a _p,Y . In the case of a uniaxially stretched product (or a sample having anisotropy in the plane), the stretching direction (or the direction in which the in-plane orientation is the highest) was aligned with the X-axis direction.

The sample was obtained as 1370cm ^-1 A of the absorbance of the peak of (C) _s,X 、A _s,Y 、A _p,X And A _p,Y Is substituted into the following formulas (p) and (q) to obtain X, Y of the film and the absorbance (k) in the Z-axis direction _X 、k _Y K _Z ). Here, it is generally considered that 1370cm ^-1 The peak of (2) is the absorption of stretching vibration from imide group C-N bond, and the transition moment is consistent with the long axis direction of the molecular chain. The absorbance was obtained by subtracting 1900cm from the peak top ^-1 ～2000cm ^-1 A value obtained by averaging the values of (a).

/>

※n ₁ : refractive index of sample (assumed to be 1.5), n ₂ : refractive index of Ge (4), θ=30°

The values of α, β, and γ in the formula (p) are obtained by substituting the refractive index and the incident angle into the form of equation (q) in which α, β, and γ are coefficients representing the contribution ratios of the light absorption coefficients in the respective axial directions in the polarization ATR. In the formulas (p) and (q), s and p represent directions of polarized light, and X, Y represents an X-axis direction and a Y-axis direction, respectively.

According to the absorbance k obtained as described above _X 、k _Y K _Z Calculating orientation parameters < cos > as directional cosine representing average orientation of molecular long axis from formulas (a) - (c) ² (yX)〉、〈cos ² (yY) cos ² (yZ). Note that < cos ] ² (yX) is an average value of values obtained by performing at least 3 measurements. For < cos ² (yY) cos ² The same applies to (yZ). The results obtained are shown in Table 1.

< measurement of Heat shrinkage >

The polyamide-imide resin films (1) to (9) produced as described above were cut into 10cm square pieces, and aluminum foils 11cm square pieces were laminated on both surfaces thereof, and the resulting laminate was used as a measurement sample. The measurement sample was put into an oven at 25℃and a 10g jig was placed at the center of the film at 4 corners, the temperature was raised to 400℃at a heating rate of 20℃per minute, the film was allowed to stand at 400℃for 2 hours, the length of the 4 sides was measured after taking out, and the average value of the lengths of the two sheets was calculated for the MD direction and the TD direction, and the shrinkage before and after heating was determined from the following formula as the length of the 1 side of the film after heating in the MD direction and the TD direction. The results obtained are shown in Table 1.

Heat shrinkage (%) = { (length of 1 side of film before heating-length of 1 side of film after heating)/(length of 1 side of film before heating) } ×100

< dent resistance test >

(1) Preparation of sample for measurement

The polyamide-imide resin films (1) to (9) produced in examples and comparative examples were laminated on a laminate of polyimide films (UPILEX, manufactured by yu, having a thickness of 165 μm) via an optically clear adhesive (OCA, storage modulus measured at 25 ℃ c.: 0.1MPa, having a thickness of 25 μm), respectively, to produce samples for measurement.

(2) Test method

The dent resistance test was performed using a pencil hardness tester (equipment name: no.553-F, manufactured by Seiko corporation) An Tian. When Japanese Journal of Educational Psychology,1995,43,100-107 are taken as references, the usual pen pressure is considered to be 200-400 g, and the pen speed is considered to be 250-350 mm/min. Therefore, in the dent resistance test, the pencil was mounted at an angle of 45 ° and the pencil speed of 300 mm/min was performed while applying a constant load (300 g). A Mitsubini pencil having a hardness of H to 9H, F, HB, B to 6B was used. The film after the test was allowed to stand at 23℃under 50% RH for 24 hours using pencils of respective hardness, and after 24 hours, the presence or absence of the pits was visually determined by moving the pencils at a distance of 15 mm. In the test, the measurement samples prepared as described above were placed on glass having a thickness of 0.7mm so that the surfaces of the polyamide-imide resin films (1) to (9) were surfaces, and the test was performed in an atmosphere of 50% RH at 23 ℃. For each film, the hardness of the pencil with the highest hardness, which was visually judged to be no dishing, was taken as the dishing-resistant pencil hardness. The higher the dent resistance pencil hardness, the more difficult the dent is to be generated and the higher the dent resistance is. The results obtained are shown in Table 1.

TABLE 1

The films of examples 1 to 5 satisfy the above-mentioned formulas (d) and (e), and exhibit dent resistance even when a pencil of HB is used. In contrast, in the case of the films of comparative example 1, comparative example 2, and comparative example 4, in which simultaneous biaxial stretching was performed at a relatively high temperature, stretching in the biaxial direction was considered insufficient, the obtained films did not satisfy the formula (e), and no improvement in dent resistance was observed. In addition, the film obtained in comparative example 3 did not satisfy the formula (d), and no improvement in dent resistance was observed.

Claims

1. A film comprising a polyimide resin, wherein when an in-plane direction of the film is defined as an X-axis, an in-plane direction of the film perpendicular to the X-axis is defined as a Y-axis, and a thickness direction of the film perpendicular to the X-axis is defined as a Z-axis, an absorbance k in each of the X-axis, Y-axis and Z-axis obtained by a polarization ATR method using infrared rays is used _X 、k _Y K _Z And are calculated from the formulas (a) - (c)<cos ² (yX)>、<cos ² (yY)>A kind of electronic device with high-pressure air-conditioning system<cos ² (yZ)>Satisfies the formula (d) and (e):

|<cos ² (yX)>-<cos ² (yY)>|＜0.09 (d)

0≤<cos ² (yZ)>＜0.25 (e)。

2. the film of claim 1, further satisfying formulas (f) and (g):

0.3≤<cos ² (yX)>≤1.0 (f)

0.3≤<cos ² (yY)>≤1.0 (g)。

3. the film according to claim 1, wherein the film satisfies formulas (h) to (j) when a heat shrinkage ratio before and after heating at 400 ℃ for 2 hours of the film in the X-axis direction is Sx and a heat shrinkage ratio at 400 ℃ for 2 hours of the film in the Y-axis direction is Sy:

10％≤Sx≤25％ (h)

10％≤Sy≤25％ (i)

|Sx-Sy|≤5％ (j)。

4. The film of claim 1 having a yellowness of 2.0 or less.

5. The film according to claim 1, which has a thickness of 45 μm or more.

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

7. A laminate comprising the film according to claim 1, and a functional layer laminated on at least one surface of the film.

8. A flexible display device comprising the film according to claim 1 and/or the laminate according to claim 7.

9. The flexible display device of claim 8, further comprising a touch sensor.

10. The flexible display device according to claim 8, further comprising a polarizing plate.