JP2023154059A - Polyimide film, laminate, member for display, touch panel member, liquid crystal display device, and organic electronic luminescent display device - Google Patents

Abstract

To provide a resin film that has excellent transparency, suitable for a display or a touch panel, and achieves improvements in both flexure resistance and surface hardness.SOLUTION: A film has anisotropy such that a ratio of tensile moduli in a tensile test with a X direction, which is one direction in a film plane, as a tensile direction and in a tensile test with a Y direction perpendicular to the X direction as the tensile direction is 1.50 or more, wherein the tensile moduli in the tensile directions are 1.8 GPa or more, respectively, the total light transmittance measured in accordance with JIS K7361-1 is 85% or more, and the yellowness calculated in accordance with JIS K7373-2006 is 5 or less. When used, the film is folded such that the folding part is perpendicular to the tensile direction in which, in a stress-strain curve obtained by a tensile test with the X direction of the film as the tensile direction and a tensile test with the Y direction of the film as the tensile direction, a strain at the yield point is 8% or more and the value of the strain at the yield point becomes larger.SELECTED DRAWING: None

Description

The present invention relates to a film, a polyimide film, a laminate, a display member, a touch panel member, a liquid crystal display device, and an organic electroluminescent display device.

Although thin sheet glass has excellent hardness and heat resistance, it has the drawbacks of being difficult to bend, easily breaking when dropped, having problems with workability, and being heavier than plastic products. For this reason, in recent years, resin products such as resin base materials and resin films have been replacing glass products from the viewpoint of processability and weight reduction, and research has been conducted on resin products that can serve as glass substitutes.

For example, with the rapid progress of displays such as liquid crystals and organic EL, and electronics such as touch panels, devices are required to be thinner, lighter, and more flexible. Conventionally, these devices have various electronic elements such as thin transistors and transparent electrodes formed on thin plate glass, but by changing this thin plate glass to a resin film, it is possible to strengthen the impact resistance of the panel itself. , making it more flexible, thinner, and lighter.

Generally, polyimide is a highly heat-resistant resin obtained by dehydrating and ring-closing polyamic acid obtained by a condensation reaction of an aromatic tetracarboxylic acid anhydride and an aromatic diamine. However, since polyimide is generally colored yellow or brown, it has been difficult to use it in fields where transparency is required, such as display applications and optical applications. Therefore, the application of polyimide with improved transparency to display members is being considered. For example, Patent Document 1 describes 1,2,4,5-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid di- at least one acyl-containing compound selected from the group consisting of anhydrides and reactive derivatives thereof; and at least one compound selected from the group consisting of at least one phenylene group and isopropylidene group, represented by a specific formula. A polyimide formed by reacting with an imino-forming compound is disclosed, and is described as being suitable for substrate materials for flat panel displays, mobile phone devices, and the like.

Further, Patent Document 2 discloses that the unit structure includes a unit structure derived from an aromatic dianhydride and an aromatic diamine, and contains an additive for improving tear strength or a functional group selected from the group consisting of a hexafluoro group, a sulfone group, and an oxy group. A transparent polyimide film is disclosed that further includes a unit structure derived from a monomer having the following properties. Patent Document 3 discloses a polyimide film with excellent transparency and heat resistance, in which the apex of the peak in a tan δ curve, which is a value obtained by dividing the loss modulus by the storage modulus, is within a specific range. ing.

Furthermore, Patent Document 4 discloses that a polyimide film that is colorless and transparent, has low residual stress generated between it and an inorganic film, and has excellent mechanical and thermal properties is obtained as a polyimide film used for a substrate of a flexible device. For this purpose, a polyimide film is disclosed in which a polyimide precursor is imidized using a specific fluorine-based aromatic diamine and a silicone compound having a siloxane skeleton having 3 to 200 silicon atoms as monomer components. . Patent Document 4 discloses that when a polyimide film with an inorganic film (SiN film) was formed using the polyimide precursor, no cracks or peeling were observed after a bending test in which bending was repeated 10 times (○), or no cracks were observed. It is described as observed (△).

Further, Patent Document 5 describes that a polyimide having a low refractive index and high refraction durability contains silicone diamine having 2 to 21 silicon atoms in an amount of 10% by weight or more based on the weight of the diamine raw material.

Furthermore, the inventors have disclosed in Patent Document 6 that a diamine residue having one or two silicon atoms in the main chain is used as a resin film that suppresses a decrease in surface hardness while improving bending resistance. Discloses a polyimide film containing polyimide containing 10 mol% or more and 50 mol% or less of the total amount of polyimide, and having a specific total light transmittance, a specific yellowness, a specific glass transition temperature, and a specific tensile modulus. .

Japanese Patent Application Publication No. 2006-199945 Special table 2014-501301 publication Special Publication No. 2012-503701 International Publication No. 2014/098235 Japanese Patent Application Publication No. 2008-64905 JP 2018-28073 Publication

Resin products that serve as glass substitutes are required to have excellent transparency.
Mobile devices with foldable screens should be folded when carried and unfolded when used. Therefore, flexible displays installed in mobile devices are required to have no display defects even when repeatedly bent, and the base materials and surface materials for flexible displays are required to have bending resistance (hereinafter referred to as "bending resistance") when repeatedly bent. (sometimes referred to as dynamic bending resistance) is required. Furthermore, mobile devices with foldable screens are often carried in a folded state, so even if the flexible display installed on a mobile device is folded for a long period of time, it will not return to its original state when flattened. The base materials and surface materials for flexible displays are also required to have the ability to recover after being bent for a long time (hereinafter sometimes referred to as static bending resistance).
On the other hand, the base materials and surface materials for flexible displays must not only withstand repeated bending, but also have functions to prevent scratches on the surface and to prevent damage to the touch sensor and display panel located underneath. is also required.
The bending resistance and surface hardness of a resin film are considered to be contradictory properties, as will be explained in detail later. However, conventional resin films are still insufficient in achieving both bending resistance and surface hardness sufficient as a protective film, and there is a need for a resin film that has both bending resistance and surface hardness sufficient as a protective film.

The present invention has been made in view of the above-mentioned problems, and its main purpose is to provide a film or resin film that is excellent in transparency and has both improved bending resistance and surface hardness.
The present invention also provides a laminate having the film or resin film, a display member comprising the film or the resin film or the laminate, a touch panel member comprising the film or the laminate, a liquid crystal display device, and an organic electroluminescent display device.

The film of the present invention has a tensile modulus ratio of 1.50 or more in a tensile test with the X direction, which is one direction in the film plane, as the tensile direction and a tensile test with the Y direction perpendicular to the X direction as the tensile direction. The tensile test was performed by cutting out a test piece measuring 40 mm in the tensile direction x 15 mm in the direction perpendicular to the tensile direction, and testing the test piece at a tensile speed of 10 mm/min between chucks in accordance with JIS K7127. Measured at 25°C with a distance of 20mm,
Each tensile modulus in the tensile test is 1.8 GPa or more,
A film whose total light transmittance measured in accordance with JIS K7361-1 is 85% or more and whose yellowness calculated in accordance with JIS K7373-2006 is 5 or less,
Among the stress-strain curves obtained by a tensile test with the X direction of the film as the tensile direction and a tensile test with the Y direction of the film as the tensile direction, the strain at the yield point is 8% or more, and the yield point This is a film that is used by being bent so that the bending part is perpendicular to the tensile direction in which the strain value is larger.

The polyimide film of the present invention has a tensile modulus ratio of 1.50 in a tensile test in which the tensile direction is in the X direction, which is one direction within the film plane, and in a tensile test in which the tensile direction is in the Y direction perpendicular to the X direction. In the tensile test, a test piece of 40 mm in the tensile direction x 15 mm in the direction perpendicular to the tensile direction was cut out, and the test piece was placed in a chuck at a tensile speed of 10 mm/min in accordance with JIS K7127. Measured at 25°C with a distance of 20mm,
Each tensile modulus in the tensile test is 1.8 GPa or more,
A polyimide film having a total light transmittance measured in accordance with JIS K7361-1 of 85% or more and a yellowness calculated in accordance with JIS K7373-2006 of 5 or less,
Among the stress-strain curves obtained by a tensile test with the X direction of the film as the tensile direction and a tensile test with the Y direction of the film as the tensile direction, the strain at the yield point is 8% or more, and the yield point This is a polyimide film that is used by being bent so that the bent portion is perpendicular to the tensile direction in which the strain value is larger.

Preferably, the polyimide film of the present invention has a Young's modulus of the film surface of 2.3 GPa or more, measured at a temperature of 25° C. using a nanoindentation method in accordance with ISO 14577, from the viewpoint of excellent surface hardness. .

In the polyimide film of the present invention, it is preferable to contain a polyimide having a structure represented by the following general formula (1) from the viewpoints of light transmittance, bending resistance, and surface hardness.

(In general formula (1), R ¹ represents a tetravalent group that is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and each of the plurality of R ^1s may be the same or different. , R ² represents a divalent group that is a diamine residue, each of the plurality of R ² may be the same or different, and at least a part of the plurality of R ² has an aromatic ring or an aliphatic ring. (n represents the number of repeating units.)

In the polyimide film of the present invention, in the polyimide having the structure represented by the general formula (1), R ² represents a divalent group that is a diamine residue, and 2.5 mol% of the total amount of R ² The above 50 mol% or less is a diamine residue having one or two silicon atoms in the main chain, and the 50 mol% or above 97.5 mol% is a diamine residue that does not have a silicon atom and has an aromatic ring or an aliphatic ring. A diamine residue having a ring is preferred from the viewpoint of improving bending resistance and surface hardness.

In the polyimide film of the present invention, in the polyimide having the structure represented by the general formula (1),
R ² represents a divalent group which is at least one type selected from diamine residues having no silicon atom, and includes a diamine residue having a hexafluoroisopropylidene skeleton in the main chain, or
^R2 represents a divalent group that is at least one type selected from a diamine residue having no silicon atom and a diamine residue having one or two silicon atoms in ^the main chain, and 2.5 mol% or more and 50 mol% or less are diamine residues having one or two silicon atoms in the main chain, and 50 mol% or more and 97.5 mol% or less of the total amount of ^R2 is a diamine residue having one or two silicon atoms in the main chain. A diamine residue having an aromatic ring or an aliphatic ring is preferable from the viewpoint of light transmittance, bending resistance, and surface hardness.

In the polyimide film of the present invention, in the polyimide having the structure represented by the general formula (1), the diamine residue having the aromatic ring or aliphatic ring in R ² in the general formula (1) is , trans-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4'-diaminodiphenylsulfone residue, 3,4'-diaminodiphenylsulfone residue, 2,2-bis(4 -aminophenyl)propane residue, 3,3'-bis(trifluoromethyl)-4,4'-[(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis (4,1-phenyleneoxy)] dianiline residue, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, 2, Consists of a 2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue and a divalent group represented by the following general formula (2) At least one type of divalent group selected from the group is preferred from the viewpoints of light transmittance, bending resistance, and surface hardness.

(In general formula (2), R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)

In the polyimide film of the present invention, in the polyimide having the structure represented by the general formula (1), R ¹ in the general formula (1) is a cyclohexanetetracarboxylic dianhydride residue, a cyclopentanetetracarboxylic acid dianhydride residue, Acid dianhydride residue, dicyclohexane-3,4,3',4'-tetracarboxylic dianhydride residue, cyclobutanetetracarboxylic dianhydride residue, pyromellitic dianhydride residue, 3, 3',4,4'-biphenyltetracarboxylic dianhydride residue, 2,2',3,3'-biphenyltetracarboxylic dianhydride residue, 4,4'-(hexafluoroisopropylidene)diphthal Acid anhydride residue, 3,4'-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene) diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride From the viewpoint of light transmittance, bending resistance, and surface hardness, preferable.

The laminate of the present invention comprises the film or polyimide film of the present invention and a hard coat layer containing at least one polymer of a radically polymerizable compound and a cationically polymerizable compound, and comprises the film or polyimide film of the present invention. This is a laminate that is used by being bent so that the bent portion is perpendicular to the tensile direction where the strain value at the yield point is greater.

The display member of the present invention includes the film or polyimide film of the present invention, or the laminate of the present invention, and the strain value at the yield point of the film or polyimide film is larger in the tensile direction. Use by folding so that the bent portions are perpendicular.

The display member of the present invention can be used for flexible displays.

The present invention also provides the film or polyimide film of the present invention, or the laminate of the present invention;
a transparent electrode made of a plurality of conductive parts arranged on one side of the film, the polyimide film, or the laminate;
a plurality of lead wires electrically connected on at least one side of the end of the conductive part,
A touch panel member is provided in which the film or polyimide film is installed so as to be bendable so that the bending portion is perpendicular to the tensile direction in which the strain value at the yield point of the film or polyimide film is larger.

The present invention also provides the film or polyimide film of the present invention, or the laminate of the present invention;
a liquid crystal display section having a liquid crystal layer between opposing substrates, disposed on one side of the film, the polyimide film, or the laminate;
Provided is a liquid crystal display device, wherein the film or polyimide film is installed so that it can be folded such that the bending portion is perpendicular to the tensile direction in which the strain value at the yield point of the film or polyimide film is larger. .

The present invention also provides the film or polyimide film of the present invention, or the laminate of the present invention;
an organic electroluminescent display section having an organic electroluminescent layer between opposing substrates, disposed on one side of the film, the polyimide film, or the laminate;
The film or polyimide film is installed so as to be bendable so that the bending part is perpendicular to the tensile direction in which the strain value at the yield point of the film or polyimide film is larger. provide.

According to the present invention, it is possible to provide a film or a resin film that has excellent transparency and has both improved bending resistance and surface hardness.
The present invention also provides a laminate having the film or resin film, a display member comprising the film or the resin film or the laminate, a touch panel member comprising the film or the resin film or the laminate, and a liquid crystal display device. , and an organic electroluminescent display device.

It is a figure for explaining the maximum stress in bending of a film. 1 is a schematic plan view showing one embodiment of a polyimide film of the present invention. This is an example of a stress-strain curve of a polyimide film. FIG. 4 is a graph of strain and dy/dx (average rate of change) of the stress-strain curve of the polyimide film of FIG. 3. FIG. It is a figure for explaining the method of a dynamic bending test. FIG. 2 is a schematic plan view of one surface of an example of the touch panel member of the present invention. 7 is a schematic plan view of the other surface of the touch panel member shown in FIG. 6. FIG. 8 is a sectional view taken along line A-A' of the touch panel member shown in FIGS. 6 and 7. FIG. FIG. 1 is a schematic plan view showing an example of a conductive member including a laminate of the present invention. It is a schematic plan view which shows another example of the electroconductive member provided with the laminated body of this invention. It is a schematic sectional view showing another example of the touch panel member of the present invention. 1 is a schematic cross-sectional view showing an example of a liquid crystal display device of the present invention. FIG. 3 is a schematic cross-sectional view showing another example of the liquid crystal display device of the present invention. 1 is a schematic cross-sectional view showing an example of an organic electroluminescent display device of the present invention. FIG. 3 is a schematic cross-sectional view showing another example of the organic electroluminescent display device of the present invention.

I. Film The film of one embodiment of the present invention has a ratio of tensile elastic modulus in a tensile test in which the tensile direction is in the X direction, which is one direction within the film plane, and in a tensile test in which the tensile direction is in the Y direction perpendicular to the X direction. has anisotropy of 1.50 or more, and in the tensile test, a test piece of 40 mm in the tensile direction x 15 mm in the direction perpendicular to the tensile direction was cut out, and the test piece was tested at a tensile speed of 10 mm in accordance with JIS K7127. /min, the distance between the chucks is 20 mm, and the measurement is performed at 25°C.
The tensile modulus in the tensile test is 1.8 GPa or more, and
A film whose total light transmittance measured in accordance with JIS K7361-1 is 85% or more and whose yellowness calculated in accordance with JIS K7373-2006 is 5 or less,
Among the stress-strain curves obtained by a tensile test with the X direction of the film as the tensile direction and a tensile test with the Y direction of the film as the tensile direction, the strain at the yield point is 8% or more, and the yield point This is a film that is used by being bent so that the bending part is perpendicular to the tensile direction where the strain value is larger.

According to the present invention, the specific total light transmittance, yellowness, and tensile modulus in a specific tensile test are greater than or equal to a specific value, and the tensile modulus has a specific anisotropy, and the tensile modulus has a specific anisotropy. In the stress-strain curve obtained by a tensile test, the strain at the yield point is 8% or more, and the bent part is used by bending it perpendicular to the tensile direction where the value of the strain at the yield point is larger. By making it into a film, it is possible to provide a film that is excellent in transparency and has both improved bending resistance and surface hardness.

In the present invention, the term "film" refers to a material in the form of a thin film or a flat plate having a thickness of approximately 1 μm to 200 μm, and includes a material called a sheet, and may also be in the form of a long sheet.
Examples of the film of the present invention include resin films.
Materials for the resin film include, for example, polyimide, polyamide, triacetylcellulose, polyethylene, polypropylene, polyacetal, polyester (polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyvinyl chloride, AS resin, ABS resin, polystyrene, and polyester. Methyl methacrylate, polyacetal, polycarbonate, polyphenylene sulfide, polyarylate, polysulfone, polyethersulfone, polyetheretherketone, liquid crystal polymer, polytetrafluoroethylene, cellulose acylate, cycloolefin polymer, MBS resin, and at least one of these Examples include copolymers containing the following. The material type is not particularly limited as long as it satisfies the physical property values within the scope of the present invention, but organic materials, silicone materials, copolymers and mixtures thereof are preferred, and among them, the glass transition temperature of the film is 150 ° C. The above is preferably used. Furthermore, in the present invention, a polyimide film or a polyamide film using polyimide or polyamide as the film material is particularly preferably used.
Hereinafter, the function, characteristics, etc. of the film of the present invention will be explained in detail by taking a polyimide film as an example. The function, characteristics, etc. of the film of the present invention may be the same as those of the polyimide film of the present invention described below.

II. Polyimide film The polyimide film of one embodiment of the present invention has a tensile elastic modulus in a tensile test in which the tensile direction is in the X direction, which is one direction within the film plane, and in a tensile test in which the tensile direction is in the Y direction orthogonal to the X direction. In the tensile test, a test piece of 40 mm in the tensile direction x 15 mm in the direction perpendicular to the tensile direction was cut out, and the test piece was subjected to tensile testing in accordance with JIS K7127. The measurement is performed at 25°C with a speed of 10 mm/min and a distance between chucks of 20 mm.
The tensile modulus in the tensile test is 1.8 GPa or more, and
A polyimide film having a total light transmittance measured in accordance with JIS K7361-1 of 85% or more and a yellowness calculated in accordance with JIS K7373-2006 of 5 or less,
Among the stress-strain curves obtained by a tensile test with the X direction of the film as the tensile direction and a tensile test with the Y direction of the film as the tensile direction, the strain at the yield point is 8% or more, and the yield point This is a polyimide film that is used by being folded so that the folded portion is perpendicular to the tensile direction in which the strain value is larger.

According to the present invention, the specific total light transmittance, yellowness, and tensile modulus in a specific tensile test are greater than or equal to a specific value, and the tensile modulus has a specific anisotropy, and the tensile modulus has a specific anisotropy. In the stress-strain curve obtained by a tensile test, the strain at the yield point is 8% or more, and the polyimide used is bent so that the bent part is perpendicular to the tensile direction where the value of the strain at the yield point is larger. By forming the resin film into a film, it is possible to provide a resin film that has excellent transparency and has both improved bending resistance and surface hardness.

The present inventors focused on polyimide among resins. Polyimide is known to have excellent durability such as heat resistance due to its chemical structure. In addition, it is known that the arrangement of internal molecular chains in polyimide films forms a certain ordered structure, and thanks to this, polyimide films have good resilience when the flat state and the folded state are repeated at a certain period at room temperature. It is thought that this method will show good results.
However, conventional resin films using transparent polyimide have problems in that they tend to break during tests that repeat the flat state and the folded state at regular intervals, are prone to creases, are difficult to return to a flat state, and have poor bending resistance. . When the bent state is maintained for a long time, tensile stress is continuously applied to the outer periphery of the bent part, causing plastic deformation of the film, which makes it difficult to recover even when the bending force is removed. It is presumed that there are.
It is believed that the tensile stress applied to the outer periphery of the bent portion of the film when bent increases as the film becomes thicker and the bending radius of the bent portion becomes smaller.
Therefore, a film that is easily plastically deformed is easily deformed during the bending test process, and this deformation deteriorates visibility when used as a member of a flexible display panel.
More specifically, it is inferred as follows.
When bending a film, tension is applied to the outer periphery of the bend, and compressive force is applied to the inner periphery of the bend. When the film is bent as shown in Figure 1, the maximum stress (σ ) is represented by the following formula (1).

E ：弾性率
y ：中立軸（曲がる時の中心となる軸）からの距離の最大値（図１の場合、膜厚ｄの半分）
φ：曲率（試験幅）
ｄ：フィルムの膜厚

E: Elastic modulus
y: Maximum distance from the neutral axis (center axis when bending) (in the case of Figure 1, half of the film thickness d)
φ: Curvature (test width)
d: Film thickness

The maximum stress (σ) is proportional to the elastic modulus and film thickness of the film, and inversely proportional to the value obtained by subtracting the film thickness from the curvature, as shown in the above equation (1). Therefore, when the elastic modulus of the film is increased, the stress applied to the film during bending also increases, causing deformation. Also in resin films, when the elastic modulus is increased, the restorability after bending tends to deteriorate and the bending resistance tends to become insufficient. On the other hand, increasing the elastic modulus of the resin film tends to improve the surface hardness. As shown in Comparative Example 6, which will be described later, a polyimide film with a high elastic modulus has good surface hardness but poor bending resistance. In this way, the bending resistance and surface hardness of a resin film are considered to be contradictory properties.
Base materials and surface materials for flexible displays are required not only to withstand repeated bending, but also to prevent scratches on the surface and to prevent damage to the touch sensor and display panel located underneath. . The higher the modulus of elasticity of the surface material, such as glass, the more the impact from the surface of the display can be diffused in the plane direction, and the more localized the impact can be alleviated. This can prevent damage to the display panel. The same thing can be said for flexible displays, and the higher the elastic modulus of the surface material is, the more advantageous it will be in protecting the display panel. On the other hand, if the elastic modulus is low, the surface material itself deforms and may be able to alleviate the impact, but the dents caused by the deformation become fixed, greatly reducing the smoothness of the display surface and deteriorating its appearance. easily damaged.

For example, in the polyimide film described in Patent Document 4, by introducing a silicone component containing three or more silicon atoms, it has a glass transition temperature below freezing and reduces residual stress generated between it and the inorganic film. It is stated that it did. However, as shown in Comparative Example 7, which will be described later, a polyimide film incorporating a silicone component containing three or more silicon atoms has a low glass transition temperature, so it has insufficient elastic modulus at room temperature, low surface hardness, There were problems in that it was easily scratched, transmitted shock to the light-emitting panel and circuits, and lacked its function as a protective film.
Moreover, the polyimide film described in Patent Document 5 is described as having high folding durability. However, as shown in Comparative Example 8 described below, the polyimide film into which silicone diamine (containing about 9 to 10 silicon atoms) corresponding to the example of Patent Document 5 is introduced has insufficient elastic modulus at room temperature; There were problems such as low surface hardness, easy scratching, insufficient function as a protective film, and poor transparency.
In view of the above, there has been a need for a resin film that has both excellent transparency, bending resistance, and surface hardness sufficient for use as a protective film. However, as described above, the bending resistance and surface hardness of a resin film are considered to be contradictory properties, and it has been difficult to achieve both excellent bending resistance and improvement in surface hardness.

In contrast, the present inventors focused on the value of strain (%) at the yield point in the stress-strain curve obtained by the tensile test, and found that the strain at the yield point of the stress-strain curve is 8% or more. It has been found that films used by being bent so that the folded portion is perpendicular to the tensile direction tend to have improved bending resistance. Although the reason for this is not certain, it is speculated as follows.
The stress-strain curve is a relationship curve between tensile stress and strain obtained in a tensile test, and is drawn with strain (%) on the horizontal axis and tensile stress (MPa) on the vertical axis. The region up to the yield point on the stress-strain curve can be regarded as an elastic deformation region, and the region after the yield point on the stress-strain curve can be regarded as a plastic deformation region. When the strain (%) at the yield point is larger than a predetermined value, the elastic deformation region becomes wider than the predetermined value, and it is estimated that the material has a property of easily returning to its original state even if bent. In other words, the amount of strain at the yield point obtained from the stress-strain curve can be expressed as the amount of deformation that can be elastically deformed, and can be considered as the amount of deformation that can restore the shape to the shape before stress is applied. Therefore, if the strain (%) at the yield point is larger than a predetermined value, the film will have improved resilience after repeated bending, as shown by the results of the bending test in the examples described later. It is presumed that this is the case.
In addition, in the Examples and Comparative Examples described below, even if polyimide films are manufactured using polyimides having the same molecular structure, if the manufacturing method is different and the state of the film is different, the stress obtained by the tensile test - In the strain curves, the values of strain (%) at the yield point are different, indicating that the bending resistance is greatly different accordingly. This indicates that the bending resistance of polyimide films does not depend only on the polyimide composition, and that the value of strain (%) at the yield point represents the state of the polyimide film related to bending resistance. It is thought that
If the bent part is bent orthogonally to the tensile direction in which the strain at the yield point of the stress-strain curve is 8% or more, the stress - The strain at the yield point of the strain curve may be less than 8%. It is believed that the surface hardness of the film can be improved by relatively increasing the tensile modulus in the tensile direction perpendicular to the tensile direction where the strain at the yield point of the stress-strain curve is 8% or more. It will be done.
In the present invention, in addition to satisfying the strain (%) at the yield point of the stress-strain curve obtained by the tensile test in at least one direction, in the tensile test, the A polyimide film is selected based on a combination of tensile modulus and specific anisotropy. According to the present invention, while improving the bending resistance by utilizing the tensile direction in which the strain value at the yield point is 8% or more and is larger, that is, the direction in which the tensile modulus is relatively small, the relative The surface hardness can be improved due to the relatively large tensile modulus, and a resin film can be provided that has both excellent bending resistance and improved surface hardness.
Further, according to the present invention, the polyimide film has the specific total light transmittance and the specific yellowness, so that the resin film has excellent transparency and has both improved bending resistance and surface hardness. It is estimated that it is possible to provide

FIG. 2 is a schematic plan view showing one embodiment of the polyimide film of the present invention.
As shown in FIG. 2, the polyimide film 101 of the present invention is a test piece measuring 40 mm in the tensile direction x 15 mm in the direction perpendicular to the tensile direction for conducting a tensile test with the X direction, which is one direction in the plane of the film, as the tensile direction. 11 and a test piece 12 measuring 40 mm in the tensile direction x 15 mm in the direction orthogonal to the tensile direction for carrying out a tensile test with the Y direction orthogonal to the X direction as the tensile direction, and conducted a tensile test. It has anisotropy such that the ratio of elastic modulus (X/Y) is 1.50 or more.
The polyimide film 101 of the present invention has a strain at the yield point of 8% in a stress-strain curve obtained by a tensile test with the X direction of the film as the tensile direction and a tensile test with the Y direction of the film as the tensile direction. If the above is the case, and the polyimide film 102 cut out from the polyimide film 101 is used by being bent so that the bent portion 14 is perpendicular to the tensile direction 13 of the tensile test in which the strain value at the yield point is larger, It has excellent bending resistance and can suppress the occurrence of folding.
Furthermore, since the polyimide film of the present invention has anisotropy in which the ratio (X/Y) of the tensile modulus is 1.50 or more, the surface hardness can be improved by utilizing the direction of the relatively large tensile modulus. This makes it possible to achieve both excellent bending resistance and improved surface hardness.
In this specification, the folded portion of the film refers to a locally bent portion formed by folding the film, or one planar portion separated by folding the film and the other planar portion separated by bending the film. Indicates a part located at the boundary between other parts.

Hereinafter, the polyimide film according to the present invention will be explained in detail.
The polyimide film according to the present invention contains polyimide and has the above-mentioned specific properties. As long as the effects of the present invention are not impaired, it may further contain other components or have other configurations.

1. tensile modulus
The polyimide film of the present invention has a tensile modulus ratio (X/Y ) has anisotropy of 1.50 or more. Here, when calculating the ratio of tensile modulus, the direction in which the value of the tensile modulus is relatively small is calculated as the Y direction. The value obtained by dividing the tensile modulus in the X direction by the tensile modulus in the Y direction is rounded to the second decimal place according to Rule B of JIS Z8401:1999.
The tensile test is performed by cutting out a test piece measuring 40 mm in the tensile direction x 15 mm in the direction orthogonal to the tensile direction, and measuring the test piece at 25°C at a tensile rate of 10 mm/min and a distance between chucks of 20 mm in accordance with JIS K7127. The polyimide film of the present invention has a tensile modulus of 1.8 GPa or more in the tensile test. That is, the tensile elastic modulus in a tensile test in which the X direction, which is one direction within the film plane, is the tensile direction is 1.8 GPa×1.50=2.7 GPa or more.
As described above, since the polyimide film of the present invention has a high tensile modulus at 25°C (room temperature), it can maintain sufficient surface hardness as a protective film even at room temperature, and can be used as a surface material or base material. Can be done.

In the polyimide film of the present invention, the ratio (X/Y) of the tensile modulus is more preferably 1.60 or more in order to improve the surface hardness.

In terms of surface hardness, the tensile modulus in the Y direction, where the value of the tensile modulus is relatively small, is preferably 2.0 GPa or more, more preferably 2.1 GPa or more, and 2.3 GPa or more. It is even more preferable that there be.
The tensile modulus in the X direction, where the value of the tensile modulus is relatively large, is preferably 3.0 GPa or more, more preferably 3.2 GPa or more, and 3.4 GPa or more from the viewpoint of surface hardness. It is even more preferable that there be.
On the other hand, the tensile modulus in the Y direction, where the value of the tensile modulus is relatively small, is preferably 5.2 GPa or less in terms of improving bending resistance. In order to improve bending resistance, the tensile modulus may be 4.0 GPa or less, 3.5 GPa or less, or 2.9 GPa or less.
The tensile modulus was measured using a tensile tester (for example, Autograph AG-X 1N, manufactured by Shimadzu Corporation, load cell: SBL-1KN), using a test machine measuring 15 mm in width x 40 mm in length (40 mm in the tensile direction x 15 mm in the direction perpendicular to the tensile direction). A test piece is cut out from a polyimide film, and the test piece is subjected to a tensile test in accordance with JIS K7127 at a tensile speed of 10 mm/min and a distance between chucks of 20 mm at 25°C for measurement. When cutting out a test piece from a film, it is preferable to cut out a portion of the film with a uniform thickness, for example, preferably from near the center of the film. As a guideline for uniform film thickness, for example, measure the film thickness at a total of five points at the four corners and the center of the cut film using a digital linear gauge (manufactured by Ozaki Seisakusho Co., Ltd., model PDN12 digital gauge). , the difference between the average film thickness at five points and the film thickness at each point is within 6% of the average film thickness.

2. Yield Point of Stress-Strain Curve The polyimide film of the present invention has a stress-strain curve that is at least In the stress-strain curve obtained from one of the tensile tests, the strain at the yield point is 8% or more. And, among the stress-strain curves obtained by a tensile test with the X direction of the film as the tensile direction and a tensile test with the Y direction of the film as the tensile direction, the strain value at the yield point is 8% or more, In addition, it is used by being bent so that the bent portion is perpendicular to the tensile direction in which the value becomes larger. The strain value at the yield point is 8% or more, and by bending the film so that the bending part is perpendicular to the direction of increasing tension, the film has better resilience after repeated bending. It becomes what it is.

Although the upper limit of the strain at the yield point is not limited, the strain at the yield point may usually be 90% or less.
The larger the tensile modulus, the greater the force required to deform, so materials with a small tensile modulus are more likely to deform. The lower limit of the tensile modulus in the present invention is 1.8 Gpa, while the tensile strength of a resin film with high tensile strength is approximately 200 N/mm ² . For films with different tensile moduli, the amount of strain to reach a tensile strength of 200 N/mm ² was calculated, and the relationship between the tensile modulus and the amount of strain at 200 N/mm ² was determined, and the amount of strain for a film with a tensile modulus of 1.8 GPa was determined. When calculated, it can be estimated that the film of the present invention having a lower limit of tensile modulus of 1.8 Gpa has a strain amount of approximately 90%. From this, approximately 90% is considered to be the upper limit.

The tensile test at the yield point of the stress-strain curve can be measured in the same manner as the tensile test at the tensile modulus.
The stress-strain curve is the relationship between the tensile stress and strain obtained in a tensile test. %) on the horizontal axis and tensile stress (MPa) on the vertical axis. The yield point of a polyimide film's stress-strain curve may be difficult to clearly see, for example as shown in FIG. Therefore, the strain (%) at the yield point of the stress-strain curve of the polyimide film of the present invention can be specifically determined as follows.
On the stress-strain curve, sampling is started from a point where the strain is 0.16%, and thereafter sampling is performed every time the strain increases by 0.21% (this is defined as dx). In other words, dx is the difference (amount of change) from the value sampled immediately before, and is 0.16% for the initial value and 0.21% thereafter. On the other hand, dy is the difference (amount of change) between the value of the tensile stress corresponding to the strain and the value sampled immediately before. After calculating dx and dy, graph the horizontal axis as strain % and the vertical axis as dy/dx (average rate of change) (for example, in the case of the stress-strain curve in Figure 3, the graph shown in Figure 4 and Become). As shown in Figure 4, the graph of strain % and dy/dx (average rate of change) is basically a downward-sloping graph, but the maximum value of dy/dx (average rate of change) is obtained. The first inflection point of dy/dx that appears beyond this point is defined as the yield point. In addition, for those in which the above-mentioned inflection point is not observed, the point where dy/dx becomes 0 for the first time is defined as the yield point.
The strain (%) at the yield point is a value rounded to the first decimal place according to Rule B of JIS Z8401:1999.

3. Total light transmittance
The polyimide film of the present invention has a total light transmittance of 85% or more as measured in accordance with JIS K7361-1. Since it has such a high transmittance, it has good transparency and can be used as a substitute material for glass. The total light transmittance of the polyimide film of the present invention measured in accordance with JIS K7361-1 is preferably 88% or more, even more preferably 89% or more, particularly 90% or more. It is preferable.

The total light transmittance measured in accordance with JIS K7361-1 can be measured, for example, with a haze meter (for example, HM150 manufactured by Murakami Color Research Institute). Note that from the measured value of the total light transmittance of a certain thickness, the total light transmittance of a different thickness can be converted into a converted value using Beer-Lambert's law, and this can be used.
Specifically, according to Beer-Lambert's law, the transmittance T is
Log ₁₀ (1/T)=kcb
It is expressed as (k=constant specific to the substance, c=concentration, b=optical path length).
In the case of the transmittance of a film, assuming that the density is constant even if the film thickness changes, c is also a constant, so the above formula can be calculated using the constant f as Log ₁₀ (1/T) = fb
(f=kc). Here, if the transmittance at a certain film thickness is known, the unique constant f of each substance can be determined. Therefore, by using the formula T=1/10 ^f·b and substituting a specific constant for f and the target film thickness for b, the transmittance at the desired film thickness can be determined.

4. Yellowness In addition, the polyimide film of the present invention has a yellowness (YI value) of 5 or less, which is calculated according to JIS K7373-2006. Since the yellowness is thus low, yellowish coloring is suppressed, light transmittance is improved, and it can be used as a glass substitute material. The yellowness index (YI value) calculated according to JIS K7373-2006 is preferably 4.5 or less, more preferably 4 or less, even more preferably 3.5 or less. .
In addition, the yellowness index (YI value) is measured using an ultraviolet-visible near-infrared spectrophotometer (for example, JASCO Corporation V-7100) and an auxiliary spectrophotometric method in accordance with JIS K7373-2006. Based on the transmittance measured at 1 nm intervals in the range of 250 nm or more and 800 nm or less using Illuminant C and a 2-degree field of view, the tristimulus values X, Y, and Z in the XYZ color system are determined, and the X, Y , Z can be calculated from the following formula.
YI=100(1.2769X-1.0592Z)/Y
In addition, from the measured value of the yellowness of a certain thickness, the yellowness of a different thickness is calculated from the above-mentioned total for each transmittance at each wavelength measured at 1 nm intervals in the range of 250 nm to 800 nm of a sample with a specific film thickness. Similar to the light transmittance, the converted value of each transmittance at each wavelength for different thicknesses can be determined according to Beer-Lambert's law, and the calculated value can be used based on the converted value.

In addition, the polyimide film of the present invention suppresses yellowish coloration, improves light transmittance, and can be suitably used as a glass substitute material. The value obtained by dividing the degree (YI value) by the film thickness (μm) (YI value/film thickness (μm)) is preferably 0.10 or less, more preferably 0.04 or less, and 0.03 The following is even more preferable.
In addition, in the present invention, the value obtained by dividing the yellowness degree (YI value) by the film thickness (μm) (YI value/film thickness (μm)) is expressed in the second decimal place according to Rule B of JIS Z8401:1999. The value shall be rounded.

5. Polyimide In the present invention, polyimide is obtained by reacting a tetracarboxylic acid component and a diamine component. After obtaining a polyamic acid precursor by polymerizing a tetracarboxylic acid component and a diamine component, it is preferable to imidize this precursor. Therefore, the polyimide used in the present invention contains a tetracarboxylic acid residue and a diamine residue in the main chain. Note that the term "tetracarboxylic acid residue" refers to a residue obtained by removing four carboxyl groups from tetracarboxylic acid, and represents the same structure as a residue obtained by removing the acid dianhydride structure from tetracarboxylic dianhydride. Moreover, a diamine residue refers to a residue obtained by removing two amino groups from a diamine.

As long as the strain (%) at the yield point of the stress-strain curve, the tensile modulus, the total light transmittance, and the yellowness specified in the present invention are obtained, film formation can be carried out in the state of the polyimide precursor. It may be carried out by a thermal imidization method in which polyimide is formed by molding the polyimide and then heat-treated to form the polyimide, or it may be carried out by forming the polyimide precursor into polyimide by chemical imidization, and then molding it in the state of a polyimide solution and removing the solvent. Alternatively, it can be produced by a combination of thermal imidization and chemical imidization.

In the polyimide used in the present invention, as the tetracarboxylic acid component that becomes a tetracarboxylic acid residue, for example, a tetracarboxylic acid component having an aromatic ring is preferable from the viewpoint of improving the surface hardness of the polyimide film.
Examples of the tetracarboxylic acid component having an aromatic ring include tetracarboxylic dianhydrides having an aromatic ring, such as pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride , 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride Acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)propane dianhydride, carboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxy phenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexa Fluoropropane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis[(3,4 -dicarboxy)benzoyl]benzene dianhydride, 1,4-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 2,2-bis{4-[4-(1,2-dicarboxy) ) phenoxy]phenyl}propane dianhydride, 2,2-bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride, bis{4-[4-(1,2- dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, 4,4'-bis[4-(1,2- dicarboxy)phenoxy]biphenyl dianhydride, 4,4'-bis[3-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy] ]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl }Sulfone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl} sulfide dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,4'-( hexafluoroisopropylidene) diphthalic anhydride, 3,3'-(hexafluoroisopropylidene) diphthalic anhydride, 4,4'-oxydiphthalic anhydride, 3,4'-oxydiphthalic anhydride, 2,3, 6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3, 4-Benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8 -Phenanthrenetetracarboxylic dianhydride and the like.

Further, as the tetracarboxylic acid component used in the present invention, a tetracarboxylic acid component having an aliphatic ring is also preferable from the viewpoint of light transmittance of the polyimide film.
Examples of the tetracarboxylic dianhydride having an aliphatic ring include cyclohexanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, and dicyclohexane-3,4,3',4'-tetracarboxylic dianhydride. Examples include anhydride, cyclobutanetetracarboxylic dianhydride, and the like.
The above-mentioned tetracarboxylic acid components can be used alone or in combination of two or more.

As the diamine component, for example, a diamine having an aromatic ring is preferable from the viewpoint of durability of the polyimide film and surface hardness.
Further, as the diamine component used in the present invention, a diamine having an aliphatic ring is also preferable from the viewpoint of light transmittance of the polyimide film.
Further, the polyimide film according to the present invention preferably contains a polyimide containing a diamine residue having an aromatic ring or an aliphatic ring and a diamine residue having a silicon atom in the main chain. By introducing a flexible molecular skeleton with silicon atoms in the main chain between the molecular skeletons containing aromatic or aliphatic rings as main components, polyimide can easily achieve both bending resistance and surface hardness. Moreover, the orientation is likely to be suppressed and the birefringence is likely to be reduced.

Examples of diamines having an aromatic ring include 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 2,2-bis(4-aminophenyl)propane, and 2,2-bis(4- (aminophenyl) hexafluoropropane, p-phenylenediamine, o-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide , 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzanilide, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 2-(3-aminophenyl) -2-(4-aminophenyl)propane, 2-(3-aminophenyl)-2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 1,1-di (4-aminophenyl)-1-phenylethane, 1-(3-aminophenyl)-1-(4-aminophenyl)-1-phenylethane, 1,3-bis(4-aminophenoxy)benzene, 1, 4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminobenzoyl)benzene, 1,4-bis(4-aminobenzoyl)benzene, 1,3-bis(4-amino-α,α -dimethylbenzyl)benzene, 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene, 1,4- Bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene, N,N'-bis(4-aminophenyl)terephthalamide, 9,9-bis(4-aminophenyl)fluorene, 3,3'- Dichloro-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-bis(4-amino phenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]ether, 2,2- Bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,3 -bis[4-(4-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(4-aminophenoxy)-α, α-dimethylbenzyl]benzene, 1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 4,4'-bis[4-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenylsulfone , 4,4'-bis[4-(4-aminophenoxy)phenoxy]diphenylsulfone, 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3'-diamino-4,4'-dibi Phenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis(4-aminophenoxy)-3,3,3',3' -tetramethyl-1,1'-spirobiindane, etc., and some or all of the hydrogen atoms on the aromatic ring of the diamine are selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group Diamines substituted with substituents can be used.

Examples of diamines having an aliphatic ring include trans-cyclohexane diamine, trans-1,4-bismethylenecyclohexane diamine, 2,6-bis(aminomethyl)bicyclo[2,2,1]heptane, and 2,5- Examples include bis(aminomethyl)bicyclo[2,2,1]heptane.

Examples of diamines having a silicon atom in the main chain include diamines represented by the following general formula (A).

(In general formula (A), L is each independently a direct bond or -O- bond, R ¹⁰ may each independently have a substituent, and does not contain an oxygen atom or a nitrogen atom. Represents a monovalent hydrocarbon group having 1 or more and 20 or less carbon atoms, which may be present. R ¹¹ is a carbon group which may independently have a substituent and may contain an oxygen atom or a nitrogen atom. Represents a divalent hydrocarbon group of the number 1 or more and 20 or less. k is a number from 0 to 200. The plurality of L, R ¹⁰ and R ¹¹ may be the same or different.)

The monovalent hydrocarbon group represented by R ¹⁰ includes an alkyl group having 1 to 20 carbon atoms, an aryl group, and a combination thereof. The alkyl group may be linear, branched, or cyclic, or may be linear or a combination of branched and cyclic.
The alkyl group having 1 to 20 carbon atoms is preferably an alkyl group having 1 to 10 carbon atoms, and specifically, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, Examples include t-butyl group, pentyl group, hexyl group, and the like. The cyclic alkyl group is preferably a cycloalkyl group having 3 or more and 10 or less carbon atoms, and specific examples include a cyclopentyl group and a cyclohexyl group. The aryl group is preferably an aryl group having 6 or more and 12 or less carbon atoms, and specifically includes a phenyl group, tolyl group, naphthyl group, and the like. Further, the monovalent hydrocarbon group represented by R ¹⁰ may be an aralkyl group, and examples thereof include a benzyl group, a phenylethyl group, a phenylpropyl group, and the like.
Examples of the hydrocarbon group that may contain an oxygen atom or a nitrogen atom include ether bond, carbonyl bond, ester bond, amide bond, and imino bond between the divalent hydrocarbon group described below and the monovalent hydrocarbon group. Included are groups bonded through at least one bond (--NH-).
The substituents that the monovalent hydrocarbon group represented by R ¹⁰ may have are not particularly limited as long as the effects of the present invention are not impaired, and include, for example, halogen atoms such as fluorine atoms and chlorine atoms. , hydroxyl group, etc.

The monovalent hydrocarbon group represented by ^R10 is an alkyl group having 1 to 3 carbon atoms, or an aryl group having 6 to 10 carbon atoms, from the viewpoint of improving bending resistance and compatibility with surface hardness. It is preferable that there be. The alkyl group having 1 to 3 carbon atoms is more preferably a methyl group, and the aryl group having 6 to 10 carbon atoms is more preferably a phenyl group.

Examples of the divalent hydrocarbon group represented by R ¹¹ include an alkylene group having 1 to 20 carbon atoms, an arylene group, and a combination thereof. The alkylene group may be linear, branched, or cyclic, or may be a combination of linear or branched and cyclic.
The alkylene group having 1 to 20 carbon atoms is preferably an alkylene group having 1 to 10 carbon atoms, such as linear groups such as methylene group, ethylene group, various propylene groups, various butylene groups, and cyclohexylene groups. Examples thereof include a combination of a branched or branched alkylene group and a cyclic alkylene group.
The arylene group is preferably an arylene group having 6 to 12 carbon atoms, and examples of the arylene group include a phenylene group, a biphenylene group, a naphthylene group, and further have a substituent for the aromatic ring described below. You can leave it there.
The divalent hydrocarbon group which may contain an oxygen atom or a nitrogen atom includes an ether bond, a carbonyl bond, an ester bond, an amide bond, and an imino bond (-NH-) between the divalent hydrocarbon groups. At least one bonded group may be mentioned.
The substituents that the divalent hydrocarbon group represented by R ¹¹ may have are the same as the substituents that the monovalent hydrocarbon group represented by R ¹⁰ above may have. It's good.

The divalent hydrocarbon group represented by ^R11 is an alkylene group having 1 to 6 carbon atoms, or an arylene group having 6 to 10 carbon atoms, from the viewpoint of improving bending resistance and compatibility with surface hardness. It is preferably an alkylene group having 2 or more and 4 or less carbon atoms.

Among them, from the viewpoint of achieving a protective film with improved bending resistance while maintaining sufficient surface hardness, diamine residues having a silicon atom in the main chain have one or two silicon atoms in the main chain. A diamine residue is preferable, and a diamine residue having two silicon atoms in the main chain is particularly preferable. Polyimide has a specific amount of short flexible molecular skeletons having one or two silicon atoms in the main chain introduced between rigid molecular skeletons containing aromatic or aliphatic rings. It is thought that it is easy to obtain a polyimide film in which the elastic deformation region is relatively large while maintaining the elastic modulus derived from the molecular skeleton containing , and it is easy to achieve both surface hardness and bending resistance.

Examples of diamines having one silicon atom in the main chain include diamines represented by the following general formula (A-1). Furthermore, examples of diamines having two silicon atoms in the main chain include diamines represented by the following general formula (A-2).

(In general formula (A-1) and general formula (A-2), L is each independently a direct bond or -O- bond, and R ¹⁰ is each independently a substituent. represents a monovalent hydrocarbon group having from 1 to 20 carbon atoms and which may contain an oxygen atom or a nitrogen atom.R ¹¹ may each independently have a substituent, and may include an oxygen atom or a nitrogen atom. or represents a divalent hydrocarbon group having 1 to 20 carbon atoms that may contain a nitrogen atom.The plurality of L, R ¹⁰ and R ¹¹ may be the same or different.)

From the viewpoint of improving bending resistance and compatibility with surface hardness, the molecular weight of the diamine residue having one or two silicon atoms in the main chain is preferably 1000 or less, more preferably 800 or less, It is even more preferably 500 or less, particularly preferably 300 or less.
Diamine residues having one or two silicon atoms in the main chain can be used alone or in combination of two or more.

Further, it is preferable that the diamine having one or two silicon atoms in the main chain is a diamine having two silicon atoms, from the viewpoint of the light transmittance of the obtained polyimide, the bending resistance, and the surface hardness. Furthermore, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 1,3-bis(4-aminobutyl)tetramethyldisiloxane, 1,3-bis(5-aminopentyl)tetramethyldisiloxane, etc. However, these compounds are preferable from the viewpoint of easy availability of these compounds and the coexistence of light transmittance and surface hardness of the resulting polyimide.

When using a diamine having a silicon atom in the main chain, the ratio of the diamine having a silicon atom in the main chain to the total amount of diamine is not particularly limited, but from the viewpoint of improving the bending resistance of the resulting polyimide film, It is preferably at least mol %, more preferably at least 2.5 mol %, even more preferably at least 5 mol %. Further, from the viewpoint of bending resistance and surface hardness of the resulting polyimide film, the content is preferably 50 mol% or less, preferably 45 mol% or less, and more preferably 30 mol% or less.

In addition, from the viewpoint of improving the surface hardness of the obtained polyimide, when the total amount of the tetracarboxylic acid component and the diamine component is 100 mol%, the total amount of the tetracarboxylic acid having an aromatic ring and the diamine having an aromatic ring is It is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 75 mol% or more.

In the present invention, the polyimide contains an aromatic ring, and (i) a fluorine atom, (ii) an aliphatic ring, and (iii) the aromatic rings may be substituted with a sulfonyl group or fluorine. It is preferable to contain at least one selected from the group consisting of structures connected by alkylene groups, and further preferably to contain a diamine residue having a silicon atom in the main chain in addition to these structures.
In the present invention, since the polyimide contains at least one selected from a tetracarboxylic acid residue having an aromatic ring and a diamine residue having an aromatic ring, the molecular skeleton becomes rigid, durability is increased, and surface hardness is increased. However, the rigid aromatic ring skeleton tends to extend the absorption wavelength to longer wavelengths, and the transmittance in the visible light region tends to decrease.
When the polyimide contains (i) a fluorine atom, the light transmittance is improved because the electronic state within the polyimide skeleton can be made difficult to transfer charges. Furthermore, when (i) fluorine atoms are included in the polyimide, hygroscopicity is suppressed, so it is possible to suppress the tendency of the plastic deformation region to expand when the hygroscopicity is high, and it is possible to improve bending resistance in a high humidity environment. .
When the polyimide contains (ii) an aliphatic ring, the light transmittance is improved because the conjugation of π electrons in the polyimide skeleton can be broken, thereby inhibiting the movement of charges within the skeleton.
When polyimide contains (iii) a structure in which aromatic rings are connected to each other by a sulfonyl group or an alkylene group which may be substituted with fluorine, the movement of charges within the skeleton is inhibited by breaking the conjugation of π electrons within the polyimide skeleton. The light transmittance is improved since it can be inhibited.

Among these, polyimide containing fluorine atoms is preferably used because it improves light transmittance, surface hardness, and bending resistance.
The content of fluorine atoms is preferably such that the ratio of the number of fluorine atoms (F) to the number of carbon atoms (C) (F/C) measured on the polyimide surface by X-ray photoelectron spectroscopy is 0.01 or more, Furthermore, it is preferably 0.05 or more. On the other hand, if the content of fluorine atoms is too high, there is a risk that the inherent heat resistance of polyimide will be reduced, so the ratio of the number of fluorine atoms (F) to the number of carbon atoms (C) (F/C) is 1 or less. It is preferable that it is, and it is more preferable that it is 0.8 or less.
Here, the above ratio measured by X-ray photoelectron spectroscopy (XPS) can be determined from the atomic percent value of each atom measured using an X-ray photoelectron spectrometer (for example, Thermo Scientific Theta Probe). .

Furthermore, from the viewpoint of surface hardness, light transmittance, and bending resistance of the obtained polyimide, it is preferable that at least one of the tetracarboxylic acid and the diamine not having a silicon atom contains an aromatic ring and a fluorine atom. Furthermore, it is preferred that both the tetracarboxylic acid and the silicon-free diamine contain an aromatic ring and a fluorine atom.
In terms of surface hardness, light transmittance, and bending resistance of the resulting polyimide, when the total amount of the tetracarboxylic acid component and diamine component is 100 mol%, a tetracarboxylic acid having an aromatic ring and a fluorine atom, and The total amount of the diamine having an aromatic ring and a fluorine atom is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 75 mol% or more.

In addition, 50% or more of the hydrogen atoms bonded to carbon atoms contained in the tetracarboxylic acid component and the diamine component are hydrogen atoms bonded directly to the aromatic ring, which improves the light transmittance of the resulting polyimide. Moreover, it is preferably used from the viewpoint of improving surface hardness and bending resistance. The proportion of hydrogen atoms (number) directly bonded to aromatic rings in all hydrogen atoms (number) bonded to carbon atoms is further preferably 60% or more, more preferably 70% or more. .
If 50% or more of the hydrogen atoms bonded to carbon atoms contained in each of the tetracarboxylic acid component and the diamine component are hydrogen atoms bonded directly to the aromatic ring, even after the heating step in the atmosphere, for example Even when stretching is performed at 200° C. or higher, it is preferable from the viewpoint of little change in optical properties, especially total light transmittance and yellowness YI value, and from the viewpoint of suppressing a decrease in bending resistance. If 50% or more of the hydrogen atoms bonded to carbon atoms are hydrogen atoms directly bonded to aromatic rings, the chemical structure of the resulting polyimide is difficult to change due to low reactivity with oxygen, and It is estimated that deterioration of the polyimide film is suppressed. Taking advantage of its high heat resistance, polyimide film is often used in devices that require processing steps that involve heating, but 50% of the hydrogen atoms bonded to carbon atoms contained in the tetracarboxylic acid component and diamine component, respectively. If the above is a hydrogen atom directly bonded to an aromatic ring, there is no need to perform these post-processes in an inert atmosphere to maintain transparency, reducing equipment costs and atmosphere control costs. The advantage is that it can be suppressed.
Here, the ratio of hydrogen atoms (number) directly bonded to aromatic rings among all hydrogen atoms (number) bonded to carbon atoms contained in polyimide is determined by It can be determined using an analyzer and NMR. For example, a sample is decomposed with an alkaline aqueous solution or supercritical methanol, the resulting decomposed products are separated by high performance liquid chromatography, and the qualitative analysis of each separated peak is performed using a gas chromatograph mass spectrometer, NMR, etc. By quantifying using high-performance liquid chromatography, it is possible to determine the ratio of hydrogen atoms (number) directly bonded to the aromatic ring among all hydrogen atoms (number) contained in the polyimide.

The polyimide film according to the present invention preferably contains a polyimide having a structure represented by the following general formula (1).

(In general formula (1), R ¹ represents a tetravalent group that is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and each of the plurality of R ^1s may be the same or different. , R ² represents a divalent group which is a diamine residue, each of the plurality of R ² may be the same or different, and at least a part of the plurality of R ² has an aromatic ring or an aliphatic ring. (N represents the number of repeating units.)

R ¹ represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and each of the plurality of R ^1s may be the same or different.
As the tetracarboxylic dianhydride having an aromatic ring and the tetracarboxylic dianhydride having an aliphatic ring in R ¹ , the same ones as mentioned above can be used.
These can be used alone or in combination of two or more.

Among them, R ¹ in the general formula (1) is a cyclohexanetetracarboxylic dianhydride residue, a cyclopentanetetracarboxylic dianhydride residue, from the viewpoint of light transmittance, bending resistance, and surface hardness in the resulting polyimide. Anhydride residue, dicyclohexane-3,4,3',4'-tetracarboxylic dianhydride residue, cyclobutanetetracarboxylic dianhydride residue, pyromellitic dianhydride residue, 3,3' , 4,4'-biphenyltetracarboxylic dianhydride residue, 2,2',3,3'-biphenyltetracarboxylic dianhydride residue, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride 3,4'-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene) diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride residue It is preferably at least one type of tetravalent group selected from the group consisting of 3,4'-oxydiphthalic anhydride residues and 3,4'-oxydiphthalic anhydride residues.

In view of particularly good light transmittance, the tetracarboxylic acid components include 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, 3,4'-(hexafluoroisopropylidene) diphthalic anhydride, 3,3 More preferably, it is at least one selected from the group consisting of '-(hexafluoroisopropylidene) diphthalic anhydride, 4,4'-oxydiphthalic anhydride, and 3,4'-oxydiphthalic anhydride.

Tetracarboxylic acid components include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 2,2',3,3'-biphenyltetracarboxylic dianhydride. a tetracarboxylic acid group (group A) suitable for improving the rigidity of the resulting polyimide, such as at least one selected from the group consisting of cyclohexanetetracarboxylic dianhydride, cyclopentanetetracarboxylic acid; Acid dianhydride, dicyclohexane-3,4,3',4'-tetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, 3 , 4'-(hexafluoroisopropylidene) diphthalic anhydride, 3,3'-(hexafluoroisopropylidene) diphthalic anhydride, 4,4'-oxydiphthalic anhydride, and 3,4'-oxydiphthalic acid It is also preferable to use a mixture with a tetracarboxylic acid group (group B) suitable for improving light transmittance, such as at least one selected from the group consisting of anhydrides. In this case, the content ratio of the tetracarboxylic acid group (group A) suitable for improving the rigidity and the tetracarboxylic acid group (group B) suitable for improving the light transmittance is The amount of the tetracarboxylic acid group (group A) suitable for improving the rigidity is 0.05 mol or more and 9 mol or less per 1 mol of the tetracarboxylic acid group (group B) suitable for improving the stiffness. The amount is preferably 0.1 mol or more and 5 mols or less, and even more preferably 0.3 mol or more and 4 mols or less.
Among them, as the group B, at least one of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride and 3,4'-(hexafluoroisopropylidene) diphthalic anhydride containing a fluorine atom is used. This is preferable from the viewpoint of improving the light transmittance of the obtained polyimide.

In the general formula (1), R ² represents a divalent group that is a diamine residue, each of the plurality of R ² may be the same or different, and at least a part of the plurality of R ² is aromatic. There is no particular restriction as long as it contains a diamine residue having a group ring or an aliphatic ring. As the divalent diamine residue, the same ones as mentioned above can be used.
These can be used alone or in combination of two or more.

As the diamine residue having an aromatic ring or an aliphatic ring contained in R ² , the same ones as mentioned above can be used.
These can be used alone or in combination of two or more.

Among these, from the viewpoints of light transmittance, bending resistance, surface hardness, and low hygroscopicity, the diamine residue having an aromatic ring or aliphatic ring in R ² in the general formula (1) is trans- Cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4'-diaminodiphenylsulfone residue, 3,4'-diaminodiphenylsulfone residue, 2,2-bis(4-aminophenyl) ) propane residue, 3,3'-bis(trifluoromethyl)-4,4'-[(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(4, 1-phenyleneoxy)] dianiline residue, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, 2,2-bis Selected from the group consisting of [4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue and a divalent group represented by the following general formula (2) It is preferable that at least one type of divalent group is used. As the divalent group represented by the following general formula (2), it is more preferable that R ³ and R ⁴ are perfluoroalkyl groups.

(In general formula (2), R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)
These can be used alone or in combination of two or more.

Further, one preferred embodiment for improving the bending resistance is that a diamine residue having a silicon atom in the main chain is included as a part of the plurality of ^R2 . The diamine residue having a silicon atom in the main chain that can be preferably used as R ² is as described above, and therefore its explanation will be omitted here.

When R ² in the general formula (1) contains a diamine residue having a silicon atom in the main chain, R ² in the general formula (1) is 2.5 mol% or more of the total amount of R ^{2 and} 50 mol % or less is a diamine residue having a silicon atom in the main chain, and 50 mol% or more and 97.5 mol% or less of the total amount of R ² does not have a silicon atom and has an aromatic ring or an aliphatic ring. A diamine residue is preferable from the viewpoint of achieving both bending resistance and surface hardness. From the viewpoint of improving bending resistance, R ² in the general formula (1) preferably has a diamine residue having a silicon atom in the main chain in an amount of 3.5 mol% or more based on the total amount of R ² , and further 5 It is preferable that it is mol% or more. Moreover, from the point of view of reducing optical distortion, the diamine residue having a silicon atom in the main chain may be more than 10 mol % or more than 15 mol % of the total amount of R ² . On the other hand, in R ² of the general formula (1), the diamine residue having a silicon atom in the main chain is preferably 45 mol% or less of the total amount of R ² in order to improve surface hardness and light transmittance. The content is preferably 40 mol% or less.
Note that 2.5 mol% or more and 50 mol% or less of the total amount of ^R2 is a diamine residue having a silicon atom in the main chain, and 50 mol% or more and 97.5 mol% or less of the total amount of ^R2 is silicon. If it satisfies that the diamine residue has no atoms and has an aromatic ring or an aliphatic ring, a diamine residue having a silicon atom in the main chain and a silicon atom can be added to R ² of the general formula (1). This does not preclude the inclusion of other diamine residues that are different from diamine residues that do not have an aromatic ring or an aliphatic ring. The content of the other diamine residue is preferably 10 mol% or less, more preferably 5 mol% or less, even more preferably 3 mol% or less, and particularly 1 mol% or less of the total amount of ^R2 . It is preferable that it is below. Examples of the other diamine residues include diamine residues that do not have a silicon atom and do not have an aromatic ring or an aliphatic ring.
Among them, 2.5 mol% or more and 50 mol% or less of the total amount of R ² is a diamine residue having a silicon atom in the main chain, and out of the total amount of R ² (100 mol %), a silicon atom in the main chain is The remainder (100%-x%) of the mol% (x mol%) of the diamine residues having 50 mol% or more and 97.5 mol% or less does not have a silicon atom and is an aromatic ring or an aliphatic ring. A diamine residue having the following is preferable.

Among them, in R ² of the general formula (1), 2.5 mol% or more and 50 mol % or less of the total amount of R ² is a diamine residue having one or two silicon atoms in the main chain, and R ² From the viewpoint of achieving both bending resistance and surface hardness, it is preferable that 50 mol% or more and 97.5 mol% or less of the total amount of the diamine residue does not have a silicon atom and has an aromatic ring or an aliphatic ring. .
Moreover, among these, R ² represents a divalent group that is at least one type selected from a diamine residue having no silicon atom and a diamine residue having one or two silicon atoms in the main chain; 2.5 mol% or more and 50 mol% or less of the total amount of ^R2 is a diamine residue having one or two silicon atoms in the main chain, and 50 mol% or more and 97.5 mol% or less of the total amount of ^R2 is a diamine residue having one or two silicon atoms in the main chain. A diamine residue having no silicon atom and having an aromatic ring or an aliphatic ring is preferable from the viewpoint of achieving both bending resistance and surface hardness.
R ² in the general formula (1) is such that the diamine residue having one or two silicon atoms in the main chain accounts for 3.5 mol% or more of the total amount of R ² in order to improve bending resistance. is preferable, and more preferably 5 mol% or more. In addition, from the viewpoint of reducing optical distortion, the diamine residue having one or two silicon atoms in the main chain may exceed 10 mol%, and may not exceed 15 mol% of the total amount of ^R2 . Also good. On the other hand, R ² in the general formula (1) has a diamine residue having one or two silicon atoms in the main chain in an amount of 45 mol% of the total amount of R ² in order to improve surface hardness and optical transparency. It is preferably at most 40 mol%, more preferably at most 40 mol%.
Among them, 2.5 mol% or more and 50 mol% or less of the total amount of R ² is a diamine residue having one or two silicon atoms in the main chain, and out of the total amount of R ² (100 mol%), the above Of the mol% (x mol%) of diamine residues having one or two silicon atoms in the main chain, the remainder (100%-x%), 50 mol% or more and 97.5 mol% or less, has silicon atoms. First, a diamine residue having an aromatic ring or an aliphatic ring is preferable.

In addition, from the viewpoint of bending resistance and surface hardness, the polyimide used in the present invention preferably has a silicon atom content (mass%) of 0.7% by mass or more and 6.5% by mass or less, It is more preferably 0.7% by mass or more and 5.5% by mass or less, and even more preferably 0.7% by mass or more and 4.2% by mass or less.
Here, the content ratio (mass %) of silicon atoms in polyimide refers to the content ratio (mass %) of silicon atoms in all the two or more polyimides when there are two or more types of polyimide, and the content ratio (mass %) of silicon atoms in the total polyimide of two or more types, and the It can be determined from the molecular weight. In addition, the content ratio (mass%) of silicon atoms in polyimide was calculated using high performance liquid chromatography, gas chromatograph mass spectrometer, NMR, elemental analysis, XPS/ESCA, and TOF for the polyimide decomposition product obtained in the same manner as above. - Can be determined using SIMS.
(Silicon atom content of polyimide (mass%))
For example, for 1 mole of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) as the acid dianhydride component, 2,2'-bis(trifluoromethyl)benzidine (TFMB) as the diamine component. When using 0.9 mol and 0.1 mol of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS), it can be calculated as follows.
The molecular weight of 1 mole of polyimide repeating unit is
6FDA origin: (C) 12.01 x 19 + (F) 19.00 x 6 + (O) 16.00 x 4 + (H) 1.01 x 6 = 412.25
TFMB origin: {(C)12.01×14+(F)19.00×6+(N)14.01×2+(H)1.01×6}×0.9=284.60
AprTMOS origin: {(C)12.01×10+(O)16.00×1+(N)14.01×2+(Si)28.09×2+(H)1.01×24}×0.1= 24.45
From this, it is calculated as 412.25+284.60+24.45=721.30.
The silicon atom content (mass%) in 1 mole of polyimide repeating units is:
(28.09×2×0.1)/721.30×100=0.8 (mass%).

In addition, from the viewpoint of achieving both bending resistance and surface hardness and light transmittance, in another preferred embodiment, in the general formula (1), R ² is a diamine residue having no silicon atom. It represents at least one selected divalent group and includes a diamine residue having a hexafluoroisopropylidene skeleton in the main chain. The diamine residue having a hexafluoroisopropylidene skeleton in its main chain preferably includes a structure in which aromatic rings are connected to each other by a hexafluoroisopropylidene group.

When R ² in the general formula (1) does not contain a diamine residue having a silicon atom in the main chain, R ² in the general formula (1) contains at least one diamine residue having no silicon atom. The diamine residue, which represents a divalent group as a species and does not have a silicon atom, has a main content in one molecule from the viewpoint of light transmittance, bending resistance, surface hardness, and low hygroscopicity. It is more preferable that the chain contains a diamine residue having a hexafluoroisopropylidene skeleton and the ratio (number %) of fluorine atoms to carbon atoms is 30% or more, and the aromatic rings are connected to each other by a hexafluoroisopropylidene group. It is even more preferable to include a structure in which aromatic rings are connected with each other with an oxy group, and a diamine residue in which the ratio (number %) of fluorine atoms to carbon atoms is 30% or more. .

Specifically, when R ² in the general formula (1) does not contain a diamine residue having a silicon atom in its main chain, the diamine residue having no silicon atom is specifically 3,3'-bis( trifluoromethyl)-4,4'-[(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(4,1-phenyleneoxy)]dianiline residue, 2, 2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, 2,2-bis[4-(4-aminophenoxy)phenyl]- 1,1,1,3,3,3-hexafluoropropane residue, 2-(3-aminophenyl)-2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoro Preferably, it is one or more diamine residues selected from the group consisting of propane and 2,2-bis(4-aminophenyl)hexafluoropropane, and 3,3'-bis(trifluoromethyl)-4 ,4'-[(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(4,1-phenyleneoxy)]dianiline residue, 2,2-bis[3- (3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1 , 3,3,3-hexafluoropropane residue, preferably one or more diamine residues selected from the group consisting of 3,3'-bis(trifluoromethyl)-4,4 '-[(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(4,1-phenyleneoxy)]dianiline residue is preferred.

When R ² in the general formula (1) does not contain a diamine residue having a silicon atom in the main chain, the above-mentioned preferred one is included in the total 100 mol% of the diamine residues not having a silicon atom in R ² . The total content of diamine residues not having silicon atoms is preferably 70 mol % or more, more preferably 80 mol % or more, and even more preferably 90 mol % or more.

The content ratio of each repeating unit and the content ratio (mol %) of each tetracarboxylic acid residue and each diamine residue in the polyimide can be determined from the molecular weight of the feed at the time of polyimide production. In addition, the content ratio (mol%) of each tetracarboxylic acid residue and each diamine residue in polyimide is the same as above for the decomposition product of polyimide obtained by decomposition with an aqueous alkaline solution or supercritical methanol. It can be determined using high performance liquid chromatography, gas chromatograph mass spectrometry, NMR, elemental analysis, XPS/ESCA and TOF-SIMS.

In the structure represented by the general formula (1), n represents the number of repeating units and is 1 or more, usually 2 or more.
The number n of repeating units in the polyimide may be appropriately selected and is not particularly limited.
The average number of repeating units is usually 10 to 2,000, more preferably 15 to 1,000.

The polyimide used in the present invention may contain one or more types.
Further, the polyimide used in the present invention may partially have a structure different from that of polyimide, such as a polyamide structure, as long as the effects of the present invention are not impaired.
In the polyimide used in the present invention, the structure represented by the general formula (1) preferably accounts for 95% or more, more preferably 98% or more, and 100% of the total repeating units of the polyimide. It is even more preferable that there be.
Examples of the structure different from the structure represented by the general formula (1) include cases where a tetracarboxylic acid residue having no aromatic ring or aliphatic ring is included, and a polyamide structure.
Examples of the polyamide structure that may be included include a polyamide-imide structure containing a tricarboxylic acid residue such as trimellitic anhydride, and a polyamide structure containing a dicarboxylic acid residue such as terephthalic acid.

The polyimide used in the present invention preferably has a number average molecular weight or a weight average molecular weight of at least 10,000, more preferably 20,000 or more, from the viewpoint of strength when formed into a film. Further, from the viewpoint of improving bending resistance, the polyimide preferably has a weight average molecular weight of 70,000 or more, more preferably 80,000 or more, and even more preferably 85,000 or more. On the other hand, if the average molecular weight is too large, the viscosity may become high and workability such as filtration may deteriorate, so it is preferably 1,000,000 or less, and more preferably 500,000 or less.
The number average molecular weight or weight average molecular weight of the polyimide used in the present invention can be measured in the same manner as the number average molecular weight or weight average molecular weight of the polyimide precursor described below.

6. Additives for Polyimide Film The polyimide film of the present invention may further contain additives in addition to the polyimide, if necessary. Examples of the additives include inorganic particles for reducing optical distortion of the polyimide film, silica filler for smooth winding, and surfactants for improving film formability and defoaming properties. It will be done.

7. Characteristics of Polyimide Film The polyimide film of the present invention has strain (%) at the yield point of the specific stress-strain curve, tensile modulus, total light transmittance, and yellowness. It is preferable that the polyimide film of the present invention further has the characteristics described below.

The polyimide film of the present invention preferably has a peak apex only in a temperature region of 150° C. or higher in a tan δ curve, which is a value obtained by dividing loss modulus by storage modulus. In the tan δ curve, if the apex of the peak exists below 150°C, the polyimide molecular chain is likely to move easily and undergo plastic deformation, which may deteriorate the bending resistance. This is because, if it does not exist, the mobility of molecular chains is suppressed, making it difficult to plastically deform, and improving bending resistance.
In addition, if the tan δ curve has its peak only in the temperature range of 150°C or higher, the loss of bending resistance due to thermal deformation can be suppressed even in high-temperature environments, such as inside a car in summer. It has improved bending resistance even under environmental conditions.
Furthermore, if the tan δ curve has the apex of the peak only in the temperature range of 150° C. or higher, the tensile modulus tends to increase and the surface hardness tends to increase.
In order to improve bending resistance and surface hardness, the polyimide film of the present invention preferably has the apex of the peak only in the temperature range of 200°C or higher in the tan δ curve, and preferably in the temperature range of 220°C or higher. It is even more preferable to have only the following. On the other hand, from the viewpoint of reducing the baking temperature, it is preferable that the apex of the peak in the tan δ curve be in a temperature range of 380° C. or lower.
In addition, the polyimide film of the present invention preferably does not have the apex of the peak in the tan δ curve in a temperature range of -150°C or higher and lower than 150°C, and further in a temperature range of -70°C or higher and lower than 150°C. Furthermore, it is preferable that the peak of the tan δ curve does not exist in a temperature range of 100° C. or lower, and more preferably that the peak of the tan δ curve does not exist in a temperature range of 0° C. or lower. When the main chain contains a diamine residue having a long siloxane bond, or when the main chain contains a large amount of diamine residue having a silicon atom, the apex of the peak in the tan δ curve is in such a low temperature region. There is.
The tan δ curve is determined from the relationship between temperature and tan δ (tan δ = loss elastic modulus (E'')/storage elastic modulus (E')) by dynamic viscoelasticity measurement, and the maximum value of the peak is the maximum value. The temperature at the top of the peak can be used as an index of the glass transition temperature. Dynamic viscoelasticity measurement is performed, for example, using a dynamic viscoelasticity measurement device RSA-G2 (TA Instruments Japan Co., Ltd.), with a measurement range of -150°C to 490°C, a frequency of 1 Hz, and an increasing temperature. This can be carried out at a temperature rate of 5° C./min. Moreover, the measurement can be performed with the sample width of 5 mm and the distance between chucks of 20 mm. When analyzing peaks and inflection points, data is digitized and analyzed from the numerical value without visual evaluation.
In addition, in the curve of temperature (horizontal axis) and tan δ (tan δ = loss elastic modulus (E'')/storage elastic modulus (E')) (vertical axis), the peak means that the value of tan δ is 0.2 or more, Preferably, it has a maximum value of 0.3 or more, and the peak width between the valleys of the peaks is 3°C or more. Regarding fine vertical fluctuations in the curve due to measurement such as noise, It is not observed as a peak at the apex of the above peaks.
The sample for measuring the tan δ curve is a polyimide film that has been left for 24 hours in an environment of 23°C ± 2°C and RH 30 to 50%, and is sampled into a 10cm square or more. Using a cutting jig with slits, cut out a piece 5 mm wide x 50 mm long (so that the sample length is 20 mm when chucked). To measure the width, use calipers to measure the width three times at different positions and record the average value. At this time, if part of the width measurement has a variation range of 3% or more of the average value, that sample is not used.

Further, in the polyimide film of the present invention, from the viewpoint of excellent surface hardness, the Young's modulus measured by the following measuring method is preferably 2.3 Gpa or more, and more preferably 2.4 Gpa or more.
Young's modulus is measured at a temperature of 25° C. according to ISO14577 using a nanoindentation method. Specifically, the measuring device is PICODENTOR HM500 manufactured by Fischer Instruments Co., Ltd., and the measuring indenter is a Vickers indenter. The Young's modulus is the value obtained by measuring eight arbitrary points on the surface of the polyimide film and taking the number average. Note that the measurement conditions are maximum indentation depth: 1000 nm, loading time: 20 seconds, and creep time: 5 seconds.

In the polyimide film of the present invention, the pencil hardness is preferably F or higher, more preferably H or higher.
The pencil hardness of the polyimide film was measured using a test pencil specified by JIS-S-6006, after conditioning the measurement sample for 2 hours at a temperature of 25°C and a relative humidity of 60%, as determined by JIS K5600-5-4. (1999) by conducting a pencil hardness test (0.98N load) on the film surface and evaluating the highest pencil hardness that does not cause scratches. For example, a pencil scratch coating hardness tester manufactured by Toyo Seiki Co., Ltd. can be used.

In the polyimide film of the present invention, from the viewpoint of bending resistance, in a tensile test to determine the strain (%) at the yield point of the specific stress-strain curve and the tensile modulus, the elongation rate (tensile The elongation (elongation) is preferably 5% or more, more preferably 7% or more. On the other hand, from the viewpoint of plastic deformation, the elongation rate (tensile elongation) is preferably 50% or less, more preferably 40% or less.
The elongation rate (%) = 100 x (L-Lo)/Lo
Lo: test length 20mm, L: test length at breakage

Since the polyimide film of the present invention has excellent bending resistance, it can be dynamically bent by bending it in accordance with the following dynamic bending test method so that the bending part is perpendicular to the tensile direction in which the strain value at the yield point is larger. When a bending test is performed, the internal angle of the test piece is preferably 140° or more, more preferably 145° or more, and even more preferably 150° or more.
[Dynamic bending test method]
Hereinafter, the method of the dynamic bending test will be explained with reference to FIG. 5.
Two movable metal plates 5 (100 mm x 30 mm) each having a movable part 5a and a non-movable part 5b are prepared, and they are arranged in parallel so that the distance between the non-movable parts 5b of the two metal plates 5 is 60 mm. Place it in The movable part 5a of the metal plate 5 is bent perpendicularly to the non-movable part 5b as shown in FIG. The test piece 1 is placed, and both ends of the test piece 1 are fixed to the movable part 5a with Kapton (registered trademark) tape so that the center of the test piece 1 is located at the center of the distance between the metal plates. Next, the movable part 5a and the non-movable part 5b are arranged in a straight line so that the state shown in FIG. The metal plates 5 on both sides are placed in parallel so that the distance between the metal plates 5 on both sides is 60 mm. In this state and in a state where the metal plates 5 on both sides are arranged in parallel so that the distance between the metal plates 5 on both sides is 2.5 mm, as shown in FIG. In an environment of relative humidity (RH) or an environment of 60° C. and 93% relative humidity (RH), the bending frequency is changed repeatedly at a rate of 90 times per minute, and the bending is repeated 200,000 times. As the test jig, a constant temperature and humidity chamber durability test system (manufactured by Yuasa System Instruments, planar unloaded U-shaped expansion/contraction test jig DMX-FS) can be used.
Thereafter, one end of the test piece is fixed, and the internal angle of the test piece is measured 30 minutes after the force applied to the test piece is released.
When testing by bending the bent part perpendicular to the tensile direction where the strain value at the yield point is larger, the tensile direction where the strain value at the yield point is larger is 100 mm from the long side. Cut out the test piece.
Note that if the film is completely returned to its original state without being affected by the dynamic bending test, the internal angle will be 180°.

The haze value of the polyimide film of the present invention is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less, from the viewpoint of light transmittance. It is preferable that the haze value can be achieved when the thickness of the polyimide film is 5 μm or more and 100 μm or less.
The haze value can be measured by a method based on JIS K-7136, for example, using a haze meter HM150 manufactured by Murakami Color Research Institute.

Further, the polyimide film of the present invention preferably has a birefringence index in the thickness direction at the wavelength of 590 nm of 0.040 or less, more preferably 0.020 or less. When having such a birefringence, the polyimide film of the present invention has reduced optical distortion. Therefore, when the polyimide film of the present invention is used as a display member, deterioration in the display quality of the display can be suppressed. The birefringence index in the thickness direction at a wavelength of 590 nm is preferably smaller, preferably 0.015 or less, more preferably 0.010 or less, and even more preferably less than 0.008. .
The birefringence in the thickness direction of the polyimide film of the present invention at the wavelength of 590 nm can be determined as follows.
First, the thickness direction retardation value (Rth) of the polyimide film is measured using a retardation measuring device (for example, manufactured by Oji Scientific Instruments Co., Ltd., product name "KOBRA-WR") at 25°C and with light at a wavelength of 590 nm. do. For the thickness direction retardation value (Rth), the retardation value at 0 degree incidence and the retardation value at oblique incidence at 40 degrees are measured, and the thickness direction retardation value Rth is calculated from these retardation values. The retardation value at an angle of incidence of 40 degrees is measured by making light with a wavelength of 590 nm enter the retardation film from a direction inclined at 40 degrees from the normal line of the retardation film.
The birefringence of the polyimide film in the thickness direction can be determined by substituting it into the formula: Rth/d. The above d represents the film thickness (nm) of the polyimide film.
Note that the thickness direction retardation value is defined as the refractive index in the slow axis direction in the in-plane direction of the film (the direction in which the refractive index in the film in-plane direction is maximum), and the refractive index in the fast axis direction in the film plane (the direction in which the refractive index is maximum in the film in-plane direction) When the refractive index in the direction in which the refractive index in the inward direction is the minimum is ny, and the refractive index in the thickness direction of the film is nz, it is expressed as Rth [nm] = {(nx + ny) / 2 - nz} × d. be able to.

Further, the atomic percent of silicon atoms (Si) on the surface of the polyimide film measured by X-ray photoelectron spectroscopy is preferably 0.1 or more and 10 or less, more preferably 0.2 or more and 5 or less.
Here, the above ratio measured by X-ray photoelectron spectroscopy (XPS) can be determined from the atomic % value of each atom measured using an X-ray photoelectron spectrometer (for example, Thermo Scientific Theta Probe). .

Further, in a preferred embodiment, the ratio (F/C) of the number of fluorine atoms (F) to the number of carbon atoms (C) on the film surface is 0.01 or more and 1 or less, as measured by X-ray photoelectron spectroscopy of the polyimide film. It is preferable that it is, and it is more preferable that it is 0.05 or more and 0.8 or less.
Further, the ratio (F/N) of the number of fluorine atoms (F) to the number of nitrogen atoms (N) on the film surface, as measured by X-ray photoelectron spectroscopy of the polyimide film, is preferably 0.1 or more and 20 or less. , and more preferably 0.5 or more and 15 or less.
Further, the ratio (F/Si) of the number of fluorine atoms (F) to the number of silicon atoms (Si) on the film surface, as measured by X-ray photoelectron spectroscopy of the polyimide film, is preferably 1 or more and 50 or less, and It is preferably 3 or more and 30 or less.

In addition, in the polyimide film of the present invention, when an adhesion test is conducted according to the adhesion test method below, the fact that the coating film does not peel off is important in terms of adhesion between the polyimide film and the hard coat layer. This is preferable from the viewpoint of surface hardness of a laminate in which a hard coat layer is laminated adjacent to a film.
[Adhesion test method]
A resin composition for adhesion evaluation prepared by adding 10 parts by mass of 1-hydroxy-cyclohexyl-phenyl-ketone to 100 parts by mass of pentaerythritol triacrylate to a 40 mass% methyl isobutyl ketone solution of pentaerythritol triacrylate. was applied onto a polyimide film test piece cut into a size of 10 cm x 10 cm, and cured by irradiation with ultraviolet rays at an exposure dose of 200 mJ/cm ² under a nitrogen stream to form a cured film with a thickness of 10 μm. The cured film is subjected to a cross-cut test in accordance with JIS K 5600-5-6, and after repeating the peeling operation with a tape 5 times, the presence or absence of peeling of the coating film is observed.

8. Structure of polyimide film The thickness of the polyimide film of the present invention may be appropriately selected depending on the use, but is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. . On the other hand, it is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and even more preferably 90 μm or less.
If the film is thin, the strength will decrease, and if the film is thick, the difference between the inner diameter and the outer diameter during bending will increase, which increases the load on the film, which may reduce the bending resistance.

Further, the polyimide film of the present invention may be subjected to surface treatments such as saponification treatment, glow discharge treatment, corona discharge treatment, ultraviolet treatment, and flame treatment.

9. Method for producing polyimide film The method for producing the polyimide film of the present invention is not particularly limited as long as it can produce the polyimide film of the present invention.
<First manufacturing method>
As a method for manufacturing the polyimide film of the present invention, for example, as a first manufacturing method,
A step of preparing a polyimide precursor resin composition containing polyamic acid, which is a polyimide precursor, and an organic solvent (hereinafter referred to as a polyimide precursor resin composition preparation step);
a step of applying the polyimide precursor resin composition to a support to form a polyimide precursor resin coating (hereinafter referred to as a polyimide precursor resin coating forming step);
a step of imidizing the polyimide precursor by heating (hereinafter referred to as an imidization step);
A step of stretching at least one of the polyimide precursor resin coating film and an imidized coating film obtained by imidizing the polyimide precursor resin coating film (hereinafter referred to as a stretching step);
A method for producing a polyimide film including:

In the first manufacturing method, at least one of the polyimide precursor resin coating film and the imidized coating film is formed so that the ratio of the tensile modulus of elasticity has anisotropy of 1.50 or more. It has a step of stretching.
Each step will be explained in detail below.

(1) Polyimide precursor resin composition preparation step The polyimide precursor resin composition prepared in the first manufacturing method contains a polyimide precursor and an organic solvent, and optionally contains additives. You can leave it there. Examples of the polyimide precursor include a polyamic acid obtained by polymerizing the above-mentioned tetracarboxylic acid component and the above-mentioned diamine component, such as a polyimide precursor represented by the following general formula (1'). . The polyimide precursor represented by the general formula (1') comprises a tetracarboxylic acid component serving as a tetracarboxylic acid residue in ^R1 of the general formula (1'), and ^R2 of the general formula (1'). It is a polyamic acid obtained by polymerization with a diamine component that becomes a diamine residue.

(In general formula (1'), R ¹ , R ² and n are the same as in general formula (1) above.)

Here, R ¹ , R ² and n in the general formula (1') can be the same as R ¹ , R ² and n in the general formula (1) explained in connection with the polyimide.

The polyimide precursor represented by the general formula (1') preferably has a number average molecular weight or a weight average molecular weight of at least 10,000, more preferably 20,000, from the viewpoint of strength when formed into a film. It is preferable that it is above. Further, from the viewpoint of improving bending resistance, the polyimide precursor represented by the general formula (1') preferably has a weight average molecular weight of 70,000 or more, more preferably 80,000 or more, and even more It is preferable that it is 85,000 or more. On the other hand, if the average molecular weight is too large, the viscosity may become high and workability such as filtration may be deteriorated, so it is preferably 1,000,000 or less, and more preferably 500,000 or less.
The number average molecular weight of the polyimide precursor can be determined by NMR (for example, AVANCE III manufactured by BRUKER). For example, after applying a polyimide precursor solution to a glass plate and drying it at 100°C for 5 minutes, 10 mg of the solid content is dissolved in 7.5 ml of dimethyl sulfoxide-d6 solvent, and NMR measurement is performed to determine whether the polyimide precursor solution is bonded to an aromatic ring. The number average molecular weight can be calculated from the peak intensity ratio of hydrogen atoms.
The weight average molecular weight of the polyimide precursor can be measured by gel permeation chromatography (GPC).
The polyimide precursor was an N-methylpyrrolidone (NMP) solution with a concentration of 0.5% by weight, and the developing solvent was a 10mmol% LiBr-NMP solution with a water content of 500ppm or less. Measurement is performed using a column (GPC LF-804 manufactured by SHODEX) under conditions of a sample injection volume of 50 μL, a solvent flow rate of 0.5 mL/min, and a temperature of 40°C. The weight average molecular weight is determined based on a polystyrene standard sample having the same concentration as the sample.

The polyimide precursor solution is obtained by reacting the above-mentioned tetracarboxylic dianhydride and the above-mentioned diamine in a solvent. The solvent used for the synthesis of the polyimide precursor (polyamic acid) is not particularly limited as long as it can dissolve the above-mentioned tetracarboxylic dianhydride and diamine; for example, an aprotic polar solvent or a water-soluble alcoholic solvent may be used. Can be used. In the present invention, among others, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone, etc. It is preferable to use an organic solvent containing a nitrogen atom such as γ-butyrolactone. Among them, when the polyimide precursor solution (polyamic acid solution) is used as it is for preparing a polyimide precursor resin composition, it is preferable to use an organic solvent containing a nitrogen atom, and among them, N,N-dimethylacetamide, N- Preferably, methyl-2-pyrrolidone or a combination thereof is used. Note that the organic solvent is a solvent containing carbon atoms.

Further, when the polyimide precursor solution is prepared by combining at least two types of diamines, an acid dianhydride may be added to a mixed solution of at least two types of diamines to synthesize a polyamic acid, or at least The two types of diamine components may be added to the reaction solution in stages at appropriate molar ratios to control, to some extent, the sequence in which each raw material is incorporated into the polymer chain.
For example, by adding an acid dianhydride in a molar ratio of 0.5 equivalent of the diamine having a silicon atom in the main chain to a reaction solution in which a diamine having a silicon atom in the main chain is reacted, acid dianhydride can be reacted. Synthesize an amic acid in which a diamine having a silicon atom in the main chain reacts with both ends of an anhydride, add all or part of the remaining diamine, add an acid dianhydride, and polymerize a polyamic acid. Also good. When polymerized by this method, diamines having silicon atoms in the main chain are introduced into the polyamic acid in a connected form via one acid dianhydride.
Polymerizing polyamic acid by such a method is preferable because the positional relationship of the amic acid having a silicon atom in the main chain is specified to some extent, and it is easy to obtain a film with excellent bending resistance while maintaining surface hardness.

When the number of moles of diamine in the polyimide precursor solution (polyamic acid solution) is a, and the number of moles of tetracarboxylic dianhydride is b, b/a may be set to 0.9 or more and 1.1 or less. It is preferably 0.95 or more and 1.05 or less, even more preferably 0.97 or more and 1.03 or less, and particularly preferably 0.99 or more and 1.01 or less. By setting it as such a range, the molecular weight (degree of polymerization) of the polyamic acid obtained can be adjusted appropriately.
The procedure of the polymerization reaction is not particularly limited and can be appropriately selected from known methods.
Alternatively, the polyimide precursor solution obtained by the synthesis reaction may be used as it is, and other components may be mixed therein as necessary, or the solvent of the polyimide precursor solution may be dried and dissolved in another solvent. May be used.

The viscosity of the polyimide precursor solution at 25° C. is preferably 500 cps or more and 200,000 cps or less from the viewpoint of forming a uniform coating film and polyimide film.
The viscosity of the polyimide precursor solution can be measured at 25° C. using a viscometer (eg, TVE-22HT, Toki Sangyo Co., Ltd.).

The polyimide precursor resin composition may contain additives as necessary. Examples of the additives include inorganic particles for reducing optical distortion of the polyimide film, silica filler for smooth winding, and surfactants for improving film formability and defoaming properties. The same materials as those described in connection with the polyimide film described above can be used.

The organic solvent used in the polyimide precursor resin composition is not particularly limited as long as it can dissolve the polyimide precursor. For example, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone, etc. containing a nitrogen atom Organic solvents such as γ-butyrolactone can be used, but among them, organic solvents containing nitrogen atoms are preferably used for the reasons mentioned above.

The content of the polyimide precursor in the polyimide precursor resin composition is 50% by mass or more in the solid content of the resin composition in order to form a polyimide film having a uniform coating film and handleable strength. The content is preferably 60% by mass or more, and the upper limit may be adjusted as appropriate depending on the components contained.
The organic solvent in the polyimide precursor resin composition preferably accounts for 40% by mass or more, and more preferably 50% by mass or more, from the viewpoint of forming a uniform coating film and polyimide film. The content is preferably 99% by mass or less.

Further, it is preferable that the polyimide precursor resin composition has a water content of 1000 ppm or less, since the storage stability of the polyimide precursor resin composition can be improved and productivity can be improved. If the polyimide precursor resin composition contains a large amount of water, the polyimide precursor may be easily decomposed.
The moisture content of the polyimide precursor resin composition can be determined using a Karl Fischer moisture meter (for example, trace moisture meter CA-200 manufactured by Mitsubishi Chemical Corporation).

The viscosity of the polyimide precursor resin composition at 25° C. at a solid content of 15% by weight is preferably 500 cps or more and 100,000 cps or less, from the viewpoint of forming a uniform coating film and polyimide film.
The viscosity of the polyimide precursor resin composition can be measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25° C. and with a sample volume of 0.8 ml.

(2) Polyimide precursor resin coating film forming step In the step of coating the polyimide precursor resin composition on a support to form a polyimide precursor resin coating, the support used has a smooth surface and is heat resistant. There are no particular limitations as long as the material is durable and solvent resistant. Examples include inorganic materials such as glass plates, metal plates with mirror-treated surfaces, and the like. Further, the shape of the support is selected depending on the coating method, and may be, for example, plate-like, drum-like, belt-like, sheet-like that can be wound up on a roll, or the like.

The coating means is not particularly limited as long as it is capable of coating the desired film thickness, and for example, known methods such as a die coater, comma coater, roll coater, gravure coater, curtain coater, spray coater, lip coater, etc. can be used. .
The coating may be performed using a single-wafer type coating device or a roll-to-roll type coating device.

After applying the polyimide precursor resin composition to a support, the solvent in the coating film is dried at a temperature of 150° C. or lower, preferably 30° C. or higher and 120° C. or lower until the coating film becomes tack-free. By setting the drying temperature of the solvent to 150° C. or lower, imidization of the polyamic acid can be suppressed.

The drying time may be adjusted as appropriate depending on the thickness of the polyimide precursor resin coating, the type of solvent, the drying temperature, etc., but it is usually 1 minute to 60 minutes, preferably 2 minutes to 30 minutes. is preferred. If it exceeds the upper limit, it is not preferable from the viewpoint of production efficiency of polyimide film. On the other hand, if it is less than the lower limit, the appearance of the resulting polyimide film may be affected due to rapid drying of the solvent.

The method for drying the solvent is not particularly limited as long as the solvent can be dried at the above temperature, and for example, an oven, drying oven, hot plate, infrared heating, etc. can be used.
When sophisticated control of optical properties is required, the atmosphere during drying of the solvent is preferably an inert gas atmosphere. The inert gas atmosphere is preferably a nitrogen atmosphere, and the oxygen concentration is preferably 100 ppm or less, more preferably 50 ppm or less. If heat treatment is performed in the atmosphere, the film may be oxidized, colored, or its performance may deteriorate.

(3) Imidization step In the first manufacturing method, the polyimide precursor is imidized by heating.
In the production method, the imidization step may be performed on the polyimide precursor in the polyimide precursor resin coating film before the stretching step, or on the polyimide precursor in the polyimide precursor resin coating film after the stretching step. It may be performed on the body, or it may be performed on both the polyimide precursor in the polyimide precursor resin coating film before the stretching process and the polyimide precursor present in the film after the stretching process.

The imidization temperature may be appropriately selected depending on the structure of the polyimide precursor.
Usually, it is preferable that the heating start temperature be 30°C or higher, and more preferably 100°C or higher. On the other hand, it is preferable that the heating end temperature is 250°C or higher.

The rate of temperature increase is preferably selected appropriately depending on the thickness of the polyimide film to be obtained, and when the thickness of the polyimide film is thick, it is preferable to slow the rate of temperature increase.
From the viewpoint of production efficiency of polyimide film, the heating rate is preferably 5°C/min or more, and more preferably 10°C/min or more. On the other hand, the upper limit of the temperature increase rate is usually 50°C/min, preferably 40°C/min or less, and more preferably 30°C/min or less. It is preferable to set the temperature increase rate to the above range from the viewpoints of suppressing poor appearance and strength reduction of the film, controlling whitening caused by imidization reaction, and improving light transmittance.

The temperature may be raised continuously or stepwise, but it is preferable to raise the temperature continuously from the viewpoint of suppressing poor appearance and strength reduction of the film and controlling whitening accompanying the imidization reaction. Moreover, in the entire temperature range mentioned above, the temperature increase rate may be constant or may be changed midway.

It is preferable that the atmosphere at the time of temperature rise during imidization is an inert gas atmosphere. The inert gas atmosphere is preferably a nitrogen atmosphere, and the oxygen concentration is preferably 500 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. If heat treatment is performed in the atmosphere, the film may be oxidized, colored, or its performance may deteriorate.
However, if 50% or more of the hydrogen atoms bonded to carbon atoms contained in polyimide are hydrogen atoms bonded directly to aromatic rings, the influence of oxygen on optical properties is small and an inert gas atmosphere may not be used. Polyimide with high light transmittance can also be obtained.

The heating method for imidization is not particularly limited as long as the temperature can be raised to the above temperature, and for example, an oven, a heating furnace, infrared heating, electromagnetic induction heating, etc. can be used.

Among these, it is more preferable that the imidization rate of the polyimide precursor is 50% or more before the stretching step. By setting the imidization rate to 50% or more before the stretching process, even if stretching is performed after the process, heating is performed at a higher temperature for a certain period of time, and imidization is performed, the appearance of the film will not be defective. Whitening is suppressed. Above all, from the viewpoint of improving the surface hardness of the polyimide film, it is preferable to set the imidization rate to 80% or more in the imidization step before the stretching step, and to allow the reaction to proceed to 90% or more, and even to 100%. is preferred. It is presumed that by stretching after imidization, the surface hardness is improved because the rigid polymer chains are easily oriented.
Note that the imidization rate can be measured by spectral analysis using infrared measurement (IR) or the like.

In order to obtain the final polyimide film, it is preferable to allow the imidization to proceed to 90% or more, further 95% or more, and even 100%.
In order to advance the imidization reaction to 90% or more, and even to 100%, it is preferable to hold the heating end temperature for a certain period of time, and the holding time is usually 1 minute to 180 minutes, more preferably 5 minutes to 150 minutes. It is preferable to set it to 1 minute.

(4) Stretching step In the first manufacturing method, the polyimide precursor resin coating film and the polyimide precursor The method includes a stretching step of stretching at least one of the imidized coating films obtained by imidizing the body resin coating film. Among others, it is preferable that the stretching step includes a step of stretching the coating film after imidization, from the viewpoint of improving the surface hardness of the polyimide film.

In the first manufacturing method, the step of stretching the film by 101% or more and 10,000% or less, when the initial dimension before stretching is taken as 100%, is preferably performed while heating at 80° C. or higher.
The heating temperature during stretching is preferably within the range of ±50° C. of the glass transition temperature of the polyimide or polyimide precursor, and preferably within the range of ±40° C. of the glass transition temperature. If the stretching temperature is too low, the film may not deform and sufficient orientation may not be induced. On the other hand, if the stretching temperature is too high, the orientation obtained by stretching may be relaxed by the temperature, and sufficient orientation may not be obtained.
The stretching step may be performed simultaneously with the imidization step. Imidization rate of 80% or more, further 90% or more, even 95% or more, especially substantially 100% After imidization, stretching the coating after imidization improves the surface hardness of the polyimide film. Preferable from this point of view.

The stretching ratio of the polyimide film is preferably 101% or more and 10000% or less, more preferably 160% or more and 500% or less, even more preferably 160% or more and 300% or less. By stretching within the above range, the surface hardness of the resulting polyimide film can be further improved.

The method of fixing the polyimide film during stretching is not particularly limited, and is selected depending on the type of stretching device and the like. Further, the stretching method is not particularly limited, and for example, it is possible to stretch the film while passing it through a heating furnace using a stretching device having a conveying device such as a tenter. The polyimide film may be stretched in only one direction (longitudinal stretching or transverse stretching), or may be stretched in two directions by simultaneous biaxial stretching, sequential biaxial stretching, diagonal stretching, or the like.
Among these, an anisotropic method in which the ratio of the tensile modulus in a tensile test in which the tensile direction is in the X direction, which is one direction within the film plane, and in a tensile test in which the tensile direction is in the Y direction orthogonal to the X direction is 1.50 or more. It is preferable to stretch the film in only one direction so as to maintain the properties.

<Second manufacturing method>
Moreover, as a manufacturing method of the polyimide film of the present invention, as a second manufacturing method,
A step of preparing a polyimide resin composition containing polyimide and an organic solvent (hereinafter referred to as a polyimide resin composition preparation step);
A step of applying the polyimide resin composition to a support and drying the solvent to form a polyimide resin coating (hereinafter referred to as polyimide resin coating forming step);
A step of stretching the polyimide resin coating (hereinafter referred to as a stretching step);
A method for producing a polyimide film including:

When the polyimide dissolves well in an organic solvent, a polyimide resin composition in which the polyimide is dissolved in an organic solvent and optionally contains additives is also preferably used instead of a polyimide precursor resin composition. be able to.
When the polyimide has a solvent solubility such that 5% by mass or more is dissolved in an organic solvent at 25° C., the production method can be suitably used.

In the polyimide resin composition preparation step, the polyimide having the above-mentioned solvent solubility can be selected from the polyimides similar to those described for the polyimide film. As for the imidization method, it is preferable to use chemical imidization using a chemical imidization agent instead of thermal dehydration in the dehydration ring-closing reaction of the polyimide precursor. When chemical imidization is performed, known compounds such as amines such as pyridine and β-picolinic acid, carbodiimides such as dicyclohexylcarbodiimide, and acid anhydrides such as acetic anhydride may be used as dehydration catalysts. The acid anhydride is not limited to acetic anhydride, but includes propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, etc., but is not particularly limited. Further, at this time, a tertiary amine such as pyridine or β-picolinic acid may be used in combination. However, if these amines remain in the film, they will reduce the optical properties, especially the yellowness (YI value), so instead of forming the film by directly casting the reaction solution that reacts the precursor to polyimide, It is preferable to form a film after purifying it by reprecipitation or the like and removing components other than polyimide to 100 ppm or less of the total weight of the polyimide.

In the polyimide resin composition preparation step, the organic solvent used in the reaction solution for chemically imidizing the polyimide precursor may be, for example, those explained in the polyimide precursor resin composition preparation step in the first production method. Similar ones can be used. In the polyimide resin composition preparation step, examples of the organic solvent used to redissolve the purified polyimide from the reaction solution include ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol mono-normal-butyl ether, Ethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ortho-dichlorobenzene, xylene, cresol, chlorobenzene, isobutyl acetate, isopentyl acetate, normal-butyl acetate, normal-propyl acetate, normal-pentyl acetate, cyclohexanol, cyclohexanone, 1.4-Dioxane, tetrachlorethylene, toluene, methyl isobutyl ketone, methylcyclohexanol, methylcyclohexanone, methyl-n-butylketone, dichloromethane, dichloroethane, and mixed solvents thereof, among others, dichloromethane, n-butyl acetate, etc. At least one selected from the group consisting of , propylene glycol monomethyl ether acetate, and mixed solvents thereof can be preferably used.

The polyimide resin composition may contain additives as necessary. As the additive, the same additives as those explained in the polyimide precursor resin composition preparation step in the first manufacturing method can be used.
Further, in the second manufacturing method, the method of controlling the moisture content of the polyimide resin composition to 1000 ppm or less, and the method of dispersing the inorganic particles in an organic solvent include the method of dispersing the polyimide precursor in the first manufacturing method. A method similar to that described in the resin composition preparation step can be used.

In addition, in the polyimide resin coating forming step in the second manufacturing method, the same support and coating method as those explained in the polyimide precursor resin coating forming step in the first manufacturing method are used. be able to.
In the polyimide resin coating forming step in the second manufacturing method, the drying temperature is preferably 80° C. or higher and 150° C. or lower under normal pressure. Under reduced pressure, the temperature is preferably in the range of 10°C or higher and 100°C or lower.

Further, the second manufacturing method may include a step of further heating the polyimide resin coating after the polyimide resin coating forming step, in order to volatilize the remaining solvent. It is preferable to include such a heating step from the viewpoint of improving film strength and chemical resistance.
The heating step can be the same as the heating imidization step in the first manufacturing method.

In addition, in the second manufacturing method, the polyimide resin coating is stretched after the polyimide resin coating film forming step in order to have anisotropy such that the ratio of the tensile modulus is 1.50 or more. It has a stretching process.
The stretching step can be similar to the stretching step in the first manufacturing method.

The second manufacturing method is preferable because it easily reduces the yellowness (YI value) of the polyimide film. According to the second manufacturing method, it is possible to suitably form a polyimide film in which the value obtained by dividing the yellowness calculated in accordance with JIS K7373-2006 by the film thickness (μm) is 0.04 or less. be.

10. Applications of Polyimide Film Applications of the polyimide film of the present invention are not particularly limited, and can be used as members such as base materials and surface materials for which glass products such as thin plate glass have conventionally been used. The polyimide film of the present invention has improved bending resistance, has sufficient surface hardness as a protective film, and has reduced optical distortion, so it can be suitably used as a display member that can accommodate curved surfaces. can.
Specifically, the polyimide film of the present invention can be used for flexible panels used in thin and bendable organic EL displays, mobile terminals such as smartphones and wristwatch-type terminals, display devices inside automobiles, wristwatches, etc. It can be suitably used for base materials and surface materials for flexible displays. In addition, the polyimide film of the present invention can be used for members for image display devices such as liquid crystal display devices and organic EL display devices, members for touch panels, members for solar cell panels such as flexible printed circuit boards, surface protection films and substrate materials, and optical waveguides. It can also be applied to other semiconductor-related parts, etc.

III. Laminate The laminate of the present invention has the above-described film or polyimide film of the present invention and a hard coat layer containing at least one polymer of a radically polymerizable compound and a cationically polymerizable compound, and comprises the film or This is a laminate that is used by bending the polyimide film so that the bending part is perpendicular to the tensile direction in which the strain value at the yield point of the polyimide film becomes larger.
Since the laminate of the present invention uses the above-described film or polyimide film of the present invention, it has excellent transparency and improved bending resistance. Furthermore, since it has a hard coat layer, it has a higher surface hardness. It is an improved film or resin film.

In the laminate of the present invention, it is preferable that the polyimide contained in the polyimide film contains a diamine residue having a silicon atom in its main chain, since the adhesion between the polyimide film and the hard coat layer is excellent. This is presumed to be due to excellent mixing between the specific polyimide film and the hard coat layer.
Further, in the laminate of the present invention, it is preferable that the polyimide contained in the polyimide film contains a diamine residue having a silicon atom in the main chain, since optical distortion is reduced. In this case, when the laminate of the present invention is used as a display member such as a surface material or a base material for a display, deterioration in display quality of the display can be suppressed.

1. Film or Polyimide Film As the film or polyimide film used in the laminate of the present invention, the film or polyimide film of the present invention described above can be used, so a description thereof will be omitted here.

2. Hard Coat Layer The hard coat layer used in the laminate of the present invention contains at least one polymer of a radical polymerizable compound and a cationic polymerizable compound.

(1) Radically polymerizable compound A radically polymerizable compound is a compound having a radically polymerizable group. The radically polymerizable group possessed by the radically polymerizable compound is not particularly limited as long as it is a functional group that can cause a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond, Specific examples include a vinyl group and a (meth)acryloyl group. Note that when the radically polymerizable compound has two or more radically polymerizable groups, these radically polymerizable groups may be the same or different.

The number of radically polymerizable groups that the radically polymerizable compound has in one molecule is preferably two or more, more preferably three or more, from the viewpoint of improving the hardness of the hard coat layer.
From the viewpoint of high reactivity, the radically polymerizable compound is preferably a compound having a (meth)acryloyl group, and a polyfunctional acrylate monomer having 2 to 6 (meth)acryloyl groups in one molecule is preferable. Compounds called urethane (meth)acrylate, polyester (meth)acrylate, and epoxy (meth)acrylate having several (meth)acryloyl groups in the molecule and oligomers with a molecular weight of several hundred to several thousand are preferred. Can be used.
In addition, in this specification, (meth)acryloyl represents each of acryloyl and methacryloyl, and (meth)acrylate represents each of acrylate and methacrylate.

Specific examples of the radically polymerizable compound include vinyl compounds such as divinylbenzene; ethylene glycol di(meth)acrylate, bisphenol A epoxy di(meth)acrylate, and 9,9-bis[4-(2-( (meth)acryloyloxyethoxy)phenyl]fluorene, alkylene oxide-modified bisphenol A di(meth)acrylate (e.g., ethoxylated (ethylene oxide modified) bisphenol A di(meth)acrylate, etc.), trimethylolpropane tri(meth)acrylate, Methylolethane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate , polyol polyacrylates such as dipentaerythritol hexa(meth)acrylate, epoxy acrylates such as diacrylate of bisphenol A diglycidyl ether, diacrylate of hexanediol diglycidyl ether, hydroxyl groups of polyisocyanate and hydroxyethyl acrylate, etc. Examples include urethane acrylates obtained by reaction of acrylates contained therein.

(2) Cationically polymerizable compound A cationically polymerizable compound is a compound having a cationically polymerizable group. The cationically polymerizable group possessed by the cationically polymerizable compound may be any functional group capable of causing a cationic polymerization reaction, and is not particularly limited, and examples thereof include an epoxy group, an oxetanyl group, and a vinyl ether group. In addition, when the said cationically polymerizable compound has two or more cationically polymerizable groups, these cationically polymerizable groups may be the same or different.

The number of cationically polymerizable groups that the cationically polymerizable compound has in one molecule is preferably two or more, more preferably three or more, from the viewpoint of improving the hardness of the hard coat layer.
In addition, as the cationically polymerizable compound, a compound having at least one of an epoxy group and an oxetanyl group as a cationically polymerizable group is preferable, and from the viewpoint of adhesion, light transmittance, and surface hardness, an epoxy group and an oxetanyl group are preferable. More preferred are compounds having two or more of at least one type of oxetanyl group in one molecule. Cyclic ether groups such as epoxy groups and oxetanyl groups are preferred from the viewpoint of low shrinkage due to polymerization reactions. In addition, among the cyclic ether groups, compounds having an epoxy group are easily available in a variety of structures, do not adversely affect the durability of the obtained hard coat layer, and are easy to control compatibility with radically polymerizable compounds. There is an advantage. In addition, among cyclic ether groups, oxetanyl groups have a higher degree of polymerization and lower toxicity than epoxy groups, and when the obtained hard coat layer is combined with a compound having an epoxy group, cations in the coating film It has the advantage of accelerating the formation of a network obtained from a polymerizable compound, and forming an independent network without leaving unreacted monomers in the film even in areas where the radically polymerizable compound is present.

As a cationic polymerizable compound having an epoxy group, for example, a polyglycidyl ether of a polyhydric alcohol having an alicyclic ring, or a compound containing a cyclohexene ring or a cyclopentene ring is treated with an appropriate oxidizing agent such as hydrogen peroxide or peracid. Alicyclic epoxy resin obtained by epoxidation; polyglycidyl ether of aliphatic polyhydric alcohol or its alkylene oxide adduct, polyglycidyl ester of aliphatic long-chain polybasic acid, homopolymer of glycidyl (meth)acrylate, Aliphatic epoxy resins such as copolymers; glycidyl ethers produced by reacting bisphenols such as bisphenol A, bisphenol F and hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts and caprolactone adducts with epichlorohydrin; and novolak epoxy resins, and glycidyl ether type epoxy resins derived from bisphenols.

Examples of the alicyclic epoxy resin include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (UVR-6105, UVR-6107, UVR-6110), bis-3,4-epoxycyclohexylmethyl adipate (UVR-6128) (The product name in parentheses is manufactured by Dow Chemical).

In addition, the above-mentioned glycidyl ether type epoxy resins include sorbitol polyglycidyl ether (Denacol EX-611, Denacol EX-612, Denacol EX-614, Denacol EX-614B, Denacol EX-622), polyglycerol polyglycidyl ether (Denacol EX-622), and polyglycerol polyglycidyl ether (Denacol EX-622). -512, Denacol EX-521), pentaerythritol polyglycidyl ether (Denacol EX-411), diglycerol polyglycidyl ether (Denacol EX-421), glycerol polyglycidyl ether (Denacol EX-313, Denacol EX-314), Trimethylolpropane polyglycidyl ether (Denacol EX-321), resortinol diglycidyl ether (Denacol EX-201), neopentyl glycol diglycidyl ether (Denacol EX-211), 1,6 hexanediol diglycidyl ether (Denacol EX- 212), Hydrobisphenol A diglycidyl ether (Denacol EX-252), Ethylene glycol diglycidyl ether (Denacol EX-810, Denacol EX-811), Polyethylene glycol diglycidyl ether (Denacol EX-850, Denacol EX-851, Denacol EX-821), propylene glycol glycidyl ether (Denacol EX-911), polypropylene glycol glycidyl ether (Denacol EX-941, Denacol EX-920), allyl glycidyl ether (Denacol EX-111), 2-ethylhexyl glycidyl ether (Denacol EX-121), phenyl glycidyl ether (Denacol EX-141), phenol glycidyl ether (Denacol EX-145), butylphenyl glycidyl ether (Denacol EX-146), diglycidyl phthalate (Denacol EX-721), hydroquinone diglycidyl ether (Denacol EX-203), diglycidyl terephthalate (Denacol EX-711), glycidyl phthalimide (Denacol EX-731), dibromophenyl glycidyl ether (Denacol EX-147), dibromoneopentyl glycol diglycidyl ether (Denacol EX-221) (The product name in parentheses is manufactured by Nagase ChemteX.)

In addition, other commercially available epoxy resins include the trade names Epicote 825, Epicote 827, Epicote 828, Epicote 828EL, Epicote 828XA, Epicote 834, Epicote 801, Epicote 801P, Epicote 802, Epicote 815, Epicote 815XA, Epicote 816A, Epicote 819, Epicote 834X90, Epicote 1001B80, Epicote 1001X70, Epicote 1001X75, Epicote 1001T75, Epicote 806, Epicote 806P, Epicote 807, Epicote 152, Epicote 154, Epicote 871, Epicote 191P, Epicote YX310, Epicote DX255, Epicote YX80 00, Epicote YX8034 (all trade names, manufactured by Japan Epoxy Resin).

Examples of cationic polymerizable compounds having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane (OXT-101), 1,4-bis-3-ethyloxetan-3-ylmethoxymethylbenzene (OXT-121) , bis-1-ethyl-3-oxetanyl methyl ether (OXT-221), 3-ethyl-3-2-ethylhexyloxymethyloxetane (OXT-212), 3-ethyl-3-phenoxymethyloxetane (OXT- 211) (the product names in parentheses are manufactured by Toagosei Co., Ltd.), and the product names Ethanakol EHO, Ethanakol OXBP, Ethanakol OXTP, and Ethanakol OXMA (trade names manufactured by Ube Industries, Ltd.).

(3) Polymerization initiator At least one polymer of the radical polymerizable compound and the cationic polymerizable compound contained in the hard coat layer used in the present invention is, for example, a polymer of the radical polymerizable compound and the cationic polymerizable compound. It can be obtained by adding a polymerization initiator to at least one species as needed and carrying out a polymerization reaction by a known method.

As the polymerization initiator, radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, etc. can be appropriately selected and used. These polymerization initiators are decomposed by at least one of light irradiation and heating to generate radicals or cations to advance radical polymerization and cationic polymerization.

Any radical polymerization initiator may be used as long as it is capable of releasing a substance that initiates radical polymerization upon at least one of light irradiation and heating. For example, examples of the photoradical polymerization initiator include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocenes, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, thioxanthone derivatives, etc. More specifically, 1,3-di(tert-butyldioxycarbonyl)benzophenone, 3,3',4,4'-tetrakis(tert-butyldioxycarbonyl)benzophenone, 3-phenyl-5- Isoxazolone, 2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethan-1-one (trade name Irgacure 651, Ciba Japan Co., Ltd.) ), 1-hydroxy-cyclohexyl-phenyl-ketone (trade name Irgacure 184, manufactured by Ciba Japan Co., Ltd.), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butane-1- (trade name Irgacure 369, manufactured by Ciba Japan Co., Ltd.), bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl) )-phenyl)titanium) (trade name Irgacure 784, manufactured by Ciba Japan Co., Ltd.), but is not limited thereto.

In addition to the above, commercially available products can be used, specifically Irgacure 907, Irgacure 379, Irgacure 819, Irgacure 127, Irgacure 500, Irgacure 754, Irgacure 250, Irgacure 1800, and Irgacure 1870 manufactured by Ciba Japan Co., Ltd. , Irgacure OXE01, DAROCUR TPO, DAROCUR1173, SpeedcureMBB, SpeedcurePBZ, SpeedcureITX, SpeedcureCTX, SpeedcureEDB, Esacure manufactured by Nihon Siberhegner Co., Ltd. ONE, Esacure KIP150, Esacure KTO46, KAYACURE DETX-S, KAYACURE CTX manufactured by Nippon Kayaku Co., Ltd. , KAYACURE BMS, KAYACURE DMBI, etc.

Further, the cationic polymerization initiator may be used as long as it is capable of releasing a substance that initiates cationic polymerization by at least one of light irradiation and heating. Examples of the cationic polymerization initiator include sulfonic acid ester, imidosulfonate, dialkyl-4-hydroxysulfonium salt, arylsulfonic acid-p-nitrobenzyl ester, silanol-aluminum complex, (η ⁶ -benzene) (η ⁵ -cyclopentadiene) enyl) iron(II), and more specifically, benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tocyphthalic acid imide, etc., but are not limited to these.

Examples of those used as radical polymerization initiators and cationic polymerization initiators include aromatic iodonium salts, aromatic sulfonium salts, aromatic diazonium salts, aromatic phosphonium salts, triazine compounds, iron arene complexes, etc. More specifically, iodonium chloride, bromide, borofluoride salt, hexafluorophosphate salt, hexafluorophosphate salt, etc. Iodonium salts such as antimonate salts, chlorides, bromides, borofluoride salts, hexafluorophosphate salts, hexafluoroantimonates of sulfoniums such as triphenylsulfonium, 4-tert-butyltriphenylsulfonium, tris(4-methylphenyl)sulfonium, etc. Sulfonium salts such as salts, 2,4,6-tris(trichloromethyl)-1,3,5-triazine, 2-phenyl-4,6-bis(trichloromethyl)-1,3,5-triazine, 2- Examples include, but are not limited to, 2,4,6-substituted-1,3,5-triazine compounds such as methyl-4,6-bis(trichloromethyl)-1,3,5-triazine. .

(4) Additives In addition to the above polymer, the hard coat layer used in the present invention may optionally contain an antistatic agent, an antiglare agent, an antifouling agent, and inorganic or organic fine particles for improving hardness. It may contain additives such as leveling agents and various sensitizers.
Note that at least one polymer of a radically polymerizable compound and a cationic polymerizable compound contained in the hard coat layer used in the present disclosure can be used in a Fourier transform infrared spectrophotometer (FTIR), a pyrolysis gas chromatograph (GC), etc. -MS) and decomposition products of polymers can be analyzed using a combination of high performance liquid chromatography, gas chromatograph mass spectrometry, NMR, elemental analysis, XPS/ESCA, TOF-SIMS, and the like.

3. Structure of Laminate The laminate of the present invention is not particularly limited as long as it has the film or polyimide film and the hard coat layer, and the hard coat layer is provided on one side of the film or polyimide film. may be laminated, or the hard coat layer may be laminated on both sides of the film or polyimide film. In addition to the above-mentioned film or polyimide film and the hard coat layer, the laminate of the present invention may also have adhesion between the film or polyimide film and the hard coat layer, for example, to the extent that the effects of the present invention are not impaired. The film or polyimide film and the hard coat layer may be laminated with another layer such as a primer layer interposed therebetween. good. Further, in the laminate of the present invention, the film or polyimide film and the hard coat layer may be located adjacent to each other. Moreover, the laminate of the present invention may further include an impact-resistant layer, a fingerprint adhesion prevention layer, an adhesive layer or an adhesive layer, and the like.

The overall thickness of the laminate of the present invention may be appropriately selected depending on the application, but from the viewpoint of strength, it is preferably 10 μm or more, and more preferably 40 μm or more. On the other hand, from the viewpoint of bending resistance, the thickness is preferably 300 μm or less, and more preferably 250 μm or less.
Further, in the laminate of the present invention, the thickness of each hard coat layer may be appropriately selected depending on the application, but it is preferably 2 μm or more and 80 μm or less, and more preferably 3 μm or more and 50 μm or less. Further, from the viewpoint of curl prevention, hard coat layers may be formed on both sides of the polyimide film.

4. Characteristics of Laminate In the laminate of the present invention, the pencil hardness of the surface on the hard coat layer side is preferably H or higher, more preferably 2H or higher, even more preferably 3H or higher.
The pencil hardness of the laminate of the present invention can be measured in the same manner as described above, except that the load is 9.8N.

The laminate of the present invention preferably has a total light transmittance of 85% or more, more preferably 88% or more, and even more preferably 90% or more, as measured in accordance with JIS K7361-1. is preferred. Since it has such a high transmittance, it has good transparency and can be used as a substitute material for glass.
The total light transmittance of the laminate of the present invention can be measured in the same manner as the total light transmittance of the polyimide film measured in accordance with JIS K7361-1.

The laminate of the present invention preferably has a yellowness index (YI value) calculated in accordance with JIS K7373-2006 of 20 or less, more preferably 15 or less, and even more preferably 10 or less. More preferably, it is particularly preferably 5 or less.
In addition, the laminate of the present invention suppresses yellowish coloration, improves light transmittance, and can be suitably used as a glass substitute material. The value obtained by dividing the degree (YI value) by the film thickness (μm) (YI value/film thickness (μm)) is preferably 0.10 or less, more preferably 0.04 or less, and 0.03 The following is even more preferable.
The yellowness (YI value) of the laminate of the present invention can be measured in the same manner as the yellowness (YI value) of the polyimide film calculated in accordance with JIS K7373-2006.

From the viewpoint of light transmittance, the haze value of the laminate of the present invention is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less.
The haze value of the laminate of the present invention can be measured in the same manner as the haze value of the polyimide film.

The birefringence index in the thickness direction of the laminate of the present invention at a wavelength of 590 nm is preferably 0.040 or less, preferably 0.020 or less, preferably 0.015 or less, and more preferably 0.040 or less, preferably 0.020 or less, preferably 0.015 or less, and more preferably 0. It is preferably less than 0.010, and even more preferably less than 0.008.
The birefringence of the laminate of the present invention can be measured in the same manner as the birefringence of the polyimide film in the thickness direction at a wavelength of 590 nm.

5. Applications of Laminate The applications of the laminate of the present invention are not particularly limited, and can be used, for example, in the same applications as the polyimide film of the invention described above.

6. Method for manufacturing a laminate The method for manufacturing a laminate of the present invention includes, for example,
forming a coating film of a composition for forming a hard coat layer containing at least one of a radically polymerizable compound and a cationically polymerizable compound on at least one surface of the film or polyimide film of the present invention;
The manufacturing method includes a step of curing the coating film.

The composition for forming a hard coat layer contains at least one kind of a radically polymerizable compound and a cationic polymerizable compound, and may further contain a polymerization initiator, a solvent, an additive, etc. as necessary.
Here, as for the radically polymerizable compound, cationic polymerizable compound, polymerization initiator, and additives contained in the hard coat layer forming composition, the same ones as those explained for the hard coat layer can be used. The solvent can be appropriately selected from known solvents.

A method for forming a coating film of the composition for forming a hard coat layer on at least one surface of a film or a polyimide film includes, for example, applying the composition for forming a hard coat layer on at least one surface of the film or polyimide film. An example of this method is to apply this by a known coating means.
The coating means is not particularly limited as long as it can coat the film to a desired thickness, and examples thereof include the same means as the means for coating the polyimide precursor resin composition on the support.

The coating film of the curable resin composition for hard coat layer is dried to remove the solvent, if necessary. Examples of the drying method include vacuum drying, heat drying, and a combination of these drying methods. Moreover, when drying under normal pressure, it is preferable to dry at 30° C. or higher and 110° C. or lower.

The curable resin composition for a hard coat layer is applied to the coating film, which is dried as necessary. , by curing the coating film by at least one of light irradiation and heating, a hard coat containing at least one polymer of a radically polymerizable compound and a cationic polymerizable compound is applied to at least one surface of the film or polyimide film. layers can be formed.

For light irradiation, ultraviolet rays, visible light, electron beams, ionizing radiation, etc. are mainly used. In the case of ultraviolet curing, ultraviolet rays emitted from ultra-high pressure mercury lamps, high-pressure mercury lamps, low-pressure mercury lamps, carbon arcs, xenon arcs, metal halide lamps, etc. are used. The irradiation amount of the energy ray source is about 50 to 5000 mJ/cm ² as a cumulative exposure amount at an ultraviolet wavelength of 365 nm.
When heating is performed, it is usually performed at a temperature of 40°C or higher and 120°C or lower. Alternatively, the reaction may be carried out by leaving it at room temperature (25° C.) for 24 hours or more.

IV. Display Member The display member of the present invention includes the above-described film or polyimide film of the present invention, or the laminate of the present invention, and the strain value at the yield point of the film or polyimide film is greater in the tensile direction. On the other hand, it is used by being bent so that the bent portions are perpendicular to each other.
Examples of the display member of the present invention include a display surface material and a display base material.
The display member of the present invention may be the film or polyimide film of the present invention described above, or the laminate of the present invention.

The display member of the present invention is used, for example, as a display surface material by being placed on the surface of various displays. The display member of the present invention is used by being arranged so as to be bendable so that the bending portion is orthogonal to the tensile direction in which the strain value at the yield point of the film or polyimide film is larger.
The display member of the present invention, like the film or polyimide film of the present invention and the laminate of the present invention described above, has excellent transparency, improved bending resistance, and has sufficient surface hardness as a protective film, so it is flexible. It can be particularly suitably used for displays.

The display member of the present invention can be used in various known displays, including, but not limited to, the displays described above in connection with the use of the polyimide film of the present invention.

In addition, when the display member of the present invention is the laminate of the present invention, the surface that becomes the outermost surface after the laminate is placed on the surface of the display may be the surface on the polyimide film side, or It may be the surface on the coat layer side. Among these, it is preferable to arrange the display member of the present invention so that the surface on the hard coat layer side is closer to the front side. Further, the display member of the present invention may have a fingerprint adhesion prevention layer on the outermost surface.

Further, the method for disposing the display member of the present invention on the surface of the display is not particularly limited, but includes, for example, a method using an adhesive layer. As the adhesive layer, a conventionally known adhesive layer that can be used for adhering display members can be used.

V. Touch Panel Member The touch panel member of the present invention includes the film, polyimide film, or laminate of the present invention described above;
a transparent electrode consisting of a plurality of conductive parts arranged on one side of the polyimide film or the laminate;
a plurality of lead wires electrically connected on at least one side of the end of the conductive part,
The film or polyimide film is installed so as to be bendable so that the bending portion is perpendicular to the tensile direction in which the strain value at the yield point of the film or polyimide film is larger.

Since the touch panel member of the present invention includes the above-described film, polyimide film, or laminate of the present invention, it has excellent bending resistance and surface hardness, and is therefore particularly suitable for use in flexible displays. It also has excellent optical properties.
The laminate of the present invention used for the touch panel member of the present invention has a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound adjacent to both surfaces of the film or polyimide film. It is preferable that the
Moreover, although the touch panel member of the present invention is not particularly limited, it is preferable that the transparent electrode is laminated in contact with one surface side of the laminate.
The touch panel member of the present invention can be used, for example, by being placed on the surface of various displays. Moreover, the touch panel member of the present invention and the film, polyimide film, or laminate of the present invention as a surface material can be arranged and used in this order on the surface of various displays.

Hereinafter, the touch panel member of the present invention will be explained using an example using the laminate of the present invention described above, but the film or polyimide film of the present invention described above may also be used in place of the laminate of the present invention described above. I can do it.
6 is a schematic plan view of one surface of an example of the touch panel member of the present invention, FIG. 7 is a schematic plan view of the other surface of the touch panel member shown in FIG. 6, and FIG. 8 is a schematic plan view of the other surface of the touch panel member shown in FIG. and AA' cross-sectional view of the touch panel member shown in FIG. 7. The touch panel member 20 shown in FIGS. 6, 7, and 8 includes a laminate 10 of the present invention, a first transparent electrode 4 disposed in contact with one surface of the laminate 10, and the other side of the laminate 10. and a second transparent electrode 5 disposed in contact with the surface. In the first transparent electrode 4, a plurality of first conductive parts 41, which are strip-shaped electrode pieces extending in the x-axis direction, are arranged at predetermined intervals. A first lead-out line 7 that is electrically connected to the first conductive part 41 is connected to the first conductive part 41 at one of its longitudinal ends. A first terminal 71 for electrical connection to an external circuit is preferably provided at the end of the first lead-out line 7 extending to the edge 21 of the laminate 10. The first conductive part 41 and the first lead-out line 7 are generally connected in the inactive area 23 located outside the active area 22 that is visible to the user of the touch panel.
For the connection between the first conductive part 41 and the first lead-out line 7, for example, as shown in FIG. 6, a connection structure in which a connecting part 24 is interposed can be adopted. Specifically, the connecting portion 24 can be formed by extending a layer of conductive material from the longitudinal end of the first conductive portion 41 to a predetermined position within the inactive area 23 . Furthermore, by overlapping at least a portion of the first lead-out line 7 on the connection part 24, a connection structure between the first conductive part 41 and the first lead-out line 7 can be formed.
The connection between the first conductive part 41 and the first lead-out line 7 is not limited to the structure in which the connection part 24 is formed as shown in FIG. For example, although not shown, the longitudinal end of the first conductive part 41 extends to the inactive area 23, and within the inactive area 23, the first conductive part 41 extends to the inactive area 23. The two may be electrically connected by running the first lead-out line 7 onto the end of the line.
Although FIG. 6 shows a form in which either one of the longitudinal ends of the first conductive part 41 and the first lead-out line 7 are connected, in the present invention, one first conductive part 41 The first lead-out line 7 may be electrically connected to both ends of the portion 41 in the longitudinal direction.

As shown in FIG. 7, the touch panel member 20 includes a second transparent electrode 5 disposed in contact with the other surface of the laminate 10. In the second transparent electrode 5, second conductive parts 51, which are a plurality of strip-shaped electrode pieces extending in the y-axis direction, are arranged at predetermined intervals in the x-axis direction. There is.
A second lead-out line 8 that is electrically connected to the second conductive part 51 is connected to one of the ends in the longitudinal direction of the second conductive part 51 .
The second lead-out line 8 extends to a position on the end edge 21 of the laminate 10 where the first lead-out line 7 described above extends and does not overlap with the first terminal 71. .
A second terminal 81 for electrical connection to an external circuit is preferably provided at the end of the second lead-out line 8 extending to the edge 21 of the laminate 10.
For the electrical connection between the second conductive part 51 and the second lead-out line 8, the same form as the electrical connection between the first lead-out line 7 and the first conductive part 41 can be applied. .

Note that the pattern in which the first lead-out line 7 is a long wiring and the second lead-out line 8 is a short wiring, as shown in FIGS. 6 and 7, is only one embodiment of the touch panel member of the present invention, and for example, It is also possible to use a pattern in which the first lead-out line 7 is a short wiring and the second lead-out line 8 is a long wiring. Further, the extending direction of the first lead-out line 7 and the extending direction of the second lead-out line 8 are not limited to the directions shown in FIGS. 6 and 7, and can be designed arbitrarily.

The conductive part included in the touch panel member of the present invention can be appropriately selected from those forming transparent electrodes in the touch panel member, and the pattern of the conductive part is not limited to those shown in FIGS. 6 and 7. For example, a capacitance method can be used to appropriately select and apply a pattern of transparent electrodes that can detect changes in capacitance due to contact or near-contact conditions, such as a finger.
The material of the conductive part is preferably a light-transmitting material, such as an indium oxide-based transparent electrode material whose main constituents are indium tin oxide (ITO), indium oxide, indium zinc oxide (IZO), etc. Examples include, but are not limited to, transparent conductive films containing tin oxide (SnO ₂ ), zinc oxide (ZnO), etc. as main constituents, and conductive polymer compounds such as polyaniline and polyacetylene. Further, the first conductive part 41 and the second conductive part 51 may be formed using the same type of conductive material, or may be formed using different types of materials. In particular, it is preferable to form the first conductive part 41 and the second conductive part 51 using the same type of conductive material from the viewpoint of more effectively suppressing the occurrence of warpage and distortion of the touch panel member.
The thickness of the conductive portion is not particularly limited, but when the conductive portion is formed by photolithography, for example, it can generally be formed to a thickness of about 10 nm to 500 nm.

The conductive material constituting the lead wire of the touch panel member of the present invention may or may not have optical transparency. Generally, the lead wire can be formed using a highly conductive metal material such as silver or copper. Specific examples include simple metals, composites of metals, composites of metals and metal compounds, and metal alloys. Examples of simple metals include silver, copper, gold, chromium, platinum, and aluminum. An example of the metal composite is MAM (a three-layer structure of molybdenum, aluminum, and molybdenum). Examples of the composite of metal and metal compound include a laminate of chromium oxide and chromium. Silver alloys and copper alloys are commonly used as metal alloys. Furthermore, examples of the metal alloy include APC (an alloy of silver, palladium, and copper). Moreover, the above-mentioned lead-out line may contain an appropriate resin component mixed with the above-mentioned metal material.
In the touch panel member of the present invention, the terminal provided at the end of the lead-out line can be formed using the same material as the lead-out line, for example.
The thickness and width of the lead-out line are not particularly limited, but when forming the lead-out line by photolithography, the thickness is generally about 10 nm to 1000 nm, and the width is 5 μm to 5 μm. It is formed to have a thickness of about 200 μm. On the other hand, when the lead line is formed by printing such as screen printing, the thickness is generally about 5 μm to 20 μm, and the width is about 20 μm to 300 μm.

The touch panel member of the present invention is not limited to the forms shown in FIGS. 6 to 8, and may be configured, for example, by laminating a first transparent electrode and a second transparent electrode on separate laminates. It may be something that
9 and 10 are schematic plan views each showing an example of a conductive member including the laminate of the present invention. A first conductive member 201 shown in FIG. 9 includes a laminate 10 of the present invention and a first transparent electrode 4 disposed in contact with one surface of the laminate 10. The transparent electrode 4 has a plurality of first conductive parts 41. A second conductive member 202 shown in FIG. 10 includes a laminate 10' of the present invention and a second transparent electrode 5 disposed in contact with one surface of the laminate 10'. The second transparent electrode 5 has a plurality of second conductive parts 51.
FIG. 11 is a schematic sectional view showing another example of the touch panel member of the present invention, and the touch panel member 20' shown in FIG. 11 includes the first conductive member 201 shown in FIG. A conductive member 202 is provided. In the touch panel member 20', the surface of the first conductive member 201 that does not have the first transparent electrode 4 and the surface of the second conductive member 202 that has the transparent electrode 5 are connected to each other via the adhesive layer 6. It is pasted together. In addition, in the present invention, for example, an adhesive layer for bonding the laminate of the present invention and the touch panel member of the present invention, an adhesive layer for bonding the touch panel members of the present invention, a touch panel member of the present invention and a display device. As the adhesive layer for adhering these, any conventionally known adhesive layer used for optical members can be appropriately selected and used. In the conductive member used in the touch panel member of the present invention, the structures and materials of the transparent electrode, lead wire, and terminal may be the same as those of the transparent electrode, lead wire, and terminal used in the touch panel member of the present invention described above. can.

VI. Liquid Crystal Display Device The liquid crystal display device of the present invention includes the above-described film, polyimide film, or laminate of the present invention, and an opposing display device arranged on one side of the film, polyimide film, or laminate. a liquid crystal display section having a liquid crystal layer between the substrates;
The film or polyimide film is installed so as to be bendable so that the bending portion is perpendicular to the tensile direction in which the strain value at the yield point of the film or polyimide film is larger.

Since the liquid crystal display device of the present invention includes the film of the present invention described above, the polyimide film, or the laminate of the present invention described above, it has excellent bending resistance and surface hardness, and is particularly suitable for use as a flexible display. It has excellent optical properties.
The laminate of the present invention used in the liquid crystal display device of the present invention includes a hard coat layer containing a polymer of at least one of a radically polymerizable compound and a cationic polymerizable compound, adjacent to both sides of the film or polyimide film. It is preferable that it has.
Furthermore, the liquid crystal display device of the present invention may include the touch panel member of the present invention described above.
Further, the counter substrate of the liquid crystal display device of the present invention may include the film, polyimide film, or laminate of the present invention.

The liquid crystal display device of the present invention will be described below using an example using the laminate of the present invention described above, but the film or polyimide film of the present invention described above may also be used instead of the laminate of the present invention described above. be able to.
FIG. 12 is a schematic cross-sectional view showing an example of the liquid crystal display device of the present invention. A liquid crystal display device 100 shown in FIG. 12 includes a laminate 10 of the present invention, a first transparent electrode 4 on one surface of the laminate 10' of the present invention, and a second transparent electrode 5 on the other surface. It has a touch panel member 20 and a liquid crystal display section 30. In the liquid crystal display device 100, the laminate 10 is used as a surface material, and the laminate 10 and the touch panel member 20 are bonded together via the adhesive layer 6.

The liquid crystal display section used in the liquid crystal display device of the present invention has a liquid crystal layer formed between substrates disposed opposite to each other, and it is possible to adopt the structure used in conventionally known liquid crystal display devices. can.
The driving method of the liquid crystal display device of the present invention is not particularly limited, and driving methods generally used for liquid crystal display devices can be adopted, such as the TN method, the IPS method, the OCB method, and the MVA method. etc. can be mentioned.
The counter substrate used in the liquid crystal display device of the present invention can be appropriately selected and used depending on the driving method of the liquid crystal display device, etc., and a substrate comprising the polyimide film or laminate of the present invention may also be used.
As the liquid crystal constituting the liquid crystal layer, various liquid crystals having different dielectric anisotropy and mixtures thereof can be used depending on the driving method of the liquid crystal display device of the present invention.
As a method for forming the liquid crystal layer, methods generally used for manufacturing liquid crystal cells can be used, such as a vacuum injection method, a liquid crystal dropping method, and the like. After forming the liquid crystal layer by the method described above, the liquid crystal cell is gradually cooled to room temperature, thereby making it possible to orient the encapsulated liquid crystal.
The liquid crystal display device of the present invention may further include colored layers of a plurality of colors and light shielding portions that define pixels between the opposing substrates. Further, the liquid crystal display section may include a backlight section having a light emitting element or a fluorescent material on the outside of the opposing substrates, at a position opposite to the side where the touch panel member is located. Furthermore, the outer surfaces of the opposing substrates may each have a polarizing plate.

FIG. 13 is a schematic cross-sectional view showing another example of the liquid crystal display device of the present invention. A liquid crystal display device 200 shown in FIG. 13 includes a laminate 10 of the present invention, a first conductive member 201 having a first transparent electrode 4 on one surface of the laminate 10' of the present invention, and It has a touch panel member 20' having a second conductive member 202 having a second transparent electrode 5 on one surface of the laminate 10'', and a liquid crystal display section 30. In the liquid crystal display device 200, the laminate 10'' and the first conductive member 201, and the first conductive member 201 and the second conductive member 202 are bonded together via the adhesive layer 6.The structure of the touch panel member 20' is, for example, The structure of the touch panel member 20' shown in FIG. 11 can be the same as that of the touch panel member 20' shown in FIG. Can be used.

VII. Organic electroluminescent display device The organic electroluminescent display device of the present invention includes the film, polyimide film, or laminate of the present invention described above, and the film, polyimide film, or laminate disposed on one side of the film, polyimide film, or laminate of the present invention. an organic electroluminescent display section having an organic electroluminescent layer between opposing substrates;
The film or polyimide film is installed so as to be bendable so that the bending portion is perpendicular to the tensile direction in which the strain value at the yield point of the film or polyimide film is larger.

Since the organic electroluminescent display device of the present invention includes the film of the present invention described above, the polyimide film, or the laminate of the present invention described above, it has excellent bending resistance and surface hardness, so it can be used as a flexible display. It can be particularly suitably used for applications, and has excellent optical properties.
The laminate of the present invention used in the organic electroluminescent display device of the present invention includes a hard layer containing at least one polymer of a radically polymerizable compound and a cationically polymerizable compound adjacent to both sides of the film or polyimide film. Preferably, it has a coating layer.
Furthermore, the organic electroluminescent display device of the present invention may include the touch panel member of the present invention described above.
Further, the counter substrate of the organic electroluminescent display device of the present invention may include the film, polyimide film, or laminate of the present invention.

The organic electroluminescent display device of the present invention will be explained below using an example using the laminate of the present invention described above, but instead of the laminate of the present invention described above, the film or polyimide film of the present invention described above may also be used. It can be used for.
FIG. 14 is a schematic cross-sectional view showing an example of the organic electroluminescent display device of the present invention. An organic electroluminescent display device 300 shown in FIG. 14 includes a laminate 10 of the present invention, a first transparent electrode 4 on one surface of the laminate 10' of the present invention, and a second transparent electrode 4 on the other surface. It has a touch panel member 20 including an electrode 5 and an organic electroluminescent display section 40. In the organic electroluminescent display device 300, the laminate 10 is used as a surface material, and the laminate 10 and the touch panel member 20 are bonded together via the adhesive layer 6.

The organic electroluminescent display section (organic EL display section) used in the organic electroluminescent display device (organic EL display device) of the present invention is an organic electroluminescent layer (organic EL layer) formed between substrates disposed facing each other. The configuration used in conventionally known organic EL display devices can be adopted.
The organic EL display section further includes a support substrate, an organic EL element including an organic EL layer, an anode layer and a cathode layer sandwiching the organic EL layer, and a sealing base material for sealing the organic EL element. You can leave it there. The organic EL layer may be any layer having at least an organic EL light emitting layer, but for example, from the anode layer side, a hole injection layer, a hole transport layer, an organic EL light emitting layer, an electron transport layer, and an electron injection layer. A material having a structure in which layers are laminated in this order can be used.
The organic EL display device of the present invention is applicable to, for example, both a passive drive type organic EL display and an active drive type organic EL display. The counter substrate used in the organic EL display device of the present invention can be appropriately selected and used depending on the driving method of the organic EL display device, etc., and a counter substrate including the laminate of the present invention may also be used.

FIG. 15 is a schematic cross-sectional view showing another example of the organic electroluminescent display device of the present invention. An organic electroluminescent display device 400 shown in FIG. 15 includes a laminate 10 of the present invention, a first conductive member 201 having a first transparent electrode 4 on one surface of the laminate 10' of the present invention, and It has a touch panel member 20' having a second conductive member 202 having a second transparent electrode 5 on one surface of the laminate 10'' of the invention, and an organic electroluminescent display section 40. Organic electroluminescent display device In 400, the laminate 10 and the first conductive member 201, and the first conductive member 201 and the second conductive member 202 are bonded together via the adhesive layer 6. Touch panel member 20' For example, the configuration of the touch panel member 20' can be similar to that of the touch panel member 20' shown in FIG. Something similar to the sex member can be used.

[Evaluation method]
Hereinafter, unless otherwise specified, measurements or evaluations were performed at 25°C.
<Weight average molecular weight of polyimide precursor>
The weight average molecular weight of the polyimide precursor is determined by preparing a solution of the polyimide precursor in N-methylpyrrolidone (NMP) at a concentration of 0.5% by weight, filtering the solution through a syringe filter (pore size: 0.45 μm), and developing it. A 10 mmol% LiBr-NMP solution with a water content of 500 ppm or less was used as a solvent, a GPC device (manufactured by Tosoh, HLC-8120, column used: GPC LF-804 manufactured by SHODEX) was used, the sample injection amount was 50 μL, and the solvent flow rate was 0.5 mL. The measurement was carried out at 40° C./min. The weight average molecular weight of the polyimide precursor was determined using a polystyrene standard sample with the same concentration as the sample (weight average molecular weight: 364,700, 204,000, 103,500, 44,360, 27,500, 13,030, 6,300, 3,070) was used as a conversion value for standard polystyrene. The elution time was compared with a calibration curve to determine the weight average molecular weight.
<Viscosity of polyimide precursor solution>
The viscosity of the polyimide precursor solution was measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25° C. with a sample volume of 0.8 ml.

<Weight average molecular weight of polyimide>
15 mg of polyimide powder is immersed in 15,000 mg of N-methylpyrrolidone (NMP), heated to 60°C in a water bath, and stirred using a stirrer at a rotation speed of 200 rpm for 3 to 60 hours until dissolution is visually confirmed. In this way, an NMP solution with a concentration of 0.1% by weight was obtained. The solution was filtered through a syringe filter (pore size: 0.45 μm), and a 30 mmol% LiBr-NMP solution with a water content of 500 ppm or less was used as a developing solvent. Refractive index (RID) detector, column used: SHODEX GPC LF-804 (two connected in series), sample injection volume 50 μL, solvent flow rate 0.4 mL/min, column temperature 37 °C, detector temperature 37 °C Measurements were made under the following conditions. The weight average molecular weight of the polyimide was determined using a polystyrene standard sample with the same concentration as the sample (weight average molecular weight: 364,700, 204,000, 103,500, 44,360, 27,500, 13,030, 6,300, 3, 070) was used as a conversion value for standard polystyrene. The elution time was compared with a calibration curve to determine the weight average molecular weight.
<Viscosity of polyimide solution>
The viscosity of the polyimide solution was measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25° C. with a sample volume of 0.8 ml.

<Total light transmittance>
It was measured using a haze meter (HM150 manufactured by Murakami Color Research Institute) in accordance with JIS K7361-1.
Further, for example, the total light transmittance at a thickness of 100 μm can be calculated using Beer-Lambert's law.
Specifically, according to Beer-Lambert's law, the transmittance T is
Log ₁₀ (1/T) = kcb
It is expressed as (k=constant specific to the substance, c=concentration, b=optical path length).
In the case of the transmittance of a film, assuming that the density is constant even if the film thickness changes, c is also a constant, so the above formula uses the constant f to calculate Log ₁₀ (1/T) = fb
(f=kc). Here, if the transmittance at a certain film thickness is known, the unique constant f of each substance can be determined. Therefore, by using the formula T=1/10 ^f·b and substituting a specific constant for f and the target film thickness for b, the transmittance at a desired film thickness can be determined.

<YI value (yellowness)>
The YI value was determined using an ultraviolet-visible-near-infrared spectrophotometer (JASCO Corporation V-7100) using a spectrophotometric method using auxiliary illuminant C and a 2-degree field of view in accordance with JIS K7373-2006. Based on the transmittance measured at 1 nm intervals in the range of 250 nm or more and 800 nm or less, calculate the tristimulus values X, Y, and Z in the XYZ color system, and calculate the tristimulus values X, Y, and Z from the following formula from the values of X, Y, and Z. Calculated.
YI=100(1.2769X-1.0592Z)/Y
Furthermore, for example, the YI value at a thickness of 100 μm is the same as the Lambertian total light transmittance for each transmittance at each wavelength measured at 1 nm intervals between 250 nm and 800 nm of a sample with a specific film thickness. The converted value of each transmittance at each wavelength for different thicknesses can be determined according to Beer's law, and the calculation can be performed based on the calculated value.

<Film thickness measurement method>
The film thickness of a polyimide film test piece cut out to a size of 10 cm x 10 cm was measured at a total of 5 points at the four corners and the center using a digital linear gauge (manufactured by Ozaki Seisakusho Co., Ltd., model PDN12 digital gauge), and the measured values were The average of these was taken as the film thickness of the polyimide film.

<Tensile test>
A test piece of polyimide film cut into a size of 15 mm x 40 mm was conditioned for 2 hours at a temperature of 25°C and a relative humidity of 60%, and then tested in accordance with JIS K7127 at a pulling speed of 10 mm/min and a distance between chucks of 20 mm. A tensile test was conducted at 25° C., and the strain (%) at the yield point, tensile modulus, and elongation were measured on the stress-strain curve obtained from the tensile test. A tensile testing machine (manufactured by Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) was used.
The test piece was a test piece with a tensile direction of 40 mm x 15 mm in a direction perpendicular to the tensile direction, with the X direction, which is one direction in the plane of the film, as the tensile direction, and a test piece with the Y direction, which is perpendicular to the X direction, as the tensile direction. A test piece measuring 40 mm in the tensile direction x 15 mm in the direction perpendicular to the tensile direction was cut out. Note that these test pieces were cut out from near the center of the film. Measure the film thickness at a total of 5 points at the four corners and the center of the cut film using the above film thickness measurement method, and check that the difference between the average film thickness at the 5 points and the film thickness at each point is within 6% of the average film thickness. A certain test piece was used.

<Dynamic bending test>
A test piece of polyimide film cut into a size of 20 mm x 100 mm was placed in a Kapton (registered trademark) in a constant temperature and humidity chamber durability test system (manufactured by Yuasa System Equipment, planar unloaded U-shaped expansion/contraction test jig DMX-FS). ) fixed with tape. Specifically, as shown in FIG. 5(B), a test piece 1 curved at half of the long side is sandwiched between metal plates 5 from both sides, so that the distance between the metal plates 5 on both sides is 60 mm. A state in which the metal plates 5 on both sides are arranged in parallel, and a state in which the metal plates on both sides are arranged in parallel so that the distance between the metal plates 5 on both sides is 2.5 mm as shown in FIG. 5(C). was repeatedly changed at a bending frequency of 90 times per minute in an environment of 60° C. and 93% relative humidity (RH), and the bending was repeated 200,000 times.
Thereafter, one end of the test piece was fixed, and the internal angle of the test piece was measured 30 minutes after releasing the force applied to the test piece.
The test pieces include a test piece in which the X direction of the tensile test is 100 mm on the long side x 20 mm in the direction orthogonal to the X direction, and a test piece in which the Y direction in the tensile test is 100 mm on the long side x 20 mm in the direction orthogonal to the Y direction. A test piece was prepared.
If the film returns completely unaffected by the dynamic bending test, the internal angle will be 180°.

<Pencil hardness>
Pencil hardness was measured using a test pencil specified by JIS-S-6006 after conditioning the measurement sample at a temperature of 25°C and a relative humidity of 60% for 2 hours. A pencil hardness test (0.98N load) specified in JIS K5600-5-4 (1999) was performed on the film surface using a hardness tester, and the highest pencil hardness that would not cause scratches was evaluated.

<Young's modulus>
The Young's modulus of the surface of a polyimide film test piece cut into a size of 15 mm x 15 mm was measured at a temperature of 25° C. according to ISO 14577 using a nanoindentation method. Specifically, the measuring device was PICODENTOR HM500 manufactured by Fischer Instruments Co., Ltd., and a Vickers indenter was used as the measuring indenter. The Young's modulus was determined by measuring eight arbitrary points on the surface of the test piece and taking the number average. The measurement conditions were maximum indentation depth: 1000 nm, loading time: 20 seconds, and creep time: 5 seconds.

(Synthesis example 1)
Dehydrated dimethylacetamide (150 g) in a 500 mL separable flask,
Then, a solution containing 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS) (1.32 g, 5.31 mmol) was added to a 4,4' -(Hexafluoroisopropylidene) diphthalic anhydride (6FDA) (1.18 g, 2.65 mmol) was gradually added so that the temperature rise was 2° C. or less, and the mixture was stirred with a mechanical stirrer for 1 hour. To this, 2,2'-bis(trifluoromethyl)benzidine (TFMB) (32.3 g, 101 mmol) was added, and after confirming complete dissolution, 4,4'-(hexafluoroisopropylidene) diphthalate was added. Acid anhydride (6FDA) (45.2 g, 102 mmol) was gradually added in several portions so that the temperature rise was 2°C or less, and polyimide precursor solution 1' (solid) in which polyimide precursor 1' was dissolved was added. 35% by weight) was synthesized. The above solution was cooled to room temperature, and dehydrated dimethylacetamide (170 g) was added thereto and stirred until it became homogeneous. Next, catalysts pyridine (33.0 g, 417 mmol) and acetic anhydride (42.6 g, 417 mmol) were added and stirred at room temperature for 24 hours to synthesize a polyimide solution. The obtained polyimide solution was transferred to a 5 L separable flask, and butyl acetate (324 g) was added thereto, followed by stirring until the solution became homogeneous. Next, methanol (720 g) was gradually added to obtain a slightly cloudy solution. Methanol (1680 g) was added all at once to the cloudy solution to obtain a white slurry. The slurry was filtered and washed five times with methanol to obtain polyimide 1 (72.0 g). The weight average molecular weight of the polyimide measured by GPC was 96,000.

(Synthesis example 2)
A solution containing 2903 g of dehydrated dimethylacetamide and 16.0 g (0.07 mol) of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS) was placed in a 500 ml separable flask. 14.6 g (0.03 mol) of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) was gradually added to a temperature controlled at 30°C so that the temperature rise was 2°C or less. The mixture was added and stirred using a mechanical stirrer for 30 minutes. 400 g (1.25 mol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) was added thereto, and after confirming that it had completely dissolved, 4,4'-(hexafluoroisopropylidene) diphthalic acid was added. 565 g (1.27 mol) of anhydride (6FDA) was gradually added in several portions so that the temperature rise was 2°C or less, and polyimide precursor solution 2 (solid content 25% by weight) in which polyimide precursor 2 was dissolved was prepared. ) was synthesized. The molar ratio of TFMB to AprTMOS (TFMB:AprTMOS) used in polyimide precursor 2 was 95:5. The viscosity at 25° C. of polyimide precursor solution 1 (solid content 25% by weight) was 95,300 cps, and the weight average molecular weight of polyimide precursor 2 measured by GPC was 183,000.

(Synthesis example 3)
A solution in which dehydrated dimethylacetamide (150 g) and 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS) (1.63 g, 6.57 mmol) were dissolved in a 500 mL separable flask. 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) (1.46 g, 3.29 mmol) was added to the liquid temperature controlled at 30°C so that the temperature rise was 2°C or less. and stirred for 1 hour using a mechanical stirrer. To this, 2,2'-bis(trifluoromethyl)benzidine (TFMB) (40.0 g, 125 mmol) was added, and after confirming that it had completely dissolved, 4,4'-(hexafluoroisopropylidene) diphthalate was added. Acid anhydride (6FDA) (54.5 g, 123 mmol) was gradually added in several portions so that the temperature rise was 2°C or less, and polyimide precursor solution 3' (solid) in which polyimide precursor 3' was dissolved was added. 40% by weight) was synthesized. The above solution was cooled to room temperature, and dehydrated dimethylacetamide (240 g) was added and stirred until it became homogeneous. Next, catalysts pyridine (39.8 g, 504 mmol) and acetic anhydride (51.4 g, 504 mmol) were added and stirred at room temperature for 24 hours to synthesize a polyimide solution. The obtained polyimide solution was transferred to a 5 L separable flask, and butyl acetate (396 g) was added thereto, followed by stirring until it became homogeneous. Next, methanol (877 g) was gradually added to obtain a slightly cloudy solution. Methanol (2050 g) was added all at once to the cloudy solution to obtain a white slurry. The slurry was filtered and washed five times with methanol to obtain polyimide 3 (87.8 g). The weight average molecular weight of the polyimide measured by GPC was 69,000.

(Synthesis example 4)
3081 g of dehydrated dimethylacetamide and 322 g (1.00 mol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) were placed in a 500 ml separable flask, and the temperature of the solution in which TFMB was dissolved was 443 g (1.00 mol) of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) was gradually added to the temperature controlled at 30°C in several portions so that the temperature rise was 2°C or less. A polyimide precursor solution 4 (solid content: 20% by weight) in which the polyimide precursor 4 was dissolved was synthesized. The viscosity of polyimide precursor solution 4 (solid content 20% by weight) at 25° C. was 383 cps, and the weight average molecular weight of polyimide precursor 4 measured by GPC was 81,000.

(Synthesis example 5)
A solution containing 169.5 g of dehydrated dimethylacetamide and 32.0 g (100 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) was dissolved in a 500 ml separable flask at a liquid temperature of 30°C. 21.7 g (99.5 mmol) of pyromellitic dianhydride (PMDA) was gradually added in several portions to a controlled area so that the temperature rise was 2°C or less, and the polyimide precursor solution 5. (solid content 20% by weight) was synthesized. The viscosity of the polyimide precursor solution 5 at 25°C was 23,400 cps, and the weight average molecular weight of the polyimide precursor 5 measured by GPC was 83,000.

(Synthesis example 6)
While introducing nitrogen gas into a 3L separable flask equipped with an oil bath and a stirring bar, 12.25 g of diphenyl silicone oil modified with amine at both ends (manufactured by Shin-Etsu Chemical Co., Ltd.: X22-1660B-3 (number average molecular weight 4400)), 3432 g of N-methyl-2-pyrrolidone (NMP) was added, followed by 222.12 g (0.5 mol) of 6FDA, and the mixture was stirred at room temperature for 30 minutes. After that, 152.99g (0.478 mol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) was added and after confirming that it had dissolved, the mixture was stirred at room temperature for 3 hours and then heated to 80℃. After heating and stirring for 4 hours, the oil bath was removed and the temperature was returned to room temperature to obtain polyimide precursor solution 6. Table 1 shows the solid content concentration of the polyimide precursor solution 6, the viscosity at 25° C., and the weight average molecular weight of the polyimide precursor 6 measured by GPC.

(Synthesis example 7)
In a 500 ml separable flask, dehydrated dimethylformamide (144.0 g) and 2,2-bis-[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoro Propane (HFBAPP) (31.2 g, 60 mmol) was added and stirred until completely dissolved. The solution was cooled to 0° C., and 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) (39.9 g, 90 mmol) was gradually added and stirred until dissolved. Next, modified silicone oil KF-8010 (trade name, manufactured by Shin-Etsu Silicone, molecular weight 860) (24.9 g, 30 mmol) was added and stirred for 4 hours to obtain a polyamic acid solution. Next, β-picoline (8.4 g, 90 mmol) as a catalyst and acetic anhydride (55.2 g, 540 mmol) were added to the above polyamic acid solution, and the mixture was stirred for 1 hour in an oil bath at 100°C to form a polyimide solution. I got it. The obtained polyimide solution was dropped into a large amount of isopropyl alcohol (IPA) to precipitate the polyimide. The polyimide obtained by filtration and extraction was stirred and washed in IPA. After filtering again, the polyimide was sufficiently dried at 80° C. under reduced pressure to obtain polyimide 7. The weight average molecular weight of polyimide 7 measured by GPC was 199,000.

In the following, the abbreviations in the table are as follows.
6FDA: 4,4'-(hexafluoroisopropylidene) diphthalic anhydride TFMB: 2,2'-bis(trifluoromethyl)benzidine AprTMOS: 1,3-bis(3-aminopropyl)tetramethyldisiloxane PMDA: Pyromellitic anhydride X22-1660B-3: Both terminal amine-modified diphenyl silicone oil (manufactured by Shin-Etsu Silicone, X22-1660B-3 (number average molecular weight 4400))
HFBAPP: 2,2-bis-[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane KF-8010: Dimethyl silicone oil modified with amine at both ends (manufactured by Shin-Etsu Silicone) , KF-8010, molecular weight 860)

Note that the solid content concentrations in Table 1 also represent the solid content concentrations of the polyimide precursor solutions for polyimides 1 and 3. The molecular weight represents the molecular weight of the polyimide precursor for polyimide precursors 2 and 4 to 6, and the molecular weight of the polyimide for polyimide 1, 3, and 7. The viscosity is the viscosity of the polyimide precursor solution for polyimide precursors 2 and 4 to 6, the viscosity of the polyimide solution prepared in the same manner as in Example 1 for polyimide 1 and 3, and the viscosity of the polyimide solution for polyimide 7 as in Comparative Example 8. It represents the viscosity when prepared.

(Example 1)
Polyimide 1 was dissolved in a mixed solvent of butyl acetate and PGMEA (8:2, volume ratio) to prepare polyimide solution 1 with a solid content of 25% by mass. The viscosity of polyimide solution 1 (solid content 25% by weight) at 25°C was 16,612 cps.
Using the polyimide solution 1 obtained as described above, a polyimide film with a thickness of 100 μm was produced by performing the following steps (i) to (iii).
(i) Polyimide solution 1 was applied onto glass and dried in a circulating oven at 120°C for 10 minutes.
(ii) Under a nitrogen stream (oxygen concentration 100 ppm or less), the temperature was raised to 300° C. at a heating rate of 10° C./min, held at 300° C. for 1 hour, and then cooled to room temperature.
(iii) It was peeled off from the glass to obtain a polyimide film.
The resulting polyimide film with a thickness of 100 μm was uniaxially stretched using a stretching device at a stretching ratio of 200% to obtain a uniaxially stretched polyimide film with a thickness of 50 μm.

(Example 2)
A polyimide solution 1 having a solid content of 25% by mass was prepared in the same manner as in Example 1, and using the polyimide solution 1, a polyimide film having a thickness of 90 μm was produced in the same manner as in Example 1.
The resulting polyimide film with a thickness of 90 μm was uniaxially stretched using a stretching device at a stretching ratio of 180% to obtain a uniaxially stretched polyimide film with a thickness of 50 μm.

(Example 3)
A polyimide solution 1 having a solid content of 25% by mass was prepared in the same manner as in Example 1, and a polyimide film having a thickness of 80 μm was produced using the polyimide solution 1 in the same manner as in Example 1.
The obtained polyimide film with a thickness of 80 μm was uniaxially stretched using a stretching device at a stretching ratio of 160% to obtain a uniaxially stretched polyimide film with a thickness of 50 μm.

(Example 4)
A polyimide solution 1 having a solid content of 25% by mass was prepared in the same manner as in Example 1, and a polyimide film having a thickness of 70 μm was produced using the polyimide solution 1 in the same manner as in Example 1.
The resulting polyimide film with a thickness of 70 μm was uniaxially stretched using a stretching device at a stretching ratio of 140% to obtain a uniaxially stretched polyimide film with a thickness of 50 μm.

(Comparative example 1)
A polyimide solution 1 having a solid content of 25% by mass was prepared in the same manner as in Example 1, and a polyimide film having a thickness of 60 μm was produced using the polyimide solution 1 in the same manner as in Example 1.
The obtained polyimide film with a thickness of 60 μm was uniaxially stretched using a stretching device at a stretching ratio of 120% to obtain a uniaxially stretched polyimide film with a thickness of 50 μm.

(Comparative example 2)
A polyimide solution 1 having a solid content of 25% by mass was prepared in the same manner as in Example 1, and a polyimide film having a thickness of 50 μm was produced using the polyimide solution 1 in the same manner as in Example 1. No stretching was performed.

(Comparative example 3)
By using polyimide precursor solution 2 and performing the following steps (1) to (3), polyimide films having the thicknesses listed in Table 2 were produced.
(1) Each polyimide precursor solution was applied onto glass and dried in a circulating oven at 120°C for 10 minutes.
(2) Under a nitrogen stream (oxygen concentration 100 ppm or less), the temperature was raised to 330°C at a temperature increase rate of 10°C/min, held at 330°C for 1 hour, and then cooled to room temperature.
(3) Each polyimide film was obtained by peeling from the glass.

(Comparative example 4)
In Comparative Example 2, a polyimide film having a thickness of 82 μm was produced in the same manner as in Comparative Example 2, except that Polyimide 3 of Synthesis Example 3 was used instead of Polyimide 1.

(Comparative Examples 5 to 7)
In Comparative Example 3, polyimide precursor solutions 4 to 6 of Synthesis Examples 4 to 6 were used instead of polyimide precursor solution 2, and the heating temperature and holding temperature were changed to 350°C. Polyimide films having the thicknesses listed in Table 2 were prepared in the same manner.

(Comparative example 8)
Polyimide 7 obtained in Synthesis Example 7 was dissolved in dimethylformamide (DMF) to prepare polyimide solution 7 with a solid content of 33.3% by mass. Using polyimide solution 7, polyimide films having the thicknesses listed in Table 2 were produced by performing the following steps (i) to (ii).
(i) Polyimide solution 7 was applied onto glass, dried in a circulating oven at 80°C for 15 minutes, and then at 250°C for 5 minutes.
(ii) It was peeled off from the glass to obtain a polyimide film.

Each of the obtained polyimide films was evaluated using the evaluation method described above. The evaluation results are shown in Table 2.

From Table 2, the polyimide films of Examples 1 to 4, which correspond to the polyimide films of the present invention, are resins that have excellent transparency, good bending resistance in a predetermined bending direction (Y direction), and improved surface hardness. It was shown to be a film.
On the other hand, the polyimide films of Comparative Examples 1 and 2 were manufactured using the same polyimide as the polyimide films of Examples 1 to 4, but the ratio of tensile modulus (X/Y) was lower than the value specified by the present invention. It is also small. The polyimide films of Comparative Examples 1 and 2 have a strain of 8% or more at the yield point of the stress-strain curve in the X direction and the Y direction, so although the bending resistance is good, the surface hardness is lower than that of the examples. It was inferior.
Further, the polyimide films of Comparative Examples 3 to 7 had a strain of less than 8% at the yield point of the stress-strain curve, and had poor bending resistance. The polyimide film of Comparative Example 6 had poor yellowness, and the polyimide films of Comparative Examples 5 and 7 had further poor pencil hardness, and the surface was easily scratched.
The polyimide film of Comparative Example 8 had a strain at the yield point of 8% or more and a tensile modulus of less than 1.8 GPa, and although it had good bending resistance, it had poor pencil hardness and the surface was easily damaged. The polyimide film of Comparative Example 8 was even worse in yellowness.

(Examples 5 to 8: Production of laminate)
To a 40% by mass solution of pentaerythritol triacrylate in methyl isobutyl ketone, 10 parts by mass of 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF, Irgacure 184) was added to 100 parts by mass of pentaerythritol triacrylate to form a hard solution. A resin composition for a coat layer was prepared.
The hard coat layer resin composition was applied onto each of the polyimide films of Examples 1 to 4, and cured by irradiating with ultraviolet rays at an exposure dose of 200 mJ/cm ² under a nitrogen stream to form a cured film with a thickness of 10 μm. , produced a laminate.
Since the polyimide film contained silicon atoms, it had good adhesion with the hard coat layer.

1 Test piece 2 Metal piece 3a, 3b Glass plate 3c, 3d Dummy test piece 11 Test piece 12 Test piece 13 Tensile test in which the strain at the yield point is 8% or more and the value of the strain at the yield point is larger. Tensile direction 14 Bending portion 101, 102 Polyimide film 10, 10', 10'' Laminated body 4 First transparent electrode 41 First conductive part 5 Second transparent electrode 51 Second conductive part 6 Adhesive layer 7 First Take-out line 71 First terminal 8 Second take-out line 81 Second terminal 20, 20' Touch panel member 21 Edge of laminate 22 Active area 23 Inactive area 24 Connection portion 201 First conductive member 202 Second conductive member 30 Liquid crystal display section 40 Organic electroluminescent display section 100, 200 Liquid crystal display device 300, 400 Organic electroluminescent display device

Claims (1)

Anisotropy such that the ratio of tensile modulus in a tensile test with the X direction, which is one direction in the film plane, as the tensile direction and in a tensile test with the Y direction perpendicular to the X direction as the tensile direction, is 1.50 or more. The tensile test was performed by cutting out a test piece measuring 40 mm in the tensile direction x 15 mm in the direction perpendicular to the tensile direction, and testing the test piece at 25°C at a tensile speed of 10 mm/min and a distance between chucks of 20 mm in accordance with JIS K7127. is to be measured,
Each tensile modulus in the tensile test is 1.8 GPa or more,
A polyimide film having a total light transmittance measured in accordance with JIS K7361-1 of 85% or more and a yellowness calculated in accordance with JIS K7373-2006 of 5 or less,
Among the stress-strain curves obtained by a tensile test with the X direction of the film as the tensile direction and a tensile test with the Y direction of the film as the tensile direction, the strain at the yield point is 8% or more, and the yield point A polyimide film that is used by being bent so that the bending part is perpendicular to the tensile direction where the strain value is larger.

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