JP7334446B2 - Films, polyimide films, laminates, display members, touch panel members, liquid crystal display devices, and organic electroluminescence display devices - Google Patents

Description

TECHNICAL FIELD The present invention relates to films, polyimide films, laminates, display members, touch panel members, liquid crystal display devices, and organic electroluminescence display devices.

Thin plate glass is excellent in hardness and heat resistance, but has drawbacks such as being difficult to bend, being easily broken if dropped, and having problems with workability, and being heavier than plastic products. For this reason, in recent years, resin products such as resin substrates and resin films have been replacing glass products in terms of workability and weight reduction, and research has been conducted on resin products that can serve as substitutes for glass.

For example, with the rapid progress in electronics such as displays such as liquid crystal and organic EL, and touch panels, there has been a demand for thinner, lighter and more flexible devices. Conventionally, these devices have various electronic elements, such as thin transistors and transparent electrodes, formed on thin sheet glass. By replacing this thin sheet glass with a resin film, the impact resistance of the panel itself is enhanced. , flexibility, thinness and weight reduction can be achieved.

Generally, polyimide is a highly heat-resistant resin obtained by a dehydration ring closure reaction of polyamic acid obtained by a condensation reaction of an aromatic tetracarboxylic anhydride and an aromatic diamine. However, since polyimide generally exhibits yellow or brown coloring, it has been difficult to use it in fields requiring transparency, such as display applications and optical applications. Therefore, application of polyimide with improved transparency to display members has been studied. For example, in Patent Document 1, 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 having at least one phenylene group and isopropylidene group represented by a specific formula A polyimide obtained by reacting with an imino-forming compound is disclosed, and is described as being suitable as a substrate material for flat panel displays, mobile phone devices, and the like.

Furthermore, Patent Document 2 includes a unit structure derived from an aromatic dianhydride and an aromatic diamine, a tear strength improving additive, 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 which further comprises a unit structure derived from a monomer having a Patent Document 3 discloses, as a polyimide film excellent in transparency and heat resistance, a polyimide film in which the highest peak of the tan δ curve, which is a value obtained by dividing the loss elastic modulus by the storage elastic modulus, is within a specific range. ing.

Further, in Patent Document 4, as a polyimide film used for a substrate of a flexible device, a polyimide film that is colorless and transparent, has low residual stress generated between it and an inorganic film, and has excellent mechanical properties and thermophysical properties is obtained. For this purpose, a polyimide film obtained by imidizing a polyimide precursor using a specific fluorine-based aromatic diamine and a silicone compound having a siloxane skeleton having 3 to 200 silicon atoms as a monomer component is disclosed. . In Patent Document 4, when a polyimide film with an inorganic film (SiN film) was formed using the polyimide precursor, neither cracks nor peeling was observed after a bending test in which bending was repeated 10 times (○). Observed (Δ) is described.

Further, Patent Document 5 describes that polyimide having a low refractive index and high folding resistance 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 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 with improved bending resistance and suppressed decrease in surface hardness. Discloses a polyimide film containing polyimide containing 10 mol% or more and 50 mol% or less of the total amount of and having a specific total light transmittance, a specific yellowness, a specific glass transition temperature, and a specific tensile modulus .

JP 2006-199945 A Japanese Patent Application Publication No. 2014-501301 Japanese Patent Publication No. 2012-503701 International Publication No. 2014/098235 Japanese Patent Application Laid-Open No. 2008-64905 JP 2018-28073 A

Resin products that are substitutes for glass are required to have excellent transparency in the first place.
Mobile devices with foldable screens should be folded when carried, and unfolded when used. For this reason, flexible displays mounted on mobile devices are required to have no display defects even when repeatedly bent. , sometimes referred to as dynamic bending resistance) is required. In addition, mobile devices with foldable screens are often carried around in a folded state, so even if the flexible display mounted on the mobile device is folded for a long time, it will return to its original shape when it is flattened. In addition, base materials and surface materials for flexible displays are also required to have resilience after being bent for a long time (hereinafter sometimes referred to as static bending resistance).
On the other hand, the base material and surface material for flexible displays must not only withstand repeated bending, but also have the function of preventing scratches on the surface and preventing damage to the touch sensor and display panel located underneath. is also required.
It is considered that the bending resistance and surface hardness of the resin film are contradictory properties, as will be described in detail later. However, the conventional resin films are still insufficient in both bending resistance and sufficient surface hardness as a protective film, and there is a demand for a resin film that has both bending resistance and sufficient surface hardness as a protective film.

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

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

The polyimide film of the present invention has a tensile modulus ratio of 1.50 in a tensile test in which the X direction, which is one direction in the film plane, is the tensile direction and in a tensile test in which the Y direction perpendicular to the X direction is the tensile direction. In the tensile test, a test piece of 40 mm in the tensile direction × 15 mm in the direction perpendicular to the tensile direction is cut out, and the test piece is subjected to JIS K7127 at a tensile speed of 10 mm / min and a chuck It is measured at 25 ° C. with a distance of 20 mm,
Each tensile modulus in the tensile test is 1.8 GPa or more,
A polyimide film having a total light transmittance of 85% or more measured according to JIS K7361-1 and a yellowness index of 5 or less calculated according to JIS K7373-2006,
The strain at the yield point is 8% or more in the stress-strain curves obtained by the tensile test with the X direction of the film as the tensile direction and the tensile test with the Y direction of the film as the tensile direction, and the yield point It 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 in is greater.

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

The polyimide film of the present invention preferably contains a polyimide having a structure represented by the following general formula (1) from the viewpoint of light transmittance, bending resistance and surface hardness.

（一般式（１）において、Ｒ^１は芳香族環又は脂肪族環を有するテトラカルボン酸残基である４価の基を表し、複数のＲ^１は各々同一であっても異なっていても良く、Ｒ^２はジアミン残基である２価の基を表し、複数のＲ^２は各々同一であっても異なっていても良く、複数のＲ^２の少なくとも一部が芳香族環又は脂肪族環を有するジアミン残基を含む。ｎは繰り返し単位数を表す。）

(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 a plurality of R ¹ may be the same or different. , R ² represents a divalent group that is a diamine residue, the plurality of R ² may be the same or different, and at least a portion of the plurality of R ² is an aromatic ring or an aliphatic ring Including diamine residues with 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 50 mol% or less 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 has no silicon atom and is an aromatic ring or aliphatic A diamine residue having a ring is preferable from the viewpoint of improving bending resistance and surface hardness.

In the polyimide film of the present invention, in the polyimide having a structure represented by the general formula (1),
R ² represents at least one divalent group selected from diamine residues having no silicon atom, and contains a diamine residue having a hexafluoroisopropylidene skeleton in its main chain, or
R ² represents a divalent group that is at least one selected from diamine residues having no silicon atoms and diamine residues having one or two silicon atoms in the main chain, and the total amount of R ² 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 R ² contain silicon atoms. From the viewpoint of light transmittance, bending resistance and surface hardness, a diamine residue having no aromatic ring or an aliphatic ring is preferable.

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 the 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[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 divalent group selected from the group is preferable from the viewpoint of light transmittance, bending resistance and surface hardness.

（一般式（２）において、Ｒ^３及びＲ^４はそれぞれ独立に、水素原子、アルキル基、またはパーフルオロアルキル基を表す。）

(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, cyclopentanetetracarboxylic acid 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 and at least one tetravalent group selected from the group consisting of 3,4'-oxydiphthalic anhydride residues, from the viewpoint of light transparency, 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 radical polymerizable compound and a cationically polymerizable compound, and the film or polyimide film It is a laminate that is used by being bent so that the bending portion is perpendicular to the tensile direction in which the strain value at the yield point becomes larger.

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 in the tensile direction in which the strain value at the yield point of the film or polyimide film becomes larger, It is used after being bent so that the bent portions are perpendicular to each other.

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

Further, the present invention provides the film or polyimide film of the present invention or the laminate of the present invention,
A transparent electrode made up of a plurality of conductive parts arranged on one surface side of the film, the polyimide film, or the laminate;
a plurality of extraction lines electrically connected to at least one end of the conductive portion;
The film or polyimide film provides a touch panel member that is foldable such that the bending portion is orthogonal to a tensile direction in which the strain value at the yield point of the film or polyimide film increases.

Further, the present invention 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 arranged on one side of the film, the polyimide film, or the laminate,
The film or polyimide film is installed 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 becomes larger, thereby providing a liquid crystal display device. .

Further, the present invention provides the film or polyimide film of the present invention or the laminate of the present invention,
an organic electroluminescence display section having an organic electroluminescence layer between opposing substrates arranged on one side of the film, the polyimide film, or the laminate,
The film or polyimide film is installed 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 becomes larger. provide.

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

FIG. 4 is a diagram for explaining the maximum stress in bending of a film; BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic plan view which shows one Embodiment of the polyimide film of this invention. It 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; It is a figure for demonstrating the method of a dynamic bending test. 1 is a schematic plan view of one surface of an example of a touch panel member of the present invention; FIG. FIG. 7 is a schematic plan view of the other surface of the touch panel member shown in FIG. 6; FIG. 8 is a cross-sectional view of the touch panel member shown in FIGS. 6 and 7 taken along line A-A'; 1 is a schematic plan view showing an example of a conductive member provided with a laminate of the present invention; FIG. FIG. 4 is a schematic plan view showing another example of a conductive member provided with the laminate of the present invention; It is a schematic sectional drawing which shows another example of the touch-panel member of this 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; FIG. 1 is a schematic cross-sectional view showing an example of an organic electroluminescence display device of the present invention; FIG. FIG. 4 is a schematic cross-sectional view showing another example of the organic electroluminescence display device of the present invention;

I. Film The film of one embodiment of the present invention is the ratio of the tensile modulus in a tensile test in which the X direction, which is one direction in the film plane, is the tensile direction and the tensile test in which the Y direction perpendicular to the X direction is the tensile direction. has an anisotropy of 1.50 or more, and the tensile test cuts out a test piece of 40 mm in the tensile direction × 15 mm in the direction perpendicular to the tensile direction, and the test piece is subjected to JIS K7127 at a tensile speed of 10 mm. / min, measured at 25 ° C. with a distance between chucks of 20 mm,
Each tensile modulus in the tensile test is 1.8 GPa or more,
A film having a total light transmittance of 85% or more measured according to JIS K7361-1 and a yellowness index of 5 or less calculated according to JIS K7373-2006,
The strain at the yield point is 8% or more in the stress-strain curves obtained by the tensile test with the X direction of the film as the tensile direction and the tensile test with the Y direction of the film as the tensile direction, and the yield point It is a film that is used by being bent so that the bent portion is perpendicular to the tensile direction in which the strain value in is greater.

According to the present invention, the specific total light transmittance, yellowness, and tensile elastic modulus of a specific or higher in a specific tensile test, furthermore, the tensile elastic modulus has a specific anisotropy, In the stress-strain curve obtained by the tensile test, the strain at the yield point is 8% or more, and the strain value at the yield point is greater. By using a film, it is possible to provide a film that is excellent in transparency and has both improved bending resistance and improved surface hardness.

In the present invention, the film refers to a thin film-like or plate-like material having a thickness of about 1 μm to 200 μm, including what is called a sheet, and may be long.
The film of the present invention includes a resin film.
Materials for the resin film include, for example, polyimide, polyamide, triacetyl cellulose, polyethylene, polypropylene, polyacetal, polyester (polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyvinyl chloride, AS resin, ABS resin, polystyrene, polyacetal. Methyl methacrylate, polyacetal, polycarbonate, polyphenylene sulfide, polyarylate, polysulfone, polyether sulfone, polyether ether ketone, liquid crystal polymer, polytetrafluoroethylene, cellulose acylate, cycloolefin polymer, MBS resin, and at least one of these and copolymers containing. Although the material type is not particularly limited as long as it satisfies the physical property values within the range of the present invention, organic materials, silicone materials, copolymers and mixtures thereof are preferable, 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 polyamide film using polyimide or polyamide as a film material is particularly preferably used.
The action, properties, etc. of the film of the present invention will be described in detail below, taking a polyimide film as an example. The action, characteristics, etc. of the film of the present invention may be the same as those of the polyimide film of the present invention, which will be described later.

II. Polyimide film The polyimide film of one embodiment of the present invention has a tensile modulus in a tensile test in which the X direction, which is one direction in the plane of the film, is the tensile direction and in a tensile test in which the Y direction perpendicular to the X direction is the tensile direction. ratio of 1.50 or more, and the tensile test cuts out a test piece of 40 mm in the tensile direction × 15 mm in the direction perpendicular to the tensile direction, and the test piece is subjected to tension according to JIS K7127. It is measured at a speed of 10 mm / min and a distance between chucks of 20 mm at 25 ° C.
Each tensile modulus in the tensile test is 1.8 GPa or more,
A polyimide film having a total light transmittance of 85% or more measured according to JIS K7361-1 and a yellowness index of 5 or less calculated according to JIS K7373-2006,
The strain at the yield point is 8% or more in the stress-strain curves obtained by the tensile test with the X direction of the film as the tensile direction and the tensile test with the Y direction of the film as the tensile direction, and the yield point It 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 in is greater.

According to the present invention, the specific total light transmittance, yellowness, and tensile elastic modulus of a specific or higher in a specific tensile test, furthermore, the tensile elastic 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 strain value at the yield point is greater. By forming the resin film into a film, it is possible to provide a resin film which is excellent in transparency and has both bending resistance and improved surface hardness.

The present inventors paid attention to 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 the molecular chains inside the polyimide film forms a certain ordered structure. It is considered that good results are shown in
However, conventional resin films using transparent polyimide have problems such as being prone to breakage in tests where the flat state and the folded state are repeated at a constant cycle, or being prone to creases, making it difficult to return to a flat state, and being inferior in bending resistance. . When the bent state is maintained for a long time, the film undergoes plastic deformation due to the continuous application of tensile stress to the outer circumference of the bent portion, which makes it difficult to restore even if the bending force is removed. It is assumed that there are
It is believed that the tensile stress applied to the outer circumference of the bent portion of the film when the film is bent increases as the thickness of the film increases and the bending radius of the bent portion decreases.
Therefore, a film that is easily plastically deformed is easily deformed during the bending test, and the deformation deteriorates visibility when used as a member of a flexible display panel.
More specifically, it is inferred as follows.
When the film is bent, tension is applied to the outer circumference of the bend and compressive force is applied to the inner circumference of the bend. ) 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) (half the film thickness d in the case of Fig. 1)
φ: Curvature (test width)
d: Film thickness of the film

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 Equation (1) above. Therefore, if the elastic modulus of the film is increased, the stress applied to the film during bending also increases, causing deformation. Also in a resin film, when the elastic modulus is increased, the restorability after being bent tends to be deteriorated and the bending resistance tends to be 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 having a large elastic modulus has good surface hardness, but poor bending resistance. Thus, it is considered that the bending resistance and surface hardness of the resin film are contradictory properties.
Base materials and surface materials for flexible displays are required not only to withstand repeated bending, but also to prevent damage to the surface and to prevent damage to the touch sensor and display panel located underneath. . When the surface material is a material with a high elastic modulus, such as glass, the impact from the surface of the display can be diffused in the plane direction, and the local impact can be mitigated. As a result, damage to the display panel can be prevented. The same thing can be said for flexible displays, and the higher the elastic modulus of the surface material, the more advantageous it is for the function of protecting the display panel. On the other hand, when the modulus of elasticity is low, the surface material itself deforms, and in some cases the impact can be mitigated. susceptible to damage.

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 the residual stress generated between it and the inorganic film is reduced. It is stated that However, as shown in Comparative Example 7, which will be described later, a polyimide film into which a silicone component containing three or more silicon atoms is introduced has a low glass transition temperature. There was a problem that it is easily scratched, and shock is transmitted to the light emitting panel and the circuit, and the function as a protective film is insufficient.
Moreover, it is described that the polyimide film described in Patent Document 5 has high folding endurance. However, as shown in Comparative Example 8 described later, the polyimide film into which silicone diamine (containing about 9 to 10 silicon atoms) corresponding to the example of Patent Document 5 is introduced lacks the elastic modulus at room temperature, There are problems such as low surface hardness, easy scratching, insufficient function as a protective film, and poor transparency.
For the above reasons, there has been a demand for a resin film that has both excellent transparency and bending resistance and sufficient surface hardness as a protective film. However, as described above, the bending resistance and surface hardness of a resin film are considered to be contradictory characteristics, and it has been difficult to achieve both excellent bending resistance and improved surface hardness.

On the other hand, the present inventors stress - in the strain curve obtained by the tensile test, focusing on the value of strain (%) at the yield point, stress - strain at the yield point of the strain curve is 8% or more. It was found that a film that is used by being folded so that the folded portion is perpendicular to the tensile direction tends to have improved bending resistance. The reason for this is not clear, but is presumed 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 area up to the yield point on the stress-strain curve can be regarded as the elastic deformation area, and the area after the yield point on the stress-strain curve can be regarded as the plastic deformation area. If 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 presumed that the material tends to return to its original state even after being bent. In other words, the strain amount at the yield point obtained by the stress-strain curve can be expressed as an elastically deformable deformation amount, and can be considered as a deformation amount that can restore the shape before stress is applied. Therefore, when the strain (%) at the yield point is larger than a predetermined value, as shown by the results of the bending test in the examples described later, the film has improved restorability after repeated bending of the film. It is presumed that
In the examples and comparative examples described later, even when a polyimide film is produced using a polyimide having the same molecular structure, if the production method is different and the state of the film is different, the stress obtained by the tensile test - The strain curves show that the strain (%) values at the yield point are different and the flexing resistance is accordingly different. This indicates that the bending resistance of a polyimide film does not depend only on the composition of the polyimide, and that the strain (%) value at the yield point represents the state of the polyimide film related to bending resistance. It is thought that
Stress - If you use it by bending so that the bending part is orthogonal to the tensile direction in which the strain at the yield point of the strain curve is 8% or more, in the tensile direction perpendicular to the tensile direction, the stress - The strain at the yield point of the strain curve may be less than 8%. It is thought that the surface hardness of the film can be improved by relatively increasing the tensile modulus in the tensile direction orthogonal to the tensile direction in which the strain at the yield point of the stress-strain curve is 8% or more. 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, while having a tensile modulus of elasticity greater than or equal to the specific The polyimide film is selected in combination with having a certain anisotropy in tensile modulus. According to the present invention, the tensile direction in which the strain value at the yield point is 8% or more and is larger, that is, the direction of the relatively small tensile elastic modulus is used to improve the bending resistance, while the other direction relative to the It is possible to improve the surface hardness by a relatively large tensile modulus, and it is possible to provide a resin film that achieves both excellent bending resistance and improved surface hardness.
Further, according to the present invention, the polyimide film having the specific total light transmittance and the specific yellowness is further provided, so that the resin film is excellent in transparency and has both improved bending resistance and surface hardness. is estimated to be able 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 of 40 mm in the tensile direction and 15 mm in the direction orthogonal to the tensile direction for performing a tensile test with the X direction, which is one direction in the film plane, as the tensile direction. 11 and a test piece 12 of 40 mm in the tensile direction and 15 mm in the direction orthogonal to the tensile direction for performing a tensile test with the Y direction orthogonal to the X direction as the tensile direction, and the tensile test is performed. It has anisotropy such that the elastic modulus ratio (X/Y) is 1.50 or more.
The polyimide film 101 of the present invention is 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. The strain at the yield point is 8%. Above, and when used by bending so that the bent portion 14 is orthogonal to the tensile direction 13 of the tensile test in which the strain value at the yield point is larger, the polyimide film 102 cut out from the polyimide film 101 , the bending resistance is excellent, and the occurrence of creases can be suppressed.
In addition, since the polyimide film of the present invention has an anisotropy in which the ratio (X/Y) of the tensile elastic modulus is 1.50 or more, the surface hardness is improved by using the direction of the relatively large tensile elastic modulus. It is possible to achieve both excellent bending resistance and improvement in surface hardness.
In this specification, the bent portion of the film refers to a locally bent portion formed by bending the film, or one planar portion divided by bending the film and the other planar portion. Indicates a part located on the boundary with a part.

The polyimide film according to the present invention will be described in detail below.
The polyimide film according to the present invention contains polyimide and has the above specific properties. As long as the effect of the present invention is not impaired, it may further contain other components and may have other constitutions.

1. tensile modulus
The polyimide film of the present invention has a tensile modulus ratio (X/Y ) has an anisotropy of 1.50 or more. Here, when obtaining the ratio of the tensile elastic moduli, the direction in which the value of the tensile elastic modulus is relatively small is calculated as the Y direction. The value obtained by dividing the tensile elastic modulus in the X direction by the tensile elastic modulus in the Y direction is a value rounded to the second decimal place according to Rule B of JIS Z8401:1999.
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 is cut out, and the test piece is measured at 25 ° C. with a tensile speed of 10 mm / min and a distance between chucks of 20 mm in accordance with JIS K7127. and 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 modulus in a tensile test in which the X direction, which is one direction in the plane of the film, is the tensile direction is 1.8 GPa×1.50=2.7 GPa or more.
Thus, 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 substrate. can be done.

In the polyimide film of the present invention, the tensile elastic modulus ratio (X/Y) is more preferably 1.60 or more from the viewpoint of improving the surface hardness.

The tensile elastic modulus in the Y direction, which has a relatively small tensile elastic modulus value, is preferably 2.0 GPa or more, more preferably 2.1 GPa or more, and 2.3 GPa or more from the viewpoint of surface hardness. It is even more preferable to have
The tensile elastic modulus in the X direction, which has a relatively large tensile elastic modulus value, 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 to have
On the other hand, the tensile elastic modulus in the Y direction, which has a relatively small tensile elastic modulus value, is preferably 5.2 GPa or less from the viewpoint of improving bending resistance. From the viewpoint of improving 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 is measured using a tensile tester (for example, manufactured by Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN), width 15 mm × length 40 mm (tensile direction 40 mm × direction perpendicular to the tensile direction 15 mm). A test piece is cut out from the polyimide film, and the test piece is subjected to a tensile test at a tensile speed of 10 mm/min and a distance between chucks of 20 mm at 25° C. in accordance with JIS K7127. When cutting out the test piece from the film, it is preferable to cut out a portion of the film having a uniform thickness, for example, it is preferable to cut out from the vicinity of the central portion of the film. As a measure of the uniformity of the film thickness, for example, the thickness of the cut film at a total of five points, four corners and the center, is measured 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 is obtained by a tensile test in which the X direction of the film is the tensile direction and a tensile test in which the Y direction of the film is the tensile direction. Of the strain curves, at least In the stress-strain curve obtained by one tensile test, the strain at the yield point is 8% or more. Then, the stress-strain curve obtained by a tensile test in which the X direction of the film is the tensile direction and a tensile test in which the Y direction of the film is 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 orthogonal to the direction of tension in which the value is greater. The strain value at the yield point is 8% or more, and by bending the film so that the bending portion is perpendicular to the larger tensile direction, the restorability after repeated bending of the film is further improved. become a thing.

Although the upper limit of the strain at the yield point is not limited, the strain at the yield point may generally be 90% or less.
Since the greater the tensile modulus of elasticity, the greater the force required for deformation, materials with a low tensile modulus are more likely to be deformed. The lower limit of the tensile modulus in the present invention is 1.8 Gpa, while the tensile strength of a resin film having a high tensile strength is approximately 200 N/mm ² . For films with different tensile elastic moduli, the amount of strain reaching a tensile strength of 200 N/mm ² is calculated, the relationship between the tensile elastic modulus and the amount of strain at 200 N/mm ² is obtained, and the amount of strain of a film with a tensile elastic modulus of 1.8 GPa. , it can be estimated that the film of the present invention having a lower limit of 1.8 Gpa of tensile modulus 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 the tensile test. %) on the horizontal axis and the tensile stress (MPa) on the vertical axis. The yield point of the stress-strain curve of polyimide films can be elusive, 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.
In the stress-strain curve, sampling starts from the point where the strain is 0.16%, and thereafter sampling is performed every 0.21% increase (this is defined as dx). That is, dx is the difference (amount of change) from the value sampled immediately before, and is 0.16% only at the initial value and 0.21% thereafter. On the other hand, dy is the difference (amount of change) in the tensile stress value corresponding to the strain from the value sampled immediately before. After calculating dx and dy respectively, graph the horizontal axis as strain % and the vertical axis as dy / dx (average rate of change) (for example, the stress in FIG. 3 - In the case of the strain curve, the graph shown in FIG. 4 and Become). The graph of strain % and dy / dx (average rate of change) is basically a downward sloping graph as shown in FIG. 4, but the maximum value of dy / dx (average rate of change) is obtained Beyond the point, the first dy/dx inflection point is defined as the yield point. For those with no inflection point, the yield point is the point at which dy/dx becomes 0 for the first time.
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 according to JIS K7361-1. Since the transmittance is high in this way, the transparency is good, and it can be used as a substitute for glass. The total light transmittance of the polyimide film of the present invention measured according to JIS K7361-1 is preferably 88% or more, more preferably 89% or more, particularly 90% or more. is preferred.

The total light transmittance measured according to JIS K7361-1 can be measured, for example, with a haze meter (eg HM150 manufactured by Murakami Color Research Laboratory). From the measured value of the total light transmittance of a certain thickness, the total light transmittance of a different thickness can be calculated by Beer-Lambert's law, and it can be used.
Specifically, according to Beer-Lambert's law, the transmittance T is
Log ₁₀ (1/T) = kcb
(k=substance-specific constant, 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 equation is Log ₁₀ (1/T)=fb
(f=kc). Here, if the transmittance at a certain film thickness is known, the intrinsic constant f of each substance can be obtained. Therefore, by using the equation T=1/10 ^f·b and substituting a specific constant for f and a target film thickness for b, the transmittance at the desired film thickness can be obtained.

4. Yellowness Index The polyimide film of the present invention has a yellowness index (YI value) of 5 or less calculated according to JIS K7373-2006. Since the degree of yellowness is low in this way, 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, and even more preferably 3.5 or less. .
Incidentally, the yellowness (YI value), in accordance with the JIS K7373-2006, using a UV-visible near-infrared spectrophotometer (e.g., JASCO Corporation V-7100), by a spectrophotometric method, auxiliary Tristimulus values X, Y, and Z in the XYZ color system are determined based on the transmittance measured at intervals of 1 nm in the range of 250 nm to 800 nm using illuminant C and a 2-degree field of view. , Z can be calculated from the following equation.
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 obtained by measuring the transmittance at each wavelength in the range of 250 nm or more and 800 nm or less of a sample with a certain thickness at intervals of 1 nm. As with the light transmittance, the conversion value of each transmittance at each wavelength of different thicknesses is obtained according to Beer-Lambert's law, and it can be calculated and used based on it.

In addition, the polyimide film of the present invention suppresses yellowish coloring, 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 are even more preferable.
In the present invention, the value obtained by dividing the yellowness index (YI value) by the film thickness (μm) (YI value/film thickness (μm)) is calculated to the second decimal place according to Rule B of JIS Z8401:1999. A rounded value.

5. Polyimide In the present invention, polyimide is obtained by reacting a tetracarboxylic acid component and a diamine component. After obtaining polyamic acid as a precursor by polymerization of 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 its main chain. The tetracarboxylic acid residue is a residue obtained by removing four carboxy groups from a tetracarboxylic acid, and has the same structure as a residue obtained by removing an acid dianhydride structure from a tetracarboxylic dianhydride. 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, the film formation is in the state of the polyimide precursor. and then heat treatment to form polyimide by thermal imidization, or after converting a polyimide precursor into polyimide by chemical imidization, it is molded in the form of a polyimide solution and the solvent is removed. Alternatively, it can be produced by a method using both thermal imidization and chemical imidization.

In the polyimide used in the present invention, as the tetracarboxylic acid component that becomes the 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 and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride. , 2,2′,3,3′-benzophenonetetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,2′,3,3′-biphenyltetracarboxylic acid acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4-di 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.

Moreover, 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 the light transmittance of the polyimide film.
Examples of the tetracarboxylic dianhydride having an aliphatic ring include cyclohexanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, dicyclohexane-3,4,3′,4′-tetracarboxylic dianhydride, anhydride, cyclobutanetetracarboxylic dianhydride, and the like.
In addition, the tetracarboxylic acid component mentioned above can also be used individually or in mixture of 2 or more types.

As the diamine component, for example, a diamine having an aromatic ring is preferable from the viewpoint of durability and surface hardness of the polyimide film.
Moreover, as the diamine component used in the present invention, a diamine having an alicyclic ring is also preferable from the viewpoint of the light transmittance of the polyimide film.
Moreover, 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 having a silicon atom in the main chain between the molecular skeletons containing an aromatic ring or an aliphatic ring as a main component, the polyimide becomes easy to achieve both bending resistance and surface hardness. Moreover, the orientation tends to be suppressed, and the birefringence tends to be reduced.

Examples of diamines having an aromatic ring include 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 2,2-bis(4-aminophenyl)propane, 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′-diphenyl Phenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis(4-aminophenoxy)-3,3,3',3' -tetramethyl-1,1'-spirobiindane and the like, 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 the substituents described herein can be used.

Examples of diamines having an aliphatic ring include trans-cyclohexanediamine, trans-1,4-bismethylenecyclohexanediamine, 2,6-bis(aminomethyl)bicyclo[2,2,1]heptane, 2,5- bis(aminomethyl)bicyclo[2,2,1]heptane and the like.

Diamines having a silicon atom in the main chain include, for example, diamines represented by the following general formula (A).

（一般式（Ａ）において、Ｌはそれぞれ独立して、直接結合又は－Ｏ－結合であり、Ｒ^１０はそれぞれ独立して、置換基を有していても良く、酸素原子又は窒素原子を含んでいても良い炭素数１以上２０以下の１価の炭化水素基を表す。Ｒ^１１はそれぞれ独立して、置換基を有していても良く、酸素原子又は窒素原子を含んでいても良い炭素数１以上２０以下の２価の炭化水素基を表す。ｋは０～２００の数である。複数あるＬ、Ｒ^１０及びＲ^１１は、それぞれ同一であっても異なっていても良い。）

(In the general formula (A), each L is independently a direct bond or -O- bond, and each R ¹⁰ is independently a substituent and contains an oxygen atom or a nitrogen atom. represents a monovalent hydrocarbon group having from ¹ to 20 carbon atoms which may be represents a divalent hydrocarbon group of number 1 or more and 20 or less, k is a number of 0 to 200. Plural L, R ¹⁰ and R ¹¹ may be the same or different.)

The monovalent hydrocarbon group represented by R ¹⁰ includes alkyl groups having 1 to 20 carbon atoms, aryl groups, and combinations thereof. The alkyl group may be linear, branched, or cyclic, or may be a combination of linear or branched and cyclic.
The alkyl group having 1 to 20 carbon atoms is preferably an alkyl group having 1 to 10 carbon atoms, specifically, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, 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 thereof 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 specific examples include a phenyl group, a tolyl group, a naphthyl group, and the like. Moreover, the monovalent hydrocarbon group represented by R ¹⁰ may be an aralkyl group, such as a benzyl group, a phenylethyl group, a phenylpropyl group, and the like.
Hydrocarbon groups which may contain an oxygen atom or a nitrogen atom include, for example, ether bonds, carbonyl bonds, ester bonds, amide bonds, and imino Groups attached by at least one bond (--NH--) are included.
The substituent that the monovalent hydrocarbon group represented by R ¹⁰ may have is not particularly limited as long as the effects of the present invention are not impaired. For example, a halogen atom such as a fluorine atom and a chlorine atom , a hydroxyl group, and the like.

The monovalent hydrocarbon group represented by R ¹⁰ is an alkyl group having 1 or more and 3 or less carbon atoms or an aryl group having 6 or more and 10 or less carbon atoms from the viewpoint of compatibility between improvement in bending resistance and surface hardness. Preferably. 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.

The divalent hydrocarbon group represented by R ¹¹ includes 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. Examples include a combination of a linear or branched alkylene group and a cyclic alkylene group.
The arylene group is preferably an arylene group having 6 to 12 carbon atoms. Examples of the arylene group include a phenylene group, a biphenylene group, a naphthylene group, and the like, and further having a substituent for an aromatic ring described later. It's okay to be there.
As the divalent hydrocarbon group which may contain an oxygen atom or a nitrogen atom, an ether bond, a carbonyl bond, an ester bond, an amide bond, and an imino bond (—NH—) are formed between the divalent hydrocarbon groups. Groups with at least one attached are included.
The substituent that the divalent hydrocarbon group represented by R ¹¹ may have is the same as the substituent that the monovalent hydrocarbon group represented by R ¹⁰ may have. good

The divalent hydrocarbon group represented by R ¹¹ is an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 10 carbon atoms from the viewpoint of compatibility between improvement in bending resistance and surface hardness. more preferably an alkylene group having 2 or more and 4 or less carbon atoms.

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

Diamines having one silicon atom in the main chain include, for example, diamines represented by the following general formula (A-1). Diamines having two silicon atoms in the main chain include, for example, diamines represented by the following general formula (A-2).

（一般式（Ａ－１）及び一般式（Ａ－２）において、Ｌはそれぞれ独立して、直接結合又は－Ｏ－結合であり、Ｒ^１０はそれぞれ独立して、置換基を有していても良く、酸素原子又は窒素原子を含んでいても良い炭素数１以上２０以下の１価の炭化水素基を表す。Ｒ^１１はそれぞれ独立して、置換基を有していても良く、酸素原子又は窒素原子を含んでいても良い炭素数１以上２０以下の２価の炭化水素基を表す。複数あるＬ、Ｒ^１０及びＲ^１１は、それぞれ同一であっても異なっていても良い。）

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

From the viewpoint of compatibility between bending resistance and 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 more preferably 500 or less, and particularly preferably 300 or less.
Diamine residues having one or two silicon atoms in the main chain may be used alone or in combination of two or more.

In addition, the diamine having one or two silicon atoms in the main chain is preferably a diamine having two silicon atoms from the viewpoint of the light transmittance of the resulting polyimide, and the bending resistance and surface hardness. Furthermore, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 1,3-bis(4-aminobutyl)tetramethyldisiloxane, 1,3-bis(5-aminopentyl)tetramethyldisiloxane, etc. are preferred from the viewpoint of the availability of these compounds and compatibility between the light transmittance and surface hardness of the polyimide obtained.

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 diamines is not particularly limited, but from the viewpoint of improving the bending resistance of the resulting polyimide film, 1 It is preferably mol % or more, more preferably 2.5 mol % or more, and even more preferably 5 mol % or more. In terms 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.

Further, 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, and 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 preferably contains at least one selected from the group consisting of a structure linked by an alkylene group, and further preferably contains a diamine residue having a silicon atom in its main chain in addition to these structures.
In the present invention, the polyimide contains at least one selected from a tetracarboxylic acid residue having an aromatic ring and a diamine residue having an aromatic ring, so that the molecular skeleton becomes rigid and durability increases, and surface hardness 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.
If the polyimide contains (i) a fluorine atom, the electron state in the polyimide skeleton can be made difficult to transfer, resulting in an improvement in light transmittance. Furthermore, when the polyimide contains (i) a fluorine atom, the hygroscopicity is suppressed, so the tendency of the plastic deformation region to expand when the hygroscopicity is high can be suppressed, and the bending resistance in a high-humidity environment can be improved. .
When (ii) an alicyclic ring is contained in the polyimide, the transmissivity of the polyimide is improved because the transfer of charges in the skeleton can be inhibited by breaking the conjugation of the π electrons in the skeleton of the polyimide.
If the polyimide contains (iii) a structure in which the aromatic rings are linked by a sulfonyl group or an alkylene group that may be substituted with fluorine, the charge transfer in the skeleton is prevented by breaking the conjugation of the π electrons in the polyimide skeleton. Light transmittance is improved from the point that it can be inhibited.

Among them, polyimide containing fluorine atoms is preferably used from the viewpoint of improving light transmittance and improving surface hardness and bending resistance.
Regarding the content of fluorine atoms, the ratio (F/C) between the number of fluorine atoms (F) and the number of carbon atoms (C) measured on the polyimide surface by X-ray photoelectron spectroscopy is preferably 0.01 or more, Furthermore, it is preferable that it is 0.05 or more. On the other hand, if the content of fluorine atoms is too high, the inherent heat resistance of polyimide may deteriorate, so the ratio (F/C) between the number of fluorine atoms (F) and the number of carbon atoms (C) is 1 or less is preferable, and more preferably 0.8 or less.
Here, the above ratio measured by X-ray photoelectron spectroscopy (XPS) can be obtained from the atomic % value of each atom measured using an X-ray photoelectron spectrometer (for example, Thermo Scientific Theta Probe). .

Further, from the viewpoint of surface hardness and light transparency of the polyimide obtained, and bending resistance, at least one of tetracarboxylic acid and diamine having no silicon atom preferably 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.
From the viewpoint of the surface hardness and light transmittance of the obtained polyimide, and the bending resistance, when the total amount of the tetracarboxylic acid component and the 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 directly bonded to the aromatic ring, thereby improving the light transmittance of the resulting polyimide. In addition, it is preferably used from the viewpoint of improving the 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 preferably 60% or more, more preferably 70% or more. .
When 50% or more of hydrogen atoms bonded to carbon atoms contained in each of the tetracarboxylic acid component and the diamine component are hydrogen atoms directly bonded to the aromatic ring, even after the heating step in the atmosphere, for example Even if it is stretched at 200° C. or higher, it is preferable from the viewpoint that the change in optical properties, particularly the total light transmittance and the yellowness YI value is small, and the decrease in bending resistance is suppressed. When 50% or more of the hydrogen atoms bonded to the carbon atoms are hydrogen atoms directly bonded to the aromatic ring, the reactivity with oxygen is low, so the chemical structure of the obtained polyimide is difficult to change, and oxidation It is presumed that deterioration of the polyimide film is suppressed. Due to its high heat resistance, polyimide film is often used in devices that require processing steps involving heating. When the above are hydrogen atoms directly bonded to the aromatic ring, there is no need to carry out these post-processes under an inert atmosphere in order to maintain transparency, so equipment costs and atmosphere control costs can be reduced. There is an advantage that it can be suppressed.
Here, the ratio of hydrogen atoms (number) directly bonded to aromatic rings in all hydrogen atoms (number) bonded to carbon atoms contained in the polyimide is determined by high-performance liquid chromatography and gas chromatograph mass It can be determined using an analyzer and NMR. For example, the sample is decomposed with an alkaline aqueous solution or supercritical methanol, the resulting decomposition 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. The ratio of hydrogen atoms (number) directly bonded to aromatic rings to all hydrogen atoms (number) contained in the polyimide can be obtained by quantification using high-performance liquid chromatography.

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

（一般式（１）において、Ｒ^１は芳香族環又は脂肪族環を有するテトラカルボン酸残基である４価の基を表し、複数のＲ^１は各々同一であっても異なっていても良く、Ｒ^２はジアミン残基である２価の基を表し、複数のＲ^２は各々同一であっても異なっていても良く、複数のＲ^２の少なくとも一部が芳香族環又は脂肪族環を有するジアミン残基を含む。ｎは繰り返し単位数を表す。）

(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 a plurality of R ¹ may be the same or different. , R ² represents a divalent group that is a diamine residue, the plurality of R ² may be the same or different, and at least a portion of the plurality of R ² is an aromatic ring or an aliphatic ring Including diamine residues with n represents the number of repeating units.)

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

Among them, from the viewpoint of light transparency, bending resistance and surface hardness of the resulting polyimide, R ¹ in the general formula (1) is a cyclohexanetetracarboxylic dianhydride residue, cyclopentanetetracarboxylic acid dianhydride residue, cyclopentanetetracarboxylic acid dianhydride residue, 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 diphthalic anhydride residue, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene)diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride residue and at least one tetravalent group selected from the group consisting of 3,4'-oxydiphthalic anhydride residues.

In terms of particularly good light transmittance, the tetracarboxylic acid component includes 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 obtained polyimide, such as at least one selected from the group consisting of cyclohexanetetracarboxylic acid 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 rigidity and the tetracarboxylic acid group (group B) suitable for improving light transmittance is 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 rigidity. more preferably 0.1 mol or more and 5 mol or less, and even more preferably 0.3 mol or more and 4 mol or less.
Among them, at least one of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride and 3,4′-(hexafluoroisopropylidene)diphthalic anhydride containing a fluorine atom is used as the group B. 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, the plurality of R ² may be the same or different, and at least part of the plurality of R ² is aromatic There is no particular limitation as long as it contains a diamine residue having an aliphatic ring or an aliphatic ring. As the divalent diamine residue, those similar to those described above can be used.
These may 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 those described above can be used.
These may be used alone or in combination of two or more.

Among them, from the viewpoint of light transmittance and bending resistance, surface hardness, and low hygroscopicity, the diamine residue having an aromatic ring or an 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 [4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, and selected from the group consisting of a divalent group represented by the following general formula (2) is preferably at least one divalent group. As the divalent group represented by the following general formula (2), R ³ and R ⁴ are more preferably perfluoroalkyl groups.

（一般式（２）において、Ｒ^３及びＲ^４はそれぞれ独立に、水素原子、アルキル基、またはパーフルオロアルキル基を表す。）
これらは単独でも、２種以上を混合して用いることもできる。

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

In addition, as a preferred embodiment for improving bending resistance, a diamine residue having a silicon atom in the main chain is included as part of a plurality of R ² . Since the diamine residue having a silicon atom in the main chain that can be preferably used as R ² is as described above, the description is omitted here.

When R ² in the general formula (1) contains a diamine residue having a silicon atom in the main chain, in R ² in the general formula (1), 2.5 mol% or more of the total amount of R ² 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 contains 3.5 mol% or more of a diamine residue having a silicon atom in the main chain of the total amount of R ² , and further 5 It is preferably mol % or more. From the viewpoint of reducing optical distortion, the diamine residue having a silicon atom in the main chain may exceed 10 mol %, or may be 15 mol % or more, of the total amount of R ² . On the other hand, from the viewpoint of improving surface hardness and light transmittance, R ² in the general formula (1) preferably contains 45 mol% or less of the total amount of R ² , the diamine residue having a silicon atom in the main chain. It is preferably 40 mol % or less.
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 50 mol% or more and 97.5 mol% or less of the total amount of R ² is silicon If it is a diamine residue having no atoms and having an aromatic ring or an aliphatic ring, R ² in the general formula (1) includes a diamine residue having a silicon atom in the main chain and a silicon atom. This does not preclude inclusion of diamine residues other than diamine residues having aromatic rings or aliphatic rings. The other diamine residue is preferably 10 mol% or less, more preferably 5 mol% or less, even more preferably 3 mol% or less, particularly 1 mol% of the total amount of R ² The following are preferred. Examples of such other diamine residues include diamine residues having no silicon atoms and no aromatic rings or aliphatic rings.
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 among the total amount of R ² (100 mol%), the silicon atom in the main chain 50 mol% or more and 97.5 mol% or less, which is the remainder (100%-x%) of the diamine residue mol% (x mol%) having no silicon atoms, an aromatic ring or an aliphatic ring is preferably a diamine residue having

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 50 mol% or more and 97.5 mol% or less of the total amount of the 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. .
Among them, R ² represents a divalent group that is at least one selected from diamine residues having no silicon atoms and diamine residues having one or two silicon atoms in the main chain, and R 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 50 mol% or more and 97.5 mol% or less of the total amount of R ² is , 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.
From the viewpoint of improving bending resistance, R ² in the general formula (1) has a diamine residue having 1 or 2 silicon atoms in the main chain, and the total amount of R ² is 3.5 mol% or more. is preferred, and more preferably 5 mol % or more. Further, from the viewpoint of reducing optical distortion, the diamine residue having one or two silicon atoms in the main chain may exceed 10 mol% of the total amount of R ² , and may be 15 mol% or more. Also good. On the other hand, from the viewpoint of improving surface hardness and light transmittance, R ² of the general formula (1) contains 45 mol% of the total amount of R ² , which is a diamine residue having one or two silicon atoms in the main chain. or less, more preferably 40 mol % or less.
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 among the total amount of R ² (100 mol%), the above 50 mol% or more and 97.5 mol% or less, which is the remainder (100%-x%) of the mol% (x mol%) of the diamine residue having one or two silicon atoms in the main chain, has a silicon atom. It is preferably a diamine residue having an aromatic ring or an aliphatic ring.

Further, from the viewpoint of bending resistance and surface hardness, the polyimide used in the present invention preferably has a silicon atom content (% by 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 (% by mass) of silicon atoms in the polyimide refers to the content ratio (% by mass) of silicon atoms in all of the two or more polyimides when two or more polyimides are used. It can be determined from the molecular weight. In addition, the silicon atom content (% by mass) in the polyimide was determined by 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 (% by mass))
For example, 2,2'-bis(trifluoromethyl)benzidine (TFMB) as a diamine component with respect to 1 mol of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) as an acid dianhydride component When 0.9 mol and 0.1 mol of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS) are used, it can be calculated as follows.
The molecular weight of 1 mol of polyimide repeating unit is
6 FDA origin: (C) 12.01 x 19 + (F) 19.00 x 6 + (O) 16.00 x 4 + (H) 1.01 x 6 = 412.25
Derived from TFMB: {(C) 12.01 x 14 + (F) 19.00 x 6 + (N) 14.01 x 2 + (H) 1.01 x 6} x 0.9 = 284.60
From AprTMOS: {(C) 12.01 x 10 + (O) 16.00 x 1 + (N) 14.01 x 2 + (Si) 28.09 x 2 + (H) 1.01 x 24} x 0.1 = 24.45
412.25+284.60+24.45=721.30.
The silicon atom content ratio (mass%) in 1 mol of the polyimide repeating unit is
(28.09×2×0.1)/721.30×100=0.8 (% by mass).

Further, from the viewpoint of achieving both bending resistance and surface hardness and light transparency, 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 case where the main chain contains a diamine residue having a hexafluoroisopropylidene skeleton. The diamine residue having a hexafluoroisopropylidene skeleton in the main chain preferably includes a structure in which aromatic rings are linked together 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) is at least one diamine residue having no silicon atom Representing a divalent group as a species, the diamine residue having no silicon atom is, among others, in terms of light transparency and bending resistance, surface hardness, and low hygroscopicity. It is more preferable to have a hexafluoroisopropylidene skeleton in the chain and contain a diamine residue having a fluorine atom ratio (% by number) of 30% or more with respect to carbon atoms, and the aromatic rings are hexafluoroisopropylidene groups. and a structure in which the aromatic rings are linked by an oxy group, and a diamine residue having a fluorine atom ratio (% by number) to carbon atoms of 30% or more. .

When R ² in the general formula (1) does not contain a diamine residue having a silicon atom in the main chain, the diamine residue having no silicon atom specifically includes 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 It is preferably 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 residues 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 residues are 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 suitable The total content of diamine residues having no 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 in the polyimide and the content ratio (mole %) of each tetracarboxylic acid residue and each diamine residue can be obtained from the molecular weight of the preparation at the time of polyimide production. In addition, the content ratio (mol%) of each tetracarboxylic acid residue and each diamine residue in the polyimide is similar to the above, with respect to the polyimide decomposition product obtained by decomposition with an alkaline aqueous solution or supercritical methanol. , high performance liquid chromatography, gas chromatograph mass spectrometer, 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 polyimide may be selected as appropriate and is not particularly limited.
The average number of repeating units is usually 10 to 2,000, preferably 15 to 1,000.

The polyimide used in the present invention may contain one or more.
In addition, 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 of the total number of repeating units of the polyimide, more preferably 98% or more, and 100% It is even more preferable to have
Structures different from the structure represented by the general formula (1) include, for example, cases in which a tetracarboxylic acid residue having no aromatic ring or aliphatic ring is included, and a polyamide structure.
Polyamide structures that may be included include, for example, polyamideimide structures containing tricarboxylic acid residues such as trimellitic anhydride, and polyamide structures containing dicarboxylic acid residues such as terephthalic acid.

At least one of the number average molecular weight and the weight average molecular weight of the polyimide used in the present invention is preferably 10,000 or more, more preferably 20,000 or more, from the viewpoint of strength when formed into a film. Moreover, 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, from the viewpoint of improving bending resistance. On the other hand, if the average molecular weight is too large, the viscosity becomes high and workability such as filtration may be lowered.
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 the optical distortion of the polyimide film, silica fillers for smooth winding, surfactants for improving film-forming properties and defoaming properties, and the like. be done.

7. Properties 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 has the properties described later.

The polyimide film of the present invention preferably has a peak apex only in a temperature range of 150° C. or higher in the tan δ curve, which is a value obtained by dividing the loss modulus by the storage modulus. In the tan δ curve, if the peak apex is present at less than 150 ° C., the polyimide molecular chain is likely to move and plastic deformation is likely to occur, and the bending resistance may be deteriorated. If it does not exist, the mobility of the molecular chain is suppressed, plastic deformation becomes difficult, and bending resistance can be improved.
In addition, if the tan δ curve has a peak apex only in a temperature range of 150° C. or higher, deterioration of bending resistance due to thermal deformation is suppressed even in a high temperature environment, such as in a car in summer. The bending resistance is improved even in the environment.
Further, if the tan δ curve has a peak only in a temperature range of 150° C. or higher, the tensile elastic modulus tends to increase and the surface hardness tends to increase.
From the viewpoint of improving bending resistance and surface hardness, the polyimide film of the present invention more preferably has a peak apex only in a temperature range of 200 ° C. or higher in the tan δ curve, and a temperature range of 220 ° C. or higher. It is even more preferred to have only On the other hand, the tan δ curve preferably has a peak apex in a temperature range of 380° C. or less from the point of view that the baking temperature can be reduced.
In addition, the polyimide film of the present invention preferably does not have a peak apex in the tan δ curve in a temperature range of −150° C. or more and less than 150° C., and further in a temperature range of −70° C. or more and less than 150° C. Furthermore, it is preferable not to have the apex of the peak in the tan δ curve in the temperature range of 100° C. or lower, and more preferably not to have the apex of the peak in the tan δ curve in the temperature range of 0° C. or lower. In the case of having a diamine residue having a long siloxane bond in the main chain or in the case of containing a large amount of diamine residue having a silicon atom in the main chain, when the tan δ curve peaks in such a low temperature region. There is
The tan δ curve is obtained 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 can be used as an index of the glass transition temperature. Dynamic viscoelasticity measurement is performed, for example, by a dynamic viscoelasticity measuring device RSA-G2 (TA Instrument Japan Co., Ltd.), with a measurement range of -150 ° C to 490 ° C and a frequency of 1 Hz. It can be carried out at a temperature rate of 5°C/min. Also, the measurement can be performed with a sample width of 5 mm and a chuck-to-chuck distance of 20 mm. When analyzing peaks and inflection points, data are quantified and analyzed numerically without visual evaluation.
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 peak is 3 ° C. or more. It is not observed as a peak at the apex of said peak.
As a sample for measuring the tan δ curve, a polyimide film was left to stand for 24 hours in an environment of 23 ° C. ± 2 ° C. RH 30 to 50%. Using a cutting jig with a slit at the bottom, a piece of 5 mm width x 50 mm length (so that the sample length becomes 20 mm when chucked) is used. The width is measured using vernier calipers, and the average value of three measurements at different positions is recorded. At this time, if part of the width measurement has a fluctuation width of 3% or more of the average value, that sample is not used.

In the polyimide film of the present invention, the Young's modulus measured by the following measurement method is preferably 2.3 Gpa or more, more preferably 2.4 Gpa or more, from the viewpoint of excellent surface hardness.
Young's modulus is measured at a temperature of 25° C. using the nanoindentation method according to ISO 14577. Specifically, as a measuring device, PICODENTOR HM500 manufactured by Fisher Instruments Co., Ltd. is used, and a Vickers indenter is used as a measuring indenter. The Young's modulus is obtained by measuring eight arbitrary points on the surface of the polyimide film and averaging the number. The measurement conditions are maximum indentation depth: 1000 nm, load time: 20 seconds, and creep time: 5 seconds.

The polyimide film of the present invention preferably has a pencil hardness of F or higher, more preferably H or higher.
The pencil hardness of the polyimide film was determined by conditioning the measurement sample for 2 hours under conditions of a temperature of 25 ° C. and a relative humidity of 60%, and then using a test pencil specified by JIS-S-6006, JIS K5600-5-4. (1999) by performing 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 film 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, the specific stress-strain (%) at the yield point of the strain curve, the tensile test for determining the tensile elastic modulus, the elongation rate (tensile 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 × (L-Lo) / Lo
Lo: test length 20 mm, L: test length at break

In the polyimide film of the present invention, from the viewpoint of excellent bending resistance, according to the dynamic bending test method described below, the bending part is perpendicular to the tensile direction in which the strain value at the yield point becomes 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]
The dynamic bending test method will be described below with reference to FIG.
Two movable metal plates 5 (100 mm × 30 mm) each having a movable portion 5a and a non-movable portion 5b are prepared, and are arranged parallel to each other so that the distance between the non-movable portions 5b of the two metal plates 5 is 60 mm. to be placed. The movable portion 5a of the metal plate 5 is bent perpendicular to the non-movable portion 5b as shown in FIG. A test piece 1 is placed, and both ends of the test piece 1 are fixed to the movable portion 5a with Kapton (registered trademark) tape so that the center of the test piece 1 is positioned at the center of the distance between the metal plates. Next, the movable portion 5a and the non-movable portion 5b are arranged in a straight line to form a state as shown in FIG. 5(B). It is sandwiched between the metal plates 5, and the metal plates 5 on both sides are arranged in parallel so that the distance between the metal plates 5 on both sides is 60 mm. In this state and in the state shown in FIG. Under the environment of relative humidity (RH), or under the environment of 60° C. and 93% relative humidity (RH), the number of bends is repeatedly changed at 90 times per minute, and the bending is repeated 200,000 times. As a test jig, an endurance test system in a constant temperature and humidity chamber (manufactured by Yuasa System Co., Ltd., non-load U-shaped stretching test jig DMX-FS for planar body) can be used.
Then, one end of the test piece is fixed, and the internal angle of the test piece is measured 30 minutes after releasing the force applied to the test piece.
When testing by bending so that the bent part is orthogonal to the tensile direction in which the strain value at the yield point is greater, the tensile direction in which the strain value at the yield point is greater is 100 mm on the long side. Cut out the test piece.
In addition, when the film is completely restored without being affected by the dynamic bending test, the internal angle is 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 transmission. 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 conforming to JIS K-7136, for example, by a haze meter HM150 manufactured by Murakami Color Research Laboratory.

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

The atomic % 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 obtained from the atomic % value of each atom measured using an X-ray photoelectron spectrometer (for example, Thermo Scientific Theta Probe). .

In a preferred embodiment, the ratio (F/C) between the number of fluorine atoms (F) and the number of carbon atoms (C) on the surface of the polyimide film measured by X-ray photoelectron spectroscopy is 0.01 or more and 1 or less. is preferable, and more preferably 0.05 or more and 0.8 or less.
In addition, the ratio (F/N) of the number of fluorine atoms (F) and the number of nitrogen atoms (N) on the surface of the polyimide film measured by X-ray photoelectron spectroscopy 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) and the number of silicon atoms (Si) on the surface of the film, measured by X-ray photoelectron spectroscopy of the polyimide film, is preferably 1 or more and 50 or less. 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 performed according to the adhesion test method described below, the fact that the coating film does not peel off is confirmed in terms of the adhesion between the polyimide film and the hard coat layer and the polyimide. It is preferable from the viewpoint of the surface hardness of the laminate in which the hard coat layer is laminated adjacent to the 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% by mass methyl isobutyl ketone solution of pentaerythritol triacrylate. is applied onto a polyimide film test piece cut into a size of 10 cm×10 cm, and cured by irradiating with ultraviolet rays at an exposure amount 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 the peeling operation with a tape is repeated five times, and then 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 application, but is preferably 1 μm or more, more preferably 5 μm or more, and still 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 still more preferably 90 μm or less.
If the thickness is thin, the strength is lowered, and if the thickness is thick, the difference between the inner diameter and the outer diameter when flexed increases, and the load on the film increases, which may reduce the bending resistance.

Moreover, the polyimide film of the present invention may be subjected to surface treatment 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 is a method capable of producing the polyimide film of the present invention.
<First manufacturing method>
As a method for producing the polyimide film of the present invention, for example, as a first production 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 film forming step);
A step of imidizing the polyimide precursor by heating (hereinafter referred to as imidization step);
A step of stretching at least one of the polyimide precursor resin coating film and the post-imidization 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 comprising

In the first production method, at least one of the polyimide precursor resin coating film and the imidized coating film is formed so as to have an anisotropic tensile modulus ratio of 1.50 or more. It has a step of stretching.
Each step will be described in detail below.

(1) Polyimide precursor resin composition preparation step The polyimide precursor resin composition prepared in the first production method contains a polyimide precursor, an organic solvent, and optionally additives. may be Examples of the polyimide precursor include a polyamic acid obtained by polymerization of the tetracarboxylic acid component described above and the diamine component described above, and examples thereof include polyimide precursors represented by the following general formula (1′). . The polyimide precursor represented by the general formula (1') includes a tetracarboxylic acid component that becomes a tetracarboxylic acid residue in R ¹ in the general formula (1'), and R ² in the general formula (1'). Polyamic acid obtained by polymerization with a diamine component that becomes a diamine residue in.

（一般式（１’）において、Ｒ^１、Ｒ^２及びｎは、前記一般式（１）と同様である。）

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

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 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 one of 10,000 or more, more preferably 20,000, in terms of strength when formed into a film. It is preferable that it is above. Further, the polyimide precursor represented by the general formula (1′) has a weight average molecular weight of preferably 70,000 or more, more preferably 80,000 or more, from the viewpoint of improving bending resistance. It is preferably 85000 or more. On the other hand, if the average molecular weight is too large, the viscosity becomes high, and workability such as filtration may be lowered.
The number average molecular weight of the polyimide precursor can be determined by NMR (eg AVANCE III manufactured by BRUKER). For example, after applying the polyimide precursor solution to a glass plate and drying at 100 ° C. for 5 minutes, 10 mg of solid content is dissolved in 7.5 ml of dimethyl sulfoxide-d6 solvent, NMR measurement is performed, and it is bonded to the aromatic ring. The number average molecular weight can be calculated from the peak intensity ratio of hydrogen atoms.
The weight average molecular weight of polyimide precursors can be measured by gel permeation chromatography (GPC).
The polyimide precursor was a N-methylpyrrolidone (NMP) solution with a concentration of 0.5% by weight, and the developing solvent was a 10 mmol% LiBr-NMP solution with a water content of 500 ppm or less. Column: GPC LF-804 (manufactured by SHODEX) is used, and measurement is performed under the conditions of a sample injection amount 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 tetracarboxylic dianhydride and the above diamine in a solvent. The solvent used for synthesizing the polyimide precursor (polyamic acid) is not particularly limited as long as it can dissolve the above-mentioned tetracarboxylic dianhydride and diamine. 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. γ-butyrolactone and the like are preferably used. Among them, when the polyimide precursor solution (polyamic acid solution) is used as it is for the preparation of the polyimide precursor resin composition, it is preferable to use an organic solvent containing a nitrogen atom, among which N,N-dimethylacetamide, N- It is preferred to use methyl-2-pyrrolidone or a combination thereof. In addition, an organic solvent is a solvent containing a carbon atom.

Further, when the polyimide precursor solution is prepared by combining at least two diamines, an acid dianhydride may be added to a mixed solution of at least two diamines to synthesize a polyamic acid, or at least The two diamine components may be added stepwise to the reaction solution at appropriate molar ratios to control the sequence in which each raw material is incorporated into the polymer chain to some extent.
For example, an acid dianhydride having a molar ratio of 0.5 equivalents of the diamine having a silicon atom in the main chain is added to a reaction solution in which a diamine having a silicon atom in the main chain is dissolved, and the acid dianhydride is reacted. Synthesize an amic acid in which a diamine having a silicon atom in the main chain at both ends of an anhydride reacts, then all or part of the remaining diamine is added thereto, and an acid dianhydride is added to polymerize a polyamic acid. Also good. When polymerized by this method, a diamine having a silicon atom in the main chain is introduced into the polyamic acid in a linked form via one acid dianhydride.
Polymerizing the polyamic acid by such a method is preferable because the positional relationship of the polyamic acid having a silicon atom in the main chain is specified to some extent, and it is easy to obtain a film having 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 can be 0.9 or more and 1.1 or less. It is preferably 0.95 or more and 1.05 or less, more preferably 0.97 or more and 1.03 or less, and particularly preferably 0.99 or more and 1.01 or less. The molecular weight (degree of polymerization) of the polyamic acid to be obtained can be appropriately adjusted by setting it to such a range.
The procedure of the polymerization reaction is not particularly limited, and a known method can be appropriately selected and used.
Further, the polyimide precursor solution obtained by the synthesis reaction may be used as it is, and other components may be mixed therein if necessary, or the solvent of the polyimide precursor solution may be dried and dissolved in another solvent. You can use it.

The viscosity of the polyimide precursor solution at 25° C. is preferably 500 cps or more and 200000 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 the optical distortion of the polyimide film, silica fillers for smooth winding, surfactants for improving film-forming properties and defoaming properties, and the like. It is possible to use the same ones as those explained in the above-mentioned polyimide film.

The organic solvent used for 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 solvent: γ-butyrolactone and the like can be used, but among them, it is preferable to use an organic solvent containing a nitrogen atom for the reason described 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 from the viewpoint of forming a uniform coating film and a polyimide film having a strength that can be handled. It is preferably 60% by mass or more, and the upper limit may be appropriately adjusted depending on the ingredients.
The organic solvent in the polyimide precursor resin composition is preferably 40% by mass or more in the resin composition from the viewpoint of forming a uniform coating film and polyimide film, and more preferably 50% by mass or more. Preferably, it is 99% by mass or less.

Moreover, 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 is improved and the productivity can be improved. If the polyimide precursor resin composition contains a large amount of water, the polyimide precursor may easily decompose.
The water content of the polyimide precursor resin composition can be determined using a Karl Fischer moisture meter (for example, trace moisture analyzer CA-200, manufactured by Mitsubishi Chemical Corporation).

The polyimide precursor resin composition preferably has a viscosity of 500 cps or more and 100,000 cps or less at 25° C. at a concentration of 15% by weight of solid content, in order to form a uniform coating film and polyimide film.
The viscosity of the polyimide precursor resin composition can be measured using a viscometer (eg, TVE-22HT, Toki Sangyo Co., Ltd.) at 25° C. with a sample amount of 0.8 ml.

(2) Polyimide precursor resin coating film forming step In the step of applying the polyimide precursor resin composition to a support to form a polyimide precursor resin coating film, the support used must have a smooth surface and heat resistance. There is no particular limitation as long as it is a material that is durable and solvent resistant. For example, an inorganic material such as a glass plate, a metal plate having a mirror-finished surface, and the like can be used. The shape of the support is selected according to the coating method, and may be, for example, a plate shape, a drum shape, a belt shape, a sheet shape that can be wound around a roll, or the like.

The coating means is not particularly limited as long as it is a method capable of coating with the desired film thickness. .
Coating may be performed using a sheet-fed type coating device, or may be performed using a roll-to-roll type coating device.

After coating the polyimide precursor resin composition on the support, the solvent in the coating film is dried at a temperature of 150° C. or less, preferably 30° C. to 120° C., 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 appropriately adjusted according to the thickness of the polyimide precursor resin coating film, 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. When the upper limit is exceeded, it is not preferable from the viewpoint of production efficiency of the polyimide film. On the other hand, when it is less than the lower limit, there is a possibility that the external appearance of the resulting polyimide film may be affected by 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.
When high-level 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. Heat treatment in air may oxidize the film, resulting in discoloration and reduced performance.

(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 before the stretching step, or the polyimide precursor in the polyimide precursor resin coating after the stretching step. Alternatively, both the polyimide precursor in the polyimide precursor resin coating before the stretching step and the polyimide precursor present in the film after the stretching step may be carried out.

The imidization temperature may be appropriately selected according to the structure of the polyimide precursor.
Generally, the temperature at which the temperature rise starts is preferably 30° C. or higher, more preferably 100° C. or higher. On the other hand, it is preferable that the heating end temperature is 250° C. or higher.

It is preferable to appropriately select the heating rate according to the thickness of the polyimide film to be obtained. When the thickness of the polyimide film is thick, the heating rate is preferably slowed.
From the viewpoint of production efficiency of the polyimide film, the rate is preferably 5° C./min or more, more preferably 10° C./min or more. On the other hand, the upper limit of the heating rate is usually 50°C/min, preferably 40°C/min or less, more preferably 30°C/min or less. The above temperature increase rate is preferable from the viewpoint of suppressing poor appearance and strength reduction of the film, controlling whitening due to 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 viewpoints of suppressing poor appearance and strength reduction of the film and controlling whitening caused by the imidization reaction. In addition, the rate of temperature increase may be constant over the entire temperature range described above, or may be changed in the middle.

The atmosphere during the temperature rise for imidization is preferably 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. Heat treatment in air may oxidize the film, resulting in discoloration and reduced performance.
However, when 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are hydrogen atoms directly bonded to the aromatic ring, the influence of oxygen on the optical properties is small and an inert gas atmosphere must be used. A polyimide having high light transmittance can also be obtained.

A heating method for imidization is not particularly limited as long as the temperature can be raised to the above temperature.

Above all, it is more preferable to set the imidization ratio of the polyimide precursor to 50% or more before the stretching step. By setting the imidization rate to 50% or more before the stretching process, stretching is performed after the process, and then heating is performed at a higher temperature for a certain period of time to imidize the film. Whitening is suppressed. Among them, from the viewpoint of improving the surface hardness of the polyimide film, the imidization rate is preferably 80% or more in the imidization step before the stretching step, and the reaction is allowed to proceed to 90% or more and even 100%. is preferred. It is presumed that stretching after imidization improves the surface hardness because rigid polymer chains are easily oriented.
Incidentally, the imidization rate can be measured by spectrum analysis by infrared measurement (IR).

In order to obtain the final polyimide film, it is preferable to proceed the reaction to imidization of 90% or more, further 95% or more, furthermore 100%.
In order to allow the reaction to progress to 90% or more, or even 100% imidization, it is preferable to hold the heating end temperature for a certain period of time. minutes is preferred.

(4) Stretching step In the first manufacturing method, the polyimide precursor resin coating film and the polyimide precursor are used in order to have anisotropy such that the tensile elastic modulus ratio is 1.50 or more. It has a stretching step of stretching at least one of the post-imidization coating films obtained by imidizing the body resin coating film. Among others, the stretching step preferably includes a step of stretching the imidized coating film from the viewpoint of improving the surface hardness of the polyimide film.

In the first production method, the step of stretching 101% or more and 10000% or less when the initial dimension before stretching is taken as 100% is preferably performed while heating at 80°C or more.
The heating temperature during stretching is preferably within the range of the glass transition temperature of the polyimide or polyimide precursor ±50°C, preferably within the range of the glass transition temperature ±40°C. If the stretching temperature is too low, the film may not be deformed 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. The imidization rate is 80% or more, further 90% or more, further 95% or more, especially substantially 100% imidization. Stretching the coating film after imidization improves the surface hardness of the polyimide film. It is preferable from the point of view.

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

The method for fixing the polyimide film during stretching is not particularly limited, and is selected according to the type of stretching equipment. The stretching method is not particularly limited, and for example, stretching can be performed while passing 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 or transverse), or may be stretched in two directions by simultaneous biaxial stretching, sequential biaxial stretching, oblique stretching, or the like.
Among them, the anisotropic where the ratio of the tensile elastic modulus in the tensile test in which the X direction, which is one direction in the film plane, is the tensile direction and the tensile test in which the Y direction orthogonal to the X direction is the tensile direction is 1.50 or more It is preferred to stretch in only one direction so as to have elasticity.

<Second manufacturing method>
Further, as a method for producing the polyimide film of the present invention, as a second production 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 film (hereinafter referred to as a polyimide resin coating film forming step);
A step of stretching the polyimide resin coating (hereinafter referred to as a stretching step);
A method for producing a polyimide film comprising:

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

In the polyimide resin composition preparation step, the polyimide can be used by selecting the above-described solvent-soluble polyimide from polyimides similar to those described in the polyimide film. As a method for imidization, it is preferable to use chemical imidization using a chemical imidization agent instead of thermal dehydration for the dehydration ring closure 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, and includes propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride and the like, but is not particularly limited. At that time, a tertiary amine such as pyridine or β-picolinic acid may be used together. However, if these amines remain in the film, the optical properties, particularly the yellowness index (YI value), will be reduced. It is preferable to purify by reprecipitation or the like to remove components other than polyimide to 100 ppm or less based on the total weight of polyimide, and then form the film.

In the polyimide resin composition preparation step, the organic solvent used in the reaction liquid for chemical imidization of the polyimide precursor includes, for example, those described in the polyimide precursor resin composition preparation step in the first production method. A similar one can be used. In the polyimide resin composition preparation step, examples of the organic solvent used for redissolving the polyimide purified 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, n-butyl acetate, n-propyl acetate, n-pentyl acetate, cyclohexanol, cyclohexanone, 1,4-dioxane, tetrachloroethylene, toluene, methyl isobutyl ketone, methyl cyclohexanol, methyl cyclohexanone, methyl-normal-butyl ketone, dichloromethane, dichloroethane and mixed solvents thereof, among others, dichloromethane, normal-butyl acetate , propylene glycol monomethyl ether acetate and a mixed solvent thereof can be preferably used.

The polyimide resin composition may contain additives as necessary. As the additive, the same one as described in the polyimide precursor resin composition preparation step in the first manufacturing method can be used.
Further, in the second production method, the method of reducing the water 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 polyimide precursor in the first production method. A method similar to the method described in the resin composition preparation step can be used.

In addition, in the polyimide resin coating film forming step in the second manufacturing method, the support and the coating method used are the same as those described in the polyimide precursor resin coating film forming step in the first manufacturing method. be able to.
In the polyimide resin coating film 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.

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

In the second manufacturing method, the polyimide resin coating film is stretched after the polyimide resin coating film forming step so as to have an anisotropic property in which the tensile modulus ratio is 1.50 or more. It has a stretching step to
The stretching step can be the same as the stretching step in the first manufacturing method.

The second manufacturing method is preferable from the viewpoint of easily reducing the yellowness (YI value) of the polyimide film. According to the second production method, a polyimide film having a value obtained by dividing the yellowness index calculated according to JIS K7373-2006 by the thickness (μm) of 0.04 or less can be preferably formed. be.

10. Use of polyimide film The use of the polyimide film of the present invention is not particularly limited, and it can be used as a member such as a base material or a surface material for which glass products such as thin plate glass have been conventionally 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. can.
Specifically, the polyimide film of the present invention is, for example, a thin and bendable flexible organic EL display, a mobile terminal such as a smartphone or a wristwatch type terminal, a display device inside an automobile, a flexible panel used for a wristwatch, etc. It can be suitably used as a substrate or surface material for flexible displays. Further, the polyimide film of the present invention can be used for image display device members such as liquid crystal display devices and organic EL display devices, touch panel members, flexible printed circuit boards, solar cell panel members such as surface protective films and substrate materials, and optical waveguides. It can also be applied to other semiconductor-related members and the like.

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

In the laminate of the present invention, when the polyimide contained in the polyimide film contains a diamine residue having a silicon atom in the main chain, it is preferable from the viewpoint of excellent adhesion between the polyimide film and the hard coat layer. This is presumed to be due to the excellent mixing of 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, from the viewpoint of reducing optical distortion. In this case, when the laminate of the present invention is used as a display member such as a surface material for a display or a base material, deterioration of the 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 above-described film or polyimide film of the present invention can be used, and thus description thereof is 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 radically polymerizable compound and a cationically 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 capable of causing a radical polymerization reaction. Examples thereof include a group containing a carbon-carbon unsaturated double bond, Specific examples include a vinyl group and a (meth)acryloyl group. 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 in one molecule of the radically polymerizable compound is preferably two or more, more preferably three or more, from the viewpoint of improving the hardness of the hard coat layer.
The radically polymerizable compound is preferably a compound having a (meth)acryloyl group from the viewpoint of high reactivity, and a polyfunctional acrylate monomer having 2 to 6 (meth)acryloyl groups in one molecule. Compounds called urethane (meth)acrylates, polyester (meth)acrylates, and epoxy (meth)acrylates having several (meth)acryloyl groups in the molecule and having a molecular weight of several hundred to several thousand are preferred. Available.
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, for example, vinyl compounds such as divinylbenzene; ethylene glycol di(meth)acrylate, bisphenol A epoxy di(meth)acrylate, 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), trimethylolpropane tri(meth)acrylate, tri Methylol ethane 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, diacrylate of bisphenol A diglycidyl ether, epoxy acrylates such as diacrylate of hexanediol diglycidyl ether, hydroxyl groups such as polyisocyanate and hydroxyethyl acrylate Urethane acrylate obtained by reaction of contained acrylate, etc. can be mentioned.

(2) Cationically polymerizable compound A cationically polymerizable compound is a compound having a cationically polymerizable group. The cationically polymerizable group of the cationically polymerizable compound is not particularly limited as long as it is a functional group capable of causing a cationic polymerization reaction. Examples thereof include an epoxy group, an oxetanyl group, and a vinyl ether group. When the 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 in one molecule of the cationically polymerizable compound is preferably two or more, more preferably three or more, from the viewpoint of improving the hardness of the hard coat layer.
As the cationically polymerizable compound, among others, a compound having at least one of an epoxy group and an oxetanyl group as a cationically polymerizable group is preferable. A compound having two or more at least one oxetanyl group in one molecule is more preferred. A cyclic ether group such as an epoxy group or an oxetanyl group is preferable from the viewpoint that shrinkage accompanying a polymerization reaction is small. In addition, among the cyclic ether groups, compounds having epoxy groups are readily available in various structures, do not adversely affect the durability of the resulting hard coat layer, and are easy to control compatibility with radically polymerizable compounds. There is an advantage. In addition, among the cyclic ether groups, the oxetanyl group has a higher degree of polymerization and is less toxic than the epoxy group. There are advantages such as increasing the network formation rate obtained from the polymerizable compound and forming an independent network without leaving unreacted monomers in the film even in a region mixed with the radically polymerizable compound.

Examples of cationic polymerizable compounds having an epoxy group include polyglycidyl ethers of polyhydric alcohols having an alicyclic ring, or compounds containing cyclohexene rings or cyclopentene rings, which are treated with a suitable 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; bisphenols such as bisphenol A, bisphenol F and hydrogenated bisphenol A, or derivatives such as alkylene oxide adducts and caprolactone adducts thereof, and glycidyl ethers produced by reaction with epichlorohydrin, and glycidyl ether type epoxy resins derived from bisphenols such as novolac epoxy resins.

The alicyclic epoxy resins include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (UVR-6105, UVR-6107, UVR-6110), bis-3,4-epoxycyclohexylmethyl adipate. (UVR-6128) (the trade names in parentheses are manufactured by Dow Chemical).

Examples of the glycidyl ether type epoxy resin include sorbitol polyglycidyl ether (Denacol EX-611, Denacol EX-612, Denacol EX-614, Denacol EX-614B, Denacol EX-622), polyglycerol polyglycidyl ether (Denacol EX -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), hydrodibisphenol 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 names in parentheses are manufactured by Nagase ChemteX Corporation.).

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

Examples of cationic polymerizable compounds having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane (OXT-101) and 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 those of Toagosei Co., Ltd.), and the product names of Etanacol EHO, Etanacol OXBP, Etanacol OXTP, and Etanacol OXMA (all of these are product names of Ube Industries).

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

As the polymerization initiator, a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and the like 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 promote radical polymerization and cationic polymerization.

Any radical polymerization initiator may be used as long as it can release a substance that initiates radical polymerization by at least one of light irradiation and heating. Examples of photoradical polymerization initiators include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocenes, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, thioxanthone derivatives and the like. 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- On (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 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, Speedcure MBB, Speedcure PBZ, Speedcure ITX, Speedcure CTX, Speedcure EDB, Esacure ONE, Esacure KIP150, Es acure KTO46, KAYACURE DETX-S manufactured by Nippon Kayaku Co., Ltd., KAYACURE CTX , KAYACURE BMS, KAYACURE DMBI, and the like.

Moreover, the cationic polymerization initiator may be capable of releasing a substance that initiates cationic polymerization by at least one of light irradiation and heating. Examples of cationic polymerization initiators include sulfonic acid esters, imidosulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η ⁶ -benzene) (η ⁵ -cyclopentadyl Examples include enyl)iron (II), and more specific examples include benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tosiphthalimide, and the like, but are not limited to these.

Examples of 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, and the like. More specifically, iodonium chlorides, bromides, borofluorides, hexafluorophosphate salts, hexafluoro Iodonium salts such as antimonate salts, sulfonium chlorides such as triphenylsulfonium, 4-tert-butyltriphenylsulfonium, tris(4-methylphenyl)sulfonium, bromides, borofluorides, hexafluorophosphate salts, hexafluoroantimonates 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 The hard coat layer used in the present invention contains, in addition to the polymer, if necessary, an antistatic agent, an antiglare agent, an antifouling agent, inorganic or organic fine particles for improving hardness, Additives such as leveling agents and various sensitizers may be contained.
At least one polymer of the radically polymerizable compound and the cationically polymerizable compound contained in the hard coat layer used in the present disclosure is a Fourier transform infrared spectrophotometer (FTIR), a pyrolysis gas chromatograph (GC) -MS) and decomposition products of the polymer can be analyzed using a combination of high performance liquid chromatography, gas chromatograph mass spectrometer, 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. Further, the laminate of the present invention, in addition to the film or polyimide film and the hard coat layer, for example, the adhesiveness between the film or polyimide film and the hard coat layer, within a range that does not impair the effects of the present invention. It may have another layer such as a primer layer for improvement, or the film or polyimide film and the hard coat layer may be laminated via another layer such as a primer layer. good. Further, in the laminate of the present invention, the film or polyimide film and the hard coat layer may be positioned adjacent to each other. Moreover, the laminate of the present invention may further have an impact-resistant layer, an anti-fingerprint layer, an adhesive or adhesive layer, and the like.

The total 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, more preferably 40 μm or more. On the other hand, from the viewpoint of bending resistance, the thickness is preferably 300 μm or less, more preferably 250 μm or less.
In addition, in the laminate of the present invention, the thickness of each hard coat layer may be appropriately selected depending on the application, but is preferably 2 μm or more and 80 μm or less, more preferably 3 μm or more and 50 μm or less. 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 hard coat layer side surface preferably has a pencil hardness of H or more, more preferably 2H or more, and even more preferably 3H or more.
The pencil hardness of the laminate of the present invention can be measured in the same manner as in the method for measuring the pencil hardness of the polyimide film, 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 the transmittance is high in this way, the transparency is good, and it can be used as a substitute 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 according to 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 more preferably 10 or less. More preferably, it is particularly preferably 5 or less.
In addition, the laminate of the present invention suppresses yellowish coloring, 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 are even more preferable.
The yellowness index (YI value) of the laminate of the present invention can be measured in the same manner as the yellowness index (YI value) of the polyimide film calculated according to JIS K7373-2006.

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 from the viewpoint of light transmission.
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 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 further preferably 0.040 or less. 010 or less, 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. Use of Laminate The use of the laminate of the present invention is not particularly limited, and, for example, it can be used for the same uses as the polyimide film of the present invention described above.

6. Method for manufacturing a laminate As a method for manufacturing a laminate of the present invention, 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 cationic polymerizable compound on at least one surface of the film or polyimide film of the present invention;
and a step of curing the coating film.

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

The 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, coating the composition for forming a hard coat layer on at least one surface of a film or a polyimide film. is applied by a known application means.
The coating means is not particularly limited as long as it is a method capable of coating with the intended film thickness, and examples thereof include the same means as those for coating the polyimide precursor resin composition on the support.

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

According to the polymerizable groups of the radically polymerizable compound and the cationically polymerizable compound contained in the curable resin composition, the curable resin composition for the hard coat layer is applied and, if necessary, dried. A hard coat containing at least one polymer of a radically polymerizable compound and a cationic polymerizable compound on at least one surface of a film or a polyimide film by curing the coating film by at least one of light irradiation and heating. Layers can be formed.

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

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 increased 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 display surface materials and display base materials.
The display member of the present invention may be the above-described film or polyimide film of the present invention, or the laminate of the present invention.

The display member of the present invention is used, for example, as a surface material for a display by arranging it so as to be positioned on the surface of various displays. The display member of the present invention is used by arranging such that the bent portion is perpendicular to the tensile direction in which the strain value at the yield point of the film or polyimide film increases.
Like the film or polyimide film of the present invention and the laminate of the present invention, the display member of the present invention has excellent transparency, improved bending resistance, and sufficient surface hardness as a protective film. It can be used particularly preferably for displays.

The display member of the present invention can be used for various known displays, and is not particularly limited. For example, it can be used for the displays described in the use of the polyimide film of the present invention.

When the display member of the present invention is the laminate of the present invention, the surface that becomes the outermost surface after placing the laminate on the surface of the display may be the surface on the side of the polyimide film, or may be a hard surface. It may be the surface on the coat layer side. Above all, it is preferable to dispose the display member of the present invention so that the surface on the hard coat layer side faces the front side. Further, the display member of the present invention may have an anti-fingerprint layer on its outermost surface.

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

V. Touch panel member The touch panel member 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,
A transparent electrode composed of a plurality of conductive parts arranged on one surface side of the polyimide film or the laminate,
a plurality of extraction lines electrically connected to at least one end of the conductive portion;
The film or polyimide film is installed 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 becomes larger.

Since the touch panel member of the present invention includes the film, polyimide film, or laminate of the present invention described above, it is excellent in bending resistance and surface hardness, so that it can be particularly suitably used for flexible displays. and has excellent optical properties.
The laminate of the present invention used for the touch panel member of the present invention includes a hard coat layer containing at least one polymer of a radically polymerizable compound and a cationic polymerizable compound adjacent to both surfaces of the film or polyimide film. It is preferable to have
Moreover, the touch panel member of the present invention is not particularly limited, but 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 arranging it so as to be positioned on the surface of various displays. Also, the touch panel member of the present invention and the film, polyimide film or laminate of the present invention as a surface material may be arranged in this order on the surface of various displays.

Hereinafter, the touch panel member of the present invention will be described with an example using the above-described laminate of the present invention, but instead of the above-described laminate of the present invention, the above-described film and polyimide film of the present invention can be used in the same manner. can be done.
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 FIG. and FIG. 8 is a cross-sectional view of the touch panel member shown in FIG. 7 taken along the line AA'. The touch panel member 20 shown in FIGS. 6, 7 and 8 includes the laminate 10 of the present invention, the first transparent electrode 4 disposed in contact with one surface of the laminate 10, and the other surface of the laminate 10. and a second transparent electrode 5 disposed in contact with the surface of the In the first transparent electrode 4, a plurality of first conductive portions 41, which are strip-shaped electrode pieces extending in the x-axis direction, are arranged at predetermined intervals. A first lead-out line 7 electrically connected to the first conductive portion 41 is connected to the first conductive portion 41 at one of its longitudinal ends. A first terminal 71 for electrical connection with 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 portion 41 and the first lead-out line 7 are generally connected within the non-active area 23 located outside the active area 22 visible to the user of the touch panel.
For the connection between the first conductive portion 41 and the first lead-out line 7, for example, as shown in FIG. 6, a connection structure with a connection portion 24 interposed can be adopted. Specifically, the connection portion 24 can be formed by extending a layer of conductive material from the longitudinal end portion of the first conductive portion 41 to a predetermined position within the non-active 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 portion 41 and the first lead-out line 7 is not limited to the structure of forming the connecting portion 24 as shown in FIG. For example, although not shown, the longitudinal end portion of the first conductive portion 41 is extended to the non-active area 23, and within the non-active area 23, the first conductive portion 41 is extended to the non-active area 23. Both may be electrically connected by running the first lead-out line 7 on the end of .
Although FIG. 6 shows a mode in which one of the longitudinal ends of the first conductive portion 41 is connected to the first lead-out line 7, in the present invention, one first conductive portion is provided. A configuration may be adopted in which the first extraction lines 7 are 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 arranged in contact with the other surface of the laminate 10 . In the second transparent electrode 5, second conductive portions 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 electrically connected to the second conductive portion 51 is connected to the second conductive portion 51 at one of its longitudinal ends.
The second lead-out line 8 extends to a position where it does not overlap the first terminal 71 at the edge 21 of the laminate 10 from which the first lead-out line 7 extends. .
A second terminal 81 for electrical connection with 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 portion 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 portion 41 can be applied. .

It should be noted that the pattern in which the first lead-out line 7 is a long wire and the second lead-out line 8 is a short wire, as shown in FIGS. 6 and 7, is merely an embodiment of the touch panel member of the present invention. It is also possible to adopt a pattern in which the first extraction line 7 is a short wiring and the second extraction line 8 is a long wiring. Moreover, the extension direction of the first lead-out line 7 and the extension direction of the second lead-out line 8 are not limited to the directions shown in FIGS. 6 and 7, and can be arbitrarily designed.

The conductive part provided in the touch panel member of the present invention can be applied by appropriately selecting the one that constitutes the transparent electrode in the touch panel member, and the pattern of the conductive part is not limited to those shown in FIGS. For example, it is possible to appropriately select and apply a transparent electrode pattern capable of detecting a change in electric capacitance due to contact or close contact with a finger, etc., by a capacitance method.
The material of the conductive portion is preferably a light-transmitting material, for example, an indium oxide-based transparent electrode material mainly composed of indium tin oxide (ITO), indium oxide, indium zinc oxide (IZO), or the like. , tin oxide (SnO ₂ ), zinc oxide (ZnO), etc., and conductive polymer compounds such as polyaniline and polyacetylene. Also, the first conductive portion 41 and the second conductive portion 51 may be formed using the same conductive material, or may be formed using different materials. In particular, forming the first conductive portion 41 and the second conductive portion 51 using the same type of conductive material is preferable 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, it can generally be formed to a thickness of about 10 nm to 500 nm.

It does not matter whether or not the conductive material constituting the extraction line provided in the touch panel member of the present invention is light-transmissive. In general, the extraction line 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 simple substances of silver, copper, gold, chromium, platinum, and aluminum. Examples of metal composites include MAM (three-layer structure of molybdenum, aluminum, and molybdenum). A laminate of chromium oxide and chromium can be exemplified as a composite of a metal and a metal compound. Silver alloys and copper alloys are commonly used as metal alloys. Moreover, APC (alloy of silver, palladium, and copper) etc. can be illustrated as a metal alloy. Further, in the lead-out line, a suitable resin component may be mixed with the metal material described above.
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 the lead-out line is formed by photolithography, it is generally formed to have a thickness of about 10 nm to 1000 nm and a width of 5 μm to 5 μm. It is formed to have a thickness of about 200 μm. On the other hand, when the lead-out line is formed by printing such as screen printing, it is generally formed with a thickness of about 5 μm to 20 μm and a width of 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. For example, the first transparent electrode and the second transparent electrode are laminated on separate laminates. can be anything.
9 and 10 are schematic plan views each showing an example of a conductive member provided with the laminate of the present invention. A first conductive member 201 shown in FIG. 9 has the laminate 10 of the present invention and the first transparent electrode 4 disposed in contact with one surface of the laminate 10, and the first conductive member 201 The transparent electrode 4 has a plurality of first conductive parts 41 . A second conductive member 202 shown in FIG. 10 has a laminate 10′ of the present invention and a second transparent electrode 5 arranged in contact with one surface of the laminate 10′. The two transparent electrodes 5 have a plurality of second conductive portions 51 .
FIG. 11 is a schematic cross-sectional view showing another example of the touch panel member of the present invention. The touch panel member 20' shown in FIG. 11 includes a first conductive member 201 shown in FIG. and a conductive member 202 . 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 via the adhesive layer 6. are pasted together. In the present invention, for example, an adhesive layer for adhering the laminate of the present invention and the touch panel member of the present invention, an adhesive layer for adhering the touch panel members of the present invention, and the touch panel member of the present invention and the display device. As the adhesive layer for adhering, etc., conventionally known adhesive layers used for optical members can be appropriately selected and used. In the conductive member used for the touch panel member of the present invention, the configuration and materials of the transparent electrodes, lead lines and terminals may be the same as those of the transparent electrodes, lead lines and terminals used for 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 comprises the above-described film, polyimide film, or laminate of the present invention, and the film, polyimide film, or laminate disposed on one side of the laminate, facing a liquid crystal display section having a liquid crystal layer between the substrates,
The film or polyimide film is installed 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 becomes larger.

Since the liquid crystal display device of the present invention includes the film of the present invention described above, the polyimide film of the present invention, 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. and 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 at least one polymer of a radical polymerizable compound and a cationically polymerizable compound adjacent to both surfaces of the film or polyimide film. It is preferable to have
Further, the liquid crystal display device of the present invention may include the touch panel member of the present invention described above.
Moreover, the opposing substrate of the liquid crystal display device of the present invention may be provided with the film, polyimide film, or laminate of the present invention.

Hereinafter, the liquid crystal display device of the present invention will be described with an example using the above-described laminate of the present invention, but instead of the above-described laminate of the present invention, the above-described film and polyimide film of the present invention are also used. 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 and a laminate 10′ of the present invention having a first transparent electrode 4 on one surface and a second transparent electrode 5 on the other surface. and a liquid crystal display section 30 . In the liquid crystal display device 100 , the layered body 10 is used as a surface material, and the layered body 10 and the touch panel member 20 are bonded together with the adhesive layer 6 interposed therebetween.

The liquid crystal display portion used in the liquid crystal display device of the present invention has a liquid crystal layer formed between substrates arranged opposite to each other, and may employ a configuration 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 a driving method generally used for liquid crystal display devices can be adopted. etc. can be mentioned.
The counter substrate used in the liquid crystal display device of the present invention can be appropriately selected and used according to the driving method of the liquid crystal display device, etc., and one provided with the polyimide film or laminate of the present invention may 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, a method generally used as a method for manufacturing a liquid crystal cell can be used, and examples thereof include a vacuum injection method and a liquid crystal dropping method. After the liquid crystal layer is formed by the above method, the liquid crystal cell is gradually cooled to normal temperature, thereby aligning the sealed liquid crystal.
The liquid crystal display device of the present invention may further have colored layers of a plurality of colors and a light-shielding portion defining pixels between the opposing substrates. Further, the liquid crystal display section may have a backlight section having a light-emitting element and a fluorescent material on the outside of the opposing substrates, on the opposite side of the touch panel member. Polarizing plates may be provided on the outer surfaces of the opposing substrates.

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. 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 configuration of the touch panel member 20' is, for example, , can be the same as the configuration of the touch panel member 20' shown in Fig. 11. As the conductive member used in the liquid crystal display device of the present invention, the same conductive member as used in the touch panel member of the present invention can be used. can be used.

VII. Organic Electroluminescence Display Device The organic electroluminescence display device of the present invention comprises the film of the present invention described above, the polyimide film, or the laminate of the present invention described above, and the film, polyimide film, or laminate disposed on one side thereof. and an organic electroluminescence display section having an organic electroluminescence layer between the opposing substrates;
The film or polyimide film is installed 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 becomes larger.

Since the organic electroluminescence display device of the present invention includes the film of the present invention, the polyimide film, or the laminate of the present invention described above, it has excellent bending resistance and surface hardness. It can be particularly suitably used for various purposes, and has excellent optical properties.
The laminate of the present invention used in the organic electroluminescence display device of the present invention is a hard film containing at least one polymer of a radically polymerizable compound and a cationic polymerizable compound adjacent to both surfaces of the film or polyimide film. It preferably has a coat layer.
Moreover, the organic electroluminescence display device of the present invention may be provided with the above-described touch panel member of the present invention.
Also, the counter substrate of the organic electroluminescence display device of the present invention may comprise the film, polyimide film or laminate of the present invention.

Hereinafter, the organic electroluminescence display device of the present invention will be described with an example using the above-described laminate of the present invention, but instead of the above-described laminate of the present invention, the above-described film and polyimide film of the present invention are also used. can be used for
FIG. 14 is a schematic cross-sectional view showing an example of the organic electroluminescence display device of the present invention. An organic electroluminescence display device 300 shown in FIG. 14 includes a laminate 10 of the present invention and a laminate 10′ of the present invention having a first transparent electrode 4 on one side and a second transparent electrode 4 on the other side. It has a touch panel member 20 having electrodes 5 and an organic electroluminescence display section 40 . In the organic electroluminescence display device 300 , the layered body 10 is used as a surface material, and the layered body 10 and the touch panel member 20 are bonded together with the adhesive layer 6 interposed therebetween.

The organic electroluminescence display portion (organic EL display portion) used in the organic electroluminescence display device (organic EL display device) of the present invention includes an organic electroluminescence layer (organic EL layer) formed between substrates arranged opposite to each other. , and a 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. may be The organic EL layer may have at least an organic EL light-emitting layer. For example, a hole injection layer, a hole transport layer, an organic EL light-emitting layer, an electron transport layer and an electron injection 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 can be applied to, for example, 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 according to the driving method of the organic EL display device, etc., and the one provided with the laminate of the present invention may be used.

FIG. 15 is a schematic cross-sectional view showing another example of the organic electroluminescence display device of the present invention. The organic electroluminescent display device 400 shown in FIG. 15 includes the laminate 10 of the present invention, the first conductive member 201 having the first transparent electrode 4 on one surface of the laminate 10' of the present invention, and the present 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 electroluminescence display section 40. Organic electroluminescence 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'. can be, for example, the same as the configuration of the touch panel member 20' shown in Fig. 11. As the conductive member used in the organic electroluminescence display device of the present invention, the conductive member used in the touch panel member of the present invention can be used. The same material as the elastic member can be used.

[Evaluation method]
Hereinafter, measurement or evaluation was performed at 25° C. unless otherwise specified.
<Weight Average Molecular Weight of Polyimide Precursor>
The weight-average molecular weight of the polyimide precursor was determined by making the polyimide precursor into an N-methylpyrrolidone (NMP) solution with a concentration of 0.5% by weight, filtering the solution through a syringe filter (pore size: 0.45 μm), and developing As a solvent, using a 10 mmol% LiBr-NMP solution with a water content of 500 ppm or less, using a GPC apparatus (manufactured by Tosoh, HLC-8120, column used: GPC LF-804 manufactured by SHODEX), sample injection amount 50 μL, solvent flow rate 0.5 mL. /min, the measurement was performed under the conditions of 40°C. 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 converted to standard polystyrene. The elution time was compared with the calibration curve to obtain the weight average molecular weight.
<Viscosity of polyimide precursor solution>
The viscosity of the polyimide precursor solution was measured using a viscometer (eg, 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 15000 mg of N-methylpyrrolidone (NMP), heated to 60 ° C. in a water bath, and stirred at a rotation speed of 200 rpm for 3 to 60 hours until dissolution is visually confirmed. By doing so, an NMP solution with a concentration of 0.1% by weight was obtained. The solution is filtered through a syringe filter (pore size: 0.45 μm), a 30 mmol% LiBr-NMP solution with a water content of 500 ppm or less is used as a developing solvent, and a GPC device (manufactured by Tosoh, HLC-8120, detector: differential Refractive index (RID) detector, column used: 2 GPC LF-804 manufactured by SHODEX connected in series), sample injection amount 50 μL, solvent flow rate 0.4 mL / min, column temperature 37 ° C., detector temperature 37 ° C. Measurement was performed under the conditions of The weight-average molecular weight of the polyimide was measured 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 converted to standard polystyrene. The elution time was compared with the calibration curve to obtain the weight average molecular weight.
<Viscosity of polyimide solution>
The viscosity of the polyimide solution was measured using a viscometer (eg, TVE-22HT, Toki Sangyo Co., Ltd.) at 25° C. with a sample volume of 0.8 ml.

<Total light transmittance>
Measured with a haze meter (HM150 manufactured by Murakami Color Research Laboratory) in accordance with JIS K7361-1.
Further, for example, the total light transmittance at a thickness of 100 μm can be converted by Beer-Lambert's law.
Specifically, according to Beer-Lambert's law, the transmittance T is
Log ₁₀ (1/T) = kcb
(k=substance-specific constant, 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 equation is Log ₁₀ (1/T) = fb
(f=kc). Here, if the transmittance at a certain film thickness is known, the intrinsic constant f of each substance can be obtained. Therefore, by using the formula T=1/10 ^f·b and substituting a specific constant for f and a target film thickness for b, the transmittance at the desired film thickness can be obtained.

<YI value (yellowness)>
YI value, in accordance with JIS K7373-2006, using a UV-visible near-infrared spectrophotometer (JASCO Corporation V-7100), by a spectrophotometric method, auxiliary illuminant C, using a 2 degrees field of view , Based on the transmittance measured at intervals of 1 nm in the range of 250 nm or more and 800 nm or less, the tristimulus values X, Y, and Z in the XYZ color system are obtained, and the values of X, Y, and Z are obtained from the following formula Calculated.
YI=100(1.2769X−1.0592Z)/Y
Further, for example, the YI value at a thickness of 100 μm is Lambertian A conversion value of each transmittance at each wavelength of different thickness is obtained by Beer's law, and it is possible to calculate and use it based on it.

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

<Tensile test>
A test piece of polyimide film cut out to 15 mm × 40 mm was conditioned at a temperature of 25 ° C. and a relative humidity of 60% for 2 hours, and then subjected to JIS K7127 with a tensile speed of 10 mm / min and a chuck distance of 20 mm. , and a tensile test was performed at 25° C., and the strain (%) at the yield point in the stress-strain curve obtained by the tensile test, the tensile modulus, and the elongation were measured. A tensile tester (manufactured by Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) was used.
As the test piece, a test piece of 40 mm in the tensile direction with the X direction, which is one direction in the film plane, as the tensile direction × 15 mm in the direction perpendicular to the tensile direction, and the Y direction perpendicular to the X direction was the tensile direction. A test piece of 40 mm in the tensile direction and 15 mm in the direction orthogonal to the tensile direction was cut out. These test pieces were cut out from near the center of the film. The film thickness at a total of 5 points in the four corners and the center of the cut film is measured by the above film thickness measurement method, and 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 specimen was used.

<Dynamic bending test>
A test piece of a polyimide film cut into a size of 20 mm × 100 mm is placed in a durability test system in a constant temperature and humidity chamber (manufactured by Yuasa System Equipment, U-shaped stretching test jig DMX-FS with no load on a planar body). Kapton (registered trademark) ) was taped. Specifically, as shown in FIG. 5B, the test piece 1 curved at half of the long side was sandwiched between metal plates 5 from both sides so that the distance between the metal plates 5 on both sides was 60 mm. The state in which the metal plates 5 on both sides are arranged parallel to each other, and the state in which 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. was repeatedly changed at 90 bending times per minute in an environment of 60° C. and 93% relative humidity (RH), and bending was repeated 200,000 times.
Then, one end of the test piece was fixed, and the inner angle of the test piece was measured 30 minutes after the force applied to the test piece was released.
In addition, as the test piece, the X direction of the tensile test is a test piece in which the long side is 100 mm × the direction perpendicular to the X direction is 20 mm, and the Y direction of the tensile test is the long side 100 mm × 20 mm in the direction perpendicular to the Y direction. A test piece was prepared.
If the film was completely restored without being affected by the dynamic bending test, the internal angle would be 180°.

<Pencil hardness>
The pencil hardness is measured by conditioning the measurement sample for 2 hours under conditions of a temperature of 25 ° C. and a relative humidity of 60%, and then using a test pencil specified by JIS-S-6006. Using a hardness tester, a pencil hardness test (0.98 N load) specified in JIS K5600-5-4 (1999) was performed on the film surface to evaluate the highest pencil hardness that does not cause scratches.

<Young's modulus>
The Young's modulus of the surface of a test piece of a polyimide film cut into 15 mm×15 mm was measured at a temperature of 25° C. in accordance with ISO 14577 using a nanoindentation method. Specifically, as a measuring device, PICODENTOR HM500 manufactured by Fisher Instruments Co., Ltd. was used, and a Vickers indenter was used as a measuring indenter. The Young's modulus was obtained by measuring eight arbitrary points on the surface of the test piece and averaging the values by number. The measurement conditions were maximum indentation depth: 1000 nm, load time: 20 seconds, and creep time: 5 seconds.

(Synthesis example 1)
In a 500 mL separable flask, dehydrated dimethylacetamide (150 g),
And, a solution of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS) (1.32 g, 5.31 mmol) dissolved therein was placed at a liquid temperature of 30° C., 4,4′. -(Hexafluoroisopropylidene)diphthalic anhydride (6FDA) (1.18 g, 2.65 mmol) was added gradually so that the temperature rise was 2° C. or less, and stirred with a mechanical stirrer for 1 hour. 2,2′-Bis(trifluoromethyl)benzidine (TFMB) (32.3 g, 101 mmol) was added thereto, 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 35% by weight) were synthesized. The above solution was cooled to room temperature and dehydrated dimethylacetamide (170 g) was added and stirred until homogeneous. Next, pyridine (33.0 g, 417 mmol) and acetic anhydride (42.6 g, 417 mmol) as catalysts were added and stirred at room temperature for 24 hours to synthesize a polyimide solution. The resulting polyimide solution was transferred to a 5 L separable flask, butyl acetate (324 g) was added, and the mixture was stirred until uniform. Methanol (720 g) was then slowly added to give a slightly cloudy solution. Methanol (1680 g) was added at once to the turbid solution to obtain a white slurry. The slurry was filtered and washed with methanol five times to obtain polyimide 1 (72.0 g). The weight average molecular weight of polyimide measured by GPC was 96,000.

(Synthesis example 2)
A solution of 2903 g of dehydrated dimethylacetamide and 16.0 g (0.07 mol) of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS) was dissolved in a 500 ml separable flask. 14.6 g (0.03 mol) of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was gradually added to the temperature controlled at 30°C so that the temperature rise was 2°C or less. It was put in and stirred with 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 was completely dissolved, 4,4′-(hexafluoroisopropylidene)diphthalic acid was added. Anhydride (6FDA) 565 g (1.27 mol) was gradually added in several portions so that the temperature rise was 2 ° C. or less, and polyimide precursor solution 2 in which polyimide precursor 2 was dissolved (solid content 25% by weight ) was synthesized. The molar ratio of TFMB and AprTMOS (TFMB:AprTMOS) used in Polyimide Precursor 2 was 95:5. The viscosity of Polyimide Precursor Solution 1 (25% by weight of solids) at 25° C. 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 of dehydrated dimethylacetamide (150 g) and 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS) (1.63 g, 6.57 mmol) dissolved in a 500 mL separable flask. To a place where the liquid temperature was controlled to 30 ° C., 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) (1.46 g, 3.29 mmol) was added so that the temperature rise was 2 ° C. or less. and stirred with a mechanical stirrer for 1 hour. 2,2′-Bis(trifluoromethyl)benzidine (TFMB) (40.0 g, 125 mmol) was added thereto, and after confirming complete dissolution, 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 40% by weight) were synthesized. The above solution was cooled to room temperature and dehydrated dimethylacetamide (240 g) was added and stirred until homogeneous. Next, pyridine (39.8 g, 504 mmol) and acetic anhydride (51.4 g, 504 mmol) as catalysts were added and stirred at room temperature for 24 hours to synthesize a polyimide solution. The resulting polyimide solution was transferred to a 5 L separable flask, butyl acetate (396 g) was added, and the mixture was stirred until uniform. Methanol (877 g) was then slowly added to give a slightly cloudy solution. Methanol (2050 g) was added at once to the turbid solution to obtain a white slurry. The slurry was filtered and washed with methanol five times to obtain polyimide 3 (87.8 g). The weight average molecular weight of 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) are placed in a 500 ml separable flask, and the temperature of the solution in which TFMB is dissolved is 443 g (1.00 mol) of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was gradually added to the temperature controlled at 30° C. in several batches so that the temperature rise was 2° C. or less. to synthesize a polyimide precursor solution 4 (solid content: 20% by weight) in which the polyimide precursor 4 was dissolved. The viscosity of the polyimide precursor solution 4 (solid content 20% by weight) at 25° C. was 383 cps, and the weight average molecular weight of the polyimide precursor 4 measured by GPC was 81,000.

(Synthesis Example 5)
A solution of 169.5 g of dehydrated dimethylacetamide and 32.0 g (100 mmol) of 2,2′-bis(trifluoromethyl)benzidine (TFMB) dissolved in a 500 ml separable flask was heated to 30° C. 21.7 g (99.5 mmol) of pyromellitic dianhydride (PMDA) was gradually added to the controlled place in several batches so that the temperature rise was 2° C. or less. (solid content 20% by weight) was synthesized. The viscosity of the polyimide precursor solution 5 at 25° C. was 23400 cps, and the weight average molecular weight of the polyimide precursor 5 measured by GPC was 83000.

(Synthesis Example 6)
While introducing nitrogen gas into a 3 L separable flask equipped with a stirring bar and equipped with an oil bath, 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 stirred at room temperature for 30 minutes. Then, after confirming that 152.99 g (0.478 mol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) was added and dissolved, the mixture was stirred at room temperature for 3 hours and then heated to 80°C. After heating and stirring for 4 hours, the oil bath was removed and the temperature was returned to room temperature to obtain a 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)
Dehydrated dimethylformamide (144.0 g) and 2,2-bis-[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoro were added to a 500 ml separable flask. 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 slowly charged and stirred until dissolved. Next, modified silicone oil KF-8010 (trade name, manufactured by Shin-Etsu Silicone Co., Ltd., 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) are added to the polyamic acid solution, and stirred in an oil bath at 100° C. for 1 hour to give a polyimide solution. got The resulting polyimide solution was dropped into a large amount of isopropyl alcohol (IPA) to precipitate polyimide. The polyimide obtained by filtration 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.

The abbreviations in the tables below 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: amine-modified dimethyl silicone oil at both ends (manufactured by Shin-Etsu Silicone , KF-8010, molecular weight 860)

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

(Example 1)
Polyimide 1 was dissolved in a mixed solvent of butyl acetate and PGMEA (8:2, volume ratio) to prepare polyimide solution 1 having a solid content of 25% by mass. The viscosity at 25° C. of polyimide solution 1 (25% by weight of solids) was 16612 cps.
Using the polyimide solution 1 obtained as described above, a polyimide film having a thickness of 100 μm was produced by carrying out the following procedures (i) to (iii).
(i) Polyimide solution 1 was applied on glass and dried in a circulation oven at 120° C. for 10 minutes.
(ii) Under a nitrogen stream (oxygen concentration of 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) Peeled off from the glass to obtain a polyimide film.
The obtained polyimide film with a thickness of 100 μm was uniaxially stretched by using a stretching device so that the stretching ratio was 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 a polyimide film having a thickness of 90 μm was produced in the same manner as in Example 1 using the polyimide solution 1.
The resulting 90 μm-thick polyimide film was uniaxially stretched using a stretching device at a stretch ratio of 180% to obtain a 50 μm-thick uniaxially stretched polyimide film.

(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 in the same manner as in Example 1 using the polyimide solution 1.
The obtained polyimide film with a thickness of 80 μm was uniaxially stretched by using a stretching device so as to have 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 in the same manner as in Example 1 using the polyimide solution 1.
The obtained 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 in the same manner as in Example 1 using the polyimide solution 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 in the same manner as in Example 1 using the polyimide solution 1. No stretching was performed.

(Comparative Example 3)
Using polyimide precursor solution 2, polyimide films having the thicknesses shown in Table 2 were produced by performing the following procedures (1) to (3).
(1) Each polyimide precursor solution was applied on glass and dried in a circulation oven at 120° C. for 10 minutes.
(2) Under a nitrogen stream (oxygen concentration of 100 ppm or less), the temperature was raised to 330°C at a heating rate of 10°C/min, held at 330°C for 1 hour, and then cooled to room temperature.
(3) Separated from the glass to obtain each polyimide film.

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

(Comparative Example 8)
Polyimide 7 obtained in Synthesis Example 7 was dissolved in dimethylformamide (DMF) to prepare polyimide solution 7 having a solid content of 33.3% by mass. Using polyimide solution 7, a polyimide film having a thickness shown in Table 2 was produced by performing the following procedures (i) to (ii).
(i) Polyimide solution 7 was applied on glass, dried in a circulation oven at 80°C for 15 minutes, and then dried at 250°C for 5 minutes.
(ii) Peeled off from the glass to obtain a polyimide film.

Each obtained polyimide film was evaluated using the evaluation method described above. Table 2 shows the evaluation results.

From Table 2, the polyimide films of Examples 1 to 4, which correspond to the polyimide films of the present invention, have excellent transparency and good bending resistance in a predetermined bending direction (Y direction), while the surface hardness is improved Resin shown to be a film.
On the other hand, the polyimide films of Comparative Examples 1 and 2 were produced using the same polyimide as the polyimide films of Examples 1 to 4, but the ratio of tensile elastic modulus (X/Y) was higher than the specified value of the present invention. is also small. In the polyimide films of Comparative Examples 1 and 2, the strain at the yield point of the stress-strain curves in the X direction and the Y direction is both 8% or more, so the bending resistance is good, but the surface hardness is lower than that of the examples. was inferior.
In addition, 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, indicating poor bending resistance. The polyimide film of Comparative Example 6 was also inferior in yellowness, and the polyimide films of Comparative Examples 5 and 7 were further inferior in pencil hardness and easily scratched on the surface.
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 methyl isobutyl ketone solution of pentaerythritol triacrylate, 10 parts by mass of 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF, Irgacure 184) is added to 100 parts by mass of pentaerythritol triacrylate to form a hard A coating layer resin composition was prepared.
The resin composition for the hard coat layer was applied onto each of the polyimide films of Examples 1 to 4, and cured by irradiating with ultraviolet light at an exposure amount of 200 mJ/cm ² under a nitrogen stream to form a cured film with a thickness of 10 μm. , to produce a laminate.
Since the polyimide film contains silicon atoms, the adhesion to the hard coat layer was good.

1 test piece 11 test piece 12 test piece 13 strain at the yield point is 8% or more, and the tensile direction of the tensile test in which the value of the strain at the yield point is larger 14 bent portion 101, 102 polyimide film 10, 10' , 10″ laminate 4 first transparent electrode 41 first conductive part 5 second transparent electrode 51 second conductive part 6 adhesive layer 7 first lead-out line 71 first terminal 8 second lead-out line 81 second terminal 20, 20' touch panel member 21 edge of laminate 22 active area 23 non-active area 24 connection portion 201 first conductive member 202 second conductive member 30 liquid crystal display section 40 organic electroluminescence display section 100, 200 Liquid crystal display device 300, 400 Organic electroluminescence display device

Claims (10)

The anisotropy is such that the ratio of the tensile elastic modulus in a tensile test in which the X direction, which is one direction in the film plane, is the tensile direction and the tensile test in which the Y direction orthogonal to the X direction is the tensile direction is 1.50 or more. In the tensile test, a test piece of 40 mm in the tensile direction × 15 mm in the direction perpendicular to the tensile direction is cut out, and the test piece is subjected to JIS K7127 at a tensile speed of 10 mm / min and a distance between chucks of 20 mm at 25 ° C. is to measure,
Each tensile modulus in the tensile test is 1.8 GPa or more,
Total light transmittance measured in accordance with JIS K7361-1 is 85% or more, yellowness calculated in accordance with JIS K7373-2006 is 5 or less, and the following general formula (1) A polyimide film containing a polyimide having a structure represented by
The strain at the yield point is 8% or more in the stress-strain curves obtained by the tensile test with the X direction of the film as the tensile direction and the tensile test with the Y direction of the film as the tensile direction, and the yield point A polyimide film that is used by bending so that the bending portion is orthogonal to the tensile direction in which the strain value in is larger.

(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 a plurality of R ¹ may be the same or different. , R ² represents a divalent group that is a diamine residue, 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 the total amount of R ² 50 mol% or more and 97.5 mol% or less of is a diamine residue having no silicon atom and having an aromatic ring or an aliphatic ring.n represents the number of repeating units.) 2. The polyimide film according to claim 1 , wherein the film surface has a Young's modulus of 2.3 GPa or more measured at a temperature of 25° C. using a nanoindentation method according to ISO 14577. In the polyimide having a structure represented by the general formula (1), the diamine residue having no silicon atom and having an aromatic ring or an 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[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue and a group consisting of a divalent group represented by the following general formula (2) The polyimide film according to claim 1 or 2 , which is at least one divalent group selected from.

(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 having a structure represented by the general formula (1), R ¹ in the general formula (1) is a cyclohexanetetracarboxylic dianhydride residue, a cyclopentanetetracarboxylic dianhydride residue, a di Cyclohexane-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 residue, 3, 4′-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,3′-(hexafluoroisopropylidene)diphthalic anhydride residue, 4,4′-oxydiphthalic anhydride residue, and 3, 4. The polyimide film according to any one of claims 1 to 3 , which is at least one tetravalent group selected from the group consisting of 4'-oxydiphthalic anhydride residues. 5. The polyimide film according to any one of claims 1 to 4 and a hard coat layer containing at least one polymer of a radically polymerizable compound and a cationically polymerizable compound, and yielding of the polyimide film A laminate that is used by being bent so that the bent portion is perpendicular to the tensile direction in which the strain value at a point becomes larger. Including the polyimide film according to any one of claims 1 to 4 or the laminate according to claim 5 , with respect to the tensile direction in which the strain value at the yield point of the polyimide film becomes larger, A display member that is used by being folded so that the folded portions are perpendicular to each other. The display member according to claim 6 , which is used for a flexible display. The polyimide film according to any one of claims 1 to 4 , or the laminate according to claim 5 ,
A transparent electrode composed of a plurality of conductive parts arranged on one surface side of the polyimide film or the laminate ,
a plurality of extraction lines electrically connected to at least one end of the conductive portion;
The touch panel member, wherein the polyimide film is installed so as to be bendable such that the bending portion is perpendicular to a tensile direction in which the strain value at the yield point of the polyimide film increases . The polyimide film according to any one of claims 1 to 4 , or the laminate according to claim 5 ,
a liquid crystal display section having a liquid crystal layer between opposing substrates arranged on one side of the polyimide film or the laminate,
A liquid crystal display device, wherein the polyimide film is bent so that the bending portion is orthogonal to a tensile direction in which the strain value at the yield point of the polyimide film increases. The polyimide film according to any one of claims 1 to 4 , or the laminate according to claim 5 ,
an organic electroluminescence display section having an organic electroluminescence layer between opposing substrates arranged on one side of the polyimide film or the laminate,
The organic electroluminescence display device, wherein the polyimide film is bent so that the bending portion is orthogonal to a tensile direction in which the strain value at the yield point of the polyimide film increases.

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