WO2018186262A1 - Polyimide film, laminate, and surface material for display - Google Patents

Abstract

The present invention provides a polyimide film comprising 2 or more polyimide layers having different Young's moduli. The total thickness of the polyimide film is 5 to 200 µm or less, and the total luminous transmittance thereof as determined by JIS K7361-1 is 85% or greater.

Description

Polyimide film, laminate, and display surface material

The present disclosure relates to a polyimide film, a laminate, and a display surface material.

Although thin plate glass is excellent in hardness, heat resistance, etc., it is difficult to bend, it is easy to break when dropped, there is a problem in workability, and it is heavy compared to plastic products. For this reason, from the viewpoint of workability and weight reduction, research on resin products that are glass substitute products has been conducted.

For example, with the rapid progress of electronics such as liquid crystal and organic EL displays and touch panels, it has become necessary to make devices thinner and lighter and more flexible. Conventionally, these devices have various electronic elements such as thin transistors and transparent electrodes formed on a thin glass plate. By changing this thin glass plate to a resin film, the impact resistance of the panel itself is enhanced. , Flexible, thin and light weight can be achieved.

Generally, a polyimide resin is a highly heat-resistant resin obtained by subjecting a polyamic acid obtained by a condensation reaction of an aromatic tetracarboxylic acid anhydride and an aromatic diamine to a dehydration ring-closing reaction. However, since polyimide resins generally show yellow or brown coloration, it has been difficult to use them in fields that require transparency, such as display applications and optical applications. Then, applying the polyimide which improved transparency to the member for a display is examined. For example, Patent Document 1 discloses 1,2,4,5-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid dicarboxylic acid as polyimide resins having high heat resistance, high transparency, and low water absorption. At least one acyl-containing compound selected from the group consisting of anhydrides and reactive derivatives thereof, and at least one compound selected from compounds having at least one phenylene group and isopropylidene group represented by a specific formula A polyimide resin obtained by reacting with an imino forming compound is disclosed, and is described as being suitable for a substrate material such as a flat panel display or a mobile phone device.

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

On the other hand, Patent Document 4 is obtained from a polyimide layer (b) including a heat-fusible polyimide layer and a specific tetracarboxylic acid component and a diamine component laminated in contact with the polyimide layer (b). A polyimide film containing a polyimide layer (a) containing polyimide is disclosed, and it is described that a metal laminate such as a copper foil is bonded to a surface having heat fusion properties of the polyimide film to form a metal laminate. ing.

JP 2006-199945 A Special table 2014-501301 gazette Special table 2012-503701 gazette International Publication 2012/133594

Mobile devices that can fold screens are often carried in a folded state, so a flexible display installed in such mobile devices will not return to its original state when it is folded back even if it is folded for a long time. It is required to pass, and the base material and the surface material for the flexible display are also required to have resilience after being bent for a long time (hereinafter sometimes referred to as static bending resistance).
However, in the conventional resin film using transparent polyimide, even if it shows a good result in a test in which the flat state and the bent state are repeated at a constant cycle, if the bent state continues for a long time, the crease will be Therefore, there is a problem that it is difficult to return to a flat surface and inferior in static bending resistance.
In addition, by increasing the elastic modulus of the resin film, the rigidity of the film is increased, so that the impact resistance can be improved. On the other hand, if the elastic modulus of the resin film is increased, the resilience after being bent is restored. Tends to deteriorate and bending resistance becomes insufficient. In fact, as shown in Comparative Example 2 to be described later, a polyimide film having a large elastic modulus has improved flex resistance although it has improved impact resistance. In order to improve the bending resistance, it is effective to reduce the film thickness because the stress applied to the film during bending can be reduced. However, in the resin film used as the surface material, if the film thickness is reduced, the rigidity of the film is lowered, and there is a problem that the function of protecting the light emitting device and the circuit from the impact is lowered. Thus, it is considered that the impact resistance and the bending resistance are contradictory characteristics in the resin film. The resin film used as the surface material has a film thickness that balances impact resistance and bending resistance. Therefore, it can provide satisfactory impact resistance compared to glass used for rigid panels that cannot be bent. However, both impact resistance and bending resistance are required.

This indication is made in view of the above-mentioned problem, and it aims at providing the resin film which is excellent in impact resistance and favorable in bending resistance.
Moreover, this indication aims at providing the surface material for displays which is the laminated body which has the said resin film, and the said resin film or the said laminated body.

The polyimide film of the present disclosure has two or more polyimide layers having different Young's moduli, has an overall thickness of 5 μm to 200 μm, and has a total light transmittance of 85% or more measured in accordance with JIS K7361-1. It is.

In the polyimide film of the present disclosure, the Young's modulus of the polyimide layer having the largest Young's modulus among the polyimide layers is 1.2 times or more of the Young's modulus of the polyimide layer having the smallest Young's modulus. It is preferable from the point of bending resistance.

The polyimide film of the present disclosure has three or more polyimide layers, and the polyimide layer having the largest Young's modulus among the polyimide layers is located on at least one surface, in terms of impact resistance and bending resistance. To preferred.

In the polyimide film of the present disclosure, it is preferable from the viewpoint of impact resistance and bending resistance that the polyimide layer having three or more polyimide layers and having the smallest Young's modulus among the polyimide layers is not located on the surface.

In the polyimide film of the present disclosure, it is preferable that the thickest layer among the polyimide layers is not a polyimide layer having the largest Young's modulus from the viewpoint of impact resistance and bending resistance.

In the polyimide film of the present disclosure, the total thickness of the polyimide layers having the largest Young's modulus among the polyimide layers is preferably 60% or less of the total thickness from the viewpoint of impact resistance and bending resistance.

In the polyimide film of the present disclosure, when a static bending test is performed according to the following static bending test method, it is preferable from the viewpoint of bending resistance that the internal angle after the test is 90 ° or more.
[Static bending test method]
A polyimide film test piece cut out to 15 mm × 40 mm is bent at a position of half of the long side, and both ends of the long side of the test piece sandwich a metal piece (100 mm × 30 mm × 6 mm) having a thickness of 6 mm from the upper and lower surfaces. Placed between glass plates (100 mm x 100 mm x 0.7 mm) from above and below with the tape fixed so that the overlap between the top and bottom surfaces of the test piece and the metal piece is 10 mm each. The test piece is fixed in a bent state with an inner diameter of 6 mm. At that time, a dummy test piece is sandwiched between the metal piece and the glass plate where there is no test piece, and is fixed with tape so that the glass plate is parallel. The test piece thus fixed in a bent state is left to stand for 24 hours in an environment of 60 ° C. and 90% relative humidity (RH), and then the glass plate and fixing tape are removed, and the test piece is attached to the test piece. Release this force. Thereafter, one end of the test piece is fixed, and the internal angle of the test piece 30 minutes after the force applied to the test piece is released is measured.

In the polyimide film of the present disclosure, the yellowness calculated by JIS K7373-2006 divided by the film thickness (μm) is 0.330 or less, so that yellowing is suppressed. From the viewpoint of improving light transmittance.

In the polyimide film of the present disclosure, the two or more polyimide layers each include an aromatic ring, and (i) a fluorine atom, (ii) an aliphatic ring, and (iii) the aromatic rings are sulfonyl groups. Or it is preferable from the point of the light transmittance and impact resistance to contain the polyimide containing at least 1 selected from the group which consists of the structure connected with the alkylene group which may be substituted by the fluorine atom.

In the polyimide film of the present disclosure, the polyimide layer having the largest Young's modulus among the polyimide layers contains polyimide having a structure represented by the following general formula (1). This is preferable from the viewpoint of bending resistance.

（一般式（１）において、Ｒ^１は３，３’，４，４’－ビフェニルテトラカルボン酸二無水物残基、３，３’，４，４’－ベンゾフェノンテトラカルボン酸二無水物残基、及びピロメリット酸二無水物残基からなる群から選択される少なくとも１種の４価の基、Ｒ^２は、２，２’－ビス（トリフルオロメチル）ベンジジン残基、４，４’－ジアミノジフェニルスルホン残基、２，２－ビス［４－（４－アミノフェノキシ）フェニル］ヘキサフルオロプロパン残基、ビス［４－（３－アミノフェノキシ）フェニル］スルホン残基、ビス［４－（４－アミノフェノキシ）フェニル］スルホン残基、４，４’－ジアミノ－２，２’－ビス（トリフルオロメチル）ジフェニルエーテル残基、１，４－ビス［４－アミノ－２－（トリフルオロメチル）フェノキシ］ベンゼン残基、２，２－ビス［４－（４－アミノ－２－トリフルオロメチルフェノキシ）フェニル］ヘキサフルオロプロパン残基、４，４’－ジアミノ－２－（トリフルオロメチル）ジフェニルエーテル残基、及び９，９－ビス（４－アミノフェニル）フルオレン残基からなる群から選ばれる少なくとも１種の２価の基を表す。ｎは繰り返し単位数を表し、１以上である。）

(In the general formula (1), R ¹ is 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride residue, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride residue. , And at least one tetravalent group selected from the group consisting of pyromellitic dianhydride residues, R ² is a 2,2′-bis (trifluoromethyl) benzidine residue, 4,4′- Diaminodiphenylsulfone residue, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4 -Aminophenoxy) phenyl] sulfone residue, 4,4'-diamino-2,2'-bis (trifluoromethyl) diphenyl ether residue, 1,4-bis [4-amino-2- (trifluoromethyl) phenoxy ] Benzene residue, 2,2-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane residue, 4,4′-diamino-2- (trifluoromethyl) diphenyl ether residue, And at least one divalent group selected from the group consisting of 9,9-bis (4-aminophenyl) fluorene residues, n represents the number of repeating units and is 1 or more.)

In the polyimide film of the present disclosure, the polyimide layer having the largest Young's modulus among the polyimide layers contains a polyimide having a structure represented by the general formula (1), and is represented by the following general formula (2). It is preferable to further include a polyimide layer containing a polyimide having a structure from the viewpoints of light transmittance, impact resistance, and bending resistance.

（一般式（２）において、Ｒ^３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、Ｒ^４は、ジアミン残基である２価の基を表し、Ｒ^４の総量の５０モル％以下が、主鎖にケイ素原子を１個又は２個有するジアミン残基であり、残りのＲ^４が、ケイ素原子を有さず、芳香族環又は脂肪族環を有するジアミン残基であり、前記残りのＲ^４のうちの半分よりも多くが、１，４－シクロヘキサンジアミン残基、ｔｒａｎｓ－１，４－ビスメチレンシクロヘキサンジアミン残基、４，４’－ジアミノジフェニルスルホン残基、３，４’－ジアミノジフェニルスルホン残基、ビス［４－（３－アミノフェノキシ）フェニル］スルホン残基、ビス［４－（４－アミノフェノキシ）フェニル］スルホン残基、２，２－ビス（４－アミノフェニル）プロパン残基、２，２－ビス（４－アミノフェニル）ヘキサフルオロプロパン残基、及び下記一般式（３）で表される２価の基からなる群から選ばれる少なくとも１種の２価の基を表す。ｎ’は繰り返し単位数を表し、１以上である。）

(In the general formula (2), R ³ is a tetravalent group is a tetracarboxylic acid residue having an aromatic ring or aliphatic ring, R ⁴ represents a divalent group which is a diamine residue, R ⁴ Is a diamine residue having one or two silicon atoms in the main chain, and the remaining R ⁴ does not have a silicon atom and has an aromatic ring or an aliphatic ring. More than half of the remaining R ⁴ is 1,4-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4′-diaminodiphenylsulfone residue. Group, 3,4'-diaminodiphenylsulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2-bis (4-aminof At least one divalent group selected from the group consisting of a divalent propane residue, a 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (3): N ′ represents the number of repeating units and is 1 or more.)

（一般式（３）において、Ｒ^５及びＲ^６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 (3), R ⁵ and R ⁶ each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)

The polyimide film of the present disclosure preferably has a polyimide layer containing a polyimide having a structure represented by the general formula (2) from the viewpoint of light transmittance and bending resistance.

The laminate of the present disclosure is a laminate having the polyimide film of the present disclosure and a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound.

In the laminate of the present disclosure, the radical polymerizable compound is a compound having two or more (meth) acryloyl groups in one molecule, and the cationic polymerizable compound is one molecule of at least one of an epoxy group and an oxetanyl group. A compound having two or more compounds is preferable from the viewpoints of hardness and adhesion of the hard coat layer, and light transmittance and impact resistance.

The display surface material of the present disclosure is the polyimide film of the present disclosure or the laminate of the present disclosure.

The display surface material of the present disclosure can be used for a flexible display.

According to the present disclosure, it is possible to provide a resin film having excellent impact resistance and good bending resistance.
Moreover, according to this indication, the surface material for displays which is the laminated body which has the said resin film, and the said resin film or the said laminated body can be provided.

It is a schematic sectional drawing which shows an example of the polyimide film which concerns on this indication. It is a schematic sectional drawing which shows another example of the polyimide film which concerns on this indication. It is a figure for demonstrating the method of a static bending test. It is a figure for demonstrating the evaluation method of impact resistance.

I. Polyimide film The polyimide film of the present disclosure has two or more polyimide layers having different Young's moduli, has an overall thickness of 5 μm or more and 200 μm or less, and has a total light transmittance of 85 measured according to JIS K7361-1. % Or more.

Such a polyimide film of the present disclosure will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view illustrating an example of a polyimide film of the present disclosure. A polyimide film 10 of the present disclosure shown in FIG. 1 has a polyimide layer 1b between a polyimide layer 1a and a polyimide layer 1a ′, and the polyimide layer 1a and the polyimide layer 1a ′ have the same Young's modulus. 1b is different in Young's modulus from the polyimide layer 1a and the polyimide layer 1a ′.
FIG. 2 is a schematic cross-sectional view illustrating another example of the polyimide film of the present disclosure. A polyimide film 11 of the present disclosure shown in FIG. 2 has a polyimide layer 1a and a polyimide layer 1b, and the polyimide layer 1a and the polyimide layer 1b have different Young's moduli.

In the present disclosure, the Young's modulus is measured using a nanoindentation method at a temperature of 25 ° C. according to ISO14577 using a cross section of a test piece obtained by cutting a polyimide film in the thickness direction. Specifically, PICODETOR® HM500 manufactured by Fisher Instruments Co., Ltd. is used as a measuring device, and a Vickers indenter is used as a measurement indenter. For each layer of the cross section of the test piece, the value obtained by measuring 8 arbitrary points and calculating the number average is taken as the Young's modulus of each layer. The measurement conditions are the maximum indentation depth: 1000 nm, weighted time: 20 seconds, and creep time: 5 seconds.

In the present disclosure, the fact that the Young's modulus of the polyimide layer is different means that the difference in Young's modulus is 0.3 GPa or more. If the difference in Young's modulus is less than 0.3 GPa, the Young's modulus of the polyimide layer is Are the same as each other.

In addition, the polyimide film of the present disclosure has a total light transmittance of 85% or more measured in accordance with JIS K7361-1. Thus, since the transmittance | permeability is high, transparency becomes favorable and it can become a glass substitute material. The total light transmittance measured in accordance with JIS K7361-1 is preferably 88% or more, and more preferably 90% or more.
The total light transmittance measured according to JIS K7361-1 can be measured by, for example, a haze meter (for example, HM150 manufactured by Murakami Color Research Laboratory).

The reason why the polyimide film of the present disclosure has excellent impact resistance and good bending resistance is estimated as follows.
A resin film having excellent bending resistance can improve impact resistance by increasing the thickness of the film. However, if the thickness of the film is too thick, bending resistance is deteriorated. On the other hand, the polyimide film of the present disclosure has two or more polyimide layers having different Young's moduli, so that it has excellent impact resistance and bending resistance. Of the two or more polyimide layers, a polyimide layer having a relatively large Young's modulus is relatively difficult to deform and has excellent impact resistance. On the other hand, a polyimide layer having a relatively small Young's modulus is relatively easily deformed and has excellent bending resistance. In the polyimide film of the present disclosure, among two or more polyimide layers, a polyimide layer having a relatively large Young's modulus improves impact resistance, and a polyimide layer having a relatively small Young's modulus improves bending resistance. Therefore, it is considered that both impact resistance and bending resistance are compatible. In terms of shock absorption, a polyimide layer having a relatively high Young's modulus has a strong tendency to diffuse the collision force on the surface, and a polyimide layer having a relatively low Young's modulus diffuses the collision force over time. The tendency is strong. In the polyimide film of the present disclosure, it is estimated that the maximum value of impact force can be appropriately diffused and reduced by combining polyimide layers having different effects of diffusing collision force in this way, It is thought that the impact resistance is further improved.

Hereinafter, the polyimide film of the present disclosure will be described in detail.
The polyimide film of the present disclosure has two or more polyimide layers having different Young's moduli, has an overall thickness of 5 μm or more and 200 μm or less, and a total light transmittance of 85% or more. Other configurations may be provided as long as the effects of the present disclosure are not impaired.

1. Configuration of Polyimide Film The polyimide film of the present disclosure is formed by laminating two or more polyimide layers having different Young's moduli and having two or more polyimide layers having different Young's moduli adjacent to each other. is there.
The polyimide film of the present disclosure may have two polyimide layers as shown in FIG. 2, or may have three polyimide layers as shown in FIG. Although not shown, it may have four or more polyimide layers.

In addition, the polyimide film of the present disclosure may be one in which at least two polyimide layers have different Young's moduli, and may include two or more polyimide layers having the same Young's modulus. Among them, from the viewpoint of improving impact resistance and bending resistance, the polyimide layers adjacent to each other are preferably polyimide layers having different Young's moduli, and relative to the polyimide layer having a relatively large Young's modulus between adjacent layers, In particular, it is more preferable that polyimide layers having a low Young's modulus are alternately laminated.

In addition, the polyimide film of the present disclosure has three or more polyimide layers, and the polyimide layer having the largest Young's modulus among the polyimide layers is located on at least one surface. Among them, the number of polyimide layers is preferably 3 or more and an odd number. Among the polyimide layers, the polyimide layer having the largest Young's modulus is located on one surface, and the polyimide layer having the largest Young's modulus The Young's modulus is preferably 1.0 times or more and less than 1.2 times the Young's modulus of the polyimide layer located on the other surface, and it is preferably 1.0 times or more and 1.1 times or less. It is more preferable from the viewpoint of suppressing the warp of the film and the bending resistance.
In addition, the polyimide film of the present disclosure has three or more polyimide layers, and it is preferable from the viewpoint of impact resistance and bending resistance that the polyimide layer having the smallest Young's modulus among the polyimide layers is not located on the surface. Especially, it is preferable that the number of polyimide layers is three or more and an odd number, and the polyimide layer having the smallest Young's modulus among the polyimide layers is located in the center.
On the other hand, the polyimide film of this indication which consists of two polyimide layers is preferable from the point which can be reduced in thickness, improving impact resistance and bending resistance. When using a polyimide film composed of two polyimide layers as the surface material, it is preferable from the viewpoint of impact resistance and bending resistance that a polyimide layer having a relatively large Young's modulus is on the surface side. In the polyimide film of the present disclosure composed of two polyimide layers, the Young's modulus of the polyimide layer having a relatively large Young's modulus is relatively high in terms of impact resistance and bending resistance, and suppressing warping of the film. In particular, the Young's modulus of the polyimide layer having a small Young's modulus is preferably 1.2 times or more and 2.0 times or less.
Among the polyimide films of the present disclosure, from the viewpoint of improving impact resistance and bending resistance, the number of polyimide layers is 3 or more and an odd number, and a polyimide layer having a relatively large Young's modulus between adjacent layers; More preferably, polyimide layers having relatively small Young's modulus are alternately laminated, and the polyimide layer located on the surface is a polyimide layer having relatively large Young's modulus, and is located on one surface. More preferably, the polyimide layer and the polyimide layer located on the other surface are polyimide layers having the largest Young's modulus among the polyimide layers, and the polyimide layer located in the center has the smallest Young's modulus. More preferably, it is a polyimide layer.
The number of polyimide layers of the polyimide film of the present disclosure is not particularly limited as long as it is 2 or more, but it is 5 layers or less from the viewpoint of thinning the polyimide film and easy production. Preferably, it is 2 layers or 3 layers. Among these, a three-layer structure in which layers having a Young's modulus larger than that of the polyimide layer are located on both surfaces of a polyimide layer having a relatively small Young's modulus is particularly preferable from the viewpoint of impact resistance.

In the polyimide film of the present disclosure, it is preferable that the Young's modulus of the polyimide layer having the largest Young's modulus is 1.2 times or more of the Young's modulus of the polyimide layer having the smallest Young's modulus in terms of impact resistance and bending resistance. More preferably, it is 1.5 times or more. On the other hand, although not particularly limited, the Young's modulus of the polyimide layer having the largest Young's modulus is preferably 4.0 times or less, and 3.0 or less times that of the polyimide layer having the smallest Young's modulus. More preferably, it may be 2.0 times or less.
In the present disclosure, the ratio of the Young's modulus of the polyimide layer having the largest Young's modulus to the Young's modulus of the polyimide layer having the smallest Young's modulus is a value rounded to the first decimal place according to the rule B of JIS Z8401: 1999. Asking.

When the polyimide film of the present disclosure has three or more polyimide layers, the difference between the Young's modulus of the polyimide layer located on one surface and the Young's modulus of the polyimide layer located on the other surface is within 1.0 GPa It is preferable from the point which suppresses the curvature of a polyimide film, it is more preferable that it is less than 0.5 GPa, and it is still more preferable that it is less than 0.3 GPa.

The Young's modulus of each polyimide layer included in the polyimide film of the present disclosure is preferably 2.0 GPa or more, more preferably 3.0 GPa or more, more preferably 3.5 GPa from the viewpoint of impact resistance and bending resistance. More preferably, it is preferably 10.0 GPa or less, more preferably 8.0 GPa or less, and even more preferably 7.0 GPa or less.
Among them, the Young's modulus of the polyimide layer having the largest Young's modulus is preferably 3.5 GPa or more, more preferably 5.0 GPa or more, and still more preferably 6.0 GPa or more. The Young's modulus of the polyimide layer having the smallest Young's modulus is preferably 4.5 GPa or less, and more preferably 4.0 GPa or less.

When the polyimide film of the present disclosure has three or more polyimide layers, the polyimide layer located on one surface and the polyimide layer located on the other surface are in the range of 50 ° C. to 250 ° C. The difference in coefficient of linear thermal expansion (CTE) is preferably within 10 ppm / ° C from the viewpoint of suppressing the warp of the polyimide film, more preferably within 5 ppm / ° C, and more preferably within 2 ppm / ° C. Even more preferred.
In addition, the linear thermal expansion coefficient (CTE) in the range of 50 ° C. to 250 ° C. of each polyimide layer is a test piece obtained by cutting out a single-layer polyimide film produced under the same material and under the same conditions as each polyimide layer to 5 mm × 15 mm. On the other hand, the elongation of the test piece is measured under the following conditions using a thermomechanical analyzer (TMA), and the coefficient of linear thermal expansion (CTE) in the range of 50 ° C. to 250 ° C. is calculated. .
<CTE measurement conditions>
Model name: TMA-60, manufactured by Shimadzu Corporation Atmosphere gas: Nitrogen gas Flow rate: 50 ml / min
Initial load: 9g
[Temperature program]
After maintaining at 30 ° C. for 10 minutes in a nitrogen atmosphere, the temperature is raised to 400 ° C. at a heating rate of 10 ° C./min and maintained at 400 ° C. for 1 minute.

The linear thermal expansion coefficient (CTE) in the range of 50 ° C. to 250 ° C. of each polyimide layer of the polyimide film of the present disclosure is not particularly limited, but may be 70 ppm / ° C. or less from the viewpoint of heat resistance. Preferably, it is 60 ppm / ° C. or less, more preferably 50 ppm / ° C. or less.

The polyimide film of the present disclosure has an overall thickness of 5 μm or more and 200 μm or less, more preferably 10 μm or more and 180 μm or less, more preferably 40 μm or more and 150 μm or less, and still more preferably from the viewpoint of bending resistance and impact resistance. Preferably they are 50 micrometers or more and 120 micrometers or less.

The thickness of each polyimide layer included in the polyimide film of the present disclosure is not particularly limited. From the viewpoint of bending resistance and impact resistance, the thickest layer among the polyimide layers is not a polyimide layer having the largest Young's modulus. It is preferable.

In the polyimide film of the present disclosure, the thickness of each polyimide layer is determined using an electron microscope such as a scanning electron microscope (SEM), a transmission electron microscope cross-sectional microscope (TEM), or a scanning transmission electron microscope (STEM). It can be measured from the observed cross section in the thickness direction.
When the interface between the polyimide layers adjacent to each other has a mixing region where the materials of each polyimide layer are mixed and the interface is unclear, the boundary for determining the thickness of the polyimide layer can be determined, for example, as follows: it can. Select the element that makes the most difference from the materials used for the two adjacent polyimide layers, and perform element mapping by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The portion where the detected amount of the element selected in (2) is the average value of the detected amounts of the elements in the two regions that are not the mixing region is defined as a boundary for determining the thickness of the polyimide layer. If the portion that is the average value of the detected amounts of elements in the two regions that are not the mixing region is a region having a thickness, the central portion in the thickness direction of the region is used as a boundary for determining the thickness of the polyimide layer.

In addition, it is preferable that the polyimide film of the present disclosure has a mixing region between polyimide layers adjacent to each other because it is excellent in interlayer adhesion, suppresses generation of interference fringes, and easily improves impact resistance. .

In addition, in the polyimide film of the present disclosure, the total thickness of the polyimide layer having the largest Young's modulus among the polyimide layers is preferably 60% or less of the total thickness of the polyimide film from the viewpoint of improving bending resistance. Preferably it is 50% or less, More preferably, it is 40% or less, More preferably, it is 30% or less. Of the polyimide layers, the total thickness of the polyimide layers having the largest Young's modulus is preferably 5% or more, more preferably 10% or more of the total thickness of the polyimide film from the viewpoint of improving impact resistance.
On the other hand, in the polyimide film of the present disclosure, the total thickness of the polyimide layers having the largest Young's modulus among the polyimide layers is 15% or more and 60% or less of the total thickness of the polyimide film while suppressing a decrease in bending resistance. From the point that impact resistance can be improved, it may be 20% or more and 60% or less.

Moreover, the polyimide film of this indication is a polyimide layer (low Young's modulus) with the smallest Young's modulus with respect to the total thickness of the polyimide layer (high Young's modulus layer) with the largest Young's modulus among the said polyimide layers from the point which improves a bending tolerance. Ratio) (total thickness of low Young's modulus layer / total thickness of high Young's modulus layer) is preferably more than 1.0, more preferably 2.0 or more. On the other hand, the ratio (total thickness of low Young's modulus layer / total thickness of high Young's modulus layer) is preferably 20 or less, and more preferably 15 or less, from the viewpoint of impact resistance. From the viewpoint of suppressing a decrease in bending resistance, the ratio (the total thickness of the low Young's modulus layer / the total thickness of the high Young's modulus layer) is preferably 0.6 or more, and 0.7 or more. Is more preferably 0.8 or more, and particularly preferably 1.0 or more.

Further, in the polyimide film of the present disclosure, the total thickness of the polyimide layer having the smallest Young's modulus (low Young's modulus layer) among the polyimide layers is not particularly limited, but is preferably 20 μm or more and 120 μm or less, It is preferable from the point of bending tolerance that it is 20 micrometers or more and less than 70 micrometers.

2. Polyimide layer Each polyimide layer of the polyimide film of the present disclosure contains at least polyimide, and further contains additives and other resins other than polyimide, as long as the effects of the present disclosure are not impaired. Also good.

(1) Polyimide A polyimide is obtained by reacting a tetracarboxylic acid component with a diamine component. It is preferable to obtain imidization by obtaining a polyamic acid by polymerization of a tetracarboxylic acid component and a diamine component. The imidization may be performed by thermal imidization or chemical imidization. Moreover, it can also manufacture by the method which used thermal imidation and chemical imidization together.

As a specific example of the tetracarboxylic acid component, tetracarboxylic dianhydride is preferably used. Cyclohexanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, dicyclohexane-3,4,3 ', 4 '-Tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic dianhydride, 2,2 ', 3,3'-benzophenone tetracarboxylic dianhydride 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxy) Phenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarbo) Ciphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ) Methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane 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-Dicarbox Ii) 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 Anhydride, {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, 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.
These tetracarboxylic dianhydrides can be used alone or in admixture of two or more.

Specific examples of the diamine component include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,3 '-Diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzanilide, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 3, 4 -Diaminodiphenylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2 , 2-di (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3 -Hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3- Bis (3-aminophenoxy) , 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-amino) Benzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3 -Amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-a No-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoro) Methylbenzyl) benzene, 2,6-bis (3-aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine, N, N′-bis (4-aminophenyl) terephthalamide, 9,9 -Bis (4-aminophenyl) fluorene, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (2,2-bis (trifluoro) Methyl) benzidine), 3,3′-dichloro-4,4′-diaminobiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3 ′ Dimethyl-4,4′-diaminobiphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] Ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide,

Bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-amino Phenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3 3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] ben 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-amino Phenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-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-dimethylbenzen) ) Phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4 , 4′-Dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 6,6′-bis (3-aminophenoxy) -3,3 3 ′, 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, , 3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis ( -Aminopropyl) polydimethylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis ( 2-aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether,

1,4-cyclohexanediamine, trans-1,4-bismethylenecyclohexanediamine (trans-1,4-bis (aminomethyl) cyclohexane), 2,6-bis (aminomethyl) bicyclo [2,2,1] heptane 2,5-bis (aminomethyl) bicyclo [2,2,1] heptane, or a part or all of the hydrogen atoms on the aromatic ring of the diamine are fluoro group, methyl group, methoxy group, trifluoromethyl group Alternatively, a diamine substituted with a substituent selected from trifluoromethoxy groups can also be used.
These diamines can be used alone or in admixture of two or more.

Further, from the viewpoint of improving light transmittance and improving impact resistance, the two or more polyimide layers each contain an aromatic ring, and (i) a fluorine atom and (ii) an aliphatic ring. And (iii) a polyimide containing at least one selected from the group consisting of a structure in which aromatic rings are connected to each other by a sulfonyl group or an alkylene group which may be substituted with a fluorine atom. If the polyimide contains an aromatic ring, the orientation is increased and the rigidity is improved, so that the impact resistance is improved, but the transmittance tends to decrease depending on the absorption wavelength of the aromatic ring.
When (i) a fluorine atom is contained in the polyimide, the light transmission is improved because the electronic state in the polyimide skeleton can be hardly transferred.
When (ii) an aliphatic ring is included in the polyimide, light transmittance is improved because the transfer of charges in the skeleton can be inhibited by breaking the π-electron conjugation in the polyimide skeleton.
When (iii) a structure in which aromatic rings are connected to each other by a sulfonyl group or an alkylene group which may be substituted with a fluorine atom is included in polyimide, the charge transfer in the skeleton is interrupted by breaking the π electron conjugation in the polyimide skeleton. The light transmittance is improved from the point that can be inhibited.

Among these, a polyimide containing an aromatic ring and containing a fluorine atom is preferably used in terms of improving light transmittance and improving impact resistance.
The content ratio of fluorine atoms in the polyimide is such that the ratio (F / C) of the number of fluorine atoms (F) and the number of carbon atoms (C) measured on the polyimide surface by X-ray photoelectron spectroscopy is 0.01 or more. Is preferable, and more preferably 0.05 or more. On the other hand, if the fluorine atom content is too high, the inherent heat resistance of the polyimide may be lowered, so the ratio (F / C) of the number of fluorine atoms (F) to the number of carbon atoms (C) is 1 or less. Preferably, it is preferably 0.8 or less.
Here, the said ratio by the measurement of X-ray photoelectron spectroscopy (XPS) can be calculated | required from the value of atomic% of each atom measured using an X-ray photoelectron spectrometer (for example, Thermo Scientific Thea Probe). .

In addition, the polyimide has a tetracarboxylic acid residue and an aromatic ring having an aromatic ring when the total of the tetracarboxylic acid residue and the diamine residue is 100 mol% from the viewpoint of improving impact resistance. The total of the diamine residues it has is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 75 mol% or more.

In addition, in this indication, the content rate of each repeating unit in a polyimide, and the content rate (mol%) of each tetracarboxylic acid residue or each diamine residue can be calculated | required from the molecular weight of preparation at the time of polyimide manufacture. In addition, the content ratio (mol%) of each tetracarboxylic acid residue and each diamine residue in the polyimide is a high-speed liquid for a decomposition product of polyimide obtained by decomposing a sample with an alkaline aqueous solution or supercritical methanol. It can be determined using chromatography, gas chromatograph mass spectrometer, NMR, elemental analysis, XPS / ESCA, TOF-SIMS and pyrolysis CG-MS.

In addition, the polyimide preferably has at least one of a tetracarboxylic acid residue and a diamine residue containing an aromatic ring and a fluorine atom from the viewpoint of improving impact resistance and light transmittance. It preferably has a tetracarboxylic acid residue containing a ring and a fluorine atom, and a diamine residue containing an aromatic ring and a fluorine atom.
The polyimide has a tetracarboxylic acid residue having an aromatic ring and a fluorine atom and an aromatic ring and a diamine residue having a fluorine atom when the total of the tetracarboxylic acid residue and the diamine residue is 100 mol%. The total is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 75 mol% or more.

In addition, it is a polyimide in which 50% or more of hydrogen atoms bonded to carbon atoms contained in polyimide are hydrogen atoms bonded directly to an aromatic ring, thereby improving light transmittance and improving rigidity. Are preferably used. The proportion of hydrogen atoms (number) directly bonded to the aromatic ring in the total hydrogen atoms (number) bonded to carbon atoms contained in the polyimide is preferably 60% or more, and more preferably 70% or more. It is preferable that
When 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide is a polyimide that is a hydrogen atom directly bonded to the aromatic ring, the film is stretched at, for example, 200 ° C. or higher even after a heating step in the atmosphere. Is preferable from the viewpoint of little change in optical characteristics, particularly total light transmittance and yellowness YI value. When polyimide is a polyimide in which 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 chemical structure of the polyimide changes due to low reactivity with oxygen. It is estimated that it is difficult. Polyimide film uses its high heat resistance and is often used in devices that require processing steps involving heating, but more than 50% of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are in the aromatic ring. In the case of polyimide, which is a hydrogen atom that is directly bonded, there is no need to carry out these subsequent processes in an inert atmosphere in order to maintain transparency, so that the cost of equipment costs and atmospheric control can be suppressed. There is.
Here, the ratio of the hydrogen atoms (number) directly bonded to the aromatic ring in the total hydrogen atoms (number) bonded to the carbon atoms contained in the polyimide is determined by high-performance liquid chromatography or gas chromatography mass of the polyimide decomposition product. It can be determined using an analyzer and NMR. For example, the sample is decomposed with an alkaline aqueous solution or supercritical methanol, and the resulting polyimide decomposition product is separated by high performance liquid chromatography, and the qualitative analysis of each separated peak is performed by a gas chromatograph mass spectrometer and NMR. The ratio of hydrogen atoms (numbers) directly bonded to the aromatic ring in the total hydrogen atoms (numbers) contained in the polyimide can be determined by performing quantitative analysis using high performance liquid chromatography. .

In addition, as a polyimide used in the present disclosure, from the viewpoint of improving the adhesion between adjacent polyimide layers, and interlayer adhesion when another layer such as a hard coat layer is further laminated on the polyimide film, silicon A polyimide containing an atom can be preferably used. Moreover, the polyimide layer containing the polyimide containing a silicon atom is preferable also from the point which improves interlayer adhesiveness and suppresses generation | occurrence | production of an interference fringe by being easy to form the said mixing area | region between adjacent polyimide layers. . Moreover, when the polyimide film has a polyimide layer containing a polyimide containing silicon atoms, it is also preferable from the viewpoint of easily improving impact resistance.
As the polyimide containing a silicon atom used in the present disclosure, a diamine residue having a silicon atom is preferably 1 mol% or more and 50 mol% or less, more preferably 2 mol, out of a total amount of diamine residues of 100 mol%. A polyimide containing 5 mol% or more and 40 mol% or less, more preferably 5 mol% or more and 30 mol% or less is preferably used.

The diamine residue having a silicon atom is preferably a diamine residue having one or two silicon atoms in the main chain.
Examples of the diamine having one silicon atom in the main chain include diamines represented by the following general formula (A). Moreover, as a diamine which has two silicon atoms in a principal chain, the diamine represented by the following general formula (B) is mentioned, for example.

（一般式（Ａ）及び一般式（Ｂ）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。）

(In the general formula (A) and the general formula (B), each L is independently a direct bond or —O— bond, and each R ¹⁰ may independently have a substituent, oxygen Represents a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain an atom or a nitrogen atom, and each R ¹¹ may independently have a substituent, and represents an oxygen atom or a nitrogen atom. Represents a divalent hydrocarbon group having 1 to 20 carbon atoms which may be contained.)

In the general formula (A) and the general formula (B), a plurality of L, R ¹⁰ , and R ¹¹ may be the same or different.
Examples of the monovalent hydrocarbon group represented by R ¹⁰ include an alkyl group having 1 to 20 carbon atoms, an aryl group, and combinations thereof. The alkyl group may be linear, branched or cyclic, and may be linear or a combination of branched and cyclic.
The alkyl group having 1 to 20 carbon atoms is preferably an alkyl group having 1 to 10 carbon atoms. Specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, Examples thereof include t-butyl group, pentyl group, hexyl group and the like. The cyclic alkyl group is preferably a cycloalkyl group having 3 to 10 carbon atoms, and specific examples include a cyclopentyl group and a cyclohexyl group. The aryl group is preferably an aryl group having 6 to 12 carbon atoms, and specific examples include a phenyl group, a tolyl group, and a naphthyl group. Further, the monovalent hydrocarbon group represented by R ¹⁰ may be an aralkyl group, and examples thereof include a benzyl group, a phenylethyl group, and a phenylpropyl group.
Examples of the hydrocarbon group that may contain an oxygen atom or a nitrogen atom include an ether bond, a carbonyl bond, an ester bond, an amide bond, and an imino bond between a divalent hydrocarbon group described later and the monovalent hydrocarbon group. And a group bonded with at least one bond (—NH—).
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 disclosure are not impaired. For example, a halogen atom such as a fluorine atom or a chlorine atom And a hydroxyl group.

The monovalent hydrocarbon group represented by R ¹⁰ is preferably an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 10 carbon atoms from the viewpoint of impact resistance and bending resistance. More preferably, it is an alkyl group having 1 to 3 carbon atoms. The alkyl group having 1 to 3 carbon atoms is more preferably a methyl group, and the aryl group having 6 to 10 carbon atoms is more preferably a phenyl group.

Examples of the divalent hydrocarbon group represented by R ¹¹ include an alkylene group having 1 to 20 carbon atoms, an arylene group, and a combination thereof. The alkylene group may be linear, branched or cyclic, and may be linear or a combination of branched and cyclic.
The alkylene group having 1 to 20 carbon atoms is preferably an alkylene group having 1 to 10 carbon atoms. For example, a linear chain such as a methylene group, an ethylene group, various propylene groups, various butylene groups, or a cyclohexylene group. And 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, and examples of the arylene group include a phenylene group, a biphenylene group, and a naphthylene group, and further have a substituent for an aromatic ring described later. You may do it.
As the divalent hydrocarbon group which may contain an oxygen atom or a nitrogen atom, the divalent hydrocarbon groups may be ether bonds, carbonyl bonds, ester bonds, amide bonds, and imino bonds (—NH—). A group bonded with at least one is exemplified.
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 preferably an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 10 carbon atoms from the viewpoint of impact resistance and bending resistance. Furthermore, an alkylene group having 2 to 4 carbon atoms is more preferable, and the alkylene group is preferably linear or branched.

Among the diamines having one or two silicon atoms in the main chain, among them, diamines having two silicon atoms are preferable from the viewpoints of light transmittance, impact resistance and bending resistance. -Bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, 1,3-bis (5-aminopentyl) tetramethyldisiloxane are readily available And light transmittance and impact resistance are preferred.

From the viewpoint of impact resistance and bending resistance, 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, and 500 or less. Is still more preferable, and it is especially preferable that it is 300 or less.
The diamine residues having one or two silicon atoms in the main chain can be used alone or in combination of two or more.

Moreover, the polyimide film of this indication contains the polyimide which has the structure represented by following General formula (1) in which the polyimide layer with the largest Young's modulus among all the polyimide layers which a polyimide film has is light-transmitting. Is preferable from the viewpoints of heat resistance, impact resistance and bending resistance.

（一般式（１）において、Ｒ^１は３，３’，４，４’－ビフェニルテトラカルボン酸二無水物残基、３，３’，４，４’－ベンゾフェノンテトラカルボン酸二無水物残基、及びピロメリット酸二無水物残基からなる群から選択される少なくとも１種の４価の基、Ｒ^２は、２，２’－ビス（トリフルオロメチル）ベンジジン残基、４，４’－ジアミノジフェニルスルホン残基、２，２－ビス［４－（４－アミノフェノキシ）フェニル］ヘキサフルオロプロパン残基、ビス［４－（３－アミノフェノキシ）フェニル］スルホン残基、ビス［４－（４－アミノフェノキシ）フェニル］スルホン残基、４，４’－ジアミノ－２，２’－ビス（トリフルオロメチル）ジフェニルエーテル残基、１，４－ビス［４－アミノ－２－（トリフルオロメチル）フェノキシ］ベンゼン残基、２，２－ビス［４－（４－アミノ－２－トリフルオロメチルフェノキシ）フェニル］ヘキサフルオロプロパン残基、４，４’－ジアミノ－２－（トリフルオロメチル）ジフェニルエーテル残基、及び９，９－ビス（４－アミノフェニル）フルオレン残基からなる群から選ばれる少なくとも１種の２価の基を表す。ｎは繰り返し単位数を表し、１以上である。）

(In the general formula (1), R ¹ is 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride residue, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride residue. , And at least one tetravalent group selected from the group consisting of pyromellitic dianhydride residues, R ² is a 2,2′-bis (trifluoromethyl) benzidine residue, 4,4′- Diaminodiphenylsulfone residue, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4 -Aminophenoxy) phenyl] sulfone residue, 4,4'-diamino-2,2'-bis (trifluoromethyl) diphenyl ether residue, 1,4-bis [4-amino-2- (trifluoromethyl) phenoxy ] Benzene residue, 2,2-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane residue, 4,4′-diamino-2- (trifluoromethyl) diphenyl ether residue, And at least one divalent group selected from the group consisting of 9,9-bis (4-aminophenyl) fluorene residues, n represents the number of repeating units and is 1 or more.)

Among these, R ^{1 in the} general formula (1) is preferably a pyromellitic dianhydride residue from the viewpoint of improving impact resistance.
R ^{2 in the} general formula (1) includes, among others, a 2,2′-bis (trifluoromethyl) benzidine residue, a bis [4- (3-aminophenoxy) phenyl] sulfone residue, and a bis [4- It is preferably at least one divalent group selected from (4-aminophenoxy) phenyl] sulfone residues from the viewpoints of light transmittance, impact resistance and bending resistance, and 2,2′-bis More preferably, it is a (trifluoromethyl) benzidine residue.

In the structure represented by the general formula (1), n represents the number of repeating units and is 1 or more.
The number of repeating units n in the polyimide may be appropriately selected according to the structure so as to exhibit a desired Young's modulus, and is not particularly limited, but is usually 10 or more and 2000 or less, and further 15 or more and 1000 or less. preferable.
Incidentally, R ¹ in the repeating units may be different from each be the same, R ² may each be different even if the same in each repeating unit.

The content ratio of the polyimide having the structure represented by the general formula (1) among all the polyimides contained in the polyimide layer having the largest Young's modulus is from the viewpoint of light transmittance, impact resistance, and bending resistance. 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and even more preferably 100% by mass.
In addition, the polyimide used for this indication can contain 1 type, or 2 or more types of polyimide which has a structure represented by the said General formula (1).

Moreover, the polyimide film of this indication contains the polyimide which has the structure where the polyimide layer with the largest Young's modulus among all the polyimide layers which a polyimide film has is represented by the said General formula (1), and the following general formula It is preferable to further have a polyimide layer containing a polyimide having a structure represented by (2) in terms of light transmittance, impact resistance, and bending resistance. That is, it is preferable that the polyimide layer different from the polyimide layer having the largest Young's modulus contains a polyimide having a structure represented by the following general formula (2).

（一般式（２）において、Ｒ^３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、Ｒ^４は、ジアミン残基である２価の基を表し、Ｒ^４の総量の５０モル％以下が、主鎖にケイ素原子を１個又は２個有するジアミン残基であり、残りのＲ^４が、ケイ素原子を有さず、芳香族環又は脂肪族環を有するジアミン残基であり、前記残りのＲ^４のうちの半分よりも多くが、１，４－シクロヘキサンジアミン残基、ｔｒａｎｓ－１，４－ビスメチレンシクロヘキサンジアミン残基、４，４’－ジアミノジフェニルスルホン残基、３，４’－ジアミノジフェニルスルホン残基、ビス［４－（３－アミノフェノキシ）フェニル］スルホン残基、ビス［４－（４－アミノフェノキシ）フェニル］スルホン残基、２，２－ビス（４－アミノフェニル）プロパン残基、２，２－ビス（４－アミノフェニル）ヘキサフルオロプロパン残基、及び下記一般式（３）で表される２価の基からなる群から選ばれる少なくとも１種の２価の基を表す。ｎ’は繰り返し単位数を表し、１以上である。）

(In the general formula (2), R ³ is a tetravalent group is a tetracarboxylic acid residue having an aromatic ring or aliphatic ring, R ⁴ represents a divalent group which is a diamine residue, R ⁴ Is a diamine residue having one or two silicon atoms in the main chain, and the remaining R ⁴ does not have a silicon atom and has an aromatic ring or an aliphatic ring. More than half of the remaining R ⁴ is 1,4-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4′-diaminodiphenylsulfone residue. Group, 3,4'-diaminodiphenylsulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2-bis (4-aminof At least one divalent group selected from the group consisting of a divalent propane residue, a 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (3): N ′ represents the number of repeating units and is 1 or more.)

（一般式（３）において、Ｒ^５及びＲ^６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 (3), R ⁵ and R ⁶ each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)

R ^{3 in the} general formula (2) is a residue obtained by removing an acid dianhydride structure from a tetracarboxylic dianhydride having an aromatic ring from the above-described tetracarboxylic acid components, or an aliphatic ring. Residues obtained by removing the acid dianhydride structure from the tetracarboxylic dianhydride possessed can be selected as appropriate, and are not particularly limited. Among these, 4,4′-, from the viewpoint of light transmittance and impact resistance (Hexafluoroisopropylidene) diphthalic anhydride residue, 3,4 '-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene) diphthalic anhydride residue, 4 More preferably, it is at least one tetravalent group selected from the group consisting of, 4'-oxydiphthalic anhydride residue and 3,4'-oxydiphthalic anhydride residue, (Hexafluoroi At least selected from the group consisting of sopropylidene) diphthalic anhydride residue, 3,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue and 3,3 ′-(hexafluoroisopropylidene) diphthalic anhydride residue It is still more preferable that it is one kind of tetravalent group.

Examples of R ³ include pyromellitic dianhydride residue, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride residue, and 2,2 ′, 3,3′-biphenyltetracarboxylic acid. A group of tetracarboxylic acid residues (group A) suitable for improving rigidity such as at least one selected from the group consisting of acid dianhydride residues, cyclohexanetetracarboxylic dianhydride residues, cyclohexane Pentanetetracarboxylic dianhydride residue, dicyclohexane-3,4,3 ′, 4′-tetracarboxylic dianhydride residue, cyclobutanetetracarboxylic dianhydride residue, 4,4 ′-(hexafluoro Isopropylidene) diphthalic anhydride residue, 3,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,3 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, Tetracarboxylic acid suitable for improving light transmittance such as at least one selected from the group consisting of 4,4′-oxydiphthalic anhydride residue and 3,4′-oxydiphthalic anhydride residue It is also preferable to use a mixture of the residue group (group B). In this case, the content ratio of the tetracarboxylic acid residue group (group A) suitable for improving the rigidity and the tetracarboxylic acid residue group (group B) suitable for improving light transmittance is , 1 mol of tetracarboxylic acid residue group (group B) suitable for improving light transmittance is 0.4% of tetracarboxylic acid residue group (group A) suitable for improving rigidity. It is preferably from 05 mol to 9 mol, more preferably from 0.1 mol to 5 mol, and still more preferably from 0.3 mol to 4 mol.
Among them, the group B includes 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residues and 3,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residues containing fluorine atoms. It is preferable to use at least one kind from the viewpoint of improvement in impact resistance and light transmittance.
When the R ³ includes a tetracarboxylic acid residue of the group A, R ⁴ of the general formula (2) includes a diamine residue having one or two silicon atoms in the main chain. It is preferable from the point of bending resistance.
In R ³ , these suitable residues are preferably contained in a total amount of 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more.

In R ⁴ of the general formula (2), the content ratio of the diamine residue having one or two silicon atoms in the main chain is not particularly limited as long as it is 50 mol% or less of the total amount of R ^4. However, a diamine residue having one or two silicon atoms in the main chain from the viewpoint of improving interlayer adhesion, suppressing generation of interference fringes, and easily improving impact resistance. It is preferable to contain 1 mol% or more and 50 mol% or less, and it is more preferable to contain 2.5 mol% or more and 40 mol% or less.
Examples of the diamine residue having one or two silicon atoms in the main chain include residues obtained by removing two amino groups from the diamine having one or two silicon atoms in the main chain described above. . Among them, a diamine residue having two silicon atoms is preferable from the viewpoint of light transmittance, impact resistance and bending resistance, and moreover, 1,3-bis (3-aminopropyl) tetramethyldimethyl. Siloxane residues, 1,3-bis (4-aminobutyl) tetramethyldisiloxane residues, 1,3-bis (5-aminopentyl) tetramethyldisiloxane residues, and the like are easily available and light transmissive. It is preferable from the viewpoint of both impact resistance.

Wherein R ⁴ is of the total amount of R ^4, the backbone remaining R ⁴ to a silicon atom by removing one or two with the diamine residues may not have a silicon atom, an aromatic ring or an aliphatic A diamine residue having a ring, and more than half of the remaining R ⁴ is 1,4-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue (trans-1,4 -Bis (aminomethyl) cyclohexane residue), 4,4'-diaminodiphenylsulfone residue, 3,4'-diaminodiphenylsulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2-bis (4-aminophenyl) propane residue, 2,2-bis (4-aminophenyl) hexafluoro At least one divalent group selected from the group consisting of a lopan residue and a divalent group represented by the general formula (3) (hereinafter, “at least one divalent group selected from the above group”). It may be said).
That is, of the total amount of ^{R 4} (100 mol%), a diamine residue having one or two silicon atoms in the main chain When x mol% (0 ≦ x ≦ 50), the ^{R 4} (100- x) 50% by mole or more and 100% by mole or less, which is mol%, is a diamine residue having no silicon atom and having an aromatic ring or an aliphatic ring, and {(100−x) / 2} of R ⁴ More than mol% is at least one divalent group selected from the above group. Among them, the proportion of at least one divalent group selected from the group of the remaining R ⁴ , that is, the total amount of diamine residues having no silicon atom and having an aromatic ring or an aliphatic ring. The proportion of at least one divalent group selected from the above group when the amount is 100 mol% is preferably 70 mol% or more from the viewpoint of surface hardness, impact resistance and light transmittance. More preferably, it is 85 mol% or more, and still more preferably 95 mol% or more. R ⁴ may be different from at least one divalent group selected from the above group, and may contain other diamine residues having no silicon atom and having an aromatic ring or an aliphatic ring. good.
Here, the diamine residue having no silicon atom and having an aromatic ring can be a residue obtained by removing two amino groups from a diamine having no silicon atom and having an aromatic ring. The diamine residue having no aliphatic ring and having an aliphatic ring can be a residue obtained by removing two amino groups from a diamine having no silicon atom and having an aliphatic ring. The diamine used for the diamine residue which does not have a silicon atom but has an aromatic ring or an aliphatic ring, which is different from at least one divalent group selected from the above group, which R ⁴ may contain For example, a diamine having no silicon atom and having an aromatic ring or an aliphatic ring can be appropriately selected from the diamines described above, and is not particularly limited.

The at least one divalent group selected from the above group includes, among others, a trans-1,4-bismethylenecyclohexanediamine residue, 4,4′-diaminodiphenylsulfone from the viewpoint of impact resistance and light transmittance. Residue, 3,4'-diaminodiphenylsulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2- At least selected from the group consisting of a bis (4-aminophenyl) propane residue, a 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the general formula (3) One type of divalent group is preferable, and a divalent group represented by the general formula (3) is more preferable. Among the divalent groups represented by the general formula (3), it is more preferable that R ⁵ and R ⁶ are perfluoroalkyl groups, and among these, a perfluoroalkyl group having 1 to 3 carbon atoms is more preferable. Preferably, it is a trifluoromethyl group or a perfluoroethyl group. The alkyl group in R ⁵ and R ⁶ in the general formula (3) is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group or an ethyl group.

Further, to improve the impact resistance of the polyimide film of the present disclosure, from the viewpoint of improving optical transparency of at least one divalent radical selected from the group of the total amount of R ^4, at least 50 mol% is preferably, in particular, at least one divalent remaining R ⁴ all but diamine residue having one or two silicon atoms in the main chain of the total amount of R ⁴ is selected from the group The group is preferably.

When the R ⁴ is different from at least one divalent group selected from the above group and contains a diamine residue having no silicon atom and having an aromatic ring or an aliphatic ring, the content ratio is Although not particularly limited, from the viewpoint of impact resistance and light transmittance, the total amount of R ⁴ (100 mol%) is preferably 30 mol% or less, more preferably 20 mol% or less. More preferably, it is 10 mol% or less.

In the structure represented by the general formula (2), n ′ represents the number of repeating units and is 1 or more.
The number of repeating units n ′ in the polyimide may be appropriately selected according to the structure so as to exhibit a desired Young's modulus, and is not particularly limited, but is usually 10 or more and 2000 or less, and further 15 or more and 1000 or less. Is preferred.
In addition, R ³ in each repeating unit may be the same or different, and R ⁴ in each repeating unit may be the same or different.

In the polyimide layer containing the polyimide having the structure represented by the general formula (2), the content ratio of the polyimide is 60% by mass or more from the viewpoint of light transmittance, impact resistance, and bending resistance. Is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.
In addition, the polyimide used for this indication can contain 1 type (s) or 2 or more types of polyimide which has a structure represented by the said General formula (2).

In addition, the polyimide film of the present disclosure preferably has a polyimide layer containing a polyimide having a structure represented by the general formula (2) from the viewpoint of light transmittance and bending resistance, and from the viewpoint of impact resistance. Is also preferable. From the viewpoint of further improving impact resistance, the polyimide film of the present disclosure contains a polyimide layer having a polyimide layer having the largest Young's modulus and having a structure represented by the general formula (1). The impact resistance can be further improved by not containing the polyimide having the structure represented by the formula (2), but the polyimide layer having the largest Young's modulus is the polyimide having the structure represented by the general formula (2). The polyimide layer containing a polyimide may be sufficient as all the polyimide layers which a polyimide film has, and the polyimide layer containing the polyimide which has a structure represented by the said General formula (2) may be sufficient as it.

Of all the polyimide layers possessed by the polyimide film, the polyimide layer having the largest Young's modulus contains a polyimide having a structure represented by the general formula (1), and the structure represented by the general formula (2) In the polyimide film further having a polyimide layer containing a polyimide having a thickness, the total thickness of the polyimide layer having the largest Young's modulus is not less than 5% and not more than 60% of the total thickness of the polyimide film. From the viewpoint of sex.
In the polyimide film which is a polyimide layer containing the polyimide which has the structure represented by the said General formula (2), all the polyimide layers which a polyimide film has, The total thickness of the polyimide layer with the largest Young's modulus is a polyimide film. 5% or more and 30% or less of the total thickness is preferable from the viewpoint of bending resistance and impact resistance, more preferably 5% or more and 20% or less, and more preferably 5% or more and 15% or less. Further preferred.

Moreover, among all the polyimide layers which a polyimide film has, the polyimide layer with the largest Young's modulus contains the polyimide which has a structure represented by the said General formula (1), and is represented by the said General formula (2). In the polyimide film further having the polyimide layer containing the polyimide having the structure, the Young's modulus of the polyimide layer having the largest Young's modulus is the Young's modulus of the polyimide layer having the smallest Young's modulus in terms of impact resistance and bending resistance. It is preferably 1.5 times or more, more preferably 1.7 times or more, and even more preferably 1.8 times or more from the viewpoint of impact resistance.
In the polyimide film in which all the polyimide layers of the polyimide film are polyimide layers containing a polyimide having the structure represented by the general formula (2), the Young's modulus is the most in terms of impact resistance and bending resistance. The Young's modulus of the large polyimide layer is preferably 1.2 times or more of the Young's modulus of the polyimide layer having the smallest Young's modulus, may be 2.0 times or less, and may be 1.8 times or less. Good.

Further, the polyimide used in the present disclosure may include a polyamide structure in a part thereof as long as the effect of the present disclosure is not impaired. Examples of the polyamide structure that may be included include a polyamideimide structure containing a tricarboxylic acid residue such as trimellitic anhydride and a polyamide structure containing a dicarboxylic acid residue such as terephthalic acid.

From the viewpoint of heat resistance, the polyimide used in the present disclosure preferably has a glass transition temperature of 200 ° C. or higher, more preferably 250 ° C. or higher, and further preferably 270 ° C. or higher. On the other hand, from the viewpoint of reducing the baking temperature, the glass transition temperature is preferably 400 ° C. or lower, more preferably 380 ° C. or lower.
The glass transition temperature of the polyimide used in the present disclosure is determined from the peak temperature of the temperature-tan δ (tan δ = loss elastic modulus (E ″) / storage elastic modulus (E ′)) curve obtained by dynamic viscoelasticity measurement. Is. The glass transition temperature of polyimide refers to the temperature of a peak at which the maximum value of the peak is maximum when there are a plurality of tan δ curve peaks. As the dynamic viscoelasticity measurement, for example, with a dynamic viscoelasticity measuring device RSA III (TA Instruments Japan Co., Ltd.), the measurement range is set to −150 ° C. to 400 ° C., the frequency is 1 Hz, and the temperature is raised. This can be done at a rate of 5 ° C./min. Further, the measurement can be performed with a sample width of 5 mm and a distance between chucks of 20 mm.
In the present disclosure, the peak of the tan δ curve refers to a peak having an inflection point that is a maximum value and a peak width that is between 3 ° C. or more between peaks and valleys, and is derived from measurement such as noise. The fine vertical fluctuation is not interpreted as the peak.

(2) Additive Each polyimide layer of the polyimide film according to the present disclosure may further contain an additive as necessary in addition to the polyimide. Examples of the additive include a silica filler for facilitating winding, and a surfactant for improving film forming property and defoaming property.

Moreover, each polyimide layer which the polyimide film which concerns on this indication has may contain other resins other than a polyimide in the range which does not impair the effect of this indication. Examples of the other resins include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyamide resins, polyamideimide resins, polyphenylene sulfide resins, polyether ether ketone resins, polyether sulfone resins, and polycarbonate resins. And polyetherimide resins, epoxy resins, phenol resins, glass-epoxy resins, polyphenylene ether resins, acrylic resins, polyolefin resins such as polyethylene and polypropylene, and polycycloolefins such as polynorbornene.
When the polyimide layer contains other resin other than polyimide, the content of the other resin is preferably 50% by mass or less and more preferably 30% by mass or less with respect to the total amount of the polyimide layer. 0% by mass is particularly preferable.

3. Characteristics of Polyimide Film Since the Young's modulus, the total light transmittance, and the linear thermal expansion coefficient in the polyimide film of the present disclosure have been described above, description thereof is omitted here.

The polyimide film of the present disclosure has an excellent bending resistance, and when the static bending test is performed according to the following static bending test method, the inner angle of the test piece is preferably 90 ° or more, and 100 ° or more. More preferably, it is 110 ° or more. When the Young's modulus of the polyimide layer on one surface and the Young's modulus of the polyimide layer on the other surface are different from each other, when the surface of the polyimide layer having a relatively large Young's modulus is bent inside Moreover, it is preferable that the internal angle of the test piece when the static bending test is performed according to the following static bending test method is equal to or more than the lower limit value.
[Static bending test method]
A polyimide film test piece cut out to 15 mm × 40 mm is bent at a position of half of the long side, and both ends of the long side of the test piece sandwich a metal piece (100 mm × 30 mm × 6 mm) having a thickness of 6 mm from the upper and lower surfaces. Placed between glass plates (100 mm x 100 mm x 0.7 mm) from above and below with the tape fixed so that the overlap between the top and bottom surfaces of the test piece and the metal piece is 10 mm each. The test piece is fixed in a bent state with an inner diameter of 6 mm. At that time, a dummy test piece is sandwiched between the metal piece and the glass plate where there is no test piece, and is fixed with tape so that the glass plate is parallel. The test piece thus fixed in a bent state is left to stand for 24 hours in an environment of 60 ° C. and 90% relative humidity (RH), and then the glass plate and fixing tape are removed, and the test piece is attached to the test piece. Release this force. Thereafter, one end of the test piece is fixed, and the internal angle of the test piece 30 minutes after the force applied to the test piece is released is measured.

The polyimide film of the present disclosure has a tensile elastic modulus at 25 ° C. of 0.5 GPa or more when a test piece of 15 mm × 40 mm is measured according to JIS K7127, the tensile speed is 10 mm / min, and the distance between chucks is 20 mm. From the viewpoint of impact resistance and bending resistance, 0.8 GPa or more is more preferable, 1.0 GPa or more is further preferable, 1.5 GPa or more is preferable, and 2.0 GPa is more preferable. The above is most preferable. The upper limit of the tensile modulus is not particularly limited, but may be 5.2 GPa or less, may be 5.0 GPa or less, may be 4.5 GPa or less, and may be 4.0 GPa or less from the viewpoint of bending resistance. It is good.
The tensile elastic modulus was determined by cutting a test piece having a width of 15 mm × a length of 40 mm from a polyimide film using a tensile tester (for example, Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) at 25 ° C. The tensile speed can be 10 mm / min, and the distance between chucks can be 20 mm.

From the viewpoint of impact resistance, the polyimide film of the present disclosure preferably has a pencil hardness of 2B or more, more preferably B or more, still more preferably HB or more, and more than H. Particularly preferred.
The pencil hardness of the polyimide film is determined by JIS K5600-5-4 using a test pencil specified by JIS-S-6006 after conditioning the sample for 2 hours at a temperature of 25 ° C. and a relative humidity of 60%. (1999), a pencil hardness test (0.98 N load) is performed on the film surface, and the highest pencil hardness that does not cause scratches can be evaluated. For example, a pencil scratch coating film hardness tester manufactured by Toyo Seiki Co., Ltd. can be used.
It is preferable that the pencil hardness of the polyimide film can be achieved on the surface of the polyimide layer having a relatively large Young's modulus.

The polyimide film of the present disclosure has a surface area where the polyimide layer is peeled off when the adhesion test is performed according to the following adhesion test method. In view of surface hardness, it is preferably 10% or less, more preferably 5% or less.
<Adhesion test>
In accordance with the grid pattern test of JIS K5400, the polyimide layer on the surface is cut into a grid pattern at intervals of 1 mm using a cutter knife to form a 100 square grid. Next, cellophane tape (Nichiban Co., Ltd.) is applied on the lattice and then peeled off. After repeating this five times, peeling of the polyimide layer on the surface is observed.

In addition, the polyimide film of the present disclosure preferably has a yellowness (YI value) calculated in accordance with JIS K7373-2006 of 30.0 or less, more preferably 20.0 or less, It is further preferably 17.0 or less, and further preferably 16.0 or less.
The yellowness (YI value) calculated according to JIS K7373-2006 is preferably 11.0 or less, more preferably 10.0 or less, and preferably 5.0 or less. More preferably, it is still more preferably 3.0 or less, and particularly preferably 2.0 or less.
When the yellowness (YI value) is equal to or lower than the upper limit, the polyimide film of the present disclosure can be prevented from being colored yellow, improve light transmittance, and serve as a glass substitute material.
The yellowness (YI value) is assisted by a spectrocolorimetric method using an ultraviolet-visible near-infrared spectrophotometer (for example, JASCO Corporation V-7100) in accordance with JIS K7373-2006. Using the illuminant C and a two-degree field of view, tristimulus values X, Y, and Z in the XYZ color system are obtained based on transmittance measured in the range of 250 nm to 800 nm at 1 nm intervals. , Z can be calculated from the following equation.
YI = 100 (1.2769X−1.0592Z) / Y

In addition, the polyimide film of the present disclosure has a yellow color calculated in accordance with JIS K7373-2006 because yellowish coloring is suppressed, light transmittance is improved, and the polyimide film can be suitably used as a glass substitute material. The value (YI value / film thickness (μm)) obtained by dividing the degree (YI value) by the film thickness (μm) is preferably 0.330 or less, more preferably 0.150 or less, and 0.100. It is still more preferable that it is below, and it is especially preferable that it is below 0.030.
In the present disclosure, the value obtained by dividing the yellowness (YI value) by the film thickness (μm) (YI value / film thickness (μm)) is the third decimal place according to the rule B of JIS Z8401: 1999. Rounded value.

The haze value of the polyimide film of the present disclosure is preferably 10 or less, more preferably 5 or less, and even more preferably 1.5 or less from the viewpoint of light transmittance.
The haze value can be measured by a method according to JIS K-7105, for example, a haze meter HM150 manufactured by Murakami Color Research Laboratory.

The polyimide film of the present disclosure preferably has a birefringence in the thickness direction at a wavelength of 590 nm of 0.040 or less, more preferably 0.025 or less, and more preferably 0.020 or less. More preferably, it is particularly preferably 0.015 or less. When the birefringence is less than or equal to the above upper limit, the optical distortion of the polyimide film is reduced, and when the polyimide film is used as a display surface material, it is possible to suppress a decrease in display quality of the display. When a film having a large birefringence in the thickness direction at a wavelength of 590 nm is placed on the display surface and the display is viewed with polarized sunglasses, rainbow unevenness may occur and visibility may be reduced. From the viewpoint of suppressing the occurrence of rainbow unevenness when viewing the display while wearing polarized sunglasses, the birefringence index in the thickness direction of the film placed on the display surface is preferably 0.040 or less. Furthermore, when the birefringence in the thickness direction of the film placed on the display surface is 0.025 or less, color reproducibility when the display is viewed from an oblique direction is improved. From the viewpoint of improving color reproducibility when the display is viewed obliquely, the birefringence index in the thickness direction of the film placed on the display surface is more preferably 0.020 or less.
In addition, the birefringence of the thickness direction in the said wavelength 590nm of the polyimide film of this indication can be calculated | required as follows.
First, the thickness direction retardation value (Rth) of the polyimide film is measured with a light of 23 ° C. and a wavelength of 590 nm using a phase difference measuring device (for example, product name “KOBRA-WR” manufactured by Oji Scientific Instruments). To do. For the thickness direction retardation value (Rth), a phase difference value at 0 degree incidence and a phase difference value at an incidence angle of 40 degrees are measured, and the thickness direction retardation value Rth is calculated from these phase difference values. The retardation value at an oblique incidence of 40 degrees is measured by making light having 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 determined by substituting it into the formula: Rth / d. Said d represents the film thickness (nm) of a polyimide film.
The thickness direction retardation value is nx the refractive index in the slow axis direction in the in-plane direction of the film (the direction in which the refractive index in the film in-plane direction is maximum), and the fast axis direction in the film plane (film surface). 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.

Moreover, as a preferable form of the polyimide film of the present disclosure, the ratio of the number of fluorine atoms (F) and the number of carbon atoms (C) on the surface of at least one film measured by X-ray photoelectron spectroscopy of the polyimide film (F / C) is preferably 0.01 or more and 1 or less, and more preferably 0.05 or more and 0.8 or less.
Moreover, the ratio (F / N) of the number of fluorine atoms (F) and the number of nitrogen atoms (N) on the surface of at least one film measured by X-ray photoelectron spectroscopy of the polyimide film is 0.1 or more and 20 or less. It is preferably 0.5 or more and 15 or less.
Here, the said ratio by the measurement of X-ray photoelectron spectroscopy (XPS) can be calculated | required from the value of atomic% of each atom measured using an X-ray photoelectron spectrometer (for example, Thermo Scientific Thea Probe). .

4). The manufacturing method of a polyimide film The manufacturing method of the polyimide film of this indication should just be a manufacturing method which can obtain the polyimide film of this indication mentioned above, and although it does not specifically limit, For example, as a 1st manufacturing method,
Preparing a polyimide molded body;
A step of preparing a polyimide precursor resin composition comprising a polyimide precursor and an organic solvent;
Applying the polyimide precursor resin composition to at least one surface of the polyimide molded body to form a polyimide precursor resin coating;
And a step of imidizing the polyimide precursor by heating.
In the first production method, as a method for producing a polyimide film having three or more polyimide layers, for example, a step of applying a polyimide precursor resin composition to form a polyimide precursor resin coating film, After performing until it becomes the desired number of layers, the method of imidizing each polyimide precursor which each polyimide precursor resin coating film contains by the process of imidating is mentioned. Two or more layers of the polyimide precursor resin coating film may be formed only on one surface of the polyimide molded body, or may be formed on both surfaces of one surface and the other surface.
As a method for producing a polyimide film having three polyimide layers by the first production method, for example,
Preparing a polyimide molded body;
Preparing a first polyimide precursor resin composition comprising a polyimide precursor and an organic solvent, and a second polyimide precursor resin composition comprising a polyimide precursor and an organic solvent;
Applying the first polyimide precursor resin composition to one surface of the polyimide molded body to form a first polyimide precursor resin coating;
Applying the second polyimide precursor resin composition to the other surface of the polyimide molded body to form a second polyimide precursor resin coating;
A step of imidizing a polyimide precursor included in the first polyimide precursor resin coating film and a polyimide precursor included in the second polyimide precursor resin coating film by heating, and including the first The manufacturing method in which the polyimide precursor resin composition and the second polyimide precursor resin composition may be the same may be mentioned.
In the first manufacturing method, the polyimide molded body and each polyimide precursor resin coating film formed to have a desired number of layers become polyimide layers.
The first production method is preferable from the viewpoint of easily reducing the birefringence of the polyimide film. According to the first production method, the birefringence in the thickness direction at a wavelength of 590 nm is 0.035 or less, more preferably 0.030 or less, more preferably 0.025 or less, more preferably 0.020 or less. A polyimide film can be suitably formed.

In the first production method, when two or more polyimide layers are formed on one surface of the polyimide molded body, each polyimide precursor resin coating film used for forming the two or more polyimide layers is used. Since the imidization step is performed after all the formation, the mixing region can be formed at the boundary between adjacent polyimide layers in the two or more polyimide layers, thereby improving interlayer adhesion and interference fringes. It is preferable from the viewpoint of suppressing the occurrence of the above.

Hereinafter, in the first production method, a step of preparing a polyimide molded body (hereinafter referred to as a polyimide molded body preparation step), a step of preparing a polyimide precursor resin composition (hereinafter referred to as a polyimide precursor resin composition preparation step). ), Applying a polyimide precursor resin composition to form a polyimide precursor resin coating film (hereinafter referred to as polyimide precursor resin coating film forming process), and a polyimide precursor contained in the polyimide precursor resin composition The step of imidization (hereinafter referred to as imidization step) will be described in detail.

(1) Polyimide molded body preparation process As a polyimide molded body used for the said 1st manufacturing method, the film-like polyimide molded body produced with the following manufacturing methods can be used, for example.
As a manufacturing method of a film-like polyimide molded body, for example, as manufacturing method A,
A step of preparing a polyimide precursor resin composition comprising a polyimide precursor and an organic solvent;
Applying the polyimide precursor resin composition to a support to form a polyimide precursor resin coating;
And a step of imidizing the polyimide precursor by heating.
The production method A is preferable from the viewpoint of easily reducing the birefringence of the polyimide film, and suitably forms a polyimide film having a birefringence in the thickness direction at a wavelength of 590 nm of 0.025 or less, more preferably 0.020 or less. Is possible. In the said 1st manufacturing method, when the said manufacturing method A is used as a manufacturing method of a polyimide molded body, it is still more preferable at the point with the high effect of reducing the birefringence of a polyimide film, and the birefringence of the thickness direction in wavelength 590nm A polyimide film having a thickness of 0.025 or less, more preferably 0.020 or less, can be suitably formed.
In the said manufacturing method A, as a polyimide precursor resin composition, the thing similar to the polyimide precursor resin composition obtained by the "polyimide precursor resin composition preparation process" mentioned later can be used, and a polyimide precursor resin is used. The method for forming the coating film and the method for imidizing can be the same as the “polyimide precursor resin coating film forming step” and the “imidization step” described later, respectively.
In the said manufacturing method A, as a support body, the thing similar to the support body used for the 2nd manufacturing method mentioned later is mentioned, for example.
The production method A may further include a stretching step of stretching at least one of the polyimide precursor resin coating film and the imidized coating film obtained by imidizing the polyimide precursor resin coating film. . The stretching step can be the same as the stretching step of the second manufacturing method described later.

Moreover, as another manufacturing method of a film-like polyimide molded body, for example, as manufacturing method B,
A step of preparing a polyimide resin composition containing polyimide and an organic solvent;
And a step of applying the polyimide resin composition to a support to form a polyimide resin coating film.
The production method B can be suitably used when the polyimide to be used has a solvent solubility such that 5% by mass or more is dissolved in an organic solvent at 25 ° C.
The production method B is preferable from the viewpoint of easily reducing the yellowness (YI value) of the polyimide film, and the yellowness (YI value) calculated in accordance with JIS K7373-2006 is divided by the film thickness (μm). A polyimide film having a value (YI value / film thickness (μm)) of 0.330 or less, more preferably 0.200 or less, and still more preferably 0.150 or less can be suitably formed.
In the said manufacturing method B, as a polyimide resin composition, the thing similar to the polyimide resin composition of the 3rd manufacturing method mentioned later can be used, As a method of forming a polyimide resin coating film, it mentions 3rd mentioned later. It can be made to be the same as that of the polyimide resin coating film formation process of the manufacturing method.
Moreover, in the said manufacturing method B, as a support body, the thing similar to the support body used for the 2nd manufacturing method mentioned later is mentioned, for example.

(2) Polyimide precursor resin composition preparation step The polyimide precursor resin composition prepared in the first production method contains a polyimide precursor and an organic solvent, and optionally contains additives. It may be.
The polyimide precursor is a polyamic acid obtained by polymerization of a tetracarboxylic acid component and a diamine component. In the first production method, the tetracarboxylic acid component and the diamine component used for the polyimide precursor are not particularly limited. For example, the tetracarboxylic dianhydride and the diamine that become the tetracarboxylic acid residue of the polyimide described above. The diamine used as a residue can be mentioned, respectively.

The number average molecular weight of the polyimide precursor is preferably 2000 or more, more preferably 4000 or more, from the viewpoint of strength when it is used as a film. On the other hand, if the number average molecular weight is too large, the viscosity is high and the workability may be lowered, so that it is preferably 1000000 or less, and more preferably 500000 or less.
The number average molecular weight of the polyimide precursor can be determined by NMR (for example, AVANCE III manufactured by BRUKER). For example, a polyimide precursor solution is applied to a glass plate and dried at 100 ° C. for 5 minutes, and then 10 mg of solid content is dissolved in 7.5 ml of dimethyl sulfoxide-d6 solvent, and NMR measurement is performed to bond to an aromatic ring. The number average molecular weight can be calculated from the peak intensity ratio of hydrogen atoms.

In addition, the polyimide precursor has a weight average molecular weight of preferably 2000 or more, and more preferably 4000 or more, from the viewpoint of strength when used as a film. On the other hand, if the weight average molecular weight is too large, the viscosity becomes high and the workability such as filtration may be lowered, and therefore it is preferably 1000000 or less, and more preferably 500000 or less.
The weight average molecular weight of the polyimide precursor can be measured by gel permeation chromatography (GPC). Specifically, the polyimide precursor was made into an N-methylpyrrolidone (NMP) solution having a concentration of 0.5% by weight, and the developing solvent was a 10 mmol% LiBr-NMP solution having a water content of 500 ppm or less. Using HLC-8120, column used: GPC LF-804 manufactured by SHODEX, measurement is performed under the conditions of a sample injection amount of 50 μL, a solvent flow rate of 0.5 mL / min, and 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 the synthesis of the polyimide precursor (polyamic acid) is not particularly limited as long as it can dissolve the above-described tetracarboxylic dianhydride and diamine. For example, an aprotic polar solvent or a water-soluble alcohol solvent is used. Can be used. In the present disclosure, among others, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone, etc. It is preferable to use an organic solvent containing a nitrogen atom of γ-butyrolactone or the like. Among them, it is preferable to use an organic solvent containing a nitrogen atom, and it is more preferable to use N, N-dimethylacetamide, N-methyl-2-pyrrolidone or a combination thereof. The organic solvent is a solvent containing carbon atoms.

Moreover, when preparing the said polyimide precursor solution combining 2 or more types of diamine, an acid dianhydride may be added to the mixed solution of 2 or more types of diamine, and a polyamic acid may be synthesize | combined. The above diamine component may be added to the reaction solution step by step at an appropriate molar ratio to control the sequence in which each raw material is incorporated into the polymer chain to some extent.
When a diamine having one or two silicon atoms in the main chain is used, for example, in a reaction solution in which a diamine having one or two silicon atoms in the main chain is dissolved, one silicon atom in the main chain or An amide in which a diamine having one or two silicon atoms in the main chain is reacted at both ends of the acid dianhydride by introducing and reacting an acid dianhydride in a molar ratio of 0.5 equivalent of two diamines The acid may be synthesized, the remaining diamine may be added in whole or in part thereto, and acid dianhydride may be added to polymerize the polyamic acid. When polymerized in this manner, a diamine having one or two silicon atoms in the main chain is introduced into the polyamic acid in a linked form via one acid dianhydride. Polymerization of polyamic acid by such a method is because the positional relationship of amic acid having one or two silicon atoms in the main chain is specified to some extent, and it is easy to obtain a film excellent in impact resistance and bending resistance. preferable.

When the number of moles of diamine in the polyimide precursor solution (polyamic acid solution) is X and the number of moles of tetracarboxylic dianhydride is Y, Y / X may be 0.9 or more and 1.1 or less. Preferably, it is 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. By setting it as such a range, the molecular weight (polymerization degree) of the polyamic acid obtained can be adjusted moderately.
The procedure of the polymerization reaction can be appropriately selected from known methods and is not particularly limited.
Moreover, the polyimide precursor solution obtained by the synthesis reaction may be used as it is, and other components may be mixed there if necessary. The solvent of the polyimide precursor solution is dried and dissolved in another solvent. It may be used.

The viscosity of the polyimide precursor solution at 25 ° C. is preferably 500 cps or more and 100,000 cps or less from the viewpoint of forming a uniform coating film and a polyimide layer.
The viscosity of the polyimide precursor solution can be measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25 ° C. and a sample amount of 0.8 ml.

The polyimide precursor resin composition may contain an additive as necessary. Examples of the additive include a silica filler for facilitating winding, and a surfactant for improving film forming property and defoaming property, and the same as described in the polyimide layer described above. Can be used.

The organic solvent used in the polyimide precursor resin composition is not particularly limited as long as the polyimide precursor can be dissolved. For example, containing nitrogen atoms such as N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone Organic solvent: γ-butyrolactone or the like can be used, and among them, an organic solvent containing a nitrogen atom is preferably used.

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 point of forming a polyimide layer having a uniform coating film and a handleable strength. Preferably, it is preferably 60% by mass or more, and the upper limit may be appropriately adjusted depending on the components contained.
The organic solvent in the polyimide precursor resin composition is preferably 40% by mass or more and more preferably 50% by mass or more in the resin composition from the viewpoint of forming a uniform coating film and a polyimide layer. Preferably, it is 99% by mass or less.

The polyimide precursor resin composition preferably has a moisture content of 1000 ppm or less from the viewpoint of improving the storage stability of the polyimide precursor resin composition and improving the productivity. If the polyimide precursor resin composition contains a large amount of moisture, the polyimide precursor may be easily decomposed.
The water content of the polyimide precursor resin composition can be determined using a Karl Fischer moisture meter (for example, a trace moisture measuring device CA-200, manufactured by Mitsubishi Chemical Corporation).

(3) Polyimide precursor resin coating film forming step In the step of applying the polyimide precursor resin composition to at least one surface of the polyimide molded body to form a polyimide precursor resin coating film, the coating means includes: The coating method is not particularly limited as long as it can be applied with a desired film thickness, and known methods such as a die coater, a comma coater, a roll coater, a gravure coater, a curtain coater, a spray coater, and a lip coater can be used.
Application may be performed by a single-wafer coating apparatus or a roll-to-roll coating apparatus.

After applying the polyimide precursor resin composition, the solvent in the polyimide precursor resin composition is dried at a temperature of 150 ° C. or lower, preferably 30 ° C. or higher and 120 ° C. or lower until the coating film is 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 film thickness of the polyimide precursor resin coating film, the type of solvent, the drying temperature, etc., but is usually 1 minute to 60 minutes, preferably 2 minutes to 30 minutes. Is preferred. When exceeding an upper limit, it is unpreferable from the surface of the production efficiency of a polyimide film. On the other hand, when the value is below the lower limit, the appearance of the resulting polyimide film may be affected by rapid solvent drying.

The method for drying the solvent is not particularly limited as long as the solvent can be dried at the above temperature. For example, an oven, a drying furnace, a hot plate, infrared heating, or the like can be used.
When high management 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, the oxygen concentration is preferably 100 ppm or less, and more preferably 50 ppm or less. When heat treatment is performed in the atmosphere, the film may be oxidized and colored, or the performance may deteriorate.

(4) Imidization process In the said 1st manufacturing method, the said polyimide precursor is imidized by heating.
The imidization temperature may be appropriately selected according to the structure of the polyimide precursor.
Usually, the temperature rise start temperature is preferably 30 ° C. or higher, more preferably 100 ° C. or higher. On the other hand, the temperature rise end temperature is preferably 250 ° C. or higher.

The rate of temperature increase is preferably selected as appropriate depending on the thickness of the polyimide layer to be obtained. When the thickness of the polyimide layer is thick, it is preferable to decrease the rate of temperature increase.
From the viewpoint of the production efficiency of the polyimide film, it 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. It is preferable to set the temperature increase rate from the viewpoint that the appearance defect and strength reduction of the film can be suppressed, and the whitening associated with the imidization reaction can be controlled, and the light transmittance is improved.

The temperature increase may be continuous or stepwise, but it is preferable to make it continuous from the viewpoint of controlling the appearance of the film, suppressing the strength reduction, and controlling the whitening associated with the imidization reaction. Moreover, in the above-mentioned whole temperature range, the temperature rising rate may be constant or may be changed in the middle.

The atmosphere at the time of temperature increase in imidation is preferably an inert gas atmosphere. The inert gas atmosphere is preferably a nitrogen atmosphere, the oxygen concentration is preferably 100 ppm or less, and more preferably 50 ppm or less. When heat treatment is performed in the atmosphere, the film may be oxidized and colored, or the performance may deteriorate.
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, there is little influence of oxygen on the optical properties, and an inert gas atmosphere is not used. In addition, a polyimide having a high light transmittance can be obtained.

The heating method for imidation is not particularly limited as long as the temperature can be raised at the above temperature. For example, an oven, a heating furnace, infrared heating, electromagnetic induction heating, or the like can be used.

In order to obtain a final polyimide film, it is preferable to proceed the reaction to 90% or more, further 95% or more, and further 100%.
In order to allow the reaction to proceed to 90% or more, more preferably 100%, it is preferable to hold at a temperature rising end temperature for a certain period of time. Minutes are preferred.
The imidation rate can be measured by analyzing the spectrum by infrared measurement (IR).

As a 2nd manufacturing method of the polyimide film of this indication, for example,
Preparing a first polyimide precursor resin composition containing a polyimide precursor and an organic solvent, and a second polyimide precursor resin composition containing a polyimide precursor and an organic solvent, respectively;
Applying the first polyimide precursor resin composition to a support to form a first polyimide precursor resin coating;
Applying the second polyimide precursor resin composition on the first polyimide precursor resin coating film to form a second polyimide precursor resin coating film;
A step of imidizing a polyimide precursor contained in the first polyimide precursor resin composition and a polyimide precursor contained in the second polyimide precursor resin composition by heating. Is mentioned.
In the second production method, as a method of producing a polyimide film having three or more polyimide layers, for example, a step of applying a polyimide precursor resin composition to form a polyimide precursor resin coating film, After performing until it becomes the desired number of layers, the method of imidizing each polyimide precursor which each polyimide precursor resin coating film contains by the process of imidating is mentioned.
As a method for producing a polyimide film having three polyimide layers by the second production method, for example,
A first polyimide precursor resin composition containing a polyimide precursor and an organic solvent, a second polyimide precursor resin composition containing a polyimide precursor and an organic solvent, a polyimide precursor, and an organic solvent. A step of preparing a third polyimide precursor resin composition comprising:
Applying the first polyimide precursor resin composition to a support to form a first polyimide precursor resin coating;
Applying the second polyimide precursor resin composition on the first polyimide precursor resin coating film to form a second polyimide precursor resin coating film;
Applying the third polyimide precursor resin composition on the second polyimide precursor resin coating to form a third polyimide precursor resin coating;
By heating, the polyimide precursor contained in the first polyimide precursor resin composition, the polyimide precursor contained in the second polyimide precursor resin composition, and the third polyimide precursor resin composition A step of imidizing a polyimide precursor contained in the first polyimide precursor resin composition and the third polyimide precursor resin composition may be the same composition, Can be mentioned.
In the said 2nd manufacturing method, each polyimide precursor resin coating film formed so that it might become a desired number of layers turns into a polyimide layer, respectively.
The second production method is preferable from the viewpoint of easily reducing the birefringence of the polyimide film. According to the second production method, it is possible to suitably form a polyimide film having a birefringence in the thickness direction at a wavelength of 590 nm of 0.025 or less, more preferably 0.020 or less.

In the second manufacturing method, the step of preparing a polyimide precursor resin composition, the step of applying a polyimide precursor resin composition to form a polyimide precursor resin coating, and the polyimide precursor resin composition contain The step of imidizing the polyimide precursor can be the same as in the first manufacturing method.

In the second manufacturing method, after forming each polyimide precursor resin coating film, performing the imidization step can form the mixing region at the boundary between adjacent polyimide layers. This is preferable from the viewpoint of improving the adhesion and suppressing the generation of interference fringes.

The support used in the second production method is not particularly limited as long as the surface is smooth and the material has heat resistance and solvent resistance. For example, an inorganic material such as a glass plate, a metal plate having a mirror-finished surface, and the like can be given. The shape of the support is selected depending on 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.

In addition, the second manufacturing method is a method of forming the polyimide precursor resin coating film after all the polyimide precursor resin coating films are formed and before imidizing, and imidizing the polyimide precursor resin coating film. You may further have the process (henceforth an extending | stretching process) of extending | stretching at least one of the laminated body of the coating film after the imidation after a process.

In the said manufacturing method, when it has an extending process, an imidation process may be performed with respect to the polyimide precursor in the said polyimide precursor resin coating film before an extending process, and the said polyimide precursor resin after an extending process You may perform with respect to the polyimide precursor in a coating film, and with respect to both the polyimide precursor in the said polyimide precursor resin coating film before an extending process, and the polyimide precursor which exists in the film | membrane after an extending process. You can go.

In the second manufacturing method, when the stretching step is performed, in the imidizing step, it is more preferable that the imidization ratio of the polyimide precursor is 50% or more before the stretching step. Even if the imidization rate is 50% or more before the stretching step, the film is stretched after the step, and then heated at a higher temperature for a certain period of time to perform imidization. Whitening is suppressed. In particular, from the point that the impact resistance of the polyimide film is improved, it is preferable that the imidization ratio is 80% or more in the imidization process before the stretching process, and the reaction is allowed to proceed to 90% or more, and further to 100%. It is preferable. By stretching after imidization, a rigid polymer chain is easily oriented, so that it is estimated that surface hardness is improved and impact resistance is improved.

In the case of having a stretching step in the second production method, it is preferable to include a step of stretching the laminate of the coating film after imidization from the viewpoint of improving the impact resistance of the polyimide film.

When the second production method has a stretching step, the step of stretching 101% or more and 10000% or less when the initial dimension before stretching is 100% is performed while heating at 80 ° C. or more. preferable.
The heating temperature during stretching is preferably in the range of glass transition temperature ± 50 ° C. of the polyimide or polyimide precursor, and preferably in the range of glass transition temperature ± 40 ° C. If the stretching temperature is too low, the film may not be deformed and the orientation may not be sufficiently induced. On the other hand, if the stretching temperature is too high, the orientation obtained by stretching is relaxed by the temperature, and there is a possibility that sufficient orientation cannot be obtained.
The stretching step may be performed simultaneously with the imidization step. 80% or more of imidization rate, more than 90%, even more than 95%, especially extending the film after imidization after substantially 100% imidation improves the impact resistance of the polyimide film This is preferable.

The draw ratio of the polyimide film is preferably from 101% to 10,000%, more preferably from 101% to 500%. By stretching in the above range, the impact resistance of the resulting 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 apparatus. Moreover, there is no restriction | limiting in particular in the extending | stretching method, For example, it can extend | stretch through a heating furnace using the extending | stretching apparatus which has conveyance apparatuses, such as a tenter. The polyimide film may be stretched only in one direction (longitudinal stretching or lateral stretching), or may be stretched in two directions by simultaneous biaxial stretching, sequential biaxial stretching, oblique stretching, or the like.

As a manufacturing method of the polyimide film of the present disclosure, as a third manufacturing method,
Preparing a polyimide molded body;
A step of preparing a polyimide resin composition containing polyimide and an organic solvent;
And a step of applying the polyimide resin composition to at least one surface of the polyimide molded body to form a polyimide resin coating film.
Moreover, as a manufacturing method of the polyimide film of this indication, as a 4th manufacturing method,
A step of preparing a first polyimide resin composition containing polyimide and an organic solvent, and a second polyimide resin composition containing polyimide and an organic solvent;
Applying the first polyimide resin composition to a support to form a first polyimide resin coating;
And a step of applying the second polyimide resin composition on the first polyimide resin coating film to form a second polyimide resin coating film.
In the third manufacturing method and the fourth manufacturing method, as a method of manufacturing a polyimide film having three or more polyimide layers, for example, a step of forming a polyimide resin coating film has a desired number of layers. The method to do is mentioned.

The third production method and the fourth production method can be suitably used when the polyimide to be used has solvent solubility such that 5% by mass or more dissolves in an organic solvent at 25 ° C.
The third manufacturing method and the fourth manufacturing method are preferable from the viewpoint of easily reducing the yellowness (YI value) of the polyimide film, and the yellowness (YI value) calculated in accordance with JIS K7373-2006. A polyimide film having a value (YI value / film thickness (μm)) divided by the film thickness (μm) of 0.330 or less, more preferably 0.200 or less, and even more preferably 0.150 or less can be suitably formed. It is.

In the third manufacturing method, the step of preparing the polyimide molded body can be the same as the polyimide molded body preparing step of the first manufacturing method. Among these, in the third manufacturing method, it is preferable to use the manufacturing method B as a method for manufacturing a polyimide molded body in terms of a high effect of reducing the yellowness (YI value) of the polyimide film, and the JIS K7373. -A polyimide whose yellowness (YI value) calculated in accordance with 2006 is divided by the film thickness (μm) (YI value / film thickness (μm)) is 0.030 or less, more preferably 0.025 or less. A film can be suitably formed. Also by the fourth manufacturing method, the value (YI value / film thickness (μm)) obtained by dividing the yellowness (YI value) calculated in accordance with JIS K7373-2006 by the film thickness (μm) is 0. A polyimide film of 030 or less, more preferably 0.025 or less can be suitably formed.
Examples of the support used in the fourth manufacturing method include the same supports as those used in the second manufacturing method.
Hereinafter, a step of preparing a polyimide resin composition (hereinafter referred to as a polyimide resin composition preparation step) and a step of forming a polyimide resin coating film (hereinafter referred to as polyimide) in the third manufacturing method and the fourth manufacturing method. The resin coating film forming step) will be described in detail.

The polyimide used in the polyimide resin composition preparation step of the third manufacturing method and the fourth manufacturing method is the polyimide having the solvent solubility described above from the same polyimides described in the polyimide layer. It can be selected and used. As a method for imidization, it is preferable to use chemical imidation using a chemical imidizing agent instead of heat dehydration for the dehydration ring-closing reaction of the polyimide precursor. In the case of performing chemical imidization, 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 a dehydration catalyst. Examples of the acid anhydride are not limited to acetic anhydride, and propionic acid anhydride, n-butyric acid anhydride, benzoic acid anhydride, trifluoroacetic acid anhydride, and the like, but are not particularly limited. At that time, a tertiary amine such as pyridine or β-picolinic acid may be used in combination. However, when these amines remain in the film, the optical properties, particularly the yellowness (YI value), are reduced. Therefore, the reaction liquid reacted from the precursor to the polyimide is not cast as it is, It is preferable to form the film after purification by reprecipitation or the like, and removing components other than polyimide to 100 ppm or less of the total weight of the polyimide.

In the polyimide resin composition preparation step of the third manufacturing method and the fourth manufacturing method, examples of the organic solvent used in the reaction solution for performing chemical imidation of the polyimide precursor include the first manufacturing method. The thing similar to what was demonstrated in the said polyimide precursor resin composition preparation process can be used. Examples of the organic solvent used when redissolving the polyimide purified from the reaction solution in the polyimide resin composition preparation step include ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol mono-normal-butyl ether, Ethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ortho-dichlorobenzene, xylene, cresol, chlorobenzene, isobutyl acetate, isopentyl acetate, normal-butyl acetate, normal-propyl acetate, normal-pentyl acetate, cyclohexanol, cyclohexanone, 1.4-Dioxane, tetrachloroethylene, toluene, methyl isobutyl ketone, methylcyclohexanol, methylcyclohexane Sanone, methyl-normal-butyl ketone, dichloromethane, dichloroethane, and mixed solvents thereof are mentioned. Among them, at least one selected from the group consisting of dichloromethane, normal-butyl acetate, propylene glycol monomethyl ether acetate, and mixed solvents thereof is used. It can be preferably used.

The polyimide resin composition may contain an additive as necessary. As said additive, the thing similar to what was demonstrated in the said polyimide precursor resin composition preparation process in a said 1st manufacturing method can be used.
Moreover, in the said 3rd manufacturing method and the said 4th manufacturing method, as a method of making the content water content of the said polyimide resin composition into 1000 ppm or less, the said polyimide precursor resin composition preparation process in a said 1st manufacturing method A method similar to the method described in the above can be used.

Further, in the polyimide resin coating film forming step in the third manufacturing method and the fourth manufacturing method, the coating method is the same as described in the polyimide precursor resin coating film forming step of the first manufacturing method. Things can be used.
In the polyimide resin coating film forming step in the third manufacturing method and the fourth manufacturing method, after applying the polyimide resin composition, the solvent is dried as necessary. The drying temperature is preferably 80 ° C. or higher and 150 ° C. or lower under normal pressure. It is preferable that the pressure be in the range of 10 ° C. to 100 ° C. under reduced pressure. In the third manufacturing method and the fourth manufacturing method, after the solvent is dried at 150 ° C. or lower, the solvent may be further dried at 150 ° C. or higher and 300 ° C. or lower.

Further, the fourth manufacturing method may include a stretching step of stretching the laminate of the polyimide resin coating film after forming all the polyimide resin coating films. The said extending process can be made to be the same as the extending process in the said 2nd manufacturing method.

5). Use of polyimide film The use of the polyimide film of the present disclosure is not particularly limited, and can be used as a member such as a base material or a surface material for which a glass product such as a thin plate glass has been conventionally used. Since the polyimide film of the present disclosure has improved impact resistance and bending resistance, it can be suitably used as a member such as a base material for display or a surface material that can handle curved surfaces.
Specifically, the polyimide film of the present disclosure is, for example, a thin and bent 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, or the like. It can be used suitably. In addition, the polyimide film of the present disclosure includes a member for an image display device such as a liquid crystal display device and an organic EL display device, a member for a touch panel, a flexible printed circuit board, a surface protection film and a substrate material for a solar cell panel, an optical waveguide, etc. The present invention can also be applied to other members, other semiconductor-related members and the like.

II. Laminate The laminate of the present disclosure is a laminate having the above-described polyimide film of the present disclosure and a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound.

Since the laminate of the present disclosure uses the polyimide film of the present disclosure described above, it has improved impact resistance and bending resistance, and further has a hard coat layer, thereby improving surface hardness, Impact resistance is further improved.

1. Polyimide film Since the polyimide film of this indication mentioned above can be used as a polyimide film used for the layered product of this indication, explanation here is omitted.

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

(1) Radical polymerizable compound The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group possessed by the radical polymerizable compound is not particularly limited as long as it is a functional group capable of causing a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond. Specific examples include a vinyl group and a (meth) acryloyl group. When the radical polymerizable compound has two or more radical polymerizable groups, these radical polymerizable groups may be the same or different from each other.

The number of radical polymerizable groups contained in one molecule of the radical polymerizable compound is preferably 2 or more, and more preferably 3 or more from the viewpoint of improving the hardness of the hard coat layer.
As the radically polymerizable compound, a compound having a (meth) acryloyl group is preferable from the viewpoint of high reactivity, and further, from the viewpoint of adhesion, light transmittance, surface hardness, and impact resistance. A compound having two or more (meth) acryloyl groups in one molecule is preferable. For example, a compound called a polyfunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in one molecule, a molecule called urethane (meth) acrylate, polyester (meth) acrylate, or epoxy (meth) acrylate An oligomer having a molecular weight of several hundreds to several thousands having several (meth) acryloyl groups therein can be preferably used.
In this specification, (meth) acryloyl represents each of acryloyl and methacryloyl, and (meth) acrylate represents each of acrylate and methacrylate.

Specific examples of the radical polymerizable compound include 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 (eg ethoxylated (ethylene oxide modified) bisphenol A di (meth) acrylate), trimethylolpropane tri (meth) acrylate, tri Methylolethane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaeryth Polyol polyacrylates such as lithol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, bisphenol A diglycidyl ether diacrylate, hexanediol diglycidyl ether diacrylate, etc. Examples include acrylates, urethane acrylates obtained by the reaction of polyisocyanate and hydroxyl group-containing acrylates such as hydroxyethyl acrylate.

(2) Cationic polymerizable compound The cationic polymerizable compound is a compound having a cationic polymerizable group. The cationic polymerizable group possessed by the cationic polymerizable compound is not particularly limited as long as it is a functional group capable of causing a cationic polymerization reaction, and examples thereof include an epoxy group, an oxetanyl group, and a vinyl ether group. When the cationic polymerizable compound has two or more cationic polymerizable groups, these cationic polymerizable groups may be the same or different from each other.

The number of cationically polymerizable groups contained in one molecule of the cationically polymerizable compound is preferably 2 or more, and more preferably 3 or more from the viewpoint of improving the hardness of the hard coat layer.
The cationic polymerizable compound is preferably a compound having at least one of an epoxy group and an oxetanyl group as the cationic polymerizable group, in terms of adhesion, light transmittance, surface hardness, and impact resistance. Therefore, a compound having two or more epoxy groups and oxetanyl groups in one molecule is more preferable. Cyclic ether groups such as epoxy groups and oxetanyl groups are preferred from the viewpoint of small shrinkage accompanying the polymerization reaction. In addition, compounds having an epoxy group among the cyclic ether groups are easily available as compounds having various structures, do not adversely affect the durability of the obtained hard coat layer, and easily control the compatibility with the radical polymerizable compound. There is an advantage. Of the cyclic ether groups, the oxetanyl group has a high degree of polymerization and low toxicity compared to the epoxy group. When the obtained hard coat layer is combined with a compound having an epoxy group, a cation in the coating film is obtained. There are advantages such as speeding up the network formation obtained from the polymerizable compound and forming an independent network without leaving unreacted monomer in the film even in a region mixed with the radical polymerizable compound.

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

Examples of the alicyclic epoxy resin include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (UVR-6105, UVR-6107, UVR-6110), bis-3,4-epoxycyclohexylmethyl adipate. (UVR-6128) (The product 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 diglycol Dil 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), dibromoneopentylglycol diglycidyl ether (Denacol EX-221) The name is made by Nagase ChemteX).

Other commercially available epoxy resins include trade names such as Epicoat 825, Epicoat 827, Epicoat 828, Epicoat 828EL, Epicoat 828XA, Epicoat 834, Epicoat 801, Epicoat 801P, Epicoat 802, Epicoat 815, Epicoat 815XA, Epicoat 816A, Epicoat 819, Epicoat 834X90, Epicoat 1001B80, Epicoat 1001X70, Epicoat 1001X75, Epicoat 1001T75, Epicoat 806, Epicoat 806P, Epicoat 807, Epicoat 152, Epicoat 154, Epicoat 871, Epicoat 191P, Epicoat YX310, Epicoat DX255, Epicoat YX8000, Etc. (above product name, Turbocharger bread epoxy resin) and the like.

Examples of the cationically polymerizable compound having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane (OXT-101), 1,4-bis-3-ethyloxetane-3-ylmethoxymethylbenzene (OXT-121). Bis-1-ethyl-3-oxetanyl methyl ether (OXT-221), 3-ethyl-3--2-ethylhexyloxymethyl oxetane (OXT-212), 3-ethyl-3-phenoxymethyl oxetane (OXT- 211) (in the parentheses, the product names are manufactured by Toa Gosei Co., Ltd.), and the product names Etanacol EHO, Etanacol OXBP, Etanacol OXTP, and Etanacol OXMA (above, trade names, manufactured by Ube Industries).

(3) Polymerization initiator At least one polymer of the radical polymerizable compound and the cationic polymerizable compound contained in the hard coat layer used in the present disclosure is, for example, the radical polymerizable compound or the cationic polymerizable compound. It can be obtained by adding a polymerization initiator to at least one kind, 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, a 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 advance radical polymerization and cationic polymerization.

The radical polymerization initiator may be any substance that can release a substance that initiates radical polymerization by light irradiation and / or heating. For example, photo radical polymerization initiators include imidazole derivatives, bisimidazole derivatives, N-aryl glycine 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-diphenylethane-1-one (trade name Irgacure 651, Ciba Japan Co., Ltd.) 1-hydroxy-cyclohexyl-phenyl Ketone (trade name Irgacure 184, manufactured by Ciba Japan), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one (trade names Irgacure 369, Ciba Japan ( Bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) titanium) (trade name Irgacure 784) However, it is not limited to these.

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, Irgacure 1870 manufactured by Ciba Japan Co., Ltd. , Irgacure OXE01, DAROCUR TPO, DAROCUR1173, Japan Siber Hegner Co., Ltd. of SpeedcureMBB, SpeedcurePBZ, SpeedcureITX, SpeedcureCTX, SpeedcureEDB, Esacure ONE, Esacure KIP150, Esacure KTO46, manufactured by Nippon Kayaku Co., of (stock) KAYACURE DETX-S, KAYACURE CTX , KAYACURE BMS, KAYACURE DMBI, etc. may be mentioned.

Moreover, the cationic polymerization initiator should just be able to discharge | release the substance which starts cationic polymerization by at least any one of light irradiation and a heating. Examples of the cationic polymerization initiator include sulfonic acid ester, imide sulfonate, dialkyl-4-hydroxysulfonium salt, arylsulfonic acid-p-nitrobenzyl ester, silanol-aluminum complex, (η ⁶ -benzene) (η ⁵ -cyclopentadidiene). Enyl) iron (II) and the like, and more specific examples include, but are not limited to, benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tosiphthalimide and the like.

Examples of radical polymerization initiators that can be used as 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 chloride such as diphenyliodonium, ditolyliodonium, bis (p-tert-butylphenyl) iodonium, bis (p-chlorophenyl) iodonium, bromide, borofluoride, hexafluorophosphate salt, hexafluoro Iodonium salts such as antimonate salts, chlorides of sulfonium such as triphenylsulfonium, 4-tert-butyltriphenylsulfonium, tris (4-methylphenyl) sulfonium, bromide, borofluoride, hexa Sulfonium salts such as fluorophosphate salts and hexafluoroantimonate salts, 2,4,6-tris (trichloromethyl) -1,3,5-triazine, 2-phenyl-4,6-bis (trichloromethyl) -1, 2,4,6-substituted-1,3,5 triazine compounds such as 3,5-triazine, 2-methyl-4,6-bis (trichloromethyl) -1,3,5-triazine, etc. It is not limited to these.

(4) Additive In addition to the polymer, the hard coat layer used in the present disclosure is, if necessary, an antistatic agent, an antiglare agent, an antifouling agent, inorganic or organic fine particles for improving hardness, You may contain additives, such as a leveling agent and various sensitizers.

3. Configuration of Laminate The laminate of the present disclosure is not particularly limited as long as it has the polyimide film and the hard coat layer, and the hard coat layer is laminated on one surface side of the polyimide film. The hard coat layer may be laminated on both sides of the polyimide film. Moreover, the laminated body of this indication is for the range which does not impair the effect of this indication other than the said polyimide film and the said hard-coat layer, for example, for improving the adhesiveness of the said polyimide film and the said hard-coat layer. It may have other layers such as a primer layer. Moreover, the laminated body of this indication WHEREIN: The said polyimide film and the said hard-coat layer may be located adjacently.
When the Young's modulus of the two polyimide layers located on the outermost surface of the polyimide film used in the laminate of the present disclosure is different from each other, and the hard coat layer is laminated on one surface of the polyimide film, Of the two polyimide layers, the hard coat layer is preferably located on the polyimide layer side having a relatively large Young's modulus from the viewpoint of improving the impact resistance.

The total thickness of the laminate of the present disclosure may be appropriately selected depending on the application, but is preferably 10 μm or more, and more preferably 40 μm or more from the viewpoint of strength and impact resistance. On the other hand, from the viewpoint of bending resistance, it is preferably 300 μm or less, and more preferably 250 μm or less.
In the laminate of the present disclosure, the thickness of each hard coat layer is preferably 2 μm or more and 80 μm or less, and more preferably 3 μm or more and 50 μm or less.

4). Characteristics of Laminate The laminate of the present disclosure preferably has a pencil hardness of HB or higher, more preferably F or higher, even more preferably H or higher, and particularly preferably 2H or higher.
The pencil hardness of the laminate of the present disclosure can be measured in the same manner except that the load is 9.8 N in the method for measuring the pencil hardness of the polyimide film.

In the laminate of the present disclosure, the total light transmittance measured in accordance with JIS K7361-1 is preferably 85% or more, more preferably 88% or more, and still more preferably 90% or more. Is preferred. Thus, since the transmittance | permeability is high, transparency becomes favorable and it can become a glass substitute material.
The total light transmittance of the laminate of the present disclosure can be measured in the same manner as the total light transmittance of the polyimide film measured according to JIS K7361-1.

In the laminated body of the present disclosure, the yellowness (YI value) calculated in accordance with JIS K7373-2006 is preferably 30 or less, more preferably 20 or less, and preferably 16 or less. Further preferred.
The yellowness (YI value) of the laminate of the present disclosure can be measured in the same manner as the yellowness (YI value) calculated based on JIS K7373-2006 of the polyimide film.

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

The birefringence in the thickness direction at a wavelength of 590 nm of the laminate of the present disclosure is preferably 0.040 or less, more preferably 0.025 or less, and still more preferably 0.020 or less, It is particularly preferable that it is 0.015 or less.
The birefringence of the laminate of the present disclosure can be measured in the same manner as the birefringence in the thickness direction at a wavelength of 590 nm of the polyimide film.

5). Use of laminated body The use of the laminated body of this indication is not specifically limited, For example, it can be used for the use similar to the use of the polyimide film of this indication mentioned above.

6). Manufacturing method of laminated body As a manufacturing method of the laminated body of the present disclosure, for example,
Forming a coating film of a hard coat layer forming composition containing at least one of a radical polymerizable compound and a cationic polymerizable compound on at least one surface of the polyimide film of the present disclosure;
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 as necessary.
Here, the radical polymerizable compound, cationic polymerizable compound, polymerization initiator and additive contained in the hard coat layer forming composition can be the same as those described in the hard coat layer. The solvent can be appropriately selected from known solvents.

As a method of forming a coating film of the hard coat layer forming composition on at least one surface of the polyimide film, for example, the hard coat layer forming composition is publicly known on at least one surface of the polyimide film. The method of apply | coating with an application | coating means is mentioned.
The application means is not particularly limited as long as it is a method that can be applied with a target film thickness, and examples thereof include the same means as the means for applying the polyimide precursor resin composition to a support.
Further, the coating amount of the curable resin composition for the hard coat layer varies depending on the performance required of the obtained laminate, but is appropriately adjusted so that the film thickness after drying is 3 μm or more and 25 μm or less. it is preferred to, coated amount 3 g / ^{m 2} or more 30 g / ^{m 2} within the following range, particularly preferably in the range of 5 g / ^{m 2} or more 25 g / ^{m 2} or less.

The solvent is removed by drying the coating film of the curable resin composition for a hard coat layer as necessary. Examples of the drying method include reduced-pressure drying or heat drying, and a combination of these. Moreover, when drying at a normal pressure, it is preferable to dry at 30 degreeC or more and 110 degrees C or less.

Depending on the radically polymerizable compound and the polymerizable group of the cationically polymerizable compound contained in the curable resin composition for the coating film applied with the hard coat layer curable resin composition and dried as necessary. A hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound on at least one surface of the polyimide film by curing the coating film by at least one of light irradiation and heating. Can be formed.

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

III. Display Surface Material The display surface material of the present disclosure is the polyimide film of the present disclosure described above or the laminate of the present disclosure described above.

The display surface material of the present disclosure is arranged and used so as to be positioned on the surface of various displays. The display surface material of the present disclosure has improved impact resistance and bending resistance, like the polyimide film of the present disclosure and the laminate of the present disclosure described above, and therefore is particularly preferably used for a flexible display. it can.

The display surface material of the present disclosure can be used for various known displays and is not particularly limited. For example, the display surface material can be used for the display described in the application of the polyimide film of the present disclosure.

In addition, when the surface material for display of this indication is the laminated body of this indication, the surface used as the outermost surface after arrange | positioning on the surface of a display may be the surface by the side of a polyimide film, or a hard-coat layer It may be the side surface. Especially, it is preferable from the point of impact resistance and bending resistance to arrange | position the display surface material of this indication so that the surface by the side of a hard-coat layer may become a surface of the front side. When the surface material for display of the present disclosure is the polyimide film of the present disclosure, and the two polyimide layers located on the outermost surface of the polyimide film have different Young's moduli, From the viewpoint of impact resistance and bending resistance, it is preferable to dispose the display surface material of the present disclosure so that the surface becomes a surface on the front side. Further, the display surface material of the present disclosure may have a fingerprint adhesion preventing layer on the outermost surface.

Further, the method for disposing the display surface material of the present disclosure on the surface of the display is not particularly limited, and examples thereof include a method through an adhesive layer. As the adhesive layer, a conventionally known adhesive layer that can be used for adhesion of a display surface material can be used.

[Evaluation methods]
Hereinafter, when there was no notice in particular, it measured or evaluated at 25 degreeC.
<Weight average molecular weight of polyimide precursor>
The weight average molecular weight of the polyimide precursor was developed by making the polyimide precursor a 0.5% by weight N-methylpyrrolidone (NMP) solution, filtering the solution through a syringe filter (pore diameter: 0.45 μm), and developing the polyimide precursor. As a solvent, a 10 mmol% LiBr-NMP solution having a water content of 500 ppm or less was used, and a GPC apparatus (manufactured by Tosoh Corporation, HLC-8120, column used: SHODEX GPC LF-804) was used. The measurement was performed under the conditions of 40 ° C./min. The weight average molecular weight of the polyimide precursor is a polystyrene standard sample having the same concentration as the sample (weight average molecular weight: 364,700, 204,000, 103,500, 44,360,27,500, 13,030, 6,300, 3,070) was used as a conversion value with respect to standard polystyrene measured. The elution time was compared with a calibration curve to determine the weight average molecular weight.
<Viscosity of polyimide precursor solution>
The viscosity of the polyimide precursor solution was measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25 ° C. and a sample amount of 0.8 ml.

<Weight average molecular weight of polyimide>
15 mg of polyimide powder is immersed in 15000 mg of N-methylpyrrolidone (NMP), and heated at 60 ° C. in a water bath, with a stirrer at a rotation speed of 200 rpm, and stirred for 3 to 60 hours until dissolution is visually confirmed. As a result, an NMP solution having a concentration of 0.1% by weight was obtained. The solution was filtered through a syringe filter (pore size: 0.45 μm), a 30 mmol% LiBr-NMP solution having a water content of 500 ppm or less was used as a developing solvent, and a GPC apparatus (manufactured by Tosoh Corporation, HLC-8120, detector: differential) Refractive index (RID) detector, column used: two SHODEX GPC LF-804s connected in series), sample injection amount 50 μL, solvent flow rate 0.4 mL / min, column temperature 37 ° C., detector temperature 37 ° C. The measurement was performed under the following conditions. The weight average molecular weight of the polyimide is the same as the polystyrene standard sample (weight average molecular weight: 364,700, 204,000, 103,500, 44,360,27,500, 13,030, 6,300, 3, 070) was used as a conversion value with respect to standard polystyrene measured. The elution time was compared with a calibration curve to determine the weight average molecular weight.
<Viscosity of polyimide solution>
The viscosity of the polyimide solution was measured using a viscometer (eg, TVE-22HT, Toki Sangyo Co., Ltd.) at 25 ° C. and a sample amount of 0.8 ml.

<Film thickness>
The film thickness of each polyimide layer possessed by the polyimide film of each example and the film thickness of the single-layer polyimide film of each comparative example were obtained by cutting a polyimide film cut into a size of 10 cm × 10 cm in the thickness direction. The cross section was observed with a scanning electron microscope (SEM), and the film thickness of each polyimide layer was measured at five points located at equal intervals from both ends in the width direction of the polyimide film, and the average value was obtained.
Since the polyimide films of Examples 7 to 12 had a mixing region where the materials of each polyimide layer were mixed at the boundary between the polyimide layers adjacent to each other, the cross section of the test piece obtained by cutting the polyimide film in the thickness direction was flying. Elemental mapping by time-of-flight secondary ion mass spectrometry (TOF-SIMS) is performed using time-type secondary ion mass spectrometry (manufactured by ION-TOF, model number TOF.SIMS5), and the detected amount of silicon atoms is mixed. The film thickness of each polyimide layer was measured using the part which becomes the average value of the detected amount of silicon atoms in two regions that are not regions as the boundary between the polyimide layers. In addition, when the part which becomes the average value of the detected amount of silicon atoms in the two regions other than the mixing region is a region having a thickness, the central part in the thickness direction of the region is used as a boundary between the polyimide layers, The film thickness was measured.

<Young's modulus>
Using a cross section of a test piece obtained by cutting a polyimide film in the thickness direction, measurement was performed using a nanoindentation method at a temperature of 25 ° C. in accordance with ISO14577. Specifically, a PICODERTOR HM500 manufactured by Fisher Instruments Co., Ltd. was used as a measuring device, and a Vickers indenter was used as a measurement indenter. For each layer of the cross section of the test piece, the value obtained by measuring eight arbitrary points and averaging the points was taken as the Young's modulus of each layer. Measurement conditions were as follows: maximum indentation depth: 1000 nm, weighted time: 20 seconds, creep time: 5 seconds.

<Linear thermal expansion coefficient (CTE)>
A test piece obtained by cutting a single-layer polyimide film into 5 mm × 15 mm was measured for the elongation of the test piece under the following conditions with a thermomechanical analyzer (TMA), and linear heat in the range of 50 ° C. to 250 ° C. The expansion coefficient (CTE) was calculated.
<CTE measurement conditions>
Model name: TMA-60, manufactured by Shimadzu Corporation Atmosphere gas: Nitrogen gas Flow rate: 50 ml / min
Initial load: 9g
[Temperature program]
After maintaining at 30 ° C. for 10 minutes in a nitrogen atmosphere, the temperature was raised to 400 ° C. at a heating rate of 10 ° C./min and maintained at 400 ° C. for 1 minute.

<Tensile modulus>
A test piece obtained by cutting a polyimide film into 15 mm × 40 mm was conditioned for 2 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 60%, and in accordance with JIS K7127, the tensile speed was 8 mm / min and the distance between chucks was 20 mm. The tensile elastic modulus at 25 ° C. was measured. A tensile tester (manufactured by Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) was used.

<Total light transmittance>
Based on JIS K7361-1, it was measured with a haze meter (HM150, manufactured by Murakami Color Research Laboratory).

<Haze value>
Based on JIS K-7105, it was measured with a haze meter (HM150 manufactured by Murakami Color Research Laboratory).

<YI value (yellowness)>
The YI value is determined according to JIS K7373-2006 using an ultraviolet-visible near-infrared spectrophotometer (JASCO Corporation V-7100), by spectrocolorimetric method, using auxiliary illuminant C, and 2 degree field of view. The tristimulus values X, Y, Z in the XYZ color system are obtained based on the transmittance measured in the range of 250 nm to 800 nm at 1 nm intervals, and calculated from the X, Y, Z values by the following formula did.
YI = 100 (1.2769X−1.0592Z) / Y
Further, a value (YI / film thickness (μm)) obtained by dividing the YI value by the total film thickness (μm) of the polyimide film was determined.

<Birefractive index>
The thickness direction retardation value (Rth) of the polyimide film was measured with a light of 23 ° C. and a wavelength of 590 nm using a phase difference measuring apparatus (product name “KOBRA-WR” manufactured by Oji Scientific Instruments). For the thickness direction retardation value (Rth), a phase difference value at 0 ° incidence and a phase difference value at an incidence angle of 40 ° were measured, and a thickness direction retardation value Rth was calculated from these retardation values. The retardation value at an oblique incidence of 40 degrees was measured by making light having 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 of the polyimide film was determined by substituting it into the formula: Rth / d (polyimide film thickness (nm)).

<Static bending test>
Hereinafter, the method of the static bending test will be described with reference to FIG.
The polyimide film test piece 10 cut out to 15 mm × 40 mm is bent at a position of half the long side, and both ends of the long side of the test piece 10 are 6 mm thick metal pieces 2 (100 mm × 30 mm × 6 mm) on the upper and lower surfaces. Glass plates (100 mm × 100 mm × 0) from above and below in a state where they are fixed with tape so that the overlap between the upper and lower surfaces of the test piece 10 and the metal piece 2 is 10 mm each. .7 mm) was sandwiched between 3a and 3b, and the test piece 10 was fixed in a bent state with an inner diameter of 6 mm. At that time, the dummy test pieces 4a and 4b are sandwiched between the metal piece 2 and the glass plate 3a and 3b where the test piece 10 is not provided, and fixed with tape so that the glass plates 3a and 3b are parallel to each other. did. The test piece 10 thus fixed in a bent state is allowed to stand for 24 hours in an environment of 60 ° C. and 90% relative humidity (RH), and then the glass plate and fixing tape are removed, and the test piece is removed. The force applied to 10 was released. Thereafter, one end of the test piece 10 was fixed, and the internal angle of the test piece 30 minutes after the force applied to the test piece 10 was released was measured.
In addition, the polyimide film of Example 11 was bent so that the polyimide layer having a relatively large Young's modulus was inside.
When the film returns completely without being affected by the static bending test, the interior angle is 180 °.

<Pencil hardness>
The pencil hardness of the polyimide film is determined by conditioning the sample for 2 hours at a temperature of 25 ° C and a relative humidity of 60%, and then using a test pencil specified by JIS-S-6006. By performing a pencil hardness test (0.98N load) as specified in JIS K5600-5-4 (1999) on the film surface using a coating film hardness tester and evaluating the highest pencil hardness without scratches. went. In addition, the polyimide film of Example 11 was subjected to a pencil hardness test on the surface of a polyimide layer having a relatively large Young's modulus.

<Impact resistance>
Hereinafter, the impact resistance evaluation method will be described with reference to FIG.
Ten pieces of 100 μm-thick aluminum foil 6 were laminated on an iron base 5, and a polyimide film test piece 10 cut out to 15 mm × 40 mm was placed thereon. The ballpoint pen 7 (BiC, 0.7 mm) is placed at a height (interval between the test piece 10 and the tip of the pole pen) of 90 mm. It evaluated by measuring the depth of 6 dents with an optical microscope (depth of focus). Tables 2 and 4 show the depths of the recesses. The smaller the depth of the dent, the better the impact resistance. The polyimide film of Example 11 was evaluated for impact resistance with the surface of the polyimide layer having a relatively large Young's modulus as the upper surface.

(Synthesis Example 1)
A 5 L separable flask was charged with 3081 g of dehydrated dimethylacetamide and 322 g (1.00 mol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB), and the temperature of the solution in which TFMB was dissolved was To the place where the temperature was controlled at 30 ° C., 443 g (1.00 mol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) was gradually divided into several times so that the temperature rise was 2 ° C. or less. The polyimide precursor solution 1 (solid content 20% by weight) in which the polyimide precursor 1 was dissolved was synthesized. The viscosity at 25 ° C. of the polyimide precursor solution 1 (solid content 20% by weight) was 34920 cps, and the weight average molecular weight of the polyimide precursor 1 measured by GPC was 408500.

(Synthesis Examples 2 to 3)
Reaction was carried out by the procedure of Synthesis Example 1 so that the raw material and solid content concentrations shown in Table 1 were obtained, and polyimide precursor solutions 2 to 3 were obtained.

(Synthesis Example 4)
A 5 L separable flask was charged with a solution in which dehydrated dimethylacetamide (2265 g) and 1,3-bis (3-aminopropyl) tetramethyldisiloxane (AprTMOS) (24.9 g) were dissolved. 4,4 ′-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA) (22.2 g) was gradually added to a temperature controlled at 30 ° C. so that the temperature rise was 2 ° C. or less. The mixture was stirred for 30 minutes with a mechanical stirrer. 2,2′-bis (trifluoromethyl) benzidine (TFMB) (288 g) was added thereto, and after confirming complete dissolution, 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride ( 6FDA) (420 g) was gradually added in several times so that the temperature rise was 2 ° C. or less, and a polyimide precursor solution 4 (solid content 25% by mass) in which the polyimide precursor 4 was dissolved was synthesized. In the polyimide precursor solution 4, the molar ratio of TFMB and AprTMOS (TFMB: AprTMOS) was 90:10, and the total mole of TFMB and AprTMOS was the same as that of TFMB in Synthesis Example 1.

In the following, the abbreviations in each table are as follows.
TFMB: 2,2′-bis (trifluoromethyl) benzidine BAPS: bis [4- (4-aminophenoxy) phenyl] sulfone AprMMOS: 1,3-bis (3-aminopropyl) tetramethyldisiloxane 6FDA: 4, 4 '-(Hexafluoroisopropylidene) diphthalic anhydride PMDA: pyromellitic dianhydride

Example 1
Using the polyimide precursor solution 1, a single-layer polyimide film having a thickness of 50 μm obtained by the following procedures (1) to (3) was prepared as a polyimide molded body A.
(1) The polyimide precursor solution 1 was apply | coated on the glass plate, and it dried for 10 minutes with 120 degreeC circulation oven.
(2) Under a nitrogen stream (oxygen concentration of 100 ppm or less), the temperature was raised to 350 ° C. at a rate of temperature rise of 10 ° C./min, held for 1 hour, and then cooled to room temperature.
(3) Peeled from the glass plate to obtain a polyimide film.
The polyimide precursor solution 2 is applied to both surfaces of the polyimide molded body A so that the film thickness after imidization is 3 μm, and is dried in a circulating oven at 120 ° C. for 10 minutes to obtain a polyimide precursor resin coating film. After forming the film, the temperature is raised to 350 ° C. under a nitrogen stream (oxygen concentration of 100 ppm or less) at a temperature rising rate of 10 ° C./minute, held for 1 hour, and then cooled to room temperature to imidize the polyimide precursor. The polyimide film of Example 1 was obtained. The resulting polyimide film has a polyimide layer with a relatively high Young's modulus (hereinafter referred to as a high Young's modulus layer) laminated on both sides of a polyimide layer with a relatively low Young's modulus (hereinafter referred to as a low Young's modulus layer). It was the multilayer polyimide film which has the layer structure made.

(Examples 2 and 3)
In Example 1, the polyimide films of Examples 2 and 3 were obtained in the same manner as in Example 1 except that the thickness of the high Young's modulus layer was as shown in Table 2.

(Examples 4 to 6)
In Example 1, instead of the polyimide molded body A, a polyimide molded body B, which is a single-layer polyimide film with a film thickness of 80 μm, prepared by changing the coating amount of the polyimide precursor solution 1, and the thickness of the high Young's modulus layer is used. The polyimide films of Examples 4 to 6 were obtained in the same manner as in Example 1 except that Table 2 was changed as shown in Table 2.

(Example 7)
In the production of the polyimide molded body A of Example 1, a single-layer polyimide film having a film thickness of 51 μm was obtained in the same manner except that the polyimide precursor solution 4 was used instead of the polyimide precursor solution 1, and the polyimide molded body was obtained. C. In the production of the polyimide film of Example 1, a polyimide film of Example 7 was obtained in the same manner as in Example 1 except that polyimide molded body C was used instead of polyimide molded body A.

(Comparative Example 1)
A single-layer polyimide film having a film thickness of 48 μm obtained in the same procedure as in (1) to (3) of Example 1 using the polyimide precursor solution 1 was used as a polyimide film of Comparative Example 1.

(Comparative Example 2)
A single-layer polyimide film having a film thickness of 49 μm obtained by the same procedure as in (1) to (3) of Example 1 using the polyimide precursor solution 2 was used as a polyimide film of Comparative Example 2.

(Comparative Example 3)
A single-layer polyimide film having a film thickness of 49 μm obtained by the same procedure as in (1) to (3) of Example 1 using the polyimide precursor solution 3 was used as a polyimide film of Comparative Example 3.

(Comparative Example 4)
A single-layer polyimide film having a film thickness of 52 μm obtained by the same procedure as in (1) to (3) of Example 1 using the polyimide precursor solution 4 was used as the polyimide film of Comparative Example 4.

(Comparative Example 5)
A single-layer polyimide film having a film thickness of 80 μm obtained by the same procedure as in (1) to (3) of Example 1 using the polyimide precursor solution 1 was used as a polyimide film of Comparative Example 5.

The polyimide films of Examples 1 to 7 and Comparative Examples 1 to 5 were evaluated using the evaluation method. The evaluation results are shown in Table 2.
In the layer configurations shown in Tables 2 and 4, “high” represents a high Young's modulus layer, and “low” represents a low Young's modulus layer. Moreover, the film thickness, Young's modulus, and linear thermal expansion coefficient (CTE) shown in Table 2 and Table 4 are the measurement results of each polyimide layer, and the other evaluation results indicate the evaluation results for the entire polyimide film. The polyimide species numbers 1 to 6 in Tables 2 and 4 correspond to polyimides obtained using the polyimide precursor solution or the polyimide solutions 1 to 6, respectively. The Young's modulus ratio (high / low) in Tables 2 and 4 is a value obtained by dividing the Young's modulus value of the polyimide layer having the highest Young's modulus by the Young's modulus value of the polyimide layer having the lowest Young's modulus. The thickness ratio (%) of the high Young's modulus layer in Tables 2 and 4 is the ratio (%) of the total thickness of the polyimide layer having the largest Young's modulus when the total thickness of the polyimide film is 100%.

From Table 2, the polyimide films of Examples 1 to 3 having a high Young's modulus layer on both sides of a low Young's modulus layer having a film thickness of 50 μm are comparative examples 1 that are single layer polyimide films having a film thickness of approximately 50 μm. The impact resistance has been improved while having the same good bending resistance as that of the film. Furthermore, the bending resistance has been improved compared to Comparative Example 2 which is a single layer polyimide film having a high Young's modulus layer. In Examples 2 and 3, the impact resistance was also improved. In addition, the polyimide films of Examples 4 to 6 having a high Young's modulus layer on both sides of a low Young's modulus layer having a thickness of 80 μm are similar to Comparative Example 5 which is a polyimide film having a low Young's modulus layer having a thickness of 80 μm. The impact resistance was improved while having good bending resistance, and the impact resistance and bending resistance were improved as compared with Comparative Example 2 which is a polyimide film of a single layer having a high Young's modulus. . The polyimide film of Example 7 having a high Young's modulus layer on both sides of a low Young's modulus layer containing silicon atoms is as good as Comparative Example 4 which is a single layer polyimide film containing a silicon atom. The impact resistance was improved while having excellent bending resistance, and the impact resistance and bending resistance were improved as compared with Comparative Example 2 which is a single layer polyimide film having a high Young's modulus layer.
Further, the single-layer polyimide films of Comparative Examples 3 and 4 were inferior in impact resistance as compared with the polyimide films of Examples 1 to 7.

(Synthesis Example 5)
A 5 L separable flask was charged with a solution in which dehydrated dimethylacetamide (2903 g) and 1,3-bis (3-aminopropyl) tetramethyldisiloxane (AprTMOS) (15.9 g) were dissolved. 4,4 ′-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA) (14.6 g) was gradually added to the temperature controlled at 30 ° C. so that the temperature rise was 2 ° C. or less. The mixture was stirred for 30 minutes with a mechanical stirrer. 2,2′-bis (trifluoromethyl) benzidine (TFMB) (387 g) was added thereto, and after confirming complete dissolution, 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride ( 6FDA) (548 g) was gradually added several times so that the temperature rise was 2 ° C. or less, and a polyimide precursor solution 5 (solid content 25% by mass) in which the polyimide precursor 5 was dissolved was synthesized.
Under a nitrogen atmosphere, the polyimide precursor solution 5 (400 g) lowered to room temperature was added to a 5 L separable flask. Thereto, dehydrated dimethylacetamide (109 g) was added and stirred until uniform. Next, pyridine (41.4 g) and acetic anhydride (53.4 g) as catalysts were added and stirred at room temperature for 24 hours to synthesize a polyimide solution. To the obtained polyimide solution, butyl acetate (406 g) was added and stirred until uniform, then methanol (3000 g) was gradually added to obtain a white slurry. The slurry was filtered and washed 5 times with methanol to obtain polyimide 5. The weight average molecular weight of the polyimide measured by GPC was 175000.
Polyimide 5 was dissolved in a solvent (dichloromethane) to prepare a polyimide solution 5 having a solid content of 15% by mass. The viscosity of the polyimide solution 5 (solid content: 15% by mass) at 25 ° C. was 4174 cps.

(Synthesis Example 6)
A polyimide 6 was obtained in the same manner as in Synthesis Example 5 except that the polyimide precursor solution 4 obtained in Synthesis Example 4 was used in place of the polyimide precursor solution 5 in the procedure of Synthesis Example 5. Table 3 shows the weight average molecular weight of polyimide 6 measured by GPC. Further, in Synthesis Example 5, polyimide solution 6 shown in Table 3 was obtained in the same manner as in Synthesis Example 5 except that polyimide 6 was used instead of polyimide 5. Table 3 shows the viscosity of the polyimide solution 6 (solid content: 15% by mass) at 25 ° C.

(Example 8)
Using the polyimide solution 6, a single-layer polyimide film having a film thickness of 47 μm obtained by the following procedures (i) to (iii) was prepared as a polyimide molded body D.
(I) The polyimide solution 6 was apply | coated on the glass plate, the film was peeled from the glass plate after natural drying.
(Ii) The film was dried in a circulation oven at 50 ° C. for 10 minutes.
(Iii) The film was heated to 200 ° C. under a nitrogen stream (oxygen concentration of 100 ppm or less) at a heating rate of 10 ° C./min, held at 200 ° C. for 1 hour, and then cooled to room temperature to obtain a polyimide film. .
The polyimide solution 5 is applied to both sides of the polyimide molded body D so that the film thickness after drying is 3 μm, and after natural drying, it is dried in a circulation oven at 50 ° C. for 10 minutes, and then under a nitrogen stream The polyimide film of Example 8 was obtained by raising the temperature to 200 ° C. at an oxygen concentration of 100 ppm or less and a heating rate of 10 ° C./min, holding at 200 ° C. for 1 hour, and then cooling to room temperature.

Example 9
In the procedure of (i) to (iii) of Example 8, except that the polyimide solution 5 was used instead of the polyimide solution 6, a film thickness of 55 μm was obtained in the same manner as in the procedures of (i) to (iii). A single-layer polyimide film was obtained and designated as polyimide molded body E.
The polyimide precursor solution 2 is applied to both sides of the polyimide molded body E so that the film thickness after imidization is 3 μm, and is dried in a circulating oven at 120 ° C. for 10 minutes to obtain a polyimide precursor resin coating film. After forming the film, the temperature is raised to 350 ° C. under a nitrogen stream (oxygen concentration of 100 ppm or less) at a temperature rising rate of 10 ° C./minute, held for 1 hour, and then cooled to room temperature to imidize the polyimide precursor. The polyimide film of Example 9 was obtained.

(Example 10)
In the procedures (i) to (iii) of Example 8, except that the polyimide solution 5 was used instead of the polyimide solution 6 and the coating amount was adjusted so that the film thickness after drying was 20 μm, the above (i ) To (iii), a single-layer polyimide film having a thickness of 20 μm was obtained, and a polyimide molded body F was obtained.
The polyimide precursor solution 2 is applied to both sides of the polyimide molded body F so that the film thickness after imidization is 15 μm, and is dried in a circulating oven at 120 ° C. for 10 minutes to obtain a polyimide precursor resin coating film. After forming the film, the temperature is raised to 350 ° C. under a nitrogen stream (oxygen concentration of 100 ppm or less) at a temperature rising rate of 10 ° C./minute, held for 1 hour, and then cooled to room temperature to imidize the polyimide precursor. The polyimide film of Example 10 was obtained.

(Example 11)
In the procedures (i) to (iii) of Example 8, except that the polyimide solution 5 was used in place of the polyimide solution 6, a film thickness of 48 μm was obtained in the same manner as the procedures (i) to (iii). A single-layer polyimide film was obtained and designated as polyimide molded body G.
The polyimide precursor solution 2 is applied to one surface of the polyimide molded body G so that the film thickness after imidization is 3 μm and dried in a circulating oven at 120 ° C. for 10 minutes. After forming the film, the temperature is raised to 350 ° C. under a nitrogen stream (oxygen concentration of 100 ppm or less) at a temperature rising rate of 10 ° C./minute, held for 1 hour, and then cooled to room temperature to imidize the polyimide precursor. The polyimide film of Example 11 was obtained.

(Example 12)
In the procedure of (1) to (3) of Example 1, except that the polyimide precursor solution 2 was used instead of the polyimide precursor solution 1, the procedure of (1) to (3) was performed, A single-layer polyimide film having a thickness of 10 μm was obtained and designated as polyimide molded body H.
The polyimide solution 5 is applied to both sides of the polyimide molded body H so that the film thickness after drying becomes 20 μm, and after natural drying, it is dried in a circulation oven at 50 ° C. for 10 minutes, and then in a nitrogen stream The polyimide film of Example 12 was obtained by raising the temperature to 200 ° C. at an oxygen concentration of 100 ppm or less and a heating rate of 10 ° C./min, holding at 200 ° C. for 1 hour, and then cooling to room temperature.

(Comparative Example 6)
A single-layer polyimide film having a film thickness of 55 μm obtained by the same procedure as in (i) to (iii) of Example 8 using the polyimide solution 5 was used as the polyimide film of Comparative Example 6.

(Comparative Example 7)
A single-layer polyimide film having a film thickness of 47 μm obtained in the same procedure as (i) to (iii) in Example 8 using the polyimide solution 6 was used as the polyimide film of Comparative Example 7.

The polyimide films of Examples 8 to 12 and Comparative Examples 6 and 7 were evaluated using the above evaluation method. The evaluation results are shown in Table 4.

From Table 4, the polyimide film of Example 8 has a high Young's modulus layer containing silicon atoms on both sides of a low Young's modulus layer containing silicon atoms. Impact resistance is improved while having good bending resistance comparable to that of Comparative Example 7 which is a polyimide film of a single layer, and compared with Comparative Example 6 which is a polyimide film of a single layer having a high Young's modulus. The bending resistance was improved and the impact resistance was also improved.
The polyimide films of Examples 9 and 10 have a high Young's modulus layer not containing silicon atoms on both sides of a low Young's modulus layer containing silicon atoms, and a single layer of a low Young's modulus layer containing silicon atoms. While having good bending resistance comparable to that of Comparative Example 6 which is a polyimide film, the impact resistance is remarkably improved, and moreover compared to Comparative Example 2 which is a polyimide film having a high Young's modulus layer single layer. The bending resistance was improved and the impact resistance was remarkably improved.
The polyimide film of Example 11 has a high Young's modulus layer not containing silicon atoms on one surface of a low Young's modulus layer containing silicon atoms, and a single layer of a low Young's modulus layer containing silicon atoms. While having good bending resistance comparable to that of Comparative Example 6 which is a polyimide film, the impact resistance is improved, and further, compared to Comparative Example 2 which is a polyimide film having a single layer of high Young's modulus. Resistance was improved and impact resistance was improved.
The polyimide film of Example 12 has a low Young's modulus layer containing silicon atoms on both sides of a high Young's modulus layer not containing silicon atoms, and a low Young modulus layer single-layer polyimide film containing silicon atoms As compared with Comparative Example 6, the impact resistance was improved, and the bending resistance was improved as compared with Comparative Example 2 which was a polyimide film having a single layer having a high Young's modulus.

Further, when the polyimide films of Examples 7 to 12 were cut in the thickness direction and the cross section was observed with a scanning electron microscope (SEM), the mixing region where the materials of each polyimide layer were mixed at the boundary between the polyimide layers adjacent to each other. Had.
Further, the polyimide films of Examples 1 to 12 were inspected for the presence of interference fringes. Specifically, one surface of the polyimide film was painted with black ink, an interference fringe inspection lamp was applied to the other surface, and reflection observation was performed visually. As a result, all the polyimide films were at a practical level. However, compared with the polyimide films of Examples 1 to 6, the polyimide films of Examples 7 to 12 had interference fringes suppressed.

Further, the polyimide films of Examples 1 to 12 were subjected to a surface polyimide layer adhesion test according to the following adhesion test method. As a result, the ratio of the area where the polyimide layer on the surface peeled was 20% or less. In Example 11, an adhesion test was performed on the surface on the high Young's modulus layer side, and in each Example other than Example 11, an adhesion test was performed on both surfaces.
<Adhesion test>
In accordance with the cross-cut test of JIS K5400, the polyimide layer on the surface was cut into a checkered pattern at intervals of 1 mm using a cutter knife to form a grid of 100 squares. Next, cellophane tape (Nichiban Co., Ltd.) was applied on the lattice and then peeled off. After repeating this five times, peeling of the polyimide layer on the surface was observed.

(Example 13)
10 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (BASF, Irgacure 184) is added to 100 parts by weight of pentaerythritol triacrylate to a 40% by weight methyl isobutyl ketone solution of pentaerythritol triacrylate. A resin composition for a coat layer was prepared.
The polyimide film of Example 1 was cut out to 10 cm × 10 cm, the hard coat layer resin composition was applied to one surface, and ultraviolet light was irradiated and cured at a dose of 200 mJ / cm ² under a nitrogen stream, and the film thickness was 10 μm. A hard coat layer, which is a cured film, was formed to produce a laminate.

(Examples 14 to 24)
In Example 13, laminates of Examples 14 to 24 were produced in the same manner as Example 13 except that the polyimide films of Examples 2 to 12 were used instead of the polyimide film of Example 1, respectively. In Example 23 using the polyimide film of Example 11, a hard coat layer was formed on the surface of the polyimide film on the high Young's modulus layer side to produce a laminate.

<Pencil hardness>
The laminates obtained in Examples 13 to 24 were conditioned 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, Toyo Seiki Co., Ltd. The pencil hardness test (9.8 N load) specified in JIS K5600-5-4 (1999) is performed on the surface of the hard coat layer side using a pencil scratch coating film hardness tester. The pencil hardness of each laminate was determined by evaluating high pencil hardness. The pencil hardnesses of the laminates obtained in Examples 13 to 24 were all 2H.

Further, among the laminates obtained in Examples 13 to 24, the laminates of Examples 20 and 24 in which the polyimide layer containing silicon atoms is positioned adjacent to the hard coat layer include the polyimide film, the hard coat layer, The adhesion was better.

1a, 1a ′, 1b Polyimide layer 10, 11 Polyimide film 2 Metal piece 3a, 3b Glass plate 4a, 4b Dummy test piece 5 Base 6 Aluminum foil 7 Ballpoint pen

Claims (16)

A polyimide film having two or more polyimide layers having different Young's moduli, an overall thickness of 5 μm or more and 200 μm or less, and a total light transmittance of 85% or more measured according to JIS K7361-1. 2. The polyimide film according to claim 1, wherein a Young's modulus of a polyimide layer having the largest Young's modulus among the polyimide layers is 1.2 times or more of a Young's modulus of a polyimide layer having the smallest Young's modulus. The polyimide film according to claim 1, wherein the polyimide film has three or more polyimide layers, and the polyimide layer having the largest Young's modulus among the polyimide layers is located on at least one surface. The polyimide film according to any one of claims 1 to 3, further comprising three or more polyimide layers, wherein the polyimide layer having the smallest Young's modulus among the polyimide layers is not located on the surface. The polyimide film according to any one of claims 1 to 4, wherein the thickest layer among the polyimide layers is not a polyimide layer having the largest Young's modulus. The polyimide film according to any one of claims 1 to 5, wherein a total thickness of polyimide layers having the largest Young's modulus among the polyimide layers is 60% or less of the total thickness. The polyimide film according to any one of claims 1 to 6, wherein when a static bending test is performed according to the following static bending test method, an internal angle after the test is 90 ° or more.
[Static bending test method]
A polyimide film test piece cut out to 15 mm × 40 mm is bent at a position of half of the long side, and both ends of the long side of the test piece sandwich a metal piece (100 mm × 30 mm × 6 mm) having a thickness of 6 mm from the upper and lower surfaces. Placed between glass plates (100 mm x 100 mm x 0.7 mm) from above and below with the tape fixed so that the overlap between the top and bottom surfaces of the test piece and the metal piece is 10 mm each. The test piece is fixed in a bent state with an inner diameter of 6 mm. At that time, a dummy test piece is sandwiched between the metal piece and the glass plate where there is no test piece, and is fixed with tape so that the glass plate is parallel. The test piece thus fixed in a bent state is left to stand for 24 hours in an environment of 60 ° C. and 90% relative humidity (RH), and then the glass plate and fixing tape are removed, and the test piece is attached to the test piece. Release this force. Thereafter, one end of the test piece is fixed, and the internal angle of the test piece 30 minutes after the force applied to the test piece is released is measured. The polyimide film according to any one of claims 1 to 7, wherein a value obtained by dividing yellowness calculated in accordance with JIS K7373-2006 by film thickness (μm) is 0.330 or less. Each of the two or more polyimide layers contains an aromatic ring, and (i) a fluorine atom, (ii) an aliphatic ring, and (iii) the aromatic rings are substituted with a sulfonyl group or a fluorine atom. The polyimide film as described in any one of Claims 1 thru | or 8 containing the polyimide containing at least 1 selected from the group which consists of the structure connected with the good alkylene group. The polyimide film as described in any one of Claims 1 thru | or 9 in which the polyimide layer with the largest Young's modulus contains the polyimide which has a structure represented by following General formula (1) among the said polyimide layers.

(In the general formula (1), R ¹ is 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride residue, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride residue. , And at least one tetravalent group selected from the group consisting of pyromellitic dianhydride residues, R ² is a 2,2′-bis (trifluoromethyl) benzidine residue, 4,4′- Diaminodiphenylsulfone residue, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4 -Aminophenoxy) phenyl] sulfone residue, 4,4'-diamino-2,2'-bis (trifluoromethyl) diphenyl ether residue, 1,4-bis [4-amino-2- (trifluoromethyl) phenoxy ] Benzene residue, 2,2-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane residue, 4,4′-diamino-2- (trifluoromethyl) diphenyl ether residue, And at least one divalent group selected from the group consisting of 9,9-bis (4-aminophenyl) fluorene residues, n represents the number of repeating units and is 1 or more.) The polyimide film of Claim 10 which further has a polyimide layer containing the polyimide which has a structure represented by following General formula (2).

(In the general formula (2), R ³ is a tetravalent group is a tetracarboxylic acid residue having an aromatic ring or aliphatic ring, R ⁴ represents a divalent group which is a diamine residue, R ⁴ Is a diamine residue having one or two silicon atoms in the main chain, and the remaining R ⁴ does not have a silicon atom and has an aromatic ring or an aliphatic ring. More than half of the remaining R ⁴ is 1,4-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4′-diaminodiphenylsulfone residue. Group, 3,4'-diaminodiphenylsulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2-bis (4-aminof At least one divalent group selected from the group consisting of a divalent propane residue, a 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (3): N ′ represents the number of repeating units and is 1 or more.)

(In general formula (3), R ⁵ and R ⁶ each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.) The polyimide film as described in any one of Claims 1 thru | or 9 which has a polyimide layer containing the polyimide which has a structure represented by following General formula (2).

(In the general formula (2), R ³ is a tetravalent group is a tetracarboxylic acid residue having an aromatic ring or aliphatic ring, R ⁴ represents a divalent group which is a diamine residue, R ⁴ Is a diamine residue having one or two silicon atoms in the main chain, and the remaining R ⁴ does not have a silicon atom and has an aromatic ring or an aliphatic ring. More than half of the remaining R ⁴ is 1,4-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4′-diaminodiphenylsulfone residue. Group, 3,4'-diaminodiphenylsulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2-bis (4-aminof At least one divalent group selected from the group consisting of a divalent propane residue, a 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (3): N ′ represents the number of repeating units and is 1 or more.)

(In general formula (3), R ⁵ and R ⁶ each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.) A laminate comprising the polyimide film according to any one of claims 1 to 12 and a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound. The radical polymerizable compound is a compound having two or more (meth) acryloyl groups in one molecule, and the cationic polymerizable compound is a compound having two or more epoxy groups or oxetanyl groups in one molecule. The laminate according to claim 13, wherein A surface material for display, which is the polyimide film according to any one of claims 1 to 12 or the laminate according to claim 13 or 14. The display surface material according to claim 15, which is used for a flexible display.

Images