JP6973476B2 - Polyimide film, laminates, and surface materials for displays - Google Patents

Description

The present disclosure relates to polyimide films, laminates, and surface materials for displays.

While thin flat glass is excellent in hardness, heat resistance, etc., it is difficult to bend, easily breaks when dropped, has problems in workability, and is heavier than plastic products. Therefore, from the viewpoint of workability and weight reduction, research on resin products that can be used as glass substitute products has been conducted.

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

Generally, the polyimide resin is a highly heat-resistant resin obtained by performing a dehydration ring closure reaction of a polyamic acid obtained by a condensation reaction of an aromatic tetracarboxylic acid anhydride and an aromatic diamine. However, since the polyimide resin is generally colored yellow or brown, it is difficult to use it in fields where transparency is required, such as display applications and optical applications. Therefore, it is being studied to apply a polyimide having improved transparency to a display member. For example, Patent Document 1 describes 1,2,4,5-cyclohexanetetracarboxylic acid and 1,2,4,5-cyclohexanetetracarboxylic 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 selected from compounds having at least one phenylene group and an isopropridene group represented by a specific formula. A polyimide resin obtained by reacting with an imino-forming compound is disclosed, and it is described that it is suitable for a substrate material such as a flat panel display and a mobile phone device.

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

On the other hand, Patent Document 4 is obtained from a polyimide layer (b) including a heat-sealing 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 foil such as a copper foil is laminated on a surface having heat fusion property of the polyimide film to form a metal laminate. ing.

Japanese Unexamined Patent Publication No. 2006-199945 Special Table 2014-501301 Publication No. Japanese Patent Publication No. 2012-503701 International Publication No. 2012/133594

Since mobile devices with foldable screens are often carried in a folded state, the flexible display mounted on such mobile devices will return to its original shape when it is returned to a flat state even if it has been folded for a long time. It is required to pass through, and the base material and surface material for flexible displays are also required to have resilience (hereinafter, may be referred to as static bending resistance) after being bent for a long time.
However, even if the conventional resin film using transparent polyimide shows good results in a test in which a flat state and a bent state are repeated at regular intervals, if the bent state continues for a long time, the bending habit will occur. There is a problem that it sticks, it is difficult to return to flatness, and it is inferior in static bending resistance.
Further, 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 restoration property after the bent state is increased. Tends to worsen and the flexural resistance becomes inadequate. In fact, as shown in Comparative Example 2 described later, the polyimide film having a large elastic modulus has improved impact resistance but deteriorated bending resistance. In order to improve the bending resistance, it is effective to reduce the film thickness of the film because the stress applied to the film at the time of bending can be reduced. However, in the resin film used as a surface material, if the film thickness is reduced, there is a problem that the rigidity of the film is lowered and the function of protecting the light emitting device and the circuit from impact is lowered. As described above, it is considered that the impact resistance and the bending resistance of the resin film are contradictory characteristics. Since the thickness of the resin film used as the surface material is set so as to balance impact resistance and bending resistance, satisfactory impact resistance can be obtained compared to glass used for rigid panels that cannot be bent. However, both impact resistance and bending resistance are required.

The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide a resin film having excellent impact resistance and bending resistance.
Another object of the present disclosure is to provide a laminate having the resin film and a surface material for a display which is the resin film or the laminate.

The polyimide film of the present disclosure has three or more polyimide layers including two or more polyimide layers having different Young's modulus, and has an overall thickness of 5 μm or more and 200 μm or less, and is measured in accordance with JIS K7631-1. a total light transmittance of Ri der 85% or more, Young's modulus is the smallest polyimide layer of said polyimide layer is not located on the surface.

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 the Young's modulus of the polyimide layer having the smallest Young's modulus in terms of impact resistance and impact resistance. It is preferable from the viewpoint of bending resistance.

In the polyimide film of the present disclosure, the largest polyimide layer Young's modulus of the previous SL polyimide layer, be located on at least one surface, from the viewpoint of impact resistance and flex resistance.

In the polyimide film of the present disclosure, it is preferable that the thickest layer of the polyimide layers is not the 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, it is preferable that the total thickness of the polyimide layer having the largest Young's modulus among the polyimide layers is 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 the static bending test is performed according to the following static bending test method, it is preferable that the internal angle after the test is 90 ° or more from the viewpoint of bending resistance.
[Static bending test method]
A polyimide film test piece cut into a size of 15 mm × 40 mm is bent at the position of half of the long side, and a metal piece (100 mm × 30 mm × 6 mm) having a thickness of 6 mm is sandwiched between both ends of the long side of the test piece from the upper and lower surfaces. Arranged and fixed with tape so that the overlap margins on both ends of the test piece and the upper and lower surfaces of the metal piece are 10 mm each, sandwiched between glass plates (100 mm x 100 mm x 0.7 mm) from above and below. , 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 the test piece does not exist, and the glass plate is fixed with tape so as to be parallel to each other. The test piece fixed in the bent state in this way is allowed to stand for 24 hours in an environment of 60 ° C. and 90% relative humidity (RH), and then the glass plate and the fixing tape are removed to the test piece. Release such force. Then, one end of the test piece is fixed, and the internal angle of the test piece is measured 30 minutes after the force applied to the test piece is released.

In the polyimide film of the present disclosure, the yellowish coloring is suppressed when the value obtained by dividing the yellowness calculated according to JIS K7373-2006 by the film thickness (μm) is 0.330 or less. , It is preferable from the viewpoint of improving light transmission.

In the polyimide film of the present disclosure, each of the three or more polyimide layers contains an aromatic ring, and (i) a fluorine atom, (ii) an aliphatic ring, and (iii) an aromatic ring are sulfonyl groups. Alternatively, it is preferable to contain a polyimide containing at least one selected from the group consisting of a structure linked with an alkylene group which may be substituted with a fluorine atom from the viewpoint of light transmission and impact resistance.

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 following general formula (1), that is, light transmission, impact resistance and impact resistance. It 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 a 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride residue, 3,3', 4,4'-benzophenone tetracarboxylic acid 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'-. Diaminodiphenyl sulfone 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 have a polyimide layer containing a polyimide having a structure from the viewpoint of light transmission, 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 the total amount is 50 mol% or less of a diamine residue having one or two silicon atoms in the main chain, the remaining R ^4, having no silicon atom, a diamine having an aromatic ring or aliphatic ring is a residue, the number remaining than half of the ^{R 4} is 1,4-cyclohexane diamine residue, trans-1,4-bis-methylene-cyclohexane diamine residue, 4,4'-diaminodiphenyl sulfone residue Group, 3,4'-diaminodiphenyl sulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2-bis At least one selected from the group consisting of (4-aminophenyl) propane residue, 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (3). Represents a divalent group of species. 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 the general formula (3), R ⁵ and R ⁶ independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)

In the polyimide film of the present disclosure, it is preferable to have a polyimide layer containing a polyimide having a structure represented by the general formula (2) from the viewpoint of light transmission 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 radically polymerizable compound and a cationically polymerizable compound.

In the laminate of the present disclosure, the radically polymerizable compound is a compound having two or more (meth) acryloyl groups in one molecule, and the cationically polymerizable compound has at least one molecule of an epoxy group and an oxetanyl group. A compound having two or more of them is preferable from the viewpoint of hardness and adhesion of the hard coat layer, and from the viewpoint of light transmission and impact resistance.

The surface material for a display 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.
Further, according to the present disclosure, it is possible to provide a laminate having the resin film and a surface material for a display which is the resin film or the laminate.

It is a schematic sectional drawing which shows an example of the polyimide film which concerns on this disclosure. It is the schematic sectional drawing which shows another example of the polyimide film which concerns on this disclosure. 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 modulus from each other, has an overall thickness of 5 μm or more and 200 μm or less, and has a total light transmittance of 85 as measured in accordance with 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 showing an example of the polyimide film of the present disclosure. The polyimide film 10 of the present disclosure shown in FIG. 1 has a polyimide layer 1b between the polyimide layer 1a and the polyimide layer 1a', the polyimide layer 1a and the polyimide layer 1a'have the same young ratio, and the polyimide layer has the same young ratio. 1b has a different young rate from the polyimide layer 1a and the polyimide layer 1a'.
FIG. 2 is a schematic cross-sectional view showing another example of the polyimide film of the present disclosure. The 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, Young's modulus is measured by using a cross section of a test piece obtained by cutting a polyimide film in the thickness direction at a temperature of 25 ° C., in accordance with ISO14577, and using a nanoindentation method. Specifically, a PICODETOR HM500 manufactured by Fisher Instruments Co., Ltd. is used as the measuring device, and a Vickers indenter is used as the measuring indenter. For each layer of the cross section of the test piece, the Young's modulus of each layer is a value obtained by measuring arbitrary points at eight points and averaging the numbers. The measurement conditions are a maximum pushing depth of 1000 nm, a weighting time of 20 seconds, and a creep time of 5 seconds.

Further, in the present disclosure, the fact that the Young's modulus of the polyimide layer is different from each other means that the difference in Young's modulus is 0.3 GPa or more, and when the difference in Young's modulus is less than 0.3 GPa, the Young's modulus of the polyimide layer is different. Are identical to each other.

Further, the polyimide film of the present disclosure has a total light transmittance of 85% or more as measured in accordance with JIS K7361-1. Since the transmittance is high as described above, the transparency is improved and the material can be used as a substitute for glass. The total light transmittance measured according to 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 Technology Laboratory).

The reason why the polyimide film of the present disclosure has excellent impact resistance and bending resistance is presumed as follows.
A resin film having excellent bending resistance can improve impact resistance by increasing the thickness of the film, but if the film is too thick, the bending resistance deteriorates. On the other hand, the polyimide film of the present disclosure has excellent impact resistance and good bending resistance because it has two or more polyimide layers having different Young's moduli. Of the two or more polyimide layers, the polyimide layer having a relatively large Young's modulus is relatively hard to be deformed and has excellent impact resistance. On the other hand, the 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, of the two or more polyimide layers, the polyimide layer having a relatively large Young's modulus improves the impact resistance, and the polyimide layer having a relatively small Young's modulus improves the bending resistance. Therefore, it is considered that both impact resistance and bending resistance are compatible. From the viewpoint of impact absorption, the polyimide layer having a relatively high Young's modulus has a strong tendency to diffuse the collision force on the surface, and the polyimide layer having a relatively low Young's modulus diffuses the collision force over time. There is a strong tendency. In the polyimide film of the present disclosure, it is presumed that the maximum value of the impact force can be appropriately diffused and reduced by combining the polyimide layers having different actions of diffusing the collision force. It is considered 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 modulus from each other, has an overall thickness of 5 μm or more and 200 μm or less, and has 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. 1. Structure of Polyimide Film The polyimide film of the present disclosure is one in which two or more polyimide layers having different Young's moduli are laminated, and two or more polyimide layers having different Young's modulus are adjacent to each other. be.
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. 1. Although not shown, it may have four or more polyimide layers.

Further, the polyimide film of the present disclosure may have at least two polyimide layers having different Young's modulus from each other, and may include two or more polyimide layers having the same Young's modulus from each other. Above all, from the viewpoint of improving impact resistance and bending resistance, it is preferable that the polyimide layers adjacent to each other are polyimide layers having different Young's modulus from each other, and are relative to the polyimide layer having a relatively large Young's modulus between the adjacent layers. It is more preferable that the polyimide layers having a small Young's modulus are alternately laminated.

Further, the polyimide film of the present disclosure has three or more polyimide layers, and the polyimide layer having the largest young ratio among the polyimide layers is located on at least one surface to have impact resistance and bending resistance. From the point of view, it is preferable, and among them, the polyimide layer having three or more layers and an odd number of layers, the polyimide layer having the largest young ratio among the polyimide layers is located on one surface, and the polyimide layer having the largest young ratio is used. The young ratio is preferably 1.0 times or more and less than 1.2 times the young ratio of the polyimide layer located on the other surface, and 1.0 times or more and 1.1 times or less is impact resistant. It is more preferable from the viewpoint of property and bending resistance, and from the viewpoint of suppressing warpage of the film.
Further, the polyimide film of the present disclosure has three or more polyimide layers, and it is preferable that the polyimide layer having the smallest Young's modulus among the polyimide layers is not located on the surface from the viewpoint of impact resistance and bending resistance. Above all, it is preferable that the number of layers of the polyimide layer is 3 or more and the number of layers is 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 the present disclosure composed of two polyimide layers is preferable because it can be thinned while improving impact resistance and bending resistance. When a polyimide film composed of two polyimide layers is used as a surface material, it is preferable to use a polyimide film having a relatively large Young's modulus on the surface side from the viewpoint of impact resistance and bending resistance. 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 relative from the viewpoint of impact resistance and bending resistance and suppressing the warp of the film. It is preferable that the Young's modulus is 1.2 times or more and 2.0 times or less the Young's modulus of the polyimide layer having a small Young's modulus.
The polyimide film of the present disclosure has a polyimide layer having three or more layers and an odd number of layers, and a polyimide layer having a relatively large young ratio between adjacent layers, in particular, from the viewpoint of improving impact resistance and bending resistance. It is more preferable that the polyimide layers having a relatively small young ratio are alternately laminated, and the polyimide layer located on the surface is a polyimide layer having a relatively large young ratio, and further, it is located on one surface. It is more preferable that the polyimide layer and the polyimide layer located on the other surface are the polyimide layers having the largest young ratio among the polyimide layers, and further, the polyimide layer located in the center has the smallest young ratio. A polyimide layer is even more preferable.
The number of layers of the polyimide layer of the polyimide film of the present disclosure is not particularly limited as long as it is two or more, but it may be five or less from the viewpoint of thinning the polyimide film and easy to manufacture. It is preferably two layers or three layers, more preferably. Above all, a three-layer structure in which a layer having a Young's modulus higher than that of the polyimide layer is located on both sides of a polyimide layer having a relatively low Young's modulus is particularly preferable from the viewpoint of impact resistance.

In the polyimide film of the present disclosure, the Young's modulus of the polyimide layer having the largest Young's modulus is preferably 1.2 times or more the Young's modulus of the polyimide layer having the smallest Young's modulus from the viewpoint of impact resistance and bending resistance. , 1.5 times or more is more preferable. 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 times or less, the Young's modulus of the polyimide layer having the smallest Young's modulus. It is more preferable, and 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 lowest Young's modulus is a value rounded to the first decimal place in accordance with Rule B of JIS Z8401: 1999. Ask as.

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. Is preferable from the viewpoint of suppressing the warp of the polyimide film, more preferably 0.5 GPa or less, and further preferably less than 0.3 GPa.

The Young's modulus of each polyimide layer of the polyimide film of the present disclosure is preferably 2.0 GPa or more, more preferably 3.0 GPa or more, and 3.5 GPa or more, respectively, from the viewpoint of impact resistance and bending resistance. The above is even more preferable, while 10.0 GPa or less is preferable, 8.0 GPa or less is more preferable, and 7.0 GPa or less is even more preferable.
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 even 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 the coefficient of linear thermal expansion (CTE) is preferably within 10 ppm / ° C., preferably within 5 ppm / ° C., and more preferably within 2 ppm / ° C. from the viewpoint of suppressing warpage of the polyimide film. Even more preferable.
The coefficient of linear thermal expansion (CTE) of each polyimide layer in the range of 50 ° C to 250 ° C is a test piece obtained by cutting a single-layer polyimide film produced under the same materials and conditions as each polyimide layer into a size of 5 mm × 15 mm. On the other hand, it can be obtained by measuring the elongation amount of the test piece under the following conditions with a thermomechanical analyzer (TMA) and calculating the coefficient of linear thermal expansion (CTE) in the range of 50 ° C to 250 ° C. ..
<CTE measurement conditions>
Model name: TMA-60, manufactured by Shimadzu Corporation Atmospheric gas: Nitrogen gas Flow rate: 50 ml / min
Initial load: 9g
[Temperature program]
After maintaining at 30 ° C. for 10 minutes under a nitrogen atmosphere, the temperature is raised to 400 ° C. at a heating rate of 10 ° C./min, and the temperature is maintained at 400 ° C. for 1 minute.

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

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, still more preferably 40 μm or more and 150 μm or less, and further more preferably, from the viewpoint of bending resistance and impact resistance. It is preferably 50 μm or more and 120 μm or less.

The thickness of each polyimide layer of the polyimide film of the present disclosure is not particularly limited, but the thickest layer among the polyimide layers is not the polyimide layer having the largest Young's modulus from the viewpoint of bending resistance and impact resistance. Is preferable.

In the polyimide film of the present disclosure, the thickness of each polyimide layer is determined by 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 cross section in the observed thickness direction.
When the interface is unclear due to a mixing region in which the materials of each polyimide layer are mixed at the boundary between the polyimide layers adjacent to each other, the boundary for determining the thickness of the polyimide layer can be determined as follows, for example. can. From the materials used for the two adjacent polyimide layers, select the element that is most likely to make a difference, perform element mapping by time-of-flight secondary ion mass spectrometry (TOF-SIMS), etc., and perform element mapping. The portion where the detected amount of the element selected in the above is the average value of the detected amount of the element in the two regions other than the mixing region is defined as the boundary when determining the thickness of the polyimide layer. When the portion where the average value of the detected amounts of the elements in the two regions other than the mixing region is the thickness is the region, the central portion in the thickness direction of the region is used as the boundary for determining the thickness of the polyimide layer.

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

Further, 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. It is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less. The total thickness of the polyimide layer having the largest Young's modulus among the polyimide layers is preferably 5% or more, more preferably 10% or more, from the viewpoint of improving the impact resistance.
On the other hand, in the polyimide film of the present disclosure, when the total thickness of the polyimide layer 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, the decrease in bending resistance is suppressed. It is preferable from the viewpoint that the impact resistance can be improved, and it may be 20% or more and 60% or less.

Further, the polyimide film of the present disclosure has the lowest Young's modulus (low Young's modulus) with respect to the total thickness of the polyimide layer (high Young's modulus layer) having the largest Young's modulus among the polyimide layers from the viewpoint of improving bending resistance. The ratio of the total thickness of the polyimide layer (total thickness of the low Young's modulus layer / total thickness of the high Young's modulus layer) is preferably 1.0 or more, and more preferably 2.0 or more. On the other hand, the ratio (total thickness of the low Young's modulus layer / total thickness of the 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 the decrease in bending resistance, the ratio (total thickness of low Young's modulus layer / total thickness of high Young's modulus layer) is preferably 0.6 or more, preferably 0.7 or more. It is more preferably 0.8 or more, further preferably 1.0 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 (low Young's modulus layer) having the smallest Young's modulus among the polyimide layers is not particularly limited, but is preferably 20 μm or more and 120 μm or less. When it is 20 μm or more and less than 70 μm, it is preferable from the viewpoint of bending resistance.

2. 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, if necessary, as long as the effects of the present disclosure are not impaired. Is also good.

(1) Polyimide Polyimide is obtained by reacting a tetracarboxylic acid component with a diamine component. It is preferable to obtain polyamic acid by polymerization of a tetracarboxylic acid component and a diamine component and imidize it. The imidization may be performed by thermal imidization or chemical imidization. It can also be produced by a method in which thermal imidization and chemical imidization are used in combination.

As a specific example of the tetracarboxylic acid component, tetracarboxylic acid dianhydride is preferably used, and cyclohexanetetracarboxylic acid dianhydride, cyclopentanetetracarboxylic acid dianhydride, dicyclohexane-3, 4, 3', 4 '-Tetracarboxylic acid dianhydride, pyromellitic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride , 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetracarboxylic acid 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-dicarboxyphenyl) ) Sulfonhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) Methan dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) Carboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 1,4-bis [ (3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, 2,2-bis {4 -[3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [ 3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, 4,4'-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4,4'-bis [ 3- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [3- (1) , 2-Dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfonate dianhydride, bis {4- [3- (1,2) − Dicarboxy) Phenoxy] phenyl} s Luhon dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride Anhydride, 4,4'-(hexafluoroisopropyridene) diphthalate anhydride, 3,4'-(hexafluoroisopropyridene) diphthalate anhydride, 3,3'-(hexafluoroisopropyridene) diphthalate anhydride , 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 1, , 2,3,4-benzenetetracarboxylic acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, 2,3,6,7-anthracenetetracarboxylic acid dianhydride, 1,2 , 7,8-Phenantrentetracarboxylic acid 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. '-Diaminodiphenylsulfide, 3,4'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone , 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) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) Benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-amino) Benzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-dimethylbenzyl) benzene 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) -Amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditri) Fluoromethylbenzyl) 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 (tri) Fluoromethyl) 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- (4- (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] benzene, 1,4-bis [ 4- (3-Aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) -α, α-dimethyl Benzyl] 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-dimethylbenzyl) phenoxy] diphenyl sulfone, 4,4' -Bis [4- (4-aminophenoxy) phenoxy] diphenyl sulfone, 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'-spirobiindan, 6,6'-bis (4-aminophenoxy) -3,3,3', 3'-tetramethyl-1,1'-spirobiindan, 1,3-bis (3-aminopropyl) Tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω -Bis (3-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, and some or all of the hydrogen atoms on the aromatic ring of the above diamine are a fluoro group, a methyl group, a methoxy group, or a trifluoromethyl group. , Or a diamine substituted with a substituent selected from the trifluoromethoxy group can also be used.
These diamines can be used alone or in admixture of two or more.

Further, from the viewpoint of improving light transmission and 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) preferably contain a polyimide containing at least one selected from the group consisting of a structure in which aromatic rings are linked to each other with a sulfonyl group or an alkylene group which may be substituted with a fluorine atom. When 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 charge transfer in the electronic state in the polyimide skeleton can be made difficult, and the light transparency is improved.
When the polyimide contains (ii) an aliphatic ring, the light transmission is improved in that the transfer of charges in the skeleton can be inhibited by breaking the conjugation of π electrons in the polyimide skeleton.
When the polyimide contains a structure in which (iii) aromatic rings are linked to each other with an alkylene group which may be substituted with a sulfonyl group or a fluorine atom, the charge transfer in the skeleton by breaking the conjugation of π electrons in the polyimide skeleton. Light transmission is improved in terms of being able to inhibit.

Among them, polyimide containing an aromatic ring and containing a fluorine atom is preferably used because it improves light transmission and impact resistance.
As for the content ratio of fluorine atoms in the polyimide, the ratio (F / C) of the number of fluorine atoms (F) to the number of carbon atoms (C) measured on the surface of the polyimide 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 content ratio of fluorine atoms is too high, the heat resistance inherent in polyimide may deteriorate. Therefore, the ratio (F / C) of the number of fluorine atoms (F) to the number of carbon atoms (C) is 1 or less. It is preferably 0.8 or less, and more preferably 0.8 or less.
Here, the above ratio measured by X-ray photoelectron spectroscopy (XPS) can be obtained from the value of the atomic% of each atom measured using an X-ray photoelectron spectrometer (for example, Thermo Scientific Theta Probe). ..

Further, from the viewpoint of improving impact resistance, 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%. The total amount of the diamine residues having is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 75 mol% or more.

In the present disclosure, the content ratio of each repeating unit in the polyimide and the content ratio (mol%) of each tetracarboxylic acid residue and each diamine residue can be obtained from the molecular weight charged at the time of polyimide production. Further, the content ratio (mol%) of each tetracarboxylic acid residue and each diamine residue in the polyimide is a high-performance liquid for the decomposition product of the polyimide obtained by decomposing the 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.

Further, it is preferable that at least one of the tetracarboxylic acid residue and the diamine residue contains an aromatic ring and a fluorine atom in the polyimide from the viewpoint of improving impact resistance and light transmission, and further, aromatic. It is preferable to have 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 a diamine residue having an aromatic ring and 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, still more preferably 75 mol% or more.

Further, the fact that 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are the hydrogen atoms directly bonded to the aromatic ring improves the light transmission and the rigidity. It is preferably used from the above. The ratio of the hydrogen atoms (number) directly bonded to the aromatic ring to the total hydrogen atoms (number) bonded to the carbon atoms contained in the polyimide is preferably 60% or more, more preferably 70% or more. Is preferable.
When 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are the hydrogen atoms directly bonded to the aromatic ring, the polyimide is stretched at, for example, 200 ° C. or higher even after being heated in the atmosphere. However, it is preferable because there is little change in the optical characteristics, particularly the total light transmittance and the yellowness YI value. When 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are polyimides, which are hydrogen atoms directly bonded to the aromatic ring, the reactivity with oxygen is low, so that the chemical structure of the polyimide changes. It is presumed that it is difficult to do. Utilizing its high heat resistance, polyimide film is often used for devices that require a processing process that involves heating, but 50% or more of the hydrogen atoms bonded to carbon atoms contained in polyimide are in the aromatic ring. In the case of polyimide, which is a hydrogen atom to be directly bonded, it is not necessary to carry out these subsequent steps in an inert atmosphere in order to maintain transparency, so there is an advantage that equipment costs and costs for atmosphere control can be suppressed. There is.
Here, the ratio of the hydrogen atoms (number) directly bonded to the aromatic ring to the total hydrogen atoms (number) bonded to the carbon atoms contained in the polyimide is determined by high performance liquid chromatography and gas chromatograph mass of the decomposition product of the polyimide. It can be determined using an analyzer and NMR. For example, the sample is decomposed with an alkaline aqueous solution or supercritical methanol, the obtained 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 analyzer and NMR. The ratio of hydrogen atoms (number) directly bonded to the aromatic ring in the total hydrogen atoms (number) contained in the polyimide can be obtained by performing the quantification using high performance liquid chromatography or the like. ..

Further, as the polyimide used in the present disclosure, silicon is used from the viewpoint of improving the adhesion between the polyimide layers adjacent to each other and the interlayer adhesion when another layer such as a hard coat layer is further laminated on the polyimide film. Polyimide containing an atom can be preferably used. Further, the polyimide layer containing a polyimide containing a silicon atom is preferable from the viewpoint of improving the interlayer adhesion and suppressing the generation of interference fringes by easily forming the mixing region between the polyimide layer and the adjacent polyimide layer. .. Further, it is preferable that the polyimide film has a polyimide layer containing a polyimide containing a silicon atom because the impact resistance can be easily improved.
As the polyimide containing a silicon atom used in the present disclosure, among them, the diamine residue having a silicon atom is preferably 1 mol% or more and 50 mol% or less, more preferably 2 out of 100 mol% of the total amount of the diamine residue. A polyimide containing 5.5 mol% or more and 40 mol% or less, more preferably 5 mol% or more and 30 mol% or less is preferably used.

As the diamine residue having a silicon atom, a diamine residue having one or two silicon atoms in the main chain is preferable.
Examples of the diamine having one silicon atom in the main chain include a diamine represented by the following general formula (A). Examples of the diamine having two silicon atoms in the main chain include diamines represented by the following general formula (B).

（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), L may be an independent direct bond or an —O— bond, and R ¹⁰ may be independent and have a substituent, and oxygen may be used. It represents a monovalent hydrocarbon group having 1 or more and 20 or less carbon atoms which may contain an atom or a nitrogen atom. R ¹¹ may independently have a substituent and may contain an oxygen atom or a nitrogen atom. It represents a divalent hydrocarbon group having 1 or more and 20 or less carbon atoms which may be contained.)

In the general formula (A) and the general formula (B), the plurality of L, R ¹⁰ and R ¹¹ may be the same or different from each other.
Examples of the monovalent hydrocarbon group represented by R ¹⁰ include an alkyl group having 1 to 20 carbon atoms, an aryl group, and a combination thereof. The alkyl group may be linear, branched or cyclic, and may be linear or a combination of branched and cyclic.
The alkyl group having 1 or more and 20 or less carbon atoms is preferably an alkyl group having 1 or more and 10 or less carbon atoms, and specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and the like. Examples thereof include a t-butyl group, a pentyl group and a hexyl group. The cyclic alkyl group is preferably a cycloalkyl group having 3 or more carbon atoms and 10 or less carbon atoms, and specific examples thereof include a cyclopentyl group and a cyclohexyl group. The aryl group is preferably an aryl group having 6 or more carbon atoms and 12 or less carbon atoms, and specific examples thereof 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 which may contain an oxygen atom or a nitrogen atom include an ether bond, a carbonyl bond, an ester bond, an amide bond, and imino, which are a divalent hydrocarbon group described later and the monovalent hydrocarbon group. Groups attached by at least one bond (-NH-) can be mentioned.
The monovalent substituent that may be a hydrocarbon group optionally having represented by R ^10, not particularly limited to the extent that the effect of the present disclosure are not impaired, for example, a fluorine atom, a halogen atom such as a chlorine atom , Hydrocarbons and the like.

The ^{monovalent hydrocarbon group represented by R 10} is preferably an alkyl group having 1 or more and 3 or less carbon atoms or an aryl group having 6 or more and 10 or less carbon atoms from the viewpoint of impact resistance and bending resistance. , It is more preferable that the alkyl group has 1 or more and 3 or less carbon atoms. The alkyl group having 1 or more and 3 or less carbon atoms is more preferably a methyl group, and the aryl group having 6 or more and 10 or less 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 group in 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 or more and 20 or less carbon atoms is preferably an alkylene group having 1 or more and 10 or less carbon atoms, and is a linear group such as a methylene group, an ethylene group, various propylene groups, various butylene groups and cyclohexylene groups. Examples thereof include a group obtained by combining a cyclic or branched alkylene group with a cyclic alkylene group.
The arylene group is preferably an arylene group having 6 or more carbon atoms and 12 or less carbon atoms, and examples of the arylene group include a phenylene group, a biphenylene group, a naphthylene group and the like, and further have a substituent for an aromatic ring described later. You may be doing it.
Divalent hydrocarbon groups that may contain oxygen or nitrogen atoms include ether bonds, carbonyl bonds, ester bonds, amide bonds, and imino bonds (-NH-) of the divalent hydrocarbon groups. Examples include at least one bonded group.
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 or more and 6 or less carbon atoms or an arylene group having 6 or more and 10 or less carbon atoms from the viewpoint of impact resistance and bending resistance. Further, it is more preferable that the alkylene group has 2 or more and 4 or less carbon atoms, and the alkylene group is preferably linear or branched.

Among the diamines having one or two silicon atoms in the main chain, the diamine having two silicon atoms is preferable from the viewpoint of light transmission, impact resistance and bending resistance, and further 1, 3 -Bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, 1,3-bis (5-aminopentyl) tetramethyldisiloxane, etc. are easily available. It is preferable from the viewpoint of achieving both light transmission and impact resistance.

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 more preferably 500 or less. It is even more preferable, and it is particularly preferable that it is 300 or less.
The diamine residue having one or two silicon atoms in the main chain may be used alone or in combination of two or more.

Further, in the polyimide film of the present disclosure, the polyimide layer having the largest Young's modulus among all the polyimide layers of the polyimide film contains a polyimide having a structure represented by the following general formula (1). It is preferable from the viewpoint of property, 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 a 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride residue, 3,3', 4,4'-benzophenone tetracarboxylic acid 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'-. Diaminodiphenyl sulfone 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.)

^{R 1} of the general formula (1) is particularly preferable because the pyromellitic acid dianhydride residue improves the impact resistance.
^{R 2} of the general formula (1) is, among others, 2,2'-bis (trifluoromethyl) benzidine residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, and bis [4- (4-Aminophenoxy) phenyl] It is preferable that it is at least one divalent group selected from the sulfone residues from the viewpoint of light transmission, impact resistance and bending resistance, and 2,2'-bis. It is more preferably 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 depending on the structure so as to show 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.
^{It should be noted that R 1} in each repeating unit may be the same or different, and R ² in each repeating unit may be the same or different.

Among all the polyimides contained in the polyimide layer having the largest Young's modulus, the content ratio of the polyimide having the structure represented by the general formula (1) is from the viewpoint of light transmission, impact resistance and bending resistance. , 60% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, still more preferably 100% by mass.
The polyimide used in the present disclosure may contain one type or two or more types of polyimide having a structure represented by the general formula (1).

Further, the polyimide film of the present disclosure contains a polyimide in which the polyimide layer having the largest Young's modulus among all the polyimide layers of the polyimide film has a structure represented by the general formula (1), and the following general formula is used. It is preferable to further have a polyimide layer containing the polyimide having the structure represented by (2) from the viewpoint of light transmission, 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 the total amount is 50 mol% or less of a diamine residue having one or two silicon atoms in the main chain, the remaining R ^4, having no silicon atom, a diamine having an aromatic ring or aliphatic ring is a residue, the number remaining than half of the ^{R 4} is 1,4-cyclohexane diamine residue, trans-1,4-bis-methylene-cyclohexane diamine residue, 4,4'-diaminodiphenyl sulfone residue Group, 3,4'-diaminodiphenyl sulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2-bis At least one selected from the group consisting of (4-aminophenyl) propane residue, 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (3). Represents a divalent group of species. 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 the general formula (3), R ⁵ and R ⁶ independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)

^{R 3} of the general formula (2) is a residue obtained by removing the acid dianhydride structure from the tetracarboxylic acid dianhydride having an aromatic ring, or an aliphatic ring, from the above-mentioned tetracarboxylic acid components. Residues obtained by removing the acid dianhydride structure from the tetracarboxylic acid dianhydride having can be appropriately selected, and are not particularly limited, but among others, 4,4'-from the viewpoint of light transmission and impact resistance. (Hexafluoroisopropylidene) Diphthalate anhydride residue, 3,4'-(hexafluoroisopropyridene) diphthalate anhydride residue, 3,3'-(hexafluoroisopropyridene) diphthalate anhydride residue, 4 , 4'-Oxydiphthalic anhydride residue, and more preferably 4,4'-at least one tetravalent group selected from the group consisting of 3,4'-oxydiphthalic anhydride residue. (Hexafluoroisopropylidene) Diphthalate anhydride residue, 3,4'-(hexafluoroisopropyridene) diphthalate anhydride residue and 3,3'-(hexafluoroisopropyridene) diphthalate anhydride residue group It is even more preferable that it is a tetravalent group of at least one selected from.

Examples of R ³ include pyromellitic acid dianhydride residue, 3,3', 4,4'-biphenyltetracarboxylic acid 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, and cyclohexanetetracarboxylic acid dianhydride residues, cyclo. Pentantetracarboxylic acid dianhydride residue, dicyclohexane-3,4,3', 4'-tetracarboxylic acid dianhydride residue, cyclobutanetetracarboxylic acid dianhydride residue, 4,4'-(hexafluoro) Isopropylidene) Diphthalate anhydride residue, 3,4'-(hexafluoroisopropyridene) diphthalate anhydride residue, 3,3'-(hexafluoroisopropyridene) diphthalate anhydride residue, 4,4' A group of tetracarboxylic acid residues suitable for improving light transmission, such as at least one selected from the group consisting of −oxydiphthalic anhydride residues and 3,4′-oxydiphthalic anhydride residues ( It is also preferable to use it in combination with 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 the light transmission is For 1 mol of the tetracarboxylic acid residue group (group B) suitable for improving light transmission, the tetracarboxylic acid residue group (group A) suitable for improving the rigidity was 0. It is preferably 05 mol or more and 9 mol or less, more preferably 0.1 mol or more and 5 mol or less, and further preferably 0.3 mol or more and 4 mol or less.
Among them, the group B includes 4,4'-(hexafluoroisopropyridene) diphthalic acid anhydride residues and 3,4'-(hexafluoroisopropyridene) diphthalic acid anhydride residues containing a fluorine atom. It is preferable to use at least one from the viewpoint of improving impact resistance and light transmission.
When the R ³ contains a tetracarboxylic dian residue of the group A, the R ⁴ of the general formula (2) may contain a diamine residue having one or two silicon atoms in the main chain. It is preferable from the viewpoint of bending resistance.
In the R ^3, these preferred residues in total, preferably contains more than 50 mol%, preferably contains more than 70 mol%, it is preferable to include even more than 90 mol%.

^{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, and is contained.} However, it is not necessary to use a diamine residue having one or two silicon atoms in the main chain from the viewpoint of improving the interlayer adhesion, suppressing the generation of interference fringes, and easily improving the impact resistance. It is preferably contained in an amount of 1 mol% or more and 50 mol% or less, and more preferably 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 the above-mentioned residue obtained by removing two amino groups from the diamine having one or two silicon atoms in the main chain. .. Of these, a diamine residue having two silicon atoms is preferable from the viewpoint of light transmission, impact resistance and bending resistance, and further, 1,3-bis (3-aminopropyl) tetramethyldi. Siloxane residues, 1,3-bis (4-aminobutyl) tetramethyldisiloxane residues, 1,3-bis (5-aminopentyl) tetramethyldisiloxane residues, etc. are easy to obtain and light-transmitting. It is preferable from the viewpoint of achieving 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, the number remaining than half of the ^{R 4} is 1,4-cyclohexane diamine residue, trans-1,4-bis-methylene-cyclohexane diamine residue (trans-l, 4 -Bis (aminomethyl) cyclohexane residue), 4,4'-diaminodiphenyl sulfone residue, 3,4'-diaminodiphenyl sulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-Aminophenoxy) phenyl] sulfone residues, 2,2-bis (4-aminophenyl) propane residues, 2,2-bis (4-aminophenyl) hexafluoropropane residues, and the general At least one divalent group selected from the group consisting of divalent groups represented by the formula (3) (hereinafter, may be referred to as "at least one divalent group selected from the above group"). ..
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) is the mole% 50 mole% to 100 mole% or less, having no silicon atom, a diamine residue having an aromatic ring or an aliphatic ring, the ^{R 4 {(100-x)} / 2} Excess mol% is the basis for at least one divalent agent selected from the group. Among them, the proportion of at least one divalent radical selected from the group of the remaining R ^4, i.e., without a said silicon atoms, the total amount of the diamine residue having an aromatic ring or aliphatic ring The ratio of at least one divalent group selected from the above group when 100 mol% is 100 mol% is preferably 70 mol% or more from the viewpoint of surface hardness, impact resistance and light transmission. , 85 mol% or more is more preferable, and 95 mol% or more is even more preferable. Incidentally, R ⁴ is different from the at least one divalent radical selected from the group having no silicon atom, also contain other diamine residue having an aromatic ring or 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 the diamine having no silicon atom and having an aromatic ring, and the silicon atom can be used. The diamine residue having an aliphatic ring without a silicon atom can be a residue obtained by removing two amino groups from a diamine having an aliphatic ring without a silicon atom. Wherein R ⁴ may contain, different from the at least one divalent radical selected from the group having no silicon atom, diamines used in the diamine residue having an aromatic ring or aliphatic ring As the diamine, for example, a diamine having no silicon atom and having an aromatic ring or an aliphatic ring can be appropriately selected and used from the above-mentioned diamines, and is not particularly limited.

Among at least one divalent group selected from the above group, trans-1,4-bismethylenecyclohexanediamine residue, 4,4'-diaminodiphenylsulfone, among others, from the viewpoint of impact resistance and light transmission. Residues, 3,4'-diaminodiphenyl sulfone residues, bis [4- (3-aminophenoxy) phenyl] sulfone residues, bis [4- (4-aminophenoxy) phenyl] sulfone residues, 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). It is preferably a divalent group of one kind, and more preferably a divalent group represented by the general formula (3). Examples of the divalent group represented by general formula (3), among others, more preferably R ⁵ and R ⁶ is a perfluoroalkyl group, among them, a perfluoroalkyl group having 1 to 3 carbon atoms It is more preferably 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% it 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 It is preferably the basis of.

Wherein R ⁴ is different from the at least one divalent radical selected from the group having no silicon atom, when containing a diamine residue having an aromatic ring or aliphatic ring, its content is it is not particularly limited, from the viewpoint of impact resistance and optical transparency, of the total amount of R ⁴ (100 mol%), preferably not more than 30 mol%, more preferably 20 mol% or less It is more preferably 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 depending on the structure so as to show 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 preferable.
^{It should be noted that 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 transmission, impact resistance and bending resistance. Is more preferable, 80% by mass or more is more preferable, 90% by mass or more is further preferable, and 100% by mass is further more preferable.
The polyimide used in the present disclosure may contain one type or two or more types of polyimide having a structure represented by the general formula (2).

Further, it is preferable that the polyimide film of the present disclosure has a polyimide layer containing a polyimide having a structure represented by the general formula (2) from the viewpoint of light transmission and bending resistance, and from the viewpoint of impact resistance. Is also preferable. From the viewpoint of further improving the impact resistance, in the polyimide film of the present disclosure, the polyimide layer having the largest young ratio contains the polyimide having the structure represented by the general formula (1), and the general formula (2). By not containing the polyimide having the structure represented by), the impact resistance can be further improved, but the polyimide layer having the largest young ratio is the polyimide having the structure represented by the general formula (2). May be a polyimide layer containing the above, and all the polyimide layers contained in the polyimide film may be a polyimide layer containing a polyimide having a structure represented by the general formula (2).

Of all the polyimide layers of the polyimide film, the polyimide layer having the largest young ratio contains the polyimide having the structure represented by the general formula (1), and the structure represented by the general formula (2). In the polyimide film further having the polyimide layer containing the polyimide having the above, the total thickness of the polyimide layer having the largest young ratio is 5% or more and 60% or less of the total thickness of the polyimide film, that is, bending resistance and impact resistance. It is preferable from the viewpoint of sex.
In the polyimide film in which all the polyimide layers of the polyimide film are polyimide layers containing the polyimide having the structure represented by the general formula (2), the total thickness of the polyimide layers having the largest young ratio is the polyimide film. 5% or more and 30% or less is preferable from the viewpoint of bending resistance and impact resistance, 5% or more and 20% or less is more preferable, and 5% or more and 15% or less is more preferable. More preferred.

Further, among all the polyimide layers of the polyimide film, the polyimide layer having the largest young ratio contains the polyimide having the structure represented by the general formula (1) and is represented by the general formula (2). In a polyimide film further having a polyimide layer containing a polyimide having such a structure, the young ratio of the polyimide layer having the largest young ratio and the young ratio of the polyimide layer having the smallest young ratio are obtained from the viewpoint of impact resistance and bending resistance. It is preferably 1.5 times or more, particularly 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 the polyimide layers containing the polyimide having the structure represented by the general formula (2), the Young's modulus is the highest in terms of impact resistance and bending resistance. The Young's modulus of the large polyimide layer is preferably 1.2 times or more, preferably 2.0 times or less, or 1.8 times or less, the Young's modulus of the polyimide layer having the smallest Young's modulus. good.

Further, the polyimide used in the present disclosure may contain a polyamide structure as a part thereof as long as the effect of the present disclosure is not impaired. Examples of the polyamide structure that may be contained include a polyamide-imide structure containing a tricarboxylic acid residue such as trimellitic acid 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 bake temperature, the glass transition temperature is preferably 400 ° C. or lower, and more preferably 380 ° C. or lower.
The glass transition temperature of the polyimide used in the present disclosure is obtained 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. It is a thing. The glass transition temperature of polyimide means the temperature of the peak at which the maximum value of the peak is the maximum when there are a plurality of peaks of the tan δ curve. As the dynamic viscoelasticity measurement, for example, the dynamic viscoelasticity measuring device RSA III (TA Instrument Japan Co., Ltd.) sets the measurement range to -150 ° C to 400 ° C, and raises the temperature at a frequency of 1 Hz. It can be performed at a speed of 5 ° C./min. Further, the sample width can be measured as 5 mm and the distance between chucks as 20 mm.
In the present disclosure, the peak of the tan δ curve has an inflection point which is a maximum value, and the peak width between the valleys of the peak is 3 ° C. or more, which is derived from the measurement of noise or the like. Small vertical fluctuations are not interpreted as the peak.

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

Further, each polyimide layer of the polyimide film according to the present disclosure may contain a resin other than polyimide as long as the effect of the present disclosure is not impaired. Examples of the other resin 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. , Polyetherimide resin, epoxy resin, phenol resin, glass-epoxy resin, polyphenylene ether resin, acrylic resin, polyolefin resin such as polyethylene and polypropylene, polycycloolefin such as polynorbornene and the like.
When the polyimide layer contains other resin other than polyimide, the content of the other resin is preferably 50% by mass or less, more preferably 30% by mass or less, based on the total amount of the polyimide layer. , 0% by mass is particularly preferable.

3. 3. Characteristics of Polyimide Film The Young's modulus, total light transmittance and coefficient of linear thermal expansion in the polyimide film of the present disclosure have been described above and are not described here.

From the viewpoint of excellent bending resistance, the polyimide film of the present disclosure preferably has an internal angle of 90 ° or more, preferably 100 ° or more, when a static bending test is performed according to the following static bending test method. It is more preferable that the temperature is 110 ° or more, and it is even more preferable that the temperature 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 so as to be inside. In addition, 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 at least the above lower limit value.
[Static bending test method]
A polyimide film test piece cut into a size of 15 mm × 40 mm is bent at the position of half of the long side, and a metal piece (100 mm × 30 mm × 6 mm) having a thickness of 6 mm is sandwiched between both ends of the long side of the test piece from the upper and lower surfaces. Arranged and fixed with tape so that the overlap margins on both ends of the test piece and the upper and lower surfaces of the metal piece are 10 mm each, sandwiched between glass plates (100 mm x 100 mm x 0.7 mm) from above and below. , 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 the test piece does not exist, and the glass plate is fixed with tape so as to be parallel to each other. The test piece fixed in the bent state in this way is allowed to stand for 24 hours in an environment of 60 ° C. and 90% relative humidity (RH), and then the glass plate and the fixing tape are removed to the test piece. Release such force. Then, one end of the test piece is fixed, and the internal angle of the test piece is measured 30 minutes after the force applied to the test piece is released.

The polyimide film of the present disclosure has a tensile elastic modulus of 0.5 GPa or more at 25 ° C., which is measured by measuring a 15 mm × 40 mm test piece in accordance with JIS K7127 with a tensile speed of 10 mm / min and a chuck distance of 20 mm. From the viewpoint of impact resistance and bending resistance, it is preferably 0.8 GPa or more, more preferably 1.0 GPa or more, further preferably 1.5 GPa or more, and 2.0 GPa or more. The above is the most preferable. The upper limit of the tensile elastic 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, or 4.0 GPa or less from the viewpoint of bending resistance. May be.
The tensile elastic modulus was determined by cutting a test piece having a width of 15 mm and a length of 40 mm from a polyimide film using a tensile tester (for example, manufactured by Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) and at 25 ° C. The tensile speed is 10 mm / min, and the distance between chucks is 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, further preferably HB or more, and more preferably H or more. Especially preferable.
The pencil hardness of the polyimide film is determined by adjusting the humidity of the measurement sample for 2 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 60%, and then using a test pencil specified by JIS-S-6006, JIS K5600-5-4. It can be performed by performing a pencil hardness test (0.98 N load) specified in (1999) on the surface of the film and evaluating the highest pencil hardness that does not cause scratches. For example, a pencil scratch coating film hardness tester manufactured by Toyo Seiki Co., Ltd. can be used.
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.

In the polyimide film of the present disclosure, when the adhesion test is performed according to the following adhesion test method, the area where the polyimide layer on the surface is peeled off is 20% or less of the whole, which is the point of adhesion between the polyimide layers. And, from the viewpoint of surface hardness, it is preferable, it is more preferably 10% or less, and even more preferably 5% or less.
<Adhesion test>
In accordance with the JIS K5400 grid test, the polyimide layer on the surface is cut in a grid pattern at 1 mm intervals using a cutter knife to form a grid of 100 squares. Next, a cellophane tape (Nichiban Co., Ltd.) is attached onto the lattice and then peeled off. This is repeated 5 times, and then the peeling of the polyimide layer on the surface is observed.

Further, in the polyimide film of the present disclosure, the yellowness (YI value) calculated in accordance with the JIS K7373-2006 is preferably 30.0 or less, more preferably 20.0 or less. It is more preferably 17.0 or less, and even more preferably 16.0 or less.
The yellowness (YI value) calculated in accordance with JIS K7373-2006 is preferably 11.0 or less, more preferably 10.0 or less, and preferably 5.0 or less. It is more preferably 3.0 or less, still more preferably 2.0 or less, and particularly preferably 2.0 or less.
When the yellowness (YI value) is not more than the upper limit value, the polyimide film of the present disclosure suppresses yellowish coloring, improves light transmission, and can be a glass substitute material.
The yellowness (YI value) is assisted by a spectrophotometric method using an ultraviolet-visible near-infrared spectrophotometer (for example, JASCO Corporation V-7100) in accordance with the JIS K7373-2006. Illuminant C, using a two-degree field of view, the tristimulus values X, Y, Z in the XYZ colorimetric system are obtained based on the transmittance measured at 1 nm intervals in the range of 250 nm or more and 800 nm or less, and the X, Y are obtained. , Z can be calculated from the following formula.
YI = 100 (1.2769X-1.592Z) / Y

Further, the polyimide film of the present disclosure suppresses yellowish coloring, improves light transmission, and can be suitably used as a glass substitute material. Therefore, the yellow color calculated in accordance with JIS K7373-2006. 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. The following is even more preferable, and 0.030 or less is particularly preferable.
In the present disclosure, the value (YI value / film thickness (μm)) obtained by dividing the yellowness (YI value) by the film thickness (μm) is placed in the third decimal place in accordance with 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 transmission.
The haze value can be measured by a method according to JIS K-7105, and can be measured by, for example, a haze meter HM150 manufactured by Murakami Color Technology Laboratory.

Further, the polyimide film of the present disclosure preferably has a birefringence index in the thickness direction at a wavelength of 590 nm, preferably 0.040 or less, more preferably 0.025 or less, and more preferably 0.020 or less. It is more preferably 0.015 or less, and particularly preferably 0.015 or less. When the birefringence is not more than the upper limit value, the optical distortion of the polyimide film is reduced, and when the polyimide film is used as a surface material for a display, deterioration of the display quality of the display can be suppressed. 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 the visibility may be deteriorated. The birefringence in the thickness direction of the film installed on the display surface is preferably 0.040 or less from the viewpoint of suppressing the occurrence of rainbow unevenness when the display is viewed with polarized sunglasses. Further, when the birefringence in the thickness direction of the film installed on the display surface is 0.025 or less, the color reproducibility when the display is viewed from an angle is improved. From the viewpoint of improving the color reproducibility when the display is viewed from an angle, the birefringence in the thickness direction of the film placed on the display surface is more preferably 0.020 or less.
The birefringence in the thickness direction of the polyimide film of the present disclosure at a wavelength of 590 nm can be determined as follows.
First, the thickness direction retardation value (Rth) of the polyimide film is measured with light at 23 ° C. and a wavelength of 590 nm using a phase difference measuring device (for example, manufactured by Oji Measuring Instruments Co., Ltd., product name “KOBRA-WR”). do. For the thickness direction retardation value (Rth), the phase difference value incident at 0 degrees and the phase difference value incident at an angle of 40 degrees are measured, and the thickness direction retardation value Rth is calculated from these phase difference values. The retardation value of the oblique 40-degree incident is measured by injecting light having a wavelength of 590 nm onto the retardation film from a direction inclined by 40 degrees from the normal of the retardation film.
The birefringence in the thickness direction of the polyimide film can be obtained by substituting it into the formula: Rth / d. The d represents the film thickness (nm) of the polyimide film.
The thickness direction retardation value is nx for the refractive index in the slow-phase axial direction (the direction in which the refractive index is maximized in the in-plane direction of the film) in the in-plane direction of the film, and the phase-advancing axial direction (the film surface) in the film surface. When the refractive index in the inward direction (the direction in which the refractive index is minimized) is ny and the refractive index in the thickness direction of the film is nz, it is expressed as Rth [nm] = {(nx + ny) /2-nz} × d. be able to.

Further, as a preferable form of the polyimide film of the present disclosure, the ratio (F /) of the number of fluorine atoms (F) to the number of carbon atoms (C) on the surface of at least one of the films measured by X-ray photoelectron spectroscopy of the polyimide film. C) is preferably 0.01 or more and 1 or less, and more preferably 0.05 or more and 0.8 or less.
Further, the ratio (F / N) of the number of fluorine atoms (F) to the number of nitrogen atoms (N) on at least one of the film surfaces 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 above ratio measured by X-ray photoelectron spectroscopy (XPS) can be obtained from the value of the atomic% of each atom measured using an X-ray photoelectron spectrometer (for example, Thermo Scientific Theta Probe). ..

4. Method for Producing Polyimide Film The method for producing the polyimide film of the present disclosure may be any production method as long as the above-mentioned polyimide film of the present disclosure can be obtained, and is not particularly limited.
The process of preparing the polyimide molded body and
A step of preparing a polyimide precursor resin composition containing a polyimide precursor and an organic solvent, and
A 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, and a step of forming the polyimide precursor resin coating film.
Examples thereof include a manufacturing method including a step of imidizing the polyimide precursor by heating.
In the first manufacturing method, as a method for manufacturing 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 is performed. Examples thereof include a method of imidizing each polyimide precursor contained in each polyimide precursor resin coating film by the imidization step after performing until a desired number of layers is reached. The polyimide precursor resin coating film having two or more layers may be formed on only one surface of the polyimide molded product, or may be formed on both sides 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,
The process of preparing the polyimide molded body and
A step of 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.
A step of applying the first polyimide precursor resin composition to one surface of the polyimide molded body to form a first polyimide precursor resin coating film.
A step of applying the second polyimide precursor resin composition to the other surface of the polyimide molded body to form a second polyimide precursor resin coating film.
The first step of imidizing the polyimide precursor contained in the first polyimide precursor resin coating film and the polyimide precursor contained in the second polyimide precursor resin coating film by heating. Examples thereof include a production method in which the polyimide precursor resin composition and the second polyimide precursor resin composition may have the same composition.
In the first manufacturing method, the polyimide molded body and each polyimide precursor resin coating film formed so as to have a desired number of layers form a polyimide layer.
The first manufacturing method is preferable because it is easy to reduce the birefringence of the polyimide film. According to the first manufacturing method, the birefringence index 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, and even more preferably 0.020 or less. A polyimide film can be suitably formed.

In the first manufacturing 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 applied. By performing the imidization step after all the formation is performed, the mixing region can be formed at the boundary between the polyimide layers adjacent to each other in the two or more polyimide layers, so that the interlayer adhesion is improved and the interference fringes are formed. It is preferable from the viewpoint of suppressing the occurrence of.

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

(1) Polyimide Molded Body Preparation Step As the polyimide molded body used in the first manufacturing method, for example, a film-shaped polyimide molded body manufactured by the following manufacturing method can be used.
As a method for manufacturing a film-shaped polyimide molded product, for example, as a manufacturing method A,
A step of preparing a polyimide precursor resin composition containing a polyimide precursor and an organic solvent, and
A step of applying the polyimide precursor resin composition to a support to form a polyimide precursor resin coating film, and a step of forming the polyimide precursor resin coating film.
Examples thereof include a manufacturing method including a step of imidizing the polyimide precursor by heating.
The manufacturing method A is preferable from the viewpoint that the birefringence of the polyimide film can be easily reduced, and a polyimide film having a birefringence in the thickness direction at a wavelength of 590 nm is preferably 0.025 or less, more preferably 0.020 or less. It is possible. In the first manufacturing method, when the manufacturing method A is used as the manufacturing method of the polyimide molded body, it is more preferable in that the effect of reducing the double refractive index of the polyimide film is high, and the double refractive index in the thickness direction at a wavelength of 590 nm is more preferable. It is possible to preferably form a polyimide film having a value of 0.025 or less, more preferably 0.020 or less.
In the production method A, as the polyimide precursor resin composition, the same polyimide precursor resin composition as that obtained in the “polyimide precursor resin composition preparation step” described later can be used, and the polyimide precursor resin can be 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 manufacturing method A, examples of the support include the same supports used in the second manufacturing method described later.
Further, the manufacturing 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.

Further, as another manufacturing method of the film-shaped polyimide molded body, for example, as the manufacturing method B,
A step of preparing a polyimide resin composition containing a polyimide and an organic solvent,
Examples thereof include a manufacturing method including 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 it dissolves in an organic solvent at 25 ° C. in an amount of 5% by mass or more.
The manufacturing method B is preferable because it is easy to reduce the yellowness (YI value) of the polyimide film, and the yellowness (YI value) calculated according to the JIS K7373-2006 is divided by the film thickness (μm). It is possible to preferably form a polyimide film having a value (YI value / film thickness (μm)) of 0.330 or less, more preferably 0.200 or less, still more preferably 0.150 or less.
In the production method B, the polyimide resin composition can be the same as the polyimide resin composition of the third production method described later, and the method for forming the polyimide resin coating film is the third method described later. The same can be applied to the polyimide resin coating film forming step of the above manufacturing method.
Further, in the manufacturing method B, examples of the support include the same supports used in the second manufacturing method described later.

(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 if necessary, contains additives and the like. May be.
The polyimide precursor is a polyamic acid obtained by polymerizing a tetracarboxylic acid component and a diamine component. In the first production method, the tetracarboxylic acid component and the diamine component used in the polyimide precursor are not particularly limited, and for example, the tetracarboxylic acid dianhydride and the diamine which are the tetracarboxylic acid residues of the above-mentioned polyimide. The diamines that are the residues can be listed respectively.

The number average molecular weight of the polyimide precursor is preferably 2000 or more, and more preferably 4000 or more, from the viewpoint of the strength of the film. On the other hand, if the number average molecular weight is too large, the viscosity becomes high and the workability may be deteriorated. Therefore, it is preferably 1,000,000 or less, and more preferably 500,000 or less.
The number average molecular weight of the polyimide precursor can be determined by NMR (for example, manufactured by BRUKER, AVANCE III). For example, a polyimide precursor solution is applied to a glass plate and dried at 100 ° C. for 5 minutes, then 10 mg of solid content is dissolved in 7.5 ml of a dimethyl sulfoxide-d6 solvent, NMR measurement is performed, and the mixture is bonded to an aromatic ring. The number average molecular weight can be calculated from the peak intensity ratio of hydrogen atoms.

Further, the polyimide precursor preferably has a weight average molecular weight of 2000 or more, and more preferably 4000 or more, from the viewpoint of strength when formed into 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 deteriorated. Therefore, it is preferably 1,000,000 or less, and more preferably 500,000 or less.
The weight average molecular weight of the polyimide precursor can be measured by gel permeation chromatography (GPC). Specifically, the polyimide precursor is a N-methylpyrrolidone (NMP) solution having a concentration of 0.5% by weight, and the developing solvent is 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-mentioned tetracarboxylic dianhydride with the above-mentioned diamine in a solvent. The solvent used for synthesizing the polyimide precursor (polyamic acid) is not particularly limited as long as the above-mentioned tetracarboxylic acid dianhydride and diamine can be dissolved, and for example, an aprotonic polar solvent or a water-soluble alcohol-based solvent can be 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; γ-butyrolactone or the like. Above all, 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 a carbon atom.

Further, when the polyimide precursor solution is prepared by combining two or more kinds of diamines, an acid dianhydride may be added to a mixed solution of two or more kinds of diamines to synthesize polyamic acid, or two kinds of diamines may be synthesized. The above diamine components 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, one silicon atom or one silicon atom in the main chain is used in a reaction solution in which a diamine having one or two silicon atoms in the main chain is dissolved. By adding an acid dianhydride having a molar ratio of 0.5 equal to that of two diamines and reacting them, an amide reacted with a diamine having one or two silicon atoms in the main chain at both ends of the acid dianhydride. An acid may be synthesized, the remaining diamine may be added in whole or in part thereof, and an acid dianhydride may be added to polymerize the polyamic acid. When polymerized by this method, 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. Polymerizing a polyamic acid by such a method is from the viewpoint that the positional relationship of the amic acid having one or two silicon atoms in the main chain can be specified to some extent, and a film having excellent impact resistance and bending resistance can be easily obtained. preferable.

When the number of moles of diamine in the polyimide precursor solution (polyamide acid solution) is X and the number of moles of tetracarboxylic acid dianhydride is Y, Y / X may be 0.9 or more and 1.1 or less. It is more preferably 0.95 or more and 1.05 or less, further preferably 0.97 or more and 1.03 or less, and particularly preferably 0.99 or more and 1.01 or less. Within such a range, the molecular weight (degree of polymerization) of the polyamic acid obtained can be appropriately adjusted.
The procedure of the polymerization reaction can be appropriately selected and used by a known method, and is not particularly limited.
Further, the polyimide precursor solution obtained by the synthesis reaction may be used as it is, and other components may be mixed therewith, if necessary, or the solvent of the polyimide precursor solution is dried and dissolved in another solvent. You may use it.

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. with a sample volume of 0.8 ml.

The polyimide precursor resin composition may contain an additive, if necessary. Examples of the additive include a silica filler for facilitating winding, a surfactant for improving film forming property and defoaming property, and the like, which are the same as those described in the above-mentioned polyimide layer. 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, it contains nitrogen atoms such as N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide and 1,3-dimethyl-2-imidazolidinone. Organic solvent; γ-butylolactone and the like can be used, but it is particularly preferable to use an organic solvent containing a nitrogen atom.

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

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

(3) Polyimide Precursor Resin Coating Form Forming Step In a 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 is used. The method is not particularly limited as long as it can be applied with a desired film thickness, and for example, known materials 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.
The coating may be performed by a single-wafer coating device or a roll-to-roll coating device.

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 becomes tack-free. By setting the drying temperature of the solvent to 150 ° C. or lower, the 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 preferable. If it exceeds the upper limit, it is not preferable from the viewpoint of the production efficiency of the polyimide film. On the other hand, if it is below the lower limit, the appearance of the obtained polyimide film may be affected by the rapid drying of the solvent.

The method for drying the solvent is not particularly limited as long as the solvent can be dried at the above temperature, and for example, an oven, a drying oven, a hot plate, infrared heating, or the like can be used.
When a high degree of control of optical properties is required, the atmosphere when the solvent is dried is preferably an inert gas atmosphere. The inert gas atmosphere is preferably a nitrogen atmosphere, preferably an oxygen concentration of 100 ppm or less, and more preferably 50 ppm or less. Heat treatment in the air can oxidize the film, causing it to color or reduce its performance.

(4) Imidization Step In the first production method, the 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, and more preferably 100 ° C. or higher. On the other hand, the temperature rise end temperature is preferably 250 ° C. or higher.

The temperature rising rate is preferably appropriately selected depending on the film thickness of the obtained polyimide layer, and when the film thickness of the polyimide layer is thick, it is preferable to slow down the temperature rising rate.
From the viewpoint of the production efficiency of the polyimide film, the temperature is preferably 5 ° C./min or more, and more preferably 10 ° C./min or more. On the other hand, the upper limit of the temperature rising rate is usually 50 ° C./min, preferably 40 ° C./min or less, and more preferably 30 ° C./min or less. It is preferable to set the temperature rise rate from the viewpoint of suppressing poor appearance and decrease in strength of the film, controlling whitening due to the imidization reaction, and improving light transmission.

The temperature rise may be continuous or stepwise, but it is preferable to raise the temperature continuously from the viewpoints of suppressing poor appearance and strength deterioration of the film and controlling whitening associated with the imidization reaction. Further, the temperature rising rate may be constant or may be changed in the middle of the above-mentioned entire temperature range.

The atmosphere at the time of temperature rise of imidization is preferably an inert gas atmosphere. The inert gas atmosphere is preferably a nitrogen atmosphere, preferably an oxygen concentration of 100 ppm or less, and more preferably 50 ppm or less. Heat treatment in the air can oxidize the film, causing it to color or reduce its performance.
However, when 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are hydrogen atoms directly bonded to the aromatic ring, the influence of oxygen on the optical properties is small, and an inert gas atmosphere is not used. A polyimide having high light transmittance can be obtained.

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

In order to obtain the final polyimide film, it is preferable to proceed the reaction to 90% or more, further 95% or more, and further 100% of imidization.
In order to allow the reaction to proceed to 90% or more and even 100% of imidization, it is preferable to keep the temperature at the end temperature for a certain period of time, and the holding time is usually 1 minute to 180 minutes, further 5 minutes to 150 minutes. It is preferably a minute.
The imidization rate can be measured by analyzing the spectrum by infrared measurement (IR) or the like.

As a second method for producing the polyimide film of the present disclosure, for example,
A step of preparing a first polyimide precursor resin composition containing a polyimide precursor and an organic solvent, and a step of preparing a second polyimide precursor resin composition containing a polyimide precursor and an organic solvent, respectively.
A step of applying the first polyimide precursor resin composition to a support to form a first polyimide precursor resin coating film, and a step of forming the first polyimide precursor resin coating film.
A step of applying the second polyimide precursor resin composition onto the first polyimide precursor resin coating film to form a second polyimide precursor resin coating film.
A production method comprising 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. Can be mentioned.
In the second 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 is performed. Examples thereof include a method of imidizing each polyimide precursor contained in each polyimide precursor resin coating film by the imidization step after performing until a desired number of layers is reached.
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 containing the same, and
A step of applying the first polyimide precursor resin composition to a support to form a first polyimide precursor resin coating film, and a step of forming the first polyimide precursor resin coating film.
A step of applying the second polyimide precursor resin composition onto the first polyimide precursor resin coating film to form a second polyimide precursor resin coating film.
A step of applying the third polyimide precursor resin composition on the second polyimide precursor resin coating film to form a third polyimide precursor resin coating film.
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. The production method comprises the step of imidizing the polyimide precursor contained in the above, and the first polyimide precursor resin composition and the third polyimide precursor resin composition may have the same composition. Can be mentioned.
In the second production method, each polyimide precursor resin coating film formed so as to have a desired number of layers becomes a polyimide layer.
The second manufacturing method is preferable because it is easy to reduce the birefringence of the polyimide film. According to the second manufacturing method, 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 can be suitably formed.

In the second production method, a step of preparing a polyimide precursor resin composition, a step of applying a polyimide precursor resin composition to form a polyimide precursor resin coating film, and a step of forming a polyimide precursor resin coating film are included. The step of imidizing the polyimide precursor can be the same as that of the first production method.

In the second manufacturing method, the mixing region can be formed at the boundary between the polyimide layers adjacent to each other by performing the imidization step after forming all the polyimide precursor resin coating films. It is preferable from the viewpoint of improving the adhesion and suppressing the generation of interference fringes.

The support used in the second manufacturing method is not particularly limited as long as it has a smooth surface and is heat resistant and solvent resistant. For example, an inorganic material such as a glass plate, a metal plate whose surface is mirror-treated, and the like can be mentioned. The shape of the support is selected by the coating method, and may be, for example, a plate shape, a drum shape, a belt shape, a sheet shape that can be wound on a roll, or the like.

In addition, the second production method is a laminate of the polyimide precursor resin coating film after all the polyimide precursor resin coating films have been formed and before the imidization step, and the imidization. It may further have a step (hereinafter referred to as a stretching step) of stretching at least one of the laminates of the coating film after imidization after the step.

When the production method has a stretching step, the imidization step may be performed on the polyimide precursor in the polyimide precursor resin coating film before the stretching step, or the polyimide precursor resin after the stretching step. This may be performed on the polyimide precursor in the coating film, or on both the polyimide precursor in the polyimide precursor resin coating film before the stretching step and the polyimide precursor existing in the film after the stretching step. You may go.

When the stretching step is performed in the second production method, it is more preferable that the imidization ratio of the polyimide precursor is 50% or more in the imidization step, especially before the stretching step. By setting the imidization ratio to 50% or more before the stretching step, even when stretching is performed after the step and then heating is performed at a higher temperature for a certain period of time to perform imidization, the appearance of the film may be poor. Whitening is suppressed. Above all, from the viewpoint of improving the impact resistance of the polyimide film, it is preferable to set the imidization ratio to 80% or more, further to 90% or more, and further to 100% in the imidization step before the stretching step. Is preferable. It is presumed that the surface hardness is improved and the impact resistance is improved because the rigid polymer chains are easily oriented by stretching after imidization.

When the second production method includes a stretching step, it is particularly 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 10,000% or less when the initial dimension before the stretching is set to 100% can be performed while heating at 80 ° C. or higher. preferable.
The heating temperature during stretching is preferably in the range of the glass transition temperature of the polyimide or the polyimide precursor ± 50 ° C., and preferably in the range of the glass transition temperature ± 40 ° C. If the stretching temperature is too low, the film may not be deformed and sufficient orientation may not be induced. On the other hand, if the stretching temperature is too high, the orientation obtained by stretching may be relaxed by the temperature, and sufficient orientation may not be obtained.
The stretching step may be performed at the same time as the imidization step. Stretching the imidized coating film after imidization of 80% or more, further 90% or more, further 95% or more, particularly substantially 100% imidization improves the impact resistance of the polyimide film. It is preferable from the viewpoint of

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

The method for fixing the polyimide film at the time of stretching is not particularly limited, and is selected according to the type of stretching apparatus and the like. Further, the stretching method is not particularly limited, and it is possible to stretch while passing through a heating furnace by using a stretching device having a transport device such as a tenter, for example. The polyimide film may be stretched in only one direction (longitudinal stretching or transverse stretching), or may be stretched in two directions by simultaneous biaxial stretching, sequential biaxial stretching, diagonal stretching, or the like.

As a method for producing the polyimide film of the present disclosure, further, as a third production method,
The process of preparing the polyimide molded body and
A step of preparing a polyimide resin composition containing a polyimide and an organic solvent,
A manufacturing method including 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 can be mentioned.
Further, as the method for producing the polyimide film of the present disclosure, as the fourth production method,
A step of preparing a first polyimide resin composition containing a polyimide and an organic solvent, and a second polyimide resin composition containing a polyimide and an organic solvent, respectively.
A step of applying the first polyimide resin composition to a support to form a first polyimide resin coating film, and a step of forming the first polyimide resin coating film.
Examples thereof include a manufacturing method including 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 for 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. There is a way to do it.

The third manufacturing method and the fourth manufacturing method can be suitably used when the polyimide used has a solvent solubility such that it dissolves in an organic solvent at 25 ° C. in an amount of 5% by mass or more.
The third manufacturing method and the fourth manufacturing method are preferable from the viewpoint that the yellowness (YI value) of the polyimide film can be easily reduced, and the yellowness (YI value) calculated in accordance with the JIS K7373-2006. Can preferably form a polyimide film having a value (YI value / film thickness (μm)) of 0.330 or less, more preferably 0.200 or less, still more preferably 0.150 or less. Is.

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

The polyimide used in the polyimide resin composition preparation step of the third production method and the fourth production method is a polyimide having the above-mentioned solvent solubility from the same polyimides as described in the polyimide layer. It can be selected and used. As a method for imidization, it is preferable to use chemical imidization using a chemical imidizing agent instead of heat dehydration for the dehydration ring closure reaction of the polyimide precursor. When 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 dehydration catalysts. The acid anhydride is not limited to acetic anhydride, and examples thereof include propionic acid anhydride, n-butyric acid anhydride, benzoic acid anhydride, and trifluoroacetic anhydride, but the acid anhydride is not particularly limited. At that time, a tertiary amine such as pyridine or β-picolinic acid may be used in combination. However, if these amines remain in the film, they deteriorate the optical properties, especially the yellowness (YI value), so the reaction solution reacted from the precursor to the polyimide is not cast as it is to form a film. It is preferable to purify by reprecipitation or the like to remove components other than polyimide to 100 ppm or less of the total weight of the polyimide before forming a film.

The organic solvent used in the reaction solution for chemically imidizing the polyimide precursor in the polyimide resin composition preparation step of the third production method and the fourth production method is, for example, in the first production method. The same thing as described in the above-mentioned polyimide precursor resin composition preparation step can be used. Examples of the organic solvent used for 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, and ethylene glycol mono-normal-butyl ether. Ethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ortho-dichlorobenzene, xylene, cresol, chlorbenzene, isobutyl acetate, isopentyl acetate, normal-butyl acetate, normal-propyl acetate, normal-pentyl acetate, cyclohexanol, cyclohexanone, 1.4-Dioxane, Tetrachlorethylene, Toluene, Methylisobutylketone, Methylcyclohexanol, Methylcyclohexanone, Methyl-normal-butylketone, dichloromethane, Dichloroethane and mixed solvents thereof, etc., among others, dichloromethane, normal-butyl acetate. , At least one selected from the group consisting of propylene glycol monomethyl ether acetate and a mixed solvent thereof can be preferably used.

The polyimide resin composition may contain an additive, if necessary. As the additive, the same additive as described in the polyimide precursor resin composition preparation step in the first production method can be used.
Further, in the third production method and the fourth production method, as a method for setting the water content of the polyimide resin composition to 1000 ppm or less, the polyimide precursor resin composition preparation step in the first production method is performed. 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 that 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 if necessary. The drying temperature is preferably 80 ° C. or higher and 150 ° C. or lower under normal pressure. Under reduced pressure, the temperature is preferably in the range of 10 ° C. or higher and 100 ° C. or lower. In the third production method and the fourth production method, the solvent may be dried at 150 ° C. or lower and then further dried at 300 ° C. or higher exceeding 150 ° C.

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 stretching step can be the same as the stretching step in the second manufacturing method.

5. Uses of Polyimide Film The use of the polyimide film of the present disclosure is not particularly limited, and it can be used as a member such as a base material or a surface material in which a glass product such as a thin flat 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 or a surface material for a display that can cope with a curved surface.
Specifically, the polyimide film of the present disclosure is used for, for example, a thin and bendable flexible type 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 suitably used. Further, 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 substrate, a member for a solar cell panel such as a surface protective film and a substrate material, and an optical waveguide. It can also be applied to members and other semiconductor-related members.

II. Laminates The laminates of the present disclosure are laminates having the polyimide film of the present disclosure described above and a hard coat layer containing at least one polymer of a radically polymerizable compound and a cationically 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, so that the surface hardness is improved and further. The impact resistance is further improved.

1. 1. Polyimide film As the polyimide film used for the laminate of the present disclosure, the above-mentioned polyimide film of the present disclosure can be used, and thus the description thereof is omitted here.

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

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

The number of radically polymerizable groups contained in one molecule of the radically polymerizable compound is preferably two or more, and more preferably three 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 transmission, 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, or a molecule called urethane (meth) acrylate, polyester (meth) acrylate, or epoxy (meth) acrylate. Monomers having a number of (meth) acryloyl groups within and having a molecular weight of several hundred to several thousand can be preferably used.
In addition, in this specification, (meth) acryloyl represents each of acryloyl and methacryloyl, and (meth) acrylate represents each of acrylate and methacrylate.

Specific examples of the radically polymerizable compound include vinyl compounds such as divinylbenzene; ethylene glycol di (meth) acrylate, bisphenol A epoxy di (meth) acrylate, and 9,9-bis [4- (2- (2- ( Meta) acryloyloxyethoxy) phenyl] fluorene, alkylene oxide-modified bisphenol A di (meth) acrylate (for example, ethoxylated (ethylene oxide modified) bisphenol A di (meth) acrylate), trimethyl propantri (meth) acrylate, tri Methylol ethanetri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate , Polyacrylate polyacrylates such as dipentaerythritol hexa (meth) acrylates, diacrylates such as bisphenol A diglycidyl ether diacrylates, epoxy acrylates such as hexanediol diglycidyl ether diacrylates, hydroxyl groups such as polyisocinates and hydroxyethyl acrylates. Examples thereof include urethane acrylate obtained by the reaction of the contained acrylate.

(2) Cationicly polymerizable compound The cationically polymerizable compound is a compound having a cationically polymerizable group. The cationically polymerizable group contained in the cationically polymerizable compound may be any functional group capable of causing a cationically polymerizable reaction, and is not particularly limited, and examples thereof include an epoxy group, an oxetanyl group, and a vinyl ether group. When the cationically polymerizable compound has two or more cationically polymerizable groups, the cationically 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 two or more, and more preferably three or more, from the viewpoint of improving the hardness of the hard coat layer.
Further, as the cationically polymerizable compound, a compound having at least one of an epoxy group and an oxetanyl group as the cationically polymerizable group is preferable, in terms of adhesion, light transmission, surface hardness and impact resistance. Therefore, a compound having at least one of an epoxy group and an oxetanyl group at least two in one molecule is more preferable. A cyclic ether group such as an epoxy group or an oxetanyl group is preferable because the shrinkage associated with the polymerization reaction is small. Further, among the cyclic ether groups, compounds having an epoxy group are easily available, compounds having various structures are easily available, the durability of the obtained hard coat layer is not adversely affected, and compatibility with radically polymerizable compounds is easily controlled. There is an advantage. Of the cyclic ether groups, the oxetanyl group has a higher degree of polymerization than the epoxy group and has low toxicity, and when the obtained hard coat layer is combined with a compound having an epoxy group, the cation in the coating film There are advantages such as increasing the network formation rate obtained from the polymerizable compound and forming an independent network without leaving an unreacted monomer in the film even in a region mixed with the radically polymerizable compound.

Examples of the cationically polymerizable compound having an epoxy group include polyglycidyl ether of a polyhydric alcohol having an alicyclic ring, or a cyclohexene ring or cyclopentene ring-containing compound with an appropriate oxidizing agent such as hydrogen peroxide or peracid. Alicyclic epoxy resin obtained by epoxidation; polyglycidyl ether of aliphatic polyhydric alcohol or its alkylene oxide adduct, polyglycidyl ester of aliphatic long chain polybasic acid, homopolymer of glycidyl (meth) acrylate, An aliphatic epoxy resin such as a copolymer; a glycidyl ether produced by reacting bisphenols such as bisphenol A, bisphenol F and hydrogenated bisphenol A, or derivatives such as alkylene oxide adducts and caprolactone adducts thereof with epichlorohydrin. And novolak epoxy resin and the like, and examples thereof include glycidyl ether type epoxy resin derived from bisphenols.

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

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) and polyglycerol polyglycidyl ether (Denacol EX). -512, Denacol EX-521), Pentaeryth Little Polyglycidyl Ether (Denacol EX-411), Diglycerol Polyglycidyl Ether (Denacol EX-421), Gglycerol Polyglycidyl Ether (Denacol EX-313, Denacol EX-314), Trimethylol Propanepolyglycidyl Ether (Denacol EX-321), Resoltinol Diglycidyl Ether (Denacol EX-201), Neopentyl Glycol Diglycidyl Ether (Denacol EX-211), 1,6 Hexanodiol 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), phenylglycidyl ether (Denacol EX-141), phenol glycidyl ether (Denacol EX-145), butylphenyl glycidyl ether (Denacol EX-146), diglycidyl phthalate (Denacol EX-721), hydroquinone diglycidyl ether (Denacol EX-203), Diglycidyl terephthalate (Denacol EX-711), Glycidyl phthalimide (Denacol EX-731), Dibromophenyl glycidyl ether (Denacol EX-147), Dibromoneopentyl glycol diglycidyl ether (Denacol EX-221) (The above is the product name in parentheses and is made by Nagase Chemtex.)

Other commercially available epoxy resins include Epicoat 825, Epicoat 827, Epicoat 828, Epicoat 828EL, Epicoat 828XA, Epicoat 834, Epicoat 801 and Epicoat 801P, Epicoat 802, Epicoat 815, Epicoat 815XA, and 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. (The above product name is made by Japan Epoxy Resin).

Examples of the cationically polymerizable compound having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane (OXT-101) and 1,4-bis-3-ethyloxetane-3-ylmethoxymethylbenzene (OXT-121). , Bis-1-ethyl-3-oxetanylmethyl ether (OXT-221), 3-ethyl-3--2-ethylhexyloxymethyloxetane (OXT-212), 3-ethyl-3-phenoxymethyloxetane (OXT-) 211) (The product name in parentheses is the product name of Toa Synthetic), and the product names include Ethanacole EHO, Ethanacole OXBP, Ethanacole OXTP, and Ethanacole OXMA (trade name, manufactured by Ube Kosan).

(3) Polymerization Initiator The polymer of at least one of the radically polymerizable compound and the cationically polymerizable compound contained in the hard coat layer used in the present disclosure is, for example, the radically polymerizable compound and the cationically polymerizable compound. It can be obtained by adding a polymerization initiator to at least one 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 promote radical polymerization and cation polymerization.

The radical polymerization initiator may be any kind as long as it can release a substance that initiates radical polymerization by at least one of light irradiation and heating. For example, examples of the photoradical polymerization initiator include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocenes, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, thioxanthone derivatives and the like. More specifically, 1,3-di (tert-butyldioxycarbonyl) benzophenone, 3,3', 4,4'-tetrakis (tert-butyldioxycarbonyl) benzophenone, 3-phenyl-5-. Isooxazolone, 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 Co., Ltd.), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane-1- On (trade name: Irgacure 369, manufactured by Ciba Japan Co., Ltd.), bis (η5-2,4-cyclopentadiene-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1-yl) ) -Phenyl) Titanium) (trade name: Irgacure 784, manufactured by Ciba Japan Co., Ltd.), etc., but is not limited thereto.

In addition to the above, commercially available products can be used, specifically, Irgacure 907, Irgacure 379, Irgacure 819, Irgacure 127, Irgacure 500, Irgacure 754, Irgacure 250, Irgacure 1800, 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 and the like.

Further, the cationic polymerization initiator may be any kind as long as it can release a substance that initiates cationic polymerization by at least one of light irradiation and heating. Cationic polymerization initiators include sulfonic acid esters, imide sulfonates, dialkyl-4-hydroxysulfonium salts, aryl sulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η ⁶ -benzene) (η ⁵ -cyclopentadi). Enyl) iron (II) and the like are exemplified, and more specific examples thereof include, but are not limited to, benzointosylate, 2,5-dinitrobenzyltosylate, N-tosiphthalateimide and the like.

Examples of the agent used as both the radical polymerization initiator and the cationic polymerization initiator include aromatic iodonium salts, aromatic sulfonium salts, aromatic diazonium salts, aromatic phosphonium salts, triazine compounds, iron arene complexes and the like. More specifically, chlorides, bromides, borofluoride salts, hexafluorophosphate salts, hexafluorocarbons of iodoniums such as diphenyliodonium, ditriliodonium, bis (p-tert-butylphenyl) iodonium, and bis (p-chlorophenyl) iodonium. Iodonium salts such as antimonate salts, sulfonium chlorides such as triphenylsulfonium, 4-tert-butyltriphenylsulfonium, tris (4-methylphenyl) sulfonium, bromides, borofluoride salts, hexafluorophosphate salts, hexafluoroantimonates. Sulfonium salts such as salts, 2,4,6-tris (trichloromethyl) -1,3,5-triazine, 2-phenyl-4,6-bis (trichloromethyl) -1,3,5-triazine, 2- Examples thereof include, but are not limited to, 2,4,6-substituted-1,3,5 triazine compounds such as methyl-4,6-bis (trichloromethyl) -1,3,5-triazine. ..

(4) Additives In addition to the above-mentioned polymer, the hard coat layer used in the present disclosure includes antistatic agents, antiglare agents, antifouling agents, and inorganic or organic fine particles for improving hardness, if necessary. It may contain additives such as a leveling agent and various sensitizers.

3. 3. Structure 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. It may be one in which the hard coat layer is laminated on both sides of the polyimide film. Further, the laminate of the present disclosure is used to improve the adhesion between the polyimide film and the hard coat layer, for example, in addition to the polyimide film and the hard coat layer, as long as the effects of the present disclosure are not impaired. It may have another layer such as a primer layer. Further, in the laminate of the present disclosure, the polyimide film and the hard coat layer may be located adjacent to each other.
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, the said. Of the two polyimide layers, it is preferable that the hard coat layer is located on the polyimide layer side having a relatively large Young's modulus from the viewpoint of improving impact resistance.

The overall thickness of the laminate of the present disclosure may be appropriately selected depending on the intended use, but is preferably 10 μm or more, 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.
Further, in the laminated body of the present disclosure, the thickness of each hardcoat 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, further 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 in the method for measuring the pencil hardness of the polyimide film except that the load is 9.8 N.

The laminated body of the present disclosure preferably has a total light transmittance of 85% or more, more preferably 88% or more, and further more than 90%, as measured in accordance with JIS K7361-1. Is preferable. Since the transmittance is high as described above, the transparency is improved and the material can be used as a substitute for glass.
The total light transmittance of the laminate of the present disclosure can be measured in the same manner as the total light transmittance measured in accordance with JIS K7361-1 of the polyimide film.

In the laminated body of the present disclosure, the yellowness (YI value) calculated in accordance with the JIS K7373-2006 is preferably 30 or less, more preferably 20 or less, and more preferably 16 or less. More 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 in accordance with the 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, still more preferably 5 or less, from the viewpoint of light transmission.
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 of the laminate of the present disclosure at a wavelength of 590 nm is preferably 0.040 or less, more preferably 0.025 or less, still more preferably 0.020 or less. It is particularly preferably 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 of the polyimide film at a wavelength of 590 nm.

5. Use of Laminate The use of the laminate of the present disclosure is not particularly limited, and for example, it can be used in the same manner as the above-mentioned use of the polyimide film of the present disclosure.

6. Method for manufacturing a laminated body As a method for manufacturing a laminated body of the present disclosure, for example,
A step of forming a coating film of a composition for forming a hard coat layer containing at least one of a radically polymerizable compound and a cationically polymerizable compound on at least one surface of the polyimide film of the present disclosure.
Examples thereof include a manufacturing method including a step of curing the coating film.

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

As a method for 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 known on at least one surface of the polyimide film. Examples thereof include a method of coating by a coating means.
The coating means is not particularly limited as long as it can be applied with a desired film thickness, and examples thereof include the same means as those for applying the polyimide precursor resin composition to the support.
The amount of coating of the curable resin composition for the hard coat layer varies depending on the required performance 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 preferable that the coating amount is in ^{the range of 3 g / m 2} or more and 30 g / m ² or less, and particularly preferably in the range of 5 g / m ² or more and 25 g / m ² or less.

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

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

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

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

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

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

When the display surface material of the present disclosure is the laminate of the present disclosure, the outermost surface after being arranged on the surface of the display may be the surface on the polyimide film side or the hard coat layer. It may be a side surface. Above all, it is preferable to arrange the surface material for a display of the present disclosure so that the surface on the hard coat layer side becomes the surface on the front side, from the viewpoint of impact resistance and bending resistance. When the surface material for a display of the present disclosure is the polyimide film of the present disclosure and the Young's modulus of the two polyimide layers located on the outermost surface of the polyimide film is different from each other, the polyimide layer side having a relatively large Young's modulus is used. It is preferable to arrange the surface material for display of the present disclosure so that the surface becomes a more front surface from the viewpoint of impact resistance and bending resistance. Further, the surface material for a display of the present disclosure may have a fingerprint adhesion prevention layer on the outermost surface.

The method for arranging the display surface material of the present disclosure on the surface of the display is not particularly limited, and examples thereof include a method via an adhesive layer. As the adhesive layer, a conventionally known adhesive layer that can be used for adhering a surface material for a display can be used.

[Evaluation method]
Hereinafter, unless otherwise specified, measurements or evaluations were performed at 25 ° C.
<Weight average molecular weight of polyimide precursor>
For the weight average molecular weight of the polyimide precursor, the polyimide precursor is prepared as a solution of N-methylpyrrolidone (NMP) having a concentration of 0.5% by weight, and the solution is filtered through a syringe filter (pore size: 0.45 μm) to develop the solution. As a solvent, a 10 mmol% LiBr-NMP solution having a water content of 500 ppm or less was used, and a GPC device (HLC-8120 manufactured by Tosoh Co., Ltd., column used: GPC LF-804 manufactured by SHODEX) was used, the sample injection amount was 50 μL, and the solvent flow rate was 0.5 mL. The measurement was carried out under the condition of / min and 40 ° C. 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, It was used as a conversion value for standard polystyrene measured based on 3,070). The elution time was compared with the calibration curve to determine the weight average molecular weight.
<Viscosity of polyimide precursor solution>
The viscosity of the polyimide precursor solution was measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25 ° C. with a sample volume of 0.8 ml.

<Weight average molecular weight of polyimide>
Immerse 15 mg of polyimide powder in 15000 mg of N-methylpyrrolidone (NMP), heat to 60 ° C in a water bath, and stir at a rotation speed of 200 rpm using a stirrer for 3 to 60 hours until dissolution is visually confirmed. By doing so, an NMP solution having a concentration of 0.1% by weight was obtained. The solution is filtered through a syringe filter (pore size: 0.45 μm), and a 30 mmol% LiBr-NMP solution having a water content of 500 ppm or less is used as a developing solvent, and a GPC device (manufactured by Tosoh, HLC-8120, detector: differential) is used. Refractometer (RID) detector, column used: SHODEX GPC LF-804 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 conditions of. The weight average molecular weight of the polyimide 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, It was used as a conversion value with respect to standard polystyrene measured based on 070). The elution time was compared with the calibration curve to determine the weight average molecular weight.
<Viscosity of polyimide solution>
The viscosity of the polyimide solution was measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25 ° C. with a sample volume of 0.8 ml.

<Film thickness>
The thickness of each polyimide layer of the polyimide film of each example and the thickness of the single-layer polyimide film of each comparative example are the test pieces obtained by cutting the 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 used.
Since the polyimide films of Examples 7 to 10 and Reference Examples 11 and 12 had a mixing region in which the materials of the respective polyimide layers were mixed at the boundary between the polyimide layers adjacent to each other, the test in which the polyimide films were cut in the thickness direction. Element mapping was performed on the cross section of the piece by the flight time type secondary ion mass spectrometry (TOF-SIMS) using the flight time type secondary ion mass spectrometry (manufactured by ION-TOF, model number TOF.SIMS5), and silicon. The film thickness of each polyimide layer was measured with the portion where the detected amount of atoms is the average value of the detected amounts of silicon atoms in the two regions other than the mixing region as the boundary between the polyimide layers. In the case of a region having a thickness where the average value of the detected amounts of silicon atoms in the two regions other than the mixing region is thick, the central portion in the thickness direction of the region is used as the boundary between the polyimide layers of each polyimide layer. The film thickness was measured.

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

<Coefficient of linear thermal expansion (CTE)>
The elongation of the test piece was measured under the following conditions with a thermomechanical analyzer (TMA) for the test piece cut out from a single-layer polyimide film to a size of 5 mm × 15 mm, and the linear heat was measured in the range of 50 ° C to 250 ° C. The coefficient of expansion (CTE) was calculated.
<CTE measurement conditions>
Model name: TMA-60, manufactured by Shimadzu Corporation Atmospheric gas: Nitrogen gas Flow rate: 50 ml / min
Initial load: 9g
[Temperature program]
After maintaining at 30 ° C. for 10 minutes under 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.

<Tension modulus>
A test piece obtained by cutting a polyimide film into a size of 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 then, in accordance with JIS K7127, a tensile speed of 8 mm / min and a chuck distance of 20 mm. , The tensile 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>
It was measured by a haze meter (HM150 manufactured by Murakami Color Technology Research Institute) in accordance with JIS K7361-1.

<Haze value>
It was measured by a haze meter (HM150 manufactured by Murakami Color Technology Research Institute) in accordance with JIS K-7105.

<YI value (yellowness)>
The YI value is based on JIS K7373-2006, using an ultraviolet-visible near-infrared spectrophotometer (JASCO Corporation V-7100), and using an auxiliary illuminant C and a two-degree field of view by a spectrophotometric method. , The tristimulus values X, Y, Z in the XYZ colorimetric system are obtained based on the transmittance measured in the range of 250 nm or more and 800 nm or less at 1 nm intervals, and calculated from the X, Y, Z values by the following formula. bottom.
YI = 100 (1.2769X-1.592Z) / Y
Further, the value (YI / film thickness (μm)) obtained by dividing the YI value by the total film thickness (μm) of the polyimide film was obtained.

<Birerefringence>
The thickness direction retardation value (Rth) of the polyimide film was measured with light at 23 ° C. and a wavelength of 590 nm using a phase difference measuring device (manufactured by Oji Measuring Instruments Co., Ltd., product name “KOBRA-WR”). For the thickness direction retardation value (Rth), the phase difference value incident at 0 degrees and the phase difference value incident at an angle of 40 degrees were measured, and the thickness direction retardation value Rth was calculated from these phase difference values. The retardation value of the oblique 40-degree incident was measured by injecting light having a wavelength of 590 nm onto the retardation film from a direction inclined by 40 degrees from the normal of the retardation film.
The birefringence of the polyimide film was obtained by substituting it into the formula: Rth / d (film thickness (nm) of the polyimide film).

<Static bending test>
Hereinafter, the method of the static bending test will be described with reference to FIG.
A polyimide film test piece 10 cut into a size of 15 mm × 40 mm is bent at the position of half of the long side, and metal pieces 2 (100 mm × 30 mm × 6 mm) having a thickness of 6 mm at both ends of the long side of the test piece 10 are placed on the upper and lower surfaces. The glass plates (100 mm x 100 mm x 0) are arranged from above and below with tape fixed so that the overlap margins between both ends of the test piece 10 and the upper and lower surfaces of the metal piece 2 are 10 mm each. .7 mm) It 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, dummy test pieces 4a and 4b are sandwiched between the metal pieces 2 and the glass plates 3a and 3b where the test pieces 10 are not present, and fixed with tape so that the glass plates 3a and 3b are parallel to each other. bottom. The test piece 10 fixed in a bent state in this way is allowed to stand for 24 hours in an environment of 60 ° C. and 90% relative humidity (RH), then the glass plate and the fixing tape are removed, and the test piece is removed. The force applied to 10 was released. Then, one end of the test piece 10 was fixed, and the internal angle of the test piece was measured 30 minutes after releasing the force applied to the test piece 10.
The polyimide film of Reference Example 11 was bent so that the polyimide layer having a relatively large Young's modulus was on the inside.
If the film is completely restored unaffected by the static bending test, the internal angle will be 180 °.

<Pencil hardness>
The pencil hardness of the polyimide film is determined by adjusting the humidity of the measurement sample for 2 hours under the conditions of a temperature of 25 ° C and a relative humidity of 60%, and then using a test pencil specified by JIS-S-6006 to scratch a pencil made by Toyo Seiki Co., Ltd. By performing a pencil hardness test (0.98N load) specified in JIS K5600-5-4 (1999) on the film surface using a coating film hardness tester, the highest pencil hardness that does not scratch is evaluated. went. The polyimide film of Reference 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 aluminum foils 6 having a thickness of 100 μm were laminated on an iron base 5, and a polyimide film test piece 10 cut out to a size of 15 mm × 40 mm was placed on the laminated aluminum foil 6. A ballpoint pen 7 (made by BiC, 0.7 mm) is installed at a height (distance between the test piece 10 and the tip of the pole pen) of 90 mm, and the ballpoint pen 7 is dropped on the upper surface of the test piece 10 to form an aluminum foil formed by the tip of the ballpoint pen 7. The depth of the dent of 6 was evaluated by measuring with an optical microscope (depth of focus). The depth of the dent is shown in Tables 2 and 4. The smaller the depth of the dent, the better the impact resistance. The polyimide film of Reference 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)
In a 5 L separable flask, 3081 g of dehydrated dimethylacetamide and 322 g (1.00 mol) of 2,2'-bis (trifluoromethyl) benzidine (TFMB) were placed, and the liquid temperature of the solution in which TFMB was dissolved was adjusted. To the place controlled to 30 ° C, 443 g (1.00 mol) of 4,4'-(hexafluoroisopropyridene) diphthalic acid anhydride (6FDA) was gradually divided into several times so that the temperature rise was 2 ° C or less. A polyimide precursor solution 1 (solid content 20% by weight) in which the polyimide precursor 1 was dissolved was synthesized. The viscosity of the polyimide precursor solution 1 (solid content 20% by weight) at 25 ° C. was 34920 cps, and the weight average molecular weight of the polyimide precursor 1 measured by GPC was 408500.

(Synthesis Examples 2-3)
In the procedure of Synthesis Example 1, the reaction was carried out so as to have the raw material and solid content concentrations shown in Table 1 to prepare polyimide precursor solutions 2 to 3.

(Synthesis Example 4)
A solution in which dehydrated dimethylacetamide (2265 g) and 1,3-bis (3-aminopropyl) tetramethyldisiloxane (AprTMOS) (24.9 g) are dissolved is placed in a 5 L separable flask. 4,4'-(hexafluoroisopropyridene) diphthalic acid anhydride (6FDA) (22.2 g) was gradually added to a place controlled to a temperature of 30 ° C. so that the temperature rise was 2 ° C. or less. The mixture was stirred with a mechanical stirrer for 30 minutes. 2,2'-Bis (trifluoromethyl) benzidine (TFMB) (288 g) was added thereto, and after confirming that it was completely dissolved, 4,4'-(hexafluoroisopropyridene) diphthalic acid anhydride ( 6FDA) (420 g) was gradually added in several portions so that the temperature rise was 2 ° C. or lower to synthesize a polyimide precursor solution 4 (solid content 25% by mass) in which the polyimide precursor 4 was dissolved. In the polyimide precursor solution 4, the molar ratio of TFMB to AprTMOS (TFMB: AprTMOS) was 90:10, and the total mole of TFMB and AprTMOS was the same as the mole of TFMB of 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 AprTMOS: 1,3-bis (3-aminopropyl) tetramethyldisiloxane 6FDA: 4, 4'-(Hexafluoroisopropyridene) diphthalic acid anhydride PMDA: pyromellitic acid dianhydride

(Example 1)
Using the polyimide precursor solution 1, a single-layer polyimide film having a film thickness of 50 μm obtained by the following procedures (1) to (3) was prepared as the polyimide molded body A.
(1) The polyimide precursor solution 1 was applied onto a glass plate and dried in a circulation oven at 120 ° C. for 10 minutes.
(2) The temperature was raised to 350 ° C. at a heating rate of 10 ° C./min under a nitrogen stream (oxygen concentration of 100 ppm or less), held for 1 hour, and then cooled to room temperature.
(3) The polyimide film was obtained by peeling from the glass plate.
The polyimide precursor solution 2 is applied to both the front and back surfaces of the polyimide molded body A so that the film thickness after imidization is 3 μm, and dried in a circulation oven at 120 ° C. for 10 minutes to coat the polyimide precursor resin coating film. After forming, the temperature was raised to 350 ° C at a temperature rise rate of 10 ° C / min under a nitrogen stream (oxygen concentration of 100 ppm or less), held for 1 hour, and then cooled to room temperature to imidize the polyimide precursor. , The polyimide film of Example 1 was obtained. In the obtained polyimide film, a polyimide layer having a relatively large Young's modulus (hereinafter referred to as a high Young's modulus layer) is laminated on both sides of a polyimide layer having a relatively small Young's modulus (hereinafter referred to as a low Young's modulus layer). It was a multi-layered polyimide film having a layered structure.

(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 having a thickness of 80 μm produced by changing the coating amount of the polyimide precursor solution 1, is used, and the thickness of the high Young's modulus layer is increased. The polyimide films of Examples 4 to 6 were obtained in the same manner as in Example 1 except that the above was 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 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. It was designated as C. In the production of the polyimide film of Example 1, the polyimide film of Example 7 was obtained in the same manner as in Example 1 except that the polyimide molded body C was used instead of the polyimide molded body A.

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

(Comparative Example 2)
Using the polyimide precursor solution 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 was used as the polyimide film of Comparative Example 2.

(Comparative Example 3)
Using the polyimide precursor solution 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 was used as the polyimide film of Comparative Example 3.

(Comparative Example 4)
Using the polyimide precursor solution 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 was used as the polyimide film of Comparative Example 4.

(Comparative Example 5)
Using the polyimide precursor solution 1, 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 was used as the polyimide film of Comparative Example 5.

The polyimide films of Examples 1 to 7 and Comparative Examples 1 to 5 were evaluated using the above 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. Further, the film thickness, Young's modulus and linear thermal expansion coefficient (CTE) shown in Tables 2 and 4 are the measurement results of each polyimide layer, and the other evaluation results show the evaluation results of the entire polyimide film. The polyimide species Nos. 1 to 6 in Tables 2 and 4 correspond to the polyimides obtained by using the polyimide precursor solution to the polyimide solution 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 high Young's modulus layers on both sides of the low Young's modulus layer having a thickness of 50 μm are comparative examples 1 which are single-layered polyimide films having a low Young's modulus of about 50 μm. The impact resistance is improved while having the same good bending resistance as the above, and the bending resistance is improved as compared with Comparative Example 2, which is a polyimide film having a high Young's modulus layer and a single layer. For Examples 2 and 3, the impact resistance was also improved. Further, the polyimide films of Examples 4 to 6 having high Young's modulus layers on both sides of the low Young's modulus layer having a thickness of 80 μm are similar to Comparative Example 5 which is a polyimide film having a single layer of low Young's modulus having a thickness of 80 μm. The impact resistance was improved while having good bending resistance, and the impact resistance and bending resistance were further improved as compared with Comparative Example 2, which is a polyimide film having a high Young's modulus layer. .. The polyimide film of Example 7 having a high Young's modulus layer on both sides of the low Young's modulus layer containing a silicon atom is as good as Comparative Example 4 which is a polyimide film of a single layer of a low Young's modulus layer containing a silicon atom. The impact resistance was improved while having a high bending resistance, and further, the impact resistance and the bending resistance were improved as compared with Comparative Example 2, which is a 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 to the polyimide films of Examples 1 to 7.

(Synthesis Example 5)
A solution in which dehydrated dimethylacetamide (2903 g) and 1,3-bis (3-aminopropyl) tetramethyldisiloxane (AprTMOS) (15.9 g) are dissolved is placed in a 5 L separable flask. 4,4'-(hexafluoroisopropyridene) diphthalic acid anhydride (6FDA) (14.6 g) was gradually added to a place where the temperature was controlled to 30 ° C. so that the temperature rise was 2 ° C. or lower. The mixture was stirred with a mechanical stirrer for 30 minutes. 2,2'-Bis (trifluoromethyl) benzidine (TFMB) (387 g) was added thereto, and after confirming that the solution was completely dissolved, 4,4'-(hexafluoroisopropyridene) diphthalic acid anhydride ( 6FDA) (548 g) was gradually added in several portions so that the temperature rise was 2 ° C. or lower to synthesize a polyimide precursor solution 5 (solid content 25% by mass) in which the polyimide precursor 5 was dissolved.
The above-mentioned polyimide precursor solution 5 (400 g) cooled to room temperature was added to a 5 L separable flask under a nitrogen atmosphere. Dehydrated dimethylacetamide (109 g) was added thereto, and the mixture was stirred until uniform. Next, the catalyst pyridine (41.4 g) and acetic anhydride (53.4 g) were added and stirred at room temperature for 24 hours to synthesize a polyimide solution. Butyl acetate (406 g) was added to the obtained polyimide solution and stirred until uniform, and then methanol (3000 g) was gradually added to obtain a white slurry. The slurry was filtered and washed with methanol 5 times to obtain polyimide 5. The weight average molecular weight of the polyimide measured by GPC was 175,000.
The 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)
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 instead 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, the polyimide solution 6 shown in Table 3 was obtained in the same manner as in the synthesis example 5 except that the polyimide 6 was used instead of the polyimide 5 in the synthesis example 5. Table 3 shows the viscosities 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 applied onto a glass plate, air-dried, and then the film was peeled off from the glass plate.
(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 the front and back surfaces 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 a heating rate of 10 ° C./min at an oxygen concentration of 100 ppm or less, holding the temperature at 200 ° C. for 1 hour, and then cooling to room temperature.

(Example 9)
In the procedure of (i) to (iii) of Example 8, the film thickness is 55 μm in the same manner as in the procedure of (i) to (iii), except that the polyimide solution 5 is used instead of the polyimide solution 6. A single-layer polyimide film was obtained and used as a polyimide molded body E.
The polyimide precursor solution 2 is applied to both the front and back surfaces of the polyimide molded body E so that the film thickness after imidization is 3 μm, and dried in a circulation oven at 120 ° C. for 10 minutes to coat the polyimide precursor resin coating film. After forming, the temperature was raised to 350 ° C at a temperature rise rate of 10 ° C / min under a nitrogen stream (oxygen concentration of 100 ppm or less), 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 procedure of (i) to (iii) of Example 8, 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. )-(Iii), a single-layer polyimide film having a film thickness of 20 μm was obtained and used as a polyimide molded body F.
The polyimide precursor solution 2 is applied to both the front and back surfaces of the polyimide molded body F so that the film thickness after imidization is 15 μm, and dried in a circulation oven at 120 ° C. for 10 minutes to coat the polyimide precursor resin coating film. After forming, the temperature was raised to 350 ° C at a temperature rise rate of 10 ° C / min under a nitrogen stream (oxygen concentration of 100 ppm or less), held for 1 hour, and then cooled to room temperature to imidize the polyimide precursor. , The polyimide film of Example 10 was obtained.

( Reference example 11)
In the procedure of (i) to (iii) of Example 8, the film thickness is 48 μm in the same manner as in the procedure of (i) to (iii), except that the polyimide solution 5 is used instead of the polyimide solution 6. A single-layer polyimide film was obtained and used as a 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 circulation oven at 120 ° C. for 10 minutes to obtain a polyimide precursor resin coating film. After forming, the temperature was raised to 350 ° C at a temperature rise rate of 10 ° C / min under a nitrogen stream (oxygen concentration of 100 ppm or less), held for 1 hour, and then cooled to room temperature to imidize the polyimide precursor. , The polyimide film of Reference Example 11 was obtained.

( Reference example 12)
In the same procedure as in (1) to (3) above, except that the polyimide precursor solution 2 was used instead of the polyimide precursor solution 1 in the procedures (1) to (3) of Example 1. A single-layer polyimide film having a thickness of 10 μm was obtained and used as a polyimide molded body H.
The polyimide solution 5 is applied to both the front and back surfaces of the polyimide molded body H so that the film thickness after drying is 20 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 Reference Example 12 was obtained by raising the temperature to 200 ° C. at a heating rate of 10 ° C./min at an oxygen concentration of 100 ppm or less, holding the temperature at 200 ° C. for 1 hour, and then cooling to room temperature.

(Comparative Example 6)
Using the polyimide solution 5, 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 was used as the polyimide film of Comparative Example 6.

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

The polyimide films of Examples 8 to 10, Reference Examples 11 and 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 a silicon atom on both sides of a low Young's modulus layer containing a silicon atom, and is a single low Young's modulus layer containing a silicon atom. While having the same good bending resistance as Comparative Example 7 which is a layered polyimide film, the impact resistance is improved, and further, compared to Comparative Example 6 which is a polyimide film having a high Young's modulus layer single layer. 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 containing no silicon atom on both sides of the low Young's modulus layer containing a silicon atom, and are a single layer of a low Young's modulus layer containing a silicon atom. While having the same good bending resistance as Comparative Example 6 which is a polyimide film, the impact resistance is remarkably improved, and further, compared with Comparative Example 2 which is a polyimide film having a high Young's modulus layer and a single layer. The bending resistance was improved, and the impact resistance was remarkably improved.
The polyimide film of Reference Example 11 has a high Young's modulus layer that does not contain a silicon atom on one surface of a low Young's modulus layer that contains a silicon atom, and is a single layer of a low Young's modulus layer that contains a silicon atom. While having the same good bending resistance as Comparative Example 6 which is a polyimide film, the impact resistance is improved, and moreover, it is bent as compared with Comparative Example 2 which is a polyimide film having a high Young's modulus layer single layer. The resistance was improved and the impact resistance was improved.
The polyimide film of Reference Example 12 has a low Young's modulus layer containing a silicon atom on both sides of a high Young's modulus layer containing no silicon atom, and is a polyimide film having a low Young's modulus layer containing a silicon atom. The impact resistance was improved as compared with Comparative Example 6, and the bending resistance was improved as compared with Comparative Example 2, which was a polyimide film having a high Young's modulus layer and a single layer.

Further, when the polyimide films of Examples 7 to 10 and Reference Examples 11 and 12 were cut in the thickness direction and their cross sections were observed with a scanning electron microscope (SEM), the polyimide layers of each polyimide layer were found at the boundaries of the polyimide layers adjacent to each other. It had a mixing region where the materials were mixed.
In addition, the polyimide films of Examples 1 to 10 and Reference Examples 11 and 12 were inspected for the presence or absence of interference fringes. Specifically, one side of the polyimide film was painted with black ink, an interference fringe inspection lamp was applied to the other side, and reflection observation was performed visually. As a result, all the polyimide films were at a practical level, but the polyimide films of Examples 7 to 10 and Reference Examples 11 and 12 had interference fringes suppressed as compared with the polyimide films of Examples 1 to 6. rice field.

Further, the polyimide films of Examples 1 to 10 and Reference Examples 11 and 12 were subjected to an adhesion test of the polyimide layer on the surface according to the following adhesion test method. As a result, the ratio of the area where the polyimide layer on the surface was peeled off was 20% or less in each case. In Reference Example 11, an adhesion test was performed on the surface on the high Young's modulus layer side, and in each Example and Reference Example other than Reference Example 11, an adhesion test was performed on both sides.
<Adhesion test>
According to the grid test of JIS K5400, the polyimide layer on the surface was cut in a grid pattern at 1 mm intervals using a cutter knife to form a grid of 100 squares. Next, cellophane tape (Nichiban Co., Ltd.) was attached onto the lattice and then peeled off. This was repeated 5 times, and then peeling of the polyimide layer on the surface was observed.

(Example 13)
To a 40% by mass methyl isobutyl ketone solution of pentaerythritol triacrylate, 10 parts by mass of 1-hydroxy-cyclohexyl-phenyl-ketone (BASF, Irgacure 184) was added to 100 parts by mass of pentaerythritol triacrylate to harden it. A resin composition for a coat layer was prepared.
The polyimide film of Example 1 was cut into a size of 10 cm × 10 cm, the resin composition for a hard coat layer was applied to one surface thereof, and ultraviolet rays were ^{irradiated at an exposure amount of 200 mJ / cm 2} under a nitrogen stream to cure the film to a thickness of 10 μm. A hard coat layer, which is a cured film of the above, was formed to prepare a laminated body.

(Examples 14 to 22 and Reference Examples 23 and 24 )
Examples 14 to 22 and Examples 13 are the same as in Example 13 except that the polyimide films of Examples 2 to 10 or Reference Examples 11 and 12 are used instead of the polyimide films of Example 1. A laminate of Reference Examples 23 and 24 was prepared. In Reference Example 23 using the polyimide film of Reference Example 11, a hard coat layer was formed on the surface of the polyimide film on the high Young's modulus layer side to prepare a laminated body.

<Pencil hardness>
The laminates obtained in Examples 13 to 22 and Reference Examples 23 and 24 were humidity-controlled for 2 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 60%, and then a test pencil specified by JIS-S-6006 was used. , Toyo Seiki Co., Ltd. Using a pencil scratch coating hardness tester, perform a pencil hardness test (9.8 N load) specified in JIS K5600-5-4 (1999) on the surface on the hard coat layer side. The pencil hardness of each laminate was determined by evaluating the highest pencil hardness that does not scratch. The pencil hardness of the laminates obtained in Examples 13 to 22 and Reference Examples 23 and 24 was 2H.

Among the laminates obtained in Examples 13 to 22 and Reference Examples 23 and 24, Examples 20 to polyimide layer containing a silicon atom located adjacent to the hard coat layer, a laminate of Reference Example 24 , The adhesion between the polyimide film and the hard coat layer was better.

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

Claims (15)

It has three or more polyimide layers including two or more polyimide layers with different Young's modulus, the total thickness is 5 μm or more and 200 μm or less, and the total light transmittance measured according to JIS K7361-1 is 85%. more der is, the Young's modulus of the polyimide layer smallest polyimide layer is not located on the surface, the polyimide film. The polyimide film according to claim 1, wherein the polyimide layer having the largest Young's modulus among the polyimide layers has a Young's modulus of 1.2 times or more the Young's modulus of the polyimide layer having the smallest Young's modulus. The largest polyimide layer Young's modulus of the previous SL polyimide layer is positioned on at least one surface, the polyimide film according to claim 1 or 2. The polyimide film according to any one of claims 1 to 3 , wherein the thickest layer of the polyimide layers is not the polyimide layer having the largest Young's modulus. The polyimide film according to any one of claims 1 to 4 , wherein the total thickness of the polyimide layer 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 5 , wherein when the static bending test is performed according to the following static bending test method, the internal angle after the test is 90 ° or more.
[Static bending test method]
A polyimide film test piece cut into a size of 15 mm × 40 mm is bent at the position of half of the long side, and a metal piece (100 mm × 30 mm × 6 mm) having a thickness of 6 mm is sandwiched between both ends of the long side of the test piece from the upper and lower surfaces. Arranged and fixed with tape so that the overlap margins on both ends of the test piece and the upper and lower surfaces of the metal piece are 10 mm each, sandwiched between glass plates (100 mm x 100 mm x 0.7 mm) from above and below. , 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 the test piece does not exist, and the glass plate is fixed with tape so as to be parallel to each other. The test piece fixed in the bent state in this way is allowed to stand for 24 hours in an environment of 60 ° C. and 90% relative humidity (RH), and then the glass plate and the fixing tape are removed to the test piece. Release such force. Then, one end of the test piece is fixed, and the internal angle of the test piece is measured 30 minutes after the force applied to the test piece is released. The polyimide film according to any one of claims 1 to 6 , wherein the value obtained by dividing the yellowness calculated according to JIS K7373-2006 by the film thickness (μm) is 0.330 or less. Each of the three or more polyimide layers contains an aromatic ring, and (i) a fluorine atom, (ii) an aliphatic ring, and (iii) an aromatic ring are substituted with a sulfonyl group or a fluorine atom. The polyimide film according to any one of claims 1 to 7 , which contains a polyimide containing at least one selected from the group consisting of structures linked by a good alkylene group. The polyimide film according to any one of claims 1 to 8 , wherein the polyimide layer having the largest Young's modulus among the polyimide layers contains a polyimide having a structure represented by the following general formula (1).

(In the general formula (1), R ¹ is a 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride residue, 3,3', 4,4'-benzophenone tetracarboxylic acid 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'-. Diaminodiphenyl sulfone 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 according to claim 9 , further comprising a polyimide layer containing a polyimide having a structure represented by the 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 the total amount is 50 mol% or less of a diamine residue having one or two silicon atoms in the main chain, the remaining R ^4, having no silicon atom, a diamine having an aromatic ring or aliphatic ring is a residue, the number remaining than half of the ^{R 4} is 1,4-cyclohexane diamine residue, trans-1,4-bis-methylene-cyclohexane diamine residue, 4,4'-diaminodiphenyl sulfone residue Group, 3,4'-diaminodiphenyl sulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2-bis At least one selected from the group consisting of (4-aminophenyl) propane residue, 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (3). Represents a divalent group of species. N'represents the number of repeating units and is 1 or more.)

(In the general formula (3), R ⁵ and R ⁶ independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.) The polyimide film according to any one of claims 1 to 8 , which has a polyimide layer containing a polyimide having a structure represented by the 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 the total amount is 50 mol% or less of a diamine residue having one or two silicon atoms in the main chain, the remaining R ^4, having no silicon atom, a diamine having an aromatic ring or aliphatic ring is a residue, the number remaining than half of the ^{R 4} is 1,4-cyclohexane diamine residue, trans-1,4-bis-methylene-cyclohexane diamine residue, 4,4'-diaminodiphenyl sulfone residue Group, 3,4'-diaminodiphenyl sulfone residue, bis [4- (3-aminophenoxy) phenyl] sulfone residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue, 2,2-bis At least one selected from the group consisting of (4-aminophenyl) propane residue, 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (3). Represents a divalent group of species. N'represents the number of repeating units and is 1 or more.)

(In the general formula (3), R ⁵ and R ⁶ independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.) A laminate having the polyimide film according to any one of claims 1 to 11 and a hard coat layer containing at least one polymer of a radically polymerizable compound and a cationically polymerizable compound. The radically polymerizable compound is a compound having two or more (meth) acryloyl groups in one molecule, and the cationically polymerizable compound is a compound having at least one of an epoxy group and an oxetanyl group in one molecule. The laminated body according to claim 12. The polyimide film according to any one of claims 1 to 11, or, the billing is a laminate according to claim 12 or 13, the surface material for a display. The display surface material according to claim 14 , which is for a flexible display.

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