JP2018203906A - Polyimide film, product using polyimide film, and laminate - Google Patents

Abstract

To provide a polyimide film having colorless transparency, low in YI and Rth, having a smooth surface low in haze, and excellent in toughness, and capable of manufacturing a film having isotropic property and less strain in whole wide compared to conventional products, and high in positioning accuracy of elements or the same during device manufacturing, a polyimide varnish for producing the polyimide film, a product using the polyimide film, and a laminate.SOLUTION: A polyimide film satisfied that (A) it contains polyimide represented by the following general formula (1), and it contains a structure represented by the following general formula (A-1), and at least one kind of structures represented by the following general formula (A-2), the following general formula (A-3), and the following general formula (A-4) as the A in the following general formula (1), and (B) arithmetic average roughness (Ra) of at least one surface of the polyimide film is 1.5 nm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polyimide film, a product using the polyimide film, and a laminate.

In recent years, instead of glass in the field of touch panel materials such as transparent electrode films, it has been studied to use a plastic film as a substrate from the viewpoint of weight reduction and thinning.
In addition, flexible devices such as flexible displays and devices having curved surfaces such as organic EL lighting and organic EL displays are being studied. In the above devices, it has been studied to use a foldable film instead of a hard substrate as a substrate for forming a surface protective layer, a color filter, a touch panel, a TFT, and the like.
As the film, for example, adoption of a polyethylene terephthalate film (PET film), a polyethylene naphthalate film (PEN film), or a cycloolefin film (COP film) having excellent optical properties is being studied.
As a film substrate for such a flexible device, a film having excellent optical properties and excellent bending resistance is required. However, the PET film and the PEN film described above have the disadvantage that the optical properties are inferior and the visibility is poor, and the COP film has a poor toughness.
On the other hand, since polyimide resin has excellent properties such as heat oxidation resistance, heat resistance, heat radiation resistance, low temperature resistance, and chemical resistance, it has been studied to adopt a polyimide film as the substrate. (Patent Documents 1 to 8 and Non-Patent Document 1).

JP 2006-137881 A Japanese translation of PCT publication 2010-510378 JP 2007-246820 A International Publication No. 2012/118020 Japanese Patent No. 4778659 European Patent Application No. 2032632 US Pat. No. 3,666,709 International Publication No. 2016/158825

Latest Polyimide (Basics and Applications) Japan Polyimide Study Group p. 113

  However, the above-described PET film and PEN film do not necessarily have a sufficient surface roughness. That is, it is desirable that the surface roughness of the polyimide film is as low as possible. In particular, when a PET film having a high arithmetic average roughness (hereinafter referred to as Ra) described in JIS B0601 (2001) is used for a touch panel, for example, the film is white and cloudy when viewed visually, and the visibility is very high. Getting worse. In addition, when laminating a transparent electrode such as ITO on a PET film having a large surface roughness, it is necessary to increase the thickness of the transparent electrode from the viewpoint of ensuring cracks and flatness of the transparent electrode layer. When it sees, a transparent electrode pattern can be confirmed and visibility deteriorates. In order to solve this, generally, an acrylic resin or the like is used to provide a planarizing layer on a PET film having a large surface roughness, and the arithmetic average roughness of the film surface is There is room for improvement.

Moreover, since visibility will deteriorate when the haze (hereinafter also referred to as haze) of the polyimide film is high, there is room for improvement in the haze of the polyimide film.
Furthermore, it is desirable that the polyimide film has a yellow index (Yellow Index; hereinafter referred to as YI) as low as possible. For example, in Patent Document 1, a polyimide film is obtained by adding pyridine as an imidization catalyst and acetic anhydride as a dehydrating agent to a polyimide precursor and drying it. There was a problem that coloring and turbidity easily remained in the obtained polyimide film due to the influence of water. In addition, polyimide resins having an aromatic ring such as polyimide made of pyromellitic dianhydride and diaminodiphenyl ether have high heat resistance, and are colored brown or yellow, have low transmittance in the visible light region, and are transparent. It has been difficult to use in fields that require high performance. As described above, when the polyimide film is colored, cloudy, or cloudy, the visibility of a display device such as a touch panel, organic EL lighting, or a flexible display is significantly reduced. Therefore, it is necessary to make YI as low as possible and increase the total light transmittance in visible light.
It is desirable that the retardation (hereinafter referred to as Rth) of the polyimide film is as low as possible. When a PET film having a high Rth is used for the touch panel, for example, when viewed through polarized sunglasses, rainbow unevenness occurs, and the visibility is greatly deteriorated. If the polyimide film has a high Rth, the visibility deteriorates.

As described above, the polyimide film can be used, for example, as a touch panel material or a film substrate for a flexible device, and it has been desired to be a material excellent in toughness. However, none of Patent Documents and Non-Patent Documents 1 disclose a method for producing polyimide that has low YI and Rth, a smooth surface, low haze (hereinafter referred to as haze), and improves toughness.
By the way, a general polyimide has poor solubility in a solvent due to a high aromatic ring density, and it has been difficult to obtain a polyimide film directly from a polyimide solution. Accordingly, a polyimide having a high solubility in a solvent and excellent workability has been desired as the polyimide constituting the polyimide film.

  The present invention has been made in view of the above-described problems, and is a polyimide film for producing a polyimide film and a polyimide film that are colorless and transparent, have low YI and Rth, have a smooth surface, low haze, and excellent toughness. It aims at providing the product using a varnish and a polyimide film, and a laminated body.

｛一般式（１）中、Ａは２価の有機基であり、Ｂは４価の有機基であり、かつｎは２以上の数である。｝
で表されるポリイミドを含有し、前記一般式（１）におけるＡとして、下記一般式（Ａ−１）：

で表される構造と、下記一般式（Ａ−２）：

｛一般式（Ａ−２）中、Ｘは、下記一般式（Ｘ−１）〜下記一般式（Ｘ−３）：

から成る群から選ばれる少なくとも１つの２価の有機基である。｝、下記一般式（Ａ−３）：

｛一般式（Ａ−３）中、ａは０又は１の数である。｝、及び下記一般式（Ａ−４）：

で表される構造のうち少なくとも１つと、を含むこと；並びに
（Ｂ）ポリイミドフィルムの少なくとも片面の算術平均粗さ（Ｒａ）が１．５ｎｍ以下であること；
を満たすことを特徴とするポリイミドフィルム。
［２］
前記ポリイミドフィルムのヘイズが１．０以下である、［１］に記載のポリイミドフィルム。
［３］
前記一般式（１）におけるＡとして、前記一般式（Ａ−１）で表される構造、及び下記一般式（Ａ−５）：

で表される構造を含む、［１］又は［２］に記載のポリイミドフィルム。
［４］
前記一般式（Ａ−１）で表される構造と前記一般式（Ａ−５）で表される構造の比（一般式（Ａ−１）で表される構造／一般式（Ａ−５）で表される構造）が、モル基準で２／８〜６／４の範囲内である、［３］に記載のポリイミドフィルム。
［５］
前記一般式（１）におけるＢとして下記一般式（Ｂ−１）〜下記一般式（Ｂ−４）：

｛一般式（Ｂ−１）中、Ｙは、下記一般式（Ｙ−１）〜下記一般式（Ｙ−３）：

から成る群から選ばれる少なくとも１つの構造である。｝

で表される構造のうち少なくとも１つを含む、［１］〜［４］のいずれか１項に記載のポリイミドフィルム。
［６］
前記一般式（１）におけるＢとして下記一般式（Ｂ−５）：

で表される構造を含む、［１］〜［５］のいずれか１項に記載のポリイミドフィルム。 The present inventors have found that the above problems can be solved by specifying the structure of polyimide contained in the polyimide film and the roughness of at least one side of the polyimide film, and have completed the present invention. That is, the present invention is as follows.
[1]
The following requirements:
(A) The following general formula (1):

{In General Formula (1), A is a divalent organic group, B is a tetravalent organic group, and n is a number of 2 or more. }
In the general formula (1), the following general formula (A-1):

And the following general formula (A-2):

{In general formula (A-2), X represents the following general formula (X-1) to the following general formula (X-3):

And at least one divalent organic group selected from the group consisting of: }, The following general formula (A-3):

{In General Formula (A-3), a is a number of 0 or 1. }, And the following general formula (A-4):

And (B) the arithmetic average roughness (Ra) of at least one side of the polyimide film is 1.5 nm or less;
The polyimide film characterized by satisfy | filling.
[2]
The polyimide film according to [1], wherein the haze of the polyimide film is 1.0 or less.
[3]
As A in the general formula (1), the structure represented by the general formula (A-1), and the following general formula (A-5):

The polyimide film as described in [1] or [2] containing the structure represented by these.
[4]
Ratio of structure represented by general formula (A-1) to structure represented by general formula (A-5) (structure represented by general formula (A-1) / general formula (A-5) The polyimide film according to [3], wherein the structure represented by formula (2) is within a range of 2/8 to 6/4 on a molar basis.
[5]
As B in the general formula (1), the following general formula (B-1) to the following general formula (B-4):

{In the general formula (B-1), Y represents the following general formula (Y-1) to the following general formula (Y-3):

At least one structure selected from the group consisting of }

The polyimide film according to any one of [1] to [4], including at least one of structures represented by:
[6]
As B in the general formula (1), the following general formula (B-5):

The polyimide film of any one of [1]-[5] containing the structure represented by these.

[7]
The following steps:
(Step A1) a step of applying a polyimide varnish containing at least the polyimide and the organic solvent on a support;
(Step A2) Step of heating the polyimide varnish to form a solvent-containing film containing a solvent at a concentration of 5% by mass to 20% by mass and peeling from the support; and (Step A3) heating the solvent-containing film The solvent-containing film is conveyed into a furnace and the following temperature profile:
(Zone 1) 3 minutes or more and less than 30 minutes within the range of 50 ° C to 100 ° C,
(Zone 2) 1 minute or more and less than 30 minutes within the range of 100 ° C to 150 ° C,
(Zone 3) Within a range of 150 ° C. to 200 ° C. for 1 minute or more and less than 30 minutes,
(Zone 4) Within a range of 200 ° C. to 250 ° C. for 1 minute or more and less than 30 minutes,
Drying the zone 1, the zone 2, the zone 3 and the zone 4 in this order according to
The manufacturing method of the polyimide film of any one of [1]-[6] containing this.
[8]
The following steps:
(Step B1) The polyimide varnish containing the polyimide and the organic solvent is coated on a heat-resistant support having a glass transition point (Tg) of 300 or higher or a glass transition point of 1% and a thermal decomposition temperature of 400 ° C. or higher. And (step B2) transporting the polyimide varnish together with the support into a heating furnace, and forming the formed solvent-containing film with the following temperature profile:
(Zone 1) 3 minutes or more and less than 30 minutes within the range of 50 ° C to 100 ° C,
(Zone 2) 1 minute or more and less than 30 minutes within the range of 100 ° C to 150 ° C,
(Zone 3) Within a range of 150 ° C. to 200 ° C. for 1 minute or more and less than 30 minutes,
(Zone 4) Within a range of 200 ° C. to 250 ° C. for 1 minute or more and less than 30 minutes,
Drying the zone 1, the zone 2, the zone 3 and the zone 4 in this order according to
The manufacturing method of the polyimide film of any one of [1]-[6] containing this.
[9]
The method for producing a polyimide film according to [7], wherein the solvent-containing film is dried while fixing both ends of the solvent-containing film in the step A3.
[10]
In the step A3, the ratio of the width of the solvent-containing film at the inlet of the heating furnace and the width of the polyimide film at the outlet of the heating furnace (width _inlet / width _outlet ) is in the range of 0.95 to 1.05 in the TD direction. The manufacturing method of the polyimide film as described in [9] which is inside.
[11]
The said polyimide varnish is a manufacturing method of the polyimide film of any one of [7]-[10] containing a lactone solvent.
[12]
The said polyimide varnish is a manufacturing method of the polyimide film of any one of [7]-[11] containing the polyimide whose imidation rate is 80% or more.
[13]
The said polyimide varnish is a manufacturing method of the polyimide film of any one of [7]-[12] containing the polyimide whose weight average molecular weight (Mw) is 40000 or more.
[14]
The manufacturing method of the polyimide film of any one of [7]-[13] whose film thickness of the said polyimide film is 1 micrometer-50 micrometers.

According to the present invention, it is possible to provide a polyimide film that is colorless and transparent, has low YI and Rth, has a smooth surface, low haze, and excellent toughness. Moreover, in this invention, it is possible to manufacture the product and laminated body which used the polyimide film provided with the desired characteristic.
Moreover, in this invention, the alignment precision of the element installed on a film can be improved.

FIG. 1 is a schematic cross-sectional view showing a polyimide film according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing the laminate according to the present embodiment. FIG. 3 is a time-temperature curve for explaining the heating of the solvent-containing film according to the present embodiment.

  Hereinafter, an embodiment of the present invention (hereinafter abbreviated as “embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.

｛一般式（１）中、Ａは２価の有機基であり、Ｂは４価の有機基であり、ｎは２以上の数である。｝ <Polyimide>
The polyimide film according to the present embodiment contains a polyimide represented by the following general formula (1).

{In General Formula (1), A is a divalent organic group, B is a tetravalent organic group, and n is a number of 2 or more. }

｛一般式（Ａ−２）中、Ｘは、下記一般式（Ｘ−１）〜下記一般式（Ｘ−３）：

から成る群から選ばれる少なくとも１つの２価の有機基である。｝

｛一般式（Ａ−３）中、ａは０または１の数である。｝

<A in General Formula (1)>
The polyimide contained in the polyimide film can be produced from acid dianhydride and diamine as raw materials. A in the general formula (1) can be obtained from a diamine.
In the present embodiment, as A in the general formula (1), a structure represented by the following general formula (A-1) (hereinafter also referred to as “structure A1”), and a general formula (A-2) shown below. ), At least one of the structures represented by the following general formula (A-3) and the following general formula (A-4) (hereinafter also referred to as “structure A2”). One polyimide film ”).

{In general formula (A-2), X represents the following general formula (X-1) to the following general formula (X-3):

And at least one divalent organic group selected from the group consisting of: }

{In general formula (A-3), a is the number of 0 or 1. }

  The structure represented by the general formula (A-1) is derived from 3,3′-diaminodiphenyl sulfone (hereinafter, also referred to as 3,3′-DDS), the general formula (A-2) ), And (X-1) in combination (corresponding to the general formula (A-5)) is 4,4′-diaminodiphenyl sulfone (hereinafter referred to as 4,4′-Diaminodiphenyl Sulphone), 4′-DDS) and the structure represented by the combination of the general formulas (A-2) and (X-2) is α, α′-bis (4-aminophenyl) -1,4-diisopropyl. The structure derived from benzene (hereinafter also referred to as BAPDB) and represented by a combination of the general formulas (A-2) and (X-3) is 4,4′-bis (4-aminophenoxybiphenyl) (hereinafter, The structure represented by the general formula (A-3) derived from APB) is derived from cyclohexyldiamine (hereinafter also referred to as CHDA) when a is 0, and 1,4-bis (amino) when a is 1. The structure represented by the general formula (A-4) is derived from bis (aminomethyl) norbornane (hereinafter also referred to as BANBDA). However, it is not limited to these compounds.

A general formula (A-5) of a combination of the general formulas (A-2) and (X-1) is shown below.

General formula (2) of the combination of general formula (A-2) and (X-2) is shown below.

General formula (3) of the combination of general formulas (A-2) and (X-3) is shown below.

The polyimide in the present embodiment includes, as A in the general formula (1), a structure represented by the general formula (A-1) (derived from 3,3′-diaminodiphenylsulfone) as an essential repeating unit, As a repeating unit to be combined with the structure of the general formula (A-1), at least one of the structures represented by the general formula (A-2), the general formula (A-3), and the general formula (A-4) ,including.
When the polyimide in this embodiment includes the above repeating unit, a film having low YI, low Rth, and excellent toughness can be obtained. It is said that the coloring of polyimide is derived from the formation of a charge transfer complex (CT complex) between polyimide molecules. The structures represented by the general formulas (A-1) to (A-4) are considered to inhibit the formation of CT complexes between polyimide molecules due to the bending of the main chain. Among these, the structures represented by the general formulas (A-1) and (A-5) can weaken the electron donating property of the N atom of the imide group due to the electron withdrawing property of the SO ₂ group, It is considered to be difficult to form and is particularly preferable.
Moreover, absorption of visible light which an aromatic polyimide has also causes the coloring of a polyimide. It is considered that the alicyclic structures of the general formula (A-3) and the general formula (A-4) can reduce the absorption of visible light as compared with the aromatic polyimide.

Moreover, it is thought that the solubility of a polyimide improves by disturbing the orientation of a polyimide. The structures represented by the general formula (A-1) to the general formula (A-4) are considered to exhibit solubility because the orientation of polyimide molecules is disturbed by the bending of the main chain. Among these, the structure represented by the general formula (A-1) is excellent because the orientation of the polyimide molecules is significantly disturbed by the bent structure of the SO ₂ group and the bent structure resulting from the bond from the 3rd and 3 ′ positions. It is thought that solubility is expressed.
Thus, the polyimide contained in the polyimide film in the present embodiment is the structure represented by the general formula (A-1), the general formula (A-2), and the general formula as A in the general formula (1). (A-3) and any one or more of the structures represented by the general formula (A-4) are included.
The present invention increases the molecular weight of the polyimide by copolymerizing the structure represented by the general formula (A-1) and the structure represented by the general formula (A-5). We have succeeded in specifically improving the toughness of the produced film. In addition, it has at least the structure represented by the general formula (A-1) and is selected from the group consisting of the structures represented by the general formulas (A-2), (A-3) and (A-4). The same effect is exhibited with polyimide having at least one structure.

In this embodiment, it is preferable to use at least the structure represented by the general formula (A-1) and the structure represented by the general formula (A-5). Below, the structure which used both 3,3'-DDS and 4,4'-DDS as a diamine is demonstrated.
The structural unit represented by the general formula (A-1) can be obtained from the 3,3′-DDS component as described above. The structure represented by the general formula (A-1) is a site for expressing solubility in a solvent.
The structural unit represented by the general formula (A-5) can be obtained from 4,4′-DDS. The structure represented by the general formula (A-5) has a glass transition point (Tg) in a polyimide film obtained by heating and drying a varnish (resin composition) obtained by dissolving the polyimide of the present embodiment in a solvent. It is a site | part for making it express in the range of 250-350 degreeC.

  In this Embodiment, it is preferable to contain both the structure represented by general formula (A-1) and the structure represented by general formula (A-5). The structural unit represented by the general formula (A-1) is preferably introduced from the viewpoint of the solubility of the polyimide. Moreover, the structural unit represented by General Formula (A-5) is adjusted from the viewpoint of a high glass transition temperature (Tg). By including both the structure represented by the general formula (A-1) and the structure represented by the general formula (A-5), the solubility of the polyimide and the elongation at break of the film that could not be achieved individually. Further, a high glass transition temperature (Tg) can be obtained while being colorless and transparent, and without impairing low retardation (Rth) and high total light transmittance.

In order to reduce Rth, the difference in refractive index between the in-plane direction and the out-of-plane direction of the film needs to be small. The structure represented by the general formula (A-1) and the general formula (A-5) have a structure in which the SO ₂ group is bent, and the bent structure is fixed because of the sp2 orbit. Therefore, it is considered that the structure represented by the general formula (A-1) and the aromatic group contained in the general formula (A-5) do not line up in one direction and exist randomly. That is, if the structure represented by the general formula (A-1) and the general formula (A-5) are present in the polyimide skeleton, the difference in refractive index between the in-plane direction and the out-of-plane direction is small, and Rth can be reduced. .

In the present embodiment, the composition ratio (structure A1 / structure A2) between the structure A1 and the structure A2 is 2/8 to 8/2 in terms of molar ratio from the viewpoint of further improving the toughness of the polyimide film. preferable. In particular, when the structure A2 has the structure represented by the general formula (A-5), the structure A1 and the structure represented by the general formula (A-5) (hereinafter also referred to as “structure A21”) The composition ratio (structure A1 / structure A21) is preferably in the range of 2/8 to 6/4, more preferably in the range of 3/7 to 4/6, in terms of molar ratio. That is, the structure A1 is preferably 20% by mole or more and 60% or less when the total amount of A in the general formula (1) is 100% by mole. In addition, the structure A21 is preferably 40% by mole or more and 80% by mole or less when the total amount of A in the general formula (1) is 100% by mole.
In addition, as the structure A1 and the structure A2, at least one of structural units represented by the general formula (A-2) to the general formula (A-4) (however, the structure represented by the general formula (A-5) described above) (Excluding the unit) (hereinafter also referred to as “structure A22”), the composition ratio of structure A1 to structure A22 (structure A1 / structure A22) is preferably 5/5 to 8/2 in molar ratio. .

  In addition, in the range which can express the target breaking elongation, More preferably, in the range which can express the target glass transition temperature (Tg), general formula (A-1) and general formula (A A small amount of structural units other than the structural unit represented by -5) can be contained. That is, the polyimide according to the present embodiment may contain a structural unit derived from a diamine component other than 4,4′-DDS and 3,3′-DDS as long as the performance is not impaired. For example, an aromatic diamine having 6 to 30 carbon atoms is preferable.

Specifically, 2,2′-bis (trifluoromethyl) benzidine (TFMB), 1,4-diaminobenzene, 4-aminobenzenesulfonic acid-4-aminophenyl ester, 4-aminobenzenesulfonic acid-3- Aminophenyl ester, 3-aminobenzenesulfonic acid-3-aminophenyl ester, 2-aminobenzenesulfonic acid-2-aminophenyl ester, 2,2′-dimethyl 4,4′-diaminobiphenyl, 1,3-diaminobenzene 4-aminophenyl 4′-aminobenzoate, 4,4′-diaminobenzoate, 4,4 ′-(or 3,4′-, 3,3′-, 2,4 ′-) diaminodiphenyl ether, 4,4 '-(Or 3,3'-) diaminodiphenyl sulfide, 4,4'-benzophenone diamine, 3,3'-benzophenone diamine 4,4′-di (4-aminophenoxy) phenyl sulfone, 4,4′-di (3-aminophenoxy) phenyl sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 2,2′-bis {4- (4-aminophenoxy) phenyl} propane, 3,3 ′, 5,5′- Tetramethyl-4,4′-diaminodiphenylmethane, 2,2′-bis (4-aminophenyl) propane, 2,2 ′, 6,6′-tetramethyl-4,4′-diaminobiphenyl, 2,2 ′ , 6,6′-tetratrifluoromethyl-4,4′-diaminobiphenyl, bis {(4-aminophenyl) -2-propyl} 1,4-benzene, 9,9-bis (4-aminophenyl) fluorene , , 9-bis (4-aminophenoxyphenyl) fluorene, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine and 3,5-diaminobenzoic acid, 2,6-diaminopyridine, 2,4- Diaminopyridine, bis (4-aminophenyl-2-propyl) -1,4-benzene, 3,3′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (3,3′-TFDB), 2 , 2′-bis [3 (3-aminophenoxy) phenyl] hexafluoropropane (3-BDAF), 2,2′-bis [4 (4-aminophenoxy) phenyl] hexafluoropropane (4-BDAF), 2 , 2′-bis (3-aminophenyl) hexafluoropropane (3,3′-6F), 2,2′-bis (4-aminophenyl) hexafluoropropane (4,4′-6) ) Can be mentioned a structural unit derived from an aromatic diamine component or the like.
9,9-bis (4-aminophenyl) fluorene and 9,9-bis (4-aminophenoxyphenyl) fluorene can be introduced when adjusting Rth because the fluorene skeleton has a negative intrinsic birefringence. it can.

In addition, 2,2′-bis (trifluoromethyl) benzidine (TFMB), 3,3′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (3,3′-TFDB), 2,2′- Bis [3 (3-aminophenoxy) phenyl] hexafluoropropane (3-BDAF), 2,2′-bis [4 (4-aminophenoxy) phenyl] hexafluoropropane (4-BDAF), 2,2′- Bis (3-aminophenyl) hexafluoropropane (3,3′-6F) and 2,2′-bis (4-aminophenyl) hexafluoropropane (4,4′-6F) are highly sterically hindered by fluorine atoms. The introduction of can suppress the formation of a CT complex between polyimide molecules, and can be introduced to reduce the YI of the film.
The structural unit derived from 2,2′-bis (trifluoromethyl) benzidine (TFMB) is represented by the following general formula (4).

｛一般式（Ｂ−１）中、Ｙは、下記一般式（Ｙ−１）〜下記一般式（Ｙ−３）：

から成る群から選ばれる少なくとも１つの構造である。｝

<B in General Formula (1)>
Next, B in the general formula (1) will be described. The said structural unit corresponding to B of General formula (1) can be obtained from an acid dianhydride.
In the present embodiment, the structural unit derived from the acid dianhydride component contained in the polyimide may be the same molecule or a molecule having a different structure.
The structural unit represented by B is preferably a structural unit represented by the following general formula (B-1) to general formula (B-4).
In the present embodiment, it is preferable that B in the general formula (1) includes at least one of structures represented by the following general formula (B-1) to the following general formula (B-4).

{In the general formula (B-1), Y represents the following general formula (Y-1) to the following general formula (Y-3):

At least one structure selected from the group consisting of }

The structure represented by combining the general formulas (B-1) and (Y-1) (corresponding to the structure of the general formula (B-5) described later) is 4,4′-oxydiphthalic dianhydride. (Hereinafter also referred to as ODPA) The structure represented by the combination of the general formula (B-1) and the general formula (Y-2) is 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride. (Hereinafter also referred to as 6FDA) The structure represented by the combination of the general formula (B-1) and the general formula (Y-3) is 9,9-diphenylfluorenic dianhydride (hereinafter also referred to as DPFLDA). The structure represented by general formula (B-2) is derived from hydroxypyromellitic dianhydride (hereinafter also referred to as HPMDA), and the structure represented by general formula (B-3) is bicyclo [2 , 2,2] oct-7-ene-2,3,5,6-tetra The structure represented by the general formula (B-4) derived from rubonic dianhydride (hereinafter also referred to as BODA) is 1,3,3a, 4,5,9b-hexahydro-5- (tetrahydro-2,5 -Dioxo-3-furanyl) naphtho [1,2-c] furan-1,3-dione (hereinafter also referred to as TDA).
DPFLDA can be introduced when adjusting Rth because the fluorene skeleton has a negative intrinsic birefringence.
The polyimide which concerns on this Embodiment is the range derived from acid dianhydride components other than the structural unit represented by the said general formula (B-4) from the said general formula (B-1) in the range which does not impair the performance. Units may be included.
For example, an aromatic tetracarboxylic dianhydride having 8 to 36 carbon atoms, an aliphatic tetracarboxylic dianhydride having 6 to 50 carbon atoms, and an alicyclic tetracarboxylic dianhydride having 6 to 36 carbon atoms It is preferable that it is a compound selected from these. The number of carbons herein includes the number of carbons contained in the carboxyl group.

More specifically, as the aromatic tetracarboxylic dianhydride having 8 to 36 carbon atoms, 4, pyromellitic dianhydride (hereinafter also referred to as PMDA) 1,2,3,4-benzenetetracarboxylic acid. Dianhydride, 3,3 ′, 4,4′-bezophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4 '-Biphenyltetracarboxylic dianhydride (hereinafter also referred to as BPDA), 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic Acid dianhydride, methylene-4,4′-diphthalic dianhydride, 1,1′-ethylidene-4,4′-diphthalic dianhydride, 2,2′-propylidene-4,4′-diphthalic acid Dianhydride, 1,2-ethylene-4,4'-diphthalic acid dianhydride 1,3-trimethylene-4,4′-diphthalic dianhydride, 1,4-tetramethylene-4,4′-diphthalic dianhydride, 1,5-pentamethylene-4,4′-diphthal Acid dianhydride, thio-4,4′-diphthalic dianhydride, sulfonyl-4,4′-diphthalic dianhydride, 1,3-bis (3,4-dicarboxyphenyl) benzene dianhydride, 1,3-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,4-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,3-bis [2- (3,4 -Dicarboxyphenyl) -2-propyl] benzene dianhydride, 1,4-bis [2- (3,4-dicarboxyphenyl) -2-propyl] benzene dianhydride, bis [3- (3,4) -Dicarboxyphenoxy) phenyl] methane dianhydride, bi [4- (3,4-Dicarboxyphenoxy) phenyl] methane dianhydride, 2,2′-bis [3- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 2,2′-bis [4- (3,4-Dicarboxyphenoxy) phenyl] propane dianhydride (hereinafter also referred to as BPADA), bis (3,4-dicarboxyphenoxy) dimethylsilane dianhydride, 1,3-bis (3 4-Dicarboxyphenyl) -1,1 ′, 3,3′-tetramethyldisiloxane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalene Tetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic Dianhydride, 1,2,7,8 can be mentioned phenanthrene tetracarboxylic dianhydride.
Examples of the aliphatic tetracarboxylic dianhydride having 6 to 50 carbon atoms include ethylene tetracarboxylic dianhydride and 1,2,3,4-butanetetracarboxylic dianhydride.

  As alicyclic tetracarboxylic dianhydride having 6 to 36 carbon atoms, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter also referred to as CBDA), cyclopentanetetracarboxylic dianhydride, Cyclohexane-1,2,3,4-tetracarboxylic dianhydride, 3,3 ′, 4,4′-bicyclohexyltetracarboxylic dianhydride, carbonyl-4,4′-bis (cyclohexane-1,2) -Dicarboxylic acid) dianhydride, methylene-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,2-ethylene-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) Acid) dianhydride, 1,1′-ethylidene-4,4′-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, 2,2′-propylidene-4,4′-bis (cyclohexa) -1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, thio-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) Acid) dianhydride, sulfonyl-4,4′-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, rel- [1S, 5R, 6R] -3-oxabicyclo [3,2,1] octane -2,4-dione-6-spiro-3 '-(tetrahydrofuran-2', 5'-dione), 4- (2,5-dioxotetrahydrofuran-3-yl) -1,2,3,4- Tetrahydronaphthalene-1,2-dicarboxylic dianhydride, ethylene glycol-bis- (3,4-dicarboxylic dianhydride phenyl) ether, 4,4′-biphenylbis (trimellitic acid monoester dianhydride And the like can be given.

In the general formula (B-1), the general formula (Y-1) and the general formula (Y-2) are the solubility of the polyimide in the solvent, and the yellowness and retardation (Rth) of the polyimide film. It is preferable from the viewpoint of reduction. Moreover, since the general formula (Y-3) has negative intrinsic birefringence, the yellowness and retardation (Rth) are reduced when the polyimide film is formed, and the coefficient of thermal expansion (CTE) is reduced. And it is preferable from a viewpoint of an improvement of a glass transition temperature (Tg).
The general formulas (B-2) to (B-4) are preferable from the viewpoints of solubility of polyimide in a solvent and reduction in yellowness when a polyimide film is formed.
Among them, from the viewpoint of solubility of polyimide as a solvent as B in the general formula (1), high total light transmittance when made into a polyimide film, low yellowness, high elastic modulus, and high elongation at break, it is derived from ODPA. It is particularly preferable to use it including a structure represented by the following general formula (B-5) as a component, and among the structural unit B derived from acid dianhydride in the polyimide represented by the general formula (1), The general formula (B-5) is preferably 50 mol% or more, more preferably 80 mol% or more, and may be 100 mol% with respect to the entire acid dianhydride.

本実施の形態に係るポリイミドは、下記一般式（５）で表されるユニット１、及び、下記一般式（６）で表されるユニット２を主として含む。

The polyimide according to the present embodiment mainly includes a unit 1 represented by the following general formula (5) and a unit 2 represented by the following general formula (6).

In the present embodiment, when units other than unit 1 and unit 2 are further included, the content of units other than unit 1 and unit 2 is preferably less than the content of units 1 and 2. These units may be bonded alternately or in a permutation in the polymer chain, and these units may be bonded at random.
The weight average molecular weight (Mw) of the polyimide is preferably 10,000 or more, more preferably 25,000 or more, and 30,000 from the viewpoint of obtaining a high elongation at break and low Rth in the polyimide film. Preferably, it is 40,000 or more. Moreover, it is preferable that the weight average molecular weight (Mw) of a polyimide is 1,000,000 or less, It is more preferable that it is 500,000 or less, It is especially preferable that it is 250,000 or less. When the weight average molecular weight is 1,000,000 or less, the solubility in a solvent is good, and the film can be applied without bleeding at a desired film thickness during processing such as coating to obtain a low Rth film. Can do. In particular, from the viewpoint of obtaining high breaking elongation and low Rth in the polyimide film, the weight average molecular weight is preferably 30,000 or more. Here, the weight average molecular weight refers to a molecular weight measured by gel permeation chromatography using polystyrene having a known number average molecular weight as a standard.

｛一般式（１）中、Ａは２価の有機基であり、Ｂは４価の有機基であり、ｎは２以上の数である。｝

<Polyimide varnish>
The polyimide according to the present embodiment as described above is used as a varnish (resin composition) obtained by dissolving it in a solvent, for example, as a raw material for producing a film or a film. Therefore, the polyimide varnish in the present embodiment is a polyimide varnish obtained by dispersing or dissolving a polyimide represented by the following general formula (1) in a solvent. The polyimide varnish has a structure represented by the general formula (A-1) described above as A in the general formula (1) and the general formulas (A-2) to (A-4) described above. It is preferable that the polyimide which has at least 1 among the structures represented by these is included. More preferably, A in the general formula (1) includes a structure represented by the following general formula (A-1) and a structure represented by the general formula (A-5). The structural unit represented by the formula (A-1) / the structural unit represented by the general formula (A-5)) is in the range of 2/8 to 6/4 in terms of molar ratio. More preferably, B represented by the general formula (1) includes a structure represented by the following general formula (B-5).

{In General Formula (1), A is a divalent organic group, B is a tetravalent organic group, and n is a number of 2 or more. }

It has also been proved by experiments described later that the polyimide in the present embodiment is excellent in solubility in a solvent. Therefore, by using the polyimide of the present embodiment, a varnish having desired characteristics can be obtained by a simple process. According to the polyimide varnish of the present embodiment, since the polyimide is appropriately dissolved, when the varnish is applied on the coated surface, a film having excellent smoothness can be formed without forming a lump. For this reason, while being able to form the resin layer of uniform thickness, high toughness can be obtained.
More preferably, in the polyimide varnish, the acid dianhydride component and the diamine component are dissolved in a solvent such as an organic solvent, and an azeotropic solvent such as toluene is added to remove water generated during imidization out of the system. Thus, it can be produced as a polyimide solution containing polyimide and a solvent (also referred to as polyimide varnish). Here, the conditions during the reaction are not particularly limited. For example, the reaction temperature is 0 ° C. to 180 ° C., and the reaction time is 3 to 72 hours. In order to sufficiently proceed the reaction with the sulfone group-containing diamine, it is preferable to carry out a heating reaction at 180 ° C. for about 12 hours. The reaction is preferably performed under an inert atmosphere such as argon or nitrogen.
Moreover, you may add basic catalysts, such as a pyridine, in the case of imidation.

  Moreover, if a solvent is a solvent which melt | dissolves a polyimide, it will not specifically limit. Examples of the reaction solvent include phenol solvents such as m-cresol; amide solvents such as N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide ( DMAc), etc .; lactone solvents such as γ-butyrolactone (GBL), δ-valerolactone, ε-caprolactone, γ-crotonolactone, γ-hexanolactone, α-methyl-γ-butyrolactone, γ-valerolactone , Α-acetyl-γ-butyrolactone, δ-hexanolactone, etc .; sulfoxide solvents such as N, N-dimethyl sulfoxide (DMSO); ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc .; Ester solvents such as methyl acetate, ethyl acetate, acetic acid One or more polar solvents selected from butyl, dimethyl carbonate and the like are useful. Among these, NMP and GBL are preferable from the viewpoint of solubility. From the viewpoint of reducing the YI of the film, GBL is more preferable.

The polyimide varnish in this Embodiment should just contain 1 or more types of the polyimide which concerns on this embodiment, and this polyimide varnish may be 1 type of varnish, and may mix and use 2 or more types. Moreover, when mixing 2 or more types of polyimide varnishes, polyimide varnishes other than the polyimide which concerns on this invention may be mixed, and a polyamic-acid varnish may be mixed.
An additive may be appropriately added to the polyimide varnish in the present embodiment. As an additive, a substance exhibiting a negative birefringence may be added in order to adjust the Rth of the film. Examples thereof include inorganic particles such as strontium carbonate or organic compounds such as polystyrene, polyvinyl naphthalene, polymethyl methacrylate, cellulose triacetate, and fluorene derivatives.
Examples of the additive include a leveling agent, a dispersing agent or a surfactant for improving the coating property of the film, a surfactant or a close contact for adjusting the peelability or adhesion from the film support. An auxiliary agent, a flame retardant for imparting flame retardancy to a film, and the like. Other additives include, for example, antioxidants, UV inhibitors, light stabilizers, plasticizers, waxes, fillers, pigments, dyes, foaming agents, antifoaming agents, dehydrating agents, antistatic agents, antibacterial agents , And fungicides.
The additive added to the polyimide varnish may be contained in the film as it is.

<Polyimide film>
FIG. 1 is a schematic cross-sectional view showing a polyimide film according to the present embodiment. The polyimide film 10 according to the present embodiment has, for example, a structure in which a resin composition layer 12 is formed on the surface of a support 11. The support 11 may not be provided. In the present embodiment, it is preferable that a support film (self-supporting film) is obtained without the support 11 from the viewpoint of maintaining strength as a film substrate. The supporting film means a film having an elongation at break of 5% or more. About the film used as the laminated body, when the peeled film has a breaking elongation of 5% or more, it corresponds to a supportable film.
As a method for measuring the breaking elongation, the method described in (Evaluation of breaking elongation and breaking strength) described later can be used.

The polyimide film in the present embodiment has excellent toughness. In experiments to be described later, breaking elongation and breaking strength are measured as indices of toughness. For example, in this embodiment including both the structures represented by the general formula (A-1) and the general formula (A-5), the structure is represented by the general formula (A-1) and the general formula (A-5). As compared with the comparative example including only one of the structures, it is possible to obtain high breaking elongation and breaking strength. As described above, when the 4,4′-DDS component is derived only from the diamine component (structure represented by the general formula (A-5)), the molecular weight of the polyimide is lowered and the toughness of the film is lowered. For this reason, in the present embodiment, it is an isomer derived from the 4,4′-DDS component and derived from the 3,3′-DDS component having a structure in which the monomer skeleton is bent as viewed from the 4,4′-DDS component ( In this case, preferably, the 3,3′-DDS component-derived amount is less than the 4,4′-DDS component-derived amount, The toughness can be improved while increasing the molecular weight.
Moreover, the yellowness degree (YI) of the polyimide film which concerns on this Embodiment can be 5.0 or less. At this time, the film thickness of the polyimide film is preferably in the range of 0.1 μm to 50 μm, more preferably in the range of 1 μm to 50 μm, and still more preferably in the range of 1 μm to 20 μm.

When used for a film substrate for a flexible device, it is preferably in the range of 1 μm to 10 μm, more preferably in the range of 1 μm to 5 μm, from the viewpoint of improving bending resistance by thinning the device. For example, a film having a thickness of less than 10 μm can be produced by stretching a polyimide film having a thickness of 10 μm or more.
Furthermore, in this embodiment, the yellowness (YI) can be adjusted to 2.0 or less. Thus, in this Embodiment, it can suppress to low yellowness, ie, a colorless and transparent polyimide film can be obtained. Note that “colorless and transparent” in the present embodiment refers to a state in which the total light transmittance of the film is 80% or more, the haze is 2 or less, and the yellowness (YI) is 5.0 or less. Therefore, the polyimide film of this Embodiment can be used suitably for the use of a touch panel, a display, and OLED illumination. For example, when using the polyimide resin according to the present embodiment as a substrate film of a transparent electrode film, a touch panel element is produced on at least one of the upper and lower surfaces of the substrate film, and the surface of the substrate film or the surface of the substrate film Even if the side facing is used as a viewing surface, it does not adversely affect the color and brightness of the screen. From the viewpoint of OLED emission characteristics, the haze of the polyimide film is preferably 1.0 or less, more preferably 0.9 or less, and even more preferably 0.8 or less. From the same viewpoint, the arithmetic average roughness (Ra) of at least one side of the polyimide film is 1.5 nm or less, preferably 1.4 nm or less, more preferably 1.3 nm or less, and further preferably 1.2 nm or less. is there.

  For example, the polyimide film of the present embodiment can be used as a substitute for glass in the same manner as the PET film or COP film. Furthermore, since the polyimide film of the present embodiment has excellent toughness, the PET film or COP film Then, it can be used for a foldable display body or a display body that follows a curved surface, which is likely to be cracked or scratched.

<Laminate>
FIG. 2 is a schematic cross-sectional view showing the laminate according to the present embodiment. The laminate 20 according to the present embodiment is provided with a transparent electrode layer 21 on the surface of the polyimide film 10.
The laminate 20 according to the present embodiment can be obtained by forming the transparent electrode layer 21 on the surface of the polyimide film 10 with a sputtering apparatus. In FIG. 2, the polyimide film 10 has a laminated structure of the support 11 and the resin composition layer 12, but may be a single layer of the resin composition layer 12. The laminated body which concerns on this Embodiment may have a transparent electrode layer on both surfaces of a polyimide film. In that case, it is preferable to have at least one transparent electrode layer 21 on each side. Moreover, an undercoat layer for imparting smoothness, a hard coat layer for imparting surface hardness, an index matching layer for improving visibility, and a gas barrier property are imparted between the transparent electrode layer and the polyimide film. Other layers such as a gas barrier layer may be included. A hard coat layer for imparting surface hardness or an index matching layer for improving visibility may be laminated on the transparent electrode layer and the polyimide film.

As described above, the polyimide film 10 manufactured using the polyimide according to the present embodiment is colorless and transparent, has a low yellowness (YI), and is excellent in toughness. Preferably, in order to have a glass transition temperature (Tg) suitable for a transparent electrode production process, the laminated body 20 of this Embodiment is suitable for use for touch-panel materials like a transparent electrode film.
When forming a transparent electrode film, the film-forming process to the polyimide film 10 surface of the transparent electrode layer 21 can be implemented in the temperature range of 80-100 degreeC, for example. In order to make the laminate exhibit desired performance, it is preferable to perform sputtering at a higher temperature to form the transparent electrode layer 21 having a low specific resistance. The transparent electrode layer 21 can be formed on both surfaces of the polyimide film 10, whereby, for example, touch panel elements can be disposed on both surfaces.

When the temperature at which the transparent electrode layer 21 is formed is higher than the glass transition temperature (Tg) of the polyimide film 10 constituting the film formation surface, problems such as shrinkage and breakage of the polyimide film may occur in a high temperature region. . Generally, when a transparent electrode layer is formed on a PET film, sputtering is performed at about 80 ° C., which is lower than about 100 ° C., which is the glass transition temperature (Tg) of the PET film. On the other hand, the polyimide film 10 according to the present embodiment has a high glass transition temperature (Tg) of about 250 ° C. or higher (based on a film thickness of 15 μm) and is excellent in heat resistance. That is, high toughness can be maintained even when the film is exposed to a high temperature of 200 ° C. or higher. Therefore, the transparent electrode layer 21 having a low specific resistance can be formed by sputtering the surface of the polyimide film 10 of the present embodiment, for example, at about 150 to 250 ° C.
In addition, the polyimide according to the present embodiment preferably has a breaking strength of 100 MPa or more on the basis of the thickness of the polyimide film of 15 μm from the viewpoint of improving the yield when the transparent electrode layer 21 is formed.
In addition, from the viewpoint of improving the performance of the transparent electrode film, the polyimide film according to the present embodiment has a glass transition temperature (Tg) of 250 ° C. or more based on the film thickness of 15 μm as described above. Is preferred.

｛一般式（１）中、Ａは２価の有機基であり、Ｂは４価の有機基であり、かつｎは２以上の数である。｝

<Polyimide film having predetermined characteristics>
The polyimide film of this Embodiment contains the polyimide represented by following General formula (1), and contains the structure represented by the following general formula (A-1) as A in the said General formula (1) ( Hereinafter, also referred to as “second polyimide film”).
A film including the structure represented by the general formula (A-1) is preferable because the polymer tends to exist isotropically in the in-plane direction and the out-of-plane direction of the film. In the second polyimide film, as A in the following general formula (1), the structure represented by the following general formula (A-1), when the total amount of A in the general formula (1) is 100 mol%, More preferably, it is contained in an amount of 20 mol% to 80%.

{In General Formula (1), A is a divalent organic group, B is a tetravalent organic group, and n is a number of 2 or more. }

  In addition, the polyimide film of this Embodiment may have structures other than the structure represented by general formula (A-1). As such a structure, the structural unit described in the above-mentioned <Polyimide> section can be mentioned. In addition, as the raw material diamine and acid dianhydride, the diamine component in the chapter <A> in the general formula (1) and the acid dianhydride component in the <B> in the general formula (1) described above are used. Those listed can be used.

It is preferable that the breaking elongation of the film is 10% or more from the viewpoint of improvement in workability when a self-supporting film is formed and bending resistance when a film substrate of a flexible device is used.
The polyimide film according to the present embodiment is excellent in toughness even in a heating environment, for example, when the element is mounted on the film while the polyimide film according to the present embodiment is sent out by roll-to-roll. Since the film is not broken and the surface is smooth, the element can be mounted on the film without any defects.

<Manufacturing method of polyimide film>
The manufacturing method of the polyimide film demonstrated above is also 1 aspect of this invention. In the present embodiment, the polyimide film can be manufactured by the following manufacturing method 1 or 2.

[Production Method 1]
Manufacturing method 1 includes the following steps:
(Step A1) a step of applying a polyimide varnish containing at least the polyimide and the organic solvent on a support;
(Step A2) A step of heating the polyimide varnish to form a solvent-containing film containing a solvent at a concentration of 5% by mass to 20% by mass and peeling from the support; and (Step A3) placing the solvent-containing film in a heating furnace. Convey the solvent-containing film with the following temperature profile:
(Zone 1) 3 minutes or more and less than 30 minutes within the range of 50 ° C to 100 ° C,
(Zone 2) 1 minute or more and less than 30 minutes within the range of 100 ° C to 150 ° C,
(Zone 3) Within a range of 150 ° C. to 200 ° C. for 1 minute or more and less than 30 minutes,
(Zone 4) Within a range of 200 ° C. to 250 ° C. for 1 minute or more and less than 30 minutes,
And drying in the order of zone 1, zone 2, zone 3 and zone 4 according to
It is characterized by including.

In the production method 1, when the solvent-containing film is dried in Step A3 after the solvent-containing film is peeled off from the support in Step A2, the temperature profile is changed to Zone 1, Zone 2, Zone 3, and Zone 4 in this order. By drying the contained film in a heating furnace, the arithmetic average roughness (Ra) of at least one side of the obtained polyimide film is controlled to 1.5 nm or less regardless of the heat resistance of the support, and the polyimide film has a low haze. It is thought that can be manufactured. In the present specification, the heating temperature related to the above temperature profile means the temperature of the film surface.
An example of a temperature profile for drying the solvent-containing film in a heating furnace is a time-temperature curve shown in FIG. From FIG. 3, it is clear that the solvent-containing film is heated stepwise in the order of zone 1, zone 2, zone 3, and zone 4.

The support used in the manufacturing method 1 corresponds to the support 11 shown in FIG. 1, is flexible, and can be bent. In the case of using the heating according to the above temperature profile by peeling the solvent-containing film from the support in the production method 1, since the support is not limited to heat resistance, an alkali glass substrate, an alkali-free glass substrate (Eagle XG (registered trademark)) , Manufactured by Corning), metal substrates such as copper substrate, aluminum substrate, SUS substrate; plastic films such as polycarbonate film, PET film, kapton (300H, manufactured by Toray Industries, Inc.), upilex (125S, manufactured by Ube Industries); and copper foil, Metal foil such as aluminum foil and SUS foil may be used. Among these, from the viewpoint of control of surface smoothness and productivity, those having few particles and protrusions such as a lubricant on the support surface are preferable, plastic films are more preferable, PET films are more preferable, polyethylene terephthalate (Cosmo Shine) A4100, manufactured by Toyobo Co., Ltd.) is particularly preferable. In the present specification, a substrate has a structure that is highly rigid and unsuitable for bending, and a film or a film substrate means a flexible structure that can be bent.
Step A1 can be performed by casting a polyimide varnish on a support using a support unwinding roll and a varnish discharge device. In Step A1, since the film is formed from a polyimide solution that has been imidized in advance, after the temporary drying in Step 2, the support can be removed to obtain a polyimide self-supporting film.
In step A2, it is considered that the solvent-containing film can be easily peeled from the support by heating the polyimide varnish. Peeling of the solvent-containing film from the support can be performed using, for example, a winding roll, an unwinding roll, a slitter or the like. Step 2 and step A3 can be performed sequentially or continuously.

When step A2 and step 3 are performed sequentially, the heating of the polyimide varnish in step A2 is regarded as pre-drying or rough drying performed before step A3. For example, by a hot air dryer, This can be done by applying air at least to the varnish coated surface.
When step A2 and step A3 are performed continuously, the heating of the polyimide varnish in step A2 is regarded as part of the step of drying the solvent-containing film according to the temperature profile in step A3, and the heating according to the temperature profile is performed. It can be performed using a combination of a heating furnace, a take-up roll, and an unwind roll that can be performed.
In step A3, it is considered that the volatilization rate of the solvent from the solvent-containing film can be controlled by heating the solvent-containing film according to the temperature profile.

In step A3, it is preferable to dry the solvent-containing film while fixing both ends of the solvent-containing film from the viewpoint of obtaining a polyimide film that is colorless and transparent, has low YI, Rth, and haze, and has excellent surface smoothness and toughness. . For example, it is possible to dry while fixing both ends of the solvent-containing film by holding the end of the solvent-containing film peeled off from the support with a tenter or the like.
When drying the solvent-containing film while fixing both ends of the solvent-containing film, the ratio of the width of the solvent-containing film at the inlet of the heating furnace and the width of the polyimide film at the outlet of the heating furnace from the viewpoint of fixing index (width _inlet / Width _exit ) is preferably in the range of 0.95 to 1.05, more preferably 0.96 to 1.04 in the lateral direction (TD direction) of the film.

[Production Method 2]
Production method 2 includes the following steps:
(Step B1) A step of coating a polyimide varnish containing polyimide and an organic solvent on a heat-resistant support having a Tg of 300 ° C. or higher or a glass transition point and a 1% thermal decomposition temperature of 400 ° C. or higher; (Step B2) The polyimide varnish is transported together with the support into a heating furnace, and the formed solvent-containing film is subjected to the following temperature profile:
(Zone 1) 3 minutes or more and less than 30 minutes within the range of 50 ° C to 100 ° C,
(Zone 2) 1 minute or more and less than 30 minutes within the range of 100 ° C to 150 ° C,
(Zone 3) Within a range of 150 ° C. to 200 ° C. for 1 minute or more and less than 30 minutes,
(Zone 4) Within a range of 200 ° C. to 250 ° C. for 1 minute or more and less than 30 minutes,
Drying in the order of zone 1, zone 2, zone 3 and zone 4 according to
It is characterized by including.
In the production method 2, the polyimide varnish is hardly volatilized in the direction in contact with the support and is not in contact with the support by transferring the polyimide varnish in the heating furnace together with the heat-resistant support in Step B2. Since the varnish easily evaporates, the volatilization direction of the solvent from the solvent-containing film is controlled, and it becomes easy to adjust the film optical properties such as haze and Rth, and the arithmetic average roughness (Ra) of the film surface is 1.5 nm. It is conceivable that the adjustment is easy as follows.
Moreover, in the manufacturing method 2, by using a heat resistant support body in process B1, a polyimide varnish can be conveyed in a heating furnace with a support body in process B2, and peeling of a solvent containing film from a support body can be omitted. The productivity of the polyimide film can be improved.

Furthermore, in the production method 2, the solvent-containing film is dried in the order of zone 1, zone 2, zone 3, and zone 4 in the order of temperature profile, so that it is colorless and transparent, has low YI, Rth, and haze, and has surface smoothness and It is thought that the polyimide film which is excellent in toughness can be manufactured.
An example of a temperature profile for drying the solvent-containing film in the heating furnace in the production method 2 is a time-temperature curve shown in FIG. From FIG. 3, it is clear that the solvent-containing film is heated stepwise in the order of zone 1, zone 2, zone 3, and zone 4.
The support used in the production method 2 corresponds to the support 11 shown in FIG. 1 and has a glass transition temperature (Tg) of 300 ° C. or higher or a glass transition from the viewpoint that shrinkage or decomposition does not occur even in a heating furnace. No point is indicated, and the 1% thermal decomposition temperature is 400 ° C. or higher. When heating according to the above temperature profile is used in Step B1 and Step B2 of Production Method 2, specifically, as a support, upilex (upilex125s, manufactured by Ube Industries), kapton (300H, manufactured by Toray Industries, Inc.), stainless steel substrate, It is preferable to use a glass substrate, an aluminum foil metal foil, or the like.

The process B1 and the process B2 of the manufacturing method 2 can be performed sequentially or continuously.
When step B1 and step B2 are sequentially performed, in step B1, for example, using a hot air dryer, preliminary drying or rough drying may be performed by applying air of about 100 ° C. to at least the varnish coating surface. it can. Thereafter, the process B2 can be performed by controlling the heating temperature in accordance with the temperature profile in the heating furnace.
When step B1 and step B2 are carried out continuously, the polyimide varnish and the heat-resistant support are conveyed to a heating furnace according to the above temperature profile using a winding roll and / or an unwinding roll after application of the polyimide varnish. You can do it.
In step B2, it is considered that the volatilization rate of the solvent from the solvent-containing film can be controlled by heating the solvent-containing film according to the temperature profile.

(varnish)
The polyimide varnish used in the production method 1 or 2 may contain the polyimide described above.
From the viewpoint that the film hardly breaks when the film is formed from a polyimide solution that has been imidized in advance in Production Method 1 or 2, the polyimide varnish preferably contains a polyimide having an imidization rate of 80% or more. From the same viewpoint, the polyimide varnish preferably contains a polyimide having a weight average molecular weight (Mw) of 40,000 or more.
As described above, the organic solvent contained in the polyimide varnish is a phenol solvent, an amide solvent, a lactone solvent, a sulfoxide solvent, a ketone solvent, an ester solvent, or the like. Among these, from the viewpoint of obtaining desired YI, Rth, haze and toughness, a lactone solvent is preferable, and GBL is more preferable. In the polyimide film obtained by the production method 1 or 2, the lactone solvent may be left as a remaining amount of at least 0.01% by mass.

(Polyimide varnish coating)
In the step A1 of the production method 1 or the step B1 of the production method 2, for example, the polyimide varnish can be coated on the support by a known coating method such as spin coating, slit coating, slot die coating, blade coating or the like. In step A1 of production method 1, blade coating is preferable from the viewpoint of castability.

(Solvent-containing film)
The solvent-containing film formed by the production method 1 or 2 preferably contains a lactone solvent at a concentration of 0.1 to 20% by mass from the viewpoint of obtaining desired YI, Rth, haze, and toughness.

(Heating process)
The heating of the solvent-containing film in the production method 1 or 2 can be performed in an air atmosphere.
From the viewpoint of producing a polyimide film having low YI, Rth, and haze, and excellent surface smoothness and toughness, the heating according to the temperature profile described above is performed so that the resulting polyimide film has a thickness of 1 μm to 50 μm. It is preferable to be performed. The film thickness of the polyimide film can be adjusted according to the basis weight of the polyimide varnish.

(Stretching of polyimide film)
If desired, a polyimide film having a thickness of less than 10 μm can be produced by stretching a polyimide film having a thickness of 10 μm or more. The polyimide film can be stretched 1.5 to 5 times by biaxial stretching while being heated to 150 ° C. to 350 ° C. with the support attached or peeled from the support. The stretching may be simultaneous biaxial stretching or sequential biaxial stretching, but simultaneous biaxial stretching is preferred from the viewpoint of low Rth of the film. The stretched polyimide film can be dried until the residual solvent is 3% by mass or less.

<Products using polyimide film>
The polyimide film which concerns on this Embodiment can be used as a substitute of glass similarly to a PET film or a COP film, for example. As described above, the polyimide film according to the present embodiment can achieve low Rth and has high elongation. For example, even if it is used for a foldable display body or a display body that follows a curved surface, the film is broken. Does not occur and is useful.
As described above, the polyimide film and laminate according to this embodiment can be used as a substrate film such as a surface protective film, a color filter, and a TFT, and an insulating protective film. These polyimide films and laminates include, for example, displays with touch panel functions, organic EL lighting, flexible displays, smartphones, tablet terminals, foldable smartphones and tablet terminals, other flexible devices, organic EL lighting with curved surfaces, It can be suitably used for products such as organic EL displays. Here, a flexible device means a flexible display, a flexible solar cell, a flexible touch panel, flexible lighting, a flexible battery etc., for example.

  Hereinafter, although this invention is further explained in full detail based on an example, these are described for description and the scope of the present invention is not limited to the following example. Various evaluations in the examples were performed as follows.

(Measurement of weight average molecular weight (Mw) and number average molecular weight (Mn))
The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) under the following conditions. As the solvent, N, N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd., for high performance liquid chromatograph) was used, and 24.8 mol / L lithium bromide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) before the measurement. , Purity 99.5%) and 63.2 mol / L phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., for high performance liquid chromatograph) were used. A calibration curve for calculating the weight average molecular weight was prepared using standard polystyrene (manufactured by Tosoh Corporation).
Column: TSK-GEL SUPER HM-H
Flow rate: 0.5 mL / min Column temperature: 40 ° C
Pump: PU-2080 (manufactured by JASCO)
Detector: RI-2031Plus (RI: differential refractometer, manufactured by JASCO)
UV-2075 Plus (UV-Vis: UV-Visible Absorber, manufactured by JASCO)

(Measurement of film thickness)
The film thickness was measured using a thickness gauge.

(Evaluation of breaking elongation and breaking strength)
Using a tensile tester (manufactured by A & D Co., Ltd .: RTG-1210), the dried sample length of 3 × 50 mm was pulled at a rate of 100 mm / min, and the elongation at break and strength at break were measured.

(Evaluation of yellowness (YI), haze, total light transmittance)
The polyimide film was measured for yellowness (YI value), haze, and total light transmittance using a D65 light source with a spectrocolorimeter (CM3600A) manufactured by Konica Minolta, Inc. Unless otherwise specified, measurement was performed on a film having a thickness of 20 ± 1 μm as a sample.

(Evaluation of surface smoothness (Ra))
The measurement area (50 μm × 50 μm) was scanned and measured using a nanoscale hybrid microscope (VN8000, manufactured by Keyence Corporation).

(Evaluation of OLED emission)
The evaluation of OLED emission was measured by the following method.
First, an OLED light emitting element was produced by the following method.
(1) On the polyimide film, silicon nitride was sputtered at 200 ° C. to form a barrier layer having a thickness of 100 nm.
(2) Indium zinc oxide (IZO) was sputtered to a thickness of 150 nm to form a transparent electrode layer.
(3) Tris (2-phenylpyridinato) iridium (III) was formed as an organic EL element by vapor deposition so as to have a thickness of 10 nm.
(4) The element was sealed with AlPEN.
The manufactured OLED element was energized, and it was confirmed whether the OLED element emitted light. Those that did not emit light at all were designated B (defect), and those that emitted light were designated A (good). Further, S (remarkably good) was emitted even after storage for 1 week at a temperature of 60 ° C. and a humidity of 90%.

Then, the synthesis | combination conditions of a polyimide and the preparation conditions of a polyimide film are demonstrated concretely.
[Synthesis Example 1]
While introducing nitrogen gas into a 500 mL separable flask equipped with a stirring rod and having a Dean-Stark tube and a reflux tube at the top, 13.4 g (55.44 mmol) of 4,4′-DDS and 3.44 g of 3,3′-DDS ( 13.86 mmol) and 50.00 g of NMP were added. Then, 21.71 g (70.00 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), 22.28 g of NMP, and 26.02 g of toluene were added at room temperature, and then the temperature was raised to 160 ° C. and 160 ° C. The mixture was heated to reflux for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed, the temperature was returned to room temperature, NMP was added so that the solid content was 20% by mass, and a polyimide NMP solution (hereinafter also referred to as polyimide varnish) was obtained.

[Synthesis Example 2]
To a 500 mL separable flask equipped with a stirring bar equipped with a Dean-Stark tube and a reflux tube at the top, while introducing nitrogen gas, 12.4 g (48.51 mmol) of 4,4′-DDS was added to 3,3′-DDS. 5.16 g (20.79 mmol) and GBL 50.00 g were added. Then, 21.71 g (70.00 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), 22.28 g of GBL, and 26.02 g of toluene were added at room temperature, and the temperature was raised to 160 ° C. The mixture was heated to reflux for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content was 20% by mass to obtain a polyimide GBL solution (hereinafter also referred to as polyimide varnish).

[Synthesis Example 3]
Except that 4,4′-DDS was changed to 10.32 g (41.58 mmol), 3,3′-DDS was changed to 6.90 g (27.72 mmol), and the reaction time at 180 ° C. was changed to 7 hours, A polyimide varnish and a polyimide film were obtained in the same manner as in Synthesis Example 2.

[Synthesis Example 4]
A polyimide varnish was obtained in the same manner as in Synthesis Example 2 except that 4,4′-DDS was changed to 8.61 g (34.65 mmol) and 3,3′-DDS was changed to 8.61 g (34.65 mmol).

[Synthesis Example 5]
A polyimide varnish was obtained in the same manner as in Synthesis Example 2 except that 4.4′-DDS was changed to 6.89 g (27.72 mmol) and 3,3′-DDS was changed to 10.34 g (41.58 mmol).

[Synthesis Example 6]
A polyimide varnish was obtained in the same manner as in Synthesis Example 4 except that 4,4′-ODPA was changed to 15.27 g (70.00 mmol) of pyromellitic dianhydride (PMDA).

[Synthesis Example 7]
A polyimide varnish was prepared in the same manner as in Synthesis Example 4 except that 4,4′-ODPA was changed to 20.59 g (70.00 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA). Obtained.

[Synthesis Example 8]
A polyimide varnish was obtained in the same manner as in Synthesis Example 4 except that 4,4′-ODPA was changed to 31.09 g (70.00 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA). It was.

[Synthesis Example 9]
A polyimide varnish was obtained in the same manner as in Synthesis Example 8 except that 4,4′-DDS was changed to 13.77 g (55.44 mmol) and 3,3′-DDS was changed to 3.44 g (13.86 mmol).

[Synthesis Example 10]
A polyimide varnish was obtained in the same manner as in Synthesis Example 8 except that the 4,4′-DDS was changed to 6.89 g (27.72 mmol) and the 3,3′-DDS was changed to 10.34 g (41.58 mmol).

[Synthesis Example 11]
Into a 500 mL separable flask equipped with a stirring bar equipped with a Dean-Stark tube and a reflux tube at the top, 1.81 (15.84 mmol) of trans-1,4-cyclohexyldiamine (CHDA) was introduced while introducing nitrogen gas. 15.73 g (63.36 mmol) of 3-DDS and 50.00 g of NMP were added. Subsequently, 4,4′-oxydiphthalic anhydride (ODPA) 24.82 g (80.00 mmol), NMP 28.67 g, and toluene 27.14 g were added at room temperature, and the temperature was raised to an internal temperature of 160 ° C. The mixture was heated to reflux for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 3 hours, the oil bath was removed, the temperature was returned to room temperature, NMP was added so that the solid content was 20% by mass, and a polyimide NMP solution (hereinafter also referred to as polyimide varnish) was obtained.

[Synthesis Example 12]
To a 500 mL separable flask equipped with a stirring bar equipped with a Dean-Stark tube and a reflux tube at the top, 4.93 g (34.65 mmol) of 1,4-bis (aminomethyl) cyclohexane (14BAC) was introduced while introducing nitrogen gas. Then, 8.61 g (34.65 mmol) of 3,3′-DDS and 50.00 g of GBL were added. Then, 21.71 g (70.00 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), 15.46 g of GBL, and 26.02 g of toluene were added at room temperature, and then the temperature was raised to 160 ° C. and 160 ° C. The mixture was heated to reflux for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 4 hours, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content was 20% by mass to obtain a polyimide GBL solution (hereinafter also referred to as polyimide varnish).

[Synthesis Example 13]
Into a 500 mL separable flask equipped with a stirring bar equipped with a Dean-Stark tube and a reflux tube at the top, 5.13 g (33.25 mmol) of bis (aminomethyl) norbornane (BANBDA) was added while introducing nitrogen gas. -8.26 g (33.25 mmol) of DDS and 50.00 g of GBL were added. Then, 21.71 g (70.00 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), 15.19 g of GBL and 24.90 g of toluene were added at room temperature, and the temperature was raised to 160 ° C. The mixture was heated to reflux for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 6 hours, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content was 20% by mass to obtain a polyimide GBL solution (hereinafter also referred to as polyimide varnish).

[Synthesis Example 14]
While introducing nitrogen gas into a 500 mL separable flask equipped with a stirring bar having a Dean-Stark tube and a reflux tube at the top, 5.11 g (13.86 mmol) of 4,4′-bis (4-aminophenoxybiphenyl) (BAPB) was introduced. ), 13.77 g (55.44 mmol) of 3,3-DDS and 50.00 g of GBL were added. Then, 21.71 g (70.00 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), 22.28 g of GBL and 25.63 g of toluene were added at room temperature, and the temperature was raised to 160 ° C. The mixture was heated to reflux for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 6 hours, the oil bath was removed, the temperature was returned to room temperature, NMP was added so that the solid content was 20% by mass, and a polyimide NMP solution (hereinafter also referred to as polyimide varnish) was obtained.

[Synthesis Example 15]
Α, α'-bis (4-aminophenyl) -1,4-diisopropylbenzene (BAPDB) was introduced into a 500 mL separable flask equipped with a stirring bar equipped with a Dean-Stark tube and a reflux tube at the top while introducing nitrogen gas. To 11.94 g (34.65 mmol), 8.61 g (34.65 mmol) of 3,3′-DDS and 50.00 g of GBL were added. Then, 21.71 g (70.00 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), 28.47 g of GBL, and 26.99 g of toluene were added at room temperature, and then the temperature was raised to 160 ° C. and 160 ° C. The mixture was heated to reflux for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 6 hours, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content was 20% by mass to obtain a polyimide GBL solution (hereinafter also referred to as polyimide varnish).

[Synthesis Example 16]
While introducing nitrogen gas into a 500 mL separable flask equipped with a stirring bar equipped with a Dean-Stark tube and a reflux tube at the top, 8.4 g (34.65 mmol) of 4,4′-DDS and 8.61 g of 3,3′-DDS (34.65 mmol) and 50.00 g of GBL were added. Subsequently, 4.86 ′ (35.00 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), 7.85 g (35.00 mmol) of hydroxypyromellitic dianhydride (HPMDA), 16.69 g of GBL, 24.41 g of toluene Was added at room temperature, and the temperature was raised to an internal temperature of 160 ° C., followed by heating at 160 ° C. for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content was 20% by mass to obtain a polyimide GBL solution (hereinafter also referred to as polyimide varnish).

[Synthesis Example 17]
While introducing nitrogen gas into a 500 mL separable flask equipped with a stirring bar equipped with a Dean-Stark tube and a reflux tube at the top, 8.4 g (34.65 mmol) of 4,4′-DDS and 8.61 g of 3,3′-DDS (34.65 mmol) and 50.00 g of GBL were added. Subsequently, 17.37 g (56.00 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), 1,3,3a, 4,5,9b-hexahydro-5- (tetrahydro-2,5-dioxo-3) -Furanyl) naphtho [1,2-c] furan-1,3-dione (TDA) 4.20 g (14.00 mmol), GBL 22.02 g, and toluene 26.07 g were added at room temperature, and the internal temperature reached 160 ° C. The temperature was raised, and the mixture was heated to reflux at 160 ° C. for 1 hour for imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content was 20% by mass to obtain a polyimide GBL solution (hereinafter also referred to as polyimide varnish).

[Synthesis Example 18]
While introducing nitrogen gas into a 500 mL separable flask equipped with a stirring bar equipped with a Dean-Stark tube and a reflux tube at the top, 8.4 g (34.65 mmol) of 4,4′-DDS and 8.61 g of 3,3′-DDS (34.65 mmol) and 50.00 g of GBL were added. Subsequently, 17.37 g (56.00 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), bicyclo [2,2,2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BODA) 3.47 g (14.00 mmol), GBL 20.67 g and toluene 25.58 g were added at room temperature, then the temperature was raised to an internal temperature of 160 ° C. and heated at 160 ° C. for 1 hour to perform imidization. went. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content was 20% by mass to obtain a polyimide GBL solution (hereinafter also referred to as polyimide varnish).

[Synthesis Example 19]
19.2 g (59.40 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) while introducing nitrogen gas into a 500 mL separable flask equipped with a stir bar equipped with a Dean-Stark tube and a reflux tube at the top , 50.00 g of GBL was added. Subsequently, 4 '-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) 26.66 g (60.00 mmol), GBL 20.69 g, and toluene 25.87 g were added at room temperature, and then the temperature was raised to 160 ° C. The mixture was heated to reflux at 160 ° C. for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed, the temperature was returned to room temperature, and NMP was added so that the solid content was 20% by mass to obtain a polyimide GBL solution (hereinafter also referred to as polyimide varnish).
The compositions of the polyimides obtained in Synthesis Examples 1 to 19 are shown in Table 1 below. Moreover, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the polyimide in the obtained polyimide varnish are shown in Table 2 below.

(How to create a film)
[Example A]
The polyimide varnish was coated on a polyethylene terephthalate (Cosmo Shine 100A4100) having a width of 508 mm as a support with a coating thickness of 150 μm and a coating width of 500 mm, and dried at 50 ° C. for 30 minutes. The residual solvent in the polyimide film at this time was 15.5 mass% concentration. The solvent-containing polyimide film was peeled off from the support, the film was conveyed into a heating furnace, and was dried with hot air under the temperature conditions shown in FIG. The width of the film at the entrance of the heating furnace before drying was 500 mm, and the width of the film at the exit of the heating furnace after drying was 495 mm.

[Example B]
A polyimide varnish was applied on a 508 mm wide upilex (product number upilex 125s, manufactured by Ube Industries) as a supporting base material with a coating thickness of 150 μm and a coating width of 500 mm, and dried at 50 ° C. for 30 minutes. The residual solvent in the polyimide film at this time was 16 mass% concentration. The upilex film with the solvent-containing polyimide film was conveyed into a heating furnace and dried under the temperature conditions shown in FIG. The width of the polyimide film at the outlet of the heating furnace after drying was 500 mm.

[Example C]
The polyimide varnish was coated on a polyethylene terephthalate (Cosmo Shine 100A4100) having a width of 508 mm as a support with a coating thickness of 150 μm and a coating width of 500 mm, and dried at 50 ° C. for 30 minutes. The residual solvent in the polyimide film at this time was 15.5 mass% concentration. This solvent-containing polyimide film was peeled from the support, and both ends were fixed with a tenter. At this time, the width of the film was 500 mm. Then, this film was conveyed in the heating furnace, and it dried on the temperature conditions shown in FIG. The width of the film at the exit of the heating furnace after drying was 495 mm.

[Example D]
A polyimide varnish is applied on upilex (product of Ube Industries, product number upilex125s) as a support at a coating thickness of 200 μm, dried at 50 ° C. for 10 minutes, and at 150 ° C. for 10 minutes, and then a resin composition layer Was peeled from the Upilex film as a support, and dried in an IR drying furnace at an IR temperature at which the film surface was 270 ° C. for 10 minutes.

(Examples 1 to 29 and Comparative Example 1)
As shown in Table 2 or 3, a polyimide film was prepared by combining any of the polyimides obtained in Synthesis Examples 1 to 19 and any of Film Preparation Examples A to D, and evaluated according to the above evaluation method. The evaluation results of Examples 1 to 29 are shown in Table 2 below, and the evaluation results of Comparative Example 1 are shown in Table 3 below.

(Reference Examples 1-3)
According to the above evaluation method, only the polyethylene terephthalate (PET) film (Cosmo Shine 100A4100) was evaluated in Reference Example 1, and the polyethylene naphthalate (PEN) film (Teijin DuPont Films Co., Ltd. “Teonex (registered trademark)”) was evaluated in Reference Example 2. In Reference Example 3, only a polyimide (PI) film (Toray DuPont "Kapton (registered trademark)") was evaluated. The evaluation results are shown in Table 4 below.

DESCRIPTION OF SYMBOLS 10 Polyimide film 11 Support body 12 Resin composition layer 20 Laminated body 21 Transparent electrode layer

Claims (14)

The following requirements:
(A) The following general formula (1):

{In General Formula (1), A is a divalent organic group, B is a tetravalent organic group, and n is a number of 2 or more. }
In the general formula (1), the following general formula (A-1):

And the following general formula (A-2):

{In general formula (A-2), X represents the following general formula (X-1) to the following general formula (X-3):

And at least one divalent organic group selected from the group consisting of: }, The following general formula (A-3):

{In General Formula (A-3), a is a number of 0 or 1. }, And the following general formula (A-4):

And (B) the arithmetic average roughness (Ra) of at least one side of the polyimide film is 1.5 nm or less;
The polyimide film characterized by satisfy | filling.   The polyimide film of Claim 1 whose haze of the said polyimide film is 1.0 or less. As A in the general formula (1), the structure represented by the general formula (A-1), and the following general formula (A-5):

The polyimide film of Claim 1 or 2 containing the structure represented by these.   Ratio of structure represented by general formula (A-1) to structure represented by general formula (A-5) (structure represented by general formula (A-1) / general formula (A-5) The polyimide film of Claim 3 which is in the range of 2/8-6/4 on the molar basis. As B in the general formula (1), the following general formula (B-1) to the following general formula (B-4):

{In the general formula (B-1), Y represents the following general formula (Y-1) to the following general formula (Y-3):

At least one structure selected from the group consisting of }

The polyimide film of any one of Claims 1-4 containing at least 1 among the structures represented by these. As B in the general formula (1), the following general formula (B-5):

The polyimide film of any one of Claims 1-5 containing the structure represented by these. The following steps:
(Step A1) a step of applying a polyimide varnish containing at least the polyimide and the organic solvent on a support;
(Step A2) Step of heating the polyimide varnish to form a solvent-containing film containing a solvent at a concentration of 5% by mass to 20% by mass and peeling from the support; and (Step A3) heating the solvent-containing film The solvent-containing film is conveyed into a furnace and the following temperature profile:
(Zone 1) 3 minutes or more and less than 30 minutes within the range of 50 ° C to 100 ° C,
(Zone 2) 1 minute or more and less than 30 minutes within the range of 100 ° C to 150 ° C,
(Zone 3) Within a range of 150 ° C. to 200 ° C. for 1 minute or more and less than 30 minutes,
(Zone 4) Within a range of 200 ° C. to 250 ° C. for 1 minute or more and less than 30 minutes,
Drying the zone 1, the zone 2, the zone 3 and the zone 4 in this order according to
The manufacturing method of the polyimide film of any one of Claims 1-6 containing this. The following steps:
(Step B1) A polyimide varnish containing at least the polyimide and the organic solvent on a heat-resistant support having a glass transition point (Tg) of 300 ° C. or higher or a glass transition point of 1% thermal decomposition temperature of 400 ° C. or higher. And (Step B2) transporting the polyimide varnish together with the support into a heating furnace, and forming the formed solvent-containing film with the following temperature profile:
(Zone 1) 3 minutes or more and less than 30 minutes within the range of 50 ° C to 100 ° C,
(Zone 2) 1 minute or more and less than 30 minutes within the range of 100 ° C to 150 ° C,
(Zone 3) Within a range of 150 ° C. to 200 ° C. for 1 minute or more and less than 30 minutes,
(Zone 4) Within a range of 200 ° C. to 250 ° C. for 1 minute or more and less than 30 minutes,
Drying the zone 1, the zone 2, the zone 3 and the zone 4 in this order according to
The manufacturing method of the polyimide film of any one of Claims 1-6 containing this.   The method for producing a polyimide film according to claim 7, wherein the solvent-containing film is dried while fixing both ends of the solvent-containing film in the step A3. In the step A3, the ratio of the width of the solvent-containing film at the inlet of the heating furnace to the width of the polyimide film at the outlet of the heating furnace (width _inlet / width _outlet ) is 0.95 to 1.05 in the TD direction. The manufacturing method of the polyimide film of Claim 9 which is in the range.   The said polyimide varnish is a manufacturing method of the polyimide film of any one of Claims 7-10 containing a lactone type | system | group solvent.   The said polyimide varnish is a manufacturing method of the polyimide film of any one of Claims 7-11 containing the polyimide whose imidation rate is 80% or more.   The said polyimide varnish is a manufacturing method of the polyimide film of any one of Claims 7-12 containing the polyimide whose weight average molecular weight (Mw) is 40000 or more.   The manufacturing method of the polyimide film of any one of Claims 7-13 whose film thickness of the said polyimide film is 1 micrometer-50 micrometers.

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