JP6956524B2 - Polyimide film, products using polyimide film, and laminates - Google Patents

Description

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

In recent years, in the field of touch panel materials such as transparent electrode films, the use of plastic films as substrates has been studied from the viewpoint of weight reduction and thinning, instead of glass.
Further, flexible devices such as flexible displays that can be bent, and devices having curved surfaces such as organic EL lighting and organic EL displays are being studied. In the above device, it is considered 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, the adoption of a polyethylene terephthalate film (PET film), a polyethylene naphthalate film (PEN film), and a cycloolefin film (COP film) having excellent optical characteristics is being studied.
As a film substrate for such a flexible device, a film having excellent optical characteristics and further excellent bending resistance is required. However, the above-mentioned PET film and PEN film have a drawback that they are inferior in optical characteristics and visibility, and a COP film is inferior in toughness.
On the other hand, since the polyimide resin has excellent properties such as heat oxidation resistance, heat resistance properties, heat resistance radiation resistance, low temperature resistance, and chemical resistance, it is also considered to use a polyimide film as the substrate. (Patent Documents 1 to 8 and Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-137881 Special Table 2010-510378 JP-A-2007-246820 International Publication No. 2012/118020 Japanese Patent No. 4786859 European Patent Application Publication No. 2032632 U.S. Pat. No. 3,666,709 International Publication No. 2016/158825

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

However, the surface roughness of the PET film and PEN film described above is not always sufficient. 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 mean roughness (hereinafter referred to as Ra) on the film surface described in JISB0601 (2001) is used for a touch panel, for example, the film becomes white and cloudy when visually viewed, and the visibility is very high. Getting worse. Further, when a transparent electrode such as ITO is laminated 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, for example, visually. When viewed, the transparent electrode pattern can be confirmed, and the visibility deteriorates. In order to solve this, generally, a flattening layer is provided on a PET film having a large surface roughness by using an acrylic resin or the like, and the arithmetic mean roughness of the surface of the film is determined. There is room for improvement.

Further, if the degree of fogging of the polyimide film (hereinafter, also referred to as haze) is high, the visibility deteriorates, so that there is room for improvement in the haze of the polyimide film.
Further, it is desirable that the yellowness (Yellow Index; hereinafter referred to as YI) of the polyimide film is 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 the polyimide film. There is a problem that coloring and turbidity tend to remain on the obtained polyimide film due to the influence of water. In addition, a polyimide resin having an aromatic ring, such as a polyimide composed of pyromeritic acid dianhydride and diaminodiphenyl ether, which has high heat resistance, is colored brown or yellow, has low transmittance in the visible light region, and is transparent. It was difficult to use in fields where sex is required. As described above, when the polyimide film is colored, cloudy, or turbid, the visibility of display devices such as touch panels, organic EL lighting, and flexible displays 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 of the polyimide film (hereinafter referred to as Rth) 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. As the polyimide film has a high Rth, the visibility deteriorates.

As described above, the polyimide film can be used as, for example, a touch panel material or a film substrate for a flexible device, and it is desired that the polyimide film is a material having excellent toughness. However, each patent document and non-patent document 1 do not disclose a method for producing polyimide for improving toughness, having a low YI and Rth, a smooth surface, and a low haze (hereinafter referred to as haze).
By the way, general polyimide has poor solubility in a solvent due to its high aromatic ring density, and it is difficult to directly obtain a polyimide film from a polyimide solution. Therefore, as the polyimide constituting the polyimide film, one having high solubility in a solvent and excellent processability has been desired.

The present invention has been made in view of the problems described above, and is a polyimide film for producing a polyimide film or a polyimide film which is colorless and transparent, has low YI and Rth, has a smooth surface, has low haze, and has excellent toughness. An object of the present invention is to provide a product using a varnish or a polyimide film, and a laminate.

｛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 the 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 the 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 contains the polyimide represented by, and as A in the general formula (1), the following general formula (A-1):

The structure represented by and the following general formula (A-2):

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

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

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

(B) The arithmetic mean roughness (Ra) of at least one side of the polyimide film shall be 1.5 nm or less;
A polyimide film characterized by satisfying.
[2]
The polyimide film according to [1], wherein the polyimide film has a haze of 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 according to [1] or [2], which comprises the structure represented by.
[4]
The ratio of the structure represented by the general formula (A-1) to the structure represented by the general formula (A-5) (structure represented by the general formula (A-1) / general formula (A-5)). The polyimide film according to [3], wherein the (structure represented by) is in the 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 is the following general formula (Y-1) to the following general formula (Y-3):

It is at least one structure selected from the group consisting of. }

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

The polyimide film according to any one of [1] to [5], which comprises the structure represented by.

[7]
The following steps:
(Step A1) A step of applying at least a polyimide varnish containing the polyimide and an organic solvent onto 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 it from the support; and (Step A3) heating the solvent-containing film. Transported into the furnace and the solvent-containing film was 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) 1 minute or more and less than 30 minutes within the range of 150 ° C to 200 ° C,
(Zone 4) 1 minute or more and less than 30 minutes within the range of 200 ° C to 250 ° C,
The step of drying the zone 1, the zone 2, the zone 3, and the zone 4 in this order according to the above;
The method for producing a polyimide film according to any one of [1] to [6], which comprises.
[8]
The following steps:
(Step B1) The polyimide varnish containing the polyimide and an organic solvent is applied onto a heat-resistant support having a glass transition point (Tg) of 300 or more or no glass transition point and a 1% thermal decomposition temperature of 400 ° C. or more. The step of working; and (step B2), the polyimide varnish was conveyed together with the support into a heating furnace, and the solvent-containing film formed was 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) 1 minute or more and less than 30 minutes within the range of 150 ° C to 200 ° C,
(Zone 4) 1 minute or more and less than 30 minutes in the range of 200 ° C to 250 ° C,
The step of drying the zone 1, the zone 2, the zone 3, and the zone 4 in this order according to the above;
The method for producing a polyimide film according to any one of [1] to [6], which comprises.
[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 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 in the range of 0.95 to 1.05 in the TD direction. The method for producing a polyimide film according to [9].
[11]
The method for producing a polyimide film according to any one of [7] to [10], wherein the polyimide varnish contains a lactone-based solvent.
[12]
The method for producing a polyimide film according to any one of [7] to [11], wherein the polyimide varnish contains a polyimide having an imidization ratio of 80% or more.
[13]
The method for producing a polyimide film according to any one of [7] to [12], wherein the polyimide varnish contains a polyimide having a weight average molecular weight (Mw) of 40,000 or more.
[14]
The method for producing a polyimide film according to any one of [7] to [13], wherein the polyimide film has a film thickness of 1 μm to 50 μm.

According to the present invention, it is possible to provide a polyimide film which is colorless and transparent, has low YI and Rth, has a smooth surface, has low haze, and has excellent toughness. Further, in the present invention, it is possible to produce a product and a laminate using a polyimide film having desired characteristics.
Further, in the present invention, it is possible to improve the alignment accuracy of the elements installed on the film.

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 a laminated body 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, one 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 can be variously modified and implemented within the scope of the gist thereof.

｛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 this embodiment contains a polyimide represented by the following general formula (1).

{In the 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 of the general formula (1) can be obtained from a diamine.
Further, 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 the following general formula (A-2). ), The following general formula (A-3), and at least one of the structures represented by the following general formula (A-4) (hereinafter, also referred to as “structure A2”) (hereinafter, “the first”. Also called "one polyimide film").

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

It is at least one divalent organic group selected from the group consisting of. }

{In the general formula (A-3), a is a 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) and the general formula (A-2). ), And (X-1) are combined to form a structure (corresponding to the general formula (A-5)) of 4,4'-diaminodiphenyl sulfone (4,4'-Diaminodiphenyl Sulfone: hereinafter, 4, Derived from 4'-DDS), the structure represented by the combination of the general formulas (A-2) and (X-2) is α, α'-bis (4-aminophenyl) -1,4-diisopropyl. Derived from benzene (hereinafter also referred to as BAPDB), the structure represented by a combination of the general formulas (A-2) and (X-3) is 4,4'-bis (4-aminophenoxybiphenyl) (hereinafter, BAPB). Derived from (also referred to as CHDA), the structure represented by the general formula (A-3) is derived from cyclohexyldiamine (hereinafter, also referred to as CHDA) when a is 0, and 1,4-bis (aminomethyl) when a is 1. ) Cyclohexane (hereinafter, also referred to as 14BAC), the structure represented by the general formula (A-4) is derived from bis (aminomethyl) norbornan (hereinafter, also referred to as BANBDA). However, the present invention is not limited to these compounds.

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

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

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

The polyimide in the present embodiment contains, as A of the general formula (1), a structure represented by the general formula (A-1) (derived from 3,3'-diaminodiphenyl sulfone) as an essential repeating unit, and further. 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) is used. ,including.
By including the repeating unit in the polyimide of the present embodiment, it is possible to obtain a film having a low YI, a small Rth, and excellent toughness. 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 all considered to inhibit the formation of CT complexes between polyimide molecules due to the bending of the main chain. Among them, the structure represented by the general formula (A-1) and (A-5) may weaken the electron-donating N atom of the imide group with electron-withdrawing possessed by an SO ₂ group, is CT complexes It is considered to be difficult to form, which is particularly preferable.
In addition, the absorption of visible light contained in the aromatic polyimide also causes the polyimide to be colored. 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.

Further, it is considered that the solubility of the polyimide is improved by disturbing the orientation of the polyimide. It is considered that all the structures represented by the general formulas (A-1) to (A-4) exhibit solubility because the orientation of the polyimide molecules is disturbed due to the bending of the main chain. Among them, the structure represented by the general formula (A-1) is excellent because the orientation of the polyimide molecule is remarkably disturbed by the bent structure of _{two SO groups and the bent structure due to the bond generated from the 3rd and 3'positions.} It is considered to exhibit solubility.
As described above, the polyimide contained in the polyimide film in the present embodiment has a structure represented by the general formula (A-1) as A of the general formula (1), and the general formula (A-2) and the general formula. (A-3) and any one or more of the structures represented by the general formula (A-4) are included.
In the present invention, the molecular weight of polyimide is increased by copolymerizing the structure represented by the general formula (A-1) and the structure represented by the general formula (A-5), and this polyimide is used. We succeeded in specifically improving the toughness of the produced film. It should be noted that at least selected from the group having a structure represented by the general formula (A-1) and consisting of structures represented by the general formulas (A-2), (A-3) and (A-4). The same effect is exhibited for a polyimide having at least one structure.

In the present 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). In the following, a configuration using both 3,3'-DDS and 4,4'-DDS as diamines will be described.
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) is 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. Is a site for expressing in the range of 250 to 350 ° C.

In the present embodiment, it is preferable to contain both the structure represented by the general formula (A-1) and the structure represented by the general formula (A-5). The structural unit represented by the general formula (A-1) is preferably introduced from the viewpoint of the solubility of polyimide. The structural unit represented by the general formula (A-5) is adjusted from the viewpoint of high glass transition temperature (Tg). By containing both the structure represented by the general formula (A-1) and the structure represented by the general formula (A-5), the solubility of polyimide and the elongation at break of the film, which could not be achieved by each of them alone, were achieved. , And a high glass transition temperature (Tg) can be obtained while being colorless and transparent, without impairing low polyimide (Rth) and high total light transmittance.

In order to reduce Rth, it is necessary that the difference in refractive index between the in-plane direction and the out-of-plane direction of the film is small. The structure represented by the general formula (A-1) and the general formula (A-5) have _{a structure in which two} SO groups are bent, and the bent structure is fixed because it is an sp2 orbital. Therefore, it is considered that the structure represented by the general formula (A-1) and the aromatic groups 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 it is considered that Rth can be reduced. ..

In the present embodiment, the composition ratio of the structure A1 and the structure A2 (structure A1 / 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 a structure represented by the general formula (A-5), it is referred to as a structure A1 and a structure represented by the general formula (A-5) (hereinafter, also referred to as “structure A21”). The composition ratio (structure A1 / structure A21) of is preferably in the range of 2/8 to 6/4, and more preferably in the range of 3/7 to 4/6 in terms of molar ratio. That is, the structure A1 is preferably 20 mol% or more and 60% or less when the total amount of A in the general formula (1) is 100 mol%. Further, the structure A21 is preferably 40 mol% or more and 80% mol% or less when the total amount of A in the general formula (1) is 100 mol%.
Further, the structure A1 and at least one of the structural units represented by the general formulas (A-2) to (A-4) as the structure A2 (however, the structure represented by the above-mentioned general formula (A-5)). (Excluding the unit) (hereinafter, also referred to as “structure A22”), the composition ratio (structure A1 / structure A22) of the structure A1 and the structure A22 is preferably 5/5 to 8/2 in terms of molar ratio. ..

The general formula (A-1) and the general formula (A) are in the range in which the desired elongation at break can be expressed, and more preferably in the range in which the target glass transition temperature (Tg) can be expressed. It can contain a small amount of structural units other than the structural units represented by -5). 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 its performance is not impaired. For example, an aromatic diamine having 6 to 30 carbon atoms is mentioned as a preferable embodiment.

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'-benzophenonediamine, 3,3'-benzophenonediamine, 4,4'-di (4-aminophenoxy) phenylsulphon, 4,4'- Di (3-aminophenoxy) phenylsulphon, 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-amino) Phenyl) 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, 9,9-bis (4-aminophenoxyphenyl) fluorene, 3,3'-dimethyl Bentzin, 3,3'-dimethoxybenzazine 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-a) Examples of constituent units derived from aromatic diamine components such as minophenyl) hexafluoropropane (4,4'-6F) can be mentioned.
9,9-bis (4-aminophenyl) fluorene and 9,9-bis (4-aminophenoxyphenyl) fluorene can be introduced when adjusting Rth because the fluorene skeleton has negative birefringence. can.

Also, 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) have high steric hindrance of fluorine atoms. Can be introduced to suppress the formation of CT complexes between the molecules of polyimide and 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 of the general formula (1) will be described. The structural unit corresponding to B in the general formula (1) can be obtained from 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 formulas (B-1) to (B-4).
In the present embodiment, it is preferable that B in the general formula (1) includes at least one of the structures represented by the following general formulas (B-1) to the following general formulas (B-4).

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

It is 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 anhydride. Derived from (hereinafter also referred to as ODPA), the structure represented by combining the general formula (B-1) and the general formula (Y-2) is 4,4'-(hexafluoroisopropylidene) diphthalic acid dianhydride. Derived from (hereinafter, also referred to as 6FDA), the structure represented by combining the general formula (B-1) and the general formula (Y-3) is 9,9-diphenylfluorenic dianhydride (hereinafter, also referred to as DPFLDA). ) Derived, the structure represented by the general formula (B-2) is derived from hydroxypyromellitic dianhydride (hereinafter, also referred to as HPMDA), and the structure represented by the general formula (B-3) is bicyclo [2]. , 2,2] Oct-7-en-2,3,5,6-tetracarboxylic acid dianhydride (hereinafter, also referred to as BODA) is derived, and the structure represented by the general formula (B-4) is 1, Derived from 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) Is.
DPFLDA can be introduced when adjusting Rth because the fluorene skeleton has negative intrinsic birefringence.
The polyimide according to the present embodiment has a structure derived from an acid dianhydride component other than the structural units represented by the general formula (B-1) to the general formula (B-4) as long as its performance is not impaired. It may include units.
For example, aromatic tetracarboxylic dianhydride having 8 to 36 carbon atoms, aliphatic tetracarboxylic dianhydride having 6 to 50 carbon atoms, and alicyclic tetracarboxylic dianhydride having 6 to 36 carbon atoms. It is preferably a compound selected from. The number of carbon atoms referred to here also includes the number of carbon atoms contained in the carboxyl group.

More specifically, as an 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 acid dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4 '-Biphenyltetracarboxylic acid dianhydride (hereinafter, also referred to as BPDA), 3,3', 4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetracarboxylic Acid dianhydride, methylene-4,4'-diphthalic hydride, 1,1'-ethylidene-4,4'-diphthalic hydride, 2,2'-propylidene-4,4'-diphthalic acid Dianhydride, 1,2-ethylene-4,4'-diphthalic acid dianhydride, 1,3-trimethylen-4,4'-diphthalic acid dianhydride, 1,4-tetramethylene-4,4'- Diphthalic hydride, 1,5-pentamethylene-4,4'-diphthalic hydride, thio-4,4'-diphthalic hydride, sulfonyl-4,4'-diphthalic hydride, 1,3-bis (3,4-dicarboxyphenyl) benzene dianhydride, 1,3-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,4-bis (3,4-dicarboxy) Phenoxy) benzene dianhydride, 1,3-bis [2- (3,4-dicarboxyphenyl) -2-propyl] benzene dianhydride, 1,4-bis [2- (3,4-dicarboxyphenyl) -2- (3,4-dicarboxyphenyl) ) -2-propyl] benzene dianhydride, bis [3- (3,4-dicarboxyphenoxy) phenyl] methane dianhydride, bis [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 hydride (Hereinafter also referred to as BPADA), bis (3,4-dicarboxyphenoxy) dimethylsilane dianhydride, 1,3-bis (3,4-dicarboxyphenyl) -1,1', 3,3'-tetra Methyldisiloxane dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic Acid dianhydride, 3,4,9,10-perylenetetracarboxylic hydride, 2,3,6 , 7-Anthracene tetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride and the like can be mentioned.
Examples of the aliphatic tetracarboxylic dianhydride having 6 to 50 carbon atoms include ethylenetetracarboxylic dianhydride and 1,2,3,4-butanetetracarboxylic dianhydride.

As the alicyclic tetracarboxylic acid dianhydride having 6 to 36 carbon atoms, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (hereinafter, also referred to as CBDA), cyclopentanetetracarboxylic acid dianhydride, Cyclohexane-1,2,3,4-tetracarboxylic dianhydride, 3,3', 4,4'-bicyclohexyltetracarboxylic hydride, carbonyl-4,4'-bis (cyclohexane-1,2,2) -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 (cyclohexane-1) , 2-Dicarboxylic acid) dianhydride, oxy-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, thio-4,4'-bis (cyclohexane-1,2-dicarboxylic 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-Dioxotetra-3-yl) -1,2,3,4-tetrahydronaphthalene -1,2-dicarboxylic acid dianhydride, ethylene glycol-bis- (3,4-dicarboxylic acid dianhydride phenyl) ether, 4,4'-biphenylbis (trimellitic acid monoesteric acid dianhydride), etc. Can be mentioned.

In the general formula (B-1), the general formula (Y-1) and the general formula (Y-2) are of the solubility of polyimide in a solvent, and the yellowness and retardation (Rth) of a polyimide film. It is preferable from the viewpoint of reduction. Further, since the general formula (Y-3) has a negative intrinsic birefringence, reduction of yellowness and retardation (Rth) when made into a polyimide film, reduction of coefficient of linear expansion (CTE), reduction of linear expansion coefficient (CTE), It is also preferable from the viewpoint of improving the glass transition temperature (Tg).
The general formulas (B-2) to (B-4) are preferable from the viewpoint of solubility of the polyimide in a solvent and reduction of yellowness when the polyimide film is formed.
Among them, B in the general formula (1) is derived from ODPA from the viewpoints of solubility of polyimide in a solvent, high total light transmittance when made into a polyimide film, low yellowness, high elasticity, and high elongation at break. It is particularly preferable to use the component including the structure represented by the following general formula (B-5), and among the constituent units 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% based on the whole 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 the units other than the unit 1 and the unit 2 are further included, the content of the units other than the unit 1 and the unit 2 is preferably smaller than the contents of the unit 1 and the unit 2. These units may be bonded alternately or in a permutation in the polymer chain, or these units may be bonded randomly.
The weight average molecular weight (Mw) of the polyimide is preferably 10,000 or more, more preferably 25,000 or more, and more preferably 30,000, from the viewpoint of obtaining high elongation at break and low Rth in the polyimide film. It is preferably 40,000 or more, and particularly preferably 40,000 or more. The weight average molecular weight (Mw) of the polyimide is preferably 1,000,000 or less, more preferably 500,000 or less, and particularly preferably 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 coated with a desired film thickness without bleeding during processing such as coating, and a low Rth film can be obtained. Can be done. In particular, from the viewpoint of obtaining high elongation at break 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 the 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) in which it is dissolved 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 in which the polyimide represented by the following general formula (1) is dispersed or dissolved in a solvent. The polyimide varnish has a structure represented by the general formula (A-1) described above and the general formulas (A-2) to (A-4) described above as A in the general formula (1). It is preferable to contain a polyimide having at least one of the structures represented by. 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), and the composition ratios thereof (the general). 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 the 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 been proved in the experiment described later that the polyimide in the present embodiment has excellent 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, it does not become a lump and a film having excellent smoothness can be formed. Therefore, a resin layer having a uniform thickness can be formed, and high toughness can be obtained.
More preferably, the polyimide varnish dissolves an acid dianhydride component and a diamine component in a solvent, for example, an organic solvent, adds a co-boiling solvent such as toluene, and removes water generated during imidization to the outside of the system. As a result, it can be produced as a polyimide solution containing a polyimide and a solvent (also referred to as a polyimide varnish). Here, the conditions at the time of reaction are not particularly limited, but 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 with the reaction with the sulfone group-containing diamines, it is preferable to carry out a heating reaction at 180 ° C. for about 12 hours. The reaction is preferably carried out in an inert atmosphere such as argon or nitrogen.
Further, at the time of imidization, a basic catalyst such as pyridine may be added.

The solvent is not particularly limited as long as it is a solvent that dissolves polyimide. Examples of the reaction solvent include phenolic solvents such as m-cresol; amide solvents such as N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF) and N, N-dimethylacetamide ( DMAc) etc .; lactone-based 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 .; Ester-based solvents, for example, one or more polar solvents selected from methyl acetate, ethyl acetate, butyl acetate, dimethyl carbonate and the like are useful. Of these, NMP and GBL are preferable from the viewpoint of solubility. GBL is more preferable from the viewpoint of reducing the YI of the film.

The polyimide varnish in the present embodiment may contain one or more types of polyimides according to the present embodiment, and the polyimide varnish may be one type of varnish or a mixture of two or more types. When two or more kinds of polyimide varnishes are mixed, a polyimide varnish other than the polyimide according to the present invention may be mixed, or a polyamic acid varnish may be mixed.
Additives 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. For example, inorganic particles such as strontium carbonate, or organic compounds such as polystyrene, polyvinylnaphthalene, polymethylmethacrylate, cellulose triacetate, and fluorene derivatives can be mentioned.
Examples of the additive include a leveling agent, a dispersant or a surfactant for improving the coatability of the film, and a surfactant or an adhesion for adjusting the peelability or adhesiveness of the film from the support. Auxiliary agent, flame retardant for imparting flame retardancy to film, etc. Other additives include, for example, antioxidants, UV inhibitors, light stabilizers, plasticizers, waxes, fillers, pigments, dyes, foaming agents, defoamers, dehydrating agents, antistatic agents, antibacterial agents. , Antifungal agent and the like.
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 to use a supportable film (self-supporting film) without the support 11 from the viewpoint of maintaining the strength of the film substrate. The supportive film means a film having a breaking elongation of 5% or more. The laminated film corresponds to a supportive film when the peeled film has a breaking elongation of 5% or more.
As a method for measuring the breaking elongation, the method described later (evaluation of breaking elongation and breaking strength) can be used.

The polyimide film in this embodiment has excellent toughness. In the experiments described later, breaking elongation and breaking strength are measured as indicators of toughness. For example, in the present embodiment including both the structures represented by the general formula (A-1) and the general formula (A-5), it is represented by the general formula (A-1) and the general formula (A-5). Compared with the comparative example containing only one of the structures, high breaking elongation and breaking strength can be obtained in each case. As described above, when the diamine component is derived only from the 4,4'-DDS 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. Therefore, in the present embodiment, it is derived from the 3,3'-DDS component, which is an isomer derived from the 4,4'-DDS component and has a structure in which the monomer skeleton is bent when viewed from the 4,4'-DDS component origin ( The structure represented by the general formula (A-1)) is contained, and at this time, the addition amount of the 3,3'-DDS component is preferably smaller than that of the 4,4'-DDS component. It is possible to improve toughness while increasing the molecular weight.
Further, the yellowness (YI) of the polyimide film according to the present embodiment can be set to 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 further preferably in the range of 1 μm to 20 μm.

When used as 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. A film having a thickness of less than 10 μm can be produced, for example, by stretching a polyimide film having a film thickness of 10 μm or more.
Further, in the present embodiment, the yellowness (YI) can be adjusted to 2.0 or less. As described above, in the present embodiment, the yellowness can be suppressed to a low level, that is, a colorless and transparent polyimide film can be obtained. The term "colorless and transparent" in the present embodiment means 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 the present embodiment can be suitably used for touch panels, displays, and OLED lighting applications. For example, when the polyimide resin according to the present embodiment is used as a substrate film for a transparent electrode film, a touch panel element is formed 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 when the side facing the screen is the visible surface, the color of the screen does not adversely affect the brightness. From the viewpoint of OLED light emission characteristics, the haze of the polyimide film is preferably 1.0 or less, more preferably 0.9 or less, still more preferably 0.8 or less. From the same viewpoint, the arithmetic mean 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, still more preferably 1.2 nm or less. be.

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, and further, since the polyimide film of the present embodiment has excellent toughness, the PET film or COP film Can be used for a foldable display body that is prone to cracking or scratching, or a display body that follows a curved surface.

<Laminated body>
FIG. 2 is a schematic cross-sectional view showing a laminated body 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 a transparent electrode layer 21 on the surface of the polyimide film 10 with a sputtering device or the like. In FIG. 2, the polyimide film 10 has a laminated structure of the support 11 and the resin composition layer 12, but it may be a single layer of the resin composition layer 12. The laminate according to the present embodiment may have transparent electrode layers on both sides of the polyimide film. In that case, it is preferable to have at least one or more transparent electrode layers 21 on both sides. Further, between the transparent electrode layer and the polyimide film, an undercoat layer for imparting smoothness, a hardcoat layer for imparting surface hardness, an index matching layer for improving visibility, and a gas barrier property are provided. It may have another layer such as a gas barrier layer for the purpose. The hard coat layer for imparting surface hardness or the 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 produced by using the polyimide according to the present embodiment is colorless and transparent, has a low yellowness (YI), and is excellent in toughness. Preferably, the laminate 20 of this embodiment is suitable for use in a touch panel material such as a transparent electrode film because it has a glass transition temperature (Tg) suitable for the transparent electrode manufacturing process.
When forming the transparent electrode film, the film forming step of the transparent electrode layer 21 on the surface of the polyimide film 10 can be carried out, for example, in a temperature range of 80 to 100 ° C. In order to exhibit the desired performance in the laminate, it is preferable to perform sputtering at a higher temperature to form the transparent electrode layer 21 having a low resistivity. The transparent electrode layer 21 can be formed on both sides of the polyimide film 10, whereby, for example, touch panel elements can be arranged on both sides.

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-forming 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 the glass transition temperature (Tg) of the PET film, which is about 100 ° C. 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, the film can maintain high toughness even when exposed to a high temperature of 200 ° C. or higher. Therefore, the surface of the polyimide film 10 of the present embodiment can be sputtered at, for example, about 150 to 250 ° C. to form a transparent electrode layer 21 having a low resistivity.
Further, the polyimide according to the present embodiment preferably has a breaking strength of 100 MPa or more based on a thickness of the polyimide film of 15 μm from the viewpoint of improving the yield when forming the transparent electrode layer 21.
Further, 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 higher based on a film thickness of 15 μm as described above. Is preferable.

｛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 with predetermined characteristics>
The polyimide film of the present embodiment contains a polyimide represented by the following general formula (1), and contains a structure represented by the following general formula (A-1) as A in the general formula (1) (1). Hereinafter, it is also referred to as "second polyimide film").
A film containing a structure represented by the general formula (A-1) is preferable because the polymer tends to be isotropically present in the in-plane direction and the out-of-plane direction of the film. In the second polyimide film, when the structure represented by the following general formula (A-1) is set as A in the following general formula (1) and the total amount of A in the general formula (1) is 100 mol%, More preferably, it is contained in an amount of 20 mol% or more and 80% or less.

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

The polyimide film of the present embodiment may have a structure other than the structure represented by the general formula (A-1). Examples of such a structure include the structural units described in the above-mentioned <polyimide> chapter. The raw material diamines and acid dianhydrides include the diamine component in the chapter <A> in the general formula (1) and the acid dianhydride component in the chapter <B> in the general formula (1). The listed ones can be used.

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

<Manufacturing method of polyimide film>
The method for producing a polyimide film described above is also an aspect of the present invention. In the present embodiment, the polyimide film can be produced by the following production method 1 or 2.

[Manufacturing method 1]
The manufacturing method 1 is based on the following steps:
(Step A1) A step of applying at least a polyimide varnish containing the polyimide and an organic solvent onto a support;
(Step A2) A step of heating a polyimide varnish to form a solvent-containing film containing a solvent at a concentration of 5% by mass to 20% by mass and peeling it from a support; and (Step A3) a solvent-containing film in a heating furnace. Transport and transfer the solvent-containing film 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) 1 minute or more and less than 30 minutes within the range of 150 ° C to 200 ° C,
(Zone 4) 1 minute or more and less than 30 minutes in the range of 200 ° C to 250 ° C,
The step of drying in the order of Zone 1, Zone 2, Zone 3, and Zone 4 according to the above;
It is characterized by including.

In the production method 1, when the solvent-containing film is peeled from the support in step A2 and then the solvent-containing film is dried in step A3, the solvent is used in the order of zone 1, zone 2, zone 3, and zone 4 in terms of temperature profile. 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 having a low haze. It is believed that the film can be manufactured. As used herein, the heating temperature with respect to the temperature profile means the temperature of the film surface.
An example of a temperature profile for drying a solvent-containing film in a heating furnace is the 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. When the solvent-containing film is peeled from the support in the production method 1 and heating according to the above temperature profile is used, the support is not bound by heat resistance, so that it is an alkali glass substrate or a non-alkali glass substrate (Eagle XG®). , Corning), copper substrate, aluminum substrate, SUS substrate and other metal substrates; polycarbonate film, PET film, kapton (300H, manufactured by Toray), upilex (125S, manufactured by Ube Kosan) and other plastic films; and copper foil, A metal foil such as an aluminum foil or a SUS foil may be used. Among these, from the viewpoint of controlling surface smoothness and productivity, those having few particles such as lubricants and protrusions on the surface of the support are preferable, plastic films are more preferable, PET films are more preferable, and polyethylene terephthalate (Cosmoshine). A4100, manufactured by Toyobo) is particularly preferable. In the present specification, a substrate has a structure having high rigidity and is not suitable for bending or the like, and a film or a film substrate has a structure which is flexible and can be bent.
Step A1 can be performed by casting a polyimide varnish on the support using a support unwinding roll and a varnish discharge device. Since the film is formed from the polyimide solution imidized in advance in the step A1, the support can be removed after the temporary drying in the step 2 to obtain a polyimide self-supporting film.
In step A2, it is considered that the solvent-containing film can be easily peeled off from the support by heating the polyimide varnish. The solvent-containing film can be peeled off from the support by using, for example, a take-up roll, a take-up roll, a slitting or the like. Step 2 and step A3 can be performed sequentially or continuously.

When step A2 and step 3 are carried out sequentially, 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 at about 100 ° C. This can be done by applying air to at least the varnished surface.
When the steps A2 and A3 are performed continuously, the heating of the polyimide varnish in the step A2 is regarded as a part of the step of drying the solvent-containing film according to the above temperature profile in the step A3, and the heating according to the above temperature profile is performed. It can be done using a combination of heating furnaces, take-up rolls, and unwind rolls that can be done.
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 above temperature profile.

In step A3, 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, it is preferable to dry the solvent-containing film while fixing both ends of the solvent-containing film. .. For example, by grasping the end portion of the solvent-containing film peeled off from the support with a tenter or the like, the solvent-containing film can be dried while fixing both ends.
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 to the width of the polyimide film at the outlet of the heating furnace (width _{inlet) from the viewpoint of the index of fixation.} / Width _outlet ) 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.

[Manufacturing method 2]
The manufacturing method 2 is based on the following steps:
(Step B1) A step of applying a polyimide varnish containing a polyimide and an organic solvent onto a heat-resistant support having a Tg of 300 ° C. or higher or no glass transition point and a 1% thermal decomposition temperature of 400 ° C. or higher; (Step B2) The polyimide varnish was transported together with the support into the heating furnace, and the solvent-containing film formed was 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) 1 minute or more and less than 30 minutes within the range of 150 ° C to 200 ° C,
(Zone 4) 1 minute or more and less than 30 minutes in the range of 200 ° C to 250 ° C,
The step of drying in the order of Zone 1, Zone 2, Zone 3, and Zone 4 according to the above;
It is characterized by including.
In the manufacturing method 2, by transporting the polyimide varnish together with the heat-resistant support into the heating furnace in step B2, the polyimide varnish is less likely to volatilize in the direction in contact with the support, and the polyimide is not in contact with the support. Since the varnish is easily volatilized, the volatilization direction of the solvent from the solvent-containing film is controlled, it is easy to adjust the film optical characteristics such as haze and Rth, and the arithmetic average roughness (Ra) of the film surface is 1.5 nm. It may be easier to adjust as follows.
Further, in the manufacturing method 2, by using the heat-resistant support in the step B1, the polyimide varnish can be conveyed into the heating furnace together with the support in the step B2, and the peeling of the solvent-containing film from the support can be omitted. , The productivity of the polyimide film can be improved.

Further, in the production method 2, the solvent-containing film is dried in the order of zone 1, zone 2, zone 3, and zone 4 for the temperature profile, so that the film is colorless and transparent, has low YI, Rth and haze, and has surface smoothness and surface smoothness. It is considered that a polyimide film having excellent toughness can be produced.
An example of the temperature profile for drying the solvent-containing film in the heating furnace in the production method 2 is the 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 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 it does not shrink or decompose even in a heating furnace. No point is shown and the 1% thermal decomposition temperature is 400 ° C. or higher. When heating according to the above temperature profile is used in steps B1 and B2 of the manufacturing method 2, specifically, the support includes upirex (upilex125s, manufactured by Ube Industries), kapton (300H, manufactured by Toray), a stainless steel substrate, and the like. It is preferable to use a glass substrate, a metal foil of aluminum foil, or the like.

Steps B1 and B2 of the manufacturing method 2 can be performed sequentially or continuously.
When step B1 and step B2 are sequentially performed, in step B1, pre-drying or rough drying can be performed by applying at least air at about 100 ° C. to the varnish-coated surface using, for example, a hot air dryer. can. After that, step B2 can be performed by controlling the heating temperature in the heating furnace according to the above temperature profile.
When step B1 and step B2 are continuously performed, after coating the polyimide varnish, the polyimide varnish and the heat-resistant support are transferred to a heating furnace according to the above temperature profile using a take-up roll and / or a take-up roll. 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 above temperature profile.

(varnish)
The polyimide varnish used in the production method 1 or 2 may contain the polyimide described above.
The polyimide varnish preferably contains a polyimide having an imidization ratio of 80% or more from the viewpoint that the film is less likely to break when the film is formed from the polyimide solution imidized in advance in the production method 1 or 2. 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-based solvent, an amide-based solvent, a lactone-based solvent, a sulfoxide-based solvent, a ketone-based solvent, an ester-based solvent, and the like. Of these, a lactone-based solvent is preferable, and GBL is more preferable, from the viewpoint of obtaining desired YI, Rth, haze and toughness. In the polyimide film obtained by the production method 1 or 2, the lactone-based solvent may be left as a remaining amount of at least 0.01% by mass.

(Polyimide varnish coating)
In step A1 of manufacturing method 1 or step B1 of manufacturing method 2, the polyimide varnish can be coated on the support by a known coating method such as spin coating, slit coating, slot die coating, and blade coating. In step A1 of the manufacturing method 1, a blade coat 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-based 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 carried out in an atmospheric atmosphere.
Heating according to the temperature profile described above is such that the thickness of the obtained polyimide film is 1 μm to 50 μm from the viewpoint of producing a polyimide film having low YI, Rth and haze and excellent surface smoothness and toughness. It is preferable that this is done in. 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 film thickness of 10 μm or more. The polyimide film can be stretched 1.5 to 5 times by biaxial stretching while heating at 150 ° C. to 350 ° C. with the support attached or peeled off from the support. The stretching may be simultaneous biaxial stretching or sequential biaxial stretching, but simultaneous biaxial stretching is preferable 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 according to the present embodiment can be used as a substitute for glass in the same manner as the PET film or the COP film, for example. As described above, the polyimide film according to the present embodiment can realize low Rth and has high elongation. Therefore, even if it is used for a foldable display body or a display body following a curved surface, the film is damaged. Is not generated and is useful.
As described above, the polyimide film and the laminate according to the present embodiment can be used as a substrate film such as a surface protective film, a color filter, a TFT, and an insulating protective film. These polyimide fims and laminates are, for example, displays having a touch panel function, organic EL lighting, flexible displays, smartphones, tablet terminals, bendable smartphones and tablet terminals, other flexible devices, organic EL lighting having curved surfaces, and the like. It can be suitably used for products such as organic EL displays. Here, the flexible device means, for example, a flexible display, a flexible solar cell, a flexible touch panel, flexible lighting, a flexible battery, and the like.

Hereinafter, the present invention will be described in more detail based on examples, but these are described for the sake of explanation, and the scope of the present invention is not limited to the following examples. Various evaluations in the example 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 a 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.) was used before measurement. , Purity 99.5%) and 63.2 mol / L phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., for high performance liquid chromatograph) were added. The 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 Corporation)
UV-2075Plus (UV-Vis: UV-Visible Absorber, manufactured by JASCO Corporation)

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

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

(Evaluation of yellowness (YI), haze, and total light transmittance)
The polyimide film was measured for yellowness (YI value), haze, and total light transmittance using a spectrophotometer (CM3600A) manufactured by Konica Minolta Co., Ltd. using a D65 light source. Unless otherwise specified, measurements were made on a film having a film thickness of 20 ± 1 μm as a sample.

(Evaluation of surface smoothness (Ra))
Using a nanoscale hybrid microscope (VN8000, manufactured by KEYENCE CORPORATION), the measurement area (50 μm × 50 μm) was scanned and measured.

(Evaluation of OLED light emission)
The evaluation of OLED light emission was measured by the following method.
First, an OLED light emitting device was manufactured by the following method.
(1) Silicon nitride was sputtered on a polyimide film 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 by vapor deposition as an organic EL element so as to have a thickness of 10 nm.
(4) The device was sealed with AlPEN.
The produced OLED element was energized, and it was confirmed whether or not the OLED element emitted light. The one that did not emit light at all was designated as B (defective), and the one that emitted light was designated as A (good). Further, the one that emitted light even after being stored at a temperature of 60 ° C. and a humidity of 90% for one week was defined as S (remarkably good).

Subsequently, the conditions for synthesizing polyimide and the conditions for producing a polyimide film will be specifically described.
[Synthesis Example 1]
4,4'-DDS 13.77 g (55.44 mmol), 3,3'-DDS 3.44 g (55.44 mmol) while introducing nitrogen gas into a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top. 13.86 mmol), 50.00 g of NMP was added. Subsequently, 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. at 160 ° C. The mixture was heated under reflux for 1 hour to imidize. After the imidization was completed, 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 NMP was added so that the solid content had a concentration of 20% by mass to obtain a polyimide NMP solution (hereinafter, also referred to as polyimide varnish).

[Synthesis Example 2]
In a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top, while introducing nitrogen gas, add 4,4'-DDS to 12.05 g (48.51 mmol) and 3,3'-DDS. To 5.16 g (20.79 mmol) and 50.00 g of GBL were added. Subsequently, 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 then the temperature was raised to 160 ° C. at 160 ° C. The mixture was heated under reflux for 1 hour to imidize. After the imidization was completed, 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 had a concentration of 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) and 3,3'-DDS was changed to 6.90 g (27.72 mmol), and the reaction time at 180 ° C. was set 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]
The polyimide varnish was used 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'-(hexafluoroisopropyridene) diphthalic acid dianhydride (6FDA). rice field.

[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 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 11]
Trans-1,4-cyclohexyldiamine (CHDA) 1.81 (15.84 mmol), 3, while introducing nitrogen gas into a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top. 15.73 g (63.36 mmol) of 3-DDS and 50.00 g of NMP were added. Subsequently, 24.82 g (80.00 mmol) of 4,4'-oxydiphthalic anhydride (ODPA), 28.67 g of NMP, and 27.14 g of toluene were added at room temperature, and then the temperature was raised to 160 ° C. at 160 ° C. The mixture was heated under reflux for 1 hour to imidize. After the imidization was completed, 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 and the temperature was returned to room temperature, and NMP was added so that the solid content had a concentration of 20% by mass to obtain a polyimide NMP solution (hereinafter, also referred to as polyimide varnish).

[Synthesis Example 12]
4.93 g (34.65 mmol) of 1,4-bis (aminomethyl) cyclohexane (14BAC) while introducing nitrogen gas into a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top. , 8,61 g (34.65 mmol) of 3,3'-DDS and 50.00 g of GBL were added. Subsequently, 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. at 160 ° C. The mixture was heated under reflux for 1 hour to imidize. After the imidization was completed, 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 had a concentration of 20% by mass to obtain a polyimide GBL solution (hereinafter, also referred to as polyimide varnish).

[Synthesis Example 13]
In a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top, while introducing nitrogen gas, 5.13 g (33.25 mmol) of bis (aminomethyl) norbornane (BANBDA) was added to 3,3'. 8.26 g (33.25 mmol) of −DDS and 50.00 g of GBL were added. Subsequently, 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 then the temperature was raised to 160 ° C. at 160 ° C. The mixture was heated under reflux for 1 hour to imidize. After the imidization was completed, 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 had a concentration of 20% by mass to obtain a polyimide GBL solution (hereinafter, also referred to as polyimide varnish).

[Synthesis Example 14]
5.11 g (13.86 mmol) of 4,4'-bis (4-aminophenoxybiphenyl) (BABP) while introducing nitrogen gas into a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top. ), 13.77 g (55.44 mmol) of 3,3-DDS and 50.00 g of GBL were added. Subsequently, 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 then the temperature was raised to 160 ° C. at 160 ° C. The mixture was heated under reflux for 1 hour to imidize. After the imidization was completed, 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 NMP was added so that the solid content had a concentration of 20% by mass to obtain a polyimide NMP solution (hereinafter, also referred to as polyimide varnish).

[Synthesis Example 15]
In a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top, α, α'-bis (4-aminophenyl) -1,4-diisopropylbenzene (BAPDB) was added 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. Subsequently, 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. at 160 ° C. The mixture was heated under reflux for 1 hour to imidize. After the imidization was completed, 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 had a concentration of 20% by mass to obtain a polyimide GBL solution (hereinafter, also referred to as polyimide varnish).

[Synthesis Example 16]
In a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top, while introducing nitrogen gas, 4,4'-DDS 8.61 g (34.65 mmol) and 3,3'-DDS 8.61 g (34.65 mmol), 50.00 g of GBL was added. Subsequently, 10.86 g (35.00 mmol) of 4,4'-oxydiphthalic anhydride (ODPA), 7.85 g (35.00 mmol) of hydroxypyromellitic anhydride (HPMDA), 16.69 g of GBL, and 24.41 g of toluene. Was added at room temperature, the temperature was raised to an internal temperature of 160 ° C., and the mixture was heated under reflux at 160 ° C. for 1 hour to carry out imidization. After the imidization was completed, 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 had a concentration of 20% by mass to obtain a polyimide GBL solution (hereinafter, also referred to as polyimide varnish).

[Synthesis Example 17]
In a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top, while introducing nitrogen gas, 4,4'-DDS 8.61 g (34.65 mmol) and 3,3'-DDS 8.61 g (34.65 mmol), 50.00 g of GBL was 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) was added. -Flanil) Naft [1,2-c] furan-1,3-dione (TDA) 4.20 g (14.00 mmol), GBL 22.02 g, and toluene 26.07 g are added at room temperature, and then the internal temperature is up to 160 ° C. The temperature was raised, and the mixture was heated under reflux at 160 ° C. for 1 hour to imidize. After the imidization was completed, 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 had a concentration of 20% by mass to obtain a polyimide GBL solution (hereinafter, also referred to as polyimide varnish).

[Synthesis Example 18]
In a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top, while introducing nitrogen gas, 4,4'-DDS 8.61 g (34.65 mmol) and 3,3'-DDS 8.61 g (34.65 mmol), 50.00 g of GBL was added. Subsequently, 17.37 g (56.00 mmol) of 4,4'-oxydiphthalic anhydride (ODPA), bicyclo [2,2,2] octo-7-ene-2,3,5,6-tetracarboxylic dianhydride After adding 3.47 g (14.00 mmol) of substance (BODA), 20.67 g of GBL, and 25.58 g of toluene at room temperature, the temperature is raised to an internal temperature of 160 ° C., and the mixture is heated under reflux at 160 ° C. for 1 hour to imidize. went. After the imidization was completed, 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 had a concentration of 20% by mass to obtain a polyimide GBL solution (hereinafter, also referred to as polyimide varnish).

[Synthesis Example 19]
19.02 g (59.40 mmol) of 2,2'-bis (trifluoromethyl) benzidine (TFMB) while introducing nitrogen gas into a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top. , GBL 50.00 g was added. Subsequently, 26.66 g (60.00 mmol) of 4'-(hexafluoroisopropyridene) diphthalic acid dianhydride (6FDA), 20.69 g of GBL, and 25.87 g of toluene were added at room temperature, and then the temperature was raised to 160 ° C. Then, the mixture was heated under reflux at 160 ° C. for 1 hour to imidize. After the imidization was completed, 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 NMP was added so that the solid content had a concentration of 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. 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 make a film)
[Creation example A]
The polyimide varnish was coated on 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 had a concentration of 15.5% by mass. The solvent-containing polyimide film was peeled off from the support, the film was conveyed into a heating furnace, and hot air-dried under the temperature conditions shown in FIG. The width of the film at the inlet of the heating furnace before drying was 500 mm, and the width of the film at the outlet of the heating furnace after drying was 495 mm.

[Creation example B]
The polyimide varnish was coated on upilex (manufactured by Ube Industries, Ltd., product number uplex125s) having a width of 508 mm 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 had a concentration of 16% by mass. The uplex 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.

[Creation example C]
The polyimide varnish was coated on 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 had a concentration of 15.5% by mass. This solvent-containing polyimide film was peeled off from the support, and both ends were fixed with a tenter. The width of the film at this time was 500 mm. Subsequently, this film was conveyed into a heating furnace and dried under the temperature conditions shown in FIG. The width of the film at the outlet of the heating furnace after drying was 495 mm.

[Creation example D]
A polyimide varnish is applied onto an upilex (manufactured by Ube Industries, Ltd., product number uplex125s) as a support with a coating thickness of 200 μm, dried at 50 ° C. for 10 minutes and at 150 ° C. for 10 minutes, and then the resin composition layer. Was peeled off from the polyimide film as a support, and dried in an IR drying oven at an IR temperature of 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 with 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 to 3)
According to the above evaluation method, only polyethylene terephthalate (PET) film (Cosmoshine 100A4100) was evaluated in Reference Example 1, and polyethylene naphthalate (PEN) film (Teijin DuPont Film Co., Ltd. "Theonex (registered trademark)") in Reference Example 2. Only the polyimide (PI) film (Toray DuPont Co., Ltd. "Capton (registered trademark)") was evaluated in Reference Example 3. The evaluation results are shown in Table 4 below.

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

Claims (13)

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

{In the 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 contains the polyimide represented by, and as A in the general formula (1), the following general formula (A-1):

The structure represented by and the following general formula (A-2):

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

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

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

(B) The arithmetic mean roughness (Ra) of at least one side of the polyimide film shall be 1.5 nm or less;
A method for producing a polyimide film, which is characterized by satisfying the above conditions.
The following steps:
(Step A1) A step of applying at least a polyimide varnish containing the polyimide and an organic solvent onto 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 it from the support;
(Step A3) The solvent-containing film is conveyed into a heating furnace, and the 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) 1 minute or more and less than 30 minutes within the range of 150 ° C to 200 ° C,
(Zone 4) 1 minute or more and less than 30 minutes within the range of 200 ° C to 250 ° C,
The step of drying the zone 1, the zone 2, the zone 3, and the zone 4 in this order according to the above;
A method for producing a polyimide film containing. The following requirements:
(A) The following general formula (1):

{In the 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 contains the polyimide represented by, and as A in the general formula (1), the following general formula (A-1):

The structure represented by and the following general formula (A-2):

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

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

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

(B) The arithmetic mean roughness (Ra) of at least one side of the polyimide film shall be 1.5 nm or less;
A method for producing a polyimide film, which is characterized by satisfying the above conditions.
The following steps:
(Step B1) A polyimide varnish containing at least the polyimide and an organic solvent is placed on a heat-resistant support having a glass transition point (Tg) of 300 ° C. or higher or no glass transition point and a 1% thermal decomposition temperature of 400 ° C. or higher. The process of coating;
(Step B2) The polyimide varnish is conveyed together with the support into a heating furnace, and the solvent-containing film formed 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) 1 minute or more and less than 30 minutes within the range of 150 ° C to 200 ° C,
(Zone 4) 1 minute or more and less than 30 minutes within the range of 200 ° C to 250 ° C,
The step of drying the zone 1, the zone 2, the zone 3, and the zone 4 in this order according to the above;
A method for producing a polyimide film containing. The method for producing a polyimide film according to claim 1 , wherein in the step A3, the solvent-containing film is dried while fixing both ends of the solvent-containing film. In 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 method for producing a polyimide film according to claim 3 , which is within the range. The method for producing a polyimide film according to any one of claims 1 to 4 , wherein the polyimide varnish contains a lactone-based solvent. The method for producing a polyimide film according to any one of claims 1 to 5 , wherein the polyimide varnish contains a polyimide having an imidization ratio of 80% or more. The method for producing a polyimide film according to any one of claims 1 to 6 , wherein the polyimide varnish contains a polyimide having a weight average molecular weight (Mw) of 40,000 or more. The method for producing a polyimide film according to any one of claims 1 to 7 , wherein the polyimide film has a film thickness of 1 μm to 50 μm. The method for producing a polyimide film according to any one of claims 1 to 8 , wherein the haze of the 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 method for producing a polyimide film according to any one of claims 1 to 9, which comprises the structure represented by. The ratio of the structure represented by the general formula (A-1) to the structure represented by the general formula (A-5) (structure represented by the general formula (A-1) / general formula (A-5)). The method for producing a polyimide film according to claim 10 , wherein the structure (represented by) is in the range of 2/8 to 6/4 on a 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 is the following general formula (Y-1) to the following general formula (Y-3):

It is at least one structure selected from the group consisting of. }

The method for producing a polyimide film according to any one of claims 1 to 11 , which comprises at least one of the structures represented by. As B in the general formula (1), the following general formula (B-5):

The method for producing a polyimide film according to any one of claims 1 to 12 , which comprises the structure represented by.

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