KR20230019064A - Polyimide film and manufacturing method thereof - Google Patents

Abstract

A colorless polyimide film having high tensile strength at break and high tensile modulus, high elongation at break, and a low coefficient of linear expansion, and a method for producing the same. A multilayer film using high-strength polyimide for (a) the outer layer and polyimide with excellent optical properties for (b) the inner layer. (a) / (b) Although it may be two layers, three or more layers are preferable. A solution of polyimide or a polyimide precursor constituting each layer is applied to a temporary support and heat-treated to obtain an imide film, but at the time of application, the next layer is applied before the previously applied layer is dried, so that each layer By forming a transitional layer in which the composition is gradually changed and mixed between the layers, heterogeneity in physical properties between layers is buffered and a balanced film is obtained.

Description

Polyimide film and manufacturing method thereof

The present invention relates to a polyimide film that is colorless and has a low linear expansion coefficient and good mechanical properties, and a method for producing the same.

Polyimide film has excellent heat resistance and good mechanical properties, and is widely used in the electrical and electronic fields as a flexible material. However, since a general polyimide film is colored yellowish brown, it cannot be applied to a portion requiring light transmission, such as a display device.

On the other hand, thinning and weight reduction of display devices are progressing, and flexibility is required. For this reason, attempts are being made to change the substrate material from glass substrates to flexible polymer film substrates, but colored polyimide films cannot be used as substrate materials for liquid crystal displays that display by turning on/off light transmission. There is no, and it can be applied only to a small part, such as peripheral circuits such as TAB and COF in which the driving circuit of the display device is mounted, or the rear side of a reflective display method or a self-emissive display device.

Against this background, development of a colorless and transparent polyimide film is progressing. As a representative example, attempts have been made to develop colorless and transparent polyimide films using fluorinated polyimide resins, semi-cyclic or full-cyclic polyimide resins, and the like (Patent Documents 1 to 3). Although these films are less colored and have transparency, mechanical properties do not rise to the level of colored polyimide films, and when industrial production and applications exposed to high temperatures are assumed, thermal decomposition or oxidation reactions occur, so Colorlessness and transparency cannot be maintained. From this point of view, a method of heat treatment while exhaling a gas with a defined oxygen content has been proposed (Patent Document 4), but its manufacturing cost is high in an environment where the oxygen concentration is less than 18%, and industrial production is very difficult.

Patent Document 1: Japanese Unexamined Patent Publication No. 11-106508 Patent Document 2: Japanese Patent Laid-Open No. 2002-146021 Patent Document 3: Japanese Unexamined Patent Publication No. 2002-348374 Patent Document 4: WO2008/146637 Publication

That is, practical properties such as heat resistance and mechanical properties and colorless transparency are in a trade-off relationship, and it has been very difficult to produce a colorless transparent polyimide film that satisfies all of them. An object of the present invention is to provide a polyimide film excellent in mechanical properties and colorless transparency.

The present inventors attempted to realize a well-balanced polyimide film by combining a plurality of polyimide resins. In general, when blending, blending, or copolymerizing resins of a plurality of components in combination, it is not always possible to obtain a result of combining only the good points of each component, and rather, there are not a few cases in which defects are increased and expressed. However, as a result of intensive research, the present inventors have found that the advantages of each component can be sufficiently brought out by combining polyimide resins to form a film to form a specific structure, and have reached the present invention.

That is, the present invention has the following configurations.

[1] a multi-layer polyimide layer in which at least two types of polyimide layers having different compositions are laminated in the thickness direction;

A transition layer in which the chemical composition changes stepwise and exists between the (a) layer constituting the multi-layer polyimide layer and the (b) layer adjacent to the (a) layer.

has,

The thickness of the transition layer has a lower limit of 3% of the total film thickness or 1 μm, and an upper limit of 10% of the total film thickness or 3 μm,

The thickness of the entire film is 3 μm or more and 120 μm or less,

The yellow index of the entire film is 5 or less,

The total light transmittance of the entire film is 86% or more.

A multilayer polyimide film, characterized in that.

[2] The (a) layer is mainly composed of polyimide having a yellow index of 10 or less and a total light transmittance of 85% or more when used alone as a film having a thickness of 25 ± 2 μm,

The (b) layer is mainly composed of polyimide having a yellow index of 5 or less and a total light transmittance of 90% or more when used alone as a film having a thickness of 25 ± 2 μm.

The multilayer polyimide film according to [1] characterized by the above.

[3] The (a) layer is present on both one side and the other side of the (b) layer,

The transition layer is between the (a) layer and the (b) layer on one side of the (b) layer, and between the (a) layer and the (b) layer on the other side of the (b) layer. exist between

The (a) layer, the transition layer, the (b) layer, the transition layer, and the (a) layer are laminated in this order.

The multilayer polyimide film according to [1] or [2], characterized by the above.

[4] The polyimide of the layer (a),

A polyimide having a chemical structure obtained by condensation polymerization of a tetracarboxylic acid anhydride containing 70% by mass or more of an alicyclic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having an amide bond in the molecule;

or

Polyi comprising a chemical structure obtained by condensation polymerization of a tetracarboxylic acid anhydride containing 30% by mass or more of an alicyclic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having a trifluoromethyl group in a molecule mid

The multilayer polyimide film according to any one of [1] to [3], characterized in that

[5] The polyimide of the layer (b),

A polyimide comprising a chemical structure obtained from a tetracarboxylic acid anhydride containing 70% by mass or more of an aromatic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having a sulfur atom in the molecule;

or

Obtained by condensation polymerization of a tetracarboxylic anhydride containing 70% by mass or more of a tetracarboxylic acid containing a trifluoromethyl group in a molecule and a diamine containing 70% by mass or more of a diamine having a trifluoromethyl group in a molecule Polyimide Containing Chemical Structure

The multilayer polyimide film according to any one of [1] to [4], characterized in that

[6] 1: (a) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to a temporary support to obtain a coating film a1;

2: within 100 seconds after the coating film a1 is formed, (b) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to the coating film a1 to obtain the coating film a1;

3: A step of heating all layers to obtain a laminate having a residual solvent amount of 0.5% by mass or less based on all layers;

The manufacturing method of the multilayer polyimide film as described in [1], [2], [4], or [5] containing at least.

[7] 1: (a) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to a temporary support to obtain a coating film a1;

2: within 100 seconds after the coating film a1 is formed, (b) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to the coating film a1 to obtain the coating film a1;

Step 3: Heating all layers to obtain a laminate having a residual solvent amount of 5% by mass or more and 40% by mass based on all layers, and then peeling from the temporary support to obtain a self-supporting film;

5: A step of gripping both ends of the self-supporting film to further obtain a film having a residual solvent amount of 0.5% by mass or less based on the entire layer;

The manufacturing method of the multilayer polyimide film as described in [1], [2], [4], or [5] containing at least.

[8] 1: (a) a step of applying a polyimide solution or a polyimide precursor solution for layer formation on a temporary support to obtain a coating film a1;

2: within 100 seconds after the coating film a1 is formed, (b) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to the coating film a1 to obtain the coating film a1;

Step 3: Within 100 seconds after the formation of the coating film ab1, (a) a step of applying a polyimide solution for layer formation or a polyimide precursor solution to the coating film ab1 to obtain the coating film aba1;

4: A step of heating all layers to obtain a laminate having a residual solvent amount of 0.5% by mass or less based on all layers;

The manufacturing method of the multilayer polyimide film in any one of [1]-[5] containing at least.

[9] 1: (a) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to a temporary support to obtain a coating film a1;

2: within 100 seconds after the coating film a1 is formed, (b) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to the coating film a1 to obtain the coating film a1;

Step 3: Within 100 seconds after the formation of the coating film ab1, (a) a step of applying a polyimide solution for layer formation or a polyimide precursor solution to the coating film ab1 to obtain the coating film aba1;

4: step of heating all layers to obtain a laminate having a residual solvent amount of 8% by mass or more and 40% by mass based on all layers, then peeling from the temporary support to obtain a self-supporting film;

5: A step of gripping both ends of the self-supporting film to further obtain a film having a residual solvent amount of 0.5% by mass or less based on the entire layer;

The manufacturing method of the multilayer polyimide film in any one of [1]-[5] containing at least.

In this invention, you may further include the following structures.

[10] A method for producing a multilayer polyimide film, characterized in that steps 1 and 2 in [6] are repeated to form five or more odd-numbered layers.

[11] The multilayer polyimide film according to [1] to [5], wherein the layer (a) has a thickness of 34% or less of the total film thickness. However, when there are a plurality of (a) layers, the total thickness of the (a) layers is 1% or more, preferably 2% or more, more preferably 4% or more, and 25% or less, preferably 25% or less, of the total thickness of the film. The multilayer polyimide film according to [1] to [5] characterized by being 13% or less, more preferably 7% or less.

The present invention realizes a heat-resistant film having excellent optical properties (colorless transparency) and sufficient mechanical properties as a flexible film to be obtained by configuring a film with a plurality of layers having different compositions.

The polyimide of layer (a) in the present invention is preferably composed of tetracarboxylic acid anhydride containing 70% by mass or more of alicyclic tetracarboxylic acid anhydride and 70% by mass or more of diamine having an amide bond in the molecule. A polyimide having a chemical structure obtained by condensation polymerization of diamine containing or a tetracarboxylic acid anhydride containing 30 mass% or more of an alicyclic tetracarboxylic acid anhydride and a diamine having a trifluoromethyl group in the molecule are 70 A polyimide having a chemical structure obtained by condensation polymerization of a diamine containing at least % by mass, and this polyimide has good mechanical properties, high elongation at break, and excellent properties of showing a low CTE, but is relatively easily colored.

The polyimide of one (b) layer is preferably a tetracarboxylic acid anhydride containing 70 mass% or more of an aromatic tetracarboxylic acid anhydride and a diamine containing 70 mass% or more of a diamine having a sulfur atom in the molecule. A polyimide having a chemical structure obtained from, or a tetracarboxylic acid anhydride containing 70 mass% or more of a tetracarboxylic acid containing a trifluoromethyl group in a molecule, and a diamine having a trifluoromethyl group in a molecule of 70 It is a polyimide containing a chemical structure obtained by condensation polymerization of diamine containing at least % by mass, and has high colorless transparency, but as a resin, it is hard and brittle, and it is difficult to give sufficient elongation at break when filmed, so it is flexible. The suitability for one use is not necessarily good, and it is also difficult to produce as a continuous film.

When both are blended or copolymerized, only a film with physical properties intermediate or lower than both can be obtained, and also tends to be stretched due to the property of layer (a), which is easy to be colored, with respect to colorless transparency.

However, as in the present invention, functions are shared by forming the polyimide of these two components as independent layers, and by applying a specific manufacturing method, balanced, that is, colorless transparency and practically sufficient film strength, high A film having elongation at break and a low coefficient of linear expansion can be obtained.

A polyimide film is obtained by applying a polyimide solution or a solution of a polyimide precursor to a support, drying it, and performing a chemical reaction as necessary. It is characterized by using a manufacturing method of coating. According to this coating method, material movement by diffusion or flow occurs in a limited thickness region on the surface where different components are in contact, and a transitional layer in which the composition changes step by step is formed. Since such a transitional layer buffers mismatches such as stress generated between layers having different physical properties, a well-balanced film can be obtained without concentration of internal strain in a specific region.

The multilayer polyimide film of the present invention has a thickness of 3 μm or more and 120 μm or less. Since the mechanical properties become good, it is preferably 4 μm or more, more preferably 5 μm or more, still more preferably 8 μm or more. Moreover, since transparency becomes good, it is preferable that it is 100 micrometers or less, More preferably, it is 80 micrometers or less, More preferably, it is 60 micrometers or less.

The multilayer polyimide film of the present invention has a yellow index of 5 or less. Since transparency becomes good, Preferably it is 4 or less, More preferably, it is 3.5 or less, More preferably, it is 3 or less. Although the lower limit is not particularly limited since the yellow index is preferably lower, it may be industrially 0.1 or more, and 0.2 or more is not a problem.

The multilayer polyimide film of the present invention has a total light transmittance of 86% or more. Since the transparency becomes good, it is preferably 87% or more, more preferably 88% or more, still more preferably 89% or more. The upper limit is not particularly limited, but industrially it may be 99% or less, and 98% or less is not a problem.

In the present invention, at least two types of polyimides having different compositions are used, and these are laminated in the thickness direction. Polyimide is generally a polymer obtained by condensation polymerization of tetracarboxylic acid anhydride and diamine. It is preferable that the at least two types of polyimide layers include a layer (a) and a layer (b), and the layer (a) and the layer (b) are mainly composed of polyimide having the following characteristics, respectively. Here, "mainly" preferably contains 70% by mass or more of the polyimide of each of the following characteristics in each layer, more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably It is 100 mass %. In addition, different compositions differ from the case where at least the resin composition of each polyimide needs to be different, and, for example, the resin composition is the same and only the presence or absence of a lubricant or the compounding amount is different.

The polyimide mainly used for the layer (a) (hereinafter, “mainly” is omitted, and “polyimide used for layer (a)” or “polyimide used for layer (a)” is simply described). ) is preferably a polyimide having a yellow index of 10 or less and a total light transmittance of 85% or more when used alone as a film having a thickness of 25±2 μm. Since the transparency becomes good, the yellow index is preferably 9 or less, more preferably 8 or less, still more preferably 7 or less. The lower limit of the yellow index is not particularly limited, but industrially it may be 0.1 or more, and 0.2 or more is not a problem. The total light transmittance is preferably 86% or higher, more preferably 87% or higher, still more preferably 88% or higher. The upper limit is not particularly limited, but industrially it may be 99% or less, and 98% or less is not a problem.

The thickness of the (a) layer in the multilayer polyimide film is preferably greater than 1 μm, more preferably 1.5 μm or more, still more preferably 2 μm or more, particularly preferably, since mechanical strength becomes good. greater than 3 μm. In addition, since transparency becomes good, it is preferably less than 119 μm, more preferably 100 μm or less, still more preferably 50 μm or less, and particularly preferably 20 μm or less.

The polyimide mainly used in the (a) layer is preferably a tetracarboxylic acid anhydride containing 70% by mass or more of an alicyclic tetracarboxylic acid anhydride and all amines when the total acid component is 100% by mass. 30% by mass of a polyimide having a chemical structure obtained by condensation polymerization of a diamine containing 70% by mass or more of diamine having an amide bond in the molecule when the component is 100% by mass, or an alicyclic tetracarboxylic acid anhydride It is a polyimide containing a chemical structure obtained by condensation polymerization of tetracarboxylic acid anhydride contained above and diamine containing 70% by mass or more of diamine having a trifluoromethyl group in a molecule.

The polyimide mainly used for the (b) layer (hereinafter, “mainly” is omitted, and “polyimide used for the (b) layer” or “polyimide used for the (b) layer” is simply described). ) is preferably a polyimide having a yellow index of 5 or less and a total light transmittance of 90% or more when used alone as a film having a thickness of 25±2 μm. Since transparency becomes good, it is preferable that the yellow index is 4 or less, More preferably, it is 3 or less. The lower limit of the yellow index is not particularly limited, but industrially it may be 0.1 or more, and 0.2 or more is not a problem. The total light transmittance is preferably 91% or higher, more preferably 92% or higher. The upper limit is not particularly limited, but industrially it may be 99% or less, and 98% or less is not a problem. It is preferable that the yellow index of the polyimide used in the (b) layer is smaller than the yellow index of the polyimide used in the (a) layer. Moreover, it is preferable that the total light transmittance of the polyimide used for the (b) layer is larger than the total light transmittance of the polyimide used for the (a) layer.

The thickness of the (b) layer in the multilayer polyimide film is preferably greater than 1 μm, more preferably 2 μm or more, still more preferably 3 μm or more, and particularly preferably greater than 4 μm. In addition, since transparency becomes good, it is preferably less than 119 μm, more preferably 100 μm or less, still more preferably 80 μm or less, and particularly preferably 50 μm or less.

The polyimide mainly used in the (b) layer is preferably a tetracarboxylic acid anhydride containing 70% by mass or more of an aromatic tetracarboxylic acid anhydride based on 100% by mass of the total acid component, and all amine components Polyimide having a chemical structure obtained from diamine containing at least 70% by mass of diamine having a sulfur atom in the molecule when 100% by mass, or tetracarboxylic acid containing at least a trifluoromethyl group in the molecule It is a polyimide having a chemical structure obtained by condensation polymerization of a tetracarboxylic acid anhydride containing 70% by mass or more of a diamine containing 70% by mass or more of a diamine having at least a trifluoromethyl group in a molecule.

As the alicyclic tetracarboxylic acid anhydride in the present invention, 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 1,2,3, 4-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,3',4,4'-bicyclohexyltetracarboxylic acid, bicyclo[2,2,1 ]heptane-2,3,5,6-tetracarboxylic acid, bicyclo[2,2,2]octane-2,3,5,6-tetracarboxylic acid, bicyclo[2,2,2]octo -7-ene-2,3,5,6-tetracarboxylic acid, tetrahydroanthracene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10 -trimethanoanthracene-2,3,6,7-tetracarboxylic acid, decahydronaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4:5,8-dimethano Naphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6,7-tetracarboxylic acid, norbonane-2 -Spiro-α-cyclopentanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid (aka "norbonane-2-spiro-2'- Cyclopentanone-5'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclopentanone-α '-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclohexanone-α'-spiro-2 ''-norbonane-5,5'',6,6''-tetracarboxylic acid (aka "norbonane-2-spiro-2'-cyclohexanone-6'-spiro-2''-norbonane -5,5'',6,6''-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-(methylnorbornane)-5 ,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclopropanone-α'-spiro-2''-norbonane-5,5'',6,6 ''-tetracarboxylic acid, norbonane-2-spiro-α-cyclobutanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, Norbonane-2-spiro-α-cycloheptanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α -Cyclooctanone-α'-spiro-2''-norbonane- 5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclononanone-α'-spiro-2''-norbonane-5,5'',6, 6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclodecanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid , Norbonane-2-spiro-α-cycloundecanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro- α-cyclododecanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclotridecanone-α '-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclotetradecanone-α'-spiro-2'' -Norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclopentadecanone-α'-spiro-2''-norbonane-5,5 '',6,6''-tetracarboxylic acid, norbonane-2-spiro(methylcyclopentanone)-α'-spiro-2''-norbonane-5,5'',6,6'' Tetracarboxylic acid, norbonane-2-spiro (methylcyclohexanone) -α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, etc. carboxylic acids and acid anhydrides thereof; Among these, dianhydrides having two acid anhydride structures are suitable, and in particular, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride is preferred, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride This is more preferable, and 1,2,3,4-cyclobutane tetracarboxylic dianhydride is still more preferable. Moreover, these may be used independently and may use 2 or more types together.

As the aromatic tetracarboxylic acid anhydride in the present invention, 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid, 4,4'-oxydiphthalic acid, bis(1,3-dioxo -1,3-dihydro-2-benzofuran-5-carboxylic acid) 1,4-phenylene, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-yl ) Benzene-1,4-dicarboxylate, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(benzene- 1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3-oxo-1 ,3-dihydro-2-benzofuran-1,1-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3 -Oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid; 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(4-isopropyl-toluene-2,5-diyloxy )]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis( naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxy seed-3,3-diyl)bis(benzene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-benzophenonetetracarboxylic acid, 4,4'- [(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid; 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene- 1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(4-isopropyl -toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1- Dioxide-3,3-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid , 3,3 ', 4,4'-benzophenone tetracarboxylic acid, 3,3 ',4,4'-diphenylsulfotetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, pyro Mellitic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]diphthalic acid, 4,4'-[spiro(xanthene-9 and tetracarboxylic acids such as ,9'-fluorene)-3,6-diylbis(oxycarbonyl)]diphthalic acid and acid anhydrides thereof. Moreover, aromatic tetracarboxylic acids may be used independently and may use 2 or more types together.

In this invention, you may use tricarboxylic acid and dicarboxylic acid in addition to tetracarboxylic acid anhydride.

Examples of tricarboxylic acids include trimellitic acid, 1,2,5-naphthalene tricarboxylic acid, diphenyl ether-3,3',4'-tricarboxylic acid, and diphenylsulfone-3,3',4 Aromatic tricarboxylic acids such as '-tricarboxylic acid, or hydrogenated products of the aromatic tricarboxylic acids such as hexahydrotrimellitic acid, ethylene glycol bistrimellitate, propylene glycol bistrimellitate, 1,4- alkylene glycol bistrimellitate such as butanediol bistrimellitate and polyethylene glycol bistrimellitate; and monohydrides and esterified products thereof. Among these, a monohydride having a single acid anhydride structure is preferable, and trimellitic anhydride and hexahydrotrimellitic anhydride are particularly preferable. In addition, these may be used individually or may be used combining plurality.

Examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid, or 1,6-cyclohexanedicarboxylic acid. Hydrogenates of the above aromatic dicarboxylic acids such as acids, oxalic acid, succinic acid, glutalic acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 2- methyl succinic acid, acid chlorides or ester compounds thereof, and the like. Among these, aromatic dicarboxylic acids and hydrogenated products thereof are suitable, and terephthalic acid, 1,6-cyclohexanedicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid are particularly preferred. In addition, dicarboxylic acids may be used independently or may be used in combination of plurality.

As the diamine having an amide bond in the molecule in the present invention, aromatic diamines and alicyclic amines can be mainly used.

Examples of aromatic diamines include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, and 1,4- Bis (4-amino-2-trifluoromethylphenoxy) benzene, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 4,4'-bis (4-aminophenoxy ) Biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide , bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy) Phenyl] -1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 4-amino-N-(4-aminophenyl)benzamide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2, 2'-trifluoromethyl-4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diamino Diphenylsulfide, 3,3'-diaminodiphenylsulfoxide, 3,4'-diaminodiphenylsulfoxide, 4,4'-diaminodiphenylsulfoxide, 3,3'-diaminodiphenyl Sulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-dia Minobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl] Methane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 1,1-bis[4-(4 -aminophenoxy)phenyl]propane, 1,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(4-aminophenoxy)phenyl]propane, 2,2 -bis[4-(4-aminophenoxy)phenyl]propane, 1,1-bis[4-(4-aminophenoxy)phenyl]butane, 1,3-bis[4-(4-aminophenoxy) phenyl] butane, 1,4-bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis[4-(4-aminophenoxy)phenyl]butane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3-methylphenyl ]propane, 2,2-bis[4-(4-aminophenoxy)-3-methylphenyl]propane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy) oxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy) cy)phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,4-bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-( 4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-amino) Phenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- ( 3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[(3-aminophenoxy)benzoyl]benzene, 1,1 -bis[4-(3-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenylsulfide, 2,2 -bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]methane, 1,1 -Bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, bis[4-(3-aminophenoxy)phenyl]sulfoxide , 4,4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'- bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4′-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenylsulfone, Bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1, 3-bis[4-(4-aminophenoc cy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3- Bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α,α- Dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4'-diphenoxy Cybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino- 4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxy Benzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4 ,5'-dibiphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino- 4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phenoxybenzoyl) benzene, 1,4-bis (3 -Amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3 -bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(4-amino-5-biphenoxy Benzoyl) benzene, 1,4-bis (4-amino-5-biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzonitrile, 4 ,4'-[9H-fluorene-9,9-diyl]bisaniline (also known as "9,9-bis(4-aminophenyl)fluorene"), spiro(xanthene-9,9'-fluorene) -2,6-diylbis(oxycarbonyl)]bisaniline, 4,4'-[spiro(xanthen-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]bisaniline , 4,4'-[spiro(xanthen-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]bisaniline, 5-amino-2-(p-aminophenyl)benzoxa sol, 6-amino-2-(p-aminophenyl)benzoate sazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2'-p-phenylenebis(5-aminobenzoxa sol), 2,2'-p-phenylenebis(6-aminobenzooxazole), 1-(5-aminobenzooxazolo)-4-(6-aminobenzooxazolo)benzene, 2,6-( 4,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(4,4'-diaminodiphenyl)benzo[1,2- d:4,5-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6 -(3,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1, 2-d:5,4-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, etc. can be heard In addition, some or all of the hydrogen atoms on the aromatic ring of the aromatic diamine may be substituted with a halogen atom, an alkyl group or alkoxyl group having 1 to 3 carbon atoms, or a cyano group, or a C 1 to 3 alkyl group or alkoxyl group Some or all of the hydrogen atoms may be substituted with halogen atoms.

Examples of alicyclic diamines include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, and 1,4-diamino. -2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclo Hexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 4,4'-methylenebis(2,6-dimethylcyclohexylamine), 9,10-bis(4-aminophenyl)adenine, 2,4-bis(4-aminophenyl)cyclobutane-1,3-dicarboxylic acid dimethyl, etc. are mentioned.

In the present invention, the (a) layer is present on both one side and the other side of the (b) layer, and the transition layer is between the (a) layer and (b) layer on one side of the (b) layer, And, it exists between the (a) layer and the (b) layer on the other side of the (b) layer, and the (a) layer, the transition layer, the (b) layer, the transition layer, and the (a) layer are laminated in this order. It is preferable to have a layered structure. Hereinafter, the layer configuration in which layers (a), transition layers, (b) layers, transition layers, and (a) layers are laminated in this order is also referred to as "(a)/(b)/(a)". Similarly, the layer structure in which (a) layer, transition layer, and (b) layer are laminated in this order is also referred to as "(a)/(b)", and (a) layer, transition layer, (b) layer, transition Layer, (a) layer, transition layer, (b) layer, transition layer, and (a) layer are laminated in the order of “(a)/(b)/(a)/(b)/(a) It is also called.

In the present invention, the (a) layer and the (b) layer have a two-layer structure of (a) / (b) or a three-layer structure of (a) / (b) / (a), and preferably, (a) / (b) / (a) / (b) / (a) may be a five-layer structure, furthermore, it is good also as a film of 7 layers, 9 layers or more odd-numbered layers. In the case of odd-numbered layers, it is preferable to arrange the (a) layer to be located in the outermost layer. Compared to the layer (b), by making the (a) layer superior in mechanical properties and having a small linear expansion coefficient as the outermost layer, the linear expansion coefficient of the entire film can be suppressed to the low side, and by providing a surface layer excellent in mechanical strength, the film Handling is improved, and the optical properties excellent in the (b) layer polyimide serving as the inner layer can be brought out to the maximum extent. The layer (b) is preferably thicker than the layer (a). The ratio of the thickness of the (b) layer to the thickness of the (a) layer is preferably greater than (b) layer/(a) layer = 1, more preferably 1.5 or more, still more preferably 2 or more. Moreover, it is preferably 20 or less, more preferably 15 or less, still more preferably 12 or less.

In the present invention, the thickness of the (a) layer, when the (a) layer is a plurality of layers, the sum of these thicknesses is preferably 34% or less of the total film thickness, more preferably 26% or less, and 13% or less It is more preferable, and it is preferable to configure so that it is more preferably 7% or less. The thickness of layer (a) is 1% or more, preferably 2% or more, more preferably 4% or more of the total film thickness. By setting the thickness of the layer (a) within this range, a film in which the mechanical properties of the layer (a) and the optical properties of the layer (b) are balanced can be obtained.

In the case of indicating the thickness of the (a) layer and the (b) layer, the (a) layer side from the center in the thickness direction of the transition layer is included in the (a) layer, and the (b) layer side is included in the (b) layer. do.

In the present invention, between the (a) layer and the (b) layer, there is a transition layer (mixed layer) whose composition continuously changes from the polyimide of the (a) layer to the polyimide of the (b) layer. The lower limit of the thickness of the transition layer is preferably either 3% of the total thickness of the film or 1 μm, and the upper limit of the thickness of the transition layer is preferably either 10% of the total thickness of the film or 3 μm. A preferred range of the lower limit is either greater than 3% of the total film thickness or 1.1 μm, more preferably either 3.2% or 1.2 μm of the total film thickness, 3.5% of the total film thickness, or It is more preferable that it is either 1.5 μm. In addition, as a preferred range of the upper limit, it is either 9% of the total thickness of the film or 2.8 µm, and more preferably 8% of the total thickness of the film or 2.6 µm. By setting the transition layer within the above range, both transparency and mechanical strength can be achieved.

In addition, the thickness of the transition layer is the thickness of the region where the polyimide of the (a) layer and the polyimide of the (b) layer are mixed and the composition is inclined from one side to the other, and the polyimide of the (a) layer of the mixed layer / ( b) refers to a range in which the composition ratio (mass ratio) of polyimide in the layer is 5/95 to 95/5. The thickness of the transition layer can be measured by cutting the film obliquely in the thickness direction and observing the composition distribution of the polyimide.

The thickness of the transition layer can be obtained from the thickness of the transition layer present at the interface and the total thickness of the film, since there is only one layer (interface) between layers when the multilayer polyimide film has a laminated structure of two layers. there is. When the multilayer polyimide film has a laminated structure of three layers, since there are two places between layers (interfaces), it can be obtained from the total thickness of each transition layer and the total thickness of the film. Similarly, when the multilayer polyimide film has a laminated structure of four or more layers, it can be obtained from the total thickness of all the transition layers and the total thickness of the film.

The polyimide used in the (a) layer in the present invention is preferably a polyimide having a yellow index of 10 or less and a total light transmittance of 85% or more when used alone as a film having a thickness of 25±2 μm. Further, the polyimide used in the (a) layer preferably has a CTE of 25 ppm/K or less, more preferably 20 ppm/K or less, has a tensile breaking strength of 100 MPa or more, preferably 120 MPa or more, and has a breaking elongation of 10%. It is more preferable that it is more than 12% further.

As a preferred polyimide for the layer (a), condensation polymerization of tetracarboxylic acid anhydride containing 70% by mass or more of alicyclic tetracarboxylic acid anhydride and diamine containing 70% by mass or more of diamine having an amide bond in the molecule A polyimide containing a chemical structure obtained by can be exemplified.

Further, as the polyimide used in the layer (a), tetracarboxylic acid anhydride containing 70 mass% or more of alicyclic tetracarboxylic acid anhydride and diamine containing 70 mass% or more of diamine having a trifluoromethyl group in the molecule A polyimide containing a chemical structure obtained by condensation polymerization of can be exemplified.

All polyimides for layers (a) can use alicyclic tetracarboxylic acid anhydrides. The content of the alicyclic tetracarboxylic acid anhydride is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and still more preferably is 95 mass% or more. Coloring is suppressed by carrying out content of an alicyclic tetracarboxylic acid in a predetermined range.

As the diamine having an amide bond in the molecule, 4-amino-N-(4-aminophenyl)benzamide is preferable. As for the diamine which has an amide bond, use of 70 mass % or more of all diamines is preferable, 80 mass % or more, and furthermore, 90 mass % or more is used.

In addition, as the diamine having a trifluoromethyl group in the molecule, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 1,4-bis(4-amino-2-trifluoro Methylphenoxy)benzene and 2,2'-trifluoromethyl-4,4'-diaminodiphenyl ether are preferred. When using a diamine compound having a fluorine atom in the molecule, particularly a diamine having a trifluoromethyl group in the molecule, the amount used is preferably 70% by mass or more, 80% by mass or more, and more preferably 90% by mass of the total diamine. Use of the above is preferable.

The polyimide used in the (b) layer in the present invention is preferably a polyimide having a yellow index of 5 or less and a total light transmittance of 90% or more when used alone as a film having a thickness of 25±2 μm.

The polyimide used in the (b) layer is selected from tetracarboxylic acid anhydride containing 70 mass% or more of aromatic tetracarboxylic acid anhydride and diamine containing 70 mass% or more of diamine having at least a sulfur atom in the molecule. Polyimide containing the obtained chemical structure can be illustrated.

Further, as the polyimide suitable for layer (b), tetracarboxylic acid anhydride containing 30 mass% or more of tetracarboxylic acid containing at least a trifluoromethyl group in a molecule, and diamine having at least a trifluoromethyl group in a molecule A polyimide having a chemical structure obtained by condensation polymerization of a diamine containing 70% by mass or more can be exemplified.

As the aromatic tetracarboxylic acid anhydride preferably used for the polyimide of the layer (b), 4,4'-oxydiphthalic acid, pyromellitic acid, and 3,3',4,4'-biphenyltetracarboxylic acid are selected from the group consisting of: desirable. The aromatic tetracarboxylic dianhydride used in the polyimide of the layer (b) is preferably 70% by mass or more, more preferably 80% by mass or more, of all tetracarboxylic acids in the polyimide of the layer (b). Preferably it is 90 mass % or more, and still more preferably 95 mass % or more. Heat resistance is improved by carrying out content of aromatic tetracarboxylic acid in a predetermined range.

As the tetracarboxylic acid containing a trifluoromethyl group in the molecule used in the polyimide of layer (b), 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride is preferable. . The tetracarboxylic acid containing a trifluoromethyl group used in the polyimide of the layer (b) in the molecule is preferably 30 mass% or more of the total tetracarboxylic acids of the polyimide of the layer (b), more preferably 45 It is mass % or more, More preferably, it is 60 mass % or more, Even more preferably, it is 80 mass % or more. Colorless transparency is improved by making the content of tetracarboxylic acid containing a trifluoromethyl group in a molecule within a predetermined range.

In the polyimide preferably used as the (b) layer of the present invention, the diamine preferably used is at least a diamine having a sulfur atom in the molecule and/or a diamine having a trifluoromethyl group in the molecule.

As the diamine having a sulfur atom in the molecule, 3,3'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, and 4,4'-diaminodiphenylsulfone can be used. In the present invention, when a diamine containing 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more of diamine having a sulfur atom in the molecule is used, and combined with an aromatic tetracarboxylic acid anhydride Even colorless transparency can be obtained.

As the diamine having a trifluoromethyl group, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 1,4-bis(4-amino-2-trifluoromethylphenoxy) Benzene and 2,2'-trifluoromethyl-4,4'-diaminodiphenyl ether are preferred.

In the case of using a diamine compound having a fluorine atom in the molecule, particularly a diamine having a trifluoromethyl group in the molecule, the amount used is preferably 70% by mass or more, 80% by mass or more, and more preferably 90% by mass or more of the total diamine. this is preferable

The polyimide of the layer (a) and the polyimide of the layer (b) in the present invention are characterized by yellow index, total light transmittance, mechanical properties, etc. when used alone as a film having a thickness of 25 ± 2 μm. Here, the operation of making a film with a thickness of 25 ± 2 μm alone is an evaluation of the scale possible in the laboratory, and the polyimide solution or the polyimide precursor solution is 10 cm square, preferably 20 cm square or larger. A film obtained by coating on a glass plate, first preheating at a temperature of up to 120°C, preheating and drying until the amount of residual solvent is 40% by mass or less of the coating film, and further heating at 300°C for 20 minutes in an inert gas such as nitrogen. It is a number obtained by evaluating . In the case of containing inorganic components such as lubricants and fillers to adjust the physical properties, the values of the physical properties of the film obtained by using a solution containing these are used.

The polyimide of the (a) layer and the polyimide of the (b) layer in the present invention may each contain a lubricant (filler). The lubricant may be an inorganic filler or an organic filler, but an inorganic filler is preferable. It does not specifically limit as a lubricant, Silica, carbon, ceramics, etc. are mentioned, Among them, silica is preferable. These lubricants may be used alone or in combination of two or more. The average particle diameter of the lubricant is preferably 10 nm or more, more preferably 30 nm or more, still more preferably 50 nm or more. Further, it is preferably 1 μm or less, more preferably 500 nm or less, and still more preferably 100 nm or less. It is preferable that content of the lubricant in the polyimide of (a) layer and the polyimide of (b) layer is 0.01 mass % or more. Since the smoothness of the polyimide film becomes good, it is more preferably 0.02% by mass or more, still more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more. Further, from the viewpoint of transparency, it is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, and particularly preferably 5% by mass or less.

A manufacturing method for obtaining the multilayer polyimide film of the present invention is described below. Among the multilayer polyimide films of the present invention, the two-layered polyimide film,

Preferably, in the air or inert gas with a temperature of 10 ° C. or more and 40 ° C. or less, and a humidity of 10% or more and 55% or less,

1: (a) Step of applying a polyimide solution or polyimide precursor solution for layer formation to a temporary support to obtain a coated film a1;

2: within 100 seconds after the coating film a1 is formed, (b) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to the coating film a1 to obtain the coating film a1;

3: A step of heating all layers to obtain a laminate having a residual solvent amount of 0.5% by mass or less based on all layers;

can be produced through

The temporary support is preferably long and flexible. In addition, it is preferable that the heating time in step 3 is 5 minutes or more and 60 minutes or less. In addition, the amount of residual solvent on the basis of the entire layer in the step 3 is determined from the mass of the coating film ab1 alone, and the mass of the temporary support is not included. In addition, the starting point of 100 seconds in step 2 is after the completion of application of the polyimide solution or polyimide precursor solution to the temporary support for layer (a) formation. The following operation is also performed in the same way.

In addition, the process of 3 is divided into two stages,

3': step of obtaining a self-supporting film by peeling from the temporary support after heating over a period of 5 minutes to 45 minutes until the amount of residual solvents based on the entire layer is 8% by mass or more and 40% by mass,

4: A step of gripping both ends of the self-supporting film and heating until the amount of residual solvent based on the entire layer is 0.5% by mass or less;

can be done with By peeling off the temporary support at the stage of the self-supporting film, by-products generated by drying and chemical reactions can be quickly discharged from the film, and the difference in physical properties and structure between the front and back can be reduced. there is.

In addition, in the case of a film having three or more layers, the (a) layer polyimide solution or polyimide precursor solution may be applied once again after the above steps 1 and 2, and the (a) layer and (b) layer are further repeatedly applied. By doing so, a further multi-layered film can be obtained.

In the present invention, the application of the polyimide solution or the polyimide precursor solution is carried out at a temperature of 10° C. or more and 40° C. or less, preferably 15° C. or more and 35° C. or less, and a humidity of 10%RH or more and 55% RH or less, preferably 20° C. or more. It is preferable to carry out on a long flexible temporary support in the atmosphere of %RH or more 50%RH or in an inert gas. Further, it is preferable to apply the next layer within 100 seconds, preferably within 50 seconds, and more preferably within 25 seconds after applying the layer before one process. The lower limit is not particularly limited, as the time until application of the next layer is preferably earlier, but industrially it may be 1 second or longer, and 2 seconds or longer may be sufficient. As the coating method, the layer to be applied first can be applied using a comma coater, bar coater, slit coater, etc., and the second and subsequent layers can be applied using a die coater, curtain coater, spray coater, or the like. Further, by using a multi-layer die, it is also possible to apply these plural layers substantially simultaneously.

The environment in which the solution is applied is preferably atmospheric air or inert gas. An inert gas can be substantially interpreted as a gas with a low oxygen concentration, and nitrogen or carbon dioxide may be used from an economic point of view.

The temperature in the coating environment affects the viscosity of the coating liquid and affects the formation of the thickness of the transition layer when the two coating liquids are mixed with each other at the interface when the two coating liquids are overlapped to form a transition layer. crazy The viscosity of the polyimide solution or polyimide precursor solution of the present invention is preferably adjusted to an appropriate viscosity range, especially in the non-contact coating method of the second layer and thereafter, and the fluidity within the above viscosity range even when this temperature range is mixed at the interface of the two layers. contributes to maintaining the appropriate

Most of the solvents used in the polyimide solution or the polyimide precursor solution are hygroscopic, and when the solvent absorbs moisture and the moisture content of the solvent increases, the solubility of the resin component decreases, and the dissolved component precipitates in the solution, resulting in a rapid increase in solution viscosity. may occur. If this situation occurs after application, formation of a transitional layer of appropriate thickness is hindered. By setting the humidity within a predetermined range, it is possible to sufficiently prevent the precipitation of such soluble components in a time of about 100 seconds or less.

As the temporary support used in the present invention, glass, metal plate, metal belt, metal drum, polymer film, metal foil and the like can be used. In the present invention, it is preferable to use a long and flexible temporary support, and films such as polyethylene terephthalate, polyethylene naphthalate, and polyimide can be used as the temporary support. It is one of the preferable aspects to give release treatment to the surface of a temporary support body.

In the present invention, after all the layers are applied, they are dried by heat treatment and subjected to a chemical reaction as needed. In the case of using a polyimide solution, it is sufficient to simply dry in the sense of solvent removal, but in the case of using a polyimide precursor solution, both drying and chemical reaction are required. The polyimide precursor here is preferably in the form of polyamic acid or polyisoimide. A dehydration condensation reaction is required to convert polyamic acid to polyimide. The dehydration condensation reaction is possible only by heating, but an imidation catalyst may be applied as needed. Even in the case of polyisoimide, it is possible to convert an isoimide bond into an imide bond by heating. It is also possible to use an appropriate catalyst in combination.

The residual solvent amount of the final film is 0.5% by mass or less, preferably 0.2% by mass or less, and more preferably 0.08% by mass or less, as an average value of all layers of the film. The heating time is preferably 5 minutes or more and 60 minutes or less, preferably 6 minutes or more and 50 minutes or less, and more preferably 7 minutes or more and 30 minutes or less. By setting the heating time within a predetermined range, the removal of the solvent and the required chemical reaction can be completed, the transition layer can be controlled to an appropriate thickness, and colorless transparency and mechanical properties, especially the elongation at break, can be maintained high. there is. When the heating time is short, the formation of the transition layer is delayed, and when the heating time is longer than necessary, the color of the film becomes stronger and the elongation at break of the film may decrease.

In the present invention, if the applied solution causes drying or chemical reaction by heating and can be separated from the temporary support in a self-supporting manner, it may be separated from the temporary support in the middle of the heating step.

More specifically, 5 minutes or more and 45 minutes or less, preferably 6 minutes or more and 30 minutes or less, still more preferably 7 minutes or more, until the average residual solvent amount of the entire film layer reaches the range of 8% by mass or more and 40% by mass. After heating for a period of 20 minutes or more and 20 minutes or less, the self-supporting film is peeled off from the temporary support, and both ends of the self-supporting film are held between clips or by piercing with pins, A step of obtaining a multilayer polyimide film by conveying in a heating environment and heating until the amount of residual solvent based on the entire layer is 0.5% by mass or less, preferably 0.2% by mass or less, and more preferably 0.08% by mass or less. can be employed.

By peeling the self-supporting film from the temporary support in the middle of the heating process and continuing the heating, water generated when the solvent is evaporated and the polyamic acid is dehydrated and ring-closed to convert to polyimide can be quickly discharged from both sides of the film. , a film with a small difference in physical properties between the front and back can be obtained.

In the present invention, the self-supporting film may be stretched. Stretching may be performed in either the film longitudinal direction (MD direction) or in the width direction (TD) of the film. Stretching in the longitudinal direction of the film can be performed using a difference in speed of the conveying roll or a difference in speed after gripping the conveying roll and both end portions. Stretching in the width direction of the film can be performed by widening between the held clips and pins. Stretching and heating may be performed simultaneously. The stretching ratio can be arbitrarily selected from 1.00 times to 2.5 times. In the present invention, by making the film have a multilayer structure, by combining a polyimide that is difficult to stretch alone and a polyimide that can be stretched, the polyimide is also stretched to a composition that is difficult to stretch, that is, easily broken by stretching. This becomes possible, and mechanical properties can be improved.

In addition, since the volume of polyimide decreases during film formation due to drying or dehydration condensation, the stretching effect is expressed even in a state where both ends are held at equal intervals (stretch ratio: 1.00 times).

In the (a) layer and (b) layer of the multilayer polyimide film of the present invention, a lubricant is added to the polyimide to impart fine irregularities to the surface of the layer (film) to improve the sliding properties of the film. desirable. A form in which the lubricant is added only to the (a) layer serving as the outer layer is preferable.

As the lubricant, inorganic or organic fine particles having an average particle diameter of about 0.03 µm to 3 µm can be used, and specific examples include titanium oxide, alumina, silica, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, and calcium pyrophosphate. , magnesium oxide, calcium oxide, and clay minerals. The content of the lubricant is preferably 0.1% by mass or more, more preferably 0.4% by mass or more, based on the polyimide (polymer). Moreover, it is preferable that it is 50 mass % or less, More preferably, it is 30 mass % or less.

Example

Hereinafter, the present invention will be described in detail using Examples, but the present invention is not limited to the following Examples unless departing from the gist thereof. In addition, each physical property value in manufacture examples and examples was measured by the following method.

<Measurement of thickness of polyimide film>

It was measured using a micrometer (Militron 1245D, manufactured by Fine Lupe Co., Ltd.).

<Tensile modulus, tensile strength (strength at break) and elongation at break>

The film was cut into a strip shape of 100 mm x 10 mm in the flow direction (MD direction) and width direction (TD direction) at the time of application, respectively, and was used as a test piece. Using a tensile tester (manufactured by Shimadzu Corporation, Autograph (R) model: AG-5000A), under the conditions of a tensile speed of 50 mm/min and a distance between chucks of 40 mm, tensile modulus and tensile strength in MD and TD directions, respectively. And the elongation at break was calculated|required, and the average value of the measured value of MD direction and TD direction was calculated|required.

<Coefficient of linear expansion (CTE)>

In the flow direction (MD direction) and the width direction (TD direction) of the film at the time of application, the expansion rate was measured under the following conditions, and at intervals of 15 ° C., such as 30 ° C. to 45 ° C. and 45 ° C. to 60 ° C. Stretching ratio/temperature was measured, this measurement was carried out up to 300°C, the average value of all measured values was calculated as CTE, and the average value of measured values in the MD and TD directions was also obtained.

device name; TMA4000S manufactured by MAC Science

sample length; 20mm

sample width; 2mm

heating start temperature; 25℃

heating end temperature; 300℃

heating rate; 5℃/min

atmosphere; argon

<Transition Layer Thickness>

The inclined cutting surface of the film is prepared by SAICAS DN-20S type (Difla Wintes Co., Ltd.), and then the inclined cutting surface is processed using brown rice IRCary 620 FTIR (Agilent Co.) using germanium crystal (incidence angle 30 °). The spectrum was obtained by the ATR method, and the increase and decrease of the characteristic peaks of each of the layers (a) and (b) and the gradient of the composition were obtained in terms of mass ratio from the calibration curve obtained in advance, and the composition of (a) layer / composition of (b) layer was obtained. The thickness in the range of the ratio of 5/95 mass ratio to 95/5 mass ratio was obtained as the thickness of the transition layer.

<Haze>

The haze of the film was measured using HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). A D65 lamp was used as the light source. In addition, the same measurement was performed three times and the arithmetic average value was adopted.

<Total light transmittance>

The total light transmittance (TT) of the film was measured using HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). A D65 lamp was used as the light source. In addition, the same measurement was performed three times and the arithmetic average value was adopted.

A result is shown to Tables 2-6.

<Yellow Index>

Using a color meter (ZE6000, manufactured by Nippon Denshoku Co., Ltd.) and a C2 light source, the tristimulus values XYZ values of the film were measured according to ASTM D1925, and the yellowness index (YI) was calculated by the following formula. In addition, the same measurement was performed three times and the arithmetic average value was adopted.

YI=100×(1.28X-1.06Z)/Y

<Warling of film>

A film cut into a square with a size of 100 mm × 100 mm is used as a test piece, the test piece is placed concavely on a plane at room temperature, and the distances from the plane at the four corners (h1rt, h2rt, h3rt, h4rt: unit mm) are measured. It was measured, and the average value was set as the amount of warpage (mm).

[Production Example 1 Production of polyamic acid solution A]

After purging the inside of the reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stirring rod with nitrogen, 22.73 parts by mass of 4,4'-diaminobenzanilide (DABAN) was mixed with 201.1 parts by mass of N,N-dimethylacetamide (DMAc). was dissolved in, and then, 19.32 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) was added separately as a solid, and then stirred at room temperature for 24 hours. Then, 173.1 parts by mass of DMAc was added and diluted to obtain a polyamic acid solution A having an NV (solid content) of 10% by mass and a reduced viscosity of 3.10 dl/g.

[Production Example 2 (a) Preparation of polyamic acid solution As containing lubricant for layer formation)]

In the polyamic acid solution A obtained in Production Example 1, a dispersion formed by dispersing colloidal silica as a lubricant in dimethylacetamide ("Snowtex (registered trademark) DMAC-ST-ZL" manufactured by Nissan Chemical Industries, Ltd.) was mixed with silica (lubricant) ) was further added so as to be 1.4% by mass in total polymer solid content in the polyamic acid solution) to obtain a uniform polyamic acid solution As.

[Production Example 3 Production of polyamic acid solution B]

After purging the inside of the reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stirring bar with nitrogen, 32.02 parts by mass of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) was added to 279.9 Dissolved in N,N-dimethylacetamide (DMAc) by mass, followed by 9.81 parts 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 15.51 parts 4,4'-oxydiamine by mass. After dividingly adding phthalic dianhydride (ODPA) as a solid, the mixture was stirred at room temperature for 24 hours. Thereafter, a polyamic acid solution B having a solid content of 17% by mass and a reduced viscosity of 3.60 dl/g was obtained.

[Production Example 4 (a) Preparation of polyamic acid solution Bs containing lubricant for layer formation)]

In the polyamic acid solution B obtained in Production Example 3, a dispersion formed by dispersing colloidal silica as a lubricant in dimethylacetamide ("Snowtex (registered trademark) DMAC-ST-ZL" manufactured by Nissan Chemical Industries, Ltd.) was mixed with silica (lubricant) ) was added so as to be 0.45% by mass in terms of the total polymer solid content in the polyamic acid solution) to obtain a uniform polyamic acid solution Bs.

[Production Example 5 (b) Production of polyimide solution C for layer formation]

2,2'-ditrifluoromethyl-4,4'-diamino ratio of 32.02 parts by mass Phenyl (TFMB), 230 parts by mass of N,N-dimethylacetamide (DMAc) were added to dissolve completely, followed by 44.42 parts by mass of 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride After dividingly adding (6FDA) as a solid, it stirred at room temperature for 24 hours. Then, a polyamic acid solution Caa having a solid content of 25% by mass and a reduced end of 1.10 dl/g was obtained.

Next, 204 parts by mass of DMAc was added to the obtained polyamic acid solution Caa to dilute the polyamic acid concentration to 15% by mass, and then 1.3 parts by mass of isoquinoline was added as an imidation accelerator. Subsequently, 12.25 parts by mass of acetic anhydride was slowly added dropwise as an imidation agent while stirring the polyamic acid solution. After that, stirring was continued for 24 hours, a chemical imidation reaction was performed, and polyimide solution Cpi was obtained.

Next, 100 parts by mass of the obtained polyimide solution Cpi was transferred to a reaction vessel equipped with a stirrer and a stirrer, and when 150 parts by mass of methanol was slowly added dropwise while stirring, precipitation of a powdery solid was confirmed.

Thereafter, the powder, which is the content of the reaction vessel, was dehydrated and filtered, washed with methanol, dried under vacuum at 50°C for 24 hours, and then heated at 260°C for 5 hours to obtain polyimide powder Cpd. 20 parts by mass of the obtained polyimide powder was dissolved in 80 parts by mass of DMAc to obtain a polyimide solution C.

[Production Example 6 (b) Preparation of polyimide solution D for layer formation]

120.5 parts by mass of 4,4'-diaminodiphenylsulfone (4,4'-DDS), 51.6 parts by mass of 3,3'-diaminodiphenylsulfone (3,3'-DDS) and 500 parts by mass of gamma butyrolactone (GBL) were added. Subsequently, after adding 217.1 parts by mass of 4,4'-oxydiphthalic dianhydride (ODPA), 223 parts by mass of GBL, and 260 parts by mass of toluene at room temperature, the internal temperature was raised to 160°C, heated to reflux at 160°C for 1 hour, and already did a drawing After completion of the imidation, the temperature was raised to 180°C, and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed, the temperature was returned to room temperature, and GBL was added so that the solid content was 20% by mass to obtain a polyimide solution D.

[Production Example 7 Production of polyamic acid solution E]

161 parts by mass of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) and N-methyl- After mixing and stirring 1090 parts by mass of 2-pyrrolidone to dissolve, 112 parts by mass of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA) was dividedly added as a solid at room temperature and stirred at room temperature for 12 hours. did. Next, 400 parts by mass of xylene was added as an azeotrope solvent, the temperature was raised to 180° C., reaction was performed for 3 hours, and an azeotropic product was separated. After confirming that the water had flowed out, the polyamic acid solution E was obtained by removing xylene while raising the temperature to 190°C over 1 hour.

[Production Example 8 (a) Preparation of polyamic acid solution Es containing lubricant for layer formation)]

In the polyamic acid solution E obtained in Production Example 7, a dispersion formed by dispersing colloidal silica as a lubricant in dimethylacetamide (manufactured by Nissan Chemical Industries, Ltd. "Snowtex (registered trademark) DMAC-ST-ZL") was mixed with silica (lubricant) ) was added so that the total polymer solid content in the polyamic acid solution was 1.0% by mass) to obtain a uniform polyamic acid solution Es.

[Production Example 9 (b) Production of polyamic acid solution Ef containing filler for layer formation)]

In the polyamic acid solution E obtained in Production Example 7, a dispersion formed by dispersing colloidal silica as a lubricant in dimethylacetamide (manufactured by Nissan Chemical Industries, Ltd. "Snowtex (registered trademark) DMAC-ST-ZL") was mixed with silica (lubricant) ) was added so that the total polymer solid content in the polyamic acid solution was 25% by mass) to obtain a polyamic acid solution Ef containing a filler.

The polyimide solutions and polyamic acid solutions (polyimide precursor solutions) obtained in Production Examples 1 to 9 were formed into films by the following method, and optical properties and mechanical properties were measured. The results are shown in Table 1.

(How to obtain a film for measuring physical properties alone)

A polyimide solution or polyamic acid solution was applied to the center of a glass plate with a side of 30 cm and an area approximately 20 cm square using a bar coater so that the final thickness was 25 ± 2 μm, and dry nitrogen was gradually flowed. Inert After heating at 100°C for 30 minutes in an oven and confirming that the amount of residual solvent in the coating film was 40 mass% or less, it was heated at 300°C for 20 minutes in a muffle furnace purged with dry nitrogen. Then, it is taken out of the muffle furnace, and the end of the dried coating film (film) is raised with a cutter knife, and it is carefully peeled from the glass to obtain a film.

(Example 1)

In an air-conditioned atmosphere at 25°C and 45% RH, the polyamic acid solution As obtained in Production Example 2 was applied to the non-slip surface of polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd., hereinafter abbreviated as PET film) using a comma coater. was applied so that the final film thickness was 5 μm, and then, 10 seconds later, the polyimide solution C obtained in Production Example 5 was applied on the polyamic acid solution As with a die coater so that the final film thickness was 20 μm. This was dried at 110°C for 10 minutes. After drying, the self-supporting film is peeled from the A4100 film as a support, passed through a pin tenter having a pin sheet on which pins are arranged, and gripped by inserting the end of the film into a pin so that the film does not break, Then, the fin sheet interval was adjusted and conveyed so as not to cause unnecessary slack, and the imidization reaction proceeded by heating under the conditions of 200°C for 3 minutes, 250°C for 3 minutes, and 300°C for 6 minutes. After that, it was cooled to room temperature for 2 minutes, and portions with poor flatness at both ends of the film were cut out with a slitter and wound into a roll to obtain a roll of film (yarn 1) having a width of 580 mm and a length of 100 m.

Table 2 shows the evaluation results of the obtained film (yarn 1).

(Examples 2 to 4)

Hereinafter, by setting conditions shown in Table 2, films (yarn 2) to (yarn 4) and comparative film (ratio 1) were obtained. Table 2 shows the results evaluated in the same way.

(Comparative Examples 1 to 4)

As Comparative Example 1, a film (ratio 1) was obtained under the same conditions as in Example 3 using only the polyamic acid solution As and having a thickness of 25 μm. Similarly, films (ratio 2) to (ratio 4) were obtained using only the polyimide solution C, the polyamic acid solution Bs, and the polyimide solution D, respectively. Each evaluation result is shown in Table 3.

Mechanical property values of the films (Ratio 1) to (Ratio 4) show higher breaking strength and higher breaking elongation than those of the test pieces obtained in Production Examples. This difference indicates the difference in the case where the production example film, which was filmed while being applied to glass, was separated from the PET film as a temporary support during heat treatment and filmed while discharging the solvent and reaction product from the front and back of the film.

(Calculation examples 1 and 2)

The numerical value shown in column 1 of the calculation example of Table 4 is the arithmetic average value of the evaluation result of the film (ratio 1) and (ratio 2). Calculation Example 2 is an average value weighted by the thickness ratio of the (a) layer and (b) layer in Examples 1 to 4.

Comparing the evaluation results of the films obtained in Examples with calculation examples, all of the films obtained in Examples had a lower haze than Calculation Examples 1 and 2, and had a higher total light transmittance. In addition, the yellow index also showed a small value, and it was shown that the optical properties were improved. In addition, both the tensile strength and the elongation at break were high in the examples, and it was found that the mechanical properties were also improved.

Moreover, it is because it has become an asymmetric structure in the film thickness direction regarding warpage.

(Comparative Examples 5 and 6)

Subsequently, according to the conditions shown in Table 5, films (ratio 5) (ratio 6) were obtained using polyamic acid solution As and polyimide solution C. Table 5 shows the evaluation results. In Comparative Example 5 in which the time interval from application of the layer (a) to application of the layer (b) was lengthened, a significant increase in haze was observed. It is presumed that whitening occurred because the solution absorbed moisture in the atmosphere because the time until heating was prolonged, and a phase-separated structure was formed in the coating film, and drying proceeded while leaving that shape. Also, the thickness of the transition layer was increased. The existence of the transition layer is necessary for the (a) layer and the (b) layer to be combined firmly and smoothly in a stepwise composition, but the transition layer portion has a mixed composition of the (a) layer and the (b) layer. Since it is a part to become, it can be seen that if this layer develops too thickly, the advantage of dividing into multiple layers and sharing functions disappears.

In Comparative Example 6, the polyimide of the (a) layer and the (b) layer were exchanged, but in this case, the synergistic effect shown in the examples was not observed, and the optical properties were obtained when each polyimide was formed into a film alone. fell than

(Examples 5 to 9, 12 and 13) [Preparation of (a)/(b)/(a) three-layer film]

In an air-conditioned atmosphere at 25°C and 45% RH, the polyamic acid solution As obtained in Production Example 2 was applied to the non-slip surface of polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd., hereinafter abbreviated as PET film) using a comma coater. was applied so that the final film thickness was 3 μm, and then, 30 seconds later, the polyimide solution C obtained in Production Example 5 was applied on the polyamic acid solution As with a die coater so that the final film thickness was 31 μm. After 30 seconds, the polyamic acid solution As was further applied using another die coater so that the final film thickness was 3 µm.

This is dried at 110 ° C. for 10 minutes, and after drying, the self-supporting film is used as a support, peeled off from the A4100 film, passed through a pin tenter having a pin sheet on which pins are arranged, and the end of the film is inserted into a pin. Gripping, conveying with the fin sheet interval adjusted so that the film does not break or unnecessary slack, and heating under the conditions of 200°C for 4 minutes, 250°C for 4 minutes, and 300°C for 6 minutes, followed by an imidization reaction. proceeded. Thereafter, the film was cooled to room temperature for 2 minutes, and portions with poor flatness at both ends of the film were cut out with a slitter and wound into a roll to obtain a roll of film (yarn 5) having a width of 580 mm and a length of 80 m. Table 6 shows the evaluation results of the obtained film (yarn 5).

Similarly, films (yarn 6) to (yarn 9) were obtained by changing the polyamic acid solution, the polyimide solution, and the operating conditions according to Tables 6 to 7. Further, films (yarn 12) and (yarn 13) were obtained according to Table 5. The evaluation results are shown in each table.

As in Examples 1 to 4, it was found that the properties were improved compared to the film produced in a single layer. Moreover, although warpage was significantly reduced compared with Examples 1 to 4, this is because the contrast in the thickness direction was improved.

(Calculation examples 3 and 4)

The numerical value shown in column 3 of the calculation example of Table 4 is the arithmetic average value of the evaluation results of the film (ratio 3) and (ratio 4). Calculation Example 4 is an average value weighted by the thickness ratio of (a) layer and (b) layer in Example 8.

Comparing the evaluation result of the film obtained in Example 8 with the calculation example, it was found that the optical properties of the film obtained in Example were improved compared to those of Calculation Examples 3 and 4. Improvements were also seen with respect to mechanical properties.

(Comparative Example 9)

Trial production of a single-layer 50 μm film was attempted using the polyamic acid solution Ef to which the filler obtained in Production Example 9 was added. Table 7 shows the set conditions. After temporary drying, the self-supporting film was peeled off from the temporary support PET and introduced into a pin tenter, but the film broke in the longitudinal direction at the initial stage of heating. Although the test was continued by adjusting the pin width, the film became very brittle during drying and conversion reaction to polyimide, and a film sufficient for physical property evaluation could not be obtained.

(Example 10)

The polyamic acid solution Es in which the filler was added only as a lubricant was used for the (a) layer, and the filler-containing polyamic acid solution Ef obtained in Production Example 9 was used for the (b) layer, under the conditions set in Table 7 (a)/ (b) / (a) The film of the structure was produced as a trial. It took time to adjust the pin width, but finally a polyimide film (yarn 10) with a width of 480 mm and a length of 50 m was obtained. Table 7 shows the evaluation results.

(Example 11)

After mirror finish using the polyamic acid solution As and the polyimide solution C obtained in Production Example, the stainless belt was coated using a three-layer coextrusion T-type die. The lip gap of the die was 150 μm for the skin layer and 500 μm for the core layer. Thereafter, heating was performed according to the conditions shown in Table 7, and the end was wound into a roll shape as a slit to obtain a film (yarn 11) having a width of 1100 mm and a length of 300 m. Table 7 shows the evaluation results.

[Production Example 10 (production of polyamic acid solution Fs containing lubricant)]

After replacing the inside of the reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stirring rod with nitrogen, 33.36 parts by mass of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB), 336.31 mass A dispersion formed by dispersing negative N-methyl-2-pyrrolidone (NMP) and colloidal silica as a lubricant in dimethylacetamide (manufactured by Nissan Chemical Industries, Ltd. "Snowtex (registered trademark) DMAC-ST-ZL") is a silica (lubricant) was added so as to be 0.3% by mass in terms of the total polymer solid content in the polyamic acid solution) and completely dissolved, followed by 9.81 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 11.34 parts by mass Partial 3,3',4,4'-biphenyltetracarboxylic acid and 4.85 parts by mass of 4,4'-oxydiphthalic dianhydride (ODPA) were separately added as solids, and then stirred at room temperature for 24 hours. . Thereafter, a polyamic acid solution Fs (molar ratio of TFMB//CBDA/BPDA/ODPA = 1.00//0.48/0.37/0.15) having a solid content of 15% by mass and a reduced viscosity of 3.50 dl/g was obtained.

[Production Example 11 (Preparation of lubricant-free polyamic acid solution F)]

After purging the inside of the reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stirring bar with nitrogen, 336.31 parts by mass of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) was added to 33.36 parts by mass. parts of N-methyl-2-pyrrolidone (NMP) was added to dissolve completely, followed by 9.81 parts of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 11.34 parts of 3,3' by mass. After dividingly adding 4,4'-biphenyltetracarboxylic acid and 4.85 parts by mass of 4,4'-oxydiphthalic dianhydride (ODPA) as solids, the mixture was stirred at room temperature for 24 hours. Then, polyamic acid solution F (molar ratio of TFMB//CBDA/BPDA/ODPA = 1.00//0.48/0.37/0.15) having a solid content of 15% by mass and a reduced viscosity of 3.50 dl/g was obtained.

(Example 14)

In an air-conditioned atmosphere at 25°C and 45% RH, using an apparatus equipped with a roll-to-roll type comma coater and a continuous drying furnace, the polyamic acid solution Fs obtained in Production Example 10 was finally coated on the non-slip surface of the PET film as a temporary support. It was applied so that the film thickness was 5 μm, and then, 10 seconds later, the polyamic acid solution F obtained in Production Example 11 was applied on the polyamic acid solution Fs by a die coater so that the final film thickness was 20 μm. This was dried at 110°C for 10 minutes.

After drying, the self-supporting film is peeled off from the PET film using the support as a support, passed through a pin tenter having a pin sheet on which pins are arranged, and gripped by inserting the ends of the film into pins so that the film does not break, In addition, the fin sheet interval is adjusted and conveyed so that unnecessary slack does not occur, and as the final heating, heating is performed under conditions of 200°C for 3 minutes, 250°C for 3 minutes, 300°C for 3 minutes, and 400°C for 3 minutes to imidize. reaction proceeded. Thereafter, the film was cooled to room temperature for 2 minutes, and portions with poor flatness at both ends of the film were cut out with a slitter and wound into a roll to obtain a roll of film (yarn 14) having a width of 530 mm and a length of 80 m. The obtained film (yarn 14) had a total film thickness of 25 μm, haze of 0.41%, total light transmittance of 88.2%, yellow index of 4.1, strength at break of 230 MPa, elongation at break of 13.1%, modulus of elasticity of 4.4 GPa, CTE of 29 ppm/K, and warpage of 0.1 mm or less. , the thickness of the transition layer was 0.9 μm.

(Example 15)

In an air-conditioned atmosphere at 25° C. and 45% RH, using an apparatus equipped with a roll-to-roll type comma coater and a continuous drying furnace, the polyamic acid solution Fs obtained in Production Example 10 was coated on the non-slip surface of a PET film as a temporary support. It was applied so that the final film thickness was 3 μm, and then, 10 seconds later, the polyamic acid solution F obtained in Production Example 11 was applied on top of the polyamic acid solution Fs by a die coater so that the final film thickness was 19 μm. A second later, the polyamic acid solution Fs was further applied with another die coater so that the final film thickness was 3 μm, and this was dried at 110° C. for 10 minutes.

After drying, the self-supporting film was used as a support and peeled from the PET film, using a pin tenter as in Example 12, at 200 ° C. for 3 minutes, at 250 ° C. for 3 minutes, at 300 ° C. for 3 minutes, at 400 ° C. for 3 minutes. By heating under the condition of 10 minutes, the imidation reaction proceeded. Thereafter, the same operation was performed to obtain a roll of film (yarn 15) having a width of 530 mm and a length of 80 m. The obtained film (yarn 15) has a three-layer structure of Fs/F/Fs, with a total film thickness of 25 μm, haze of 0.43%, total light transmittance of 88.1%, yellow index of 4.1, strength at break of 180 MPa, elongation at break of 12.5%, and modulus of elasticity of 4.2 GPa. , CTE of 30 ppm/K, warpage of 0.1 mm or less, and transition layer thickness (air side/base side) of 1.2 μm/1.3 μm.

(Comparative Example 10)

In an air-conditioned atmosphere at 25° C. and 45% RH, using an apparatus equipped with a roll-to-roll comma coater and a continuous drying furnace, the polyamic acid solution As obtained in Production Example 2 was finally coated on the non-slip surface of the PET film as a temporary support. It applied so that the film thickness might become 20 micrometers. Next, by heating at 110° C. for 5 minutes as primary heating with a continuous drying machine, a semi-dried coating Agfx having a residual solvent amount of 28% by mass was obtained, and each temporary support was wound into a roll shape.

The dried film Agfx having self-supporting properties is peeled from the PET film as a support, passed through a pin tenter having a pin sheet on which pins are arranged, and gripped by inserting the ends of the film into pins so that the film does not break. The fin sheet interval was adjusted and conveyed so as not to cause unnecessary slack, and as the final heating, the imidation reaction proceeded by heating under the conditions of 200°C for 3 minutes, 250°C for 3 minutes, and 300°C for 6 minutes. Thereafter, it was cooled to room temperature for 2 minutes, and portions with poor flatness at both ends of the film were cut out with a slitter and wound into a roll to obtain a roll of polyimide film (ratio 10a) having a width of 530 mm and a length of 50 m.

The obtained roll of polyimide film (ratio 10a) was again set in the above-described apparatus, the polyimide film (ratio 10a) was unrolled, and polyimide solution C obtained in Production Example 5 was added thereon to a final film thickness of 5 µm. It was applied with a coater. This was dried at 110°C for 10 minutes as secondary heating.

After drying, the film is passed through a pin tenter having a pin sheet on which pins are arranged, and the end of the film is inserted into the pin to hold the film. As heating, it heated on conditions of 3 minutes at 200 degreeC, 3 minutes at 250 degreeC, and 6 minutes at 300 degreeC, and imidation reaction was advanced. Thereafter, it was cooled to room temperature for 2 minutes, and portions with poor flatness at both ends of the film were cut out with a slitter and wound into a roll to obtain a roll of polyimide film (ratio 10b) with a width of 450 mm and a length of 30 m.

The obtained polyimide film (ratio 10b) has a two-layer structure of As (20 μm) / C (5 μm), and has a total film thickness of 25 μm, haze of 0.63%, total light transmittance of 86.9%, yellow index of 4.3, breaking strength of 154 MPa, Elongation at break was 18%, elasticity was 3.9 GPa, CTE was 19.6 ppm/K, deflection was 2.8 mm or less, and the thickness of the transition layer was 0.0 μm. The amount of warping of the film is large compared to that of Examples.

(Comparative Example 11)

In an air-conditioned atmosphere at 25°C and 45% RH, the polyamic acid solution As obtained in Production Example 2 was applied onto a glass substrate using an applicator so that the final film thickness was 3 μm, and then, after 60 seconds, Production Example 5 The polyimide solution C obtained in was applied on the polyamic acid solution As with an applicator so that the final film thickness was 31 μm. After 60 seconds, the polyamic acid solution As was further applied using an applicator so that the final film thickness was 3 mu m. On the other hand, the final film thickness in this comparative example is a value obtained from the film thickness obtained by separately applying each solution to a glass substrate alone.

This was dried at 110 ° C. for 20 minutes in an inert oven, then heated at 200 ° C. for 10 minutes and 250 ° C. for 10 minutes with a vacuum dryer, and at 350 ° C. for 5 minutes using a muffle furnace, and the imidation reaction It progressed, and it peeled from the glass substrate and obtained the polyimide film (ratio 11).

The obtained polyimide film (ratio 11) is evaluated as a film intended to have a three-layer structure of As (3 µm)/C (31 µm)/As (3 µm). The characteristics of the polyimide film ratio 11 were: total film thickness 37 μm, haze 5.2%, total light transmittance 83.9%, yellow index 1.8, strength at break 130 MPa, elongation at break 5.8%, elasticity 3.9 GPa, CTE 37 ppm/K, warpage 3.5 mm , the thickness of the transition layer (air side/base side) was 3.5 µm/5.6 µm. Compared with Example 5, the warp amount of the film was large, and the haze value was also high. The thickness of the transition layer is thicker than the intended As layer at the time of application, and rather than a multilayer structure, it is close to a state in which the composition is half mixed, and both strength and elongation are reduced, so it is assumed that the expected functional separation did not occur .

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

As described above, it was found that the multilayer polyimide film of the present invention has better optical properties and mechanical properties than when polyimides of different compositions were formed into films independently. Further, according to the manufacturing method of the present invention, it is possible to form a transitional layer having a specific thickness and a composition gradient between layers of different compositions separated into multiple layers and functionally divided, thereby making it possible to form a well-balanced film.

Since the multilayer polyimide film of the present invention has excellent optical properties, colorless transparency, excellent mechanical properties, and a relatively low CTE, it can be used as a member of a flexible and lightweight display device or as a touch panel requiring transparency. It can be used for switch elements, pointing devices, and the like.

Claims (9)

A multilayer polyimide layer in which at least two types of polyimide layers having different compositions are laminated in the thickness direction;
A transition layer in which the chemical composition changes with an inclination, which exists between the (a) layer constituting the multi-layer polyimide layer and the (b) layer adjacent to the (a) layer.
has,
The thickness of the transition layer has a lower limit of 3% of the total film thickness or 1 μm, and an upper limit of 10% of the total film thickness or 3 μm,
The thickness of the entire film is 3 μm or more and 120 μm or less,
The yellow index of the entire film is 5 or less,
The total light transmittance of the entire film is 86% or more.
A multilayer polyimide film, characterized in that. According to claim 1,
The (a) layer is mainly composed of polyimide having a yellow index of 10 or less and a total light transmittance of 85% or more when used alone as a film having a thickness of 25 ± 2 μm,
The (b) layer is mainly composed of polyimide having a yellow index of 5 or less and a total light transmittance of 90% or more when used alone as a film having a thickness of 25 ± 2 μm.
A multilayer polyimide film, characterized in that. According to claim 1 or 2,
The (a) layer is present on both one side and the other side of the (b) layer,
The transition layer is between the (a) layer and the (b) layer on one side of the (b) layer, and between the (a) layer and the (b) layer on the other side of the (b) layer. exist between
The (a) layer, the transition layer, the (b) layer, the transition layer, and the (a) layer are laminated in this order.
A multilayer polyimide film, characterized in that. According to any one of claims 1 to 3,
The polyimide of the layer (a),
A polyimide having a chemical structure obtained by condensation polymerization of a tetracarboxylic acid anhydride containing 70% by mass or more of an alicyclic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having an amide bond in the molecule,
or
Polyi comprising a chemical structure obtained by condensation polymerization of a tetracarboxylic acid anhydride containing 30% by mass or more of an alicyclic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having a trifluoromethyl group in a molecule mid
A multilayer polyimide film, characterized in that. According to any one of claims 1 to 4,
The polyimide of the layer (b),
A polyimide comprising a chemical structure obtained from a tetracarboxylic acid anhydride containing 70% by mass or more of an aromatic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having a sulfur atom in the molecule;
or
Obtained by condensation polymerization of a tetracarboxylic acid anhydride containing 70% by mass or more of a tetracarboxylic acid containing a trifluoromethyl group in a molecule and a diamine containing 70% by mass or more of a diamine having a trifluoromethyl group in a molecule Polyimide Containing Chemical Structure
A multilayer polyimide film, characterized in that. 1: (a) Step of applying a polyimide solution or polyimide precursor solution for layer formation to a temporary support to obtain a coated film a1;
2: within 100 seconds after the coating film a1 is formed, (b) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to the coating film a1 to obtain the coating film a1;
3: A step of heating all layers to obtain a laminate having a residual solvent amount of 0.5% by mass or less based on all layers;
The manufacturing method of the multilayer polyimide film of Claim 1, Claim 2, Claim 4, or Claim 5 containing at least. 1: (a) Step of applying a polyimide solution or polyimide precursor solution for layer formation to a temporary support to obtain a coated film a1;
2: within 100 seconds after the coating film a1 is formed, (b) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to the coating film a1 to obtain the coating film a1;
Step 3: Heating all layers to obtain a laminate having a residual solvent amount of 5% by mass or more and 40% by mass based on all layers, and then peeling from the temporary support to obtain a self-supporting film;
5: A step of gripping both ends of the self-supporting film to further obtain a film having a residual solvent amount of 0.5% by mass or less based on the entire layer;
The manufacturing method of the multilayer polyimide film of Claim 1, Claim 2, Claim 4, or Claim 5 containing at least. 1: (a) Step of applying a polyimide solution or polyimide precursor solution for layer formation on a temporary support to obtain a coating film a1;
2: within 100 seconds after the coating film a1 is formed, (b) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to the coating film a1 to obtain the coating film a1;
Step 3: Within 100 seconds after the formation of the coating film ab1, (a) a step of applying a polyimide solution for layer formation or a polyimide precursor solution to the coating film ab1 to obtain the coating film aba1;
4: A step of heating all layers to obtain a laminate having a residual solvent amount of 0.5% by mass or less based on all layers;
The manufacturing method of the multilayer polyimide film as described in any one of Claims 1-5 containing at least. 1: (a) Step of applying a polyimide solution or polyimide precursor solution for layer formation to a temporary support to obtain a coated film a1;
2: within 100 seconds after the coating film a1 is formed, (b) a step of applying a polyimide solution or a polyimide precursor solution for layer formation to the coating film a1 to obtain the coating film a1;
Step 3: Within 100 seconds after the formation of the coating film ab1, (a) a step of applying a polyimide solution for layer formation or a polyimide precursor solution to the coating film ab1 to obtain the coating film aba1;
4: step of heating all layers to obtain a laminate having a residual solvent amount of 8% by mass or more and 40% by mass based on all layers, then peeling from the temporary support to obtain a self-supporting film;
5: A step of gripping both ends of the self-supporting film to further obtain a film having a residual solvent amount of 0.5% by mass or less based on the entire layer;
The manufacturing method of the multilayer polyimide film as described in any one of Claims 1-5 containing at least.