TW202222932A - Colorless multilayer polyimide film, laminate body, and flexible electronic device manufacturing method - Google Patents

Abstract

The present invention provides a colorless polyimide film which has a high tensile strength at break and a high tensile modulus of elasticity, while having a high elongation at break and a low linear expansion coefficient. This multilayer film uses a polyimide, to which less than 0.05 mass% of an inorganic filler is added, as an outer layer (a), and a polyimide, to which 1-35 mass% of an inorganic filler is added, as an inner layer (b). This multilayer polyimide film is obtained by applying a polyimide solution or polyimide precursor solution for forming the layer (a) to a provisional support, drying the solution until the solvent content reaches 5-40 mass%, subsequently applying a polyimide solution or polyimide precursor solution for forming the layer (b) to the provisional support, repeating the application in the same manner as necessary, and finally carrying out a heat treatment. A white film is obtained if an inorganic filler having a high refractive index is used for the inner layer, while a colorless transparent film is obtained if an inorganic filler having a refractive index that is close to the refractive index of a polyimide resin is used.

Description

Colorless multilayer polyimide film, laminate, and method for producing flexible electronic device

The present invention relates to a colorless polyimide film with low coefficient of linear expansion and good mechanical properties, further relates to a laminate of the polyimide film and an inorganic substrate, and further relates to the flexibility formed by the laminate Manufacturing method of electronic device.

Polyimide films are widely used in electrical and electronic fields as materials having excellent heat resistance, good mechanical properties, and flexibility. However, since a normal polyimide film is colored yellowish-brown, it cannot be applied to a portion that needs to transmit light, such as a display device. On the other hand, display devices are being made thinner and lighter, and further flexibility is being pursued. Therefore, an attempt was made to replace the substrate material from a glass substrate to a flexible polymer film substrate, but the colored polyimide film could not be used as a substrate material for a liquid crystal display that performs display by transmitting light through ON/OFF. It can only be applied to peripheral circuits such as TAB and COF mounted with the drive circuit of the display device, and to very few parts such as the rear side of the reflective display method or self-luminous display device.

From this background, the development of a colorless and transparent polyimide film was carried out. As a representative example, attempts have been made to develop colorless and transparent polyimide films using fluorinated polyimide resins, semi-alicyclic or fully alicyclic polyimide resins (Patent Documents 1 to 3). These films are less colored and have transparency, but their mechanical properties cannot be improved to the level of colored polyimide films. When industrial production is assumed, and applications exposed to high temperatures are used, thermal decomposition or oxidation reactions will occur. Colorless and transparent are not necessarily maintained. From this point of view, a method of performing heat treatment while blowing a gas with a predetermined oxygen content has been proposed (Patent Document 4). However, in an environment where the oxygen concentration is less than 18%, the manufacturing cost is high and industrial production is extremely difficult.

In addition, attempts have been made to blend a colorless filler (white pigment) with a colorless transparent polyimide to produce a white heat-resistant film (Patent Documents 5 and 6). [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 11-106508 [Patent Document 2] Japanese Patent Laid-Open No. 2002-146021 [Patent Document 3] Japanese Patent Laid-Open No. 2002-348374 [Patent Document 4] WO2008/146637 [Patent Document 5] Japanese Patent Laid-Open No. 2008-169237 [Patent Document 6] Japanese Patent Laid-Open No. 2010-031258

[The problem to be solved by the invention]

Half-alicyclic or fully alicyclic polyimide, if the monomer component having an alicyclic structure is added, although colorless transparency is obtained, it becomes hard and brittle, the elongation at break decreases, and production as a film becomes difficult. . On the other hand, when an aromatic monomer or a monomer having an amide bond in the molecule is introduced, the toughness is improved and the mechanical properties of the film are improved, but it becomes easy to be colored and the colorless transparency is lowered. By introducing a filler (inorganic component) with a refractive index close to that of the resin component, heat resistance and colorless transparency are improved, the coefficient of linear expansion is further reduced, and the processability is improved, but the resin becomes hard and brittle in terms of physical properties, and mechanical properties are reduced. A white heat-resistant film can be obtained by introducing a filler containing a substance having a large difference in refractive index with the polyimide resin, but if the amount is mixed in an amount sufficient to obtain the same high degree of whiteness and shielding properties, the film becomes brittle and becomes brittle. Difficult to industrialize production. That is, practical properties such as heat resistance and mechanical properties are in a trade-off relationship with colorlessness (transparency or whiteness), and it is very difficult to manufacture a transparent polyimide film that satisfies all colorless properties. [means to solve the problem]

The present inventors attempted to realize a balanced polyimide film by combining a plurality of polyimide resins. Usually, when resins of multiple components are combined and blended, mixed, or copolymerized, it is not always possible to obtain a result that only combines the advantages of each component, but there are many examples where the disadvantages are multiplied and manifested. However, the inventors of the present invention have continued to study hard, and as a result, they have found that by combining polyimide resins to form a specific structure and forming a thin film, the advantages of each component can be fully utilized, and they have further discovered that this technology can be used to divert existing manufacturing equipment. The present invention is achieved by a method of manufacturing a flexible electronic device.

That is, the present invention has the following configuration. [1] A multilayer polyimide film, characterized in that the thickness is 3 μm or more and 120 μm or less, the yellowness index is 5 or less, and at least two layers of (a) layer and (b) layer are included; (a) layer: a layer containing a polyimide composition with an inorganic filler content of less than 0.05 mass %, (b) Layer: A layer containing a polyimide composition having an inorganic filler content of 1 mass % or more and 35 mass % or less. [2] The multilayer polyimide film according to [1], wherein the structure of the multilayer polyimide film is a three-layer structure of (a)/(b)/(a). [3] The multilayer polyimide film according to [1], wherein the structure of the multilayer polyimide film is a three-layer structure of (a)/(b)/(c); further, here, ( c) Layer: a layer containing a polyimide composition with an inorganic filler content of 0.3 mass % or less. [4] The multilayer polyimide film according to any one of the above [1] to [3], wherein the chemical structure of the polyimide in all layers is the same. [5] The multilayer polyimide film according to any one of the above [1] to [4], wherein the coefficient of linear expansion is 50 ppm/°C or less. [6] The multilayer polyimide film according to any one of [1] to [5], wherein the total light transmittance is 80% or more. [7] The multilayer polyimide film according to any one of [1] to [6], wherein the surface of the layer (a) is formed with a polyethylene terephthalate film (PET film) manufactured by Toyobo Co., Ltd. ) The coefficient of static friction between the inner surfaces of the roll of "COSMOSHINE (registered trademark) A4100" is 1.50 or less. [8] The multilayer polyimide film according to any one of [1] to [7], wherein the 10-point average roughness Rz of the surface of the layer (a) is 15 nm or more. [9] A laminate comprising the multilayer polyimide film according to any one of the above [1] to [8] and an inorganic substrate. [10] A method of manufacturing a flexible electronic device, wherein the electronic device is formed on the surface of the multilayer polyimide film of the laminate according to the above [9], followed by peeling from an inorganic substrate.

The present invention may further include the following configurations. [11] A method for producing a multilayer polyimide film as described in any one of [1] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: A step of heating the entire layer to obtain a layered body having a residual solvent content of 0.5 mass % or less based on the entire layer. [12] A method for producing a multilayer polyimide film as described in any one of [1] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: heating the whole layer to obtain a layered product with a residual solvent content of 5% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 4: A step of holding both ends of the self-supporting film and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer. [13] A method for producing a multilayer polyimide film as described in any one of [1], [2], [4] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: within 100 seconds after the coating film a1b1 is made, the polyimide solution or polyimide precursor solution for layer (a) is applied to the coating film a1b1 to obtain the coating film a1b1a1 The step of; 4: A step of heating the entire layer to obtain a layered body having a residual solvent content of 0.5 mass % or less based on the entire layer. [14] A method for producing a multilayer polyimide film as described in any one of [1], [2], [4] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: within 100 seconds after the coating film a1b1 is made, the polyimide solution or polyimide precursor solution for layer (a) is applied to the coating film a1b1 to obtain the coating film a1b1a1 The step of; 4: heating the whole layer to obtain a layered product with a residual solvent content of 8% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 5: A step of holding both ends of the self-supporting film, and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer.

The present invention may further include the following configurations. [15] A method for producing a multilayer polyimide film as described in any one of [1] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: A step of heating the entire layer to obtain a layered body having a residual solvent content of 0.5 mass % or less based on the entire layer. [16] A method for producing a multilayer polyimide film as described in any one of [1] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: heating the whole layer to obtain a layered product with a residual solvent content of 5% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 5: A step of holding both ends of the self-supporting film, and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer. [17] A method for producing a multilayer polyimide film as described in any one of [1], [2], [4] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: drying the coating film a2b1 to obtain the coating film a2b2 with a residual solvent content of 5-40% by mass on the basis of the whole layer; 5: the step of applying the polyimide solution or polyimide precursor solution for layer formation (a) on the coating film a2b2 to obtain the coating film a2b2a1; 6: A step of heating the entire layer to obtain a layered body having a residual solvent amount based on the entire layer of 0.5 mass % or less. [18] A method for producing a multilayer polyimide film as described in any one of [1], [2], [4] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: drying the coating film a2b1 to obtain the coating film a2b2 with a residual solvent content of 5-40% by mass on the basis of the whole layer; 5: the step of applying the polyimide solution or polyimide precursor solution for layer formation (a) on the coating film a2b2 to obtain the coating film a2b2a1; 6: heating the whole layer to obtain a layered product with a residual solvent content of 8% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 7: A step of holding both ends of the self-supporting film and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer.

The present invention may further include the following configurations. [19] A method for producing a multilayer polyimide film as described in any one of [1], [3] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: within 100 seconds after the coating film a1b1 is made, the polyimide solution or the polyimide precursor solution for layer (c) formation is applied to the coating film a1b1 to obtain the coating film a1b1c1 The step of; 4: A step of heating the entire layer to obtain a layered body having a residual solvent content of 0.5 mass % or less based on the entire layer. [20] A method for producing a multilayer polyimide film as described in any one of [1], [3] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: within 100 seconds after the coating film a1b1 is made, the polyimide solution or the polyimide precursor solution for layer (c) formation is applied to the coating film a1b1 to obtain the coating film a1b1c1 The step of; 4: heating the whole layer to obtain a layered product with a residual solvent content of 8% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 5: A step of holding both ends of the self-supporting film, and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer. [21] A method for producing a multilayer polyimide film according to any one of [1], [3] to [8], which at least comprises: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: drying the coating film a2b1 to obtain the coating film a2b2 with a residual solvent content of 5-40% by mass on the basis of the whole layer; 5: the step of coating the polyimide solution or polyimide precursor solution for layer formation (c) on the coating film a2b2 to obtain the coating film a2b2c1; 6: A step of heating the entire layer to obtain a layered body having a residual solvent amount based on the entire layer of 0.5 mass % or less. [22] A method for producing a multilayer polyimide film as described in any one of [1], [3] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: drying the coating film a2b1 to obtain the coating film a2b2 with a residual solvent content of 5-40% by mass on the basis of the whole layer; 5: the step of coating the polyimide solution or polyimide precursor solution for layer formation (c) on the coating film a2b2 to obtain the coating film a2b2c1; 6: heating the whole layer to obtain a layered product with a residual solvent content of 8% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 7: A step of holding both ends of the self-supporting film and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer.

The present invention may further include the following configurations. [23] A method for producing a multilayer polyimide film as described in any one of [1], [2], [4] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: heating the entire layer to obtain a coating film (a1b1)2 with a residual solvent content of 5% by mass or more and 40% by mass based on the entire layer; 4: the step of applying the polyimide solution or polyimide precursor solution for layer formation (a) on the coating film (a1b1) 2 to obtain the coating film (a1b1) 2a1; 5: A step of heating the entire layer to obtain a layered body having a residual solvent content of 0.5 mass % or less based on the entire layer. [24] A method for producing a multilayer polyimide film as described in any one of [1], [2], [4] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: heating the entire layer to obtain a coating film (a1b1)2 with a residual solvent content of 5% by mass or more and 40% by mass based on the entire layer; 4: the step of applying the polyimide solution or polyimide precursor solution for layer formation (a) on the coating film (a1b1) 2 to obtain the coating film (a1b1) 2a1; 5: heating the entire layer to obtain a layered product with a residual solvent content of 8% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 6: A step of holding both ends of the self-supporting film and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer. [25] A method for producing a multilayer polyimide film as described in any one of [1], [3] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: heating the entire layer to obtain a coating film (a1b1)2 with a residual solvent content of 5% by mass or more and 40% by mass based on the entire layer; 4: the step of applying the polyimide solution or polyimide precursor solution for layer formation (c) on the coating film (a1b1) 2 to obtain the coating film (a1b1) 2c1; 5: A step of heating the entire layer to obtain a layered body having a residual solvent content of 0.5 mass % or less based on the entire layer. [26] A method for producing a multilayer polyimide film as described in any one of [1], [3] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: within 100 seconds after the coating film a1 is made, the (b) polyimide solution or polyimide precursor solution for layer formation is coated on the coating film a1 to obtain the coating film a1b1 The step of; 3: heating the entire layer to obtain a coating film (a1b1)2 with a residual solvent content of 5% by mass or more and 40% by mass based on the entire layer; 4: the step of applying the polyimide solution or polyimide precursor solution for layer formation (c) on the coating film (a1b1) 2 to obtain the coating film (a1b1) 2c1; 5: heating the entire layer to obtain a layered product with a residual solvent content of 8% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 6: A step of holding both ends of the self-supporting film and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer.

The present invention may further include the following configurations. [27] A method for producing a multilayer polyimide film as described in any one of [1], [2], [4] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: within 100 seconds after the coating film a2b1 is made, the polyimide solution or polyimide precursor solution for layer (a) formation is applied to the coating film a2b1 to obtain the coating film a2b1a1 The step of; 5: A step of heating the entire layer to obtain a layered body having a residual solvent content of 0.5 mass % or less based on the entire layer. [28] A method for producing a multilayer polyimide film as described in any one of [1], [2], [4] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: within 100 seconds after the coating film a2b1 is made, the polyimide solution or polyimide precursor solution for layer (a) formation is applied to the coating film a2b1 to obtain the coating film a2b1a1 The step of; 5: heating the entire layer to obtain a layered product with a residual solvent content of 8% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 6: A step of holding both ends of the self-supporting film and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer. [29] A method for producing a multilayer polyimide film as described in any one of [1], [3] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: within 100 seconds after the coating film a2b1 is made, the polyimide solution or the polyimide precursor solution for layer formation (c) is coated on the coating film a2b1 to obtain the coating film a2b1c1 The step of; 5: A step of heating the entire layer to obtain a layered body having a residual solvent content of 0.5 mass % or less based on the entire layer. [30] A method for producing a multilayer polyimide film as described in any one of [1], [3] to [8], comprising at least: 1: the step of coating (a) the polyimide solution or polyimide precursor solution for layer formation on the temporary support to obtain the coating film a1; 2: the step of drying the coating film a1 to obtain the coating film a2 with a residual solvent content of 5-40% by mass; 3: the step of applying the polyimide solution or polyimide precursor solution for layer formation (b) on the coating film a2 to obtain the coating film a2b1; 4: within 100 seconds after the coating film a2b1 is made, the polyimide solution or the polyimide precursor solution for layer formation (c) is coated on the coating film a2b1 to obtain the coating film a2b1c1 The step of; 5: heating the entire layer to obtain a layered product with a residual solvent content of 8% by mass or more and 40% by mass, peeling off the temporary support to obtain a self-supporting film; 6: A step of holding both ends of the self-supporting film and further heating to obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer. [31] A method for producing a multilayer polyimide film, characterized by repeating 1 and 2 in the aforementioned [11] to [30] to form five or more odd-numbered layers. [32] The multilayer polyimide film according to [1] to [6], wherein the thickness of the (a) layer is 25% or less of the total thickness of the film; however, when there are multiple (a) layers (a) The total thickness of the layers is 1% or more of the total thickness of the film, preferably 2% or more, more preferably 4% or more, and 25% or less, preferably 13% or less, and further preferably 7% or less. [33] The multilayer polyimide film according to [3] to [6], wherein the sum of the thickness of the layer (a) and the thickness of the layer (c) is 25% or less of the total thickness of the film. [34] A method for producing a multilayer polyimide film according to any one of [1] to [8], [22], and [23], which at least comprises: forming a polyimide film for layer (a) Imide solution or polyimide precursor solution and (b) polyimide solution or polyimide precursor solution for layer formation are simultaneously coated on the temporary support, and then the whole layer is heated to obtain a full layer. The step of the layered body in which the residual solvent amount based on the layer is 0.5 mass % or less. [35] A method for producing a multilayer polyimide film according to any one of [1] to [8], [32], and [33], which at least comprises: forming a polymer for layer (a) Imide solution or polyimide precursor solution and (b) polyimide solution or polyimide precursor solution for layer formation are simultaneously coated on the temporary support, and then the whole layer is heated to obtain a full layer. The layered product with a residual solvent content of 8% by mass or more and 40% by mass on the basis of the layer is peeled off from the temporary support, and after forming a self-supporting film, both ends of the self-supporting film are held and heated, and further The step of obtaining a thin film with a residual solvent content of 0.5 mass % or less based on the whole layer. [36] A method for producing a multilayer polyimide film according to any one of [3] to [8], [32], and [33], which at least comprises: a polymer for forming the (a) layer. Imide solution or polyimide precursor solution, and (b) polyimide solution or polyimide precursor solution for layer formation, (c) polyimide solution or polyimide precursor solution for layer formation After the imine precursor solution is simultaneously applied on the temporary support, the entire layer is heated to obtain a layered body having a residual solvent content of 0.5 mass % or less on the basis of the entire layer. [37] A method for producing a multilayer polyimide film according to any one of [3] to [8], [32], and [33], which at least comprises: forming a polymer for layer (a) Imide solution or polyimide precursor solution, and (b) polyimide solution or polyimide precursor solution for layer formation, (c) polyimide solution or polyimide precursor solution for layer formation After the imine precursor solution is simultaneously coated on the temporary support, the whole layer is heated to obtain a layered body with a residual solvent content of 8% by mass or more and 40% by mass based on the whole layer, and then peeled off from the temporary support body. After the supportable film, both ends of the self-supporting film are held and heated to further obtain a film with a residual solvent content of 0.5 mass % or less on the basis of the whole layer. [38] The method for producing a multilayer polyimide film according to any one of [11] to [37], wherein the temporary support contacts the polyimide solution or the polyimide precursor solution on the surface 10 The point average roughness Rz is 20 nm or more. [Effect of invention]

The polyimide composition of the layer (b) in the present invention has a low CTE by containing an inorganic filler. Furthermore, when an inorganic filler having a large refractive index difference with the resin is used, it becomes a white film with high opacity. However, compared with resins without adding inorganic fillers, the CTE is reduced by 5 ppm/°C or more, and the polyimide composition is obtained by adding inorganic fillers, and the inorganic fillers are added at a level with sufficient shielding properties. The polyimide composition has a strong tendency to become brittle, and it may be extremely difficult to manufacture a long continuous film at an industrial level. In the present invention, the inorganic filler in the outer layer is reduced by combining with the polyimide composition of the (a) layer with a small content of the inorganic filler, and more preferably combining with the polyimide composition of the (c) layer and forming multiple layers. And increase the inorganic filler in the inner layer to achieve the overall balance of the film's physical properties, and at the same time achieve a transparent heat-resistant film that can be manufactured at an industrial production level. The polyimide film is obtained by coating a polyimide solution or a polyimide precursor solution on a support, drying it, and performing a chemical reaction as required. The present invention can form a transition layer of slanted composition between the coated layers by applying a solution of the various components to the next layer of each component before drying the previously coated layer. The transition layer can also be formed by repeating coating for each component and drying until it loses fluidity until it becomes semi-solid to form a multi-layer structure, followed by final heating after forming the necessary layers The steps of drying and chemical reactions required to obtain a solid film are performed. Due to the chemical stability of polyimide, for example, even if the first polyimide composition layer is coated with a second polyimide solution of different composition (or the same chemical composition) or a polyimide precursor solution and obtain a solid polyimide film by heating and drying or catalytic action, etc., and no chemical bond is formed between the first polyimide layer and the second polyimide layer, so the bonding strength of the interface is Weak, only films that are easy to peel between layers can be obtained. However, as in the present invention, the operation of applying the second polyimide composition layer is repeated in an undried state or in a semi-dried state of the previously applied layer (the first polyimide composition layer). , the solvent concentration of the first coating part is low, and the solvent concentration of the latter coating part is high, so the diffusion of the solvent across the interface occurs due to the concentration gradient, and the dissolved polyimide also moves with the solvent. Therefore, microscopic flow mixing occurs near the interface, forming an extremely thin transition layer with a tilted chemical composition. The transition layer can buffer the mismatch of stress or the like between layers with different physical properties, and at the same time, can show the strong bonding strength between the layers, so as to obtain a multilayer film with good balance of stable properties.

[Form for carrying out the invention]

The multilayer polyimide film of the present invention has a thickness of 3 μm or more and 120 μm or less. From the viewpoint of improving mechanical properties, the thickness is preferably 4 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more. Moreover, 100 micrometers or less is preferable in terms of transparency becoming favorable, 80 micrometers or less are more preferable, and 60 micrometers or less are still more preferable.

The multi-layer polyimide film of the present invention has a yellowness index of 5 or less. From the viewpoint of improving transparency, it is preferably 4 or less, more preferably 3.5 or less, and still more preferably 3 or less. The lower limit is not particularly limited because the yellowness index is preferably lower, but industrially, it may be 0.1 or more, or 0.2 or more.

The multi-layer polyimide film of the present invention preferably has a linear expansion coefficient of 50 ppm/°C or less. More preferably, it is 45 ppm/°C or less, and still more preferably 40 ppm/°C or less. The lower limit is not particularly limited, but industrially, 1 ppm/°C or more is sufficient, and 5 ppm/°C or more may be sufficient.

The total light transmittance of the multilayer polyimide film of the present invention is preferably above 86%. From the viewpoint of improving transparency, it is preferably 87% or more, more preferably 88% or more, and still more preferably 89% or more. The upper limit is not particularly limited, but industrially, it may be 99% or less, or 98% or less.

The present invention uses at least two polyimide compositions. One polyimide composition contains at least a polyimide resin and an inorganic filler, and the other polyimide composition contains a polyimide resin, and the content of the inorganic filler is optional. The polyimide solution or the polyimide precursor solution in the present invention contains at least a polyimide resin or a polyimide precursor and a solvent. When a layer to which an inorganic filler is further added is formed, a solution in which the inorganic filler is dispersed in advance is used. Polyimide resins (hereinafter also referred to only as polyimide) are generally polymers obtained by polycondensation of tetracarboxylic anhydride and diamine.

As the polyimide preferably used in the present invention, a polyimide obtained by polycondensation of the following tetracarboxylic anhydride and diamine can be exemplified: Acid anhydrides, and diamines containing 70% by mass or more of diamines having an amide bond in the molecule; or polyimides obtained by polycondensation of the following tetracarboxylic anhydrides and diamines: containing 70% by mass or more of lipids The tetracarboxylic anhydride of a cyclic tetracarboxylic anhydride, and the diamine containing 70 mass % or more of diamines which have a trifluoromethyl group in a molecule|numerator. Moreover, as the polyimide preferably used in the present invention, the polyimide obtained from the following tetracarboxylic anhydride and diamine can be exemplified: tetracarboxylic anhydride containing 70% by mass or more of aromatic tetracarboxylic anhydride, with a diamine containing at least 70% by mass or more of a sulfur atom in the molecule; or a polyimide obtained by polycondensation of the following tetracarboxylic anhydride and diamine: The tetracarboxylic anhydride of fluoromethyl tetracarboxylic acid, and the diamine containing 70 mass % or more of diamines which have a trifluoromethyl group in a molecule|numerator at least.

As the alicyclic tetracarboxylic 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'-bicyclohexanetetracarboxylic 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]oct-7-ene-2,3, 5,6-Tetracarboxylic acid, Tetrahydroanthracene-2,3,6,7-tetracarboxylic acid, Tetrahydro-1,4:5,8:9,10-Trimethylanthracene-2,3,6,7- Tetracarboxylic acid, decahydronaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4:5,8-dimethylnaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1, 4-Ethyl-5,8-methylnaphthalene-2,3,6,7-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane -5,5'',6,6''-tetracarboxylic acid (alias "norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5' ',6,6''-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-(methylnorbornane)-5,5' ',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-norbornane-5,5'',6,6''- Tetracarboxylic acid (alias "norbornane-2-spiro-2'-cyclohexanone-6'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid"), Methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbornate Alkane-2-spiro-α-cycloacetone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-ring Butanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cycloheptanone-α'-spiro- 2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclooctanone-α'-spiro-2''-norbornane- 5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclononanone-α'-spiro-2''-norbornane-5,5'',6, 6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclodecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-5,5'',6,6''-tetracarboxylic acid Bornane-2-spiro-α-cycloundecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro- α-Cyclododecone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotridecone- α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotetradecone-α'-spiro-2' '-norbornane-5,5' ',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentadecanone-α'-spiro-2''-norbornane-5,5'',6,6'' -Tetracarboxylic acid, norbornane-2-spiro-α-(methylcyclopentanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, Norbornane-2-spiro-α-(methylcyclohexanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid and other tetracarboxylic acids and such anhydrides. Among them, dianhydrides with two acid anhydride structures are preferred, especially 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 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 acid Dianhydride is more preferred, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride is further preferred. In addition, these may be used individually or in combination of 2 or more types.

As the aromatic tetracarboxylic anhydride in the present invention, 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid, 4,4'-oxydiphthalic acid, Bis(1,3-dioxy-1,3-dihydro-2-benzofuran-5-carboxylic acid) 1,4-phenylene, bis(1,3-dioxy-1,3-dihydro) -2-benzofuran-5-yl)benzene-1,4-dicarboxylate, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzoate Furan-1,1-diyl)bis(benzene-1,4-diyloxy)]diphenyl-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3-Oxygen-1,3-dihydro-2-benzofuran-1,1-diyl)bis(toluene-2,5-diyloxy)]diphenyl-1 ,2-dicarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(1,4-xylene-2,5 -diyloxy)]diphenyl-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)]diphenyl-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxygen -1,3-Dihydro-2-benzofuran-1,1-diyl)bis(naphthalene-1,4-diyloxy)]diphenyl-1,2-dicarboxylic acid, 4,4'- [4,4'-(3H-2,1-benzoxathiole-1,1-dioxide-3,3-diyl)bis(benzene-1,4-diyloxy) ] Diphenyl-1,2-dicarboxylic acid, 4,4'-benzophenone tetracarboxylic acid, 4,4'-[(3H-2,1-benzoxathioate-1,1-dioxide- 3,3-Diyl)bis(toluene-2,5-diyloxy)]diphenyl-1,2-dicarboxylic acid, 4,4'-[(3H-2,1-benzooxythiol- 1,1-Dioxide-3,3-diyl)bis(1,4-xylene-2,5-diyloxy)]diphenyl-1,2-dicarboxylic acid, 4,4'-[ 4,4'-(3H-2,1-benzooxythiol-1,1-dioxide-3,3-diyl)bis(4-isopropyl-toluene-2,5-diyloxy) base)] diphenyl-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzooxythiol-1,1-dioxide-3,3-dioxide base)bis(naphthalene-1,4-diyloxy)]diphenyl-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4, 4'-benzophenone tetracarboxylic acid, 3,3',4,4'-diphenyltetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4' - Biphenyltetracarboxylic acid, pyromellitic acid, 4,4'-[spiro(dibenzopyran-9,9'-pyrene)-2,6-diylbis(oxycarbonyl)]diphthalate Formic acid, 4,4'-[spiro(dibenzopyran-9,9'-pyrene)-3,6-diylbis(oxycarbonyl)] Tetracarboxylic acids such as diphthalic acid and acid anhydrides thereof. In addition, aromatic tetracarboxylic acids may be used alone or in combination of two or more.

In the present invention, tricarboxylic acid and dicarboxylic acid can be used in addition to tetracarboxylic anhydride. As tricarboxylic acids, trimellitic acid, 1,2,5-naphthalene tricarboxylic acid, diphenyl ether-3,3',4'-tricarboxylic acid, diphenylene-3,3',4'- Aromatic tricarboxylic acids such as tricarboxylic acid, or hydrogenated products of the above aromatic tricarboxylic acids such as hexahydrotrimellitic acid, ethylene glycol bis-trimellitate, propylene glycol bis-trimellitate, 1,4-butane Alkanediol bis-trimellitate such as glycol bis-trimellitate and polyethylene glycol bis-trimellitate, and monoanhydrides and esters thereof. Among these, monoanhydrides having one acid anhydride structure are preferred, and trimellitic anhydride and hexahydrotrimellitic anhydride are particularly preferred. In addition, these may be used individually or in combination of two or more.

Examples of the dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, and 4,4'-oxydibenzoic acid, or 1,6-ring Hydrogenates of the above aromatic dicarboxylic acids such as hexanedicarboxylic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, Dodecanedioic acid, 2-methylsuccinic acid, and acyl chlorides or esters of these. Among these, aromatic dicarboxylic acids and their hydrides are preferred, and terephthalic acid, 1,6-cyclohexanedicarboxylic acid, and 4,4'-oxydibenzoic acid are particularly preferred. In addition, the dicarboxylic acids may be used alone or in combination of two or more.

As a diamine which has an amide bond in a molecule|numerator in this invention, an aromatic diamine and an alicyclic amine can be mainly used. Examples of aromatic diamines include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2- Propyl]benzene, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl Benzene, 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]thiane, 2,2-bis[4 -(3-Aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoro Propane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 4-amino-N-(4-aminophenyl)benzylamide, 3, 3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2'-trifluoromethyl-4,4'-diphenyl ether Amino diphenyl ether, 3,3'-diamino diphenyl sulfide, 3,4'-diamino diphenyl sulfide, 4,4'-diamino diphenyl sulfide, 3, 3'-diaminodiphenylene, 3,4'-diaminodiphenylene, 4,4'-diaminodiphenylene, 3,3'-diaminodiphenyl Diphenyl, 3,4'-diaminodiphenylene, 4,4'-diaminodiphenylene, 3,3'-diaminobenzophenone, 3,4'-diaminodiphenylmethane Ketone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl Phenylmethane, 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 Alkane, 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-aminobenzene oxy)-3-methylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3-methylphenyl]propane, 2-[4-(4-aminophenoxy) Phenoxy)phenyl]-2-[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy) base)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy) 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)benzene base] ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfene, bis[4-(4-amine bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,3- Bis[4-(4-aminophenoxy)benzyl]benzene, 1,3-bis[4-(3-aminophenoxy)benzyl]benzene, 1,4-bis[4- (3-Aminophenoxy)benzyl]benzene, 4,4'-bis[(3-aminophenoxy)benzyl]benzene, 1,1-bis[4-(3-amino]benzene Phenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl sulfide, 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]sulfenylene, 4,4'-bis[3-(4-aminophenoxy)benzyl]diphenyl ether, 4,4'-bis[3- (3-Aminophenoxy)benzyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone , 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenylene, bis[4-{4-(4-aminophenoxy) Phenoxy}phenyl] benzene, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4- (4-Aminophenoxy)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-cyanobenzene oxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4'-diphenoxybenzophenone, 4,4'-diamino-5, 5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxydi Benzophenone, 4,4'-Diamino-5-phenoxybenzophenone, 3,4'-Diamino-4-phenoxybenzophenone, 3,4'-Diamino -5'-phenoxybenzophenone, 3,3'-diamino-4,4'-dibenzoxybenzophenone, 4,4'-diamino- 5,5'-dibenzoxybenzophenone, 3,4'-diamino-4,5'-dibenzoxybenzophenone, 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-phenoxybenzyl)benzene, 1,4-bis(3- Amino-4-phenoxybenzyl)benzene, 1,3-bis(4-amino-5-phenoxybenzyl)benzene, 1,4-bis(4-amino-5-benzene) Oxybenzyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzyl)benzene benzene, 1,3-bis(4-amino-5-biphenoxybenzyl)benzene, 1,4-bis(4-amino-5-biphenoxybenzyl)benzene, 2,6-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzonitrile, 4,4'-[9H-perylene-9,9-diyl]dianiline (alias "9,9-bis(4-aminophenyl) fluoride"), spiro(dibenzopyran-9,9'- fluoride)-2,6-diylbis(oxycarbonyl)]bis Aniline, 4,4'-[spiro(dibenzopyran-9,9'-pyrene)-2,6-diylbis(oxycarbonyl)]dianiline, 4,4'-[spiro(diphenyl) Pyran-9,9'-Pyridine)-3,6-diylbis(oxycarbonyl)]dianiline, 5-amino-2-(p-aminophenyl)benzoxazole, 6-amine Base-2-(p-aminophenyl)benzoxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzene Acetazole, 2,2'-p-phenylene bis(5-aminobenzoxazole), 2,2'-p-phenylene bis(6-aminobenzoxazole), 1-(5 -aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d : 5,4-d']bis oxazole, 2,6-(4,4'-diaminodiphenyl) benzo[1,2-d: 4,5-d'] bis oxazole, 2 ,6-(3,4'-Diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl) Phenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:5 ,4-d'] two oxazoles, 2,6-(3,3'-diaminodiphenyl) benzo[1,2-d:4,5-d'] two oxazoles, etc. In addition, a part or all of the hydrogen atoms on the aromatic ring of the above-mentioned aromatic diamine may be substituted by a halogen atom, an alkyl group having 1 to 3 carbon atoms, an alkoxy group, or a cyano group, and the aforementioned alkyl group having 1 to 3 carbon atoms may be substituted. Alternatively, some or all of the hydrogen atoms of the alkoxy group may be further substituted with a halogen atom.

Examples of alicyclic diamines include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethyl cyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-propylcyclohexane Butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-secondarybutylcyclohexane, 1,4-diamino-2 -Tertiary butylcyclohexane, 4,4'-methylenebis(2,6-dimethylcyclohexylamine), 9,10-bis(4-aminophenyl)adenine, 2,4 - Dimethyl bis(4-aminophenyl)cyclobutane-1,3-dicarboxylate, etc.

As the inorganic filler used in the polyimide composition in the present invention, fine particles of an electrically insulating inorganic substance are preferable. Moreover, it is preferable that it is microparticles|fine-particles containing an inorganic substance whose linear expansion coefficient is 0-15 ppm/degreeC. More preferably, they are fine particles containing an inorganic substance having a linear expansion coefficient of 1 to 14 ppm/°C, and still more preferably fine particles containing an inorganic substance having a linear expansion coefficient of 2 to 13 ppm/°C. Specifically, metal oxides such as aluminum oxide, silicon oxide, magnesium oxide, zinc oxide, zirconium oxide, tin oxide, titanium oxide, and calcium oxide, metal fluorides such as calcium fluoride, metal sulfides such as zinc sulfide, and sulfuric acid can be used. Metal sulfates such as calcium and barium sulfate, phosphates such as calcium phosphate, fine particles such as alkaline zinc molybdate, alkaline calcium zinc molybdate, molybdenum white, and nitrate. Among them, aluminum oxide, silicon oxide, magnesium oxide, zinc oxide, zirconium oxide, tin oxide, rutile titanium oxide, calcium fluoride, barium sulfate or calcium phosphate are preferred.

In the present invention, when an inorganic filler containing a substance having a high refractive index, preferably an inorganic filler containing a substance having a refractive index of 1.98 or more at a wavelength of 550 nm at 25° C. is used, a film with a very high whiteness can be obtained. From the viewpoint of further improvement of the whiteness, a more preferable refractive index is 1.99 or more, and a further more preferable refractive index is 2.00 or more. The lower limit of the refractive index of such an inorganic filler is not particularly limited, but is preferably 4 or less, more preferably 3 or less. In addition, the present invention can improve the total light transmittance of the film by using an inorganic filler containing a substance having a refractive index of 1.4 or more and less than 1.98 at a wavelength of 550 nm and 25°C, preferably 80% or more, more preferably When it is increased to 85% or more, a so-called colorless and transparent film can be obtained. From the viewpoint of further improvement in colorless transparency, a more preferable refractive index is 1.42 or more and 1.97 or less, and more preferably 1.44 or more and 1.96 or less. In addition, by making the difference of the refractive index of a polyimide resin and an inorganic filler into 0.1 or less, the film whose haze value is 5 or less can be obtained. The lower limit of the average diameter of the particles of the inorganic filler used in the present invention is preferably 10 nm, more preferably 20 nm, and still more preferably 50 nm. Further, the upper limit is preferably 5 μm, more preferably 1.5 μm, and still more preferably 0.3 μm. By using an inorganic filler within a predetermined range, a film with excellent flatness can be obtained. Furthermore, when particles of 0.3 μm or less are used, a film with excellent light transmittance can be obtained in particular.

The multilayer polyimide film of the present invention includes at least two layers of (a) layer and (b) layer. The layer (a) may or may not contain an inorganic filler, and when it is contained, the content of the inorganic filler must be less than 0.05% by mass. Preferably it is 0.04 mass % or less, More preferably, it is 0.03 mass % or less. The layer (b) must contain an inorganic filler, and the content of the inorganic filler is 1 mass % or more and 35 mass % or less. Preferably it is 3 mass % or more and 32 mass % or less, More preferably, it is 6 mass % or more and 28 mass % or less. That is, the layer (a) having a suppressed inorganic filler content and high toughness reinforces the (b) layer that has a large inorganic filler content and a low coefficient of linear expansion but tends to become brittle. The polyimide composition contained in the layer (a) is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass. Moreover, the said polyimide composition contained in the said (b) layer becomes like this. Preferably it is 80 mass % or more, More preferably, it is 90 mass % or more, More preferably, it is 95 mass % or more, Especially preferably, it is 100 mass %. In the case where the (a) layer contains an inorganic filler, the ratio ((b)/(a)) of the inorganic filler content of the (a) layer to the inorganic filler content of the (b) layer ((b)/(a)) is preferably more than 20, more preferably 100 Above, more preferably 500 or more, still more preferably 1000 or more, particularly preferably 1250 or more. Moreover, 10000 or less are preferable, 8000 or less are more preferable, 5000 or less are still more preferable, and 3000 or less are especially preferable.

In the present invention, the multilayer polyimide film is preferably made into a three-layer structure of (a)/(b)/(a). The warpage of the film can be suppressed by making a three-layer structure and symmetric in the thickness direction. In the present invention, the structure of the multilayer polyimide film can be further made into a three-layer structure of (a)/(b)/(c). This structure is basically a structure in which a layer (a) with a small inorganic filler content and a layer (c) sandwich a layer (b) with a large inorganic filler content. Preferably, the inorganic filler content of the (c) layer is set to 0.3 mass % or less, more preferably 0.1 mass % or less, and more preferably substantially 0 mass %, whereby a highly smooth surface can be realized on one side surface of the outer layer of the multilayer film. In the case of the three-layer structure of (a)/(b)/(a), the ratio ((b)/(a)) of the inorganic filler content of (a) to the inorganic filler content of layer (b) is also as described above. In the case of the three-layer structure of (a)/(b)/(c), the ratio ((c)/(a)) of the inorganic filler content of (a) to the inorganic filler content of the (c) layer is preferably less than 1. It is more preferably 0.5 or less, still more preferably 0.2 or less, still more preferably 0.1 or less, and particularly preferably 0.

In addition, the inorganic fillers added to the (a) layer, (b) layer, and (c) layer may be the same inorganic filler or different inorganic fillers. For example, by using inorganic fillers with uniform particle size in the (a) layer or (c) layer of the outer layer, and using inorganic fillers with good transparency in the inner layer (b) layer, the protrusions on the surface of the film can be homogeneous and the film A film with high colorless transparency as a whole.

In addition, the polyimide resins used in the layers (a), (b), and (c) may all be polyimide resins of the same chemical composition, or may be different polyimide resins. For example, the inner layer (b) uses a polyimide resin with a high CTE control effect by adding inorganic fillers, and the outer layers (a) and (c) use a high-toughness polyimide resin. In this way, a thin film having an overall balance can be obtained.

The present invention can also be multi-layered in the form of 4 or more layers, preferably odd-numbered layers, for example: (a) layer or (c) layer/(b) layer/(a) layer or (c) layer/( b) Composition of layer/(a) or (c) layer. Specifically, (a) layer/(b) layer/(a) layer/(b) layer, (a) layer/(b) layer/(c) layer/(b) layer, (c) layer Layer/(b)/(a)/(b) 4-layer structure; (a)/(b)/(a)/(b)/(a), (a) /(b)layer/(a)layer/(b)layer/(c)layer,(a)layer/(b)layer/(c)layer/(b)layer/(a)layer,(a)layer /(b) layer/(c) layer/(b) layer/(c) layer, (c) layer/(b) layer/(a) layer/(b) layer/(c) layer. In addition, you may insert a 4th resin layer (d), a 5th resin layer (e) layer, etc. into arbitrary layers in the range which does not impair the effect of this invention. In addition, depending on the use in a single-sided production device, etc., the roles pursued for the two sides of the corresponding film are different, so the composition or surface roughness of the two sides can be changed. In the case where the present invention has the layer (a) or the layer (c), it is preferably constituted in the following manner: the total thickness of the layer (a) and the layer (c) is preferably 34% or less of the total thickness of the film, more preferably It is 26% or less, more preferably 13% or less, and more preferably 7% or less. In the case of having the (a) layer and the (c) layer, the total thickness of the (a) layer and the (c) layer is preferably 1% or more of the total thickness of the film, more preferably 2% or more, and still more preferably 4%. %above. By setting the thicknesses of the (a) layer and (c) layer within this range, a thin film in which the toughness of the outer layer and the optical properties and low CTE properties of the inner layer are balanced can be obtained.

The present invention preferably exists between layers (a) and (b): a transition layer whose composition continuously changes from the polyimide of the (a) layer to the polyimide of the (b) layer. The upper limit of the thickness of the transition layer is preferably 8% or less of the total thickness of the film, or 3 μm or less, more preferably 3% or less, or 1 μm or less. In addition, the thickness of the transition layer refers to the thickness of the region where the polyimide of the (a) layer and the polyimide of the (b) layer are mixed to form a region that gradually slopes from one side to the other, and (a) of the mixed layer The compositional ratio (mass ratio) of the polyimide of the layer/polyimide of the (b) layer is in the range of 5/95 to 95/5. The thickness of the transition layer can be determined by cutting the film diagonally in the thickness direction and observing the composition distribution of polyimide. The transition layer between layer (b) and layer (c) is also the same.

The multilayer polyimide film of the present invention can be laminated with an inorganic substrate to produce a laminated body. The inorganic substrate may be any plate-shaped one that can be used as a substrate containing inorganic substances, and examples thereof include glass plates, ceramic plates, semiconductor wafers, metals, etc. as the main body, and glass plates, ceramic plates, etc. Plates, semiconductor wafers, and metal composites, which are laminated, those in which these are dispersed, those containing fibers, and the like.

A flexible electronic device can be manufactured by forming an electronic device on the multilayer polyimide film surface of the laminate of the present invention, and then peeling it off from an inorganic substrate.

Next, the manufacturing method for obtaining the multilayer polyimide film of this invention is demonstrated. In the multi-layer polyimide film of the present invention, the polyimide film composed of two layers can be produced on a long and flexible temporary support through the following steps: 1: the step of coating (a) a polyimide solution or a polyimide precursor solution for layer formation; 2: the step of coating (b) the polyimide solution or the polyimide precursor solution for layer formation within 100 seconds after the aforementioned coating; 3: Next, a step of heating for 5 minutes or more and 60 minutes or less until the average residual solvent amount of the whole layer becomes 0.5 mass % or less. Furthermore, the third step can also be divided into two stages and divided into the following two steps: 3': the step of heating the whole layer for a period of 5 minutes to 45 minutes until the residual solvent content of the whole layer becomes 8% by mass to 40% by mass, and then peeled off from the temporary support to obtain a self-supporting film; 4: A step of holding both ends of the self-supporting film and further heating until the residual solvent amount of the entire layer becomes 0.5 mass % or less. By peeling off the temporary support at the stage of the self-supporting film, by-products generated by drying and chemical reaction can be quickly discharged from the film, and the poor physical properties and structure of the front and back can be further reduced.

In addition, when it is used as a thin film of 3 or more layers, it is sufficient to apply the polyimide solution or polyimide precursor solution for (a) layer formation or (c) layer formation again after the above-mentioned 1 and 2. More layers of thin films can be obtained by further repeating the recoating.

In the present invention, as another method of thinning, it can be produced on a long and flexible temporary support through the following steps: 1: the step of coating (a) a polyimide solution or a polyimide precursor solution for layer formation; 2: a step of drying the layer (a) so that the residual solvent content of the layer becomes 5 to 40% by mass; 3: the step of coating the polyimide solution or the polyimide precursor solution for the formation of the (b) layer on the (a) layer; 4: Next, the step of heating for 5 minutes or more and 60 minutes or less until the average residual solvent amount of the whole layer becomes 0.5 mass % or less is preferable. Furthermore, the fourth step can also be divided into two stages and divided into the following two steps: 4': the step of heating the entire layer for a period of 5 minutes to 45 minutes until the residual solvent content of the whole layer becomes 8% by mass to 40% by mass, and then peeled off from the temporary support to obtain a self-supporting film; 5: A step of holding both ends of the self-supporting film, and further heating until the residual solvent amount of the entire layer becomes 0.5 mass % or less. By peeling off the temporary support at the stage of the self-supporting film, by-products generated by drying and chemical reaction can be quickly discharged from the film, and the poor physical properties and structure of the front and back can be further reduced.

In addition, when it is used as a thin film of 3 or more layers, it is sufficient to apply the polyimide solution or polyimide precursor solution for (a) layer formation or (c) layer formation again after the above-mentioned 1 and 2. More layers of films can be obtained by repeated coating.

In the present invention, the temperature is preferably 10°C or higher and 40°C or lower, preferably 15°C or higher and 35°C or lower, and the humidity is 10%RH or higher and 55%RH or lower, preferably 20%RH or higher and 50%RH in the atmosphere or The coating of the polyimide solution or the polyimide precursor solution is carried out on a long and flexible temporary support in an inert gas. As a coating method, the first layer can be coated by a comma coater, bar coater, slot coater, etc., and the second layer can be coated by a die coater, curtain coater, sprayer, or the like. Also, these multiple layers can also be applied practically simultaneously by using a multi-layer die.

The environment of the coating solution is preferably the atmosphere or an inert gas. The inert gas can be interpreted as a gas having a substantially low oxygen concentration, and from an economical point of view, nitrogen gas or carbon dioxide may be used.

The temperature in the coating environment will affect the viscosity of the coating solution and the formation of the thickness of the transition layer when the two coating solutions are mixed with each other at the interface when the two coating solutions are overlapped to form a transition layer. The viscosity of the polyimide solution or polyimide precursor solution of the present invention is particularly preferably adjusted to an appropriate viscosity range in the non-contact coating method after the second layer. Mixing at the interface also helps to properly maintain fluidity in this viscosity range.

When the polyimide solution or polyimide precursor solution is coated, the next layer of polyimide solution or polyimide precursor solution is coated on it within 100 seconds, the coated polyimide solution The viscosity 1 of the amine solution or polyimide precursor solution is preferably not significantly higher than the viscosity 2 of the previously coated polyimide solution or polyimide precursor solution. Specifically, the ratio of viscosity represented by viscosity 1/viscosity 2 is preferably 1.5 or less, more preferably 1.0 or less, and still more preferably 0.8 or less. If it is higher than this, the coating surface below may be dragged in the coating step, which may cause abnormal appearance. In addition, in order to prevent the above-mentioned abnormal appearance, the value of viscosity 2 measured at 25°C using an E-type viscometer is preferably 20 Pa·s or more, more preferably 50 Pa·s or more. If it is lower than this, since fluidity|liquidity is high, it may become a cause of abnormal appearance when superimposing the solution on the top surface. From the viewpoint of workability, the viscosity of the polyimide solution or the polyimide precursor solution is preferably 300 Pa·s or less, more preferably 200 Pa·s or less.

The solvent used in the polyimide solution or polyimide precursor solution is mostly hygroscopic. If the solvent absorbs moisture and the water content of the solvent increases, the solubility of the resin component will decrease, and it will dissolve into the solution. A situation in which the viscosity of a solution increases rapidly. When such a situation occurs after coating, the internal structure of the film becomes non-uniform, and hole-like defects may occur, thereby hindering mechanical properties. In the present invention, it is preferable to limit the humidity of the coating environment to a predetermined range, and to enter the heating and drying step within 100 seconds after the coating is finished.

As the temporary support used in the present invention, glass, metal plate, metal tape, metal cylinder, polymer film, metal foil, etc. can be used. In the present invention, a long and flexible temporary support is preferably used, and films such as polyethylene terephthalate, polyethylene naphthalate, and polyimide can be used as the temporary support. It is one of the preferred aspects to apply a mold release treatment to the surface of the temporary support.

The surface roughness of the temporary support can also be adjusted by performing surface treatment. Surface treatment methods can be used: plasma treatment, corona discharge treatment, wet sandblasting treatment, chemical treatment, and the like. It is also possible to further apply a mold release treatment after the surface treatment.

In the present invention, the polyimide solution or the polyimide precursor solution is preferably coated on the temporary support, dried until the residual solvent content of the coating film becomes 5 to 40% by mass, and then the next layer is applied. It is dried until the residual solvent amount is 40% by mass, and the applied coating liquid is sufficient to lose fluidity and reach a semi-solid dry state. When the residual solvent content of the coating film is 5 mass % or less, when the next solution is applied, the re-swelling of the previously dried coating film becomes inhomogeneous, and the boundary between the two adjacent layers may be disturbed. Therefore, the range of the residual solvent content of 5 to 40 mass % is that the diffusion and movement of the solvent of the coating liquid at the boundary surface can be uniformly performed, and a transition layer of an appropriate thickness can be formed by microscopic flow mixing. In the present invention, after all layers are applied, drying and chemical reactions as required are accelerated by heat treatment. In the case of using a polyimide solution, only drying is required in the sense of removing the solvent, but in the case of using a polyimide precursor solution, both drying and chemical reaction become necessary. Here, the polyimide precursor is preferably in the form of polyimide or polyisoimide. Dehydration condensation is required to convert polyamides into polyimides. The dehydration condensation reaction can be carried out only by heating, but the imidization catalyst can also function as needed. In the case of polyisoimide, it can also be converted from isoimide bonds to imide bonds by heating. In addition, an appropriate catalyst may be used in combination. The residual solvent content of the final multilayer polyimide film is based on the average value of the entire film, and the residual solvent content is preferably 0.5 mass % or less, more preferably 0.2 mass % or less, and still more preferably 0.08 mass % or less . The heating time is preferably 5 minutes or more and 60 minutes or less, more preferably 6 minutes or more and 50 minutes or less, and further preferably 7 minutes or more and 30 minutes or less. By limiting the heating time to a predetermined range, the removal of the solvent and the necessary chemical reaction can be completed, and the thickness of the transition layer can be controlled to an appropriate thickness, and the colorless transparency, mechanical properties, especially elongation at break can be maintained at a high level. When the heating time is short, the formation of the transition layer is slow, and if the heating time is longer than necessary, the coloring of the film becomes stronger, and the elongation at break of the film decreases.

In the present invention, as long as the applied solution can be dried or chemically reacted by heating and can be peeled off from the temporary support due to self-support, it can also be peeled off from the temporary support in the middle of the heating step. More specifically, it is possible to use heating for a time of preferably 5 minutes or more and 45 minutes or less, more preferably 6 minutes or more and 30 minutes or less, and still more preferably 7 minutes or more and 20 minutes or less, until the residual solvent amount of the entire thin film layer is reached. After reaching the range of 5% by mass to 40% by mass, the self-supporting film is peeled off from the temporary support, and the ends of the self-supporting film are held by clipping or poking with a clip, and heating the film. Conveying in the environment, and further heating until the residual solvent amount of the whole layer is preferably 0.5 mass % or less, more preferably 0.2 mass % or less, and further preferably 0.08 mass % or less, thereby obtaining a multi-layer polyimide film step . By peeling off the self-supporting film from the temporary support in the middle of the heating step and continuing to heat it further, the water generated when the solvent is evaporated and the polyimide is converted to polyimide through dehydration and ring closure can be rapidly removed from both sides of the film. After discharging, a film with little difference in physical properties between the inside and the outside can be obtained.

The present invention can also extend the aforementioned self-supporting film. The stretching may be either of the film longitudinal direction (MD direction) and the film width direction (TD), or both. The stretching in the longitudinal direction of the film can be performed using the speed difference between the conveying rollers or the speed difference between the conveying rollers and the both ends being held. The extension in the width direction of the film can be carried out by spreading between the holding clips or needles. Extending and heating can also be performed simultaneously. The stretching ratio can be arbitrarily selected between 1.00 times and 2.5 times. In the present invention, a polymer of a composition that is difficult to stretch (ie, prone to fracture due to stretching) is combined by combining a polyimide that is difficult to stretch alone and a polyimide that is stretchable by making the film into a multilayer structure. Imide also becomes extensible, which can improve mechanical properties. In addition, the volume of the polyimide is reduced in the middle of film formation due to drying or dehydration condensation, and the stretching effect is exhibited even in the state where both ends are held at equal intervals (the stretching ratio is 1.00 times). [Example]

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to the following examples unless the gist of the present invention is exceeded. In addition, each physical property value etc. in a manufacture example and an Example were measured by the following method.

<Thickness measurement of multilayer polyimide film> The thicknesses of the multilayer polyimide films A to F were measured using a micrometer (Millitron 1245D, manufactured by Feinpruf).

<tensile elastic modulus, tensile strength (breaking strength), and breaking elongation> The multilayered polyimide film was cut out in the flow direction (MD direction) and the width direction (TD direction) at the time of coating, respectively, and a rectangle of 100 mm×10 mm was cut out to be a test piece. Using a tensile testing machine (manufactured by Shimadzu Corporation, Autograph(R) model name AG-5000A), under the conditions of a tensile speed of 50 mm/min and a distance between the clamps of 40 mm, the tensile elastic modulus was obtained for the MD direction and the TD direction, respectively. The average value of the measured values in the MD direction and the TD direction was obtained from the number, tensile strength and elongation at break.

<Coefficient of Linear Expansion (CTE)> In the flow direction (MD direction) and width direction (TD direction) of the multilayer polyimide film at the time of coating, the stretch ratio was measured under the following conditions. The expansion ratio/temperature at the interval of °C was measured up to 300 °C, the average value of all the measured values was calculated as CTE, and the average value of the measured values in the MD direction and the TD direction was further obtained. Machine name: TMA4000S manufactured by MAC Science Corporation Sample length: 20mm Sample width: 2mm Heating start temperature: 25°C Heating end temperature: 300°C Heating rate: 5℃/min Gas environment: Argon

<Transition layer thickness> A chamfered section of the film was made by SAICAS DN-20S type (DAIPLA WINTES), and then the chamfered section was subjected to a micro-IRCary 620 FTIR (Agilent) using a micro-ATR using germanium crystals (incidence angle 30°). The spectrum is obtained by the method, and the inclination of the composition is calculated from the increase and decrease of the characteristic peaks of the layers (a) and (b), and the calibration curve obtained in advance by mass ratio conversion, and the composition of the layer (a) / (b) The thickness of the layer composition ratio in the range of 5/95 mass ratio to 95/5 mass ratio is taken as the thickness of the transition layer.

＜Haze＞ The haze of the film was measured using HAZEMETER (NDH5000, manufactured by Nippon Denshoku Corporation). A D65 lamp was used as the light source. Moreover, the same measurement was performed three times, and the arithmetic mean value was used.

<Total light transmittance> The total light transmittance (TT) of the film was measured using HAZEMETER (NDH5000, manufactured by Nippon Denshoku Corporation). A D65 lamp was used as the light source. Moreover, the same measurement was performed three times, and the arithmetic mean value was used.

＜Yellow index＞ Using a colorimeter (ZE6000, manufactured by Nippon Denshoku Co., Ltd.) and a C2 light source, the tristimulus value XYZ value of the film was measured according to ASTM D1925, and the yellowness index (YI) was calculated by the following formula. Moreover, the same measurement was performed three times, and the arithmetic mean value was used. YI=100×(1.28X－1.06Z)/Y

＜Warpage of film＞ A film cut into a square with a size of 100 mm × 100 mm was used as a test piece, and the test piece was placed in a concave shape at room temperature on a flat surface, and the distances from the four corners to the flat surface (h1rt, h2rt, h3rt, h4rt) were measured. : unit mm), and the average value was taken as the warpage amount (mm).

<Coefficient of Static Friction> According to JIS K-7125, using a tensile tester (TENSILON RTG-1210 manufactured by A&D Corporation), in an environment of 23°C and 65%RH, the surface of the (a) layer of the film and the polyparaphenylene were obtained. Coefficient of static friction of ethylene dicarboxylate film (PET film) "COSMOSHINE (registered trademark) A4100 (manufactured by Toyobo Co., Ltd., without surface treatment, film 1 in Table 2)" when the inner surface of the roll is joined. In addition, the weight of the reel (spindle) after winding the upper film was 1.5 kg, and the size of the bottom area of the reel was 39.7 mm ² . In addition, the tensile speed at the time of friction measurement was 200 mm/min.

<10-point average roughness Rz> For the measurement of the surface roughness, a scanning probe microscope E-Sweep (manufactured by SII Corporation) was used, and the surface morphology was observed by the DFM mode. The cantilever system used DF20 (supplied by SII Corporation). The point 1 cm away from the end of the test piece (100 mm × 100 mm) of the film is set as the first point, and the length from the first point is 1/20 of the film width in the direction at right angles to the film conveying direction. Select 10 points at intervals, and observe the 5μm square of each point selected above. The number of X data and the number of Y data are respectively set to 512 (accumulation times). The obtained data were obtained by calculating the 10-point average roughness (Rz) using the attached software after performing tilt correction. The tilt correction uses the secondary tilt correction (Auto2) performed by the attached software.

[Production Example 1: Production of Polyamic Acid (PAA) Solution A] After nitrogen substitution was carried out in a reaction vessel equipped with a nitrogen introduction tube, a reflux tube, and a stirring bar, 22.73 parts by mass of 4,4'-diaminobenzylaminobenzene (DABAN) was added to 201.1 parts by mass of N,N -Dimethylacetamide (DMAc) was dissolved, and 19.32 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) was added in batches in a solid state, Stir at room temperature for 24 hours. Thereafter, 173.1 parts by mass of DMAc was added and diluted to obtain a polyamic acid solution A of 10 mass % of NV (solid content) and a reduced viscosity of 3.10 dl/g.

[Production Example 2: Production of Polyamic Acid (PAA) Solution B] After nitrogen substitution was carried out in a reaction vessel equipped with a nitrogen introduction tube, a reflux tube, and a stirring bar, 32.02 parts by mass of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB ) was dissolved in 279.9 parts by mass of N,N-dimethylacetamide (DMAc), followed by 9.81 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 15.51 parts by mass The 4,4'-oxydiphthalic dianhydride (ODPA) was added in batches in a solid state, and 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 3: Production of Polyimide (PI) Solution C] 32.02 parts by mass of 2,2'-bis(trifluoromethyl)-4,4'-bis was added to a reaction vessel equipped with a nitrogen gas introduction tube, a Dean-Stark tube, a reflux tube, a thermometer, and a stirring bar while introducing nitrogen gas. Amino biphenyl (TFMB) and 230 parts by mass of N,N-dimethylacetamide (DMAc) were completely dissolved, and then 44.42 parts by mass of 4,4'-(2,2-hexafluoro) After isopropylidene)diphthalic dianhydride (6FDA) was added in batches in a solid state, it was stirred at room temperature for 24 hours. Thereafter, a polyamic acid solution Caa having a solid content of 25% by mass and a reduced viscosity of 1.10 dl/g was obtained. Next, after adding 204 mass parts of DMAc to the obtained polyamic acid solution Caa and diluting so that the concentration of polyamic acid might become 15 mass %, 1.3 mass parts of isoquinolines were added as an imidization accelerator. Next, 12.25 parts by mass of acetic anhydride was slowly dropped as an imidizing agent while stirring the polyamic acid solution Caa. Then, stirring was continued for 24 hours, and chemical imidization reaction was performed, and the polyimide solution Cpi was obtained. Next, when 100 parts by mass of the obtained polyimide solution Cpi was moved to a reaction vessel equipped with a stirring device and a stirrer, and 150 parts by mass of methanol was slowly dropped while stirring, the precipitation of powdery solid was confirmed. Thereafter, the powder of the content of the reaction vessel was dehydrated and filtered, washed with methanol, vacuum-dried at 50° C. for 24 hours, and further heated at 260° C. for 5 hours to obtain polyimide powder Cpd. Polyimide solution C was obtained by dissolving 20 parts by mass of the obtained polyimide powder Cpd in 80 parts by mass of DMAc.

[Production Example 4: Production of Polyimide (PI) Solution D] 120.5 parts by mass of 4,4'-diaminodiphenylene (4,4'-DDS) was added to a reaction vessel equipped with a nitrogen gas introduction tube, a Dean-Stark tube, a reflux tube, a thermometer, and a stirring bar while introducing nitrogen gas. , 51.6 parts by mass of 3,3'-diaminodiphenylene (3,3'-DDS), and 500 parts by mass of γ-butyrolactone (GBL). Next, 217.1 parts by mass of 4,4'-oxydiphthalic dianhydride (ODPA), 223 parts by mass of GBL, and 260 parts by mass of toluene were added at room temperature, and the temperature was raised to an internal temperature of 160° C. Heating and refluxing was performed at °C for 1 hour to carry out imidization. After the imidization was completed, the temperature was raised to 180°C, and the reaction was continued while extracting toluene. After 12 hours of reaction, the oil bath was removed, the temperature was returned to room temperature, and GBL was added so that the solid content might be 20% by mass concentration, and a polyimide solution D was obtained.

[Production Example 5: Production of Polyimide (PI) Solution E] In a reaction vessel equipped with a nitrogen introduction tube, a reflux tube, and a stirring bar, 161 parts by mass of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) was mixed with nitrogen in a nitrogen atmosphere. After 1090 parts by mass of N-methyl-2-pyrrolidone was mixed and stirred to dissolve, 112 parts by mass of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA) was added to a solid at room temperature. It was added in portions while stirring at room temperature for 12 hours. Next, 400 parts by mass of xylene was added as an azeotropic solvent, the temperature was raised to 180° C., and the reaction was performed for 3 hours, and the azeotropic produced water was separated. The completion of the outflow of water was confirmed, and the polyimide solution E was obtained by removing xylene while raising the temperature to 190° C. for 1 hour.

[Production Example 6: Production of Polyamic Acid (PAA) Solution F)] After nitrogen substitution was carried out in a reaction vessel equipped with a nitrogen gas introduction tube, a reflux tube, and a stirring bar, 11.36 parts by mass of 4,4'-diaminobenzylaminobenzene (DABAN) and 16.01 parts by mass of 2,2 '-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) and 201.1 parts by mass of N,N-dimethylacetamide (DMAc) were completely dissolved. Next, 19.32 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) was added in batches in a solid state, followed by stirring at room temperature for 24 hours. Thereafter, 173.1 parts by mass of DMAc was added and diluted to obtain a polyamic acid solution F of 10 mass % of NV (solid content) and a reduced viscosity of 3.10 dl/g.

[Production Example 7 (Production of Polyamic Acid Solution G)] After nitrogen substitution was carried out in a reaction vessel equipped with a nitrogen introduction tube, a reflux tube, and a stirring bar, 22.0 parts by mass of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 252.1 parts by mass of N,N were added. -Dimethylacetamide (DMAc) was completely dissolved, and then 22.0 parts by mass of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added in batches in a solid state Then, it was stirred at room temperature for 24 hours. Then, the solid content (NV) of 11 mass % and the reduction viscosity of 3.5 dl/g of polyamic acid solution G were obtained.

[Production Example 8 (Production of Polyamic Acid Solution H)] After nitrogen substitution was carried out in a reaction vessel equipped with a nitrogen introduction tube, a reflux tube, and a stirring bar, 25.6 parts by mass of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 305.6 parts by mass of N,N were added. - Dimethylacetamide (DMAc) and let it dissolve completely. Next, 9.42 parts by mass of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 7.45 parts by mass of 4,4'-oxydiphthalic anhydride (ODPA), 4.71 parts by mass Portions of 1,2,3,4,-cyclobutanetetracarboxylic anhydride (CBDA) were added in portions in a solid state, followed by stirring at room temperature for 24 hours. Thereafter, a polyamic acid solution H having a solid content (NV) of 11% by mass and a reduced viscosity of 3.5 dl/g was obtained.

The polyimide solutions and polyimide solutions (polyimide precursor solutions) obtained in the production examples were thinned by the following methods, and optical properties and mechanical properties were measured. The results are shown in Table 1. (Method for obtaining a film for measuring physical properties alone) A bar coater was used to coat a polyimide solution or a polyamide solution with a final thickness of 25±2 μm on an area of about 20 cm square in the center of a 30 cm glass plate, and a dry nitrogen gas was quietly flowing in the area. After heating at 100°C for 30 minutes in an inert oven, and after confirming that the residual solvent content of the coating film was 40% by mass or less, it was heated at 300°C for 20 minutes in a furnace replaced with dry nitrogen. Next, it was taken out from the furnace, and one end of the dried coating film (film) was lifted up with a utility knife, and the film was carefully peeled off from the glass to obtain a film.

(Example 1) Table 3 was added to the polyamic acid solution A obtained in Production Example 1 so that silica (slip agent) was 0.02 mass % with respect to the total polymer solid content in the polyamic acid solution. Inorganic filler No. 2 shown: a dispersion prepared by dispersing colloidal silica in dimethylacetamide (“SNOWTEX (registered trademark) DMAC-ST-ZL” manufactured by Nissan Chemical Industry Co., Ltd.) and uniformly dispersing it. In the polyimide solution C obtained in Production Example 3, inorganic filler No. 1 shown in Table 3: calcium fluoride particles with an average particle diameter of 0.2 μm, manufactured by STELLA CHEMIFA Co., Ltd., were first dispersed in DMAC using an attritor. Then, it was added so that it might become 20 mass % with respect to the polymer solid content total amount in a polyimide solution, and it mixed and stirred uniformly, and it was made to disperse|distribute. Each of the prepared solutions containing inorganic fillers was viscous adjusted by adding DMAc and diluting. In an atmosphere adjusted to 25°C and 45% RH, the film was processed using a roll-to-roll type notch wheel coater, multiple die coaters, and a continuous drying furnace and heat treatment furnace. manufacture. First, the polyamic acid solution A in which the aforementioned inorganic filler No. 2 was dispersed was applied on the film 2 (see Table 2) of the temporary support using a corner wheel coater so that the final film thickness would be 1 μm, as the first Floor. Next, 10 seconds later, the polyimide solution C in which the inorganic filler No. 1 was dispersed was applied by a die coater so that the final film thickness would be 23 μm on the first layer that was applied earlier to serve as the second layer. . Furthermore, 10 seconds after the second layer was applied, the same polyamic acid solution A with inorganic filler No. 2 dispersed as that of the first layer was applied by a die coater so that the final film thickness was 1 μm as the third layer. (This coating method is hereinafter referred to as "sequential wet/wet method"). After coating the third layer, it was dried in a continuous drying furnace at 110° C. for 10 minutes to obtain a self-supporting film with a residual solvent content of 31% by mass. This self-supporting film is peeled off from the film 2 serving as a support, and the end of the film is held by inserting the needles through a pin tenter having a pin card piece equipped with needles, so that the film does not break and is maintained in a stable manner. The needle-comb piece interval was adjusted and conveyed so as not to cause unnecessary sagging, and the imidization reaction was carried out by heating under the conditions of 3 minutes at 200°C, 3 minutes at 250°C, and 6 minutes at 300°C. After that, the film was cooled to room temperature for 2 minutes, and the film with poor flatness at both ends was cut out with a cutter and wound into a roll to obtain a roll of the film (actual 1) with a width of 580 mm and a length of 100 m. Table 4 shows the evaluation results of the obtained film (Example 1).

(Examples 2 to 38) (Comparative Examples 1 to 11) Next, in the same manner as in Example 1, a film was produced and evaluated by combining the polyamide solution or polyimide solution shown in Table 1, the temporary support shown in Table 2, and the inorganic filler shown in Table 3. . The results are shown in Tables 4 to 11. In addition, in the comparative example, the case of a single layer was die coating. Compared with Example 3, Comparative Example 1 and Comparative Example 2 showed that the CTE was high. In addition, since the film of Comparative Example 1 was poor in sliding properties, it was difficult to suppress the winding wrinkles when the film was wound at 14 m. Therefore, the film was cut and recovered as a roll having a width of 580 mm and a length of 14 m.

In Examples 1 to 8 and 12 to 16, high light transmittance was obtained, and the haze, which represents the haze of the film, was also low. However, in Examples 9 to 11, which used inorganic fillers with high refractive index, the haze was low. increase, the transmittance decreases. However, the yellowness index suppression was low and these films were shown to have a high degree of whiteness. That is, although these are not transparent, it is also a colorless film high.

In Examples 17 to 22, the same polyimide resin components were used in the layers (a), (b), and (c), and the content of the inorganic filler in each layer was changed. Comparative Examples 3 to 8 correspond to Examples 17 to 22, and are produced so that only the (b) layer has the same film thickness. Examples 17 to 22 show low CET compared to the films of the same resin composition without the addition of inorganic fillers shown in Table 1 and produced on a laboratory scale, showing the effect of adding inorganic fillers. However, with respect to Comparative Examples 3 to 8 without the layers (a) and (c), film breakage occurred when the self-supporting film was peeled off from the temporary support base, so that the film holding by needles could not be performed, and the film could not be held. A film sufficient for evaluation was obtained. In addition, in Examples 17-22, the resin composition of each layer was the same, so the thickness of the transition layer could not be measured.

(Examples 23 to 25) Table 3 was added to the polyamic acid solution A obtained in Production Example 1 so that silica (slip agent) was 0.02 mass % with respect to the total polymer solid content in the polyamic acid solution. Inorganic filler No. 2 shown: a dispersion prepared by dispersing colloidal silica in dimethylacetamide (“SNOWTEX (registered trademark) DMAC-ST-ZL” manufactured by Nissan Chemical Industry Co., Ltd.) and uniformly dispersing it. In the polyimide solution C obtained in Production Example 3, inorganic filler No. 3 shown in Table 3: Silicon dioxide particles SEAHOSTAR (registered trademark) S150 with an average particle diameter of 1.5 μm manufactured by Nippon Shokubai Co., Ltd. After dispersing in DMAC by an attritor, it was added so that it might become 25 mass % with respect to the total amount of polymer solid content in a polyimide solution, and it mixed and stirred uniformly, and made it disperse|distribute.

In an atmosphere adjusted to 25°C and 45%RH, using a roll-to-roll cutaway wheel coater, multiple die coaters, a continuous drying furnace, and a continuous heat treatment furnace, the inorganic fillers described above were dispersed. The polyamic acid solution A of No. 2 was applied on the non-slip surface of the film 2 (see Table 2) of the temporary support so that the final film thickness would be 3 μm. Next, it heated at 110 degreeC for 5 minutes as a primary heating by a continuous dryer, and produced the semi-drying film whose residual solvent amount is 18 mass %, and wound up into a roll shape together with a temporary support body. This semi-dry film is called GF (green film). The obtained roll was set in the above-mentioned apparatus again, the above-mentioned semi-dry film was rolled out together with the temporary support, and the polyimide in which the above-mentioned inorganic filler No. 3 was dispersed was applied by a die coater so that the final film thickness would be 19 μm. After the solution C was applied on the semi-dried film, it was dried at 110° C. for 10 minutes. After drying, the residual solvent amount was 23% by mass, and the self-supporting film was peeled off from the film 2 as a support, and the film was held by inserting the needles through a pin tenter having a pin card sheet with needles arranged. The end portion is conveyed by adjusting the gap between the pins and combs so that the film does not break and does not cause unnecessary sagging, and is heated under the conditions of 3 minutes at 200°C, 3 minutes at 250°C, and 6 minutes at 300°C. As the final heating, the necessary imidization reaction is carried out while drying. After that, the film was cooled to room temperature for 2 minutes, and the poor flatness portions at both ends of the film were cut out with a cutter and wound into a roll to obtain a roll of the film (actual 23) with a width of 510 mm and a length of 100 m. Table 9 shows the evaluation results of the obtained film (Example 23). In addition, this coating method is called "wet/GF method".

The following conditions were set by the conditions shown in Table 9, and thin films (actual 24) to (actual 25) were obtained. The results after the same evaluation are shown in Table 9. All of them showed low CTE and high transparency, and there was no particular problem with regard to mechanical strength from the viewpoint of workability. In addition, only Example 23 shows a large warpage, but this is because it is a film that is asymmetric in the thickness direction.

(Examples 26 to 28) Table 3 was added to the polyamic acid solution B obtained in Production Example 2 so that silica (slip agent) was 0.02 mass % with respect to the total polymer solid content in the polyamic acid solution. Inorganic filler No. 2 shown: a dispersion prepared by dispersing colloidal silica in dimethylacetamide (“SNOWTEX (registered trademark) DMAC-ST-ZL” manufactured by Nissan Chemical Industry Co., Ltd.) and uniformly dispersing it. In the polyimide solution F obtained in Production Example 6, inorganic filler No. 3 shown in Table 3: Silicon dioxide particles SEAHOSTAR (registered trademark) S150 with an average particle size of 1.5 μm manufactured by Nippon Shokubai Co., Ltd. After dispersing in DMAC by an attritor, it was added so that it might become 25 mass % with respect to the total amount of polymer solid content in a polyimide solution, and it mixed and stirred uniformly, and made it disperse|distribute. Film 2 was coated using a 3-layer co-extrusion T-die under the combinations and conditions shown in Table 9. That is, the order of the polyamic acid solution B containing the inorganic filler, the polyamic acid solution F containing the inorganic filler, and the polyamic acid solution B not containing the inorganic filler. Thereafter, heating was performed according to the conditions shown in Table 9, and the ends were cut and wound into rolls to obtain a film with a width of 1100 mm and a length of 250 m (actual 26). Furthermore, the heat treatment time was adjusted by adjusting the coating thickness and the line speed in the same manner, and the multilayer films Real 27 and Real 28 were obtained. The evaluation results are shown in Table 9. All showed low CTE and high transparency, colorless, and further showed good mechanical properties.

[Table 1] Polyimide (PI) solution or Polyamide acid (PAA) solution Manufacturing Example 1 Manufacturing Example 2 Manufacturing Example 3 Manufacturing Example 4 Manufacturing Example 5 Manufacturing Example 6 Manufacturing Example 7 Manufacturing Example 8 PAA solution A PAA solution B PI solution C PI solution D PI solution E PAA solution F PAA solution G PAA solution H Acid component input mass % 6FDA - - 100 - - - - - ODPA - 61 - 100 - - - 30 CBDA 100 39 - - - 100 - 40 CHDA - - - - 100 - - - BPDA - - - - - - 100 30 Diamine component input mass % TFMB - 100 100 - 100 50 100 100 4,4'-DDS - - - 70 - - - - 3,3'-DDS - - - 30 - - - - DABAN 100 - - - - 50 - - membrane thickness μm 25 25 25 25 25 25 25 25 haze % 0.34 0.28 0.28 0.31 0.29 0.31 0.40 0.31 total light transmittance % 86.3 85.2 90.3 92.4 90.5 89.2 86.8 87.9 yellow index 6.8 8.3 1.3 3.4 3.7 5.2 3.3 6.3 Breaking strength MPa 165 170 134 126 127 154 252 113 Elongation at break % 15.4 12.8 22.6 18.4 10.6 14.3 43.2 6.9 Tensile modulus of elasticity GPa 7.8 3.5 3.7 3.5 3.3 5.6 4.3 4.2 CTE ppm/℃ 17 18 48 51 38 29 25 twenty three warping mm 1.8 1.2 0.6 0.3 1.0 1.2 1.1 1.6

[Table 2] Temporary Support No. substance name 10 point average roughness surface treatment Trademark/manufacturer, etc. [nm] 1 PET 14 none COSMOSHINE (registered trademark) A4100 / Toyobo Co., Ltd. 2 PET 80 plasma treatment COSMOSHINE (registered trademark) A4100 / Toyobo Co., Ltd. 3 PET 291 wet sandblasting COSMOSHINE (registered trademark) A4100 / Toyobo Co., Ltd.

[table 3] Filler No. Inorganic substance name CTE ppm/℃ refractive index The average particle size Trademark/manufacturer, etc. [ppm/℃] [μm] 1 calcium fluoride 19 1.44 0.2 STELLA CHEMIFA Co., Ltd. 2 Silicon oxide 0.6 1.47 0.08 SNOWTEX (registered trademark) DMAC-ST-ZL / Nissan Chemical Co., Ltd. 3 Silicon oxide 0.6 1.47 1.5 SEAHOSTAR (registered trademark) KE150 / Nippon Shokubai Co., Ltd. 4 Barium sulfate 7 1.64 0.6 Sedimentable barium sulfate TS-3 Takehara Chemical Co., Ltd. 5 calcium phosphate 13 1.65 4.5 3[Ca ₃ (PO ₄ ) ₂ ]･Ca(OH) ₂ -hydroxyapatite/Taiping Chemical Industry Co., Ltd. 6 Magnesium oxide 11 1.74 0.7 KYOWAMAG (registered trademark) MF150 / Kyowa Chemical Industry 7 Alumina 6 1.75 1.0 SA32 / Nippon Light Metal Corporation 8 Tin oxide 7 1.96 0.5 ET-500 / Ishihara Industrial Co., Ltd. 9 Zinc oxide 3.5 2.1 0.55 Japanese Pharmacopoeia Zinc Oxide / Sakai Chemical Industry 10 Zirconia 8 2.21 0.01 TZ-3Y-E /Tosoh Co., Ltd. 11 Titanium oxide (rutile type) 6 2.78 0.26 R-820 / Ishihara Industrial Co., Ltd.

[Table 4] Example/Comparative Example Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Film name Real 1 real 2 real 3 real 4 than 1 than 2 temporary support No. 2 3 1 2 Rz of the side contacting layer (a) nm 80 291 14 80 (a) layer resin A A A A - A Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) - No.2 (0.02) thickness [μm] 1 1 1 1 - 1 (b) layer resin C C C C C C Filler No. (mixing amount) [quality%] No.1 (20%) No.2 (20%) No.3 (20%) No.1 (20%) - - thickness [μm] twenty three twenty three twenty three twenty three 25 twenty three (a) layer or (c) layer resin A A A A - A Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) - No.2 (0.02) thickness [μm] 1 1 1 1 - 1 total film thickness [μm] 25 25 25 25 25 25 Coating method successive wet/wet Die coating successive wet/wet dry condition (Temperature [°C] × Time [min] 110℃×10min Residual solvent content of self-supporting film [quality%] 29 29 31 26 27 27 Heat treatment conditions temperature [°C] 200-250-300 time [minute] 3 - 3 - 6 haze % 2.5 2.2 4.2 4.5 0.8 0.5 total light transmittance % 86.3 87.5 88.1 89.4 91.8 89.9 yellow index 1.1 0.8 1.3 1.3 1.5 1.4 Breaking strength MPa 132 133 144 142 139 164 Elongation at break % 23.2 23.3 22.0 22.2 19.8 18.1 Tensile modulus of elasticity GPa 3.3 3.2 3.7 3.8 3.7 3.7 CTE ppm/℃ 39 33 34 35 48 46 warping mm 0.6 0.4 0.4 0.4 0.5 0.25 Static friction coefficient 1.1 1.2 0.8 0.7 2.4 1.2 10 point average roughness nm 48 42 88 78 8 44 transition layer thickness (a) layer/(b) interlayer μm 0.63 0.61 0.61 0.61 - 0.64 (b) layer/(a) or (c) interlayer μm 0.53 0.57 0.55 0.60 - 0.52 Others, quality, operability, etc. good good good good difficult to roll good

[table 5] Example/Comparative Example Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Film name real 5 real 6 real 7 real 8 real 9 real 10 temporary support No. 2 Rz of the side contacting layer (a) nm 80 (a) layer resin A A A A A A Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) thickness [μm] 1 1 1 1 1 1 (b) layer resin C C C C C C Filler No. (mixing amount) [quality%] No.4 (20%) No.5 (20%) No.6 (20%) No.7 (20%) No.8 (20%) No.9 (20%) thickness [μm] twenty three twenty three twenty three twenty three twenty three twenty three (a) layer or (c) layer resin A A A A A A Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) thickness [μm] 1 1 1 1 1 1 total film thickness μm 25 25 25 25 25 25 Coating method successive wet/wet dry condition (Temperature [°C] × Time [min] 110℃×10min Residual solvent content of self-supporting film [quality%] 27 26 twenty four 28 twenty four 31 Heat treatment conditions temperature [°C] 200-250-300 time [minute] 3 - 3 - 6 haze % 1.1 1.0 0.9 1.3 16.1 30.8 total light transmittance % 91.5 92.4 88.8 86.1 77.5 66.1 yellow index 1.7 1.3 1.4 1.2 0.9 0.9 Breaking strength MPa 134 127 129 130 138 135 Elongation at break % 22.1 20.1 21.2 22.8 20.1 20.2 Tensile modulus of elasticity GPa 3.2 2.9 3.2 3.2 3.2 3.5 CTE ppm/℃ 35 35 34 33 33 34 warping mm 0.5 0.6 0.3 0.3 0.4 0.7 Static friction coefficient 1 1.1 1.1 1.3 1.2 0.9 10 point average roughness nm 39 41 44 41 48 52 transition layer thickness (a) layer/(b) interlayer μm 0.66 0.62 0.66 0.68 0.71 0.74 (b) layer/(a) or (c) interlayer μm 0.58 0.53 0.53 0.52 0.55 0.51 Others, quality, operability, etc. good good good good smoky smoky

[Table 6] Example/Comparative Example Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 Film name Real 11 real 12 real 13 real 14 real 15 real 16 temporary support No. 2 Rz of the side contacting layer (a) nm 80 (a) layer resin A A A A A A Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) - - No.2 (0.02) No.2 (0.02) thickness [μm] 1 1 1 1 2 3 (b) layer resin C C C C C C Filler No. (mixing amount) [quality%] No.10 (20%) No.11 (20%) No.2 (20%) No.2 (20%) No.2 (20%) No.2 (20%) thickness [μm] twenty three twenty three twenty three 5 46 69 (a) layer or (c) layer resin A A A A A A Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) - - - - thickness [μm] 1 1 1 1 2 3 total film thickness μm 25 25 25 7 50 75 Coating method successive wet/wet dry condition (Temperature [°C] × Time [min] 110℃×10min 110℃×3min 110℃ for 15 minutes 110℃ for 20 minutes Residual solvent content of self-supporting film [quality%] 27 25 29 33 twenty one 33 Heat treatment conditions temperature [°C] 200-250-300 time [minute] 3 - 3 - 6 1-1-2 5-5-10 7-7-15 haze % 61.1 97.3 2.1 2.2 2.3 2.2 total light transmittance % 59.1 34.7 88.5 92.9 84.3 82.3 yellow index 0.6 0.6 1.2 0.3 1.7 3.0 Breaking strength MPa 148 155 155 139 170 168 Elongation at break % 21.8 20.1 21.3 19.5 25.1 27.8 Tensile modulus of elasticity GPa 3.6 3.4 3.4 3.4 3.5 3.4 CTE ppm/℃ 36 33 33 34 32 32 warping mm 0.3 0.5 0.4 0.0 0.6 1.5 Static friction coefficient 1.2 1.1 1.2 1.0 1.1 1.1 10 point average roughness nm 43 48 44 42 41 41 transition layer thickness (a) layer/(b) interlayer μm 0.61 0.51 0.55 0.61 1.33 1.81 (b) layer/(a) or (c) interlayer μm 0.60 0.53 0.61 0.52 1.21 1.76 Others, quality, operability, etc. high whiteness high whiteness good good good good

[Table 7] Example/Comparative Example Example 17 Example 18 Example 19 Example 20 Example 21 Example 22 Film name real 17 real 18 real 19 real 20 real 21 real 22 temporary support No. 2 Rz of coating surface nm 80 (a) layer resin A B C D E F Filler No. (mixing amount) [quality%] - - - - - - thickness [μm] 3 3 3 3 3 3 (b) layer resin A B C D E F Filler No. (mixing amount) [quality%] No.3 (30%) No.3 (30%) No.3 (30%) No.3 (30%) No.3 (30%) No.3 (30%) thickness [μm] 19 19 19 19 19 19 (a) layer or (c) layer resin A B C D E F Filler No. (mixing amount) [quality%] - - - - - - thickness [μm] 3 3 3 3 3 3 total film thickness μm 25 25 25 25 25 25 Coating method successive wet/wet dry condition (Temperature [°C] × Time [min] 110℃×10min Residual solvent content of self-supporting film [quality%] 31 25 30 27 twenty four 25 Heat treatment conditions temperature [°C] 200-250-300 time [minute] 3 - 3 - 6 haze % 1.3 1.1. 1.0 1.2 0.9 1.0 total light transmittance % 82.8 81.1 86.6 88.1 87.0 84.8 yellow index 4.1 4.7 1.3 2.9 3.2 4.3 Breaking strength MPa 155 143 121 111 109 128 Elongation at break % 16.4 11.2 13.8 14.0 12.0 12.6 Tensile modulus of elasticity GPa 3.7 3.5 3.8 3.6 3.5 3.8 CTE ppm/℃ 13 14 35 42 28 twenty two warping mm 0.5 0.9 0.6 0.4 1.1 0.8 Static friction coefficient 1.1 1.2 1.0 1.0 1.0 1.1 10 point average roughness nm 43 42 49 48 45 39 transition layer thickness (a) layer/(b) interlayer μm - - - - - - (b) layer/(a) or (c) interlayer μm - - - - - - Others, quality, operability, etc. good good good good good good

[Table 8] Example/Comparative Example Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Film name than 3 than 4 than 5 than 6 than 7 than 8 temporary support No. 2 Rz of coating surface nm 80 (a) layer resin - - - - - - Filler No. (mixing amount) [quality%] - - - - - - thickness [μm] - - - - - - (b) layer resin A B C D E F Filler No. (mixing amount) [quality%] No.3 (30%) No.3 (30%) No.3 (30%) No.3 (30%) No.3 (30%) No.3 (30%) thickness [μm] 25 25 25 25 25 25 (a) layer or (c) layer resin - - - - - - Filler No. (mixing amount) [quality%] - - - - - - thickness [μm] - - - - - - total film thickness μm 25 25 25 25 25 25 Coating method Die coating dry condition (Temperature [°C] × Time [min] 110℃×10min Residual solvent content of self-supporting film [quality%] 31 twenty three 30 27 27 28 Heat treatment conditions temperature [°C] Breaks when peeling the self-supporting film from the temporary support substrate time [minute] haze % total light transmittance % yellow index Breaking strength MPa Elongation at break % Tensile modulus of elasticity GPa CTE ppm/℃ warping mm Static friction coefficient 10 point average roughness nm transition layer thickness (a) layer/(b) interlayer μm (b) layer/(a) or (c) interlayer μm Others, quality, operability, etc.

[Table 9] Example/Comparative Example Example 23 Example 24 Example 25 Example 26 Example 27 Example 28 Film name real 23 real 24 real 25 real 26 real 27 real 28 temporary support No. 2 Rz of coating surface nm 80 (a) layer resin A B B B B B Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) thickness [μm] 3 2 2 2 4 6 (b) layer resin C F F F F F Filler No. (mixing amount) [quality%] No.3 (25%) No.3 (25%) No.3 (25%) No.3 (25%) No.3 (25%) No.3 (30%) thickness [μm] 19 twenty one 9 twenty one 42 63 (a) layer or (c) layer resin - B B B B F Filler No. (mixing amount) [quality%] - - - - - - thickness [μm] - 2 2 2 4 6 total film thickness μm twenty two 25 13 25 50 75 Coating method wet/GF Simultaneous wet/wet dry condition (Temperature [°C] × Time [min] 110℃×5min+10min 110℃×3min 110℃ for 15 minutes 110℃ for 20 minutes Residual solvent content of self-supporting film [quality%] twenty two 20 15 33 31 34 Heat treatment conditions temperature [°C] 200-250-300 200-250-300 200-250-300 200-250-300 200-250-300 time [minute] 3 - 3 - 6 2-2-4 1-1-2 5-5-10 7-7-15 haze % 4.4 4.9 3.7 4.3 68.1 7.5 total light transmittance % 86.6 86.5 90.1 87.4 84.3 80.9 yellow index 1.3 4.1 3.4 4.5 4.6 4.8 Breaking strength MPa 151 144 131 150 154 161 Elongation at break % 19.2 19.3 16.0 20.4 20.1 22.7 Tensile modulus of elasticity GPa 3.8 3.7 3.7 3.5 3.6 3.5 CTE ppm/℃ 28 twenty three twenty three twenty four 26 27 warping mm 6.3 0.1 0.1 0.3 0.4 0.2 Static friction coefficient 1.1 1.0 1.0 1.1 1.2 1.1 10 point average roughness nm 44 45 41 38 40 40 transition layer thickness (a) layer/(b) interlayer μm 0.11 0.07 0.06 0.82 1.23 2.06 (b) layer/(a) or (c) interlayer μm - 0.06 0.06 0.70 1.20 1.99 Others, quality, operability, etc. good good good good good good

(Application Example 1) First, the multilayer polyimide film (Example 25) obtained in Example 25 was cut out into a rectangle of 360 mm×460 mm. Next, using a UV/O ₃ irradiator (SKR1102N-03 manufactured by LAN TECHNICAL), the (a) layer side was irradiated with UV/O ₃ for 3 minutes as a film surface treatment. At this time, the distance between the UV/O ₃ lamp and the film was set to 30mm. 3-Aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., KBM-903) was applied as a silane coupling agent to display glass (370 mm×470 mm, glass substrate of 0.7 mm thickness: Nippon Electric Glass Co., Ltd.) by a sprayer OA10G). In addition, the glass substrate used was dry-cleaned by irradiating with a UV/O ₃ irradiator (SKR1102N-03, manufactured by LAN TECHNICAL) for 1 minute after washing with pure water and drying. Next, the glass substrate coated with the silane coupling agent was set in a roll laminator equipped with a silicone rubber roller, and 500 ml of pure water was firstly dripped onto the silane coupling agent coated surface by means of a dropper so as to spread over the entire substrate. Wet the substrate. The surface-treated surface of the multi-layer polyimide film (Example 25) that has been subjected to the aforementioned surface treatment is overlapped with the silane coupling agent-coated surface of the glass substrate (that is, the surface moistened with pure water), while the glass substrate is removed from the surface. The glass substrate and the polyimide film were laminated to obtain a temporary laminate while pressing one of them while extruding the pure water between the polyimide film and the glass substrate with the rotating roll in order. The laminator used is a laminator with an effective roll width of 650mm made by MCK Company, and the laminating conditions are the original air pressure: 0.5MPa, lamination speed: 50mm/sec, roll temperature: 22°C, ambient temperature 22°C, humidity 55%RH. The obtained temporary laminate was heat-treated at 200° C. for 10 minutes in a clean oven to obtain a laminate comprising a multi-layered polyimide film and a glass substrate.

A tungsten film (75 nm in thickness) was formed on the polyimide thin film surface of the obtained laminate by the following steps, and a silicon oxide film (150 nm in thickness) was further laminated and formed as an insulating film without contacting the air. Next, a silicon oxynitride film (thickness: 100 nm) to be the base insulating film was formed by plasma CVD, and an amorphous silicon film (thickness: 54 nm) was further formed without contact with air.

A TFT element was fabricated using the obtained amorphous silicon film. First, an amorphous silicon thin film is patterned to form a silicon region of a predetermined shape, a gate insulating film, a gate electrode, a source region or a drain by doping the active region are appropriately performed. The formation of the region, the formation of the interlayer insulating film, the formation of the source electrode and the drain electrode, the activation treatment, and the fabrication of the P-channel TFT array. Along about 0.5mm inside the periphery of the TFT array, the polyimide film portion was burnt off by UV-YAG laser, and peeled off by picking it up from the end of the incision with a thin razor-shaped blade to obtain a Flexible A3 size TFT array. The peeling can be performed with very little force and can be peeled off without causing damage to the TFT. Even if the obtained flexible TFT array was wound around a 5 mmφ round rod, no performance degradation was observed, and good characteristics were maintained.

(Examples 29 to 32) (Comparative Examples 10 to 11) The polyimide solution or polyimide solution shown in Table 10 was combined with the inorganic filler shown in Table 10, and a film was produced and evaluated in the same manner as in Example 1. The results are shown in Table 10. In addition, in the case of a single layer in the comparative example, die coating was used.

(Example 33) Table 3 was added to the polyamic acid solution A obtained in Production Example 1 so that silica (slip agent) was 0.02 mass % with respect to the total polymer solid content in the polyamic acid solution. Inorganic filler No. 2 shown: a dispersion prepared by dispersing colloidal silica in dimethylacetamide (“SNOWTEX (registered trademark) DMAC-ST-ZL” manufactured by Nissan Chemical Industry Co., Ltd.) and uniformly dispersing it. In the polyimide solution C obtained in Production Example 3, inorganic filler No. 1 shown in Table 3: calcium fluoride particles with an average particle diameter of 0.2 μm, manufactured by STELLA CHEMIFA Co., Ltd., were first dispersed in DMAC using an attritor. Then, it was added so that it might become 20 mass % with respect to the polymer solid content total amount in a polyimide solution, and it mixed and stirred uniformly, and it was made to disperse|distribute. In an atmosphere adjusted to 25°C and 45% RH, the film was produced using an apparatus equipped with a roll-to-roll type notch wheel coater, multiple die coaters, a continuous drying furnace, and a heat treatment furnace. First, the polyamide solution A in which the inorganic filler No. 2 was dispersed was applied to the non-slip surface of the film 2 (see Table 2) of the temporary support using a corner wheel coater so that the final film thickness would be 1 μm. up as the first layer. Next, 10 seconds later, the polyimide solution C in which the inorganic filler No. 1 was dispersed was applied by a die coater so that the final film thickness would be 23 μm on the first layer that was applied earlier to serve as the second layer. . Next, it heated at 110 degreeC for 5 minutes as a primary heating by a continuous dryer, and produced the semi-drying film whose residual solvent amount is 22 mass %, and wound up into a roll shape together with a temporary support body. This semi-dry film is called GF (green film). The obtained roll was set again in the aforementioned apparatus, the aforementioned semi-dry film was taken out together with the temporary support, and the same inorganic filler No. 2 dispersed in the first layer was applied by a die coater so that the final film thickness was 1 μm. The polyamide solution A was coated on the semi-dried film as the third layer (this coating method is hereinafter referred to as "wet/GF (wet/wet) method"). After coating the third layer, it was dried in a continuous drying furnace at 110° C. for 10 minutes to obtain a self-supporting film with a residual solvent content of 18% by mass. This self-supporting film is peeled off from the film 2 serving as a support, and the end of the film is held by inserting the needles through a pin tenter having a pin card piece equipped with needles, so that the film does not break and is maintained in a stable manner. The needle-comb piece interval was adjusted and conveyed so as not to cause unnecessary sagging, and the imidization reaction was carried out by heating under the conditions of 3 minutes at 200°C, 3 minutes at 250°C, and 6 minutes at 300°C. After that, the film was cooled to room temperature for 2 minutes, and the film with poor flatness at both ends was cut out with a cutter and wound into a roll to obtain a roll of film (actual 33) with a width of 580 mm and a length of 100 m. Table 11 shows the evaluation results of the obtained film (Example 33).

(Examples 34 and 35) Next, in the same manner as in Example 31, a film was produced and evaluated by combining the polyamide solution or polyimide solution shown in Table 11, the temporary support shown in Table 2, and the inorganic filler shown in Table 3. .

(Example 36) Table 3 was added to the polyamic acid solution A obtained in Production Example 1 so that silica (slip agent) was 0.02 mass % with respect to the total polymer solid content in the polyamic acid solution. Inorganic filler No. 2 shown: a dispersion prepared by dispersing colloidal silica in dimethylacetamide (“SNOWTEX (registered trademark) DMAC-ST-ZL” manufactured by Nissan Chemical Industry Co., Ltd.) and uniformly dispersing it. In the polyimide solution C obtained in Production Example 3, inorganic filler No. 1 shown in Table 3: calcium fluoride particles with an average particle diameter of 0.2 μm, manufactured by STELLA CHEMIFA Co., Ltd., were first dispersed in DMAC using an attritor. Then, it was added so that it might become 20 mass % with respect to the polymer solid content total amount in a polyimide solution, and it mixed and stirred uniformly, and it was made to disperse|distribute.

In an atmosphere adjusted to 25°C and 45% RH, using a roll-to-roll cutaway wheel coater and multiple die coaters, a continuous drying furnace, and a continuous heat treatment furnace, the final film thickness was 1 μm. The polyamic acid solution A in which the aforementioned inorganic filler No. 2 was dispersed was applied to the non-slip surface of the film 2 (refer to Table 2) of the temporary support. Next, it heated at 110 degreeC for 5 minutes as a primary heating by a continuous dryer, and produced the semi-drying film whose residual solvent amount is 18 mass %, and wound up into a roll shape together with a temporary support body. This semi-dry film is called GF (green film). The obtained roll was set in the above-mentioned apparatus again, the above-mentioned semi-dry film was rolled out together with the temporary support, and the polyimide solution in which the above-mentioned inorganic filler No. 1 was dispersed was applied by a die coater so that the final film thickness would be 23 μm. C is applied on the semi-dried film. 10 seconds after the coating of the second layer, the same polyamic acid solution A with inorganic filler No. 2 dispersed as that of the first layer was applied by a die coater so that the final film thickness was 1 μm, as the third layer ( This coating method is hereinafter referred to as "wet/wet/GF method"). After coating the third layer, it was dried at 110° C. for 10 minutes with a continuous dryer. After drying, the residual solvent amount was 23% by mass, and the self-supporting film was peeled off from the film 2 as a support, and the film was held by inserting the needles through a pin tenter having a pin card sheet with needles arranged. The end portion is conveyed by adjusting the gap between the pins and combs so that the film does not break and does not cause unnecessary sagging, and is heated under the conditions of 3 minutes at 200°C, 3 minutes at 250°C, and 6 minutes at 300°C. As the final heating, the necessary imidization reaction is carried out while drying. After that, the film was cooled to room temperature for 2 minutes, and the poor flatness portions at both ends of the film were cut out with a cutter and wound into a roll to obtain a roll of the film (actual 36) with a width of 510 mm and a length of 100 m. Table 11 shows the evaluation results of the obtained film (Example 36).

Films (real 37) and (real 38) were obtained by setting the conditions shown in Table 11 below. The results after the same evaluation are shown in Table 11. All of them showed low CTE and high transparency, and no problem was seen in particular from the viewpoint of workability regarding mechanical strength.

[Table 10] Example/Comparative Example Example 29 Example 30 Example 31 Example 32 Comparative Example 10 Comparative Example 11 Film name real 29 real 30 real 31 real 32 than 10 than 11 temporary support No. 2 3 2 Rz of coating surface nm 80 291 80 (a) layer resin A A G G - - Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) - - thickness [μm] 1 1 1 1 - - (b) layer resin G H H H G H Filler No. (mixing amount) [quality%] No.2 (20%) No.2 (20%) No.2 (20%) No.2 (20%) No.2 (20%) No.2 (20%) thickness [μm] twenty three twenty three twenty three twenty three 25 25 (a) layer or (c) layer resin A A G G - - Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) - - thickness [μm] 1 1 1 1 - - total film thickness [μm] 25 25 25 25 25 25 Coating method successive wet/wet successive wet/wet Die coating dry condition (Temperature [°C] × Time [min] 110℃×10min Residual solvent content of self-supporting film [quality%] 34 35 34 34 37 34 Heat treatment conditions temperature [°C] 200-250-300 Breaks when peeling the self-supporting film from the temporary support substrate time [minute] 3 - 3 - 6 haze % 0.4 0.9 0.5 0.8 total light transmittance % 87.1 87.0 87.8 86.9 yellow index 3.1 3.8 3.7 4.5 Breaking strength MPa 217 110 127 118 Elongation at break % 22.8 5.9 6.1 6.7 Tensile modulus of elasticity GPa 4.5 4.9 5.1 4.5 CTE ppm/℃ twenty two twenty three twenty two twenty two warping mm 1.1 0.9 1.2 1.3 Static friction coefficient 1.1 0.9 0.9 0.6 10 point average roughness nm 45 48 47 83 transition layer thickness (a) layer/(b) interlayer μm 0.61 0.55 0.54 0.66 (b) layer/(a) or (c) interlayer μm 0.56 0.60 0.58 0.52 Others, quality, operability, etc. good good good good

[Table 11] Example/Comparative Example Example 33 Example 34 Example 35 Example 36 Example 37 Example 38 Film name real 33 real 34 real 35 real 36 real 37 real 38 temporary support No. 2 Rz of coating surface nm 80 (a) layer resin A A G A A G Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) thickness [μm] 1 1 1 1 1 1 (b) layer resin C H H C H H Filler No. (mixing amount) [quality%] No.1 (20%) No.2 (20%) No.1 (20%) No.1 (20%) No.2 (20%) No.1 (20%) thickness [μm] twenty three twenty three twenty three twenty three twenty three twenty three (a) layer or (c) layer resin A A G A A G Filler No. (mixing amount) [quality%] No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) No.2 (0.02) thickness [μm] 1 1 1 1 1 1 total film thickness [μm] 25 25 25 25 25 25 Coating method wet/GF(wet/wet) wet/wet/GF dry condition (Temperature [°C] × Time [min] 110℃×10min Residual solvent content of self-supporting film [quality%] twenty four 27 twenty three twenty four 26 31 Heat treatment conditions temperature [°C] 200-250-300 time [minute] 3 - 3 - 6 haze % 2.1 1.7 1.2 1.2 1.7 1.3 total light transmittance % 87.2 85.3 87.5 87.3 86.4 87.3 yellow index 1.5 4.7 4.6 1.4 4.2 3.9 Breaking strength MPa 129 176 181 133 183 196 Elongation at break % 21.2 12.9 12.7 22.3 10.7 10.9 Tensile modulus of elasticity GPa 3.3 3.5 4.1 3.3 3.5 3.9 CTE ppm/℃ 38 twenty one twenty two 36 twenty three twenty three warping mm 0.7 1.1 1.5 0.8 1.2 1.6 Static friction coefficient 1.1 1.1 1.1 1.0 1.1 0.9 10 Average roughness nm 45 47 54 43 48 48 transition layer thickness (a) layer/(b) interlayer μm 0.56 0.67 0.60 0.11 0.09 0.09 (b) layer/(a) or (c) interlayer μm 0.08 0.10 0.09 0.54 0.57 0.55 Others, quality, operability, etc. good good good good good good [Possibility of Industrial Use]

As described above, compared to the case of separately forming the polyimide films of different compositions into thin films, the multilayer polyimide film of the present invention exhibits good optical properties and mechanical properties. In addition, according to the manufacturing method of the present invention, it becomes possible to form a transition layer with a specific thickness and a gradient of composition between layers of different compositions that are divided into multiple layers and share functions, so that a balanced thin film can be formed. The multilayer polyimide film of the present invention has excellent optical properties, colorless transparency, excellent mechanical properties, and low CTE. Therefore, by bonding the film to a flat and rigid inorganic substrate such as glass After that, various electronic device processing is performed on the thin film, and finally, it is peeled off from the inorganic substrate, and a flexible electronic device can be produced.

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Claims (10)

A multilayer polyimide film, characterized by a thickness of 3 μm to 120 μm, a yellowness index of 5 or less, and at least two layers of (a) layer and (b) layer; (a) layer: a layer containing a polyimide composition with an inorganic filler content of less than 0.05 mass %, (b) Layer: A layer containing a polyimide composition in which the content of the inorganic filler is 1 mass % or more and 35 mass % or less. The multilayer polyimide film according to claim 1, wherein the laminated structure of the multilayer polyimide film is a three-layer structure of (a)/(b)/(a). The multi-layer polyimide film of claim 1, wherein the laminated structure of the multi-layer polyimide film is a three-layer structure of (a)/(b)/(c); Here, (c) layer: the layer containing the polyimide composition whose content of an inorganic filler is 0.3 mass % or less. The multilayer polyimide film of any one of claims 1 to 3, wherein the chemical structure of the polyimide of all layers is the same. The multilayer polyimide film according to any one of claims 1 to 4, wherein the coefficient of linear expansion is below 50 ppm/°C. The multilayer polyimide film according to any one of claims 1 to 5, wherein the total light transmittance is above 80%. The multi-layer polyimide film according to any one of claims 1 to 6, wherein the surface of the layer (a) is made of a polyethylene terephthalate film "COSMOSHINE (registered trademark) A4100" manufactured by Toyobo Co., Ltd. The coefficient of static friction between the inner surfaces of the roll is 1.50 or less. The multilayer polyimide film according to any one of claims 1 to 7, wherein the 10-point average roughness Rz of the surface of the (a) layer is 15 nm or more. A laminate comprising the multilayer polyimide film as claimed in any one of claims 1 to 8 and an inorganic substrate. A method of manufacturing a flexible electronic device, wherein the electronic device is formed on the surface of the multilayer polyimide film of the laminate according to claim 9, and then peeled off from an inorganic substrate.