Polyimide laminate, polyimide laminate with support, thin-film transistor device, and method for producing polyimide laminate

Abstract

A polyimide laminate (10) comprises a first polyimide layer (11), an inorganic layer (12), and a second polyimide layer (13), in that order. The inorganic layer (12) contains a silicon oxide layer containing silicon oxide having a higher silicon ratio than the stoichiometric composition, and does not contain an amorphous silicon layer. The polyimide contained in the second polyimide layer (13) has a tetracarboxylic dianhydride residue and a diamine residue. The diamine residue contains a siloxane diamine residue.

Description

Polyimide laminate, polyimide laminate with support, thin film transistor device, and method for producing polyimide laminate

[0001] The present invention relates to a polyimide laminate, a polyimide laminate with a support, a thin film transistor device, and a method for producing a polyimide laminate.

[0002] Displays equipped with organic light-emitting diodes (hereinafter, sometimes referred to as "OLED displays") are known as displays used in smartphones, televisions, in-vehicle displays, etc. OLED displays can have a problem in which, when the display screen is switched, the previous image remains (hereinafter, sometimes referred to as "image retention") (see Patent Document 1).

[0003] On the other hand, in OLED displays, illuminance is adjusted by controlling the current of thin film transistors (hereinafter sometimes referred to as "TFTs"). For example, in the OLED display disclosed in Patent Document 2, TFTs are disposed on a polyimide laminate having a first polyimide layer, a silicon oxide layer, an amorphous silicon layer, and a second polyimide layer in this order. In Patent Document 2, the adhesion between the silicon oxide layer and the second polyimide layer is improved by disposing an amorphous silicon layer between the silicon oxide layer and the second polyimide layer.

[0004] International Publication No. 2019 / 073929 Japanese Patent Application Laid-Open No. 2021-105704

[0005] In OLED displays having polyimide laminates as disclosed in Patent Document 2 and the like, image retention is caused by the fact that the resistance of the amorphous silicon layer in the polyimide laminate is relatively low, so that electrons are attracted to the amorphous silicon layer by the electric field of the TFT, making the polyimide laminate more likely to become charged. However, if an amorphous silicon layer is not provided in the polyimide laminate, the adhesion between the silicon oxide layer (inorganic layer) and the second polyimide layer may decrease.

[0006] In view of the above, an object of the present invention is to provide a polyimide laminate having excellent adhesion between an inorganic layer and a polyimide layer in a configuration in which no amorphous silicon layer is interposed between two polyimide layers, a method for producing the same, and a support-attached polyimide laminate and a thin-film transistor device that include the polyimide laminate.

[0007] <Aspects of the Present Invention> The present invention includes the following aspects.

[0008] [1] A polyimide laminate comprising a first polyimide layer, an inorganic layer, and a second polyimide layer in this order, wherein the inorganic layer contains a silicon oxide layer containing silicon oxide having a higher silicon ratio than that of a stoichiometric composition, but does not contain an amorphous silicon layer, the second polyimide layer and the silicon oxide layer are in contact with each other, and the polyimide contained in the second polyimide layer has a tetracarboxylic dianhydride residue and a diamine residue, and the diamine residue includes a siloxane diamine residue.

[0009] [2] The polyimide laminate according to [1] above, wherein the silicon oxide having a higher silicon content than that of the stoichiometric composition is represented by the following general formula (1): SiOx (1) (in the general formula (1), x represents a real number of 1.3 or more and less than 2.0):

[0010] [3] The polyimide laminate according to [1] or [2] above, wherein the siloxane diamine residue is a divalent organic group represented by the following general formula (2):

[0011]

[0012] In the general formula (2), R １ and R ２ each independently represents a divalent hydrocarbon group, and n represents an integer of 1 or more and 5 or less.

[0013] [4] The polyimide laminate according to any one of [1] to [3] above, wherein the tetracarboxylic dianhydride residues include 3,3',4,4'-biphenyltetracarboxylic dianhydride residues.

[0014] [5] The polyimide laminate according to any one of [1] to [4], wherein the diamine residue further contains a p-phenylenediamine residue.

[0015] [6] The polyimide laminate according to any one of [1] to [5] above, having a thickness of 5 μm or more and 30 μm or less.

[0016] [7] The polyimide laminate according to [6], wherein the thickness of the first polyimide layer is greater than the thickness of the second polyimide layer.

[0017] [8] The polyimide laminate according to any one of [1] to [7], wherein the adhesion strength between the inorganic layer and the second polyimide layer is 0.20 N / cm or more.

[0018] [9] A polyimide laminate with a support, comprising: a support; and the polyimide laminate according to any one of [1] to [8], wherein the support is disposed on the first polyimide layer side of the polyimide laminate.

[0019]

[10] The supported polyimide laminate according to [9], wherein the adhesion strength between the support and the first polyimide layer is 0.10 N / cm or more.

[0020]

[11] A thin film transistor device comprising the polyimide laminate according to any one of [1] to [8] above, and a thin film transistor layer disposed on the second polyimide layer of the polyimide laminate.

[0021]

[12] A method for producing a polyimide laminate according to any one of [1] to [8] above, comprising: a step Sa of forming the inorganic layer on the first polyimide layer; a step Sb of applying a solution containing a precursor of the polyimide contained in the second polyimide layer to a main surface of the inorganic layer opposite to the first polyimide layer; and a step Sc of heating the coating film obtained in the step Sb to imidize the precursor.

[0022]

[13] The method for producing a polyimide laminate according to

[12] , wherein the solution containing the precursor further contains an imidazole compound having a boiling point of 250°C or higher and 400°C or lower.

[0023]

[14] The method for producing a polyimide laminate according to

[12] or

[13] , wherein in the step Sa, the inorganic layer is formed by plasma-enhanced chemical vapor deposition.

[0024] According to the present invention, it is possible to provide a polyimide laminate having excellent adhesion between an inorganic layer and a polyimide layer in a configuration in which no amorphous silicon layer is interposed between two polyimide layers, a method for producing the same, and a support-attached polyimide laminate and a thin-film transistor device that include the polyimide laminate.

[0025] 1 is a cross-sectional view showing an example of a polyimide laminate according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view showing another example of a polyimide laminate according to the first embodiment of the present invention; FIG. 3 is a cross-sectional view showing an example of a supported polyimide laminate according to a second embodiment of the present invention.

[0026] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited thereto. In addition, all academic and patent documents described in this specification are incorporated herein by reference.

[0027] First, the terms used in this specification will be explained. A "structural unit" refers to a repeating unit that constitutes a polymer. A "polyimide" is a polymer containing a structural unit represented by the following general formula (3) (hereinafter, sometimes referred to as "structural unit (3)").

[0028]

[0029] In general formula (3), X １ represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from a tetracarboxylic dianhydride), and X ２ represents a diamine residue (a divalent organic group derived from a diamine).

[0030] The content of the structural unit (3) relative to all structural units constituting the polyimide is, for example, 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, even more preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%.

[0031] The "polyamic acid" is a polymer containing a structural unit represented by the following general formula (4) (hereinafter, sometimes referred to as "structural unit (4)").

[0032]

[0033] In general formula (4), A １ represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from a tetracarboxylic dianhydride), A ２ represents a diamine residue (a divalent organic group derived from a diamine).

[0034] The content of the structural unit (4) relative to all structural units constituting the polyamic acid is, for example, 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, even more preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%.

[0035] Polyimide is an imide of polyamic acid. Therefore, when the content of the structural unit (4) relative to all structural units constituting the polyamic acid is 100 mol %, the polyimide, which is an imide of the polyamic acid, is represented by X in the general formula (3). １ As A in general formula (4) １ and X in general formula (3) ２ As A in general formula (4) ２ The residue is represented by:

[0036] The "main surface" of a layered material (more specifically, a polyimide layer, an inorganic layer, etc.) refers to a surface perpendicular to the thickness direction of the layered material. Unless otherwise specified, the "thickness (film thickness)" of a layered material is the arithmetic mean value of 10 measured values ​​obtained by observing a cross section of the layered material cut in the thickness direction with an electron microscope, randomly selecting 10 measurement points from the cross-sectional image, and measuring the thicknesses of the selected 10 measurement points.

[0037] Unless otherwise specified, the "linear expansion coefficient" refers to the linear expansion coefficient at elevated temperatures from 100°C to 400°C.

[0038] Hereinafter, the compound name may be followed by "based" to refer to the compound and its derivatives in a comprehensive manner. Furthermore, when the compound name is followed by "based" to represent the name of a polymer, unless otherwise specified, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, tetracarboxylic acid dianhydrides may be referred to as "acid dianhydrides."

[0039] Unless otherwise specified, the components and functional groups exemplified in this specification may be used alone or in combination of two or more kinds.

[0040] The drawings referred to in the following description mainly show each component in a schematic manner for ease of understanding, and the size, number, shape, etc. of each component shown may differ from the actual size, number, shape, etc. of each component due to the convenience of creating the drawings. Furthermore, for convenience of explanation, in drawings described later, the same components as those in previously described drawings may be assigned the same reference numerals, and their explanation may be omitted.

[0041] <First Embodiment: Polyimide Laminate> A polyimide laminate according to a first embodiment of the present invention is a polyimide laminate comprising, in this order, a first polyimide layer, an inorganic layer, and a second polyimide layer. The inorganic layer contains a silicon oxide layer containing silicon oxide with a higher silicon content compared to the stoichiometric composition, and does not contain an amorphous silicon layer. The second polyimide layer and the silicon oxide layer are in contact with each other. The polyimide contained in the second polyimide layer has a tetracarboxylic dianhydride residue and a diamine residue. The diamine residue of the polyimide contained in the second polyimide layer includes a siloxane diamine residue.

[0042] Hereinafter, a "silicon oxide layer containing silicon oxide having a higher proportion of silicon compared to the stoichiometric composition" may be referred to as a "specific silicon oxide layer." Note that in this specification, the "specific silicon oxide layer" does not refer to an amorphous silicon layer.

[0043] The polyimide laminate according to the first embodiment has excellent adhesion between the inorganic layer and the polyimide layer, even though the inorganic layer does not include an amorphous silicon layer (adhesion layer). The reason for this is presumed to be as follows.

[0044] In the polyimide laminate according to the first embodiment, the specific silicon oxide layer in the inorganic layer is in contact with the second polyimide layer. Furthermore, in the polyimide laminate according to the first embodiment, the polyimide contained in the second polyimide layer contains a siloxane diamine residue. Because the siloxane bond sites in the siloxane diamine residue have a high affinity with the specific silicon oxide layer, the adhesion between the specific silicon oxide layer and the second polyimide layer tends to be high. Therefore, the polyimide laminate according to the first embodiment does not use an amorphous silicon layer (adhesion layer), thereby suppressing the occurrence of afterimages and exhibiting excellent adhesion between the inorganic layer and the polyimide layer.

[0045] In the first embodiment, in order to obtain a polyimide laminate having excellent adhesion between the inorganic layer and the polyimide layer, it is preferable that the silicon oxide contained in the specific silicon oxide layer (silicon oxide having a higher silicon content compared to the stoichiometric composition) is silicon oxide represented by the following general formula (1): SiOx (1)

[0046] In general formula (1), x represents a real number of 1.3 or more and less than 2.0. Hereinafter, silicon oxide represented by general formula (1) may be simply referred to as "SiOx." Furthermore, a specific silicon oxide layer containing SiOx may be referred to as an "SiOx layer."

[0047] In the first embodiment, when the specific silicon oxide layer is a SiOx layer, in order to obtain a polyimide laminate having excellent adhesion between the inorganic layer and the polyimide layer, the content of SiOx in the SiOx layer is preferably 80% by weight or more and 100% by weight or less, more preferably 90% by weight or more and 100% by weight or less, still more preferably 95% by weight or more and 100% by weight or less, even more preferably 99% by weight or more and 100% by weight or less, and may even be 100% by weight, relative to the total amount of the SiOx layer. Note that components other than SiOx in the SiOx layer include, for example, components derived from the raw materials for forming the SiOx layer.

[0048] In the first embodiment, when the specific silicon oxide layer is a SiOx layer, in order to obtain a polyimide laminate having superior adhesion between the inorganic layer and the polyimide layer, x is preferably a real number of 1.6 or more and less than 2.0, and more preferably a real number of 1.7 or more and less than 2.0.

[0049] [Configuration of Polyimide Laminate] The configuration of the polyimide laminate according to the first embodiment will be described below with reference to the drawings.

[0050] FIG. 1 is a cross-sectional view showing an example of a polyimide laminate according to the first embodiment. As shown in FIG. 1, a polyimide laminate 10 includes a first polyimide layer 11, an inorganic layer 12, and a second polyimide layer 13, in this order. The inorganic layer 12 contains a specific silicon oxide layer and does not contain an amorphous silicon layer. In the example shown in FIG. 1, the inorganic layer 12 is a single inorganic layer made of a specific silicon oxide layer. In addition, the second polyimide layer 13 and the specific silicon oxide layer (inorganic layer 12 in the example shown in FIG. 1) are in contact with each other.

[0051] The polyimide contained in the second polyimide layer 13 has a tetracarboxylic dianhydride residue and a diamine residue. The diamine residue of the polyimide contained in the second polyimide layer 13 includes a siloxane diamine residue. Hereinafter, a polyimide having a siloxane diamine residue may be referred to as a "specific polyimide."

[0052] The first polyimide layer 11 and the second polyimide layer 13 may contain components (additives) other than polyimide. Examples of additives that can be used include dyes, surfactants, leveling agents, plasticizers, silicones, fillers, sensitizers, and silane coupling agents. The polyimide content in the first polyimide layer 11 and the polyimide content in the second polyimide layer 13 are, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may even be 100% by weight, based on the total weight of each polyimide layer.

[0053] In order to improve productivity while ensuring electrical insulation, the thickness of the inorganic layer 12 is preferably 10 nm or more and 2000 nm or less, more preferably 50 nm or more and 1500 nm or less, and even more preferably 100 nm or more and 1000 nm or less.

[0054] In order to improve productivity while ensuring flexibility, the thickness of the polyimide laminate 10 is preferably 5 μm or more and 30 μm or less. Furthermore, when the thickness of the polyimide laminate 10 is 5 μm or more and 30 μm or less, in order to suppress the occurrence of afterimages, it is preferable that the thickness of the first polyimide layer 11 be greater than the thickness of the second polyimide layer 13. In order to further suppress the occurrence of afterimages, the thickness of the first polyimide layer 11 is preferably 1.5 times or more the thickness of the second polyimide layer 13, and more preferably 1.5 times or more and 2.0 times the thickness of the second polyimide layer 13.

[0055] To obtain a polyimide laminate having superior adhesion between the inorganic layer and the polyimide layer, the adhesion strength between the inorganic layer 12 and the second polyimide layer 13 is preferably 0.20 N / cm or more, and more preferably 0.50 N / cm or more. The upper limit of the adhesion strength between the inorganic layer 12 and the second polyimide layer 13 is not particularly limited, but is, for example, 2.00 N / cm or less. The adhesion strength between the inorganic layer 12 and the second polyimide layer 13 can be adjusted, for example, by changing at least one of the type of siloxane diamine residue contained in the specific polyimide in the second polyimide layer 13 and the content of the siloxane diamine residue. The adhesion strength between the inorganic layer and the second polyimide layer is measured by the same method as in the examples described below or a method equivalent thereto.

[0056] In order to obtain a polyimide laminate suitable for use as a substrate for a flexible display, it is preferable that the inorganic layer 12 and the second polyimide layer 13 do not peel off when the polyimide laminate 10 is folded. Specifically, it is preferable that the inorganic layer 12 and the second polyimide layer 13 do not peel off in a seam folding test described below.

[0057] An example of the first embodiment has been described above with reference to Fig. 1, but the polyimide laminate according to the first embodiment is not limited to the polyimide laminate 10 shown in Fig. 1. For example, the inorganic layer included in the polyimide laminate according to the first embodiment may have a multilayer structure (a structure of two or more layers) as long as the specific silicon oxide layer is located on the surface layer on the second polyimide layer side. Fig. 2 shows a cross-sectional view of a polyimide laminate including a two-layer inorganic layer as another example of the polyimide laminate according to the first embodiment.

[0058] In the polyimide laminate 20 shown in FIG. 2 , the inorganic layer 21 has a silicon nitride layer 22 and a specific silicon oxide layer 23, in this order from the first polyimide layer 11 side. The silicon nitride layer 22 can be a layer containing SiNy (where y is a real number greater than or equal to 0.5 and less than 1.33). To ensure electrical insulation while increasing productivity, the thickness of the specific silicon oxide layer 23 is preferably 10 nm to 2000 nm, more preferably 50 nm to 1500 nm, and even more preferably 100 nm to 1000 nm. To ensure electrical insulation while increasing productivity, the thickness of the silicon nitride layer 22 is preferably 10 nm to 2000 nm, more preferably 50 nm to 1500 nm, and even more preferably 100 nm to 1000 nm.

[0059] When the silicon nitride layer 22 is a layer containing SiNy (y is a real number greater than or equal to 0.5 and less than 1.33), in order to obtain a polyimide laminate having superior adhesion between the inorganic layer and the polyimide layer, the content of SiNy (y is a real number greater than or equal to 0.5 and less than 1.33) in the silicon nitride layer 22 is preferably 80% by weight to 100% by weight, more preferably 90% by weight to 100% by weight, even more preferably 95% by weight to 100% by weight, still more preferably 99% by weight to 100% by weight, and may even be 100% by weight. Note that components other than SiNy in the silicon nitride layer 22 include, for example, components derived from the raw materials used to form the silicon nitride layer 22.

[0060] 2 shows an example in which the inorganic layer 21 is composed of a silicon nitride layer 22 and a specific silicon oxide layer 23, but the inorganic layer may have a three-layer structure in which a silicon nitride layer is sandwiched between two specific silicon oxide layers, or may have an inorganic layer having a four-layer or greater structure in which specific silicon oxide layers and silicon nitride layers are alternately stacked. The other configurations of the polyimide laminate 20 (such as the preferred thickness range of the polyimide laminate and the preferred thickness ratio of the two polyimide layers) are the same as those of the polyimide laminate 10 described above (see FIG. 1).

[0061] [Polyimide contained in the second polyimide layer] Next, the polyimide (specific polyimide) contained in the second polyimide layer will be described. The specific polyimide is obtained by imidizing a polyamic acid precursor. The polyamic acid is obtained by reacting a tetracarboxylic dianhydride with a diamine in an organic solvent. Therefore, the specific polyimide has a tetracarboxylic dianhydride residue and a diamine residue.

[0062] In addition, in the specific polyimide, the diamine residue has a siloxane diamine residue, that is, the specific polyimide has a siloxane diamine residue as the diamine residue.

[0063] In order to obtain a polyimide laminate having excellent adhesion between the inorganic layer and the polyimide layer, the siloxane diamine residue is preferably a divalent organic group represented by the following general formula (2).

[0064]

[0065] In general formula (2), R １ and R ２ each independently represents a divalent hydrocarbon group, and n represents an integer of 1 or more and 5 or less. In order to obtain a polyimide laminate having excellent adhesion between the inorganic layer and the polyimide layer, R １ and R ２ are each independently preferably an alkylene group having from 1 to 5 carbon atoms, more preferably an alkylene group having from 2 to 4 carbon atoms. In order to obtain a polyimide laminate having superior adhesion between the inorganic layer and the polyimide layer, n is preferably from 1 to 3, more preferably 1.

[0066] In order to obtain a polyimide laminate having particularly excellent adhesion between the inorganic layer and the polyimide layer, the siloxane diamine residue is preferably a residue of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (hereinafter, sometimes referred to as "PAM-E").

[0067] The specific polyimide may have a residue other than a siloxane diamine residue (another diamine residue) as the diamine residue. Examples of diamines for forming other diamine residues include p-phenylenediamine (hereinafter sometimes referred to as "PDA"), 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,5-bis(4-aminophenoxy)pentane, 1,3-bis(4-aminophenoxy)-2,2-dimethylpropane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-diaminobenzanilide, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene, 1,4-cyclohexanediamine, and 4,4'-methylenebis(cyclohexaneamine).

[0068] In order to reduce the linear expansion coefficient of the second polyimide layer, the specific polyimide preferably has a PDA residue as a diamine residue. In this case, in order to further reduce the linear expansion coefficient of the second polyimide layer, the content of the PDA residue is preferably 50 mol% to 99.9 mol%, more preferably 70 mol% to 99.9 mol%, even more preferably 90 mol% to 99.9 mol%, still more preferably 95 mol% to 99.9 mol%, and particularly preferably 99.0 mol% to 99.9 mol%, based on the total diamine residues constituting the specific polyimide.

[0069] In order to obtain a polyimide laminate having superior adhesion between the inorganic layer and the polyimide layer, the content of the siloxane diamine residue is preferably 0.1 mol % or more and 2.0 mol % or less, more preferably 0.1 mol % or more and 1.0 mol % or less, still more preferably 0.2 mol % or more and 0.9 mol % or less, and particularly preferably 0.3 mol % or more and 0.8 mol % or less, based on the total diamine residues constituting the specific polyimide.

[0070] In order to obtain a polyimide laminate having excellent adhesion between the inorganic layer and the polyimide layer while reducing the linear expansion coefficient of the second polyimide layer, the total content of siloxane diamine residues and PDA residues is preferably 70 mol % or more and 100 mol % or less, more preferably 90 mol % or more and 100 mol % or less, even more preferably 95 mol % or more and 100 mol % or less, still more preferably 99 mol % or more and 100 mol % or less, and may be 100 mol %, based on all diamine residues constituting the specific polyimide.

[0071] Examples of the acid dianhydride for forming the tetracarboxylic dianhydride residue in the specific polyimide include 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter, sometimes referred to as "BPDA"), pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8 ... Examples of acid dianhydrides include phthalenetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 4,4'-sulfonyldiphthalic anhydride, p-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, m-terphenyl-3,3',4,4'-tetracarboxylic dianhydride, etc. As the acid dianhydride, a compound in which a substituent is bonded to the aromatic ring of the acid dianhydride listed above may also be used.

[0072] Furthermore, an alicyclic tetracarboxylic acid dianhydride can also be used as the acid dianhydride. Examples of the alicyclic tetracarboxylic acid dianhydride include (1S,2R,4S,5R)-cyclohexanetetracarboxylic acid dianhydride (cis,cis,cis-1,2,4,5-cyclohexanetetracarboxylic acid dianhydride), (1S,2S,4R,5R)-cyclohexanetetracarboxylic acid dianhydride, (1R,2S,4S,5R)-cyclohexanetetracarboxylic acid dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid dianhydride, 5-(dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride, Examples include 4-(2,5-dioxotetrahydrofuran-3-yl)-tetralin-1,2-dicarboxylic acid anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic acid dianhydride, bicyclo-3,3',4,4'-tetracarboxylic acid dianhydride, 1,2,3,4-cyclopentane tetracarboxylic acid dianhydride, 1,2,3,4-cyclobutane tetracarboxylic acid dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic acid dianhydride, and 1,4-dimethyl-1,2,3,4-cyclobutane tetracarboxylic acid dianhydride.

[0073] In order to reduce the linear expansion coefficient of the second polyimide layer, the specific polyimide preferably has a BPDA residue as an acid dianhydride residue. In this case, in order to further reduce the linear expansion coefficient of the second polyimide layer, the content of the BPDA residue is preferably 50 mol% to 100 mol%, more preferably 70 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, still more preferably 95 mol% to 100 mol%, and may even be 100 mol%, based on the total acid dianhydride residues constituting the specific polyimide.

[0074] In order to obtain a polyimide laminate having excellent adhesion between the inorganic layer and the polyimide layer in a high-temperature process, it is preferable that the specific polyimide does not contain fluorine. When the specific polyimide does not contain fluorine, generation of hydrogen fluoride in a high-temperature process can be suppressed. This can suppress poor adhesion between the inorganic layer and the polyimide layer due to hydrogen fluoride.

[0075] [Polyimide contained in the first polyimide layer] The polyimide contained in the first polyimide layer may be the above-mentioned specific polyimide or a polyimide other than the specific polyimide. In order to obtain a polyimide laminate having excellent adhesion between the inorganic layer and the first polyimide layer, it is preferable that the polyimide contained in the first polyimide layer is the specific polyimide. When the polyimide contained in the first polyimide layer is the specific polyimide, the specific polyimide contained in the first polyimide layer and the specific polyimide contained in the second polyimide layer may be the same type or different types.

[0076] The first polyimide layer preferably has a linear expansion coefficient of 20 ppm / K or less, and therefore the polyimide contained in the first polyimide layer preferably has a rigid structure. Examples of rigid polyimides include polyimides having PDA residues and BPDA residues. The linear expansion coefficient of the first polyimide layer can be measured by the same method as in the examples described below or a method equivalent thereto.

[0077] When the polyimide contained in the first polyimide layer is a specific polyimide, the preferred embodiment of the polyimide contained in the first polyimide layer is the same as the above-mentioned [Polyimide contained in the second polyimide layer].

[0078] [Preferred Aspects of the First Embodiment] In order to obtain a polyimide laminate having excellent adhesion between the inorganic layer and the polyimide layer while reducing the linear expansion coefficient of the second polyimide layer, the polyimide laminate according to the first embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, and even more preferably satisfies the following condition 3. Condition 1: The specific polyimide contained in the second polyimide layer has a siloxane diamine residue and a PDA residue as diamine residues. Condition 2: The above condition 1 is satisfied, and the content of the siloxane diamine residue is 0.1 mol % or more and 2.0 mol % or less with respect to all diamine residues constituting the specific polyimide contained in the second polyimide layer. Condition 3: The above condition 2 is satisfied, and the specific polyimide contained in the second polyimide layer has a BPDA residue as an acid dianhydride residue.

[0079] Second Embodiment: Supported Polyimide Laminate Next, a supported polyimide laminate according to a second embodiment of the present invention will be described. The supported polyimide laminate according to the second embodiment includes a support and the polyimide laminate according to the first embodiment described above. In the supported polyimide laminate according to the second embodiment, the support is disposed on the first polyimide layer side of the polyimide laminate. The supported polyimide laminate according to the second embodiment includes the polyimide laminate according to the first embodiment, and therefore exhibits excellent adhesion between the inorganic layer and the polyimide layer. Therefore, when the supported polyimide laminate according to the second embodiment is used as, for example, a substrate material for manufacturing a flexible display, it is easy to handle when forming a TFT layer or an OLED layer. In the following description, details that overlap with those of the first embodiment may be omitted.

[0080] The configuration of a supported polyimide laminate according to the second embodiment will be described below with reference to Fig. 3. Fig. 3 is a cross-sectional view showing an example of a supported polyimide laminate according to the second embodiment. As shown in Fig. 3, a supported polyimide laminate 100 includes a support 101 and a polyimide laminate 10, and the support 101 is disposed on the first polyimide layer 11 side of the polyimide laminate 10. In the supported polyimide laminate 100 shown in Fig. 3, the support 101 and the first polyimide layer 11 are in contact with each other.

[0081] Examples of the support 101 include a glass substrate, a metal plate, and a polyethylene terephthalate film (PET film), with a glass substrate being preferred from the viewpoint of heat resistance. When a glass substrate is used as the support 101, alkali-free glass is preferred as the material for the glass substrate because it contains relatively few mobile ions. Furthermore, the surface of the glass substrate may be provided with one or more coating layers selected from the group consisting of a silicon oxide layer, a silicon nitride layer, and an amorphous silicon layer.

[0082] When the supported polyimide laminate 100 is used as a substrate material for manufacturing a flexible display, the adhesion strength between the support 101 and the first polyimide layer 11 is preferably 0.10 N / cm or more to improve handleability when forming a TFT layer or an OLED layer. The upper limit of the adhesion strength between the support 101 and the first polyimide layer 11 is not particularly limited, but is, for example, 2.00 N / cm or less. When the polyimide in the first polyimide layer 11 contains a siloxane diamine residue, the adhesion strength between the support 101 and the first polyimide layer 11 can be adjusted, for example, by changing at least one of the type of the siloxane diamine residue and the content of the siloxane diamine residue. The adhesion strength between the support and the first polyimide layer is measured by the same method as in the examples described below or a method equivalent thereto.

[0083] Third Embodiment: Thin-Film Transistor Device Next, a thin-film transistor device according to a third embodiment of the present invention will be described. The thin-film transistor device according to the third embodiment includes the polyimide laminate according to the first embodiment described above and a thin-film transistor layer (TFT layer) disposed on the second polyimide layer of the polyimide laminate. Because the thin-film transistor device according to the third embodiment includes the polyimide laminate according to the first embodiment, the TFT layer exhibits excellent adhesion between the inorganic layer and the polyimide layer while suppressing the occurrence of image retention. In the third embodiment, the TFT layer may be disposed directly on the surface of the second polyimide layer (e.g., the main surface 13a of the second polyimide layer 13 opposite the inorganic layer 12 shown in FIG. 3 ) or indirectly via a silicon oxide layer, a planarization layer, or the like.

[0084] The thin-film transistor device according to the third embodiment can be applied to display devices such as OLED displays, electronic paper, etc. When the thin-film transistor device according to the third embodiment is applied to an OLED display, examples of the configuration of the OLED display other than the polyimide laminate include the configurations described in JP 2021-105704 A, for example.

[0085] <Fourth embodiment: method for manufacturing a polyimide laminate> Next, a method for manufacturing a polyimide laminate according to a fourth embodiment of the present invention will be described. The method for manufacturing a polyimide laminate according to the fourth embodiment is a suitable method for manufacturing the polyimide laminate according to the first embodiment described above. In the following description, the description of the same content as in the first and second embodiments may be omitted.

[0086] The method for producing a polyimide laminate according to the fourth embodiment includes steps Sa, Sb, and Sc. In step Sa, an inorganic layer is formed on a first polyimide layer. In step Sb, a solution (polyamic acid solution) containing a precursor of the polyimide (specific polyimide) contained in the second polyimide layer is applied to the main surface of the inorganic layer opposite the first polyimide layer. In step Sc, the coating film obtained in step Sb is heated to imidize the precursor (polyamic acid).

[0087] The method for producing a polyimide laminate according to the fourth embodiment may include steps (other steps) other than steps Sa, Sb, and Sc. Examples of other steps include a step of preparing a polyamic acid solution, a step of forming a first polyimide layer, and a step of peeling the polyimide laminate from the support. Each step included in an example of the production method according to the fourth embodiment will be described in detail below.

[0088] [Process for Preparing Polyamic Acid Solution] The polyamic acid solution can be prepared (polyamic acid synthesis) using any known method or a combination thereof. A specific example of a polyamic acid synthesis method is a method in which a diamine and a tetracarboxylic dianhydride are reacted in an organic solvent. When synthesizing polyamic acid using a diamine and a tetracarboxylic dianhydride, the desired polyamic acid (a polymer of a diamine and a tetracarboxylic dianhydride) can be obtained by adjusting the molar amount of the diamine (or, if multiple diamines are used, the molar amount of each diamine) and the molar amount of the tetracarboxylic dianhydride (or, if multiple tetracarboxylic dianhydrides are used, the molar amount of each tetracarboxylic dianhydride). The molar fraction of each residue in the polyimide formed from the polyamic acid corresponds, for example, to the molar fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the polyamic acid.

[0089] In order to improve the adhesion between the inorganic layer and the polyimide layer while improving the film quality of the resulting polyimide film, the molar ratio obtained by dividing the total amount of tetracarboxylic dianhydrides used in the synthesis by the total amount of diamines used in the synthesis is preferably 0.950 or more and 1.050 or less, more preferably 0.980 or more and 1.020 or less, and even more preferably 0.990 or more and 1.010 or less. Hereinafter, the molar ratio obtained by dividing the total amount of tetracarboxylic dianhydrides used in the synthesis by the total amount of diamines used in the synthesis (total amount of tetracarboxylic dianhydrides / total amount of diamines) may be referred to as the "acid dianhydride / diamine ratio."

[0090] The temperature conditions for the reaction between the diamine and the tetracarboxylic dianhydride, i.e., the synthesis reaction of the polyamic acid, are not particularly limited, but are, for example, in the range of 10° C. to 150° C. The reaction time for the synthesis reaction of the polyamic acid is, for example, in the range of 10 minutes to 30 hours.

[0091] Examples of organic solvents that can be used when reacting a diamine with a tetracarboxylic dianhydride include urea-based solvents such as N,N-dimethylethylurea; sulfoxide-based solvents such as dimethyl sulfoxide; sulfone-based solvents such as tetramethyl sulfone; amide-based solvents such as N,N-dimethylformamide, N,N-diethylformamide, N-methyl-2-pyrrolidone, and N-butyl-2-pyrrolidone; ester-based solvents such as γ-butyrolactone; alkyl halide-based solvents such as chloroform; aromatic hydrocarbon-based solvents such as toluene; phenol-based solvents such as phenol; ketone-based solvents such as cyclopentanone; and ether-based solvents such as tetrahydrofuran. These solvents are typically used alone, but two or more may be used in combination as needed. When polyamic acid is obtained by the above-described synthesis method, the reaction solution (post-reaction solution) itself may be used as a polyamic acid solution. In this case, the organic solvent in the polyamic acid solution is the same as the organic solvent used in the reaction in the above-described synthesis method. Alternatively, a polyamic acid solution may be prepared by dissolving the solid polyamic acid obtained by removing the solvent from the reaction solution in an organic solvent.

[0092] The polyamic acid solution may contain additives such as dyes, surfactants, leveling agents, plasticizers, silicones, sensitizers, and silane coupling agents. Furthermore, a filler may be added to the polyamic acid solution to improve various film properties such as sliding properties, thermal conductivity, electrical conductivity, corona resistance, and loop stiffness. Any filler may be used, but preferred examples include fillers made of silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, and the like.

[0093] The concentration of polyamic acid in the polyamic acid solution is not particularly limited, and is, for example, 5% by weight to 40% by weight, preferably 8% by weight to 30% by weight, based on the total amount of the polyamic acid solution.

[0094] An imidazole-based compound can also be added to the polyamic acid solution. In this specification, the term "imidazole-based compound" refers to a compound having a 1,3-diazole ring (1,3-diazole ring structure). Examples of the imidazole-based compound include, but are not limited to, imidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4,5-triphenylimidazole, and 4,5-diphenylimidazole. Furthermore, a compound containing a 1,3-diazole ring in a condensed ring may also be used as the imidazole-based compound. Examples of imidazole compounds containing a 1,3-diazole ring in the condensed ring include benzimidazole and 2-phenylbenzimidazole.

[0095] The content of the imidazole compound is preferably 0.1 part by weight or more and 1.0 part by weight or less, and more preferably 0.2 part by weight or more and 0.8 part by weight or less, relative to 100 parts by weight of polyamic acid in the polyamic acid solution. By adding 0.1 part by weight or more of the imidazole compound, the film strength of the polyimide can be improved, and by setting the content of the imidazole compound to 1.0 part by weight or less, the storage stability of the polyamic acid can be maintained at a good level.

[0096] In order to improve the film strength of the polyimide and thereby further enhance the adhesion between the inorganic layer and the polyimide layer, the polyamic acid solution preferably contains an imidazole-based compound having a boiling point of 250° C. or higher and 400° C. or lower. Examples of imidazole-based compounds having a boiling point of 250° C. or higher and 400° C. or lower include imidazole, 2-methylimidazole, 2-phenylimidazole, benzimidazole, 2-phenylbenzimidazole, 2,4,5-triphenylimidazole, and 4,5-diphenylimidazole.

[0097] Next, the step of forming the first polyimide layer, step Sa, step Sb, step Sc, and the step of peeling the polyimide laminate from the support will be described with reference to FIG. 3 as needed.

[0098] [Step of Forming First Polyimide Layer] The method for forming the first polyimide layer is not particularly limited, and various known methods can be used. An example of the method for forming the first polyimide layer will be described below.

[0099] First, a polyamic acid solution (more specifically, a solution containing polyamic acid, which is a precursor of the polyimide constituting the first polyimide layer 11) is applied to one main surface 101a of the support 101 to form a coating film containing polyamic acid. The method for applying the polyamic acid solution to one main surface 101a of the support 101 is not particularly limited, and a method using a conventional coating device (coating tool) such as a bar coater, die coater, Comma Coater (registered trademark), reverse coater, or knife coater can be employed. Next, the coating film is heated, for example, at a temperature of 40°C or higher and 200°C or lower. The heating time is, for example, 3 minutes or longer and 120 minutes or shorter. Next, to promote imidization of the polyamic acid in the coating film, the coating film is heated, for example, at a maximum temperature of 200°C or higher and 500°C or lower. The heating time (heating time at the maximum temperature) is, for example, 1 minute or longer and 300 minutes or shorter. It is preferable to gradually increase the temperature from a low temperature to the maximum temperature. The temperature rise rate is preferably 2°C / min or more and 10°C / min or less, and more preferably 4°C / min or more and 10°C / min or less. The maximum temperature is preferably 250°C or more and 470°C or less. A maximum temperature of 250°C or more allows for sufficient imidization, while a maximum temperature of 470°C or less can suppress thermal degradation of the polyimide. The temperature may be maintained at any desired temperature for any desired time before reaching the maximum temperature. The imidization reaction can be carried out in air, under reduced pressure, or in an inert gas such as nitrogen. Known heating devices such as a hot air oven, infrared oven, vacuum oven, inert oven, and hot plate can be used. Through these steps, the polyamic acid in the coating film is imidized, and a first polyimide layer 11 is formed on one main surface 101a of the support 101.

[0100] [Step Sa] Step Sa is a step of forming an inorganic layer 12 on the first polyimide layer 11. For example, when forming the inorganic layer 12 shown in Fig. 3, a specific silicon oxide layer that will become the inorganic layer 12 is formed on the main surface 11a of the first polyimide layer 11 opposite the support 101 side by, for example, sputtering or plasma-enhanced chemical vapor deposition (plasma CVD). In order to form a high-resistance, dense film, the plasma CVD method is preferred as the method for forming the inorganic layer 12.

[0101] When the inorganic layer 12 is formed by plasma CVD on the main surface 11a of the first polyimide layer 11 opposite the support 101 side, the main surface 11a of the first polyimide layer 11 tends to have an uneven shape. Therefore, when the inorganic layer 12 is formed by plasma CVD on the main surface 11a of the first polyimide layer 11 opposite the support 101 side, the adhesion between the first polyimide layer 11 and the inorganic layer 12 tends to be high.

[0102] When forming the specific silicon oxide layer by the plasma CVD method, the film formation temperature is preferably 280° C. or higher and 400° C. or lower, more preferably 320° C. or higher and 400° C. or lower, from the viewpoint of increasing the film density. When forming the specific silicon oxide layer by the plasma CVD method, the film formation gas is preferably silane (SiH ４ ) and nitrous oxide (N ２ O) is preferred.

[0103] When a silicon nitride layer is formed by plasma CVD before forming the specific silicon oxide layer, the temperature for forming the silicon nitride layer is preferably 280° C. or higher and 400° C. or lower, more preferably 320° C. or higher and 400° C. or lower, from the viewpoint of increasing the film density. Silane (SiH ４ ) and ammonia (NH ３ ) is preferred.

[0104] [Step Sb] Step Sb is a step of applying a solution (polyamic acid solution) containing a precursor of the polyimide (specific polyimide) contained in the second polyimide layer 13 to the main surface 12a of the inorganic layer 12 opposite to the first polyimide layer 11. The method of applying the polyamic acid solution in step Sb can be the same as the method of applying the polyamic acid solution in the above-mentioned [Step of Forming a First Polyimide Layer], except that a polyamic acid solution containing polyamic acid, which is a precursor of the polyimide constituting the second polyimide layer 13, is used.

[0105] [Step Sc] In step Sc, the coating film obtained in step Sb is heated to imidize the precursor (polyamic acid). The imidization method in step Sc can be the same as the imidization method in the above-mentioned [Step of Forming a First Polyimide Layer].

[0106] [Step of Peeling Polyimide Laminate from Support] The method for peeling the polyimide laminate 10 from the support 101 is not particularly limited, and any known method can be used. Examples of known methods include a method of peeling the polyimide laminate 10 by hand, a method of peeling the polyimide laminate 10 using a mechanical device such as a drive roll or a robot, and a method of irradiating a laser beam from the support 101 side toward the first polyimide layer 11 to separate the polyimide laminate 10 from the support 101. In order to easily peel the polyimide laminate 10, a release layer may be provided on the surface of the support 101 facing the first polyimide layer 11.

[0107] Through the steps described above, a polyimide laminate 10 having a three-layer structure consisting of the first polyimide layer 11, the inorganic layer 12, and the second polyimide layer 13 is obtained.

[0108] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0109] <Preparation of Polyamic Acid Solutions> The methods for preparing polyamic acid solutions P1 to P6 used in the Examples and Comparative Examples are described below. Note that the compounds and reagents are abbreviated as follows. The preparation of polyamic acid solutions P1 to P6 was all carried out under a nitrogen atmosphere. NMP: N-methyl-2-pyrrolidone PDA: p-phenylenediamine PAM-E: 1,3-bis(3-aminopropyl)tetramethyldisiloxane BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride APS: 3-aminopropyltriethoxysilane 2PhI: 2-phenylimidazole

[0110] [Preparation of Polyamic Acid Solution P1] 155.3 g of NMP was placed in a 500 mL glass separable flask equipped with a stainless steel stirrer and a nitrogen inlet tube as the organic solvent for polymerization. Next, 8.01 g of PDA was added to the flask and dissolved in the flask while stirring the contents in an atmosphere at 23°C. Next, 14.82 g of a previously prepared PAM-E solution (solvent: NMP, PAM-E concentration: 1 wt%) was added to the flask while stirring the contents in an atmosphere at 23°C, followed by the addition of 21.85 g of BPDA. Next, the contents of the flask were stirred for 6 hours in an atmosphere at 90°C, after which NMP was added to the flask to obtain Polyamic Acid Solution P1 with a solids concentration of 11 wt% and a viscosity of 40 poise. In the preparation of Polyamic Acid Solution P1, the dianhydride / diamine ratio was 0.995.

[0111] [Preparation of Polyamic Acid Solution P2] Polyamic acid solution P2 was prepared in the same manner as polyamic acid solution P1, except that the diamines used were charged in the amounts shown in Table 1, and the acid dianhydride / diamine ratio was set as shown in Table 1. The total amount of diamines used in preparing polyamic acid solution P2 was the same as the total amount of acid dianhydrides used in preparing polyamic acid solution P1.

[0112] [Preparation of Polyamic Acid Solution P3] A polyamic acid solution was prepared in the same manner as in the polyamic acid solution P2, and then 2PhI was added to the resulting polyamic acid solution to obtain polyamic acid solution P3. The amount of 2PhI added was 0.3 parts by weight per 100 parts by weight of polyamic acid.

[0113] [Preparation of Polyamic Acid Solution P4] 170.0 g of NMP was placed in a 500 mL glass separable flask equipped with a stainless steel stirrer and a nitrogen inlet tube as the organic solvent for polymerization. Next, 8.09 g of PDA was added to the flask and dissolved while stirring the contents in an atmosphere at 23°C. Next, 21.91 g of BPDA was added to the flask while stirring the contents in an atmosphere at 23°C. Next, the contents in the flask were stirred for 6 hours in an atmosphere at 90°C, after which APS was added to the flask, and the contents were further stirred. Next, NMP was added to the flask to obtain polyamic acid solution P4 with a solids concentration of 11 wt% and a viscosity of 40 poise. The amount of APS added was 0.2 mol% relative to 100 mol% of PDA used. In the preparation of polyamic acid solution P4, the dianhydride / diamine ratio was 0.995.

[0114] [Preparation of Polyamic Acid Solution P5] Polyamic acid solution P5 was prepared in the same manner as polyamic acid solution P4, except that APS was not added.

[0115] [Preparation of Polyamic Acid Solution P6] A polyamic acid solution was prepared in the same manner as in the polyamic acid solution P5, and then 2PhI was added to the resulting polyamic acid solution to obtain polyamic acid solution P6. The amount of 2PhI added was 0.3 parts by weight per 100 parts by weight of polyamic acid.

[0116] Table 1 shows the acid dianhydrides used and their charge ratios, the diamines used and their charge ratios, the amounts of 2PhI and APS added, and the acid dianhydride / diamine ratio for polyamic acid solutions P1 to P6. In Table 1, a "-" indicates that the corresponding component was not used. In Table 1, the values ​​in the "Acid Dianhydride" column represent the content (unit: mol%) of each acid dianhydride relative to the total amount of acid dianhydrides used. In Table 1, the values ​​in the "Diamine" column represent the content (unit: mol%) of each diamine relative to the total amount of diamines used. In Table 1, the values ​​in the "2PhI" column represent the amount (unit: parts by weight) of 2PhI relative to 100 parts by weight of the synthesized polyamic acid. In Table 1, the values ​​in the "APS" column represent the content (unit: mol%) relative to 100 mol% of PDA used. Furthermore, for each of the polyamic acid solutions P1 to P6, the molar fraction of each polyamic acid residue in the prepared polyamic acid solution was consistent with the molar fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the polyamic acid.

[0117]

[0118] <Preparation of Supported Polyimide Laminates and Polyimide Laminates> Hereinafter, the methods for preparing the supported polyimide laminates of Examples 1 to 3 and Comparative Examples 1 to 3 and the polyimide laminates of Examples 1 to 3 and Comparative Examples 1 to 3 will be described.

[0119] [Example 1] (Formation of First Polyimide Layer) The polyamic acid solution P1 was applied to a Corning glass substrate (trade name: Lotus NXT, material: alkali-free glass, thickness: 0.5 mm, size: 100 mm × 100 mm) as a support using a bar coater, and heated in a hot air oven at a temperature of 120 ° C. for 30 minutes. Next, the obtained glass substrate with the coating film was heated from 20 ° C. to 450 ° C. at a heating rate of 7 ° C. / min in a nitrogen atmosphere, and then heated at a temperature of 450 ° C. for 10 minutes to imidize the polyamic acid in the coating film, thereby obtaining a laminate L1 of the glass substrate and a first polyimide layer (thickness: 10 μm).

[0120] (Formation of Inorganic Layer) Next, an inorganic layer (a single inorganic layer consisting of a SiOx layer) was formed on the first polyimide layer of the obtained laminate L1 by plasma CVD. Specifically, the film formation temperature was set to 380° C., and the gas type was SiH ４ and N ２ Using O, a 600 nm thick SiOx layer was formed on the first polyimide layer, resulting in a laminate L2 having a three-layer structure of glass substrate / first polyimide layer / inorganic layer (SiOx layer). The SiOx layer of the obtained laminate L2 was analyzed using an X-ray photoelectron spectrometer ("PHI Quantera II" manufactured by ULVAC-PHI, Inc.), and it was confirmed that x in SiOx was 1.7. When analyzing with the X-ray photoelectron spectrometer, monochromated AlKα was used as the X-ray source, and the detection depth was set to 4 to 5 nm, and elemental analysis of Si, O, and N was performed.

[0121] (Formation of Second Polyimide Layer) Next, polyamic acid solution P1 was applied to the main surface of the inorganic layer of the obtained laminate L2 opposite to the first polyimide layer side using a bar coater, and heated in a hot air oven for 30 minutes at a temperature of 120° C. Next, the obtained laminate L2 with coating film was heated from 20° C. to 450° C. at a heating rate of 7° C. / min in a nitrogen atmosphere, and then heated at a temperature of 450° C. for 10 minutes to imidize the polyamic acid in the coating film, thereby obtaining a supported polyimide laminate (supported polyimide laminate of Example 1) having a four-layer structure of glass substrate / first polyimide layer / inorganic layer / second polyimide layer (thickness: 6 μm).

[0122] (Peeling from Glass Substrate) Next, the layers of the obtained supported polyimide laminate other than the support were cut into a size of 3 cm × 4 cm using a cutter knife. Next, the cut polyimide laminate was peeled off from the glass substrate at a peel angle of 90° to obtain a polyimide laminate having a three-layer structure of a first polyimide layer / an inorganic layer / a second polyimide layer (the polyimide laminate of Example 1).

[0123] [Examples 2 and 3] Supported polyimide laminates of Examples 2 and 3, and polyimide laminates of Examples 2 and 3, respectively, were obtained in the same manner as in Example 1, except that the types of polyamic acid solutions used in forming the first polyimide layer and the second polyimide layer were as shown in Table 2.

[0124] [Comparative Examples 1 to 3] Supported polyimide laminates of Comparative Examples 1 to 3 and polyimide laminates of Comparative Examples 1 to 3 were obtained in the same manner as in Example 1, except that the types of polyamic acid solutions used in forming the first polyimide layer and the second polyimide layer were as shown in Table 2. In all of Comparative Examples 1 to 3, when the polyimide laminate was peeled off from the glass substrate, the adhesion strength between the second polyimide layer and the inorganic layer was too small, and therefore the second polyimide layer partially peeled off.

[0125] <Measurement Method and Evaluation Method> [Linear Expansion Coefficient of First Polyimide Layer] For samples for measuring the linear expansion coefficient of the first polyimide layer of Example 1 and Comparative Example 1, a first polyimide layer was formed by the method described above, and then peeled off from the glass substrate to obtain a polyimide film (size: 10 mm × 3 mm) for measurement. Next, using a thermal analyzer (Hitachi High-Tech Science Corporation, "TMA / SS120CU"), the linear expansion coefficient of the polyimide film was measured with a load of 29.4 mN applied to the long side of the polyimide film. Specifically, in a nitrogen atmosphere, the polyimide film was heated from 20°C to 550°C at a heating rate of 5°C / min, cooled to 20°C at a heating rate of 40°C / min, and then heated again to 550°C at a heating rate of 5°C / min. The linear expansion coefficient was calculated from the strain from 100°C to 400°C during the second heating.

[0126] [Cross-section folding test] First, each polyimide laminate was cut into 10 mm widths with a cutter knife to obtain evaluation samples. The obtained evaluation samples were then folded 180° with a 0.2 mm thick plastic plate sandwiched between them, and a 1 kg weight was placed on the folded portion for 5 seconds. The weight was then removed, the evaluation sample was opened 180°, and the weight was placed again on the folded portion for 5 seconds with the inner side facing downwards. After removing the weight, the folded portion was observed under a microscope to confirm the presence or absence of delamination between the second polyimide layer and the inorganic layer.

[0127] [Adhesion Strength] (Adhesion Strength Between Inorganic Layer and Second Polyimide Layer) First, a 10 mm wide cut was made with a cutter knife in accordance with ASTM D1876-01 in the layer other than the support of each supported polyimide laminate to obtain a measurement sample. Next, the obtained measurement sample was used to measure the average peel strength when the second polyimide layer was peeled off 50 mm at a temperature of 23 ° C. and a relative humidity of 55% under conditions of a tensile speed of 50 mm / min and a peel angle of 90°. The obtained value was taken as the adhesion strength. When the adhesion strength was 0.20 N / cm or more, it was evaluated as "excellent adhesion between the inorganic layer and the second polyimide layer." On the other hand, when the adhesion strength was less than 0.20 N / cm, it was evaluated as "poor adhesion between the inorganic layer and the second polyimide layer."

[0128] (Adhesion Strength Between Support and First Polyimide Layer) First, a 10 mm wide cut was made with a cutter knife in accordance with ASTM D1876-01 in the layer other than the support of each supported polyimide laminate to obtain a measurement sample. Next, for the obtained measurement sample, a tensile tester ("Strograph VES1D" manufactured by Toyo Seiki Seisaku-sho, Ltd.) was used to measure the average peel strength when peeling 50 mm of the first polyimide layer (specifically, the polyimide laminate) at a temperature of 23 ° C. and a relative humidity of 55% under conditions of a tensile speed of 50 mm / min and a peel angle of 90°. The obtained value was taken as the adhesion strength. When the adhesion strength was 0.10 N / cm or more, it was evaluated as "excellent adhesion between the support and the first polyimide layer." On the other hand, when the adhesion strength was less than 0.10 N / cm, it was evaluated as "poor adhesion between the support and the first polyimide layer."

[0129] <Results> Table 2 shows the polyamic acid solutions used, the linear expansion coefficients of the first polyimide layer, the evaluation results of the seam folding test, the adhesion strength between the inorganic layer and the second polyimide layer, and the adhesion strength between the support and the first polyimide layer for Examples 1 to 3 and Comparative Examples 1 to 3. In Table 2, "-" means that no measurement was performed.

[0130]

[0131] As shown in Tables 1 and 2, the polyimide contained in the second polyimide layer in Examples 1 to 3 contained a siloxane diamine residue (PAM-E residue). As shown in Table 2, the adhesion strength between the inorganic layer and the second polyimide layer in Examples 1 to 3 was 0.20 N / cm or more. Therefore, the polyimide laminates of Examples 1 to 3 had excellent adhesion between the inorganic layer and the second polyimide layer.

[0132] As shown in Tables 1 and 2, the polyimide contained in the second polyimide layer did not contain a siloxane diamine residue in Comparative Examples 1 to 3. As shown in Table 2, the adhesion strength between the inorganic layer and the second polyimide layer was less than 0.20 N / cm in Comparative Examples 1 to 3. Therefore, the polyimide laminates of Comparative Examples 1 to 3 did not have excellent adhesion between the inorganic layer and the second polyimide layer.

[0133] The above results demonstrate that the present invention can provide a polyimide laminate having excellent adhesion between an inorganic layer and a polyimide layer in a configuration in which no amorphous silicon layer is interposed between two polyimide layers.

[0134] 10, 20 Polyimide laminate 11 First polyimide layer 12, 21 Inorganic layer 13 Second polyimide layer 100 Supported polyimide laminate 101 Support

Claims

1. A polyimide laminate comprising, in this order, a first polyimide layer, an inorganic layer, and a second polyimide layer, wherein the inorganic layer contains a silicon oxide layer containing silicon oxide with a higher silicon content than in the stoichiometric composition, but does not contain an amorphous silicon layer, the second polyimide layer and the silicon oxide layer are in contact with each other, and the polyimide contained in the second polyimide layer has a tetracarboxylic dianhydride residue and a diamine residue, and the diamine residue includes a siloxane diamine residue.

2. The polyimide laminate according to claim 1, wherein the silicon oxide having a higher silicon content than the stoichiometric composition is represented by the following general formula (1): SiOx (1) (in general formula (1), x represents a real number of 1.3 or more and less than 2.0).

3. The polyimide laminate according to claim 1, wherein the siloxane diamine residue is a divalent organic group represented by the following general formula (2): (In the general formula (2), R １ and R ２ each independently represents a divalent hydrocarbon group, and n represents an integer of 1 or more and 5 or less.

4. The polyimide laminate according to claim 1, wherein the tetracarboxylic dianhydride residues include 3,3',4,4'-biphenyltetracarboxylic dianhydride residues.

5. The polyimide laminate of claim 1, wherein the diamine residues further include p-phenylenediamine residues.

6. The polyimide laminate according to claim 1, having a thickness of 5 μm or more and 30 μm or less.

7. The polyimide laminate according to claim 6, wherein the thickness of said first polyimide layer is greater than the thickness of said second polyimide layer.

8. The polyimide laminate according to claim 1, wherein the adhesive strength between the inorganic layer and the second polyimide layer is 0.20 N / cm or more.

9. A polyimide laminate with a support, comprising a support and the polyimide laminate according to any one of claims 1 to 8, wherein the support is disposed on the first polyimide layer side of the polyimide laminate.

10. A supported polyimide laminate according to claim 9, wherein the adhesive strength between the support and the first polyimide layer is 0.10 N / cm or more.

11. A thin film transistor device comprising the polyimide laminate according to any one of claims 1 to 8 and a thin film transistor layer disposed on the second polyimide layer of the polyimide laminate.

12. A method for producing a polyimide laminate according to any one of claims 1 to 8, comprising: step Sa of forming the inorganic layer on the first polyimide layer; step Sb of applying a solution containing a precursor of the polyimide contained in the second polyimide layer to a main surface of the inorganic layer opposite to the first polyimide layer; and step Sc of heating the coating film obtained in step Sb to imidize the precursor.

13. The method for producing a polyimide laminate according to claim 12, wherein the solution containing the precursor further contains an imidazole compound having a boiling point of 250°C or higher and 400°C or lower.

14. The method for producing a polyimide laminate according to claim 12, wherein in step Sa, the inorganic layer is formed by plasma-enhanced chemical vapor deposition.

Images