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

Abstract

The polyimide laminate (10) of the present application has, in order, a first polyimide layer (11), an inorganic layer (12), and a second polyimide layer (13). The inorganic layer (12) contains a silicon oxide layer and does not contain an amorphous silicon layer, and the silicon oxide layer contains silicon oxide having a larger ratio of silicon than the stoichiometric composition. 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

Technical Field

[0001] This invention relates to a polyimide laminate, a polyimide laminate with a support, a thin-film transistor device, and a method for manufacturing a polyimide laminate. Background Technology

[0002] As displays used in smartphones, televisions, automotive displays, etc., displays equipped with organic light-emitting diodes (hereinafter sometimes referred to as "OLED displays") are known. In OLED displays, when switching between display screens, there is sometimes a problem of persistent image retention before the switch (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 stack having a first polyimide layer, a silicon oxide layer, an amorphous silicon layer, and a second polyimide layer in sequence. 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] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2019 / 073929

[0007] Patent Document 2: Japanese Patent Application Publication No. 2021-105704 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] In the OLED display with a polyimide stack disclosed in Patent Document 2, the following are examples of causes of image retention: Because the amorphous silicon layer in the polyimide stack has low resistance, electrons are drawn to the amorphous silicon layer by the electric field of the TFT, making the polyimide stack more easily charged. However, if the amorphous silicon layer is not provided in the polyimide stack, the adhesion between the silicon oxide layer (inorganic layer) and the second polyimide layer decreases.

[0010] In view of the above, the object of the present invention is to provide a polyimide laminate with excellent adhesion between the inorganic layer and the polyimide layer in a configuration in which no amorphous silicon layer is interposed between the two polyimide layers, a method for manufacturing the same, a polyimide laminate with a support having the polyimide laminate, and a thin film transistor device.

[0011] Solution for solving the problem

[0012] <Forms of the Invention>

[0013] The present invention includes the following forms.

[0014] [1] A polyimide laminate comprising, sequentially comprising a first polyimide layer, an inorganic layer and a second polyimide layer,

[0015] The aforementioned inorganic layer contains a silicon oxide layer but not an amorphous silicon layer, wherein the silicon oxide layer comprises silicon oxide with a high proportion of silicon relative to the stoichiometric composition.

[0016] The second polyimide layer is in contact with the silicon oxide layer.

[0017] The polyimide contained in the second polyimide layer has tetracarboxylic dianhydride residues and diamine residues.

[0018] The diamine residues mentioned above include siloxane diamine residues.

[0019] [2] The polyimide laminate described in [1] above, wherein the silicon oxide with a high ratio of silicon to the stoichiometric composition is represented by the following general formula (1).

[0020] SiOx (1)

[0021] (In the above general formula (1), x represents a real number greater than 1.3 and less than 2.0.)

[0022] [3] The polyimide laminate as described in [1] or [2] above, wherein the siloxane diamine residue is a divalent organic group represented by the following general formula (2).

[0023] [Chemistry 1]

[0024]

[0025] In the above general formula (2), R 1 and R 2 Each of the two groups represents a divalent hydrocarbon group independently, and n represents an integer between 1 and 5.

[0026] [4] The polyimide laminate as described in any of [1] to [3] above, wherein the tetracarboxylic dianhydride residues include 3,3',4,4'-biphenyltetracarboxylic dianhydride residues.

[0027] [5] The polyimide laminate described in any of [1] to [4] above, wherein the diamine residues further include p-phenylenediamine residues.

[0028] [6] The polyimide laminate described in any of [1] to [5] above has a thickness of 5 μm or more and 30 μm or less.

[0029] [7] The polyimide laminate as described in [6] above, wherein the thickness of the first polyimide layer is greater than the thickness of the second polyimide layer.

[0030] [8] The polyimide laminate as described in any of [1] to [7] above, wherein the adhesion strength between the inorganic layer and the second polyimide layer is 0.20 N / cm or more.

[0031] [9] A polyimide laminate with a support, comprising a support and a polyimide laminate as described in any one of [1] to [8] above.

[0032] The aforementioned support is disposed on the side of the first polyimide layer of the aforementioned polyimide laminate.

[0033]

[10] The polyimide laminate with a support as described in [9] above, wherein the adhesion strength between the support and the first polyimide layer is 0.10 N / cm or more.

[0034]

[11] A thin film transistor device comprising: a polyimide stack as described in any one of [1] to [8] above, and a thin film transistor layer disposed on the second polyimide layer of the polyimide stack.

[0035]

[12] A method for manufacturing a polyimide laminate, which is a method for manufacturing a polyimide laminate as described in any one of [1] to [8] above, the method comprising the following steps:

[0036] In step Sa, the inorganic layer is formed on the first polyimide layer;

[0037] In step Sb, a solution containing the precursor of the polyimide contained in the second polyimide layer is coated onto the main surface of the inorganic layer opposite to the side of the first polyimide layer; and

[0038] In step Sc, the coating film obtained through step Sb is heated to imidize the precursor.

[0039]

[13] The method for manufacturing a polyimide laminate as described in

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

[0040]

[14] The method for manufacturing a polyimide laminate as described in

[12] or

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

[0041] The effects of the invention

[0042] According to the present invention, a polyimide laminate with excellent adhesion between the inorganic layer and the polyimide layer in a configuration in which an amorphous silicon layer is not interposed between two polyimide layers is provided, as well as a method for manufacturing the same, and a polyimide laminate with a support having the polyimide laminate and a thin film transistor device. Attached Figure Description

[0043] Figure 1 A cross-sectional view showing an example of a polyimide laminate according to the first embodiment of the present invention.

[0044] Figure 2 A cross-sectional view showing another example of a polyimide laminate according to the first embodiment of the present invention.

[0045] Figure 3 A cross-sectional view showing an example of a polyimide laminate with a support according to the second embodiment of the present invention. Detailed Implementation

[0046] The following describes suitable embodiments of the present invention in detail, but the present invention is not limited thereto. Furthermore, all academic and patent documents described in this specification are incorporated herein by reference.

[0047] First, the terms used in this specification will be explained. “Structural unit” refers to a repeating unit that constitutes a polymer. “Polyimide” is a polymer that contains the structural unit represented by the following general formula (3) (hereinafter sometimes referred to as “structural unit (3)”).

[0048]

[0049] In general formula (3), X 1 X represents a tetracarboxylic dianhydride residue (derived from a tetravalent organic group of tetracarboxylic dianhydride). 2 It represents a diamine residue (an organic group derived from the divalent form of a diamine).

[0050] The content of structural unit (3) relative to all structural units constituting 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, even more preferably 90 mol% or more and 100 mol% or less, and may also be 100 mol%.

[0051] "Polyamic acid" is a polymer containing the structural unit represented by the following general formula (4) (hereinafter sometimes referred to as "structural unit (4)").

[0052] [Chemistry 3]

[0053]

[0054] In general formula (4), A 1 Indicates a tetracarboxylic dianhydride residue (derived from a tetravalent organic group of tetracarboxylic dianhydride), A 2 It represents a diamine residue (an organic group derived from the divalent form of a diamine).

[0055] The content of structural unit (4) relative to all structural units constituting 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, even more preferably 90 mol% or more and 100 mol% or less, and may also be 100 mol%.

[0056] Polyimide is an imide derivative of polyamic acid. Therefore, when the content of structural unit (4) relative to all structural units constituting polyamic acid is 100 mol%, the polyimide as an imide derivative of polyamic acid has A in general formula (4). 1 The residues represented are X in general formula (3). 1 And has A in general formula (4) 2 The residues represented are X in general formula (3). 2 .

[0057] The "main face" of a layered material (more specifically, a polyimide layer, an inorganic layer, etc.) refers to the face of the layered material orthogonal to the thickness direction. Unless otherwise specified, the "thickness (film thickness)" of the layered material is the arithmetic mean of 10 measurements obtained by observing a cross-section of the layered material cut along the thickness direction using an electron microscope, randomly selecting 10 measurement sites from the cross-sectional image, and measuring the thickness of these 10 sites.

[0058] Unless otherwise specified, the "coefficient of linear expansion" is the coefficient of linear expansion when the temperature rises from 100°C to 400°C.

[0059] Hereafter, the term "system" is sometimes added after the compound name to provide a general overview of the compound and its derivatives. Furthermore, when "system" is added after the compound name to indicate a polymer, unless otherwise specified, it means that the repeating unit of the polymer originates from the compound or its derivatives. Additionally, tetracarboxylic dianhydrides are sometimes written as "acid dianhydrides".

[0060] Unless otherwise stated, the ingredients or functional groups illustrated in this specification may be used alone or in combination of two or more.

[0061] For ease of understanding, the figures referenced in the following description primarily and schematically illustrate their constituent elements. From the viewpoint of convenient figure creation, the dimensions, number, shape, etc., of the constituent elements in the illustrations may sometimes differ from the actual figures. Furthermore, for ease of explanation, sometimes in the figures described later, the same symbols are used to label the same constituent parts as in the figures described earlier, and their descriptions are omitted.

[0062] <First Embodiment: Polyimide Laminate>

[0063] The polyimide laminate of the first embodiment of the present invention is a polyimide laminate comprising a first polyimide layer, an inorganic layer, and a second polyimide layer sequentially. The inorganic layer contains a silicon oxide layer but does not contain an amorphous silicon layer, and the silicon oxide layer comprises silicon oxide with a silicon ratio greater than the stoichiometric composition. The second polyimide layer is in contact with the silicon oxide layer. The polyimide contained in the second polyimide layer has tetracarboxylic dianhydride residues and diamine residues. The diamine residues of the polyimide contained in the second polyimide layer include siloxane diamine residues.

[0064] Hereinafter, "a silicon oxide layer containing silicon oxide at a ratio greater than that of silicon relative to its stoichiometric composition" will sometimes be referred to as "a specific silicon oxide layer". It should be noted that, in this specification, "a specific silicon oxide layer" does not refer to an amorphous silicon layer.

[0065] Although the inorganic layer of the polyimide laminate in the first embodiment does not contain an amorphous silicon layer (adhesive layer), the adhesion between the inorganic layer and the polyimide layer is excellent. The reason for this is speculated to be as follows.

[0066] In the polyimide laminate of the first embodiment, a specific silicon oxide layer in the inorganic layer is bonded to the second polyimide layer. Furthermore, in the polyimide laminate of the first embodiment, the polyimide contained in the second polyimide layer includes siloxane diamine residues. Since the siloxane bond sites in the siloxane diamine residues have a high affinity for the specific silicon oxide layer, the adhesion between the specific silicon oxide layer and the second polyimide layer tends to be higher. Therefore, the polyimide laminate of the first embodiment suppresses the generation of image retention by not using an amorphous silicon layer (adhesion layer), and the adhesion between the inorganic layer and the polyimide layer is excellent.

[0067] In the first embodiment, in order to obtain a polyimide laminate with better adhesion between the inorganic layer and the polyimide layer, the silicon oxide contained in the specific silicon oxide layer (silicon oxide with a large ratio of silicon to stoichiometric composition) is preferably silicon oxide represented by the following general formula (1).

[0068] SiOx (1)

[0069] In general formula (1), x represents a real number greater than 1.3 and less than 2.0. Hereinafter, silicon oxide represented by general formula (1) will sometimes be referred to simply as "SiOx". In addition, a specific silicon oxide layer containing SiOx will sometimes be referred to as "SiOx layer".

[0070] In the first embodiment, when the specific silicon oxide layer is a SiOx layer, in order to obtain a polyimide laminate with better adhesion between the inorganic layer and the polyimide layer, the SiOx content in the SiOx layer relative to the total amount of 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, further preferably 95% by weight or more and 100% by weight or less, further more preferably 99% by weight or more and 100% by weight or less, and may also be 100% by weight. It should be noted that, as components other than SiOx in the SiOx layer, for example, components derived from the raw materials used to form the SiOx layer can be listed.

[0071] In the first embodiment, when the specific silicon oxide layer is a SiOx layer, in order to obtain a polyimide laminate with better 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.

[0072] [Composition of polyimide laminates]

[0073] Hereinafter, the structure of the polyimide laminate of the first embodiment will be described with reference to the figures.

[0074] Figure 1 This is a cross-sectional view showing an example of the polyimide laminate of the first embodiment. Figure 1 As shown, the polyimide laminate 10 sequentially comprises a first polyimide layer 11, an inorganic layer 12, and a second polyimide layer 13. The inorganic layer 12 contains a specific silicon oxide layer but does not contain an amorphous silicon layer. Figure 1 In the example shown, inorganic layer 12 is a single inorganic layer containing a specific silicon oxide layer. Furthermore, the second polyimide layer 13 is adjacent to the specific silicon oxide layer ( Figure 1 In the example shown, inorganic layer 12 is connected.

[0075] The polyimide contained in the second polyimide layer 13 has a tetracarboxylic acid 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 will sometimes be referred to as a "specific polyimide".

[0076] The first polyimide layer 11 and the second polyimide layer 13 may contain components other than polyimide (additives). Examples of additives 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, relative to the total amount of each polyimide layer, is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may also be 100% by weight.

[0077] To ensure electrical insulation and improve productivity, 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.

[0078] To ensure flexibility and improve productivity, 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, to suppress image retention, the thickness of the first polyimide layer 11 is preferably greater than the thickness of the second polyimide layer 13. To further suppress image retention, the thickness of the first polyimide layer 11 is preferably 1.5 times or more the thickness of the second polyimide layer 13, more preferably 1.5 times or more and 2.0 times or less the thickness of the second polyimide layer 13.

[0079] To obtain a polyimide laminate with better 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, more preferably 0.50 N / cm or more. There is no particular upper limit to the adhesion strength between the inorganic layer 12 and the second polyimide layer 13, for example, it is 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 residues contained in a specific polyimide in the second polyimide layer 13 and the content of such siloxane diamine residues. The method for measuring the adhesion strength between the inorganic layer and the second polyimide layer is the same as or based on the method described in the following examples.

[0080] To obtain a polyimide laminate suitable for a flexible display substrate, it is preferable that the inorganic layer 12 and the second polyimide layer 13 do not peel off when the polyimide laminate 10 is bent. Specifically, it is preferable that the inorganic layer 12 and the second polyimide layer 13 do not peel off during the folding test described later.

[0081] The above is for reference only. Figure 1An example of the first embodiment has been described, but the polyimide laminate of the first embodiment is not limited to... Figure 1 The polyimide laminate 10 shown. For example, the inorganic layer included in the polyimide laminate of the first embodiment may also have a multilayer structure (a structure with 2 or more layers), as long as the specific silicon oxide layer is located on the surface layer next to the second polyimide layer. Figure 2 The cross-sectional view shown is of a polyimide laminate with an inorganic layer having a two-layer structure, as another example of the polyimide laminate of the first embodiment.

[0082] Figure 2 The inorganic layer 21 of the polyimide laminate 20 shown has a silicon nitride layer 22 and a specific silicon oxide layer 23 sequentially from the first polyimide layer 11 side. The silicon nitride layer 22 can include layers containing SiNy (y represents a real number of 0.5 or more and less than 1.33). To ensure electrical insulation and improve productivity, the thickness of the specific silicon oxide layer 23 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. Furthermore, to ensure electrical insulation and improve productivity, the thickness of the silicon nitride layer 22 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.

[0083] When the silicon nitride layer 22 is a layer containing SiNy (y represents a real number of 0.5 or more and less than 1.33), in order to obtain a polyimide laminate with better adhesion between the inorganic layer and the polyimide layer, the content of SiNy (y represents a real number of 0.5 or more and less than 1.33) in the silicon nitride layer 22 relative to the total amount of the silicon nitride layer 22 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, more preferably 95% by weight or more and 100% by weight or less, more preferably 99% by weight or more and 100% by weight or less, and may also be 100% by weight. It should be noted that, as components other than SiNy in the silicon nitride layer 22, components derived from the raw materials used to form the silicon nitride layer 22 can be listed, for example.

[0084] It should be noted that, although in Figure 2The example shown is an inorganic layer 21 comprising a silicon nitride layer 22 and a specific silicon oxide layer 23. However, the inorganic layer can be a three-layer structure where the silicon nitride layer is sandwiched between two specific silicon oxide layers, or it can be an inorganic layer with a structure of four or more layers obtained by alternately stacking specific silicon oxide layers and silicon nitride layers. Other components of the polyimide laminate 20 (preferred thickness range of the polyimide laminate, preferred ratio of the thicknesses of the two polyimide layers, etc.) are the same as those of the polyimide laminate 10 described above (see reference 10). Figure 1 )same.

[0085] [The polyimide contained in the second polyimide layer]

[0086] Next, the polyimide (specific polyimide) contained in the second polyimide layer will be described. The specific polyimide is obtained by imidization of a polyamic acid as a precursor. The polyamic acid is obtained by reacting a tetracarboxylic dianhydride with a diamine in an organic solvent. Therefore, the specific polyimide has tetracarboxylic dianhydride residues and diamine residues.

[0087] Furthermore, in certain polyimides, the diamine residues include siloxane diamine residues. That is, certain polyimides have siloxane diamine residues as diamine residues.

[0088] In order to obtain a polyimide laminate with better 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).

[0089] [Chemistry 4]

[0090]

[0091] In general formula (2), R 1 and R 2 Each of the following groups independently represents a divalent hydrocarbon group, and n represents an integer greater than 1 and less than 5. To obtain a polyimide laminate with better adhesion between the inorganic layer and the polyimide layer, as R... 1 and R 2 Preferably, each of the alkylene atoms is an alkylene group having 1 or more and 5 or less carbon atoms, more preferably an alkylene group having 2 or more and 4 or less carbon atoms. Furthermore, in order to obtain a polyimide laminate with better adhesion between the inorganic layer and the polyimide layer, n is preferably 1 or more and 3 or less, more preferably n is 1.

[0092] In order to obtain a polyimide laminate with particularly excellent adhesion between the inorganic layer and the polyimide layer, the preferred residue of the siloxane diamine is a residue of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (hereinafter sometimes referred to as "PAM-E").

[0093] Certain polyimides may have residues other than siloxane diamine residues (other diamine residues) as diamine residues. Examples of diamines used to form 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'-diaminobenzoylaniline, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene, 1,4-cyclohexanediamine, 4,4'-methylenebis(cyclohexylamine), etc.

[0094] To reduce the coefficient of linear expansion of the second polyimide layer, the specific polyimide preferably has PDA residues as diamine residues. In this case, to further reduce the coefficient of linear expansion of the second polyimide layer, the content of PDA residues relative to all diamine residues constituting the specific polyimide is preferably 50 mol% or more and 99.9 mol% or less, more preferably 70 mol% or more and 99.9 mol% or less, further preferably 90 mol% or more and 99.9 mol% or less, more preferably 95 mol% or more and 99.9 mol% or less, and particularly preferably 99.0 mol% or more and 99.9 mol% or less.

[0095] In order to obtain a polyimide laminate with better adhesion between the inorganic layer and the polyimide layer, the content of siloxane diamine residues relative to all diamine residues constituting a specific polyimide 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, further 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.

[0096] In order to reduce the coefficient of linear expansion of the second polyimide layer and obtain a polyimide laminate with better adhesion between the inorganic layer and the polyimide layer, the total content of siloxane diamine residues and PDA residues relative to all diamine residues constituting a specific polyimide is preferably 70 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less, further preferably 95 mol% or more and 100 mol% or less, further more preferably 99 mol% or more and 100 mol% or less, and may also be 100 mol%.

[0097] Examples of acid dianhydrides used to form tetracarboxylic dianhydride residues in specific polyimides include: 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as "BPDA"), pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5 Examples of dianhydrides include 6-naphthalenetetracarboxylic dianhydride, 4,4'-oxophthalic 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-peryltetracarboxylic dianhydride, 4,4'-sulfonylphthalic anhydride, p-triphenyl-3,4,3',4'-tetracarboxylic dianhydride, and meta-triphenyl-3,3',4,4'-tetracarboxylic dianhydride. Compounds formed by bonding substituents to the aromatic ring of the aforementioned dianhydrides can also be used as acid dianhydrides.

[0098] In addition, alicyclic tetracarboxylic dianhydrides can also be used as acid dianhydrides. Examples of alicyclic tetracarboxylic dianhydrides include: (1S,2R,4S,5R)-cyclohexanetetracarboxylic dianhydride (cis,cis,cis-1,2,4,5-cyclohexanetetracarboxylic dianhydride), (1S,2S,4R,5R)-cyclohexanetetracarboxylic dianhydride, (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride, 5-(dioxotetrahydrofuranyl)-3-methyl-3-cyclohexene-1, 2-Dicarboxylic anhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-tetrahydronaphthalene-1,2-dicarboxylic anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic anhydride, bicyclo-3,3',4,4'-tetracarboxylic anhydride, 1,2,3,4-cyclopentanetetracarboxylic anhydride, 1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,4-dimethyl-1,2,3,4-cyclobutanetetracarboxylic anhydride, etc.

[0099] To reduce the coefficient of linear expansion of the second polyimide layer, the specific polyimide preferably has BPDA residues as dianhydride residues. In this case, to further reduce the coefficient of linear expansion of the second polyimide layer, the content of BPDA residues relative to all dianhydride residues constituting the specific polyimide is preferably 50 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less, more preferably 95 mol% or more and 100 mol% or less, and may also be 100 mol%.

[0100] To obtain a polyimide laminate with excellent adhesion between the inorganic layer and the polyimide layer during high-temperature processing, the specific polyimide is preferably fluorine-free. When the specific polyimide is fluorine-free, the generation of hydrogen fluoride during high-temperature processing can be suppressed. This, in turn, suppresses the occurrence of poor adhesion between the inorganic layer and the polyimide layer caused by hydrogen fluoride.

[0101] [The polyimide contained in the first polyimide layer]

[0102] The polyimide contained in the first polyimide layer may be the specific polyimide mentioned above, or it may be a polyimide other than the specific polyimide. To obtain a polyimide laminate with excellent adhesion between the inorganic layer and the first polyimide layer, the polyimide contained in the first polyimide layer is preferably 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.

[0103] Since the coefficient of linear expansion of the first polyimide layer is preferably 20 ppm / K or less, the polyimide contained in the first polyimide layer is preferably of a rigid structure. Examples of rigid polyimides include polyimides containing PDA residues and BPDA residues. It should be noted that the method for determining the coefficient of linear expansion of the first polyimide layer is the same as or based on the method described in the examples below.

[0104] When the polyimide contained in the first polyimide layer is a specific polyimide, the preferred form of the polyimide contained in the first polyimide layer is the same as that described above for the polyimide contained in the second polyimide layer.

[0105] [Preferred embodiment of the first embodiment]

[0106] In order to reduce the coefficient of linear expansion of the second polyimide layer and obtain a polyimide laminate with better adhesion between the inorganic layer and the polyimide layer, the polyimide laminate of 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.

[0107] Condition 1: The specific polyimide contained in the second polyimide layer has siloxane diamine residues and PDA residues as diamine residues.

[0108] Condition 2: The conditions of Condition 1 above are met, and the content of siloxane diamine residues is more than 0.1 mol% and less than 2.0 mol% relative to all diamine residues of the specific polyimide contained in the second polyimide layer.

[0109] Condition 3: Condition 2 above is satisfied, and the specific polyimide contained in the second polyimide layer has BPDA residues as acid dianhydride residues.

[0110] <Second Embodiment: Polyimide Laminate with Support>

[0111] Next, the polyimide laminate with a support according to the second embodiment of the present invention will be described. The polyimide laminate with a support according to the second embodiment includes a support and the polyimide laminate of the first embodiment described above. In the polyimide laminate with a support according to the second embodiment, the support is disposed on the side of the first polyimide layer of the polyimide laminate. Since the polyimide laminate with a support according to the second embodiment includes the polyimide laminate of the first embodiment, the adhesion between the inorganic layer and the polyimide layer is excellent. Therefore, for example, when the polyimide laminate with a support according to the second embodiment is used as a substrate material for manufacturing a flexible display, the processability when forming a TFT layer or OLED layer is improved. In the following description, descriptions that are repeated in the first embodiment are sometimes omitted.

[0112] The following is for reference. Figure 3 The structure of the polyimide laminate with support in the second embodiment will be described. Figure 3 This is a cross-sectional view showing an example of a polyimide laminate with a support according to the second embodiment. Figure 3 As shown, the polyimide laminate 100 with a support includes a support 101 and a polyimide laminate 10, with the support 101 disposed on the side of the first polyimide layer 11 of the polyimide laminate 10. Furthermore, Figure 3 In the polyimide laminate 100 with support shown, the support 101 is in contact with the first polyimide layer 11.

[0113] Examples of materials that can be used as the support 101 include glass substrates, metal plates, and polyethylene terephthalate (PET) films; from the viewpoint of heat resistance, glass substrates are preferred. When using a glass substrate as the support 101, alkali-free glass is preferred as the material of the glass substrate in terms of having relatively few mobile ions. Furthermore, one or more coating layers selected from the group consisting of silicon oxide layers, silicon nitride layers, and amorphous silicon layers can be formed on the surface of the glass substrate.

[0114] When the polyimide laminate 100 with a support 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 processability during the formation of the TFT layer or OLED layer. There is no particular upper limit to the adhesion strength between the support 101 and the first polyimide layer 11, for example, it is 2.00 N / cm or less. When the polyimide in the first polyimide layer 11 contains siloxane diamine residues, 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 siloxane diamine residues and the content of the siloxane diamine residues. The method for measuring the adhesion strength between the support and the first polyimide layer is the same as or based on the method described in the following examples.

[0115] <Third Embodiment: Thin Film Transistor Device>

[0116] Next, a thin-film transistor device according to a third embodiment of the present invention will be described. The thin-film transistor device of the third embodiment includes the polyimide laminate of the first embodiment described above, and a thin-film transistor layer (TFT layer) disposed on a second polyimide layer of the polyimide laminate. Since the thin-film transistor device of the third embodiment includes the polyimide laminate of the first embodiment, image retention is suppressed, and the adhesion between the inorganic layer and the polyimide layer is excellent. In the third embodiment, the TFT layer can be directly disposed on the surface of the second polyimide layer (e.g., ...). Figure 3 The main surface 13a) of the second polyimide layer 13 shown, which is opposite to the inorganic layer 12, can also be indirectly disposed with a silicon oxide layer or a planarization layer in between.

[0117] The thin-film transistor device of the third embodiment can be applied to display devices such as OLED displays and electronic paper. When the thin-film transistor device of the third embodiment is applied to an OLED display, the configuration of the OLED display other than the polyimide laminate can be, for example, the configuration described in Japanese Patent Application Publication No. 2021-105704.

[0118] <Fourth Embodiment: Method for Manufacturing Polyimide Laminates>

[0119] Next, a method for manufacturing the polyimide laminate according to the fourth embodiment of the present invention will be described. The method for manufacturing the polyimide laminate of the fourth embodiment is a suitable method for manufacturing the polyimide laminate of the first embodiment described above. In the following description, descriptions that are repeated in the first and second embodiments are sometimes omitted.

[0120] The method for manufacturing 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 a second polyimide layer is coated on the main surface of the inorganic layer opposite to the side of the first polyimide layer. In step Sc, the coating film obtained in step Sb is heated to imidize the precursor (polyamic acid).

[0121] The method for manufacturing the polyimide laminate according to the fourth embodiment may also include steps other than steps Sa, Sb, and Sc (other steps). Examples of other steps include the preparation of the polyamic acid solution, the formation of the first polyimide layer, and the step of peeling the polyimide laminate off the self-supporting body. Hereinafter, each step included in an example of the manufacturing method of the fourth embodiment will be described in detail.

[0122] [Preparation process of polyamic acid solution]

[0123] As a method for preparing polyamic acid solutions (a method for synthesizing polyamic acid), all known methods and combinations thereof can be used. An example of a method for synthesizing polyamic acid is the reaction of a diamine with a tetracarboxylic dianhydride in an organic solvent. When using a diamine and a tetracarboxylic dianhydride to synthesize polyamic acid, the desired polyamic acid (a polymer of diamine and tetracarboxylic dianhydride) can be obtained by adjusting the amount of the diamine (or the amount of each diamine when using multiple diamines) and the amount of the tetracarboxylic dianhydride (or the amount of each tetracarboxylic dianhydride when using multiple tetracarboxylic dianhydrides). The molar fraction of each residue in the polyimide formed from the polyamic acid is, for example, consistent with the molar fraction of each monomer used in the synthesis of the polyamic acid (each monomer corresponding to each residue).

[0124] To improve the quality of the obtained polyimide film and enhance the adhesion between the inorganic layer and the polyimide layer, the molar ratio (total molar ratio) obtained by dividing the total mass of the tetracarboxylic dianhydride used in the synthesis by the total mass of the diamine 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 (total mass of tetracarboxylic dianhydride / total mass of diamine) obtained by dividing the total mass of the tetracarboxylic dianhydride used in the synthesis by the total mass of the diamine used in the synthesis is sometimes referred to as "acid dianhydride / diamine ratio".

[0125] The temperature conditions for the reaction of diamine with tetracarboxylic dianhydride, i.e., the synthesis of polyamic acid, are not particularly limited, but can be, for example, in the range of 10°C to 150°C. The reaction time for the synthesis of polyamic acid can be, for example, in the range of 10 minutes to 30 hours.

[0126] Examples of organic solvents that can be used to react diamines with tetracarboxylic dianhydrides include: urea solvents such as N,N-dimethylethylurea; sulfoxide solvents such as dimethyl sulfoxide; sulfone solvents such as tetramethyl sulfone; amide solvents such as N,N-dimethylformamide, N,N-diethylformamide, N-methyl-2-pyrrolidone, and N-butyl-2-pyrrolidone; ester solvents such as γ-butyrolactone; halogenated alkyl solvents such as chloroform; aromatic hydrocarbon solvents such as toluene; phenolic solvents such as phenol; ketone solvents such as cyclopentanone; and ether solvents such as tetrahydrofuran. These solvents are usually used alone, but two or more can be combined appropriately as needed. When polyamic acid is obtained by the above-described synthetic method, the reaction solution (the solution after the reaction) itself can be used as a polyamic acid solution. In this case, the organic solvent in the polyamic acid solution is the organic solvent used in the above-described synthetic method. Alternatively, a polyamic acid solution can be prepared by dissolving the solid polyamic acid obtained by removing the solvent from the reaction solution in an organic solvent.

[0127] Additives such as dyes, surfactants, leveling agents, plasticizers, silicones, sensitizers, and silane coupling agents can be added to polyamic acid solutions. Furthermore, fillers can be added to polyamic acid solutions to improve various film properties such as lubricity, thermal conductivity, electrical conductivity, corona resistance, and ring stiffness. Any filler can be used; preferred examples include fillers containing silicon oxide, titanium oxide, aluminum oxide, silicon nitride, boron nitride, dicalcium phosphate, calcium phosphate, and mica.

[0128] The concentration of polyamic acid in the polyamic acid solution is not particularly limited, but relative to the total amount of polyamic acid solution, it is, for example, 5% by weight or more and 40% by weight or less, preferably 8% by weight or more and 30% by weight or less.

[0129] Imidazole compounds may also be added to the polyamic acid solution. In this specification, imidazole compounds refer to compounds having a 1,3-diazole ring (1,3-diazole ring structure). There are no particular limitations on imidazole compounds; examples include: imidazole, 2-methylimidazolium, 2-undecylimidazolium, 2-heptadecanylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 2-phenylimidazolium, 2-phenyl-4-methylimidazolium, 1-benzyl-2-methylimidazolium, 1-benzyl-2-phenylimidazolium, 2,4,5-triphenylimidazolium, 4,5-diphenylimidazolium, etc. Furthermore, compounds containing a 1,3-diazole ring in a fused ring may also be used as imidazole compounds. Examples of imidazole compounds containing a 1,3-diazole ring in a fused ring include benzimidazole and 2-phenylbenzimidazole.

[0130] The content of the imidazole compound relative to 100 parts by weight of polyamic acid in the polyamic acid solution is preferably 0.1 parts by weight or more and 1.0 parts by weight or less, more preferably 0.2 parts by weight or more and 0.8 parts by weight or less. By containing 0.1 parts by weight or more of the imidazole compound, the film strength of the polyimide can be improved, and by keeping the content of the imidazole compound at 1.0 parts by weight or less, the storage stability of the polyamic acid can be well maintained.

[0131] To further improve the adhesion between the inorganic layer and the polyimide layer by increasing the film strength of the polyimide, the polyamic acid solution preferably contains an imidazole-based compound with a boiling point of 250°C to 400°C. Examples of imidazole-based compounds with boiling points of 250°C to 400°C include: imidazole, 2-methylimidazole, 2-phenylimidazole, benzimidazole, 2-phenylbenzimidazole, 2,4,5-triphenylimidazole, and 4,5-diphenylimidazole.

[0132] Secondly, appropriate reference Figure 3 The process of forming the first polyimide layer, process Sa, process Sb, process Sc, and the process of peeling the polyimide laminate from the self-supporting body are described.

[0133] [The process of forming the first polyimide layer]

[0134] There are no particular limitations on the method for forming the first polyimide layer, and various known methods can be used. An example of a method for forming the first polyimide layer will be described below.

[0135] First, a polyamic acid solution (specifically, a solution containing polyamic acid as a precursor of the polyimide constituting the first polyimide layer 11) is coated onto a main surface 101a of the support 101 to form a coating film containing polyamic acid. The method for coating the polyamic acid solution onto the main surface 101a of the support 101 is not particularly limited, and a method using a conventionally known coating apparatus (coating device) such as a rod coater, die coater, corner wheel coater (registered trademark), reverse coater, or blade coater can be employed. Second, the coating film is heated, for example, at a temperature of 40°C or higher and 200°C or lower. The heating time at this time is, for example, 3 minutes or more and 120 minutes or less. Third, to promote the 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 at this time (heating time at the maximum temperature) is, for example, 1 minute or more and 300 minutes or less. At this point, it is preferable to gradually increase the temperature from a low temperature to the maximum temperature. The heating rate is preferably 2°C / min or more and 10°C / min or less, more preferably 4°C / min or more and 10°C / min or less. Furthermore, the maximum temperature is preferably in the range of 250°C or more and 470°C or less. If the maximum temperature is 250°C or more, imidization can be carried out sufficiently, and if the maximum temperature is 470°C or less, thermal degradation of the polyimide can be suppressed. In addition, it is possible to maintain the temperature at any temperature for any time until the maximum temperature is reached. The imidization reaction can be carried out in air, under reduced pressure, or inactive gases such as nitrogen. Furthermore, as a heating device, known devices such as hot air ovens, infrared ovens, vacuum ovens, non-oxidizing ovens, and heating plates can be used. Through these processes, the polyamic acid in the coated film is imidized, and a first polyimide layer 11 is formed on a main surface 101a of the support 101.

[0136] [Process Sa]

[0137] Process Sa is the process of forming an inorganic layer 12 on the first polyimide layer 11. For example, in the formation of... Figure 3 In the case of the inorganic layer 12 shown, 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 to the support 101 side using, for example, sputtering or plasma chemical vapor deposition (plasma CVD). To form a high-resistivity and dense film, plasma CVD is preferably the method for forming the inorganic layer 12.

[0138] It should be noted that when an inorganic layer 12 is formed on the main surface 11a of the first polyimide layer 11 opposite to the support 101 side using plasma CVD, the main surface 11a of the first polyimide layer 11 tends to become uneven. Therefore, if an inorganic layer 12 is formed on the main surface 11a of the first polyimide layer 11 opposite to the support 101 side using plasma CVD, the adhesion between the first polyimide layer 11 and the inorganic layer 12 tends to be higher.

[0139] When forming a specific silicon oxide layer by plasma CVD, from the viewpoint of increasing film density, 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. The preferred film formation gases for forming the specific silicon oxide layer by plasma CVD are silane (SiH4) and nitrous oxide (N2O).

[0140] When a silicon nitride layer is formed by plasma CVD before forming a specific silicon oxide layer, from the viewpoint of increasing film density, the film-forming temperature of the silicon nitride layer is preferably 280°C to 400°C, more preferably 320°C to 400°C. The preferred film-forming gases for forming the silicon nitride layer by plasma CVD are silane (SiH4) and ammonia (NH3).

[0141] [Process Sb]

[0142] Step Sb is a process of coating a solution (polyamic acid solution) containing a precursor of the polyimide (specific polyimide) contained in the second polyimide layer 13 onto the main surface 12a of the inorganic layer 12 opposite to the side of the first polyimide layer 11. As for the coating method of the polyamic acid solution in step Sb, in addition to using a polyamic acid solution containing polyamic acid as a precursor of the polyimide constituting the second polyimide layer 13, the same method as the coating method of the polyamic acid solution in the above-described [formation step of the first polyimide layer] can be used.

[0143] [Process Sc]

[0144] Step Sc is a process of imidizing the precursor (polyamic acid) by heating the coating film obtained in step Sb. The imidization method in step Sc can be the same as the imidization method in the [first polyimide layer formation step] described above.

[0145] [Process for peeling polyimide laminates from self-supporting substrates]

[0146] There are no particular limitations on the method for peeling the polyimide laminate 10 from the self-supporting body 101, and known methods can be used. Examples of known methods include: peeling the polyimide laminate 10 by hand; peeling the polyimide laminate 10 using a mechanical device such as a drive roller or a robotic arm; and irradiating the first polyimide layer 11 from the side of the self-supporting body 101 with a laser to separate the polyimide laminate 10 from the self-supporting body 101. To facilitate the peeling of the polyimide laminate 10, a release layer can be provided on the surface of the self-supporting body 101 on the side of the first polyimide layer 11.

[0147] After the above-described process, a polyimide laminate 10 with a three-layer structure comprising a first polyimide layer 11, an inorganic layer 12, and a second polyimide layer 13 is obtained.

[0148] [Example]

[0149] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0150] <Preparation of polyamic acid solution>

[0151] The preparation methods of polyamic acid solutions P1 to P6 used in the examples and comparative examples are described below. It should be noted that the compounds and reagents will be referred to by the following abbreviations. Furthermore, the preparation of polyamic acid solutions P1 to P6 was carried out under a nitrogen atmosphere.

[0152] NMP: N-methyl-2-pyrrolidone

[0153] PDA: p-phenylenediamine

[0154] PAM-E: 1,3-bis(3-aminopropyl)tetramethyldisiloxane

[0155] BPDA: 3,3',4,4'-Biphenyltetracarboxylic acid dianhydride

[0156] APS: 3-Aminopropyltriethoxysilane

[0157] 2PhI: 2-Phenylidene Imidazole

[0158] [Preparation of polyamic acid solution P1]

[0159] 155.3 g of NMP was added as the organic solvent for polymerization to a 500 mL separable glass flask equipped with a stirrer with a stainless steel stirring rod and a nitrogen inlet tube. Then, under an atmosphere of 23°C, while stirring the contents of the flask, 8.01 g of PDA was added and dissolved. Next, under an atmosphere of 23°C, while stirring the contents of the flask, 14.82 g of a pre-prepared PAM-E solution (solvent: NMP, PAM-E concentration: 1 wt%) was added, followed by 21.85 g of BPDA. Then, under an atmosphere of 90°C, the contents of the flask were stirred for 6 hours, and NMP was added to the flask to obtain a polyamic acid solution P1 with a solid content of 11 wt% and a viscosity of 40 poise. It should be noted that in the preparation of polyamic acid solution P1, the acid dianhydride / diamine ratio was 0.995.

[0160] [Preparation of polyamic acid solution P2]

[0161] Except for setting the diamine addition ratio and the dianhydride / diamine ratio as shown in Table 1, polyamic acid solution P2 was obtained using the same method as polyamic acid solution P1. It should be noted that the total mass of diamines used in preparing polyamic acid solution P2 was the same as the total mass of dianhydrides used in preparing polyamic acid solution P1.

[0162] [Preparation of polyamic acid solution P3]

[0163] After preparing a polyamic acid solution using the same method as for polyamic acid solution P2, 2PhI was added to the obtained polyamic acid solution to obtain polyamic acid solution P3. The amount of 2PhI added was 0.3 parts by weight relative to 100 parts by weight of polyamic acid.

[0164] [Preparation of polyamic acid solution P4]

[0165] 170.0 g of NMP was added as the organic solvent for polymerization to a 500 mL separable glass flask equipped with a stirrer with a stainless steel stirring rod and a nitrogen inlet tube. Then, under an atmosphere of 23°C, while stirring the contents of the flask, 8.09 g of PDA was added and dissolved. Next, under an atmosphere of 23°C, while stirring the contents of the flask, 21.91 g of BPDA was added. Then, under an atmosphere of 90°C, while stirring the contents of the flask, APS was added, and the contents of the flask were stirred again. Finally, NMP was added to the contents of the flask to obtain a polyamic acid solution P4 with a solid content of 11% by weight and a viscosity of 40 poise. The amount of APS added was 0.2 mol% relative to 100 mol% of PDA used. It should be noted that in the preparation of polyamic acid solution P4, the acid dianhydride / diamine ratio was 0.995.

[0166] [Preparation of polyamic acid solution P5]

[0167] Except for the absence of APS, polyamic acid solution P5 was obtained by the same method as polyamic acid solution P4.

[0168] [Preparation of polyamic acid solution P6]

[0169] After preparing a polyamic acid solution using the same method as for polyamic acid solution P5, 2PhI was added to the obtained polyamic acid solution to obtain polyamic acid solution P6. The amount of 2PhI added was 0.3 parts by weight relative to 100 parts by weight of polyamic acid.

[0170] For polyamic acid solutions P1-P6, the dianhydrides used and their addition ratios, the diamines used and their addition ratios, the amounts of 2PhI and APS added, and the dianhydride / diamine ratio are shown in Table 1. It should be noted that in Table 1, "-" indicates that the component was not used. Furthermore, in Table 1, the values ​​in the "Dianhydride" column represent the content of each dianhydride relative to the total amount of dianhydrides used (in mole %). In Table 1, the values ​​in the "Diamine" column represent the content of each diamine relative to the total amount of diamine used (in mole %). In Table 1, the values ​​in the "2PhI" column represent the amount of 2PhI relative to 100 parts by weight of the synthesized polyamic acid (in parts by weight). In Table 1, the values ​​in the "APS" column represent the content relative to 100 mol% of the PDA used (in mole %). Furthermore, for all polyamic acid solutions P1 to P6, the molar fraction of each residue of polyamic acid in the prepared polyamic acid solution is consistent with the molar fraction of each monomer (corresponding to each residue) used in the synthesis of polyamic acid.

[0171] [Table 1]

[0172]

[0173] <Fabrication of Polyimide Laminates with Supports>

[0174] The following describes the methods for manufacturing the polyimide laminates with supports of Examples 1-3 and Comparative Examples 1-3, as well as the methods for manufacturing the polyimide laminates of Examples 1-3 and Comparative Examples 1-3.

[0175] [Example 1]

[0176] (Formation of the first polyimide layer)

[0177] Using a rod coater, a polyamic acid solution P1 was coated onto a glass substrate (trade name: Lotus NXT, material: alkali-free glass, thickness: 0.5 mm, size: 100 mm × 100 mm) manufactured by Corning Corporation, which served as the support. The substrate was then heated in a hot air oven at 120°C for 30 minutes. The resulting coated glass substrate was then heated from 20°C to 450°C at a rate of 7°C / min under a nitrogen atmosphere, and then heated at 450°C for 10 minutes to imidize the polyamic acid in the coating, resulting in a laminate L1 consisting of the glass substrate and the first polyimide layer (thickness: 10 μm).

[0178] (Formation of the inorganic layer)

[0179] Then, an inorganic layer (a single-layer inorganic layer containing a SiOx layer) was formed on the first polyimide layer of the obtained laminate L1 using plasma CVD. Specifically, the film formation temperature was set to 380°C, and SiH4 and N2O were used as gaseous species to form a 600 nm thick SiOx layer on the first polyimide layer, resulting in a laminate L2 consisting of a glass substrate, the first polyimide layer, and the inorganic layer (SiOx layer). The SiOx layer of the obtained laminate L2 was analyzed using an X-ray photoelectron spectroscopy (ULVAC-PHI "PHI Quantera II") instrument, confirming that the x-value of SiOx was 1.7. It should be noted that when performing the analysis using the aforementioned X-ray photoelectron spectroscopy instrument, monochromatic AlKα was used as the X-ray source, and the detection depth was set to 4–5 nm to perform elemental analysis of Si, O, and N.

[0180] (Formation of the second polyimide layer)

[0181] Then, using a bar coater, a polyamic acid solution P1 was coated onto the main surface of the inorganic layer of the obtained laminate L2, opposite to the side of the first polyimide layer. The laminate was then heated in a hot air oven at 120°C for 30 minutes. Next, under a nitrogen atmosphere, the obtained laminate L2 with the coated film was heated from 20°C to 450°C at a rate of 7°C / min, and then heated at 450°C for 10 minutes to imidize the polyamic acid in the coated film, resulting in a supported polyimide laminate consisting of four layers: a glass substrate, a first polyimide layer, an inorganic layer, and a second polyimide layer (thickness: 6 μm) (the supported polyimide laminate of Example 1).

[0182] (Separation from the glass substrate)

[0183] Then, the layers of the obtained polyimide laminate with support, excluding the support, are cut into 3 cm × 4 cm dimensions using a cutting blade. Then, the cut polyimide laminate is peeled off from the glass substrate at a peel angle of 90° to obtain a polyimide laminate consisting of three layers: a first polyimide layer, an inorganic layer, and a second polyimide layer (the polyimide laminate of Example 1).

[0184] [Examples 2 and 3]

[0185] Except that the types of polyamic acid solutions used in the formation of the first and second polyimide layers are set as shown in Table 2, the polyimide laminates with supports of Examples 2 and 3, as well as the polyimide laminates of Examples 2 and 3, were obtained by the same method as in Example 1.

[0186] [Comparative Examples 1-3]

[0187] Except that the types of polyamic acid solutions used in the formation of the first and second polyimide layers were set as shown in Table 2, the polyimide laminates with supports of Comparative Examples 1-3 and the polyimide laminates of Comparative Examples 1-3 were obtained by the same method as in Example 1. It should be noted that, for all Comparative Examples 1-3, when the polyimide laminate was peeled off from the glass substrate, the second polyimide layer partially peeled off because the adhesion strength between the second polyimide layer and the inorganic layer was too weak.

[0188] <Measurement and Evaluation Methods>

[0189] [Coefficient of linear expansion of the first polyimide layer]

[0190] As samples used to determine the coefficient of linear expansion of the first polyimide layer in Examples 1 and Comparative Example 1, the first polyimide layer was formed using the method described above, and then peeled off from the glass substrate to obtain a polyimide film (size: 10 mm × 3 mm) for measurement. The coefficient of linear expansion of the polyimide film was then measured using a thermal analysis apparatus (TMA / SS120CU manufactured by Hitachi High-Tech Science Co., Ltd.) under a load of 29.4 mN applied to the long side of the polyimide film. Specifically, the polyimide film was heated from 20°C to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, then cooled to 20°C at a cooling rate of 40°C / min, and then heated again to 550°C at a heating rate of 5°C / min. The coefficient of linear expansion was calculated based on the strain from 100°C to 400°C during the second heating.

[0191] [Folding and Hemming Test]

[0192] First, each polyimide laminate was cut into 10 mm wide pieces using a cutting tool to obtain evaluation samples. Then, with a 0.2 mm thick plastic sheet sandwiched between the samples, the evaluation samples were bent 180°, and a 1 kg weight was placed on the bent portion for 5 seconds. The weight was then removed, and the evaluation samples were opened 180°, with the inside facing down during bending, and the weight was placed on the bent portion again for 5 seconds. After removing the weight, the bent portion was observed under a microscope to confirm the presence or absence of delamination between the second polyimide layer and the inorganic layer.

[0193] [Seam strength]

[0194] (Adhesion strength between the inorganic layer and the second polyimide layer)

[0195] First, according to ASTM D1876-01 specifications, a 10 mm wide slit was cut into each layer of the polyimide laminate with a support, excluding the support, using a cutting tool to obtain test specimens. Then, for the obtained test specimens, a tensile testing machine (Toyo Seiki Co., Ltd.'s "Strograph VES1D") was used at 23°C and 55% relative humidity, at a tensile speed of 50 mm / min and a peel angle of 90°. The average peel strength at 50 mm was measured on the second polyimide layer, and this value was taken as the adhesion strength. When the adhesion strength is 0.20 N / cm or higher, it is evaluated as "excellent adhesion between the inorganic layer and the second polyimide layer." Conversely, when the adhesion strength is less than 0.20 N / cm, it is evaluated as "poor adhesion between the inorganic layer and the second polyimide layer."

[0196] (Adhesion strength between the support and the first polyimide layer)

[0197] First, according to ASTM D1876-01, a 10 mm wide slit was cut into each layer of the polyimide laminate with a support, excluding the support, using a cutting tool to obtain test specimens. Then, for the obtained test specimens, a tensile testing machine (Toyo Seiki Co., Ltd.'s "Strograph VES1D") was used at 23°C and 55% relative humidity, at a tensile speed of 50 mm / min and a peel angle of 90°. The average peel strength at 50 mm was measured on the first polyimide layer (specifically, the polyimide laminate), and the obtained value was taken as the adhesion strength. When the adhesion strength is 0.10 N / cm or higher, it is evaluated as "excellent adhesion between the support and the first polyimide layer." On the other hand, when the adhesion strength is less than 0.10 N / cm, it is evaluated as "poor adhesion between the support and the first polyimide layer."

[0198] <Results>

[0199] For Examples 1-3 and Comparative Examples 1-3, the polyamic acid solution used, the coefficient of linear expansion of the first polyimide layer, the evaluation results of the 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 are shown in Table 2. It should be noted that in Table 2, "-" indicates that it was not measured.

[0200] [Table 2]

[0201]

[0202] As shown in Tables 1 and 2, in Examples 1-3, the second polyimide layer contains polyimide residues of siloxane diamine (PAM-E residues). As shown in Table 2, in Examples 1-3, the adhesion strength between the inorganic layer and the second polyimide layer is 0.20 N / cm or higher. Therefore, the adhesion between the inorganic layer and the second polyimide layer of the polyimide laminates in Examples 1-3 is excellent.

[0203] As shown in Tables 1 and 2, in Comparative Examples 1-3, the polyimide contained in the second polyimide layer did not contain siloxane diamine residues. As shown in Table 2, in Comparative Examples 1-3, the adhesion strength between the inorganic layer and the second polyimide layer was less than 0.20 N / cm. Therefore, the adhesion between the inorganic layer and the second polyimide layer of the polyimide laminates in Comparative Examples 1-3 was poor.

[0204] Based on the above results, it can be seen that, according to the present invention, a polyimide laminate with excellent adhesion between the inorganic layer and the polyimide layer is provided in a configuration in which no amorphous silicon layer is interposed between the two polyimide layers.

[0205] Explanation of reference numerals in the attached figures

[0206] 10, 20 polyimide laminate

[0207] 11 First polyimide layer

[0208] Inorganic layers 12, 21

[0209] 13 Second polyimide layer

[0210] 100 polyimide laminates with supports

[0211] 101 Support

Claims

1. A polyimide laminate, comprising sequentially a first polyimide layer, an inorganic layer, and a second polyimide layer, The inorganic layer contains a silicon oxide layer but not an amorphous silicon layer, wherein the silicon oxide layer comprises silicon oxide with a high ratio of silicon to its stoichiometric composition. The second polyimide layer is in contact with the silicon oxide layer. The second polyimide layer contains polyimide residues of tetracarboxylic dianhydride and diamine residues. The diamine residues include siloxane diamine residues.

2. The polyimide laminate according to claim 1, wherein, The silicon oxide with a high silicon ratio compared to its stoichiometric composition is represented by the following general formula (1). SiOx (1) In the general formula (1), x represents a real number greater than 1.3 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 of the two groups represents a divalent hydrocarbon group independently, and n represents an integer greater than 1 and less than 5.

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 according to claim 1, wherein, The diamine residues also include p-phenylenediamine residues.

6. The polyimide laminate according to claim 1, wherein the thickness is 5 μm or more and 30 μm or less.

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

8. The polyimide laminate according to claim 1, wherein, The adhesion strength between the inorganic layer and the second polyimide layer is greater than 0.20 N / cm.

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

10. The polyimide laminate with a support according to claim 9, wherein, The adhesion strength between the support and the first polyimide layer is greater than 0.10 N / cm.

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

12. A method for manufacturing a polyimide laminate, which is a method for manufacturing the polyimide laminate according to any one of claims 1 to 8, the method comprising the following steps: In step Sa, the inorganic layer is formed on the first polyimide layer; Step Sb involves coating the main surface of the inorganic layer, opposite to the side of the first polyimide layer, with a solution containing a precursor of the polyimide contained in the second polyimide layer; and In step Sc, the coating film obtained through step Sb is heated to imidize the precursor.

13. The method for manufacturing the polyimide laminate according to claim 12, wherein, The solution containing the precursor also contains an imidazole compound with a boiling point above 250°C and below 400°C.

14. The method for manufacturing the polyimide laminate according to claim 12, wherein, In the process Sa, the inorganic layer is formed by plasma chemical vapor deposition.

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