Laminate

Abstract

Provided is a laminate including: a support substrate; a polyimide resin layer on the support substrate; and an inorganic film on the polyimide resin layer, wherein the glass transition temperature of a polyimide resin constituting the polyimide resin layer is 300°C or higher, and the stress of the inorganic film is a compressive stress. Also provided is a laminate manufacturing method including: a step for applying a polyimide resin varnish or a polyimide resin precursor varnish onto a support substrate, and applying heat thereto to obtain a polyimide resin layer; and a step for further forming an inorganic film having a compressive stress on the polyimide resin layer.

Description

Laminate

[0001] The present invention relates to a laminate and a method for manufacturing the laminate.

[0002] In the semiconductor field, advances in three-dimensional packaging technology have created a demand for materials that can withstand processes such as TSV formation, backside wiring, CVD, and hybrid bonding. Due to their excellent mechanical properties, heat resistance, and insulating properties, polyimide resins have traditionally been explored for various uses in fields such as electrical and electronic components, and their use as insulating films has also been attempted. However, resin materials such as polyimides are rarely used alone due to concerns about moisture absorption and decomposition-induced gas release, and inorganic films such as SiO and SiN are often used as buffer layers or barrier layers. For example, Patent Document 1 discloses a polyimide film formed by imidizing a polyimide precursor having bis(trifluoromethyl)benzidine and siloxane structural units, which has a glass transition temperature of 150 to 380°C and an imide group concentration of 2.00 to 3.70 mmol / g, with the aim of achieving colorless transparency, low residual stress, improved mechanical properties, thermal properties, and bending resistance; a laminate comprising a polyimide film and a support; and a flexible substrate comprising a polyimide film and an inorganic film.

[0003] International Publication No. 2014 / 098235

[0004] In the semiconductor field, inorganic films are laminated onto resin materials such as polyimide as described above, and therefore, these laminates are required to have high film-forming properties. In particular, CVD and hybrid bonding (Cu-Cu bonding) require even higher heat resistance of 300°C or higher. In processes involving temperatures higher than the inorganic film formation temperature after inorganic film formation, even polyimides with high heat resistance can experience problems such as cracking and peeling. Therefore, there has been a need for a laminate comprising a polyimide resin, an inorganic film, and a supporting substrate that can be used in high-temperature processes. The present invention has been made in light of these circumstances, and an object of the present invention is to provide a laminate that has excellent film-forming properties and also excellent heat resistance.

[0005] The present inventors have found that the above-mentioned problems can be solved by a laminate having a polyimide resin layer having a glass transition temperature of 300°C or higher on a supporting substrate, and further having an inorganic film in which the stress is compressive, and have thereby completed the invention.

[0006] That is, the present invention relates to the following items [1] to [8]. [1] A laminate comprising a supporting substrate, a polyimide resin layer on the supporting substrate, an inorganic film on the polyimide resin layer, the polyimide resin constituting the polyimide resin layer having a glass transition temperature of 300°C or higher, and the stress of the inorganic film being compressive stress. [2] The laminate according to item [1] above, wherein the inorganic film contains silicon. [3] The laminate according to item [1] or [2] above, wherein the inorganic film is silicon oxide or silicon nitride. [4] The laminate according to any one of items [1] to [3] above, wherein the polyimide resin layer has a film thickness of 0.5 to 300 μm. [5] The laminate according to any one of items [1] to [4] above, wherein the inorganic film has a thickness of 1 to 1,000 nm. [6] The laminate according to any one of items [1] to [5] above, wherein the supporting substrate contains silicon. [7] The laminate according to any one of [1] to [6], wherein the supporting substrate is silicon, silicon carbide, gallium nitride, gallium oxide, aluminum nitride, or diamond. [8] A method for producing a laminate, comprising the steps of applying a polyimide resin varnish or a polyimide resin precursor varnish onto a supporting substrate and heating the applied varnish to obtain a polyimide resin layer, and further comprising the step of forming an inorganic film having compressive stress on the polyimide resin layer.

[0007] According to the present invention, it is possible to provide a laminate having excellent film-forming properties and excellent heat resistance. Because the laminate of the present invention has the properties described above, it is useful as a laminate in semiconductor processes. That is, the laminate of the present invention is useful as a laminate for semiconductor memories, LSI stacking, CMOS image sensors, MEMS encapsulation, optical devices, LED applications, etc.

[0008] [Laminate] The laminate of the present invention is a laminate having a supporting substrate, a polyimide resin layer on the supporting substrate, and an inorganic film on the polyimide resin layer, wherein the glass transition temperature of the polyimide resin constituting the polyimide resin layer is 300°C or higher, and the stress of the inorganic film is compressive stress.

[0009] <Supporting substrate> The laminate of the present invention has a supporting substrate. The supporting substrate is preferably silicon, silicon carbide, gallium nitride, gallium oxide, aluminum nitride, or diamond, and more preferably silicon. When the supporting substrate is silicon, the laminate of the present invention has excellent film-forming properties and heat resistance, which are particularly advantageous effects of the laminate of the present invention. Furthermore, silicon is excellent as a supporting substrate in the present invention because it has excellent yield in the crystallization process and easy availability of raw materials.

[0010] The thickness of the support substrate is preferably 1 μm to 1 mm, more preferably 2 μm to 900 μm, even more preferably 10 to 800 μm, and even more preferably 100 to 700 μm. When there are multiple support substrates, the above thickness refers to the thickness of each support substrate, and the thicknesses of the multiple support substrates may be the same or different. The shape of the support substrate is not particularly limited. For example, when the support substrate is a silicon substrate, it may be a silicon substrate on which an interlayer insulating layer (low-k film) is formed. Examples of interlayer insulating layers include silicon oxide films and silicon nitride films, with silicon nitride films being preferred.

[0011] <Polyimide Resin Layer and Polyimide Resin> The laminate of the present invention has a polyimide resin layer on the supporting substrate. The polyimide resin constituting the polyimide resin layer has a glass transition temperature of 300°C or higher.

[0012] The thickness of the polyimide resin layer is preferably 0.5 to 300 μm, more preferably 1 to 100 μm, even more preferably 1 to 50 μm, still more preferably 1 to 30 μm, and even more preferably 5 to 20 μm.

[0013] The polyimide resin has a glass transition temperature of 300°C or higher. The polyimide resin has a glass transition temperature of preferably 350°C or higher, more preferably 380°C or higher, even more preferably 400°C or higher, still more preferably 420°C or higher, still more preferably 430°C or higher, and still more preferably 440°C or higher. There is no upper limit, but it is preferably 550°C or lower. When the glass transition temperature of the polyimide resin is in the above range, the laminate of the present invention has excellent heat resistance and is useful as a laminate in semiconductor processes.

[0014] The polyimide resin constituting the polyimide resin layer is not limited in structure as long as it has a glass transition temperature of 300° C. or higher, but the polyimide resin preferably has a structural unit of the following general formula (1):

[0015] The polyimide resin preferably has a structural unit of formula (1), more preferably has at least one structural unit selected from the group consisting of a structural unit of formula (1a) below and a structural unit of formula (1b) below, and even more preferably has a structural unit of formula (1b) below:

[0016] The polyimide resin having the structural unit of formula (1a) more preferably contains at least one selected from the group consisting of a repeating unit represented by the following formula (2a) and a repeating unit represented by the following formula (3a), even more preferably contains a repeating unit represented by the following formula (2a), and even more preferably contains a repeating unit represented by the following formula (2a) and a repeating unit represented by the following formula (3a).

[0017] The "repeating unit" in the polyimide resin refers to an imide unit containing a structural unit derived from one tetracarboxylic dianhydride and a structural unit derived from one diamine. The ratio of the repeating unit represented by formula (2a) to the sum of the repeating units represented by formula (2a) and formula (3a) is preferably 30 to 100 mol%, and from the viewpoint of transparency, it is more preferably 40 to 100 mol%, even more preferably 50 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, even more preferably 80 to 100 mol%, even more preferably 90 to 100 mol%, and may even be 100 mol%. Furthermore, from the viewpoint of heat resistance and strength, it is more preferably 30 to 90 mol%, even more preferably 30 to 80 mol%, even more preferably 30 to 70 mol%, even more preferably 30 to 60 mol%, and even more preferably 30 to 50 mol%.

[0018] From the viewpoint of heat resistance and mechanical strength, the sum of the repeating units represented by formula (2a) and the repeating units represented by formula (3a) is preferably 50 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, still 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%, with 100 mol% being even more preferred from the viewpoint of heat resistance and mechanical strength.

[0019] From the viewpoint of transparency, the repeating unit represented by formula (2a) preferably accounts for 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more of all repeating units of the polyimide resin, with the upper limit being 100 mol% or less.

[0020] The polyimide resin may contain repeating units other than the repeating units represented by formula (2a) and the repeating units represented by general formula (3a). The content of repeating units other than the repeating units represented by formula (2a) and the repeating units represented by general formula (3a) is preferably 50 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, still more preferably 10 mol% or less, still more preferably 5 mol% or less, still more preferably 1 mol% or less, still more preferably 0 mol%, and even more preferably zero, based on the total repeating units of the polyimide resin.

[0021] The polyimide resin having the structural unit of formula (1b) further preferably contains a repeating unit represented by the following formula (2b):

[0022] From the viewpoint of heat resistance and mechanical strength, the repeating unit represented by formula (2b) is preferably 50 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, still 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%, with 100 mol% being even more preferred from the viewpoint of heat resistance and adhesion.

[0023] The polyimide resin may contain a repeating unit other than the repeating unit represented by formula (2b). The content of repeating units other than the repeating unit represented by formula (2b) is preferably 50 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, still more preferably 10 mol% or less, still more preferably 5 mol% or less, still more preferably 1 mol% or less, still more preferably 0 mol%, and even more preferably zero, based on the total repeating units of the polyimide resin.

[0024] As described above, the polyimide resin more preferably contains at least one repeating unit selected from the group consisting of a repeating unit represented by formula (2a), a repeating unit represented by formula (3a), and a repeating unit represented by formula (2b), and even more preferably contains a repeating unit represented by formula (2b). By containing the repeating unit represented by formula (2b), the polyimide resin can be dissolved in any solvent when preparing a varnish, and is particularly preferred because it can be well dissolved in an ester-based solvent.

[0025] <Structural Units of Polyimide Resin> The polyimide resin has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine. In the polyimide resin, structural unit A and structural unit B form an imide structure. The structural unit A preferably includes at least one selected from the group consisting of a structural unit (A1) derived from a compound represented by formula (a1) below, a structural unit (A2) derived from a compound represented by formula (a2) below, and a structural unit (A3) derived from a compound represented by formula (a3) ​​below. The structural unit B preferably includes at least one selected from the group consisting of a structural unit (B1) derived from a compound represented by formula (b1) below, a structural unit (B2) derived from a compound represented by formula (b2) below, and a structural unit (B3) derived from a compound represented by formula (b3) below.

[0026] (Structural Unit A) The structural unit A is a structural unit derived from a tetracarboxylic dianhydride, and preferably includes at least one selected from the group consisting of structural unit (A1) derived from a compound represented by formula (a1), structural unit (A2) derived from a compound represented by formula (a2), and structural unit (A3) derived from a compound represented by formula (a3), and more preferably includes structural unit (A3) derived from a compound represented by formula (a3). When structural unit (A1) derived from a compound represented by formula (a1) is included, it is even more preferable that structural unit (A1) derived from a compound represented by formula (a1) and structural unit (A2) derived from a compound represented by formula (a2) are included. The compound represented by formula (a1) is 4,4'-oxydiphthalic anhydride (ODPA). By using structural unit (A1) derived from a compound represented by formula (a1) as a structural unit of a polyimide resin, the polyimide resin will have excellent heat resistance and strength. The compound represented by formula (a2) is 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA). By using the structural unit (A2) derived from the compound represented by formula (a2) as a structural unit of the polyimide resin, it is possible to further improve heat resistance and strength. The compound represented by formula (a3) ​​is 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA). By using the structural unit (A3) derived from the compound represented by formula (a3) ​​as a structural unit of the polyimide resin, it is possible to further improve heat resistance and adhesion.

[0027] The total ratio of the structural unit (A1), the structural unit (A2), and the structural unit (A3) in the structural unit A is preferably 50 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, still more preferably 95 mol% or more and 100 mol% or less, even more preferably 99 mol% or more and 100 mol% or less, and may be 100 mol%, with 100 mol% being even more preferred from the viewpoint of heat resistance and mechanical strength.

[0028] When the structural unit A contains the structural unit (A1) and the structural unit (A2), the total ratio of the structural unit (A1) and the structural unit (A2) in the structural unit A is preferably 50 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, even more preferably 95 mol% or more and 100 mol% or less, even more preferably 99 mol% or more and 100 mol% or less, and may be 100 mol%, and 100 mol% is even more preferable from the viewpoint of heat resistance and mechanical strength.

[0029] The ratio of the structural unit (A1) to the total of the structural unit (A1) and the structural unit (A2) is preferably 30 to 100 mol%, and from the viewpoints of heat resistance, strength, and transparency, it is more preferably 40 to 100 mol%, even more preferably 50 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, even more preferably 80 to 100 mol%, even more preferably 90 to 100 mol%, or even 100 mol%. Also, from the viewpoint of heat resistance and strength, it is more preferably 30 to 90 mol%, even more preferably 30 to 80 mol%, even more preferably 30 to 70 mol%, even more preferably 30 to 60 mol%, and even more preferably 30 to 50 mol%.

[0030] From the viewpoints of heat resistance, strength, and transparency, the proportion of the structural unit (A1) in the structural unit A is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, with the upper limit being 100 mol% or less.

[0031] When the structural unit A contains the structural unit (A3), the proportion of the structural unit (A3) in the structural unit A is preferably 50 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, still more preferably 95 mol% or more and 100 mol% or less, even more preferably 99 mol% or more and 100 mol% or less, and may be 100 mol%, with 100 mol% being even more preferred from the viewpoint of heat resistance and adhesion.

[0032] The structural unit A may contain a structural unit other than the structural unit (A1), the structural unit (A2), and the structural unit (A3). Such structural units are not particularly limited, but include structural units derived from aromatic tetracarboxylic dianhydrides other than the structural unit (A1), the structural unit (A2), and the structural unit (A3), structural units derived from alicyclic tetracarboxylic dianhydrides, and structural units derived from aliphatic tetracarboxylic dianhydrides.

[0033] Examples of aromatic tetracarboxylic dianhydrides that provide structural units derived from aromatic tetracarboxylic dianhydrides other than the structural unit (A1), the structural unit (A2), and the structural unit (A3) include pyromellitic anhydride (PMDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 9,9-bis(trifluoromethyl)-9H-xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA), 2,2-bis[4-( 3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), hydroquinone diphthalic anhydride (HQDEA), ethylene glycol bis(trimellitate) dianhydride (TMEG), p-phenylene bis(trimellitate) dianhydride (TAHQ), 4,4 '-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2',3,3',5,5'-hexamethyl[1,1'-biphenyl]-4,4'-diyl bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylate) (TMPBP-TME), 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11, Examples of suitable structural units include 9'-[9H]fluorene]-1,3,7,9-tetrone (SFDA), 4,4'-thiodiphthalic anhydride, 5-[4-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione, 5-[3-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione, and p-biphenylenebis(trimellitic acid monoester acid anhydride) (BP-TME). Among these, pyromellitic anhydride (PMDA) is preferred. By including a structural unit derived from PMDA as structural unit A, a laminate having excellent adhesion, step-filling properties, flatness, and heat resistance can be obtained.

[0034] Examples of alicyclic tetracarboxylic dianhydrides that provide structural units derived from alicyclic tetracarboxylic dianhydrides include cyclohexane-1,2,4,5-tetracarboxylic dianhydride (HPMDA), cyclohexane-1,2,3,4-tetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclopentanetetracarboxylic dianhydride, 3,3',4,4'-bicyclohexyltetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, decahydro-1,4:5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic dianhydride (DNDA), 5,5'-(1,4-phenylene)-bis[hexahydro-4,7- Methanoisobenzofuran-1,3-dione], 5,5'-bis-2-norbornene-5,5',6,6'-tetracarboxylic acid-5,5',6,6'-dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5',6,6'-tetracarboxylic acid anhydride (CpODA), 2,2-propylidene-4,4'-bis(cyclohexane Examples of aliphatic tetracarboxylic acid dianhydrides that provide structural units derived from aliphatic tetracarboxylic acid dianhydrides include 1,2,3,4-butanetetracarboxylic acid dianhydride, ... In this specification, the term "aromatic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more aromatic rings, the term "alicyclic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more alicyclic rings but no aromatic rings, and the term "aliphatic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing neither an aromatic ring nor an alicyclic ring.

[0035] (Structural Unit B) Structural unit B is a structural unit derived from a diamine, and preferably includes at least one selected from the group consisting of structural unit (B1) derived from a compound represented by formula (b1), structural unit (B2) derived from a compound represented by formula (b2), and structural unit (B3) derived from a compound represented by formula (b3). More preferably, it includes at least one selected from the group consisting of structural unit (B1) derived from a compound represented by formula (b1) and structural unit (B2) derived from a compound represented by formula (b2). Even more preferably, it includes structural unit (B1) derived from a compound represented by formula (b1). The compound represented by formula (b1) is 4-aminophenyl-4-aminobenzoate (4-BAAB). By including structural unit (B1) in structural unit B, the resulting polyimide resin has excellent heat resistance and can also have improved adhesion. The compound represented by formula (b2) is bis(4-aminophenyl)terephthalate (APTP). When the structural unit B includes the structural unit (B2), the heat resistance of the resulting polyimide resin is excellent, and the adhesion of the polyimide resin can also be improved. The compound represented by formula (b3) is 1,4-bis(4-aminobenzoyloxy)benzene. When the structural unit B includes the structural unit (B3), the heat resistance of the resulting polyimide resin is excellent, and the adhesion of the polyimide resin can also be improved.

[0036] The total ratio of the structural unit (B1), the structural unit (B2), and the structural unit (B3) in the structural unit B is preferably 30 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, still more preferably 95 to 100 mol%, or even 100 mol%, and the structural unit B may consist of only at least one selected from the group consisting of the structural unit (B1), the structural unit (B2), and the structural unit (B3). The ratio of the structural unit (B1) in the structural unit B is preferably 30 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, still more preferably 95 to 100 mol%, or even 100 mol%, and the structural unit B may consist of only the structural unit (B1). The proportion of the structural unit (B2) in the structural unit B is preferably 30 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, still more preferably 95 to 100 mol%, or even 100 mol%, and the structural unit B may consist solely of the structural unit (B2). The proportion of the structural unit (B3) in the structural unit B is preferably 30 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, still more preferably 95 to 100 mol%, or even 100 mol%, and the structural unit B may consist solely of the structural unit (B3). When the proportions of the structural unit (B1), the structural unit (B2), and the structural unit (B3) are within the above ranges, the resulting polyimide resin has excellent heat resistance, and the coatability of the varnish and the adhesion of the polyimide resin are also improved.

[0037] The structural unit B may contain structural units other than the structural unit (B1), the structural unit (B2), and the structural unit (B3). Diamines that provide such structural units are not particularly limited, but include aromatic diamines, alicyclic diamines, and aliphatic diamines excluding the compounds represented by formula (b1), the compounds represented by formula (b2), and the compounds represented by formula (b3). Examples of aromatic diamines include 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFMB), 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-5,5'-diaminobiphenyl, 2,2-bis(4-aminophenyl)hexafluoropropane (HFDA), 2 , 2-bis(3-amino-4-methylphenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP), 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (4,4'-DDS), 3,3'-diaminodiphenyl sulfone (3,3'-DDS ), 4,4'-diamino-2,2'-dimethylbiphenyl (mTB), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4,4'-diaminobiphenyl (benzidine), 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminobenzophenone, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 5-amino-1,3,3-trimethyl -1-(4-aminophenyl)-indan (5-TMDM), 6-amino-1,3,3-trimethyl-1-(4-aminophenyl)-indan (6-TMDM), 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene (BisAM), 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene (BisAP), 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl (BODA), 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone [4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4-diaminobenzanilide, 4-aminobenzoate-4-aminophenyl, 3,4-diaminobenzanilide, and the like. Examples of alicyclic diamines include 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane, 1,3-cyclohexyldiamine, 1,4-cyclohexyldiamine, isophoronediamine, bis(aminomethyl)norbornane, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexyl ether, and 2,2-bis(4-aminocyclohexyl)propane. Examples of aliphatic diamines include ethylenediamine and hexamethylenediamine. In this specification, aromatic diamine refers to a diamine containing one or more aromatic rings, alicyclic diamine refers to a diamine containing one or more alicyclic rings but no aromatic rings, and aliphatic diamine refers to a diamine containing neither an aromatic ring nor an alicyclic ring. The structural units other than the structural units (B1), (B2), and (B3) optionally contained in the structural unit B may be one type, or two or more types.

[0038] The polyimide resin may contain a structure other than a polyimide chain (a structure formed by imide bonding between structural unit A and structural unit B) as long as it does not impair the present invention. Examples of structures other than polyimide chains that can be contained in a polyimide resin include structures containing amide bonds. It is preferable that the polyimide resin contains a polyimide chain (a structure formed by imide bonding between structural unit A and structural unit B) as its main structure. Therefore, the proportion of polyimide chains in the polyimide resin is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 99% by mass or more, and even more preferably 100% by mass.

[0039] <Method for Producing Polyimide Resin> The polyimide resin may be produced by any method, but is preferably produced by the following method. The polyimide resin may be produced by polymerizing a diamine (hereinafter also referred to as a diamine component) with a tetracarboxylic dianhydride (hereinafter also referred to as a tetracarboxylic acid component) to directly obtain a polyimide. Alternatively, the polyimide resin may be produced by polymerizing a diamine with a tetracarboxylic dianhydride to obtain a polyamic acid or an imide-amic acid copolymer, which is a precursor of the polyimide resin (polyimide resin precursor), and then imidizing the polyimide resin when producing a laminate. Among these, a method in which a polyimide resin precursor is obtained and then imidized when producing a laminate is preferred. Here, methods for producing an imide-amic acid copolymer, which is a polyimide resin precursor, and polyamic acid, as well as a method for producing a polyimide resin directly, will be described. Note that the polyimide resin precursor and polyimide resin may also be collectively referred to as a polymer.

[0040] (Method for producing imide-amic acid copolymer, which is a polyimide resin precursor) A preferred method for producing a polymer containing both imide units and amic acid units (hereinafter also referred to as imide-amic acid copolymer) comprises the following steps 1 and 2: Step 1: A step of reacting a tetracarboxylic dianhydride with a diamine in the presence of a solvent to obtain an imide oligomer; Step 2: A step of mixing the imide oligomer obtained in step 1 with at least one of a tetracarboxylic dianhydride and a diamine, and polymerizing the mixture.

[0041] [Step 1] Step 1 is a step of reacting a tetracarboxylic dianhydride with a diamine in the presence of a solvent to obtain an imide oligomer. The tetracarboxylic dianhydride and the diamine constitute an imide moiety. In Step 1, the ratio of the diamine to the tetracarboxylic dianhydride is preferably 1.01 to 2 mol, more preferably 1.05 to 1.9 mol, and even more preferably 1.1 to 1.7 mol.

[0042] There are no particular limitations on the method for reacting a tetracarboxylic dianhydride with a diamine to obtain an imide oligomer in step 1, and known methods can be used. Specific reaction methods include: (1) a method in which a tetracarboxylic dianhydride, a diamine, and a solvent are charged into a reactor, and the mixture is stirred at 10 to 110°C for 0.5 to 30 hours, and then the temperature is raised to carry out an imidization reaction; (2) a method in which a diamine and a solvent are charged into a reactor and dissolved, and then a tetracarboxylic dianhydride is charged, and the mixture is stirred at 10 to 110°C for 0.5 to 30 hours as needed, and then the temperature is raised to carry out an imidization reaction; and (3) a method in which a tetracarboxylic dianhydride, a diamine, and a solvent are charged into a reactor, and the temperature is immediately raised to carry out an imidization reaction.

[0043] The imidization reaction is preferably carried out while removing water generated during the production using a Dean-Stark apparatus, etc. By performing such an operation, the degree of polymerization and the imidization rate can be further increased.

[0044] In the imidization reaction, a known imidization catalyst can be used. Examples of the imidization catalyst include base catalysts and acid catalysts. Examples of the base catalyst include organic base catalysts such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline; and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate. Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, hydroxybenzoic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, and naphthalenesulfonic acid. The imidization catalysts described above may be used alone or in combination of two or more. Of the above, from the viewpoint of ease of handling, a base catalyst is preferred, an organic base catalyst is more preferred, one or more selected from triethylamine and triethylenediamine is even more preferred, and triethylamine is even more preferred.

[0045] The temperature of the imidization reaction is preferably 120 to 250° C., more preferably 160 to 200° C., from the viewpoint of the reaction rate and suppression of gelation, etc. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

[0046] The above method provides a solution containing an imide oligomer dissolved in a solvent. The solution containing the imide oligomer obtained in step 1 may contain at least a portion of the components used as the tetracarboxylic dianhydride or diamine in step 1 as unreacted monomers, as long as the effects of the present invention are not impaired.

[0047] [Step 2] Step 2 is a step of mixing the imide oligomer obtained in step 1 with at least one of a tetracarboxylic dianhydride and a diamine, followed by polymerization.

[0048] In the entire process of steps 1 and 2, the ratio of the diamine component to the tetracarboxylic acid component is preferably 0.9 to 1.1 moles.

[0049] In step 2, the method for polymerizing the imide oligomer, tetracarboxylic dianhydride, and diamine obtained in step 1 is not particularly limited, and known methods can be used. Specific reaction methods include (1) a method in which the imide oligomer and at least one of the tetracarboxylic dianhydride and diamine are charged into a reactor and stirred at 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours, and (2) a method in which the imide oligomer and a solvent are charged into a reactor and dissolved, and then at least one of the tetracarboxylic dianhydride and diamine is charged and stirred at 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours. When the reaction is carried out at 80°C or below, the molecular weight of the copolymer obtained in step 2 does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, allowing the copolymer to be produced stably.

[0050] The concentration of the copolymer in the resulting solution is preferably 1 to 50% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass.

[0051] (Method for Producing Polyamic Acid, a Polyimide Resin Precursor) When the polyimide resin precursor is polyamic acid, a preferred method for producing the polyimide resin precursor is to react a tetracarboxylic dianhydride with a diamine in the presence of a solvent to obtain a polyamic acid. The method for polymerizing the tetracarboxylic dianhydride and the diamine is not particularly limited, and known methods can be used. Specific reaction methods include charging a solution containing the diamine and a solvent and the tetracarboxylic dianhydride into a reactor and stirring for 1 to 72 hours at a temperature preferably in the range of 0 to 120°C, more preferably 5 to 80°C. The ratio of the diamine component to the tetracarboxylic acid component is preferably 0.9 to 1.1 moles. When the reaction is carried out at 80°C or below, the molecular weight of the polyamic acid does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, allowing for stable production of the polyamic acid.

[0052] The concentration of the polyamic acid in the resulting solution is preferably 1 to 50% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass.

[0053] (Method for Producing Polyimide Resin) A preferred method for directly obtaining a polyimide resin is a method in which a tetracarboxylic dianhydride and a diamine are reacted in the presence of a solvent to obtain a polyimide resin.

[0054] The method for polymerizing the tetracarboxylic dianhydride and the diamine is not particularly limited, and any known method can be used. Specific reaction methods include (1) a method in which a solution containing the diamine and a solvent and the tetracarboxylic dianhydride are charged into a reactor, and the mixture is stirred at 10 to 110°C for 0.5 to 30 hours as needed, and then the temperature is raised to carry out the imidization reaction, and (2) a method in which a solution containing the diamine and a solvent and the tetracarboxylic dianhydride are charged into a reactor, and the temperature is immediately raised to carry out the imidization reaction.

[0055] The imidization reaction is preferably carried out while removing water generated during the production using a Dean-Stark apparatus, etc. By performing such an operation, the degree of polymerization and the imidization rate can be further increased.

[0056] In the imidization reaction, a known imidization catalyst can be used. Examples of the imidization catalyst include base catalysts and acid catalysts. Examples of the base catalyst include organic base catalysts such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline; and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate. Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, hydroxybenzoic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, and naphthalenesulfonic acid. The imidization catalysts described above may be used alone or in combination of two or more. Of the above, from the viewpoint of ease of handling, a base catalyst is preferred, an organic base catalyst is more preferred, one or more selected from triethylamine and triethylenediamine is even more preferred, and triethylamine is even more preferred.

[0057] The temperature of the imidization reaction is preferably 120 to 250° C., more preferably 160 to 200° C., from the viewpoint of the reaction rate and suppression of gelation, etc. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

[0058] The concentration of the polyimide in the resulting solution is preferably 1 to 50% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass.

[0059] Next, raw materials used in the production methods of the imide-amic acid copolymer, polyamic acid, and polyimide resin will be described.

[0060] [Tetracarboxylic acid dianhydride] The tetracarboxylic acid dianhydride used as a raw material in the production method is preferably the tetracarboxylic acid dianhydride described in the structural unit A of the polyimide resin. Examples of tetracarboxylic acid dianhydrides include, but are not limited to, acid dianhydrides, and may be derivatives thereof as long as they provide the structural unit A. Examples of such derivatives include tetracarboxylic acids (free acids) and alkyl esters of the tetracarboxylic acids. Of these, acid dianhydrides are preferred.

[0061] [Diamine] The diamine used as a raw material in the production method is preferably the diamine described above for the structural unit B of the polyimide resin. Examples of diamines include, but are not limited to, diamines, and may be derivatives thereof as long as they provide the structural unit B in the polymer. Examples of such derivatives include diisocyanates corresponding to the diamines. Among these, diamines are preferred.

[0062] [End-capping Agent] In addition to the tetracarboxylic acid component and diamine component described above, a terminal-capping agent may also be used in the production of the polymer. In the production of the imide-amidic acid copolymer, the terminal-capping agent is preferably used in step 2. Preferred terminal-capping agents are acid anhydrides, monoamines, or dicarboxylic acids. The amount of terminal-capping agent introduced is preferably 0.0001 to 20 mol, more preferably 0.1 to 10 mol, and even more preferably 0.5 to 5 mol, per mol of the tetracarboxylic acid component. Recommended monoamine terminal-capping agents include, for example, methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, o-aminophenol, m-aminophenol, p-aminophenol, o-aminobenzoic acid, m-aminobenzoic acid, and p-aminobenzoic acid. Of these, benzylamine, aniline, o-aminophenol, m-aminophenol, p-aminophenol, o-aminobenzoic acid, m-aminobenzoic acid, and p-aminobenzoic acid are preferably used. As the dicarboxylic acid end-capping agent, dicarboxylic acids are preferred, and a portion of the dicarboxylic acid may be ring-closed. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenonedicarboxylic acid, 3,4-benzophenonedicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, trimellitic anhydride, and the like are recommended. Of these, phthalic acid, phthalic anhydride, and trimellitic anhydride are preferably used.

[0063] [Solvent] The solvent used in the method for producing a polymer may be any solvent capable of dissolving the polymer to be produced, such as an aprotic solvent, a phenolic solvent, an ether solvent, or a carbonate solvent.

[0064] Specific examples of aprotic solvents include amide solvents such as cyclic amides and chain amides, phosphorus-containing amide solvents, sulfur-containing solvents, ketone solvents, and ester solvents including cyclic esters. Among these, the solvent preferably contains at least one selected from the group consisting of cyclic amides, chain amides, and cyclic esters, and more preferably contains a cyclic amide. Examples of cyclic amides include N-methylpyrrolidone, N-methylcaprolactam, and 1,3-dimethylimidazolidinone, with N-methylpyrrolidone being preferred. Examples of chain amides include N,N-dimethylformamide, N,N-dimethylacetamide, and tetramethylurea. Examples of cyclic esters include γ-butyrolactone and γ-valerolactone. Other examples of ester solvents include 2-methoxy-1-methylethyl acetic acid. Examples of phosphorus-containing amide solvents include hexamethylphosphoric amide and hexamethylphosphine triamide. Examples of sulfur-containing solvents include dimethyl sulfone, dimethyl sulfoxide, and sulfolane. Examples of the ketone solvent include acetone, methyl ethyl ketone, cyclohexanone, and methylcyclohexanone.

[0065] Specific examples of phenol-based solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol. Specific examples of ether-based solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane. Specific examples of carbonate-based solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above solvents, preferred are solvents that contain at least one selected from the group consisting of cyclic amides, linear amides, and cyclic esters, more preferred are solvents that contain at least one selected from the group consisting of cyclic amides and cyclic esters, and even more preferred are solvents that contain cyclic esters. More specifically, the solvent contains at least one selected from the group consisting of N-methylpyrrolidone and γ-butyrolactone, and even more preferably γ-butyrolactone. The above solvents may be used alone or in combination of two or more.

[0066] (Polyimide Resin Precursor) In the method for producing a polyimide resin and the method for producing a laminate described below, the polyimide resin precursor used as a raw material for the polyimide resin is not limited in structure as long as the resulting polyimide resin has a glass transition temperature of 300°C or higher, as described above. However, it is preferable that the polyimide resin precursor has a structural unit represented by the following general formula (1):

[0067] The polyimide resin precursor preferably has a structural unit of formula (1), more preferably has at least one structural unit selected from the group consisting of a structural unit of formula (1a) below and a structural unit of formula (1b) below, and even more preferably has a structural unit of formula (1b) below:

[0068] The polyimide resin precursor having the structural unit of formula (1a) more preferably contains at least one selected from the group consisting of a repeating unit represented by formula (4a) below and a repeating unit represented by formula (5a) below, even more preferably contains a repeating unit represented by formula (4a) below, and still more preferably contains a repeating unit represented by formula (4a) below and a repeating unit represented by formula (5a) below. (In formula (4a) and formula (5a), X 1 and X 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

[0069] The "repeating unit" in the polyimide resin precursor is an amic acid unit containing a structural unit derived from one tetracarboxylic dianhydride and a structural unit derived from one diamine. 1 and X 2 are each independently at least one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and an alkylsilyl group having 3 to 9 carbon atoms, preferably at least one selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom. The ratio of the repeating unit represented by formula (4a) to the total of the repeating unit represented by formula (4a) and the repeating unit represented by formula (5a) is preferably 30 to 100 mol%, and from the viewpoint of transparency, more preferably 40 to 100 mol%, even more preferably 50 to 100 mol%, still more preferably 60 to 100 mol%, still more preferably 70 to 100 mol%, still more preferably 80 to 100 mol%, still more preferably 90 to 100 mol%, or even 100 mol%. Furthermore, from the viewpoint of heat resistance and strength, it is more preferably 30 to 90 mol%, even more preferably 30 to 80 mol%, still more preferably 30 to 70 mol%, even more preferably 30 to 60 mol%, and still more preferably 30 to 50 mol%.

[0070] From the viewpoint of heat resistance and mechanical strength, the sum of the repeating units represented by formula (4a) and the repeating units represented by formula (5a) is preferably 50 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, still 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%, with 100 mol% being even more preferred from the viewpoint of heat resistance and mechanical strength.

[0071] From the viewpoint of transparency, the repeating unit represented by formula (4a) preferably accounts for 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more of the total repeating units of the polyimide resin precursor, with the upper limit being 100 mol% or less.

[0072] The polyimide resin precursor may contain repeating units other than the repeating unit represented by formula (4a) and the repeating unit represented by general formula (5a). The content of repeating units other than the repeating unit represented by formula (4a) and the repeating unit represented by general formula (5a) is preferably 50 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, still more preferably 10 mol% or less, still more preferably 5 mol% or less, still more preferably 1 mol% or less, still more preferably 0 mol%, and even more preferably none, based on the total repeating units of the polyimide resin precursor.

[0073] The polyimide resin precursor having the structural unit of formula (1b) preferably contains a repeating unit represented by the following formula (4b). (In formula (4b), X 1 and X 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

[0074] In the formula (4b), X 1 and X 2 are each independently at least one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and an alkylsilyl group having 3 to 9 carbon atoms, preferably at least one selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom. From the viewpoint of heat resistance and mechanical strength, the repeating unit represented by formula (4b) is preferably 50 mol% to 100 mol%, more preferably 70 mol% to 100 mol%, based on all repeating units of the polyimide resin precursor. Even more preferably, it is 80 mol% to 100 mol%, still more preferably 90 mol% to 100 mol%, still more preferably 95 mol% to 100 mol%, still more preferably 99 mol% to 100 mol%, and may be 100 mol%, with 100 mol% being even more preferred from the viewpoint of heat resistance and adhesion.

[0075] The polyimide resin precursor may contain a repeating unit other than the repeating unit represented by formula (4b). The content of repeating units other than the repeating unit represented by formula (4b) is preferably 50 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, still more preferably 10 mol% or less, still more preferably 5 mol% or less, still more preferably 1 mol% or less, still more preferably 0 mol%, and even more preferably zero, based on the total repeating units of the polyimide resin precursor.

[0076] As described above, the polyimide resin precursor more preferably contains at least one repeating unit selected from the group consisting of a repeating unit represented by formula (4a), a repeating unit represented by formula (5a), and a repeating unit represented by formula (4b), and even more preferably contains a repeating unit represented by formula (4b). By containing the repeating unit represented by formula (4b), the polyimide resin precursor can be dissolved in any solvent when preparing a varnish, and is particularly preferred because it can be well dissolved in an ester-based solvent.

[0077] In addition, when the polyimide resin precursor is an imide-amic acid copolymer, it preferably contains the repeating units described in this section and the repeating units described in the section on polyimide resins. Specifically, the imide moiety preferably contains at least one selected from the group consisting of a repeating unit represented by formula (2b), a repeating unit represented by formula (2a), and a repeating unit represented by formula (3a), more preferably at least one selected from the group consisting of a repeating unit represented by formula (2b) and a repeating unit represented by formula (2a) below, and even more preferably a repeating unit represented by formula (2b). And, the amic acid moiety preferably contains at least one selected from the group consisting of a repeating unit represented by formula (4b), a repeating unit represented by formula (4a), and a repeating unit represented by formula (5a), more preferably at least one selected from the group consisting of a repeating unit represented by formula (4b) and a repeating unit represented by formula (4a) below, and even more preferably a repeating unit represented by formula (4b).

[0078] <Varnish> The laminate of the present invention is preferably obtained by a laminate manufacturing method including a step of applying a polyimide resin varnish or a polyimide resin precursor varnish to a supporting substrate and heating the applied varnish to obtain a polyimide resin layer, and a step of forming an inorganic film having compressive stress on the polyimide resin layer. The varnish used in manufacturing the laminate will be described below. However, since the preferred varnish is the same for both a varnish containing a polyimide resin and an organic solvent that constitutes the polyimide resin layer and a varnish containing a polyimide resin precursor and an organic solvent that constitutes the polyimide resin layer, they will be collectively described below as "varnish".

[0079] The varnish contains the polyimide resin and an organic solvent, or a polyimide resin precursor and an organic solvent. The solvent is not particularly limited as long as it dissolves the polyimide resin or polyimide resin precursor. However, it is preferable to use the compounds described above as solvents used in the production of polyimide resins or polyimide resin precursors, either alone or in combination of two or more. Among the above solvents, the varnish preferably contains at least one selected from the group consisting of cyclic amides, linear amides, and cyclic esters, more preferably cyclic amides, and even more preferably N-methylpyrrolidone. The varnish may be the polyimide resin solution or polyimide resin precursor solution obtained by the above-described method for producing a polyimide resin or polyimide resin precursor, or a solution obtained by adding a solvent or a solution obtained by reducing the solvent content by concentration or the like.

[0080] In the case of a varnish containing a polyimide resin precursor, the varnish may further contain an imidization catalyst and a dehydration catalyst from the viewpoint of efficiently proceeding with the imidization of the amic acid moiety. The imidization catalyst may be an imidization catalyst having a boiling point of 40°C or higher and 180°C or lower, with amine compounds having a boiling point of 180°C or lower being preferred. An imidization catalyst having a boiling point of 180°C or lower prevents the polyimide film obtained from the laminate formed and drying at high temperatures from becoming discolored, which could impair its appearance. Furthermore, an imidization catalyst having a boiling point of 40°C or higher can prevent the polyimide film from volatilizing before the imidization has progressed sufficiently. Examples of amine compounds suitable for use as imidization catalysts include pyridine and picoline. The above imidization catalysts may be used alone or in combination of two or more. Examples of dehydration catalysts include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; carbodiimide compounds such as dicyclohexylcarbodiimide; and the like. These may be used alone or in combination of two or more.

[0081] The polyimide resin or polyimide resin precursor contained in the varnish is solvent-soluble, allowing for a high concentration varnish. The varnish preferably contains 1 to 40% by mass of the polyimide resin or polyimide resin precursor, more preferably 3 to 40% by mass, and even more preferably 5 to 30% by mass. The viscosity of the varnish is preferably 0.1 to 200 Pa·s, more preferably 1 to 20 Pa·s. The viscosity of the varnish is measured at 25°C using an E-type viscometer. The varnish may also contain various additives, such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, defoamers, fluorescent brighteners, crosslinking agents, polymerization initiators, and photosensitizers, as long as they do not impair the required properties of the polyimide film.

[0082] <Inorganic Film> The laminate of the present invention is a laminate comprising a supporting substrate, a polyimide resin layer on the supporting substrate, and an inorganic film on the polyimide resin layer, wherein the stress of the inorganic film is compressive stress. The stress of the inorganic film is compressive stress.

[0083] The stress of the inorganic film being compressive stress means that the stress S of the inorganic film calculated by the following Stoney formula is a negative value. Note that the laminate shown below refers to a laminate in which the supporting substrate, the polyimide resin layer, and the inorganic film are laminated in this order, and the pre-laminate refers to a laminate in which the supporting substrate and the polyimide resin layer are laminated in this order, before the inorganic film is laminated.

[0084] (In the formula, S is the stress (average value) (Pa) of the inorganic film, E / (1-ν) is the biaxial elastic modulus (Pa) of the preliminary laminate (supporting substrate / polyimide resin layer), h is the thickness (m) of the preliminary laminate (supporting substrate / polyimide resin layer), t is the thickness (m) of the inorganic film, R1 is the radius of curvature of the preliminary laminate (supporting substrate / polyimide resin layer) at 25°C, and R2 is the radius of curvature of the laminate (supporting substrate / polyimide resin layer / inorganic film) at 25°C.) The stress of the inorganic film can be specifically calculated by the method described in the examples.

[0085] Generally, polyimides have a positive coefficient of linear expansion, and therefore, polyimide resin layers exhibit positive stress. The polyimide resin layer of the laminate of the present invention contains a structure derived from a specific acid dianhydride and a specific diamine, which allows the resin itself to have excellent heat resistance, resulting in excellent inorganic film-forming properties. Furthermore, by forming an inorganic film having compressive stress, the stress of the entire laminate is alleviated, and therefore the laminate of the present invention has excellent annealing resistance, i.e., heat resistance, making it useful as a laminate in semiconductor processes.

[0086] The inorganic film preferably contains silicon. The inorganic film more preferably contains at least one selected from the group consisting of silicon oxide and silicon nitride, and even more preferably contains silicon nitride. The inorganic film more preferably consists of at least one selected from the group consisting of silicon oxide and silicon nitride, and the inorganic film is more preferably silicon oxide or silicon nitride, and even more preferably silicon nitride. When the inorganic film is silicon nitride, the effects of the present invention can be fully exhibited, and the film has excellent film-forming properties and heat resistance. Furthermore, silicon nitride has excellent barrier properties and chemical stability, making it an excellent inorganic film to be used in the laminate of the present invention. The inorganic film is an insulating film. That is, the inorganic film functions as an insulating film and a barrier film in the laminate, and also functions as a buffer film.

[0087] The thickness of the inorganic film is preferably 1 to 1,000 nm, more preferably 1 to 400 nm, even more preferably 10 to 300 nm, still more preferably 20 to 200 nm, and even more preferably 50 to 150 nm. When the thickness of the inorganic film is within the above range, the effects of the present invention can be fully exhibited, and the film-forming property and heat resistance become excellent.

[0088] [Method for Producing Laminate] The laminate of the present invention may be obtained by any production method as long as it has the above-mentioned configuration, but is preferably produced by the following method. Specifically, it is preferably produced by a laminate production method comprising the steps of applying a polyimide resin varnish or a polyimide resin precursor varnish to a supporting substrate and heating the applied varnish to obtain a polyimide resin layer, and further comprising the step of forming an inorganic film having compressive stress on the polyimide resin layer.

[0089] In the present production method, the supporting substrate, polyimide resin varnish, polyimide resin precursor varnish, polyimide resin, polyimide resin precursor, and inorganic film are as described above in this specification, and the preferred ranges are also as described above in this specification.

[0090] (Step of Obtaining Polyimide Resin Layer) This production method first includes a step of applying a polyimide resin varnish or a polyimide resin precursor varnish to a supporting substrate and heating the applied varnish to obtain a polyimide resin layer. This step provides a pre-laminate in which a polyimide resin layer is laminated on a supporting substrate. In the next step, an inorganic film is formed on the pre-laminate to form the laminate of the present invention.

[0091] The heating temperature is preferably 300°C or higher, more preferably 300 to 500°C. The heating time is typically 1 minute to 6 hours, preferably 10 minutes to 3 hours, and more preferably 20 minutes to 2 hours. To remove the solvent contained in the varnish, preheating at 60 to 250°C may be performed before heating to 300°C or higher. The preheating temperature is preferably 60 to 250°C, more preferably 70 to 180°C. The preheating time is preferably 1 minute to 6 hours, more preferably 5 minutes to 2 hours, and even more preferably 10 minutes to 1 hour. Preheating may be performed multiple times. Examples of heating atmospheres include air gas, nitrogen gas, oxygen gas, hydrogen gas, and nitrogen / hydrogen mixed gas. However, to suppress discoloration of the resulting polyimide resin, nitrogen gas with an oxygen concentration of 100 ppm or less and nitrogen / hydrogen mixed gas with a hydrogen concentration of 0.5% or less are preferred.

[0092] (Step of forming an inorganic film) The laminate of the present invention has a polyimide resin layer on a support substrate, an inorganic film on the polyimide resin layer, and the stress of the inorganic film is compressive stress. In this step, an inorganic film having compressive stress is formed on the polyimide resin layer of the preliminary laminate obtained in the previous step. The inorganic film may be formed by any method, but is preferably formed by sputtering, CVD film formation, or vacuum deposition. In other words, the method of forming the inorganic film is preferably sputtering, CVD film formation, or vacuum deposition, more preferably sputtering or CVD film formation, and even more preferably CVD film formation. Even more preferably, it is plasma CVD film formation.

[0093] The following conditions are preferred for plasma CVD film formation conditions for forming an inorganic film having compressive stress. The plasma generation power supply frequency may be any frequency used in a typical plasma processing apparatus and may be adjusted appropriately depending on other conditions. However, it is preferable to use 380 kHz, more preferably to use 380 kHz and 13.56 MHz in combination, and even more preferably to alternate between 380 kHz and 13.56 MHz. The RF output is preferably 20 to 60 W, more preferably 20 to 50 W, and even more preferably 20 to 40 W. The film formation temperature is preferably 200 to 400°C, more preferably 200 to 360°C. The film formation time may be selected appropriately depending on the type of inorganic film raw material, the required film thickness, etc., but is preferably 1 to 20 minutes, more preferably 3 to 15 minutes.

[0094] The laminate obtained in this manner has excellent film-forming properties and heat resistance, and is therefore useful as a laminate in semiconductor processes, such as for semiconductor memories, LSI stacks, CMOS image sensors, MEMS encapsulation, optical devices, and LED applications.

[0095] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these examples in any way.

[0096] <Physical Properties of Polyimide Resin> (1) Glass Transition Temperature of Polyimide Resin The glass transition temperature of the polyimide resin constituting the polyimide resin layer in the laminates of the Examples and Comparative Examples was measured as follows: The polyamic acid varnish obtained in the Examples and Comparative Examples (Production of Polyamic Acid Varnish) was applied to a supporting substrate (4-inch silicon wafer), held at 100°C on a hot plate for 10 minutes, and then heated to 400°C at a heating rate of 5°C / min in a nitrogen atmosphere in a hot air dryer, and heated at 400°C for 30 minutes to evaporate the solvent and thermally imidize, thereby obtaining a polyimide film (thickness 10 μm). The obtained polyimide film was subjected to TMA measurement using a thermomechanical analyzer "TMA 7100C" manufactured by Hitachi High-Tech Science Corporation, with a sample size of 4 mm x 20 mm, in tensile mode, under conditions of a load of 50 mN and a heating rate of 10 ° C / min, with the temperature rising from 40 ° C to 500 ° C. The point at which an inflection point of elongation was observed was extrapolated to determine the glass transition temperature (Tg). The higher the glass transition temperature (Tg), the better the heat resistance. The glass transition temperatures of the polyimide resins are shown in Table 1.

[0097] <Physical Properties of Inorganic Film> (1) Stress of Inorganic Film Using a residual stress measuring device "FLX-2320-S" (manufactured by KLA-Tencor Corporation), the radius of curvature R1 at 25°C of the preliminary laminate (support substrate / polyimide resin layer) obtained in each Example and Comparative Example (production of preliminary laminate) was measured. Next, as described below, an inorganic film (silicon nitride film) was formed on the polyimide resin layer of the preliminary laminate (support substrate / polyimide resin layer) under the conditions of each Example and Comparative Example to obtain a laminate (support substrate / polyimide resin layer / inorganic film). Thereafter, using a residual stress measuring device "FLX-2320-S" (manufactured by KLA-Tencor Corporation), the radius of curvature R2 at 25°C of the resulting laminate (support substrate / polyimide resin layer / inorganic film) was measured. Using the R1 and R2 obtained above, the stress S of the inorganic film was calculated using the following Stoney equation. The stress S is the stress generated between the preliminary laminate and the inorganic film. A positive value of the stress S indicates tensile stress, and a negative value indicates compressive stress.

[0098] (In the formula, S is the stress (average value) of the inorganic film (Pa), E / (1-ν) is the biaxial elastic modulus of the preliminary laminate (Pa), h is the thickness of the preliminary laminate (m), and t is the thickness of the inorganic film (m). As described above, R1 is the radius of curvature of the preliminary laminate (supporting substrate / polyimide resin layer) at 25°C, and R2 is the radius of curvature of the laminate (supporting substrate / polyimide resin layer / inorganic film) at 25°C.) In this example, the biaxial elastic modulus of the preliminary laminate was approximated by the biaxial elastic modulus of the supporting substrate because the influence of the polyimide layer was extremely small.

[0099] <Process Evaluation> Process evaluation of the laminate was performed by the following method. (1) Inorganic Film Formability (Evaluation of Film Formability) The presence or absence of cracks in the inorganic film of the laminate (support substrate / polyimide resin layer / inorganic film) obtained in the Examples and Comparative Examples was visually evaluated. As a result of evaluation without using a microscope, those that showed no cracks were further evaluated using a microscope (magnification 100x). The smaller the crack size, the fewer defects there are during film formation, the higher the heat resistance, and the better. Those that have no cracks are better without defects during film formation, and the higher the heat resistance. A: No cracks are visible in the inorganic film even when magnified 100x with a microscope. C: No cracks are visible in the inorganic film with the naked eye, but cracks are visible in the inorganic film when magnified 100x with a microscope. D: Cracks are visible in the inorganic film with the naked eye. (2) Annealing resistance (evaluation of heat resistance) The laminates (support substrate / polyimide resin layer / inorganic film) obtained in the examples and comparative examples were heated and annealed at 400°C for 1 hour. The presence or absence of cracks in the inorganic film of the laminates (support substrate / polyimide resin / inorganic film) after annealing treatment was visually evaluated. Evaluation was performed visually and under a microscope. As a result of evaluation without using a microscope, those that showed no cracks were further evaluated under a microscope (magnification 100x). The smaller the crack size, the fewer defects there were during film formation, and the higher the heat resistance, which is good. Those that showed no cracks were free of defects during film formation, and the higher the heat resistance, which is good. A: No cracks were observed in the inorganic film even when magnified 100x under a microscope. C: No cracks were observed in the inorganic film with the naked eye, but cracks were observed in the inorganic film when magnified 100x under a microscope. D: Cracks were observed in the inorganic film with the naked eye.

[0100] The tetracarboxylic acid components and diamine components used in the examples and comparative examples, as well as their abbreviations, are as follows: <Tetracarboxylic acid components> ODPA: 4,4'-oxydiphthalic anhydride (manufactured by Manac Corporation; compound represented by formula (a1)) s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation; compound represented by formula (a2)) DSDA: 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (manufactured by ChinaTech Chemical (Tianjin) Co., Ltd.; compound represented by formula (a3)) PMDA: pyromellitic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) <Diamine components> 4-BAAB: 4-aminophenyl-4-aminobenzoate (manufactured by Nihon Junryo Pharmaceutical Co., Ltd.; compound represented by formula (b1)) APTP: bis(4-aminophenyl)terephthalate (manufactured by Tokyo Chemical Industry Co., Ltd.; compound represented by formula (b2))

[0101] The abbreviations for the solvents and catalysts used in the examples and comparative examples are as follows: NMP: N-methyl-2-pyrrolidone (manufactured by Tokyo Pure Chemical Industries, Ltd.) GBL: γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation)

[0102] <Production of Laminate (Support Substrate / Polyimide Resin Layer / Inorganic Film)> Example 1 (Production of Polyamic Acid Varnish) A 1 L five-necked round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark condenser, a thermometer, and a glass end cap was charged with 34.836 g (0.100 mol) of APTP and 294.927 g of NMP, and the system was stirred at 50 ° C. under a nitrogen atmosphere at a rotation speed of 200 rpm to obtain a solution. To this solution, 15.511 g (0.050 mol) of ODPA, 14.711 g (0.050 mol) of s-BPDA, and 73.732 g of NMP were added all at once, and the mixture was stirred for 3 hours while maintaining the temperature at 50 ° C. with a mantle heater. Then, 108.429 g of NMP was added to obtain a polyamic acid varnish with a solids concentration of 12% by mass.

[0103] (Production of Pre-Laminate) The obtained polyamic acid varnish was then applied to a support substrate (4-inch silicon wafer, thickness 525 μm±25 μm) and held at 80° C. on a hot plate for 20 minutes. The temperature was then increased to 400° C. at a rate of 5° C. / min in a nitrogen atmosphere in a hot air dryer. The mixture was heated at 400° C. for 60 minutes to evaporate the solvent and induce thermal imidization, forming a polyimide resin layer (thickness 10 μm) on the support substrate, thereby obtaining a pre-laminate (support substrate / polyimide resin layer). The "radius of curvature R1" was measured at this point.

[0104] (Production of Laminate) Next, an inorganic film (silicon nitride film) was formed on the polyimide resin layer of the preliminary laminate (support substrate / polyimide resin layer) under the following conditions to obtain a laminate (support substrate / polyimide resin layer / inorganic film). The evaluation results of the obtained laminate are shown in Table 1.

[0105] (Inorganic film formation conditions) Equipment: Plasma CVD equipment MPX-CVD (manufactured by Sumitomo Precision Products Co., Ltd.) Film formation method: PE-CVD Film thickness: 1,000 Å Upper electrode temperature: 250°C Lower electrode temperature: 350°C Film formation time: 8 minutes 15 seconds Plasma generation power supply frequency: 13.56 MHz (HF) and 380 kHz (LF) were alternately switched. 45 cycles were applied, with 13.56 Hz (HF) for 7 seconds and 380 kHz (LF) for 4 seconds. This is indicated as "HFLF" in Table 1. RF output: 30 W Gas flow rate: SiH4 / NH3 / N2=10 / 10 / 2000 sccm

[0106] Example 2 A laminate (support substrate / polyimide resin layer / inorganic film) was obtained in the same manner as in Example 1, except that the plasma generation power frequency was changed to 380 kHz (LF) among the film formation conditions for the inorganic film (silicon nitride film). The evaluation results of the obtained laminate are shown in Table 1.

[0107] Example 3 A polyamic acid varnish having a solids concentration of 12% by mass was obtained in the same manner as in Example 1, except that in the production of the polyamic acid varnish, ODPA and s-BPDA were changed to 35.828 g (0.100 mol) of DSDA, APTP was changed to 22.825 g (0.100 mol) of 4-BAAB, the solvent NMP was changed to GBL, and the amount of GBL used for dilution was changed. Next, a laminate (support substrate / polyimide resin layer / inorganic film) was obtained in the same manner as in Example 2, except that the polyamic acid varnish obtained here was used. The evaluation results of the obtained laminate are shown in Table 1.

[0108] Example 4 A laminate (support substrate / polyimide resin layer / inorganic film) was obtained in the same manner as in Example 2, except that the film formation conditions for the inorganic film (silicon nitride film) were changed to a film formation time of 41 minutes 15 seconds and a film thickness of 5,000 Å. The evaluation results of the obtained laminate are shown in Table 1.

[0109] Example 5 A laminate (support substrate / polyimide resin layer / inorganic film) was obtained in the same manner as in Example 3, except that the film formation conditions for the inorganic film (silicon nitride film) were changed to a film formation time of 41 minutes 15 seconds and a film thickness of 5,000 Å. The evaluation results of the obtained laminate are shown in Table 1.

[0110] Example 6 A laminate (support substrate / polyimide resin layer / inorganic film) was obtained in the same manner as in Example 2, except that ODPA and s-BPDA were changed to 25.080 g (0.070 mol) of DSDA and 6.544 g (0.030 mol) of PMDA, APTP was changed to 22.825 g (0.100 mol) of 4-BAAB, and the film formation conditions for the inorganic film (silicon nitride film) were changed to a film formation time of 41 minutes 15 seconds and a film thickness of 5,000 Å. The evaluation results of the obtained laminate are shown in Table 1.

[0111] Example 7 A laminate (support substrate / polyimide resin layer / inorganic film) was obtained in the same manner as in Example 2, except that ODPA and s-BPDA were changed to 17.914 g (0.050 mol) of DSDA and 10.906 g (0.050 mol) of PMDA, and APTP was changed to 22.825 g (0.100 mol) of 4-BAAB. The evaluation results of the obtained laminate are shown in Table 1.

[0112] Example 8 A laminate (support substrate / polyimide resin layer / inorganic film) was obtained in the same manner as in Example 7, except that the film formation conditions for the inorganic film (silicon nitride film) were changed to a film formation time of 41 minutes 15 seconds and a film thickness of 5,000 Å. The evaluation results of the obtained laminate are shown in Table 1.

[0113] Comparative Example 1 A laminate (support substrate / polyimide resin layer / inorganic film) was obtained in the same manner as in Example 1, except that the plasma generation power supply frequency was changed to 13.56 MHz (HF) among the film formation conditions for the inorganic film (silicon nitride film). The evaluation results of the obtained laminate are shown in Table 1.

[0114] Comparative Example 2 A laminate (support substrate / polyimide resin layer / inorganic film) was obtained in the same manner as in Comparative Example 1, except that, among the film formation conditions for the inorganic film (silicon nitride film), the lower electrode temperature was changed to 400° C. and the RF output was changed to 70 W. The evaluation results of the obtained laminate are shown in Table 1.

[0115]

[0116] As shown in Table 1, the laminates of the examples have excellent film-forming properties and also excellent heat resistance. Therefore, the laminates of the present invention have the properties described above and are therefore useful as laminates in semiconductor processes. That is, the laminates of the present invention are useful as laminates for semiconductor memories, LSI stacks, CMOS image sensors, MEMS encapsulation, optical devices, LEDs, and the like.

Claims

1. A laminate comprising a support substrate, a polyimide resin layer on the support substrate, an inorganic film on the polyimide resin layer, wherein the glass transition temperature of the polyimide resin constituting the polyimide resin layer is 300°C or higher, and the stress of the inorganic film is compressive stress.

2. The laminate according to claim 1, wherein the inorganic film contains silicon.

3. The laminate according to claim 1 or 2, wherein the inorganic film is silicon oxide or silicon nitride.

4. The laminate according to claim 1 or 2, wherein the thickness of the polyimide resin layer is 0.5 to 300 μm.

5. The laminate according to claim 1 or 2, wherein the thickness of the inorganic film is 1 to 1,000 nm.

6. The laminate according to claim 1 or 2, wherein the support substrate contains silicon.

7. The laminate according to claim 1 or 2, wherein the supporting substrate is silicon, silicon carbide, gallium nitride, gallium oxide, aluminum nitride, or diamond.

8. A method for manufacturing a laminate, comprising the steps of applying a polyimide resin varnish or a polyimide resin precursor varnish onto a support substrate, heating to obtain a polyimide resin layer, and further forming an inorganic film having compressive stress on the polyimide resin layer.