Polyimide precursor composition and method for producing the same

Abstract

Provided is a polyimide precursor that is for producing a flexible electronic device substrate and that provides a polyimide that has reduced charge buildup and particularly has a film form. For this polyimide precursor, when a pair of electrodes 2a and 2b spaced apart from each other by an interval d are formed on a 10 μm-thick polyimide film 1 formed using the polyimide precursor, and the polyimide film is irradiated with a laser beam ω while a direct-current voltage is applied to the pair of electrodes such that a field intensity of 0.1-10 V / μm is achieved, two SHG beams 2ω observed between the electrodes exhibit a symmetry ratio of at least 0.5. Symmetry ratio (LR ratio) = Ismall / Ilarge, where Ilarge represents the peak intensity of the SHG beam having the higher intensity, and Ismall represents the peak intensity of the SHG beam having the lower intensity.

Description

[Technical Field]

[0001] The present invention relates to a polyimide precursor composition that is suitably used for electronic device applications such as substrates for flexible electronic devices, and further relates to a polyimide film for flexible electronic device substrates, a laminate containing a polyimide film, a flexible electronic device substrate, and a flexible electronic device. [Background technology]

[0002] Glass has traditionally been used as a substrate for displays such as liquid crystal displays and organic electroluminescence (EL) displays. However, when glass is thinned to reduce weight, it lacks strength and becomes fragile. Therefore, lightweight and flexible plastic substrates have been proposed as an alternative to glass substrates. In displays such as liquid crystal displays and EL displays, semiconductor elements such as TFTs are formed on the substrate to drive each pixel. Therefore, the substrate must have heat resistance and dimensional stability. Polyimide film is expected to be a promising substrate for displays because of its excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability.

[0003] For example, Patent Document 1 discloses a method for manufacturing a flexible device, which includes forming a polyimide film on a glass substrate to obtain a polyimide film / glass substrate laminate, forming elements and circuits required for the device on the polyimide film / glass substrate laminate, and then irradiating the glass substrate with a laser from the glass substrate side to peel off the glass substrate.

[0004] However, Non-Patent Document 1 reports a problem in which an afterimage phenomenon is observed in flexible displays that use polyimide film as a substrate, which is thought to be caused by charging up of polyimide. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 221607 [Non-patent literature]

[0006] [Non-Patent Document 1] S. Hong et al., “Alleviation of Recoverable Residual Image Phenomenon of Flexible Organic Light-emitting Diode display”, SID Digest p105-108 (2019) Summary of the Invention [Problem to be solved by the invention]

[0007] To solve the image retention phenomenon described in Non-Patent Document 1, it is thought that it is necessary to reduce charge buildup near the polyimide surface, but no solution to this problem is known. Therefore, it is necessary to properly evaluate charge buildup near the polyimide surface and provide a polyimide film that is optimal for flexible electronic devices, particularly as a substrate for organic electroluminescence (EL) displays and liquid crystal displays.

[0008] The present invention aims to provide a polyimide precursor for producing a flexible electronic device substrate, which provides a polyimide with reduced charge-up, particularly a polyimide in the form of a film, and a polyimide film for a flexible electronic device, as well as a laminate substrate including the polyimide film, and electronic devices including the same, such as a flexible display. [Means for solving the problem]

[0009] The present invention relates to the following.

[0010] 1. A polyimide precursor for manufacturing flexible electronic device substrates, comprising: A polyimide precursor is used to form a polyimide film having a thickness of 10 μm, and a pair of electrodes are formed on the polyimide film with a distance d therebetween. When a laser beam is irradiated onto the polyimide film while applying a DC voltage to the pair of electrodes so that the electric field strength is 0.1 to 10 V / μm, two SHG beams observed between the pair of electrodes exhibit a symmetry ratio of 0.5 or more. (However, the symmetry ratio is a value expressed by the following formula: Symmetry ratio (LR ratio) = I small / I large Here, I large is the peak intensity of the stronger SHG light, I small represents the peak intensity of the SHG light with the smaller intensity.

[0011] 2. The polyimide precursor according to item 1, wherein the polyimide precursor has a weight average molecular weight of 80,000 to 300,000.

[0012] 3. The polyimide precursor according to item 2, wherein the polyimide precursor contains at least a polyamic acid.

[0013] 4. All tetracarboxylic acid components and all diamine components constituting the polyimide precursor are represented by the formula: 1≦X / Y≦1.05 (wherein X represents the number of moles of the tetracarboxylic acid component, and Y represents the number of moles of the diamine component.) 4. The polyimide precursor according to any one of items 1 to 3, which satisfies the above condition.

[0014] 5. The polyimide precursor is composed of a tetracarboxylic acid component, a diamine component, and a carboxylic acid monoanhydride, and is represented by the following formulas (1) and (2): Equation (1) 0.97≦X / Y<1.00 Formula (2) 1.0≦(X+Z / 2) / Y≦1.05 (In the formula, X represents the number of moles of the tetracarboxylic acid component, Y represents the number of moles of the diamine component, and Z represents the number of moles of the carboxylic acid monoanhydride.) 4. The polyimide precursor according to any one of items 1 to 3, which satisfies the above condition.

[0015] 6. The polyimide precursor according to item 4 or 5, wherein the proportion of 3,3',4,4'-biphenyltetracarboxylic dianhydride in all tetracarboxylic acid components is 60 mol % or more, and the amount of p-phenylenediamine in all diamine components is 60 mol % or more.

[0016] 7. A polyimide film for flexible electronic device substrates obtained from the polyimide precursor according to any one of items 1 to 6 above.

[0017] 8. A laminate comprising the polyimide film according to item 7 above and a glass substrate.

[0018] 9. A flexible electronic device substrate comprising the polyimide film of item 7 above or the laminate of item 8 above.

[0019] 10. A flexible electronic device comprising the flexible electronic device substrate according to item 9 above and a TFT element.

[0020] 11. A method for producing a flexible electronic device according to item 9 or 10, comprising: a step of applying a solution composition containing a polyimide precursor onto a carrier substrate and imidizing the solution composition to form a laminate having the carrier substrate and a polyimide film; A manufacturing method characterized by:

[0021] Furthermore, the present application also discloses a method for evaluating the charge-up characteristics of polyimide. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a polyimide precursor for producing a flexible electronic device substrate that provides a polyimide with reduced charge-up, specifically a polyimide that exhibits a symmetry ratio (LR ratio) of 0.5 or more in an SHG measurement described below, particularly a polyimide in the form of a film. According to another aspect of the present invention, it is possible to provide a polyimide film for a flexible electronic device that exhibits a LR ratio of 0.5 or more in an SHG measurement and has reduced charge-up. According to yet another aspect of the present invention, it is possible to provide a laminate substrate including a polyimide film having the above properties, and a flexible electronic device such as a flexible display, particularly an organic electroluminescence (EL) display.

[0023] When the polyimide film of the present invention is used as a substrate for, for example, an organic EL display, a liquid crystal display, or the like, afterimages due to charge-up are reduced, and thus a flexible display having excellent image display performance can be provided. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram illustrating a system for measuring SHG light. [Figure 2] (a) A diagram for explaining the dipole when the polyimide film is an ideal insulator. (b) A diagram for showing the SHG light intensity. [Figure 3] This is a diagram (image) of SHG light observed for a polyimide film with small charge buildup. [Figure 4] 1A is a diagram illustrating the state of dipoles when a voltage is applied to a polyimide film where charge buildup occurs, and FIG. 1B is a diagram illustrating the SHG light intensity. [Figure 5] This is a diagram (image) of SHG light observed for a polyimide film with a large charge buildup. DETAILED DESCRIPTION OF THE INVENTION

[0025] <<Method for Evaluating Polyimide Film Based on SHG Symmetry Ratio (LR Ratio)>> First, a method for evaluating a polyimide film and a polyimide precursor composition will be described. This evaluation method includes the steps of providing a polyimide film provided with a first electrode and a second electrode spaced apart by a predetermined interval on the film, irradiating laser light while applying a predetermined voltage between the first electrode and the second electrode, measuring the light intensities of the SHG light generated near the first electrode and the SHG light generated near the second electrode, comparing the light intensity of the SHG light generated near the first electrode with the light intensity of the SHG light generated near the second electrode, and obtaining a symmetry ratio (LR ratio) described later, and evaluating the polyimide or the polyimide precursor based on the symmetry ratio (LR ratio). It has these steps.

[0026] Specifically described with reference to the drawings, FIG. 1 is a diagram showing an example of the measurement system used in the present invention. A polyimide film 1 is formed on a substrate 3 that is transparent to the irradiated laser light, and a first electrode 2a and a second electrode 2b are provided on the film surface at a predetermined interval d. As an example, the substrate 3 is a glass substrate, the thickness of the polyimide film is 10 μm, the interval d is 50 μm, the wavelength λ (frequency ω) of the irradiated laser light is 920 nm, and the voltage between the electrodes is 50 V. Also, the intensity measurement of the SHG light is performed within a range of 4 μm from the electrode ends.

[0027] SHG (Second Harmonic Generation) is known as a phenomenon in which light (second harmonic; frequency 2ω) having a vibration frequency twice that of the light (fundamental wave; frequency ω) incident on a medium is generated based on the second-order non-linear optical effect. SHG is not observed when a polyimide film is irradiated with laser light, but when a voltage is applied between the electrodes 2a and 2b, polarization occurs in the polyimide molecules, and SHG emission is observed near the electrodes between the electrodes 2a and 2b.

[0028] Figure 2(a) is a plan view of the measurement system shown in Figure 1, showing a schematic representation of the polarization of polyimide molecules. In an ideal insulator where charge buildup does not occur, polarization, or dipoles 4, are generated in response to the voltage applied between electrodes 2a and 2b. As shown in Figure 2(a), adjacent dipoles 4 cancel each other out in the center between electrodes 2a and 2b. However, polarization remains near electrodes 2a and 2b (residual dipoles). Therefore, when laser light (fundamental light) is irradiated, two SHG lights with peaks of optical intensity are observed near electrodes 2a and 2b, as shown schematically in Figure 2(b). Figure 3 shows an image of actual SHG light.

[0029] Here, the symmetry ratio (LR ratio; left-right ratio) of the intensities of the two SHG lights is defined as follows: Symmetry ratio (LR ratio) = I small / I large (where I large is the peak intensity of the stronger SHG light, I small represents the peak intensity of the SHG light with the smaller intensity.)

[0030] In the case of an ideal insulator, the polarization strength near both electrodes is the same, so the intensities of the SHG light generated near the two electrodes are equal and the symmetry ratio (LR ratio) is 1.

[0031] Next, when charge buildup occurs in the polyimide film, as shown in the schematic diagram of Figure 4(a), applying 50 V to electrode 2a and 0 V to electrode 2b results in electrons (charge 5) being injected from electrode 2b into the polyimide film. The injected electrons then cancel out the electric field of the residual dipole described above, resulting in a decrease in the SHG light intensity near electrode 2b, as shown in Figure 4(b). This results in a difference in the SHG intensity near electrode 2a and electrode 2b. Therefore, the symmetry ratio (LR ratio) becomes smaller than 1. Figure 5 shows an image of actual SHG light. The more electrons injected (i.e., the greater the charge buildup), the more dipoles are canceled out, resulting in a weaker electric field. As a result, the difference in the intensity of the SHG light generated near the two left and right electrodes becomes larger. In other words, the more significant the charge buildup, the smaller the symmetry ratio (LR ratio), approaching zero.

[0032] In this evaluation method, the substrate 3 may be any material that transmits laser light (fundamental light); typically, glass substrates such as alkali-free glass, borosilicate glass, and quartz glass can be used. The thickness of the polyimide film 1 is not particularly limited, but if it is too thick, the polyimide to be measured may absorb the laser's fundamental light (frequency ω) and / or SHG light (frequency ω), affecting the measurement. A thicker film does not necessarily improve measurement accuracy; therefore, the thickness is typically 50 μm or less, preferably 30 μm or less, and more preferably 20 μm or less. The lower limit of the thickness is also not particularly limited, but is typically 0.5 μm or more, preferably 1 μm or more. Since a too large distance d weakens the electric field strength, the distance d is typically 100 μm or less, preferably 80 μm or less. Considering the ease of electrode formation, the distance d is typically 10 μm or more, preferably 20 μm or more.

[0033] The voltage between the electrodes can be determined in relation to the distance d, but is usually 300 V or less, preferably 200 V or less, and more preferably 100 V or less. The relationship between the distance d and the voltage between the electrodes is preferably determined so that the electric field strength is 0.1 to 10 V / μm, and preferably 0.5 to 1.0 V / μm. Furthermore, the voltage is generally applied in the form of a square wave with a duty ratio (proportion of voltage application time in one cycle) of 0.1 to 0.9 between 0 V and a predetermined voltage, rather than applying a continuous direct current, and the frequency is preferably about 1 mHz to 100 GHz.

[0034] The laser light to be irradiated is preferably selected so that the fundamental light (wavelength λ; frequency ω) and SHG light (wavelength λ / 2; frequency 2ω) are in the range of high transmittance in the absorption spectrum of the polyimide film, and generally, it is preferable to use laser light with a wavelength in the range of 800 nm to 1500 nm. Furthermore, the laser device may be a continuous wave laser, but a pulsed laser with a high peak power is usually preferred.

[0035] The SHG light may be measured within a range of 10 μm, preferably 5 μm, for example 4 μm, from the electrode end.

[0036] As an evaluation standard for polyimide films, the symmetry ratio (LR ratio) that serves as the pass standard can be determined depending on the purpose, but if the LR ratio is 0.5 or more, it can be said to be an excellent polyimide film with little charge-up, based on the purpose of the present invention and the measurement conditions described below. An LR ratio of 0.6 or more is preferable, and an LR ratio of 0.7 or more is more preferable.

[0037] The development of polyimides that focus on these charge-up characteristics has not been reported or actually undertaken. Naturally, existing polyimides do not satisfy the symmetry ratio (LR ratio) in SHG measurements, which is related to the charge-up characteristics described above. Furthermore, since the charge-up characteristics are thought to be affected by the state near the polyimide's surface, any chemical structure is acceptable as long as the desired charge-up characteristics are satisfied.

[0038] <<Polyimide, polyimide precursor>> The polyimide or its precursor (polyimide precursor) of the present invention is not particularly limited in chemical structure as long as it satisfies the above-mentioned symmetry ratio (LR ratio), and the chemical structure may be appropriately selected depending on the desired function. The polyimide precursor is a compound represented by the following general formula I:

[0039] [ka] (In general formula I, X1 is a tetravalent aliphatic or aromatic group, Y1 is a divalent aliphatic or aromatic group, and R1 and R2 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.) The polyamic acid includes a polymer having a repeating unit represented by the formula: where R1 and R2 are hydrogen atoms. Particularly preferred is a polyamic acid in which R1 and R2 are hydrogen atoms. Partially imidized polymers, i.e., polymers containing repeating units in which at least one of the two amide structures in formula I is imidized, are also included in the "polyimide precursor" and "polyamic acid" (when the remaining R1 and R2 are hydrogen atoms). However, the imidization rate is preferably 50% or less, more preferably 30% or less, and even more preferably 10% or less.

[0040] The polyimide may also be represented by the following general formula II:

[0041] [ka] (In the formula, X1 is a tetravalent aliphatic or aromatic group, and Y1 is a divalent aliphatic or aromatic group.) It has a repeating unit represented by the following formula:

[0042] The chemical structure of such polyimides will be explained below in terms of the structures of X1 and Y2 in the repeating unit (general formula (I)) and the monomers (tetracarboxylic acid component, diamine component, and other components) used in the production, followed by an explanation of the production method.

[0043] In the present invention, the term "polyimide precursor" is used to mean not only a polymer (including an oligomer, a dimer, etc.) containing a plurality of repeating units represented by the general formula I, but also a monomer compound or the like, so long as it is a compound that constitutes at least a part of the molecular structure of "polyimide" after imidization. Therefore, in the present application, the "polyimide precursor" may also be a mixture containing a monomer compound.

[0044] In the present invention, the term "tetracarboxylic acid component" refers to a tetracarboxylic acid derivative that constitutes the molecular structure of a "polyimide" after imidization, and includes tetracarboxylic acids, tetracarboxylic acid dianhydrides, and other tetracarboxylic acid derivatives such as tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides. Furthermore, in the present invention, the term "tetracarboxylic acid component constituting a polyimide precursor" is used to encompass not only tetracarboxylic acid derivatives incorporated into polyamic acid molecules but also tetracarboxylic acid derivatives present as monomer compounds. While not particularly limited, it is convenient to use tetracarboxylic acid dianhydrides as the main component of the tetracarboxylic acid component in manufacturing, and the following description will discuss such an example. Meanwhile, the diamine component is a diamine compound having two amino groups (-NH2) that is used as a raw material for producing polyimides. The term "diamine component constituting a polyimide precursor" is used to encompass not only diamine compounds incorporated into polyamic acid molecules but also diamine compounds present as monomer compounds.

[0045] In this specification, the term "polyimide film" refers to both a film formed on a substrate and a film without a supporting substrate (including a free-standing film). When used as a substrate, the polyimide of the present invention is preferably in the form of a film. The polyimide of the present invention may also be in the form of a layer discretely present on a supporting substrate or a layer formed of a different material.

[0046] In one aspect of the present invention, the weight average molecular weight (Mw) of the polyimide precursor is preferably 80,000 or more, more preferably 82,000 or more, most preferably 85,000 or more, and preferably 300,000 or less, more preferably 280,000 or less, most preferably 260,000 or less. The weight average molecular weight is determined based on a calibration curve obtained from standard polystyrene using a GPC apparatus. When a polyimide film is formed from a polyimide precursor having a weight average molecular weight within the above range, a polyimide film excellent in charge-up characteristics (i.e., having little charge-up) can be obtained. If the weight average molecular weight is too large, the viscosity may increase and it may not be suitable for forming a film with a desired thickness. Therefore, the weight average molecular weight is preferably within the above range. The method for adjusting the weight average molecular weight of the polyimide precursor will be described in detail in the section <Production of Polyimide Precursor>.

[0047] <<Structure and Monomers in the Repeating Unit>> <X1 and Tetracarboxylic Acid Component>

[0048] As the tetravalent group having an aromatic ring of X1, a tetravalent group having an aromatic ring with 6 to 40 carbon atoms is preferable.

[0049] Examples of the tetravalent group having an aromatic ring include the following.

[0050] [Chemical formula] (In the formula, Z1 is a direct bond or the following divalent group:

[0051] [Chemical formula] and any of them. However, Z2 in the formula is a divalent organic group, and Z3 and Z4 are each independently an amide bond, an ester bond, or a carbonyl bond, and Z5 is an organic group containing an aromatic ring.)

[0052] Specific examples of Z2 include aliphatic hydrocarbon groups having 2 to 24 carbon atoms and aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0053] Specific examples of Z5 include aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0054] As the tetravalent group having an aromatic ring, the following are particularly preferred, since they can provide the resulting polyimide material with both high heat resistance and high transparency.

[0055] [ka] (wherein Z1 is a direct bond or a hexafluoroisopropylidene bond.)

[0056] Here, Z1 is more preferably a direct bond, since this allows the resulting polyimide material to have high heat resistance, high transparency, and a low coefficient of linear thermal expansion.

[0057] Additionally, preferred groups include those in which Z1 in the above formula (9) is the following formula (3A):

[0058] [ka] Examples of such compounds include compounds having a fluorenyl-containing group represented by the formula: Z 11 and Z 12 are each independently, preferably the same, a single bond or a divalent organic group. 11 and Z 12 As the group, an organic group containing an aromatic ring is preferable, and for example, a group represented by the formula (3A1):

[0059] [ka] (Z 13 and Z 14 are, independently of one another, a single bond, -COO-, -OCO- or -O-, where Z 14 When attached to a fluorenyl group, Z 13-COO-, -OCO- or -O- with Z 14 is preferably a single bond; R 91 is an alkyl group having 1 to 4 carbon atoms or a phenyl group, preferably methyl, and n is an integer of 0 to 4, preferably 1. The structure represented by

[0060] Examples of tetracarboxylic acid components that provide repeating units of general formula (II) in which X1 is a tetravalent group having an aromatic ring include, for example, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid, pyromellitic acid, 3,3 Examples of suitable dianhydrides include 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, 4,4'-oxydiphthalic acid, bis(3,4-dicarboxyphenyl)sulfone, m-terphenyl-3,4,3',4'-tetracarboxylic acid, p-terphenyl-3,4,3',4'-tetracarboxylic acid, biscarboxyphenyldimethylsilane, bisdicarboxyphenoxydiphenyl sulfide, and sulfonyldiphthalic acid. These dianhydrides are preferably used as the main monomer components. Examples of tetracarboxylic acid components that provide repeating units of general formula (II) in which X1 is a tetravalent group having an aromatic ring containing a fluorine atom include 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride. Further, a preferred compound is (9H-fluorene-9,9-diyl)bis(2-methyl-4,1-phenylene)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate). The tetracarboxylic acid component may be used alone or in combination of two or more kinds.

[0061] The tetravalent group having an alicyclic structure of X1 is preferably a tetravalent group having an alicyclic structure with 4 to 40 carbon atoms, and more preferably has at least one 4- to 12-membered aliphatic ring, more preferably a 4-membered or 6-membered aliphatic ring. Preferred tetravalent groups having a 4-membered or 6-membered aliphatic ring include the following:

[0062] [ka] (In the formula, R 31 ~R 38 are each independently a direct bond or a divalent organic group. 41 ~R 47 R each independently represents one selected from the group consisting of groups represented by the formulas: -CH2-, -CH=CH-, -CH2CH2-, -O-, and -S-. 48 is an organic group containing an aromatic ring or an alicyclic structure.

[0063] R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 , R 38 Specific examples of the bond include a direct bond, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, an oxygen atom (—O—), a sulfur atom (—S—), a carbonyl bond, an ester bond, and an amide bond.

[0064] R 48 Examples of the organic group containing an aromatic ring include the following:

[0065] [ka] (Wherein, W1 is a direct bond or a divalent organic group, n 11 ~n 13 each independently represents an integer of 0 to 4, and R 51 , R 52 , R 53are each independently an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group.

[0066] Specific examples of W1 include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

[0067] [ka] (R in Equation (6) 61 ~R 68 each independently represents a direct bond or a divalent group represented by the formula (5).

[0068] As the tetravalent group having an alicyclic structure, the following are particularly preferred because they can provide the resulting polyimide with high heat resistance, high transparency, and a low coefficient of linear thermal expansion.

[0069] [ka]

[0070] Examples of tetracarboxylic acid components that provide repeating units of formula (II) in which X1 is a tetravalent group having an alicyclic structure include 1,2,3,4-cyclobutanetetracarboxylic acid, isopropylidenediphenoxybisphthalic acid, cyclohexane-1,2,4,5-tetracarboxylic acid, [1,1'-bi(cyclohexane)]-3,3',4,4'-tetracarboxylic acid, [1,1'-bi(cyclohexane)]-2,3,3',4'-tetracarboxylic acid, [1,1'-bi(cyclohexane)]-2,2',3,3'-tetracarboxylic acid, 4,4'-methylenebis(cyclohexane-1,2-dicarboxylic acid), 4,4'-(propane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic acid), 4,4'-oxybis(cyclohexane-1,2-dicarboxylic acid), 4,4'-thiobis(cyclohexane-1,2-dicarboxylic acid), 4,4'-sulfonylbis( cyclohexane-1,2-dicarboxylic acid), 4,4'-(dimethylsilanediyl)bis(cyclohexane-1,2-dicarboxylic acid), 4,4'-(tetrafluoropropane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic acid), octahydropentalene-1,3,4,6-tetracarboxylic acid, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic acid, 6-(carboxymethyl)bicyclo[2. 2.1]heptane-2,3,5-tricarboxylic acid, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid, bicyclo[2.2.2]oct-5-ene-2,3,7,8-tetracarboxylic acid, tricyclo[4.2.2.02,5]decane-3,4,7,8-tetracarboxylic acid, tricyclo[4.2.2.02,5]dec-7-ene-3,4,9,10-tetracarboxylic acid, 9-oxatricyclo[4.2.1.02,5]Nonane-3,4,7,8-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane 5,5'',6,6''-tetracarboxylic acid, (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethanonaphthalene-2c,3c,6c,7c-tetracarboxylic acid, (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethanonaphthalene-2t,3t,6c,7c-tetracarboxylic acid, and derivatives such as the tetracarboxylic dianhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides of these tetracarboxylic acids can be mentioned. The tetracarboxylic acid component may be used alone or in combination of multiple types.

[0071] <Y1 and diamine component> As the divalent group having an aromatic ring of Y1, a divalent group having an aromatic ring with 6 to 40 carbon atoms, more preferably 6 to 20 carbon atoms, is preferred.

[0072] Examples of the divalent group having an aromatic ring include the following.

[0073] [Chemical formula] (In the formula, W1 is a direct bond or a divalent organic group, and n 11 ~n 13 each independently represents an integer of 0 to 4, and R 51 , R 52 , R 53 are each independently an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group.)

[0074] Specific examples of W1 include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

[0075] [Chemical formula]

[0076] [ka] (R in Equation (6) 61 ~R 68 each independently represents a direct bond or a divalent group represented by the formula (5).

[0077] Here, it is particularly preferable that W1 is one selected from the group consisting of a direct bond or a group represented by the formula: -NHCO-, -CONH-, -COO-, and -OCO-, since this allows the obtained polyimide to have high heat resistance, high transparency, and a low linear thermal expansion coefficient at the same time. 61 ~R 68 It is also particularly preferred that is either a direct bond or a divalent group represented by the formula (6), which is one selected from the group consisting of groups represented by the formulas: -NHCO-, -CONH-, -COO-, and -OCO-.

[0078] Additionally, preferred groups include those in which W1 in the above formula (4) is the following formula (3B):

[0079] [ka] Examples of such compounds include compounds having a fluorenyl-containing group represented by the formula: Z 11 and Z 12 are each independently, preferably the same, a single bond or a divalent organic group. 11 and Z 12 As the group, an organic group containing an aromatic ring is preferable, for example, a group represented by the formula (3B1):

[0080] [ka] (Z 13 and Z 14 are, independently of one another, a single bond, -COO-, -OCO- or -O-, where Z 14 When attached to a fluorenyl group, Z 13 -COO-, -OCO- or -O- with Z 14is preferably a single bond; R 91 is an alkyl group having 1 to 4 carbon atoms or a phenyl group, preferably phenyl, and n is an integer of 0 to 4, preferably 1. The structure represented by

[0081] Another preferred group is a compound in which W1 in the above formula (4) is a phenylene group, that is, a terphenyldiamine compound, and particularly preferred is a compound in which all bonds are para-bonded.

[0082] Another preferred group is a group in which W1 in the above formula (4) is R 61 and R 62 is a 2,2-propylidene group.

[0083] Yet another preferred group is one in which W1 in the above formula (4) is represented by the following formula (3B2):

[0084] [ka] Examples of the compound include compounds represented by the following formula:

[0085] Examples of diamine components that provide repeating units of general formula (II) in which Y1 is a divalent group having an aromatic ring include p-phenylenediamine, m-phenylenediamine, benzidine, 3,3'-diamino-biphenyl, 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, m-tolidine, 4,4'-diaminobenzanilide, 3,4'-diaminobenzanilide, N,N'-bis(4-aminophenyl)terephthalamide, N,N'-p-phenylenebis(p-aminobenzamide), 4-aminophenyl 4,4'-diaminobenzoate, bis(4-aminophenyl) terephthalate, biphenyl-4,4'-dicarboxylic acid bis(4-aminophenyl) ester, p-phenylene bis(p-aminobenzoate), bis(4-aminophenyl)-[1,1'-biphenyl]-4,4'-dicarboxylate, [1,1'-biphenyl]-4,4'-diylbis(4-aminobenzoate), 4,4'-oxydianiline, 3,4'-oxydianiline, 3,3'-oxydianiline, p-methylenebis(phenylenediamine), 1,3-bis(4-aminophenyl) bis(aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, bis(4-aminophenyl)sulfone, 3,3'-bis(trifluoromethyl)benzidine, 3,3'-bis((aminophenoxy)phenyl)propane, 2,2 '-Bis(3-amino-4-hydroxyphenyl)hexafluoropropane, bis(4-(4-aminophenoxy)diphenyl)sulfone, bis(4-(3-aminophenoxy)diphenyl)sulfone, octafluorobenzidine, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 2,4-bis(4-aminoanilino)-6-amino-1,3,5-triazine, 2,4-bis(4-aminoanilino)-6-methylamino-1,3,Examples of diamine components that provide repeating units of general formula (II) in which Y1 is a divalent group having an aromatic ring containing a fluorine atom include 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, and 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. Additionally, preferred diamine compounds include 4,4'-(((9H-fluorene-9,9-diyl)bis([1,1'-biphenyl]-5,2-diyl))bis(oxy))diamine, [1,1':4',1"-terphenyl]-4,4"-diamine, and 4,4'-([1,1'-binaphthalene]-2,2'-diylbis(oxy))diamine. The diamine components may be used alone or in combination.

[0086] The divalent group having an alicyclic structure of Y1 is preferably a divalent group having an alicyclic structure with 4 to 40 carbon atoms, and more preferably has at least one 4- to 12-membered aliphatic ring, more preferably a 6-membered aliphatic ring.

[0087] Examples of the divalent group having an alicyclic structure include the following.

[0088] [ka] (In the formula, V1 and V2 each independently represent a direct bond or a divalent organic group, and n 21 ~n 26 each independently represents an integer of 0 to 4, and R 81 ~R 86 are each independently an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group, and R 91 , R92 , R 93 are each independently one selected from the group consisting of groups represented by the formula: -CH2-, -CH=CH-, -CH2CH2-, -O-, and -S-.

[0089] Specific examples of V1 and V2 include a direct bond and a divalent group represented by the above formula (5).

[0090] As the divalent group having an alicyclic structure, the following are particularly preferred because they can provide the resulting polyimide with both high heat resistance and a low coefficient of linear thermal expansion.

[0091] [ka] Among the divalent groups having an alicyclic structure, the following are preferred.

[0092] [ka]

[0093] Examples of diamine components that provide repeating units of general formula (II) in which Y1 is a divalent group having an alicyclic structure include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 1,2-diaminocyclohexane, 1,3-diaminocyclobutane ...tert-butylcyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2- Examples of the diamine component include 4-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, diaminobicycloheptane, diaminomethylbicycloheptane, diaminooxybicycloheptane, diaminomethyloxybicycloheptane, isophoronediamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis(aminocyclohexyl)methane, bis(aminocyclohexyl)isopropylidene, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, and 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane. The diamine component may be used alone or in combination.

[0094] Among these tetracarboxylic acid derivatives, 3,3',4,4'-biphenyltetracarboxylic dianhydride is particularly preferred, and among diamine compounds, p-phenylenediamine is particularly preferred. It is particularly preferred that the proportion of 3,3',4,4'-biphenyltetracarboxylic dianhydride in all tetracarboxylic acid components is 60 mol % or more, and that the amount of p-phenylenediamine in all diamine components is 60 mol % or more.

[0095] <Production of Polyimide Precursor> The production of the polyimide precursor of the present invention includes a polymerization step of reacting a tetracarboxylic acid component (preferably a tetracarboxylic dianhydride) with a diamine component in at least an organic solvent so that the weight-average molecular weight (Mw) of the polyimide precursor becomes as described above (preferably 80,000 or more and 300,000 or less).

[0096] The organic solvent is not particularly limited, but examples thereof include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylpropionamide, 3-methoxy-N,N-dimethylpropanamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-vinyl-2-pyrrolidone; cyclic ester solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, and α-methyl-γ-butyrolactone; carbonate solvents such as ethylene carbonate and propylene carbonate; glycol-based solvents such as triethylene glycol; phenol-based solvents such as m-cresol, p-cresol, 3-chlorophenol, and 4-chlorophenol; acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, and dimethyl sulfoxide. In addition, other common organic solvents, for example, alcoholic solvents such as methanol and ethanol, phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, tetrahydrofuran, dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl Other examples of organic solvents that can be used include ethyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, N-methylcaprolactam, hexamethylphosphorotriamide, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, 1,4-dioxane, dimethyl sulfoxide, dimethyl sulfone, diphenyl ether, diphenyl sulfone, tetramethylurea, anisole, turpentine, mineral spirits, petroleum naphtha-based solvents, biodegradable methyl lactate, ethyl lactate, and butyl lactate. One or more organic solvents may be used.

[0097] When carrying out a polymerization reaction to obtain a polyimide precursor, the concentration of all monomers in the organic solvent (substantially equal to the solids concentration of the polyimide precursor solution) may be appropriately selected depending on the purpose of use and the purpose of production. The solids concentration of the obtained polyimide precursor solution is, for example, 30% by mass or less, preferably 20% by mass or less, and in a preferred embodiment, 15% by mass or less, based on the total amount of the polyimide precursor and the solvent. However, if the solids concentration is too low, productivity and handling during use may be impaired, so the solids concentration is preferably 2% by mass or more, more preferably 5% by mass or more.

[0098] The polyimide precursor solution produced at such a concentration may be used as is for film production, or may be diluted or concentrated as necessary. For film production by casting coating, it is also preferable to use a polyimide precursor solution of 5 to 20 mass %.

[0099] The solution viscosity of the polyimide precursor solution at 30°C is not particularly limited, but is preferably 1000 Pa·s (10,000 Poise) or less, more preferably 500 Pa·s or less, even more preferably 500 Pa·s or less, particularly preferably 400 Pa·s or less, and more preferably 0.1 Pa·s or more, even more preferably 0.5 Pa·s or more, and particularly preferably 1 Pa·s or more for ease of handling. A solution viscosity exceeding 1000 Pa·s can result in a loss of fluidity, making it difficult to uniformly apply the solution to a carrier substrate such as metal or glass. A solution viscosity below 0.1 Pa·s can result in sagging or repellency during application to a carrier substrate such as metal or glass, making it difficult to obtain a polyimide film with high performance. Polyimide precursor solutions produced with such viscosities can be used as is or diluted or concentrated as necessary. For film production by cast coating, a viscosity of 1 to 20 Pa·s (10 to 200 Poise) is preferred.

[0100] An example of a method for producing the polyimide precursor of the present invention will be described. In order for the polyimide precursor to have a desirable weight average molecular weight, it is preferable that it contains at least a polyamic acid. In addition, all of the tetracarboxylic acid components and all of the diamine components constituting the polyimide precursor are represented by the formula: 1≦X / Y≦1.05 (wherein X represents the number of moles of the tetracarboxylic acid component, and Y represents the number of moles of the diamine component.) It is preferable that the following relationship is satisfied. X / Y is more preferably 1.02 or less, even more preferably 1.01 or less, and is also very preferably equal to 1. These ranges are preferably applied when no dicarboxylic acid anhydride is used, and are preferably satisfied in the following production methods (1) to (4).

[0101] (1) One example of a method for producing a polyimide precursor is to produce a solution of a polyimide precursor (polyamic acid) by polymerizing a tetracarboxylic dianhydride and a diamine compound in an organic solvent, preferably in substantially equimolar amounts, so that the X / Y ratio falls within the aforementioned range. The reaction temperature is not limited, but can be, for example, 25°C or higher, preferably higher than 40°C, and for example, 100°C or lower, preferably 80°C or lower, and more preferably 70°C or lower. The reaction time can be about 0.2 hours or higher, preferably 2 hours or higher, and about 60 hours or lower, preferably 48 hours or lower.

[0102] (2) Another example of a method for producing a polyimide precursor includes a first step in which a tetracarboxylic dianhydride is reacted with a slight excess of a diamine compound to produce an amine-terminated polyamic acid, and a second step in which the tetracarboxylic acid is added. In this method, the molecular weight of the amine-terminated polyamic acid can be adjusted by adjusting the ratio of the tetracarboxylic dianhydride to the diamine compound in the first step. By adjusting the ratio of all tetracarboxylic acid components to all diamine components used, preferably substantially equimolar, so that the ratio falls within the aforementioned range of X / Y, i.e., by adjusting the number of moles of tetracarboxylic acid added in the second step to the number of moles of the excess diamine compound in the first step, the amount of functional groups at the polyimide terminals after imidization can be reduced to essentially zero.

[0103] The reaction temperature is not limited, but may be, for example, 25°C or higher, preferably higher than 40°C, and for example, 100°C or lower, preferably 80°C or lower, more preferably 70°C or lower, and the reaction time may be about 0.2 hours or longer, preferably 2 hours or longer, preferably about 60 hours or shorter, more preferably 48 hours or shorter.

[0104] (3) An example of a different method for producing a polyimide precursor includes a first step for producing a carboxylic acid-terminated polyamic acid and a second step for producing a diamine-terminated polyamic acid. In the first step, for example, a diamine compound is reacted with a slight excess of a tetracarboxylic dianhydride in an organic solvent to produce an anhydride-terminated polyamic acid, and the anhydride groups are then hydrolyzed to obtain a carboxylic acid-terminated polyamic acid. Water for hydrolysis may be added together with the organic solvent from the beginning, or may be added after the reaction of the diamine compound with the tetracarboxylic dianhydride. In the second step, a tetracarboxylic dianhydride and a slight excess of a diamine compound are further added to produce a diamine-terminated polyamic acid.

[0105] In the first and second steps, adjusting the ratio of the tetracarboxylic dianhydride to the diamine compound allows for adjustment of the molecular weight of the carboxylic acid-terminated polyamic acid and the amine-terminated polyamic acid. That is, the weight-average molecular weight of the polyimide precursor of the present invention can be adjusted. Furthermore, by adjusting the ratio of all tetracarboxylic acid components to all diamine components used so that they fall within the aforementioned X / Y range, preferably substantially equimolar, the amount of functional groups at the polyimide terminals after imidization can be reduced to essentially zero.

[0106] Although the example in which Steps 1 and 2 are carried out continuously in one reaction vessel has been described, Steps 1 and 2 can also be carried out in separate reaction vessels, and the resulting polyamic acid solutions can be mixed to produce the polyimide precursor solution of the present invention. The reaction temperatures in Steps 1 and 2 are not limited, but can be, for example, 25°C to 100°C, preferably higher than 40°C, and for example, 80°C or lower, preferably 70°C or lower. The reaction time can be about 0.2 hours or longer, preferably 2 hours or longer, and preferably about 60 hours or shorter, more preferably 48 hours or shorter.

[0107] (4) A different example of a method for producing a polyimide precursor is a method that combines the above (3) with (2). For example, when producing a carboxylic acid-terminated polyamic acid and an amine-terminated polyamic acid in the first and second steps of (3) above, the components are adjusted so that the amount of diamine in the polyamic acid produced in the second step is increased, and then a tetracarboxylic acid is added in the third step (corresponding to the second step of (2)). The ratio of all tetracarboxylic acid components to all diamine components used is preferably substantially equimolar so as to fall within the aforementioned range of X / Y, and the reaction temperature and time are also the same.

[0108] (5) Another example of a different method for producing a polyimide precursor includes a method that includes adding a carboxylic acid monoanhydride in addition to a tetracarboxylic acid component and a diamine component and reacting them. The carboxylic acid monoanhydride is preferably a dicarboxylic acid monoanhydride, and may be an aromatic carboxylic acid monoanhydride or an aliphatic carboxylic acid monoanhydride. Aromatic carboxylic acid monoanhydrides are particularly preferred. The aromatic carboxylic acid monoanhydride preferably has an aromatic ring having 6 to 30 carbon atoms, more preferably an aromatic ring having 6 to 15 carbon atoms, and even more preferably an aromatic ring having 6 to 10 carbon atoms.

[0109] Examples of carboxylic acid monoanhydrides include aromatic carboxylic acid monoanhydrides such as phthalic anhydride, 2,3-benzophenonedicarboxylic anhydride, 3,4-benzophenonedicarboxylic anhydride, 1,2-naphthalenedicarboxylic anhydride, 2,3-naphthalenedicarboxylic anhydride, 1,8-naphthalenedicarboxylic anhydride, 1,2-anthracenedicarboxylic anhydride, 2,3-anthracenedicarboxylic anhydride, and 1,9-anthracenedicarboxylic anhydride, and alicyclic carboxylic acid monoanhydrides such as maleic anhydride, succinic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, itaconic anhydride, and trimellitic anhydride. Among these, phthalic anhydride is preferred.

[0110] When a carboxylic acid monoanhydride is added, it is more preferable that the following formulae (1) and (2) are satisfied.

[0111] Equation (1) 0.97≦X / Y<1.00 Formula (2) 1.0≦(X+Z / 2) / Y≦1.05 (In the formula, X represents the number of moles of the tetracarboxylic acid component, Y represents the number of moles of the diamine component, and Z represents the number of moles of the carboxylic acid monoanhydride.)

[0112] When X / Y is 0.97 or more, the molecular weight of the polyimide precursor (particularly polyamic acid) is increased, improving the strength and heat resistance of the resulting polyimide film. X / Y is preferably 0.98 or more. When X / Y is less than 1.00, the diamine component becomes excessive relative to the tetracarboxylic acid component, which can form amino groups that can be end-capped with carboxylic acid monoanhydride. By appropriately adjusting X / Y, the weight-average molecular weight of the resulting polyamic acid can be controlled.

[0113] Furthermore, when (X+Z / 2) / Y is 1 or greater, this means that all amino groups are end-capped with carboxylic acid monoanhydrides or that no amino groups remain after imidization, improving charge-up properties. (X+Z / 2) / Y is more preferably 1.02 or less, and even more preferably 1.01 or less. The closer it is to 1, the less free carboxylic acid monoanhydrides there are, and the more improved the strength and charge-up properties of the resulting polyimide film.

[0114] In the case of a production method in which a carboxylic acid monoanhydride is added, a preferred method generally includes a first step in which a tetracarboxylic acid component and a diamine component are reacted in a solvent, preferably in a molar ratio that satisfies the above-mentioned formula (1), to obtain a polyimide precursor (particularly a polyamic acid) having amino groups at its terminals, and a second step in which a carboxylic acid monoanhydride is then added, preferably in a molar ratio that satisfies the above-mentioned formula (2), to react and cap the terminals of the polyimide precursor (particularly a polyamic acid).

[0115] In the first step, the reaction is carried out at a relatively low temperature, for example, 100°C or lower, preferably 80°C or lower, to suppress the imidization reaction. While not limited to these, the reaction temperature is typically 25°C or higher, preferably 40°C or higher, more preferably 50°C or higher, and typically 100°C or lower, preferably 80°C or lower. The reaction time is typically about 0.1 hours or higher, preferably about 2 hours or higher, and typically about 24 hours or lower, preferably about 12 hours or lower. By maintaining the reaction temperature and reaction time within the above ranges, a solution composition of a high molecular weight polyimide precursor can be efficiently obtained. The reaction can be carried out in an air atmosphere, but is typically carried out in an inert gas atmosphere, preferably a nitrogen gas atmosphere.

[0116] In the second step, the reaction temperature may be appropriately set, but from the viewpoint of reliably capping the ends of the polyimide precursor, it is preferably 25° C. or higher, preferably 70° C. or lower, more preferably 60° C. or lower, and even more preferably 50° C. or lower. The reaction time is usually about 0.1 hour or higher and about 24 hours or lower.

[0117] If thermal imidization is to be performed, an imidization catalyst, an organic phosphorus-containing compound, inorganic fine particles, etc. may be added to the polyimide precursor solution as needed. If chemical imidization is to be performed, a cyclization catalyst, a dehydrating agent, inorganic fine particles, etc. may be added to the polyimide precursor solution as needed. If necessary, inorganic fine particles, etc. may be added to the polyimide solution.

[0118] Examples of the imidization catalyst include substituted or unsubstituted nitrogen-containing heterocyclic compounds, N-oxide compounds of the nitrogen-containing heterocyclic compounds, substituted or unsubstituted amino acid compounds, and aromatic hydrocarbon compounds or aromatic heterocyclic compounds having a hydroxyl group. In particular, lower alkylimidazoles such as 1,2-dimethylimidazole, N-methylimidazole, N-benzyl-2-methylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, and 5-methylbenzimidazole, benzimidazoles such as N-benzyl-2-methylimidazole, phenylimidazoles such as 2-phenylimidazole, isoquinoline, and substituted pyridines such as 3,5-dimethylpyridine, 3,4-dimethylpyridine, 2,5-dimethylpyridine, 2,4-dimethylpyridine, and 4-n-propylpyridine can be preferably used. The amount of the imidization catalyst used is preferably at least 0.01 equivalent, particularly at least about 0.02 equivalent, and at most 2 equivalents, particularly at most 1 equivalent, relative to the amount of the amic acid unit of the polyamic acid. The use of the imidization catalyst can improve the physical properties of the resulting polyimide film, particularly the elongation and edge tear resistance.

[0119] Examples of organic phosphorus-containing compounds include phosphate esters such as monocaproyl phosphate, monooctyl phosphate, monolauryl phosphate, monomyristyl phosphate, monocetyl phosphate, monostearyl phosphate, triethylene glycol monotridecyl ether phosphate monoester, tetraethylene glycol monolauryl ether phosphate monoester, diethylene glycol monostearyl ether phosphate monoester, dicaproyl phosphate, dioctyl phosphate, dicapryl phosphate, dilauryl phosphate, dimyristyl phosphate, dicetyl phosphate, distearyl phosphate, tetraethylene glycol mononeopentyl ether phosphate diester, triethylene glycol monotridecyl ether phosphate diester, tetraethylene glycol monolauryl ether phosphate diester, diethylene glycol monostearyl ether phosphate diester, trimethyl phosphate, and triphenyl phosphate triester, as well as amine salts of these phosphate esters. Examples of the amine include ammonia, monomethylamine, monoethylamine, monopropylamine, monobutylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, monoethanolamine, diethanolamine, and triethanolamine.

[0120] Examples of the cyclization catalyst include aliphatic tertiary amines such as trimethylamine and triethylenediamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as isoquinoline, pyridine, α-picoline, and β-picoline.

[0121] Examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride.

[0122] Examples of inorganic fine particles include inorganic oxide powders such as fine titanium dioxide powder, silicon dioxide (silica) powder, magnesium oxide powder, aluminum oxide (alumina) powder, and zinc oxide powder; inorganic nitride powders such as fine silicon nitride powder and titanium nitride powder; inorganic carbide powders such as silicon carbide powder; and inorganic salt powders such as fine calcium carbonate powder, calcium sulfate powder, and barium sulfate powder. Two or more of these inorganic fine particles may be used in combination. Known methods can be used to uniformly disperse these inorganic fine particles.

[0123] In one embodiment, the polyimide precursor solution preferably does not contain a silane coupling agent such as an alkoxysilane. In polyimide films using a silane coupling agent, the silane coupling agent may bleed out. This can lead to problems such as a decrease in the charge-up characteristics of the polyimide film (a decrease in the LR ratio), a decrease in adhesive strength, and swelling of the laminate. Furthermore, adding or reacting a silane coupling agent to a polyimide precursor solution can also cause the problem of a decrease in the viscosity stability of the polyimide precursor solution. To avoid these problems, it is preferable not to use a silane coupling agent.

[0124] In this manner, a high molecular weight polyimide precursor, particularly preferably a polyamic acid, is finally obtained.

[0125] In the present invention, it is preferable that the polyimide produced from the polyimide precursor satisfies the characteristics shown in the following aspects. In one embodiment of the present invention, the weight fraction of imide groups (—C(O)NC(O)—) in the polyimide repeating units (i.e., the general formula II) is preferably less than 38.3 wt %, and in a specific embodiment, more preferably 30 wt % or less.

[0126] Here, the polyimide may be a copolymer, i.e., at least one of the tetracarboxylic acid component and the diamine component that give the polyimide may contain two or more compounds. In this case, the weight fraction of the imide group is calculated as a weighted average based on the ratio of the monomers charged. The weight fraction of groups other than the imide group is calculated in the same manner. In the following description, when the weight fraction of a specific group is mentioned, the polyimide includes both a homopolymer and a copolymer.

[0127] In one embodiment of the present invention, the weight fraction of functional groups in the polyimide repeating unit is preferably small. The "functional group in the repeating unit" defined here refers to the portion of the polyimide repeating unit other than the aromatic ring and saturated alkyl chain, such as -O- (ether bond), -CO- (carbonyl group), -COO- (ester), and -SO2-. F and Cl, which substitute hydrogen atoms in the aromatic ring and saturated alkyl chain, are not included in the "functional group in the repeating unit."

[0128] The combined amount of imide groups and "functional groups in the repeating unit" is preferably less than 38.3% by weight, more preferably 30% by weight or less, and even more preferably 25% by weight or less, of the polyimide repeating unit.

[0129] In addition, in one embodiment of the present invention, it is preferable that the content of functional groups other than those mentioned above is low, and it is highly preferable that they are completely absent, regardless of whether they are present in the polyimide repeating unit, at the terminal, or as a separate compound. Such undesirable functional groups include Si-containing groups (siloxane bonds, silyl groups, etc.).

[0130] In a preferred embodiment of the present invention, the tetracarboxylic acid component forming the repeating unit preferably contains a compound selected from tetracarboxylic acid dianhydrides having a fluorene structure in the molecule and tetracarboxylic acid dianhydrides having three or more benzene rings per functional group other than two acid anhydride groups (groups corresponding to the above-mentioned "functional groups in the repeating unit"). Preferred compounds also include compounds that do not have a functional group corresponding to the "functional groups in the repeating unit" other than the two acid anhydride groups, and in this case, the number of benzene rings is preferably two or more, more preferably three or more.

[0131] In a preferred embodiment of the present invention, the diamine component forming the repeating unit preferably contains a compound selected from diamines having a fluorene structure in the molecule and diamines having three or more benzene rings for each functional group other than two amine groups (a group corresponding to the above-mentioned "functional group in the repeating unit"). Note that preferred compounds also include compounds that do not have a functional group corresponding to the "functional group in the repeating unit" other than the two amine groups, and in this case, the number of benzene rings is preferably two or more, more preferably three or more.

[0132] In a preferred embodiment of the present invention, it is preferable that each of the tetracarboxylic acid component and the diamine component forming the repeating unit contains a compound selected from the above-mentioned compounds, i.e., compounds having a fluorene structure in the molecule, and compounds having three or more benzene rings per "functional group in the repeating unit" (including cases where there are no functional groups).

[0133] In one embodiment of the present invention, it is also preferable that the "amount of terminal functional groups" is small. The "amount of terminal functional groups" is calculated based on the charge ratio of the tetracarboxylic acid component and the diamine component when producing the polyimide (when producing the polyamic acid), the purity of each component, the amount of end-capping agent added, and the amount of reactive additive added. The amount of terminal functional groups is calculated from the charge ratio of the tetracarboxylic acid component and the diamine component as follows.

[0134] Since the degree of polymerization of a polyimide obtained with a tetracarboxylic dianhydride / diamine ratio of 1 is theoretically ∞, the terminal group is set to 1 / ∞ = 0. If the tetracarboxylic dianhydride and diamine are not charged in equimolar amounts, for example, if the diamine is in excess, a polyimide with a degree of polymerization n having the structure of formula (II-B) is theoretically produced. n is (Formula) Tetracarboxylic dianhydride / diamine ratio=n / (n+1) The formula weight of the repeating unit is a, and the molecular weight of one terminal diamine is a b Then, the formula weight of polyimide with a degree of polymerization n is (a*n+a b ) so the amount of terminal amine is 2 / (a*n+a b ) [unit: mol / g] In the examples of the present application, the value is expressed in μmol / g.

[0135] [ka]

[0136] In one embodiment of the present invention, the amount of terminal amine groups is preferably 30 μmol / g or less, more preferably 20 μmol / g or less, and even more preferably 10.5 μmol / g or less. In another embodiment of the present invention, the amount of all terminal functional groups is preferably 30 μmol / g or less, more preferably 20 μmol / g or less, and even more preferably 10.5 μmol / g or less.

[0137] In one preferred embodiment of the present invention, the combined weight fraction of imide groups and "functional groups in repeating units" is 30% by weight or less and the "amount of terminal functional groups" is 20 μmol / g or less. In another preferred embodiment, the combined weight fraction of imide groups and "functional groups in repeating units" is 40% by weight or less and the "amount of terminal functional groups" is 10.5 μmol / g or less. It is also highly preferred that the combined weight fraction of imide groups and "functional groups in repeating units" is 30% by weight or less and the "amount of terminal functional groups" is 10.5 μmol / g or less.

[0138] Controlling the functional groups in the polyimide (imide groups, functional groups in the repeating units, and terminal functional groups) as described above is an element that must be considered in order to obtain the polyimide having the charge-up properties of the present invention.

[0139] <<Polyimide film manufacturing method>> The production of polyimide, particularly the production of a polyimide film via a laminate in which a polyimide film is formed on a carrier substrate, will be described below.

[0140] An example of a method for producing a polyimide film is outlined below. (1) A method of forming a polyimide film by casting a polyimide precursor (particularly a polyamic acid) solution or a polyimide precursor solution composition prepared by adding an imidization catalyst, a dehydrating agent, inorganic fine particles, etc. to a polyimide precursor solution as needed onto a carrier substrate and heating the solution to dehydrate, cyclize, and remove the solvent (thermal imidization); (2) A method in which a cyclization catalyst and a dehydrating agent are added to a polyimide precursor (particularly a polyamic acid) solution, and further inorganic fine particles or the like are optionally added to form a polyimide precursor solution composition, which is cast on a carrier substrate and chemically dehydrated and cyclized, and then heated to remove the solvent and imidize, thereby forming a polyimide film (chemical imidization); Examples include:

[0141] <Production of Laminates and Electronic Devices> In the manufacture of electronic devices, a polyimide precursor solution (including a composition solution containing additives, if necessary) is first cast onto a carrier substrate, followed by heat treatment for imidization and desolvation (mainly desolvation in the case of a polyimide solution) to form a polyimide film, resulting in a laminate of the carrier substrate and polyimide film. While the carrier substrate is not particularly limited, glass substrates such as soda-lime glass, borosilicate glass, and alkali-free glass, as well as metal substrates such as iron, stainless steel, and copper, are commonly used. The method for casting the polyimide precursor solution and polyimide solution onto the carrier substrate is not particularly limited, but examples include conventional methods such as spin coating, screen printing, bar coating, and electrodeposition. When using a polyimide precursor solution, the heat treatment conditions are not particularly limited, but it is preferable to dry the solution at a temperature ranging from 50°C to 150°C, followed by treatment at a maximum heating temperature of, for example, 150°C or higher, preferably 200°C or higher, more preferably 250°C or higher, and for example, 600°C or lower, preferably 550°C or lower, and more preferably 500°C or lower. The heat treatment conditions when using a polyimide solution are not particularly limited, but the maximum heating temperature is, for example, 100°C or higher, preferably 150°C or higher, more preferably 200°C or higher, and is, for example, 600°C or lower, preferably 500°C or lower, more preferably 450°C or lower.

[0142] The thickness of the polyimide film is preferably 1 μm or more. If the thickness is less than 1 μm, the polyimide film will not maintain sufficient mechanical strength, and may be unable to withstand stress and break when used, for example, as a flexible device substrate. The thickness of the polyimide film is also preferably 20 μm or less. If the thickness of the polyimide film exceeds 20 μm, it may become difficult to thin the flexible device. To further thin the polyimide film while maintaining sufficient durability for a flexible device, the thickness of the polyimide film is more preferably 2 to 10 μm.

[0143] The resulting polyimide film is firmly laminated to a carrier substrate such as a glass substrate, etc. The peel strength between the carrier substrate such as a glass substrate and the polyimide film, as measured in accordance with JIS K6854-1, is generally 50 mN / mm or more, preferably 100 mN / mm or more, more preferably 200 mN / mm or more, and even more preferably 300 mN / mm or more.

[0144] A second layer such as a resin film or an inorganic film may be laminated on the resulting polyimide film to form a flexible device substrate. In particular, an inorganic film is suitable as a water vapor barrier layer. Examples of water vapor barrier layers include silicon nitride (SiN x ), silicon oxide (SiO x ), silicon oxynitride (SiO x N y Examples of suitable inorganic films include inorganic films containing inorganic substances selected from the group consisting of metal oxides, metal nitrides, and metal oxynitrides, such as aluminum oxide (Al2O3), titanium oxide (TiO2), and zirconium oxide (ZrO2). Generally, methods for forming these thin films include physical vapor deposition (CVD) methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods such as plasma CVD and catalytic chemical vapor deposition (Cat-CVD). This second layer can also be a multi-layer structure. Even in devices with a second layer on a polyimide film, the polyimide film may affect the semiconductor layer through the second layer. Therefore, the polyimide of the present invention, which has excellent charge-up properties, is preferably used to improve device characteristics and durability.

[0145] A flexible device substrate may be formed by laminating a polyimide film on a resin film or an inorganic film using a polyimide precursor solution in the same manner as in the case of the carrier substrate.

[0146] The polyimide film obtained by the present invention can be firmly laminated to an inorganic film as a substrate. The peel strength between the polyimide film and the inorganic film (e.g., a silicon oxide film) measured in accordance with JIS K6854-1 is generally 20 mN / mm or more, preferably 30 mN / mm or more, more preferably 40 mN / mm or more, and even more preferably 50 mN / mm or more.

[0147] In the manufacture of electronic devices, elements and circuits necessary for the device are formed on the formed laminate (particularly the polyimide film). The elements and circuits to be formed and the manufacturing process vary depending on the type of device. For example, when manufacturing an organic electroluminescence (EL) display or liquid crystal display (LCD) with TFTs, an amorphous silicon TFT is formed on the polyimide film. The TFT includes, for example, a gate metal layer, a semiconductor layer such as an amorphous silicon film, a silicon nitride gate dielectric layer, and an ITO pixel electrode. Further structures necessary for the organic electroluminescence (EL) display or liquid crystal display can be formed on top of this by known methods. The polyimide film obtained in the present invention has excellent properties such as heat resistance and toughness, so the method for forming circuits, etc. is not particularly limited.

[0148] When a flexible device is desired as the electronic device, a device substrate (especially a polyimide film) having a circuit or the like formed on its surface is peeled off from a carrier substrate. The peeling method is not particularly limited, and can be performed by, for example, laser peeling, in which a laser or the like is irradiated from the carrier substrate side to peel off, or mechanical peeling, in which the substrate is mechanically peeled off.

[0149] The polyimides and polyimide films of the present invention (including those having a second layer such as a resin film or an inorganic film laminated thereon) are particularly suitable as substrates for electronic devices that require thinning and flexibility. The term "flexible (electronic) device" as used herein means that the device itself is flexible, and the device is typically completed by forming a semiconductor layer (such as a transistor or diode as an element) on a substrate. It does not refer to, for example, COF (chip-on-film) devices in which "rigid" semiconductor elements such as IC chips are mounted on a conventional FPC (flexible printed wiring board). Flexible (electronic) devices suitable for use with the polyimides and polyimide films of the present invention described above and below include display devices such as liquid crystal displays, organic electroluminescence (EL) displays, and electronic paper, as well as light-receiving devices such as solar cells and CMOS.

[0150] The polyimide of the present invention can be used in a variety of applications. However, in order to achieve the effect of excellent charge-up properties, it is preferably used in a device in which the polyimide is in direct contact with a semiconductor or in a device in which the polyimide is laminated via a thin film (e.g., a thin film of 200 nm or less, preferably 100 nm or less, such as the above-mentioned second layer).

[0151] In addition, in the above explanation, a method of forming elements and circuits on a laminate of a polyimide film and a carrier substrate was described, but elements and circuits may also be formed on a single polyimide film as long as there is no problem in forming the elements and circuits.

[0152] The semiconductors include silicon such as single crystal silicon, amorphous silicon, and polysilicon (which may be doped with p-type or n-type impurities), as well as gallium nitride and other compound semiconductors. [Example]

[0153] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples.

[0154] The measurement methods of the characteristics used in the following examples are shown below.

[0155] <Evaluation of Varnish> (1) Viscosity The viscosity was measured at a measurement temperature of 23 °C, 25 °C or 30 °C using an E-type viscometer. (2) Measurement of weight-average molecular weight The weight-average molecular weight was measured under the following conditions. Apparatus: HLC-8320GPC manufactured by Tosoh Column: TSKgel Super AWM-H 9um 6.0mm I.D. x 15cm manufactured by Tosoh Eluent: NMP (10 mmol / L LiCl, 30 mmol / L phosphoric acid) Measurement temperature: 40 °C Flow rate: 0.5 mL / min Detection method: RI Measurement quantity: 20 μL

[0156] <Measurement method of SHG characteristics> (1) Evaluation sample As shown in Fig. 1, a polyimide film 1 (10 μm thick) was formed on a glass substrate 3 to prepare a polyimide / glass laminate. Silver electrodes 2a and 2b were formed on the polyimide surface of the polyimide / glass laminate so that the electrode distance was 50 μm, and a measurement sample was created.

[0157] (2) SHG measurement conditions While applying a voltage between the silver electrodes of the element in Fig. 1, the SH light generated when the laser was irradiated from the glass side was detected. The laser conditions, voltage conditions, and detection wavelength conditions at that time are as follows. Laser: 920 nm, 80 fs, 1 kHz, 10 - 15 mW, irradiated from the glass wafer side Applied voltage waveform: rectangular wave, duty ratio 0.5, between 0 V and +50 V, 1 kHz SH light detection wavelength: 460 nm SH light measurement position: measured on the polyimide film in the range of 0 to 4 μm from the electrode end (3) SHG evaluation The SHG light intensity near both electrodes (within the range of 0 to 4 μm) when a voltage was applied was subtracted from the intensity before the voltage was applied as a baseline, and the smaller of these values ​​was divided by the larger of these values ​​to calculate the symmetry ratio (LR ratio). A ratio of 0.5 or greater was evaluated as ◯ (pass), and a ratio below 0.5 was evaluated as × (fail).

[0158] The monomers and solvents used in the examples and comparative examples are shown below.

[0159] [ka]

[0160] [ka]

[0161] <Synthesis example of polyamic acid (polyimide precursor) solution (varnish)> [Synthesis Example 1] (Used in Example 1) 3300 g of NMP and 268.80 g (2.485 mol) of PPD were placed in a 5 L separable flask and stirred at 50°C for 30 minutes under a nitrogen atmosphere, after which 725 g (2.464 mol) of s-BPDA and 1000 g of NMP were added and reacted.

[0162] 7.74 g (0.021 mol) of s-BPTA was added to the reaction mixture and stirred, after which the reaction was terminated. The final viscosity was 3482 Poise at 30°C, the total acid-amine ratio was 1.00, and the monomer concentration was 18.9 wt%. The resulting varnish was diluted with NMP to a monomer concentration of 10.0 wt%. The viscosity was 50.2 Poise at 30°C.

[0163] [Synthesis Example 2] (Used in Example 2) A 5L separable flask was charged with 4100g of NMP and 21.50g of water and heated to 50°C under a nitrogen atmosphere. 30.11g (0.278mol) of PPD was added and stirred for 1 hour. 97.25g (0.331mol) of s-BPDA and 100g of NMP were then added and stirred for 1 hour.

[0164] To the reaction mixture, 404.35 g (1.374 mol) of s-BPDA, 158.05 g (1.461 mol) of PPD, and 100 g of NMP were added and stirred for 2 hours, after which 5.12 g (0.018 mol) of s-BPDA was added and reacted.

[0165] Finally, 6.37 g (0.017 mol) of s-BPTA was added and stirred for 2 hours to complete the reaction. The final viscosity was 29.8 Poise at 25°C, the total acid-amine ratio was 1.00, and the monomer concentration was 14.0 wt%.

[0166] [Synthesis Example 3] (Used in Example 3) A 5-L separable flask was charged with 3000 g of NMP and 21.50 g of water and heated to 50°C under a nitrogen atmosphere. Then, 52.59 g (0.202 mol) of DATP was added and stirred for 30 minutes. 77.99 g (0.265 mol) of s-BPDA and 650 g of NMP were added and stirred for 3 hours.

[0167] To the reaction mixture, 282.25 g (0.959 mol) of s-BPDA, 276.04 g (1.060 mol) of DATP, and 650 g of NMP were added and stirred for 2 hours, after which 4.08 g (0.14 mol) of s-BPDA was added and reacted.

[0168] Finally, 8.78 g (0.024 mol) of s-BPTA was added and stirred for 2 hours to complete the reaction. The final viscosity at this point was 70.7 Poise @ 30°C, the total acid-amine ratio was 1.00, and the monomer concentration was 14.0 wt%.

[0169] [Synthesis Example 4] (Used in Example 4) 3200 g of NMP and 406.86 g (2.032 mol) of 4,4'-ODA were placed in a 5 L separable flask and stirred at 50°C for 1 hour under a nitrogen atmosphere, after which 425.42 g (1.951 mol) of PMDA and 950 g of NMP were added and reacted. 20.65 g (0.081 mol) of PMA was added to the reaction mixture and stirred for 2 hours to complete the reaction, at which point the final viscosity was 12.2 Poise at 30°C, the total acid-amine ratio was 1.00, and the monomer concentration was 17.1 wt%.

[0170] [Synthesis Example 5] (Used in Example 5) A 5L separable flask was charged with 4100g of NMP and 21.50g of water and heated to 50°C under a nitrogen atmosphere. 30.11g (0.278mol) of PPD was added and stirred for 1 hour. 97.25g (0.331mol) of s-BPDA and 100g of NMP were then added and stirred for 1 hour.

[0171] To the reaction mixture, 404.35 g (1.374 mol) of s-BPDA, 158.05 g (1.461 mol) of PPD, and 100 g of NMP were added and stirred for 2 hours, after which 5.12 g (0.018 mol) of s-BPDA was added and reacted.

[0172] Finally, 5.15 g (0.035 mol) of phthalic anhydride was added and stirred for 2 hours to complete the reaction. The final viscosity at this point was 29.5 Poise at 25°C, the total acid-amine ratio was 1.00, and the monomer concentration was 13.9 wt%. The total acid-amine ratio was calculated as (moles of s-BPDA + moles of phthalic anhydride ÷ 2) ÷ (moles of PPD).

[0173] [Synthesis Example 6] (Used in Comparative Example 1) A 5L separable flask was charged with 3800g of NMP and 20.00g of water and heated to 50°C under a nitrogen atmosphere. Then, 43.01g (0.398mol) of PPD was added and stirred for 1 hour. 153.55g (0.522mol) of s-BPDA and 100g of NMP were added and stirred for 3 hours.

[0174] To the reaction mixture, 563.02 g (1.914 mol) of s-BPDA, 225.79 g (2.088 mol) of PPD, and 100 g of NMP were added and stirred for 2 hours, after which 5.85 g (0.019 mol) of s-BPDA was added and reacted.

[0175] Finally, 10.92 g (0.030 mol) of s-BPTA was added and stirred for 2 hours to complete the reaction. The final viscosity at this point was 51.9 Poise @ 30°C, the total acid-amine ratio was 1.00, and the monomer concentration was 20.0 wt%.

[0176] [Synthesis Example 7] (Used in Comparative Example 2) 3900 g of NMP and 188.16 g (1.740 mol) of PPD were placed in a 5 L separable flask and stirred at 50°C for 30 minutes under a nitrogen atmosphere, after which 501.1 g (1.704 mol) of s-BPDA and 400 g of NMP were added and reacted.

[0177] 0.64 g (0.002 mol) of s-BPTA was added to the reaction mixture to complete the polymerization. The final viscosity at this point was 31.8 Poise at 25°C, the total acid-amine ratio was 0.980, and the monomer concentration was 13.8 wt%.

[0178] [Synthesis Example 8] (Used in Comparative Example 3) A 5L separable flask was charged with 3413.80g of NMP, 161.72g (1.495mol) of PPD, and 2.41g (0.012mol) of ODA, and the mixture was stirred at 50°C for 30 minutes under a nitrogen atmosphere. Then, 439.11g (1.492mol) of s-BPDA was added, and the solution temperature was raised to approximately 90°C over 10 minutes while stirring under a nitrogen atmosphere, until the raw materials were completely dissolved. Stirring was continued at 90°C for 3 hours.

[0179] After the reaction mixture was quickly cooled to approximately 50°C in a water bath, 29.45 g of a 1% NMP solution of 3-aminopropyltriethoxysilane (γ-APS) was added to perform alkoxysilane modification. 0.02 parts by weight of an acrylic surface conditioner was added per 100 parts by weight of the alkoxysilane-modified polyamic acid solids. To this alkoxysilane-modified polyamic acid solution, 4.552 g (0.031 mol) of phthalic anhydride was added and the reaction was stirred for 60 minutes under a nitrogen atmosphere at 50°C to complete the polymerization. The final viscosity at this point was 29.4 Poise @ 23°C, the total acid-to-amine ratio was 1.00, and the monomer concentration was 11.1 wt%.

[0180] [Synthesis Example 9] (Used in Comparative Example 4) A 5L separable flask was charged with 3,500g of N,N-dimethylacetamide and 650.07g (2.209mol) of s-BPDA and stirred thoroughly. Then, 241.88g (2.236mol) of PPD and 600g of N,N-dimethylacetamide were added and stirred at room temperature. After stirring, 1.316g (0.004mol) of s-BPDA and 8.192g (0.022mol) of s-BPTA were added and stirred at room temperature for approximately 6 hours to complete the polymerization. The final viscosity at this point was 315 Poise at 30°C, the total acid-amine ratio was 1.00, and the monomer concentration was 18.0wt%.

[0181] [Synthesis Example 10] (Used in Example 6) 3700 g of DMI and 147.84 g (1.367 mol) of PPD were placed in a 5 L separable flask and stirred at 50°C for 30 minutes under a nitrogen atmosphere, after which 398.14 g (1.353 mol) of s-BPDA and 750 g of DMI were added and reacted.

[0182] After adding 5.01 g (0.014 mol) of s-BPTA to the reaction mixture and stirring, the reaction was terminated. The final viscosity was 70.6 Poise at 30°C, the total acid-amine ratio was 1.00, and the monomer concentration was 11.0 wt%.

[0183] <Examples 1 to 6 and Comparative Examples 1 to 4> The polyamic acid solution prepared in Synthesis Example was spin-coated onto an alkali-free glass wafer, and the wafer was heated at 120°C, 150°C, 200°C, and 250°C for 10 minutes each, and then at 450°C for 5 minutes to form a 10 μm-thick polyimide film, thereby producing a polyimide / glass laminate.

[0184] The charge-up characteristics of the produced polyimide / glass laminate were measured, and the results are shown in Table 1.

[0185] [Table 1] [Industrial Applicability]

[0186] The polyimide of the present invention is suitable for use in electronic devices, such as substrates for flexible devices. [Explanation of symbols]

[0187] 1 Polyimide film 2a, 2b electrode 3. Circuit Board 4 Dipoles 5 electrons (charged)

Claims

1. A polyimide precursor for producing a flexible electronic device substrate, comprising: A polyimide film having a thickness of 10 μm is formed using the polyimide precursor, and a pair of electrodes is formed on the polyimide film with an inter-electrode distance d described below. When a laser beam is irradiated onto the polyimide film under the laser beam conditions described below while a voltage is applied to the pair of electrodes under the applied voltage conditions described below, two SHG beams observed between the pair of electrodes exhibit a symmetry ratio of 0.5 or more, The polyimide precursor is composed of a tetracarboxylic acid component, a diamine component, and a carboxylic acid monoanhydride, and is represented by the following formulas (1) and (2): Formula (1) 0.97≦X / Y<1.00 Formula (2) 1.0≦(X+Z / 2) / Y≦1.05 (In the formula, X represents the number of moles of the tetracarboxylic acid component, Y represents the number of moles of the diamine component, and Z represents the number of moles of the carboxylic acid monoanhydride.) and a polyimide precursor having a weight average molecular weight of 240,856 or more and 300,000 or less. (however, Inter-electrode distance d: 50 μm; Applied voltage conditions: square wave, duty ratio 0.5, between 0 V and +50 V, 1 kHz; Laser light conditions: wavelength 920 nm, pulse width 80 fs, frequency 1 kHz, output 10-15 mW and The symmetry ratio is a value expressed by the following formula: Symmetry ratio (LR ratio) = I ｓｍａｌｌ / I ｌａｒｇｅ Here, I ｓｍａｌｌ and I ｌａｒｇｅ is the peak intensity of the two peaks of the SHG light observed between the electrodes, and I ｌａｒｇｅ is the peak intensity of the SHG light with a higher intensity, I ｓｍａｌｌ represents the peak intensity of the SHG light with the smaller intensity.

2. A polyimide precursor for producing a flexible electronic device substrate, comprising: A polyimide film having a thickness of 10 μm is formed using the polyimide precursor, and a pair of electrodes is formed on the polyimide film with an inter-electrode distance d described below. When a laser beam is irradiated onto the polyimide film under the laser beam conditions described below while a voltage is applied to the pair of electrodes under the applied voltage conditions described below, two SHG beams observed between the pair of electrodes exhibit a symmetry ratio of 0.5 or more, All tetracarboxylic acid components and all diamine components constituting the polyimide precursor are represented by the formula: 1≦X / Y≦1.05 (wherein X represents the number of moles of the tetracarboxylic acid component, and Y represents the number of moles of the diamine component.) Fulfilling A polyimide precursor in which the proportion of 3,3',4,4'-biphenyltetracarboxylic dianhydride in all tetracarboxylic acid components is 60 mol % or more, the amount of p-phenylenediamine in all diamine components is 60 mol % or more, and the polyimide precursor has a weight average molecular weight of 240,856 to 300,000. (however, Inter-electrode distance d: 50 μm; Applied voltage conditions: square wave, duty ratio 0.5, between 0 V and +50 V, 1 kHz; Laser light conditions: wavelength 920 nm, pulse width 80 fs, frequency 1 kHz, output 10-15 mW and The symmetry ratio is a value expressed by the following formula: Symmetry ratio (LR ratio) = I ｓｍａｌｌ / I ｌａｒｇｅ Here, I ｓｍａｌｌ and I ｌａｒｇｅ is the peak intensity of the two peaks of the SHG light observed between the electrodes, and I ｌａｒｇｅ is the peak intensity of the SHG light with a higher intensity, I ｓｍａｌｌ represents the peak intensity of the SHG light with the smaller intensity.

3. The polyimide precursor according to claim 1 or 2, which contains at least a polyamic acid.

4. A polyimide film for flexible electronic device substrates obtained from the polyimide precursor according to claim 1 or 2.

5. A laminate comprising the polyimide film according to claim 4 and a glass substrate.

6. A flexible electronic device substrate comprising the polyimide film of claim 4.

7. A flexible electronic device comprising the flexible electronic device substrate according to claim 6 and a TFT element.

8. 8. A method for manufacturing a flexible electronic device according to claim 7, comprising the steps of: a step of applying a solution composition containing a polyimide precursor onto a carrier substrate and imidizing the solution composition to form a laminate having the carrier substrate and a polyimide film; A manufacturing method characterized by:

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