TW202323460A - Poly(amic acid) varnish and method for producing poly(amic acid) varnish - Google Patents

Abstract

A poly(amic acid) varnish which comprises a solvent and a poly(amic acid) obtained by reacting a tetracarboxylic acid and a diamine and which, when examined after having been introduced into a cell with an optical path length of 10 mm and been degassed therein for 15 minutes, has a light transmittance at 390-nm wavelength of 70% or greater.

Description

Polyamide acid varnish and method for producing polyamide acid varnish

The invention relates to a polyamide acid varnish and a method for producing the polyamide acid varnish.

Conventionally, epoxy resins and acrylic resins have been known as colorless and transparent coating resins or adhesive resins. However, these resins have problems in heat resistance and chemical resistance. Therefore, transparent polyimides excellent in heat resistance, chemical resistance, mechanical properties, electrical properties, etc. have begun to be used for these applications.

When used in applications requiring transparency, of course polyimide also requires transparency. On the other hand, there is a problem that it is difficult to obtain a colorless and transparent polyimide, and it is easy to obtain a yellowed polyimide. Therefore, various studies have been conducted on methods for obtaining polyimides with high transparency.

For example, Patent Document 1 describes that if a polyamide varnish having a transmittance of 35% or more at a wavelength of 450 nm measured at an optical path length of 1 cm is used, the obtained polyimide film is less likely to turn yellow. , if a polyamide varnish with a transmittance of 85% or more at a wavelength of 600 nm is used, it is easy to obtain a colorless and transparent polyimide film.

In addition, Patent Document 2 describes a polyamic acid varnish and a polyimide obtained by reacting an alicyclic diamine and an aromatic tetracarboxylic dianhydride. In addition, it is described that by purifying at least one of the alicyclic diamine and the aromatic tetracarboxylic dianhydride, and then reacting, the b* value of the obtained polyimide can be suppressed due to impurities. decline. [Prior art literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2019-214657 [Patent Document 2] Japanese Patent Laid-Open No. 2013-23583

[Problem to be Solved by the Invention]

As is also clear from the description of Patent Document 1, in polyamic acid varnishes used for producing polyimides, the light transmittance may vary greatly from one varnish to another. According to the new findings of the inventors of the present invention, even for varnishes prepared from the same raw materials and using the same manufacturing method, it may be possible to clearly identify the The degree of coloring difference.

On the other hand, the inventors of the present invention have discovered a method of quantifying the degree of coloration by a novel method through previous studies. Furthermore, it has been found that the b* value of the polyamic acid varnish whose transmittance measured by a novel method is at least a certain level is low enough to impart a highly transparent polyimide; Obtained by reducing the amount of specific impurities contained in diamine.

In Patent Document 2, a polyamic acid varnish or the like using a monomer from which impurities have been removed by purification by a sublimation method, etc. is also proposed, but b* of the obtained polyimide cannot be sufficiently reduced. value without full transparency.

In view of the above problems, an object of the present invention is to provide a polyamic acid varnish which can quantify the coloring degree by a novel method and obtain a transparent Highly resistant polyimide. [Means to solve the problem]

[1] A polyamic acid varnish comprising polyamic acid obtained by reacting tetracarboxylic acid and diamine, and a solvent, introduced into a cell with an optical path length of 10 mm, and degassed in the cell The light transmittance at a wavelength of 390 nm measured after 15 minutes was 70% or more. [2] The polyamic acid varnish according to [1], wherein the diamine does not contain an oxygen atom in its molecular structure. [3] The polyamic acid varnish according to [1] or [2], wherein the diamine is measured by a fluorescent X-ray method (X-Ray Fluorescence analysis (XRF)). Oxygen atom content rate of 4 atomic % or less. [4] The polyamic acid varnish according to any one of [1] to [3], wherein the polyamic acid is obtained by reacting an aromatic tetracarboxylic acid and an alicyclic diamine. [5] The polyamic acid varnish according to any one of [1] to [4], wherein the solvent is N-methyl-2-pyrrolidone. [6] The polyamic acid varnish according to any one of [1] to [5], wherein when a polyimide film having a thickness of 10 μm is formed by heating at a heating temperature of 280° C., L* The b* value in the a*b* colorimetric system is 1.0 or less. [7] The polyamic acid varnish according to any one of [1] to [6], wherein the wavelength is 390 nm when a polyimide film having a thickness of 10 μm is formed by heating at a heating temperature of 280° C. The light transmittance is above 80%.

[8] A method for producing a polyamic acid varnish, comprising: a step of purifying diamine by recrystallization; and a step of reacting the purified diamine with tetracarboxylic acid. [9] The method for producing polyamic acid varnish according to [8], wherein in the step of purifying by the recrystallization method, the diamine is measured by fluorescent X-ray method (XRF). Oxygen atom content rate of 4 atomic % or less. [10] The method for producing a polyamide acid varnish according to [8] or [9], wherein the recrystallization method is performed in a hydrocarbon solvent. [11] The method for producing polyamic acid varnish according to any one of [8] to [10], further comprising: storing the polyamide varnish in a container with a light shielding rate of 90% or more at a wavelength of 220 nm to 800 nm diamine step, and using the recrystallization method to purify the stored diamine. [Effect of the invention]

According to the present invention, there are provided a polyamic acid varnish capable of quantifying the coloring degree by a novel method and obtaining transparency, and a method for producing polyimide from the polyamic acid varnish High polyimide.

As described above, conventionally, the light transmittance was directly measured after introducing the polyamic acid varnish into the measurement tank. However, in the conventional method of measuring light transmittance, the measured value of light transmittance measured for the same polyamic acid varnish may become unstable, and it cannot be said that the measured light transmittance can be sufficiently secured. value reliability.

On the other hand, the inventors of the present invention have discovered a new measurement method in which polyamic acid varnish is introduced into the tank for measurement, and then the polyamic acid varnish is tested in the tank in the past studies. Light transmittance was measured after degassing.

That is, in the conventional measurement method, when the polyamic acid varnish is introduced into the tank for measurement, air bubbles are inevitably mixed into the varnish. Since the measured value of the light transmittance fluctuates due to the air bubbles mixed in, it is considered that the measured value becomes unstable. On the other hand, in the measurement of the light transmittance in this embodiment, after introducing the polyamic acid varnish into the tank for measurement, the polyamic acid varnish is degassed inside the tank, whereby the The air bubbles inevitably mixed are also removed from the polyamide varnish. By measuring the light transmittance on this basis, it is possible to suppress fluctuations in the measured value due to the incorporation of air bubbles, and to obtain a more reliable measured value of the light transmittance.

Furthermore, in the above-mentioned measurement method, it was found that: if the transmittance of light with a wavelength of 390 nm is equal to or higher than a certain varnish, a polyimide film having a sufficiently reduced b* value can be obtained; It is obtained by using a diamine component (a diamine component whose oxygen atom content rate is not more than a certain level) in which the amount of specific impurities caused by carbonates has been reduced. Hereinafter, the configuration of the present invention will be described.

One embodiment of the present invention relates to a polyamide acid varnish for making transparent polyimide.

1. Polyamide varnish The polyamic acid varnish contains polyamic acid which is a reaction product of a tetracarboxylic acid component and a diamine component, and a solvent.

The polyamic acid is known as a polyimide precursor, and may be a reaction product obtained by reacting a tetracarboxylic acid component and a diamine component by a known method.

The tetracarboxylic acid component can be an aromatic tetracarboxylic acid component or an aliphatic tetracarboxylic acid component, and the glass transition temperature (Tg) or thermal expansion coefficient of polyimide can be increased to improve heat resistance or increase tensile elongation. From the viewpoint of mechanical properties such as tensile strength, an aromatic tetracarboxylic acid component is preferable.

Examples of aromatic tetracarboxylic acid components include 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, 2,2',3,3' -Biphenyltetracarboxylic acid, 4,4'-oxydiphthalic acid, fluorenylidene diphthalic acid, etc. Among these, 3,3',4,4'-biphenyltetracarboxylic acid and 4,4'-oxydiphthalic acid are preferable from the viewpoint of further improving the transparency and heat resistance of polyimide. Phthalic acid, more preferably 3,3',4,4'-biphenyltetracarboxylic acid. These aromatic tetracarboxylic acids may be anhydrides (dianhydrides).

Examples of aliphatic tetracarboxylic acid components include cyclohexane-1,2,4,5-tetracarboxylic acid, [1,1'-bis(cyclohexane)]-3,3',4,4'-tetracarboxylic acid, Carboxylic acid, [1,1'-bis(cyclohexane)]-2,3,3',4'-tetracarboxylic acid, [1,1'-bis(cyclohexane)]-2,2', 3,3'-tetracarboxylic acid, 4,4'-methylenebis(cyclohexane-1,2-dicarboxylic acid), 4,4'-(propane-2,2-diyl)bis(cyclohexane Hexane-1,2-dicarboxylic acid), 4,4'-oxybis(cyclohexane-1,2-dicarboxylic acid), bicyclo[2.2.2]oct-7-ene-2,3, 5,6-tetracarboxylic acid, 4,4'-thiobis(cyclohexane-1,2-dicarboxylic acid), 4,4'-sulfonylbis(cyclohexane-1,2-dicarboxylic acid acid), 4,4'-(dimethylsilanediyl)bis(cyclohexane-1,2-dicarboxylic acid), 4,4'-(hexafluoroisopropylidene)diphthalic acid and 4,4'-(tetrafluoropropane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic acid), etc. These aliphatic tetracarboxylic acids may be anhydrides (dianhydrides).

The diamine component may be an aromatic diamine component, an aliphatic diamine component, or diamines having a spirobiindane ring, siloxane diamines, and the like. Among them, as described later, from the viewpoint of reducing the amount of specific impurities such as carbonates that cause coloring, a diamine component that does not contain an oxygen atom in the molecular structure is preferable.

Examples of aromatic diamine components include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 2,4-toluenediamine, 2,5-toluenediamine, 2,6-toluenediamine, 2,2 '-bis(trifluoromethyl)benzidine and 2,2'-bis(4-aminophenyl)hexafluoropropane, etc.

The aliphatic diamine component may be an alicyclic diamine component or an alkylene diamine component. Examples of alicyclic diamine components include: 1,4-diaminomethylcyclohexane (1,4-BAC), 1,3-diaminomethylcyclohexane ( 1,3-BAC), norbornane diamine (norbornane diamine, NBDA), 1,4-diamino cyclohexane (1,4-diamino cyclohexane, DACH), isophorone diamine and 4,4 '-methylenebis(cyclohexylamine) etc. Among these, 1,4-diaminocyclohexane is preferred from the viewpoint of further improving the heat resistance of polyimide, further improving transparency, and making coloring less likely to occur. Furthermore, 1,4-diaminomethylcyclohexane has geometric isomers including a cis-body and a trans-body, and any of these may be used. Among them, it is more preferable that the content ratio of the trans-isomer to the cis-isomer (trans-isomer+cis-isomer=100%) is 60% to 100% for the trans-isomer and 0% to 40% for the cis-isomer. The content ratio of the cis-isomer and the trans-isomer can be determined by ¹ H-NMR ( ¹ H-Nuclear Magnetic Resonance, ¹ H-NMR).

Among the impurities contained in these diamine components or tetracarboxylic dianhydride components, specific impurities such as carbonates contained in the diamine components tend to reduce the light transmittance at a wavelength of 390 nm of the polyamic acid varnish described later. It is easy to increase the coloring (b* value) after imidization. Therefore, the amount of specific impurities such as carbonate contained in the diamine component is preferably as small as possible. Specifically, the oxygen atom content of the diamine is preferably at most 4 atomic %, more preferably at most 3 atomic %, and still more preferably at most 1 atomic %. Furthermore, it is preferable that the oxygen atom content rate of diamine is the oxygen atom content rate derived from the impurity of diamine.

The oxygen atom content rate of diamine can be measured using a fluorescent X-ray method (XRF), specifically, a wavelength dispersive fluorescent X-ray apparatus (Wavelength dispersive X-ray spectrometer (WDX)). For example, measurement can be performed by molding a sample into a tablet, using ZSX Primus IV manufactured by Rigaku as a measurement device, and using Rh (aperture = Φ10) in an X-ray tube mm), and use the fundamental parameter (Fundamental Parameter) method to carry out the quantitative analysis of the oxygen atom content rate under vacuum.

The oxygen atom content rate of diamine can be reduced by purifying a diamine component by a recrystallization method, or storing in a light-shielding container under nitrogen atmosphere, for example.

When diamine is dissolved in N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP) to make a 10 wt% solution, the light transmittance at a wavelength of 390 nm is preferably 50 More than 60%, more preferably more than 70%, more preferably more than 80%. The upper limit is not limited, but may be, for example, 99% or less, or may be 95% or less. Specifically, the light transmittance of the diamine can be measured by using a Marucci Spec ( Multi spec)-1500 is used to measure the ultraviolet (UV)-visible spectrum with a wavelength of 300 nm to 800 nm, and obtain the transmittance of light with a wavelength of 390 nm.

Similarly to the above, the transmittance of diamine can be improved by, for example, purifying a diamine component by a recrystallization method, or storing it in a light-shielding container under a nitrogen atmosphere.

The solvent may be any known solvent capable of dissolving polyamic acid or polyimide. Examples of solvents include: ester-based solvents containing methyl acetate, ethyl acetate, butyl acetate, and dimethyl carbonate; containing γ-butyrolactone (γ-butyrolactone, GBL), δ-valerolactone, ε- Caprolactone, γ-crotonyl lactone, γ-caprolactone (γ-hexanolactone), α-methyl-γ-butyrolactone, γ-valerolactone, α-acetyl-γ-butyrolactone and δ-caprolactone and other lactone-based solvents; ketone-based solvents including acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; phenol-based solvents including m-cresol and the like; Diethylsulfone, Ethylphenylsulfone, Diethylsulfone, Diphenylsulfone, Cyclobutane, Bisphenol S, Solapsone, Dapsone, Bisphenol A Polysulfone and Cyclobutane Thyrine-based solvents such as N,N-dimethylsulfoxide (DMSO) and the like; N-methyl-2-pyrrolidone (NMP), Amide-based solvents such as N,N-dimethylformamide (N,N-dimethylformamide, DMF) and N,N-dimethylacetamide (N,N-Dimethylacetamide, DMAc), etc.

In addition, these tetracarboxylic-acid components, a diamine component, and a solvent may each use only 1 type, and may use multiple types together.

2. Manufacturing method of polyamide acid varnish The polyamic acid varnish can be obtained by adding a tetracarboxylic acid component and a diamine component to a solvent, making them react, and making it polyamic acid. From the viewpoint of obtaining a polyamic acid varnish having a light transmittance of a certain level or higher, the diamine component to be reacted is preferably purified by a recrystallization method.

That is, the polyamic acid varnish of this embodiment can be manufactured through the process of purifying diamine by the recrystallization method, and the process of making purified diamine and tetracarboxylic acid react.

The purification by the recrystallization method in the process of purifying by the recrystallization method is a method of dissolving diamine in a solvent, cooling and recrystallizing it. In the sublimation method, it is a method to remove components that are relatively easy to gasify. In contrast, in the recrystallization method, for example, unlike sublimation methods, components that are relatively difficult to gasify, such as carbonates remaining in diamine, can be removed. . As mentioned above, it is preferable to purify diamine by the recrystallization method so that the said oxygen atom content rate may be 4 atomic % or less. In addition, the purification rate by the recrystallization method is faster than that of the sublimation method, and a large amount of solid can be purified at one time, and a dedicated device is not required. In addition, it can also be applied to diamines with low thermal stability. From these viewpoints, the recrystallization method is also preferable.

The solvent used in the recrystallization method should be a solvent that can dissolve diamine, and it can include: hydrocarbon solvents such as hexane, butane, pentane, and heptane; alcohol solvents such as methanol and ethanol; 2-methoxy Ether solvents such as ethanol and 2-ethoxyethanol, etc. Among these, hydrocarbon-based solvents are preferred, and hexane is more preferred.

Moreover, it is preferable to store the diamine purified by the recrystallization method in a light-shielding container. That is, it is preferable that the polyamic acid varnish further includes a step of storing it in a container with a light-shielding rate of 90% or more at a wavelength of 220 nm to 800 nm under a nitrogen atmosphere before the step of purifying by the recrystallization method. amine.

The solvent used in the step of carrying out the reaction may be the same solvent as that contained in the polyamic acid varnish.

From the viewpoint of adjusting the applicability of the varnish when producing polyimide, in the polyamic acid varnish, the content of polyamic acid relative to the total mass of the varnish is preferably 1% by mass or more and 50% by mass. % or less, more preferably 10 mass % or more and 45 mass % or less.

The intrinsic viscosity (η) of the polyamide acid varnish is not particularly limited, but is preferably 0.3 dL/g-2.0 dL/g, more preferably 0.6 dL/g-1.5 dL/g. When the intrinsic viscosity (η) of the polyamic acid varnish is within the above-mentioned range, it is easy to achieve both coatability and film-forming properties.

The intrinsic viscosity (η) of the polyamic acid varnish can be adjusted by the molar ratio (molar ratio) of the tetracarboxylic acid component and the diamine component when preparing the polyamic acid varnish. In addition, the intrinsic viscosity (η) is obtained by using an Ubbelohde viscosity tester at 25°C when the concentration of polyamic acid in N-methyl-2-pyrrolidone (NMP) is 0.5 g/dL. measured value.

From the viewpoint of adjusting the coatability of the varnish when producing polyimide, the viscosity of the polyamic acid varnish measured at 25°C by an E-type viscometer is preferably 500 mPa·s or more and 100,000 mPa·s or less, more preferably 3,000 mPa·s or more and 60,000 mPa·s or less, still more preferably 4,500 mPa·s or more and 20,000 mPa·s or less.

(Light transmittance of varnish and its measurement method) In this embodiment, the polyamic acid varnish is introduced into a tank with an optical path length of 10 mm, and the light transmittance at a wavelength of 390 nm measured after degassing in the tank is 70% or more.

As described above, in the measurement of the light transmittance in this embodiment, after the polyamic acid varnish is introduced into the tank for measurement, the polyamic acid varnish is degassed inside the tank, whereby ( Bubbles inevitably mixed in when the polyamic acid varnish is introduced into the tank for measurement) are removed from the polyamic acid varnish. By measuring the light transmittance on this basis, it is possible to suppress the variation of the measured value due to the incorporation of air bubbles, and obtain a more reliable measured value of the light transmittance.

Degassing can be performed, for example, by putting the tank into which the polyamic acid varnish is introduced into the inside of the drier, setting the inside of the drier to 10.3 kPa with a pump connected to the drier, and leaving the tank to stand 1 minute or more and 30 minutes or less. The air pressure in the drier should just be 1.0 kPa to 50.0 kPa, preferably 5.0 kPa to 20.0 kPa, more preferably 5.0 kPa to 15.0 kPa.

If the optical path length measured by the above method is 10 mm and the light transmittance at a wavelength of 390 nm is 80% or more, polyimide with higher transparency can be produced. Furthermore, according to the findings of the inventors of the present invention, even if the polyamic acid varnish whose light transmittance is lower and whose coloring can be confirmed visually in the varnish can be used, it is possible to produce a polyamide varnish with sufficiently high transparency. imide. From this point of view, the light transmittance of the polyamic acid varnish at an optical path length of 10 mm and a wavelength of 390 nm measured by the above method may be 98% or less, or may be 70% to 95%. This was not the case in the conventional method of measuring light transmittance, but by measuring the light transmittance of varnishes using the above-mentioned method, it was confirmed that even if varnishes with low light transmittances of varnishes were used, unexpectedly high transparency can be produced. Polyimide.

The light transmittance of polyamic acid varnish can be improved not only by properly selecting the type of diamine component or tetracarboxylic acid component constituting the polyamic acid varnish, but also by reducing the diamine component or tetracarboxylic dianhydride. Impurities contained in the components, especially the amount of specific impurities such as carbonates contained in the diamine component, specifically, the oxygen atom content rate of the diamine component is decreased to increase. The method of reducing the amount of specific impurities is not particularly limited, and methods such as purification by recrystallization of the diamine component or storage under light-shielding may be used as described above.

(b* value after imidization) When the polyamide acid varnish is heated at 280° C. to form a polyimide film with a thickness of 10 μm, the b* value in the L*a*b* color system is preferably 1.0 or less. When the b* value is measured in the transmission mode using a colorimeter (for example, a tristimulus value direct-reading colorimeter (Colour Cute i CC-i type) manufactured by Suga Testing Equipment Co., Ltd.) value.

(Light transmittance after imidization) When the polyamide varnish is heated at 280° C. to form a polyimide film with a thickness of 10 μm, the transmittance of light having a wavelength of 390 nm is preferably 80% or more. The transmittance can be measured by UV-visible spectroscopy.

The b* value and light transmittance after imidation can also be adjusted by the oxygen atom content rate of the diamine used for preparation of polyamic acid varnish similarly to the above, for example. That is, even if it is the same kind of diamine, by reducing the oxygen atom content rate of a diamine, a b* value will become low easily, and a light transmittance will become high easily.

3. Polyimide membrane Polyamic acid varnish can be used to make polyimide film by coating and imidizing the surface of the substrate.

The substrate to which the polyamide acid varnish is applied is not particularly limited as long as it has solvent resistance and heat resistance. The substrate is preferably a substrate having good peelability of the obtained polyimide layer, preferably glass, a flexible substrate including metal or a heat-resistant polymer film, or the like. Examples of flexible substrates containing metals include: Contains copper, aluminum, stainless steel, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zirconium, gold, cobalt, titanium, tantalum, zinc, lead, tin, silicon, bismuth , indium, or metal foils of these alloys. It is also possible to apply a release agent on the surface of the metal foil.

On the other hand, examples of the flexible substrate comprising a heat-resistant polymer film include polyimide films, aramid films, polyetheretherketone films, polyetheretherketone films, and the like. The flexible substrate comprising a heat-resistant polymer film may contain a release agent or an antistatic antistatic agent, and may also be coated with a release agent or an antistatic agent on the surface. Since the obtained polyimide film has good peelability and high heat resistance and solvent resistance, the base material is preferably a polyimide film.

The method of coating the polyamic acid varnish on the substrate is not particularly limited as long as it can be coated with a constant thickness. Examples of coating methods include those using coating devices such as die coaters, chip coaters, roll coaters, gravure coaters, curtain coaters, spray coaters, and lip coaters. method. The thickness of the formed coating film may be appropriately selected according to the desired thickness of the polyimide film.

The imidization is carried out by heating the coating film of polyamic acid varnish and imidating (ring-closing) the polyamic acid. Specifically, while raising the temperature, the coating film of the polyamic acid varnish is heated to imidate the polyamic acid. In addition, at this time, the solvent in the coating film is removed. Thereafter, it is heated at a predetermined temperature for a certain period of time. The temperature rise can be performed by a known method using an oven, a heating furnace, or the like.

After imidization (ring closure) of polyamic acid, the substrate can be peeled off to obtain a polyimide film.

From the viewpoint of further improving heat resistance, the glass transition temperature (Tg) of the polyimide film is preferably from 270°C to 330°C, more preferably from 280°C to 320°C, and still more preferably from 290°C. And below 310°C. The glass transition temperature (Tg) can be measured by a thermomechanical analysis device (thermomechanical analyzer (thermomechanical analyzer, TMA)).

The thickness of the polyimide film is not particularly limited, and can be appropriately selected according to the use of the polyimide film and the like. For example, when a polyimide film is used for an adhesive sheet, the thickness can be set to about 5 μm to 10 μm. On the other hand, when it is used for the protective layer of various members, it can be made into about 10 micrometers - 25 micrometers.

In addition, from the viewpoint of further improving transparency, the polyimide film preferably has a transmittance of light having a wavelength of 390 nm of 70% or more. The transmittance can be measured by the same method as described above. Furthermore, the thickness of the polyimide film at the time of measuring the light transmittance is not particularly limited, and it is the thickness of the polyimide film actually produced (that is, the polyimide film at the time of use). The light transmittance was measured.

In addition, from the viewpoint of further improving transparency, the b* value in the L*a*b* colorimetric system of the polyimide film is preferably 1.5 or less. The b* value can be measured by the same method as described above. Furthermore, the thickness of the polyimide film at the time of measuring the b* value is not particularly limited, and is the thickness of the polyimide film actually produced (that is, the polyimide film at the time of use) *values are determined. [Example]

Hereinafter, the present invention will be described more specifically with reference to examples, but the scope of the present invention is not limited to the description of examples.

1. Tetracarboxylic dianhydride and diamine components The abbreviations of the tetracarboxylic dianhydride and the diamine component used in an Example are as follows, respectively.

[Tetracarboxylic dianhydride component] s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Co., Ltd., which has a light shielding rate of 90% or more at 220 nm to 800 nm under a nitrogen atmosphere Store in a light-shielding container)

[Diamine component] t-DACH: trans-1,4-diaminocyclohexane

Six types of t-DACH-1 to t-DACH-6 prepared under the conditions in Table 1 below were used for t-DACH. [Table 1] diamine type manufacturer storage conditions purification t-DACH-1 t-DACH Manufactured by Company A Store in a light-shielding container ^* under a nitrogen atmosphere Recrystallization t-DACH-2 t-DACH Manufactured by Kobe Natural Products Chemical Co., Ltd. Purification condition 1 t-DACH-3 t-DACH Manufactured by Jiangsu Qingquan Chemical Co. Ltd. Purification condition 2 t-DACH-4 t-DACH Manufactured by Jiangsu Qingquan Chemical Co. Ltd. Purification conditions 2 × twice t-DACH-5 t-DACH Manufactured by Tokyo Chemical Co., Ltd. none t-DACH-6 t-DACH Manufactured by Jiangsu Qingquan Chemical Co. Ltd. none ※Store in a container with a shading rate of 90% or more for light with a wavelength of 220 nm to 800 nm

The purification conditions 1 and 2 described in Table 1 are as follows.

<Purification Condition 1> In a reaction vessel, 120 kg of t-DACH-6 (DACH manufactured by Jiangsu Qingquan Chemical Co. Ltd.) was added to 600 kg of hexane under a nitrogen atmosphere, and sealed to a nitrogen-displaced inside the flask. While stirring this, t-DACH was completely dissolved by heating at 60° C. for 5 minutes with warm water from the outside of the reaction vessel. Next, in order to remove the tar component which precipitated at the bottom, after transferring to another reaction container which replaced with nitrogen, it cooled to room temperature, and recrystallized. Thereafter, the reaction vessel was filtered with filter paper to obtain recrystallized t-DACH.

<Purification Condition 2> In a glove box with a humidity of 25%, 20 g of t-DACH-6 (DACH manufactured by Jiangsu Qingquan Chemical Co. Ltd.) was added to 100 g of hexane, and sealed in a nitrogen-purged inside the flask. Stirring this, it heated at 50 degreeC for 20 minutes in an oil bath, and dissolved DACH completely. Next, in order to remove the tar component which precipitated at the bottom, after transferring to another flask purged with nitrogen, it cooled to room temperature and recrystallized. Thereafter, filtration was performed with filter paper in a glove box to obtain recrystallized t-DACH.

About the prepared diamine, XRF measurement, gas chromatography (Gas Chromatography, GC) measurement, and light transmittance measurement were performed by the following methods.

(Fluorescence X-ray (XRF) measurement) The oxygen atom content rate of diamine was measured using the wavelength dispersive fluorescent X-ray apparatus (WDX). Specifically, the sample was molded into a tablet, and a ZSX Primus IV manufactured by Rigaku was used as a measurement device, and Rh (aperture = Φ10 mm) was used in an X-ray tube, and a vacuum Next, the quantitative analysis of the oxygen atom content was carried out by using the basic parameter method.

(GC assay) A liquid obtained by dissolving 20 mg of a sample in 5 mL of methanol was used as a measuring solution, and 8890/5977BN manufactured by Agilent Technologies was used, and DB-1 (0.25 mm×30 m, film thickness 0.25 f( The column with hook f) Km) implements GC with a heating program of 100°C (5 minutes (5 min.)) to 320°C (holding: 3 minutes (hold: 3 min.)) and a heating rate of 10°C/min analyze.

(Measurement of light transmittance) Mix either of each t-DACH with N-methyl-2-pyrrolidone (NMP) to prepare a 10 wt% solution. The wavelength of t-DACH was obtained by performing UV-visible spectrum measurement in the wavelength range of 300 nm to 800 nm for the solution immediately after preparation using Multi spec-1500 manufactured by Shimadzu Corporation. The transmittance of light at 390 nm.

Table 2 shows the measurement results of t-DACH.

[Table 2] t-DACH-1 t-DACH-2 t-DACH-3 t-DACH-4 t-DACH-5 t-DACH-6 XRF Oxygen atom content rate (%) below detection limit below detection limit 2.4128 3.3402 5.1153 7.6294 GC purity(%) 100 100 100 100 100 100 Transmittance @390 nm (%) 83.7 50.1 64 69.1 18.4 9.1

2. Preparation of polyamide acid varnish (Preparation Example 1 to Preparation Example 3, Preparation Example 5 and Preparation Example 6) Add 10.28 g (0.090 mol) of t-DACH in Table 3 and 207.54 g (equivalent to 15% by mass) of NMP in a flask including a thermometer, a condenser, a nitrogen gas inlet tube, and a stirring blade, and place under a humidity of 50%, Stirring was carried out under a nitrogen atmosphere to obtain a homogeneous solution. Thereafter, it was cooled to 15° C., 26.35 g (0.090 mol) of s-BPDA was charged therein in the form of powder, and stirred as it was. After about 1 hour, heat and viscosity increase gradually. As a result of heating up and reacting at an internal temperature of 60°C to 70°C for 1 hour, a uniform solution was obtained. Thereafter, it was cooled to room temperature, and aged overnight at room temperature to obtain a pale yellow viscous varnish.

(preparation example 4) Add 5.71 g (0.050 mol) of t-DACH-4 and 114.05 g (equivalent to 15% by mass) of NMP in a flask including a thermometer, a condenser, a nitrogen gas inlet tube, and a stirring blade, and place it under a humidity of 50% under nitrogen Stir under ambient conditions to make a homogeneous solution. Thereafter, it was cooled to 15° C., 14.42 g (0.050 mol) of s-BPDA was charged therein in the form of powder, and stirred as it was. After about 1 hour, heat and viscosity increase gradually. As a result of heating up and reacting at an internal temperature of 60°C to 70°C for 1 hour, a uniform solution was obtained. Thereafter, it was cooled to room temperature, and aged overnight at room temperature to obtain a pale yellow viscous varnish.

(Measurement of light transmittance) The light transmittance was measured for each polyamide varnish. The polyamic acid varnish prepared by using NMP so that the concentration of polyamic acid becomes 10% by mass is put into a quartz cell with an optical path length of 10 mm, placed inside a desiccator connected to a diaphragm pump, and desiccated in the desiccator. The internal setting was 10.3 kPa, and degassing was performed for 15 minutes. The degassed polyamic acid varnish was measured by UV-visible spectroscopy in the wavelength range of 300 nm to 800 nm using Multi spec-1500 manufactured by Shimadzu Corporation, and a wavelength of 390 nm was obtained. The transmittance of light in nm.

(Determination of intrinsic viscosity) At a polymer concentration of 0.5 g/dL, NMP, and 25°C, the intrinsic viscosity η (dL/g) of the polyamic acid varnish was measured using an Ubbelohde viscosity tube.

3. Imidization and determination (polyimide film 1) The polyamic acid varnish prepared in Preparation Example 1 was coated on a glass substrate with a doctor blade to form a coating film of the polyamic acid varnish. Put the coating film of the polyamic acid varnish together with the substrate into an inert oven, control the oxygen concentration in the inert oven to be below 0.1% by volume, and heat the environment in the oven from 50°C to 280°C for 115 minutes (rate of temperature increase: 2°C/min), and then kept at 280°C for 2 hours. After heating, it was cooled naturally in an inert oven. Thereafter, it was immersed in distilled water, and the formed polyimide film with a thickness of 10 μm was peeled from the substrate. The light transmittance and b* value of the obtained polyimide film were measured.

(polyimide film 2 to polyimide film 6) Except that the polyamic acid varnish was changed to the polyamic acid varnish prepared in Preparation Example 2 to Preparation Example 6, polyimide film 2 to polyimide film 1 were obtained in the same manner as polyimide film 1. film6. The light transmittance and b* value of the obtained polyimide film were measured.

(Measurement of light transmittance) For each polyimide film, the UV-visible spectrum measurement in the wavelength range of 300 nm to 800 nm was performed using Multi spec-1500 manufactured by Shimadzu Corporation, and the transmittance of light with a wavelength of 390 nm was obtained. .

(Determination of b* value) For each polyimide film, use a tristimulus value direct-reading colorimeter (Colour Cute i CC-i type) manufactured by Suga Testing Machine, and measure in the transmission mode and the measurement method 0°di b* value as an index of the yellow hue of the polyimide film.

The light transmittance and intrinsic viscosity of the light with a wavelength of 390 nm of the polyamic acid varnish used to make polyimide films 1 to 6, and the wavelength of the obtained polyimide film at 390 nm The light transmittance and b* value of the light are shown in Table 3.

[table 3] Preparation example 1 2 3 4 5 6 composition Tetracarboxylic acid component type s-BPDA Diamine component type t-DACH-1 t-DACH-2 t-DACH-3 t-DACH-4 t-DACH-5 t-DACH-6 Oxygen atom content rate (%) below detection limit below detection limit 2.4128 3.3402 5.1153 7.6294 GC purity (%) 100 100 100 100 100 100 Transmittance @390 nm (%) 83.7 50.1 64 69.1 18.4 9.1 evaluate varnish Intrinsic viscosity (dL/g) 1.12 1.16 1.14 1.12 0.97 1.12 Transmittance @390 nm (%) 91.3 86.9 83.5 75.7 49.5 51.2 membrane Transmittance @390 nm (%) 81.8 81.7 81.7 80.7 79.3 79.5 b*value (-) 0.87 0.91 0.92 0.97 1.18 1.11 Remark Example Example Example Example comparative example comparative example

As shown in Table 3, it can be seen that the polyamic acid varnishes of Preparation Examples 1 to 4 using a diamine having an oxygen atom content of 4 atomic % or less are higher than those of Preparation Example 5 using a higher oxygen atom content. Compared with the polyamic acid varnish of the diamine of Preparation Example 6, the light transmittance is higher, whereby a polyimide film with high light transmittance and low b* value can be obtained.

This application claims priority based on Japanese Patent Application No. 2021-140251 filed on August 30, 2021. All the content described in this application specification is used for this application specification. [industrial availability]

The polyamic acid varnish of the present invention is suitable for producing a polyimide having a high transmittance of visible light and little coloration. This polyimide can be applied to panel substrates of various display devices.

none

none

Claims (11)

A polyamide varnish comprising: polyamic acid obtained by reacting tetracarboxylic acid with diamine, and a solvent, and Introduced into a tank with an optical path length of 10 mm, and measured after degassing in the tank for 15 minutes, the light transmittance at a wavelength of 390 nm is 70% or more. The polyamic acid varnish as described in claim item 1, wherein, The diamine does not contain oxygen atoms in the molecular structure. The polyamic acid varnish as described in claim 1 or claim 2, wherein, The diamine has an oxygen atom content rate measured by a fluorescent X-ray method (X-ray fluorescence analysis) of 4 atomic % or less. The polyamic acid varnish as described in claim 1 or claim 2, wherein, The polyamic acid is obtained by reacting aromatic tetracarboxylic acid and alicyclic diamine. The polyamic acid varnish as described in claim 1 or claim 2, wherein, The solvent is N-methyl-2-pyrrolidone. The polyamide varnish as described in claim 1 or claim 2, wherein, The b* value in the L*a*b* colorimetric system when it is heated at a heating temperature of 280° C. to form a polyimide film with a thickness of 10 μm is 1.0 or less. The polyamic acid varnish as described in claim 1 or claim 2, wherein, The transmittance of light with a wavelength of 390 nm when heating at a heating temperature of 280°C to form a polyimide film with a thickness of 10 μm is 80% or more. A kind of manufacture method of polyamide acid varnish, comprising: A step of purifying the diamine by recrystallization; and a step of reacting the purified diamine with a tetracarboxylic acid. The manufacture method of polyamide acid varnish as described in claim item 8, wherein, In the step of purifying by the recrystallization method, the oxygen atom content of the diamine measured by a fluorescent X-ray method (X-ray fluorescence analysis) is set to be 4 atomic % or less. The manufacture method of polyamic acid varnish as described in claim item 8 or claim item 9, wherein, The recrystallization method is carried out in a hydrocarbon solvent. The manufacture method of polyamide acid varnish as described in claim item 8 or claim item 9, further comprising: The step of storing the diamine in a container with a light shielding rate of 90% or more at a wavelength of 220 nm to 800 nm, and The stored diamine is purified by the recrystallization method.