KR20230095952A - Polyimide resin, polyimide varnish and polyimide film - Google Patents

Abstract

A polyimide resin comprising structural unit A derived from tetracarboxylic dianhydride and structural unit B derived from diamine, wherein structural unit A is derived from tetracarboxylic dianhydride having two nobonane skeletons in the molecule. It contains unit (A1), structural unit B contains structural unit (B1) derived from the compound represented by the following formula (b1), and the ratio of structural unit (B1) in structural unit B is 35 mol% More than 95 mol% or less, a polyimide resin.

Description

Polyimide resin, polyimide varnish and polyimide film

The present invention relates to polyimide resins, polyimide varnishes and polyimide films.

Various uses of polyimide resins are being studied in fields such as electric and electronic components. For example, it is desired to replace a glass substrate used in an image display device such as a liquid crystal display or an OLED display with a plastic substrate for the purpose of reducing the weight or flexibility of the device, and a polyimide film suitable as the plastic substrate research is in progress.

Films used for image display devices are required to have various optical properties. For example, when light emitted from a display element passes through a plastic substrate and exits, the plastic substrate is required to be transparent.

In order to satisfy the performance as described above, development of polyimide resins having various compositions has been conducted. For example, in Patent Document 1, for the purpose of obtaining a polyimide film excellent in transparency and high heat resistance, an acid dianhydride having a norbonane skeleton and 9,9-bis(4-aminophenyl)fluorene as a diamine component A polyimide film including a structure consisting of a combination of and is disclosed.

Japanese Unexamined Patent Publication No. 2019-059959

Polyimide films are required to replace glass substrates, and transparency is required.

Here, when manufacturing an image display device, for example, since heat treatment is performed in a state in which an inorganic film is laminated on a polyimide film, outgas generated from the polyimide film is accumulated between the layers of the polyimide film and the inorganic film, thereby As a result, coloring such as yellowing may occur on the polyimide film. Therefore, the polyimide film is required to have heat resistance so that discoloration is suppressed when exposed to a high temperature in a state where the inorganic film is laminated.

In addition, when manufacturing an image display device, for example, since the process temperature may exceed 400 ° C., a polyimide film serving as a substrate is required to have heat resistance that can withstand high temperatures of 400 ° C. or higher. A polyimide film having a high glass transition temperature (Tg) and excellent heat resistance may cause problems such as cracks in the inorganic film when exposed to high temperatures in a state in which the inorganic film is laminated. Therefore, the polyimide film is required to have heat resistance that does not cause problems such as cracks in the inorganic film when exposed to high temperatures in a state where the inorganic film is laminated.

The present invention has been made in view of such a situation, and an object of the present invention is a polyimide resin and a polyimide varnish capable of obtaining a polyimide film having excellent heat resistance when transparency and an inorganic film are laminated, and laminating the transparency and an inorganic film. It is providing the polyimide film which was excellent in heat resistance at the time of doing it.

The inventors of the present invention have discovered that a polyimide resin containing a structural unit derived from tetracarboxylic dianhydride having two nobonane skeletons in a molecule and a structural unit derived from a specific diamine can solve the above problems, and the present invention came to complete.

That is, the present invention relates to the following <1> to <12>.

<1> A polyimide resin containing structural unit A derived from tetracarboxylic dianhydride and structural unit B derived from diamine,

Constituent unit A contains a structural unit (A1) derived from tetracarboxylic dianhydride having two nobonane skeletons in the molecule,

Structural unit B contains a structural unit (B1) derived from a compound represented by the following formula (b1),

The polyimide resin whose ratio of the structural unit (B1) in structural unit B is 35 mol% or more and 95 mol% or less.

[Formula 1]

<2> Structural unit (A1) is a structural unit (A11) derived from a compound represented by the following formula (a11), a structural unit (A12) derived from a compound represented by the following formula (a12), a structural unit derived from the following formula (a13) as described in <1>, comprising at least one selected from the group consisting of a structural unit (A13) derived from a compound represented by ) and a structural unit (A14) derived from a compound represented by the following formula (a14) polyimide resin.

[Formula 2]

<3> Structural unit A further includes a structural unit (A2), and the structural unit (A2) is derived from a compound represented by the following formula (a21), and is represented by the following formula (a22): The polyimide resin according to <1> or <2>, containing at least one member selected from the group consisting of structural units (A22) derived from a compound.

[Formula 3]

<4> Structural unit B further contains structural unit (B2), structural unit (B21) derived from a compound represented by the following formula (b21), structural unit (B21) represented by the following formula (b22) From the group consisting of a structural unit (B22) derived from a compound, a structural unit (B23) derived from a compound represented by the following formula (b23), and a structural unit (B24) derived from a compound represented by the following formula (b24) The polyimide resin as described in any one of <1>-<3> containing at least one chosen.

[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

<5> The polyimide resin according to <4>, wherein the structural unit (B2) includes a structural unit (B21) derived from a compound represented by the following formula (b21).

[Formula 8]

<6> A polyimide varnish obtained by dissolving the polyimide resin according to any one of <1> to <5> in an organic solvent.

<7> A polyimide film containing the polyimide resin according to any one of <1> to <5>.

<8> In accordance with JIS K7127: 1999, distance between chucks: 50 mm, test piece size: 10 mm × 70 mm, tensile speed: 20 mm / min, and measurement temperature: tensile break elongation (引張破斷伸び) measured under the conditions of 23 ° C. The polyimide film as described in <7> which is 9.5% or more.

<9> The polyimide film according to <7> or <8>, which has a total light transmittance of 80% or more, as measured in accordance with JIS K7136:2000.

<10> The polyimide film according to any one of <7> to <9>, which is used as a transparent substrate constituting a display device.

<11> A method for producing a polyimide film including a step of removing an organic solvent after applying or molding the polyimide varnish according to <6> into a film.

<12> An image display device comprising the polyimide film according to any one of <7> to <10> as a transparent substrate.

According to the present invention, it is possible to provide a polyimide resin and a polyimide varnish capable of obtaining a polyimide film having excellent transparency and heat resistance when an inorganic film is laminated thereon, and a polyimide film excellent in transparency and heat resistance when an inorganic film is laminated thereon. can

Modes for carrying out the present invention (hereinafter, simply referred to as "this embodiment") will be described in detail. The present embodiment below is an example for explaining the present invention, and does not limit the content of the present invention. This invention can be implemented with appropriate modifications within the scope of the gist. In this embodiment, it can be said that a rule deemed desirable can be arbitrarily employed, and a combination of desirable ones is more desirable. In the present embodiment, description of "XX to YY" means "not less than XX and not more than YY".

[Polyimide resin]

The polyimide resin of the present invention is a polyimide resin comprising structural unit A derived from tetracarboxylic dianhydride and structural unit B derived from diamine, wherein structural unit A has a tetracarboxylic acid dianhydride having two nobonane skeletons in its molecule. It contains a structural unit (A1) derived from carboxylic acid dianhydride, and structural unit B contains a structural unit (B1) derived from a compound represented by the following formula (b1), and the structural unit in structural unit B ( The ratio of B1) is 35 mol% or more and 95 mol% or less.

[Formula 9]

The reason why a polyimide film excellent in transparency and heat resistance when laminated with an inorganic film can be obtained by using the polyimide resin of the present invention is not exactly clear, but it is nonlinear with the norbornane skeleton and has a small molecular weight, that is, already Since it has a structural unit (B1) having a high waste gas concentration, it is possible to improve toughness and heat resistance while maintaining transparency well, so that transparency and heat resistance when inorganic films are laminated (suppression of coloring and cracking of inorganic films) are improved. It is considered excellent.

<Component A>

Structural unit A is a structural unit derived from tetracarboxylic dianhydride occupying a polyimide resin.

Structural unit A includes a structural unit (A1) derived from tetracarboxylic dianhydride having two nobonane skeletons in the molecule.

From the viewpoints of heat resistance, transparency and optical isotropy, the structural unit (A1) is a structural unit (A11) derived from a compound represented by the following formula (a11), a structural unit derived from a compound represented by the following formula (a12) ( A12), a structural unit (A13) derived from a compound represented by the following formula (a13), and a structural unit (A14) derived from a compound represented by the following formula (a14). It is preferable to do this, and the structural unit (A11) derived from the compound represented by the following formula (a11) and the compound derived from the compound represented by the following formula (a12) from the viewpoint of making the molecular skeleton more rigid and improving heat resistance more It is more preferable to include at least one selected from the group consisting of a structural unit (A12) and a structural unit (A14) derived from a compound represented by the following formula (a14), and a compound represented by the following formula (a11) It is more preferable to include at least one selected from the group consisting of a structural unit (A11) derived from and a structural unit (A14) derived from a compound represented by the following formula (a14). It is more preferable to include a structural unit (A11) derived from the indicated compound.

[Formula 10]

When the structural unit A contains the structural unit (A1) derived from tetracarboxylic dianhydride having two nobonane skeletons in the molecule, the heat resistance, transparency and optical isotropy of the obtained polyimide film can be improved.

The structural unit A may further include a structural unit A2 in addition to the structural unit A1. Examples of the structural unit (A2) include a structural unit (A21) derived from a compound represented by the following formula (a21), and a structural unit (A22) derived from a compound represented by the following formula (a22). At least one selected from

[Formula 11]

The compound represented by the formula (a21) is biphenyltetracarboxylic dianhydride (BPDA), and specific examples thereof include 3,3',4,4'-biphenyltetracarb represented by the following formula (a211s) 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a211a), 2 represented by the following formula (a211i): and 2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA). Among them, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a211s) is preferable.

[Formula 12]

The ratio of the structural unit (A1) in the structural unit A is preferably 40 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% from the viewpoints of heat resistance, transparency and optical isotropy. % or more, more preferably 80 mol% or more, still more preferably 85 mol% or more, even more preferably 90 mol% or more, still more preferably 95 mol% or more, still more preferably 99 mol% more than % Although the upper limit of the ratio is not particularly limited, it is 100 mol% or less.

In addition, when structural unit A further contains structural unit (A2), the ratio of structural unit (A2) in structural unit A is preferably 60 mol% or less from viewpoints of heat resistance, transparency, and optical isotropy. , More preferably 40 mol% or less, still more preferably 30 mol% or less, still more preferably 20 mol% or less, still more preferably 15 mol% or less, still more preferably 10 mol% or less , more preferably 5 mol% or less, still more preferably 1 mol% or less. Although the lower limit of the ratio is not particularly limited, it is 0.01 mol% or more.

Structural unit A may also contain structural units other than structural unit (A1) and structural unit (A2). The tetracarboxylic dianhydride that gives such a structural unit is not particularly limited, but 4,4'-oxydiphthalic dianhydride, pyromellitic dianhydride, and 4,4'-(hexafluoroisopropylidene)di aromatic tetracarboxylic dianhydrides such as phthalic anhydride (however, compounds represented by formula (a21) or (a22) are excluded); Alicyclic tetracarboxylic acid dianhydrides such as 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride and 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (however, formulas (a11) to (a14) ) Excluding the compound represented by any one of); and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride.

Meanwhile, in the present specification, an aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more aromatic rings, and an alicyclic tetracarboxylic dianhydride includes one or more alicyclic rings and also an aromatic ring. means a tetracarboxylic dianhydride that does not contain, and the aliphatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride that does not contain either an aromatic ring or an alicyclic ring.

The structural unit arbitrarily included in structural unit A may be one kind or two or more kinds.

<Component B>

Structural unit B is a structural unit derived from diamine occupying the polyimide resin.

The structural unit B includes a structural unit (B1) derived from a compound represented by the following formula (b1).

[Formula 13]

The compound represented by formula (b1) is 1,3-phenylenediamine. When structural unit B contains structural unit (B1), toughness can be improved while heat resistance is maintained.

The ratio of the structural unit (B1) in the structural unit B is 35 mol% or more, preferably 40 mol% or more, more preferably 45 mol% or more, from the viewpoint of improving the heat resistance when the inorganic film is laminated. More preferably, it is 50 mol% or more, More preferably, it is 60 mol% or more. The ratio of the structural unit (B1) in the structural unit B is 95 mol% or less, preferably 90 mol% or less, more preferably 85 mol%, from the viewpoint of improving polymerizability, solubility, transparency and optical isotropy. or less, more preferably 80 mol% or less, still more preferably 75 mol% or less.

The structural unit B may also contain structural units other than the structural unit (B1).

It is preferable that structural unit B further contains structural unit (B2) in addition to structural unit (B1). The structural unit (B2) is, for example, a structural unit (B21) derived from a compound represented by the following formula (b21), a structural unit (B22) derived from a compound represented by the following formula (b22), a structural unit derived from the following formula ( It preferably contains at least one selected from the group consisting of a structural unit (B23) derived from a compound represented by b23) and a structural unit (B24) derived from a compound represented by the following formula (b24). A structural unit (B21) derived from a compound represented by the following formula (b21), and a structural unit (B23) derived from a compound represented by the following formula (b23), from the viewpoint of stiffening the skeleton and further improving heat resistance: It is more preferable to include at least one selected from the group consisting of, and it is more preferable to include a structural unit (B21) derived from a compound represented by the following formula (b21). When the structural unit B contains the structural unit (B2), the heat resistance is particularly improved, and the optical isotropy is further improved. In addition, the solubility of the imidized resin is improved by the structural unit (B2), and the polymerization can proceed more effectively.

[Formula 14]

[Formula 15]

[Formula 16]

[Formula 17]

When the structural unit B further contains the structural unit (B2), the ratio of the structural unit (B2) in the structural unit B is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably It is preferably 15 mol% or more, more preferably 20 mol% or more, and more preferably 25 mol% or more. The upper limit of the ratio is 65 mol% or less, preferably 60 mol% or less, more preferably 55 mol% or less, still more preferably 50 mol% or less, still more preferably 40 mol% or less.

When structural unit B further contains structural unit (B2), the ratio of the total of structural unit (B1) and structural unit (B2) in structural unit B is preferably 50 mol% or more, more preferably is 70 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% or more, still more preferably 99 mol% or more. The upper limit of the ratio of the total of the structural units (B1) and (B2) in the structural unit B is not particularly limited, and is, for example, 100 mol% or less. The structural unit B may consist of only the structural unit (B1) and the structural unit (B2).

When structural unit B further contains structural unit (B2), the molar ratio [(B1)/(B2)] of structural unit (B1) to structural unit (B2) in structural unit B is , From the viewpoint of improving toughness and heat resistance, it is preferably 35/65 to 95/5, more preferably 40/60 to 90/10, still more preferably 45/55 to 85/15, still more preferably It is preferably 50/50 to 80/20, more preferably 60/40 to 75/25.

Structural unit B may also contain structural units other than structural unit (B1) and structural unit (B2). The diamine giving such a structural unit is not particularly limited, but 1,4-phenylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4' -Diamine, 4,4'-diaminodiphenyl ether, 4,4'-diamino-2,2'-bistrifluoromethyldiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4 '-Diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-inden-5-amine, α,α'-bis(4-aminophenyl) )-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis[4- (4-aminophenoxy)phenyl]propane, and aromatic diamines such as 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane (however, formulas (b1), (b21) to ( b24) Excluding the compound represented by any one); alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.

Meanwhile, in the present specification, aromatic diamine means diamine containing one or more aromatic rings, and alicyclic diamine means diamine containing one or more alicyclic rings and not containing aromatic rings. Aliphatic diamine means diamine containing one or more alicyclic rings. It means diamine containing neither an aromatic ring nor an alicyclic ring.

The structural unit arbitrarily included in structural unit B may be one type or two or more types.

<Characteristics of polyimide resin>

The weight average molecular weight of the polyimide resin is preferably 5,000 to 300,000 from the viewpoint of mechanical strength of the polyimide film obtained. On the other hand, the weight average molecular weight of the polyimide resin can be determined, for example, from a standard polymethyl methacrylate (PMMA) conversion value measured by gel filtration chromatography.

The polyimide resin may also contain structures other than the polyimide chain (a structure formed by imide bonding of structural units A and B). Examples of structures other than the polyimide chain that can be contained in the polyimide resin include structures containing an amide bond.

The polyimide resin preferably contains, as a main structure, a polyimide chain (a structure obtained by imide bonding of structural units A and B). Therefore, the proportion of the polyimide chain in the polyimide resin is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and particularly preferably 99% by mass. or more, and is 100% by mass or less. The polyimide resin may consist only of a polyimide chain.

The polyimide resin composition containing the polyimide resin can form a polyimide film having excellent toughness and heat resistance while maintaining transparency and optical isotropy, and suitable physical property values of the polyimide film are as follows.

The total light transmittance is preferably 80% or more, more preferably 85% or more, still more preferably 88% or more, still more preferably 88.5% or more when the polyimide resin is used as a film with a thickness of 10 μm. , more preferably 89% or more.

The yellow index (YI) is preferably 10.0 or less, more preferably 5.0 or less, still more preferably 3.0 or less, even more preferably 2.5 or less, when a polyimide resin is used as a film with a thickness of 10 μm. , more preferably 2.0 or less.

The absolute value of the thickness retardation (Rth) is preferably 200 nm or less, more preferably 180 nm or less, still more preferably 160 nm or less, still more preferably 140 nm or less, when a polyimide resin is used as a film with a thickness of 10 μm. am.

In addition, the film that can be formed using the polyimide resin has good mechanical properties and heat resistance, and has suitable physical property values as described below.

The tensile strength is preferably 70 MPa or more, more preferably 80 MPa or more, still more preferably 90 MPa or more, when the polyimide resin is used as a film having a thickness of 10 μm.

The tensile modulus of elasticity is preferably 1.0 GPa or more, more preferably 1.5 GPa or more, still more preferably 2.0 GPa or more, still more preferably 2.3 GPa or more when the polyimide resin is used as a film having a thickness of 10 μm.

The tensile elongation at break is preferably 9.5% or more, more preferably 10.0% or more, still more preferably 10.5% or more when the polyimide resin is used as a film having a thickness of 10 μm. The upper limit of tensile elongation at break is preferably 20.0% or less, more preferably 15.0% or less, still more preferably 13.5% or less.

The glass transition temperature (Tg) is preferably 380°C or higher, more preferably 400°C or higher, still more preferably 410°C or higher.

The 5% weight loss temperature (Td5%) is preferably 460°C or higher, more preferably 470°C or higher, still more preferably 480°C or higher.

The heat resistance when the inorganic film is laminated is preferable when a 300 nm thick SiO ₂ film is formed on a polyimide film by sputtering, and an ITO (indium tin oxide) film is formed thereon to form a lamination film with a thickness of 1230 nm. "400 ° C., 1 hour annealing treatment" does not cause problems such as cracks and yellowing in the laminated film, more preferably "420 ° C., 1 hour annealing treatment" does not cause cracks, yellowing, etc. in the laminated film that no problem occurs.

On the other hand, the above-mentioned physical property values in the present invention can be specifically measured by the method described in Examples.

<Method for producing polyimide resin>

The polyimide resin of the present invention can be produced by reacting a tetracarboxylic acid component containing a compound imparting the above-mentioned structural unit (A1) with a compound imparting the above-mentioned structural unit (B1).

Examples of the compound imparting the structural unit (A1) include compounds represented by any one of formulas (a11) to (a14), but are not limited thereto, and may be derivatives thereof within the scope of imparting the same structural unit. there is. Examples of the derivative include tetracarboxylic acids corresponding to tetracarboxylic dianhydrides represented by any of formulas (a11) to (a14), and alkyl esters of the tetracarboxylic acids. Especially, tetracarboxylic dianhydride represented by formula (a11) is preferable.

The tetracarboxylic acid component may further contain a compound providing the structural unit (A2) in addition to the compound providing the structural unit (A1).

The compound giving the structural unit (A2) includes a compound represented by formula (a21), a compound represented by formula (a22), etc. It may be a derivative.

The tetracarboxylic acid component contains preferably 40 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% of the compound that gives the structural unit (A1). or more, more preferably 85 mol% or more, still more preferably 90 mol% or more, still more preferably 95 mol% or more, still more preferably 99 mol% or more. Although the upper limit of the ratio is not particularly limited, it is 100 mol% or less.

The tetracarboxylic acid component may contain any compound other than the compound providing the structural unit (A1) and the compound providing the structural unit (A2).

Examples of such optional compounds include the above-mentioned aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aliphatic tetracarboxylic dianhydride, and derivatives thereof (tetracarboxylic acid, alkyl ester of tetracarboxylic acid, etc.) can be heard

The compound optionally included in the tetracarboxylic acid component may be one type or two or more types.

Examples of the compound imparting the structural unit (B1) include compounds represented by formula (b1), but are not limited thereto, and may be derivatives thereof within the scope of imparting the same structural unit. Examples of the derivative include diisocyanate corresponding to the compound represented by formula (b1). As a compound which gives structural unit (B1), the compound represented by formula (b1) (namely, diamine) is preferable.

The diamine component may contain a compound that imparts the structural unit (B2) in addition to the compound that imparts the structural unit (B1). Examples of the compound giving the constituent unit (B2) include compounds represented by formula (b21), compounds represented by formula (b22), compounds represented by formula (b23), and compounds represented by formula (b24). It may be, but is not limited thereto, and may be a derivative thereof within the scope of giving the same structural unit. Examples of the derivative include diisocyanates corresponding to the compound represented by formula (b21), the compound represented by formula (b22), the compound represented by formula (b23), and the compound represented by formula (b24). As the compound giving the structural unit (B2), the compound represented by formula (b21), the compound represented by formula (b22), the compound represented by formula (b23), and the compound represented by formula (b24) (i.e., diamine) is preferred.

The diamine component is 35 mol% or more, preferably 40 mol% or more, more preferably 45 mol% or more, still more preferably 50 mol% or more, still more preferably It contains 60 mol% or more. The upper limit of the ratio is 95 mol% or less, preferably 90 mol% or less, more preferably 85 mol% or less, still more preferably 80 mol% or less, still more preferably 75 mol% or less.

When the diamine component contains a compound imparting the structural unit (B2), the compound imparting the structural unit (B2) is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 15 mol% or more, more preferably 20 mol% or more, more preferably 25 mol% or more. The upper limit of the ratio is 65 mol% or less, preferably 60 mol% or less, more preferably 55 mol% or less, still more preferably 50 mol% or less, still more preferably 40 mol% or less.

When the diamine component contains the compound providing the structural unit (B2), the compound providing the structural unit (B1) and the compound providing the structural unit (B2) are included in a total amount, preferably 50 mol% or more, , More preferably 70 mol% or more, still more preferably 90 mol% or more, still more preferably 95 mol% or more, still more preferably 99 mol% or more. The upper limit is not particularly limited, and the diamine component contains, for example, 100 mol% or less in total of the compound providing the structural unit (B1) and the compound providing the structural unit (B2). The diamine component may consist only of the compound which provides structural unit (B1) and the compound which provides structural unit (B2).

The molar ratio [(B1)/(B2)] of the compound giving the structural unit (B1) and the compound giving the structural unit (B2) in the diamine component is the polymerizability, solubility, transparency, optical isotropy, toughness and heat resistance. From the viewpoint of improving, preferably 35/65 to 95/5, more preferably 40/60 to 90/10, even more preferably 45/55 to 85/15, still more preferably 50/60 It is 50 to 80/20, more preferably 60/40 to 75/25.

The diamine component may further contain an arbitrary compound other than the compound providing the structural unit (B1) and the compound providing the structural unit (B2).

Examples of such optional compounds include the above-mentioned aromatic diamines, alicyclic diamines, and aliphatic diamines, and derivatives thereof (such as diisocyanates).

1 type may be sufficient as the compound contained arbitrarily in a diamine component, and 2 or more types may be sufficient as it.

In the production of the polyimide resin of the present invention, the ratio of the amount of the tetracarboxylic acid component and the diamine component used in the production of the polyimide resin is preferably 0.9 to 1.1 mol of the diamine component per 1 mol of the tetracarboxylic acid component.

Further, in the production of the polyimide resin of the present invention, in addition to the tetracarboxylic acid component and the diamine component described above, an end capping agent can also be used for the production of the polyimide resin. As the end capping agent, monoamines or dicarboxylic acids are preferable. The amount of the end capping agent to be introduced is preferably 0.0001 to 0.1 mole, more preferably 0.001 to 0.06 mole per mole of the tetracarboxylic acid component. Examples of the monoamine endcapping agent include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine , 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. are mentioned, and benzylamine and aniline are preferable. As the dicarboxylic acid endcapping agent, dicarboxylic acids are preferable, and some of them may be ring-closing. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenone dicarboxylic acid, 3,4-benzophenone dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, Cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, etc. are mentioned, and phthalic acid and phthalic anhydride are preferable.

The method for reacting the tetracarboxylic acid component and the diamine component described above is not particularly limited, and a known method can be used.

As a specific reaction method, (1) a method of introducing a tetracarboxylic acid component, a diamine component, and a reaction solvent into a reactor, stirring at 0 to 10 ° C. for 0.5 to 30 hours, and then raising the temperature to perform an imidation reaction, ( 2) After dissolving the diamine component and the reaction solvent in a reactor, the tetracarboxylic acid component is added, stirred at room temperature of 0 to 10 ° C. for 0.5 to 30 hours as necessary, and then the temperature is raised to perform an imidation reaction. , (3) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are introduced into a reactor, and the temperature is raised immediately to carry out an imidation reaction.

The reaction solvent used for production of the polyimide resin may be one capable of dissolving the polyimide to be produced without inhibiting the imidation reaction. Examples thereof include aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

Specific examples of the aprotic solvent include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), N-methylcaprolactam, and 1,3-dimethyl Amide-based solvents such as imidazolidinone and tetramethylurea, lactone-based solvents such as γ-butyrolactone (GBL) and γ-valerolactone, phosphorus-containing solvents such as hexamethylphosphoricamide and hexamethylphosphinetriamide Amide-based solvents, sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane, ketone-based solvents such as acetone, cyclohexanone, and methylcyclohexanone, amine-based solvents such as picoline and pyridine, acetic acid (2-methyl ester solvents such as oxy-1-methylethyl); and the like.

Specific examples of the phenolic solvent include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6 -Xylenol, 3,4-xylenol, 3,5-xylenol, etc. are mentioned.

Specific examples of the ether solvent include 1,2-dimethoxyethane, bis(2-methoxyethyl) ether, 1,2-bis(2-methoxyethoxy)ethane, and bis[2-(2-methoxyethyl) ether. oxyethoxy) ethyl] ether, tetrahydrofuran, 1,4-dioxane, and the like.

In addition, specific examples of the carbonate-based solvent include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate.

Among the above reaction solvents, aprotic solvents are preferred, amide solvents and lactone solvents are more preferred, and lactone solvents are still more preferred. In addition, the above reaction solvents may be used alone or in combination of two or more.

In the imidation reaction, it is preferable to carry out the reaction while removing water generated during production using a Dean Stark apparatus or the like. By performing such an operation, the degree of polymerization and the imidation rate can be further increased.

In the above imidation reaction, a known imidation catalyst can be used. Examples of the imidation catalyst include base catalysts and acid catalysts.

Examples of the base catalyst include pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine (TEA), tripropylamine, Organic base catalysts such as tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, N,N-diethylaniline, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, etc. of inorganic base catalysts.

Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methyl benzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. The above imidation catalysts may be used alone or in combination of two or more.

Among the above, from the viewpoint of handleability, it is preferable to use a base catalyst, more preferably an organic base catalyst, and even more preferable to use triethylamine or triethylenediamine.

The temperature of the imidation reaction is preferably 120 to 250°C, more preferably 160 to 200°C, from the viewpoint of reaction rate and suppression of gelation and the like. In addition, the reaction time is preferably 0.5 to 10 hours after the outflow of generated water starts.

[Polyimide varnish]

The polyimide varnish of the present invention is obtained by dissolving the polyimide resin of the present invention in an organic solvent. That is, the polyimide varnish of the present invention contains the polyimide resin of the present invention and an organic solvent, and the polyimide resin is dissolved in the organic solvent.

The organic solvent may be any organic solvent capable of dissolving the polyimide resin, and is not particularly limited, but it is preferable to use the above compounds alone or in a mixture of two or more as the reaction solvent used for producing the polyimide resin.

The polyimide varnish of the present invention may be a polyimide solution itself in which a polyimide resin obtained by a polymerization method is dissolved in a reaction solvent, or may be a product diluted by adding a solvent to the polyimide solution.

Since the polyimide resin of the present invention has solvent solubility, it can be used as a high-concentration varnish stable at room temperature. It is preferable that the polyimide varnish of this invention contains 5-40 mass % of the polyimide resin of this invention, and it is more preferable that it contains 5-20 mass %. The viscosity of the polyimide varnish is preferably 1 to 200 Pa·s, and more preferably 1 to 100 Pa·s. The viscosity of the polyimide varnish is a value measured at 25°C using an E-type viscometer.

In addition, the polyimide varnish of the present invention is an inorganic filler, an adhesion promoter, a release agent, a flame retardant, a UV stabilizer, a surfactant, a leveling agent, an antifoaming agent, an optical brightening agent, a crosslinking agent, Various additives such as polymerization initiators and photosensitizers may be included.

The manufacturing method of the polyimide varnish of this invention is not specifically limited, A well-known method can be applied.

[Polyimide film]

The polyimide film of the present invention contains the polyimide resin of the present invention. Therefore, the polyimide film of the present invention is excellent in heat resistance, transparency, toughness, optical isotropy, peelability and chemical resistance. Suitable physical property values of the polyimide film of the present invention are as described above as <characteristics of polyimide resin>.

The method for producing the polyimide film of the present invention is not particularly limited, and known methods can be used. For example, after applying the polyimide varnish of the present invention in the form of a film on a smooth support such as a glass plate, metal plate, or plastic, or molding it into a film form, organic solvents such as reaction solvents and diluting solvents contained in the varnish are applied. The method of removing a solvent by heating, etc. are mentioned. As the method for producing the polyimide film of the present invention, a method including a step of removing the organic solvent after applying or molding the polyimide varnish into a film is preferable.

Examples of the coating method include known coating methods such as spin coating, slit coating, and blade coating, and spin coating and slit coating are preferable. Among them, a slit coat is more preferable from the viewpoint of improving chemical resistance by controlling intermolecular orientation and workability.

As a method of removing the organic solvent contained in the varnish by heating, the organic solvent is evaporated at a temperature of 150 ° C. or less to make it tack-free, and then the temperature above the boiling point of the organic solvent used (not particularly limited, but preferably 200 ~500 °C) is preferred. In addition, it is preferable to dry under an air atmosphere or a nitrogen atmosphere. Any of reduced pressure, normal pressure, and pressurization may be sufficient as the pressure of dry atmosphere.

The method of peeling the polyimide film formed on the support from the support is not particularly limited, but a mechanical peel-off method, a laser lift-off method, or the like can be used.

Further, the polyimide film of the present invention can also be produced using a polyamic acid varnish obtained by dissolving polyamic acid in an organic solvent.

The polyamic acid contained in the polyamic acid varnish is a precursor of the polyimide resin of the present invention, comprising a tetracarboxylic acid component containing a compound imparting the above-mentioned structural unit (A1), and the above-mentioned structural unit (B1 ) It is a product of polyaddition of a diamine component containing a compound that gives By imidating (dehydration ring closure) this polyamic acid, the final product, the polyimide resin of the present invention, is obtained.

As the organic solvent contained in the polyamic acid varnish, the organic solvent contained in the polyimide varnish of the present invention can be used.

In the production of the polyimide film of the present invention, the polyamic acid varnish may be a polyamic acid solution itself obtained by subjecting a tetracarboxylic acid component and a diamine component to a polyaddition reaction in a reaction solvent, or the polyamic acid solution It may be diluted by further adding a solvent.

The method for producing the polyimide film using the polyamic acid varnish is not particularly limited, and a known method can be used. For example, a polyamic acid varnish is applied in the form of a film on a smooth support such as a glass plate, metal plate, or plastic, or molded into a film form, and an organic solvent such as a reaction solvent or a diluting solvent contained in the varnish is heated. A polyimide film can be manufactured by removing and obtaining a polyamic acid film, and imidating the polyamic acid in the polyamic acid film by heating.

The heating temperature when drying the polyamic acid varnish to obtain a polyamic acid film is preferably 50 to 120°C. The heating temperature when imidizing the polyamic acid by heating is preferably 200 to 450°C.

On the other hand, the method of imidation is not limited to thermal imidation, and chemical imidation can also be applied.

The thickness of the polyimide film of the present invention can be appropriately selected depending on the application, etc., and is preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, still more preferably 8 to 80 μm, and still more preferably 10 to 80 μm. am. When the thickness is 1 to 250 μm, practical use as a self-supporting film becomes possible.

The thickness of the polyimide film can be easily controlled by adjusting the solid content concentration and viscosity of the polyimide varnish.

In the polyimide film of the present invention, tensile break elongation measured in accordance with JIS K7127: 1999 under the conditions of chuck distance: 50 mm, test piece size: 10 mm × 70 mm, tensile speed: 20 mm/min, and measurement temperature: 23 ° C. Silver is preferably 9.5% or more, more preferably 10.0% or more, still more preferably 10.5% or more from the viewpoint of further suppressing cracking of the inorganic film when the inorganic film is exposed to a high temperature in a laminated state. The upper limit of tensile elongation at break is preferably 20.0% or less, more preferably 15.0% or less, still more preferably 13.5% or less.

In the polyimide film of the present invention, the total light transmittance measured in accordance with JIS K7136: 2000 is preferably 80% or more, more preferably 85% or more, still more preferably from the viewpoint of further improving transparency. 88% or more, more preferably 88.5% or more, still more preferably 89% or more.

The polyimide film of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor components, optical members, solar cells, and image display devices, and is particularly suitable as a transparent substrate constituting these devices. used The polyimide film of this invention is used especially suitably as a transparent substrate which comprises image display apparatuses, such as a liquid crystal display, an OLED display, and a touch panel.

[Image display device]

The image display device of the present invention includes the polyimide film of the present invention as a transparent substrate.

An image display device of the present invention includes, for example, a transparent substrate made of the polyimide film of the present invention and a display portion provided on the transparent substrate.

The display unit is not particularly limited, but, for example, TFT elements, organic EL elements, color filters, LEDs, transistors, electron emission elements, electronic ink, electrophoretic elements, GLV (grating light valves), MEMS (micro-electro- Display element using mechanical system), DMD (digital micromirror device), DMS (digital micro shutter), IMOD (interferometric modulation) element, electrowetting element, piezoelectric ceramic display, display using carbon nanotube A small element etc. are mentioned.

As an image display apparatus of this invention, a liquid crystal display, an OLED display, a touch panel etc. are mentioned, for example.

The image display device of the present invention can be manufactured based on known information except for using the polyimide film of the present invention as a transparent substrate.

The image display device of the present invention uses the polyimide film of the present invention, which has excellent heat resistance when inorganic films are laminated thereon, as a transparent substrate, so cracks of the inorganic film and discoloration of the transparent substrate are less likely to occur, and reliability is excellent.

Example

Hereinafter, the present invention will be specifically described by examples. However, the present invention is not limited at all by these examples.

<Film properties and evaluation>

Each physical property of the films obtained in Examples and Comparative Examples was measured according to the method shown below.

(1) Film thickness

The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation.

(2) Tensile strength, tensile modulus, and tensile elongation at break

Tensile strength, tensile modulus and tensile elongation at break were measured in accordance with JIS K7127:1999 using a tensile tester "Strograph VG-1E" manufactured by Toyo Seiki Co., Ltd. The distance between the chucks was 50 mm, the size of the test piece was 10 mm × 70 mm, the test speed (tensile speed) was 20 mm / min, and the measurement temperature was 23 ° C.

(3) Glass transition temperature (Tg)

Using a thermomechanical analyzer "TMA/SS6100" manufactured by Hitachi High-Tech Science Co., Ltd., a sample size of 3 mm × 20 mm in tensile mode, a load of 0.1 N, and a heating rate of 10 ° C / min, at a temperature sufficient to remove residual stress. The temperature was raised to remove residual stress, and then cooled to room temperature. After that, the elongation of the test piece was measured under the same conditions as the treatment for removing the residual stress, and the inflection point of the elongation was extrapolated to determine the glass transition temperature.

(4) Total light transmittance, and yellow index (YI)

The total light transmittance was based on JIS K7136: 2000, and YI was measured based on ASTM E313-05 (D light source, 65°) using a color and turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku Kogyo Co., Ltd., respectively.

(5) 5% weight reduction temperature (Td5%)

A differential thermal gravimetric simultaneous measuring device "NEXTA STA200RV" manufactured by Hitachi High-Tech Science Co., Ltd. was used. The temperature of the sample was raised to 40 to 150 °C at a heating rate of 10 °C/min, maintained at 150 °C for 30 minutes to remove moisture, and then heated to 510 °C. Compared to the weight after holding at 150 ° C. for 30 minutes, the temperature when the weight decreased by 5% was set as the 5% weight loss temperature. The higher the weight loss temperature, the better the heat resistance.

(6) Thickness phase difference (Rth) (evaluation of optical isotropy)

The thickness retardation (Rth) was measured using an ellipsometer "M-220" manufactured by Nippon Spectroscopy Corporation. The value of the thickness phase difference in the measurement wavelength of 590 nm was measured. On the other hand, Rth is expressed by the following formula when nx is the largest in-plane refractive index of the polyimide film, ny is the smallest refractive index, nz is the refractive index in the thickness direction, and d is the thickness of the film.

Rth=[{(nx+ny)/2}-nz]×d

(7) Evaluation of heat resistance of laminated film

In imitation of the manufacturing process of the image display device, a laminated film was produced, and the heat resistance of the laminated film was evaluated. The laminated film was prepared as follows.

Without peeling the polyimide films obtained in Examples and Comparative Examples from the glass plate, a SiO ₂ film having a thickness of 300 nm was formed on the polyimide film by sputtering, and an ITO (indium tin oxide) film having a thickness of 1230 nm was formed thereon and laminated thereon. got a stop

Then, annealing (heating) was performed on the obtained laminated film at 400°C for 1 hour.

The presence or absence of problems (crack, yellowing, etc.) of the laminated film before and after annealing was visually observed, and the heat resistance of the polyimide film (laminated film) laminated with the inorganic film was evaluated according to the following criteria.

○: Problems such as cracks and yellowing do not occur in the laminated film before and after annealing.

× (crack or yellowing): problems such as cracks and yellowing occur in the laminated film before and after annealing

If there is no problem, the polyimide film is excellent in heat resistance when an inorganic film is laminated thereon.

<abbreviation of ingredients, etc.>

The tetracarboxylic acid component and diamine component used in Examples and Comparative Examples, and their symbols are as follows.

(Tetracarboxylic acid component)

CpODA: Norbonane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (manufactured by ENEOS Co., Ltd.; Formula Compound represented by (a11))

BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation, compound represented by formula (a211s) (s-BPDA))

BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene diacid anhydride (manufactured by JFE Chemical Co., Ltd.; compound represented by formula (a22))

(diamine component)

MPD: 1,3-phenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.; compound represented by formula (b1))

BAFL: 9,9-bis(4-aminophenyl)fluorene (manufactured by JFE Chemical Co., Ltd.; compound represented by formula (b21))

TFMB: 2,2'-bis(trifluoromethyl)benzidine (manufactured by Seika Corporation; compound represented by formula (b22))

PPD: 1,4-phenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.)

<Preparation of polyimide resin, varnish and polyimide film>

Example 1

In a 500 mL five-necked round bottom flask equipped with a stainless steel half-moon-shaped stirring blade, nitrogen inlet tube, Dean Stark with cooling tube, thermometer, and glass end cap, 5.407 g (0.050 mol) of MPD and 17.423 g (0.050 mol) of BAFL ), and 73.521 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added, and stirred at a rotation speed of 200 rpm under a nitrogen atmosphere at a system temperature of 70° C. to obtain a solution.

To this solution, 38.438 g (0.100 mol) of CpODA and 18.380 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added all at once, and then 0.506 g of triethylamine (manufactured by Kanto Chemical Co., Ltd.) as an imidation catalyst, 0.056 g of triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, heated with a mantle heater, and the temperature within the reaction system was raised to 190°C over about 20 minutes. The distilled-off components were collected, and the reaction system was refluxed for 3 hours while maintaining the temperature inside the reaction system at 190°C while adjusting the number of revolutions according to the increase in viscosity.

Thereafter, γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) was added so that the solid content concentration was 15% by mass, and the temperature inside the reaction system was cooled to 100° C., and then stirred for about 1 hour to homogenize to obtain a polyimide varnish. .

Subsequently, the obtained polyimide varnish was applied on a glass plate by spin coating, maintained at 80° C. for 20 minutes on a hot plate, and then heated in a nitrogen atmosphere at 400° C. in a hot air dryer for 30 minutes (heating rate 5 °C/min), and the solvent was evaporated to obtain a film.

Example 2

Same as Example 1 except that the amount of MPD was changed from 5.407 g (0.050 mole) to 7.570 g (0.070 mole) and the amount of BAFL was changed from 17.423 g (0.050 mole) to 10.454 g (0.030 mole). According to the method, a polyimide varnish having a solid content concentration of 15% by mass was obtained.

A film was obtained in the same manner as in Example 1 using the obtained polyimide varnish.

Example 3

Same as Example 1 except that the amount of MPD was changed from 5.407 g (0.050 mole) to 8.651 g (0.080 mole) and the amount of BAFL was changed from 17.423 g (0.050 mole) to 6.969 g (0.020 mole). According to the method, a polyimide varnish having a solid content concentration of 15% by mass was obtained.

A film was obtained in the same manner as in Example 1 using the obtained polyimide varnish.

Example 4

The amount of CpODA was changed from 38.438 g (0.100 mole) to 30.750 g (0.080 mole), 5.885 g (0.020 mole) of BPDA was used, and the amount of MPD was changed from 5.407 g (0.050 mole) to 6.488 g (0.060 mole). A polyimide varnish having a solid content concentration of 15% by mass was obtained in the same manner as in Example 1, except that the amount of BAFL was changed from 17.423 g (0.050 mol) to 13.938 g (0.040 mol).

A film was obtained in the same manner as in Example 1 using the obtained polyimide varnish.

Example 5

The amount of CpODA was changed from 38.438 g (0.100 mole) to 34.594 g (0.090 mole), 4.584 g (0.010 mole) of BPAF was used, and the amount of MPD was changed from 5.407 g (0.050 mole) to 6.488 g (0.060 mole). A polyimide varnish having a solid content concentration of 15% by mass was obtained in the same manner as in Example 1, except that the amount of BAFL was changed from 17.423 g (0.050 mol) to 13.938 g (0.040 mol).

A film was obtained in the same manner as in Example 1 using the obtained polyimide varnish.

Comparative Example 1

A polyimide varnish having a solid content concentration of 15% by mass was obtained in the same manner as in Example 1, except that MPD was not used and the amount of BAFL was changed from 17.423 g (0.050 mol) to 34.845 g (0.100 mol). .

A film was obtained in the same manner as in Example 1 using the obtained polyimide varnish.

Comparative Example 2

The amount of CpODA was changed from 38.438 g (0.100 mole) to 23.063 g (0.060 mole), 11.769 g (0.040 mole) of BPDA was used, no MPD was used, and the amount of BAFL was changed from 17.423 g (0.050 mole) to 13.938 A polyimide varnish having a solid content concentration of 15% by mass was obtained in the same manner as in Example 1, except that it was changed to g (0.040 mol) and 19.214 g (0.060 mol) of TFMB was used.

A film was obtained in the same manner as in Example 1 using the obtained polyimide varnish.

Comparative Example 3

The amount of CpODA was changed from 38.438 g (0.100 mole) to 34.594 g (0.090 mole), BPAF was used at 4.584 g (0.010 mole), no MPD was used, and the amount of BAFL was changed from 17.423 g (0.050 mole) to 15.680 A polyimide varnish having a solid content concentration of 15% by mass was obtained in the same manner as in Example 1, except that it was changed to g (0.045 mol) and 17.613 g (0.055 mol) of TFMB was used.

A film was obtained in the same manner as in Example 1 using the obtained polyimide varnish.

Comparative Example 4

Synthesis was attempted in the same manner as in Example 2, except that 7.570 g (0.070 mol) of MPD was changed to 7.570 g (0.070 mol) of PPD, but after adding the imidation catalyst, the temperature was raised to 190 ° C. A solid precipitated along with the drying, and a polyimide varnish was not obtained.

Comparative Example 5

10.814 g (0.100 mol) of MPD and 182.403 g of NMP were added to a 300 mL 5-necked round bottom flask equipped with a stainless steel half-moon-shaped stirring blade, a nitrogen inlet tube, a Dean Stark with a cooling tube, a thermometer, and a glass end cap. , The solution was obtained by stirring at a rotational speed of 200 rpm under a nitrogen atmosphere at a system internal temperature of 25°C.

To this solution, 29.422 g (0.100 mol) of BPDA and 45.601 g of NMP were charged at once and stirred for 3 hours to obtain a polyamic acid varnish having a solid content concentration of 15.0% by mass.

Subsequently, the obtained polyamic acid varnish was applied on a glass plate by spin coating, maintained at 80° C. for 20 minutes on a hot plate, and then heated in a nitrogen atmosphere at 430° C. in a hot air dryer for 60 minutes (heating rate 5°C/min), and the solvent was evaporated to obtain a film.

Comparative Example 6

A polyimide varnish having a solid content concentration of 15% by mass was obtained in the same manner as in Example 1, except that MPD was not used as the diamine and 16.012 g (0.050 mol) of TFMB was used.

A film was obtained in the same manner as in Example 1 using the obtained polyimide varnish.

Comparative Example 7

The synthesis was attempted in the same manner as in Example 1, except that the amount of MPD was changed from 5.407 g (0.050 mol) to 10.814 g (0.100 mol) and BAFL was not used, but after adding the imidation catalyst, In the process of raising the temperature to 190 ° C., solids were precipitated along with imidation, so that polyimide varnish was not obtained.

The above physical properties were measured and evaluated for the polyimide films obtained in Examples and Comparative Examples. The obtained results are shown in Table 1.

[Table 1]

As shown in Table 1, the polyimide films of Examples were excellent in transparency and heat resistance when an inorganic film was laminated thereon. In addition, it can be seen that the polyimide films of Examples have good optical isotropy. Comparative Examples 1 and 6 were excellent in optical isotropy, but inferior in heat resistance of the laminated film. Comparative Example 2 was inferior in optical isotropy and heat resistance of the laminated film. In Comparative Example 3, the heat resistance of the laminated film was inferior. In Comparative Examples 4 and 7, since the solubility of the imidized resin was poor and precipitated, polymerization did not proceed thereafter and polyimide varnish could not be obtained. In Comparative Example 5, transparency, optical isotropy, and heat resistance of the laminated film were all inferior.

Therefore, a polyimide film prepared using an acid dianhydride having two nobonane skeletons in a molecule as a tetracarboxylic acid component and MPD as a diamine component is a liquid crystal film with excellent transparency, optical isotropy, and heat resistance of a laminated film. It can be suitably used as a transparent substrate constituting display devices such as displays, OLED displays, and touch panels.

Claims (12)

A polyimide resin containing structural unit A derived from tetracarboxylic dianhydride and structural unit B derived from diamine,
The structural unit A includes a structural unit (A1) derived from tetracarboxylic dianhydride having two nobonane skeletons in the molecule,
The structural unit B contains a structural unit (B1) derived from a compound represented by the following formula (b1),
The polyimide resin whose ratio of the said structural unit (B1) in the said structural unit B is 35 mol% or more and 95 mol% or less.
[Formula 1]

According to claim 1,
The structural unit (A1) is a structural unit (A11) derived from a compound represented by the following formula (a11), a structural unit (A12) derived from a compound represented by the following formula (a12), and a structural unit derived from the following formula (a13). A polyimide resin comprising at least one member selected from the group consisting of a structural unit (A13) derived from a compound represented by a structural unit (A13) derived from a compound represented by the following formula (a14), and a structural unit (A14) derived from a compound represented by the following formula (a14).
[Formula 2]

According to claim 1 or 2,
The structural unit A further includes a structural unit (A2), and the structural unit (A2) is derived from a compound represented by the following formula (a21), and a structural unit (A21) represented by the following formula (a22) A polyimide resin containing at least one selected from the group consisting of structural units (A22) derived from compounds.
[Formula 3]

According to any one of claims 1 to 3,
The structural unit B further includes a structural unit (B2), and the structural unit (B2) is derived from a compound represented by the following formula (b21), a structural unit (B21), a compound represented by the following formula (b22) Selected from the group consisting of a structural unit derived from (B22), a structural unit derived from a compound represented by the following formula (b23) (B23), and a structural unit derived from a compound represented by the following formula (b24) (B24) Polyimide resin containing at least one which becomes.
[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

According to claim 4,
The polyimide resin in which the said structural unit (B2) contains the structural unit (B21) derived from the compound represented by the following formula (b21).
[Formula 8]

A polyimide varnish obtained by dissolving the polyimide resin according to any one of claims 1 to 5 in an organic solvent. A polyimide film comprising the polyimide resin according to any one of claims 1 to 5. According to claim 7,
Based on JIS K7127: 1999, distance between chucks: 50 mm, test piece size: 10 mm × 70 mm, tensile speed: 20 mm / min, and measurement temperature: 9.5% or more at break elongation measured under the conditions of 23 ° C. A polyimide film. According to claim 7 or 8,
A polyimide film having a total light transmittance of 80% or more, as measured in accordance with JIS K7136:2000. According to any one of claims 7 to 9,
A polyimide film used as a transparent substrate constituting a display device. A method for producing a polyimide film, comprising a step of removing an organic solvent after applying or molding the polyimide varnish according to claim 6 into a film. An image display device comprising the polyimide film according to any one of claims 7 to 10 as a transparent substrate.