KR102391365B1 - Polyimide film - Google Patents

Abstract

A transparent polyimide-based film having excellent flexibility is provided.
A polyimide-based film satisfying the following condition (I) is provided. Condition (I): In the small-angle X-ray scattering profile I(q) represented by both logarithmic plots of wavenumber q (unit: Å ⁻¹ ) and scattering intensity I of the polyimide-based film, the tangent at q=0.03 Assuming the tangent F(q), the maximum value of I(q)/F(q) exceeds 1.5 when 0.003<q≤0.018.

Description

Polyimide-based film {POLYIMIDE FILM}

The present invention relates to a polyimide-based film.

DESCRIPTION OF RELATED ART Conventionally, glass has been used as a material of transparent members, such as a base material of various display members, such as a solar cell and a display, and a front plate. However, there was a fault that the glass was fragile and heavy. Moreover, regarding thickness reduction and weight reduction of a display, and increase in flexibility in recent years, it did not have sufficient material. For this reason, instead of glass, a polyimide-type film is examined as a transparent member of a flexible device (for example, refer patent document 1, 2).

Specification of US Patent No. 8207256 Japanese Patent Laid-Open No. 2008-163309

However, the conventional polyimide-based film did not have sufficient flexibility.

The polyimide-based film according to the present invention satisfies the following condition (I).

Condition (I): The small-angle X-ray scattering profile I(q) of the polyimide-based film expressed as a positive logarithmic plot of the wavenumber q (unit: Å ⁻¹ ) and the scattering intensity I In this case, when the tangent line at q=0.003 is the tangent F(q), the maximum value of I(q)/F(q) exceeds 1.5 when 0.003<q≤0.018.

Here, it is preferable that yellowness YI of the said film is 10 or less.

Moreover, as for the said film, it is preferable that Haze is 1 % or less. Moreover, as for the said film, it is preferable that the total light transmittance in 550 nm is 85 % or more.

In addition, the film may include silica particles.

The polyimide-based film of the present invention has good flexibility.

BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram which shows the example of a small-angle X-ray profile, and both a vertical axis and a horizontal axis are logarithmic plots.

(Polyimide-based film)

The polyimide-based film according to the present embodiment satisfies the following condition (I).

Condition (I): In the small-angle X-ray scattering profile I(q) represented by both logarithmic plots of wavenumber q (unit: Å ⁻¹ ) and scattering intensity I of the polyimide-based film, the tangent at q=0.003 Assuming that the tangent F(q) is 0.003<q≤0.018, the maximum value of I(q)/F(q) exceeds 1.5.

A small-angle X-ray scattering profile is obtained by small-angle X-ray scattering measurement.

The small-angle X-ray scattering profile indicates the wavenumber dependence of the scattering intensity with a scattering angle of 2θ of less than 10 degrees among the scattered X-rays scattered by atoms constituting the film when X-rays are incident on the film. The small-angle X-ray scattering profile is usually expressed not as the angle θ but as the scattering intensity I with respect to the wavenumber (absolute value of the scattering vector) q. The wavenumber q is calculated from (4π/λ)sinθ, and λ represents the wavelength of the X-ray. Examples of the wavelength of X-rays include 0.1 to 3 angstroms. Moreover, it is preferable that the scattering angle 2θ is 5 degrees or less.

Such X-rays can be used for SPring-8, PF ring, etc., and a small-angle X-ray scattering profile of sufficient intensity can be obtained in a short time by using radiated X-rays.

An example of a small-angle X-ray profile is shown in FIG. Referring to FIG. 1 , each profile a to c has a tangent F(q) at a point of wavenumber q=0.003 Å ⁻¹ . The maximum value of I(q)/F(q) in the wavelength range of 0.003<q≤0.018 is the value of the position _qa where the value of F(q) and the value of I(q) are the most distant in the above range. is calculated from As for the small-angle X-ray profile of the polyimide-based film, the peak may not be in the range of 0.003<q≤0.018 like the profile a, and the peak may be in the range of 0.003<q≤0.018 like the profile b. What is necessary is just to calculate the maximum value of I(q)/F(q) in the said range when a peak does not exist in the said range like the profile a. Further, in the small-angle X-ray profile of the polyimide-based film, the tangent line F(q) may have a slope like the profile c.

The maximum value of I(q)/F(q) in 0.003<q≤0.018 is larger than 1.5, Preferably it is larger than 1.8, More preferably, it is larger than 2.2. The upper limit of the maximum value of I(q)/F(q) in 0.003<q≤0.018 may be 10 or 8 may be sufficient as it. It is a small-angle X-ray profile of a polyimide-type film, Comprising: It corresponds to the polyimide-type film concerning this embodiment to satisfy the said conditions.

(Polyimide-based polymer)

The polyimide-based film contains a polyimide-based polymer. In this specification, a polyimide-type polymer|macromolecule means the polymer containing at least 1 type or more of the repeating structural unit represented by Formula (PI), Formula (a), Formula (a'), or Formula (b). Especially, if the repeating structural unit represented by Formula (PI) is a main structural unit of a polyimide-type polymer|macromolecule, it is preferable from a viewpoint of the intensity|strength and transparency of a film. The repeating structural unit represented by the formula (PI) is preferably 40 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more, based on all the repeating structural units of the polyimide-based polymer. , and particularly preferably 90 mol% or more, and particularly more preferably 98 mol%.

[Formula 1]

G in the formula (PI) represents a tetravalent organic group, and A represents a divalent organic group. G ² in formula (a) represents a trivalent organic group, and A ² represents a divalent organic group. G ³ in formula (a') represents a tetravalent organic group, and A ³ represents a divalent organic group. G ⁴ and A ⁴ in the formula (b) each represent a divalent organic group.

In the formula (PI), the organic group of the tetravalent organic group represented by G (hereinafter sometimes referred to as the organic group of G) includes a group selected from the group consisting of an acyclic aliphatic group, a cyclic aliphatic group and an aromatic group. there is. From the viewpoint of transparency and flexibility of the polyimide-based film, the organic group of G is preferably a cyclic aliphatic group and an aromatic group. Examples of the aromatic group include a monocyclic aromatic group, a condensed polycyclic aromatic group, and a non-condensed polycyclic aromatic group in which the aromatic groups are connected to each other directly or by a bond. From the viewpoint of transparency of the resin film and suppression of coloration, the organic group of G is a cyclic aliphatic group having a fluorine-based substituent, a monocyclic aromatic group having a fluorine-based substituent, a condensed polycyclic aromatic group having a fluorine-based substituent, or a non-condensed group having a fluorine-based substituent It is preferable that it is a polycyclic aromatic group. In this specification, a fluorine-type substituent means the group containing a fluorine atom. The fluorine-based substituent is preferably a fluoro group (fluorine atom, -F) and a perfluoroalkyl group, more preferably a fluoro group and a trifluoromethyl group.

More specifically, the organic group of G is, for example, a saturated or unsaturated cycloalkyl group, a saturated or unsaturated heterocycloalkyl group, an aryl group, a heteroaryl group, an arylalkyl group, an alkylaryl group, a heteroalkylaryl group, and any of these. It is selected from groups having two groups (which may be the same) of which are linked to each other either directly or by a bonding group. Examples of the bonding group include -O-, an alkylene group having 1 to 10 carbon atoms, -SO ₂ -, -CO- or -CO-NR- (R is an alkyl group having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, or a propyl group, or a hydrogen atom represents) can be mentioned.

Carbon number of the tetravalent organic group represented by G is 2-32 normally, Preferably it is 4-15, More preferably, it is 5-10, More preferably, it is 6-8. When the organic group of G is a cyclic aliphatic group or an aromatic group, at least one of the carbon atoms constituting these groups may be substituted with a hetero atom. Examples of the hetero atom include O, N or S.

Specific examples of G include groups represented by the following formulas (20), (21), (22), (23), (24), (25) or (26). * in the formula represents a bond. Z in formula (26) is a single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar-C (CH ₃ ) ₂ -Ar- or -Ar-SO ₂ -Ar-. Ar represents a C6-C20 aryl group, for example, a phenylene group is mentioned. At least one of the hydrogen atoms in these groups may be substituted with a fluorine-based substituent.

[Formula 2]

In the formula (PI), the organic group of the divalent organic group represented by A (hereinafter sometimes referred to as the organic group of A) includes a group selected from the group consisting of an acyclic aliphatic group, a cyclic aliphatic group and an aromatic group. there is. It is preferable that the divalent organic group represented by A is a cyclic aliphatic group and an aromatic group. Examples of the aromatic group include a monocyclic aromatic group, a condensed polycyclic aromatic group, and a non-condensed polycyclic aromatic group having two or more aromatic rings and connected to each other directly or by a bonding group. It is preferable that the fluorine-type substituent is introduce|transduced into the organic group of A from a viewpoint of transparency of a resin film and suppression of coloring.

More specifically, the organic group of A is, for example, a saturated or unsaturated cycloalkyl group, a saturated or unsaturated heterocycloalkyl group, an aryl group, a heteroaryl group, an arylalkyl group, an alkylaryl group, a heteroalkylaryl group, and within these It is selected from groups having any two groups (which may be the same) and they are linked to each other either directly or by a bonding group. Examples of the hetero atom include O, N or S, and examples of the bonding group include -O-, an alkylene group having 1 to 10 carbon atoms, -SO ₂ -, -CO- or -CO-NR- (R is a methyl group, an ethyl group, and a C1-C3 alkyl group or hydrogen atom, such as a propyl group) is mentioned.

Carbon number of the divalent organic group represented by A is 2-40 normally, Preferably it is 5-32, More preferably, it is 12-28, More preferably, it is 24-27.

As a specific example of A, group represented by the following Formula (30), Formula (31), Formula (32), Formula (33), or Formula (34) is mentioned. * in the formula represents a bond. Z ¹ to Z ³ are each independently, a single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -SO ₂ -, -CO- or -CO-NR-(R is a methyl group , an alkyl group having 1 to 3 carbon atoms, such as an ethyl group or a propyl group, or a hydrogen atom). In the following groups, it is preferable that Z ¹ and Z ² and Z ² and Z ³ each exist in a meta position or a para position with respect to each ring. In addition, it is preferable that the ^single bond of Z1 and the terminal, the single bond of Z2 and the terminal, and the single bond ^of Z3 and the terminal ^exist in meta-position or para-position, respectively. One example of A is that Z ¹ and Z ³ are -O-, and Z ² is -CH ₂ -, -C(CH ₃ ) ₂ - or -SO ₂ -. One or two or more of the hydrogen atoms in these groups may be substituted with a fluorine-based substituent.

[Formula 3]

At least one of A and G is at least one hydrogen atom among the hydrogen atoms constituting them do. Further, when the organic group of A and the organic group of G are each a cyclic aliphatic group or an aromatic group, it is preferable that at least one of A and G has a fluorine-based substituent, and it is more preferable that both of A and G have a fluorine-based substituent .

G ² in formula (a) is a trivalent organic group. This organic group can be selected from the same group as the organic group of G in Formula (PI) except for the point that it is a trivalent group. As an example of G2, the group in which any one of the four bonds of the group represented by Formula (20) - Formula (26) given as a specific example ^of G was substituted with the hydrogen atom is mentioned. A ² in formula (a) can be selected from the same group as A in formula (PI).

G ³ in the formula (a') can be selected from the same groups as G in the formula (PI). A ³ in the formula (a') can be selected from the same groups as A in the formula (PI).

G ⁴ in formula (b) is a divalent organic group. This organic group can be selected from the same groups as the organic group of G in Formula (PI) except for the point that it is a divalent group. Examples of G ⁴ include groups in which any two of the four bonds in the groups represented by formulas (20) to (26) given as specific examples of G are substituted with hydrogen atoms. A ⁴ in formula (b) can be selected from the same group as A in formula (PI).

The polyimide-based polymer contained in the polyimide-based film includes diamines, tetracarboxylic acid compounds (including acid chloride compounds and tetracarboxylic acid compound analogues such as tetracarboxylic dianhydride) or tricarboxylic acid compounds (acid chloride). It may be a condensed polymer obtained by polycondensing at least one of compounds and tricarboxylic acid compound analogs such as tricarboxylic acid anhydride). Further, a dicarboxylic acid compound (including analogs such as an acid chloride compound) may be polycondensed. The repeating structural unit represented by Formula (PI) or Formula (a') is normally derived from diamines and a tetracarboxylic acid compound. The repeating structural unit represented by Formula (a) is normally derived from diamines and a tricarboxylic acid compound. The repeating structural unit represented by Formula (b) is normally derived from diamines and a dicarboxylic acid compound.

As a tetracarboxylic-acid compound, an aromatic tetracarboxylic-acid compound, an alicyclic tetracarboxylic-acid compound, and an acyclic aliphatic tetracarboxylic-acid compound are mentioned. These may use 2 or more types together. The tetracarboxylic acid compound is preferably tetracarboxylic dianhydride. As tetracarboxylic dianhydride, aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and acyclic aliphatic tetracarboxylic dianhydride are mentioned.

From the viewpoints of solubility of the polyimide-based polymer in a solvent and transparency and flexibility when a polyimide-based film is formed, the tetracarboxylic acid compound is preferably an alicyclic tetracarboxylic compound, an aromatic tetracarboxylic acid compound, or the like. From the viewpoint of transparency of the resin film and suppression of coloring, the tetracarboxylic acid compound is preferably an alicyclic tetracarboxylic acid compound having a fluorine-based substituent and an aromatic tetracarboxylic acid compound having a fluorine-based substituent, and an alicyclic tetracarboxylic acid compound having a fluorine-based substituent. It is more preferable that it is a carboxylic acid compound.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acid, alicyclic tricarboxylic acid, acyclic aliphatic tricarboxylic acid, and their derivative acid chloride compounds, acid anhydrides, and the like. The tricarboxylic acid compound is preferably an aromatic tricarboxylic acid, an alicyclic tricarboxylic acid, an acyclic aliphatic tricarboxylic acid, and a derivative acid chloride compound thereof. A tricarboxylic acid compound may use together 2 or more types.

It is preferable that the tricarboxylic acid compound is an alicyclic tricarboxylic acid compound and an aromatic tricarboxylic acid compound from a viewpoint of the solubility with respect to the solvent of a polyimide-type polymer|macromolecule, and transparency and flexibility at the time of forming a polyimide-type film. From the viewpoint of transparency of the resin film and suppression of coloring, the tricarboxylic acid compound is preferably an alicyclic tricarboxylic acid compound having a fluorine-based substituent and an aromatic tricarboxylic acid compound having a fluorine-based substituent.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acid, alicyclic dicarboxylic acid, acyclic aliphatic dicarboxylic acid, and their derivative acid chloride compounds, acid anhydrides, and the like. The dicarboxylic acid compound is preferably an acid chloride compound of aromatic dicarboxylic acid, alicyclic dicarboxylic acid, acyclic aliphatic dicarboxylic acid, and their derivatives. A dicarboxylic acid compound may use 2 or more types together.

It is preferable that the dicarboxylic acid compound is an alicyclic dicarboxylic acid compound or an aromatic dicarboxylic acid compound from a viewpoint of the solubility with respect to the solvent of a polyimide-type polymer|macromolecule, and transparency and flexibility at the time of forming a polyimide-type film. From the viewpoint of transparency of the resin film and suppression of coloring, the dicarboxylic acid compound is preferably an alicyclic dicarboxylic acid compound having a fluorine-based substituent and an aromatic dicarboxylic acid compound having a fluorine-based substituent.

As diamines, aromatic diamine, alicyclic diamine, and aliphatic diamine are mentioned. Diamines may use these 2 or more types together. From the viewpoints of solubility of the polyimide-based polymer in a solvent and transparency and flexibility when a polyimide-based film is formed, the diamine is preferably an alicyclic diamine or an aromatic diamine having a fluorine-based substituent.

The polyimide-type polymer|macromolecule may be a copolymer containing a plurality of said repeating structural units of a different kind. The weight average molecular weight of polyimide-type polymer|macromolecule is 10,000-500,000 normally. The weight average molecular weight of polyimide-type polymer|macromolecule becomes like this. Preferably it is 50,000-500,000, More preferably, it is 70,000-400,000. A weight average molecular weight is the standard polystyrene conversion molecular weight measured by GPC. When the weight average molecular weight of the polyimide-based polymer is large, high flexibility tends to be easily obtained. However, when the weight average molecular weight of the polyimide-based polymer is too large, the viscosity of the varnish increases and processability tends to decrease.

Polyimide-type polymer|macromolecule may contain halogen atoms, such as a fluorine atom, which can be introduce|transduced by the above-mentioned fluorine-type substituent etc. When the polyimide-based polymer contains a halogen atom, the elastic modulus of the resin film can be improved and yellowness can be reduced. Thereby, it can suppress that a wound, a wrinkle, etc. generate|occur|produce in a resin film, and can improve transparency of a resin film. The halogen atom is preferably a fluorine atom. It is preferable that it is 1 mass % - 40 mass %, and, as for content of the halogen atom in polyimide-type polymer|macromolecule, it is more preferable that it is 1-30 mass % on the basis of the mass of polyimide-type polymer|macromolecule.

The polyimide-type film may contain the 1 type(s) or 2 or more types of ultraviolet absorbers. An ultraviolet absorber can be suitably selected from what is normally used as a ultraviolet absorber in the field|area of a resin material. The ultraviolet absorber may contain the compound which absorbs the light of a wavelength of 400 nm or less. As the ultraviolet absorber that can be appropriately combined with the polyimide-based polymer, for example, at least one compound selected from the group consisting of a benzophenone-based compound, a salicylate-based compound, a benzotriazole-based compound, and a triazine-based compound; can be heard

In this specification, a "system compound" refers to the derivative of the compound to which the said "system compound" is given. For example, a "benzophenone-based compound" refers to a compound having benzophenone as a parent skeleton and a substituent bonded to benzophenone.

The quantity of a ultraviolet absorber is 0.5 mass % or more normally with respect to the total mass of a resin film, Preferably it is 1 mass % or more, More preferably, it is 2 mass % or more, More preferably, it is 3 mass % or more. Moreover, the quantity of a ultraviolet absorber is 10 mass % or less normally, Preferably it is 8 mass % or less, More preferably, it is 6 mass % or less. When the ultraviolet absorber is included in these amounts, the weather resistance of the polyimide-based film can be particularly effectively improved.

(inorganic particles)

The polyimide-type film may further contain an inorganic particle from a viewpoint of raising intensity|strength. The particle containing a silicon atom is mentioned as an inorganic particle, A silica particle is mentioned as the particle|grain containing the said silicon atom. As another inorganic particle, a titania particle, an alumina particle, a zirconia particle, etc. are mentioned.

The average primary particle diameter of an inorganic particle is 100 nm or less normally. Transparency of a film tends to improve that the average primary particle diameter of an inorganic particle is 100 nm or less. The measurement of the primary particle diameter of an inorganic particle can be made into the positive direction diameter by a transmission electron microscope (TEM). An average primary particle diameter can measure 10 primary particle diameters by TEM observation, and can be calculated|required as those average values.

In the polyimide-based film, the blending ratio of polyimide and inorganic particles is, in terms of mass ratio, preferably 1:9 to 10:0, more preferably 3:7 to 10:0, and 3:7 to 8: It is more preferable that it is 2, and it is still more preferable that it is 3:7-7:3. It shows the tendency which transparency and mechanical strength improve that the compounding ratio of a polyimide and an inorganic particle is in said range.

Inorganic particles may be bonded to each other by molecules having a siloxane bond (-SiOSi-).

The polyimide-based film may contain another component to the extent that transparency and flexibility are not impaired. As another component, coloring agents, such as antioxidant, a mold release agent, a stabilizer, and a bluing agent, a flame retardant, a lubricant, a thickener, a leveling agent, etc. are mentioned, for example.

The polyimide-based film may contain an organosilicon compound such as a quaternary alkoxysilane such as tetraethyl orthosilicate (TEOS (Tetra Ethyl Ortho Silicate)) or a silsesquioxane derivative.

It is preferable that components other than a polyimide and an inorganic material are more than 0 % and 20 mass % or less with respect to the mass of a polyimide-type film. More preferably, it is more than 0% and 10 mass % or less.

Although the thickness of a polyimide-type film is adjusted suitably according to a use, Usually, it is 10-500 micrometers, it is preferable that it is 15-200 micrometers, and it is more preferable that it is 20-100 micrometers.

It is preferable that the total light transmittance based on JISK7105:1981 is 85 % or more, and, as for this polyimide-type film, it is more preferable that it is 90 % or more.

Moreover, it is preferable that Haze based on JISK7105:1981 is 1 % or less, and, as for this polyimide-type film, it is more preferable that it is 0.9 % or less.

Moreover, it is preferable that yellowness YI based on JISK7373:2006 is 10 or less, as for this polyimide-type film, it is more preferable that it is 5 or less, It is more preferable that it is 3 or less.

Such a polyimide-based film is excellent in flexibility. Although it is not clear why such a polyimide-based film has excellent flexibility, it has a structure that affects X-ray scattering, such as agglomerated structure and microstructure in the nanoscale, and the structure is a size that does not scatter visible light, Moreover, it is thought that the structure has contributed to the improvement of a flexibility that it has a uniform size distribution to some extent or more.

In the small-angle X-ray scattering profile, wavenumber q=0.003 and wavenumber q=0.018 correspond to lengths of 209 nm and 35 nm, respectively. Having a structure such as a peak in the X-ray scattering profile in this range means having a periodic structure in that range. Therefore, defining F(q) as a tangent at q = 0.003 corresponding to 209 nm and having a portion at which I(q) is greatly farther from the tangent at 0.003 < q ≤ 0.018 represents the structure of the above size. It has shown what it has in a certain quantity and a film.

Moreover, even when it has a structure of the said size, when the size of a structure is non-uniform|heterogenous, there exists a tendency hard to obtain sufficient flexibility. In such a case where the size of the structure is non-uniform, the peak of the X-ray scattering profile becomes broad, and as a result, the maximum value of I(q)/F(q) becomes small. Therefore, saying that the maximum value of I(q)/F(q) has q exceeding 1.5 means that it contains a certain amount of a nano-sized structure that does not impair the transparency of the material, and the size of the structure means that it has some degree of uniformity.

(Manufacturing method)

Next, an example of the manufacturing method of the polyimide-type film of this embodiment is demonstrated. A polyimide-type film is a solid content contained in a polyimide-type polymeric varnish.

The polyimide-based polymer varnish is prepared by dissolving a solvent-soluble polyimide polymerized using a known polyimide synthesis method in a solvent. The solvent may be any solvent that dissolves the polyimide, for example, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL), N-methylpyrrolidone (NMP), ethyl acetate, methylethylketone (MEK), tetrahydrofuran, 1,4-dioxane, acetone, cyclopentanone, dimethylsulfoxide, xylene, and combinations thereof Available.

As a polyimide, what is necessary is just a solvent-soluble polyimide, and it may have the structure mentioned above.

The polyimide-based polymer varnish may further contain water. Content of water is 0.1-10 mass % normally with respect to the mass of a polyimide-type polymeric varnish.

When the varnish contains water, it is easy to obtain a film having a structure showing the above-described small-angle X-ray profile. Although the reason why the structure of a polyimide-type film changes by addition of water is not clear, it is thought that the structure formation of a polyimide is affected by the presence of water at the time of solvent drying.

The polyimide-type polymer|macromolecule varnish can contain the above-mentioned inorganic particle further. When the polyimide-based polymer varnish contains inorganic particles, when the polyimide-based polymer varnish contains water, gelation of the inorganic particles is suppressed, and it is considered to affect the structure formation of the polyimide-based polymer.

When the polyimide-based polymer varnish contains inorganic particles, the polyimide-based polymer varnish may contain a metal alkoxide such as an alkoxysilane to improve solution stability. Preferably, it is an alkoxysilane which has an amino group. Alkoxysilane contributes to bond formation between inorganic particles.

The addition amount of a metal alkoxide is 0.1-10 mass parts normally with respect to 100 mass parts of inorganic particles, and it is preferable that it is 0.5-5 mass parts.

In addition, additives may be further added to the polyimide-based polymer varnish, and as additives, for example, coloring agents such as antioxidants, mold release agents, stabilizers, and bluing agents, flame retardants, lubricants, thickeners, leveling agents, etc. may be added. do.

The adjusted polyimide-based varnish is then applied onto a PET substrate, a SUS belt, or a glass substrate by a known roll-to-roll or arrangement method to form a coating film. This coating film becomes a film by drying and peeling from a base material. You may further dry a film after peeling.

Drying of a coating film is performed by evaporating a solvent under conditions of an inert atmosphere or reduced pressure suitably at the temperature of 50-350 degreeC. Evaporation of the solvent may be performed under air. When carrying out in air|atmosphere, it is preferable from a viewpoint of coloring that temperature shall be 230 degreeC or less.

(purpose)

Since such a polyimide-based film is transparent and has excellent flexibility, it can be used as a component of a flexible display. For example, it can be used as a front plate (window film) for surface protection of a flexible display.

Moreover, it can also be set as the laminated body which added various functional layers, such as an ultraviolet-ray absorption layer, a hard-coat layer, an adhesion layer, a hue adjustment layer, and a refractive index adjustment layer, to this polyimide-type film.

Example

Hereinafter, although an Example and a comparative example demonstrate this invention more concretely, this invention is not limited to the following Example.

(Example 1)

A compound represented by Formula (1), a compound represented by Formula (2), a compound represented by Formula (3), a solvent (γ-butyrolactone and dimethylacetamide) and a catalyst in a polymerization tank (chamber) substituted with nitrogen put in The dosage is 75.0 g of the compound represented by Formula (1), 36.5 g of the compound represented by Formula (2), 76.4 g of the compound represented by Formula (3), 438.4 g of γ-butyrolactone, 313.1 g of dimethylacetamide, and 1.5 g of catalyst. did. The molar ratio of the compound represented by Formula (2) and the compound represented by Formula (3) is 3:7, the molar ratio of the sum of the compound represented by Formula (2) and the compound represented by Formula (3) to the compound represented by Formula (1) , 1.00:1.02.

[Formula 4]

After stirring the mixture in the polymerization tank to dissolve the raw material in the solvent, the temperature of the mixture was raised to 100°C, and then the temperature was raised to 200°C and kept warm for 4 hours to polymerize the polyimide. In addition, during this heating, water in the liquid was removed. Then, the polyimide was obtained by refinement|purification and drying.

Next, a γ-butyrolactone solution of polyimide adjusted to a concentration of 20% by mass, a solution in which silica particles having a solid content concentration of 30% by mass are dispersed in γbutyrolactone, a dimethylacetamide solution of an alkoxysilane having an amino group, and water; were mixed and stirred for 30 minutes.

Here, the mass ratio of silica and polyimide is 60:40, the amount of the alkoxysilane having an amino group is 1.67 parts based on 100 parts by mass of silica and polyimide in total, and water is 10 parts by mass based on 100 parts by mass of silica and polyimide in total. made wealth

The mixed solution was apply|coated to a glass substrate, it heated at 50 degreeC for 30 minutes, and 140 degreeC for 10 minutes, and the solvent was dried. Thereafter, the film was peeled from the glass substrate, a metal mold was attached and heated at 210°C for 1 hour to obtain a transparent polyimide-based film having a thickness of 50 µm.

(Example 2)

It carried out similarly to Example 1 except having used the "Neoprim" made by Mitsubishi Gas Chemicals Corporation as a polyimide, and having made the mass ratio of a silica and polyimide 55:45.

(Example 3)

It carried out similarly to Example 2 except storing the mixed solution adjusted in Example 2 at 40 degreeC for 24 hours before apply|coating to a glass substrate.

(Comparative Example 1)

A mixed solution was prepared in the same manner as in Example 1 except that water was not added, and the mixed solution was stored at 40°C for 24 hours before applying it to a glass substrate.

(Measurement of small angle X-ray scattering profile)

The small-angle X-ray scattering profile of each obtained film was acquired by the USAXS apparatus of SPring-8 under the following conditions. The wavelength λ of the X-ray was 2 Å, and the range of the wave number q was 0.002 to 0.02 Å ⁻¹ .

From the obtained profile, when the maximum value of I(q)/F(q) in 0.003<q≤0.018 was calculated|required, Example 1 was 2.5, and Comparative Example 1 was 1.1.

(Evaluation of flexibility)

A sample (10 mm x 100 mm) cut out from each film was bent 180 degrees at the central part of the longitudinal direction, and the bent part was observed by pressing the bent part with a finger. A result is shown in Table 1. A case in which the bent portion is broken is denoted by C, and the case in which the bent portion is not broken is denoted by A.

(YI's evaluation)

The yellowness (Yellow Index: YI) of the films of an Example and a comparative example was measured with the ultraviolet-visible near-infrared spectrophotometer V-670 made from JASCO Corporation based on JISK7373:2006. After background measurement was performed in the absence of a sample, the film was set in a sample holder and transmittance measurement was performed for light of 300 to 800 nm to determine tristimulus values (X, Y, Z). YI was computed based on the following formula.

YI=100×(1.2769X-1.0592Z)/Y

(Haze's assessment)

Haze (%) of the film was measured with a fully automatic direct-reading haze computer HGM-2DP manufactured by Suga Test Co., Ltd. in accordance with JIS K 7105:1981.

(Evaluation of total light transmittance Tr)

The total light transmittance of the film was measured with a fully automatic direct-reading haze computer HGM-2DP manufactured by Suga Test Co., Ltd. in accordance with JIS K 7105-1:1981. These results are shown in Table 1.

Claims (5)

A polyimide-based polymer which is a polymer comprising at least one repeating structural unit represented by formula (PI), formula (a), formula (a′) or formula (b),

(G in formula (PI) represents a tetravalent organic group, A represents a divalent organic group. In formula (a), G ² represents a trivalent organic group, and A ² represents a divalent organic group. Formula (a') In G ³ represents a tetravalent organic group, A ³ represents a divalent organic group. G ⁴ and A ⁴ in the formula (b) represent a divalent organic group, respectively.)
A polyimide-based film that satisfies the following condition (I).
Condition (I): In the small-angle X-ray scattering profile I(q) represented by both logarithmic plots of wavenumber q (unit: Å ⁻¹ ) and scattering intensity I of the polyimide-based film, the tangent at q=0.003 Let the tangent F(q) be,
For 0.003<q≤0.018, the maximum value of I(q)/F(q) exceeds 1.5. The method of claim 1,
A polyimide-based film having a yellowness YI of 10 or less. 3. The method of claim 1 or 2,
A polyimide-based film having a haze of 1% or less. 3. The method of claim 1 or 2,
A polyimide-based film having a total light transmittance of 85% or more. 3. The method of claim 1 or 2,
A polyimide-based film comprising silica particles.

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