KR101876524B1 - Polyimide film - Google Patents

Abstract

A transparent polyimide film excellent in flexibility is provided.
A polyimide-based film satisfying the following condition (I) is provided. Condition (I): In the incinerated X-ray scattering profile I (q) represented by both logarithmic plots of the wavenumber q (unit: Å ^-1 ) and the scattering intensity I of the polyimide film, the tangent line at q = 0.03 , The maximum value of I (q) / F (q) exceeds 0.00 in the range of 0.003 <q? 0.018.

Description

Polyimide film

The present invention relates to a polyimide-based film.

BACKGROUND ART Conventionally, glass has been used as a material for a transparent member such as a substrate of various display members such as a solar cell or a display and a front plate. However, the glass had the drawback of being fragile and heavy. In addition, in recent years, there has been no sufficient material regarding the thickness, weight, and flexibility of the display. For this reason, a polyimide-based film has been studied as a transparent member of a flexible device instead of glass (see, for example, Patent Documents 1 and 2).

U.S. Patent No. 8207256 Japanese Unexamined Patent Application Publication No. 2008-163309

However, the conventional polyimide-based film is not sufficiently flexible.

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

Condition (I): in: (Å ^-1 units) and the amount (兩) Incineration (小角) X-ray scattering profile I (q) represented in a logarithmic plot of the scattering intensity (I) of the polyimide-based film, a wave number (波數) q , The maximum value of I (q) / F (q) exceeds 1.5 at 0.003 <q? 0.018 when the tangent line at q = 0.003 is tangential line F (q).

Here, it is preferable that the film has a yellowness degree YI of 10 or less.

The film preferably has a haze of 1% or less. It is also preferable that the film has a total light transmittance of 85% or more at 550 nm.

In addition, the film may comprise silica particles.

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

Fig. 1 is a conceptual diagram showing an example of the incineration X-ray profile, and both the ordinate axis and the abscissa axis are algebraic plots.

(Polyimide-based film)

The polyimide film related to this embodiment satisfies the following condition (I).

Condition (I): In the incinerated X-ray scattering profile I (q) represented by both logarithmic plots of the wavenumber q (unit: Å ^-1 ) and the scattering intensity I of the polyimide film, the tangent line at q = 0.003 (Q), the maximum value of I (q) / F (q) exceeds 0.00 in the range of 0.003 <q? 0.018.

The incineration X-ray scattering profile is obtained by incineration X-ray scattering measurement.

The incineration X-ray scattering profile indicates the wave number dependence of the scattering intensity with the scattering angle 2? Of less than 10 ° among scattered X-rays scattered by the atoms constituting the film when X-rays enter the film. The incidence angle X-ray scattering profile is usually expressed by the scattering intensity I with respect to the wave number (the absolute value of the scattering vector) q, not the angle?. The wave number q is calculated from (4π / λ) sin θ, and λ represents the wavelength of the X-ray. The wavelength of the X-ray is 0.1 to 3 Å. The scattering angle 2? Is preferably 5 ° or less.

Such X-rays can be used as SPring-8, PF ring or the like, and an incinerated X-ray scattering profile of sufficient intensity can be obtained in a short time by using synchrotron X-rays.

Fig. 1 shows an example of the incineration X-ray profile. Referring to Fig. 1, each profile a to c has a tangent line F (q) at a wavenumber q = 0.003 Å ^-1 . The maximum value of I (q) / F (q) in the wavelength range 0.003 <q? 0.018 is the value of the position q _{a at which} the value of F (q) . The incinerated X-ray profile of the polyimide-based film may not have a peak in the range of 0.003 <q? 0.018 as in the profile a, and a peak in the range of 0.003 <q? 0.018 as in the profile b. When the peak is not in the above range as in the profile a, the maximum value of I (q) / F (q) in the above range may be calculated. Further, in the incineration 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 the range of 0.003 <q? 0.018 is larger than 1.5, preferably larger than 1.8, and more preferably 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. It is an incinerated X-ray profile of a polyimide-based film, which corresponds to the polyimide-based film according to the present embodiment.

(Polyimide-based polymer)

The polyimide-based film includes a polyimide-based polymer. In the present specification, the polyimide-based polymer means a polymer containing at least one or more repeating structural units represented by formula (PI), formula (a), formula (a ') or formula (b). Among them, the repeating structural unit represented by the formula (PI) is preferably the main structural unit of the polyimide-based polymer in view of the strength and transparency of the film. The repeating structural unit represented by the formula (PI) is preferably at least 40 mol%, more preferably at least 50 mol%, still more preferably at least 70 mol%, based on the total repeating structural units of the polyimide polymer , Particularly preferably 90 mol% or more, and even more preferably 98 mol%.

[Chemical Formula 1]

G in the formula (PI) represents a tetravalent organic group, and A represents a divalent organic group. G ² in the formula (a) represents a trivalent organic group, and A ² represents a divalent organic group. G ³ in the 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 a quadrivalent organic group represented by G (hereinafter sometimes referred to as an organic group of G) includes a group selected from the group consisting of a non-cyclic aliphatic group, a cyclic aliphatic group and an aromatic group have. From the viewpoints of the transparency and the bendability 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 an aromatic group is linked directly or via a bond. From the viewpoints of transparency and inhibition of coloration of the resin film, the organic group of G may be 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- It is preferably a polycyclic aromatic group. In the present specification, the fluorine-based substituent means a 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 may be, 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, (Which may be the same) and are connected to each other directly or by a bonding group. Examples of the bonding group include -O-, an alkylene group of 1 to 10 carbon atoms, -SO ₂ -, -CO- or -CO-NR- (R represents an alkyl group having 1 to 3 carbon atoms such as a methyl group, ).

The number of carbon atoms of the tetravalent organic group represented by G is usually 2 to 32, preferably 4 to 15, more preferably 5 to 10, and still more preferably 6 to 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). The * in the formula represents the binding hand. Z in formula (26) represents a single bond, -O-, -CH ₂ -, -C (CH ₃ ) ₂ -, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, (CH ₃ ) ₂ -Ar- or -Ar-SO ₂ -Ar-. Ar represents an aryl group having 6 to 20 carbon atoms, and examples thereof include a phenylene group. At least one of the hydrogen atoms of these groups may be substituted with a fluorine-based substituent.

(2)

In the formula (PI), an organic group of a divalent organic group represented by A (hereinafter sometimes referred to as an 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 have. The divalent organic group represented by A 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 having two or more aromatic rings, which are bonded to each other directly or via a bonding group. From the viewpoint of transparency and inhibition of coloring of the resin film, it is preferable that the organic group of A is introduced with a fluorine-based substituent.

More specifically, the organic group of A may be, 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 they are selected from groups which are arbitrary two groups (which may be the same) and which are connected to each other 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 represents a methyl group, An alkyl group having 1 to 3 carbon atoms such as a methyl group or a propyl group, or a hydrogen atom).

The number of carbon atoms of the divalent organic group represented by A is usually 2 to 40, preferably 5 to 32, more preferably 12 to 28, and most preferably 24 to 27.

Specific examples of A include groups represented by the following formulas (30), (31), (32), (33) or (34). The * in the formula represents the binding hand. Z ¹ to Z ³ each independently represent a single bond, -O-, -CH ₂ -, -C (CH ₃ ) ₂ -, -SO ₂ -, -CO- or -CO-NR- , 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 group, it is preferable that Z ¹ and Z ² and Z ² and Z ³ are respectively in a meta position or a para position with respect to each ring. It is preferable that Z ¹ and a terminal single bond, Z ² and a terminal single bond, and Z ³ and a terminal single bond are respectively in a meta position or a para position. 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 hydrogen atoms of these groups may be substituted with a fluorine-based substituent.

(3)

At least one of A and G may be substituted with at least one hydrogen atom constituting the hydrogen atoms thereof by at least one functional group selected from the group consisting of a fluorine-based substituent, a hydroxyl group, a sulfone group and an alkyl group having 1 to 10 carbon atoms do. In the case where the organic group of A and the organic group of G are each a cyclic aliphatic group or aromatic group, it is preferable that at least one of A and G has a fluorine-based substituent, more preferably both A and G have a fluorine-based substituent .

G ² in the 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 that it is a trivalent group. Examples of G ² include groups in which any one of the four bonding hands of the groups represented by the formulas (20) to (26) introduced as G specific examples is substituted with a hydrogen atom. A ² in the formula (a) can be selected from the same group as A in the formula (PI).

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

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

The polyimide-based polymer contained in the polyimide-based film can be obtained by reacting a diamine with a tetracarboxylic acid compound (including a tetracarboxylic acid compound analog such as an acid chloride compound and tetracarboxylic acid dianhydride) or a tricarboxylic acid compound A compound and a tricarboxylic acid compound analog such as a tricarboxylic anhydride), or a condensation-type polymer obtained by polycondensation of at least one of them. Alternatively, a dicarboxylic acid compound (including an analogue such as an acid chloride compound) may be polycondensed. The repeating structural unit represented by the formula (PI) or the formula (a ') is usually derived from a diamine and a tetracarboxylic acid compound. The repeating structural unit represented by the formula (a) is usually derived from a diamine and a tricarboxylic acid compound. The repeating structural unit represented by the formula (b) is usually derived from a diamine and a dicarboxylic acid compound.

Examples of the tetracarboxylic acid compound include aromatic tetracarboxylic acid compounds, alicyclic tetracarboxylic acid compounds and acyclic aliphatic tetracarboxylic acid compounds. These may be used in combination of two or more. The tetracarboxylic acid compound is preferably tetracarboxylic dianhydride. Examples of the tetracarboxylic dianhydride include aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and acyclic aliphatic tetracarboxylic dianhydride.

The tetracarboxylic acid compound is preferably an alicyclic tetracarboxylic acid compound, an aromatic tetracarboxylic acid compound or the like from the viewpoints of solubility in a solvent of a polyimide-based polymer and transparency and bending property when a polyimide-based film is formed. From the viewpoints of transparency and inhibition of coloration of the resin film, 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. The alicyclic tetra And more preferably a carboxylic acid compound.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, alicyclic tricarboxylic acids, acyclic aliphatic tricarboxylic acids and their acid chloride compounds and acid anhydrides. The tricarboxylic acid compounds are preferably aromatic tricarboxylic acids, alicyclic tricarboxylic acids, acyclic aliphatic tricarboxylic acids and their flexible acid chloride compounds. The tricarboxylic acid compound may be used in combination of two or more.

The tricarboxylic acid compound is preferably an alicyclic tricarboxylic acid compound and an aromatic tricarboxylic acid compound from the viewpoints of solubility in a solvent of a polyimide-based polymer and transparency and flexibility in the case of forming a polyimide-based film. From the viewpoints of transparency and inhibition of coloration of the resin film, 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 acids, alicyclic dicarboxylic acids, acyclic aliphatic dicarboxylic acids and their flexible acid chloride compounds and acid anhydrides. The dicarboxylic acid compounds are preferably aromatic dicarboxylic acids, alicyclic dicarboxylic acids, acyclic aliphatic dicarboxylic acids and their flexible acid chloride compounds. The dicarboxylic acid compound may be used in combination of two or more.

The dicarboxylic acid compound is preferably an alicyclic dicarboxylic acid compound or an aromatic dicarboxylic acid compound from the viewpoints of solubility in a solvent of a polyimide-based polymer and transparency and bending property in the case of forming a polyimide-based film. From the viewpoints of transparency and inhibition of coloring of the resin film, 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.

Examples of the diamines include aromatic diamines, alicyclic diamines and aliphatic diamines. The diamines may be used in combination of two or more. From the viewpoints of solubility in a solvent of a polyimide-based polymer and transparency and flexibility in the case of forming a polyimide-based film, the diamines are preferably aromatic diamines having alicyclic diamines or fluorine-based substituents.

The polyimide-based polymer may be a copolymer containing a plurality of the above-mentioned repeating structural units of different kinds. The weight average molecular weight of the polyimide-based polymer is usually from 10,000 to 500,000. The weight average molecular weight of the polyimide-based polymer is preferably 50,000 to 500,000, more preferably 70,000 to 400,000. The weight average molecular weight is the standard polystyrene reduced molecular weight measured by GPC. If the weight average molecular weight of the polyimide-based polymer is high, high flexibility is likely to be obtained. However, if the weight average molecular weight of the polyimide-based polymer is too large, the viscosity of the varnish tends to be high and the workability tends to decrease.

The polyimide-based polymer may contain a halogen atom such as a fluorine atom which can be introduced by the fluorine-based substituent described above. When the polyimide-based polymer contains a halogen atom, the elastic modulus of the resin film can be improved and the yellowness degree can be reduced. As a result, occurrence of scratches and wrinkles on the resin film can be suppressed, and transparency of the resin film can be improved. The halogen atom is preferably a fluorine atom. The content of the halogen atom in the polyimide-based polymer is preferably 1% by mass to 40% by mass, and more preferably 1% by mass to 30% by mass, based on the mass of the polyimide-based polymer.

The polyimide-based film may contain one or more ultraviolet absorbers. The ultraviolet absorber can be appropriately selected from what is conventionally used as an ultraviolet absorber in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400 nm or less. Examples of the ultraviolet absorber which can be suitably combined with the polyimide-based polymer include at least one kind of compound selected from the group consisting of benzophenone compounds, salicylate compounds, benzotriazole compounds, and triazine compounds .

In the present specification, the "system (compound)" refers to a derivative of the compound to which the "compound" is imparted. For example, the "benzophenone compound" refers to a compound having a substituent bonded to benzophenone and benzophenone as a matrix skeleton.

The amount of the ultraviolet absorber is usually 0.5% by mass or more, preferably 1% by mass or more, more preferably 2% by mass or more, and further preferably 3% by mass or more, based on the total mass of the resin film. The amount of the ultraviolet absorber is usually 10 mass% or less, preferably 8 mass% or less, and more preferably 6 mass% or less. By including the ultraviolet absorber in the amount thereof, the weather resistance of the polyimide-based film can be particularly effectively increased.

(Inorganic particles)

The polyimide-based film may further contain inorganic particles from the viewpoint of increasing the strength. Examples of the inorganic particles include particles containing a silicon atom, and examples of particles containing the silicon atom include silica particles. Examples of other inorganic particles include titania particles, alumina particles and zirconia particles.

The average primary particle diameter of the inorganic particles is usually 100 nm or less. When the average primary particle diameter of the inorganic particles is 100 nm or less, transparency of the film tends to be improved. The primary particle diameter of the inorganic particles can be measured in a fixed direction by a transmission electron microscope (TEM). The average primary particle diameter can be determined as an average value by measuring ten primary particle diameters by TEM observation.

In the polyimide-based film, the blending ratio of the polyimide and the inorganic particles is preferably 1: 9 to 10: 0, more preferably 3: 7 to 10: 0, 2, more preferably from 3: 7 to 7: 3. When the blending ratio of the polyimide and the inorganic particles is within the above range, transparency and mechanical strength tend to be improved.

The inorganic particles may be bonded to each other by a molecule having a siloxane bond (-SiOSi-).

The polyimide-based film may contain another component as long as it does not impair transparency and flexibility. Examples of other components include antioxidants, releasing agents, stabilizers, coloring agents such as bluing agents, flame retardants, lubricants, thickeners, and leveling agents.

The polyimide-based film may contain an organic silicon compound such as a quaternary alkoxysilane such as tetraethyl orthosilicate (TEOS) or a silsesquioxane derivative.

The components other than the polyimide and the inorganic material are preferably more than 0% and not more than 20% by mass with respect to the mass of the polyimide film. More preferably more than 0% but not more than 10% by mass.

The thickness of the polyimide-based film is appropriately adjusted depending on the application, but is usually from 10 to 500 탆, preferably from 15 to 200 탆, more preferably from 20 to 100 탆.

The polyimide-based film preferably has a total light transmittance according to JIS K7105: 1981 of 85% or more, more preferably 90% or more.

In this polyimide-based film, the haze in accordance with JIS K 7105: 1981 is preferably 1% or less, more preferably 0.9% or less.

Further, the polyimide-based film preferably has a yellowness degree YI of 10 or less, more preferably 5 or less, and more preferably 3 or less, in accordance with JIS K 7373: 2006.

Such a polyimide-based film is excellent in flexibility. The reason why such a polyimide-based film is excellent in flexibility is not clear, but it has a structure that has any structure that affects X-ray scattering such as aggregation structure and microstructure in a nanoscale, its structure does not scatter visible light, Also, it is considered that the presence of the structure with a uniform size distribution contributes to the improvement of the bending property.

In the incineration X-ray scattering profile, the wavenumber q = 0.003 and the wavenumber q = 0.018 correspond to the lengths of 209 nm and 35 nm, respectively. The X-ray scattering profile in this range having a structure such as a peak means having a periodic structure in the range. Therefore, the fact that F (q) is defined as a tangent at q = 0.003 corresponding to 209 nm and that the portion far from I (q) from the tangent has 0.003 < q? 0.018 means that the structure of the above- And the amount of the film in the film.

In addition, even if the structure has the above-mentioned size, sufficient flexibility is hardly obtained when the size of the structure is uneven. When the size of the structure is not uniform, the peak of the X-ray scattering profile becomes broad, and consequently the maximum value of I (q) / F (q) becomes small. Therefore, the fact that the maximum value of I (q) / F (q) has q exceeding 1.5 means that a nano-sized structure which does not hinder the transparency of the material is contained in a certain amount, Is a certain degree of uniformity.

(Manufacturing method)

Next, an example of a manufacturing method of the polyimide film of the present embodiment will be described. The polyimide-based film is a solid content solid contained in the polyimide-based polymer varnish.

The polyimide-based polymer varnish is prepared by dissolving the polymerized solvent-soluble polyimide in a solvent by using a known synthesis method of polyimide. The solvent may be any solvent that dissolves the polyimide, and examples thereof include N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), dimethylsulfoxide (DMSO) (GBL), N-methylpyrrolidone (NMP), ethyl acetate, methyl ethyl ketone (MEK), tetrahydrofuran, 1,4-dioxane, acetone, cyclopentanone, dimethyl sulfoxide, Can be used.

The polyimide may be a solvent-soluble polyimide, and may be the above-described structure.

The polyimide-based polymer varnish may also contain water. The content of water is usually 0.1 to 10 mass% with respect to the mass of the polyimide-based polymer varnish.

By containing water in the varnish, it is easy to obtain a film having a structure showing the above-described incineration X-ray profile. The reason why the structure of the polyimide-based film is changed by the addition of water is not clear, but it is considered that the presence of water at the time of solvent drying affects the structure formation of the polyimide.

The polyimide-based polymer varnish may further contain the inorganic particles described above. In the case where the polyimide-based polymer varnish contains inorganic particles, it is considered that the polyimide-based polymer varnish contains water so that the gelation of the inorganic particles is suppressed, thereby affecting 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 alkoxysilane to improve solution stability. Preferably, it is an alkoxysilane having an amino group. The alkoxysilane contributes to the bond formation between the inorganic particles.

The addition amount of the metal alkoxide is usually 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass based on 100 parts by mass of the inorganic particles.

The polyimide-based polymer varnish may further contain an additive. As the additive, for example, a coloring agent such as an antioxidant, a releasing agent, a stabilizer, a bluing agent, a flame retardant, a lubricant, a thickener, do.

The prepared polyimide varnish is then applied onto a PET substrate, an SUS belt, or a glass substrate by a known roll-to-roll or batch method to form a coated film. The coating film is dried and peeled off from the substrate to become a film. After the peeling, the film may be further dried.

The coating film is dried by suitably evaporating the solvent under an inert atmosphere or a reduced pressure at a temperature of 50 to 350 ° C. Evaporation of the solvent may be carried out under atmospheric conditions. In the case of performing in an atmosphere, the temperature is preferably 230 DEG C or less from the viewpoint of coloring.

(Usage)

Such a polyimide-based film is transparent and excellent in flexibility, so that 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.

Further, a laminate obtained by adding various functional layers such as an ultraviolet absorbing layer, a hard coat layer, an adhesive layer, a color adjusting layer, and a refractive index adjusting layer to the polyimide film may be used.

Example

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Example 1)

(1), a compound represented by the formula (2), a compound represented by the formula (3), a solvent (? -Butyrolactone and dimethylacetamide), and a catalyst Respectively. The charged amount was 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 gamma -butyrolactone, 313.1 g of dimethylacetamide, did. The molar ratio of the compound represented by formula (2) to the compound represented by formula (3) is 3: 7, the compound represented by formula (2) and the compound represented by formula (3) , And 1.00: 1.02.

[Chemical Formula 4]

The mixture in the polymerization vessel was stirred to dissolve the raw material in the solvent, and then the mixture was heated to 100 DEG C, then heated to 200 DEG C, and kept warm for 4 hours to polymerize the polyimide. During this heating, water in the liquid was removed. Thereafter, the polyimide was obtained by purification and drying.

Next, a solution of a polyimide? -Butyrolactone solution having a concentration of 20% by mass, a solution in which silica particles having a solid concentration of 30% by mass were dispersed in? -Butyrolactone, a dimethylacetamide solution of an alkoxysilane having an amino group, And the mixture was stirred for 30 minutes.

Here, the mass ratio of silica to polyimide was 60:40, the amount of alkoxysilane having an amino group was 1.67 parts based on 100 parts by mass of the total of silica and polyimide, and the amount of water was 10 parts by mass per 100 parts by mass of silica and polyimide I made it.

The mixed solution was applied to a glass substrate and heated at 50 DEG C for 30 minutes and at 140 DEG C for 10 minutes to dry the solvent. Thereafter, the film was peeled off from the glass substrate, and a metal mold was attached and heated at 210 DEG C for 1 hour to obtain a transparent polyimide film having a thickness of 50 mu m.

(Example 2)

The same procedure as in Example 1 was performed except that polyimide was used as "Neoprim" manufactured by Mitsubishi Gas Chemical Company, and the mass ratio of silica and polyimide was changed to 55:45.

(Example 3)

The same procedure as in Example 2 was carried out except that the mixed solution prepared in Example 2 was stored at 40 캜 for 24 hours before it was applied 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 占 폚 for 24 hours before coating on the glass substrate.

(Measurement of incineration X-ray scattering profile)

The incinerated X-ray scattering profile of each of the obtained films was obtained by the USAXS apparatus of SPring-8 under the following conditions. The wavelength? Of the X-ray was 2 占 and the range of the wave number q was 0.002? 0.02? ^-1 .

From the obtained profile, the maximum value of I (q) / F (q) at 0.003 <q? 0.018 was determined.

(Evaluation of flexibility)

A sample (10 mm x 100 mm) cut out from each film was bent 180 degrees from the center in the longitudinal direction, and the bent portion was observed by pressing the bent portion with a finger. The results are shown in Table 1. C represents the case where the bent portion is broken, and A represents the case where the bent portion is not broken.

(Evaluation of YI)

The yellow index (YI) of the films of Examples and Comparative Examples was measured by an ultraviolet visible near infrared spectrophotometer V-670 manufactured by Nippon Bunko K. K., according to JIS K 7373: 2006. After performing the background measurement in the absence of the sample, the film was set in the sample holder, and the transmittance was measured with respect to the light of 300 to 800 nm to obtain the tristimulus values (X, Y, Z). YI was calculated based on the following equation.

YI = 100 x (1.2769X-1.0592Z) / Y

(Evaluation of Haze)

The haze (%) of the film was measured in accordance with JIS K 7105: 1981 with a fully automatic Hayes computer HGM-2DP manufactured by Suga Tester.

(Evaluation of total light transmittance Tr)

The total light transmittance of the film was measured in accordance with JIS K 7105-1: 1981, using a fully automatic Hayes computer HGM-2DP manufactured by Suga Tester. The results are shown in Table 1.

Claims (9)

(I) satisfying the following condition (I): &quot; (I) &quot;
Condition (I): In the incineration X-ray scattering profile I (q) represented by both logarithmic plots of the wave number q (unit: Å ^-1 ) and the scattering intensity I of the front plate of the flexible display, the tangent Is a tangent line F (q)
For 0.003 &lt; q? 0.018, the maximum value of I (q) / F (q) exceeds 1.5. The method according to claim 1,
Yellow Front Panel of Flexible Display with YI of 10 or less. 3. The method according to claim 1 or 2,
Front panel of flexible display with haze less than 1%. 3. The method according to claim 1 or 2,
A front panel of a flexible display having a total light transmittance of 85% or more. The method of claim 3,
A front panel of a flexible display having a total light transmittance of 85% or more. 3. The method according to claim 1 or 2,
A front panel of a flexible display comprising silica particles. The method of claim 3,
A front panel of a flexible display comprising silica particles. 5. The method of claim 4,
A front panel of a flexible display comprising silica particles. 6. The method of claim 5,
A front panel of a flexible display comprising silica particles.

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