KR102270652B1 - Polyimide Film Comprising Two or More Fillers Having Different Particle Diameter and Electronic Device Comprising the Same - Google Patents

Abstract

The present invention includes an inorganic filler comprising a first group of fillers having a particle diameter (D50) in the range of 2 μm to 2.7 μm and a second group of fillers having an average particle diameter (D50) in the range of 1 μm to 1.7 μm, Provided is a polyimide film satisfying the relational expression 1: 0.7 ≤ (D90-D10)/(D50) ≤ 1.2 for each particle size of the first filler group and the second filler group.

Description

Polyimide Film Comprising Two or More Fillers Having Different Particle Diameter and Electronic Device Comprising the Same}

The present invention relates to a polyimide film including two or more fillers having different particle diameters, and an electronic device including the same.

Polyimide (PI) is a polymer material with the highest level of heat resistance, chemical resistance, electrical insulation, and chemical resistance among organic materials based on an imide ring with excellent chemical stability along with a rigid aromatic main chain. .

Accordingly, polyimide is widely used as a core material for automobiles, aerospace fields, and flexible circuit boards. Recently, as a colorless and transparent polyimide film has been developed, optical properties, bending resistance, abrasion resistance, dimensional stability, etc. are required for display insulation. , is also used as a protective film.

The polyimide film may be prepared by preparing a polyamic acid solution as a precursor, forming the polyamic acid solution into a thin film, and then heat-treating the polyamic acid solution.

The polyimide film prepared in this way may be processed into a nip-roll or the like to improve smoothness, or may be corona-treated for surface modification, and may be wound and stored by a roll.

However, since a conventional polyimide film has a low average roughness, when the finishing treatment is performed as described above, a blocking phenomenon may be induced on the film surface, and there is a limitation in the process in which winding is not easy.

For this reason, adding fillers such as titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica to the polyamic acid solution, which is the precursor of the polyimide film, improves the average roughness of the film and minimizes the blocking phenomenon. are being considered

However, the inorganic fillers listed above do not have excellent compatibility with the polyamic acid solution, which is a precursor of polyimide, and thus have poor dispersibility. In addition, inorganic fillers are generally amorphous, in which particle shapes are not uniform, have a large specific surface area, and are characterized by easy bonding of particles having complementary shapes to each other.

Therefore, the inorganic filler is not easily dispersed in the polyamic acid solution, and may be aggregated.

The aggregated inorganic filler may form large and small protrusions on the surface of the polyimide film, thereby reducing smoothness, transmittance, and the like of the polyimide film. Also, the protrusion may damage an object to which the polyimide film is adhered or contacted, for example, a surface of a display.

The protrusion may act as a fatal disadvantage in a polyimide film for a display, which not only reduces transparency and transmittance of the polyimide film, but also induces light scattering, which requires excellent optical properties.

Accordingly, there is a high need for a novel polyimide film that can solve these problems at once.

An object of the present invention is to provide a polyimide film having no surface defects such as protrusions, having predetermined average roughness and smoothness, and having excellent transmittance.

In one aspect of the present invention, an inorganic filler including a plurality of filler groups each belonging to a specific average particle diameter (D50) range is disclosed as an essential factor for achieving the above object.

In particular, the plurality of filler groups may satisfy the specific relational expression (1) of the present invention. In this particular case, the inorganic filler can be uniformly dispersed in the base film to minimize agglomeration.

As a result, the polyimide film of the present invention may have an advantage in that protrusions due to filler aggregation do not substantially occur despite including the filler.

The polyimide film may also have predetermined average roughness, smoothness, and excellent transmittance by including filler groups in which the inorganic fillers have different average particle diameters, and based on this, it can be applied to technical fields such as displays. can

In another aspect of the present invention, the polyimide film may have a predetermined modulus suitable for an electronic device that is variably deformed in shape, such as a display device.

Accordingly, the present invention has a practical object to provide specific examples thereof.

In one embodiment, the present invention provides a polyimide film comprising a base film made of polyimide and an inorganic filler dispersed in the base film,

The polyimide film may have a modulus of 5.0 GPa or more,

The inorganic filler includes a first filler group having an average particle diameter (D50) in the range of 2 μm to 2.7 μm and a second filler group having an average particle diameter (D50) in the range of 1 μm to 1.7 μm,

The first filler group and the second filler group may satisfy the following relational expression 1 for particle diameters, respectively.

0.7 ≤ (D90-D10)/D50 ≤ 1.2 (1)

In one embodiment, the present invention provides a method of making a polyimide film.

In one embodiment, the present invention provides an electronic device comprising a polyimide film as at least one of an optical film, an insulating film and a protective film.

The electronic device may be a display device or a wearable device whose shape is variably deformed through at least one selected from bending, bending, and rolling, and the polyimide film may be an electronic device that is deformed together in response to the deformation of the electronic device. .

Hereinafter, embodiments of the present invention will be described in more detail in the order of "polyimide film" and "method for producing polyimide film" according to the present invention.

Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

Accordingly, since the configuration of the embodiments described in the present specification is only one of the most preferred embodiments of the present invention and does not represent all the technical spirit of the present invention, various equivalents and modifications that can be substituted for them at the time of the present application It should be understood that examples may exist.

In this specification, the singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as "comprise", "comprising" or "have" are intended to designate the presence of an embodied feature, number, step, element, or a combination thereof, but one or more other features or It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, elements, or combinations thereof.

As used herein, "dianhydride (dianhydride)" is intended to include its precursors or derivatives, which may not technically be dianhydrides, but nevertheless react with diamines to form polyamic acids. and this polyamic acid can be converted back to polyimide.

As used herein, "diamine" is intended to include precursors or derivatives thereof, which may not technically be diamines, but will nevertheless react with dianhydrides to form polyamic acids, which in turn are polyamic acids. can be converted to mid.

Where an amount, concentration, or other value or parameter is given herein as a range, a preferred range, or a recitation of a preferred upper value and a preferred lower value, any pair of any upper range limit, or any pair of upper range limits, whether or not ranges are separately disclosed. It is to be understood that the preferred values and any lower range limits or all ranges formed by the preferred values are specifically disclosed. When a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoint and all integers and fractions within the range. It is intended that the scope of the invention not be limited to the particular values recited when defining the ranges.

polyimide film

The polyimide film according to the present invention may include a base film made of polyimide and an inorganic filler dispersed in the base film.

Here, the inorganic filler may include a first filler group having an average particle diameter (D50) in the range of 2 μm to 2.7 μm and a second filler group having an average particle diameter (D50) in the range of 1 μm to 1.7 μm. . The first filler group and the second filler group may satisfy the following Relational Expression 1 for particle diameters, respectively:

0.7 ≤ (D90-D10)/(D50) ≤ 1.2 (1)

Even a filler group having the same average particle diameter may have a different particle size distribution, and may have different effects on the effect depending on the particle size distribution. This particle size distribution can be confirmed by D10, D50, and D90.

D90 is the particle size of the smallest particle among 10% of particles with a large particle diameter in the filler group, D10 is the particle size of the largest particle among 10% of particles with a small particle diameter in the filler group, and the average particle diameter (D50) is It is the particle size of the largest particle among 50% of the small particle size in the filler group.

Various factors may be related to the particle size deviation between particles constituting the filler group, and the difference between D90 and D10 may also be considered as one of such factors.

In summary, the larger the difference between D90 and D10, the greater the particle size deviation between the particles constituting the filler group, and vice versa, the smaller the particle size deviation.

In this regard, when the inorganic fillers of a single filler group are dispersed in the base film, there is a large particle size deviation, that is, outside the range of Relation 1, 'large particles' having a particle size of about D90 in some part of the base film It means 'non-uniform distribution of particles', in which there are more 'small particles' with particle diameters around D10 in other parts.

The non-uniform distribution of the inorganic filler in the base film causes the polyimide film to have non-uniform surface roughness, and as large particles or small particles are concentrated on any part of the base film, the projections derived from the inorganic filler are on the surface of the polyimide film. This can lead to problems forming.

Accordingly, it can be understood as a factor capable of suppressing the protrusion formation that the particle size deviation of the particles constituting the filler group is small.

Even if the particle diameter deviation is at an appropriate level, if the average particle diameter of the filler group is excessively large, the number of particles that settle by gravity in the polyamic acid solution, which is a precursor of the base film, may increase. Thus, the particles may be biased towards a portion of the base film, which is another example of the non-uniform distribution of particles described above. In addition, the filler group having an excessively large average particle diameter may contribute to the improvement of the average roughness of the polyimide film, but may reduce the smoothness and transmittance of the film. On the other hand, in the case of a polyimide film for a display that requires high quality, filler particles themselves having an excessively large particle diameter may be recognized as a defect.

In addition, even if the particle size deviation is at an appropriate level, if the average particle diameter of the filler group is excessively small, the filler particles are likely to agglomerate in the polyamic acid solution due to an increase in the specific surface area of the filler group, which may cause the formation of protrusions. have. In addition, the filler group having an excessively small average particle diameter may contribute to improvement of smoothness and transmittance, but may significantly lower the average roughness, which may act as a cause of generating additional defects such as scratches in the manufacturing process of the film.

That is, it is difficult to solve the above problem with any one of the particle diameter deviation and the average particle diameter of the filler group.

Moreover, when the average particle diameter is large, the difference between D90 and D10 may appear large even if the particle distribution is even, and if the average particle diameter is small, the difference between D90 and D10 may appear small even if the particle distribution is uneven. There is a limit to representing the particle size distribution only with the difference between and D10.

Therefore, the particle size distribution can be represented only when the relationship between D10, D50, and D90 is established as in Relation 1 above, and the desired effect of the present invention can be achieved only when the range of Relation 1 is satisfied. .

When the filler group satisfies Relational Equation 1, it is assumed that the dispersion efficiency of the particles constituting the filler group is increased so that the particles can be relatively uniformly distributed on the base film, and in fact, the polyimide film of the present invention has substantially no protrusions. It may not or may contain a very small amount of protrusions, and average roughness, smoothness, and transmittance may also be inherent at appropriate levels. This will be clearly demonstrated in 'Specific contents for carrying out the invention'.

The polyimide film of the present invention also has a characteristic that can be expressed from the first filler group and the second filler group through the inorganic filler including the first filler group and the second filler group, each having an average particle diameter in a range different from each other. They are characterized in that they act complementary to each other to inherently maintain an appropriate level of average roughness, smoothness, and transmittance.

As described above, any one of the average roughness, smoothness, and transmittance of the polyimide film may be sacrificed depending on the average particle diameter of the filler group, and if a single filler group belonging to one average particle diameter range is used, they will be difficult to be compatible with each other .

However, in the polyimide film of the present invention, the first filler group having a relatively large average particle diameter range maintains an appropriate level of average roughness, and the smoothness and transmittance are adjusted to an appropriate level by the second filler group having a relatively small average particle diameter range. It is a novel polyimide film in which average roughness, which is difficult to be compatible with each other, and smoothness and transmittance are compatible to a predetermined level because it can be intrinsic.

In one specific example, the polyimide film has a haze of 12 or less, specifically 10 or less, and an average roughness of 20 nm or more, specifically 20 nm to 50 nm, more specifically 20 nm to 40 nm. Since the haze is inversely proportional to the transmittance, it can be expected that the transmittance of the polyimide film of the present invention is excellent. Specifically, the polyimide film of the present invention may have a transmittance of 0.4 to 0.6 with respect to a relative value of 1, which is a theoretical maximum transmittance.

In one specific example for the above implementation, the first filler group has a D90 of 3.0 μm to 4.1 μm, a D10 of 1.0 μm to 1.6 μm, and the second filler group has a D90 of 1.5 μm to 2.5 μm, and D10 It may be 0.7 μm to 1.2 μm.

When the D90 of the first filler group is less than the above range, the specific surface area based on the entire inorganic filler is increased, which is not preferable because aggregation of particles may be induced. In addition, when D90 of the first filler group exceeds the above range, it is not preferable because the number of particles that settle by gravity in the polyamic acid solution may increase.

When D10 of the first filler group is less than the above range, the specific surface area based on the entire inorganic filler is increased, which is not preferable because aggregation of particles may be induced. In addition, when D10 of the first filler group exceeds the above range, a large particle size deviation from large particles of the second filler group, for example, particles of D90 may be exhibited, and in this case, the non-uniform distribution of the inorganic filler is deepened. This is not desirable because it can be

In the case of D90 and D10 of the second filler group, similar disadvantages to those of the previous first filler group may occur, so it is preferable to be selected from the above range.

In one specific example for the above implementation, the polyimide film may include an inorganic filler in an amount of 0.05 wt% to 0.3 wt% based on the total weight thereof.

If the content of the inorganic filler exceeds the above range, the mechanical properties of the polyimide film may be greatly reduced, and if it is less than the above range, the intended effect of the present invention may not be expressed.

In addition, if the content of the first and second filler groups constituting the inorganic filler is out of harmony with the scope of the present invention, for example, the content of the second filler group is too high, and therefore the content of the first filler group is When reduced, the average roughness may be lowered, but smoothness and transmittance are not significantly improved by the second filler group.

Conversely, if the content of the first filler group is too high and the content of the second filler group is reduced accordingly, the effect of improving smoothness and transmittance by the second filler group is not expressed, and uneven distribution may be induced.

That is, when the content of the first filler group and the second filler group is at a certain appropriate level, the characteristics that can be expressed in each of them are balanced, and the intended effect of the present invention can be expressed, but the above-mentioned appropriate level Any deviation can disrupt this balance and negatively affect the polyimide film.

Accordingly, the present invention discloses a preferred content of the first filler group and the second filler group.

In one example for this, the inorganic filler, based on the total weight of the first filler group, 60% to 80% by weight, specifically 65% to 75% by weight, more specifically 68% by weight % to 72% by weight. The inorganic filler may also contain 20% to 40% by weight of the second filler group, specifically 25% to 35% by weight, more specifically 28% to 32% by weight, based on the total weight thereof. may include

When using the first filler group and the second filler group selected within this content range, it should be understood that the desired effect of the present invention can be expressed.

On the other hand, in some cases, for the purpose of improving the smoothness of the polyimide film, the inorganic filler may further include a third filler group having an average particle diameter (D50) in the range of 0.3 µm to 0.6 µm and satisfying Relational Expression 1 have.

However, since the third filler group has a small average particle diameter, it is easy to aggregate, and may reduce the average roughness of the polyimide film, it may be preferable to be included in a limited amount. In one specific example, the inorganic filler is based on the total weight of the third filler group in an amount of 5 wt% or more to less than 20 wt%, specifically 5 wt% to 10 wt%, more specifically It may be included in an amount of 7 wt% to 10 wt%.

When the inorganic filler further includes a third filler group, a portion of the second filler group may be included in the form of being replaced by the third filler group, and in this case, the weight ratio of the third filler group to the second filler group ( The weight of the third filler group/the weight of the second filler group) may be 0.1 to 1.

The third filler group may have a D90 of 0.4 μm to 0.9 μm, and a D10 of 0.2 μm to 0.4 μm.

When the D90 of the third filler group is less than the above range, the specific surface area based on the entire inorganic filler is increased, which is not preferable because agglomeration of particles may be induced. Moreover, when D90 of the said 3rd filler group exceeds the said range, it is difficult to expect smoothness improvement. In addition, when D10 of the third filler group is less than the above range, the specific surface area based on the entire inorganic filler may increase and agglomeration of particles may be induced, and if it exceeds the above range, it is difficult to expect smoothness improvement.

The inorganic filler of the present invention may be at least one selected from the group consisting of silica, calcium phosphate, calcium carbonate, and barium sulfate having excellent compatibility with the polyamic acid solution, and specifically, it may be spherical silica having poor agglomeration properties. have.

In one specific example, the polyimide constituting the base film may be derived from imidization of a polyamic acid formed by polymerization of a dianhydride monomer and a diamine monomer.

The diamine monomer that can be used for polymerization of the polyamic acid is an aromatic diamine, and may be classified as follows.

1) 1,4-diaminobenzene (or paraphenylenediamine, PPD, PDA), 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,5-dia As a diamine having one benzene ring in its structure, such as minobenzoic acid (or DABA), a diamine having a relatively rigid structure;

2) 4,4'-diaminodiphenyl ether (or oxydianiline, ODA), diaminodiphenyl ether such as 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane ( p-methylenedianiline), 3,4'-diaminodiphenylmethane (m-methylenedianiline), 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4 , 4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, bis(4-aminophenyl) Sulfide, 4,4'-diaminobenzanilide, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine (or o-tolidine), 2,2'-dimethylbenzidine (or m-tolidine) , 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl Ether, 3,3'-diaminodiphenylsulfide, 3,4'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 3,4' -diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diamino-4,4' -Dichlorobenzophenone, 3,3'-diamino-4,4'-dimethoxybenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'- Diaminodiphenylmethane, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1, 3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenylsulfoxide diamines having two benzene rings in the structure, such as side, 3,4'-diaminodiphenylsulfoxide, 4,4'-diaminodiphenylsulfoxide and the like;

3) 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,4-bis(4-amino) Phenyl)benzene, 1,3-bis(4-aminophenoxy)benzene (or TPE-R), 1,4-bis(3-aminophenoxy)benzene (or TPE-Q) 1,3-bis(3) -Aminophenoxy)-4-trifluoromethylbenzene, 3,3'-diamino-4-(4-phenyl)phenoxybenzophenone, 3,3'-diamino-4,4'-di (4 -Phenylphenoxy)benzophenone, 1,3-bis(3-aminophenylsulfide)benzene, 1,3-bis(4-aminophenylsulfide)benzene, 1,4-bis(4-aminophenylsulfide)benzene , 1,3-bis(3-aminophenylsulfone)benzene, 1,3-bis(4-aminophenylsulfone)benzene, 1,4-bis(4-aminophenylsulfone)benzene, 1,3-bis[2 -(4-aminophenyl)isopropyl]benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, 1,4-bis[2-(4-aminophenyl)isopropyl]benzene, etc. likewise, a diamine having three benzene rings in its structure;

4) 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[3-(3-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[4- (3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl]ketone, bis[3-(4-aminophenoxy) cy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[3-(3-aminophenoxy)phenyl]sulfide , bis[3-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[3- (3-aminophenoxy)phenyl]sulfone, bis[3-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy) Cy)phenyl]sulfone, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane , bis[4-(4-aminophenoxy)phenyl]methane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy) Phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP), 2,2-bis [3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(4-aminophenoxy)phenyl]-1, 1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane; A diamine having four benzene rings in its structure, such as 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane.

These can be used individually or in combination of 2 or more types depending on necessity.

The dianhydride monomer that can be used for polymerization of the polyamic acid may be an aromatic tetracarboxylic dianhydride.

The aromatic tetracarboxylic dianhydride is pyromellitic dianhydride (or PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (or s-BPDA), 2,3 ,3',4'-biphenyltetracarboxylic dianhydride (or a-BPDA), oxydiphthalic dianhydride (or ODPA), diphenylsulfone-3,4,3',4'-tetracar Voxylic dianhydride (or DSDA), bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3, 3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride ( or BTDA), bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, p-phenylenebis(trimellitic monoester acid) anhydride), p-biphenylenebis(trimellitic monoester acid anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, p-terphenyl -3,4,3',4'-tetracarboxylic dianhydride, 1,3-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,4-bis (3,4-di Carboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propanedian Hydride (BPADA), 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4'-(2,2-hexafluoro and rhoisopropylidene)diphthalic acid dianhydride. These can be used individually or in combination of 2 or more types depending on necessity.

In one specific example, the dianhydride monomer that can be particularly preferably used in the present invention is pyromellitic dianhydride (PMDA) and/or 3,3',4,4'-biphenyltetracarboxylic dian It may include hydride (BPDA), and the diamine monomer that may be particularly preferably used in the present invention may include 1,4-diaminobenzene (PPD).

The diamine monomer is also 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether (3,4'-ODA), p-methylenedianiline ( p-MDA), m-methylenedianiline (m-MDA), and m-phenylene diamine (MPD) may further include one or more selected from the group consisting of.

At this time, based on the total moles of the dianhydride monomer, the content of the pyromellitic dianhydride (PMDA) and/or 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is 95 mol% or more,

Based on the total number of moles of the diamine monomer, the content of 1,4-diaminobenzene (PPD) may be 70 mol% or more.

At this content, the polyimide film according to the present invention may have a predetermined modulus, specifically 5.0 GPa or more, and more specifically 5.0 GPa or more to 10.0 Gpa or less, while satisfying the following Relational Expression 2.

12 μm ≤ T * L ≤ 40 μm (2)

Here, T is the thickness of the polyimide film, 30 μm to 50 μm, L is the transmittance of the polyimide film, which is a relative value to 1, which is the theoretical maximum transmittance, and is 0.4 to 0.8, specifically 0.4 to 0.6.

A polyimide film that satisfies this relationship is, for example, a display device requiring optical properties based on excellent light transmittance, in particular, an insulation of a display device whose shape is variably deformed through at least one selected from bending, bending and rolling , may be suitable as a protective film.

In one example, a display device in which both ends are deformed in the same direction, for example, bent, has an inner surface facing the deformation direction and an outer surface opposite to the display device. When the display device is deformed, the force is transmitted from both ends of the display device toward the center on the inner surface, and the force is transferred from the center to both ends of the display device on the outer surface.

If the polyimide film is added to the outer surface of the display device that is deformed as described above, a tensile force is formed on the polyimide film by the force transmitted from the center to both ends of the display device. In this case, if the modulus of the polyimide film is too high, the polyimide film may have a brittle characteristic and may not be deformed in a tensile direction. In this case, the polyimide film may cause a problem of shortening the lifespan of the display by applying stress to the inside of the display.

Conversely, when the polyimide film is added to the inner surface, a separate tensile force is not formed, and the polyimide film tends to be compressed by the force transmitted from both ends toward the center. Accordingly, it may be advantageous that the polyimide film added to the inner surface has a high modulus and thus has a strong compressive force. The polyimide film of the present invention has a modulus of 5.0 GPa or more, and is deformed based on a relatively high modulus. It may be specialized to be added to the outer surface of the display device. However, the above has been described as a non-limiting example of the polyimide film according to the present invention, and emphasizes that the use of the polyimide film of the present invention is not limited thereto.

Manufacturing method of polyimide film

The method for producing a polyimide film according to the present invention comprises:

preparing a polyamic acid solution by polymerizing a dianhydride monomer and a diamine monomer in an organic solvent;

preparing a precursor composition by mixing an inorganic filler with the polyamic acid solution; and

After forming the precursor composition on a support, imidization may include forming a polyimide film.

The method of polymerizing the polyamic acid is, for example,

(1) a method in which the whole amount of the diamine monomer is put in an organic solvent, and then the dianhydride monomer is added so as to be substantially equimolar with the diamine monomer and polymerized;

(2) a method in which the entire amount of the dianhydride monomer is placed in an organic solvent, and then the diamine monomer is added so as to be substantially equimolar with the dianhydride monomer and polymerized;

(3) After some components of the diamine monomer are put in the organic solvent, some components of the dianhydride monomer are mixed in a ratio of about 95 mol% to 105 mol% with respect to the reaction component, and the remaining diamine monomer components are added thereto a method of polymerization by successively adding the remaining dianhydride monomer components so that the diamine monomer and the dianhydride monomer are substantially equimolar;

(4) After the dianhydride monomer is put in the organic solvent, some components of the diamine compound are mixed in a ratio of 95 mol% to 105 mol with respect to the reaction component, then another dianhydride monomer component is added and the remaining diamine a method of polymerization by adding a monomer component so that the diamine monomer and the dianhydride monomer are substantially equimolar; and

(5) a part of the diamine monomer component and a part of the dianhydride monomer component in an organic solvent are reacted such that any one of them is in excess to form a first polymer, and a part of the diamine monomer component and a part of the dianhydride monomer component in another organic solvent A method of forming a second polymer by reacting so that any one is in excess, then mixing the first and second polymers, and completing the polymerization. At this time, when the diamine monomer component is excessive when forming the first polymer , In the second polymer, the dianhydride monomer component is in excess, and when the dianhydride monomer component is in excess in the first polymer, the diamine monomer component is in excess in the second polymer, and the first and second polymers are mixed. and a method of polymerization such that all the diamine monomer components and the dianhydride monomer components used in these reactions are substantially equimolar.

However, the above method is an example for helping the practice of the present invention, and the scope of the present invention is not limited thereto, and any known method may be used.

As the diamine monomer and dianhydride monomer, the same monomers as described in the previous embodiment may be used.

The organic solvent is not particularly limited as long as it is a solvent in which diamine, dianhydride monomer, and polyamic acid can be dissolved, but as an example, it may be an aprotic polar solvent.

Non-limiting examples of the aprotic polar solvent include amide solvents such as N,N'-dimethylformamide (DMF), N,N'-dimethylacetamide (DMAc), p-chlorophenol, and o-chloro and phenolic solvents such as phenol, N-methyl-pyrrolidone (NMP), gamma butyrolactone (GBL), and Diglyme, and these may be used alone or in combination of two or more.

In some cases, the solubility of the polyamic acid may be adjusted by using an auxiliary solvent such as toluene, tetrahydrofuran, acetone, methyl ethyl ketone, methanol, ethanol, or water.

In one example, the organic solvent that can be particularly preferably used for preparing the polyamic acid solution of the present invention may be N,N'-dimethylformamide and N,N'-dimethylacetamide, which are amide solvents.

The polyamic acid of the polyamic acid solution prepared as described above may have a weight average molecular weight of 150,000 g/mole or more to 1,000,000 g/mole or less, and specifically 260,000 g/mole or more to 700,000 g/mole or less, and more specifically, It may be 280,000 g/mole or more and 500,000 g/mole or less.

The polyamic acid having such a weight average molecular weight may be preferable for producing a polyimide film having more excellent heat resistance and mechanical properties.

In general, the weight average molecular weight of the polyamic acid may be proportional to the viscosity of the polyamic acid solution containing the polyamic acid and the organic solvent, and the weight average molecular weight of the polyamic acid may be controlled within the above range by adjusting the viscosity.

This is because the viscosity of the polyamic acid solution is proportional to the polyamic acid solid content, specifically, the total amount of the dianhydride monomer and the diamine monomer used in the polymerization reaction. However, the weight average molecular weight does not represent a one-dimensional linear proportional relationship with respect to the viscosity, but is proportional in the form of a log function.

That is, even if the viscosity is increased to obtain a polyamic acid having a higher weight average molecular weight, the range in which the weight average molecular weight can be increased is limited, whereas when the viscosity is excessively high, a precursor composition through a die in the film forming process of the polyimide film During ejection, a problem of fairness may occur due to an increase in pressure inside the die.

Accordingly, the polyamic acid solution of the present invention may contain 15 wt% to 20 wt% of polyamic acid solid content and 80 wt% to 85 wt% of an organic solvent, in which case the viscosity is 90,000 cP or more to 350,000 cP or less, specifically may be 100,000 cP or more to 300,000 cP. Within this viscosity range, the weight average molecular weight of the polyamic acid may fall within the above range, and the precursor composition may not cause problems in the film forming process described above.

The step of preparing a precursor composition by mixing an inorganic filler with the polyamic acid solution includes milling or ultrasonically dispersing a mixture of an inorganic filler and an organic solvent, and then mixing the mixture with the polyamic acid solution to prepare a precursor composition; Alternatively, it may include the step of preparing a precursor composition by milling a mixture of an inorganic filler and an organic solvent mixed with the polyamic acid solution.

For the milling, use of, but not limited to, a bead milling method may be considered. Bead milling has an advantage in dispersion because it can effectively stir even when the flow rate of the mixture is low. However, it should be understood that this is only an example for helping the implementation of the invention.

After forming the precursor composition on a support, imidization to form a polyimide film, thermal imidization method, chemical imidization method, or a complex imidization method using the thermal imidization method and chemical imidization method in combination This can be used.

This will be described in more detail through the following non-limiting examples.

<Thermal imidization method>

The thermal imidization method is a method of inducing an imidization reaction with a heat source such as hot air or an infrared dryer, excluding a chemical catalyst,

drying the precursor composition to form a gel film; and

It may include a process of heat-treating the gel film to obtain a polyimide film.

Here, the gel film can be understood as a film intermediate having self-supporting properties in an intermediate step for conversion from polyamic acid to polyimide.

In the process of forming the gel film, the precursor composition is cast in a film form on a support such as a glass plate, aluminum foil, endless stainless belt, or stainless drum, and then the precursor composition on the support is 50 ℃ to 200 ℃, Specifically, it may be drying at a variable temperature in the range of 80 ℃ to 200 ℃.

Accordingly, partial curing and/or drying of the precursor composition may occur to form a gel film. It can then be peeled off the support to obtain a gel film.

In some cases, a process of stretching the gel film may be performed to control the thickness and size of the polyimide film obtained in the subsequent heat treatment process and to improve orientation, and stretching is performed in the machine transport direction (MD) and the machine transport direction It may be performed in at least one direction among the transverse directions TD.

The gel film thus obtained is fixed in a tenter and then heat treated at a variable temperature in the range of 50 ° C to 650 ° C, specifically 150 ° C to 600 ° C to remove water, residual solvent, etc. remaining in the gel film, and Almost all amic acid groups can be imidated to obtain the polyimide film of the present invention.

In some cases, the polyimide film obtained as described above may be heat-finished at a temperature of 400 ° C. to 650 ° C. for 5 seconds to 400 seconds to further harden the polyimide film. This may be done under a certain tension in order to relieve the stress.

<Chemical imidization method>

The chemical imidization method is a method of accelerating imidization of an amic acid group by adding a dehydrating agent and/or an imidizing agent to the precursor composition.

Here, "dehydrating agent" means a substance that promotes a ring closure reaction through dehydration action on polyamic acid, and as a non-limiting example thereof, aliphatic acid anhydride, aromatic acid anhydride, N,N'- dialkylcarbodiimide, halogenated lower aliphatic, halogenated lower patty acid anhydride, aryl phosphonic dihalide, thionyl halide, and the like. Among them, aliphatic acid anhydride may be preferable from the viewpoint of availability and cost, and non-limiting examples thereof include acetic anhydride (AA), propion acid anhydride, and lactic acid anhydride. These etc. are mentioned, These can be used individually or in mixture of 2 or more types.

In addition, "imidizing agent" means a substance having an effect of promoting a ring closure reaction with respect to polyamic acid, for example, an imine-based component such as an aliphatic tertiary amine, an aromatic tertiary amine, and a heterocyclic tertiary amine can Among these, a heterocyclic tertiary amine may be preferable from the viewpoint of reactivity as a catalyst. Non-limiting examples of heterocyclic tertiary amines include quinoline, isoquinoline, β-picoline (BP), pyridine, and the like, and these may be used alone or in combination of two or more.

It is preferable to exist in the range of 0.5-5 mol with respect to 1 mol of amic acid groups in a polyamic acid, and, as for the addition amount of a dehydrating agent, it is especially preferable to exist in the range of 1.0 mol - 4 mol. Further, the amount of the imidizing agent added is preferably in the range of 0.05 mol to 2 mol, particularly preferably in the range of 0.2 mol to 1 mol, based on 1 mol of the amic acid group in the polyamic acid.

If the dehydrating agent and the imidizing agent are less than the above ranges, chemical imidization may be insufficient, cracks may be formed in the polyimide film to be produced, and the mechanical strength of the film may also be reduced. In addition, if these addition amounts exceed the above range, imidization may proceed excessively quickly. In this case, it may be difficult to cast in a film form or the prepared polyimide film may exhibit brittle characteristics, which is not preferable. not.

<Complex imidization method>

In conjunction with the above chemical imidization method, a composite imidization method in which thermal imidization is additionally performed may be used for the production of the polyimide film.

Specifically, the complex imidization method includes a chemical imidization process in which a dehydrating agent and/or an imidization agent are added to the precursor composition at low temperature; and a thermal imidization process of drying the precursor composition to form a gel film, and heat-treating the gel film.

When performing the chemical imidization process, the type and amount of the dehydrating agent and the imidizing agent may be appropriately selected as described in the above chemical imidization method.

In the process of forming the gel film, a precursor composition containing a dehydrating agent and/or an imidizing agent is cast in a film form on a support such as a glass plate, aluminum foil, endless stainless belt, or stainless drum, and then on the support. The precursor composition is dried at varying temperatures ranging from 50° C. to 200° C., specifically from 80° C. to 200° C. In this process, the dehydrating agent and/or the imidizing agent may act as a catalyst to rapidly convert the amic acid group to the imide group.

In some cases, a process of stretching the gel film may be performed to control the thickness and size of the polyimide film obtained in the subsequent heat treatment process and to improve orientation, and stretching is performed in the machine transport direction (MD) and the machine transport direction It may be performed in at least one direction among the transverse directions TD.

As for the volatile matter content of the gel film, the bar described in the previous thermal imidization method may be applied as it is.

The gel film thus obtained is fixed in a tenter and then heat treated at a variable temperature ranging from 50 ° C to 650 ° C, specifically from 150 ° C to 600 ° C to remove water, catalyst, residual solvent, etc. remaining in the gel film, By imidization of almost all of the remaining amic acid groups, the polyimide film of the present invention can be obtained. Even in such a heat treatment process, the dehydrating agent and/or the imidizing agent act as a catalyst, so that the amic acid group can be rapidly converted into the imide group, thereby realizing a high imidization rate.

In some cases, the polyimide film obtained as described above may be heat-finished at a temperature of 400 ° C. to 650 ° C. for 5 seconds to 400 seconds to further harden the polyimide film. This may be done under a certain tension in order to relieve the stress.

The present invention provides the advantages of a polyimide film including an inorganic filler, specifically, a polyimide film including an inorganic filler that satisfies the specific Relational Expression 1 of the present invention and has a plurality of filler groups having different particle diameters from the above. has been described in detail.

In summary, the polyimide film of the present invention has substantially no protrusions due to filler aggregation, and it is difficult to be compatible with each other due to filler groups having different average particle diameters, and the average roughness, smoothness, and transmittance are inherent at an appropriate level. can do.

1 is a photograph of a surface of a polyimide film according to Example 1. FIG.
2 is a photograph of the surface of the polyimide film according to Comparative Example 6.

Hereinafter, through specific examples of the invention, the operation and effect of the invention will be described in more detail. However, these embodiments are merely presented as an example of the invention, and the scope of the invention is not defined thereby.

<Example 1>

Preparation Example 1-1: Preparation of precursor composition

In a 1.0 L reactor, 520.60 g of dimethylformamide (DMF) as an organic solvent was added under a nitrogen atmosphere. After setting the temperature to 25 °C, 26.63 g of PPD as a diamine monomer is added, stirring for 30 minutes to confirm that the monomer is dissolved, 50.73 g of BPDA as a dianhydride monomer, and 14.51 g of PMDA are added, and finally viscosity A polyamic acid solution was prepared by adjusting the final input amount to be 100,000 cP to 150,000 cP.

Then, a precursor composition was prepared by mixing an inorganic filler including a first filler group and a second filler group having the following characteristics in a polyamic acid solution at 0.15% of the polyamic acid solid content:

-First filler group: spherical silica having an average particle diameter (D50) of 2 μm, D10 of 1.1 μm, and D90 of 3.0 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1 µm, D10 of 0.7 µm, and D90 of 1.5 µm, 30 wt% based on the total weight of inorganic fillers.

Preparation Example 1-2: Preparation of polyimide film

After adding 3.0 g of isoquinoline (IQ), 20.8 g of acetic anhydride (AA), and 16.2 g of DMF as a catalyst to 100 g of the precursor composition prepared in Preparation Example 1-1, uniformly mixed with a SUS plate (100SA, Sandvik) ) was cast to 470 μm using a doctor blade and dried in a temperature range of 100°C to 200°C.

Then, the film was peeled off the SUS plate, fixed to a pin frame, and transferred to a high-temperature tenter.

The film was heated from 200 °C to 600 °C in a high-temperature tenter, cooled at 25 °C, and separated from the fin frame to obtain a polyimide film having a width*length of 1 m*1 m and a thickness of 50 µm.

<Example 2>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group and a second filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 2.7 μm, D10 of 1.5 μm, and D90 of 4.1 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1.7 µm, D10 of 1.2 µm, and D90 of 2.5 µm, 30 wt% based on the total weight of inorganic fillers.

<Example 3>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group and a second filler group having the following characteristics was used.

-First filler group: spherical silica having an average particle diameter (D50) of 2.2 μm, D10 of 1.3 μm, and D90 of 3.3 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1.3 μm, D10 of 0.9 μm, and D90 of 1.9 μm, 30 wt% based on the total weight of inorganic fillers.

<Example 4>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group and a second filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 2.2 μm, D10 of 1.3 μm, and D90 of 3.3 μm, 80% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1.3 µm, D10 of 0.9 µm, and D90 of 1.9 µm, 20 wt% based on the total weight of inorganic fillers.

<Example 5>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group, a second filler group, and a third filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 2 μm, D10 of 1.1 μm, and D90 of 3.0 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1 μm, D10 of 0.7 μm, and D90 of 1.5 μm, 20% by weight based on the total weight of inorganic fillers;

-Third filler group: spherical silica having an average particle diameter (D50) of 0.3 µm, D10 of 0.2 µm, and D90 of 0.42 µm, 10% by weight based on the total weight of inorganic fillers.

<Example 6>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group, a second filler group, and a third filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 2.7 μm, D10 of 1.5 μm, and D90 of 4.1 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1.7 µm, D10 of 1.2 µm, and D90 of 2.5 µm, 20% by weight based on the total weight of inorganic fillers;

-Third filler group: spherical silica having an average particle diameter (D50) of 0.6 µm, D10 of 0.4 µm, D90 of 0.9 µm, and 10 wt% based on the total weight of inorganic fillers.

<Example 7>

A polyimide film was prepared in the same manner as in Example 1, except that 23.40 g of PPD and 4.82 g of MDA were used as diamine monomers.

<Comparative Example 1>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group and a second filler group having the following characteristics was used:

-First filler group: calcium phosphate having an average particle diameter (D50) of 2 μm, D10 of 0.7 μm, and D90 of 5.3 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: barium sulfate having an average particle diameter (D50) of 1 μm, D10 of 0.4 μm, and D90 of 2.3 μm, and 30 wt% based on the total weight of inorganic fillers.

<Comparative Example 2>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a single filler group having the following characteristics was used:

- Filler group: calcium phosphate having an average particle diameter (D50) of 2 μm, D10 of 0.7 μm, and D90 of 5.3 μm, 100% by weight based on the total weight of the inorganic filler.

<Comparative Example 3>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group and a second filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 3 μm, D10 of 1.7 μm, and D90 of 4.7 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1 µm, D10 of 0.7 µm, and D90 of 1.5 µm, 30 wt% based on the total weight of inorganic fillers.

<Comparative Example 4>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group and a second filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 2 μm, D10 of 1.1 μm, and D90 of 3.0 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 0.6 µm, D10 of 0.4 µm, and D90 of 0.9 µm, 30 wt% based on the total weight of inorganic fillers.

<Comparative Example 5>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group and a second filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 2 μm, D10 of 1.1 μm, and D90 of 3.0 μm, 50% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1 µm, D10 of 0.7 µm, D90 of 1.5 µm, and 50 wt% based on the total weight of inorganic fillers.

<Comparative Example 6>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group and a second filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 2 μm, D10 of 0.8 μm, and D90 of 3.5 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1 μm, D10 of 0.3 μm, and D90 of 1.8 μm, 30 wt% based on the total weight of inorganic fillers.

<Comparative Example 7>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group and a second filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 2 μm, D10 of 1.5 μm, and D90 of 2.6 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1 µm, D10 of 0.7 µm, and D90 of 1.3 µm, 30 wt% based on the total weight of inorganic fillers.

<Comparative Example 8>

A polyimide film was prepared in the same manner as in Example 1, except that an inorganic filler including a first filler group, a second filler group, and a third filler group having the following characteristics was used:

-First filler group: spherical silica having an average particle diameter (D50) of 2 μm, D10 of 1.1 μm, and D90 of 3.0 μm, 70% by weight based on the total weight of inorganic fillers;

-Second filler group: spherical silica having an average particle diameter (D50) of 1 μm, D10 of 0.7 μm, and D90 of 1.5 μm, 10% by weight based on the total weight of inorganic fillers;

-Third filler group: spherical silica having an average particle diameter (D50) of 0.3 µm, D10 of 0.2 µm, and D90 of 0.4 µm, 20% by weight based on the total weight of inorganic fillers.

The inorganic fillers used in the above Examples and Comparative Examples are briefly summarized in Table 1 below.

Types of inorganic fillers 1st filler group 2nd filler group 3rd filler group Characteristic content D50 D10 D90 content D50 D10 D90 content D50 D10 D90 Example 1 spherical silica 70 2 1.1 3.0 30 One 0.7 1.5 - - - - Example 2 spherical silica 70 2.7 1.5 4.1 30 1.7 1.2 2.5 - - - - Example 3 spherical silica 70 2.2 1.3 3.3 30 1.3 0.9 1.9 - - - - Example 4 spherical silica 80 2.2 1.3 3.3 20 1.3 0.9 1.9 - - - - Example 5 spherical silica 70 2 1.1 3.0 20 One 0.7 1.5 10 0.3 0.2 0.42 Example 6 spherical silica 70 2.7 1.5 4.1 20 1.7 1.2 2.5 10 0.6 0.4 0.9 Example 7 spherical silica 70 2 1.1 3.0 30 One 0.7 1.5 - - - - Comparative Example 1 Calcium Phosphate/Barium Sulfate 70 2 0.7 5.3 30 One 0.4 2.3 - - - - Comparative Example 2 calcium phosphate 100 2 0.7 5.3 - - - - - - - - Comparative Example 3 spherical silica 70 3 1.7 4.7 30 One 0.7 1.5 - - - - Comparative Example 4 spherical silica 70 2 1.1 3.0 30 0.6 0.4 0.9 - - - - Comparative Example 5 spherical silica 50 2 1.1 3.0 50 One 0.7 1.5 - - - - Comparative Example 6 conception
silica 70 2 0.8 3.5 30 One 0.3 1.8 - - - - Comparative Example 7 conception
silica 70 2 1.5 2.6 30 One 0.7 1.3 - - - - Comparative Example 8 spherical silica 70 2 1.1 3.0 10 One 0.7 1.5 20 0.3 0.2 0.4

Whether the fillers used in Examples 1 to 6 and Comparative Examples 1 to 8 satisfy the following Relational Expression 1 are summarized in Table 2 below.

0.7 ≤ (D90-D10)/(D50) ≤ 1.2 (1)

1st filler group 2nd filler group 3rd filler group Relation 1 Satisfied Relation 1 Satisfied Relation 1 Satisfied Example 1 0.95 O 0.80 O - - Example 2 0.96 O 0.76 O - - Example 3 0.91 O 0.77 O - - Example 4 0.91 O 0.77 O - - Example 5 0.95 O 0.80 O 0.73 O Example 6 0.96 O 0.76 O 0.83 O Example 7 0.95 O 0.80 O - - Comparative Example 1 2.30 X 1.90 X - - Comparative Example 2 2.30 X - - - - Comparative Example 3 1.00 O 0.80 O - - Comparative Example 4 0.95 O 0.83 O - - Comparative Example 5 0.95 O 0.80 O - - Comparative Example 6 1.35 X 1.50 X - - Comparative Example 7 0.55 X 0.60 X - - Comparative Example 8 0.95 O 0.80 O 0.67 X

<Experimental Example 2: Characteristic evaluation of polyimide film>

1) Average roughness evaluation: The average roughness of each polyimide film was measured using the ISO1997 method, and the measurement conditions were cut off 0.25mm, measuring speed 0.1mm/sec, and average value measured 5 times under the conditions of measuring length 3mm per one time. was used. In this case, the air side of the polyimide film (the opposite side of the surface in contact with the plate or tenter) was used as the surface for measuring the average roughness. The above average roughness results are shown in Table 3 below.

2) Surface defect evaluation: The surface of the polyimide film prepared in Examples and Comparative Examples was observed under a microscope to check the number of defects with a major axis of 30 um or more per unit area of 1 m * 1 m, and the results are shown in Table 3 and FIG. 1 (Example 1) and FIG. 2 (Comparative Example 6).

3) Haze evaluation: The haze value was measured on the A light source using the HM150 model.

4) Transmittance evaluation: Transmittance was measured by the method presented in ASTM D1003 in the visible region using HunterLab's ColorQuesetXE model.

However, the transmittance is shown in Table 3 below as a relative value to 1, which is the theoretical maximum transmittance in an arbitrary object.

average illuminance
(nm) surface defects
(Count) haze transmittance Example 1 25.6 4 8.3 0.53 Example 2 40.2 3 11.6 0.41 Example 3 31.5 One 9.1 0.55 Example 4 30.9 One 9.0 0.48 Example 5 22.1 5 7.9 0.61 Example 6 35.8 5 11.3 0.44 Example 7 24.6 3 7.9 0.56 Comparative Example 1 16.7 45 8.3 0.44 Comparative Example 2 17.3 41 6.8 0.48 Comparative Example 3 44.9 31 10.2 0.45 Comparative Example 4 24.5 15 13.7 0.33 Comparative Example 5 30.3 28 14.5 0.30 Comparative Example 6 41.7 33 8.6 0.48 Comparative Example 7 30.2 16 14.2 0.36 Comparative Example 8 28.3 30 13.1 0.37

From the results of Table 3, all of the examples in which Relational Expression 1 is satisfied, D50, D90, and D10 are within the scope of the present invention, and the content of each filler group is also within the scope of the present invention has an average roughness of 20 nm or more, and 12 or less. It exhibited haze, transmittance of 0.4 or more, and excellent smoothness.

It can also be seen that the embodiment has no surface defects (protrusions). In this regard, referring to FIG. 1 in which the surface of the polyimide film according to Example 1 is photographed, it can be seen that the polyimide film has a smooth surface.

On the other hand, it can be seen that comparative examples that are unsatisfied with at least one of various factors according to the present invention, specifically the type of filler group, content, particle size, and Relational Expression 1, have poor at least one of average roughness, haze, transmittance, and smoothness. have. From the results of these comparative examples, it should be noted that, when carried out according to the present invention, the average roughness, transmittance and smoothness that are difficult to be compatible with each other can be compatible to an appropriate level.

In addition, since the comparative example deviating from the present invention as described above includes a plurality of surface defects, for example, as in FIG. 2 , the conventional problem is included as it is.

<Experimental Example 3: Modulus evaluation of polyimide film>

For the polyimide film of Examples, the modulus was measured by the method specified in ASTM D882 using the Instron 5564 model, and the results are shown in Table 4.

modulus
(Gpa) Example 1 5.1 Example 2 6.2 Example 3 5.5 Example 4 5.8 Example 5 6.7 Example 6 5.8 Example 7 5.9

From the results of Table 4, it can be seen that the polyimide film according to the present invention has a modulus of 5.0 GPa or more.

Although described above with reference to the embodiments of the present invention, those of ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above content.

Claims (14)

A polyimide film comprising a base film made of polyimide and an inorganic filler dispersed in the base film,
The polyimide film has a modulus of 5.0 GPa or more,
The inorganic filler includes a first filler group having an average particle diameter (D50) in the range of 2 μm to 2.7 μm and a second filler group having an average particle diameter (D50) in the range of 1 μm to 1.7 μm,
Each of the first filler group and the second filler group satisfies the following Relational Expression 1 with respect to the particle size,
Based on the total weight of the inorganic filler, a polyimide film comprising 60 wt% to 80 wt% of the first filler group and 20 wt% to 40 wt% of the second filler group:
0.7 ≤ (D90-D10)/D50 ≤ 1.2 (1) According to claim 1,
The inorganic filler is at least one polyimide film selected from the group consisting of silica, calcium phosphate, calcium carbonate and barium sulfate. 3. The method of claim 2,
The inorganic filler is a spherical silica polyimide film. According to claim 1,
A polyimide film comprising an inorganic filler in an amount of 0.05 wt% to 0.3 wt% based on the total weight of the polyimide film. According to claim 1,
The first filler group has a D90 of 3.0 μm to 4.1 μm, and a D10 of 1.0 μm to 1.6 μm,
The second filler group is a polyimide film having a D90 of 1.5 μm to 2.5 μm and a D10 of 0.7 μm to 1.2 μm. According to claim 1,
The polyimide film has a haze of 12 or less, an average roughness of 20 nm or more, and a polyimide film having 10 or less surface defects with a long diameter of 30 um or more per unit area of 1 m * 1 m. According to claim 1,
The polyimide film is a polyimide film satisfying the following relation 2:
12 μm ≤ T * L ≤ 40 μm (2)
Here, T is the thickness of the polyimide film, from 30 μm to 50 μm, and L is the transmittance in the visible region of the polyimide film, a value relative to 1, which is the theoretical maximum transmittance, and is 0.4 to 0.8. According to claim 1,
The polyimide constituting the base film is a polyimide film derived from imidization of a polyamic acid formed by polymerization of a dianhydride monomer and a diamine monomer. 9. The method of claim 8,
The dianhydride monomer comprises pyromellitic dianhydride (PMDA) and/or 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA),
The diamine monomer is a polyimide film comprising 1,4-diaminobenzene (PPD). 10. The method of claim 9,
The diamine monomer is 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether (3,4'-ODA), p-methylenedianiline (p- MDA), m-methylenedianiline (m-MDA), and m-phenylene diamine (MPD) polyimide film further comprising at least one selected from the group consisting of. 10. The method of claim 9,
Based on the total number of moles of the dianhydride monomer, the content of the pyromellitic dianhydride (PMDA) and/or 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is 95 mol% or more,
Based on the total number of moles of the diamine monomer, the content of the 1,4-diaminobenzene (PPD) is 70 mol% or more, the polyimide film. A method for producing the polyimide film according to claim 1, comprising:
preparing a polyamic acid solution by polymerizing a dianhydride monomer and a diamine monomer in an organic solvent;
preparing a precursor composition by mixing an inorganic filler with the polyamic acid solution; and
After forming the precursor composition into a film on a support, the imidization method comprising the step of forming a polyimide film. An electronic device comprising the polyimide film according to claim 1 as at least one of an optical film, an insulating film, and a protective film. 14. The method of claim 13,
The electronic device is a display device or a wearable device whose shape is variably deformed through at least one selected from bending, bending and rolling,
The polyimide film is deformed together in response to the deformation of the electronic device.

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