KR20190092345A - Polyimide film - Google Patents

Abstract

The present invention provides an optical film, which can be used as a front plate material of a flexible display and has good visibility of white printing of a bezel part. A polyimide film contains at least one polyimide-based polymer and has the yellow degree YI which is more than 0 and less than 1.0.

Description

Polyimide Film {POLYIMIDE FILM}

The present invention relates to a polyimide film.

At present, image display apparatuses, such as a liquid crystal display device and an organic electroluminescence display, are widely utilized not only for television but for various uses, such as a mobile telephone and a smart watch. With the expansion of such a use, the image display apparatus (flexible display) which has a flexible characteristic is calculated | required, and the flexibility of each member is also required.

The image display device is constituted of a polarizing plate, a retardation plate, a front plate, and the like in addition to display elements such as a liquid crystal display element or an organic EL display element. In order to achieve a flexible display, all of these members need to have flexible characteristics. When the member of an image display apparatus consists of a polymeric material which has a flexible characteristic (for example, patent document 1), since the member is easy to bend, application to a flexible display is comparatively easy to implement. However, glass, which has been used as a front plate material of an image display device until now, has high transparency and can express high hardness depending on the type of glass, but is very rigid and fragile. Use as a material is difficult.

In the image display device, for the purpose of protecting and supporting the display portion, there is usually an outer frame portion having a predetermined width at the periphery of the display substrate. This outer frame portion is called the bezel portion or the frame portion. The bezel portion is usually printed by any color tone, and the user visually recognizes the color tone of the bezel portion through the front plate located on the bezel portion.

Japanese Unexamined Patent Application Publication No. 2016-93992

However, when the conventional polyimide-based film was used as the front plate material of the image display device having the bezel portion subjected to white printing, the visibility of white printing of the bezel portion was sometimes not good. For example, Patent Literature 1 discloses a polyimide film having a yellowness of about 2, but in such a polyimide film of yellowness, the white color of the bezel portion cannot be maintained, and white printing is visually recognized. It may become.

This invention is made | formed in view of the subject which the said prior art has, and it aims at providing the optical film which can be used as a front plate material of a flexible display, and is excellent in the visibility of white printing of a bezel part.

MEANS TO SOLVE THE PROBLEM The present inventors earnestly examined about the various characteristic of the optical film used as a front plate material in order to solve the said subject. As a result, it was surprisingly found that the above-mentioned problem was solved by the polyimide film whose yellowness YI was 0 <YI <1.0, and came to complete this invention. Since the polyimide film which has yellowness YI of the said range is difficult to achieve with thickness more than 30 micron, it has not been paid attention conventionally. However, the present inventors found that by adjusting the yellowness of the polyimide film to the above range and using it as the front plate material, the visibility of white printing of the bezel portion was improved and the visibility of the display portion was not impaired.

That is, this invention includes the following suitable aspects.

[1] A polyimide film containing at least one polyimide polymer and having a yellowness YI of 0 <YI <1.0.

[2] The polyimide film according to the above [1], wherein the thickness is 20 to 200 µm.

[3] The polyimide film according to the above [1] or [2], wherein a total light transmittance is 88.0% or more.

[4] The polyimide film according to any one of the above [1] to [3], further containing at least one bluing agent.

[5] a single layer containing a bluing agent and a polyimide polymer, a laminate having at least a layer containing a bluing agent and a polyimide polymer, or a base layer containing a polyimide polymer; The polyimide film in any one of said [1]-[4] which is a laminated body which has at least a color adjustment layer containing a bluing agent.

[6] The addition amount of the bluing agent based on the total mass of the layer in each layer containing the bluing agent containing at least one layer of bluing agent is referred to as X (ppm); [1] to [4] wherein the product (X × Y) of X and Y calculated as the thickness of the layer is Y (μm) is calculated for all the layers containing the bluing agent and the sum is 300 to 4,500. 5] The polyimide film according to any one of items.

[7] The bluing agent is formula (6):

[Formula 1]

[In Formula (6), X <^1> represents OH, NHR <^1>, or NR <^1> R <^2> , X <^2> represents NHR <^3> or NR <^3> R <^4> , and R <^1> , R <^2> , R <^3> and R <^4> are mutually independent And a phenyl group substituted by a linear or branched alkyl group having 1 to 6 carbon atoms or a linear or branched alkyl group having 1 to 6 carbon atoms.]

The polyimide film in any one of said [1]-[6] which is represented by and is a compound which has a 1% thermogravimetric reduction temperature of 220 degreeC or more.

[8] The bluing agent is formula (1) to formula (3):

[Formula 2]

The polyimide film as described in said [7] which is at least 1 sort (s) chosen from the group which consists of a compound represented by these.

[9] The polyimide film according to any one of the above [1] to [8], further containing silica particles.

Since the polyimide film of this invention has the yellowness YI of 0 <YI <1.0 which is the said predetermined range, for example, when using it as a front plate material of the flexible display which has the bezel part in which the white printing was performed, for example. Excellent visibility.

1 shows an example including a white bezel and a portion covered by a polyimide film.

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described in detail.

[Polyimide Film]

(Yellow Degree YI)

The polyimide film of this invention has the characteristic that yellowness YI is 0 <YI <1.0. Yellowness YI is based on JISK7373: 2006, and transmittance | permeability measurement with respect to the light of 300-800 nm is performed by the ultraviolet visible spectrophotometer (For example, the spectrophotometer V-670 by the Japan Spectrometer). From the three stimulus values (x, y and z) to be measured, it is calculated by the following equation.

Yellowness YI of the polyimide film of this invention is 0 <YI <1.0. The polyimide film which has such a yellowness looks bluish when visually recognized by the film alone. Therefore, when the polyimide film having such yellowness YI is used as the front plate material of the flexible display having, for example, a white bezel portion, the white printing of the bezel portion is also considered to be bluish. However, it was found that when YI is in the above-described range, although the film looks bluish when visually recognized by the film alone, when used as the front plate material, the white color of the bezel portion is maintained while maintaining the visibility of the display portion.

When the yellowness of the polyimide film is 0 or less, since the blue light of the film is too strong, the white printing and the display portion of the bezel portion are visually recognized bluish, which is not preferable. Moreover, as blue light becomes strong, since the total light transmittance of a film may also fall, visibility falls. From a viewpoint of making it easy to visually recognize the white color of a bezel part, it is preferable that yellowness exceeds 0, and it is more preferable that it is 0.01 or more.

When the yellowness of the polyimide film is 1 or more, even when the film alone appears bluish, when used as a front panel material of a flexible display having a bezel portion subjected to white printing, the blue light is not sufficient, Negative white color is not retained and is yellowish. From the viewpoint of facilitating the visibility of the white color of the bezel portion, the yellowness is preferably less than 1.0, more preferably 0.99 or less.

As a method of adjusting yellowness to the said range, the method of adding a colorless transparent inorganic particle etc. to the polyimide resin to be used, the method of adding a bluing agent, etc. are mentioned, for example.

(Polyimide Polymer)

The polyimide film of this invention contains a polyimide type polymer. In this specification, a polyimide type polymer is a polymer containing the repeating structural unit containing both the polymer (polyimide) containing the repeating structural unit containing an imide group, an imide group, and an amide group, And a polymer containing both a repeating structural unit containing an imide group and a repeating structural unit containing an amide group.

A polyimide-type polymer can be manufactured using the tetracarboxylic acid compound and diamine compound mentioned later as a main raw material, for example. In one embodiment of the present invention, the polyimide polymer has a repeating structural unit represented by the following formula (10). Here, G is a tetravalent organic group and A is a divalent organic group. The polyimide-based polymer may include a structure represented by two or more types of formulas (10) in which G and / or A are different.

[Formula 3]

In addition, the polyimide-based polymer contains at least one selected from the group consisting of structures represented by formulas (11), (12) and (13) within a range not impairing various physical properties of the polyimide film. You may be.

[Formula 4]

G and G ¹ are each independently a tetravalent organic group, Preferably they are the organic group which may be substituted by the hydrocarbon group or the fluorine-substituted hydrocarbon group. The organic group is preferably a tetravalent organic group having 4 to 40 carbon atoms. The hydrocarbon group and the fluorine-substituted hydrocarbon group preferably have 1 to 8 carbon atoms. Examples G and G ^1, formula 20, formula 21, formula 22, formula 23, formula 24, formula 25, formula 26, formula 27, formula 28 Or the group represented by Formula (29) and a trivalent C6 or less chain hydrocarbon group are illustrated.

[Formula 5]

In formulas (20) to (29),

* Represents a bonding hand,

Z is a single bond, -O-, -CH _2- , -CH ₂ -CH _2- , -CH (CH ₃ )-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -Ar -, -SO _2- , -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar-C (CH ₃ ) ₂ -Ar- or- Ar-SO ₂ -Ar- is represented. Ar represents the C6-C20 arylene group which may be substituted by the fluorine atom, and a phenylene group is mentioned as a specific example. Because it is easy to suppress the yellowness of the resultant film, G and G ¹ are preferably equation (20), Equation 21, Equation 22, Equation 23, Equation 24, Equation 25, It is group represented by Formula (26) or Formula (27).

G ² is a trivalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. The organic group is preferably a trivalent organic group having 4 to 40 carbon atoms. Carbon number of a hydrocarbon group and a fluorine-substituted hydrocarbon group becomes like this. Preferably it is 1-8. G ² As the equation (20), Equation 21, Equation 22, Equation 23, Equation 24, Equation 25, Equation 26, Equation 27, Equation (28) or ( The group by which any one of the bonds of group represented by 29) is substituted by the hydrogen atom, and a trivalent C6 or less chain hydrocarbon group are illustrated.

G ³ is a divalent organic group, preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group. The organic group is preferably a divalent organic group having 4 to 40 carbon atoms. Carbon number of a hydrocarbon group and a fluorine-substituted hydrocarbon group becomes like this. Preferably it is 1-8. As G ³ , formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula ( Among the bonds of the group represented by 29), a group in which two non-adjacent groups are substituted with a hydrogen atom and a chain hydrocarbon group having 6 or less carbon atoms are exemplified.

A, A ¹ , A ² and A ³ are each independently a divalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Carbon number of the said organic group becomes like this. Preferably it is 4-40. Preferably carbon number of a hydrocarbon group or a fluorine-substituted hydrocarbon group is 1-8. As the A, A ^1, A ² and A ^3, formula 30, formula 31, formula 32, formula 33, formula 34, formula 35, formula 36, formula (37 ) Or a group represented by formula (38); Groups in which they are substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; And a chain hydrocarbon group having 6 or less carbon atoms.

[Formula 6]

In formulas (30) to (38),

* Represents a bonding hand,

Z ¹ , Z ² and Z ³ are each independently a single bond, -O-, -CH _2- , -CH ₂ -CH _2- , -CH (CH ₃ )-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO ₂ -or -CO-.

One example is that Z ¹ and Z ³ are -O-, and Z ² is -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) ₂ -or -SO _2- . It is preferable that the bonding position with respect to each ring of Z <^1> and Z <^2> , and the bonding position with respect to each ring of Z <^2> and Z <^3> is a meta position or a para position with respect to each ring, respectively.

The polyimide film of this invention may contain polyamide. A polyamide is a polymer mainly containing the repeating structural unit containing an amide group. The polyamide which concerns on this embodiment is a polymer which has a repeating structural unit represented by said formula (13) as a main. Preferable examples and specific examples are the same as those of G ³ and A ^{3 in} the polyimide polymer. G ³ and / or A ³ may include a structure represented by two or more kinds of formulas (13).

The polyimide polymer can be obtained, for example, by polycondensation of a diamine and a tetracarboxylic acid compound (tetracarboxylic acid dianhydride, etc.), for example, JP-A-2006-199945 or JP-2008-A. It can synthesize | combine according to the method described in Unexamined-Japanese-Patent No. 163107. As a commercial item of a polyimide, Mitsubishi Gas Chemical Co., Ltd. Neoprem (registered trademark), Kawamura Industries Co., Ltd. KPI-MX300F, etc. are mentioned.

As a tetracarboxylic acid compound used for the synthesis | combination of a polyimide, Aromatic tetracarboxylic acid compounds, such as aromatic tetracarboxylic dianhydride; And aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. A tetracarboxylic acid compound may be used independently and may use 2 or more types together. In addition to the dianhydride, the tetracarboxylic acid compound may be a tetracarboxylic acid compound flexible body such as an acid chloride compound.

Specific examples of the aromatic tetracarboxylic dianhydride include 4,4'-oxydiphthalic dianhydride (may be described as OPDA), 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2, 2 ', 3,3'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (may be described as BPDA), 2,2 ', 3, 3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-diphenylsulfontetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2, 2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 '-(hexafluoroisopropylidene) di Phthalic acid dianhydride (may be described as 6FDA), 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1 , 2-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-di Carboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 '-(p-phenylenedioxy) diphthalic acid dianhydride, 4,4'-(m-phenylenedioxy) Diphthalic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, and 1,2,4,5-benzenetetracarboxylic dianhydride.

Among these, 4,4'- oxydiphthalic acid dianhydride, 3,3 ', 4,4'- benzophenone tetracarboxylic dianhydride, 2,2', 3,3'- benzophenone tetracarboxylic acid 2 Anhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-diphenyl Sulfontetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3 , 4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA), 1,2-bis (2,3-dicarboxyphenyl) ethane 2 Anhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxy Phenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 '-(p-phenylenedioxy) diphthalic acid dianhydride And 4, 4 '-(m-phenylenedioxy) diphthalic acid dianhydride, More preferably, 4,4'- oxydiphthalic acid dianhydride, 3,3', 4,4'-biphenyl tetracarboxylic acid 2 is mentioned. Anhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA), bis (3,4-dicarboxyphenyl Methane dianhydride and 4,4 '-(p-phenylenedioxy) diphthalic acid dianhydride. These can be used individually or in combination of 2 or more types.

As aliphatic tetracarboxylic dianhydride, a cyclic or acyclic aliphatic tetracarboxylic dianhydride is mentioned. A cyclic aliphatic tetracarboxylic dianhydride is tetracarboxylic dianhydride which has alicyclic hydrocarbon structure, As a specific example, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, 1,2,3,4-cyclo Cycloalkanetetracarboxylic dianhydride, such as butanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5 And 6-tetracarboxylic dianhydride, dicyclohexyl 3,3'-4,4'-tetracarboxylic dianhydride and positional isomers thereof. These can be used individually or in combination of 2 or more types. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride, and the like. It can be used in combination of 2 or more type. Moreover, you may use combining a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride.

Among the tetracarboxylic dianhydrides, 1,2,4,5-cyclohexanetetracarboxylic dianhydride and bicyclo [2.2.2] oct-7-ene-2,3,5 from the viewpoint of high transparency and low colorability Preference is given to, 6-tetracarboxylic acid dianhydride and 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof.

In addition, the polyimide-based polymer according to the present embodiment, in addition to the tetracarboxylic acid anhydride used for the above-mentioned polyimide synthesis, within the range of not impairing the various physical properties of the polyimide film, tetracarboxylic acid, tricarboxylic acid and Dicarboxylic acid and those anhydrides and derivatives may be further reacted.

As tetracarboxylic acid, the water adduct of the anhydride of the said tetracarboxylic acid compound is mentioned.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acid, aliphatic tricarboxylic acid, their flexible acid chloride compounds, and acid anhydrides, and two or more kinds thereof may be used in combination. Specific examples include anhydrides of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3- anhydride; And phthalic anhydride and benzoic acid include a single bond, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO ₂ -or a phenylene group.

As a dicarboxylic acid compound, aromatic dicarboxylic acid, aliphatic dicarboxylic acid, those flexible acid chloride compounds, an acid anhydride, etc. are mentioned, You may use 2 or more types together. Specific examples include terephthalic acid; Isophthalic acid; Naphthalenedicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; The dicarboxylic acid compound of the chain hydrocarbon having 8 or less carbon atoms and the two benzoic acids are a single bond, -CH _2- , -S-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -O-,- And NR ⁹ —, —C (═O) —, —SO ₂ — or compounds linked by a phenylene group, and their acid chloride compounds. Here, R <^9> represents the C1-C12 hydrocarbon group which may be substituted by the halogen atom.

As a dicarboxylic acid compound, Preferably, it is terephthalic acid; Isophthalic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; And two benzoic acid skeletons are compounds linked by —CH ₂ —, —C (═O) —, —O—, —NR ⁹ —, —SO ₂ — or a phenylene group, more preferably terephthalic acid; 4,4'-biphenyldicarboxylic acid; And two benzoic acid skeletons are linked by -O-, -NR ^9- , -C (= 0)-or -SO _2- . These can be used individually or in combination of 2 or more types.

The ratio of the tetracarboxylic acid compound to the total of the tetracarboxylic acid compound, the tricarboxylic acid compound, and the dicarboxylic acid compound is preferably 40 mol% or more, more preferably 50 mol% or more, further preferably Is at least 70 mol%, even more preferably at least 90 mol%, particularly preferably at least 98 mol%.

As a diamine used for the synthesis | combination of a polyimide, aliphatic diamine, aromatic diamine, or a mixture thereof is mentioned, for example. In addition, in this embodiment, "aromatic diamine" represents the diamine in which the amino group is couple | bonded with the aromatic ring directly, and may contain the aliphatic group or other substituent in a part of the structure. The aromatic ring may be monocyclic or condensed ring, and examples thereof include, but are not limited to, benzene ring, naphthalene ring, anthracene ring, fluorene ring and the like. Among these, it is preferable that an aromatic ring is a benzene ring. Moreover, "aliphatic diamine" shows the diamine in which an amino group is couple | bonded with the aliphatic group directly, and may contain the aromatic ring and other substituents in a part of the structure.

Examples of the aliphatic diamines include acyclic aliphatic diamines such as hexamethylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornanediamine, and 4,4. Cyclic aliphatic diamine, such as "-diamino dicyclohexyl methane, etc. are mentioned. These can be used individually or in combination of 2 or more types.

Examples of the aromatic diamine include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2 Aromatic diamines having one aromatic ring, such as 6-diaminonaphthalene; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether (may be described as ODA), 3,4'-diaminodi Phenylether, 3,3'-diaminodiphenylether, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 1,4 -Bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy ) Phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2'-dimethylbenzidine , 2,2'-bis (trifluoromethyl) benzidine (also called 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl, sometimes described as TFMB), 4 , 4'-bis (4-aminophenoxy) biphenyl, 9,9-bis (4-aminophenyl) fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene, 9,9- Bis (4-amino-3-chlorophenyl) fluorene, 9,9 Aromatic diamine which has two or more aromatic rings, such as -bis (4-amino-3- fluorophenyl) fluorene, is mentioned.

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

The aromatic diamine is preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether , 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 1,4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] Sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy ) Phenyl] propane, 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine (TFMB), 4,4'-bis (4-aminophenoxy) biphenyl.

The aromatic diamine is more preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylether, 4,4'-diaminodi Phenylsulfone, 1,4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane And 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine (TFMB), and 4,4'-bis (4-aminophenoxy) biphenyl.

Among the diamines, from the viewpoint of high transparency and low colorability, it is preferable to use one or more selected from the group consisting of aromatic diamines having a biphenyl structure. 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine (TFMB), 4,4'-bis (4-aminophenoxy) biphenyl and 4,4'-diaminodiphenyl It is more preferable to use at least one selected from the group consisting of ethers, and even more preferably to use 2,2'-bis (trifluoromethyl) benzidine (TFMB).

The polyimide polymer and polyamide which are polymers containing at least 1 type of repeating structural unit represented by Formula (10), Formula (11), Formula (12), or Formula (13) are a diamine, a tetracarboxylic acid compound ( Tetracarboxylic acid compound flexible bodies such as acid chloride compounds and tetracarboxylic dianhydride), tricarboxylic acid compounds (tricarboxylic acid compound flexible bodies such as acid chloride compounds and tricarboxylic acid anhydrides) and dicarboxylic acid compounds (acid chloride compounds) It is a condensation type polymer which is a polycondensation product with at least 1 type of compound contained in the group which consists of dicarboxylic acid compound flexible bodies, such as these. In addition to these, a dicarboxylic acid compound (including flexible bodies, such as an acid chloride compound) may be used as a starting raw material. The repeating structural unit represented by Formula (11) is usually derived from diamines and tetracarboxylic acid compounds. The repeating structural unit represented by the formula (12) is usually derived from a diamine and a tricarboxylic acid compound. The repeating structural unit represented by the formula (13) is usually derived from a diamine and a dicarboxylic acid compound. Specific examples of the diamine and tetracarboxylic acid compounds are as described above.

The molar ratio of the diamine and carboxylic acid compounds such as the tetracarboxylic acid compound is preferably suitably adjusted in the range of 0.9 mol or more to 1.1 mol or less of tetracarboxylic acid with respect to 1 mol of diamine. In order to express high corrosion resistance, since it is preferable that the polyimide polymer obtained is high molecular weight, it is more preferable that they are 0.98 mol or more and 1.02 mol of tetracarboxylic acid with respect to 1 mol of diamines, and 0.99 mol or more and 1.01 mol It is more preferable that it is below.

Moreover, it is preferable that the ratio of the amino group which occupies for the terminal of a polymer obtained is low from a viewpoint of suppressing the yellowness of the polyimide polymer film obtained, and carboxylic acid compounds, such as a tetracarboxylic acid compound, are 1 mol or more with respect to 1 mol of diamines. desirable.

The weight average molecular weight of the polyimide polymer and the polyamide is preferably 10,000 to 500,000, more preferably 50,000 to 500,000, and still more preferably 70,000 to 450,000. The larger the weight average molecular weight of the polyimide polymer and the polyamide is, the more likely it is to express high flex resistance when filmed. Therefore, it is preferable that a weight average molecular weight is more than the said minimum from a viewpoint of being easy to raise the bending resistance of a film. On the other hand, the smaller the weight average molecular weight of the polyimide polymer and the polyamide is, the easier it is to lower the viscosity of the varnish and tend to be easier to improve processability. Moreover, there exists a tendency for the stretchability of a polyimide film to improve easily. Therefore, from a viewpoint of workability and stretchability, it is preferable that a weight average molecular weight is below the said upper limit. In addition, a weight average molecular weight can measure GPC and can obtain | require by standard polystyrene conversion.

In one preferred embodiment of the present invention, the polyimide polymer and the polyamide contained in the polyimide film of the present invention may be a halogen atom such as a fluorine atom which can be introduced by the fluorine-containing substituent or the like described above. You may include it. When the polyimide polymer and the polyamide contain a halogen atom, it is easy to improve the elastic modulus of the polyimide film and to reduce the yellowness (YI value). When the elasticity modulus of a polyimide film is high, it is easy to suppress generation | occurrence | production of a flaw and wrinkles in a polyimide film, and when yellowness of a polyimide film is low, it becomes easy to improve transparency of a film. The halogen atom is preferably a fluorine atom. As a preferable fluorine-containing substituent in order to contain a fluorine atom in a polyimide polymer and a polyamide, a fluoro group and a trifluoromethyl group are mentioned, for example.

The content of the halogen atom in the polyimide polymer or polyamide is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, based on the mass of the polyimide polymer or the polyamide. . 10 mass% or more may be sufficient as the lower limit of content of a halogen atom, and 20 mass% or more may be sufficient as it. The range of content of a preferable halogen atom is 5-30 mass%. When content of a halogen atom is 1 mass% or more, it will be easy to improve the elasticity modulus at the time of film-forming, to reduce water absorption, to reduce YI value further, and to improve transparency more. When content of a halogen atom exceeds 40 mass%, synthesis may become difficult. A fluorine-type substituent may exist in any of diamine or a carboxylic acid compound, and may exist in both.

In one embodiment of the present invention, the polyimide polymer can be produced by a polycondensation reaction of a diamine and a tetracarboxylic acid compound. In this polycondensation reaction, an imidation catalyst may exist. As an imidation catalyst, For example, aliphatic amines, such as tripropylamine, dibutylpropylamine, and ethyl dibutylamine; Alicyclic amines (monocyclic) such as N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepine; Alicyclic amines (polycyclic) such as azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane, and azabicyclo [3.2.2] nonane; And 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4 Aromatic amines such as -cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and isoquinoline.

Although the reaction temperature of a diamine and a tetracarboxylic acid compound is not specifically limited, For example, it is 50-350 degreeC. Although reaction time is not specifically limited, for example, It is about 30 minutes-about 48 hours. If necessary, the reaction may be performed under inert atmosphere or reduced pressure. Moreover, you may perform reaction in a solvent, As a solvent, the solvent mentioned later used for preparation of a polyimide varnish is mentioned, for example.

In one Embodiment of this invention, content of the polyimide-type polymer in a polyimide film is based on the total mass of a polyimide film, Preferably it is 40 mass% or more, More preferably, 50 mass% It is above, More preferably, it is 70 mass% or more. It is preferable that content of a polyimide type polymer is more than the said minimum from a viewpoint of easy flexibility. In addition, content of the polyimide-type polymer in a polyimide film is 100 mass% or less normally based on the total mass of a polyimide film.

(Blueing agent)

The polyimide film of the present invention preferably further contains a colorant, more preferably a bluing agent. Blueing agent is an additive (dye, pigment) which absorbs the light of wavelength range, such as yellow from yellow, and adjusts a color in visible region, for example, ultramarine blue, royal blue, cobalt blue. Inorganic dyes and pigments such as organic dyes and pigments such as phthalocyanine-based bluing agents and condensed polycyclic bluing agents. Although a bluing agent is not specifically limited, From a heat resistant, light resistance, and solubility viewpoint, a condensation polycyclic bluing agent is preferable and an anthraquinone bluing agent is more preferable. In view of heat resistance, the bluing agent preferably has a 1% thermal weight loss temperature of 220 ° C or higher. The thermal weight loss temperature of the bluing agent can be obtained by measuring the weight loss of the sample when the temperature is raised at a constant rate using thermal gravimetric measurement (TG). The 1% thermal weight loss temperature can be obtained as the temperature at which the weight loss becomes 1% with respect to the introduction weight. In addition, in this specification, 1% thermogravimetric reduction temperature is also called "pyrolysis temperature."

Examples of the condensed polycyclic bluing agent include an anthraquinone bluing agent, an indigo bluing agent, and a phthalocyanine bluing agent.

Anthraquinone-based bluing agent, Formula (5):

[Formula 7]

It is a bluing agent containing the anthraquinone ring represented by the following. As an anthraquinone-based bluing agent, Preferably Formula (6):

[Formula 8]

[In Formula (6), X <^1> represents OH, NHR <^1>, or NR <^1> R <^2> , X <^2> represents NHR <^3> or NR <^3> R <^4> , and R <^1> , R <^2> , R <^3> and R <^4> are mutually independent And a phenyl group substituted by a linear or branched alkyl group having 1 to 6 carbon atoms or a linear or branched alkyl group having 1 to 6 carbon atoms.]

The compound which has a general formula shown by these is mentioned. X <^1> and X <^2> in Formula (6) may mutually be same or different. In the compound represented by the formula (6), at least one of X ¹ and X ² in the formula preferably has a phenyl group substituted with a linear or branched alkyl group having 1 to 6 carbon atoms, and X ¹ or X ² is It is more preferable to have a phenyl group substituted with a linear or branched alkyl group having 1 to 6 carbon atoms.

As an anthraquinone bluing agent, More preferably, the compound represented by Formula (1)-Formula (3) is mentioned.

[Formula 9]

An anthraquinone-based bluing agent can also be obtained as a commercial item. Examples of commercially available products include, for example, Plast Blue 8510, Plast Blue 8514, Plast Blue 8516, Plast Blue 8520, Plast Blue 8540, Plast Blue 8580, and Plast Blue 8590 (above, all manufactured by Arimoto Chemical Industries, Ltd.). For example, Macrolex violet B, Macrolex violet 3R, Macrolex blue RR (all made by Bayer), for example, Diamond resin B, Diamond violet D, Diamond resin J, Diamond resin blue For example, Sumplast Violet B, Sumplast Blue OA, Sumplast Blue GP, Sumplast Turk Blue G, Sumplast Blue, etc. S, Sumplast Green G (all are made by Sumitomo Chemical Co., Ltd.), etc. are mentioned.

An indigo-based bluing agent is a bluing agent containing a phosphorus room or a thioindoxyl. Indigo-based bluing agent is also available as a commercial item. As a commercial item, Dystar Indigo 4B Coll Liq, DyStar Indigo Coat, Dystar Indigo Vat (all are made from Daistar), etc. are mentioned, for example.

The phthalocyanine-based bluing agent is a bluing agent containing the cyclic structure in which four phthalic acid imides bridge | crosslinked by the nitrogen atom. Phthalocyanine-based bluing agent can also be obtained as a commercial item. As a commercial item, Chromofine Blue, Chromofine Green (all are made by Dainit Seika Co., Ltd.), Pigment Blue 15, Pigment Blue 16 (all are made by Tokyo Kasei Kogyo Co., Ltd.), etc. are mentioned, for example. .

From the viewpoint of heat resistance, light resistance and solubility, the polyimide film of the present invention preferably contains an anthraquinone-based bluing agent, more preferably at least one bluing agent having a structure represented by formula (5). And it is more preferable to contain at least 1 type of bluing agent which has a structure represented by Formula (6), At least 1 type of blue chosen from the group which consists of a compound represented by Formula (1)-Formula (3). Particular preference is given to containing a blowing agent. In addition, the compound represented by Formula (1)-Formula (3) can be obtained also as a commercial item. Commercially available products include Sumplast Violet B (compound represented by Formula (1), thermal decomposition temperature: 277 ° C), Sumplast Blue OA (compound represented by Formula (2), thermal decomposition temperature: 248 ° C) and Sumipla Straw GP (compound represented by Formula (3), thermal decomposition temperature: 255 degreeC) is mentioned.

A bluing agent may be used individually by 1 type, and may use 2 or more types together. From the viewpoint of keeping the total light transmittance high, the total amount of the bluing agent used (compound amount) is preferably relatively low, and the type of bluing agent to be used is also preferably smaller.

When the polyimide film of this invention contains a bluing agent, from a viewpoint of the moldability of a film, the 1% thermoweight reduction temperature of a bluing agent becomes like this. Preferably it is 220 degreeC or more, More preferably, it is 240 degreeC or more. The method for measuring the 1% thermal weight loss temperature of the bluing agent is as described above.

When the polyimide film of the present invention contains a bluing agent, the content of the bluing agent is preferably 5 ppm or more, more preferably 8 ppm or more, further preferably based on the total mass of the polyimide film. 10 ppm or more. When content of a bluing agent is more than the said minimum, since YI is fully reduced and it is easy to improve the visibility of white printing of a bezel part, it is preferable. Moreover, the said content becomes like this. Preferably it is 55 ppm or less, More preferably, it is 50 ppm or less. When content of a bluing agent is below the said upper limit, since the total light transmittance does not fall too much and it is easy to make both the visibility of the white printing of a bezel part, and general visibility compatible, it is preferable.

When the polyimide film or laminate contains a bluing agent and contains at least one layer of bluing agent, the amount of bluing agent added based on the total mass of the layer with respect to each layer containing the bluing agent Is calculated as X (ppm) and the thickness of the layer is Y (µm), and the product (X × Y) of X and Y in each layer is calculated for all the layers containing the bluing agent, The total value is preferably 300 to 4,500, more preferably 400 to 4,250, and still more preferably 500 to 4,000. If the sum of the product (XxY) of X and Y exists in said range, it will be easy to obtain the polyimide film which has desired yellowness YI.

(Inorganic particles)

The polyimide film of the present invention may further contain inorganic materials such as inorganic particles in addition to the polyimide polymer from the viewpoint of increasing the strength. Examples of the inorganic material include inorganic particles such as titania particles, alumina particles, zirconia particles, and silica particles, and silicon compounds such as quaternary alkoxysilanes such as tetraethyl ortho silicate. From the standpoint of the stability of the polyimide varnish for producing the polyimide film, the inorganic material is preferably inorganic particles, more preferably silica particles. As the silica particles, a silica sol obtained by dispersing the silica particles in an organic solvent or the like may be used, or a silica fine particle powder prepared by a gas phase method may be used. However, since the handling is easy, it is preferable to use a silica sol. Herein, the inorganic particles may be bonded by a molecule having a siloxane bond.

The average primary particle diameter of the inorganic particles is preferably 5 to 100 nm, more preferably 10 to 100 nm, still more preferably 10 to 90 nm, and particularly preferably 20 to 80 nm. It is preferable that the average primary particle diameter of an inorganic particle is below the said upper limit from a viewpoint of easy transparency of a polyimide film. Moreover, it is preferable that the average primary particle diameter of an inorganic particle is more than the said minimum from a viewpoint of the cohesion force of an inorganic particle not being too high, and being easy to handle. Here, the average primary particle diameter of the inorganic material which can be contained in a polyimide film can be determined by measuring the average value of ten points of the positive direction diameter by a transmission electron microscope. In addition, the particle size distribution of the inorganic particle before forming a polyimide film can be measured using a commercially available laser diffraction type particle size distribution meter.

When the polyimide film contains an inorganic material, the content of the inorganic material in the polyimide film is preferably 0 mass% or more and 90 mass% or less, more preferably 0 mass based on the total mass of the polyimide film. % Or more and 60 mass% or less, More preferably, they are 0 mass% or more and 40 mass% or less. When content of an inorganic material exists in the said range, there exists a tendency which is easy to make transparency and mechanical property of a polyimide film compatible.

In one embodiment of the present invention, the polyimide film of the present invention contains silica particles. When silica particle is contained, it is easy to improve mechanical strength, for example, elasticity modulus, flex resistance, etc. The average primary particle diameter of the silica particles is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 15 nm or more, particularly preferably 20 nm or more, preferably 100 nm or less, more preferably. Preferably it is 80 nm or less, More preferably, it is 60 nm or less, Especially preferably, it is 40 nm or less. If the average primary particle diameter of a silica particle is the said range, aggregation of a silica particle can be suppressed and haze and yellowness (YI value) of a polyimide film can be reduced. In addition, the average primary particle diameter of a silica particle can be measured by a BET method, for example. The content of the silica particles is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, particularly preferably based on the mass of the polyimide film. It is 20 mass% or more, Preferably it is 60 mass% or less, More preferably, it is 50 mass% or less. If content of a silica particle is more than the said minimum, it will be easy to improve elasticity modulus and bending resistance, and if content of a silica particle is below the said upper limit, it will be easy to reduce cloudiness and yellowness (YI value) more.

(UV absorber)

The polyimide film may contain 1 type, or 2 or more types of ultraviolet absorbers. A ultraviolet absorber can be suitably selected from what is normally used as a 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. As a ultraviolet absorber, the at least 1 sort (s) of compound chosen from the group which consists of a benzophenone type compound, a salicylate type compound, a benzotriazole type compound, and a triazine type compound is mentioned, for example. Since the deterioration of a polyimide resin is suppressed because a polyimide film contains a ultraviolet absorber, the visibility of a polyimide film can be improved.

In this specification, a "system compound" refers to the compound to which the said "system compound" is attached, and its derivative (s). For example, a "benzophenone type compound" refers to a compound having a benzophenone and a substituent bonded to benzophenone as a parent skeleton.

When the polyimide film contains a ultraviolet absorber, the content of the ultraviolet absorber is preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 3% by mass, based on the total mass of the polyimide film. It is above, Preferably it is 10 mass% or less, More preferably, it is 8 mass% or less, More preferably, it is 6 mass% or less. When the ultraviolet absorber is in the above range, the weather resistance of the polyimide film is particularly effectively increased, and a polyimide film having high transparency can be obtained.

(Other additives)

The polyimide film may contain other additive further in the range which does not impair transparency, flexibility, and retardation. Examples of other additives include antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, leveling agents, and the like.

The content of the other additives is preferably 0% by mass or more and 20% by mass or less, more preferably 0% by mass or more and 10% by mass or less with respect to the mass of the polyimide film.

(thickness)

Yellow thickness YI should just be in the range of 0 <YI <1.0, and the thickness of the polyimide film of this invention can be adjusted suitably according to a use. The thickness of a polyimide film becomes like this. Preferably it is 20-200 micrometers, More preferably, it is 25-150 micrometers, More preferably, it is 30-100 micrometers, Especially preferably, it is 50-100 micrometers. In the present invention, the thickness can be measured by a contact type digital indicator. It is preferable that thickness is more than the said minimum, since it is easy to improve the handleability as a film and to raise pencil hardness etc. easily. Moreover, since thickness is easy to raise the bending tolerance of a film, it is preferable that it is below the said upper limit.

(Total light transmittance)

The polyimide film of the present invention preferably has a total light transmittance of 88.0% or more, more preferably 88.5% or more, even more preferably 89.0% or more, particularly preferably 89.5% or more, according to JIS K 7105: 1981, Very preferably at least 90.0%. When the total light transmittance of a polyimide film is more than the said minimum, sufficient visibility can be ensured when a polyimide film is assembled to an image display apparatus. In addition, the upper limit of the total light transmittance of a polyimide film is 100% or less normally. It is preferable that it is 88.0% or more in the range of the thickness of the said film, and, as for the total light transmittance, it is more preferable to show said numerical value when measured at thickness of 50-100 micrometers.

(Visibility)

Since the polyimide film of this invention is 0 <YI <1.0, yellowness YI is excellent in visibility, when using it as a front plate material of the flexible display which has the bezel part in which white printing was performed. In the evaluation of visibility, the viewer viewed the sample at a viewing distance of 1 m and 2 m under irradiation intensity of 1000 to 2000 lx (lux), and evaluated the white color of the bezel part in four steps. The visibility of the polyimide film is a polyimide film having a thickness of 50 to 100 µm, and when the yellowness YI is 0.01 or more and the total light transmittance is 89.0% or more, the film is applied to a commercially available white bezel printed display. When the color tone at the time of installation is visually observed, the white bezel appears white and tends to be able to recognize characters more correctly. Further, as a polyimide film having a thickness of 50 to 100 µm, when the yellowness YI is 0.01 or more and the total light transmittance is 90.0% or more, the color tone when the film is installed on a commercially available white bezel printed display When visually observed, the white bezel appears white and tends to be able to recognize characters more clearly.

When the yellowness degree YI of the polyimide film is 1 or more or 0 or less, even when the total light transmittance is 89.0% or more, when the color tone when the film is installed on a commercially available white bezel printed display is visually observed, White bezels tend to be perceived as yellowish white or bluish white.

(Layer composition)

The layer structure of the polyimide film of this invention is not specifically limited, A single layer may be sufficient and the multilayer of two or more layers may be sufficient. When a polyimide film is a multilayered structure, two or more layers containing the bluing agent may be contained. From the viewpoint of thinning of the image display device and economical efficiency, it is preferable to include the bluing agent and the polyimide polymer in one layer, and specifically, it is a single layer containing the bluing agent and the polyimide polymer, or the bluing agent and the poly It is more preferable that it is a laminated body which has at least the layer containing a mid type polymer. In addition, from the viewpoint of impact resistance characteristics, the polyimide film of the present invention preferably has a multilayer structure of two or more layers, and is a laminate having at least a layer containing a bluing agent and a polyimide polymer, or a polyimide polymer It is more preferable that it is a laminated body which has at least the base material layer containing and the color adjustment layer containing a bluing agent, and it is still more preferable that it is a laminated body which has at least the layer containing a bluing agent and a polyimide type polymer. When forming a layer containing a bluing agent and a polyimide polymer, a bluing agent is added to a solvent containing the polyimide polymer to prepare a varnish, coating the varnish, and drying the solvent contained in the varnish to form a film. Filmmaking Here, a normal bluing agent often accompanies deterioration, such as thermal decomposition, at the time of film forming which dries a solvent from a varnish. Therefore, it is preferable to use the bluing agent which has a thermal decomposition temperature of at least 200 degreeC from a viewpoint which makes a layer contain a bluing agent and a polyimide polymer, and is easy to achieve the function of a color adjustment layer in a single layer. The polyimide film containing a bluing agent and a polyimide polymer in one layer is preferable from a thinning of an image display apparatus, and an economical viewpoint.

[Polyimide Laminate]

The polyimide laminated body which laminated | stacked one or more functional layers further to the polyimide film of the said laminated constitution may be sufficient as the polyimide film of this invention. In this specification, when simply calling it "polyimide film", any of the polyimide film and polyimide laminated body of the said laminated constitution may be sufficient, and either corresponds. As a functional layer, the layer which has various functions, such as a hard coating layer, an ultraviolet absorbing layer, an adhesion layer, a refractive index adjustment layer, and a primer layer, is mentioned. The thickness of a functional layer can be adjusted to a suitable thickness according to the kind of functional layer laminated | stacked on a polyimide film. The polyimide film may be provided with single or multiple functional layers. In addition, one functional layer may have a plurality of functions. For example, when the polyimide film of this invention is a single layer structure, the said functional layer may be formed in a single layer polyimide film, and the polyimide laminated body of a multilayer structure may be obtained. Moreover, when the polyimide film of this invention has the said base material layer and a color adjustment layer at least, a bluing agent is provided in the functional layer which has various functions, such as said hard coating layer, an ultraviolet-ray absorption layer, an adhesion layer, a refractive index adjustment layer, a primer layer. May be added to make these functional layers a color adjustment layer. Moreover, when the polyimide film of this invention has at least the said base material layer and a color adjustment layer, you may laminate | stack a functional layer further on this.

It is preferable that a hard coat layer is arrange | positioned at the visual side of a polyimide film. The thickness of a hard coat layer can be 2 micrometers-20 micrometers, for example. The hard coat layer may have a single layer structure or a multilayered structure. The hard coat layer comprises a hard coat layer resin, and as the hard coat layer resin, for example, ultraviolet rays such as acrylic resins, epoxy resins, urethane resins, benzyl chloride resins, vinyl resins or silicone resins, or mixed resins thereof. Curable resin, electron beam curing type, or thermosetting resin can be mentioned. In particular, it is preferable that a hard coat layer contains acrylic resin from mechanical properties, such as surface hardness, and an industrial viewpoint.

As the acrylic resin, urethane acrylate, urethane methacrylate (hereinafter, acrylate and / or methacrylate are referred to as (meth) acrylate), alkyl (meth) acrylate, ester (meth) acrylate, and epoxy ( Meth) acrylate, its polymer, a copolymer, etc. are mentioned. Specifically, methyl (meth) acrylate, butyl (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, phenyl (meth) acrylate, ethylene glycol di (meth) acrylate , Propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, polymers and copolymers thereof, and the like. have.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays, and includes, for example, a main material selected from an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, and ultraviolet rays dispersed in the main material. It consists of an absorbent. By providing an ultraviolet absorbing layer as a functional layer, the change of the yellowness by light irradiation can be suppressed easily. The thickness of an ultraviolet absorbing layer can be 2 micrometers-20 micrometers, for example.

An adhesion layer is a layer which has a sticky function, and has a function which adhere | attaches a polyimide film and a polyimide laminated body to another member. As a formation material of an adhesion layer, a well-known thing can be used normally. For example, a thermosetting resin composition or a photocurable resin composition can be used.

The adhesion layer may be comprised with the resin composition containing the component which has a polymeric functional group. In this case, firm adhesion can be realized by further polymerizing the resin composition constituting the adhesive layer after bringing the polyimide film or the polyimide laminate into close contact with other members. 0.1 N / cm or more, or 0.5 N / cm or more may be sufficient as the adhesive strength of a polyimide film or a polyimide laminated body, and an adhesion layer.

The adhesion layer may contain the thermosetting resin composition or the photocurable resin composition as a material. In this case, the resin composition can be polymerized and cured by supplying energy afterwards.

The pressure-sensitive adhesive layer may be a layer adhered to the object by pressure, called a pressure sensitive adhesive (PSA). The pressure-sensitive adhesive may be an adhesive which is "a substance which has adhesiveness at room temperature and adheres to the adherend by light pressure" (JIS K6800), and "contains a specific component in a protective film (microcapsule), and suitable means. Until the film is broken by pressure (heat, etc.), the adhesive may be a capsule adhesive (JIS K6800) capable of retaining stability.

A refractive index adjustment layer is a layer which has a function of refractive index adjustment, has a refractive index different from a polyimide film, and is a layer which can provide predetermined refractive index to the polyimide laminated body which has this. The refractive index adjustment layer may be, for example, a resin selected as appropriate, and a resin layer further containing a pigment, as the case may be, or a thin film of metal.

Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide and tantalum oxide. The average particle diameter of the pigment may be 0.1 µm or less. By making the average particle diameter of a pigment into 0.1 micrometer or less, the diffuse reflection of the light which permeate | transmits a refractive index adjustment layer can be prevented, and the fall of transparency can be prevented.

Examples of the metal used for the refractive index adjusting layer include metal oxides or metals such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride. Nitride is mentioned.

You may arrange | position a primer layer between polyimide film and a functional layer for the purpose of improving adhesiveness between these layers. When a functional layer is arrange | positioned on both surfaces of a polyimide film, a primer layer may be arrange | positioned only between a polyimide film and one functional layer, and between a polyimide film and one functional layer, and a polyimide film, The primer layer may be arrange | positioned at both sides with the other functional layer. The thickness of a primer layer can be 0.5 micrometer-5 micrometers.

A primer layer is a layer formed from a primer, and can improve the adhesiveness of a polyimide film and a hard coating layer. The compound contained in a primer layer may be chemically bonded at the interface with the polyimide polymer etc. which are contained in a polyimide film.

As a primer agent, the primer agent of the epoxy-type compound of a ultraviolet curable type, a thermosetting type, or a two-liquid curing type is mentioned, for example. The primer may be a polyamic acid. These are suitable for improving the adhesiveness of a polyimide film and a hard coat layer.

The primer may contain the silane coupling agent. The silane coupling agent may chemically bond with the silicon compound which may be included in the polyimide film by a condensation reaction. A silane coupling agent can be used suitably especially when the compounding ratio of the silicon compound which can be contained in a polyimide film is high.

A silane coupling agent is a compound which has a silicon atom and the alkoxy silyl group which has 1-3 alkoxy groups covalently bonded to the said silicon atom. A compound containing a structure in which two or more alkoxy groups are covalently bonded to a silicon atom is preferable, and a compound containing a structure in which three alkoxy groups are covalently bonded to a silicon atom is more preferable. As said alkoxy group, a methoxy group, an ethoxy group, isopropoxy group, n-butoxy group, tert-butoxy group, etc. are mentioned, for example. Especially, since a methoxy group and an ethoxy group can improve the reactivity with a silicon material, it is preferable.

It is preferable that a silane coupling agent has a substituent with high affinity with a polyimide film and a hard-coat layer. From a viewpoint of affinity with the polyimide polymer contained in a polyimide film, it is preferable that the substituent of a silane coupling agent is an epoxy group, an amino group, a ureido group, or an isocyanate group. In the case where the hard coating layer contains (meth) acrylates, the silane coupling agent that can be used for the primer layer is preferable because the affinity is increased if the silane coupling agent has an epoxy group, a methacryl group, an acryl group, an amino group, or a styryl group. . Among these, the silane coupling agent which has a substituent chosen from a methacryl group, an acryl group, and an amino group is preferable because it shows the tendency which is excellent in affinity with a polyimide film and a hard-coat layer.

It is preferable from a viewpoint of manufacture that a bluing agent is added to the functional layer mentioned above, Preferably a hard coat layer and / or a primer layer, and these functional layers are made into a color adjustment layer. Therefore, in this embodiment, it is preferable that the color adjustment layer contains resin described above with respect to the hard coat layer and / or primer layer, and other components, and contains resin described above with respect to the hard coat layer and other components. It is more preferable. In one Embodiment of this invention in which the polyimide film of this invention has a base material layer and a color adjustment layer at least, content of the bluing agent contained in a color adjustment layer is a resin component contained in a color adjustment layer, Preferably it is hard It is preferably at least 100 ppm, more preferably at least 300 ppm and even more preferably at least 500 ppm, based on the coating forming component, more preferably acrylic resin. When content of a bluing agent is more than the said minimum, since the thickness of a hard coat layer can be put in an appropriate range, it is preferable. The content is preferably 4,000 ppm or less, more preferably 3,000 ppm or less, still more preferably 2,500 ppm or less. When content of a bluing agent is below the said upper limit, since high transmittance can be maintained, it is preferable.

[Manufacturing method]

An example of the manufacturing method of the polyimide film of this invention is demonstrated.

In one embodiment of the present invention, the polyimide film is, for example, the following steps:

(a) applying a liquid (polyimide varnish) containing a polyimide-based polymer to a substrate to form a coating film (coating step), and

(b) drying the coated liquid (polyimide varnish) to form a polyimide film (film forming step)

It can manufacture by the manufacturing method containing these. Steps (a) and (b) may usually be performed in this order.

In the coating step, first, a liquid (polyimide varnish) containing a polyimide polymer is prepared. In order to prepare a polyimide varnish, the said tetracarboxylic acid compound, the said diamine, and other components are mixed as needed, and made to react, and the polyimide liquid mixture is prepared. A solvent (polyimide varnish) containing a polyimide polymer is prepared by adding and stirring a solvent, the bluing agent, an ultraviolet absorber, and other additives as necessary to the polyimide liquid mixture. Instead of the polyimide liquid mixture, a solution such as a purchased polyimide polymer or a solution such as a purchased polyimide polymer may be used.

The solvent used for preparation of a polyimide varnish will not be specifically limited if a polyimide polymer can be melt | dissolved. As such a solvent, For example, Amide type solvents, such as N, N- dimethylacetamide and N, N- dimethylformamide; lactone solvents such as γ-butyrolactone and γ-valerolactone; Sulfur-based solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; Carbonate solvents such as ethylene carbonate and propylene carbonate; And combinations thereof (mixed solvents). Among these solvents, amide solvents or lactone solvents are preferable. Moreover, water may be contained in a polyimide varnish.

Next, a coating film is formed by casting | flow_spreading etc. using polyimide varnish on a base material, such as a resin base material, an SUS belt, or a glass base material, for example by a well-known roll-to-roll or a batch system. .

In a film formation process, a polyimide film can be formed by drying a coating film and peeling from a base material. You may perform the drying process which dries a polyimide film further after peeling. Drying of a coating film can be performed at the temperature of 50-350 degreeC normally. As needed, you may dry a coating film under the conditions of inert atmosphere or reduced pressure.

You may perform the surface treatment process which surface-treats on at least one surface of a polyimide film. As surface treatment, UV ozone treatment, plasma treatment, and corona discharge treatment are mentioned, for example.

As an example of a resin base material, PET film, PEN film, a polyimide film, a polyamideimide film, etc. are mentioned. Especially, a PET film, a PEN film, a polyimide film, and a polyamide-imide film are preferable from a viewpoint of excellent heat resistance. Moreover, PET film is more preferable from a viewpoint of adhesiveness with a polyimide film, and cost.

When the polyimide film of this invention is a monolayer containing a polyimide polymer and a bluing agent, such a layer adds at least 1 bluing agent to the liquid (polyimide varnish) containing the said polyimide polymer further By using the obtained polyimide varnish, it can manufacture similarly to the above. Here, a normal bluing agent often accompanies deterioration, such as thermal decomposition, at the time of film forming which dries a solvent from a varnish. Therefore, in one preferable aspect of the present invention in which the bluing agent and the polyimide polymer are contained in one layer, it is preferable to use a bluing agent having a thermal decomposition temperature of at least 220 ° C or higher.

When the polyimide film of the present invention is a laminate having at least a layer containing a polyimide-based polymer and a bluing agent, such a laminate is added to, for example, a liquid (polyimide varnish) containing the polyimide-based polymer. The polyimide varnish obtained by adding at least one bluing agent to the substrate may be coated on the substrate to be produced as a laminate, or a single layer containing the polyimide polymer and the bluing agent obtained as described above are separately provided. You may manufacture by bonding to the layer of or providing the above-mentioned functional layer in the said single layer. Also in this aspect, since a bluing agent and a polyimide polymer are contained in one layer, it is preferable to use the bluing agent which has a thermal decomposition temperature of at least 220 degreeC or more.

When the polyimide film of this invention is a laminated body which has at least the base material layer containing a polyimide-type polymer, and the color adjustment layer containing a bluing agent, such a laminated body is the following process:

(c) It can manufacture by the process (coating film formation process) which apply | coats the composition (henceforth a "bluing agent composition") containing a bluing agent on a polyimide film, and forms a coating film.

In a coating film formation process, a bluing agent composition is prepared first. For example, a bluing agent composition may contain the said hard-coat layer resin and a photoinitiator, an organic solvent, and / or an inorganic oxide as needed, and may be prepared by mixing these components. In this case, the color adjustment layer containing a bluing agent also has the function of a hard-coat layer. In this embodiment, as a photoinitiator, a benzoin compound, a benzophenone type compound, an alkyl phenone type compound, an acyl phosphine oxide type compound, a triazine type compound, an iodonium salt, a sulfonium salt, etc. are mentioned, for example. As an organic solvent, For example, Alcohol solvents, such as ethanol, ethylene glycol, isopropyl alcohol, and propylene glycol; Ester solvents such as ethyl acetate and γ-butyrolactone; Ketone solvents such as acetone, methyl ethyl ketone, and cyclopentanone; Aliphatic hydrocarbon solvents such as pentane; And aromatic hydrocarbon solvents such as toluene and xylene. A photoinitiator and / or an organic solvent may be individual, or may be used in combination of 2 or more type. Moreover, the hard coat layer composition may also contain the other additives described above.

Next, a bluing agent composition is apply | coated on a polyimide film, and a coating film is formed. The formation order of a polyimide film and a coating film may be reversed, and after apply | coating a bluing agent composition on a base material and forming a coating film, you may form the coating film of a polyimide film on the coating film. Moreover, you may stick together to a polyimide film using a well-known adhesive agent and / or adhesive.

You may dry the coating film formed on the polyimide film. Drying of a coating film can be performed by evaporating a solvent at the temperature of 50-150 degreeC, and a drying time is 30 to 180 second normally. You may dry in air | atmosphere, inert atmosphere, or under reduced pressure.

In a hardening process, a high energy ray (active energy ray) is irradiated to a coating film (resin composition), and a coating film is hardened and a color adjustment layer is formed. Irradiation intensity is suitably determined by the composition of a bluing agent composition, and although it does not specifically limit, irradiation of the wavelength range effective for activation of a photoinitiator is preferable. The irradiation intensity is preferably 0.1 to 6,000 dl / cm 2, more preferably 10 to 1,000 dl / cm 2, still more preferably 20 to 500 dl / cm 2. If irradiation intensity is in the said range, appropriate reaction time can be ensured and the yellowing and deterioration of resin by the heat radiated | emitted from a light source and the heat generation at the time of hardening reaction can be suppressed. The irradiation time may be appropriately selected depending on the composition of the hard coat layer composition, and is not particularly limited, but the amount of accumulated light represented as the product of the irradiation intensity and the irradiation time is preferably 10 to 10,000 mJ / cm 2, more preferably. 50 to 1,000 mJ / cm 2, more preferably 80 to 500 mJ / cm 2. When the accumulated light amount is within the above range, a sufficient amount of active species derived from the photopolymerization initiator can be generated, and the curing reaction can proceed more reliably, and the irradiation time is not too long, and good productivity can be maintained. Moreover, since the hardness of a color adjustment layer can be further improved by going through the irradiation process in this range, it is useful.

Moreover, when hardening a photocurable adhesive agent by irradiation of a high energy ray, it is preferable to perform hardening on the conditions which optical functions, such as retardation and transparency of a polyimide film, do not fall.

[Image display device]

The polyimide film of this invention is useful as a front plate of an image display apparatus, especially a front plate (window film) of a flexible display. In another embodiment of this invention, the image display apparatus provided with the polyimide film of this invention, especially a flexible display are also provided. The flexible display which concerns on this embodiment has the said flexible film and the said polyimide film which functions as a front plate, overlapping with a flexible functional layer, for example. That is, the front panel of the flexible display is arranged on the viewer side on the flexible functional layer. This front plate has a function of protecting the flexible functional layer.

As an image display apparatus, wearable devices, such as a television, a smartphone, a mobile telephone, car navigation, a tablet PC, a portable game machine, an electronic paper, an indicator, a bulletin board, a clock, and a smart watch, etc. are mentioned. As a flexible display, it is all the image display apparatus which has a flexible characteristic.

Such an image display device, especially a flexible display, can be advantageously used as a wearable device such as a television, a smartphone, a mobile phone, a car navigation device, a tablet PC, a portable game machine, an electronic paper, an indicator, a bulletin board, a clock, a smart watch, or the like. have. This image display device has flexible characteristics and has a predetermined range of yellowness YI, and therefore is excellent in visibility when used as a front panel material of a flexible display having, for example, a white-printed bezel portion. .

EXAMPLE

In the following, the present invention will be described in more detail with reference to Examples. "%" "Part" in an example means the mass% and a mass part unless there is particular notice. First, the evaluation method is described.

<Total light transmittance measurement>

The total light transmittance of the sample was measured by the fully automatic direct reading haze computer HGM-2DP by the Suga test company based on JISK7105: 1981.

<Measurement of weight average molecular weight>

Gel Permeation Chromatography (GPC) Measurement

(1) Pretreatment Method

The sample was dissolved in γ-butyrolactone (GBL) to make a 20% by mass solution, diluted 100-fold with DMF eluent, and filtered with 0.45 µm membrane filter to obtain a measurement solution.

(2) measurement conditions

Column: TSKgel SuperAWM-H × 2 + SuperAW2500 × 1 (6.0 mm I.D. × 150 mm × 3)

Eluent: DMF (with 10 mM lithium bromide)

Flow rate: 0.6 mL / min.

Detector: RI Detector

Column temperature: 40 ℃

Injection volume: 20 μL

Molecular Weight Standard: Standard Polystyrene

<Measurement of yellowness (YI value)>

The yellowness (Yellow Index: YI value) of the sample was measured using the ultraviolet-visible near-infrared spectrophotometer V-670 made from Nippon Kasei Co., Ltd. in accordance with JIS K 7373: 2006. After background measurement was performed in the absence of a sample, the sample was placed in a sample holder, the transmittance measurement for light of 300 to 800 nm was performed, and three stimulus values (x, y, z) were obtained. The YI value was calculated based on the following formula.

<Evaluation of visibility of white color>

About the produced film, the visibility at the time of visually observing the hue when the film was installed in the commercially available white bezel printed display is shown in Table 1. In the determination of visibility, the viewer viewed the sample at a viewing distance of 1 m and 2 m under irradiation intensity of 1000 to 2000 lx (lux), and evaluated the white color of the bezel part in four steps. The visibility of the letters is less clear than when the characters are clearly visible than "very good" and "very good", but when the characters can be recognized correctly, "good" and when the characters cannot be recognized correctly or are difficult to recognize We make case "bad".

(Double-circle): A white bezel appears white, and the visibility of the character displayed on a display is very good.

○: The white bezel appears white, and the visibility of the characters displayed on the display is good.

(Triangle | delta): Although the white bezel is clearly colored and cannot be called white, the visibility of a character is favorable.

X: The white bezel is clearly colored and cannot be said to be white, and the visibility of a character is also bad.

Production Example 1 Preparation of Polyimide Varnish (1) Containing Polyimide Polymer (1)

In a nitrogen atmosphere, 1.25 g of isoquinoline was introduced into a reaction vessel to which a vacuum pump equipped with a solvent trap and a filter was connected. Next, 375.00 g of γ-butyrolactone (GBL) and 104.12 g of 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl (TFMB) were added to the reaction vessel, and the mixture was charged. Was dissolved by stirring. Further, 145.88 g of 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) was added to the reaction vessel, and then the temperature was started in an oil bath while stirring the mixture.

The molar ratio of TFMB and 6FDA added was 1.00: 0.99, and the monomer concentration in the mixture was 40 mass%. The pressure was reduced to 650 mmHg at the place where the internal temperature of the reaction container reached 80 degreeC, and it heated up to 180 degreeC internal temperature continuously. After internal temperature reached 180 degreeC, heat stirring was further performed for 4 hours. Then, it doubled | pressured to atmospheric pressure, cooled internal temperature to 155 degreeC, and obtained the polyimide solution. GBL was added at 155 degreeC to prepare the homogeneous solution whose solid content of polyimide is 24 mass%, and the polyimide varnish (1) which is a homogeneous solution was taken out from the reaction container after that. The GPC measurement was performed on the polyimide in the obtained polyimide varnish and the weight average molecular weight was 360,000. Moreover, the fluorine atom content of polyimide was 31.3 mass%.

Production Example 2 Polyimide Varnish (2) Containing Polyimide Polymer (2)

As the polyimide varnish (2), "Neoprim (registered trademark) C6A20" by Mitsubishi Gas Chemical Co., Ltd. was used. "Neoprim C6A20" contains 22 mass% of polyimide-type polymer (2) in (gamma) -butyrolactone solvent.

Production Example 3 Preparation of Polyimide Varnish (3) Containing Polyimide Polymer (3)

40.00 g (124.91 mmol) and 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl (TFMB) in a 1 L separable flask with a stirring blade under nitrogen atmosphere 682.51 g of, N-dimethylacetamide (DMAc) was added and TFMB was dissolved in DMAc while stirring at room temperature. Next, 16.78 g (37.77 mmol) of 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) was added to the flask, and the mixture was stirred at room temperature for 3 hours. Thereafter, 3.72 g (12.59 mmol) of 4,4'-oxybis (benzoyl chloride) (OBBC) was added to the flask, followed by 15.34 g (75.55 mmol) of terephthaloyl chloride (TPC), followed by 1 hour at room temperature. Stirred. Subsequently, 8.21 g (88.14 mmol) of 4-methylpyridine and 15.43 g (151.10 mmol) of acetic anhydride were added to the flask, and after stirring for 30 minutes at room temperature, the temperature was raised to 70 ° C. using an oil bath, and further 3 It stirred for hours and obtained the polyimide varnish (3) containing a polyimide-type polymer (3).

The obtained polyimide varnish (3) was cooled to room temperature, poured into a large amount of methanol in a yarn form, and the precipitate precipitate was taken out, and after immersing in methanol for 6 hours, it was washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C to obtain a polyimide polymer (3) having a weight average molecular weight Mw of 430,000. The weight average molecular weight was measured similarly to Example 1. The fluorine atom content of the polyimide was 26 mass%.

Example 1

To 200.00 g of polyimide varnish (1) obtained in Production Example 1, 18.40 g of GBL and 11.82 g of N, N-dimethylacetamide (DMAc) and 1.50 mg of Smiplast Violet B (compound represented by Formula (1)) The solids in the polyimide varnish were further diluted by 31 ppm). Using the diluted polyimide varnish, the coating film was shape | molded by cast molding on PET (polyethylene terephthalate) film. Then, the coating film was dried by heating at 50 degreeC for 30 minutes and 140 degreeC for 10 minutes, and the coating film was peeled off from PET film. Then, the polyimide film which has a thickness of 80 micrometers was obtained by heating a coating film at 200 degreeC for 40 minutes.

Example 2

A polyimide film was obtained in the same manner as in Example 1 except that the amount of the bluing agent added was 0 ppm. Subsequently, 12.0 mg (500 ppm of solids in Z-624) of Smiplast Violet B (compound represented by Formula (1)) was added to 24.0 g of Z-624 manufactured by AICA, on a polyimide film, It coated using the wire bar so that the thickness after drying might be 5 micrometers, and the coating film was formed. After drying the obtained coating film at 120 degreeC for 1 minute, ultraviolet-ray was irradiated with the ultraviolet irradiation amount 500mJ / cm <2>, the coating film was hardened | cured, and the hard-coat layer of thickness 5micrometer was formed.

Comparative Example 1

A polyimide film was obtained in the same manner as in Example 1 except that the amount of the bluing agent added was 0.63 ppm.

Comparative Example 2

A polyimide film was obtained in the same manner as in Example 2 except that the amount of the bluing agent added was 10 ppm.

Example 3

A polyimide film was obtained in the same manner as in Example 1 except that Simiplast Blue OA (compound represented by Formula (2)) was used instead of Smiplast Violet B, and the amount of bluing agent added was 50 ppm. . Thus, the obtained polyimide film was heated at 200 degreeC for 40 minutes, and the polyimide film which has a thickness of 50 micrometers was obtained.

Example 4

A polyimide film was obtained in the same manner as in Example 1 except that Simiplast Blue GP (compound represented by Formula (3)) was used instead of Smiplast Violet B, and the amount of bluing agent added was 50 ppm. . Thus, the obtained polyimide film was heated at 200 degreeC for 40 minutes, and the polyimide film which has a thickness of 50 micrometers was obtained.

Example 5

A polyimide film was obtained in the same manner as in Example 1 except that the amount of the bluing agent added was 10 ppm. Thus, the obtained polyimide film was heated at 200 degreeC for 40 minutes, and the polyimide film which has a thickness of 50 micrometers was obtained.

Example 6

A polyimide film was obtained in the same manner as in Example 1 except that the amount of the bluing agent added was 47 ppm and the polyimide polymer obtained in Production Example 2 was used instead of the polyimide polymer obtained in Production Example 1.

Comparative Example 3

A polyimide film was obtained in the same manner as in Example 6 except that the amount of the bluing agent added was 63 ppm.

[Comparative Example 4]

A polyimide film was obtained in the same manner as in Example 6 except that the amount of the bluing agent added was 0.63 ppm.

Example 7

`` Neoprim C6A20 '' (γ-butyrolactone solvent, 22% by mass) manufactured by Mitsubishi Gas Chemical Co., Ltd., a polyimide varnish (2), silica particles having a solid content concentration of 30% by mass (γ-butyrolactone) A solution obtained by dispersing a particle diameter of 23 nm) and 38 ppm of SumiPlast Violet B were mixed and stirred for 30 minutes to obtain a polyimide varnish (2 '). Here, the mass ratio of the solid content of a silica particle and the solid content of a polyimide type polymer was 30:70.

Next, the coating film was shape | molded by casting on the PET (polyethylene terephthalate) film. Then, the coating film was dried by heating at 50 degreeC for 30 minutes and 140 degreeC for 10 minutes, and the coating film was peeled off from PET film. Then, the polyimide film which has a thickness of 80 micrometers was obtained by heating a coating film for 40 minutes at 200 degreeC.

Example 8

A polyimide film was obtained in the same manner as in Example 7 except that the amount of the bluing agent added was 50 ppm.

Example 9

20 g of polyimide-based polymer (3) powder obtained in Production Example 3, 272.093 g of γ-butyrolactone, and 30 parts by mass of silica particles (average primary particle diameter 27 nm) in solid content concentration in γ-butyrolactone 2.00 mg (50 ppm with respect to solid content in a polyimide varnish) were mixed with 66.534 g and Sumplast violet B, and it stirred for 30 minutes, and obtained polyimide varnish (3 '). Here, the mass ratio of the solid content of a silica particle and the solid content of a polyimide type polymer was 50:50. Next, the coating film was shape | molded by casting on the PET (polyethylene terephthalate) film. Then, the coating film was dried by heating at 50 degreeC for 30 minutes and 140 degreeC for 10 minutes, and the coating film was peeled off from PET film. Then, the polyimide film which has a thickness of 50 micrometers was obtained by heating a coating film at 200 degreeC for 40 minutes.

[Comparative Example 5]

A polyimide film was obtained in the same manner as in Example 7 except that the amount of the bluing agent added was 0.63 ppm.

Reference Example 1

50 µm was carried out in the same manner as in Example 9 except that copper phthalocyanine (manufactured by DIC Corporation, product name FASTOGEN Blue CA5380) was used instead of Smiplast Violet B (1.417 mg (50 ppm based on the solid content in the polyimide varnish)). A polyimide film having a thickness of was obtained.

The total light transmittance and the yellowness (YI value) of the polyimide films of Examples 1 to 9, Comparative Examples 1 to 5, and Reference Example 1 obtained as described above were measured. In addition, the addition amount of a bluing agent based on the total mass of the layer containing a bluing agent is called X (ppm), and the thickness of the layer containing a bluing agent is called Y (micrometer), and the product of X and Y (X × Y) was calculated. In addition, in this Example and a comparative example, since the layer containing a bluing agent is one layer, the product of said X and Y is the sum of the product of X and Y with respect to all the layers containing a bluing agent as it is. . The results obtained are shown in Table 1 below. In addition, the thickness of the film in Table 1 is the thickness of the film (single layer or laminated body) of this invention, and the thickness of a bluing layer is the thickness (Y micrometer) of the layer containing the bluing agent in the film of this invention. . In addition, in the kind column of the bluing agent of Table 1, Sumplast violet B is "B", Sumplast blue OA is "OA", Sumplast blue GP is "GP", and copper phthalocyanine is "Cu" Represent each.

From the above, it is understood that preferably, when an anthraquinone-based bluing agent is contained as a bluing agent, the film has a desired YI value in a small amount of use and a film having a high total light transmittance is obtained.

It is thought that the polyimide films of Examples 1 to 9 having the yellowness YI in the predetermined range have good visibility of white color and can be suitably used as the front plate material of a flexible display having a bezel portion on which white printing is performed. do.

1: white bezel
2: polyimide film cover
3: polyimide film uncovered part

Claims (11)

At least one polyimide-based polymer and a bluing agent including at least one selected from the group consisting of an anthraquinone-based bluing agent, an indigo-based bluing agent, and a phthalocyanine-based bluing agent, and a bluing agent and a polyimide-based polymer It is a single layer containing the, or a laminate having at least a layer containing a bluing agent and a polyimide-based polymer, or a laminate having at least a hard coating layer containing a base layer and a bluing agent containing a polyimide-based polymer, In each layer containing a bluing agent, the addition amount of the bluing agent on the basis of the total mass of the layer is X (ppm), and the product of X and Y calculated as the thickness of the layer is Y (µm). The value which computed and summed (X * Y) with respect to all the layers containing a bluing agent is 300-4,500, and yellowness YI is 0 <YI <1.0,
The polyimide film is a polyimide film containing one or more selected from the group consisting of repeating units represented by the following formulas (10), (11), (12) and (13).

And Equation (10) to (13) of the, G and G ¹ are each independently a tetravalent organic group, G ² is a trivalent organic group, G ³ is a divalent organic group, A, A ^1, A ² And A ³ are each independently a divalent organic group.] The method of claim 1,
The polyimide film whose thickness is 20-200 micrometers. The method of claim 1,
The polyimide film whose total light transmittance is 88.0% or more. The method of claim 2,
The polyimide film whose total light transmittance is 88.0% or more. The method according to any one of claims 1 to 4,
The bluing agent is a polyimide film which is an anthraquinone type bluing agent. The method of claim 5,
Blueing agent, Formula (6):

[In Formula (6), X <^1> represents OH, NHR <^1>, or NR <^1> R <^2> , X <^2> represents NHR <^3> or NR <^3> R <^4> , and R <^1> , R <^2> , R <^3> and R <^4> are mutually independent And a phenyl group substituted by a linear or branched alkyl group having 1 to 6 carbon atoms or a linear or branched alkyl group having 1 to 6 carbon atoms.]
And a compound having a 1% thermal weight loss temperature of 220 ° C. or higher. The method of claim 6,
Blueing agent is Formula (1)-Formula (3):

The polyimide film which is at least 1 sort (s) chosen from the group which consists of a compound represented by these. The method according to any one of claims 1 to 4,
Furthermore, the polyimide film containing a silica particle. The method of claim 5,
Furthermore, the polyimide film containing a silica particle. The method of claim 6,
Furthermore, the polyimide film containing a silica particle. The method of claim 7, wherein
Furthermore, the polyimide film containing a silica particle.

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