JP2007091828A - Polyimide rein and polyimide resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyimide resin useful for a retardation film due to actualization of a wide view angle of a liquid crystal display and prevention of discoloration of screen. <P>SOLUTION: The polyimide resin comprises an essential component of 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropanoic acid dianhydride (6FDA) as an acid dianhydride being the raw material of polymerization of the polyimide resin and one or several kinds of 4,4'-oxybisphthalic anhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene acid dianhydride and bis(3,4-dicarboxyphenyl)sulfone dianhydride as other acid dianhydrides. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polyimide resin and a polyimide resin film.

  A liquid crystal display device uses a retardation plate for the purpose of optical compensation. Conventionally, a stretched polymer film has often been used as the retardation plate, but if the difference between the in-plane maximum refractive index (nx) and the thickness direction refractive index (nz) is increased, the following formula 1 It has been proposed that the retardation value Rth in the thickness direction calculated in (1) can be expressed even if the film thickness (d) is small, and the retardation film can be thinned (see, for example, Patent Document 1 or Patent Document 2). ).

ポリイミド樹脂膜は配向性が高く、複屈折（面内屈折率と厚み方向屈折率の差）が大きく発現する特徴を持っており、位相差フィルム用途に好適に用いられる。しかし、液晶表示装置の画面の表示特性が改善できない場合もあった。
特開２００３−３４４８５６号公報 特表平８−５１１８１２号公報

The polyimide resin film has a high orientation and has a characteristic that a large amount of birefringence (difference between the in-plane refractive index and the refractive index in the thickness direction) is exhibited, and is suitably used for retardation film applications. However, there are cases where the display characteristics of the screen of the liquid crystal display device cannot be improved.
JP 2003-344856 A Japanese National Patent Publication No. 8-511812

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a polyimide resin useful for use in a retardation film in order to realize a wide viewing angle of a liquid crystal display device and prevention of coloring of a screen. To do.

As a result of intensive studies, the inventors of the present invention mainly comprise the structures of the following general formula 1 and general formula 2, and when the content ratios are expressed as x ₁ and x ₂ , respectively, x ₁ : y ₁ = 5: 95-95: 5 It discovered that the polyimide resin characterized by it was a polyimide resin useful for retardation film use.

（Ａｒは、脂肪族基又は芳香族基である。また、Ｒ¹は、下記一般式群１に示す構造から選ば れる少なくとも一種の構造である。）

(Ar is an aliphatic group or an aromatic group. R ¹ is at least one structure selected from the structures shown in the following general formula group 1.)

また、前記Ａｒは、一般式１、及び一般式２の両方の構造において、各々その少なくとも一部は下記一般式３の構造を有することが好ましい。

The Ar preferably has a structure represented by the following general formula 3 in each of the structures represented by the general formula 1 and the general formula 2.

さらに、前記Ａｒは、前記一般式３以外に、主として下記一般式群２に示す構造から選ばれる少なくとも一種の構造を有し、かつ、一般式３の構造をｘ₂とし、前記一般式群２から選ばれる少なくとも１種の構造をｙ₂としたとき、これらの構造の構成比が、ｘ₂：ｙ₂＝５：９５〜９５：５であることが好ましい。

In addition to the general formula 3, Ar has at least one structure mainly selected from the structures shown in the following general formula group 2, and the structure of the general formula 3 is x ₂ , and the general formula group 2 When at least one structure selected from y is y ₂ , the composition ratio of these structures is preferably x ₂ : y ₂ = 5: 95 to 95: 5.

（Ｒ²は、フッ素、塩素、臭素のいずれかのハロゲン基、またはアルキル基である。）
本発明のポリイミド樹脂膜は、主として上述した本発明のポリイミド樹脂からなり、δｎｄ４４６．７／δｎｄ５４７．９の値と、Ｒｔｈ４４６．７／Ｒｔｈ５４７．９の値と、が異なる値であることを特徴とする。

(R ² is a halogen group of any one of fluorine, chlorine and bromine, or an alkyl group.)
The polyimide resin film of the present invention is mainly composed of the above-described polyimide resin of the present invention, and is characterized in that the value of δnd446.7 / δnd547.9 is different from the value of Rth446.7 / Rth547.9. To do.

(However, δnd446.7 and δnd547.9 represent the product of the maximum in-plane refractive index difference and thickness at wavelengths 446.7 nm and 547.9 nm, respectively, and Rth446.7 and Rth547.9 each have a wavelength 446. Represents thickness direction retardation at 0.7 nm and 547.9 nm.)
The value of δnd446.7 / δnd547.9 is preferably larger than the value of Rth446.7 / Rth547.9.

  Further, the value of Rth446.7 / Rth547.9 is preferably smaller than 1.09.

  Such a polyimide resin film of the present invention preferably has a light transmittance of light having a wavelength of 450 nm at a thickness of 5 μm of 80% or more.

  In a retardation film application for the purpose of optical compensation, by using the polyimide resin of the present invention and a polyimide resin film mainly composed of this resin, a wide viewing angle of a liquid crystal display device and prevention of coloring of a screen can be realized. .

  The gist of the polyimide resin according to the present invention is a polyimide resin having a main skeleton mainly composed of the structures of the following general formulas 1 and 2.

（Ａｒは、脂肪族基又は芳香族基である。また、Ｒ¹は、下記一般式群１に示す構造から選ばれる少なくとも一種の構造である。）

(Ar is an aliphatic group or an aromatic group. R ¹ is at least one structure selected from the structures shown in the following general formula group 1.)

本発明のポリイミド樹脂は、一般式１の構造をｘ₁とし、一般式２の構造をｙ₁としたとき、これらの構造の構成比がx₁：y₁＝５：９５〜９５：５である。この構成比は、x₁：y₁＝５５：４５〜９０：１０とすることが好ましい。構成比がx₁：y₁＝８０：２０よりもx₁が大きくy₁が小さい場合、複屈折が小さくなり、構成比がx₁：y₁＝５５：４５よりもx₁が小さくy₁が大きい場合、ポリイミド樹脂を膜状に成形した場合の透明性が乏しくなる。

In the polyimide resin of the present invention, when the structure of the general formula 1 is x ₁ and the structure of the general formula 2 is y ₁ , the composition ratio of these structures is x ₁ : y ₁ = 5: 95 to 95: 5. is there. This composition ratio is preferably x ₁ : y ₁ = 55: 45 to 90:10. Composition ratio x _1: y ₁ = 80: when x ₁ than 20 large y ₁ is small, the birefringence is small, composition ratio x _1: y ₁ = 55: x ₁ is smaller y ₁ than 45 Is large, the transparency when the polyimide resin is formed into a film is poor.

  Further, in the polyimide resin of the present invention, it is preferable that at least a part of the Ar in the structures of the general formulas 1 and 2 has the structure of the following general formula 3, respectively. The remaining part is preferably at least one structure selected from the structures shown in the following general formula group 2.

（Ｒ²は、フッ素、臭素、塩素のいずれかのハロゲン基、またはアルキル基である。）
また、本発明のポリイミド樹脂において、一般式３の構造をｘ₂とし、一般式群２から選ばれる少なくとも１種の構造をｙ₂としたとき、これらの構造の構成比をｘ₂とｙ₂で表した場合、ｘ₂：ｙ₂＝５：９５〜９５：５とすることが好ましく、ｘ₂：ｙ₂＝３０：７０〜８０：２０とすることがさらに好ましい。

(R ² is a halogen group of any one of fluorine, bromine and chlorine, or an alkyl group.)
In the polyimide resin of the present invention, when the structure of the general formula 3 is x ₂ and at least one structure selected from the general formula group 2 is y ₂ , the composition ratio of these structures is x ₂ and y _2. X ₂ : y ₂ = 5: 95 to 95: 5 is preferable, and x ₂ : y ₂ = 30: 70 to 80:20 is more preferable.

  Such a polyimide resin of the present invention has 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoro as an acid dianhydride as a polymerization raw material. Propanic acid dianhydride (6FDA) is included as an essential component, and other acid dianhydrides include 4,4'-oxybisphthalic anhydride (ODPA), 3,3 ', 4,4'- Any one of benzophenone tetracarboxylic dianhydride (BTDA), 9,9-bis (3,4-dicarboxyphenyl) fluorenic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride Or it uses in combination of multiple types. Among these, the acid dianhydride used in combination includes 4,4′-oxybisphthalic anhydride (ODPA), 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA), 9,9-bis (3,4-dicarboxyphenyl) fluorenic dianhydride is preferably used, and 4,4'-oxybisphthalic anhydride (ODPA), 3,3 ', 4,4'-benzophenone Tetracarboxylic dianhydride (BTDA) is more preferably used, and 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA) is particularly preferably used.

  In addition to the above, acid dianhydrides that can be used in combination include, for example, pyromellitic dianhydride, 2,5-difluoropyromellitic dianhydride, 2-fluoropyromellitic dianhydride 2,5-bistrifluoromethylpyromellitic dianhydride, 2-trifluoromethylpyromellitic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2' -Substituted-3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride Anhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2-bis (4-trimellitic acid monoester acid phenyl) propanoic acid dianhydride, 2,2-bis (4-tri Merit acid Noester acid phenyl) -1,1,1,3,3,3-hexafluoropropanoic acid dianhydride, p-biphenylbis (trimellitic acid monoester acid anhydride), p-phenylenebis (trimellitic acid monoester) Acid anhydride), p-substituted phenylene bis (trimellitic acid monoester acid anhydride), 4,4'-biphenylene bis (trimellitic acid monoester acid anhydride), 1,4-naphthalene bis (trimellitic acid mono) Ester acid anhydride), 2,6-naphthalenebis (trimellitic acid monoester acid anhydride), and the like.

  The diamine that is a polymerization raw material for the polyimide resin of the present invention is not particularly limited as long as it can provide birefringence and transparency to the polyimide resin film. For example, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (TFMB), 4,4′-diamino-benzophenone, 9,9-bis (4-aminophenyl) fluorene, 9,9 -Bis (4-amino-2-fluorophenyl) fluorene, 9,9-bis (4-amino-2-bromophenyl) fluorene, 9,9-bis (4-amino-2-chlorophenyl) fluorene, 9,9 -Bis (4-amino-3-fluorophenyl) fluorene (BFAF), 9,9-bis (4-amino-3-bromophenyl) fluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9,9-bis (4-amino-2-trifluoromethylphenyl) fluorene, 9,9-bis (4-amino-3-trifluoromethylphenyl) fluorene Emissions, bis (4-aminophenyl) sulfone, 1,4-diaminobenzene, 1,3-diaminobenzene, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, and the like.

  Among them, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (TFMB), 4,4′-diamino-benzophenone, 9,9-bis (4-aminophenyl) fluorene, 9,9- Bis (4-amino-2-fluorophenyl) fluorene, 9,9-bis (4-amino-2-bromophenyl) fluorene, 9,9-bis (4-amino-2-chlorophenyl) fluorene, 9,9- Bis (4-amino-3-fluorophenyl) fluorene (BFAF), 9,9-bis (4-amino-3-bromophenyl) fluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9 , 9-bis (4-amino-2-trifluoromethylphenyl) fluorene, 9,9-bis (4-amino-3-trifluoromethylphenyl) fluorene Bis (4-aminophenyl) sulfone is preferred, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (TFMB), 9,9-bis (4-amino-3-fluorophenyl). Fluorene (BFAF) is particularly preferred.

  The weight average molecular weight of the polyimide resin of the present invention is preferably 30,000 or more and 200,000 or less as measured by GPC PEG (polyethylene glycol) conversion. If the weight average molecular weight is less than 30,000, there may be a problem in durability. Moreover, since the solubility to an organic solvent will fall if a weight average molecular weight is 200,000 or more, difficulty may arise when using the polyimide resin of this invention dissolved in an organic solvent as a soluble polyimide resin. is there.

  Furthermore, the imidation ratio of the polyimide resin of the present invention is preferably 80% or more. If it is less than 80%, it is not preferable in terms of transparency and retardation development ability. Preferably it is 90% or more, More preferably, it is 95% or more, More preferably, it is 99% or more.

  Moreover, when using the polyimide resin of this invention as molded objects, such as a film, it is preferable from the point of the stability of the molded object that the amount of residual solvents shall be less than 1%.

  The polyimide resin of the invention can be used as a polyimide resin film as a molded body. Such a polyimide resin film of the present invention has a preferable film thickness of 1 μm to 50 μm, and may be a single film or a coating layer. Further, when the polyimide resin film of the present invention is used as an optical film, it is preferable that the light transmittance at a wavelength of 450 nm at a thickness of 5 μm is 80% or more because light can efficiently pass through the polyimide resin film.

  When the polyimide resin film of the present invention is used as the coating layer, an inorganic material such as glass or a plastic material such as polycarbonate, PMMA, cellulose, or cycloolefin polymer can be used as a support for supporting the film. When a plastic material such as polycarbonate, PMMA, cellulose, or cycloolefin polymer is used as the support, it is preferable to use the polyimide resin in a state of a polyimide resin film by casting a polyimide resin solution dissolved in an organic solvent.

  The organic solvent for casting is an organic solvent for dissolving a polyimide resin into a polyimide resin solution for casting in a polyimide resin film forming step in which a polyimide resin solution is cast on a support made of a polymer and dried.

  The organic solvent for casting is not particularly limited as long as it is a solvent that dissolves the polyimide resin. For example, amide solvents such as NMP (N-methylpyrrolidone) and DMF (N, N-dimethylformamio), ester solvents such as ethyl acetate, halogen solvents such as chloroform and dichloromethane, ethers such as dioxolane and diethyl ether A system solvent, a ketone solvent such as MEK (methyl ethyl ketone), MIBK (methyl isobutyl ketone), and cyclohexanone, an aromatic hydrocarbon solvent such as toluene and xylene, and the like can be used. Further, as long as the polyimide resin can be dissolved, a non-solvent that does not dissolve the polyimide resin or a poor solvent that is difficult to dissolve may be used as a mixed solvent in a timely manner.

  Among the above-mentioned organic solvents for casting, halogen solvents such as chloroform and dichloromethane, ether solvents such as dioxolane and diethyl ether, ketone solvents such as MEK (methyl ethyl ketone), MIBK (methyl isobutyl ketone) and cyclohexanone, toluene and xylene Aromatic hydrocarbon solvents such as are preferable in the polyimide resin film forming step in that they do not damage the base material of the support film made of a polymer. Among them, MEK (methyl ethyl ketone), MIBK (methyl isobutyl ketone), More preferred are ketone solvents such as cyclohexanone.

  The birefringence of the polyimide resin film of the present invention is the difference between the in-plane refractive index and the thickness direction refractive index, and is preferably 0.02 or more and 0.15 or less. If the birefringence of the polyimide resin film is less than 0.02, when used for a retardation film, the thickness of the film required for the expression of properties increases, and coloring may become a problem. If the birefringence exceeds 0.15, it may be difficult to control the thickness of the polyimide resin film in applications where uniform birefringence characteristics are required.

  In the polyimide resin film of the present invention, it is preferable that the values of δnd446.7 / δnd547.9 and Rth446.7 / Rth547.9 are different from each other at a wavelength of 400 to 800 nm from the viewpoint of widening the viewing angle and preventing coloration of the screen. Here, δnd represents a front phase difference, and 446.7 and 547.9 are measurement wavelengths of the phase difference. Rth represents the thickness retardation, and 446.7 and 547.9 are thickness retardation wavelength.

  Further, in the polyimide resin film of the present invention, the value of δnd446.7 / δnd547.9 at a wavelength of 400 to 800 nm is larger than the value of Rth446.7 / Rth547.9, in view angle enlargement and screen coloring prevention. To more preferable.

  Further, it is more preferable that the value of Rth446.7 / Rth547.9 at a wavelength of 400 to 800 nm of the polyimide resin film is smaller than 1.09 from the viewpoint of widening the viewing angle and preventing coloration of the screen.

  Next, the manufacturing method of the polyimide resin of this invention is demonstrated. The method for producing a polyimide resin generally includes three steps of (1) polymerization of polyamic acid, (2) imidation of polyamic acid, and (3) extraction of the polyimide resin.

(1) Polymerization of polyamide acid The method for producing polyamide acid is not limited to the following method, and various methods can be used. An example is shown below.

  Dispersing the acid dianhydride in an organic solvent, which is a polymerization solvent in which diamine is dissolved, and completely dissolving and polymerizing by stirring, dissolving the acid dianhydride in an organic solvent, which is a polymerization solvent, and There are a method of polymerizing with a diamine after dispersion and / or a method of polymerizing by reacting a mixture of an acid dianhydride and a diamine in an organic solvent which is a polymerization solvent, but a known polymerization method can be used. That's fine.

  The reaction time is preferably about 1 to 5 hours, but the reaction is preferably performed until the viscosity of the polyamic acid solution is 5 Pa · s or more, more preferably 10 Pa · s or more, and most preferably Is preferably about 20 Pa · s or more. When the viscosity of the polyamic acid solution is 20 Pa · s or more, it is most preferable in handling when the polyamic acid solution is molded into a polyimide resin. The viscosity is kept at 23 ° C. in a water bath kept at 23 ° C., and the rotor is No. 7 can be measured at 4 rpm.

  The reaction apparatus is preferably equipped with a temperature adjusting apparatus for controlling the reaction temperature, and the reaction solution temperature is preferably 60 ° C. or less, and more preferably 40 ° C. or less in terms of controlling the reaction.

  The organic solvent that is a polymerization solvent used for the polymerization of the polyamic acid is not particularly limited as long as the polyamic acid is dissolved and the polyamic acid polymerization reaction proceeds. For example, ureas such as tetramethylurea, N, N-dimethylethylurea, dimethylsulfoxide, diphenylsulfone, sulfoxides or sulfones such as tetramethylsulfone, N, N-dimethylacetamide (DMAc), N, N-dimethyl An aprotic solvent of formamide (DMF), N, N′-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyllactone, hexamethylphosphate triamide, or phosphorylamides, Examples include halogenated alkyls such as chloroform and methylene chloride, aromatic hydrocarbons such as benzene and toluene, phenols such as phenol and cresol, and ethers such as dimethyl ether, diethyl ether, and p-cresol methyl ether. Can be generally may be used in combination but employing these solvents alone, two or more depending on necessity. Of these, amides such as DMF, DMAc and NMP are preferably used. Moreover, the organic solvent which can fully melt | dissolve the polyimide resin finally obtained is preferable.

  From the viewpoint of handling, it is preferable that the polyamic acid in the polyamic acid solution is dissolved by 5 to 50 wt%, preferably 10 to 40 wt% of the polyamic acid in the organic solvent.

  The molar ratio of the acid dianhydrides and diamines used in the reaction for producing the polyamic acid solution is preferably 0.9 or more and 1.5 or less, more preferably 0, when calculated by the following formula. .95 or more and 1.3 or less, particularly preferably 0.98 or more and 1.2 or less, unreacted acid dianhydride or diamine in a polyimide resin obtained from a polyamic acid solution It is preferable in reducing the amount.

(2) Imidation of polyamic acid A method for producing a solution containing a soluble polyimide resin by imidizing a solution containing a polyamic acid will be described. As a method for imidizing a solution containing polyamic acid, there are a thermal imidization method in which dehydration and ring closure is thermally performed, and a chemical imidization method using a dehydrating agent.

  The thermal imidization is generally performed by adding an azeotropic solvent such as toluene that azeotropes with water generated during the imidation reaction to the polyamic acid solution and then heating. In the thermal imidization method, an imidization accelerator can be used in combination.

  In this invention, the imidation ratio of the polyimide resin obtained can be improved, without reducing molecular weight by making the conditions at the time of imidating a polyamic acid into a specific condition. That is, it is preferable to imidize the solution containing polyamic acid using a tertiary amine as an imidization accelerator. Such an imidization accelerator is not particularly limited as long as it is a tertiary amine, but heterocyclic tertiary amines such as pyridine, quinoline and isoquinoline are particularly preferable.

  Moreover, it is preferable that the temperature at the time of imidation is below the boiling point of the organic solvent used by 40 degreeC-imidation, and heating time is 0.5 to 20 hours. If the temperature is 40 ° C. or lower, the imidization rate may be lowered, which is not preferable. The temperature for imidization is preferably 50 ° C. to the boiling point of the organic solvent used for imidization, but heating at 150 ° C. or lower is preferable to prevent coloring of the polyimide resin.

  In chemical imidization, an aliphatic acid anhydride such as acetic anhydride or an aromatic acid anhydride is used as a dehydrating agent. Among these, it is preferable to use acetic anhydride because it is suitable for the polyimide resin extraction step.

(3) Extraction of polyimide resin The precipitation method of the polyimide resin is a method of depositing the polyimide resin from the solution containing the polyimide resin obtained as described in the above (1) and (2), and there are various known methods. The polyimide resin can be selected by adding a polyimide resin solution containing a polyimide resin, a dehydrating agent, an imidization accelerator, etc. into a poor solvent of the polyimide resin, or by adding a poor solvent to the polyimide resin solution. Can be achieved in a solid state. Examples of the method for introducing the poor solvent into the polyimide resin solution include a method of introducing it in droplets and a method of adding it in a thread form, but there is no particular limitation as long as the polyimide resin is precipitated in the poor solvent. The polyimide resin of the present invention is in the form of solids including threads, powders, flakes, and various forms, and the desired solids can be obtained by pulverizing the precipitated polyimide resin if necessary. it can.

  The poor solvent for the polyimide resin used in the present invention is not particularly limited to those that are miscible with the organic solvent used as the solvent for dissolving the polyimide resin. For example, water, methyl alcohol, ethyl alcohol, isopropyl alcohol , Ethylene glycol, triethylene glycol, 2-butyl alcohol, 2-propyl alcohol, 2-hexyl alcohol, cyclopentyl alcohol, cyclohexyl alcohol, phenol, t-butyl alcohol and the like. Among the above alcohols, secondary or tertiary alcohols such as isopropyl alcohol, 2-butyl alcohol, 2-pentyl alcohol, phenol, cyclopentyl alcohol, cyclohexyl alcohol, and t-butyl alcohol increase the imidization ratio of the resulting polyimide resin. From the viewpoint of stabilization, 2-propyl alcohol is more preferable. The amount of the poor solvent is preferably extracted in an amount of 2 times or more, more preferably 3 times or more of the polyimide resin solution.

  In order to obtain a polyimide resin from a polyimide resin solvent, it may be difficult to obtain a polyimide resin having a desired shape after drying only by the above extraction. This is because the polyimide resin contains a large amount of solvent, and the desired polyimide resin containing almost no organic solvent can be obtained by washing the polyimide resin with the poor solvent.

  The polyimide resin obtained as described above is preferably dried to remove the poor solvent, but the method may be vacuum drying or hot air drying. However, when used for optical purposes, coloring at the time of drying may be a problem, so it is desirable to carry out at 200 ° C. or lower.

  About the acid dianhydride which is a raw material of a polyimide resin, and the diamine, the kind and quantity were changed, the various polyimide resin was obtained, and also the stretched polyimide film | membrane was created from this polyimide resin, and various evaluation was performed. The results are shown in Table 1.

以下、表１に示す各実施例・比較例により本発明を具体的に説明するが、本発明はこれら実施例のみに限定されるものではない。

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples shown in Table 1. However, the present invention is not limited to these Examples.

Example 1
In this example, a glass separable flask was provided as a reaction vessel, two paddle blades were provided as a stirring device in the separable flask, and a device having a cooling capacity of 20.9 kJ / min was provided as a cooling device. A polyamic acid was synthesized using a reactor.

  As a synthesis procedure, diamine was dissolved in a polymerization solvent, and then acid dianhydride was added to proceed the polymerization reaction. During the polymerization reaction, in order to prevent moisture from being mixed, the polymerization reaction was carried out by flowing nitrogen gas dehydrated by passing through silica gel at a rate of 0.05 L / min.

  Specifically, first, 212.1 g of N, N-dimethylformamide (DMF) is charged as a polymerization solvent into the separable flask, and 2,2′-bis (trifluoromethyl)-is used as a diamine. 40.0 g (0.125 mol) of 4,4′-diaminobiphenyl (TFMB) was dissolved.

  Next, 12.3 g (0.037 mol) of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA) as an acid dianhydride, 2,2-bis (3, 4-Dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropanoic acid dianhydride (6FDA) 38.8 g (0.087 mol), ie (BTDA: 6FDA = 3: 7) Added and stirred until completely dissolved.

  After complete dissolution, the mixture was stirred for 2 hours. At this time, the charged concentration of the aromatic diamine compound and aromatic tetracarboxylic dianhydride in the reaction solution is 30% by weight with respect to the total reaction solution.

  20 g of pyridine as an imidization catalyst (molar ratio of imidization accelerator / amide group in polyamic acid = 2) is added to the above solution and completely dispersed. To the dispersed solution, 15.3 g of acetic anhydride as a dehydrating agent was added at a rate of 1 g per minute (molar ratio of dehydrating agent / amide group in polyamic acid = 1.2), and the mixture was further stirred for 30 minutes. After stirring, the internal temperature was raised to 100 ° C., and heating and stirring were performed for 5 hours.

  To the place where the reaction solution was stirred at 200 revolutions, 0.5 L of 2-propyl alcohol was added dropwise to obtain a polyimide resin slurry. The obtained polyimide resin slurry was washed 5 times with 1 L of 2-propyl alcohol.

  Then, this polyimide resin slurry was heat-dried at 100 degreeC with the vacuum dryer, and polyimide resin was obtained. The weight average molecular weight of the polyimide resin thus obtained was measured. In addition, a stretched polyimide film was prepared using the method described below, and the wavelength dispersion and image quality evaluation of the stretched polyimide film were evaluated.

(Creation of stretched polyimide film)
A solution obtained by dissolving a polyimide resin in methyl isobutyl ketone (MIBK) so as to have a solid component concentration of 10% was applied onto a PET film with a bar coater, and then dried at 50 ° C. for 2 minutes. Thereafter, the formed polyimide resin film was peeled off from the PET film and cut out as a raw film having a width of 50 mm and a length of 100 mm. A 350 g weight was hung at the lengthwise tip of the original film, and in that state, it was dried in a hot air oven at 160 ° C. for 10 minutes to obtain a stretched polyimide resin film having a thickness of 5 μm.

(Wavelength dispersion)
Wavelength dispersion characteristics of the obtained stretched polyimide resin film were measured by Kobra-WR (manufactured by Oji Scientific Co., Ltd.), and values of δnd446.7 / δnd547.9 and Rth446.7 / Rth547.9 were obtained.

(Molecular weight)
The weight average molecular weight (Mw) was measured with the apparatus and conditions described in Table 2 to obtain the molecular weight.

（画質評価）
延伸ポリイミド樹脂膜を偏光板に貼り合わせた後、パネルに組み込んで画質の評価を実施した。画質の評価は、良いものを○として、改善が不足しているものを△にした。評価結果を表１に示す。

(Image quality evaluation)
After the stretched polyimide resin film was bonded to the polarizing plate, it was incorporated into a panel and image quality was evaluated. In the evaluation of the image quality, “Good” indicates “Good” and “Good” indicates “No”. The evaluation results are shown in Table 1.

(Example 2)
44.4 g (0.100 mol) of 6FDA as the acid dianhydride and 7.7 g (0.025 mol) of 4,4′-oxybisphthalic anhydride (ODPA), that is, (6FDA: ODPA = 8: 2) A polyimide resin was synthesized in the same manner as in Example 1 except that 40.0 g of TFMB was used as the diamine, and this polyimide resin and the stretched polyimide film were evaluated.

(Example 3)
55.5 g (0.125 mol) of 6FDA was used as the acid dianhydride, 20.0 g (0.063 mol) of TFMB as the diamine, and 9,9-bis (4-amino-3-fluorophenyl) fluorene (BFAF) 24 A polyimide resin was synthesized in the same manner as in Example 1 except that 0.0 g (0.063 mol), that is, (TFMB: BFAF = 5: 5) was used, and the polyimide resin and the stretched polyimide film were evaluated.

Example 4
6FDA 44.4 g (0.100 mol) and 4,4′-oxybisphthalic anhydride (ODPA) 7.7 g (0.025 mol) were used as the acid dianhydride, and TFMB 20.0 (0.005 mol) was used as the diamine. 063 mol) g and 9,9-bis (4-amino-3-fluorophenyl) fluorene (BFAF) 24.0 g (0.063 mol) were used, ie (6FDA: ODPA = 8: 2 / TFMB): A polyimide resin was synthesized in the same manner as in Example 1 except that BFAF = 5/5), and the polyimide resin and the stretched polyimide film were evaluated.

(Comparative Example 1)
A polyimide resin was synthesized in the same manner as in Example 1 except that 6FDA55.5 (0.125 mol) g was used as the acid dianhydride, and this polyimide resin and the stretched polyimide film were evaluated.

As shown in Table 1, the image quality evaluation result was worse in the comparative example than the image quality evaluation result in each example was good.

Claims (7)

It consists mainly of the structure of the following general formula 1 and general formula 2, and when these content ratios are expressed as x ₁ and x ₂ respectively, x ₁ : y ₁ = 5: 95 to 95: 5, Polyimide resin.

(Ar is an aliphatic group or an aromatic group. R ¹ is at least one structure selected from the structures shown in the following general formula group 1.)

(R ² is a halogen group of any one of fluorine, bromine and chlorine, or an alkyl group.) 2. The polyimide resin according to claim 1, wherein the Ar has a structure represented by the following general formula 3 in each of the general formula 1 and the general formula 2 structures.

In addition to the general formula 3, the Ar has at least one structure selected from the structures shown in the following general formula group 2 and the structure of the general formula 3 is x ₂ and is selected from the general formula group 2. 3. The polyimide resin according to claim 2, wherein the composition ratio of these structures is x ₂ : y ₂ = 5: 95 to 95: 5, where y ₂ is at least one kind of structure.

(R ² is a halogen group of any one of fluorine, chlorine and bromine, or an alkyl group.)
  The value of δnd446.7 / δnd547.9 and the value of Rth446.7 / Rth547.9 are different values, mainly from the polyimide resin according to any one of claims 1 to 3. Polyimide resin films (where δnd446.7 and δnd547.9 represent the product of the maximum in-plane refractive index difference and thickness at wavelengths of 446.7 nm and 547.9 nm, respectively, and Rth446.7 and Rth547.9 represent , And represents the thickness direction retardation at wavelengths of 446.7 nm and 547.9 nm, respectively).   5. The polyimide resin film according to claim 4, wherein a value of δnd446.7 / δnd547.9 is larger than a value of Rth446.7 / Rth547.9.   6. The polyimide resin film according to claim 5, wherein the value of Rth 446.7 / Rth 547.9 is smaller than 1.09.   The polyimide resin film according to any one of claims 4 to 6, wherein a light transmittance of light having a wavelength of 450 nm at a thickness of 5 µm is 80% or more.