JP5182886B2 - NOVEL DIAMINE, POLYIMIDE PRECURSOR, POLYIMIDE, COATING OPTICAL COMPENSATION FILM COMPRISING THE SAME, AND METHOD FOR PRODUCING THE SAME - Google Patents

Description

  The present invention relates to a novel diamine compound containing a fluorenyl group, a polyimide precursor obtained using the diamine compound, a polyimide and a production method thereof, an optical compensation film for a liquid crystal display comprising the polyimide, and a production method thereof.

  Conventionally, plasma displays have been the mainstream for large flat panel displays (FPDs) represented by television, but recently, demand for large liquid crystal televisions has rapidly expanded due to advances in the technology for increasing the size of liquid crystal displays (LCD). doing.

  Reduction of the viewing angle dependency of contrast is one of the most important required characteristics in the usage form of an LCD such as a large liquid crystal television. In recent years, LCDs in VA (vertical alignment) mode and IPS (in-plane alignment switching) mode, which are advantageous for widening the viewing angle, have been adopted in large liquid crystal televisions.

  Among LCD components, liquid crystal cells and polarizing films inherently have optical anisotropy, so an optical compensation film suitable for each of these members is used for the purpose of maintaining high contrast over a wide viewing angle. It has been.

  In general, a negative C plate and a positive A plate are used in combination as an optical compensation film for a liquid crystal layer in a VA mode LCD. Recently, a polymer film that is biaxially stretched at the same time is applied to the former.

  The retardation film is required not only to prevent a decrease in contrast when viewed obliquely but also to have a color compensation function by compensating for retardation (birefringence) wavelength dependency.

  In the liquid crystal molecular material used for the liquid crystal cell, the wavelength dependence of retardation (birefringence) often becomes normal wavelength dispersion in which the retardation (birefringence) value decreases as the wavelength increases. For example, in a STN mode LCD, since a liquid crystal material often has normal dispersion characteristics, a polycarbonate phase difference film having positive and large wavelength dispersion characteristics is used. On the other hand, in the VA mode liquid crystal cell, the retardation (birefringence) wavelength dependency of the liquid crystal layer may be considerably smaller than usual due to the liquid crystal material and color filter used. In order to compensate for this, the retardation (birefringence) A retardation film having a small wavelength dependency of refraction (ie, having a low wavelength dispersion characteristic) is required.

  Recently, a cycloolefin polymer film stretched biaxially has been adopted as a retardation film for a VA mode liquid crystal cell for the above purpose. However, in order to insert the retardation film between the polarizing film and the liquid crystal cell, a step of laminating using an adhesive is necessary, which is disadvantageous for thinning the panel. On the other hand, a method of imparting a retardation function to a part of a polarizer protective film (for example, a triacetyl cellulose (TAC) film) of a polyvinyl alcohol / iodine polarizing film or using a retardation film having a polarizing film protective function Attempts have also been made to reduce the number of members in the LCD.

  As described above, in order to develop a large birefringence in order to apply the transparent polymer material to the retardation film, it is usually necessary to mechanically stretch the polymer film at a high magnification. If a polymer varnish dissolved in a solvent that does not erode the polarizer protective film is applied and dried on the protective film, high retardation (birefringence) and low wavelength dispersion can be achieved without any stretching operation. If there is a transparent polymer material, the LCD manufacturing process can be remarkably simplified, and a material effective for cost reduction and thinning can be provided.

  A technique for producing a negative C plate by developing a transparent and relatively high retardation (birefringence) by simply applying and drying a polyimide varnish is disclosed (for example, Patent Document 1). There was still room for improvement in the chromatic dispersion characteristics.

JP 2008-280417 A

  The present invention has high transparency, high retardation (birefringence), low wavelength dispersion of retardation (birefringence), high solubility in a solvent that does not erode the polarizer protective film (varnish stability), and sufficient film toughness. In addition, an alicyclic polyimide useful as a coating-type optical compensation (retardation) film material for liquid crystal displays, its precursor, a novel diamine compound for producing these, an optical compensation film containing this polyimide, and its An object is to provide a manufacturing method.

    As a result of accumulating intensive studies in view of the above problems, the following general formula (8):

（式（８）中、Ａは４価の脂肪族基を表し、Ｐ_nは各々独立に、フッ素原子、塩素原子、臭素原子、炭素数１〜６の直鎖状もしくは分岐状アルキル基、炭素数１〜６の直鎖状もしくは分岐状アルコキシ基を表し、ｎは置換基の数を表す０から４の整数である。）
で表される繰り返し単位を有するポリイミドとこれを含有する共重合体が偏光子保護フィルムを浸蝕しない溶媒に溶解して安定なワニスを与え、これを偏光子保護フィルム上に塗布・乾燥することで上記産業分野において極めて有益な光学補償フィルム（位相差フィルム）となることを見出し、本発明を完成するに至った。

(In formula (8), A represents a tetravalent aliphatic group, and P _n each independently represents a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, carbon, A linear or branched alkoxy group having 1 to 6 is represented, and n is an integer of 0 to 4 representing the number of substituents.
A polyimide having a repeating unit represented by the following and a copolymer containing the same are dissolved in a solvent that does not erode the polarizer protective film to give a stable varnish, and this is applied and dried on the polarizer protective film. The present inventors have found that the optical compensation film (retardation film) is extremely useful in the industrial field and has completed the present invention.

That is, the gist of the present invention is as follows.
(I) The following general formula (1):

で表されるフルオレニル基含有ジアミン化合物。
（式（１）中、置換基Ｐ_nは各々独立に、フッ素原子、塩素原子、臭素原子、炭素数１〜６の直鎖状もしくは分岐状アルキル基、炭素数１〜６の直鎖状もしくは分岐状アルコキシ基を表し、ｎは置換基の数を表す０から４の整数である。）
（ＩＩ）下記一般式（２）：

The fluorenyl group containing diamine compound represented by these.
(In Formula (1), each substituent P _n is independently a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched chain group having 1 to 6 carbon atoms, or Represents a branched alkoxy group, and n is an integer of 0 to 4 representing the number of substituents.)
(II) The following general formula (2):

で表される繰り返し単位を有するポリイミド前駆体。
（式（２）中、Ａは４価の脂肪族基を表し、Ｐ_nは各々独立に、フッ素原子、塩素原子、臭素原子、炭素数１〜６の直鎖状もしくは分岐状アルキル基、炭素数１〜６の直鎖状もしくは分岐状アルコキシ基を表し、ｎは置換基の数を表す０から４の整数である。）
（ＩＩＩ）前記一般式（２）で表されるイミド前駆体単位のモル分率をＸとすると、Ｘが０．０１〜０．９９の範囲である、（ＩＩ）記載のポリイミド前駆体共重合体。
（ＩＶ）下記一般式（３）：

The polyimide precursor which has a repeating unit represented by these.
(In the formula (2), A represents a tetravalent aliphatic group, and P _n each independently represents a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, carbon A linear or branched alkoxy group having 1 to 6 is represented, and n is an integer of 0 to 4 representing the number of substituents.
(III) When the molar fraction of the imide precursor unit represented by the general formula (2) is X, X is in the range of 0.01 to 0.99. Coalescence.
(IV) The following general formula (3):

（式（３）中、Ａは前記と同義である。Ｂは下記式（４）〜（７）：

(In Formula (3), A is as defined above. B is the following Formulas (4) to (7):

からなる群から選ばれる少なくとも１種を表す。）
で表されるイミド前駆体単位をさらに含有することを特徴とする（ＩＩＩ）に記載のポリイミド前駆体の共重合体。
（Ｖ）下記一般式（８）：

Represents at least one selected from the group consisting of )
The polyimide precursor copolymer as described in (III), further comprising an imide precursor unit represented by the formula:
(V) The following general formula (8):

で表される繰り返し単位を有するポリイミド。
（式（８）中、Ａは４価の脂肪族基を表し、Ｐ_nは各々独立に、フッ素原子、塩素原子、臭素原子、炭素数１〜６の直鎖状もしくは分岐状アルキル基、炭素数１〜６の直鎖状もしくは分岐状アルコキシ基を表し、ｎは置換基の数を表す０から４の整数である。）
（ＶＩ）上記一般式（８）で表されるイミド単位のモル分率をＹとすると、Ｙが０．０１〜０．９９の範囲である、（Ｖ）記載のポリイミド共重合体。
（ＶＩＩ）下記一般式（９）：

The polyimide which has a repeating unit represented by these.
(In formula (8), A represents a tetravalent aliphatic group, and P _n each independently represents a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, carbon, A linear or branched alkoxy group having 1 to 6 is represented, and n is an integer of 0 to 4 representing the number of substituents.
(VI) The polyimide copolymer according to (V), wherein Y is in the range of 0.01 to 0.99, where Y is the molar fraction of the imide unit represented by the general formula (8).
(VII) The following general formula (9):

（式（９）中、Ａは４価の脂肪族基を表し、Ｂは前記式（４）〜（７）からなる群から選ばれる少なくとも１種）で表されるイミド単位をさらに含有することを特徴とする（ＶＩ）記載のポリイミド共重合体。
（ＶＩＩＩ） （ＩＩ）〜（ＩＶ）のいずれかに記載のポリイミド前駆体を、加熱あるいは脱水環化試薬を用いてイミド化反応させることを特徴とする、（Ｖ）〜（ＶＩＩ）のいずれかに記載のポリイミドの製造方法。
（ＩＸ） （Ｖ）〜（ＶＩＩ）のいずれかに記載のポリイミドを、ケトン系溶媒、芳香族炭化水素系溶媒、エステル系溶媒の少なくとも１つに選ばれる溶媒に５重量％以上の濃度で均一に溶解して得られるワニス。
（Ｘ） （Ｖ）〜（ＶＩＩ）のいずれかに記載のポリイミドからなる光学補償フィルム。
（ＸＩ） （ＩＸ）に記載のポリイミドワニスを基板上に塗布・乾燥することを特徴とする光学補償フィルムの製造方法。
（ＸＩＩ） 波長４００ｎｍにおける光透過率が８０％以上、波長４５０ｎｍおよび５５０ｎｍにおけるリタデーション（Ｒｅ）または複屈折（△ｎ）の比（Ｒｅ₄₅₀／Ｒｅ₅₅₀＝△ｎ₄₅₀／△ｎ₅₅₀）が１．０３以下、且つ引張試験において１０％以上の破断伸びを有する、（Ｘ）に記載の光学補償フィルム。
（ＸＩＩＩ） ナトリウムランプのＤ線（５８９ｎｍ）における複屈折が０．０２以上である（Ｘ）に記載の光学補償フィルム。

(In the formula (9), A represents a tetravalent aliphatic group, and B further contains an imide unit represented by the formula (4) to (7)). The polyimide copolymer as described in (VI) characterized by these.
(VIII) Any one of (V) to (VII), wherein the polyimide precursor according to any one of (II) to (IV) is subjected to an imidization reaction using heating or a dehydrating cyclization reagent. The manufacturing method of the polyimide as described in.
(IX) The polyimide according to any one of (V) to (VII) is uniformly added at a concentration of 5% by weight or more in a solvent selected from at least one of a ketone solvent, an aromatic hydrocarbon solvent, and an ester solvent. Varnish obtained by dissolution in
(X) An optical compensation film comprising the polyimide according to any one of (V) to (VII).
(XI) A method for producing an optical compensation film, comprising applying and drying the polyimide varnish described in (IX) on a substrate.
(XII) The light transmittance at a wavelength of 400 nm is 80% or more, and the ratio of retardation (Re) or birefringence (Δn) at wavelengths 450 nm and 550 nm (Re ₄₅₀ / Re ₅₅₀ = Δn ₄₅₀ / Δn ₅₅₀ ) is 1. The optical compensation film according to (X), having an elongation at break of not more than 03 and not less than 10% in a tensile test.
(XIII) The optical compensation film according to (X), wherein the birefringence of the sodium lamp at the D line (589 nm) is 0.02 or more.

  According to the present invention, by using a novel fluorenyl group-containing diamine compound, high transparency, high retardation (birefringence), low wavelength dispersion of retardation (birefringence), high organic solvent solubility (varnish stability) ), And an alicyclic polyimide having sufficient film toughness can be produced, and an optical compensation film material and a production method thereof can be provided using this polyimide. This cycloaliphatic polyimide exhibits large retardation (birefringence) and low wavelength dispersion by applying and drying the varnish due to its characteristic self-orientation. It is extremely useful as an optical compensation film.

The infrared absorption spectrum of the polyimide thin film in Example 2 is represented. The relationship between the wavelength and Δn in Example 2 is represented. The infrared absorption spectrum of the polyimide thin film in Example 4 is represented.

Embodiments of the present invention will be described in detail below, but these are examples of the embodiments of the present invention and the present invention is not limited to these contents.
<Molecular design to meet required characteristics>
First, the transparency of the polyimide constituting the optical compensation film of the invention will be described. In a conventional wholly aromatic polyimide system obtained from an aromatic tetracarboxylic dianhydride and an aromatic diamine, as disclosed in Progress in Polymer Science, 26, 259-335 (2001), the diimide moiety is electron-accepting. The diamine moiety acts as an electron donor, and the polyimide film is markedly colored by intramolecular and intermolecular charge transfer interactions. On the other hand, since the polyimide of the present invention is produced using an alicyclic tetracarboxylic dianhydride, the diimide site becomes an alicyclic structure, and the electron acceptability of the diimide site is significantly reduced. Certain charge transfer interactions are disturbed and can be completely colorless and transparent.

  The optical compensation film of the present invention is characterized in that the polyimide layer of the present invention is directly formed on a substrate without using an adhesive. At that time, when the substrate is a polarizer protective film (for example, a TAC film) with low heat resistance, a high temperature heat treatment step of 250 ° C. or higher in which thermal imidization is performed after applying and drying the polyimide precursor varnish on the polarizer protective film is There is a risk of causing thermal deformation of the polarizer protective film, making it difficult to apply. Therefore, a process which does not require a thermal imidization process, that is, a method of forming an optical compensation film by applying and drying a polyimide varnish on a substrate is preferable.

  When the polarizer protective film is a cellulose acetate film such as a TAC film, the film is not eroded as a solvent for the polyimide varnish and is applied even at a temperature lower than 140 to 150 ° C. which is the upper limit temperature limit of the cellulose acetate film. It is necessary to select a solvent that can sufficiently dry the membrane, for example, a ketone solvent, an aromatic hydrocarbon solvent, and an ester solvent. In other words, in addition to the excellent transparency as described above, the polyimide used is required to have high solubility in these solvents at room temperature in order to form a stable varnish.

  Moreover, as one measure for controlling the wavelength dispersion of the retardation (birefringence) of the transparent polyimide film formed from the polyimide varnish as described above, by using a fluorenyl group-containing monomer having a cardo type structure, For example, Japanese Patent Application Laid-Open No. 2007-302719 proposes a method in which a fluorenyl group is bonded as a side difference so that the molecular plane is orthogonal to the polymer main chain. These are components in which the orthogonal fluorenyl group has negative orientation birefringence, canceling out the component with positive orientation birefringence mainly composed of an imide skeleton, and controlling the wavelength dispersion characteristics to low wavelength dispersion and reverse wavelength dispersion. ing.

  As a cardo-type fluorenyl group-containing monomer applicable to a polyimide system, the following formula (10):

で表される９，９−ビス（４−アミノフェニル)フルオレン、特開２００７−３０２７１９で提案されている９，９−ビス（３−アミノプロピル）フルオレンが知られている。しかしながら、ポリイミドの溶媒溶解性、高いリタデーション（複屈折）、リタデーション（複屈折）の低波長分散特性には改善の余地があった。

9,9-bis (4-aminophenyl) fluorene, and 9,9-bis (3-aminopropyl) fluorene proposed in Japanese Patent Application Laid-Open No. 2007-302719 are known. However, there is room for improvement in the solvent solubility of polyimide, high retardation (birefringence), and low wavelength dispersion characteristics of retardation (birefringence).

  In contrast, the following formula (1):

で表される本発明のフルオレニル基含有ジアミンを用いた場合、脂環式テトラカルボン酸二無水物と重合して得られたポリイミドは、様々なケトン系溶媒、芳香族炭化水素系溶媒及びエステル系溶媒に室温で高い溶解性を示し、且つそのポリイミドワニスから形成されたフィルムは優れた透明性及びリタデーション（複屈折）の低波長分散特性を同時に発現することが可能となる。

When the fluorenyl group-containing diamine of the present invention represented by the formula (1) is used, the polyimide obtained by polymerization with the alicyclic tetracarboxylic dianhydride has various ketone solvents, aromatic hydrocarbon solvents and ester solvents. A film that is highly soluble in a solvent at room temperature and that is formed from the polyimide varnish can simultaneously exhibit excellent transparency and low wavelength dispersion characteristics of retardation (birefringence).

  Here, in formula (1), each substituent Pn is independently a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a linear chain having 1 to 6 carbon atoms. Alternatively, it represents a branched alkoxy group, and n is an integer of 0 to 4 representing the number of substituents. Examples of the linear or branched alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, and a propyl group. Examples of the linear or branched alkoxy group having 1 to 6 carbon atoms include a methoxy group, Examples thereof include an ethoxy group and a propoxy group. Two or more different types of Pn may be used.

  In addition to the low wavelength dispersion characteristic of retardation (birefringence) as described above, the magnitude of birefringence is also important. It is more preferable that the birefringence takes a positive value and the absolute value thereof is larger, so that the optical compensation film used for obtaining a certain optical compensation function can be set thinner.

The birefringence of the optical compensation film according to the present invention will be described below. Film surface direction X and Y-axis, if put the film thickness direction and Z-axis, equal X and Y directions of the refractive index _{(n x = n y = n} in) and the refractive index of the Z-direction (n _z ) In order to produce a higher negative C plate retardation film, a polymer film is usually biaxially stretched at a high magnification and orthogonally and the polymer chains are oriented as parallel as possible to the film surface (hereinafter referred to as surface). (Referred to as inner orientation).
Without any mechanical stretching operation as described above, a relatively large birefringence only solution cast film process the varnish is _{(△ n = n in -n z} ) usually not easy to express the formula ( In addition to the fluorenyl group-containing diamine of the present invention represented by 1), the following formulas (11) to (14):

で表される剛直な構造のモノマーを共重合成分として併用することで、キャスト製膜工程でポリイミド鎖の面内配向（フィルム面に対して平行な方向への配向）を誘起して高い複屈折を発現させることが可能となる。

High birefringence by inducing in-plane orientation of the polyimide chain (orientation in the direction parallel to the film surface) in the cast film forming process by using a monomer having a rigid structure represented by Can be expressed.

  In addition to the above, the toughness of the polyimide film can be further improved by using a diamine monomer such as 4,4'-oxydianiline having a bending bond as the diamine component to be copolymerized.

<Method for producing fluorenyl group-containing diamine>
The manufacturing method of diamine represented by Formula (1) of this invention is not specifically limited, A well-known method is applicable. Specifically, the following formula (15):

（式（１５）中、Ｒは水素原子またはアセトキシを表し、Ｐ_nは各々独立に、フッ素原子、塩素原子、臭素原子、炭素数１〜６の直鎖状もしくは分岐状アルキル基、炭素数１〜６の直鎖状もしくは分岐状アルコキシ基を表し、ｎは置換基の数を表す０から４の整数である。）
で表されるフルオレニル基含有ジオールまたはその誘導体と下記式（１６）：

(In formula (15), R represents a hydrogen atom or acetoxy, and P _n each independently represents a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or 1 carbon atom. Represents a linear or branched alkoxy group of ˜6, and n is an integer of 0 to 4 representing the number of substituents.)
And a fluorenyl group-containing diol represented by the following formula (16):

（式（１６）中、Ｘはヒドロキシ基、塩素原子、または臭素原子を表す。）
で表されるニトロ安息香酸またはその誘導体を反応させて下記式（１７）：

(In formula (16), X represents a hydroxy group, a chlorine atom, or a bromine atom.)
Is reacted with a nitrobenzoic acid represented by the following formula (17):

で表されるジニトロ体とし、次いでニトロ基を還元することで、本発明の下記式（１）：

And then reducing the nitro group, the following formula (1) of the present invention:

で表されるジアミンを製造することができる。

The diamine represented by these can be manufactured.

  Among diamines represented by the general formula (1), as an example, 9,9-bis (4-hydroxyphenyl) fluorene (hereinafter referred to as BPFL) or a derivative thereof and 2 equivalents of 4-nitrobenzoic acid (hereinafter referred to as 4) -NBA) or a derivative thereof is used as a starting material to carry out an esterification reaction to obtain the following formula (18):

で表されるジニトロ体（以下ＮＢＢＰＦＬと称する）を合成し、ついで得られたジニトロ体のニトロ基を還元することで下記式（１９）：

Is synthesized (hereinafter referred to as NBBPFL), and then the nitro group of the obtained dinitro compound is reduced to obtain the following formula (19):

で表されるジアミン（以下ＡＢＢＰＦＬと称する）を製造する方法について以下に説明する。

A method for producing a diamine represented by the following (hereinafter referred to as ABBPFL) will be described below.

  As a method applicable in the esterification reaction, for example, the hydroxyl group of BPFL and the carboxyl group of 4-NBA are directly dehydrated at a high temperature, or dehydrated and condensed using a dehydrating reagent such as N, N′-dicyclohexylcarbodiimide. Or BPFL diacetate and 4-NBA are reacted at high temperature and deacetated to esterify (transesterification method), the carboxyl group of 4-NBA is converted to an acid halide, and BPFL In the presence of a deoxidizing agent (base) (acid halide method), a method in which a carboxyl group in 4-NBA is activated and esterified using a tosyl chloride / N, N-dimethylformamide / pyridine mixture Etc. Among the above-mentioned methods, the transesterification method and the acid halide method, particularly the acid halide method, can be preferably applied in terms of economy and reactivity.

As an example, an acid halide method, that is, a method of synthesizing a dinitro compound represented by the formula (13) by esterifying 4-nitrobenzoic acid chloride (hereinafter referred to as 4-NBC) and BPFL will be specifically described.
4-Nitrobenzoic acid chloride (hereinafter referred to as 4-NBC) (A mol) is dissolved in a well-dehydrated solvent and sealed with a septum cap or the like. To this solution, BPFL (0.5 × A mol) and an appropriate amount of a deoxidizing agent dissolved in the same solvent are slowly dropped with a syringe or a dropping funnel. After completion of the dropwise addition, the reaction mixture is stirred for 1 to 24 hours. When the solubility of the target compound in the solvent used in the synthesis is high, first, the base hydrochloride as a by-product is filtered off from the reaction mixture, and the filtrate is evaporated using an evaporator, and 1-24 at 50 to 150 ° C. Vacuum dry for a time to obtain a powdery crude product. If the target product has low solubility or extremely high solute concentration, the target product precipitates with the base hydrochloride salt as a by-product, so the mixture is filtered and washed with a large amount of water. Only the hydrochloride is dissolved and removed. The product thus obtained may be used as it is in the subsequent reduction step, but may be purified in advance by recrystallization from an appropriate solvent.

  In the esterification reaction, the amount of 4-NBC added is preferably a 2-fold molar amount with respect to BPFL. However, in view of ease of separation of 4-NBC, an excess amount of 4-NBC is added and reacted. There is no problem.

  In the esterification reaction, usable solvents are not particularly limited as long as they do not react with the raw materials, 4-NBC and BPFL, and dissolve them well. Tetrahydrofuran, 1,4-dioxane, Ethyl acetate, methyl acetate, γ-butyrolactone, dimethyl sulfoxide, acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, diglyme, triglyme, picoline, pyridine, chloroform, dichloromethane, 1,2-dichloroethane, toluene, xylene, N-methyl-2 -Aprotic solvents such as pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone, etc. It is done. These solvents may be used alone or in combination of two or more. Tetrahydrofuran is preferably used from the viewpoints of solubility of the reaction reagent, solvent distillation after the reaction, and ease of drying and removal.

  The esterification reaction is performed at −10 to 50 ° C., but is preferably performed at 0 to 30 ° C. from the viewpoint of productivity and manufacturing cost. If the reaction temperature is higher than 50 ° C., some side reactions occur, which may reduce the yield, which is not preferable.

  Although it does not specifically limit as a deoxidizer which can be used for the said esterification reaction, Organic tertiary amines, such as a pyridine, a triethylamine, N, N- dimethylaniline, Epoxys, such as a propylene oxide, Potassium carbonate, Sodium hydroxide, etc. An inorganic base is mentioned. From the viewpoint of production cost and ease of separation, pyridine is preferably used.

  The esterification reaction can be performed in a solute concentration range of 5 to 50% by weight. The reaction is carried out in the range of 10 to 40% by weight in consideration of control of side reaction, improvement of yield, filtration step of precipitate and separation / removal step of excess deoxidizer and hydrochloride as a by-product. It is preferable to carry out in the range of 20 to 40% by weight. By carrying out the reaction at such a high concentration, the target product can be precipitated from the reaction solution with a higher yield.

  When pyridine is used as a deoxidizer, pyridine hydrochloride is formed as a by-product, which precipitates together with the target product because of its low solubility in a solvent such as tetrahydrofuran. Since the target product is insoluble in water, but pyridine hydrochloride is readily soluble in water, only the pyridine hydrochloride can be dissolved and removed by washing the precipitate sufficiently with water. At that time, it is possible to easily determine whether or not the pyridine hydrochloride has been completely removed by collecting the washing solution as needed and visually checking whether or not a white precipitate of silver chloride is formed by dropping a 1% silver nitrate aqueous solution. .

  Next, two nitro groups at the terminals of the obtained dinitro compound (NBBPFL) are reduced to obtain a diamine (ABBPFL) represented by the formula (19). At this time, the method of the reduction reaction is not particularly limited, and a known method can be applied. For example, when the dinitro compound is soluble in a hydrogen donating solvent such as ethanol, it can be easily reduced by using tin chloride as a catalyst. Further, a method in which a dinitro compound is dissolved in a solvent and stirred in a hydrogen atmosphere using palladium / carbon as a catalyst can also be applied. The solvent that can be used at this time is not particularly limited as long as it dissolves the dinitro compound. At that time, if the solubility of the dinitro compound in the solvent used is low, the reaction solution may be heated to 30 to 200 ° C. In addition, a method using hydrous hydrazine instead of hydrogen in the presence of ethanol is also applicable. From the viewpoint of wide range of application range of solvent and reaction temperature for dissolving the dinitro compound and ease of post-treatment, a method of reducing palladium / carbon as a catalyst in a hydrogen atmosphere is preferably used.

  For example, when NBBPFL is reduced using palladium / carbon, it is performed as follows. First, NBBPFL is dissolved in a solvent in a three-necked flask, and a catalytic amount of palladium / carbon powder is added thereto. Next, the reaction solution is bubbled by blowing hydrogen or brought into a hydrogen atmosphere and reacted for 1 to 24 hours. After completion of the reaction, palladium / carbon is removed by filtration, and the solvent of the filtrate is distilled off with an evaporator. The obtained precipitate is vacuum-dried at 50 to 180 ° C. for 1 to 24 hours to obtain a crude product. This is recrystallized from an appropriate solvent and purified, and finally dried in a vacuum at 50 to 180 ° C. for 1 to 24 hours to obtain a highly pure fluorenyl group-containing diamine that can be subjected to a polymerization reaction.

  The solvent that can be used in the reduction reaction is not particularly limited. For example, tetrahydrofuran, ethyl acetate, ethanol, 1,4-dioxane, picoline, pyridine, acetone, chloroform, toluene, xylene, dichloromethane, chloroform, 1, 2-dichloroethane, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, hexamethylphosphoramide, dimethyl sulfoxide, γ-butyrolactone, 1,3- Examples include dimethyl-2-imidazolidinone, diglyme, and triglyme. These solvents may be used alone or in combination of two or more. N, N-dimethylformamide is preferably used from the viewpoint of solubility of the reaction reagent, easiness of evaporation of the solvent after the reaction and easiness of drying and removal.

<Method for producing polyimide precursor>
The polyimide precursor constituting the optical compensation film according to the present invention is represented by the following general formula (2):

（式（２）中、Ａは４価の脂肪族基を表し、Ｐ_nは各々独立に、フッ素原子、塩素原子、臭素原子、炭素数１〜６の直鎖状もしくは分岐状アルキル基、炭素数１〜６の直鎖状もしくは分岐状アルコキシ基を表し、ｎは置換基の数を表す０から４の整数である。）
で表すイミド前駆体単位を含有する。
また、本発明に係るポリイミドの前駆体は下記一般式（３）：

(In the formula (2), A represents a tetravalent aliphatic group, and P _n each independently represents a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, carbon A linear or branched alkoxy group having 1 to 6 is represented, and n is an integer of 0 to 4 representing the number of substituents.
The imide precursor unit represented by is contained.
The polyimide precursor according to the present invention is represented by the following general formula (3):

（式（３）中、Ａは前述の通りである。Ｂは下記式（４）〜（７）からなる群より選ばれる少なくとも１つである）で表される少なくとも１種のイミド前駆体単位をさらに含有していてもよい。
一般式（４）；

(In the formula (3), A is as described above. B is at least one selected from the group consisting of the following formulas (4) to (7)). May further be contained.
General formula (4);

一般式（５）；

General formula (5);

一般式（６）；

General formula (6);

一般式（７）；

General formula (7);

ポリイミド前駆体を構成する前記一般式（２）で表される単位と前記一般式（３）で表される単位のモル比、一般式（２）／一般式（３）＝１／９９〜９９／１である。特に好ましくは５／９５〜８０／２０である。

The molar ratio of the unit represented by the general formula (2) and the unit represented by the general formula (3) constituting the polyimide precursor, general formula (2) / general formula (3) = 1/99 to 99 / 1. Particularly preferred is 5/95 to 80/20.

  The method for producing the polyimide precursor constituting the optical compensation film according to the present invention is not particularly limited, and a known method can be applied. More specifically, it is obtained by the following method. First, diamine is dissolved in a polymerization solvent, and substantially equimolar amount of the alicyclic tetracarboxylic dianhydride powder is gradually added to the solution, and 0 to 100 ° C., preferably 20 using a mechanical stirrer. Stir at -60 ° C for 0.5-150 hours, preferably 1-48 hours. In this case, the monomer concentration is 5 to 50% by weight, preferably 10 to 40% by weight. By carrying out polymerization in this monomer concentration range, a polyimide precursor solution having a uniform and high degree of polymerization can be obtained. When the polymerization degree of the polyimide precursor increases too much and the polymerization solution becomes difficult to stir, it can be appropriately diluted with the same solvent.

  From the viewpoint of the toughness of the polyimide film, it is desirable that the degree of polymerization of the polyimide precursor is as high as possible. By performing the polymerization in the above monomer concentration range, the degree of polymerization of the polymer is sufficiently high, and the solubility of the monomer and the polymer can be sufficiently ensured. When polymerization is performed at a concentration lower than the above range, the degree of polymerization of the polyimide precursor may not be sufficiently high, and when polymerization is performed at a concentration higher than the above monomer concentration range, the monomer and the polymer to be generated are not sufficiently dissolved. It may become. In addition, when an aliphatic diamine is used, salt formation often occurs at the initial stage of polymerization and the polymerization is hindered. However, in order to increase the severity as much as possible while suppressing the salt formation, attention should be paid to the monomer concentration at the time of polymerization. It is.

  Further, from the viewpoint of polyimide film toughness and varnish handling, the intrinsic viscosity of the polyimide precursor is preferably in the range of 0.1 to 5.0 dL / g, and in the range of 0.3 to 3.0 dL / g. It is more preferable.

The aliphatic tetracarboxylic dianhydride that can be used in the polymerization is not particularly limited as long as the required characteristics of the polyimide constituting the optical compensation film according to the present invention and the polymerization reactivity of the polyimide precursor are not impaired. , (1S, 2R, 4S, 5R) -cyclohexanetetracarboxylic dianhydride (cis, cis, cis-1,2,4,5-cyclohexanetetracarboxylic dianhydride), (1S, 2S, 4R, 5R) ) -Cyclohexanetetracarboxylic dianhydride, (1R, 2S, 4S, 5R) -cyclohexanetetracarboxylic dianhydride, bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic acid Anhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5- (dioxotetrahydrofuryl-3-methyl) -3-Cyclohexene-1,2-dicarboxylic acid anhydride, 4- (2,5-dioxotetrahydrofuran-3-yl) -tetralin-1,2-dicarboxylic acid anhydride, tetrahydrofuran-2,3,4,5 -Tetracarboxylic dianhydride, bicyclo-3,3 ', 4,4'-tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3 4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,4-dimethyl-1,2,3,4-cyclobutanetetracarboxylic acid And dianhydrides, 1,2,3,4-n-butanetetracarboxylic dianhydrides, etc. Two or more of these may be used in combination, among the above aliphatic tetracarboxylic dianhydrides. , 1S, 2S, 4R, 5R) -cyclohexanetetracarboxylic dianhydride, (1R, 2S, 4S, 5R) -cyclohexanetetracarboxylic from the viewpoint of total reactivity, polyimide solubility and in-plane orientation in the film forming process Acid dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,4-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride are preferred The above aliphatic tetracarboxylic dianhydride should be used as the tetracarboxylic dianhydride component from the viewpoint of suppressing the coloration of the polyimide used in the fragrance, but it does not significantly impair the required characteristics such as transparency. A group tetracarboxylic dianhydride can also be partially used as a copolymerization component. Although not particularly limited, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, 3 , 3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, hydroquinone-bis (trimellitate anhydride), pyromellitic acid Examples include dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenylsulfone tetracarboxylic dianhydride, and the like. Two or more of these may be used. When copolymerizing, the usage-amount (content rate) of these aromatic tetracarboxylic dianhydrides is 0-30 mol% with respect to the total tetracarboxylic dianhydride usage-amount.

  It can be used as a copolymer component of the fluorenyl group-containing diamine represented by the formula (1) of the present invention as long as the required characteristics of the polyimide constituting the optical compensation film according to the present invention and the polymerization reactivity of the polyimide precursor are not impaired. Examples of the aliphatic diamine include, but are not limited to, for example, 4,4′-methylenebis (cyclohexylamine), 4,4′-methylenebis (2-methylcyclohexylamine), isophoronediamine, trans-1,4-diaminocyclohexane. Cis-1,4-diaminocyclohexane, 1,4-cyclohexanebis (methylamine), 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,6-bis (aminomethyl) bicyclo [2.2.1] Heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] de 1,3-diaminoadamantane, 2,2-bis (4-aminocyclohexyl) propane, 2,2-bis (4-aminocyclohexyl) hexafluoropropane, 1,3-propanediamine, 1,4-tetramethylene Examples include diamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, and the like. Two or more of these may be used in combination.

  It can be used as a copolymer component of the fluorenyl group-containing diamine represented by the formula (1) of the present invention as long as the required characteristics of the polyimide constituting the optical compensation film according to the present invention and the polymerization reactivity of the polyimide precursor are not impaired. Examples of the aromatic diamine include, but are not limited to, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodurene, 4,4′-diaminodiphenylmethane, 4,4′-methylenebis (2-methylaniline), 4,4′-methylenebis (2-ethylaniline), 4,4′-methylenebis (2,6-dimethylaniline), 4 , 4′-methylenebis (2,6-diethylaniline), 4,4′-diaminodiphenyl ether, 3,4 ′ Diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 2,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 4,4′-diaminobenzophenone, 3,3′- Diaminobenzophenone, 4,4′-diaminobenzanilide, 4-aminophenyl-4′-aminobenzoate, benzidine, 3,3′-dihydroxybenzidine, 3,3′-dimethoxybenzidine, o-tolidine, m-tolidine, 2 , 2′-bis (trifluoromethyl) benzidine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene 4,4'-bis (4-aminophenoxy) biphenyl Bis (4- (3-aminophenoxy) phenyl) sulfone, bis (4- (4-aminophenoxy) phenyl) sulfone, 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 2,2- Bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, p-terphenylenediamine, 9,9-bis (4-aminophenyl) fluorene, 2,7-diaminofluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9,9-bis (4-amino-3-fluorophenyl) fluorene, 9,9-bis (4-amino- 3-methylphenyl) fluorene and the like. Two or more of these may be used in combination.

From the viewpoint of the development of birefringence in a polyimide film, a diamine having a rigid and highly linear structure effective for inducing in-plane orientation of polyimide chains in the cast film forming process, that is, p-phenylenediamine, 2-trifluoromethyl -1,4-phenylenediamine, 2,5-diaminotoluene, 3,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, 4-aminophenyl-4'-aminobenzoate, benzidine, 3,3'- Dihydroxybenzidine, 3,3′-dimethoxybenzidine, o-tolidine, m-tolidine, 2,2′-bis (trifluoromethyl) benzidine, p-terphenylenediamine, trans-1,4-diaminocyclohexane and the like as diamine components Can be used as a polyimide film retardation (Birefringence), 2,2′-bis (trifluoromethyl) benzidine, 3,3′-bis (trifluoromethyl) benzidine, 2-trifluoromethyl-1 from the viewpoint of low wavelength dispersibility and solvent solubility , 4-phenylenediamine and the like are particularly preferably used. Further, the content of the rigid structure diamine is in the range of 10 to 99 mol%, preferably 30 to 99 mol% of the total amount of diamine used.
The polymerization solvent that can be used when polymerizing the polyimide precursor is not particularly limited as long as it sufficiently dissolves the monomer and the polymer during the polymerization reaction. For example, N, N-dimethylformamide, N, N-dimethylacetamide Amide solvents such as N-methylpyrrolidone and hexamethylphosphoramide, cyclic ester solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone and α-methyl-γ-butyrolactone Are preferably used. In addition to the above, cyclic ketone solvents such as cyclopentanone and cyclohexanone, carbonate solvents such as ethylene carbonate and propylene carbonate, ether solvents such as diglyme, triglyme, tetrahydrofuran and 1,4-dioxane, m-cresol, Phenol solvents such as P-cresol, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide and the like can also be used.

The polyimide precursor obtained as described above can be isolated as a powder by dropping, filtering and drying the polymerization solution into a large amount of poor solvent such as water or methanol.
<Production method of polyimide>
The polyimide constituting the optical compensation film according to the present invention is represented by the following general formula (8):

（式中、Ａ及びＰ_nは前記の通り）で表すイミド単位を含有する。

(Wherein A and P _n are as described above).

  Further, the polyimide according to the present invention has the following general formula (9):

（式中、Ａ及びＢは前記の通り）で表される少なくとも１種のイミド単位をさらに含有していてもよい。

(Wherein A and B are as described above) may further contain at least one imide unit.

  The molar ratio of the unit represented by the general formula (2) and the unit represented by the general formula (3) constituting the polyimide of the present invention, the general formula (2) / general formula (3) is 1/99 to 99/1. Particularly preferred is 5/95 to 80/20.

  The imide unit represented by the general formulas (8) and (9) may contain two or more kinds.

  The polyimide constituting the optical compensation material of the present invention can be produced by subjecting the polyimide precursor obtained by the above method to a dehydration ring-closing reaction (imidation reaction). The imidization method is not particularly limited, and a known method can be applied.

  First, a method for producing a polyimide film will be described. When the substrate to be used is extremely high in heat resistance such as glass, quartz, copper, aluminum, stainless steel, silicon, etc., a process of thermal imidization can be applied after forming the polyimide precursor film. In this case, first, a polyimide precursor polymerization solution (varnish) is cast on these substrates and dried in an oven at 40 to 180 ° C., preferably 50 to 150 ° C. Next, a polyimide film is produced by heating the obtained polyimide precursor film on a substrate in a vacuum, in an inert gas such as nitrogen, or in air at 200 to 400 ° C., more preferably 250 to 350 ° C. Can do. The heating temperature is preferably 200 ° C. or higher from the viewpoint of sufficiently carrying out the imidization ring-closing reaction, and 400 ° C. or lower from the viewpoint of the thermal stability of the produced polyimide film. Moreover, it is desirable to perform imidization in a vacuum or in an inert gas, but if the imidization temperature is not too high, imidation may be performed in air.

  Also, in the imidation reaction, instead of the heat treatment as described above, the polyimide precursor film formed on the substrate is converted into a solution containing a dehydration cyclization reagent such as acetic anhydride in the presence of a tertiary amine such as pyridine or triethylamine. It is also possible to carry out by dipping. In addition, a polyimide precursor film partially or almost completely imidized is prepared by previously charging and stirring these dehydrating cyclization reagents in a polyimide precursor varnish, and applying and drying it onto the substrate. This can be further heat-treated as described above to obtain a polyimide film.

  The dehydration cyclization reagent can be charged into the polyimide precursor varnish and stirred at −20 to 150 ° C., preferably 20 to 80 ° C. for 0.5 to 48 hours to complete the chemical imidization. When the polyimide is soluble in the reaction solution, the reaction solution can be dropped and filtered into a large amount of poor solvent such as water or methanol to isolate the polyimide as a powder. Moreover, a polyimide powder can be redissolved in the said polymerization solvent to make a polyimide varnish.

  When the polyimide precursor polymerization solution is diluted as it is or with the same solvent, the polyimide varnish of the present invention is used when the solution is heated to 150 to 250 ° C. and dissolved in the solvent used by the polyimide itself. It can be manufactured easily. When insoluble in the solvent, the polyimide powder can be obtained as a precipitate. At this time, toluene, xylene or the like may be added in order to azeotropically distill off water or the like which is a by-product of imidization. Further, a base such as γ-picoline can be added as a catalyst. The obtained varnish can be dropped, filtered and dried in a large amount of poor solvent such as water or methanol to isolate the polyimide as a powder.

  From the viewpoint of suppressing the molecular weight reduction of the polyimide as much as possible, it is preferable to imidize the varnish without heating by adding and stirring a chemical imidizing reagent, rather than heating and imidizing the polyimide precursor varnish.

  Although it does not specifically limit as a solvent which can be used when melt | dissolving a polyimide powder in a solvent again to make a varnish, The said polymerization solvent can be used. Moreover, when apply | coating and drying a polyimide varnish on a polarizer protective film and forming a polyimide film, the solvent which does not erode a polarizer protective film is used suitably. For example, when a typical TAC film is used as a polarizer protective film, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, α-methyl-γ-butyrolactone, butyl acetate, acetic acid Ester solvents such as ethyl and isobutyl acetate, ketone solvents such as methyl isobutyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl ethyl ketone and acetone, and aromatic solvents such as toluene and xylene are preferably used. In particular, methyl isobutyl ketone and toluene are preferably used from the viewpoints of availability, film forming property (degree of TAC erosion, ensuring window width of film forming conditions) and productivity.

  In addition, the polyimide can be polymerized in one step without forming a polyimide precursor by reacting tetracarboxylic dianhydride and diamine in a solvent at a high temperature. At this time, the reaction solution may be maintained in a temperature range of 130 to 250 ° C., preferably 150 to 200 ° C. from the viewpoint of promoting the reaction. When the polyimide is insoluble in the solvent used, the polyimide is obtained as a precipitate, and when soluble, it is obtained as a polyimide varnish. The polymerization solvent is not particularly limited, and examples of usable solvents include aprotic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide. However, a phenol solvent such as m-cresol or an amide solvent such as NMP is more preferably used. In order to azeotropically distill off water, which is a by-product of the imidization reaction, to these solvents, toluene, xylene, or the like can be added. A base such as γ-picoline can be added as an imidization catalyst. The resulting varnish can be dropped, filtered and dried in a large amount of poor solvent such as water or methanol to isolate the polyimide as a powder. When the polyimide is soluble in a solvent, the powder can be redissolved in the above solvent to obtain a polyimide varnish.

  A polyimide film can also be formed by applying the polyimide varnish on a substrate and drying at 40 to 400 ° C., preferably 100 to 350 ° C. In particular, when the polarizer protective film is a TAC film, when the polyimide film is formed on the TAC film, drying is performed at 40 to 150 ° C., preferably 50 to 140 ° C. from the viewpoint of heat resistance of the TAC film.

  By adding and stirring a dehydrating reagent such as N, N′-dicyclohexylcarbodiimide or trifluoroacetic anhydride into the polyimide precursor solution and reacting at 0 to 150 ° C., preferably 20 to 100 ° C., the polyimide isomer is obtained. A certain polyisoimide is formed. The isoimidization reaction can also be performed by immersing the polyimide precursor film in a solution containing the dehydrating reagent. After polyisoimide varnish is formed in the same procedure as described above, it can be easily converted to polyimide by heat treatment at 250 to 400 ° C., preferably 270 to 350 ° C.

Additives such as oxidation stabilizers, fillers, adhesion promoters, silane coupling agents, photosensitizers, photopolymerization initiators, sensitizers, end-capping agents, crosslinking agents, etc., as necessary, in the polyimide and its precursors <Required characteristics of polyimide>
In order to form the polyimide film of the present invention on a substrate by a solution casting method, the solubility of the polyimide used in an organic solvent is required. When the substrate is a polarizer protective film such as a TAC film, it is necessary to use a ketone solvent, an ester solvent and an aromatic solvent that do not corrode the TAC film as a solvent for the polyimide varnish. That is, the polyimide to be used is required to have high solubility in these solvents.

  Moreover, it is desirable that the cast film forming (drying) temperature is as low as possible from the viewpoint of suppressing the heat resistance of the polarizer protective film and the relaxation of the orientation of the polyimide chain during the cast film forming process. For this reason, it is desirable that the boiling point of the solvent used for solution casting is lower. For example, when the polarizer protective film is a TAC film, the drying temperature is limited to 150 ° C. or lower in order to prevent thermal deformation. From this point of view, the boiling point of the solvent for the polyimide varnish is 180 ° C. or lower, which does not hinder the coating drying process, but is preferably 150 ° C. or lower. In consideration of productivity, it is more preferably 130 ° C. or lower.

  Although the polyimide film of the present invention is completely uncolored visually, if the transparency is expressed more quantitatively, the light transmittance at a wavelength of 400 nm of a film having a thickness of 20 μm is 80% as an index of transparency. If it is the above, there is no practical problem, but 85% or more is more preferable.

  The polyimide film desirably exhibits sufficient film toughness. As an index, it is necessary that the film does not break by a 180 ° bending test. If expressed more quantitatively, there is no practical problem if the elongation at break of the test piece is 5% or more in the tensile test, but 10% or more is more preferable.

The polyimide film desirably has a lower retardation (birefringence) wavelength dispersion characteristic. As an index, if the ratio of retardation (Re) or birefringence (Δn) at 450 nm and 550 nm (Re ₄₅₀ / Re ₅₅₀ = Δn ₄₅₀ / Δn ₅₅₀ ) is in the range of 1.00 to 1.04, it is practical. There is no hindrance, but a range of 1.00 to 1.03 is more preferable.

The polyimide film of the present invention desirably has a higher retardation (birefringence) value. Although retardation birefringence value at a wavelength of 589nm sodium lamp as an indicator of _{(birefringence) △ n (n in -n z} ) is not practical problem as long as 0.01 or more, preferably more if 0.02 or more . From the relationship of retardation Re = Δn × d (d is film thickness), the higher the birefringence value of the polyimide film, the more advantageous is that the optical compensation film can be set thinner.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, it is not limited to these Examples. The physical property values in the following examples were measured by the following methods.

<Infrared absorption spectrum>
The infrared absorption spectrum of the fluorenyl group-containing diamine was measured by the KBr method using a Fourier transform infrared spectrophotometer (FT-IR5300 manufactured by JASCO Corporation). Moreover, the infrared absorption spectrum of the polyimide thin film (about 5 micrometers thickness) was measured with the transmission method.

^<1 H-NMR spectrum>
A ¹ H-NMR spectrum of a fluorenyl group-containing diamine was measured in deuterated dimethyl sulfoxide (DMSO-d ₆ ) using a JEOL NMR spectrophotometer (ECP400).

<Differential scanning calorimetry (melting point and melting curve)>
The melting point and melting curve of the fluorenyl group-containing diamine were measured using a differential scanning calorimeter (DSC3100) manufactured by Bruker AXS in a nitrogen atmosphere at a heating rate of 5 ° C./min.

<Intrinsic viscosity>
The reduced viscosity obtained by measuring a 0.5 wt% polyimide precursor or polyimide solution at 30 ° C. using an Ostwald viscometer was regarded as the intrinsic viscosity.

<Cutoff wavelength (transparency)>
Using a UV-visible spectrophotometer (V-530) manufactured by JASCO Corporation, the visible / ultraviolet transmittance from 200 nm to 900 nm was measured. The wavelength (cutoff wavelength) at which the transmittance was 0.5% or less was used as an index of transparency. The shorter the cutoff wavelength, the better the transparency of the polyimide film.

<Light transmittance (transparency)>
The light transmittance at a wavelength of 400 nm of a polyimide film (film thickness: about 20 μm) was measured using an ultraviolet-visible spectrophotometer (V-530) manufactured by JASCO Corporation. The higher the transmittance, the better the transparency of the polyimide film.

<Birefringence: Δn and its wavelength dispersion>
Using an Abbe refractometer with a polarizer (NAR-1T SOLID) manufactured by Atago Co., Ltd., at a constant wavelength in a direction (n _in ) and a direction (n _out ) parallel to the film surface of the polyimide film (film thickness: about 20 μm) The refractive index (sodium lamp wavelength 589 nm) was measured, and the birefringence (Δn = n _in −n _out ) was determined from the difference between these refractive indexes. In addition, when obtaining the birefringence wavelength dispersion, a monochromatic light obtained by dispersing light from a xenon lamp light source with a diffraction grating (bandpass 10 nm) instead of a sodium lamp as a light source is introduced into the refractometer through an optical fiber cable. The birefringence at each wavelength (450, 486, 546, 550, 587, 656 nm) was measured.

[Example 1]
<Synthesis of fluorenyl group-containing diamine (ABBPFL)>
The fluorenyl group-containing diamine (ABBPFL) of the present invention was synthesized as follows. First, 11.13 g (60 mol) of 4-NBC was dissolved in 38 mL of tetrahydrofuran (THF) sufficiently dehydrated with Molecular Sieves 4A, and sealed with a septum cap to obtain A solution. Next, 10.51 g (30 mol) of BPFL was dissolved in 28 mL of THF, and 7.3 mL (90 mmol) of pyridine was added thereto, which was sealed with a septum cap to obtain a solution B. While liquid A was cooled in an ice bath, liquid B was dropped into liquid A using a syringe and stirred for 3 hours. Thereafter, 15 mL of THF was further added, followed by stirring at room temperature for 12 hours. The deposited precipitate was separated by filtration and washed with THF and water. Washing with water was repeated and washed with water until chloride ions were not confirmed as silver chloride white precipitate during washing, so that pyridine hydrochloride was dissolved and removed. This was vacuum-dried at 100 ° C. for 12 hours to obtain a light yellow powdery product (yield: 55%). From the FT-IR spectrum and ¹ H-NMR spectrum, it was confirmed that the obtained product was the target dinitro compound (NBBPFL) represented by the following formula (18). Since a sharp melting peak was observed by DSC measurement, the product was highly pure and used as it was in the next reduction step.

ＦＴ−ＩＲ（ＫＢｒ）： １７４０ｃｍ^-1（エステルＣ＝Ｏ伸縮振動吸収帯）、１５２８ｃｍ^-1（ニトロ基非対称伸縮振動吸収帯）、１３４６ｃｍ^-1（ニトロ基対称伸縮振動吸収帯）、１２６５ｃｍ^-1（Ｃ−Ｏ−Ｐｈ伸縮振動）
¹Ｈ−ＮＭＲ（ＤＭＳＯ−ｄ₆）： δ８．４２ｐｐｍ（末端ベンゼン環上のプロトン、ｄ、４Ｈ、相対積分強度４．０６）、δ８．３４ｐｐｍ（末端ベンゼン環上のプロトン、ｄ、４Ｈ、相対積分強度４．０６），δ８．００ｐｐｍ（ｄ、２Ｈ、相対積分強度２．００）、δ７．５５ｐｐｍ（ｄ、２Ｈ、相対積分強度２．０２）、δ７．４５ｐｐｍ（ｔ、２Ｈ、相対積分強度２．０２）、δ７．３８ｐｐｍ（ｔ、２Ｈ、相対積分強度２．０２）、δ７．２〜７．３ｐｐｍ（ｍ、８Ｈ、相対積分強度８．０６）
ＤＳＣ： 融点２９０．４℃。

FT-IR (KBr): 1740 cm ⁻¹ (ester C═O stretching vibration absorption band), 1528 cm ⁻¹ (nitro group asymmetric stretching vibration absorption band), 1346 cm ⁻¹ (nitro group symmetric stretching vibration absorption band), 1265 cm ⁻¹ (C-O-Ph stretching vibration)
¹ H-NMR (DMSO-d ₆ ): δ 8.42 ppm (protons on the terminal benzene ring, d, 4H, relative integral intensity 4.06), δ 8.34 ppm (protons on the terminal benzene ring, d, 4H, relative Integral intensity 4.06), δ 8.00 ppm (d, 2H, relative integral intensity 2.00), δ 7.55 ppm (d, 2H, relative integral intensity 2.02), δ 7.45 ppm (t, 2H, relative integral intensity) 2.02), δ 7.38 ppm (t, 2H, relative integral intensity 2.02), δ 7.2-7.3 ppm (m, 8H, relative integral intensity 8.06)
DSC: mp 290.4 ° C.

  Next, the nitro group of NBBPFL was reduced. NBBPFL 5.00 g (7.71 mmol) and palladium / carbon powder 0.17 g were placed in a hydrogen inlet tube and a three-necked flask equipped with a condenser, and 15 mL of DMF was added and heated to 80 ° C. to dissolve NBBPFL. Next, hydrogen was introduced and stirred at 80 ° C. for 5 hours. After the reaction, palladium / carbon was filtered and removed, the solvent of the filtrate was distilled off with an evaporator, and the deposited precipitate was washed with water to obtain a gray crude product (yield 96%). The pale yellow crystals obtained by recrystallizing this twice from a 1,4-dioxane / toluene mixed solution (volume ratio: 1/6) were vacuum-dried at 130 ° C. for 12 hours to obtain a product. From the FT-IR spectrum and 1H-NMR spectrum, it was confirmed that the obtained product was the target fluorenyl group-containing diamine (ABBPFL) represented by the following formula (19). A sharp melting peak by DSC measurement was seen, indicating that the product was highly pure.

ＦＴ−ＩＲ（ＫＢｒ）： ３４８２、３３７４ｃｍ^-1（アミノ基Ｎ−Ｈ伸縮振動）、１７１１ｃｍ^-1（エステル基Ｃ＝Ｏ伸縮振動）、１２６９ｃｍ^-1（Ｃ−Ｏ−Ｐｈ伸縮振動）
¹Ｈ−ＮＭＲ（ＤＭＳＯ−ｄ₆）： δ６．３ｐｐｍ（アミンプロトン、ｓ、４Ｈ、相対積分強度４．００）、δ６．６２ｐｐｍ（アミノ基のオルト位の芳香族プロトン、ｄ、４Ｈ、相対積分強度４．００）、δ７．７５ｐｐｍ（カルボニル基のオルト位の芳香族プロトン、ｄ、４Ｈ、相対積分強度４．００）、δ７．９７ｐｐｍ（ｄ、２Ｈ、相対積分強度２．００）、δ７．３５〜７．５５ｐｐｍ（６Ｈ、相対積分強度６．００）、δ７．０５〜７．２０ｐｐｍ（８Ｈ、相対積分強度８．００）、
ＤＳＣ： 融点２８１．１℃。

FT-IR (KBr): 3482, 3374 cm ⁻¹ (amino group N—H stretching vibration), 1711 cm ⁻¹ (ester group C═O stretching vibration), 1269 cm ⁻¹ (C—O—Ph stretching vibration)
¹ H-NMR (DMSO-d ₆ ): δ 6.3 ppm (amine proton, s, 4 H, relative integral intensity 4.00), δ 6.62 ppm (aromatic proton in the ortho position of the amino group, d, 4 H, relative integral Intensity 4.00), δ 7.75 ppm (aromatic protons at the ortho position of the carbonyl group, d, 4H, relative integral intensity 4.00), δ 7.97 ppm (d, 2H, relative integral intensity 2.00), δ 7. 35 to 7.55 ppm (6H, relative integral intensity 6.00), δ 7.05 to 7.20 ppm (8H, relative integral intensity 8.00),
DSC: mp 281.1 ° C.

[Example 2]
<Polymerization of polyimide precursor, imidization and evaluation of polyimide film characteristics>
In a well-dried sealed reaction vessel with a stirrer, 3.5 mmol of 2,2′-bis (trifluoromethyl) benzidine (hereinafter referred to as TFMB) and a fluorenyl group-containing diamine (ABBPFL) represented by the formula (19) of the present invention ) 1.5 mmol was added and dissolved in N, N-dimethylacetamide (DMAc) sufficiently dehydrated with molecular sieves 4A, and then (1R, 2S, 4S, 5R) -cyclohexanetetracarboxylic dianhydride powder was added to this solution. 5 mmol (Iwatani Gas Co., Ltd., hereinafter referred to as PMDA-HS) was added at once. At this time, the total monomer concentration is 30% by weight. Since the viscosity of the solution increased and it became difficult to stir, DMAc was added as appropriate, and finally diluted to a total monomer concentration of 21% by weight. Finally, the mixture was stirred for 72 hours to obtain a transparent, uniform and viscous polyimide precursor solution. The intrinsic viscosity of this polyimide precursor measured in DMAc was 0.654 dL / g. To this polyimide precursor solution, an excessive amount of acetic anhydride / pyridine (volume ratio 7/3) was added dropwise with stirring, and the mixture was stirred at room temperature for 24 hours for chemical imidization. At this time, the reaction solution did not gel. After the chemical imidization was completed, the reaction solution was dropped into a large amount of methanol, and the polyimide was precipitated and filtered, sufficiently washed with methanol, and then vacuum dried at 100 ° C. to obtain a polyimide powder. The intrinsic viscosity of this polyimide measured in DMAc was 0.699 dL / g. In order to form a film, the polyimide powder was dissolved in cyclopentanone (10% by weight), applied to a glass substrate, dried at 60 ° C. for 1 hour, 100 ° C. for 10 minutes, and further at 150 ° C. for 15 minutes to obtain a film thickness of about A 10 μm transparent polyimide film was obtained. This polyimide film did not break even in the 180 ° bending test and showed sufficient flexibility. Similarly, when a thin film having a thickness of 5 μm was separately prepared and an infrared absorption spectrum was measured by a transmission method, it was confirmed that the chemical imidization was almost completed. The infrared absorption spectrum of the polyimide thin film is shown in FIG.

When the transparency of the polyimide film was evaluated, the light transmittance at 400 nm was 86.5%, and the cutoff wavelength was 313 nm, which showed extremely high transparency. The birefringence measured using a sodium lamp as the light source was 0.0203, indicating a relatively high birefringence value. In addition, Re ₄₅₀ / Re ₅₅₀ = 1.02, indicating very low wavelength dispersion. FIG. 2 shows a plot of birefringence (Δn) against a wide range of wavelengths.

[Example 3]
<Synthesis of fluorenyl group-containing diamine (ABBCFL)>
The fluorenyl group-containing diamine (ABBCFL) of the present invention was synthesized as follows. First, 18.56 g (100 mol) of 4-NBC was dissolved in 39 mL of tetrahydrofuran (THF) sufficiently dehydrated with Molecular Sieves 4A, and sealed with a septum cap to obtain A solution. Next, the following formula (20):

で表される９，９−ビス（４−ヒドロキシ−３−メチルフェニル)フルオレン（東京化成製、以下ＢＣＦＬと称する）１９．０２ｇ（５０ ｍｏｌ）をＴＨＦ３２ｍＬに溶解し、これにピリジン１１．９ｍＬ（１５０ｍｍｏｌ）を加えてセプタムキャップで密栓しＢ液とした。Ａ液を氷浴中で冷却しながら、Ａ液にＢ液をシリンジを用いて滴下し、３時間攪拌し更に室温で１２時間攪拌した。析出した沈殿を濾別してＴＨＦ次いで水で洗浄した。水洗は洗液中に塩素イオンが塩化銀白色沈殿として確認されなくなるまで、水で繰り返し洗浄してピリジン塩酸塩を溶解除去した。これを１００℃で１２時間真空乾燥して黄白色の粉末状生成物を得た（収率：７１％）。ＦＴ−ＩＲスペクトルおよび¹Ｈ−ＮＭＲスペクトルより、得られた生成物は目的とする下記式（２１）で表されるジニトロ体（ＮＢＢＣＦＬ）であることが確認された。これをそのまま次の還元工程に用いた。

19.9 g (50 mol) of 9,9-bis (4-hydroxy-3-methylphenyl) fluorene represented by the following formula (Tokyo Chemical Industry Co., Ltd., hereinafter referred to as BCFL) was dissolved in THF 32 mL, and pyridine 11.9 mL ( 150 mmol) was added, and the solution was sealed with a septum cap to give solution B. While liquid A was cooled in an ice bath, liquid B was dropped into liquid A using a syringe, stirred for 3 hours, and further stirred at room temperature for 12 hours. The deposited precipitate was separated by filtration and washed with THF and water. Washing with water was repeated and washed with water until chloride ions were not confirmed as a silver chloride white precipitate in the washing solution to dissolve and remove pyridine hydrochloride. This was vacuum-dried at 100 ° C. for 12 hours to obtain a yellowish white powdery product (yield: 71%). From the FT-IR spectrum and the ¹ H-NMR spectrum, it was confirmed that the obtained product was the target dinitro compound (NBBCFL) represented by the following formula (21). This was directly used in the next reduction step.

ＦＴ−ＩＲ（ＫＢｒ）： ３１１１ｃｍ^-1、３０５４ｃｍ^-1（芳香族Ｃ−Ｈ伸縮振動吸収帯）、２９５３ｃｍ^-1、２９２４ｃｍ^-1（脂肪族Ｃ−Ｈ伸縮振動吸収帯）、１７４２ｃｍ^-1（エステル基Ｃ＝Ｏ伸縮振動吸収帯）、１５３０ｃｍ^-1（ニトロ基非対称伸縮振動吸収帯）、１３４６ｃｍ^-1（ニトロ基対称伸縮振動吸収帯）、１２６７ｃｍ^-1（Ｃ−Ｏ−Ｐｈ伸縮振動）
¹Ｈ−ＮＭＲ（ＤＭＳＯ−ｄ₆）： δ８．３〜８．４５ｐｐｍ（末端ベンゼン環上ニトロ基のｏ−およびｍ−位のプロトン、８Ｈ、相対積分強度８．３４）、δ７．９７ｐｐｍ（フロオレン基上４および５位のプロトン、２Ｈ、相対積分強度２．０４）、δ７．５６ｐｐｍ（２Ｈ、相対積分強度２．００）、δ７．３５〜７．５ｐｐｍ（ｄ、４Ｈ、相対積分強度４．２８）、δ７．０５〜７．３５ｐｐｍ（ｔ、６Ｈ、相対積分強度６．１８）、δ２．１ｐｐｍ（メチル基プロトン、６Ｈ、相対積分強度６．０８）
ＤＳＣ： 融点３０２．８℃。

FT-IR (KBr): 3111 cm ⁻¹ , 3054 cm ⁻¹ (aromatic C—H stretching vibration absorption band), 2953 cm ⁻¹ , 2924 cm ⁻¹ (aliphatic C—H stretching vibration absorption band), 1742 cm ⁻¹ (ester) Group C = O stretching vibration absorption band), 1530 cm ⁻¹ (nitro group asymmetric stretching vibration absorption band), 1346 cm ⁻¹ (nitro group symmetry stretching vibration absorption band), 1267 cm ⁻¹ (C—O—Ph stretching vibration)
¹ H-NMR (DMSO-d ₆ ): δ 8.3 to 8.45 ppm (protons at the o- and m-positions of the nitro group on the terminal benzene ring, 8H, relative integral intensity 8.34), δ 7.97 ppm (fluorene) Protons at the 4th and 5th positions, 2H, relative integral intensity 2.04), δ 7.56 ppm (2H, relative integral intensity 2.00), δ 7.35 to 7.5 ppm (d, 4H, relative integral intensity 4. 28), δ 7.05 to 7.35 ppm (t, 6H, relative integral intensity 6.18), δ 2.1 ppm (methyl group proton, 6H, relative integral intensity 6.08)
DSC: mp 302.8 ° C.

Next, the nitro group of NBCPFL was reduced as follows. NBBPFL 6.83 g (10.1 mmol) and palladium / carbon powder 0.23 g were placed in a hydrogen inlet tube and a three-neck flask with a condenser, and 105 mL of DMF was added and heated to 80 ° C. to dissolve NBCBCFL. Next, hydrogen was introduced and stirred at 80 ° C. for 4 hours. After the reaction, palladium / carbon is filtered off and removed, the solvent of the filtrate is evaporated and concentrated with an evaporator, the reaction solution is dropped into a large amount of water, and the precipitated precipitate is washed well with water to give a gray crude product. Obtained (yield 95%). The white powder obtained by recrystallizing this from a 1,4-dioxane / toluene mixed solution (volume ratio: 2/5) was vacuum-dried at 80 ° C. for 12 hours to obtain a product. From the FT-IR spectrum and ¹ H-NMR spectrum, it was confirmed that the obtained product was a target fluorenyl group-containing diamine (ABCCFFL) represented by the following formula (22). A sharp melting peak by DSC measurement was seen, indicating that the product was highly pure.

ＦＴ−ＩＲ（ＫＢｒ）： ３４７４ｃｍ^-1、３３７２ｃｍ^-1および３２２１ｃｍ^-1（アミノ基Ｎ−Ｈ伸縮振動吸収帯）、３０６３ｃｍ^-1（芳香族Ｃ−Ｈ伸縮振動吸収帯）、２９６１ｃｍ^-1（脂肪族Ｃ−Ｈ伸縮振動吸収帯）、１７０１ｃｍ^-1（エステル基Ｃ＝Ｏ伸縮振動）、１２７５ｃｍ^-1（Ｃ−Ｏ−Ｐｈ伸縮振動）
¹Ｈ−ＮＭＲ（ＤＭＳＯ−ｄ₆）：δ２．１ｐｐｍ（メチル基プロトン、６Ｈ、相対積分強度５．９８） δ６．２ｐｐｍ（アミノ基プロトン、ｓ、４Ｈ、相対積分強度３．９６）、δ６．６３ｐｐｍ（アミノ基のオルト位の芳香族プロトン、ｄ、４Ｈ、相対積分強度３．９８）、δ６．９５〜７．１ｐｐｍ（芳香族プロトン、６Ｈ、相対積分強度６．００）、δ６．９５〜７．１ｐｐｍ（芳香族プロトン、６Ｈ、相対積分強度６．００）、δ７．３〜７．６ｐｐｍ（芳香族プロトン、６Ｈ、相対積分強度５．９８）、δ７．７７ｐｐｍ（カルボニル基のオルト位の芳香族プロトン、ｄ、４Ｈ、相対積分強度３．９８）、δ７．９６ｐｐｍ（フロオレン基上４および５位のプロトン、２Ｈ、相対積分強度２．００）
ＤＳＣ： 融点２８８．４℃。

FT-IR (KBr): 3474 cm ⁻¹ , 3372 cm ⁻¹ and 3221 cm ⁻¹ (amino group N—H stretching vibration absorption band), 3063 cm ⁻¹ (aromatic C—H stretching vibration absorption band), 2961 cm ⁻¹ (fat Group C—H stretching vibration absorption band), 1701 cm ⁻¹ (ester group C═O stretching vibration), 1275 cm ⁻¹ (C—O—Ph stretching vibration)
¹ H-NMR (DMSO-d ₆ ): δ 2.1 ppm (methyl group proton, 6H, relative integral intensity 5.98) δ 6.2 ppm (amino group proton, s, 4H, relative integral intensity 3.96), δ 6. 63 ppm (aromatic proton at the ortho position of amino group, d, 4H, relative integral intensity 3.98), δ 6.95 to 7.1 ppm (aromatic proton, 6H, relative integral intensity 6.00), δ 6.95 7.1 ppm (aromatic proton, 6H, relative integral intensity 6.00), δ 7.3-7.6 ppm (aromatic proton, 6H, relative integral intensity 5.98), δ 7.77 ppm (at the ortho position of the carbonyl group) Aromatic proton, d, 4H, relative integral intensity 3.98), δ 7.96 ppm (protons at positions 4 and 5 on the fluorene group, 2H, relative integral intensity 2.00)
DSC: mp 288.4 ° C.

[Example 4]
In a well-dried sealed reaction vessel equipped with a stirrer, 4 mmol) and 1 mmol of a fluorenyl group-containing diamine (ABCFL) represented by the formula (22) of the present invention were placed, and the N, N- After dissolving in dimethylacetamide (DMAc), PMDA-HS 5 mmol was added to this solution all at once. At this time, the total monomer concentration is 30% by weight. Since the viscosity of the solution increased and it became difficult to stir, DMAc was added as appropriate, and finally diluted to a total monomer concentration of 19% by weight. Finally, the mixture was stirred for 90 hours to obtain a transparent, uniform and viscous polyimide precursor solution. To this polyimide precursor solution, an excessive amount of acetic anhydride / pyridine (volume ratio 7/3) was added dropwise with stirring, and the mixture was stirred at room temperature for 24 hours for chemical imidization. At this time, the reaction solution did not gel. After the chemical imidization was completed, the reaction solution was dropped into a large amount of methanol, and the polyimide was precipitated and filtered, sufficiently washed with methanol, and then vacuum dried at 100 ° C. to obtain a polyimide powder. The intrinsic viscosity of this polyimide measured in DMAc was 0.72 dL / g. The varnish (17% by weight) obtained by dissolving this polyimide powder in cyclopentanone was uniform and showed high stability at room temperature. This varnish was applied to a glass substrate and dried in a hot air dryer at 60 ° C. for 1 hour, at 100 ° C. for 10 minutes, and further at 150 ° C. for 15 minutes to obtain a transparent polyimide film having a thickness of about 15 μm. This polyimide film did not break even in the 180 ° bending test and showed sufficient flexibility. Similarly, when a thin film having a thickness of 5 μm was separately prepared and an infrared absorption spectrum was measured by a transmission method, it was confirmed that imidization was almost completed. The infrared absorption spectrum of the polyimide thin film is shown in FIG. When the transparency of this polyimide film was evaluated, the light transmittance at 400 nm was 88.6%, and the cutoff wavelength was 312 nm, indicating extremely high transparency. The birefringence measured using a sodium lamp as the light source was 0.020, indicating a relatively high birefringence value. In addition, Re ₄₅₀ / Re ₅₅₀ = 1.025, indicating extremely low wavelength dispersion.

[Comparative Example 1]
TFMB (4 mmol) and the diamine represented by the formula (10), that is, 9,9-bis (4-aminophenyl) fluorene (1 mmol), were dissolved in DMAc (monomer concentration: 15.9% by weight). 1S, 2S, 4R, 5R) -cyclohexanetetracarboxylic dianhydride powder (manufactured by Iwatani Gas Co., Ltd.) 2.5 mmol and 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride powder ( Sitraconic anhydride was irradiated with ultraviolet rays and synthesized by dimerization reaction) 2.5 mmol was sequentially added, and the mixture was stirred at room temperature for 72 hours for polymerization. The intrinsic viscosity of the obtained polyimide precursor was 0.659 dL / g. Similarly to the method described in Example 2, chemical imidization, isolation, re-dissolution in cyclopentanone and casting were performed to prepare a polyimide film. The polyimide film had a light transmittance of 89.6% at 400 nm and a cut-off wavelength of 291 nm, indicating extremely high transparency. The birefringence measured using a sodium lamp as the light source was 0.0265, indicating a relatively high birefringence value. However, the value Re ₄₅₀ / Re ₅₅₀ indicating the wavelength dispersion of retardation was 1.08, and the wavelength dispersion was not so low. This is because the fluorenyl group-containing diamine of the present invention was not used for the diamine component.

Claims (13)

The following general formula (1):

The fluorenyl group containing diamine compound represented by these.
(In Formula (1), each substituent P _n is independently a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched chain group having 1 to 6 carbon atoms, or Represents a branched alkoxy group, and n is an integer of 0 to 4 representing the number of substituents.) The following general formula (2):

The polyimide precursor which has a repeating unit represented by these.
(In the formula (2), A represents a tetravalent aliphatic group, and P _n each independently represents a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, carbon A linear or branched alkoxy group having 1 to 6 is represented, and n is an integer of 0 to 4 representing the number of substituents.   The polyimide precursor copolymer according to claim 2, wherein X is in the range of 0.01 to 0.99, where X is a molar fraction of the imide precursor unit represented by the general formula (2). The following general formula (3):

(In Formula (3), A is as defined above. B is the following Formulas (4) to (7):

Represents at least one selected from the group consisting of The polyimide precursor copolymer according to claim 3, further comprising an imide precursor unit represented by: The following general formula (8):

The polyimide which has a repeating unit represented by these.
(In formula (8), A represents a tetravalent aliphatic group, and P _n each independently represents a fluorine atom, a chlorine atom, a bromine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, carbon, A linear or branched alkoxy group having 1 to 6 is represented, and n is an integer of 0 to 4 representing the number of substituents.   The polyimide copolymer of Claim 5 whose Y is the range of 0.01-0.99, when the molar fraction of the imide unit represented by the said General formula (8) is set to Y. The following general formula (9):

(In the formula (9), A represents a tetravalent aliphatic group, and B represents the following formulas (4) to (7).

The polyimide copolymer according to claim 6, further comprising an imide unit represented by at least one selected from the group consisting of:   The method for producing a polyimide according to any one of claims 5 to 7, wherein the polyimide precursor according to any one of claims 2 to 4 is subjected to an imidization reaction using heating or a dehydrating cyclization reagent. .   The polyimide according to any one of claims 5 to 7 is obtained by uniformly dissolving at a concentration of 5% by weight or more in a solvent selected from at least one of a ketone solvent, an aromatic hydrocarbon solvent, and an ester solvent. Varnish. An optical compensation film comprising the polyimide according to claim 5.   A method for producing an optical compensation film, comprising applying and drying the polyimide varnish according to claim 9 on a substrate. The light transmittance at a wavelength of 400 nm is 80% or more, and the ratio of retardation (Re) or birefringence (Δn) at wavelengths of 450 nm and 550 nm (Re ₄₅₀ / Re ₅₅₀ = Δn ₄₅₀ / Δn ₅₅₀ ) is 1.03 or less, The optical compensation film according to claim 10, which has a breaking elongation of 10% or more in a tensile test.   The optical compensation film according to claim 10, wherein the sodium lamp has a birefringence of 0.02 or more at the D line (589 nm).

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