JP2010024350A - Polyimide resin solution for coating, laminate using the same, optical compensation member and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide resin solution for coating, containing a polyimide resin produceable at a low cost and having high organic solvent solubility, and at least one of organic solvents, to provide an optical compensation member obtained by using a laminate formed by coating the solution on a supporter, and having sufficient optical compensation ability (e.g., birefringence-manifesting property), and to provide a liquid crystal display device using the member. <P>SOLUTION: The polyimide resin solution for the coating contains the polyimide resin produceable at a low cost, having the high organic solvent solubility, and prepared from two or more acid dianhydrides including MCTC having an alicyclic structure, and a diamine having a benzidine structure, and at least one organic solvent. The optical compensation member obtained by using the solution, and having the sufficient optical compensation ability (e.g., the birefringence-manifesting property), and the liquid crystal display device using the member are also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyimide resin solution for coating containing polyimide and a liquid crystal display device using the same.

  For a liquid crystal display device, a retardation film for the purpose of optical compensation is generally used. For example, Patent Document 1 discloses 2,2-bis (3,4-dicarboxyphenyl) -1, It is obtained by dissolving a soluble polyimide composed of 1,1,3,3,3-hexafluoropropanoic dianhydride (6FDA) and 2,2′-bis (trifluoromethyl) benzidine (TFMB) in an organic solvent. An optical compensation member using a polyimide layer obtained by casting the obtained polyimide resin solution on a support and then drying the solvent is described. However, polyimides using acid dianhydrides containing fluorine are generally expensive and have not been fully satisfactory in terms of cost.

  For example, Patent Document 2 discloses an organic solvent-soluble polyimide comprising 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride (MCTC) and TFMB. Although listed as applications of this polyimide, the interlayer insulating film of semiconductor elements, passivation film, buffer coat film, insulating film for multilayer printed circuit board, thin film transistor protective film of liquid crystal display element, organic It was only the electrode protective film of the EL element.

  Further, for example, Patent Document 3 discloses a thermosetting resin solution composition containing a polyamic acid obtained by reacting an acid dianhydride containing at least one alicyclic tetracarboxylic dianhydride and a diamine in a solvent. Things are listed. However, this composition is thermosetting and requires a complicated curing treatment after coating. Furthermore, since it is for color filters, the birefringence value described in the examples was as low as 0.01 or less.

Further, Patent Document 4 discloses a retardation film made of a polyimide resin. However, only the method of heating and curing polyamic acid to obtain polyimide is disclosed in the examples, and there was no specific disclosure about a resin solution containing polyimide.
WO2005 / 118686 WO2003 / 02899 JP 2002-114907 A JP2007-122037

  The present invention provides a polyimide resin solution that can be produced at low cost and has high organic solvent solubility and a coating polyimide resin solution containing at least one organic solvent, and the solution is coated on a support. An object of the present invention is to provide an optical compensation member having a sufficient optical compensation capability using the laminate formed as described above, and a liquid crystal display device using the member.

  As a result of intensive studies in view of the above problems, the present inventors have found that a polyimide resin prepared from a specific acid dianhydride and a diamine can be produced at low cost and has high organic solvent solubility, By using a polyimide resin solution containing a resin and at least one organic solvent and coating on a support, it is possible to produce an optical compensation member having excellent optical compensation capability (for example, birefringence). The headline and the present invention were completed.

Specifically, the present invention provides (I) a polyimide resin solution for coating, which contains a polyimide resin represented by the following general formula (1) and at least one organic solvent.

(R ¹ may be the same or different, —H, —F, —Cl, —I, —OH, —CH ₃ , —CF ₃ , —SO ₄ , —C (CH ₃ ) ₃ , —COOH, 1 represents a group selected from the group consisting of —CO—NH ₂ , R ² may be the same or different, and —H, —F, —Cl, —I, —OH, —CH ₃ , —CF ₃ , —SO ₄ , —C (CH ₃ ) ₃ , —COOH, —CO—NH ₂ represents one group, R ³ is a tetravalent organic group, and m and n are m: n = 95: 5 to 60:40 is satisfied.)
(II) The polyimide resin solution for coating as described in (I), wherein R ^{1 in the} general formula (1) is —CF ₃ and R ² is —H.

(III) One of (I) and (II), wherein R ^{3 in the} general formula (1) is at least one tetravalent organic group selected from the following structural formula group (2): The polyimide resin solution for coating as described in the item.

(IV) In any one of (I) to (III), R ^{3 in the} general formula (1) is at least one tetravalent organic group represented by the following structural formula (3) The polyimide resin solution for coating as described.

  (V) The organic solvent is at least one selected from the group consisting of N, N-dimethylformamide, N, N-dimethylacetamide, dioxolane, ethyl acetate, toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and cyclopentanone. The manufacturing method according to any one of (I) to (IV), wherein the method is selected.

  (VI) A laminate comprising the coating polyimide resin solution according to any one of (I) to (V), which is applied to a support.

  (VII) An optical compensation member comprising the laminate according to (VI).

(VIII) A liquid crystal display device having the optical compensation member according to (VII).
About.

  According to the present invention, a polyimide resin solution that can be produced at low cost and has high organic solvent solubility and a coating polyimide resin solution containing at least one organic solvent can be obtained. In addition, an optical compensation member having sufficient optical compensation ability using the solution, and a liquid crystal display device using the member can be obtained.

  The gist of the present invention is a polyimide resin solution for coating, which contains a polyimide resin represented by the following general formula (1) and at least one organic solvent. Here, the polyimide resin solution for coating in the present invention can be applied to a support and a solvent can be dried to form a laminate. The solution can be applied to a support and dried to form a laminate having optical compensation ability, and a complicated operation such as curing is not required after the application, so that the production process can be simplified.

(M and n satisfy m: n = 95: 5 to 60:40)
R ^{1 s} may be the same or different and are —H, —F, —Cl, —I, —OH, —CH ₃ , —CF ₃ , —SO ₄ , —C (CH ₃ ) ₃ , —COOH, — One group selected from the group consisting of CO—NH ₂ is shown, and —CF ₃ is particularly preferable from the viewpoint of the organic solvent solubility and transparency of the resin.

R ² may be the same or different and are —H, —F, —Cl, —I, —OH, —CH ₃ , —CF ₃ , —SO ₄ , —C (CH ₃ ) ₃ , —COOH, — One group selected from the group consisting of CO—NH ₂ is shown, and —H is particularly preferable.
R ³ is a tetravalent organic group, and is not particularly limited, but is preferably at least one tetravalent organic group selected from the following structural formula group (2).

More preferably, R ³ is at least one tetravalent organic group selected from the following structural formula group (3).

  M and n satisfy m: n = 95: 5 to 60:40, preferably 90:10 to 60:40, and more preferably 85:15 to 65:35.

  The method for producing the polyimide resin represented by the general formula (1) is not particularly limited, and a known method such as imidation of a corresponding polyamic acid as a precursor by various imidization methods can be used.

  An example is described about the manufacturing method of a polyamic acid. The method for producing the polyamic acid is not limited to the following method, and various methods can be used.

  The polyamic acid is not particularly limited, but can be prepared, for example, by copolymerization of acid dianhydride and diamine. The polyamic acid which is a precursor of the polyimide resin represented by the general formula (1) is 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride. It is prepared from at least two acid dianhydrides including (MCTC) and a diamine having a benzidine structure.

  At least two acid dianhydrides containing MCTC are dispersed in an organic solvent in which a diamine having a benzidine structure is dissolved, and the polymerization reaction is carried out by completely dissolving the mixture by stirring. Two or more of the at least two acid dianhydrides may be added simultaneously, or may be added individually one by one. After complete dissolution, it is preferable to react for 1 to 60 hours.

  The reaction apparatus is preferably provided with a temperature adjusting device for controlling the reaction temperature. The reaction solution temperature is preferably 40 ° C. or lower, and more preferably 30 ° C. or lower because the reaction proceeds efficiently and the viscosity of the polyamic acid tends to increase.

  Examples of the organic solvent used for the polymerization of the polyamic acid include ureas such as tetramethylurea, N, N-dimethylethylurea, sulfoxides or sulfones such as dimethyl sulfoxide, diphenylsulfone, and tetramethylsulfone, N, N Amides such as dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), N, N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyllactone, hexamethylphosphoric triamide Or aprotic solvents of phosphorylamides, alkyl halides such as chloroform and methylene chloride, aromatic hydrocarbons such as benzene and toluene, phenols such as phenol and cresol, dimethyl ether, diethyl ether, p-cresol methyl Can ethers such as ether and the like. Usually, these solvents are used alone, but two or more kinds may be used in appropriate combination as required. Of these, amides such as DMF, DMAc, and NMP are preferably used.

  The weight% of the polyamic acid in the polyamic acid solution is preferably 5 to 50% by weight of the polyamic acid in the organic solvent, more preferably 10 to 40% by weight, and 15 to 30% by weight dissolved. It is particularly preferable from the viewpoint of handling.

  The molecular weight of the polyamic acid prepared by the above method can be measured, for example, by gel permeation chromatography (GPC). The weight average molecular weight of the polyamic acid when measured by the GPC method using DMF as a developing solvent and polyethylene glycol as a conversion standard sample is 10,000 or more, when the polyamic acid is molded into a polyimide resin molded body. From the viewpoint of strength, it is preferably 500,000 or less from the viewpoint of ease of processing.

  The acid dianhydride used in the present invention is at least two acid dianhydrides including MCTC. MCTC is preferably used in a ratio of 95 to 60 mol% in all acid dianhydrides, more preferably in a ratio of 90 to 60 mol%, and in a ratio of 85 to 65 mol%. Is particularly preferred. When used in the above range, the solubility of the resulting polyimide resin in an organic solvent is improved, which is preferable in terms of handling.

  The acid dianhydride other than MCTC is not particularly limited. For example, pyromellitic dianhydride (PMDA), 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 2,2 -Bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropanoic acid dianhydride (6FDA), p-phenylenebis (trimellitic acid monoester acid anhydride) ( TMHQ), naphthalene-2,3,6,7-tetracarboxylic dianhydride (NTCDA), 2,2-bis (4-trimellitic acid monoester acid phenyl) propanoic acid dianhydride (ESDA), 3, 3,4,4-biphenyltetracarboxylic dianhydride (BPDA), 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4′-oxydi Aromatic dianhydrides such as talic dianhydride (ODPA) are preferred, PMDA, BTDA, and TMHQ are more preferred, and BTDA is particularly preferred from the viewpoint of birefringence and the solubility of the resulting polyimide resin in an organic solvent. Used. When using 2 or more types of acid dianhydrides other than MCTC, the mixing ratio is not particularly limited.

  Diamines used in the present invention are represented by the general formula (4).

(In the formula, R ⁴ may be the same or different, —H, —F, —Cl, —I, —OH, —CH ₃ , —CF ₃ , —SO ₄ , —C (CH ₃ ) ₃ , 1 represents a group selected from the group consisting of —COOH and —CO—NH ₂ , R ⁵ may be the same or different, and —H, —F, —Cl, —I, —OH, —CH _{3; , -CF 3, -SO 4, -C} (CH 3) 3, -COOH, shows one group selected from the group consisting of -CO-NH _2.)
Specifically, 2,2′-bis (trifluoromethyl) benzidine (TFMB), 2,2′-dimethylbenzidine, 2,2′-bis (trichloromethyl) benzidine, 2,2′-di-tert- Butylbenzidine, 2,2'-difluorobenzidine, 2,2'-dichlorobenzidine, 2,2'-dibromobenzidine, 2,2'-diethylbenzidine, 2,2'-dihydroxybenzidine, 2,2'-disulfonic acid It is preferable to use benzidine or the like. In particular, from the viewpoint of transparency and solubility, it is preferable to use TFMB, 2,2′-dimethylbenzidine, or 2,2′-dichlorobenzidine. In particular, it is preferable to use TFMB.

  The molar ratio of the acid dianhydrides and diamines used in the reaction for producing the polyamic acid solution is a value obtained by dividing the number of moles of all acid dianhydrides by the number of moles of all diamines used. It is preferably 1.5 or more, more preferably 0.95 or more and 1.3 or less, and particularly preferably 0.98 or more and 1.2 or less in the polyimide resin obtained from the polyamic acid solution. It is preferable when reducing unreacted acid dianhydride and diamine.

  Next, the imidization method of a polyamic acid is described. As a method for imidizing a polyamic acid solution, there are a thermal imidization method for thermally dehydrating and cyclizing, a chemical imidization method using a dehydrating agent and a catalyst, and a method using the above two methods in combination.

  Among these, the method using the thermal imidization method and the chemical imidization method in combination is preferable because a polyimide resin having a small amount of coloring and a high imidization ratio can be prepared.

  Examples of the dehydrating agent used in the chemical imidization method include aliphatic acid anhydrides such as acetic anhydride and aromatic acid anhydrides. Among them, it is preferable to use acetic anhydride from the viewpoint of the polyimide resin extraction step. Examples of the catalyst include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine, isoquinoline, β-picoline, γ-picoline, and lutidine. And the like. However, since it may be colored depending on the catalyst used, it is preferable to appropriately select a catalyst suitable for the polyimide resin. In particular, catalysts that can be suitably used in the present invention are pyridine, isoquinoline, and β-picoline.

  The amount of the dehydrating agent and the catalyst added to the polyamic acid depends on the chemical structural formula constituting the polyamic acid, but is preferably the dehydrating agent mole number / the amide group mole number in the polyamic acid = 10 to 0.001. The number of moles of medium amide group is preferably 10 to 0.001. More preferably, the number of moles of dehydrating agent / the number of amide groups in the polyamic acid is preferably 5 to 0.01, and the number of moles of amide groups in the catalyst / polyamic acid is preferably 5 to 0.01.

  In the thermal imidization method used in combination with the chemical imidization method, it is preferable to heat the stirring solution by adding a dehydrating agent and a catalyst to the polyamic acid solution at 150 ° C. or less, and at 120 ° C. or less. More preferably, heating at 100 ° C. or lower is particularly preferable because molecular weight reduction and coloring are suppressed. The heating time is preferably 1 hour or more and 10 hours or less, and more preferably 1 hour or more and 5 hours or less in order to advance the imidization reaction and suppress molecular weight reduction and coloring.

  The polyimide resin solution after the imidization reaction may be used as it is as a coating resin solution for forming a laminate, but the polyimide resin can be extracted once by extraction. As a suitable method for extracting the polyimide resin, there is a method in which the polyimide resin solution after the imidization reaction is put into a poor solvent. The poor solvent for the polyimide resin used in the present invention is a poor solvent for the corresponding polyimide, such as water, 1-propanol, 2-propanol, methanol, ethanol, ethylene glycol, triethylene glycol, and the like, and polyamic acid and polyimide resin Those that are miscible with the organic solvent used as the dissolution solvent are used, and alcohols are particularly preferably used.

  An example of a polyimide resin extraction method using alcohols is described below. When injecting the polyimide resin solution into a poor solvent, the polyimide resin solution is diluted with a reaction solvent so that the solid content concentration of the polyimide solution is 15% by weight or less, preferably 10% by weight or less. Inject and inject. The amount of the poor solvent is preferably 3 times or more the weight of the polyimide resin solution.

  It is preferable to purify the extracted polyimide resin by washing. The solvent used for washing may be the same as or different from the solvent used for extraction. For example, water, 1-propanol, 2-propanol, methanol, ethanol, ethylene glycol, triethylene glycol, etc., which is a poor solvent for the corresponding polyimide, which is mixed with the organic solvent used as the dissolving solvent for the polyamic acid and the polyimide resin is used. In particular, alcohols are preferably used.

  The polyimide resin purified by washing is preferably further purified by drying. The drying temperature when drying is performed in the presence of oxygen is preferably 200 ° C. or less from the viewpoint of suppressing resin coloring. Even when drying is performed in a vacuum or in an inert gas atmosphere, it is preferably performed at 150 ° C. or lower.

  The molecular weight of the polyimide resin prepared by the above method can be measured, for example, by gel permeation chromatography (GPC). The weight average molecular weight of the resin as measured by GPC using DMF as a developing solvent and polyethylene glycol as a conversion standard sample is preferably 10,000 or more from the viewpoint of strength when molded into a polyimide resin molded body. , 500,000 or less is preferable from the viewpoint of ease of processing.

  The obtained resin represented by the general formula (1) can be dissolved again in an organic solvent and used as a polyimide resin solution for coating. When dissolved and used, the laminate is formed by coating the support and drying and removing the organic solvent. The laminate may be used after processing such as removing the support, or may be used as it is together with the support.

  When it is dissolved again in an organic solvent, ureas such as tetramethylurea and N, N-dimethylethylurea, sulfoxides or sulfones such as dimethylsulfoxide, diphenylsulfone and tetramethylsulfone, N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), N, N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyllactone, amides such as hexamethylphosphoric triamide, or phosphoryl Amido aprotic solvents, halogenated alkyls such as chloroform and methylene chloride, aromatic hydrocarbons such as benzene, toluene, p-xylene, m-xylene and mesitylene, esters such as methyl acetate and ethyl acetate , Phenol, cresol Lumpur ethers, dioxolane, dimethyl ether, diethyl ether, p- ethers such as cresol methyl ether, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), can be used acetone, ketones such as diethyl ketone. Usually, these solvents are used alone, but two or more of them may be used in appropriate combination as required. The solvent used for preparing the polyimide resin solution is appropriately selected depending on the use form and the support type. DMF, DMAc, dioxolane, ethyl acetate, toluene, acetone, MEK, MIBK, cyclohexanone, and cyclopentanone are preferably applicable to various supports, and solvents such as MIBK, MEK, cyclohexanone, and cyclopentanone are particularly preferable, and MIBK MEK is particularly preferably used because it has high volatility and can easily form a laminate.

  The higher the solubility of the polyimide resin solution for coating in the organic solvent, the higher the solid content concentration in the solution. When the polyimide resin solution is dissolved in the organic solvent again to form a laminate, the organic solvent is volatilized. This is preferable because the amount of the organic solvent remaining in the laminate can be reduced. The solid content concentration of the polyimide resin solution for coating used for laminate formation (formation of coating film having optical compensation ability) is preferably 5% by weight or more, more preferably 10% by weight or more, and 15% by weight. The above is particularly preferable.

  As the support, various types can be used, and a glass plate or a metal plate can also be used. However, from the viewpoint of weight reduction and the like, a support made of a polymer, and further, an organic high used for optical applications. A support made of a molecule can be preferably used. Specific materials constituting the support include, for example, polymethyl methacrylate (PMMA), triacetyl cellulose (TAC), cellulose acylate, cellulose ether, polyethylene terephthalate (PET), polycarbonate (PC), polyester, and alicyclic structure. Cyclic olefin, polysulfone, polyarylate, polystyrene and the like. In particular, celluloses such as PMMA and TAC, PET, and cyclic olefins having an alicyclic structure are preferable, and celluloses such as TAC, PET, and cyclic olefins having an alicyclic structure can be particularly preferably used. In addition, it is preferable that a support body is a film form from viewpoints, such as weight reduction. An annealed support may be used.

  The polyimide resin solution for coating prepared by the above method may be used as an optical compensation member for a VA (vertical alignment) type liquid crystal display. In a VA display, light leakage in an oblique direction during black display is a problem. In order to improve the light leakage, an optical compensation member having a large birefringence (Δn) expression in the thickness direction is used. Δn is given by Δn = (nx + ny) / 2−nz, where nx is the maximum refractive index in the plane, ny is the minimum refractive index, and nz is the refractive index in the thickness direction. Say the value. Specifically, the polyimide resin solution for coating of the present invention can be used for an optical compensation member that compensates for retardation caused by liquid crystal in a VA display.

  The retardation (Re) is represented by the equation Re = Δn × d, where d is the thickness of the optical compensation member. Δn is preferably 0.020 ≦ Δn ≦ 0.150, and more preferably 0.025 ≦ Δn ≦ 0.100. In the case of Δn <0.020, it is necessary to increase the film thickness in order to develop the retardation necessary for optical compensation. For this reason, the quantity of the organic solvent to volatilize also increases, drying time becomes long and productivity may worsen. Further, since the film thickness is increased, the amount of resin used is increased, which is not preferable in terms of cost. When Δn> 0.150, slight thickness variations cause retardation variations, which is not preferable in terms of quality. The thickness of the thin film is preferably in the range of 1 to 30 μm, more preferably in the range of 1 to 20 μm, and particularly preferably in the range of 2 to 20 μm from the viewpoint of productivity and cost. . When the thickness is 30 μm or more, the amount of the organic solvent to be volatilized increases, the drying time becomes longer, and the productivity may deteriorate. Further, since the film thickness is increased, the amount of resin used is increased, which is not preferable in terms of cost. When the thickness is 1 μm or less, it is difficult to control the thickness, and slight thickness unevenness causes variations in retardation, which is not preferable in terms of quality.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

[Evaluation methods]
The numerical values described in the examples are based on the following evaluation methods.

(Molecular weight)
The weight average molecular weight (Mw) of the polyimide resin obtained by synthesis was measured by gel permeation chromatography. The measurement conditions are as shown in Table 1.

(Solubility)
0.1 g of the polyimide resin obtained by synthesis and 1.9 g of methyl isobutyl ketone (MIBK), methyl ethyl ketone (MEK), or cyclohexanone (CPN) are put in a sample tube bottle and allowed to stand at room temperature for half a day. If it was a homogeneous solution, it was soluble, and if it remained undissolved, it was insoluble.

(Preparation of polyimide resin layer)
A polyimide resin solution obtained by dissolving a polyimide resin obtained by synthesis in MIBK or CPN is placed on a glass plate (cover glass (35 mm × 50 mm) made by Matsunami Glass Industry) with a bar coater and a film thickness of 50 μm. To 150 μm, dried in a hot air oven at 90 ° C. for 10 minutes, and subsequently dried at 160 ° C. (when the solvent is MIBK) or 200 ° C. (when the solvent is CPN) for 20 minutes. A polyimide resin layer was formed.

(Measurement of film thickness)
The film thickness of the polyimide resin layer produced above was measured with FT / IR-4100 manufactured by JASCO Corporation. A refractive index of 1.55 was used.

(Measurement of birefringence)
The birefringence (Δn) in the thickness direction of the polyimide resin layer prepared and measured above was measured with KOBRA-WR manufactured by Oji Scientific Instruments. The measurement wavelength is 590 nm, Nave is 1.55, in-plane retardation, and retardation when tilted by 40 ° about the slow axis of the polyimide resin layer as a rotation axis, (= (Nx + ny) / 2−nz) was calculated.

[Synthesis of resin]
Example 1
A stirrer capable of stirring a stainless steel stirring rod equipped with a nitrogen introduction tube, a polytetrafluoroethylene vacuum seal, and four stainless steel propeller blades (one blade diameter of 50 mm and 60 mm each) at a maximum of 300 rpm, and a cylinder In a reaction vessel consisting of a separable flask (capacity 500 ml) made of a round-bottomed glass, 16.0 g of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylformamide (DMF) were passed under nitrogen flow. ) 70.0 g was added and stirred well. After the start of stirring, a 20 ° C. water bath was installed, and the flask was immersed and kept warm. After confirming that TFMB was completely dissolved in DMF, the stirring was once stopped and 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride was stopped. (MCTC) 9.2g was put into the flask and stirring was started again. Two hours after MCTC was added, stirring was once stopped, and 4.8 g of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA) was put into the flask, and stirring was started again. After stirring for 3 hours, the water bath was removed, and a 60 ° C. hot water bath was installed instead, and the inside of the flask was heated to promote polymerization of the polyamic acid. 15 hours after the start of warming in the hot water bath, 31.2 g of DMF was added to the flask to dilute the solution, 7.4 g of pyridine was added 3 minutes after the addition of DMF, and 11.5 g of acetic anhydride was added 7 minutes after the addition of pyridine. I put it in. After adding acetic anhydride, the temperature of the hot water bath was set to 100 ° C., and the imidization reaction of the polyamic acid was started. Four hours after the hot water bath was set at 100 ° C., the hot water bath was removed and quenched in an ice bath to complete the imidization reaction. After sufficiently cooling the polyimide resin solution thus obtained, 21.5 g of DMF was added to the flask to reduce the viscosity of the solution, followed by 51.3 g of 2-propanol (IPA). This solution was poured into 377.1 g of IPA separately prepared using a dropping funnel to precipitate the resin. The precipitated resin was collected by decantation, and the obtained resin was stirred in 300.0 g of IPA for 20 minutes to wash the resin. After washing, the resin was collected by vacuum filtration. The resin obtained by repeating washing and filtration two more times was vacuum-dried at 100 ° C. overnight to obtain 27.4 g of a polyimide resin.

  The obtained polyimide resin had Mw = 27,000 and Mw / Mn = 1.7, and was soluble in any of MIBK, MEK, and CPN. A 30 wt% CPN solution was prepared, a polyimide resin layer having a thickness of 10.3 μm was prepared by the above method, and Δn measured was 0.029. Similarly, a polyimide layer prepared by preparing a 20 wt% MIBK solution had a film thickness of 12.3 μm and Δn of 0.030.

(Example 2)
In a reaction vessel similar to that of Example 1, 16.4 g of TFMB and 70.0 g of N, N-dimethylformamide (DMF) were placed under nitrogen flow and well stirred. After the start of stirring, a 20 ° C. water bath was installed, and the flask was immersed and kept warm. After confirming that TFMB was completely dissolved in DMF, stirring was once stopped, 12.8 g of MCTC was placed in the flask, and stirring was started again. Twenty-five hours after MCTC was added, stirring was once stopped, 0.8 g of BTDA was placed in the flask, and stirring was started again. Three hours after adding BTDA, 29.4 g of DMF was added to the flask to dilute the solution, 8.1 g of pyridine was added 3 minutes after the addition of DMF, and 12.6 g of acetic anhydride was added 7 minutes after the addition of pyridine. I put it in. Shortly after the addition of acetic anhydride, the reaction solution gelled. After the addition of acetic anhydride, a 100 ° C. hot water bath was installed to initiate the imidization reaction of the polyamic acid. Gelation resolved within 10 minutes. Four hours after the temperature of the hot water bath was set to 100 ° C., the hot water bath was removed and quenched in an ice bath to complete the imidization reaction. After sufficiently cooling the polyimide resin solution thus obtained, 21.5 g of DMF was added to the flask to reduce the viscosity of the solution, and subsequently 102.8 g of IPA was added. This solution was put into 350.0 g of IPA separately prepared using a dropping funnel to precipitate the resin. Thereafter, the resin was washed and dried in the same manner as in Example 1 to obtain 26.1 g of a polyimide resin.

  The obtained polyimide resin had Mw = 23,000 and Mw / Mn = 1.6, and was soluble in any of MIBK, MEK, and CPN. A 30 wt% MIBK solution was prepared, a 9.5 μm-thick polyimide resin layer was prepared by the above method, and Δn measured was 0.021.

(Example 3)
In a reaction vessel similar to that in Example 1, 15.0 g of TFMB and 70.0 g of N, N-dimethylformamide (DMF) were placed under nitrogen flow and well stirred. After starting the stirring, a 20 ° C. water bath was installed, and the flask was immersed to keep the temperature warm. After confirming that TFMB was completely dissolved in DMF, stirring was temporarily stopped, and 8.6 g of MCTC was placed in the flask, and stirring was started again. Two hours after the MCTC was added, stirring was once stopped, and 6.4 g of p-phenylenebis (trimellitic acid monoester anhydride) (TMHQ) was put into the flask, and stirring was started again. After stirring for 3 hours, the water bath was removed, and a 60 ° C. hot water bath was installed instead, and the inside of the flask was heated to promote polymerization of the polyamic acid. Nineteen hours after the introduction of TMHQ, an imidization reaction was performed in the same manner as in Example 1 to precipitate a resin, which was washed and dried to obtain 27.7 g of a polyimide resin.

  The obtained polyimide resin had Mw = 28,000 and Mw / Mn = 1.8 and was soluble in MEK and CPN, but insoluble in MIBK solution. A 30 wt% CPN solution was prepared, a polyimide resin layer having a film thickness of 12.3 μm was prepared by the above method, and Δn measured was 0.037.

Example 4
In a reaction vessel similar to that in Example 1, 16.9 g of TFMB and 70.0 g of N, N-dimethylformamide (DMF) were placed under nitrogen flow and well stirred. After the start of stirring, a 20 ° C. water bath was installed, and the flask was immersed and kept warm. After confirming that TFMB was completely dissolved in DMF, stirring was temporarily stopped, 9.7 g of MCTC was placed in the flask, and stirring was started again. Two hours after the MCTC was charged, stirring was once stopped, and 3.4 g of pyromellitic dianhydride (PMDA) was put into the flask, and stirring was started again. After stirring for 5 hours, the water bath was removed, and a 60 ° C. hot water bath was installed instead, and the inside of the flask was heated to promote polymerization of the polyamic acid. 15 hours after the start of warming in the hot water bath, 28.8 g of DMF was added to the flask to dilute the solution, 8.3 g of pyridine was added 3 minutes after the addition of DMF, and 18.9 g of acetic anhydride was added 7 minutes after the addition of pyridine. I put it in. After adding acetic anhydride, the temperature of the hot water bath was set to 100 ° C., and the imidization reaction of the polyamic acid was started. Four hours after the hot water bath was set at 100 ° C., the hot water bath was removed and quenched in an ice bath to complete the imidization reaction. After sufficiently cooling the polyimide resin solution thus obtained, 21.5 g of DMF was added to the flask to reduce the viscosity of the solution, and 120.0 g of IPA was subsequently added. This solution was put into 325.7 g of IPA separately prepared using a dropping funnel to precipitate the resin. Thereafter, the resin was washed and dried in the same manner as in Example 1 to obtain 27.0 g of a polyimide resin.

  The obtained polyimide resin had Mw = 27,000 and Mw / Mn = 1.8, and was soluble in any of MIBK, MEK, and CPN. A 30 wt% CPN solution was prepared, a polyimide resin layer having a film thickness of 9.1 μm was prepared by the above method, and Δn measured was 0.037.

(Comparative Example 1)
In a reaction vessel similar to that of Example 1, 16.4 g of TFMB and 70.0 g of N, N-dimethylformamide (DMF) were placed under nitrogen flow and well stirred. After confirming that TFMB was completely dissolved in DMF, stirring was once stopped, 13.6 g of MCTC was placed in the flask, and stirring was started again. 20 hours after MCTC was added, a 60 ° C. hot water bath was installed, and the inside of the flask was heated to promote polymerization of the polyamic acid. Five hours after the start of warming in the hot water bath, 29.3 g of DMF was added to the flask to dilute the solution, 8.1 g of pyridine was added 3 minutes after the addition of DMF, and 12.6 g of acetic anhydride was added 7 minutes after the addition of pyridine. I put it in. Shortly after the addition of acetic anhydride, gelation of the reaction solution was observed, but it disappeared within 5 minutes. After adding acetic anhydride, the temperature of the hot water bath was set to 100 ° C., and the imidization reaction of the polyamic acid was started. Four hours after the hot water bath was set at 100 ° C., the hot water bath was removed and quenched in an ice bath to complete the imidization reaction. After sufficiently cooling the polyimide resin solution thus obtained, 50.0 g of DMF was added to the flask to reduce the viscosity of the solution, and 51.3 g of IPA was subsequently added. This solution was poured into 377.1 g of IPA separately prepared using a dropping funnel to precipitate the resin. Since the deposited resin did not settle in the solution, the resin was collected by filtration under reduced pressure. The obtained resin was stirred in 300.0 g of IPA for 20 minutes to wash the resin. After washing, the resin was collected by vacuum filtration. The resin obtained by repeating washing and filtration twice more was vacuum-dried at 100 ° C. overnight to obtain 25.8 g of a polyimide resin.

  The obtained polyimide resin had Mw = 22,000 and Mw / Mn = 1.5, and was soluble in any of MIBK, MEK, and CPN. A 30 wt% CPN solution was prepared, a polyimide resin layer having a thickness of 13.0 μm was prepared by the above method, and Δn was measured to be 0.017.

(Comparative Example 2)
In a reaction vessel similar to that in Example 1, 15.7 g of TFMB and 70.0 g of DMF were placed in a nitrogen stream and stirred well. After the start of stirring, a 20 ° C. water bath was installed, and the flask was immersed and kept warm. After confirming that TFMB was completely dissolved in DMF, stirring was once stopped, 6.5 g of MCTC was put into the flask, and stirring was started again. Two hours after MCTC was added, stirring was once stopped, 7.9 g of BTDA was placed in the flask, and stirring was started again. After stirring for 5 hours, the water bath was removed, and a 60 ° C. hot water bath was installed instead, and the inside of the flask was heated to promote polymerization of the polyamic acid. 17 hours after the start of warming in the hot water bath, 30.3 g of DMF was added to the flask to dilute the solution, 7.7 g of pyridine was added 3 minutes after the addition of DMF, and 12.0 g of acetic anhydride was added 7 minutes after the addition of pyridine. I put it in. After adding acetic anhydride, the temperature of the hot water bath was set to 100 ° C., and the imidization reaction of the polyamic acid was started. Thereafter, the imidization reaction was terminated in the same manner as in Example 1, the resin was precipitated, the resin was washed, and dried to obtain 27.6 g of a polyimide resin.

  The obtained polyimide resin had Mw = 30,000 and Mw / Mn = 1.8, and was insoluble in any of MIBK, MEK, and CPN.

(Comparative Example 3)
In a reaction vessel similar to that in Example 1, 12.4 g of TFMB and 113.3 g of N, N-dimethylacetamide (DMAc) were placed under nitrogen flow and well stirred. After confirming that TFMB was completely dissolved in DMAc, the stirring was temporarily stopped, and 7.6 g of cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) was placed in the flask, and stirring was performed again. Started. After the start of stirring, a 20 ° C. water bath was installed, and the flask was immersed and kept warm. 54 hours after charging CBDA, 12.3 g of pyridine, 9.6 g of acetic anhydride, and 44.9 g of DMAc were charged all at once in this order. After 2 minutes, the reaction solution had gelled. Gelation did not disappear even after 16 hours, and polyimide resin could not be obtained.

  Table 2 shows the evaluation results of Examples 1 to 4 and Comparative Examples 1 to 3. In Examples 1 to 4, the birefringence value in the thickness direction was as high as 0.020 or more. In addition, at least two solvents selected from MIBK, MEK and CPN showed high solubility.

Claims (8)

A polyimide resin solution for coating, comprising a polyimide resin represented by the following general formula (1) and at least one organic solvent.
(R ¹ may be the same or different, —H, —F, —Cl, —I, —OH, —CH ₃ , —CF ₃ , —SO ₄ , —C (CH ₃ ) ₃ , —COOH, 1 represents a group selected from the group consisting of —CO—NH ₂ , R ² may be the same or different, and —H, —F, —Cl, —I, —OH, —CH ₃ , —CF ₃ , —SO ₄ , —C (CH ₃ ) ₃ , —COOH, —CO—NH ₂ represents one group, R ³ is a tetravalent organic group, and m and n are m: n = 95: 5 to 60:40 is satisfied.) The polyimide resin solution for coating according to claim 1, wherein R ^{1 in the} general formula (1) is —CF ₃ and R ² is —H. The coating according to claim 1, wherein R ^{3 in the} general formula (1) is at least one tetravalent organic group selected from the following structural formula group (2). Polyimide resin solution.
The polyimide for coating according to any one of claims 1 to 3, wherein R ^{3 in the} general formula (1) is at least one tetravalent organic group represented by the following structural formula (3). Resin solution.
  The organic solvent is selected from the group consisting of N, N-dimethylformamide, N, N-dimethylacetamide, dioxolane, ethyl acetate, toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and cyclopentanone. The polyimide resin solution for coating according to any one of claims 1 to 4, wherein:   A laminate comprising the coating polyimide resin solution according to any one of claims 1 to 5 coated on a support.   An optical compensation member comprising the laminate according to claim 6.   A liquid crystal display device comprising the optical compensation member according to claim 7.