JP2016091032A - Polarizing plate and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizer which imparts only a small retardation, despite a manufacturing step of stretching a film comprising a transparent protective film and a hydrophilic polymer coating film laminated together, and offers superior optical properties, and to provide a manufacturing method therefor.SOLUTION: A polarizer is obtained by integrally stretch-treating a laminate of a base material film and a hydrophilic polymer coating film, and dyeing the hydrophilic polymer layer using a dichroic pigment, where the base material film is formed using a thermoplastic resin that minimizes an increase in retardation caused by stretch treatment and the base material layer functions as a transparent protective film. A diol component represented by a formula (1) is used for the thermoplastic resin. (In the formula, Zand Zrepresent aromatic hydrocarbon rings, Rand Rrepresent inactive substituent groups, k1 and k2 each represent an integer between 0 and 4, Rand Rrepresent alkylene groups, m1 and m2 each represent an integer of 1 or more, Rand Rrepresent inactive substituent groups, and p1 and p2 each represent an integer or 0 or more.)SELECTED DRAWING: None

Description

  The present invention relates to a polarizing plate useful as an element member of an image display device such as a liquid crystal display device or an organic electroluminescence (EL) display device, a production method thereof, and a laminated film (or stretched) useful for producing the polarizing plate. Laminated film) and a method for producing the same.

  The polarizing plate used in the image display device is required to have high transmittance and degree of polarization in order to provide an excellent image. A polarizer of such a polarizing plate has been conventionally dyed with a polyvinyl alcohol-based resin film with iodine or a dichroic dye, cross-linked, and oriented by a method such as uniaxial stretching, and then washed with water and dried. Manufactured. A transparent protective film such as triacetyl cellulose is bonded to one or both surfaces of this polarizer with an adhesive, and used as a polarizing plate.

  In the above production method, since a polyvinyl alcohol-based resin film is used, there is a limit to reducing the thickness of the film from the viewpoint of film processability, processability such as cutting of the film by high stretching, and productivity. There was a limit to the thickness of the polarizer. From such points, the polarizer obtained by the above production method usually has a thickness exceeding 30 μm. On the other hand, in recent years, in mobile devices such as smart phones and tablets, the thickness of image display devices has been regarded as important, and the demand for thinner polarizing plates has been increasing. The thickness of polyvinyl alcohol resin films used for polarizers has increased. Also, a thickness of less than 10 μm is required.

  In order to meet such demands, JP 2009-093074 A (Patent Document 1) describes a hydrophilic polymer solution (such as an acrylic resin film, a polypropylene film, or a norbornene resin film) in a base material layer (such as an acrylic resin film, a polypropylene film, or a norbornene resin film). Polyvinyl alcohol (PVA) aqueous solution) is applied and dried, the resulting laminate is stretched, a dichroic substance is adsorbed on the hydrophilic polymer layer of the stretched laminate, and dyed to produce a polarizing plate. And a protective film is also attached to the polarizer layer (PVA layer). This document also describes that the hydrophilic polymer layer is transferred to another substrate.

  Regarding the transfer of the hydrophilic polymer layer, Japanese Patent Application Laid-Open No. 2011-081399 (Patent Document 3), Japanese Patent Application Laid-Open No. 2012-13312 (Patent Document 4) and Japanese Patent Application Laid-Open No. 2012-073563 (Patent Document 5) include: PVA resin is applied to a base resin film (amorphous polyester resin film, etc.), the resulting laminated film is stretched, the stretched PVA resin layer is dyed with a dichroic dye, and the dyed PVA resin After a protective film (optical film) is bonded to the layer (polarizing film) via an adhesive, the base resin film is peeled and removed, and the polarizing film is transferred to the protective film (optical film) to produce a polarizing plate. It is described to do.

  Some of the polarizing plates using such a method have already been mass-produced. However, the polarizing plate manufactured by the mass production process is not formed by directly laminating a polyvinyl alcohol (PVA) resin on a transparent protective film, but is laminated with a base film as described in Patent Document 1. It is manufactured by transferring the stretched PVA resin layer to a transparent protective film.

  Specifically, it is manufactured by the following method. First, a PVA aqueous solution is coated on a polyethylene terephthalate (PET) film surface-treated by corona treatment or the like, and then dried, the laminated film on which a PVA coating film having a thickness of several μm is formed is wound on a roll, The film is stretched uniaxially at the free end and immersed in an aqueous iodine solution, then uniaxially stretched at the free end in water, washed with water, dried, and wound on a roll. The PVA layer of the stretched laminated film wound around the roll is pressure-bonded with the pressure-sensitive adhesive applied to the triacetyl cellulose film and the roll, the PET layer is peeled off, and the PVA layer is transferred to the triacetyl cellulose film and bonded. The polarizing plate is manufactured by winding it on a roll.

  In such a manufacturing method, the number of processes is large, the yield in the transfer process is reduced, and the transfer film on which the PVA layer is transferred is discarded, resulting in an increase in manufacturing cost.

  In order to improve the above production method, Japanese Patent Application Laid-Open No. 2011-1000016 (Patent Document 2) discloses that the hydrophilic polymer layer of the stretched laminate has a thickness of 2 to 10 μm, and the hydrophilic polymer layer is a polarizer. It is described that the base material layer functions as a transparent protective film. In the method described in this document, the transfer process of the PVA layer becomes unnecessary by using the base film coated with PVA as the transparent protective film.

  However, the stretching treatment increases the retardation of the base film, impairs optical isotropy, and cannot function as a transparent protective film. On the contrary, if the stretching is insufficient, the orientation of the PVA is lowered and a sufficient degree of polarization cannot be obtained. In particular, when a PET film, for example, is used as the base film, the expression of retardation is large with stretching and it is not suitable as a transparent protective film. On the other hand, when triacetyl cellulose is used as the base film, the glass transition temperature of triacetyl cellulose is high, so the stretching temperature is too high compared to the glass transition temperature of PVA, and the orientation of PVA is disturbed even when stretched. The degree of polarization cannot be improved, and the performance as a polarizing plate is lowered.

JP 2009-093074 A (claims, paragraph [0069], examples) JP 2011-1000016 (Claims) JP 2011-081399 A (Claims) JP 2012-133312 A (Claims) JP 2012-073563 A (Claims)

  Accordingly, an object of the present invention is to provide a polarizing plate having a small retardation and excellent optical characteristics even when a laminated film in which a transparent protective film and a hydrophilic polymer coating film are laminated, and a method for producing the same, Another object of the present invention is to provide a laminated film (or stretched laminated film) useful for forming such a polarizing plate and a method for producing the same.

  Another object of the present invention is to form a polarizing plate capable of achieving both high orientation of the hydrophilic polymer coating film and low retardation accompanying the orientation of the base film, a method for producing the same, and such a polarizing plate. The object is to provide a useful laminated film (or stretched laminated film) and a method for producing the same.

  Still another object of the present invention is to provide a laminated film (or stretched laminated film) useful for producing a polarizing plate with a small number of steps without requiring a transfer step of a polarizer to a transparent protective film, and a method for producing the same. Is to provide.

  Another object of the present invention is to provide a laminated film (or stretched laminated film) useful for producing a thin-film polarizing plate at low cost, a production method thereof, and a polarizing plate and a production method thereof.

  Still another object of the present invention is to provide an image display device using a polarizing plate (or an optical film laminated with a polarizing plate) and a polarizing plate (or an optical film laminated with a polarizing plate).

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that a base film formed of a thermoplastic resin (such as a polyester resin) having a 9,9-bisarylfluorene skeleton and a coating film of a hydrophilic polymer When a polarizing plate is produced by stretching the laminated film and dyeing the generated hydrophilic polymer layer with a dichroic dye, the retardation of the base film layer can be reduced even if the stretching treatment is performed. That the high orientation of the film and the low retardation accompanying the orientation of the base film can be compatible, and that the base film layer can function as a transparent protective layer without transferring the polarizer to another transparent protective film. As a result, the present invention has been completed.

  That is, the polarizing plate of the present invention comprises a hydrophilic polymer layer obtained by integrally stretching a base film and a coating film of a hydrophilic polymer formed on the surface of the base film in a laminated form. Is dyed with a dichroic dye. In such a polarizing plate, the base film is formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton.

  The thermoplastic resin may be a polyester resin having a diol component (A) and a dicarboxylic acid component (B) as a monomer component (polymerization component). In this thermoplastic resin, the diol component (A) Contains at least a fluorenediol component represented by the following formula (1), that is, 9,9-bis (hydroxy (poly) alkoxyaryl) fluorene (A1).

(Wherein Z ¹ and Z ² are aromatic hydrocarbon rings, R ^1a and R ^1b are inert to the reaction, k 1 and k 2 are each an integer of 0 to 4, R ^2a and R ^2b are alkylene groups, m 1 And m2 each represents an integer of 1 or more, R ^3a and R ^3b each represent a substituent inert to the reaction, and p1 and p2 each represent an integer of 0 or more.)

In the fluorenediol component (A1) represented by the formula (1), Z ¹ and Z ² are benzene rings or naphthalene rings, k 1 and k ² are 0, R ^2a and R ^2b are alkylene groups, and m 1 and m 2 are respectively An integer of 1 to 5, R ^3a and R ^3b may be an alkyl group, a cycloalkyl group, an aryl group, and p1 and p2 may each be an integer of 0 to 2. Such a fluorenediol component (A1) may be, for example, 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene when Z ¹ and Z ² are benzene rings.

In the thermoplastic resin, the diol component (A) includes a fluorenediol component (A1) represented by the formula (1), an aliphatic diol (A2-1), an alicyclic diol (A2-2), and And at least one diol component (A2) selected from aromatic diols (A2-3), for example, fluorenediol component (A1) represented by the formula (1) and aliphatic Diol (A2-1), for example, C _2-10 alkanediol (A2-1) such as ethylene glycol may be included. In the diol component (A), the ratio of the fluorenediol component (A1) represented by the formula (1) may be 15 mol% or more. For example, the diol component (A) comprises 9,9-bis (hydroxy (poly) C _2-6 alkoxy C _6-12 aryl) fluorene (A1) and C _2-6 alkanediol (A2-1), The former / the latter may be included at a ratio of about 20/80 to 90/10 (molar ratio).

The dicarboxylic acid component (B) is an aliphatic dicarboxylic acid or alkane dicarboxylic acid (B1-1), an alicyclic dicarboxylic acid (B1-2) and an aromatic dicarboxylic acid (B1-3). The acid (B1) may be included. The dicarboxylic acid component (B) contains at least C _4-12 cycloalkane-dicarboxylic acid (such as 1,4-cyclohexanedicarboxylic acid) (B1-2) and C _6-12 arene-dicarboxylic acid (such as terephthalic acid) ( It may contain at least one dicarboxylic acid (B1) selected from B1-3). In the dicarboxylic acid component (B), the proportion of the alicyclic dicarboxylic acid (B1-2) may be 50 mol% or more. For example, when the dicarboxylic acid component (B) contains C _5-10 cycloalkane-dicarboxylic acid (B1-2) and benzenedicarboxylic acid (such as terephthalic acid) (B1-3), the ratio between the two is The latter may be about 60/40 to 100/0 (molar ratio).

  The polyester resin having the diol component (A) and the dicarboxylic acid component (B) as monomer components may be a homopolyester resin, and at least one of the diol component (A) and the dicarboxylic acid component (B). Alternatively, a copolyester resin prepared using a plurality of monomer components may be used.

The thermoplastic resin may have a relatively high molecular weight. For example, the weight average molecular weight of the thermoplastic resin may be about 4 × 10 ⁴ to 15 × 10 ⁴ , and the glass transition temperature is 60 to 135. It may be about ° C. Further, the retardation Re of the stretched substrate film is small, and may be about 0 to 200 nm in terms of thickness 25 μm when measured at a wavelength of 590 nm.

  Furthermore, the hydrophilic polymer may contain a polyvinyl alcohol-based resin, and the stretched hydrophilic polymer layer may be thin, for example, about 1 to 10 μm.

  The polarizing plate of the present invention may have high optical properties, the degree of polarization may be 95% or more, and the single transmittance of the polarizing plate may be 30% or more.

  In such a polarizing plate, a hydrophilic polymer coating film is formed on the base film formed of the thermoplastic resin, the produced laminated film is stretched, and the stretched hydrophilic polymer layer has two colors. It can manufacture by dyeing with a sex pigment.

  The stretching condition of the laminated film may be a stretching temperature of about 60 to 150 ° C., a stretching ratio of about 4 to 8 times, or may be uniaxially stretched.

  The present invention also includes a laminated film before being subjected to a stretching treatment and a stretched laminated film before being subjected to dyeing with a dichroic dye on a hydrophilic polymer layer stretched by the stretching treatment. That is, the laminated film is a laminated film in which a transparent protective film and a hydrophilic polymer coating film are laminated, and the hydrophilic polymer coating film is stretched in a laminated form with the transparent protective film, and two colors The transparent protective film is formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton. The stretched laminated film is a stretched laminated film in which a transparent protective film and a hydrophilic polymer coating film are stretched in a laminated form (integrated form), and the stretched hydrophilic polymer layer has two colors. The transparent protective film is formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton.

  The present invention further includes a method for producing the laminated film and the stretched laminated film. The laminated film can be produced by forming a hydrophilic polymer coating film on one surface of a transparent protective film formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton. , 9-bisarylfluorene skeleton A thermoplastic film formed on one surface of a transparent protective film formed of a thermoplastic resin, and the resulting laminated film (transparent protective film and hydrophilic polymer coating film) Can be manufactured by stretching.

  In the present specification and claims, “9,9-bis (hydroxy (poly) alkoxyaryl) fluorene” means 9,9-bis (hydroxyalkoxyaryl) fluorene and 9 unless otherwise specified. , 9-bis (hydroxypolyalkoxyaryl) fluorene. In the present specification and claims, unless otherwise specified, the term “dicarboxylic acid component” refers not only to dicarboxylic acids but also ester-forming derivatives of dicarboxylic acids (eg, lower alkyl esters, acid halides, acid anhydrides). It is used to mean including things.

  In the present invention, since a film formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton is used as the base film, the stretched layer of the hydrophilic polymer coating film functions as a polarizer and is stretched. The material film can function as a transparent protective film layer having a small retardation, and a polarizing plate having excellent optical properties can be produced efficiently. In addition, since the base film is formed of a predetermined thermoplastic resin, the retardation can be reduced even if the base film is stretched or oriented while the hydrophilic polymer coating film is highly oriented, and these characteristics can be achieved at the same time. . Furthermore, a polarizing plate can be produced with a small number of steps without requiring a step of transferring the polarizer to the transparent protective film, which is industrially advantageous. Moreover, since the transparent protective film and the hydrophilic polymer coating film are stretched, the thin film polarizing plate (polarizer) can be manufactured at a low cost. Therefore, it is useful as a polarizing plate (or an optical film in which polarizing plates are laminated) of an image display device.

  In the polarizing plate of the present invention, a base film and a hydrophilic polymer coating film formed on the surface of the base film are stretched in a laminated form, and the stretched hydrophilic polymer layer is dichroic. It is dyed with a pigment. That is, the polarizing plate of the present invention includes a stretched laminated film obtained by stretching a laminated film (or coated film) obtained by coating or laminating a hydrophilic polymer coating film on a base film. In the laminated film in which the base film and the hydrophilic polymer coating film are laminated in close contact with each other, the base film and the hydrophilic polymer coating film are integrally stretched in the stretching process. Therefore, the stretched and dyed hydrophilic polymer coating film (hydrophilic polymer layer) can function as a polarizing plate (polarizer), and the stretched base film layer can function as a transparent protective film. The transfer process of the hydrophilic polymer layer (or polarizer layer) to the transparent protective film is not necessary. In addition, the dyed hydrophilic polymer layer (polarizer layer) can be thinned with the stretching treatment.

  As the base film, properties required as a transparent protective film of a conventional polarizer, for example, properties such as transparency, optical isotropy, mechanical strength, thermal stability, moderate water permeability, dimensional stability, etc. It is required to satisfy. In the present invention, in addition to these properties, further required properties such as high stretchability, low retardation even when uniaxially stretched at high magnification, and high adhesion to hydrophilic polymers In order to satisfy the above, the base film is formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton. Such a thermoplastic resin may be a polyamide resin or a polycarbonate resin, but is usually a polyester resin having a diol component (A) and a dicarboxylic acid component (B) as monomer components (polymerization component). There may be.

[Polyester resin]
The polyester resin is a resin in which the diol component (A) and the dicarboxylic acid component (B) are used as a polymerization component (monomer component) and polymerized together with esterification, and the diol component (A) and / or the dicarboxylic acid component (B ) Has a 9,9-bisarylfluorene skeleton.

[Diol component (A)]
The diol component (A) includes at least a fluorenediol component represented by the following formula (1), that is, a diol component (A1) having a hydroxy (poly) alkoxyaryl group at the 9,9-position of fluorene. Yes.

(Full orange all component (A1))
The diol component (A1) can be typically represented by the following formula (1).

(Wherein Z ¹ and Z ² are aromatic hydrocarbon rings, R ^1a and R ^1b are inert substituents for the reaction, k1 and k2 are each an integer of 0 to 4, R ^2a and R ^2b are alkylene groups, m1 and m2 are each an integer of 1 or more, R ^3a and R ^3b are substituents inert to the reaction, and p1 and p2 are each an integer of 0 or more.)

In the above formula (1), the aromatic hydrocarbon ring represented by the rings Z ¹ and Z ² is, for example, a monocyclic hydrocarbon ring (such as a benzene ring) or a condensed polycyclic hydrocarbon ring. The condensed polycyclic hydrocarbon ring may be a condensed bicyclic hydrocarbon ring (for example, a C _8-12 condensed bicyclic hydrocarbon ring such as a naphthalene ring or an azulene ring, preferably a C _9-12 condensed dicyclic ring). Cyclic hydrocarbon ring, more preferably C _10-12 condensed bicyclic hydrocarbon ring), condensed tricyclic hydrocarbon ring (for example, C _12-14 condensed tricyclic hydrocarbon ring such as anthracene ring, phenanthrene ring, etc.) Or the like. Rings Z ¹ and Z ² may be different from each other, and may usually be the same. Preferred rings Z ¹ and Z ² include a benzene ring, a condensed bicyclic or tricyclic aromatic hydrocarbon ring (a naphthalene ring, an anthracene ring, etc.), and a C _6-12 arene ring (particularly a benzene ring, Naphthalene ring).

In the formula (1), examples of the groups R ^1a and R ^1b include a cyano group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydrocarbon group [eg, alkyl group, aryl group, (phenyl group) Non-reactive substituents such as a C _6-10 aryl group such as a halogen atom, a cyano group or an alkyl group (particularly an alkyl group). Examples of the alkyl group include C _1-12 alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and a t-butyl group (for example, a C _1-8 alkyl group, particularly a C group such as a methyl group). _1-4 alkyl group) and the like. The types of the radicals R ^1a and R ^1b may be the same or different from one another. Substitution positions of the groups R ^1a and R ^1b may be, for example, 2-position, 7-position, 2- and 7-position of fluorene. The substitution numbers k1 and k2 may be about 0 to 4 (for example, 0 to 2), preferably 0 or 1, particularly 0. The substitution numbers k1 and k2 may be the same or different from each other. In addition, when k1 and k2 are plural (two or more), the types of groups R ^1a and groups R ^1b substituted on each benzene ring of fluorene may be the same or different.

In the formula (1), examples of the alkylene group represented by the groups R ^2a and R ^2b include an ethylene group, a propylene group (1,2-propanediyl group), a trimethylene group, and a 1,2-butanediyl group. A linear or branched C _2-6 alkylene group such as a tetramethylene group, preferably a C _2-4 alkylene group, and more preferably a C _2-3 alkylene group. The groups R ^2a and R ^2b may be different from each other and may usually be the same.

The number (addition moles) m1 and m2 of oxyalkylene groups (OR ^2a and OR ^2b ) may be 1 or more, for example, 1 to 12 (for example, 1 to 8), preferably 1 to 5 (for example, 1 to 4), more preferably 1 to 3 (for example, 1 or 2), especially 1. The substitution numbers m1 and m2 may be the same or different. When m1 and m2 are 2 or more, the repeating unit of the alkylene group of the groups R ^2a and R ^2b may be formed of different types of alkylene groups, and may be generally formed of the same alkylene group. .

In the formula (1), the substitution positions of the hydroxy (poly) alkoxy groups [—O— (R ^2a O) _m1 —H] and [—O— (R ^2b O) _m2 —H] are not particularly limited, For example, when rings Z ¹ and Z ² are benzene rings, they may be 2-position, 3-position or 4-position, and are usually 3-position or 4-position (preferably 4-position). In many cases. The position of the hydroxy (poly) alkoxy group is such that when the rings Z ¹ and Z ² are naphthalene rings, the 1,5-position, 1,6-position, 2,5-position, 2,6-position, etc. It may be substituted with a naphthyl group in an arbitrary positional relationship, and is usually often substituted with a naphthyl group in a 1,5-position or 2,6-position positional relationship.

Examples of the substituent R ^3a and R ^3b include an alkyl group (eg, a C _1-6 alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and a t-butyl group), a cycloalkyl group, and the like. (For example, C _5-8 cycloalkyl group such as cyclohexyl group), aryl group (for example, C _6-10 aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, etc.), aralkyl group (for example, benzyl group) A hydrocarbon group such as a C _6-10 aryl-C _1-4 alkyl group such as a phenethyl group; an alkoxy group (eg, a C _1-6 alkoxy group such as a methoxy group or an ethoxy group), a cycloalkyloxy group (e.g., a C _5-8 cycloalkyl group such as cyclohexyl group), an aryloxy group (e.g., Fe Carboxymethyl including _{C 6-10} aryloxy group such as a group), aralkyloxy group (e.g., _{C 6-10} aryl _{-C 1-4} alkyl group such as a benzyl group); an alkylthio group (e.g., such as a methylthio group C _1-8 alkylthio group etc.); acyl group (eg C _1-6 alkyl-carbonyl group such as acetyl group); halogen atom (eg fluorine atom, chlorine atom, bromine atom, iodine atom etc.); nitro group A cyano group; a dialkylamino group (eg, a diC _1-4 alkyl-amino group such as a dimethylamino group); a dialkylcarbonylamino group (eg, a diC _1-4 alkyl-carbonylamino group such as a diacetylamino group); And the like.

Preferred groups R ^3a and R ^3b include, for example, an alkyl group (C _1-6 alkyl group, preferably C _1-4 alkyl group, particularly a methyl group), an alkoxy group (C _1-4 alkoxy group etc.), cycloalkyl, and the like. Group (C _5-8 cycloalkyl group), aryl group (C _6-12 aryl group such as phenyl group) and the like.

  The substitution numbers p1 and p2 may be, for example, 0 to 4 (for example, 0 to 3), preferably 0 to 2 (for example, 0 or 1), respectively. The substitution numbers p1 and p2 may be the same or different from each other.

The substitution positions of the groups R ^3a and R ^3b are not particularly limited. For example, when the rings Z ¹ and Z ² are benzene rings, when the substitution numbers p1 and p2 are 1, the 2-position, the 3-position or the 4-position When the substitution numbers p1 and p2 are 2, they may be in the 2,6-position, 3,4-position, or 3,5-position.

In the fluorenediol component (A1) represented by the formula (1), the rings Z ¹ and Z ² are benzene rings or naphthalene rings, k 1 and k ² are 0, R ^2a and R ^2b are alkylene groups, and m 1 and m 2 are Each may be an integer of 1 to 5, R ^3a and R ^3b may be an alkyl group, a cycloalkyl group, an aryl group, and p1 and p2 may each be an integer of 0 to 2.

  Typical fluorenediol components (A1) include 9,9-bis (hydroxy (poly) alkoxyphenyl) fluorenes, 9,9-bis (hydroxy (poly) alkoxynaphthyl) fluorenes, and the like.

As 9,9-bis (hydroxy (poly) alkoxyphenyl) fluorenes, in the formula (1), the rings Z ¹ and Z ² are substituted or unsubstituted benzene rings, and R ^2a and R ^2b are linear or A branched C _2-4 alkylene group, compounds in which m1 and m2 are 1, and k1 and k2 are each 0, such as (i) 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene, 9 , 9-bis [4- (2-hydroxypropoxy) phenyl] fluorene such as 9,9-bis (hydroxy _{C 2-4} alkoxyphenyl) fluorene, (ii) 9,9-bis [4- (2-hydroxyethoxy ) -3-methylphenyl] fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-isopropylphenyl) fluorene, 9,9-bis (4- (2-hydride) Loxyethoxy) -3-isobutylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-t-butylphenyl) fluorene, 9,9-bis [4- (2-hydroxyethoxy)- 9,9-bis (hydroxy C _2-4 alkoxy such as 3,5-dimethylphenyl] fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-tert-butyl-5-methylphenyl) fluorene 9,9-bis (hydroxy C _2-4 ) such as mono- or di-C _1-4 alkylphenyl) fluorene, (iii) 9,9-bis (4- (2-hydroxyethoxy) -3-cyclohexylphenyl) fluorene alkoxy _{C 5-10} cycloalkyl phenyl) fluorene, (iv) 9,9-bis [4- (2-hydroxyethoxy) -3-phenyl-phenylene ] Fluorene, 9,9-bis [4- (2-hydroxypropoxy) -3-phenyl phenyl] 9,9-bis fluorene (hydroxy _{C 2-4} alkoxy _{C 6-10} aryl phenyl) fluorene; ring Z A compound in which ¹ and Z ² are substituted or unsubstituted benzene rings, R ^2a and R ^2b are linear or branched C _2-4 alkylene groups, m1 and m2 are 2 to 5, and k1 and k2 are 0, respectively. That is, in the above compounds (i) to (iv), a compound in which m1 and m2 are 2 to 5, such as 9,9-bis (hydroxyC _2-4 alkoxyC _2-4 alkoxyphenyl) fluorene, 9- bis (hydroxy _{C 2-4} alkoxy _{C 2-4} alkoxy - mono- or _{di-C 1-4} alkyl phenyl) fluorene, 9,9-bis (hydroxy _{C 2-} An alkoxy _{C 2-4} alkoxy _{C 6-10} aryl phenyl) fluorene includes.

As 9,9-bis (hydroxy (poly) alkoxynaphthyl) fluorenes, for example, rings Z ¹ and Z ² are substituted or unsubstituted naphthalene rings, and R ^2a and R ^2b are linear or branched C _{2. -4} alkylene group, a compound in which m1 and m2 are 1, and k1 and k2 are each 0, for example, (v) 9,9-bis (hydroxyalkoxynaphthyl) fluorene [for example, 9,9-bis [6- (2 -Hydroxyethoxy) -2-naphthyl] fluorene, 9,9-bis [5- (2-hydroxyethoxy) -1-naphthyl] fluorene, 9,9-bis [6- (2-hydroxypropoxy) -2-naphthyl ] fluorene such as 9,9-bis (hydroxy _{C 2-4} alkoxy naphthyl) fluorene; ring ^{Z 1} and ^{Z 2} are substituted or unsubstituted naphthalene ring, ^{R 2} And ^{R 2b} is linear or branched _{C 2-4} alkylene group, m1 and m2 is 2 to 5, compounds k1 and k2 are each 0, i.e., the compound in (v), m1 and m2 are 2 compounds which are 5, for example, and the like 9,9-bis (hydroxy _{C 2-4} alkoxy _{C 2-4} alkoxy naphthyl) fluorene.

These fluorenediol components (A1) can be used alone or in combination of two or more. Preferred fluorenediol component (A1) is 9,9-bis (hydroxyC _2-4 alkoxyphenyl) fluorene, such as 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9,9-bis 9,9-bis (C _1-4 alkyl-hydroxy C _2-4 alkoxyphenyl) fluorene such as (4- (2-hydroxyethoxy) -3-methylphenyl) fluorene, 9,9-bis (4- (2 - hydroxyethoxy) -3-phenylphenyl) 9,9-bis fluorene (hydroxy _{C 2-4} alkoxyphenyl phenyl) fluorene, 9,9-bis (5- (2-hydroxyethoxy) -1-naphthyl) fluorene , 9,9-bis [6- (2-hydroxyethoxy) -2-naphthyl) fluorene, etc. Alkoxy _{C 2-4} alkoxy naphthyl] fluorene, in particular 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, with 9,9-bis (6- (2-hydroxyethoxy) -2-naphthyl) fluorene is there.

  The diol component (A) only needs to contain at least the fluorenediol component (A1). The fluorenediol component (A1), the aliphatic diol (A2-1), the alicyclic diol (A2-2), and the fragrance At least one other diol component (A2) selected from group diol (A2-3) may be contained to form a copolyester resin.

(Other diol component (A2))
The other diol component (A2) may be at least one selected from the aliphatic diol (A2-1), the alicyclic diol (A2-2), and the aromatic diol (A2-3).

  By combining the fluorenediol component (A1) and the aliphatic diol (A2-1), the polymerization efficiency can be improved and the toughness and heat resistance of the copolyester resin can be adjusted, as well as low birefringence copolymerization. A polyester resin can be prepared. In particular, the retardation can be suppressed even when stretched, and the glass transition temperature (or stretching temperature) of the copolyester resin can be adjusted in accordance with the stretching temperature of the hydrophilic polymer.

Examples of the aliphatic diol (A2-1) include linear or branched alkanediol (ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3 C _2-10 alkanediols such as butanediol, 1,4-butanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, neopentylglycol, 1,6-hexanediol , Preferably C _2-6 alkanediol, more preferably C _2-4 alkanediol), polyalkanediol (eg, di- or tri-C _2-4 alkanediol such as diethylene glycol, dipropylene glycol, triethylene glycol, etc.), etc. Can be illustrated. The aliphatic diol (A2-1) may be used alone or in combination of two or more. Preferred aliphatic diols (A2-1) are alkane diols, for example C _2-4 alkane diols such as ethylene glycol.

  By combining the fluorenediol component (A1) and the alicyclic diol (A2-2), a low birefringence copolymer polyester resin can be prepared and stretched without significantly reducing the heat resistance of the polyester resin. Can also suppress the expression of retardation.

As the alicyclic diol (A2-2), for example, cycloalkanediol (for example, C _5-8 cycloalkanediol such as cyclohexanediol), di (hydroxyalkyl) cycloalkane (for example, di ( Hydroxy C _1-4 alkyl) C _5-8 cycloalkane and the like), isosorbide and the like. The alicyclic diol (A2-2) may be used alone or in combination of two or more.

Examples of the aromatic diol (A2-3) include dihydroxyarene (hydroquinone, resorcinol, etc.), bisphenols (eg, bis (hydroxyphenyl) C _1-10 alkanes such as biphenol, bisphenol A, etc.), di (hydroxyalkyl). ) Arenes (for example, di (hydroxy C _1-4 alkyl) C _6-10 arenes such as 1,3-benzenedimethanol and 1,4-benzenedimethanol), alkylene oxide adducts of bisphenols, and the like. . Aromatic diols (A2-3) may be used alone or in combination of two or more.

Of the other diol components (A2), aliphatic diol (A2-1) and alicyclic diol (A2-2), particularly at least aliphatic diol (A2-1) are preferred. That is, the diol component (A) includes a fluorenediol component (A1) represented by the above formula (1) such as 9,9-bis (hydroxy (poly) C _2-6 alkoxy C _6-12 aryl) fluorene, and the like. And an aliphatic diol (preferably a C _2-10 alkane diol such as ethylene glycol, particularly a C _2-6 alkane diol) (A2-1).

  The proportion of the fluorenediol component (A1) in the diol component (A) (or the proportion of units derived from the fluorenediol component (A1) in the structural unit of the polyester) is 10 mol% or more (for example, 15 to 15%). 90 mol%), preferably 15 mol% (for example, 15 to 85 mol%), more preferably 20 mol% or more (for example, 20 to 80 mol%), particularly 25 mol% or more (for example, 25 to 70 mol%). ) Degree. The ratio of the fluorenediol component (A1) can be selected according to the type of the other diol component (A2), and the ratio of the fluorenediol component (A1) to the other diol component (A2) is, for example, the former / the latter (Molar ratio) = 10/90 to 100/0 (for example, 15/85 to 95/5) can be selected, for example, 20/80 to 90/10 (for example, 25/75 to 80/20) , Preferably, it may be about 30/70 to 75/25 (for example, 40/60 to 70/30). In addition, a retardation becomes small, so that there is much content rate of the structural unit derived from fluorangeol (A1).

  In a preferred embodiment, the fluorenediol component (A1) and the aliphatic diol (alkanediol) (A2-1) are mixed with the former / the latter (molar ratio) = 10/90 to 90/10, preferably 25/75 to The copolymerized polyester resin may be formed by introducing it into the polyester resin at a ratio of 85/15, more preferably about 30/70 to 80/20. In particular, since the optical properties of the polarizing plate can be improved, the ratio of the fluorenediol component (A1) to the aliphatic diol (A2-1) is, for example, the former / the latter (molar ratio) = 50/50 to 90. / 10, preferably 60/40 to 88/12, more preferably about 70/30 to 85/15 (particularly 75/25 to 82/18).

  In particular, the copolyester resin having a large proportion of aliphatic diol (alkanediol) (A2-1) is novel and is not particularly known to be used as a resin for a protective film. In such a copolyester resin, since the monomer component includes a fluorenediol component (A1) and an aliphatic diol (alkanediol), the birefringence of the copolyester resin is small, and the retardation of the copolyester resin is not reduced. The increase can be effectively suppressed. In such a copolyester resin, the ratio of the fluorenediol component (A1) and the aliphatic diol (alkanediol) (A2-1) is, for example, the former / the latter (molar ratio) = 10 / 90-60. / 40 (for example, 15/85 to 55/45), 20/80 to 50/50 (for example, 25/75 to 50/50), more preferably 30/70 to 45/55 ( For example, it may be about 30/70 to 40/60).

  In addition, the ratio of each diol may be a ratio of units derived from each diol component in the structural unit of the polyester, or may be a component ratio in the reaction system.

  If necessary, a small amount of a polyol component having three or more hydroxyl groups [for example, alkane polyol such as glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, etc.] [for example, diol component (A) and polyol component 10 mol% or less (for example, about 0.1 to 8 mol%, preferably about 0.2 to 5 mol%) may be used.

[Dicarboxylic acid component (B)]
The dicarboxylic acid component (B) is an aliphatic dicarboxylic acid or alkane dicarboxylic acid (B1-1), an alicyclic dicarboxylic acid (B1-2) and an aromatic dicarboxylic acid (B1-3). The acid (B1) may be included.

Examples of the aliphatic dicarboxylic acid (B1-1) include alkane dicarboxylic acids (for example, C _4-14 alkane dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid, preferably C _6-12 alkane dicarboxylic acids). Acid), unsaturated aliphatic dicarboxylic acid (for example, C _2-10 alkene-dicarboxylic acid such as maleic acid, fumaric acid, and itaconic acid). A preferred aliphatic dicarboxylic acid (B1-1) is an alkanedicarboxylic acid.

Examples of the alicyclic dicarboxylic acid component (B1-2) include cycloalkane dicarboxylic acids (for example, C _5-10 cycloalkane dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid). , Di- or tricycloalkane dicarboxylic acids (eg, decalin dicarboxylic acid, norbornane dicarboxylic acid, adamantane dicarboxylic acid, tricyclodecane dicarboxylic acid, etc.), cycloalkene dicarboxylic acids (eg, C _5-10 cycloalkene-- such as cyclohexene dicarboxylic acid, etc. Dicarboxylic acid), di- or tricycloalkene dicarboxylic acid (for example, norbornene dicarboxylic acid) and the like.

Examples of the aromatic dicarboxylic acid component (B1-3), for example, monocyclic aromatic dicarboxylic acids [such as phthalic acid, terephthalic acid, such as isophthalic acid, alkyl isophthalate (e.g., 4-methyl isophthalic acid C _1- C _6-10 arene dicarboxylic acid and the like such as _4- alkylisophthalic acid], condensed polycyclic aromatic dicarboxylic acid [eg naphthalenedicarboxylic acid (eg 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, etc.) 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, etc.), condensed polycyclic C _10-24 arene-dicarboxylic acid such as anthracene dicarboxylic acid and phenanthrene dicarboxylic acid, preferably the fused polycyclic _{C 10-16} arene - dicarboxylic acid, still more preferably Fused polycyclic _{C 10-14} arenes - such as dicarboxylic acids, aryl array Nji carboxylic acid [e.g., biphenyl dicarboxylic acid (e.g., 2,2'-biphenyl dicarboxylic acid, 4,4'-biphenyl and di-carboxylic acids), such as C _6-10 aryl-C _6-10 arene dicarboxylic acid etc.], diaryl alkane dicarboxylic acid [eg diphenyl alkane dicarboxylic acid (eg 4,4′-diphenylmethane dicarboxylic acid etc.), etc. diC _6-10 aryl C _{1 -6} alkane-dicarboxylic acid and the like], diaryl ketone dicarboxylic acid [for example, di-C _6-10 aryl ketone-dicarboxylic acid such as diphenyl ketone dicarboxylic acid (for example, 4.4′-diphenyl ketone dicarboxylic acid)], etc. Is mentioned.

  The aromatic dicarboxylic acid component (B1-3) is a dicarboxylic acid having a fluorene skeleton, such as 2,7-dicarboxyfluorene, 2,7-dicarboxy-9,9-dimethylfluorene, It may be a compound (B2) represented by 1) or (2-2). A dicarboxylic acid (fluorene carboxylic acid) having such a fluorene skeleton can reduce birefringence without reducing the refractive index and heat resistance, and can effectively suppress an increase in retardation associated with stretching.

(Wherein R ^4a and R ^4b are substituents inert to the reaction, q1 and q2 are each an integer of 0 to 4, and X ^1a and X ^1b are divalent hydrocarbon groups which may have a substituent. R represents an integer of 0 to 4.)

In the above formulas (2-1) and (2-2), the hydrocarbon group represented by the group X ^1a or X ^1b is a linear or branched alkylene group such as a methylene group, an ethylene group, or trimethylene. And C _1-8 alkylene groups such as a group, a propylene group, a 2-ethylethylene group, and a 2-methylpropane-1,3-diyl group. Preferred alkylene groups are linear or branched C _1-6 alkylene groups (eg, C _1-4 alkylene such as methylene group, ethylene group, trimethylene group, propylene group, 2-methylpropane-1,3-diyl group). Group).

  Examples of the substituent of the alkylene group include an aryl group (such as a phenyl group) and a cycloalkyl group (such as a cyclohexyl group).

X ^1a is often a linear or branched C _2-4 alkylene group (eg, ethylene group, propylene group), and X ^1b is a linear or branched C _1-3 alkylene group (eg, Methylene group, ethylene group) in many cases. The alkylene group X ^1a having a substituent may be, for example, a 1-phenylethylene group, a 1-phenylpropane-1,2-diyl group, or the like.

  The coefficient r can be selected from an integer of 0 to 4, and may be generally 0 to 2, preferably 0 or 1.

In the formulas (2-1) and (2-2), the groups R ^4a and R ^4b , q1 and q2 are the same as R ^1a and R ^1b , k1 and k2 described in the formula (1) including preferred embodiments. It is.

A typical compound represented by the formula (2-1) is a compound in which X ^1a is a C _2-6 alkylene group, such as 9,9-bis (2-carboxyethyl) fluorene, 9,9-bis. 9,9-bis (carboxy C _2-6 alkyl) fluorene such as (2-carboxypropyl) fluorene. A representative compound represented by the formula (2-2) is a compound in which r = 0 and X ^1b is a C _1-6 alkylene group, for example, 9- (1-carboxy-2-carboxyethyl) ) Fluorene, r = 1 and X ^1b is a C _1-6 alkylene group, for example, 9- (carboxy-carboxy C _2-6 such as 9- (2-carboxy-3-carboxypropyl) fluorene Alkyl) fluorene and the like. The full orange carboxylic acid may be used alone or in combination of two or more. A preferred fluorenedicarboxylic acid component is a compound represented by the formula (2-1), for example, 9,9-bis (carboxyalkyl) fluorenes [for example, 9,9-bis (carboxyC _2-4 alkyl) fluorene. ] Etc. are included.

The dicarboxylic acid component (B) is not limited to a free carboxylic acid, but may be an ester-forming derivative of the dicarboxylic acid, such as an ester [for example, an alkyl ester [for example, a lower alkyl ester such as a methyl ester or an ethyl ester (for example, , C _1-4 alkyl ester, especially C _1-2 alkyl ester, etc.]], acid halide (eg, acid chloride, etc.), acid anhydride, and the like.

These dicarboxylic acid components (B) can be used alone or in combination of two or more. In order to reduce birefringence, aliphatic dicarboxylic acid (B1-1) and alicyclic dicarboxylic acid (B1-2) are preferable. In order to improve heat resistance, aromatic dicarboxylic acid (B1-3) For example, a condensed polycyclic aromatic dicarboxylic acid component such as naphthalenedicarboxylic acid, a monocyclic aromatic dicarboxylic acid component such as terephthalic acid (benzenecarboxylic acid, etc.) and the like are preferable. In addition, the said full orange carboxylic acid can improve heat resistance, can reduce birefringence, and can suppress the increase in the retardation accompanying extending | stretching. In particular, the alicyclic dicarboxylic acid (B1-2) can reduce birefringence without impairing heat resistance, and can suppress an increase in retardation associated with stretching. Therefore, the dicarboxylic acid component (B) includes alicyclic dicarboxylic acids (for example, C _4-12 cycloalkane-dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid) (B1-2) and aromatic dicarboxylic acids (terephthalic acid). C _6-12 arene such as - dicarboxylic acid, including fluorene carboxylic acid) (B1-3) at least one dicarboxylic acid selected from (B1), of in particular at least alicyclic dicarboxylic acids (B1-2) Is preferred.

  The dicarboxylic acid component (B) is alicyclic dicarboxylic acid (B1-2) in an amount of 10 to 100 mol% (for example, 20 to 95 mol%), preferably 30 to 100 mol% (for example, 40 to 90 mol%). It may be included in a proportion. In a preferred embodiment, the dicarboxylic acid component (B) contains the alicyclic dicarboxylic acid (B1-2) in an amount of usually 50 mol% or more (50 to 100 mol%), preferably 60 mol% or more (for example, 65 to 95). Mol%), more preferably 70 mol% or more (for example, 75 to 90 mol%), particularly 80 mol% or more (80 to 100 mol%).

The ratio of alicyclic dicarboxylic acid (B1-2) such as C _5-10 cycloalkane-dicarboxylic acid and aromatic dicarboxylic acid (benzene dicarboxylic acid) (B1-3) is the former / the latter (molar ratio) = 25/75 to 100/0 (for example, 50/50 to 100/0), preferably 60/40 to 100/0 (for example, 65/35 to 95/5), more preferably 70/20 to 100/0 (For example, about 75/25 to 90/10). In particular, from the viewpoint of improving the optical properties of the polarizing plate, the ratio of the alicyclic dicarboxylic acid (B1-2) and the aromatic dicarboxylic acid (B1-3) is, for example, the former / the latter (molar ratio) = 80 / It may be 20 to 100/0, preferably 90/10 to 100/0, and more preferably about 95/5 to 100/0. The dicarboxylic acid component (B) may be an alicyclic dicarboxylic acid alone.

A preferred embodiment of the polyester resin is fluorenediol (A1) and alkanediol ( _C2-4 alkanediol etc.) (A2-1) with the former / the latter (molar ratio) = 15 / 85-55 / 45 (for example, Diol component (A) contained at a ratio of 20/80 to 50/50), C _5-10 cycloalkane-dicarboxylic acid (1,4-cyclohexanedicarboxylic acid etc.) (B1-2) and aromatic dicarboxylic acid (terephthalate) Acid, benzenedicarboxylic acid such as isophthalic acid, C _6-10 arenedicarboxylic acid such as naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid (B1-3), and the former / the latter (molar ratio) = 75 / It is a novel copolyester resin formed with a dicarboxylic acid component (B) contained at a ratio of 25 to 100/0 (for example, 80/20 to 100/0) Excellent in stretchability, be stretched retardation is small, is suitable for forming a transparent protective film layer can be prepared drawable copolyester resin so as to correspond to the stretching temperature of the hydrophilic polymer.

  The ratio of each dicarboxylic acid may be a ratio of units derived from each dicarboxylic acid component in the structural unit of the polyester, or may be a component ratio in the reaction system.

  If necessary, a small amount of a polycarboxylic acid component having three or more carboxyl groups (for example, an aromatic polycarboxylic acid such as trimellitic acid or pyromellitic acid or an ester-forming derivative thereof) [for example, dicarboxylic acid] You may use 10 mol% or less (for example, about 0.1-8 mol%, Preferably about 0.2-5 mol%) with respect to the total amount of an acid component and a polycarboxylic acid component].

  The polyester resin can be prepared by the reaction of the diol component (A) and the dicarboxylic acid component (B), and the production method of the polyester resin is not particularly limited, and is a conventional method such as a transesterification method or a direct polymerization method. It may be prepared by a polymerization method, a solution polymerization method, an interfacial polymerization method, or the like. In the polymerization reaction, an ester exchange catalyst, a polycondensation catalyst, a heat stabilizer, a light stabilizer, a polymerization regulator, or the like may be used.

  Transesterification catalysts include alkaline earth metals (magnesium, calcium, barium, etc.), transition metals (manganese, zinc, cobalt, titanium, etc.), etc. (alkoxides, organic acid salts, inorganic acid salts, metal oxides, etc.) Etc. The type of polycondensation catalyst is not particularly limited, and the alkaline earth metal, transition metal, periodic table group 13 metal (such as aluminum), periodic table group 14 metal (such as germanium), periodic table group 15 metal (antimony) Etc.), for example, germanium compounds such as germanium dioxide, germanium hydroxide, germanium oxalate, germanium tetraethoxide, germanium-n-butoxide, antimony compounds such as antimony trioxide, antimony acetate, and antimony ethylene recolate, Examples thereof include titanium compounds such as tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, titanium oxalate, and titanium potassium oxalate. These catalysts may be used alone or in admixture of two or more. Examples of the heat stabilizer include phosphorus compounds such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, phosphorous acid, trimethyl phosphite, and triethyl phosphite.

  In the reaction, the use ratio of the diol component (A) and the dicarboxylic acid component (B) can be selected from the same range as described above, and a predetermined component may be used in excess if necessary. For example, a diol component such as ethylene glycol that can be distilled from the reaction system may be used in excess of the proportion of units introduced into the polyester resin. The reaction may be performed in the presence or absence of a solvent.

The reaction can be performed in an inert gas (nitrogen, helium, etc.) atmosphere. The reaction can also be performed under reduced pressure (for example, about 1 × 10 ² to 1 × 10 ⁴ Pa). Depending on the polymerization method, for example, the reaction temperature in the melt polymerization method may be 150 to 300 ° C, preferably 180 to 290 ° C, more preferably about 200 to 280 ° C.

[Resin characteristics and production method]
The thermoplastic resin (especially polyester resin) has a feature that the value of birefringence is small, and the value of birefringence (3 times birefringence) when the test piece is stretched 3 times is, for example, −100 × 10 ^−4. To + 120 × 10 ⁻⁴ (for example, −80 × 10 ⁻⁴ to + 100 × 10 ⁻⁴ ), preferably −50 × 10 ⁻⁴ to + 70 × 10 ⁻⁴ (for example, −30 × 10 ⁻⁴ to + 50 × 10) ^-4 ) degree. Three-fold birefringence is measured using a retardation measuring device (RETS-100, manufactured by Otsuka Electronics Co., Ltd.) at a measurement temperature of 20 ° C., with a parallel Nicol rotation method, and measuring the retardation value at a wavelength of 600 nm. It can be calculated by dividing by the thickness of the part. In addition, the test piece used for the measurement press-molds the resin at 160 to 240 ° C., prepares a film having a thickness of 100 to 400 μm, cuts the obtained film into a 15 × 50 mm strip, and has a glass transition temperature (Tg). ) It can be prepared by stretching uniaxially at a temperature of + 10 ° C. at a stretch ratio of 3 times and 25 mm / min.

The thermoplastic resin (particularly the polyester resin) may have a relatively high molecular weight. For example, the weight average molecular weight of the thermoplastic resin (particularly the polyester resin) is 4 × 10 ⁴ to 15 × 10 ⁴ (for example, 5 × 10 ^{4 to} 13 × 10 ⁴ ), preferably 6 × 10 ^{4 to} 12 × 10 ⁴ (for example, 7 × 10 ^{4 to} 11 × 10 ⁴ ), and more preferably 7.5 × 10 ⁴ to 10 × 10 ⁴ ( For example, it may be about 8 × 10 ⁴ to 10 × 10 ⁴ ). Furthermore, the weight average molecular weight of the thermoplastic resin (particularly polyester resin) is, for example, 3 × 10 ⁴ to 10 × 10 ⁴ , preferably 3.5 × 10 ⁴ to 8 × 10, in relation to the optical properties of the polarizing plate. ⁴ , More preferably, it may be about 4 × 10 ^{4 to} 5 × 10 ⁴ . The molecular weight can be measured as a molecular weight in terms of polystyrene using gel permeation chromatography.

  Furthermore, the glass transition temperature of the polyester resin is relatively low as compared with a general thermoplastic resin having a 9,9-bisarylfluorene unit, for example, 60 to 135 ° C. (for example, 65 to 125 ° C.), preferably 70-120 degreeC (for example, 75-115 degreeC), More preferably, about 80-110 degreeC (for example, 85-100 degreeC) may be sufficient. Furthermore, from the point which is excellent in heat resistance, the glass transition temperature of a polyester resin may be 90-135 degreeC, for example, Preferably it is 100-130 degreeC, More preferably, about 110-125 degreeC may be sufficient. The glass transition temperature can be measured using a differential scanning calorimeter.

  Since it has a 9,9-bisarylfluorene skeleton, a base film formed of such a thermoplastic resin (particularly a polyester resin) has a small retardation even when the stretch ratio is high, and is suitable as a transparent protective film. That is, in order to control the expression of retardation due to uniaxial stretching to the minimum, it is effective to use a polymer having as small intrinsic birefringence as possible derived from the structure of the polymer. The thermoplastic resin (copolyester resin) is composed of 9,9-bisarylfluorene units in the structural unit, two main arene rings (benzene ring, naphthalene ring, etc.) and side chain fluorene rings ( The three condensed aromatic rings have a conformation perpendicular to each other, so that the polarizability cancels out and exhibits extremely small intrinsic birefringence. Therefore, the polyester resin (particularly copolymerized polyester resin) having the 9,9-bisarylfluorene unit is characterized in that the retardation does not increase even when uniaxially stretched.

  Furthermore, since the thermoplastic resin (especially polyester resin) is used, it is possible to achieve both high orientation of the hydrophilic polymer coating film and low retardation accompanying the orientation of the base film, and the polarizing plate can be produced effectively. That is, in the method in which the base film and the hydrophilic polymer coating are integrally uniaxially stretched, the hydrophilic polymer coating is required to be highly oriented, while the base film has the polymer. Even if it is oriented, low retardation is required. For this reason, in ordinary polymer films, as described above, the advanced orientation of the hydrophilic polymer coating film and the low retardation associated with the orientation of the base film are contradictory requirements, making it difficult to achieve both. It is. On the other hand, in this invention, while forming a base film with the polyester resin (especially copolymer polyester resin) which has a 9, 9- bis aryl fluorene unit, while being able to adjust a glass transition temperature, it is peculiar to resin. As a property, it has the property that the development of retardation after stretching is very small, so even if the coating film of hydrophilic polymer is highly stretched and oriented, the retardation of the base film layer can be reduced and the conflicting required performance Can be compatible.

  In order to stretch the base film at a high magnification, the molecular weight needs to be large to some extent. However, as shown by the formula (1), when a monomer having a bulky 9,9-bisarylfluorene unit is used, the degree of polymerization cannot be increased and it is difficult to obtain a high molecular weight resin. On the other hand, when the proportion of the monomer having 9,9-bisarylfluorene units is reduced, the molecular weight increases, but at the same time the glass transition temperature also decreases. There is. Therefore, it is necessary to design the glass transition temperature of the thermoplastic resin (particularly polyester resin) from the viewpoints of stretching conditions such as stretching temperature and stretch ratio, and heat resistance as a polarizing plate. In particular, a polyester resin (such as a copolyester resin) having a suitable glass transition temperature and molecular weight is stretched under suitable stretching conditions, thereby increasing the degree of orientation of the hydrophilic polymer and the substrate after stretching. The expression of retardation of the film can be minimized.

  Furthermore, a typical completely saponified polyvinyl alcohol used for a polarizing plate of an image display device has a glass transition temperature of 85 ° C., and is uniaxial at a temperature as close as possible to the glass transition temperature or higher than the glass transition temperature. Stretching is convenient for highly orienting polyvinyl alcohol, and it is further advantageous that it can be stretched at a high magnification. On the other hand, the stretching of the base film is preferably performed at a temperature at which the expression of retardation is reduced, that is, at a temperature as high as possible as compared with the glass transition temperature. However, it is difficult to find a stretching temperature suitable for both the hydrophilic polymer and the base film resin by lowering the glass transition temperature of the base film below 85 ° C. When the polyester resin is used, the heat resistance level of the polarizing plate is not satisfied. In this invention, since the said polyester resin is used, even if it extends | stretches by a high magnification, a low retardation can be maintained, maintaining heat resistance.

  Note that the thermoplastic resin (particularly the polyester resin) may contain an additive. Examples of the additives include stabilizers (for example, antioxidants, ultraviolet absorbers, heat stabilizers, anti-coloring agents), lubricants, plasticizers, mold release agents, flame retardants, antistatic agents, and the like. The content of these additives can be selected to such an extent that the transparency, heat resistance, optical isotropy, mechanical strength, water permeability, etc. of the base film are not impaired.

[Laminated film (stretched laminated film), polarizing plate and production method thereof]
The base film is formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton, and the thickness of the base film is not particularly limited, and is, for example, 1 to 300 μm, preferably 5 to 200 μm, and more preferably 10 It may be about ˜150 μm (for example, 15 to 100 μm).

  A thin film such as a surface treatment such as a corona discharge treatment or a primer layer may be formed on the surface of the base film in order to enhance the adhesion to the hydrophilic polymer coating film.

  The method for forming the base film is not particularly limited, and for example, an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, a hot press method, and the like can be used. Law, casting method. In the T-die method, an extruder equipped with a single screw or twin screw can be used. In the casting method, the resin is dissolved in a soluble organic solvent (tetrahydrofuran, acetone, methyl ethyl ketone, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, etc.), and the solution is removed from a smooth peeling base, for example, heat resistant. It can be produced by casting on a flat plate or roll such as a film, a steel belt, or a metal foil, evaporating and removing the solvent, and peeling from the peeling base.

[Hydrophilic polymer]
Examples of the hydrophilic polymer that forms the coating film of the hydrophilic polymer include polyvinyl alcohol resins such as polyvinyl alcohol and derivatives thereof. Examples of polyvinyl alcohol derivatives include modified polyvinyl alcohol resins copolymerized with copolymerizable monomers, polyvinyl formal, and polyvinyl acetal. As the copolymerizable monomer, a component copolymerizable with a carboxylic acid vinyl ester such as vinyl acetate, for example, an unsaturated carboxylic acid or a derivative thereof ((meth) acrylic acid, (meth) acrylic acid alkyl ester, etc.), Examples thereof include unsaturated sulfonic acids or derivatives thereof (such as styrene sulfonic acid and 2-vinylnaphthalene sulfonic acid), olefins (such as α-C _2-10 olefins such as ethylene and propylene), and the like. These copolymerizable monomers can be used alone or in combination of two or more. The amount of the copolymerizable monomer used may be about 0 to 25 mol% with respect to the total monomers.

  A preferred hydrophilic polymer is polyvinyl alcohol. The degree of saponification of polyvinyl alcohol may be, for example, about 80 to 100%. That is, a fully saponified polyvinyl alcohol having a saponification degree of 95 to 100%, preferably about 97 to 100%, and a partially saponified polyvinyl alcohol having a saponification degree of 80 to 95%, preferably about 85 to 93%. May be. The degree of polymerization of the polyvinyl alcohol-based resin may be, for example, about 100 to 10000, preferably about 1000 to 10000.

[Polarizing plate and manufacturing method thereof]
The polarizing plate is a step of forming a hydrophilic polymer coating film by applying an aqueous solution containing a hydrophilic polymer to one surface of the base film (transparent protective film) and then drying it (lamination). A step of preparing a film), a step of stretching the produced laminated film (coating film) (a step of preparing a stretched laminated film), a step of dyeing the stretched hydrophilic polymer layer with a dichroic dye, In addition, it can be prepared through a step of cross-linking the hydrophilic polymer layer if necessary, and the stretched hydrophilic polymer layer (polarizer) can be transferred to another substrate (transparent protective film) via an adhesive. No transfer process is required. Therefore, the number of processes can be greatly reduced, the manufacturing equipment can be simplified, and the yield is improved. Furthermore, secondary materials such as a transfer film are not required, and the manufacturing cost can be greatly reduced. In addition, the extending | stretching process of a laminated | multilayer film may be performed in several processes including the preliminary extending | stretching preliminarily stretched with a small magnification, and the dyeing | staining process and crosslinking process of a laminated | multilayer film may be performed in arbitrary processes. For example, the laminated film may be prestretched, the produced prestretched laminated film may be dyed and / or crosslinked, and the produced dyed prestretched laminated film may be further stretched to prepare a polarizing plate. .

  An aqueous solution (coating solution) containing a hydrophilic polymer can be prepared by dissolving a hydrophilic polymer in a powder form or the like in hot water. The concentration of the hydrophilic polymer in the aqueous solution is not particularly limited, and may be, for example, about 1 to 30% by weight (for example, 5 to 15% by weight). Application of the aqueous solution onto the substrate film may be performed by a wire bar coating method, a roll coating method, a spin coating method, a screen coating method, a fountain coating method, a dipping method, a spray method, or the like. A laminated film can be prepared by drying the coating film of the hydrophilic polymer formed on at least one surface of the base film. The drying temperature of the coating film is usually 50 to 150 ° C., preferably about 80 to 130 ° C., and the drying time is usually about 5 to 30 minutes.

  The thickness of the dry coating film of the hydrophilic polymer is not particularly limited, and may be, for example, about 1 to 50 μm (for example, 2 to 30 μm), usually 2 to 20 μm (for example, 3 to 15 μm), preferably About 5-10 micrometers (for example, 5-8 micrometers) may be sufficient.

  In addition, the thickness of a laminated | multilayer film may be about 2-350 micrometers (for example, 5-250 micrometers), for example, Preferably about 10-150 micrometers (for example, 15-75 micrometers) may be sufficient.

  The stretching process is performed in the form of a laminated film (integrated form) in which a base film and a hydrophilic polymer coating are laminated, and the base film and the hydrophilic polymer coating are integrated. It is stretched and a stretched laminated film can be prepared.

  The stretching process is usually performed by uniaxial stretching. Uniaxial stretching may be either longitudinal stretching that extends in the longitudinal direction of the laminated film (coating film) or lateral stretching that extends in the width direction. The stretching method is not particularly limited, and a conventional method such as an inter-roll stretching method, a heated roll stretching method, a compression stretching method, or a tenter stretching method can be used.

  The stretching treatment may be either a dry stretching method performed in air or a wet stretching method performed in water, or both may be used in combination. Depending on the glass transition temperature of the base film resin, wet stretching may not be possible. Therefore, it is preferable to use a dry stretching method with few restrictions on the stretching temperature. The stretching temperature of the laminated film can be selected according to the glass transition temperature of the hydrophilic polymer and the base film, and in particular, a temperature not lower than the glass transition temperature (Tg) of the base film [for example, Tg ° C to (Tg + 50 ° C). ], For example, (Tg + 1) ° C to (Tg + 30) ° C, preferably (Tg + 3) ° C to (Tg + 20) ° C, more preferably (Tg + 5) ° C to (Tg + 15) ° C. The specific stretching temperature may be, for example, 60 to 150 ° C., preferably 70 to 140 ° C., more preferably about 75 to 130 ° C., and even a highly heat-resistant film without breaking. From the point which can be extended | stretched easily, for example, 100-160 degreeC, Preferably it is 110-150 degreeC, More preferably, about 120-140 degreeC may be sufficient.

  As long as the degree of polarization as a polarizing plate can be secured, the stretch ratio of the laminated film is not particularly limited, and may be about 1.5 to 15 times (for example, 3 to 8 times), but usually 4 to 8 times. (For example, 4 to 7 times). If the draw ratio is small, the orientation of the hydrophilic polymer, and hence the degree of polarization, decreases.If the draw ratio is too high, the stretched laminated film breaks or the orientation direction of the hydrophilic polymer is disturbed. The degree of polarization decreases.

  In the present invention, the thickness of the stretched hydrophilic polymer layer, and hence the thickness of the polarizing plate (polarizer layer) can be reduced. In the stretched laminated film, the stretched hydrophilic polymer layer has a thickness of, for example, about 0.1 to 10 μm (for example, 1 to 10 μm), preferably about 1.5 to 8 μm (for example, 2 to 7 μm). Also good. The stretched laminated film may have a thickness of, for example, 1 to 150 μm (for example, 5 to 100 μm), preferably about 10 to 75 μm.

  Further, in the stretched laminated film and the polarizing plate, the retardation Re of the stretched base film layer is also small, and when measured at a wavelength of 590 nm, the thickness is converted into a range of about 0 to 200 nm (for example, 0 to 150 nm) in terms of 25 μm. It may be selected, and may be about 0 to 120 nm (for example, 1 to 100 nm), preferably about 5 to 80 nm (for example, 10 to 75 nm), and more preferably about 15 to 50 nm (for example, 20 to 40 nm).

  The dyeing treatment is performed by bringing the dichroic dye into contact with the hydrophilic polymer layer of the stretched laminated film (specifically, immersing the stretched laminated film in a solution containing the dichroic dye) and adsorbing it. Can do. Illustrative examples of the dichroic dye include iodine and organic dyes. For organic dyes, reference can be made to paragraph [0054] of Patent Document 2. A preferred dichroic dye is iodine.

  For the dyeing treatment, an aqueous solution having a dichroic dye (or iodine) concentration of about 0.02 to 5% by weight (for example, 0.05 to 0.2% by weight) can be used. Alternatively, a dissolution aid of iodine) may be included. Examples of the dissolution aid include alkali metal iodides such as potassium iodide that promote iodine solubility, and the concentration of the dissolution aid ranges from 0.1 to 5% by weight (for example, 0.2 to 1.. 5% by weight). The immersion temperature is 20 to 40 ° C., preferably 20 to 35 ° C., and the immersion time can be selected from the range of about 10 seconds to 30 minutes, even if it is about 15 seconds to 5 minutes (for example, 150 to 300 seconds). However, it may be, for example, 3 to 30 minutes, preferably 5 to 20 minutes, and more preferably about 8 to 15 minutes from the viewpoint of improving the optical properties of the polarizing plate. The dyeing process can be performed before or simultaneously with or after the stretching process.

  When the hydrophilic polymer layer is oriented in the stretching direction by the stretching process and the dichroic dye (or iodine) is adsorbed by the dyeing process, the dichroic dye (or iodine) is arranged in the stretching direction to make the dichroism. It functions as a polarizer that absorbs light oscillating in the stretching direction and transmits light oscillating in a direction perpendicular to the stretching direction.

  The crosslinking treatment is not always necessary, but it is effective for improving the heat resistance of the polarizer. Examples of the crosslinking agent for the crosslinking treatment include boron compounds such as boron, borate, and borax, glyoxal, and glutaraldehyde. When a boron compound is used as the crosslinking agent, the crosslinking treatment is performed at a boron concentration of 0.1 to 5% by weight (for example, 0.36 to 0.83% by weight) and a potassium iodide concentration of 0.1 to 10% by weight (for example, It is preferable to use an aqueous solution of about 4 to 7% by weight). When potassium iodide is added to the boron aqueous solution, a lightly colored polarizer, that is, a neutral gray polarizer can be obtained.

  The crosslinking treatment can be performed by immersing in an aqueous solution of a crosslinking agent. The immersion temperature may be 15 to 60 ° C. (for example, 20 to 50 ° C.), and the immersion time may be about 15 seconds to 5 minutes (for example, 30 to 120 seconds).

  In addition, the said dyeing | staining process and a crosslinking process can also be performed simultaneously by mix | blending the said crosslinking agent in a dyeing | staining solution.

  After the crosslinking treatment, the polarizing plate can be prepared by washing and drying. The washing treatment can be performed by washing (washing treatment) the dyed and cross-linked stretched laminated film with an alkali metal iodide aqueous solution and / or pure water (ion exchange water, distilled water, etc.). It may be soaked in water and washed with water. The washing treatment with the alkali metal iodide aqueous solution and the water washing treatment may be performed by immersing the stretched laminated film at 10 to 45 ° C. (for example, 25 to 30 ° C.) for about 10 to 300 seconds (for example, 10 to 30 seconds). Good.

  Drying can be performed at a temperature of 40 to 100 ° C. for about 10 to 500 seconds.

  The obtained laminated film may be heated and fixed, for example, at a temperature of about 100 to 160 ° C, preferably about 110 to 150 ° C, and more preferably about 120 to 140 ° C. The heating time is, for example, 30 seconds to 1 hour, preferably 1 to 30 minutes, more preferably about 5 to 20 minutes.

  In the stretched laminated film thus obtained, the stretched base film layer can be used as a transparent protective film layer, and is transparently protected on a dyed / crosslinked hydrophilic polymer layer (polarizer or polarizer layer). A polarizing plate can be produced by laminating films.

  As a transparent protective film to be bonded to a hydrophilic polymer layer (polarizer or polarizer layer), an optically transparent film having high adhesion to a hydrophilic polymer coating film, such as a triacetyl cellulose film, cellulose, etc. Examples thereof include cellulose ester films such as acetate propionate films, modified acrylic resin films, and cyclic olefin resin films. From the viewpoints of transparency, mechanical strength, and optical isotropy, a triacetyl cellulose film is preferable. The thickness of the transparent protective film may be about 1 to 200 μm (for example, 5 to 150 μm).

  In order to improve the adhesive force with the hydrophilic polymer layer, the transparent protective film may be subjected to a surface modification treatment. For example, surface modification may be performed by corona discharge treatment, glow discharge treatment, acid treatment, alkali treatment, ultraviolet irradiation treatment, or the like.

  As the adhesive, a water-based adhesive is usually used. The aqueous adhesive is not particularly limited, and examples thereof include an isocyanate adhesive, a polyvinyl alcohol adhesive, a gelatin adhesive, a vinyl latex adhesive, an aqueous polyurethane adhesive, and an aqueous polyester adhesive. A preferred adhesive is a polyvinyl alcohol-based adhesive.

  In the method of the present invention, not only a thinner polarizing plate can be produced, but also the laminated film is subjected to a stretching treatment, so that the film can be prevented from being cut due to the stretching treatment, and the productivity can be improved.

  The polarizing plate of the present invention has high optical properties. Specifically, the degree of polarization may be 95% or more, for example, 96 to 99.99%, preferably 98 to 99.98%. (For example, 99 to 99.97%), more preferably 99.2 to 99.95% (particularly 99.5 to 99.9%). In the present invention, the degree of polarization can be measured using a retardation measuring device, and in detail, can be measured by the method described in the examples described later.

  The polarizing plate of the present invention is also excellent in transparency, and the single transmittance of the polarizing plate may be 30% or more, for example, 30 to 49%, preferably 35 to 48%, more preferably 40 to 40%. It is about 45%. In the present invention, the single transmittance can be measured by using a retardation measuring device, and can be measured in detail by the method described in Examples described later.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

  In addition, the characteristic of resin and the characteristic of a polarizing plate were measured as follows.

(Molecular weight)
Using gel permeation chromatography (manufactured by Tosoh Corporation, “HLC-8120GPC”), the sample was dissolved in chloroform, and the molecular weight (weight average molecular weight Mw) was measured in terms of polystyrene.

(Glass-transition temperature)
The glass transition temperature Tg of the polyester resin was measured using a differential scanning calorimeter (“DSC 6220” manufactured by Seiko Instruments Inc.) according to JIS K7121.

(Phase difference)
The base film was stretched under the same stretching conditions (temperature and magnification) as in the preparation of the polarizing plate, and the retardation of the obtained stretched film was measured.

  That is, the phase difference of the stretched polyester resin film was measured using a phase difference meter (“RETS-100” manufactured by Otsuka Electronics Co., Ltd.) at a wavelength of 590 nm, the refractive index nx in the slow axis direction of the film, The refractive index ny in the axial direction and the refractive index nz in the thickness direction were measured, and the front phase difference Re was calculated from these measured values and the film thickness d based on the following formula. The table shows the front phase difference Re converted to a thickness of 25 μm.

      Front phase difference Re = (nx−ny) × d

(Single transmittance of polarizing plate)
In the state of the laminated polarizing plate (with a transparent protective film), the single transmittance of the polarizing plate was measured using a retardation measuring device (“RETS-100” manufactured by Otsuka Electronics Co., Ltd.). The single transmittance is the transmittance (Tp) when two identical polarizing plates are superimposed with their transmission axes parallel to each other, and the transmittance (Tc) when they are superimposed with their transmission axes orthogonal to each other. ) Was measured at a wavelength of 550 nm and calculated by the following equation.

      Single transmittance (%) = (Tp + Tc) / 2

(Polarization degree of polarizing plate)
In the state of the laminated polarizing plate (with a transparent protective film), the optical property (polarization degree) of the polarizing plate was measured using a retardation measuring device (“RETS-100” manufactured by Otsuka Electronics Co., Ltd.). The degree of polarization is the transmittance (Tp) when two identical polarizing plates are superimposed with their transmission axes parallel to each other, and the transmittance (Tc) when they are superimposed with their transmission axes orthogonal to each other. Was measured at a wavelength of 550 nm and calculated by the following equation.

Polarization degree (%) = {(Tp−Tc) / (Tp + Tc)} ^1/2 × 100

(Polyester resin preparation example 1)
9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene (Osaka Gas Chemical Co., Ltd., hereafter referred to as BPEF) 0.25 mol, ethylene glycol (Kanto Chemical Co., Ltd., EG) 2.75 mol, 1,4-cyclohexanedicarboxylic acid (manufactured by Nikko Rica Co., Ltd., hereinafter referred to as CHDA) 1.00 mol was charged into the reaction vessel and dissolved, and as a transesterification catalyst, Manganese acetate tetrahydrate (manufactured by Kanto Chemical Co., Ltd.) 2.0 × 10 ⁻⁴ mol and calcium acetate monohydrate (manufactured by Kanto Chemical Co., Ltd.) 8.0 × 10 ⁻⁴ mol were added. The mixture was gradually heated to 230 ° C. in accordance with a conventional method while stirring to conduct a transesterification reaction. After extracting a predetermined amount of methanol out of the system, the polymerization catalyst germanium oxide (manufactured by Kanto Chemical Co., Ltd.) 2.0 × 10 ⁻³ mol and the coloring inhibitor trimethyl phosphoric acid (manufactured by Kanto Chemical Co., Ltd.) 1 .4 × 10 ⁻³ mol was added, heated while reducing pressure, and after reaching 270 ° C. and 0.13 kPa, stirring was continued until a predetermined torque was reached. The polymer was extracted from the bottom of the can, and the strand that passed through the water was cut to obtain a pellet (resin 1).

  The obtained pellets were analyzed by NMR. As shown in Table 1, 100 mol% of the carboxylic acid component introduced into the polyester resin was derived from CHDA, 25 mol% of the diol component was derived from BPEF, and 75 mol%. Was derived from EG.

(Preparation Examples 2 to 4 of polyester resin)
Pellets (resins 2 to 4) were obtained in the same manner as in Preparation Example 1 except that the composition of the polyester resin (introduction composition of the diol component and / or dicarboxylic acid component) was changed to the conditions shown in Table 1. In Table 1, DMT represents dimethyl terephthalate (manufactured by Kanto Chemical Co., Inc.). The composition ratio shown in Table 1 is the composition ratio of the polyester resin analyzed by NMR similarly to the above. Polyester resin pellets were prepared in the same manner as in Preparation Example 1 using Resins 2 and 3 as diol components in the raw material composition (prepared composition) using 0.8 mol of BPEF and 2.2 mol of EG.

[Example 1]
(Polyester film production)
The pellet (resin 2) obtained in Preparation Example 2 was melt-pressed with a hot press apparatus to prepare a film.

(Preparation of aqueous polyvinyl alcohol solution)
Polyvinyl alcohol (Wako Pure Chemical Industries, Ltd., average polymerization degree 2000, saponification degree 98%) was dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 10% by weight.

(Formation of polyvinyl alcohol coating)
The surface of the polyester film, which is a base film, is subjected to corona discharge treatment, coated with the aqueous polyvinyl alcohol solution using an applicator, and then dried at Tg-20 ° C. for 10 minutes, and the polyvinyl alcohol coating film is formed on the base film. Formed. The thickness of the dried polyvinyl alcohol layer (polarizing layer) was about 10 μm.

(Extension process)
The laminated film on which the polyvinyl alcohol coating film was formed was subjected to free end uniaxial stretching at each temperature and stretching ratio shown in Table 2 to prepare a stretched laminated film.

(Boric acid treatment / dyeing treatment)
The stretched laminated film was immersed in a boric acid aqueous solution (boric acid / water = 3/97 (weight ratio)) at 30 ° C. for 30 seconds. Then, it was immersed in the iodine solution (iodine / potassium iodide / water = 0.3 / 2.1 / 97.6 (weight ratio)) of 30 degreeC for the time of Table 2, and the polarizing plate was obtained.

[Examples 4 to 20 and Comparative Example 1]
A polarizing plate was obtained in the same manner as in Example 1 except that the pellet type and film stretching conditions were as shown in Table 2. In Examples 9 to 20, the obtained polarizing plate (stretched film) was heat-fixed at the same temperature as the stretching temperature for 10 minutes, and in Examples 17 to 18 and 20, 5% by weight of iodine Washed with an aqueous potassium halide solution for 420 seconds.

[Examples 2-3]
(Boric acid treatment / stretching treatment)
The laminated film formed with the polyvinyl alcohol coating film obtained in the same manner as in Example 1 was immersed in an aqueous boric acid solution (boric acid / water = 3/97 (weight ratio)) at 30 ° C. for 30 seconds. The laminated film after immersion was subjected to free end uniaxial stretching at a temperature and a stretching ratio shown in Table 2 in an aqueous boric acid solution (boric acid / potassium iodide / water = 4/5/91 (weight ratio)). A stretched laminated film was obtained.

(Dyeing process)
The obtained stretched laminated film was immersed in an iodine solution (iodine / potassium iodide / water = 0.3 / 2.1 / 97.6 (weight ratio)) at 30 ° C. for the time described in Table 2.

  The results are shown in Table 2.

  From Table 2, in the present invention, the thickness of the polarizer layer can be reduced, the retardation is small even when the base film is stretched, and the stretched base film layer can function as a transparent protective film. It is possible to achieve both stretching and low retardation of the base film layer. On the other hand, in Comparative Example 1, the film was stretched under the conditions of 85 ° C. × 6 times and 130 ° C. × 6 times.

The thermoplastic resin (especially polyester resin) used in the present invention has excellent optical properties such as high refractive index, low birefringence, and high transparency, and suppresses an increase in retardation even when stretched. In addition, by adjusting the composition of the monomer of the resin, the thermoplastic resin (particularly, the polyester resin) can be stretched in conformity with the stretching conditions of the hydrophilic polymer. Therefore, the polarizing plate (polarizing film) of this invention is useful as an optical film of image display apparatuses, such as a liquid crystal display device and an organic electroluminescence display, especially as a display member, individually or laminated | stacked with a protective film.

Claims (17)

  A polarizing plate in which a base film and a coating film of a hydrophilic polymer formed on the surface of the base film are stretched in a laminated form, and the stretched hydrophilic polymer layer is dyed with a dichroic dye The polarizing plate is formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton. The thermoplastic resin is a polyester resin having a diol component (A) and a dicarboxylic acid component (B) as monomer components, and the diol component (A) is at least represented by the following formula (1):

(Wherein Z ¹ and Z ² are aromatic hydrocarbon rings, R ^1a and R ^1b are inert substituents for the reaction, k1 and k2 are each an integer of 0 to 4, R ^2a and R ^2b are alkylene groups, m1 and m2 are each an integer of 1 or more, R ^3a and R ^3b are substituents inert to the reaction, and p1 and p2 are each an integer of 0 or more.)
The polarizing plate of Claim 1 containing the full orange all component (A1) represented by these. The thermoplastic resin is a polyester resin having a diol component (A) and a dicarboxylic acid component (B) as monomer components,
The diol component (A) is a fluorenediol component (A1) represented by the formula (1) of claim 2, an aliphatic diol (A2-1), an alicyclic diol (A2-2), and an aromatic diol. And at least one diol component (A2) selected from (A2-3),
The dicarboxylic acid component (B) is at least one dicarboxylic acid (B1) selected from aliphatic dicarboxylic acid (B1-1), alicyclic dicarboxylic acid (B1-2) and aromatic dicarboxylic acid (B1-3) The polarizing plate according to claim 1, which is a copolyester resin containing The thermoplastic resin is a polyester resin having a diol component (A) and a dicarboxylic acid component (B) as monomer components, and the diol component (A) is represented by Z ¹ in formula (1) of claim 2 and Z ² is a benzene ring or naphthalene ring, k1 and k2 are each 0, R ^2a and R ^2b are alkylene groups, m1 and m2 are each an integer of 1 to 5, R ^3a and R ^3b are alkyl groups cycloalkyl groups, aryl groups , A fluorenediol component (A1) in which p1 and p2 are each an integer of 0 to 2, and a C _2-10 alkanediol (A2-1),
The dicarboxylic acid component (B) is at least one dicarboxylic acid (B1) selected from at least C _4-12 cycloalkane-dicarboxylic acid (B1-2) and C _6-12 arene-dicarboxylic acid (B1-3). The polarizing plate according to claim 1, which is a copolyester resin containing.   A diol component (A) in which the thermoplastic resin contains the fluorenediol component (A1) represented by the formula (1) of claim 2 in a proportion of 15 mol% or more, and an alicyclic dicarboxylic acid (B1-2) The polarizing plate according to claim 1, wherein the polarizing plate is a polyester resin having a dicarboxylic acid component (B) containing 50 mol% or more as a monomer component. The thermoplastic resin comprises 9,9-bis (hydroxy (poly) C _2-6 alkoxy C _6-12 aryl) fluorene (A1) and C _2-6 alkanediol (A2-1), the former / the latter = 20. Diol component (A) containing at a ratio of / 80 to 90/10 (molar ratio), C _5-10 cycloalkane-dicarboxylic acid (B1-2) and benzenedicarboxylic acid (B1-3) The polarizing plate according to any one of claims 1 to 5, which is a copolyester resin having a dicarboxylic acid component (B) contained at a ratio of 60/40 to 100/0 (molar ratio) as a monomer component.   The polarizing plate according to claim 1, wherein the retardation Re of the stretched substrate film is 0 to 200 nm in terms of a thickness of 25 μm when measured at a wavelength of 590 nm. The polarizing plate according to claim 1, wherein the thermoplastic resin has a weight average molecular weight of 4 × 10 ⁴ to 15 × 10 ⁴ and a glass transition temperature of 60 to 135 ° C.   The polarizing plate according to claim 1, wherein the hydrophilic polymer contains a polyvinyl alcohol-based resin.   The polarizing plate according to claim 1, wherein the stretched hydrophilic polymer layer has a thickness of 1 to 10 μm.   The polarizing plate according to any one of claims 1 to 10, which has a degree of polarization of 95% or more and a single transmittance of 30% or more.   A method for producing a polarizing plate by forming a coating film of a hydrophilic polymer on a base film, stretching the produced laminated film, dyeing the stretched hydrophilic polymer layer with a dichroic dye, A method for producing a polarizing plate, wherein the substrate film is formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton.   The method for producing a polarizing plate according to claim 12, wherein the laminated film is uniaxially stretched at a stretching temperature of 60 to 150 ° C and a stretching ratio of 4 to 8 times.   A stretched laminated film in which a transparent protective film and a hydrophilic polymer coating film are stretched in a laminated form, wherein the stretched hydrophilic polymer layer is dyed with a dichroic dye to form a polarizer A stretched laminated film in which the transparent protective film is formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton.   The method for producing a stretched laminated film according to claim 14, wherein a hydrophilic polymer coating film is formed on one surface of the transparent protective film, and the produced laminated film is stretched.   A laminated film in which a transparent protective film and a hydrophilic polymer coating film are laminated, wherein the hydrophilic polymer coating film is stretched in a laminated form with a transparent protective film and dyed with a dichroic dye. A laminated film, which is a coating film for forming a polarizer, and the transparent protective film is formed of a thermoplastic resin having a 9,9-bisarylfluorene skeleton. The method for producing a laminated film according to claim 16, wherein a hydrophilic polymer coating film is formed on one surface of the transparent protective film.