JP7568617B2 - Dicarboxylic acids, their production method and use - Google Patents

Description

The present invention relates to a novel dicarboxylic acid or derivative thereof having a fluorene skeleton, as well as a method for producing the same and uses thereof.

Optical plastics (or optical resin materials) are superior to optical glass in terms of light weight, impact resistance (or flexibility), safety, and moldability (or productivity), and are used in a variety of optical components. However, their optical properties, such as refractive index and birefringence, and heat resistance (thermal stability), are still inferior to those of optical glass, and their use may be limited depending on the application and usage environment, so efforts are underway to improve them.

Patent Document 1 discloses a polyester resin having as its polymerization components a diol component (A) including a diol component (A1) having a hydroxy(poly)alkoxy fused polycyclic aromatic group at each of the 9,9-positions of the fluorene skeleton, and a dicarboxylic acid component (B) including a dicarboxylic acid component (B1) having a fluorene skeleton.

Furthermore, Patent Document 2 discloses a thermoplastic resin containing a repeating unit represented by the following formula (1):

(In the formula, ring Z represents an aromatic hydrocarbon ring; R ¹ and R ² represent a hydrocarbon group having 1 to 12 carbon atoms which may contain a hydrogen atom, a halogen atom, or an aromatic group; Ar ¹ and Ar ² represent an aromatic group having 6 to 10 carbon atoms which may contain a substituent; L ¹ and L ² represent a divalent linking group; j and k represent integers of 0 or more; m and n represent 0 or 1; and W is at least one selected from the group represented by the following formula (2) or (3).)

(In the formula, X represents a divalent linking group.)

JP 2016-69643 A International Publication No. 2019/044214

In the examples of Patent Document 1, a polyester resin is prepared by reacting a dicarboxylic acid component containing 9,9-di(2-methoxycarbonyl)fluorene (FDPM) with a diol component containing 9,9-bis[6-(2-hydroxyethoxy)-2-naphthyl]fluorene (BNEF), and the resulting polyester resin exhibits both a high refractive index and low birefringence and a high glass transition temperature.

However, in recent years, with the increasing performance of optical devices such as cameras and image display devices, more advanced properties are also required for optical components, and even the polyester resin obtained in Patent Document 1 may not be able to fully satisfy such required properties.

In addition, in the examples of Patent Document 2, polycarbonate resins, polyester carbonate resins, polyester resins, etc. are prepared that contain 9,9-bis[4-(2-hydroxyethoxy)phenyl]-2,7-di(2-naphthyl)fluorene (BPDN2) and the like as a diol component (polymerization component).

Although these resins also have a relatively good balance of high refractive index, low birefringence, and high glass transition temperature, this is still not sufficient, and it is particularly difficult to achieve a better balance between high refractive index and low birefringence.

Therefore, there is a demand for the development of resins or resin raw materials with excellent optical properties and heat resistance.

Therefore, the object of the present invention is to provide a novel dicarboxylic acid or its derivative exhibiting a high refractive index and high heat resistance, as well as a production method and use thereof.

As a result of extensive research to achieve the above object, the inventors discovered that a dicarboxylic acid having a specific chemical structure in which aryl groups are bonded to positions 1 to 8 of a fluorene skeleton has excellent optical properties and heat resistance, and that when used as a polymerization component, it is unexpectedly possible to form a resin with remarkably excellent properties, even though the structural unit described in Patent Document 2 does not have an aryl group at the 9,9-position that tends to improve the refractive index and glass transition temperature, and thus completed the present invention.

That is, the dicarboxylic acid or its derivative of the present invention is represented by the following formula (I).

(In the formula, Z ^1a and Z ^1b each independently represent an arene ring, R ^1a and R ^1b each independently represent a substituent, k1 and k2 each independently represent an integer of 0 or more, m1 and m2 each independently represent an integer of 0 to 4, R ^2a and R ^2b each independently represent a substituent, n1 and n2 each independently represent an integer of 0 to 4, A ^1a and A ^1b each independently represent a linear or branched alkylene group, m1+n1 and m2+n2 each are 4 or less, and at least one of m1 and m2 is 1 or more).

In the above formula (I), Z ^1a and Z ^1b may be a fused polycyclic arene ring, m1 and m2 may be an integer of 1 to 2, and A ^1a and A ^1b may be a linear or branched C _2-6 alkylene group.

The present invention encompasses a method for producing the dicarboxylic acid or a derivative thereof, comprising a step of coupling reaction between a compound having a fluorene skeleton and a compound having an arene ring skeleton corresponding to rings ^Z1a and ^Z1b in formula (I).

The present invention also includes a resin containing at least a first dicarboxylic acid unit (A1) represented by the following formula (1) as the dicarboxylic acid unit (A):

(In the formula, Z ^1a , Z ^1b , R ^1a , R ^1b , k1, k2, ml, m2, R ^2a , R ^2b , n1, n2, A ^1a , A ^1b , ml+n1, and m2+n2 are each the same as in formula (I) above).

The resin may be a polyester resin having the dicarboxylic acid unit (A) and the diol unit (B). The diol unit (B) may contain at least one diol unit selected from the first diol unit (B1) represented by the following formula (3), the second diol unit (B2) represented by the following formula (4), and the third diol unit (B3) represented by the following formula (5), and preferably contains at least one diol unit selected from the first diol unit (B1) and the second diol unit (B2).

(In the formula, ^A2 represents a linear or branched alkylene group, and q represents an integer of 1 or more).

(In the formula, ^Z3a and ^Z3b each independently represent an arene ring, ^R4 represents a substituent, r represents an integer of 0 to 8, ^R5a and ^R5b each independently represent a substituent, s1 and s2 each independently represent an integer of 0 or more, ^A3a and ^A3b each independently represent a linear or branched alkylene group, and t1 and t2 each independently represent an integer of 0 or more).

(In the formula, ^A4 represents a direct bond (single bond) or a linear or branched alkylene group, ^A5a and ^A5b each independently represent a linear or branched alkylene group, ^R6a and ^R6b each independently represent a substituent, u1 and u2 each independently represent an integer of 0 or more, and v1 and v2 each independently represent an integer of 0 to 6).

The diol unit (B) may contain both the first diol unit (B1) and the second diol unit (B2), and the ratio (B1/B2) of the first diol unit (B1) to the second diol unit (B2) may be B1/B2 (molar ratio) = approximately 10/90 to 90/10.

The dicarboxylic acid unit (A) may further contain at least one dicarboxylic acid unit selected from a second dicarboxylic acid unit (A2) represented by the following formula (2) and a third dicarboxylic acid unit (A3) which is an aliphatic dicarboxylic acid unit.

(In the formula, ^Z2 represents an arene ring, ^R3 represents a substituent, and p represents an integer of 0 or more).

The ratio (A1/A2) of the first dicarboxylic acid unit (A1) to the second dicarboxylic acid unit (A2) may be about A1/A2 (molar ratio) = 95/5 to 30/70. The ratio of the first dicarboxylic acid unit (A1) to the third dicarboxylic acid unit (A3) may be A1/A3 (molar ratio) = 90/10 to 20/80, and the ratio of the second dicarboxylic acid unit (A2) to the third dicarboxylic acid unit (A3) may be A2/A3 (molar ratio) = 25/75 to 1/99.

The resin may be a resin described in (i) or (ii) below.
(i) is formed from a structural unit derived from 9,9-bis(carboxy _C2-4 alkyl)-2,7-di(2-naphthyl)fluorene as the first dicarboxylic acid unit (A1); a naphthalene dicarboxylic acid unit as the second dicarboxylic acid unit (A2); a structural unit derived from a linear or branched _C2-4 alkylene glycol as the first diol unit (B1); and a structural unit derived from 9,9-bis[hydroxy _C2-3 alkoxy naphthyl]fluorene as the second diol unit (B2);
(ii) A resin in which the ratio of the first dicarboxylic acid unit (A1) to the second dicarboxylic acid unit (A2) is A1/A2 (molar ratio) = 85/15 to 50/50; and the ratio of the first diol unit (B1) to the second diol unit (B2) (B1/B2) is B1/B2 (molar ratio) = 50/50 to 95/5. (ii) A resin in which a structural unit derived from 9,9-bis( _carboxyC2-4 alkyl)-2,7-di(2-naphthyl)fluorene as the first dicarboxylic acid unit (A1); a naphthalene dicarboxylic acid unit as the second dicarboxylic acid unit (A2); a _C2-6 alkane-dicarboxylic acid unit as the third dicarboxylic acid unit (A3); a structural unit derived from a linear or branched _C2-4 alkylene glycol as the first diol unit (B1); and a structural unit derived from _2-3 alkoxynaphthyl]fluorene,
A resin in which a ratio of the first dicarboxylic acid unit (A1) to the second dicarboxylic acid unit (A2) is A1/A2 (molar ratio) = 99/1 to 80/20; a ratio of the first dicarboxylic acid unit (A1) to the third dicarboxylic acid unit (A3) is A1/A3 (molar ratio) = 65/35 to 45/55; a ratio of the second dicarboxylic acid unit (A2) to the third dicarboxylic acid unit (A3) is A2/A3 (molar ratio) = 25/75 to 1/99; and a ratio of the first diol unit (B1) to the second diol unit (B2) (B1/B2) is B1/B2 (molar ratio) = 85/15 to 65/35.

The present invention also includes a molded article containing the resin. The molded article may be an optical member such as an optical film or an optical lens.

In addition, the present invention may solve the following problems as secondary objectives.

That is, another object of the present invention is to provide a dicarboxylic acid or a derivative thereof capable of forming a resin exhibiting a high refractive index and high heat resistance even when contained in a small proportion as a polymerization component, as well as a method for producing the same and uses thereof.

Yet another object of the present invention is to provide a dicarboxylic acid or a derivative thereof capable of exhibiting a large negative birefringence (large birefringence on the minus (-) side), as well as a method for producing the same and uses thereof.

Another object of the present invention is to provide a resin and a molded body containing the resin that can achieve a good balance of a high refractive index, a low Abbe number, low birefringence (low absolute value of birefringence) and high heat resistance, while also having high moldability.

In this specification and claims, the term "derivative" of a dicarboxylic acid is used to mean not only ester (or amide)-forming derivatives such as dicarboxylic acid esters, dicarboxylic acid halides, and dicarboxylic acid anhydrides, but also compounds that can be converted from dicarboxylic acids by conventional methods, such as dicarboxylic acid amides and dicarboxylic acid salts.

Examples of the dicarboxylate ester include alkyl esters of dicarboxylate components, particularly lower alkyl esters, such as _C1-4 alkyl esters such as methyl ester, ethyl ester, and t-butyl ester. Examples of the dicarboxylate halides include dicarboxylate chlorides and dicarboxylate bromides. Examples of the dicarboxylate salts include metal salts, specifically alkali metal salts such as sodium salts, and ammonium salts.

In addition, "dicarboxylic acid unit" means a constituent unit derived from a dicarboxylic acid component, that is, a unit (or a divalent group) obtained by removing OH (hydroxyl group) from the two carboxyl groups of the corresponding dicarboxylic acid. Note that "dicarboxylic acid component" is used to mean not only dicarboxylic acid but also derivatives that can be used as polymerization components, such as the ester (or amide) forming derivatives. The ester forming derivatives may be monoesters (half esters) or diesters. In addition, "dicarboxylic acid component" (including compounds exemplified as dicarboxylic acid components) may be used synonymously with the corresponding "dicarboxylic acid unit".

Similarly, a "diol unit" refers to a structural unit derived from a diol component, i.e., a unit (or divalent group) obtained by removing hydrogen atoms from the two hydroxyl groups of the corresponding diol, and a "diol component" (including compounds exemplified as diol components) may be used synonymously with the corresponding "diol unit."

In this specification and claims, the number of carbon atoms of a substituent may be indicated as _C1 , _C6 , _C10 , etc. For example, an alkyl group having 1 carbon atom is indicated as a " _C1 alkyl" and an aryl group having 6 to 10 carbon atoms is indicated as a " _C6-10 aryl."

In addition, in this specification and claims, terms such as "low birefringence" or "low birefringence" mean that the absolute value of birefringence is low (i.e., close to zero), unless otherwise specified.

The novel dicarboxylic acid or its derivative of the present invention has a high refractive index and high heat resistance. Therefore, when used as a polymerization component, even if the content ratio of the dicarboxylic acid to the entire resin is small, a resin exhibiting a high refractive index and high heat resistance can be formed. In addition, the dicarboxylic acid or its derivative can also exhibit a large negative birefringence (large birefringence on the minus (-) side or negative side). Furthermore, the resin can satisfy a high refractive index, low Abbe number, low birefringence (low absolute value of birefringence), and high heat resistance in a well-balanced manner, and has high moldability, so that deterioration, coloring (or discoloration), distortion, and even a decrease in surface smoothness in the molded body can be suppressed.

[Dicarboxylic acid component or derivative thereof]
The novel dicarboxylic acid of the present invention is represented by the following formula (I):

(In the formula, Z ^1a and Z ^1b each independently represent an arene ring, R ^1a and R ^1b each independently represent a substituent, k1 and k2 each independently represent an integer of 0 or more, m1 and m2 each independently represent an integer of 0 to 4, R ^2a and R ^2b each independently represent a substituent, n1 and n2 each independently represent an integer of 0 to 4, A ^1a and A ^1b each independently represent a linear or branched alkylene group, m1+n1 and m2+n2 each are 4 or less, and at least one of m1 and m2 is 1 or more).

In the formula (I), examples of the arene ring (aromatic hydrocarbon ring) represented by ^Z1a and ^Z1b include a monocyclic arene ring such as a benzene ring, a polycyclic arene ring, etc. Examples of the polycyclic arene ring include a fused polycyclic arene ring (fused polycyclic aromatic hydrocarbon ring) and a ring-assembled arene ring (ring-assembled polycyclic aromatic hydrocarbon ring).

Examples of the fused polycyclic arene ring include fused bicyclic arene rings, fused tricyclic arene rings, and other fused bicyclic to tetracyclic arene rings. Examples of the fused bicyclic arene ring include fused bicyclic C _10-16 arene rings, such as a naphthalene ring and an indene ring. Examples of the fused tricyclic arene ring include fused tricyclic C _14-20 arene rings, such as an anthracene ring and a phenanthrene ring. A preferred fused polycyclic arene ring is a fused polycyclic C _10-14 arene ring, such as a naphthalene ring.

Examples of the ring assembly arene ring include biarene rings such as biphenyl ring, phenylnaphthalene ring, binaphthyl ring, etc.; terarene rings such as terphenyl ring, etc. A preferred ring assembly arene ring is a C _12-18 biarene ring such as a biphenyl ring.

In this specification and claims, the term "ring assembly arene ring" means two or more ring systems (arene ring systems) directly linked by single bonds or double bonds, and the number of bonds directly linking the rings is one less than the number of ring systems. For example, as described above, phenylnaphthalene rings and binaphthyl rings are classified as ring assembly arene rings even though they have a fused polycyclic arene ring skeleton, and are clearly distinguished from "fused polycyclic arene rings" such as naphthalene rings (non-ring assembly arene rings).

Preferred rings Z ^1a and Z ^1b include C _6-14 arene rings, more preferably C _6-12 arene rings such as benzene ring, naphthalene ring and biphenyl ring, still more preferably C _6-10 arene rings such as benzene ring and naphthalene ring, particularly preferably a naphthalene ring.

The types of rings Z ^1a and Z ^1b may be different from each other, but are usually the same. When m1 or m2 is 2 or more, the types of the two or more rings Z ^1a or Z ^1b may be the same or different from each other.

In addition, rings Z ^1a and Z ^1b may be substituted at any of positions 1 to 4 and positions 5 to 8 of the fluorene skeleton, but are usually often substituted at positions 2, 3 and/or 7. When m1 and m2 are 1, preferred substitution positions (or bonding positions) are positions that are symmetrical on the paper of formula (I) such as 1,8-positions, 2,7-positions, 3,6-positions and 4,5-positions, and particularly preferred are 2,7-positions.

When rings Z ^1a and Z ^1b are naphthalene rings, the bonding positions of rings Z ^1a and Z ^1b to the fluorene skeleton may be either the 1st or 2nd position of the naphthalene ring. From the viewpoint of improving heat resistance by increasing the 5% mass reduction temperature and the glass transition temperature of the resin, the 1st position of the naphthalene ring is preferable, but from the viewpoint of preparing a resin having a high refractive index, a low Abbe number, and a low birefringence (or a large negative birefringence) in a well-balanced manner, the 2nd position of the naphthalene ring is particularly preferable.

Examples of the substituents (non-reactive substituents or non-polymerizable substituents) represented by R ^1a and R ^1b include halogen atoms, hydrocarbon groups (or groups [-R ^A ]), groups [-OR ^A ] (wherein R ^A represents the above-mentioned hydrocarbon group), groups [-SR ^A ] (wherein R ^A represents the above-mentioned hydrocarbon group), acyl groups, nitro groups, cyano groups, and mono- or di-substituted amino groups.

Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

Examples of the hydrocarbon group represented by R 1 ^A include an alkyl group, a cycloalkyl group, an aryl group, and an aralkyl group.

Examples of the alkyl group include a linear or branched _C1-10 alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, and a t-butyl group, and are preferably a linear or branched _C1-6 alkyl group, and more preferably a linear or branched _C1-4 alkyl group.

Examples of the cycloalkyl group include a C _5-10 cycloalkyl group such as a cyclopentyl group and a cyclohexyl group.

Examples of the aryl group include C _6-12 aryl groups such as a phenyl group, an alkylphenyl group, a biphenylyl group, a naphthyl group, etc. Examples of the alkylphenyl group include mono- to tri-C _1-4 alkyl-phenyl groups such as a methylphenyl group (or a tolyl group) and a dimethylphenyl group (or a xylyl group).

Examples of the aralkyl group include a C _6-10 aryl-C _1-4 alkyl group such as a benzyl group or a phenethyl group.

Examples of the group [-OR ^A ] include an alkoxy group, a cycloalkyloxy group, an aryloxy group, and an aralkyloxy group, and specific examples of the group correspond to the examples of the hydrocarbon group R ^A. Examples of the alkoxy group include a linear or branched C _1-10 alkoxy group such as a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, an isobutoxy group, and a t-butoxy group. Examples of the cycloalkyloxy group include a C _5-10 cycloalkyloxy group such as a cyclohexyloxy group. Examples of the aryloxy group include a C _6-10 aryloxy group such as a phenoxy group. Examples of the aralkyloxy group include a C _6-10 aryl- _{C 1-4} alkyloxy group such as a benzyloxy group.

Examples of the group [-SR ^A ] include alkylthio groups, cycloalkylthio groups, arylthio groups, and aralkylthio groups, and specific examples include groups corresponding to the examples of the hydrocarbon group R ^A. Examples of the alkylthio group include C _1-10 alkylthio groups such as methylthio group, ethylthio group, propylthio group, n-butylthio group, and t-butylthio group. Examples of the cycloalkylthio group include C _5-10 cycloalkylthio groups such as cyclohexylthio group. Examples of the arylthio group include C _6-10 arylthio groups such as thiophenoxy group. Examples of the aralkylthio group include C _6-10 aryl-C _1-4 alkylthio groups such as benzylthio group.

The acyl group includes a C _1-6 alkyl-carbonyl group such as an acetyl group.

Examples of the mono- or di-substituted amino group include a dialkylamino group, a bis(alkylcarbonyl)amino group, etc. Examples of the dialkylamino group include a di-C _1-4 alkylamino group such as a dimethylamino group. Examples of the bis(alkylcarbonyl)amino group include a bis(C _1-4 alkyl-carbonyl)amino group such as a diacetylamino group.

Representative examples of these groups R ^1a and R ^1b include hydrocarbon groups, alkoxy groups, acyl groups, nitro groups, cyano groups, and substituted amino groups. When k1 or k2 is 1 or more, preferred groups R ^1a and R ^1b are alkyl groups and alkoxy groups, specifically, linear or branched C _1-6 alkyl groups such as methyl groups, and linear or branched C _1-4 alkoxy groups such as methoxy groups, among which alkyl groups, particularly linear or branched C _1-4 alkyl groups such as methyl groups, are preferred. When the group R ^1a or R ^1b is an aryl group, the group R ^1a or R ^1b may form the ring assembly arene ring together with the ring Z ^1a or Z ^1b , respectively.

The substitution numbers k1 and k2 may be selected depending on the types of rings ^Z1a and ^Z1b , and can be selected, for example, from integers of about 0 to 7. Preferred ranges are, in the following stepwise order, integers of 0 to 6, integers of 0 to 5, integers of 0 to 4, integers of 0 to 3, and integers of 0 to 2, more preferably 0 or 1, and particularly preferably 0.

The substitution numbers k1 and k2 of the groups R ^1a and R ^1b may be different from each other, but are usually the same. When the substitution number k1 or k2 is 2 or more, the types of the two or more groups R ^1a or R ^1b substituted on the same ring Z ^1a or Z ^1b may be the same or different from each other. In addition, the types of the groups R ^1a and R ^1b substituted on different rings Z ^1a and Z ^1b may be different from each other, but are usually the same. The substitution positions of the groups R ^1a and R ^1b are not particularly limited, and may be selected according to the types of the rings Z ^1a and Z ^1b .

The numbers of substitutions m1 and m2 in the group [-Z ^1a -(R ^1a ) _k1 ] and the group [-Z ^1b -(R ^1b ) _k2 ] (hereinafter also referred to as Z ^1- containing groups) are, for example, integers of about 1 to 3, preferably 1 or 2, and more preferably 1. m1 and m2 may be different from each other, but are usually often the same. At least one of m1 and m2 is an integer of 1 or more, preferably both are integers of 1 or more, and more preferably both are 1.

In addition, when m1 or m2 is 2 or more, the types of two or more Z ^1- containing groups substituted on the same benzene ring among the two benzene rings forming the fluorene skeleton may be the same or different. In addition, the types of Z ^1- containing groups substituted on different benzene rings among the two benzene rings forming the fluorene skeleton, that is, the group [-Z ^1a -(R ^1a ) _k1 ] and the group [-Z ^1b -(R ^1b ) _k2 ] may be the same or different, and are usually the same.

The substituents (non-reactive or non-polymerizable substituents) represented by R ^2a and R ^2b may be any substituent other than the ^Z1- containing group, and representative examples include hydrocarbon groups such as alkyl groups (excluding aryl groups), halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms, and cyano groups. Examples of the alkyl groups include linear or branched C _1-6 alkyl groups such as methyl groups, ethyl groups, and t-butyl groups. When the number of substitutions n1 or n2 is 1 or more, preferred R ^2a and R ^2b are linear or branched C _1-4 alkyl groups such as methyl groups.

The substitution numbers n1 and n2 of R ^2a and R ^2b are, for example, integers of about 0 to 3, preferably integers of 0 to 2, more preferably 0 or 1, and particularly 0. n1 and n2 may be different from each other, but are usually the same. When n1 or n2 is 2 or more, the types of R ^2a or R ^2b substituted on the same benzene ring among the two benzene rings forming the fluorene skeleton may be the same or different from each other. In addition, the types of R ^2a and R ^2b substituted on different benzene rings among the two benzene rings forming the fluorene skeleton may be the same or different from each other, and are usually the same. In addition, the substitution positions of R ^2a and R ^2b are not particularly limited, and may be substituted at positions other than the substitution position of the Z ^1- containing group.

Each of m1+n1 and m2+n2 is, for example, an integer of 0 to 4, preferably an integer of 1 to 3, more preferably 1 or 2, and even more preferably 1. Although m1+n1 and m2+n2 may be different from each other, they are usually the same.

Examples of the linear or branched alkylene groups represented by groups A ^1a and A ^1b include linear or branched C _1-8 alkylene groups such as methylene, ethylene, trimethylene, propylene, 1,2-butanediyl, and 2-methylpropane-1,3-diyl. Preferred alkylene groups include linear or branched C _1-6 alkylene groups such as methylene, ethylene, trimethylene, propylene, and 2-methylpropane-1,3-diyl, more preferably linear or branched C _1-4 alkylene groups, and even more preferably linear or branched C _2-4 alkylene groups, and among these, linear or branched C _2-3 alkylene groups such as ethylene and propylene are preferred, with ethylene being particularly preferred.

Representative examples of dicarboxylic acids represented by formula (I) include dicarboxylic acids in which m1 and m2 are 1, i.e., 9,9-bis(carboxyalkyl)-diarylfluorenes, more specifically, 9,9-bis(carboxyalkyl)-diphenylfluorene, 9,9-bis(carboxyalkyl)-dinaphthylfluorene, etc.

Examples of the 9,9-bis(carboxyalkyl)-diphenylfluorene include 9,9-bis(carboxyC 2-6 alkyl)-diphenylfluorenes such as 9,9-bis(2-carboxyethyl)-1,8-diphenylfluorene, 9,9-bis(2-carboxyethyl)-2,7-diphenylfluorene, 9,9-bis(2-carboxyethyl)-3,6-diphenylfluorene, 9,9-bis(2-carboxyethyl)-4,5-diphenylfluorene, and 9,9-bis(2 _- carboxypropyl)-2,7-diphenylfluorene.

Examples of the 9,9-bis(carboxyalkyl)-dinaphthylfluorene include 9,9-bis(2-carboxyethyl)-1,8-di(2-naphthyl)fluorene, 9,9-bis(2-carboxyethyl)-2,7-di(2-naphthyl)fluorene, 9,9-bis(2-carboxyethyl)-3,6-di(2-naphthyl)fluorene, 9,9-bis(2-carboxyethyl)-4,5-di(2-naphthyl)fluorene, 9,9-bis(2-carboxypropyl)-2,7-di(2-naphthyl)fluorene, and 9,9-bis( ₂ -carboxyethyl)-2,7-di(1-naphthyl)fluorene.

Among these dicarboxylic acids represented by the formula (I), 9,9-bis(carboxy C _2-4 alkyl)-2,7-diphenylfluorene such as 9,9-bis(2-carboxyethyl)-2,7-diphenylfluorene; 9,9-bis(carboxy C 2-4 alkyl)-2,7-dinaphthylfluorene are preferred, and 9,9-bis(carboxy C _2-4 alkyl)-2,7-dinaphthylfluorene such as 9,9-bis(2-carboxyethyl)-2,7-di(2-naphthyl)fluorene and 9,9-bis(2-carboxyethyl)-2,7-di( ₁ -naphthyl)fluorene are more preferred. Among these, from the viewpoint of being able to prepare a resin having a high refractive index, a low Abbe number, and a low birefringence (or a birefringence large on the negative side) in a well-balanced manner, 9,9-bis(carboxy C 2-4 alkyl)-2,7-dinaphthylfluorene such as 9,9-bis(2-carboxyethyl)-2,7-di(2-naphthyl)fluorene is more preferred. _2-3 alkyl)-2,7-di(2-naphthyl)fluorene is particularly preferred.

The dicarboxylic acid represented by formula (I) or its derivative has a high refractive index and high heat resistance.

The refractive index of the dicarboxylic acid or its derivative represented by formula (I) may be, for example, about 1.7 to 2 at a temperature of 25°C and a wavelength of 589 nm, and preferred ranges are as follows, in the following order: 1.75 to 1.95, 1.8 to 1.9, 1.81 to 1.88, 1.82 to 1.87, 1.83 to 1.86, 1.84 to 1.85.

The melting point of the dicarboxylic acid or its derivative represented by formula (I) may be, for example, about 100 to 250°C, and preferred ranges are as follows, in steps: 130 to 240°C, 150 to 230°C, 160 to 220°C, 170 to 210°C, 175 to 205°C, 180 to 200°C, and 185 to 195°C.

The 5% mass reduction temperature of the dicarboxylic acid or derivative thereof represented by the formula (I) may be, for example, about 300 to 450°C, and preferred ranges may be 350 to 430°C, 360 to 420°C, 370 to 410°C, 375 to 405°C, 380 to 400°C, and 385 to 395°C in the following stepwise order, but is more preferably 380 to 420°C, even more preferably 385 to 410°C, and particularly preferably 390 to 405°C.

In this specification and claims, the refractive index, melting point and 5% mass reduction temperature of the dicarboxylic acid represented by formula (I) or its derivative can be measured by the method described in the examples below.

(Method for producing dicarboxylic acid or its derivative)
The method for producing the dicarboxylic acid or derivative thereof of the present invention is not particularly limited, and may be produced by a conventional method, for example, a method including at least a step of coupling a compound having a fluorene skeleton with a compound having an arene ring skeleton corresponding to rings Z ^1a and Z ^1b in formula (I) to introduce an aryl group corresponding to the compound having an arene ring skeleton into at least one substitution position selected from positions 2 to 8 of the fluorene skeleton. More specifically, the dicarboxylic acid or derivative thereof represented by formula (II) below may be produced by coupling reaction (or cross-coupling reaction) with compounds represented by formulas (IIIa) and (IIIb) below according to the following reaction formula (hereinafter also referred to as the first production method).

(In the formula, X ^1a and X ^1b each independently represent a reactive group capable of forming a carbon-carbon bond (or a direct bond) by a coupling reaction; X ^2a represents a reactive group capable of forming a carbon-carbon bond together with the reactive group X ^1a and X ^2b represents a reactive group capable of forming a carbon-carbon bond together with the reactive group X ^1b by a coupling reaction; Z ^1a , Z ^1b , R ^1a , R ^1b , k1, k2, m1, m2, R ^2a , R ^2b , n1, n2, A ^1a , A ^1b , m1+n1 and m2+n2 are each the same as those in formula (I) above, including preferred embodiments.)

The coupling reaction is not particularly limited, and examples thereof include conventional coupling reactions, such as coupling reactions using a palladium catalyst (or a palladium(0) catalyst) such as the Suzuki-Miyaura coupling reaction, the Migita-Kosugi-Stille coupling reaction, the Negishi coupling reaction, and the Hiyama coupling reaction, and coupling reactions using a nickel catalyst (or a nickel(0) catalyst) such as the Kumada-Tamao-Corriu coupling reaction. Of these coupling reactions, the Suzuki-Miyaura coupling reaction is often used.

The reactive groups X ^1a and X ^1b , as well as X ^2a and X ^2b , can be appropriately selected depending on the type of the coupling reaction. When synthesis is performed by the Suzuki-Miyaura coupling reaction, one of the reactive groups, for example, the groups X ^1a and X ^1b , can be a halogen atom or a fluorinated alkane sulfonyloxy group. Examples of the halogen atom can be an iodine atom, a bromine atom, a chlorine atom, and the like. Examples of the fluorinated alkane sulfonyloxy group can be a fluorinated C _1-4 alkane sulfonyloxy group such as a trifluoromethanesulfonyloxy group (or a group [-OTf]).

These one-reactive groups may be used alone or in combination of two or more. Among these one-reactive groups, a halogen atom is preferred, an iodine atom and a bromine atom are more preferred, and a bromine atom is usually used more frequently.

In the Suzuki-Miyaura coupling reaction, examples of the other reactive group capable of coupling with the one reactive group, such as groups ^X2a and ^X2b , include boronic acid groups (dihydroxyboryl groups or groups [-B(OH) ₂ ]), boronic acid ester groups, etc. Examples of the boronic acid ester groups include dialkoxyboryl groups such as dimethoxyboryl groups, diisopropoxyboryl groups, and dibutoxyboryl groups; pinacolatoboryl groups (or groups [-Bpin]), 1,3,2-dioxaborinane-2-yl groups, and 5,5-dimethyl-1,3,2-dioxaborinane-2-yl groups, and cyclic boronic acid ester groups.

These other reactive groups may be used alone or in combination of two or more. Of the other reactive groups, the group [-B(OH) ₂ ] is usually used frequently.

The groups ^X1a and ^X1b , and the groups ^X2a and ^X2b may be any pair of reactive groups capable of coupling reaction with each other, and the groups ^X1a and ^X1b may be the other reactive group such as a boronic acid group, and the groups ^X2a and ^X2b may be one reactive group such as a halogen atom. Usually, however, the groups ^X1a and ^X1b are one reactive group such as a halogen atom, and the group ^X2 is often the other reactive group such as a boronic acid group.

The dicarboxylic acid represented by the formula (II) or a derivative thereof is usually a dicarboxylic acid ester exemplified as the ester-forming derivative, etc. Specific examples of the dicarboxylic acid represented by the formula (II) or a derivative thereof include compounds corresponding to preferred embodiments of the dicarboxylic acid represented by the formula (I), such as 9,9-bis(C _1-4 alkoxy-carbonyl-C _2-6 alkyl)-dihalofluorenes such as 9,9-bis(2-methoxycarbonylethyl)-2,7-dibromofluorene, 9,9-bis(2-ethoxycarbonylethyl)-2,7-dibromofluorene, and 9,9-bis(2-methoxycarbonylpropyl)-2,7-dibromofluorene.

The dicarboxylic acid represented by the formula (II) or a derivative thereof may be prepared, for example, in accordance with the method described in JP-A-2005-89422, specifically, by reacting a 9H-fluorene having no substitution at the 9-position, such as 2,7-dibromofluorene, with an acrylic acid ester, such as methyl acrylate, or a haloacetic acid ester, such as methyl bromoacetate, in the presence of a base catalyst, such as trimethylbenzylammonium hydroxide.

The compounds represented by the formulae (IIIa) and (IIIb) include compounds corresponding to the preferred embodiments of the dicarboxylic acid represented by the formula (I), such as phenylboronic acid, 1-naphthylboronic acid, and 2-naphthylboronic acid, with 2-naphthylboronic acid being preferred. The compounds represented by the formulae (IIIa) and (IIIb) are usually the same compound in many cases. The compounds represented by the formulae (IIIa) and (IIIb) can be commercially available products, etc.

The ratio of the dicarboxylic acid or derivative thereof represented by formula (II) to the total amount of the compounds represented by formulas (IIIa) and (IIIb) may be, for example, the former/latter (molar ratio) of about 1/2 to 1/10, and preferred ranges are, in the following stepwise order, 1/2.2 to 1/8, 1/2.5 to 1/5, and 1/2.7 to 1/3.3, while more preferred ranges are, in the following stepwise order, 1/2 to 1/3, 1/2 to 1/2.5, and 1/2.03 to 1/2.1.

When synthesizing by the Suzuki-Miyaura coupling reaction, the reaction is usually carried out in the presence of a palladium catalyst. Examples of palladium catalysts include conventional coupling catalysts such as palladium (0) catalysts and palladium (II) catalysts.

Examples of the palladium(0) catalyst include palladium(0)-phosphine complexes such as tetrakis(triphenylphosphine)palladium(0) [or Pd(PPh ₃ ) ₄ ] and bis(tri-t-butylphosphine)palladium(0) [or Pd(P(t-Bu) ₃ ) ₂ ].

Examples of the palladium (II) catalyst include palladium (II)-phosphine complexes such as [1,2-bis(diphenylphosphino)ethane]palladium (II) dichloride [or PdCl ₂ (dppe)], [1,3-bis(diphenylphosphino)propane]palladium (II) dichloride [or PdCl ₂ (dppp)], [1,1'-bis(diphenylphosphino)ferrocene]palladium (II) dichloride [or PdCl ₂ (dppf)], bis(triphenylphosphine)palladium (II) dichloride [or PdCl ₂ (PPh ₃ ) ₂ ], and bis(tri-o-tolylphosphine)palladium (II) dichloride [or PdCl ₂ (P(o-tolyl) ₃ ) ₂ ]. When a palladium (II) catalyst is used, the reaction is initiated by reduction to a zero-valent complex by a reducing compound in the reaction system, such as a phosphine, an amine, or an organometallic reagent.

The palladium catalyst may be prepared in situ by adding a catalyst precursor such as tris(dibenzylideneacetone)dipalladium(0) chloroform complex [or Pd ₂ (dba) _{3.CHCl 3} ] and a ligand such as a phosphine or a carbene.

These catalysts can be used alone or in combination of two or more. Among these catalysts, palladium(0)-phosphine complexes such as Pd(PPh ₃ ) ₄ are usually used. The ratio of the catalyst may be, for example, about 0.01 to 0.1 moles, preferably 0.03 to 0.07 moles, in terms of metal, per mole of the dicarboxylic acid represented by the formula (II) or its derivative, but is usually preferably a small amount of about 0.0001 to 0.001 moles, more preferably 0.0003 to 0.0007 moles, and particularly preferably 0.0004 to 0.0006 moles.

The Suzuki-Miyaura coupling reaction may be carried out in the presence of a base. Examples of bases include metal carbonates or hydrogen carbonates, metal hydroxides, metal fluorides, metal phosphates, metal organic acid salts, and metal alkoxides.

Examples of metal carbonates or bicarbonates include alkali metal carbonates or bicarbonates such as sodium carbonate, potassium carbonate, cesium carbonate, and sodium bicarbonate, as well as thallium(I) carbonate.

Examples of metal hydroxides include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and cesium hydroxide, alkaline earth metal hydroxides such as barium hydroxide, and thallium(I) hydroxide.

Examples of metal fluorides include alkali metal fluorides such as potassium fluoride and cesium fluoride.

Examples of metal phosphates include alkali metal phosphates such as tripotassium phosphate.

Examples of metal organic acid salts include alkali metal acetates such as potassium acetate.

Examples of metal alkoxides include alkali metal alkoxides such as sodium methoxide, sodium ethoxide, and potassium t-butoxide.

These bases can be used alone or in combination of two or more. Usually, metal carbonates such as potassium carbonate are often used. The ratio of the base may be, for example, about 0.1 to 50 moles, preferably 1 to 25 moles, more preferably 1.5 to 6 moles, and particularly preferably 2 to 3 moles, per mole of the dicarboxylic acid represented by formula (II) or its derivative.

The coupling reaction may be carried out in the presence or absence of a phase transfer catalyst. Examples of phase transfer catalysts include tetraalkylammonium halides such as tetrabutylammonium bromide (TBAB) and trioctylmethylammonium chloride. These phase transfer catalysts can be used alone or in combination of two or more. Of these phase transfer catalysts, TBAB is usually used.

The coupling reaction may be carried out in the absence or presence of a solvent inert to the reaction. Examples of the solvent include water; alcohols such as methanol and ethanol; ethers such as cyclic ethers and chain ethers; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; nitriles such as acetonitrile and benzonitrile; amides such as N,N-dimethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxides such as dimethyl sulfoxide; and hydrocarbons such as aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons.

Examples of cyclic ethers include dioxane and tetrahydrofuran. Examples of chain ethers include dialkyl ethers such as diethyl ether and diisopropyl ether, and glycol ethers. Examples of the glycol ethers include (poly)alkylene glycol monoalkyl ethers such as methyl cellosolve and methyl carbitol, and (poly)alkylene glycol dialkyl ethers such as dimethoxyethane.

Examples of aliphatic hydrocarbons include hexane and dodecane. Examples of alicyclic hydrocarbons include cyclohexane. Examples of aromatic hydrocarbons include toluene and xylene.

These solvents can be used alone or in combination of two or more. Among these solvents, a mixture of water and a chain ether such as dimethoxyethane, or a mixture of water and aromatic hydrocarbons is usually used, and a mixture of water and toluene is preferred.

The coupling reaction may be carried out under an inert gas atmosphere, for example, nitrogen; or a rare gas such as helium or argon. The reaction temperature is, for example, 50 to 200°C, preferably 60 to 100°C, more preferably 75 to 95°C, and particularly preferably 80 to 90°C. The reaction time is not particularly limited and may be, for example, about 1 to 10 hours.

After completion of the reaction, if necessary, the reaction mixture may be separated and purified by conventional separation and purification methods, such as washing, extraction, filtration, dehydration, concentration, decantation, recrystallization, reprecipitation, chromatography, adsorption, or a combination of these.

In addition, the dicarboxylic acid represented by formula (I) or its derivative may be used to produce a compound represented by formula (I) by a second production method shown in the following reaction scheme.

(In the formula, X ^1a , X ^1b , X ^2a and X ^2b are the same as those in the formulas (II), (IIIa) and (IIIb) including preferred embodiments thereof, and Z ^1a , Z ^1b , R ^1a , R ^1b , k1, k2, ml, m2, R ^2a , R ^2b , n1, n2, A ^1a , A ^1b , ml+n1 and m2+n2 are the same as those in the formula (I) including preferred embodiments thereof.)

In the second production method, instead of the dicarboxylic acid represented by formula (II) or its derivative in the first production method, 9H-fluorenes represented by the following formula (IV) are used to couple with the compounds represented by the formulas (IIIa) and (IIIb), and the resulting compound represented by formula (V) is used as a 9H fluorene unsubstituted at the 9-position in the method described in the above-mentioned JP-A-2005-89422 to produce the compound represented by formula (I). That is, in the second production method, the order of introduction of the A ^1a or A ^1b- containing group substituting the 9-position of the fluorene skeleton and the Z ^1- containing group is different from that in the first production method.

The 9H-fluorenes represented by the formula (IV) include 9H-fluorenes having a reactive group capable of coupling and unsubstituted at the 9-position, such as dihalofluorenes such as 2,7-dibromofluorene. The compound represented by the formula (IV) may be a commercially available product.

[Resin having dicarboxylic acid unit (A)]
The resin of the present invention may be formed by using a dicarboxylic acid component (A) containing at least the dicarboxylic acid represented by the formula (I) or a derivative thereof as a polymerization component. Therefore, the resin contains at least a first dicarboxylic acid unit (A1) represented by the following formula (1). Such a resin having a dicarboxylic acid unit (A) is usually a thermoplastic resin, and representative examples thereof include polyester resins such as polyester carbonate resins, which contain at least a diol component as a polymerization component, and polyamide resins, which contain a diamine component as a polymerization component.

Optical resin materials are often required to have excellent water absorption resistance (or low moisture absorption) because if the refractive index or dimensions change due to moisture absorption, the optical properties become unstable and the material cannot be used for precision optical components. Therefore, of these resins, polyester resins such as polyester resin and polyester carbonate resin are preferred from the viewpoint of water absorption resistance (or low moisture absorption), and polyester resin is even more preferred from the viewpoint of ease of improving the refractive index and glass transition temperature (or heat resistance).

(Dicarboxylic acid unit (A))
(A1) First dicarboxylic acid unit

(In the formula, Z ^1a , Z ^1b , R ^1a , R ^1b , k1, k2, m1, m2, R ^2a , R ^2b , n1, n2, A ^1a , A ^1b , m1+n1, and m2+n2 are each the same as in formula (I) above, including preferred embodiments.)

The resin of the present invention contains at least the first dicarboxylic acid unit (A1) represented by the formula (1), and therefore the refractive index and heat resistance can be greatly improved. In addition, it appears that the resin is easy to achieve both high heat resistance and high moldability by suppressing an excessive increase in the glass transition temperature. In addition, it appears that the Abbe number can be greatly reduced with the improvement in the refractive index.

In addition, the first dicarboxylic acid unit (A1) has the property of significantly biasing the birefringence (or orientation birefringence) of the resin to the negative (-) side (or negative side) (or can express a large negative birefringence). Since most resins or their constituent units usually exhibit positive birefringence upon stretching or orientation, the introduction of the first dicarboxylic acid unit (A1) makes it easy to adjust the absolute value of the birefringence (or orientation birefringence) to a low value. Therefore, a high refractive index, a low Abbe number, and high heat resistance and low birefringence, which are usually in a trade-off relationship, can be achieved in a well-balanced manner at an even higher level.

In this specification and claims, "positive" and "negative" birefringence mean that when a resin film is uniaxially stretched and oriented, where nx is the refractive index in the stretching direction and ny is the refractive index in the direction perpendicular to the stretching direction within the film plane, then "positive" is when nx-ny>0 and "negative" is when nx-ny<0.

Representative examples of the first dicarboxylic acid unit (A1) include the dicarboxylic acid units corresponding to the dicarboxylic acids exemplified in the section on the dicarboxylic acid represented by formula (I), including preferred embodiments. The first dicarboxylic acid unit (A1) may be contained alone or in combination of two or more kinds.

(A2) Second dicarboxylic acid unit The dicarboxylic acid unit (A) does not necessarily contain the second dicarboxylic acid unit (A2) represented by the following formula (2), but may contain it as necessary. When the second dicarboxylic acid unit (A2) is contained, the birefringence can be adjusted to the plus (+) side (or positive side) while maintaining a relatively high refractive index and glass transition temperature.

(In the formula, ^Z2 represents an arene ring, ^R3 represents a substituent, and p represents an integer of 0 or more).

In the formula (2), examples of the arene ring (aromatic hydrocarbon ring) represented by ring ^Z2 include arene rings similar to those of rings ^Z1a and ^Z1b described in the section on the dicarboxylic acid represented by formula (I) (or the first dicarboxylic acid unit (A1)). Preferred examples of ring ^Z2 include _C6-14 arene rings such as a benzene ring, a naphthalene ring, and a biphenyl ring, and are more preferably _C6-12 arene rings. Among these, ring Z2 may be a _C6-10 arene ring such as a benzene ring or a naphthalene ring, but from the viewpoint of easily maintaining a high refractive index and heat resistance, a _C10-12 polycyclic arene ring such as a naphthalene ring or a biphenyl ring is preferred, and a fused polycyclic arene ring such as a naphthalene ring is particularly preferred.

Examples of the substituent represented by ^R3 (non-reactive substituent or non-polymerizable substituent) include the same substituents as the groups ^R1a and ^R1b described in the section on the dicarboxylic acid represented by formula (I) (or the first dicarboxylic acid unit (A1)).

Among these groups R ³ , representative examples include halogen atoms, hydrocarbon groups such as alkyl groups, cycloalkyl groups, aryl groups, and aralkyl groups, alkoxy groups, acyl groups, nitro groups, cyano groups, and substituted amino groups. When p is 1 or more, preferred groups R ³ include alkyl groups, specifically linear or branched C _1-6 alkyl groups such as methyl groups; aryl groups, specifically C _6-14 aryl groups such as phenyl groups; and alkoxy groups, specifically linear or branched C _1-4 alkoxy groups such as methoxy groups. Among these, alkyl groups and aryl groups are preferred, and in particular linear or branched C _1-4 alkyl groups such as methyl groups and C _6-10 aryl groups such as phenyl groups are preferred. When the group R ³ is an aryl group, the group R ³ may form a ring assembly arene ring together with the ring Z ² .

The number of substitutions p of the group ^R3 can be selected according to the type of ring ^Z2 , and is, for example, an integer of about 0 to 6, preferably an integer of 0 to 4, 0 to 2, more preferably 0 or 1, particularly 0, in a stepwise manner. When p is 2 or more, the types of the two or more groups ^R3 may be the same or different from each other. In addition, the substitution position of the group ^R3 is not particularly limited, and it is sufficient that it is substituted at a position other than the bonding position between the two carbonyl groups [-C(=O)-] and the ring ^Z2 .

The substitution positions of the two carbonyl groups [-C(=O)-] are not particularly limited, and for example, when ring ^Z2 is a benzene ring, the two carbonyl groups [-C(=O)-] may be substituted at any of the o-position, m-position, or p-position, and among these, it is preferable to substitute at the m-position or p-position, and particularly it is preferable to substitute at the p-position. When ring ^Z2 is a naphthalene ring, the two carbonyl groups [-C(=O)-] may be substituted at any of the 1-8 positions, but usually, one carbonyl group is substituted at the 1- or 2-position of a naphthyl group, and the other carbonyl group is substituted at the 5- or 8-position, and for example, it is preferable to substitute at the 1,5-position or 2,6-position, and particularly it is preferable to substitute at the 2,6-position. When ring ^Z2 is a biphenyl ring, the two carbonyl groups [-C(=O)-] may be substituted in any positional relationship, but usually, they are substituted on different benzene rings in many cases, and may be substituted at the 2,2'-positions, 3,3'-positions or 4,4'-positions, particularly 4,4'-positions, but are preferably substituted at the 2,2'-positions.

Representative examples of the second dicarboxylic acid component (A2) corresponding to the second dicarboxylic acid unit (A2) include benzenedicarboxylic acids corresponding to the unit in which ring ^Z2 in the formula (2) is a benzene ring; polycyclic arenedicarboxylic acids corresponding to the unit in which ring ^Z2 is a polycyclic arene ring; and ester-forming derivatives thereof.

Examples of benzene dicarboxylic acids include benzene dicarboxylic acid, alkyl benzene dicarboxylic acid, etc. Examples of benzene dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, etc. Examples of alkyl benzene dicarboxylic acids include C _1-4 alkyl-benzene dicarboxylic acids such as 5-methylisophthalic acid, etc.

Examples of polycyclic arene dicarboxylic acids include condensed polycyclic arene dicarboxylic acids and ring-assembled arene dicarboxylic acids.

Examples of the condensed polycyclic arene dicarboxylic acid include naphthalene dicarboxylic acids such as 1,2-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 1,8-naphthalene dicarboxylic acid, 2,3-naphthalene dicarboxylic acid, and 2,6-naphthalene dicarboxylic acid; anthracene dicarboxylic acid; and condensed polycyclic C _10-24 arene-dicarboxylic acids such as phenanthrene dicarboxylic acid. A preferred condensed polycyclic arene dicarboxylic acid is a condensed polycyclic C _10-14 arene-dicarboxylic acid.

Examples of the ring-assembled arene dicarboxylic acids include biC _6-10 arene-dicarboxylic acids such as 2,2'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, and 4,4'-biphenyldicarboxylic acid, with biphenyldicarboxylic acid being preferred.

The second dicarboxylic acid unit (A2) derived from these second dicarboxylic acids may be used alone or in combination of two or more. Among these second dicarboxylic acid units (A2), benzene dicarboxylic acids, specifically, benzene dicarboxylic acids such as isophthalic acid and terephthalic acid; condensed polycyclic arene dicarboxylic acids; and dicarboxylic acid units derived from ring-assembled arene dicarboxylic acids are preferred. Among these, condensed polycyclic C _10-14 arene-dicarboxylic acids; biC _6-10 arene-dicarboxylic acids are preferred from the viewpoint of easiness in improving refractive index and heat resistance, and more preferably naphthalene dicarboxylic acid; biphenyl dicarboxylic acids such as 2,2'-biphenyl dicarboxylic acid, and in particular, dicarboxylic acid units derived from 2,6-naphthalene dicarboxylic acid are preferred.

(A3) Third dicarboxylic acid unit The dicarboxylic acid unit (A) does not necessarily have to contain an aliphatic dicarboxylic acid unit as the third dicarboxylic acid unit (A3), but may contain it if necessary. The third dicarboxylic acid unit (A3) can suppress an excessive increase in glass transition temperature without significantly changing the birefringence when combined with the first dicarboxylic acid unit (A1), and can efficiently prepare a resin that has a better balance between heat resistance and moldability (or productivity), which are in a trade-off relationship.

Examples of the aliphatic dicarboxylic acid component for forming the third dicarboxylic acid unit (A3) (aliphatic dicarboxylic acid unit) include alkanedicarboxylic acids, specifically, _C2-12 alkane-dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and decanedicarboxylic acid; unsaturated aliphatic dicarboxylic acids, specifically, _C2-10 alkene-dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid, and ester-forming derivatives thereof.

These third dicarboxylic acid units (A3) may be used alone or in combination of two or more. Among these third dicarboxylic acid units (A3), dicarboxylic acid units derived from alkanedicarboxylic acids such as _C2-10 alkanedicarboxylic acid units are preferred, _C2-8 alkanedicarboxylic acid units are more preferred, and _C2-6 alkanedicarboxylic acid units such as adipic acid units are particularly preferred.

The dicarboxylic acid unit (A) does not necessarily contain a fourth dicarboxylic acid unit (A4) represented by the following formula (1-0), but may contain it as necessary. When the fourth dicarboxylic acid unit (A4) is contained, the birefringence can be reduced (or adjusted to the negative (-) side) while maintaining a relatively high refractive index, but if the proportion of the fourth dicarboxylic acid unit (A4) is too high, the refractive index and heat resistance may decrease.

(In the formula, R ^2a , R ^2b , n1, n2, A ^1a and A ^1b are the same as those in formula (I) above, including preferred embodiments thereof.)

The fourth dicarboxylic acid component for forming the fourth dicarboxylic acid unit (A4) corresponds to a dicarboxylic acid component that does not have a ^Z1- containing group (m1 = m2 = 0) in the above formula (I), and representative examples of the fourth dicarboxylic acid component include structural units in which A ^1a and A ^1b are linear or branched C _2-6 alkylene groups, such as 9,9-bis(carboxy C _2-6 alkyl)fluorenes such as 9,9-bis(2-carboxyethyl)fluorene and 9,9-bis(2-carboxypropyl)fluorene.

These fourth dicarboxylic acid units (A4) may be used alone or in combination of two or more. Among these fourth dicarboxylic acid units (A4), a structural unit derived from 9,9-bis(carboxy _C2-5 alkyl)fluorene is preferable, and a structural unit derived from 9,9-bis(carboxy _C2-4 alkyl)fluorene is more preferable, among which a structural unit derived from 9,9-bis(carboxy _C2-3 alkyl)fluorene such as 9,9-bis(2-carboxyethyl)fluorene or 9,9-bis(2-carboxypropyl)fluorene is particularly preferable, and a structural unit derived from 9,9-bis(2-carboxyethyl)fluorene is particularly preferable.

(A5) Fifth dicarboxylic acid unit The dicarboxylic acid unit (A) does not necessarily contain a dicarboxylic acid unit (fifth dicarboxylic acid unit (A5)) different from the first dicarboxylic acid unit (A1), the second dicarboxylic acid unit (A2), the third dicarboxylic acid unit (A3) and the fourth dicarboxylic acid unit (A4), but may contain such a dicarboxylic acid unit if necessary.

Examples of the fifth dicarboxylic acid unit (A5) include structural units derived from an aromatic dicarboxylic acid component (excluding the first dicarboxylic acid unit (A1), the second dicarboxylic acid unit (A2) and the fourth dicarboxylic acid unit (A4)), an alicyclic dicarboxylic acid component, etc.

Examples of the aromatic dicarboxylic acid component include diarylalkanedicarboxylic acids, specifically, diC _6-10 aryl C _1-6 alkane-dicarboxylic acids such as 4,4'-diphenylmethanedicarboxylic acid; diarylketonedicarboxylic acids, specifically, di(C _6-10 aryl)ketone-dicarboxylic acids such as 4.4'-diphenylketonedicarboxylic acid; and ester-forming derivatives thereof.

Examples of the alicyclic dicarboxylic acid component include cycloalkane dicarboxylic acids, specifically, C _{5-10 cycloalkane-dicarboxylic acids such as 1,4-cyclohexane dicarboxylic acid; bridged cyclic cycloalkane dicarboxylic acids, specifically, di- or tricycloalkane dicarboxylic acids such as decalin dicarboxylic acid, norbornane dicarboxylic acid, adamantane dicarboxylic acid, tricyclodecane dicarboxylic acid; cycloalkene dicarboxylic acids, specifically, C 5-10 cycloalkene} -dicarboxylic acids such as cyclohexene dicarboxylic acid; bridged cyclic cycloalkene dicarboxylic acids, specifically, di- or tricycloalkene dicarboxylic acids such as norbornene dicarboxylic acid; and ester-forming derivatives thereof.

These dicarboxylic acid units (A5) may be used alone or in combination of two or more. The proportion of the fifth dicarboxylic acid unit (A5) may be selected from the range of, for example, 50 mol% or less, specifically, about 0 to 30 mol%, based on the total dicarboxylic acid units (A). Preferred ranges are 20 mol% or less, 10 mol% or less, and 5 mol% or less in the following stepwise order, and it is preferable that the fifth dicarboxylic acid unit (A5) is not substantially contained.

The proportion of the first dicarboxylic acid unit (A1) can be selected, for example, from 1 mol% or more, specifically from a range of about 10 to 100 mol%, relative to the total dicarboxylic acid unit (A). From the viewpoint of improving the refractive index and heat resistance, preferred ranges are, in the following stepwise order, 30 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, and 95 mol% or more. It is particularly preferable that the proportion is 100 mol%, that is, that the polymer is substantially formed only of the first dicarboxylic acid unit (A1). From the viewpoint of easily reducing the absolute value of birefringence while maintaining a relatively high refractive index and heat resistance, the proportion of the first dicarboxylic acid unit (A1) may be, for example, about 50 to 100 mol%, preferably 60 to 90 mol%, and more preferably 70 to 80 mol%, based on the total dicarboxylic acid unit (A). From the viewpoint of further reducing the absolute value of birefringence while maintaining the balance of each property, about 30 to 90 mol%, for example 35 to 85 mol%, is further preferable, and furthermore, stepwise thereafter, 40 to 80 mol%, 45 to 75 mol%, and 50 to 70 mol% are preferable. Among these, 60 to 70 mol%, particularly 65 to 70 mol%, is most preferable from the viewpoint of achieving a particularly high refractive index. If the proportion of the first dicarboxylic acid unit (A1) is too small, it may be difficult to sufficiently improve the refractive index or heat resistance, or it may be difficult to achieve a good balance between optical properties such as a high refractive index, a low absolute value of birefringence, and a low Abbe number, and heat resistance. Conversely, if the proportion is too large, it may be difficult to adjust the absolute value of birefringence low, and it may be difficult to achieve a good balance between the optical properties and heat resistance.

It is preferable to combine the first dicarboxylic acid unit (A1) with at least one dicarboxylic acid unit selected from the second dicarboxylic acid unit (A2) and the third dicarboxylic acid unit (A3). It is preferable to combine at least the first dicarboxylic acid unit (A1) and the second dicarboxylic acid unit (A2) from the viewpoint of easily achieving a good balance between the optical properties and heat resistance by adjusting the absolute value of birefringence to a low value. Such a combination often results in a resin with excellent moldability. Therefore, the ratio of the total amount of the first dicarboxylic acid unit (A1) and the second dicarboxylic acid unit (A2) to the entire dicarboxylic acid unit (A) can be selected from, for example, 1 mol% or more, specifically, about 10 to 100 mol%, and the preferred range is 30 mol% or more, 50 mol% or more, 55 mol% or more in the following stepwise manner, and from the viewpoint of being able to particularly increase the refractive index while maintaining the balance of the above-mentioned respective properties, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more in the following stepwise manner is preferred, and it is particularly preferred that the dicarboxylic acid unit (A) is formed substantially only from the first dicarboxylic acid unit (A1) and the second dicarboxylic acid unit (A2). If the ratio of the total amount of the first dicarboxylic acid unit (A1) and the second dicarboxylic acid unit (A2) is too small, there is a risk that the optical properties and heat resistance cannot be well balanced.

When the second dicarboxylic acid unit (A2) is contained, the ratio (A1/A2) of the first dicarboxylic acid unit (A1) to the second dicarboxylic acid unit (A2) can be selected from a wide range, for example, A1/A2 (molar ratio) = 99.9/0.1 to 1/99, and preferably in the following stepwise manner: 99/1 to 10/90, 95/5 to 30/70, 90/10 to 50/50, 85/15 to 60/40, 80/20 to 65/35, 78 However, from the viewpoint of achieving a good balance between the optical properties and heat resistance, 95/5 to 45/55, for example 90/10 to 50/50, is preferred, and from the viewpoint of achieving a particularly high refractive index while maintaining the balance of the above-mentioned properties, the following stepwise ratios are more preferred: 85/15 to 50/50, 80/20 to 55/45, 75/25 to 60/40, and particularly 70/30 to 65/35. If the second dicarboxylic acid unit (A2) is too much, the birefringence may increase too much and the absolute value may not be reduced, and conversely, if the amount is too little, the birefringence may increase (to the negative side) and the absolute value may not be reduced.

In addition, when a third dicarboxylic acid unit (A3) is contained in order to achieve a good balance between the optical properties and heat resistance while achieving an even better balance between heat resistance and moldability (or productivity), which are in a trade-off relationship, the proportion of the total amount of the first dicarboxylic acid unit (A1) and the third dicarboxylic acid unit (A3) relative to the total amount of the dicarboxylic acid units (A) can be selected, for example, from 1 mol% or more, specifically from a range of about 10 to 100 mol%, with preferred ranges being 30 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, and 85 mol% or more, in the following stepwise order, with 90 to 95 mol% being particularly preferred. The ratio (A1/A3) of the first dicarboxylic acid unit (A1) to the third dicarboxylic acid unit (A3) may be selected, for example, from a range of about A1/A3 (molar ratio) = 90/10 to 20/80, preferably 80/20 to 40/60, 70/30 to 45/55, 65/35 to 50/50, and particularly preferably 60/40 to 55/45. If the amount of the third dicarboxylic acid unit (A3) is too large, the refractive index and heat resistance may be significantly reduced, and conversely, if the amount is too small, it may be difficult to achieve both high levels of heat resistance and moldability.

In addition, when the fourth dicarboxylic acid unit (A4) is included, the ratio of the total amount of the first dicarboxylic acid unit (A1) and the fourth dicarboxylic acid unit (A4) can be selected from, for example, 1 mol% or more, specifically, from a range of about 10 to 100 mol% relative to the entire dicarboxylic acid unit (A), and the preferred ranges are 30 mol% or more, 50 mol% or more, 70 mol% or more, and 90 mol% or more in the following stepwise manner. In addition, the ratio (A1/A4) of the first dicarboxylic acid unit (A1) to the fourth dicarboxylic acid unit (A4) may be selected from, for example, a range of A1/A4 (molar ratio) = about 90/10 to 10/90, and preferably 70/30 to 20/80, 60/40 to 30/70, and 50/50 to 35/65 in the following stepwise manner.

(Diol Unit (B))
The resin of the present invention preferably has a diol unit (B) for forming a polyester resin. The diol unit (B) is not particularly limited, but usually contains at least one diol unit selected from the first diol unit (B1) represented by the formula (3), the second diol unit (B2) represented by the formula (4) and the third diol unit (B3) represented by the formula (5), and preferably contains at least one diol unit selected from the first diol unit (B1) and the second diol unit (B2). From the viewpoint of facilitating a large improvement in refractive index, it is preferable to contain at least the first diol unit (B1), and from the viewpoint of improving optical properties such as a high refractive index and a low absolute value of birefringence and heat resistance in a well-balanced manner, it is preferable to contain both the first diol unit (B1) and the second diol unit (B2).

(B1) First Diol Unit Although the first diol unit (B1) represented by the following formula (3) does not have any aromatic skeleton, it may unexpectedly improve the refractive index of the resin without significantly decreasing it by combining with the first dicarboxylic acid unit (A1). In addition, the first diol unit (B1) increases the polymerization reactivity and easily increases the molecular weight, and may suppress an excessive increase in the glass transition temperature or impart flexibility or toughness to the resin, thereby greatly improving the moldability and handling.

(In the formula, ^A2 represents a linear or branched alkylene group, and q represents an integer of 1 or more).

In the formula (3), examples of the alkylene group represented by ^A2 include linear or branched _C2-12 alkylene groups such as ethylene, propylene, trimethylene, 1,2-butanediyl, 1,3-butanediyl, tetramethylene, 1,5-pentanediyl, 1,6-hexanediyl, 1,8-octanediyl, and 1,10-decanediyl. Preferred alkylene groups ^A2 are, in the following order, linear or branched _C2-10 alkylene groups, linear or branched _C2-8 alkylene groups, linear or branched _C2-6 alkylene groups, and linear or branched _C2-4 alkylene groups, more preferably linear or branched _C2-3 alkylene groups such as ethylene and propylene, and particularly preferably ethylene.

The repeat number q can be selected, for example, from the range of about 1 to 10, and preferred ranges are 1 to 8, 1 to 6, 1 to 4, 1 to 3, and 1 to 2 in the following stepwise order, with 1 being particularly preferred. The repeat number q may be an average value (arithmetic mean value or additive mean value), and preferred embodiments are the same as those in the range of integers described above. When q is 2 or more, the types of the two or more oxyalkylene groups (-A ² O-) may be different from each other, but are usually the same in most cases.

Examples of the first diol component corresponding to the first diol unit (B1) include alkanediols (or alkylene glycols), polyalkanediols (or polyalkylene glycols), etc.

Examples of the alkylene glycol include compounds in which q is 1 and ^A2 corresponds to the alkylene group exemplified in the formula (3), specifically, linear or branched C2-12 alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, tetramethylene glycol (or 1,4-butanediol), 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, and _1,10 -decanediol, and preferred aspects are similar to those corresponding to the alkylene group ^A2 .

The polyalkylene glycol is a compound in which, in the above formula (3), q is 2 or more, for example, about 2 to 10, and ^A2 corresponds to the above-mentioned alkylene group, specifically, di- or deca-linear or branched _C2-12 alkylene glycols such as diethylene glycol, dipropylene glycol, and triethylene glycol are exemplified, preferably di- or hexa-linear or branched _C2-6 alkylene glycols, and more preferably di- or tetra-linear or branched _C2-4 alkylene glycols.

These first diol units (B1) may be contained alone or in combination of two or more. A preferred first diol unit (B1) is an alkylene glycol, from the viewpoint of facilitating improvement of the refractive index and preventing a decrease in heat resistance, more preferably a linear or branched C _2-6 alkylene glycol such as ethylene glycol or 1,5-pentanediol, still more preferably a linear or branched C _2-4 alkylene glycol such as ethylene glycol, propylene glycol, or 1,4-butanediol, among which a linear or branched C _2-3 alkylene glycol such as ethylene glycol or propylene glycol, particularly a structural unit derived from ethylene glycol, is preferred. In addition, when forming a polyester carbonate together with a carbonate unit described later, a linear or branched C _4-6 alkylene glycol such as 1,5-pentanediol is preferred from the viewpoint of adjusting the glass transition temperature and suppressing side reactions to improve reactivity.

When the diol unit (B) contains the second diol unit (B2) represented by the following formula (4), the heat resistance can be improved while maintaining a relatively high refractive index. In addition, the absolute value of the birefringence can be significantly reduced in some cases.

(In the formula, ^Z3a and ^Z3b each independently represent an arene ring, ^R4 represents a substituent, r represents an integer of 0 to 8, ^R5a and ^R5b each independently represent a substituent, s1 and s2 each independently represent an integer of 0 or more, ^A3a and ^A3b each independently represent a linear or branched alkylene group, and t1 and t2 each independently represent an integer of 0 or more).

In the formula (4), examples of the arene rings represented by Z ^3a and Z ^3b include the same arene rings as those exemplified as the rings Z ^1a and Z ^1b described in the section on the dicarboxylic acid represented by the formula (I) (or the first dicarboxylic acid unit (A1)). The types of rings Z ^3a and Z ^3b may be the same or different from each other, and are usually the same in many cases. Among the rings Z ^3a and Z ^3b , C _6-12 arene rings such as a benzene ring, a naphthalene ring, and a biphenyl ring are preferred, and C _6-10 arene rings such as a benzene ring and a naphthalene ring are more preferred. In addition, from the viewpoint of being able to satisfy optical properties such as a high refractive index and a low absolute value of birefringence and high heat resistance in a well-balanced manner, polycyclic arene rings such as a condensed polycyclic arene ring are preferred, and more preferably a condensed polycyclic C _10-14 arene ring, and particularly preferably a naphthalene ring.

The substitution position of rings ^Z3a and ^Z3b bonded to the 9-position of the fluorene ring is not particularly limited. For example, when rings ^Z3a and ^Z3b are benzene rings, they may be any position, when rings ^Z3a and ^Z3b are naphthalene rings, they may be either 1-position or 2-position, preferably 2-position, when rings ^Z3a and ^Z3b are biphenyl rings, they may be either 2-position, 3-position or 4-position, preferably 3-position.

Examples of the substituent represented by ^R4 (non-reactive substituent or non-polymerizable substituent) include hydrocarbon groups such as alkyl groups and aryl groups; cyano groups; and halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. Examples of the alkyl groups include linear or branched _C1-6 alkyl groups such as methyl groups, ethyl groups, propyl groups, isopropyl groups, n-butyl groups, and t-butyl groups. Examples of the aryl groups include _C6-10 aryl groups such as phenyl groups.

When r is 1 or more, preferred groups ^R4 are alkyl groups, cyano groups and halogen atoms, more preferably alkyl groups, particularly straight or branched C _1-4 alkyl groups such as methyl groups.

The number of substitutions r of the group R ⁴ is, for example, an integer of about 0 to 7, and the preferred ranges are, in the following stepwise order, integers of 0 to 6, integers of 0 to 4, integers of 0 to 3, integers of 0 to 2, more preferably 0 or 1, particularly 0. When r is 2 or more, the types of the two or more groups R ⁴ may be the same or different from each other. The substitution position of the group R ⁴ is not particularly limited, and is, for example, the 2-position to 7-position of the fluorene ring, usually the 2-position, 3-position and/or 7-position, and preferably the 2-position or the 2,7-position.

Examples of the substituents (non-reactive substituents or non-polymerizable substituents) represented by ^R5a and ^R5b include the same groups as the substituents exemplified as ^R1a and ^R1b described in the section on the dicarboxylic acid represented by formula (I) (or the first dicarboxylic acid unit (A1)).

Representative examples of these groups R ^5a and R ^5b include halogen atoms; hydrocarbon groups such as alkyl groups, cycloalkyl groups, aryl groups, and aralkyl groups; alkoxy groups; acyl groups; nitro groups; cyano groups; and substituted amino groups. When the number of substitutions s1 or s2 is 1 or more, preferred groups R ^5a and R ^5b include alkyl groups, cycloalkyl groups, aryl groups, and alkoxy groups, and more preferred groups include linear or branched C _1-6 alkyl groups such as methyl groups, C _5-8 cycloalkyl groups such as cyclohexyl groups, C _6-14 aryl groups such as phenyl groups, and linear or branched C _1-4 alkoxy groups such as methoxy groups. Among these, alkyl groups and aryl groups are preferred, and in particular linear or branched C _1-4 alkyl groups such as methyl groups, and C _6-10 aryl groups such as phenyl groups are preferred. When the group R ^5a or R ^5b is an aryl group, the group R ^5a or R ^5b may form the above-mentioned ring assembly arene ring together with the ring Z ^3a or Z ^3b .

The substitution numbers s1 and s2 of the groups ^R5a and ^R5b may each be an integer of 0 or more and may be appropriately selected depending on the type of the ring ^Z3a or ^Z3b . For example, they may be an integer of about 0 to 8. Preferred ranges are, in the following stepwise order, integers of 0 to 4, integers of 0 to 3, and integers of 0 to 2, with 0 or 1 being preferred, and 0 being particularly preferred.

The number of substitutions s1 and s2 in different rings ^Z3a and ^Z3b may be different from each other, but are usually the same. When the number of substitutions s1 or s2 is 2 or more, the types of ^R5a or ^R5b substituted on the same ring ^Z3a or ^Z3b may be the same or different from each other. In addition, the types of groups ^R5a and ^R5b bonded to different rings ^Z3a and ^Z3b may be the same or different from each other. In particular, when s1 and s2 are 1, rings ^Z3a and ^Z3b may be benzene rings, naphthalene rings or biphenyl rings, and groups ^R5a and ^R5b may be methyl groups. The substitution positions of the groups ^R5a and ^R5b are not particularly limited as long as they are substituted at a position other than the bonding positions of the rings ^Z3a and ^Z3b to the ether bond (-O-) and the 9-position of the fluorene ring, and usually, in the rings ^Z3a and ^Z3b , they are often substituted at the ortho position (the carbon atom adjacent to the bonding position of the ether bond) relative to the ether bond (-O-).

Examples of the alkylene groups A ^3a and A ^3b include linear or branched C _2-6 alkylene groups such as ethylene group, propylene group (1,2-propanediyl group), trimethylene group, 1,2-butanediyl group, and tetramethylene group. When the repeat number t1 or t2 is 1 or more, linear or branched C _2-4 alkylene groups are preferred, and linear or branched C _2-3 alkylene groups such as ethylene group and propylene group are more preferred, with ethylene group being particularly preferred.

The repetition numbers (number of moles added) t1 and t2 of the oxyalkylene groups (-OA ^3a -) and (-OA ^3b -) may each be 0 or more, and may be selected from the range of integers of, for example, about 0 to 15, with preferred ranges being 0 to 10, 0 to 8, 0 to 6, 0 to 4, 0 to 2, and 0 to 1, in the following stepwise order. The repetition numbers t1 and t2 are usually 1 or more in order to improve polymerization reactivity, and may be selected from the range of integers of, for example, about 1 to 15, with preferred ranges being 1 to 10, 1 to 8, 1 to 6, 1 to 4, 1 to 3, and 1 to 2, in particular 1 being preferred. In the present specification and claims, the "repetition number (number of moles added)" may be an average value (arithmetic mean value, arithmetic mean value) or an average number of moles added, and preferred embodiments are the same as the above preferred ranges (range of integers). If the repetition numbers t1 and t2 are too large, the refractive index and heat resistance may decrease.

Furthermore, the two repeat numbers t1 and t2 may be the same or different. When t1 or t2 is 2 or more, the types of the two or more oxyalkylene groups (-OA ^3a -) or (-OA ^3b -) may be the same or different. Furthermore, the types of the (poly)oxyalkylene groups (-OA ^3a -) and (-OA ^3b -) bonded to different rings Z ^3a and Z ^3b via an ether bond (-O-) may be the same or different.

The substitution positions of the groups [-O-( ^A3aO ) _t1- ] and [-O-( ^A3bO ) _t2- ] (also referred to as ether-containing groups) on the rings ^Z3a and ^Z3b are not particularly limited as long as they are substituted at appropriate positions on the rings ^Z3a and ^Z3b , respectively. When the rings ^Z3a and ^Z3b are benzene rings, the substitution position of the ether-containing group is often any one of the 2-position, 3-position, or 4-position, particularly the 3-position or 4-position, and particularly the 4-position, of the phenyl group bonded to the 9-position of the fluorene ring. Furthermore, when rings Z ^3a and Z ^3b are naphthalene rings, the ether-containing group is often substituted at any one of the 5- to 8-positions of the naphthyl group bonded to the 9-position of the fluorene ring, for example, the 1- or 2-position of the naphthalene ring is substituted with respect to the 9-position of the fluorene ring (substitution in a 1-naphthyl or 2-naphthyl relationship), and often is substituted with respect to this substitution position in a 1,5-position or 2,6-position relationship, particularly in a 2,6-position relationship. Furthermore, when rings Z ^3a and Z ^3b are ring-assembly arene rings, the substitution position of the ether-containing group is not particularly limited, and may be substituted, for example, on the arene ring bonded to the 9-position of the fluorene or on an arene ring adjacent to this arene ring. For example, when rings ^Z3a and ^Z3b are biphenyl rings (or rings ^Z3a and ^Z3b are benzene rings, s1 and s2 are 1, and ^R5a and ^R5b are phenyl groups), the 3- or 4-position of the biphenyl ring may be bonded to the 9-position of the fluorene, and when the 3-position of the biphenyl ring is bonded to the 9-position of the fluorene, the substitution position of the ether-containing group may be, for example, any of the 2-, 4-, 5-, 6-, 2'-, 3'-, and 4'-positions of the biphenyl ring, and is preferably substituted at the 6- or 4'-position, and in particular at the 6-position.

Examples of the second diol component corresponding to the second diol unit (B2) include 9,9-bis(hydroxyaryl)fluorenes in which t1 and t2 are 0 in the above formula (4); and 9,9-bis[hydroxy(poly)alkoxyaryl]fluorenes in which t1 and t2 are 1 or more, for example, about 1 to 10. In this specification and claims, unless otherwise specified, "(poly)alkoxy" is used to mean both an alkoxy group and a polyalkoxy group.

Examples of 9,9-bis(hydroxyaryl)fluorenes include 9,9-bis(hydroxyphenyl)fluorene, 9,9-bis(alkyl-hydroxyphenyl)fluorene, 9,9-bis(aryl-hydroxyphenyl)fluorene, and 9,9-bis(hydroxynaphthyl)fluorene.

Examples of 9,9-bis(hydroxyphenyl)fluorene include 9,9-bis(4-hydroxyphenyl)fluorene.

Examples of the 9,9-bis(alkyl-hydroxyphenyl)fluorene include 9,9-bis[(mono- or di-)C 1-4 alkyl-hydroxyphenyl]fluorenes such as 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, and 9,9-bis( ₄ -hydroxy-3,5-dimethylphenyl)fluorene.

Examples of the 9,9-bis(aryl-hydroxyphenyl)fluorene include 9,9-bis(C _6-10 aryl-hydroxyphenyl)fluorenes such as 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene.

Examples of 9,9-bis(hydroxynaphthyl)fluorene include 9,9-bis(6-hydroxy-2-naphthyl)fluorene and 9,9-bis(5-hydroxy-1-naphthyl)fluorene.

Examples of 9,9-bis[hydroxy(poly)alkoxyaryl]fluorenes include 9,9-bis[hydroxy(poly)alkoxyphenyl]fluorene, 9,9-bis[alkyl-hydroxy(poly)alkoxyphenyl]fluorene, 9,9-bis[aryl-hydroxy(poly)alkoxyphenyl]fluorene, and 9,9-bis[hydroxy(poly)alkoxynaphthyl]fluorene.

Examples of the 9,9-bis[hydroxy(poly)alkoxyphenyl]fluorene include 9,9-bis[hydroxy(mono- to deca)C _2-4 alkoxy-phenyl]fluorenes such as 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene, 9,9-bis[4-(2-(2-hydroxyethoxy)ethoxy)phenyl]fluorene, and 9,9-bis[4-(2-hydroxypropoxy)phenyl]fluorene.

Examples of the 9,9-bis[alkyl-hydroxy(poly)alkoxyphenyl]fluorene include 9,9-bis[4-(2-hydroxyethoxy)-3-methylphenyl]fluorene, 9,9-bis[4-(2-(2-hydroxyethoxy)ethoxy)-3-methylphenyl]fluorene, 9,9-bis[4-(2-hydroxyethoxy)-3,5-dimethylphenyl]fluorene, and 9,9-bis[4-(2-hydroxypropoxy)-3-methylphenyl]fluorene, and other 9,9-bis[(mono or di)C _1-4 alkyl-hydroxy(mono to deca)C _2-4 alkoxy-phenyl]fluorenes.

Examples of the 9,9-bis[aryl-hydroxy(poly)alkoxyphenyl]fluorene include 9,9-bis[C 6-10 aryl-hydroxy(mono- to deca)C _2-4 alkoxy-phenyl]fluorenes such as 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis[4-(2-(2-hydroxyethoxy)ethoxy)-3 _- phenylphenyl]fluorene, and 9,9-bis(4-(2-hydroxypropoxy)-3-phenylphenyl)fluorene.

Examples of the 9,9-bis[hydroxy(poly)alkoxynaphthyl]fluorene include 9,9-bis[hydroxy(mono- to deca)C 2-4 alkoxy-naphthyl]fluorenes such as 9,9-bis[6-(2-hydroxyethoxy)-2-naphthyl]fluorene, 9,9-bis[5-(2-hydroxyethoxy)-1-naphthyl]fluorene, 9,9-bis[6-(2-(2-hydroxyethoxy)ethoxy)-2-naphthyl]fluorene, and 9,9-bis[6-( ₂ -hydroxypropoxy)-2-naphthyl]fluorene.

These second diol units (B2) may be contained alone or in combination of two or more kinds. Of the second diol units (B2), preferred are 9,9-bis[hydroxy(poly)alkoxyaryl]fluorenes such as 9,9- _bis [hydroxy(mono- or hexa) _{C2-4alkoxyC6-10aryl} ]fluorene, more preferred are 9,9-bis[hydroxy(mono- or di) _C2-4alkoxy - _C6-10aryl ]fluorene, and further preferred are 9,9-bis[hydroxyC2-3alkoxy-C6-10aryl]fluorene such as 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene, 9,9-bis[4-(2-hydroxyethoxy) _-3 -phenylphenyl]fluorene, and 9,9-bis[6-(2-hydroxyethoxy)-2-naphthyl]fluorene. _6-12 aryl]fluorene, and in particular, a structural unit derived from 9,9-bis[hydroxy C 2-3 alkoxynaphthyl]fluorene such as 9,9-bis[6-(2-hydroxyethoxy)-2-naphthyl]fluorene is preferred, since it can impart high heat resistance while maintaining _{a high} refractive index and can also reduce the absolute value of birefringence.

(B3) Third Diol Unit The diol unit (B) may or may not contain a third diol unit (B3) represented by the following formula (5) as necessary. When the third diol unit (B3) is contained, it seems that it is possible to impart a high refractive index and a low Abbe number while suppressing an excessive increase in the glass transition temperature and maintaining the birefringence or suppressing an increase in the birefringence.

(In the formula, ^A4 is a direct bond (single bond) or a linear or branched alkylene group, ^A5a and ^A5b each independently represent a linear or branched alkylene group, ^R6a and ^R6b each independently represent a substituent, u1 and u2 each independently represent an integer of 0 or more, and v1 and v2 each independently represent an integer of 0 to 6).

In the formula (5), examples of the alkylene group represented by ^A4 include linear or branched _C1-4 alkylene groups such as a methylene group, an ethylene group, a propylene group, a trimethylene group, a 1,2-butanediyl group, a tetramethylene group, etc. From the viewpoint of optical properties such as a high refractive index, a low Abbe number, and a low birefringence, ^A4 is preferably a direct bond or a _C1-2 alkylene group such as a methylene group, and particularly preferably a direct bond.

The alkylene groups represented by the groups A ^5a and A ^5b constituting the oxyalkylene groups (-OA ^5a -) and (-OA ^5b -) are, for example, the same as the alkylene groups A ^3a and A ^3b exemplified in the above formula (4), including preferred embodiments thereof.

The repeat numbers u1 and u2 of the oxyalkylene groups (-OA ^5a -) and (-OA ^5b -) can be selected, for example, from the range of about 0 to 15, and the preferred ranges are 0 to 10, 0 to 8, 0 to 6, 0 to 4, 0 to 2, and 0 to 1, in the following stepwise order. In addition, u1 and u2 are usually 1 or more, because they have high polymerization reactivity, excellent optical properties such as high refractive index, low Abbe number, and low birefringence, and heat resistance, and can also suppress coloration. For example, they can be selected from the range of about 1 to 15, and the preferred ranges are 1 to 10, 1 to 8, 1 to 6, 1 to 4, 1 to 3, and 1 to 2, in the following stepwise order, and 1 is particularly preferred. In addition, u1 and u2 may be the average number of moles added, and the preferred embodiment is the same as the above preferred range (the above integer range). If u1 and u2 are too large, the heat resistance and refractive index may be reduced.

u1 and u2 may be the same or different, and when u1 or u2 is 2 or more, the types of the two or more oxyalkylene groups (-OA ^5a -) or (-OA ^5b -) may be the same or different. Also, the types of the groups [-(OA ^5a ) _u1 -O-] and [-(OA ^5b ) _u2 -O-] bonded to different naphthalene rings via an ether bond (-O-) may be the same or different.

The substitution positions of the groups [-(OA ^5a ) _u1 -O-] and [-(OA ^5b ) _u2 -O-] may be any of the 2- to 4-positions and the 2'- to 4'-positions relative to A ⁴ which is bonded to the 1,1'-positions of the naphthalene ring. From the viewpoint of reducing birefringence, the 2,2'-positions are particularly preferred.

Examples of the substituents (non-reactive or non-polymerizable substituents) represented by ^R6a and ^R6b include the same groups as those exemplified as ^R1a and ^R1b in the section on the dicarboxylic acid represented by formula (I) (or the first dicarboxylic acid unit (A1)). When the number of substitutions v1 or v2 is 1 or more, preferred groups ^R6a and ^R6b are halogen atoms such as bromine atoms.

The substitution numbers v1 and v2 are, for example, 0 to 4, preferably 0 to 2, 0 or 1, particularly 0. v1 and v2 may be the same or different. When v1 or v2 is 2 or more, the types of the two or more groups R ^6a or R ^6b may be the same or different. Furthermore, the types of the groups R ^6a and R ^6b substituted on two different naphthalene rings may be the same or different.

The substitution positions of the groups R ^6a and R ^6b are not particularly limited as long as they are positions other than the substitution positions of A ⁴ and the groups [-(OA ^5a ) _u1 -O-] and [-(OA ^5b ) _u2 -O-], and are often the 3- to 8-positions and/or the 3'- to 8'-positions relative to A ⁴ which is bonded to the 1,1'-positions of the two naphthalene rings.

Representative examples of the third diol component corresponding to the third diol unit (B3) include dihydroxy-1,1'-binaphthalenes in which ^A4 is a direct bond. Examples of dihydroxy-1,1'-binaphthalenes include dihydroxy-1,1'-binaphthalene such as 2,2'-dihydroxy-1,1'-binaphthalene;bis[hydroxy(poly)alkoxy]-1,1'-binaphthalene; and the like.

Examples of bis[hydroxy(poly)alkoxy]-1,1'-binaphthalene include 2,2'-bis[hydroxy(mono- to deca)C _2-4 alkoxy]-1,1'-binaphthalene such as 2,2'-bis(2-hydroxyethoxy)-1,1'-binaphthalene, 2,2'-bis(2-hydroxypropoxy)-1,1'-binaphthalene, and 2,2'-bis[2-(2-hydroxyethoxy)ethoxy]-1,1'-binaphthalene.

These third diol units (B3) may be contained alone or in combination of two or more. Among the third diol units (B3), from the viewpoints of suppressing coloration, excellent optical properties such as a high refractive index, a low Abbe number, and a low birefringence, and exhibiting relatively high polymerization reactivity, 2,2'-bis[hydroxy(mono- to hexa)C _2-4 alkoxy]-1,1'-binaphthalene is preferred, among which 2,2'-bis[hydroxy(mono- or di)C _2-4 alkoxy]-1,1'-binaphthalene is preferred, and in particular, a structural unit derived from 2,2'-bis[hydroxy(C _2-3 alkoxy)-1,1'-binaphthalene such as 2,2'-bis(2-hydroxyethoxy)-1,1'-binaphthalene is preferred.

(B4) Fourth Diol Unit The diol unit (B) does not necessarily contain a diol unit (fourth diol unit (B4)) different from the first diol unit (B1), the second diol unit (B2), and the third diol unit (B3), but may contain such a diol unit as necessary.

Examples of the fourth diol unit (B4) include alicyclic diols, aromatic diols (excluding the second diol unit (B2) and the third diol unit (B3)), and structural units derived from alkylene oxide (alkylene carbonate or haloalkanol) adducts of these diol components.

Examples of alicyclic diols include cycloalkane diols such as cyclohexanediol; bis(hydroxyalkyl)cycloalkanes such as cyclohexanedimethanol; and hydrogenated aromatic diols such as hydrogenated bisphenol A, which are exemplified below.

Examples of aromatic diols include dihydroxyarenes such as hydroquinone and resorcinol; aromatic aliphatic diols such as benzenedimethanol; bisphenols such as bisphenol A, bisphenol F, bisphenol AD, bisphenol C, bisphenol G, and bisphenol S; and biphenols such as p,p'-biphenol.

Examples of the alkylene oxide (corresponding alkylene carbonate or haloalkanol) adduct of these diol components include a _C2-4 alkylene oxide adduct, preferably a _C2-3 alkylene oxide adduct such as an ethylene oxide adduct or a propylene oxide adduct, and the number of moles added is not particularly limited. Specific examples include an adduct in which about 2 to 10 moles of ethylene oxide are added to 1 mole of a diol such as bisphenol A.

The diol unit (B) may contain these fourth diol units (B4) alone or in combination of two or more.

The proportion of the total amount of the first diol unit (B1), the second diol unit (B2) and the third diol unit (B3) relative to the entire diol unit (B) can be selected, for example, from 1 mol% or more, specifically from a range of about 10 to 100 mol%, and preferred ranges are as follows, in stages: 30 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, and it is particularly preferable that the proportion is 100 mol%, and that the fourth diol unit (B4) is not substantially included.

The proportion of the first diol unit (B1) may be, for example, about 1 mol% or more relative to the entire diol unit (B), and the preferred ranges are 5 mol% or more, 10 mol% or more, 15 mol% or more, and 20 mol% or more in the following stepwise order. In terms of easiness in improving the refractive index, the proportion is preferably 25 mol% or more, and more preferably 30 mol% or more, 40 mol% or more, 50 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, and 95 mol% or more in the following stepwise order. It is more preferable that the proportion is substantially 100 mol%, that is, that it is formed only of the first diol unit (B1). From the viewpoint of achieving a good balance between a high refractive index, a low absolute value of birefringence, high heat resistance, and high moldability, and particularly achieving high heat resistance, the ratio is preferably 1 to 50 mol%, and more preferably ranges are 5 to 40 mol%, 10 to 30 mol%, 15 to 25 mol%, and 20 to 25 mol%, in the following stepwise order. From the viewpoint of achieving a good balance between the above properties and particularly achieving a high refractive index, the ratio is preferably 50 to 100 mol%, and more preferably ranges are 60 to 95 mol%, 70 to 90 mol%, and 75 to 85 mol%, in the following stepwise order, and most preferably 75 to 80 mol%.

If the proportion of the first diol unit (B1) is too small, the refractive index may not be significantly improved, the polymerization reaction may not proceed easily, and productivity may decrease. Conversely, if the proportion is too high, the heat resistance may decrease, and the absolute value of the birefringence may not be reduced.

When the diol unit (B) contains both the first diol unit (B1) and the second diol unit (B2), the ratio (B1/B2) may be selected from the range of B1/B2 (molar ratio) = 1/99 to 99/1, for example, 10/90 to 90/10, preferably 15/85 to 85/15. In order to achieve a good balance between a high refractive index, a low absolute value of birefringence, high heat resistance, and high moldability, and to achieve particularly high heat resistance, the ratio is preferably 1/99 to 50/50, and more preferably the following ranges in stages: 5/95 to 40/60, 10/90 to 30/70, 15/85 to 25/75, and 20/80 to 25/75. From the viewpoint of achieving a high refractive index while satisfying the above-mentioned properties in a well-balanced manner, the ratio is preferably 50/50 to 99/1, and more preferably the following stepwise ranges: 60/40 to 95/5, 70/30 to 90/10, and 75/25 to 85/15, and most preferably 75/25 to 80/20. If the ratio of the second diol unit (B2) is too low, there is a risk that the heat resistance will decrease and that the absolute value of the birefringence cannot be adjusted to a low value, whereas if the ratio is too high, there is a risk that not only the absolute value of the birefringence cannot be adjusted to a low value, but also that the moldability will decrease.

When the diol unit (B) contains both the first diol unit (B1) and the third diol unit (B3), the ratio (B1/B3) of B1/B3 (molar ratio) may be selected from a range of about 1/99 to 99/1, for example, 10/90 to 90/10, and preferred ranges are 20/80 to 80/20, 30/70 to 70/30, and 40/60 to 60/40, in the following stepwise order.

(Carbonate Unit (C))
The resin does not necessarily contain the carbonate unit (C), but may contain the carbonate unit (C) together with the diol unit (B) to form a polyester carbonate resin. In this specification and claims, the term "carbonate unit" refers to a structural unit derived from a carbonate bond forming component, i.e., a carbonyl group [-C(=O)-], which forms a carbonate bond together with the terminal oxygen atoms of the two diol units bonded adjacent to this carbonyl group. Therefore, the carbonate bond forming component may be any compound capable of forming a carbonate bond by reacting with the two diol components, and representative carbonate bond forming components include, for example, phosgenes such as phosgene and triphosgene, and carbonate diesters such as diphenyl carbonate.

These carbonate bond forming components can be used alone or in combination of two or more. Among these carbonate bond forming components, carbonic acid diesters such as diphenyl carbonate are preferred from the viewpoint of safety, etc.

The ratio of the total amount of dicarboxylic acid units (A) and carbonate units (C) in the resin to the diol units (B) is the former/latter (molar ratio) = 1/0.8 to 1/1.2, preferably 1/0.9 to 1/1.1, and is usually preferably approximately equimolar. The ratio (A/C) of dicarboxylic acid units (A) to carbonate units (C) may be selected from the range of A/C (molar ratio) = about 99/1 to 1/99, for example, 90/10 to 10/90, and preferably the following stepwise: 80/20 to 20/80, 70/30 to 30/70, 60/40 to 40/60. If the ratio of carbonate units (C) is too high, the refractive index and heat resistance may decrease.

The resin does not have to contain other structural units (D) different from the dicarboxylic acid units (A), diol units (B), and carbonate units (C), but may contain them, if necessary, to the extent that the effects of the present invention are not impaired.

Other structural units (D) include, for example, structural units derived from hydroxyalkanoic acids and corresponding lactones, and multifunctional polymerization components having three or more carboxyl groups and/or hydroxyl groups.

Examples of the hydroxyalkanoic acids and corresponding lactones include hydroxyalkanoic acids such as lactic acid, 3-hydroxybutyric acid, and 6-hydroxyhexanoic acid; lactones corresponding to hydroxyalkanoic acids such as ε-caprolactone.

Examples of the polyfunctional polymerization components include polyfunctional polymerization components having a total of three or more carboxyl groups and/or hydroxyl groups, such as trivalent or higher polycarboxylic acids such as trimellitic acid and pyromellitic acid, and trivalent or higher polyhydric alcohols such as glycerin and pentaerythritol.

The proportion of such other structural units (D) relative to the total amount of structural units (the total amount of dicarboxylic acid units (A), diol units (B), carbonate units (C), and other structural units (D)) is, for example, 50 mol% or less, with preferred ranges being 40 mol% or less, 30 mol% or less, 20 mol% or less, 10 mol% or less, and 5 mol% or less in the following stepwise order, and usually, other structural units (D) are not substantially contained in the polymer. The proportion may be about 0 to 10 mol%, for example, 0.01 to 1 mol%.

In order to achieve a good balance between a high refractive index (or a low Abbe number), a low absolute value of birefringence, and high heat resistance, the resin of the present invention preferably contains at least a first diol unit (B1) and a second diol unit (B2) in addition to the first dicarboxylic acid unit (A1); and in order to achieve a particularly low absolute value of birefringence, it is even more preferable that the resin of the present invention contains at least a second dicarboxylic acid unit (A2), a first diol unit (B1), and a second diol unit (B2) in addition to the first dicarboxylic acid unit (A1). Among such resins having an excellent balance of properties, (i) a polyester resin formed from a first dicarboxylic acid unit (A1), a second dicarboxylic acid unit (A2), a first diol unit (B1) and a second diol unit (B2) (hereinafter, also referred to as resin (i)); or (ii) a polyester resin formed from a first dicarboxylic acid unit (A1), a second dicarboxylic acid unit (A2), a third dicarboxylic acid unit (A3), a first diol unit (B1) and a second diol unit (B2) (hereinafter, also referred to as resin (ii)) is particularly preferred, from the viewpoint of low birefringence and effective use in applications such as optical lenses, and resin (i) is the most preferred.

(Resin (i))
Resin (i) can be adjusted to have a particularly high refractive index while satisfying a good balance of high refractive index (or low Abbe number), low birefringence, high heat resistance, and high moldability.

A preferred combination of structural units forming the resin (i) is a combination of a structural unit derived from 9,9-bis(carboxyC _2-4 alkyl)-2,7-di(2-naphthyl)fluorene, such as 9,9-bis(2-carboxyethyl)-2,7-di(2-naphthyl)fluorene, as the first dicarboxylic acid unit (A1); a naphthalene dicarboxylic acid unit, such as 2,6-naphthalene dicarboxylic acid, as the second dicarboxylic acid unit (A2); a structural unit derived from a linear or branched C _2-4 alkylene glycol, such as ethylene glycol, as the first diol unit (B1); and a structural unit derived from 9,9-bis[hydroxyC _2-3 alkoxy naphthyl]fluorene, such as 9,9-bis[6-(2-hydroxyethoxy)-2-naphthyl]fluorene, as the second diol unit (B2).

In the resin (i), the ratio (A1/A2) of the first dicarboxylic acid unit (A1) to the second dicarboxylic acid unit (A2) is, for example, A1/A2 (molar ratio) = 85/15 to 50/50, preferably 80/20 to 55/45, more preferably 75/25 to 60/40, even more preferably 70/30 to 65/35, and particularly preferably 69/31 to 66/34. If there is too much second dicarboxylic acid unit (A2), the birefringence may increase too much, and conversely, if there is too little, the birefringence may become large on the (-) side.

In resin (i), the ratio (B1/B2) of the first diol unit (B1) to the second diol unit (B2) is, for example, B1/B2 (molar ratio) = 50/50 to 95/5, preferably 60/40 to 90/10, more preferably 70/30 to 85/15, particularly preferably 75/25 to 80/20, and most preferably 76/24 to 79/21. If the ratio of the second diol unit (B2) is too low, there is a risk that the heat resistance will decrease or that the absolute value of the birefringence cannot be adjusted to a low value, whereas if the ratio is too high, not only will the absolute value of the birefringence not be able to be adjusted to a low value, but moldability may also decrease.

(Resin (ii))
Resin (ii) satisfies a good balance of high refractive index (or low Abbe number), low birefringence, high heat resistance and high moldability, and in particular can achieve a high degree of compatibility between high heat resistance and high moldability.

A preferred combination of structural units forming the resin (ii) is a combination of a structural unit derived from 9,9-bis(carboxyC _2-4 alkyl)-2,7-di(2-naphthyl)fluorene, such as 9,9-bis(2-carboxyethyl)-2,7-di(2-naphthyl)fluorene, as the first dicarboxylic acid unit (A1); a naphthalene dicarboxylic acid unit, such as 2,6-naphthalene dicarboxylic acid, as the second dicarboxylic acid unit (A2); a C _2-6 alkane-dicarboxylic acid unit, such as adipic acid, as the third dicarboxylic acid unit (A3); a structural unit derived from a linear or branched C _2-4 alkylene glycol, such as ethylene glycol, as the first diol unit (B1); and a structural unit derived from 9,9-bis[hydroxyC _2-3 alkoxy naphthyl]fluorene, such as 9,9-bis[6-(2-hydroxyethoxy)-2-naphthyl]fluorene, as the second diol unit (B2).

In the resin (ii), the ratio (A1/A2) of the first dicarboxylic acid units (A1) to the second dicarboxylic acid units (A2) is, for example, A1/A2 (molar ratio) = 99/1 to 80/20, preferably 95/5 to 85/15, and more preferably 93/7 to 87/13. If the amount of the second dicarboxylic acid units (A2) is too large, the birefringence may increase too much, and conversely, if the amount is too small, the birefringence may increase toward the (-) side.

In the resin (ii), the ratio (A1/A3) of the first dicarboxylic acid unit (A1) to the third dicarboxylic acid unit (A3) is, for example, A1/A3 (molar ratio) = 65/35 to 45/55, preferably 60/40 to 50/50, more preferably 60/40 to 55/45, and particularly preferably 59/41 to 56/44. If the amount of the third dicarboxylic acid unit (A3) is too large, the refractive index and heat resistance may be significantly reduced, and conversely, if the amount is too small, it may be difficult to achieve both high levels of heat resistance and moldability.

In the resin (ii), the ratio (A2/A3) of the second dicarboxylic acid units (A2) to the third dicarboxylic acid units (A3) is, for example, A2/A3 (molar ratio) = 25/75 to 1/99, preferably 20/80 to 5/95, and more preferably 15/85 to 10/90. If the amount of the second dicarboxylic acid units (A2) is too large, the birefringence may increase too much, and conversely, if the amount is too small, the birefringence may become large on the (-) side.

In resin (ii), the ratio (B1/B2) of the first diol unit (B1) to the second diol unit (B2) is, for example, B1/B2 (molar ratio) = 85/15 to 65/35, preferably 80/20 to 70/30, and more preferably 78/22 to 72/27. If the ratio of the second diol unit (B2) is too small, it may not be possible to adjust the absolute value of the birefringence low, and conversely, if it is too high, moldability may decrease.

[Method of producing resin]
The method for producing the resin is not particularly limited except that the dicarboxylic acid component (A) containing the first dicarboxylic acid component (A1) is used as a polymerization component, and a conventional method can be used depending on the type of resin or other polymerization components (copolymerization components). For example, in the case of a polyester resin such as a polyester resin, the dicarboxylic acid component (A) corresponding to each dicarboxylic acid unit described above, the diol acid component (B) corresponding to the diol unit described above, and if necessary, the carbonate bond forming component (C) can be reacted to produce the resin, and the resin can be prepared by a conventional method, specifically, a melt polymerization method such as an ester exchange method or a direct polymerization method, a solution polymerization method, or an interfacial polymerization method, and the melt polymerization method is preferred. The reaction may be carried out in the presence or absence of a solvent depending on the polymerization method.

The ratio of the dicarboxylic acid component (A) to the diol component (B) is usually, for example, 1/1.2 to 1/0.8, preferably 1/1.1 to 1/0.9, but it does not necessarily have to be in this range. At least one component selected from each dicarboxylic acid component (A) and each diol component (B) may be used in excess of the planned introduction ratio. For example, the first diol component (B1), such as ethylene glycol, which can be distilled from the reaction system, may be used in excess of the ratio (or introduction ratio) introduced into the resin. In addition, when a carbonate bond forming component (C) is used, the ratio of the total amount of the dicarboxylic acid component (A) and the carbonate bond forming component (C) to the diol component (B) is, for example, 1/1.2 to 1/0.8, preferably 1/1.1 to 1/0.9, for example, the former/latter (molar ratio). In addition, taking into consideration volatilization and decomposition during the reaction, the carbonate bond-forming component (C) may be used in a slight excess over the planned introduction ratio. For example, the carbonate bond-forming component (C) may be used in an excess of 0.1 to 5 mol %, preferably 2 to 3 mol %, over the total amount of the dicarboxylic acid units (A) and the carbonate units (C) (the total amount planned to be introduced into the resin).

The reaction may be carried out in the presence of a catalyst. As the catalyst, a conventional esterification catalyst, for example, a metal catalyst, etc., can be used. As the metal catalyst, for example, a metal compound containing an alkali metal such as sodium; an alkaline earth metal such as magnesium, calcium, barium; a transition metal such as titanium, manganese, cobalt; a metal of Group 12 of the periodic table such as zinc, cadmium; a metal of Group 13 of the periodic table such as aluminum; a metal of Group 14 of the periodic table such as germanium, lead; a metal of Group 15 of the periodic table such as antimony, etc., is used. As the metal compound, for example, an alkoxide; an organic acid salt such as acetate or propionate; an inorganic acid salt such as borate or carbonate; an oxide, etc., or a hydrate thereof may be used. Representative examples of metal compounds include germanium compounds such as germanium dioxide, germanium hydroxide, germanium oxalate, germanium tetraethoxide, and germanium-n-butoxide; antimony compounds such as antimony trioxide, antimony acetate, and antimony ethylene glycolate; titanium compounds such as tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate (titanium (IV) tetrabutoxide), titanium oxalate, and potassium titanium oxalate; manganese compounds such as manganese acetate tetrahydrate; and calcium compounds such as calcium acetate monohydrate.

These catalysts can be used alone or in combination of two or more. When using a plurality of catalysts, each catalyst can be added according to the progress of the reaction. Among these catalysts, manganese acetate tetrahydrate, calcium acetate monohydrate, germanium dioxide, titanium (IV) tetrabutoxide, etc. are preferred. The amount of the catalyst used is, for example, 0.01×10 ⁻⁴ to 100×10 ⁻⁴ mol, preferably 0.1×10 ⁻⁴ to 40×10 ⁻⁴ mol, per mol of the dicarboxylic acid component (A).

The reaction may be carried out in the presence of a stabilizer such as a heat stabilizer or an antioxidant, if necessary. Usually, a heat stabilizer is often used, and examples of the heat stabilizer include phosphorus compounds such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dibutyl phosphate (dibutyl phosphate or dibutyl phosphate), phosphorous acid, trimethyl phosphite, and triethyl phosphite. Of these, dibutyl phosphate is often used. The amount of the heat stabilizer used is, for example, 0.01×10 ⁻⁴ to 100×10 ⁻⁴ moles, preferably 0.1×10 ⁻⁴ to 40×10 ⁻⁴ moles, per mole of the dicarboxylic acid component (A).

The reaction is usually carried out in an atmosphere of an inert gas, for example, nitrogen gas; or a rare gas such as helium or argon. The reaction can also be carried out under reduced pressure, for example, about 1×10 ² to 1×10 ⁴ Pa. Usually, the transesterification reaction is often carried out under an atmosphere of an inert gas such as nitrogen gas, and the polycondensation reaction is often carried out under reduced pressure. The reaction temperature can be selected depending on the polymerization method, and for example, the reaction temperature in the melt polymerization method is 150 to 320° C., preferably 180 to 310° C., and more preferably 200 to 300° C.

[Resin characteristics and molded products]
(Characteristics)
The resin of the present invention has a high refractive index and high heat resistance because it contains the first dicarboxylic acid unit (A1). In addition, the resin can have excellent optical properties (high refractive index, low Abbe number, low absolute value of birefringence) and high heat resistance in a highly balanced manner.

The glass transition temperature Tg of the resin may be, for example, in the range of about 100 to 250°C, and the preferred ranges are, in the following stepwise order, 110 to 230°C, 120 to 210°C, and 130 to 200°C. From the viewpoint of having a good balance between optical properties such as a high refractive index, a low Abbe number, and a low absolute value of birefringence, and high heat resistance, and also having high moldability, 135 to 200°C is preferred, and the more preferred ranges are, in the following stepwise order, 140 to 190°C, 145 to 185°C, 145 to 180°C, 148 to 175°C, 150 to 170°C, and 150 to 165°C. Although 150 to 160°C is also acceptable, 155 to 165°C is particularly preferred from the viewpoint of achieving a high degree of both high heat resistance and high moldability.

If the glass transition temperature Tg is too low, the heat resistance may decrease, and the material may be prone to deterioration or discoloration (or coloring) during molding and/or use, or may be prone to deformation in high-temperature environments after being molded into a specified shape, making it impossible to use the material in applications that require high heat resistance (or thermal stability), such as automotive optical lenses. On the other hand, if the glass transition temperature Tg is too high, molding processes such as injection molding must be performed at high temperatures, which not only reduces moldability (or productivity), but also causes deterioration and coloring of the resulting molded product due to the increase in molding temperature, and may require a special mold for cooling in order to suppress distortion in the molded product and prevent a decrease in surface smoothness.

Normally, when an aromatic ring is introduced into the chemical structure of a resin to give it a high refractive index, the molecular skeleton becomes rigid, and the glass transition temperature rises along with the refractive index. However, in the high refractive index region that has been required in recent years, for example, in resins having nD of 1.7 or more, preferably 1.71 or more, the glass transition temperature becomes particularly high, making it even more difficult to achieve both high moldability (or productivity). However, the resin of the present invention has a high refractive index and heat resistance, but is surprisingly easy to suppress an excessive increase in the glass transition temperature, and therefore can achieve a good balance between the excellent optical properties and high heat resistance, as well as high moldability.

The refractive index nD of the resin can be selected, for example, from a range of about 1.68 to 1.75 at a temperature of 20°C and a wavelength of 589 nm, and is preferably in the following stepwise order: 1.69 to 1.74, 1.7 to 1.735, 1.71 to 1.73, and more preferably 1.715 to 1.725.

The Abbe number of the resin is, for example, 20 or less at a temperature of 20°C. Since the Abbe number usually tends to decrease with an increase in the refractive index, the resin of the present invention, which exhibits a high refractive index, can be effectively used in applications requiring a lower Abbe number, such as optical components in various cameras, specifically, camera lenses using a combination of concave and convex lenses. In the optical systems of various cameras, a concave lens with a low Abbe number is used to reduce (or cancel) the chromatic aberration (bleed) that occurs in a convex lens, and is usually composed of a combination of multiple concave and convex lenses. The resin of the present invention can fully meet the low Abbe number required for the concave lens. The Abbe number of the resin in such applications is, for example, 18 or less, preferably 15 or less, more preferably 10 to 14, and even more preferably 10.5 to 13.5 at a temperature of 20°C.

The birefringence of a resin may be evaluated by the birefringence (triple birefringence) of a stretched film obtained by uniaxially stretching a film formed from the resin alone at a stretching temperature of glass transition temperature Tg+10° C., a stretching speed of 25 mm/min, and a stretching ratio of 3. The absolute value of the triple birefringence of the stretched film can be selected from a range of, for example, 300×10 ⁻⁴ or less at a measurement temperature of 20° C. and a wavelength of 600 nm, and preferred ranges are, in the following stepwise order, 200×10 ⁻⁴ or less, 100×10 ⁻⁴ or less, 50×10 ⁻⁴ or less, 40×10 ⁻⁴ or less, 30×10 ⁻⁴ or less, 25×10 ⁻⁴ or less, 20×10 ⁻⁴ or less, more preferably 15×10 ⁻⁴ or less, and particularly preferably 10×10 ⁻⁴ or less. Usually, it is about 0 to 35×10 ⁻⁴ , for example, 0.001×10 ⁻⁴ to 25×10 ⁻⁴ .

The weight average molecular weight Mw of the resin can be measured by gel permeation chromatography (GPC) or the like, and can be selected from a range of, for example, about 10,000 to 1,000,000 in terms of polystyrene. Preferred ranges are as follows, in stages: 20,000 to 200,000, 30,000 to 150,000, 40,000 to 120,000, 50,000 to 110,000, 60,000 to 100,000, 70,000 to 90,000, and 75,000 to 85,000, but are more preferably 40,000 to 70,000, and particularly preferably 43,000 to 63,000. If the weight average molecular weight Mw is too low, there is a risk that the heat resistance and moldability (productivity) may be easily reduced.

In this specification and claims, the glass transition temperature Tg, refractive index nD, Abbe number, triple birefringence, and weight average molecular weight Mw can be measured by the method described in the examples below.

(Molded body)
The molded article of the present invention contains at least the resin and has excellent optical properties such as a high refractive index, a low absolute value of birefringence, and a low Abbe number, as well as high heat resistance, and can therefore be used as an optical member such as an optical film (or optical sheet) or an optical lens. Such a molded article may contain conventional additives. Examples of the additives include fillers or reinforcing agents, colorants such as dyes and pigments, conductive agents, flame retardants, plasticizers, lubricants, release agents, antistatic agents, dispersants, flow control agents, leveling agents, defoamers, surface modifiers, hydrolysis inhibitors, carbon materials, stabilizers, and stress reducing agents. Examples of the stabilizers include antioxidants, ultraviolet absorbers, and heat stabilizers. Examples of the stress reducing agents include silicone oils, silicone rubbers, various plastic powders, and various engineering plastic powders. These additives may be used alone or in combination of two or more.

The molded body can be manufactured using, for example, injection molding, injection compression molding, extrusion molding, transfer molding, blow molding, pressure molding, casting molding, etc.

The shape of the molded body is not particularly limited, and examples include one-dimensional structures such as linear, fibrous (or fiber-like) and thread-like structures, two-dimensional structures such as film-like, sheet-like and plate-like structures, and three-dimensional structures such as concave or convex lens-like, rod-like and hollow (tubular) structures.

In particular, the resin of the present invention is useful for forming optical films because it has various excellent optical properties. Therefore, the present invention also includes films (optical films or optical sheets) formed from the resin.

The average thickness of such a film can be selected from a range of approximately 1 to 1000 μm depending on the application, for example, 1 to 200 μm, preferably 5 to 150 μm, and more preferably 10 to 120 μm.

Such films (optical films) can be produced by forming (or molding) the resin into a film using a conventional film-forming method, such as a casting method (solvent casting method), a melt extrusion method, or a calendar method.

The film may be a stretched film. The film of the present invention can maintain low birefringence even if it is a stretched film. Such a stretched film may be either a uniaxially stretched film or a biaxially stretched film.

The stretching ratio in each direction in uniaxial or biaxial stretching is, for example, 1.1 to 10 times, preferably 1.2 to 6 times, and more preferably 1.5 to 3 times. In the case of biaxial stretching, it may be equal stretching, for example, stretching about 1.5 to 5 times in both the longitudinal and transverse directions, or uneven stretching, for example, stretching about 1.1 to 4 times in the longitudinal direction and about 2 to 6 times in the transverse direction. In the case of uniaxial stretching, it may be longitudinal stretching, for example, stretching about 2.5 to 8 times in the longitudinal direction, and transverse stretching, for example, stretching about 1.2 to 5 times in the transverse direction.

The average thickness of the stretched film is, for example, 1 to 150 μm, preferably 3 to 120 μm, and more preferably 5 to 100 μm.

Such a stretched film can be obtained by stretching the film (or unstretched film) after film formation. There are no particular limitations on the stretching method, and in the case of uniaxial stretching, either the wet stretching method or the dry stretching method may be used, and in the case of biaxial stretching, either the tenter method (flat method) or the tube method may be used, although the tenter method, which has excellent uniformity in the stretched thickness, is preferred.

The molded article may also be joined or adhered to another substrate, and the type or material of the substrate is not particularly limited, and may be, for example, a substrate having a one-dimensional, two-dimensional, or three-dimensional shape formed from a resin material, a ceramic material, a metal material, etc. For example, if the molded article is in the form of a film, it may be combined with a substrate having a two-dimensional shape such as a film to form a laminate or laminate film.

Representative examples of the substrate having the two-dimensional shape include ceramic substrates such as glass substrates, resin films, etc., and are usually transparent substrates. Examples of the resin forming the resin film include polyolefin resins such as linear olefin resins and cyclic olefin resins (or cycloolefin resins); (meth)acrylic resins; styrene resins; polyester resins such as polyalkylene arylate resins, polyarylate resins, and polycarbonate resins; and polyamide resins. In particular, the substrate may be used by laminating it with a resin film formed from a cycloolefin resin, polyamide resin, or the like.

The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Details of the evaluation items and raw materials are shown below.

[Evaluation method]
(HPLC)
A sample was dissolved in acetonitrile and measured using an HPLC (high performance or high performance liquid chromatograph) apparatus "LC-2010A HT" manufactured by Shimadzu Corporation and an ODS-80TM column manufactured by Tosoh Corporation, and the HPLC purity [area %] was calculated.

(FD-MS)
Mass spectrometry (MS) was performed using the following measuring device and conditions.

Equipment used: “JMS-T200GC” manufactured by JEOL Ltd.
Ionization method: FD (field desorption)
Emitter: Carbon Emitter current: 0-50mA (25mA/min).

(Melting Point)
A differential scanning calorimeter ("EXSTAR DSC6200" manufactured by SII NanoTechnology, Inc.) was used to perform measurements under conditions of a nitrogen atmosphere, a measurement temperature of 30 to 300° C., and a temperature rise rate of 10° C./min. From the obtained DSC chart (DSC curve), the peak top temperature of the endothermic peak due to melting was determined as the melting point.

(5% mass loss temperature)
Using a thermogravimetric-differential thermal analyzer (TG-DTA) ("TG/DTA6200" manufactured by SII NanoTechnology Co., Ltd.), the following was performed under conditions of a nitrogen atmosphere and a heating rate of 10°C/min. The temperature at which the mass of the sample decreased by 5% by mass was measured.

(Polymer Composition)
The sample was dissolved in deuterated chloroform containing tetramethylsilane as an internal standard, and ^1H -NMR spectrum was measured using a nuclear magnetic resonance apparatus ("AVANCE III HD" manufactured by BRUKER). For the spectrum obtained, the integral value of the peak derived from each monomer used in the polymerization was obtained, and the proportion of each monomer component (structural unit) introduced into the polymer was calculated.

(Glass transition temperature Tg)
The measurement was performed using a differential scanning calorimeter ("EXSTAR6000 DSC6220 ASD-2" manufactured by SII NanoTechnology Inc.) in a nitrogen gas atmosphere at a temperature increase rate of 10° C./min.

(Molecular Weight)
The sample was dissolved in chloroform, and the weight average molecular weight Mw in terms of polystyrene was determined using gel permeation chromatography ("HLC-8320GPC" manufactured by Tosoh Corporation).

(Refractive index nD)
The refractive indexes of 2-DNFDP-m and 1-DNFDP-m obtained in Examples 1 and 2, and FDP-m obtained in Comparative Example 1 were measured at a temperature of 25° C. and a wavelength of 589 nm (D line) using a refractometer (DR-M2 (circulating thermostatic bath 60-C3) manufactured by Atago Co., Ltd.). The refractive index was calculated by extrapolating the concentration to 100% by mass in a calibration curve (approximation line) prepared by dissolving a sample in chloroform to prepare solutions with concentrations of 7.67% by mass and 16.8% by mass and measuring the refractive index of the obtained solutions.

The refractive index of the resin sample was measured as follows. The sample was hot pressed at 200-240°C to form a film with a thickness of 200-300 μm. This film was cut into strips measuring 20-30 mm in length and 10 mm in width to obtain test pieces. The refractive index nD of the obtained test pieces at 589 nm (D line) was measured using a multi-wavelength Abbe refractometer (DR-M4 (circulating thermostatic bath 60-C3) manufactured by Atago Co., Ltd.) at a measurement temperature of 20°C and diiodomethane as the contact liquid.

(Abbe number)
Using the test piece for measuring the refractive index nD at 589 nm (D line), the refractive indexes nF and nC were measured in the same manner as for the refractive index nD, except that the measurement wavelengths were changed to 486 nm (F line) and 656 nm (C line). The Abbe number was calculated from the refractive indexes nF, nD, and nC at the respective wavelengths by the following formula.

(Abbe number) = (nD-1)/(nF-nC).

(Birefringence (stretched 3 times))
The sample was hot pressed at 200 to 240 ° C. to form a film having a thickness of 200 to 600 μm. The film was cut into a rectangular shape having a width of 10 mm and a length of 50 mm, and uniaxially stretched in the longitudinal direction at a temperature of glass transition temperature Tg + 10 ° C. at 25 mm / min so that the stretch ratio was 3 times (so that the length of 50 mm became 150 mm) to obtain a test piece. The retardation of the obtained test piece was measured by the parallel Nicol rotation method under the conditions of a measurement temperature of 20 ° C. and a measurement wavelength of 600 nm using a retardation film / optical material inspection device (manufactured by Otsuka Electronics Co., Ltd. "RETS-100"), and the value was divided by the thickness of the measurement site to calculate the birefringence (or triple birefringence).

[Resin raw materials]
(Dicarboxylic acid component)
2-DNFDP-m: 9,9-bis(2-methoxycarbonylethyl)-2,7-di(2-naphthyl)fluorene, synthesized according to Example 1 (Examples 1A and 1B) described later. 1-DNFDP-m: 9,9-bis(2-methoxycarbonylethyl)-2,7-di(1-naphthyl)fluorene, synthesized according to Example 2 described later. FDP-m: 9,9-bis(2-methoxycarbonylethyl)fluorene [or 9,9-bis(2-carboxyethyl)fluorene or dimethyl ester of fluorene-9,9-dipropionic acid], synthesized according to Comparative Example 1 described later. DMN: 2,6-bis(methoxycarbonyl)naphthalene DA: 2,2'-biphenyldicarboxylic acid AA-m: dimethyl adipate (carbonate bond forming component)
DPC: Diphenyl carbonate (diol component)
BNEF: 9,9-bis[6-(2-hydroxyethoxy)-2-naphthyl]fluorene, synthesized according to Synthesis Example 1 described in JP-A-2018-59074 BINOL-2EO: 2,2'-bis(2-hydroxyethoxy)-1,1'-binaphthyl, synthesized according to Synthesis Example 2 described in JP-A-2018-59074 1,5-PDO: 1,5-pentanediol EG: ethylene glycol.

Example 1A Preparation of 2-DNFDP-m 9,9-bis(2-methoxycarbonylethyl)-2,7-dibromofluorene (DBrFDP-m) was synthesized in the same manner as in Example 1 described in JP 2005-89422 A, except that methyl acrylate [37.9 g (0.44 mol)] was used instead of t-butyl acrylate and 2,7-dibromo-9H-fluorene [54.7 g (0.17 mol)] was used instead of fluorene.

In a reactor, 192.3 g (0.39 mol) of DBrFDP-m, 200 g (1.2 mol) of 2-naphthylboronic acid, 4.3 L of dimethoxyethane, and 1 L of 2M aqueous sodium carbonate solution were charged, and 22.4 g (19.4 mmol) of tetrakis(triphenylphosphine)palladium(0) [or Pd(PPh ₃ ) ₄ ] was added under a nitrogen stream, and the mixture was heated and refluxed at an internal temperature of 71 to 78° C. for 5 hours to cause a reaction. After cooling to room temperature, 2.0 L of toluene and 500 mL of ion-exchanged water were added, and the mixture was washed by extracting and separating five times. The organic layer changed from deep orange to brown. Insoluble matter was filtered and concentrated to obtain 305 g of brown crude crystals. The obtained crude crystals were dissolved by heating in a mixture of 1.5 kg of ethyl acetate and 300 g of isopropyl alcohol (IPA), cooled to 10°C or less with ice water, and stirred for 1 hour to precipitate crystals. The precipitated crystals were filtered and dried under reduced pressure to obtain 130 g of gray-brown crystals. The obtained gray-brown crystals were purified by column chromatography (silica gel carrier, developing solvent chloroform:ethyl acetate (volume ratio) = 4:1), recrystallized with methanol, and dried under reduced pressure to obtain 116 g of 9,9-bis(2-methoxycarbonylethyl)-2,7-di(2-naphthyl)fluorene (2-DNFDP-m) represented by the following formula (white crystals, yield 54.9%, HPLC purity 99.4 area%). The results of ¹ H-NMR and FD-MS are shown below.

¹ H-NMR (CDCl ₃ , 300 MHz): δ (ppm) 1.7 (t, 4H), 2.6 (t, 4H), 3.4 (s, 6H), 7.5 (m, 4H) , 7.7-8.0 (m, 14H), 8.1 (s, 2H)
FD-MS: m/z 590 (M+).

The refractive index nD was 1.845, the melting point was 191°C, and the 5% mass loss temperature was 390°C.

Example 1B Preparation of 2-DNFDP-m DBrFDP-m was synthesized in the same manner as in Example 1 described in JP 2005-89422 A, except that methyl acrylate [31.0 g (0.36 mol)] was used instead of t-butyl acrylate and 2,7-dibromo-9H-fluorene [54.7 g (0.17 mol)] was used instead of fluorene.
In a reactor, 193.5 g (0.39 mol) of DBrFDP-m, 137.5 g (0.80 mol) of 2-naphthylboronic acid, 4.3 L of toluene, and 0.5 L of 2M aqueous sodium carbonate solution were charged, and 0.22 g (0.19 mmol) of Pd(PPh ₃ ) ₄ was added under a nitrogen stream, and the mixture was heated and refluxed at an internal temperature of 83 to 90° C. for 5 hours to react. After the reaction, 500 mL of ion-exchanged water was added, and the mixture was washed by extracting and separating five times. After draining, powdered activated carbon (Osaka Gas Chemicals Co., Ltd.'s "Special Shirasagi") was added to the organic layer to remove palladium, and insoluble matter was removed by filtration. The organic layer was concentrated to remove 3.8 L of toluene, and then 0.1 L of isopropyl alcohol (IPA) was added, cooled to 10° C. or less with ice water, and stirred for 1 hour to precipitate crystals. The precipitated crystals were filtered and dried under reduced pressure to obtain white crystals. 194.9 g of 2-DNFDP-m was obtained (white crystals, yield 84.7%, HPLC purity 99.8% by area). The results of ¹ H-NMR, FD-MS, refractive index nD, melting point, and 5% mass loss temperature were all similar to those of Example 1A.

Example 2 Preparation of 1-DNFDP-m DBrFDP-m was synthesized in the same manner as in Example 1B.
In a reactor, 176.6 g (0.36 mol) of DBrFDP-m, 134.7 g (0.78 mol) of 1-naphthylboronic acid, 1.95 L of dimethoxyethane, and 0.44 L of 2M aqueous sodium carbonate solution were charged, and under a nitrogen stream, 6.2 g (5.4 mmol) of Pd(PPh ₃ ) ₄ was added, and the mixture was heated and refluxed at an internal temperature of 70 to 77°C for 5 hours to cause a reaction. After cooling to 50°C, 1.0 L of toluene and 500 mL of ion-exchanged water were added, and the mixture was washed by extracting the liquid 5 times. Insoluble matter was filtered and concentrated, and then dissolved by heating in a mixture of 0.18 kg of ethyl acetate and 870 g of isopropyl alcohol (IPA), cooled to 3°C or less, and stirred for 1 hour to precipitate crystals. The precipitated crystals were filtered and dried under reduced pressure to obtain 199.6 g of pale yellow crystals. The obtained crystals were purified by column chromatography (silica gel carrier, developing solvent chloroform:ethyl acetate (volume ratio) = 500:1), then recrystallized from methanol and dried under reduced pressure to obtain 176 g of 9,9-bis(2-methoxycarbonylethyl)-2,7-di(1-naphthyl)fluorene (1-DNFDP-m) represented by the following formula (light yellow crystals, yield 84.3%, HPLC purity 98.7% by area). The results of ¹ H-NMR are shown below.

¹ H-NMR (CDCl ₃ , 300 MHz): δ (ppm) 1.8 (t, 4H), 2.5 (t, 4H), 3.5 (s, 6H), 7.5-7.6 ( m, 12H), 7.9 (m, 8H).

The refractive index nD was 1.784, the melting point was 142.2°C, and the 5% mass loss temperature was 401°C.

Comparative Example 1: Preparation of FDP-m FDP-m was synthesized in the same manner as in Example 1 of JP-A-2005-89422, except that methyl acrylate [37.9 g (0.44 mol)] was used instead of t-butyl acrylate. The refractive index nD of FDP-m was 1.559, the melting point was 83°C, and the 5% mass loss temperature was 240°C.

The evaluation results for Examples 1 (1A, 1B) to 2 and Comparison Example 1 are shown in Table 1.

As is clear from the results in Table 1, the introduction of naphthyl groups in the DNFDP-m obtained in the examples resulted in an extremely high 5% mass loss temperature and a significant improvement in heat resistance (temperature at which the compound decomposes and/or volatilizes) compared to the FDP-m in Comparative Example 1. In addition, 2-DNFDP-m had a higher melting point, and 1-DNFDP-m had a higher 5% mass loss temperature.

[Comparative Example 2]
A polyester resin was prepared according to Example 1 described in JP-A-2014-218645.

[Comparative Example 3]
In the reactor, FDP-m (23.70 g (70 mmol)) as a dicarboxylic acid component, DA (16.97 g (70 mmol)), BNEF (64.10 g (119 mmol)) as a diol component, EG (18.68 g (301 mmol)), titanium (IV) tetrabutoxide (8.2 mg (24 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (37.8 mg (180 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 250 ° C. under a nitrogen gas atmosphere, stirred, and transesterification reaction was performed. After removing the alcohol component generated by the transesterification reaction, the temperature was gradually raised to 300 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was performed until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 3]
In the reactor, 2-DNFDP-m (23.63 g (40 mmol)) as a dicarboxylic acid component, EG (7.45 g (120 mmol)) as a diol component, titanium (IV) tetrabutoxide (1.4 mg (4 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (8.4 mg (40 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 245 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 280 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 4]
Into the reactor, 1-DNFDP-m (23.63 g (40 mmol)) as a dicarboxylic acid component, EG (7.45 g (120 mmol)) as a diol component, titanium (IV) tetrabutoxide (1.4 mg (4 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (8.4 mg (40 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 245 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 280 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 5]
In the reactor, 2-DNFDP-m (23.63 g (40 mmol)) as a dicarboxylic acid component, DA (9.69 g (40 mmol)), BNEF (36.68 g (68 mmol)) as a diol component, EG (10.68 g (172 mmol)), titanium (IV) tetrabutoxide (8.2 mg (24 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (16.8 mg (80 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 260 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 295 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 6]
In the reactor, 2-DNFDP-m (23.63 g (40 mmol)) as a dicarboxylic acid component, BNEF (17.24 g (32 mmol)) as a diol component, EG (5.46 g (88 mmol)), titanium (IV) tetrabutoxide (1.4 mg (4 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (8.4 mg (40 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 250 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 7]
In the reactor, 2-DNFDP-m (28.35 g (48 mmol)) as a dicarboxylic acid component, DMN (2.91 g (12 mmol)), BNEF (14.54 g (27 mmol)), EG (13.22 g (213 mmol)) as a diol component, titanium (IV) tetrabutoxide (2.0 mg (6 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (12.6 mg (60 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere, stirred, and transesterification reaction was performed. After removing the alcohol component generated by the transesterification reaction, the temperature was gradually raised to 285 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was performed until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 8]
In the reactor, 2-DNFDP-m (41.35 g (70 mmol)) as a dicarboxylic acid component, DMN (7.33 g (30 mmol)), BNEF (16.16 g (30 mmol)) as a diol component, EG (16.77 g (270 mmol)), titanium (IV) tetrabutoxide (4.3 mg (12.5 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (26.3 mg (125 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere, stirred, and transesterification reaction was performed. After removing the alcohol component generated by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was performed until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 9]
In the reactor, 2-DNFDP-m (16.54 g (28 mmol)) as a dicarboxylic acid component, DMN (2.93 g (12 mmol)), BNEF (4.31 g (8 mmol)), EG (6.95 g (112 mmol)) as a diol component, titanium (IV) tetrabutoxide (1.7 mg (5 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (10.5 mg (50 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 250 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 10]
In the reactor, 1-DNFDP-m (16.54 g (28 mmol)) as a dicarboxylic acid component, DMN (2.93 g (12 mmol)), BNEF (4.31 g (8 mmol)), EG (6.21 g (100 mmol)) as a diol component, titanium (IV) tetrabutoxide (1.7 mg (5 μmol)) as a catalyst for transesterification and polycondensation reaction, dibutyl phosphate (10.5 mg (50 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 280 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 11]
In the reactor, 2-DNFDP-m (32.13 g (54.4 mmol)) as a dicarboxylic acid component, DMN (6.25 g (25.6 mmol)), BNEF (8.62 g (16 mmol)), EG (13.91 g (224 mmol)) as a diol component, titanium (IV) tetrabutoxide (2.7 mg (8 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (21.0 mg (100 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 12]
In the reactor, 2-DNFDP-m (35.44 g (60 mmol)) as a dicarboxylic acid component, DMN (9.77 g (40 mmol)), BNEF (10.77 g (20 mmol)) as a diol component, EG (17.38 g (280 mmol)), titanium (IV) tetrabutoxide (4.3 mg (12.5 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (26.3 mg (125 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere, stirred, and transesterification reaction was performed. After removing the alcohol component generated by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was performed until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 13]
In the reactor, 2-DNFDP-m (14.77 g (25 mmol)) as a dicarboxylic acid component, DMN (6.11 g (25 mmol)), BNEF (5.38 g (10 mmol)), EG (8.70 g (140 mmol)) as a diol component, titanium (IV) tetrabutoxide (1.7 mg (5 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (10.5 mg (50 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 250 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 14]
In the reactor, 2-DNFDP-m (33.09 g (56 mmol)) as a dicarboxylic acid component, DMN (5.86 g (24 mmol)), BNEF (4.31 g (8 mmol)), EG (14.4 g (232 mmol)) as a diol component, titanium (IV) tetrabutoxide (2.6 mg (7.5 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (21.0 mg (100 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 15]
In the reactor, 2-DNFDP-m (11.53 g (19.5 mmol)) as a dicarboxylic acid component, DMN (2.56 g (10.5 mmol)), BINOL-2EO (5.62 g (15 mmol)), EG (4.67 g (75 mmol)) as a diol component, titanium (IV) tetrabutoxide (1.3 mg (3.75 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (3.2 mg (15 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 250 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 16]
In the reactor, 2-DNFDP-m (28.35 g (48 mmol)) and AA-m (5.57 g (32 mmol)) were charged as dicarboxylic acid components, BNEF (32.32 g (60 mmol)) and EG (11.19 g (180 mmol)) were charged as diol components, titanium (IV) tetrabutoxide (2.7 mg (8 μmol)) was charged as a catalyst for transesterification and polycondensation, and dibutyl phosphate (16.8 mg (80 μmol)) was charged as a heat stabilizer, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 285 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 17]
In the reactor, 2-DNFDP-m (25.05 g (42.4 mmol)), DMN (1.37 g (5.6 mmol)), AA-m (5.57 g (32 mmol)) as dicarboxylic acid components, BNEF (32.32 g (60 mmol)), EG (11.18 g (180 mmol)) as diol components, titanium (IV) tetrabutoxide (2.7 mg (8 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (16.8 mg (80 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere, stirred, and transesterification reaction was performed. After removing the alcohol component generated by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was performed until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 18]
In the reactor, 2-DNFDP-m (23.63 g (40 mmol)), DMN (1.95 g (8 mmol)), AA-m (5.57 g (32 mmol)) as dicarboxylic acid components, BNEF (32.32 g (60 mmol)), EG (11.18 g (180 mmol)) as diol components, titanium (IV) tetrabutoxide (2.7 mg (8 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (16.8 mg (80 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere, stirred, and transesterification reaction was performed. After removing the alcohol component generated by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was performed until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 19]
In the reactor, 2-DNFDP-m (23.63 g (40 mmol)) and FDP-m (13.54 g (40 mmol)) were charged as dicarboxylic acid components, BNEF (32.32 g (60 mmol)) and EG (11.18 g (180 mmol)) were charged as diol components, titanium (IV) tetrabutoxide (2.7 mg (8 μmol)) was charged as a catalyst for transesterification and polycondensation, and dibutyl phosphate (16.8 mg (80 μmol)) was charged as a heat stabilizer, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 20]
In the reactor, 2-DNFDP-m (16.54 g (28 mmol)), DMN (1.95 g (8 mmol)), FDP-m (14.89 g (44 mmol)) as dicarboxylic acid components, BNEF (32.32 g (60 mmol)), EG (11.18 g (180 mmol)) as diol components, titanium (IV) tetrabutoxide (2.7 mg (8 μmol)) as a catalyst for transesterification and polycondensation reaction, and dibutyl phosphate (16.8 mg (80 μmol)) as a heat stabilizer were charged, and the mixture was gradually heated to 240 ° C. under a nitrogen gas atmosphere and stirred to carry out a transesterification reaction. After removing the alcohol component produced by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and the polycondensation reaction was carried out until a predetermined stirring torque was reached while removing EG. After the reaction was completed, the contents were removed from the reactor to obtain a polyester resin.

[Example 21]
In the reactor, 2-DNFDP-m (23.63 g (40 mmol)) as a dicarboxylic acid component, DPC (9.08 g (42.4 mmol)) as a carbonate bond forming component, BNEF (32.32 g (60 mmol)) as a diol component, 1,5-PDO (2.08 g (20 mmol)), titanium (IV) tetrabutoxide (2.7 mg (8 μmol)) as a catalyst for transesterification and polycondensation reaction were charged, and the mixture was heated and stirred at 210 ° C. for 1 hour under a nitrogen gas atmosphere, and then gradually heated to 240 ° C. and stirred to perform a transesterification reaction. After removing the alcohol component and phenol component generated by the transesterification reaction, the temperature was gradually raised to 290 ° C. and 130 Pa, the pressure was reduced, and a polycondensation reaction was performed until a predetermined stirring torque was reached. After the reaction was completed, the contents were removed from the reactor to obtain a polyester carbonate resin.

The charging ratios for the examples and comparative examples are shown in Table 2, and the evaluation results of each obtained polyester resin, i.e., the polymer composition ratio (the proportion of constituent units derived from each polymerization component used in the preparation) and each physical property value, are shown in Table 3.

In Example 15, there were no highly volatile monomer components other than EG, and no sublimation of by-products was observed during polymerization. Therefore, based on the polymerization conditions such as the feed ratio and reaction method, the polymer composition ratio is estimated to be approximately 2-DNFDP-m/DMN/BINOL-2EO/EG (molar ratio) = 65/35/50/50.

As is clear from Table 3, all of the polyester resins obtained in the examples showed a remarkably high refractive index nD and a low Abbe number. They also had high glass transition temperatures Tg, excellent heat resistance, and high moldability.

Comparing Examples 3 and 6, the diol units in Example 3 were only EG units with no aromatic ring (or benzene ring) skeleton, yet the refractive index was slightly higher than in Example 6, which contained BNEF units with many aromatic rings. It was found that the refractive index could be increased surprisingly efficiently by combining 2-DNFDP-m units with EG units.

Furthermore, comparing Example 3 with Comparative Example 2 in which FDP-m was used instead of 2-DNFDP-m, it can be seen that by replacing 50 mol% of the FDP-m units in the entire resin with 2-DNFDP-m units, nD can be improved by approximately 0.124 and Tg can be improved by approximately 66°C. In particular, in the field of optical materials, an improvement in nD of even approximately 0.01 is seen to be advantageous, and therefore the improvement in refractive index is believed to be significant.

On the other hand, when comparing Examples 16 and 17 of Patent Document 2, by using Example 16, which uses BPDN2 (a compound having 2-naphthyl groups at the 2,7-positions of BPEF) instead of 50 mol% BPEF (9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene) in Example 17, nD is improved by 0.036 and Tg is improved by 14°C.

Comparing the examples of this application with those of Patent Document 2, by replacing 50 mol % of the structural units having a fluorene skeleton with structural units having a 2,7-di(2-naphthyl)fluorene skeleton with respect to the entire resin, the examples of this application have a significantly improved nD of about 3.4 times and a significantly improved Tg of about 4.7 times compared to Patent Document 2. That is, although the two are the same in that the 2,7-positions of the fluorene skeleton are substituted with 2-naphthyl groups, the examples of this application have a significantly higher degree of improvement in nD and Tg per unit amount introduced (unit mole %) with respect to the entire resin, and far exceed the values expected from Patent Document 2. In particular, in the examples of this application, the structural units do not have aromatic rings at the 9,9-positions of the fluorene skeleton, which are likely to improve the refractive index and heat resistance, but such a remarkable degree of improvement was unexpected.

Furthermore, a comparison between Example 3 and Comparative Example 2 confirmed that 2-DNFDP-m has greater negative birefringence (the property of biasing birefringence toward the negative (-) side) than FDP-m, and also has the effect of significantly lowering the Abbe number.

Comparing Examples 3 and 4, Example 3, which used 2-DNFDP-m, had a slightly lower Tg than Example 4, which used 1-DNFDP-m, but had a high refractive index, a low Abbe number, and large negative birefringence, and thus exhibited significantly superior optical properties.

Among these examples, Example 3 was superior in terms of high refractive index, and Example 6 was superior in terms of satisfying a good balance between high refractive index, high heat resistance, and low birefringence. In particular, although high refractive index and low birefringence, and high heat resistance and high moldability (or productivity) are mutually contradictory properties, Examples 7 to 9, 11, 14, and 16 to 18 are preferred in terms of being able to satisfy all of these properties in a good balance, and among these, Examples 9, 11, and 17 to 18 are more preferred in terms of having a good balance of these properties, exhibiting particularly low birefringence and being particularly useful for applications such as optical lenses, and Example 11 is even more preferred in terms of its high refractive index and Example 17 in terms of its high heat resistance, and of these, Example 11 is particularly preferred.

The dicarboxylic acid or its derivative of the present invention exhibits a high refractive index and heat resistance, and can therefore be effectively used as a resin raw material or as an additive (or resin additive) such as a refractive index improver or heat resistance improver.

In addition, since the resin of the present invention exhibits excellent optical properties such as a high refractive index, a low Abbe number, and a low birefringence, as well as high heat resistance, it may be used in a variety of applications, such as coating agents or coating films, specifically, paints, inks, protective films for electronic devices and liquid crystal components, etc.; adhesives, pressure sensitive adhesives; resin fillers; electrical and electronic materials or electrical and electronic parts (electrical and electronic devices), specifically, antistatic agents, carrier transport agents, light emitting bodies, organic photosensitive bodies, thermal recording materials, photochromic materials, holographic recording materials, charged trays, conductive sheets, optical disks, inkjet printers, digital paper, color filters, organic EL elements, organic semiconductor lasers, dye-sensitized solar cells, sensors, EMI shielding films, etc.; mechanical materials or mechanical parts (equipment), specifically, automotive materials or parts, aerospace-related materials or parts, sliding members, etc.

The resin of the present invention has a good balance between excellent optical properties and high heat resistance, making it particularly useful as an optical component.

Representative optical components include optical films (optical sheets) such as films for liquid crystal displays and films for organic electroluminescence displays; optical lenses such as lenses for glasses and cameras; prisms, holograms, optical fibers, etc.

Examples of optical films include polarizing films, polarizing elements and polarizing plate protective films that constitute polarizing films, phase difference films, alignment films, viewing angle expansion (compensation) films, diffusion plates (films), prism sheets, light guide plates, brightness enhancement films, near-infrared absorbing films, reflective films, anti-reflection (AR) films, reflection reduction (LR) films, anti-glare (AG) films, transparent conductive (ITO) films, anisotropic conductive films (ACF), electromagnetic shielding (EMI) films, films for electrode substrates, films for color filter substrates, barrier films, color filter layers, black matrix layers, and adhesive or release layers between optical films. These optical films can be effectively used as optical films for displays such as liquid crystal displays (LCDs), organic electroluminescent displays (OLEDs), plasma displays (PDPs), field emission displays (FEDs), and electronic paper. Specific examples of the optical films include televisions; personal computers (PCs) such as desktop PCs, notebook PCs, and tablet PCs; smartphones, mobile phones; car navigation systems; and devices or equipment equipped with flat panel displays (FPDs) such as touch panels.

Examples of optical lenses include glasses lenses, contact lenses, camera lenses, VTR zoom lenses, pickup lenses, Fresnel lenses, solar concentrating lenses, objective lenses, and rod lens arrays. In particular, the optical lenses are suitable for use in lenses that require a low Abbe number, such as camera lenses. Typical examples of devices or equipment that can be equipped with such optical lenses include small or mobile devices with camera functions, such as smartphones, mobile phones, and digital cameras; and in-vehicle cameras, such as drive recorders and backup cameras (rear cameras). In particular, the resin of the present invention has high heat resistance, and can therefore be suitable for use in applications where use in high-temperature environments, such as in-vehicle optical lenses, is anticipated.

Claims (13)

The following formula (I)

(In the formula, Z ^1a and Z ^1b each independently represent a C _6-12 arene ring, R ^1a and R ^1b each independently represent a hydrocarbon group , k1 and k2 each independently represent an integer of 0 to 2 , m1 and m2 each independently represent an integer of 0 to 4, R ^2a and R ^2b each independently represent a hydrocarbon group (excluding aryl groups) , n1 and n2 each independently represent an integer of 0 to 2 , A ^1a and A ^1b each independently represent a linear or branched C _1-6 alkylene group, m1+n1 and m2+n2 each are 4 or less, and at least one of m1 and m2 is 1 or more.)
or a derivative thereof ,
The dicarboxylic acid or a derivative thereof, wherein the derivative is at least one selected from a dicarboxylic acid ester, a dicarboxylic acid halide, a dicarboxylic acid anhydride, a dicarboxylic acid amide, and a dicarboxylic acid salt . The dicarboxylic acid or derivative thereof according to claim 1, wherein, in the formula (I), Z ^1a and Z ^1b are condensed polycyclic arene rings, m1 and m2 are integers of 1 to 2, and A ^1a and A ^1b are linear or branched C _2-6 alkylene groups. A step of coupling reaction of a dicarboxylic acid represented by the following formula (II) or a derivative thereof with compounds represented by the following formulas (IIIa) and (IIIb):

(wherein X ^1a and X ^1b each independently represent a reactive group capable of forming a carbon-carbon bond by a coupling reaction; X ^2a represents a reactive group capable of forming a carbon-carbon bond together with the reactive group X ^1a and X ^2b represents a reactive group capable of forming a carbon-carbon bond together with the reactive group X ^1b by a coupling reaction; Z ^1a , Z ^1b , R ^1a , R ^1b , k1, k2, m1, m2, R ^2a , R ^2b , n1, n2, A ^1a , A ^1b , m1+n1 and m2+n2 are each the same as in formula (I) above); or
A step of reacting a compound represented by the following formula (V) with an acrylic acid ester or a haloacetic acid ester:

(In the formula, Z ^1a , Z ^1b , R ^1a , R ^1b , k1, k2, m1, m2, R ^2a , R ^2b , n1, n2, m1+n1 and m2+n2 are the same as those in formula (I).
3. A method for producing the dicarboxylic acid or a derivative thereof according to claim 1 or 2 , comprising : A resin having at least a dicarboxylic acid unit (A), wherein the dicarboxylic acid unit (A) is represented by the following formula (1):

(In the formula, Z ^1a , Z ^1b , R ^1a , R ^1b , k1, k2, m1, m2, R ^2a , R ^2b , n1, n2, A ^1a , A ^1b , m1+n1, and m2+n2 are the same as those in formula (I) of claim 1.)
The resin includes a first dicarboxylic acid unit (A1) represented by the formula: The polyester resin having the dicarboxylic acid unit (A) and the diol unit (B),

(In the formula, ^A2 represents a linear or branched alkylene group, and q represents an integer of 1 or more.)
A first diol unit (B1) represented by the following formula (4):

(In the formula, ^Z3a and ^Z3b each independently represent an arene ring, ^R4 represents a substituent, r represents an integer of 0 to 8, ^R5a and ^R5b each independently represent a substituent, s1 and s2 each independently represent an integer of 0 or more, ^A3a and ^A3b each independently represent a linear or branched alkylene group, and t1 and t2 each independently represent an integer of 0 or more.)
and a second diol unit (B2) represented by the following formula (5):

(In the formula, ^A4 represents a direct bond (single bond) or a linear or branched alkylene group, ^A5a and ^A5b each independently represent a linear or branched alkylene group, ^R6a and ^R6b each independently represent a substituent, u1 and u2 each independently represent an integer of 0 or more, and v1 and v2 each independently represent an integer of 0 to 6.)
The resin according to claim 4, further comprising a third diol unit (B3) represented by the following formula: The resin according to claim 5, wherein the diol unit (B) contains both the first diol unit (B1) and the second diol unit (B2), and the ratio of B1/B2 (molar ratio) is 10/90 to 90/10. The dicarboxylic acid unit (A) may further be represented by the following formula (2):

(In the formula, ^Z2 represents an arene ring, ^R3 represents a substituent, and p represents an integer of 0 or more.)
The resin according to any one of claims 4 to 6, comprising at least one dicarboxylic acid unit selected from a second dicarboxylic acid unit (A2) represented by the formula: and a third dicarboxylic acid unit (A3) which is an aliphatic dicarboxylic acid unit. The resin according to claim 7, wherein the ratio of the first dicarboxylic acid unit (A1) to the second dicarboxylic acid unit (A2) is A1/A2 (molar ratio) = 95/5 to 30/70. a ratio of the first dicarboxylic acid unit (A1) to the third dicarboxylic acid unit (A3) is A1/A3 (molar ratio)=90/10 to 20/80;
The resin according to claim 7 or 8, wherein the ratio of the second dicarboxylic acid unit (A2) to the third dicarboxylic acid unit (A3) is A2/A3 (molar ratio) = 25/75 to 1/99. The resin according to any one of claims 7 to 9, which is the following (i) or (ii):
(i) is formed from a structural unit derived from 9,9-bis(carboxy _C2-4 alkyl)-2,7-di(2-naphthyl)fluorene as the first dicarboxylic acid unit (A1); a naphthalene dicarboxylic acid unit as the second dicarboxylic acid unit (A2); a structural unit derived from a linear or branched _C2-4 alkylene glycol as the first diol unit (B1); and a structural unit derived from 9,9-bis[hydroxy _C2-3 alkoxy naphthyl]fluorene as the second diol unit (B2);
(ii) A resin in which the ratio of the first dicarboxylic acid unit (A1) to the second dicarboxylic acid unit (A2) is A1/A2 (molar ratio) = 85/15 to 50/50; and the ratio of the first diol unit (B1) to the second diol unit (B2) (B1/B2) is B1/B2 (molar ratio) = 50/50 to 95/5. (ii) A resin in which a structural unit derived from 9,9-bis( _carboxyC2-4 alkyl)-2,7-di(2-naphthyl)fluorene as the first dicarboxylic acid unit (A1); a naphthalene dicarboxylic acid unit as the second dicarboxylic acid unit (A2); a _C2-6 alkane-dicarboxylic acid unit as the third dicarboxylic acid unit (A3); a structural unit derived from a linear or branched _C2-4 alkylene glycol as the first diol unit (B1); and a structural unit derived from _2-3 alkoxynaphthyl]fluorene,
A resin in which a ratio of the first dicarboxylic acid unit (A1) to the second dicarboxylic acid unit (A2) is A1/A2 (molar ratio) = 99/1 to 80/20; a ratio of the first dicarboxylic acid unit (A1) to the third dicarboxylic acid unit (A3) is A1/A3 (molar ratio) = 65/35 to 45/55; a ratio of the second dicarboxylic acid unit (A2) to the third dicarboxylic acid unit (A3) is A2/A3 (molar ratio) = 25/75 to 1/99; and a ratio of the first diol unit (B1) to the second diol unit (B2) (B1/B2) is B1/B2 (molar ratio) = 85/15 to 65/35. A molded body comprising the resin according to any one of claims 4 to 10. The molded article according to claim 11, which is an optical component. The molded article according to claim 11 or 12, which is an optical film or an optical lens.