JP5308262B2 - Polycarbonate resin and film - Google Patents

Description

  The present invention relates to a polycarbonate resin and a film having negative birefringence, a low photoelastic constant, and good fluidity.

  Conventionally, a polycarbonate resin (hereinafter referred to as PC-A) obtained by reacting a carbonate precursor with 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A) has transparency, heat resistance, mechanical properties. It has been widely used in many fields as an engineering plastic because of its excellent characteristics and dimensional stability. Furthermore, in recent years, utilization of the transparency as an optical material in the fields of optical disks, films, lenses and the like has been developed.

  However, when PC-A is used, since positive birefringence is high and the photoelastic constant is high, optical distortion occurs when used as an optical application, causing various problems. For example, when used in an optical lens, there is a drawback that the birefringence of the molded product increases. Further, when used as a retardation film, there is a problem that the change in birefringence due to stress is large and light leakage occurs.

  Therefore, various methods have been studied as countermeasures for the above problems. As one of the methods, a technique for reducing the photoelastic constant of the resin itself by changing the monomer structure is known. An aromatic polycarbonate copolymer using a bisphenol monomer having a specific structure is disclosed (for example, see Patent Documents 1 to 3).

  Moreover, when 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, bisphenol A and a carbonate precursor are reacted, an aromatic polycarbonate resin having a low photoelastic coefficient and having negative birefringence is obtained. It is known that it can be used as a retardation film (see, for example, Patent Document 4). However, the reduction in photoelasticity is not sufficient, and further reduction is required. Further, since it is a copolymer of positive and negative birefringent monomers, the negative birefringence expression is not sufficient, and further negative birefringence expression is also required. Therefore, it is conceivable to increase the ratio of 9,9-bis (4-hydroxy-3-methylphenyl) fluorene and bring it closer to the homopolymer, thereby reducing the photoelastic coefficient and improving the negative birefringence. In the interfacial polymerization method, the reaction cannot proceed because a large amount of gel insoluble in the solvent is generated, and even in the melt polymerization method using carbonic acid diester, the glass transition temperature of the polymerization product is very high and the fluidity is poor. The molecular body could not be polymerized. Therefore, a polymer having a high photoelastic coefficient and a high negative birefringence has not yet been provided.

Japanese Patent Laid-Open No. 02-099521 Japanese Patent Laid-Open No. 02-128336 Japanese Patent Laid-Open No. 02-208840 JP 2001-194530 A

  An object of the present invention is to provide a polycarbonate resin having negative birefringence, a low photoelastic constant, and good fluidity.

  As described above, in the conventional interfacial polymerization method of polycarbonate resin composed of 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, since the oligomer is insoluble in the solvent, it may precipitate and polymerization may not proceed. I know. Further, according to the study by the present inventors, it has been found that a melt polymerization method using a carbonic acid diester cannot obtain a high molecular weight substance because the homopolymer of the product has a high melt viscosity. Therefore, as a result of intensive research to achieve the above object, by polymerizing a diol having a specific structure having an alkyl group having a large steric hindrance, the solubility of the oligomer is improved, and a high molecular weight homopolymer is obtained. I found out that It has also been found that polymerization is possible by a melt polymerization method using a carbonic acid diester. Furthermore, the homopolymer has a surprisingly high negative birefringence compared with the polycarbonate containing conventional 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, and has a photoelastic constant. Low and good fluidity. And it discovered that the optical film using this polycarbonate resin showed a favorable optical characteristic.

［式中、Ｒ₁、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６は夫々独立して、水素原子、炭素原子数１〜１０の炭化水素基であり、Ｒ₁、Ｒ_２が結合して炭素環、もしくは複素環を形成しても良い。また、Ｒ_４、Ｒ_５が結合して炭素環、もしくは複素環を形成しても良い。ｍおよびｎは同一または異なる１〜４の整数を示す。］
で表される繰り返し単位（Ａ）を含む、２０℃の塩化メチレン溶液で測定された比粘度が０．２０〜１．５０であることを特徴とするポリカーボネート樹脂。
２．繰り返し単位（Ａ）が下記式

［式中、Ｒ₁、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６は夫々独立して、水素原子、炭素原子数１〜１０の炭化水素基であり、Ｒ₁、Ｒ_２が結合して炭素環、もしくは複素環を形成しても良い。また、Ｒ_４、Ｒ_５が結合して炭素環、もしくは複素環を形成しても良い。］
で表される繰り返し単位（Ａ１）である上記１記載のポリカーボネート樹脂。
３．繰り返し単位（Ａ１）が下記式で表される繰り返し単位（Ａ２）または（Ａ３）または（Ａ４）である上記１記載のポリカーボネート樹脂。

４．光弾性係数が４０×１０^−１２Ｐａ^−１以下である上記１記載のポリカーボネート樹脂。
５．ガラス転移温度が１３０℃〜２２０℃である上記１記載のポリカーボネート樹脂。
６．繰り返し単位（Ａ）の割合は、全繰り返し単位中９０モル％以上である上記１記載のポリカーボネート樹脂。
７．上記１記載のポリカーボネート樹脂を素材とする光学成形品。
８．上記１記載のポリカーボネート樹脂を素材とする光学フィルム。
９．下記式（１）で表される複屈折率（Δｎ）が−３．０×１０^−３以下である上記８記載の光学フィルム。
Δｎ＝ Ｒ（５５０）／ ｄ （１）
ｄは、フィルムの厚み、Ｒ（５５０）は波長５５０ｎｍにおけるフィルム面内の位相差値を示す。 That is, the present invention is as follows.
1. Following formula

[Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, and R ₁ and R ₂ are bonded to each other. Thus, a carbocycle or a heterocycle may be formed. R ₄ and R ₅ may combine to form a carbocyclic or heterocyclic ring. m and n represent the same or different integers of 1 to 4. ]
A polycarbonate resin having a specific viscosity of 0.20 to 1.50 measured with a methylene chloride solution at 20 ° C. containing the repeating unit (A) represented by
2. The repeating unit (A) is represented by the following formula

[Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, and R ₁ and R ₂ are bonded to each other. Thus, a carbocycle or a heterocycle may be formed. R ₄ and R ₅ may combine to form a carbocyclic or heterocyclic ring. ]
2. The polycarbonate resin according to the above 1, which is a repeating unit (A1) represented by
3. 2. The polycarbonate resin according to 1 above, wherein the repeating unit (A1) is a repeating unit (A2) or (A3) or (A4) represented by the following formula.

4). 2. The polycarbonate resin as described in 1 above, which has a photoelastic coefficient of 40 × 10 ⁻¹² Pa ⁻¹ or less.
5. 2. The polycarbonate resin as described in 1 above, which has a glass transition temperature of 130 ° C to 220 ° C.
6). 2. The polycarbonate resin as described in 1 above, wherein the proportion of the repeating unit (A) is 90 mol% or more in all repeating units.
7). An optically molded article made of the polycarbonate resin described in 1 above.
8). 2. An optical film made of the polycarbonate resin described in 1 above.
9. 9. The optical film as described in 8 above, wherein the birefringence (Δn) represented by the following formula (1) is −3.0 × 10 ⁻³ or less.
Δn = R (550) / d (1)
d represents the thickness of the film, and R (550) represents the in-plane retardation value at a wavelength of 550 nm.

  The polycarbonate resin of the present invention has an unprecedented high negative birefringence, a low photoelastic constant, and good fluidity.

Hereinafter, the present invention will be described in detail.
<Polycarbonate resin>
(Structural unit)
The polycarbonate resin of the present invention contains a unit (A) represented by the above formula. In the unit (A), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are each independently a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, and R ₁ , R ₂ May combine to form a carbocyclic or heterocyclic ring. R ₄ and R ₅ may combine to form a carbocyclic or heterocyclic ring. m and n represent the same or different integers of 1 to 4. Examples of the hydrocarbon group include an alkyl group having 1 to 10 carbon atoms and a cycloalkyl group having 5 to 10 carbon atoms. Preferably, (A) is represented by the formula (A1). Specifically, 9,9-bis (4-hydroxy-3-isopropylphenyl) fluorene, 9,9-bis (4-hydroxy-3-isobutylphenyl) fluorene, 9,9-bis (4-hydroxy-3) -Sec-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-tert-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-isopentylphenyl) fluorene, 9,9-bis It is a polycarbonate resin derived from (4-hydroxy-3-cyclohexylphenyl) fluorene, 9,9-bis (4-hydroxy-3-cyclopentylphenyl) fluorene and the like. In particular, 9,9-bis (4-hydroxy-3-sec-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-tert-butylphenyl) fluorene, 9,9-bis (4-hydroxy-) The units represented by the formulas (A2), (A3), and (A4) derived from 3-cyclohexylphenyl) fluorene have a low photoelasticity because the alkyl group having a large steric hindrance suppresses the rotation of the phenyl group. Therefore, it is preferable because the solubility of the polymer is increased and the polymerization property is good. Among these, (A2) is more preferable because it greatly increases fluidity and is excellent in moldability. The proportion of the polycarbonate resin of the present invention containing (A) is more preferably 90 mol% or more and more preferably 95 mol% or more because the target optical characteristics are more easily expressed.

(Production method)
The polycarbonate resin of the present invention is produced by a reaction means known per se for producing an ordinary aromatic polycarbonate resin, for example, a method of reacting an aromatic dihydroxy component with a carbonate precursor such as a carbonic acid diester. Next, basic means for these manufacturing methods will be briefly described.

In a reaction using, for example, phosgene as a carbonate precursor, the reaction is usually performed in the presence of an acid binder and a solvent. As the acid binder, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or an amine compound such as pyridine is used. As the solvent, for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. In order to accelerate the reaction, a catalyst such as a tertiary amine or a quaternary ammonium salt can also be used. In that case, reaction temperature is 0-40 degreeC normally, and reaction time is several minutes-5 hours. In the polycarbonate resin of the present invention, monofunctional phenols that are usually used as a terminal terminator can be used in the polymerization reaction. Particularly in the case of a reaction using phosgene as a carbonate precursor, monofunctional phenols are generally used as a terminator for controlling the molecular weight, and the resulting aromatic polycarbonate resin has a terminal monofunctional phenol. Since it is blocked by a group based on, it is superior in thermal stability as compared to those not.
Such monofunctional phenols may be used as long as they are used as an end stopper for aromatic polycarbonate resins.

  The transesterification reaction using a carbonic acid diester as a carbonate precursor is performed by a method in which an aromatic dihydroxy component in a predetermined ratio is stirred with a carbonic acid diester while heating with an inert gas atmosphere to distill the generated alcohol or phenols. . The reaction temperature varies depending on the boiling point of the alcohol or phenol produced, but is usually in the range of 120 to 300 ° C. The reaction is completed while distilling off the alcohol or phenol produced under reduced pressure from the beginning. Moreover, you may add a terminal stopper, antioxidant, etc. as needed.

  Examples of the carbonic acid diester used in the transesterification include esters such as an aryl group having 6 to 12 carbon atoms and an aralkyl group which may be substituted. Specific examples include diphenyl carbonate, ditolyl carbonate, and bis (chlorophenyl) carbonate. Of these, diphenyl carbonate is particularly preferred. The amount of diphenyl carbonate used is preferably 0.97 to 1.10 mol, more preferably 1.00 to 1.06 mol, per 1 mol of the total of dihydroxy compounds.

In the melt polymerization method, a polymerization catalyst can be used to increase the polymerization rate. Examples of the polymerization catalyst include alkali metal compounds, alkaline earth metal compounds, nitrogen-containing compounds, and metal compounds.
As such compounds, organic acid salts, inorganic salts, oxides, hydroxides, hydrides, alkoxides, quaternary ammonium hydroxides, and the like of alkali metals and alkaline earth metals are preferably used. It can be used alone or in combination.

  Examples of the alkali metal compound include sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium carbonate, sodium acetate, potassium acetate, cesium acetate, lithium acetate, Sodium stearate, potassium stearate, cesium stearate, lithium stearate, sodium borohydride, sodium benzoate, potassium benzoate, cesium benzoate, lithium benzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, phosphorus Examples thereof include dilithium oxyhydrogen, disodium phenylphosphate, disodium salt of bisphenol A, dipotassium salt, cesium salt, dilithium salt, sodium salt of phenol, potassium salt, cesium salt, and lithium salt.

  Alkaline earth metal compounds include magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, magnesium diacetate, calcium diacetate, strontium diacetate, diacetate Barium etc. are mentioned.

  Examples of nitrogen-containing compounds include quaternary ammonium hydroxides having alkyl, aryl groups, etc., such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and trimethylbenzylammonium hydroxide. Can be mentioned. Further, tertiary amines such as triethylamine, dimethylbenzylamine, and triphenylamine, and imidazoles such as 2-methylimidazole, 2-phenylimidazole, and benzimidazole can be used. Moreover, bases or basic salts such as ammonia, tetramethylammonium borohydride, tetrabutylammonium borohydride, tetrabutylammonium tetraphenylborate, tetraphenylammonium tetraphenylborate, and the like can be given. Examples of the metal compound include zinc aluminum compounds, germanium compounds, organotin compounds, antimony compounds, manganese compounds, titanium compounds, zirconium compounds and the like. These compounds may be used alone or in combination of two or more.

The amount of these polymerization catalysts used is preferably 1 × 10 ⁻⁹ to 1 × 10 ⁻² equivalent, preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻⁵ equivalent, more preferably 1 × with ^respect to 1 mol of the diol component. It is selected in the range of 10 ⁻⁷ to 1 × 10 ⁻³ equivalents.

  In addition, a catalyst deactivator can be added at a later stage of the reaction. As the catalyst deactivator to be used, a known catalyst deactivator is effectively used. Among them, sulfonic acid ammonium salt and phosphonium salt are preferable. Furthermore, salts of dodecylbenzenesulfonic acid such as tetrabutylphosphonium salt of dodecylbenzenesulfonic acid and salts of paratoluenesulfonic acid such as tetrabutylammonium salt of paratoluenesulfonic acid are preferable.

  Further, as esters of sulfonic acid, methyl benzenesulfonate, ethyl benzenesulfonate, butyl benzenesulfonate, octyl benzenesulfonate, phenyl benzenesulfonate, methyl paratoluenesulfonate, ethyl paratoluenesulfonate, butyl paratoluenesulfonate, Octyl paratoluenesulfonate, phenyl paratoluenesulfonate and the like are preferably used. Among these, dodecylbenzenesulfonic acid tetrabutylphosphonium salt is most preferably used. The amount of the catalyst deactivator used is preferably 0.5 to 50 mol per mol of the catalyst when at least one polymerization catalyst selected from alkali metal compounds and / or alkaline earth metal compounds is used. It can be used in a proportion, more preferably in a proportion of 0.5 to 10 mol, still more preferably in a proportion of 0.8 to 5 mol.

  In addition, heat stabilizers, plasticizers, light stabilizers, polymerized metal deactivators, flame retardants, lubricants, antistatic agents, surfactants, antibacterial agents, ultraviolet absorbers, release agents, etc. Additives can be blended.

(Specific viscosity: η _SP )
When the specific viscosity (η _SP ) of the polycarbonate resin of the present invention is less than 0.20, the strength and the like are lowered, and when it exceeds 1.50, the molding properties are lowered. The range of 50 is preferable, the range of 0.23 to 1.20 is more preferable, and the range of 0.25 to 1.00 is more preferable. Moreover, it is also possible to mix the polycarbonate resin whose specific viscosity is outside the above range within the range in which the moldability and the like are maintained. For example, a small amount of a high molecular weight polycarbonate resin component having a specific viscosity exceeding 1.50 may be blended. In this case, the specific viscosity of the polycarbonate resin mixture obtained by mixing polycarbonate resins having different specific viscosities may be in the above range.

The specific viscosity referred to in the present invention was determined using an Ostwald viscometer from a solution obtained by dissolving 0.7 g of a polycarbonate resin in 100 ml of methylene chloride at 20 ° C.
Specific viscosity (η _SP ) = (t−t ₀ ) / t ₀
[T ₀ is methylene chloride falling seconds, t is sample solution falling seconds]

  In addition, when measuring the specific viscosity of the polycarbonate resin of this invention, it can carry out in the following way. That is, the polycarbonate resin is dissolved in 20 to 30 times the weight of methylene chloride, and the soluble component is collected by celite filtration, and then the solution is removed and dried sufficiently to obtain a solid component soluble in methylene chloride. Using a Ostwald viscometer, the specific viscosity at 20 ° C. is determined from a solution of 0.7 g of the solid dissolved in 100 ml of methylene chloride.

(Glass transition temperature: Tg)
The glass transition temperature (Tg) of the polycarbonate resin of the present invention is preferably in the range of 130 to 220 ° C, more preferably 140 to 210 ° C. When the glass transition temperature (Tg) is lower than 130 ° C., the heat resistance stability is poor. Moreover, when using as a phase difference film, the phase difference change at the time of a heat test becomes large, which is a problem. On the other hand, if the glass transition temperature (Tg) is higher than 220 ° C., the viscosity is too high and molding becomes difficult. The glass transition temperature (Tg) is measured at 29 ° C./min using a 2910 type DSC manufactured by TA Instruments Japan.

<Optical molded product>
The polycarbonate resin of the present invention is molded by an arbitrary method such as an injection molding method, a compression molding method, an extrusion molding method, or a solution casting method. Since the polycarbonate resin of the present invention is excellent in moldability and thermal stability, it can be used as various molded articles. In particular, it is advantageously used as an optical molding suitable for structural or functional material applications of optical components such as optical discs, optical lenses, liquid crystal panels, optical cards, sheets, films, optical fibers, connectors, vapor-deposited plastic reflectors, and displays. can do. Among these, it can be used particularly advantageously as an optical film or an optical disk substrate.

<Optical film>
The optical film of the present invention will be described. This optical film is a film used for optical applications. Specifically, a retardation film, a plastic substrate film, a polarizing plate protective film, an antireflection film, a brightness enhancement film, an optical disk protective film, a diffusion film, and the like can be given. In particular, a retardation film, a polarizing plate protective film, and an antireflection film are preferable.

  Examples of the method for producing an optical film include known methods such as a solution casting method, a melt extrusion method, a hot pressing method, and a calendar method. As a method for producing the optical film of the present invention, a solution casting method and a melt extrusion method are preferable, and a melt extrusion method is particularly preferable from the viewpoint of productivity.

  In the melt extrusion method, a method of extruding a resin using a T die and feeding it to a cooling roll is preferably used. The temperature at this time is determined from the molecular weight, Tg, melt flow characteristics, etc. of the polycarbonate polymer, but is in the range of 180 to 350 ° C, more preferably in the range of 200 to 320 ° C. When the temperature is lower than 180 ° C., the viscosity is increased, and the orientation and stress strain of the polymer tend to remain, which is not preferable. On the other hand, when the temperature is higher than 350 ° C., problems such as thermal deterioration, coloring, and die line (stripe) from the T-die are likely to occur.

  In addition, since the polycarbonate resin used in the present invention has good solubility in an organic solvent, a solution casting method can also be applied. In the case of the solution casting method, methylene chloride, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, dioxolane, dioxane and the like are preferably used as the solvent. The amount of residual solvent in the film used in the solution casting method is preferably 2% by weight or less, more preferably 1% by weight or less. If it exceeds 2% by weight, if the residual solvent is large, the glass transition temperature of the film is remarkably lowered, which is not preferable from the viewpoint of heat resistance.

  As thickness of the unstretched optical film of this invention, the range of 30-400 micrometers is preferable, More preferably, it is the range of 40-300 micrometers. When such a film is further stretched to obtain a retardation film, it may be appropriately determined within the above range in consideration of a desired retardation value and thickness of the optical film.

  The unstretched optical film thus obtained is stretched and oriented to form a retardation film. The machine axis direction in which the film is formed is referred to as the film forming direction or the longitudinal direction, and the direction perpendicular to the film forming direction and the film thickness direction is referred to as the lateral direction or the width direction. As the stretching method, a known method such as longitudinal uniaxial stretching, lateral uniaxial stretching using a tenter or the like, or simultaneous biaxial stretching or sequential biaxial stretching in combination thereof can be used. Moreover, although it is preferable from a point of productivity to perform continuously, you may carry out by a batch type. The stretching temperature is preferably in the range of (Tg-20 ° C) to (Tg + 50 ° C), more preferably in the range of (Tg-10 ° C) to (Tg + 30 ° C) with respect to the glass transition temperature (Tg) of the polycarbonate resin. is there. If the stretching temperature is low, the phase difference tends to be easily developed. This temperature range is preferable because the molecular motion of the polymer is appropriate, relaxation due to stretching is unlikely to occur, orientation is easily suppressed, and a desired in-plane retardation is easily obtained.

  Although the draw ratio is determined by the target retardation value, it is 1.05 to 5 times, more preferably 1.1 to 4 times in the vertical and horizontal directions, respectively. This stretching may be performed in a single stage or in multiple stages. When the magnification in the stretching direction is increased, the phase difference tends to be easily developed. In addition, said Tg in the case of extending | stretching the film obtained by the solution cast method means the glass transition temperature containing the trace amount solvent in this film.

(Photoelastic constant)
The absolute value of the photoelastic constant of the polycarbonate resin is 40 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 35 × 10 ⁻¹² Pa ⁻¹ or less, and even more preferably 30 × 10 ⁻¹² Pa ⁻¹ or less. If the absolute value is larger than 40 × 10 ⁻¹² Pa ⁻¹ , birefringence caused by residual stress during molding is large, which is not preferable. The photoelastic constant is measured using a Spectroellipometer M-220 manufactured by JASCO Corporation by cutting out a test piece having a length of 50 mm and a width of 10 mm from the central portion of the unstretched film.

(Phase difference value)
The in-plane retardation value R is defined by the following equation, and is a characteristic that represents a phase delay between the X direction of light transmitted through the film in the vertical direction and the vertical Y direction.
_{R (550) = (n x} -n y) × d (1-1)
Where _nx is the refractive index in the main stretching direction in the film plane, _ny is the refractive index in the direction perpendicular to the main stretching direction in the film plane, d is the thickness of the film, and R (550) is the wavelength of 550 nm. The retardation value in the film plane is shown. Here, the main stretching direction means a stretching direction in the case of uniaxial stretching, and a direction in which the degree of orientation is increased in the case of biaxial stretching. Refers to the orientation direction. The retardation value is measured by longitudinally stretching an unstretched film 2.0 times at a stretching temperature of Tg + 10 ° C., and measuring the center portion of the obtained film using Spectroellipometer M-220 manufactured by JASCO Corporation.

(Thickness etc.)
The thickness of the optical film of the present invention is preferably 20 to 200 μm, more preferably 20 to 150 μm. If it is this range, the desired phase difference value by extending | stretching will be easy to obtain, and film forming will be easy and preferable.
The optical film of the present invention has a low photoelastic constant of the polycarbonate resin constituting it. Therefore, the change of the phase difference with respect to the stress is small, and the liquid crystal display device provided with such a retardation film has excellent display stability.
The optical film of the present invention has high transparency. The total light transmittance of the optical film of the present invention having a thickness of 100 μm is preferably 85% or more, more preferably 88% or more. The haze value of the optical film of the present invention is preferably 5% or less, more preferably 3% or less.
The film of the present invention can be used for a retardation film.

(Birefringence)
The birefringence (Δn) of the polycarbonate polymer is determined by the following formula.
Δn = R (550) / d (1)
d represents the thickness of the film, and R (550) represents the in-plane retardation value at a wavelength of 550 nm.
The value of Δn is −3.0 × 10 ⁻³ or less, more preferably −4.0 × 10 ⁻³ or less, and further preferably −5.0 × 10 ⁻³ or less. When it is larger than −3.0 × 10 ⁻³ , the retardation development property is too low, and when it is used as a retardation film, it is necessary to increase the film thickness, which is a problem because the display cannot be thinned. The lower limit of Δn is not particularly limited, but is preferably −20 × 10 ⁻³ or more from the viewpoint of stretching stability.

  Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto. In the examples, “parts” means “parts by weight”. The resins used and the evaluation methods used in the examples are as follows.

1. Specific Viscosity Measurement The viscosity was determined using an Ostwald viscometer from a solution of 0.7 g of polycarbonate resin in 100 ml of methylene chloride at 20 ° C.
Specific viscosity (η _SP ) = (t−t ₀ ) / t ₀
[T ₀ is methylene chloride falling seconds, t is sample solution falling seconds]

2. Glass transition temperature measurement Using a polycarbonate resin and a thermal analysis system DSC-2910 manufactured by TA Instruments Co., Ltd., under a nitrogen atmosphere (nitrogen flow rate: 40 ml / min) in accordance with JIS K7121. Temperature increase rate: Measured under conditions of 20 ° C./min.

3. Photoelastic constant measurement A test piece having a length of 50 mm and a width of 10 mm was cut out from the center of the unstretched film, and the photoelastic constant was measured using Spectroellipometer M-220 manufactured by JASCO Corporation.

4). Retardation value measurement The phase difference in 550 nm was measured for the obtained film center part using Spectrolepometer M-220 by JASCO Corporation.
Further, the birefringence (Δn) was determined from the following formula.
Δn = R (550) / d (1)
d represents the thickness of the film, and R (550) represents the in-plane retardation value at a wavelength of 550 nm.

[Example 1]
<Manufacture of polycarbonate resin>
In a reactor equipped with a thermometer, a stirrer and a reflux condenser, 21540 parts of ion-exchanged water and 4930 parts of a 48% aqueous sodium hydroxide solution were placed, and 9,9-bis (4-hydroxy-3-sec-butylphenyl) fluorene (hereinafter referred to as “9,9-bis (4-hydroxy-3-sec-butylphenyl) fluorene”) was introduced. After dissolving 7910 parts (sometimes abbreviated as “BSBF”) and 15 parts of hydrosulfite, 14530 parts of methylene chloride were added, and then 2200 parts of phosgene was blown in at 15 to 25 ° C. with stirring for 60 minutes. . After completion of phosgene blowing, 181.2 parts of p-tert-butylphenol and 705 parts of 48% aqueous sodium hydroxide solution were added, and after emulsification, 5.9 parts of triethylamine was added and stirred at 28 to 33 ° C. for 1 hour to complete the reaction. did. After completion of the reaction, the product was diluted with methylene chloride, washed with water, acidified with hydrochloric acid, washed with water, and when the conductivity of the aqueous phase became almost the same as that of ion-exchanged water, the methylene chloride was evaporated with a kneader, A white polymer was obtained. The specific viscosity and Tg of the obtained polycarbonate resin were measured. The results are shown in Table 1.

<Manufacture of optical film>
Next, this copolymer was dissolved in methylene chloride to prepare a dope having a solid concentration of 19% by weight. A cast film was produced from this dope solution by a known method, and the photoelastic coefficient was measured. Further, the film was uniaxially stretched 2.0 times in the length direction at Tg + 10 ° C. to obtain a stretched film having a thickness of 51 μm. The birefringence was calculated by measuring the retardation of the stretched film. The results are shown in Table 1.

[Example 2]
<Manufacture of polycarbonate resin>
18BF parts of BSBF, 893 parts of diphenyl carbonate, and 1.8 × 10 ⁻² parts of tetramethylammonium hydroxide and 1.6 × 10 ⁻⁴ parts of sodium hydroxide as a catalyst were heated to 180 ° C. and melted in a nitrogen atmosphere. Thereafter, the degree of vacuum was adjusted to 13.4 kPa over 30 minutes. Thereafter, the temperature was raised to 260 ° C. at a rate of 20 ° C./hr, held at that temperature for 10 minutes, and then the degree of vacuum was set to 133 Pa or less over 1 hour. The reaction is carried out with stirring for a total of 6 hours. After the completion of the reaction, 4 times mole of the catalyst amount of tetrabutylphosphonium salt of dodecylbenzenesulfonate is added to deactivate the catalyst, and then discharged from the bottom of the reaction tank under nitrogen pressure. The pellet was obtained by cutting with a pelletizer while cooling in a water bath. The specific viscosity and glass transition temperature of the pellets were measured and listed in Table 1.

<Manufacture of optical film>
Next, a 15 mm biaxial extrusion kneader manufactured by Technobel Co., Ltd. was attached with a T die having a width of 150 mm and a lip width of 500 μm and a film take-up device, and the resulting polycarbonate copolymer was formed into a film to form a transparent extruded film. Obtained. A transparent extruded film was obtained by film-forming the obtained polycarbonate resin. The photoelastic coefficient was measured using a sample cut from the vicinity of the center of the obtained film. Moreover, the sample was cut out from the film center part vicinity, and it uniaxially stretched 2.0 times in the length direction at 167 degreeC (Tg + 10 degreeC), and obtained the stretched film of thickness 52 micrometers. The birefringence was calculated by measuring the retardation of the stretched film. The results are shown in Table 1.

[Example 3]
<Manufacture of polycarbonate resin>
The same operation as in Example 1 except that 7910 parts of 9,9-bis (4-hydroxy-3-tert-butylphenyl) fluorene (hereinafter sometimes abbreviated as “BTBF”) was used instead of BSBF. To obtain an aromatic polycarbonate polymer. The specific viscosity and glass transition temperature of the pellets were measured and listed in Table 1.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1, and the photoelastic coefficient was measured. Moreover, the sample was cut out from the film center part vicinity, and it uniaxially stretched 2.0 times in the length direction at Tg + 10 degreeC, and obtained the stretched film of thickness 52 micrometers. The birefringence was calculated by measuring the retardation of the stretched film. The results are shown in Table 1.

[Example 4]
<Production of polycarbonate polymer>
Except for using 8355 parts of 9,9-bis (4-hydroxy-3-cyclohexylphenyl) fluorene (hereinafter sometimes abbreviated as “BCHF”) in place of BSBF, the same operation as in Example 1 was performed. An aromatic polycarbonate resin was obtained. The specific viscosity and glass transition temperature of the pellets were measured and listed in Table 1.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1, and the photoelastic coefficient was measured. Further, a sample was cut out from the vicinity of the center of the film and uniaxially stretched 2.0 times in the length direction at Tg + 10 ° C. to obtain a stretched film having a thickness of 49 μm. The birefringence was calculated by measuring the retardation of the stretched film. The results are shown in Table 1.

[Example 5]
<Production of polycarbonate polymer>
Except having used 1BF parts of BSBF and 46 parts of BPA, the same operation as Example 2 was performed and the aromatic polycarbonate resin was obtained. The specific viscosity and glass transition temperature of the pellets were measured and listed in Table 1.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 2, and the photoelastic coefficient was measured. Moreover, the sample was cut out from the film center part vicinity, and it uniaxially stretched 2.0 times in the length direction at Tg + 10 degreeC, and obtained the 50-micrometer-thick stretched film. The birefringence was calculated by measuring the retardation of the stretched film. The results are shown in Table 1.

[Comparative Example 1]
<Manufacture of polycarbonate resin>
To a reactor equipped with a thermometer, a stirrer, and a reflux condenser, 9809 parts of ion-exchanged water and 2271 parts of 48% sodium hydroxide aqueous solution were added to dissolve 1775 parts of BPA and 3.5 parts of sodium hydrosulfite, and 7925 parts of methylene chloride. Then, 1000 parts of phosgene was blown in at a temperature of 16 to 20 ° C. with stirring for 60 minutes. After completion of the phosgene blowing, 52.6 parts of p-tert-butylphenol and 327 parts of 48% aqueous sodium hydroxide solution were added, and 1.57 parts of triethylamine was further added, followed by stirring at 20 to 27 ° C. for 40 minutes to complete the reaction. . The methylene chloride layer containing the product was washed with dilute hydrochloric acid and pure water, and then methylene chloride was evaporated to obtain a polycarbonate resin. The specific viscosity and glass transition temperature of the pellets were measured and listed in Table 1.

<Manufacture of optical film>
The obtained polycarbonate resin was pelletized by a 15φ biaxial extrusion kneader. Next, a film was prepared in the same manner as in Example 2, and the photoelastic coefficient was measured. Further, a sample was cut out from the vicinity of the center of the film and uniaxially stretched 2.0 times in the length direction at Tg + 10 ° C. to obtain a stretched film having a thickness of 49 μm. The birefringence was calculated by measuring the retardation of the stretched film. The results are shown in Table 1. Since this film has a high photoelastic constant of 80 × 10 ⁻¹² Pa ⁻¹ , birefringence is likely to occur when stress is applied.

[Comparative Example 2]
<Manufacture of polycarbonate resin>
To a reactor equipped with a thermometer, a stirrer, and a reflux condenser, 9809 parts of ion exchange water and 2271 parts of 48% sodium hydroxide aqueous solution were added, and 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (hereinafter “ 2936 parts (sometimes abbreviated as "BCF") and 4.5 parts sodium hydrosulfite are dissolved, 6604 parts of methylene chloride are added, and then 1000 parts of phosgene are blown in at 16 to 20 ° C while stirring. As a result, a large amount of insoluble matter was precipitated, and a high molecular weight product was not obtained.

[Comparative Example 3]
<Manufacture of polycarbonate resin>
Except for using two components of BPA 266 parts and BCF 2496 parts, the same operation as in Comparative Example 1 was performed to obtain an aromatic polycarbonate resin. The specific viscosity and glass transition temperature of the pellets were measured and listed in Table 1. The polycarbonate had a very high glass transition temperature and was difficult to mold.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1, and the photoelastic coefficient was measured. Moreover, the sample was cut out from the film center part vicinity, and it uniaxially stretched 2.0 times in the length direction at Tg + 10 degreeC, and obtained the stretched film of thickness 63 micrometers. The birefringence was calculated by measuring the retardation of the stretched film. The results are shown in Table 1. This film has a high photoelastic constant of 38 × 10 ⁻¹² Pa ⁻¹ and a large birefringence due to stress. Therefore, light leakage occurs when used as a retardation film, which is not preferable.

  The polycarbonate resin of the present invention is useful as an optical film for optical molded products, liquid crystal display devices, organic EL displays and the like.

Claims (9)

Following formula

[Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, and R ₁ and R ₂ are bonded to each other. Thus, a carbocycle or a heterocycle may be formed. R ₄ and R ₅ may combine to form a carbocyclic or heterocyclic ring. m and n represent the same or different integers of 1 to 4. ]
A polycarbonate resin having a specific viscosity of 0.20 to 1.50 measured with a methylene chloride solution at 20 ° C. containing the repeating unit (A) represented by The repeating unit (A) is represented by the following formula

[Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, and R ₁ and R ₂ are bonded to each other. Thus, a carbocycle or a heterocycle may be formed. R ₄ and R ₅ may combine to form a carbocyclic or heterocyclic ring. ]
The polycarbonate resin of Claim 1 which is a repeating unit (A1) represented by these. The polycarbonate resin according to claim 1, wherein the repeating unit (A1) is a repeating unit (A2) or (A3) or (A4) represented by the following formula.

The polycarbonate resin according to claim 1, which has a photoelastic coefficient of 40 × 10 ⁻¹² Pa ⁻¹ or less.   The polycarbonate resin according to claim 1, which has a glass transition temperature of 130C to 220C.   The polycarbonate resin according to claim 1, wherein the proportion of the repeating unit (A) is 90 mol% or more in all repeating units.   An optical molded article made from the polycarbonate resin according to claim 1.   An optical film made of the polycarbonate resin according to claim 1. The optical film according to claim 8, wherein the birefringence (Δn) represented by the following formula (1) is −3.0 × 10 ⁻³ or less.
Δn = R (550) / d (1)
d represents the thickness of the film, and R (550) represents the in-plane retardation value at a wavelength of 550 nm.