JP5580017B2 - Polycarbonate resin and optical film with low photoelastic constant - Google Patents

Description

  The present invention relates to a polycarbonate resin having a high photoelastic constant and a fluidity suitable for molding, and capable of realizing negative birefringence, and an optical film using the same.

  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. For example, an aromatic polycarbonate resin using a bisphenol monomer having a specific structure is disclosed (for example, see Patent Documents 1 to 3). However, this polycarbonate resin has a problem that the photoelastic constant is not sufficiently reduced, and birefringence changes due to stress tend to occur.

  Further, it is known that a polycarbonate resin having a low photoelastic constant can be obtained by reacting a carbonate precursor with bisphenol A and 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (for example, Patent Document 4). reference). However, this polycarbonate resin still has a problem that the photoelastic constant is not sufficiently reduced, and birefringence changes due to stress still tend to occur. Moreover, since glass transition temperature (Tg) is high and fluidity | liquidity is low, there exists a problem that the high temperature is required for extending | stretching of a film and the special processing equipment different from the past is required.

Also, a carbonate precursor is added to tricyclo (5.2.1.0 ^2.6 ) decandimethanol, an aliphatic diol, and 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, an aromatic diol. It is known that when reacted, a polycarbonate resin having a lower flow rate than a reaction between aromatic diols and good fluidity can be obtained (see, for example, Patent Document 5). In applications such as an optical film in which a reduction in birefringence due to stress is particularly required, the photoelastic constant has not been sufficiently reduced.

  On the other hand, an optical film using a polycarbonate resin is suitably used as a retardation film and a protective film for a polarizing plate. The retardation film is used in a liquid crystal display device or the like, and has functions such as color compensation, viewing angle expansion, and antireflection. A polycarbonate resin containing a fluorene-based bisphenol skeleton has been proposed as a retardation film having negative birefringence (see, for example, Patent Document 6, Patent Document 7, and Patent Document 8). However, in any case, the glass transition temperature (Tg) is high, a high temperature is required for stretching the film, and special processing equipment different from the conventional one is required. In addition, the photoelastic constant is high, the birefringence due to stress is large, and there is a problem that light leakage occurs when used as a retardation film.

  Therefore, a polycarbonate resin having a low photoelastic constant and a fluidity suitable for molding and capable of realizing negative birefringence and an optical film using the same have 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 2004-331688 A JP 2000-169573 A WO01 / 009649 JP 2001-194530 A JP 2006-323254 A

  An object of the present invention is to provide a polycarbonate resin that has a low photoelastic constant and a fluidity suitable for molding and can realize negative birefringence, and an optical film using the polycarbonate resin.

As a result of extensive research, the present inventors have achieved a surprisingly low photoelastic constant by reacting a specific amount of a diol having a specific structure having a highly sterically hindered alkyl group with an aliphatic diol at a specific ratio. It was clarified that a polycarbonate resin having high fluidity suitable for molding can be obtained. Furthermore, the inventors have investigated that an optical film using this resin can exhibit a desired negative birefringence, and have completed the present invention.
That is, the present invention is as follows.

で表される繰り返し単位（Ａ２）と下記式

[式（Ｂ）中、Ｒ_７は炭素原子数２〜１８のアルキル基、炭素原子数４〜２０のシクロアルキレン基、酸素原子、窒素原子、硫黄原子を含んでも良い。ｒは０または１の整数を示す。]
で表される繰り返し単位（Ｂ）からなり、それら繰り返し単位（Ａ２）成分と繰り返し単位（Ｂ）成分とのモル比（Ａ２／Ｂ）が６０／４０以上９０／１０未満の範囲で、２０℃の塩化メチレン溶液で測定された比粘度が０．２０〜１．５０であるポリカーボネート樹脂を用いてなるフィルムであって、該フィルムが
下記式（１）および（２）を満たす光学フィルム。
Ｒ（４５０）＜Ｒ（５５０）＜Ｒ（６５０） （１）
Ｒ（６５０）＜０ （２）
[但し、Ｒ（４５０）、Ｒ（５５０）およびＲ（６５０）は夫々、波長４５０ｎｍ、５５０ｎｍ、６５０ｎｍにおけるフィルム面内の位相差値を示す。] 1. Repeat unit is the following formula

The repeating unit (A2) represented by the following formula

[In the formula (B), R ₇ may contain an alkyl group having 2 to 18 carbon atoms, a cycloalkylene group having 4 to 20 carbon atoms, an oxygen atom, a nitrogen atom, or a sulfur atom. r represents an integer of 0 or 1. ]
The molar ratio ( A2 / B) of the repeating unit ( A2 ) component to the repeating unit (B) component is within the range of 60/40 or more and less than 90/10, and 20 ° C. a of the measured specific viscosity in a methylene chloride solution is using a 0.20 to 1.50 der Lupo polycarbonate resin film, the film is
An optical film satisfying the following formulas (1) and (2).
R (450) <R (550) <R (650) (1)
R (650) <0 (2)
[However, R (450), R (550), and R (650) represent retardation values in the film plane at wavelengths of 450 nm, 550 nm, and 650 nm, respectively. ]

2. 2. The optical film as described in 1 above , wherein the glass transition temperature of the polycarbonate resin is 100 ° C. to 180 ° C.
3. The optical film of any one of said 1-2 whose photoelastic constant of polycarbonate resin is 30 * 10 <^-12> Pa < ^{-1 >} or less .
4). The liquid crystal display device which comprised the optical film of any one of said 1-3 .

  The polycarbonate resin of the present invention has a surprisingly low photoelastic constant and fluidity suitable for molding by reacting a carbonate precursor with a diol having a specific structure having an alkyl group having a large steric hindrance and an aliphatic diol. It has become possible.

  Furthermore, by using the polycarbonate resin of the present invention, an optical film having a low photoelastic constant and exhibiting negative birefringence can be provided. In particular, the optical film of the present invention can be suitably used as a polarizing plate protective film or a retardation film, and can maintain its performance continuously even after a thermal unevenness test. Therefore, the industrial effect that it produces is exceptional.

It is explanatory drawing of the thermal nonuniformity evaluation of an Example.

Hereinafter, the present invention will be described in detail.
<Polycarbonate resin>
The polycarbonate resin of the present invention can be obtained by combining the component (A2) and the component (B).

(Repeating unit (A2) )
Repeat Unit used in the present invention (A2) is 9, induced 9- bis (4-hydroxy -3-sec-butylphenyl) fluorene down or al. Unit represented by (A2) is photoelastic is estimated to be lower by a large group of sterically hindered to inhibit the rotation of the phenyl group, further, the rise is liquidity, also in moldability excellent Ru.

(Repeating unit (B))
The repeating unit (B) used in the present invention has an aliphatic structure and a carbonate bond as shown in the repeating unit (B) (hereinafter, the formula (B)). In the formula (B), R ₇ is an alkylene group having 2 to 18 carbon atoms or a cycloalkylene group having 4 to 20 carbon atoms, and may contain an oxygen atom, a nitrogen atom, or a sulfur atom. The formula (B) can be obtained by reacting various aliphatic chain diols and alicyclic diols with a carbonate precursor. For example, the aliphatic chain diol has 20 or less and 2 or more carbon atoms, preferably 10 or less and 2 or more, and particularly preferably 6 or less and 3 or more. When this value is increased, the heat resistance is lowered and the cost is increased. In addition, the alicyclic diol is not particularly limited, but a compound containing a 5-membered ring structure or a 6-membered ring structure is usually used. By including a 5-membered ring structure or a 6-membered ring structure, the heat resistance can be increased. The 6-membered ring structure may be fixed in a chair shape or a boat shape by a covalent bond. The number of carbon atoms contained in the alicyclic diol is 20 or less and 4 or more, preferably 20 or less and 5 or more. The larger this value, the more difficult the synthesis, the more difficult the purification, and the higher the cost. The smaller the number of carbon atoms, the easier the purification and the easier it is to obtain.

  Examples of the aliphatic chain diol represented by the formula (B) when the carbonate precursor is reacted include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5- Examples include pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, and diethylene glycol.

When the carbonate precursor is reacted, the alicyclic diol that becomes the formula (B) is represented by the following formula (B1) (wherein R ₉ represents an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. ) And contains various isomers. Specifically, when r = 0, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, when r = 1, 1,2-cyclohexanedimethanol, 1,3-cyclohexanediol, Examples include cyclohexanedimethanol and 1,4-cyclohexanedimethanol.

  Moreover, the following (B2) formula (In formula, s is represented by 0 or 1) is mentioned as an alicyclic diol used as a formula (B) when making a carbonate precursor react, Various isomers are shown. contains.

  When the carbonate precursor is reacted, the following (B3) formula (wherein t is represented by 0 or 1) is exemplified as the alicyclic diol to be the formula (B), and various isomers are contained. Specifically, when r = 0, 2,6-decalindiol, 1,5-decalindiol, 2,3-decalindiol, and when r = 1, 2,6-decalindimethanol, 1,5-decal Examples thereof include phosphorus dimethanol and 2,3-decalin dimethanol.

  The following (B4) formula is mentioned as an alicyclic diol which becomes the formula (B) when the carbonate precursor is reacted, and various isomers are contained. Specifically, when r = 0, 2,3-norbornanediol, 2,5-norbornanediol, when r = 1, 2,3-norbornane dimethanol, 2,5-norbornane dimethanol and the like can be mentioned. .

  The following (B5) formula is mentioned as an alicyclic diol which becomes the formula (B) when the carbonate precursor is reacted, and various isomers are contained. Specifically, when r = 0, 1,3-adamantanediol and the like, and when r = 1, 1,3-adamantane dimethanol and the like can be mentioned.

  In addition, when the carbonate precursor is reacted, the alicyclic diol containing a heteroatom represented by the formula (B) is a diol compound composed of a heterocyclic compound having 4 to 10 members, A diol compound containing oxygen, nitrogen and sulfur atoms. Among these, a preferable hetero atom is an oxygen atom.

  Examples of the oxygen-containing heterocyclic diol that is converted to the formula (B) when the carbonate precursor is reacted include condensed polycyclic ether diols such as isosorbide and 3,9-bis (1,1-dimethyl-2-hydroxyethyl). -2,4,8,10-tetraoxaspiro [5.5] undecane, heterocyclic spiro compounds such as cyclic ether diols such as 1,4-anhydroerythritol, 2- (5-ethyl-5-hydroxymethyl- And cyclic acetal diols such as 1,3-dioxan-2-yl) -2-methylpropan-1-ol.

Moreover, as a nitrogen-containing heterocyclic diol which becomes a formula (B) when a carbonate precursor is reacted, for example, 3,4-pyrrolidinediol, 3,4-dimethylpiperidinediol, N-ethyl-3,4-piperidinediol N-heterocyclic diols such as N-ethyl-3,5-piperidinediol.
Moreover, S-heterocyclic diols, such as deoxythio fructose, are mentioned as a sulfur containing heterocyclic diol which will become Formula (B) when a carbonate precursor is made to react.

  In addition, the said alicyclic diol is an example of the cyclic diol which can be used for this invention, Comprising: It is not limited to these at all. These aliphatic diols may be used alone or in combination of two or more. However, when one kind is used alone, the composition ratio can be easily controlled, so that chromatic dispersion can be easily controlled. Among these aliphatic diols, from the viewpoint of heat resistance, optical properties, and mechanical properties, diols represented by the above formula (B1) including tricyclodecanedimethanol including 1,4-cyclohexanedimethanol (B2) and 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane as the other diol, 2- ( Cyclic acetal diols such as 5-ethyl-5-hydroxymethyl-1,3-dioxan-2-yl) -2-methylpropan-1-ol, isosorbide, 1,3-propanediol, 1,4-butanediol, 1 , 6-hexanediol is preferred.

(Composition ratio)
The composition ratio of the polycarbonate resin of the present invention is such that the molar ratio ( A2 / B) between the component (A2) and the component (B) is 60/40 or more and less than 90/10. More preferably, they are 65/35 or more and less than 90/10, More preferably, they are 70/30 or more and 89/11 or less. (It may be adjusted to a desired composition ratio by blending the homopolymer of the component (A2) , the homopolymer of the component (B), and the copolymer of the component (A2) and the component (B)). When the molar ratio ( A2 / B) between the component ( A2 ) and the component (B) is less than 60/40, negative birefringence cannot be realized, which is not preferable. Further, when the molar ratio ( A2 / B) of the component ( A2 ) to the component (B) is 90/10 or more, the photoelastic constant of the polycarbonate resin is undesirably high. The composition of the polycarbonate resin of the present invention may contain a repeating unit derived from another diol component to the extent that the effect is not lost in addition to the component ( A2 ) and the component (B). The proportion is preferably less than 10% mol with respect to the number of moles of the previous repeating unit. The molar ratio is measured and calculated by proton NMR of JNM-AL400 manufactured by JEOL Ltd.

(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. It is necessary to be in the range of 50, preferably in the range of 0.23 to 1.20, more preferably in the range of 0.25 to 1.00. You may use together with other resin in the range which does not impair the effect of this invention.

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 lower limit of the glass transition temperature (Tg) of the polycarbonate resin of the present invention is preferably 100 ° C, more preferably 130 ° C, and still more preferably 140 ° C. When Tg is higher than 100 ° C., the thermal stability tends to be good. Further, when used as a retardation film, the deformation of the film during the heat resistance test is small, so that the change in retardation is likely to be small. On the other hand, the upper limit of the glass transition temperature (Tg) is preferably 180 ° C, more preferably 170 ° C, and still more preferably 160 ° C. Moreover, when the glass transition temperature (Tg) is higher than 180 ° C., the viscosity is too high and molding tends to be difficult. The glass transition temperature (Tg) is measured at 29 ° C./min using a 2910 type DSC manufactured by TA Instruments Japan.

(Photoelastic constant)
The absolute value of the photoelastic constant of the polycarbonate resin of the present invention is 30 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 25 × 10 ⁻¹² Pa ⁻¹ or less, further preferably 22 × 10 ⁻¹² Pa ⁻¹ or less, Most preferably, it is 20 × 10 ⁻¹² Pa ⁻¹ or less. When the absolute value exceeds 30 × 10 ⁻¹² Pa ⁻¹ , the change in birefringence due to stress is large, and light leakage tends to occur when used for a retardation film or the like, which is not preferable. The photoelastic constant is measured using a spectroellipometer M-220 manufactured by JASCO Corporation for an unstretched film.

(Relationship between glass transition temperature and photoelastic constant)
According to the resin composition of the present invention, since the ratio of the diol component represented by the formula (A2) is large, if the same photoelastic constant is increased by increasing Tg, the heat after the heat described later is applied. Light leakage can be greatly suppressed. From such a viewpoint, Tg is preferably 130 ° C, and more preferably 140 ° C.

(Production method of polycarbonate resin)
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 diol component with a carbonate precursor such as a carbonic acid diester. Next, basic means for these manufacturing methods will be briefly described.

  The transesterification reaction using a carbonic acid diester as a carbonate precursor is carried out by a method in which an aromatic diol component in a predetermined ratio is stirred with a carbonic acid diester while heating under an inert gas atmosphere to distill the resulting 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. You may add a terminal terminator, 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. Furthermore, 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 ⁻² equivalent, more preferably 1 ×, relative 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 also 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.

<Optical molded product>
An optical molded article using the polycarbonate resin of the present invention is molded by any method such as an injection molding method, a compression molding method, an extrusion molding method, or a solution casting method. The polycarbonate resin of the present invention has a low photoelastic constant and can exhibit a desired negative birefringence by stretching, so that it can be advantageously used as an optical film. Of course, the polycarbonate resin of the present invention has a low photoelastic constant and is excellent in moldability, so an optical disk, an optical lens, a liquid crystal panel, an optical card, a sheet, a film, an optical fiber, a connector, a vapor deposition plastic reflector, a display. It can be advantageously used as an optical molded article suitable for the structural material or functional material application of an optical component.

<Optical film>
(Wavelength dispersion)
By stretching an unstretched film using the polycarbonate of the present invention, it has a feature that in a visible light region having a wavelength of 400 to 800 nm, the retardation in the film plane becomes smaller as the wavelength becomes shorter. That is, the following formula (1)
R (450) <R (550) <R (650) (1)
Meet. However, R (450), R (550), and R (650) represent retardation values in the film plane at wavelengths of 450 nm, 550 nm, and 650 nm, respectively. Satisfying the above equation (1) is preferable from the viewpoint that optical compensation is possible at a wide wavelength range.

Here, the in-plane retardation value R is defined by the following equation, and is a characteristic that expresses a phase delay between the X direction of light transmitted through the film in the vertical direction and the vertical Y direction.
_{R = (n x -n y)} × d
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, and d is the thickness of the film. 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 optical film using the polycarbonate resin of the present invention satisfies the condition of the following formula (2).
R (650) <0 (2)
This optical film exhibits extremely excellent characteristics particularly when used for a retardation film of an in-plane switching (IPS) mode liquid crystal display device. Of course, the present invention is not limited to the retardation film of the IPS mode liquid crystal display device, but may be used for other purposes such as a plastic substrate film, a polarizing plate protective film, an antireflection film, a brightness enhancement film, an optical disk protective film, and a diffusion film.

  Wavelength dispersibility was determined by cutting out a test piece having a length of 100 mm and a width of 70 mm from an unstretched film, and longitudinally stretching 2.0 times at a stretching temperature of Tg + 10 ° C., and the resulting optical film was made by Spectrophotometer M- Measure using 220.

  Examples of the method for producing the optical film include known methods such as a solution casting method, a melt extrusion method, a hot press method, and a calendar method. Of these, the solution casting method and the melt extrusion method are preferable, and the melt extrusion method is particularly preferable from the viewpoint of productivity.

  In the melt extrusion method, a method of feeding a resin to an extrusion cooling roll using a T die is preferably used. The melt extrusion temperature at this time is determined from the molecular weight, Tg, melt flow characteristics, etc. of the polycarbonate resin, but is in the range of 180 to 350 ° C, and 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.

  Further, since the polycarbonate resin of 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 obtained by the solution casting method is preferably 2% by weight or less, more preferably 1% by weight or less. If it exceeds 2% by weight, the glass transition temperature of the film is remarkably lowered, which is not preferable in terms of heat resistance.

  The thickness of the unstretched film using the polycarbonate of the present invention is preferably in the range of 30 to 400 μm, more preferably in the range of 40 to 300 μm. When the unstretched film is further stretched to form a retardation film, for example, it may be appropriately determined within the above range in consideration of the desired retardation value and thickness of the optical film.

  The unstretched film using the polycarbonate of the present invention 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 in terms 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. 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. If the stretching temperature is low, the phase difference tends to be easily developed.

  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. In addition, said Tg in the case of extending | stretching the unstretched film obtained by the solution cast method means the glass transition temperature containing the trace amount solvent in this unstretched film.

(Total light transmittance)
The total light transmittance of the optical film of the present invention is preferably 85% or more, more preferably 88% or more, of the optical film having a thickness of 100 μm. Total light transmittance was measured using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.).

(HAZE)
The HAZE of the optical film of the present invention is preferably 5% or less, more preferably 3% or less. The haze was measured using a haze meter (Nippon Denshoku Industries, NDH5000).

  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. Polymer composition ratio (NMR)
Measurement was performed by proton NMR of JNM-AL400 manufactured by JEOL Ltd., and the polymer composition ratio was calculated. The composition ratio is shown by the molar ratio of repeating units.

2. 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]

3. 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.

4). Photoelastic constant measurement The unstretched film was measured using Spectroellipometer M-220 manufactured by JASCO Corporation.

5. Measurement of retardation and wavelength dispersion The stretched film was measured using Spectroellipometer M-220 manufactured by JASCO Corporation.

6). Evaluation of heat unevenness in a transmissive configuration A structure in which a polarizer film in which iodine is adsorbed and oriented in polyvinyl alcohol is sandwiched between two triacetylcellulose films, and an acrylic pressure-sensitive adhesive layer is provided on one side thereof A linear polarizing plate was prepared. The stretched film prepared in the example was subjected to corona discharge treatment under the condition of an integrated irradiation amount of 1500 J, and the corona discharge treatment surface was bonded to the linear polarizing plate at an angle of 45 ° to the acrylic pressure-sensitive adhesive layer side. Two polarizing plates were prepared, and bonded to alkali-free glass (Corning Japan, trade name: EAGLE2000) with an adhesive as shown in FIG. Visual evaluation of the light leakage of the transmitted light when the backlight is applied to the circularly polarizing plate after 200 hours at 85 ° C. is evaluated as ○ when there is no light leakage, Δ when there is a small amount of light leakage from the edge, the whole A case where light omission was observed was marked with x.

[Example 1]
<Manufacture of polycarbonate resin>
1268.2 parts of 9,9-bis (4-hydroxy-3-sec-butylphenyl) fluorene (hereinafter sometimes abbreviated as “BSBF”), 3,9-bis (2-hydroxy-1,1-dimethyl) Ethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane (hereinafter sometimes abbreviated as SPG) 208.6 parts, diphenyl carbonate 749.7 parts, and sodium hydroxide 1. 6 × 10 ⁻⁴ parts were heated to 180 ° C. in a nitrogen atmosphere and melted. 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 60 ° C./hr and maintained 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 completion of the reaction, tetrabutylphosphonium salt of dodecylbenzenesulfonic acid twice the amount of the catalyst 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 resin was formed into a film at 290 ° C. so that the transparent extrusion A stretched film was obtained. A 50 mm × 10 mm size sample was cut out from the obtained unstretched film, and the photoelastic constant was measured using the sample. Further, an unstretched film of 100 mm length and 70 mm width cut out in the same manner was uniaxially stretched 2.0 times in the length direction at 158 ° C. (Tg + 10 ° C.) to obtain an optical film. The optical film was measured for retardation and wavelength dispersion. Furthermore, this optical film was bonded as shown in FIG. 1 by a known method, and thermal unevenness evaluation was performed. The results are shown in Table 1.

[Example 2]
<Manufacture of polycarbonate resin>
Except for using BSBF1363.4 parts, tricyclo [5.2.1.0 ^2,6 ] decanedimethanol (hereinafter sometimes abbreviated as TCDDM) 94.2 parts, and diphenyl carbonate 749.7 parts. Exactly the same operation as 1 was performed 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>
Next, an unstretched film was prepared in the same manner as in Example 1. The photoelastic constant of the obtained unstretched film was evaluated in the same manner as in Example 1. In the same manner as in Example 1, the unstretched film was uniaxially stretched 2.0 times at Tg + 10 ° C., and phase difference measurement and wavelength dispersion were measured. The results are shown in Table 1.

[Example 3]
<Manufacture of polycarbonate resin>
Except for using BSBF 1395.1 parts, TCDDM 80.7 parts, and diphenyl carbonate 749.7 parts, the same operation as in Example 1 was performed 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>
Next, an unstretched film was prepared in the same manner as in Example 1. The photoelastic constant of the obtained unstretched film was evaluated in the same manner as in Example 1. In the same manner as in Example 1, the unstretched film was uniaxially stretched 2.0 times at Tg + 10 ° C., and phase difference measurement and wavelength dispersion were measured. Furthermore, this optical film was bonded as shown in FIG. 1 by a known method, and thermal unevenness evaluation was performed. 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 exchange water and 2271 parts of 48% aqueous sodium hydroxide solution are added, and 2,2-bis (4-hydroxyphenyl) propane (hereinafter abbreviated as BPA). 1775 parts and 3.5 parts of sodium hydrosulfite were dissolved, 7925 parts of methylene chloride was added, and then 1000 parts of phosgene was blown in at 16 to 20 ° C. for 60 minutes while stirring. 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 powder were measured and listed in Table 1.

<Manufacture of optical film>
The obtained polycarbonate resin was pelletized by a 15φ biaxial extrusion kneader. Next, an unstretched film was prepared in the same manner as in Example 1. The photoelastic constant of the obtained unstretched film was evaluated in the same manner as in Example 1. In the same manner as in Example 1, the unstretched film was uniaxially stretched 2.0 times at Tg + 10 ° C., and phase difference measurement and wavelength dispersion were measured. Furthermore, this optical film was bonded as shown in FIG. 1 by a known method, and thermal unevenness evaluation was performed. The results are shown in Table 1. As a result of thermal unevenness evaluation, light leakage occurred, which is not preferable as a retardation film.

[Comparative Example 2]
<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% aqueous sodium hydroxide solution were added, and 585 parts of BPA, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene. 1969 parts (hereinafter may be abbreviated as BCF) and 4.5 parts of sodium hydrosulfite are dissolved, 6604 parts of methylene chloride are added, and then 1000 parts of phosgene is added for 60 minutes at 16 to 20 ° C. with stirring. In short, I blew in. After completion of the phosgene blowing, 70 parts of p-tert-butylphenol and 327 parts of a 48% aqueous sodium hydroxide solution were added, 1.57 parts of triethylamine was further added, and the reaction was terminated by stirring at 20 to 27 ° C. for 40 minutes. The methylene chloride layer containing the product was washed with dilute hydrochloric acid and pure water, and then the methylene chloride was evaporated to obtain a polycarbonate resin. The specific viscosity and glass transition temperature of the powder were measured and listed in Table 1.

<Manufacture of optical film>
Next, the obtained polycarbonate resin 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. The photoelastic constant of the obtained unstretched film was evaluated in the same manner as in Example 1. In the same manner as in Example 1, the unstretched film was uniaxially stretched 2.0 times at Tg + 10 ° C., and phase difference measurement and wavelength dispersion were measured. Furthermore, this optical film was bonded as shown in FIG. 1 by a known method, and thermal unevenness evaluation was performed. As a result of heat resistance evaluation, light leakage occurred, which is not preferable as an optical film.

[Comparative Example 3]
<Manufacture of polycarbonate resin>
Except for using 1102.5 parts of BCF, 100.9 parts of TCDDM, and 749.7 parts of diphenyl carbonate, the same operation as in Example 1 was performed 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>
Next, an unstretched film was prepared in the same manner as in Example 1. The photoelastic constant of the obtained unstretched film was evaluated in the same manner as in Example 1. As in Example 1, uniaxial stretching of the unstretched film at Tg + 10 ° C. at 2.0 times was attempted, but the film was brittle and could not be stretched. The results are shown in Table 1.

[Comparative Example 4]
Except for using 71BF parts of BSBF, 573.3 parts of SPG, and 749.7 parts of diphenyl carbonate, the same operation as in Example 1 was performed 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>
Next, an unstretched film was prepared in the same manner as in Example 1. The photoelastic constant of the obtained unstretched film was evaluated in the same manner as in Example 1. In the same manner as in Example 1, the film was uniaxially stretched by 2.0 times at Tg + 10 ° C., and phase difference measurement and wavelength dispersion were measured. Furthermore, this optical film was bonded as shown in FIG. 1 by a known method, and thermal unevenness evaluation was performed.

  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.

1. Polarizing plate 2. 2. stretched film Inorganic glass4. Stretched film 5. Polarizer

Claims (4)

Repeat unit is the following formula

The repeating unit ( A2 ) represented by the following formula

[In the formula (B), R ₇ may contain an alkyl group having 2 to 18 carbon atoms, a cycloalkylene group having 4 to 20 carbon atoms, an oxygen atom, a nitrogen atom, or a sulfur atom. r represents an integer of 0 or 1. ]
The molar ratio ( A2 / B) of the repeating unit ( A2 ) component to the repeating unit (B) component is within the range of 60/40 or more and less than 90/10, and 20 ° C. a of the measured specific viscosity in a methylene chloride solution is using a 0.20 to 1.50 der Lupo polycarbonate resin film, the film is
An optical film satisfying the following formulas (1) and (2).
R (450) <R (550) <R (650) (1)
R (650) <0 (2)
[However, R (450), R (550), and R (650) represent retardation values in the film plane at wavelengths of 450 nm, 550 nm, and 650 nm, respectively. ] The optical film according to claim 1 , wherein the polycarbonate resin has a glass transition temperature of 100C to 180C . The optical film according to claim 1, wherein the polycarbonate resin has a photoelastic constant of 30 × 10 ⁻¹² Pa ⁻¹ or less . The liquid crystal display device which comprised the optical film of any one of Claims 1-3 .

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