JP5587617B2 - Polycarbonate resin and film with low photoelastic constant - Google Patents

Description

  The present invention relates to a polycarbonate resin and a film that have a low photoelastic constant, good melt viscosity, good tear strength of an unstretched film, and can exhibit desired reverse wavelength dispersibility when stretched.

In general, an optical film, particularly a retardation film, is used in a display device such as a liquid crystal display device, and has functions such as color compensation, viewing angle expansion, and antireflection.
As the retardation film, λ / 4 plate and λ / 2 plate are known, and thermoplastic polymers such as polycarbonate, polyethersulfone, polysulfone and the like obtained by polycondensation of bisphenol A are used as the material. The λ / 4 plate and λ / 2 plate obtained by stretching films of these materials have the property that the phase difference increases as the wavelength becomes shorter. For this reason, there is a problem that the wavelengths that can function as the λ / 4 plate and the λ / 2 plate are limited to specific wavelengths.

  As a method for controlling the wavelength in a wide band, a method is known in which two or more specific birefringent films having different wavelength dependences of the retardation are laminated at a specific angle. (For example, refer to Patent Document 1) In these cases, since a plurality of retardation films are used, a process of bonding them together or adjusting the bonding angle is necessary, and there is a problem in productivity. In addition, since the entire thickness of the retardation film is increased, there is a problem that the light transmittance is lowered and becomes thicker or darker when incorporated in an apparatus.

  In recent years, there has been proposed a method of widening a band with a single film without performing such lamination (see Patent Document 2). The film is a method of stretching a polymer film comprising a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy. However, since the reaction between aromatic diols has a high photoelastic constant, birefringence due to stress is large, and there is a problem that light leakage occurs when used as a retardation film. In addition, since it has a high Tg (glass transition temperature), it requires a high temperature for film stretching and the like, and requires special processing equipment different from the conventional one, so that the workability is not always sufficient. I could not say.

  Therefore, as a film having a low photoelastic constant and a Tg excellent in processability and having a good reverse wavelength dispersibility, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene and spiroglycol are used. Phase difference films have been proposed (see Patent Documents 3 and 4). However, since the unstretched film is easily torn and difficult to handle in the stretching process, further improvement in tear strength has been demanded. Moreover, in order to suppress the decomposition product by the shear at the time of melt film forming, the further reduction of melt viscosity was also calculated | required.

Japanese Patent Laid-Open No. 02-120804 International Publication No. 2000/026705 Pamphlet International Publication No. 2006/041190 Pamphlet International Publication 2008/156186 Pamphlet

  The object of the present invention is that the photoelastic constant is low, the melt viscosity is suitable for melt film formation, the tear strength is high when an unstretched film is formed, and the desired reverse wavelength dispersibility can be exhibited when stretched. It is to provide a polycarbonate resin and a film.

  As a result of intensive research, the present inventors have reacted the diol having a fluorene skeleton, a cyclic acetal diol, and an aliphatic diol with a carbonate precursor at a specific ratio, so that the photoelastic constant is low and the melt viscosity is low. The present inventors have determined that a polycarbonate resin can be obtained that has a good tear strength when it is made into an unstretched film. Furthermore, it has been found that a desired reverse wavelength dispersion can be expressed in an optical film by stretching an unstretched film using this resin, and the present invention has been completed.

［式中、Ｒ_１及びＲ_２は夫々独立して炭素原子数１〜１０の炭化水素基、またはハロゲン 原子を示し、ｍ及びｎは同一または異なる０〜４の整数を示す。］
で表される繰り返し単位（Ａ）、下記式（Ｂ）

［式中、Ｒ_３〜Ｒ_６は夫々独立して水素原子または炭素原子数１〜１０のアルキル基であ る。］
で表される繰り返し単位（Ｂ）、及び下記式（Ｃ）

［式中、Ｒ _７ は炭素原子数３〜８の直鎖脂肪族ジオールから誘導されるアルキレン基、 または下記式（Ｃ１）の脂環式ジオールから誘導されるシクロアルキレン基である。］

［式中、Ｒ _８ は炭素原子数１〜１２のアルキル基、水素原子であり、ｒは０または１を表す。］
で表される繰り返し単位（Ｃ）を主たる繰り返し単位とし、上記繰り返し単位（Ａ）、 （Ｂ）、及び（Ｃ）のモル数の合計を基準として、繰り返し単位（Ａ）が２０〜４０モ ル％、繰り返し単位（Ｂ）が５０〜７９モル％、繰り返し単位（Ｃ）が１〜１０モル％ を占めるポリカーボネート樹脂。
２．温度２８０℃、せん断速度１２２ｓ^−１における溶融粘度が１０〜５００Ｐａ・ｓ の範囲にある上記１記載の樹脂。
３．上記１または２のいずれかに記載の樹脂を用いてなる未延伸フィルム。
４．偏光板保護フィルムまたは光ディスク用透過層フィルムとして用いる上記３記載 の未延伸フィルム。
５．上記３記載の未延伸フィルムを延伸してなり、波長４５０ｎｍ、５５０ｎｍ、及 び６５０ｎｍにおけるフィルム面内の位相差値Ｒ（４５０）、Ｒ（５５０）、及びＲ（ ６５０）が、下記式（１）及び（２）
０．６０ ＜ Ｒ（４５０）／Ｒ（５５０）＜１．００ （１）
１．０１ ＜ Ｒ（６５０）／Ｒ（５５０）＜１．４０ （２）
を満たす延伸フィルム。
６．位相差フィルムとして用いる上記５記載の延伸フィルム。
７．上記６記載の位相差フィルムを具備した液晶表示装置。 That is, the present invention is as follows.
1. The repeating unit is represented by the following formula (A)

[Wherein, R ₁ and R ₂ each independently represent a hydrocarbon group having 1 to 10 carbon atoms or a halogen atom, and m and n represent the same or different integers of 0 to 4. ]
The repeating unit (A) represented by the following formula (B)

[Wherein, R _{3 to} R ₆ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. ]
And a repeating unit (B) represented by the following formula (C):

[Wherein, R ₇ is an alkylene group derived from a linear aliphatic diol having 3 to 8 carbon atoms, or a cycloalkylene group derived from an alicyclic diol of the following formula (C1) . ]

[Wherein R ₈ represents an alkyl group having 1 to 12 carbon atoms or a hydrogen atom, and r represents 0 or 1. ]
And the repeating unit (A) is 20 to 40 moles based on the total number of moles of the repeating units (A), (B), and (C). %, Polycarbonate resin occupying 50 to 79 mol% of repeating units (B) and 1 to 10 mol% of repeating units (C).
2. 2. The resin according to 1 above, wherein the melt viscosity at a temperature of 280 ° C. and a shear rate of 122 s ^{−1 is} in the range of 10 to 500 Pa · s.
3. 3. An unstretched film using the resin according to either 1 or 2 above.
4). 4. The unstretched film according to 3 above, which is used as a polarizing plate protective film or a transmission layer film for optical disks.
5. The unstretched film described in 3 above is stretched, and the in-plane retardation values R (450), R (550), and R (650) at wavelengths of 450 nm, 550 nm, and 650 nm are expressed by the following formula (1). ) And (2)
0.60 <R (450) / R (550) <1.00 (1)
1.01 <R (650) / R (550) <1.40 (2)
A stretched film that satisfies
6). 6. The stretched film according to 5 above, which is used as a retardation film.
7). 7. A liquid crystal display device comprising the retardation film as described in 6 above.

The polycarbonate resin and film of the present invention have a low photoelastic constant and melt viscosity because a specific proportion of a specific aliphatic diol is copolymerized in addition to a diol having a fluorene skeleton and a cyclic acetal diol. When used as an unstretched film, it exhibits high tear strength.
Furthermore, desired reverse wavelength dispersion can be expressed in the optical film by stretching the unstretched film.

It is explanatory drawing of the thermal nonuniformity evaluation of an Example. It is explanatory drawing of light omission 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 repeating unit (A), the repeating unit (B), and the repeating unit (C).

(Repeating unit (A))
The repeating unit (A) used in the present invention is a repeating unit having a fluorene skeleton as shown in the formula (A), and these R ₁ and R ₂ are hydrocarbon groups having 1 to 10 carbon atoms ( Alkyl group, cycloalkyl group, aryl group, aralkyl group, alkenyl group and the like) or halogen group (fluorine atom, chlorine atom, bromine atom and the like). Preferably they are a C1-C6 alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkenyl group, or a halogen group (a fluorine atom, a chlorine atom, a bromine atom, etc.). m and n represent the same or different integers of 0 to 4. Specifically, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 9,9-bis (4-hydroxy-3-ethylphenyl) Fluorene, 9,9-bis (4-hydroxy-3-n-propylphenyl) fluorene, 9,9-bis (4-hydroxy-3-isopropylphenyl) fluorene, 9,9-bis (4-hydroxy-3- n-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-sec-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-tert-butylphenyl) fluorene, 9,9-bis Derived from (4-hydroxy-3-cyclohexylphenyl) fluorene, 9,9-bis (4-hydroxy-3-phenylphenyl) fluorene, etc. The repeating unit to be illustrated is exemplified. In particular, a repeating unit derived from 9,9-bis (4-hydroxy-3-methylphenyl) fluorene is preferable from the viewpoint of having a low photoelastic constant.

(Repeating unit (B))
The repeating unit (B) used in the present invention has a structure having a spiro ring as shown in the formula (B). (B) In formula, R < ₃ > -R < ₆ > is respectively independently a hydrogen atom or a C1-C10 alkyl group. In particular, an alkyl group having 1 to 3 carbon atoms is preferable, and a methyl group is more preferable. The structure having a spiro ring represented by the formula (B) is presumed to reduce the photoelastic constant and improve the heat resistance.

  Specifically, 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-bis (1,1 -Diethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane), 3,9-bis (1,1-dipropyl-2-hydroxyethyl) -2,4, Examples thereof include a repeating unit derived from 8,10-tetraoxaspiro [5.5] undecane. Among them, a repeating unit derived from 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane (hereinafter abbreviated as spiroglycol). Is preferable from the viewpoint of having a low photoelastic constant.

(Repeating unit (C))
The repeating unit (C) used in the present invention has an aliphatic structure as shown in the formula (C). In the formula (C), R ₇ is an amide derived from a linear aliphatic diol having 3 to 8 carbon atoms.
It is a cycloalkylene group derived from a ruylene group or an alicyclic diol of the above formula (C1) . Since the aliphatic structure shown in Formula (C) has a highly flexible skeleton, it is estimated that the tear strength is improved.

  Examples of the aliphatic linear diol from which the repeating unit (C) is derived when the carbonate precursor is reacted include a linear aliphatic diol having 3 to 8 carbon atoms, particularly preferably 3 carbon atoms. -6 linear aliphatic diols. When the linear aliphatic diol has less than 2 carbon atoms, the boiling point is low, and it is difficult to polymerize as charged, so there is a problem in stable productivity. Specifically, it is derived from 1,6-hexanediol, 1,5-pentanediol, 1,4-butanediol, 1,3-propanediol, 1,7-heptanediol, 1,8-octanediol, and the like. Are preferred. Among these, 1,6-hexanediol and 1,4-butanediol are particularly preferable because they are excellent in imparting flexibility and fluidity.

In addition, as the alicyclic diol from which the repeating unit (C) is derived when the carbonate precursor is reacted, the following (C1) formula (wherein R ₈ is an alkyl group having 1 to 12 carbon atoms, Represents 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.

Among preferred cycloaliphatic diol, 1,4-cyclohexane dimethacrylate no le is particularly preferred since it is excellent in flexibility and fluidity of imparting.
As the aliphatic diol from which the repeating unit of the formula (C) is derived when the carbonate precursor is reacted, an aliphatic linear diol is preferable because it is excellent in imparting flexibility and fluidity.

(Composition ratio)
The composition ratio of the polycarbonate resin of the present invention is based on the total of repeating units (A), (B), and (C), with the above repeating units (A), (B), and (C) as the main repeating units. The repeating unit (A) occupies 20 to 40 mol%, the repeating unit (B) 50 to 79 mol%, and the repeating unit (C) 1 to 10 mol%. By setting it as such a ratio, the polycarbonate resin which has the characteristic which has a low photoelastic constant and has the melt viscosity suitable for melt film forming is given. On the basis of the sum of the repeating units (A), (B) and (C), when the repeating unit (C) occupies a proportion of 1 to 10 mol%, the melt viscosity is lowered and the moldability is excellent, and The tear strength in the stretched film is also improved. In addition, good reverse wavelength dispersion characteristics are exhibited by stretching. As the main repeating unit, the total of repeating units (A), (B), and (C) is 90 mol% or more, preferably 95 mol% or more, more preferably 100 mol%.

The proportion of the repeating unit (A) is preferably 25 to 40 mol%, more preferably 30 to 40 mol%, particularly preferably 31 to 37 mol%.
The proportion of the repeating unit (B) is preferably 55 to 74 mol%, more preferably 56 to 68 mol%, particularly preferably 58 to 64 mol%.
The proportion of the repeating unit (C) is preferably 1 to 9 mol%, more preferably 2 to 8 mol%, and particularly preferably 2 to 6 mol%.

(Specific viscosity: η _SP )
The polycarbonate resin of the present invention has a specific viscosity (η _SP ) in the range of 0.20 to 1.50, which makes it easier to express the molding process properties to a higher degree, and a range of 0.23 to 1.20 is more preferable. A range of 0.25 to 1.00 is particularly preferable.

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 100 to 150 ° C, more preferably 110 to 140 ° C. When the glass transition temperature (Tg) is 100 ° C. or higher, the heat stability is excellent. When used as a retardation film, the change in retardation during the heat resistance test is small and good. Further, when the glass transition temperature (Tg) is 150 ° C. or lower, the viscosity is suitable for molding, which is good. The glass transition temperature (Tg) is measured at 29 ° C./min using a 2910 type DSC manufactured by TA Instruments Japan.

(Melt viscosity)
The polycarbonate resin of the present invention has a melt viscosity of preferably 10 to 500 Pa · s, more preferably 100 to 400 Pa · s at a temperature of 280 ° C. and a shear rate of 122 s ⁻¹ . When it is 10 Pa · s or more, it can be easily melted uniformly and a film with small thickness unevenness can be obtained, and when it is 500 Pa · s or less, it is hardly affected by shearing force, and it can be decomposed and deteriorated on the film. It becomes easy to suppress defects such as foaming, foreign matter, and die lines. Although melt viscosity is based also on the kind of repeating unit (C), for example, it can be made low by increasing the ratio.

(Photoelastic constant)
The absolute value of the photoelastic constant of the polycarbonate resin of the present invention is preferably 20 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 18 × 10 ⁻¹² Pa ⁻¹ or less, and particularly preferably 16 × 10 ⁻¹² Pa ^−1. It is as follows. An absolute value of 20 × 10 ⁻¹² Pa ⁻¹ or less is preferable because a change in birefringence due to stress is small and light leakage hardly occurs when used for a retardation film or the like. The photoelastic constant is measured using a spectroellipometer M-220 manufactured by JASCO Corporation for an unstretched film.

(Tear strength)
The tear strength of the unstretched film of the polycarbonate resin of the present invention is preferably 1.0 N or more, more preferably 1.2 N or more. If it is 1.0 N or more, cracking hardly occurs during film production, which is good. The tear strength can be increased by increasing the proportion of the repeating unit (C), for example.

(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 polycarbonate resin, for example, a method of reacting a 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 a predetermined proportion of a diol component is stirred with a carbonic acid diester under heating in an inert gas atmosphere to distill the resulting alcohol or phenol. 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 to be used is preferably 0.97 to 1.10 mol, more preferably 1.00 to 1.06 mol, per 1 mol of the total diol.

  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 use amount of these catalyst deactivators is preferably 0.5 to 1 per mole of the metal compound 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 of 50 mol, more preferably in a proportion of 0.5 to 10 mol, still more preferably in a proportion of 0.8 to 5 mol.
Further, the polycarbonate resin of the present invention may be used in combination with other resins as long as the effects are not impaired.

  Furthermore, heat stabilizers, plasticizers, light stabilizers, polymerized metal deactivators, flame retardants, lubricants, antistatic agents, surfactants, antibacterial agents, ultraviolet absorbers, mold 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. Since the polycarbonate resin of the present invention has a low photoelastic constant and can achieve desired wavelength dispersion by stretching, it can be advantageously used as an optical film. Of course, the polycarbonate resin of the present invention has a low photoelastic constant and excellent moldability, so that it is an optical disk substrate, optical lens, liquid crystal panel, optical card, sheet, film, optical fiber, connector, vapor-deposited plastic reflector, display. It can also be advantageously used as an optical molded article suitable for the structural material or functional material application of optical parts.

<Optical film>
Specifically, the optical film using the polycarbonate resin of the present invention is a retardation film, a placel substrate film, a polarizing plate protective film, an antireflection film, a brightness enhancement film, a transmission layer film for optical disks, a protective film for optical disks, Examples thereof include a diffusion film. In particular, a retardation film and an antireflection film are preferable.

  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 (streak) 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, 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.

  The thickness of the unstretched film using the polycarbonate resin 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 obtain a retardation film, it is in the range of 20 to 200 μm, more preferably 20 to 150 μm, although it relates to the target retardation value. If it is this range, the desired phase difference value by extending | stretching will be easy to be obtained, and film forming is also easy and preferable.

  An unstretched film using the polycarbonate resin of the present invention becomes a retardation film by stretching and orientation. 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 combining them 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. . 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 film.

(Wavelength dispersion)
By stretching an unstretched film using the polycarbonate resin of the present invention, an optical film exhibiting reverse wavelength dispersion that becomes smaller as the retardation in the film plane becomes shorter in the visible light region having a wavelength of 400 to 800 nm. Can be obtained. A stretched film obtained by stretching an unstretched film using the polycarbonate resin of the present invention satisfies the conditions of the following formulas (1) and (2).
0.60 <R (450) / R (550) <1.00 (1)
1.01 <R (650) / R (550) <1.40 (2)
Preferably, the conditions of the following formulas (1-1) and (2-1) are satisfied.
0.65 <R (450) / R (550) <0.92 (1-1)
1.02 <R (650) / R (550) <1.35 (2-1)
More preferably, the conditions of the following formulas (1-2) and (2-2) are satisfied.
0.70 <R (450) / R (550) <0.91 (1-2)
1.03 <R (650) / R (550) <1.30 (2-2)

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.

Moreover, it is preferable that retardation value R (550) in the film plane in wavelength 550nm of an optical film is R (550)> 50nm. A single optical film can be used as a broadband λ / 4 plate or λ / 2 plate without being laminated. In such applications, it is further desirable that 100 nm <R (550) <180 nm for a λ / 4 plate and 220 nm <R (550) <330 nm for a λ / 2 plate.
The wavelength dispersibility of the optical film was measured using Spectroellipometer M-220 manufactured by JASCO Corporation.

  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)
The polymer composition ratio (molar ratio) was calculated by proton NMR of JNM-AL400 manufactured by JEOL Ltd.

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). Melt viscosity measurement Capillary length: 10 mm, capillary diameter: 1.0 mm, barrel diameter: 9.55 mm, temperature: 280 ° C., shear rate: 122 s ⁻¹ using a capillary rheometer (product name Capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd.) Measured under conditions.

5. Measurement of photoelastic constant An unstretched film was cut into a size of 50 mm in the film forming direction and 10 mm in the width direction perpendicular thereto, and the photoelastic constant was measured using the sample. Measurement was performed using Spectroellipometer M-220 manufactured by JASCO Corporation.

6). Measurement of tear strength An unstretched film having a thickness of 150 mm in the film forming direction and a test piece having a thickness of 50 mm and a thickness of 80 μm in the width direction perpendicular thereto was prepared and measured according to JIS K7128-1.

7). Stretch resistance measurement When an unstretched film is 150 mm in the film forming direction and a test piece having a thickness of 50 mm and 80 μm in the width direction perpendicular to the film is made and stretched 3 times at a temperature 10 ° C. higher than the Tg of the film, ○, when breaking, it was marked as x.

8). Measurement of retardation value and wavelength dispersibility The stretched optical film was measured using Spectroellipometer M-220 manufactured by JASCO Corporation.

9. 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 non-alkali glass (Corning Japan, trade name: EAGLE2000) through an adhesive as shown in FIG. Immediately after the configured circularly polarizing plate was stored at 85 ° C. for 30 minutes, the light leakage of the transmitted light when the backlight was applied was visually evaluated. If there was no light leakage, ○, and if there was a small amount of light leakage from the edge, Δ The case where light leakage was observed as a whole was rated as x. Light leakage occurs when stress is generated in the film adhered to the glass due to thermal expansion of the retardation film, and birefringence occurs due to the generated stress. Therefore, the higher the photoelastic constant, the greater the light leakage. Light leakage at room temperature before heating becomes less black as the reverse wavelength dispersion is better.

10. Evaluation of light leakage in the reflection type configuration A polarizing plate and alkali-free glass similar to those used for the thermal unevenness evaluation in the transmission type configuration were prepared and bonded together with an adhesive as shown in FIG. The reflection structure thus constructed was placed on a reflection plate, and when light was applied from above at room temperature, the reflected light did not escape and was black, the case of amber was Δ, and the case of blue was ×. The better the inverse wavelength dispersibility, the more black the light is not lost.

[Example 1]
<Manufacture of polycarbonate resin>
3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane (hereinafter abbreviated as SPG) 76.6 parts, 9,9- Bis (4-hydroxy-3-methylphenyl) fluorene (hereinafter abbreviated as BCF) 51.4 parts, 1,6-hexanediol (hereinafter abbreviated as HD) 1.4 parts, diphenyl carbonate 87.8 parts, and as a catalyst 1.6 × 10 ⁻⁴ parts of sodium bicarbonate 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 held at that temperature for 10 minutes, and then the pressure reduction was reduced to 133 Pa over 1 hour. The reaction was carried out with stirring for a total of 5 hours. After completion of the reaction, 1.5 times mole of the catalyst amount of tetrabutylphosphonium salt of dodecylbenzenesulfonic acid was added to deactivate the catalyst, and then pressurized with nitrogen from the bottom of the reaction vessel. While being discharged and cooled in a water bath, the pellets were obtained by cutting with a pelletizer. The specific viscosity, glass transition temperature, and melt viscosity of the pellets were measured and listed in Table 1.

<Manufacture of optical film>
Next, a 15 mmφ twin screw extruder 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 260 ° C., and transparent extrusion unstretched A film was obtained. The resulting unstretched film was evaluated for photoelastic constant, tear strength, and stretch resistance. In addition, an unstretched film of 100 mm in the film forming direction, 70 mm size in the width direction perpendicular to the film forming direction and 90 μm in thickness is uniaxially stretched at 167 ° C. (Tg + 10 ° C.) 2.0 times in the length direction to obtain an optical film having a thickness of 64 μm. Obtained. The retardation value and wavelength dispersion of this optical film were measured. Furthermore, using this optical film, a circularly polarizing plate was prepared as shown in FIG. Moreover, the reflection structure of FIG. 2 was created by the method of the previous 10 using this optical film, and the light omission evaluation of reflected light was implemented. The results are shown in Table 2.

[Example 2]
<Manufacture of polycarbonate resin>
Except for using 76.6 parts of SPG, 48.4 parts of BCF, 2.4 parts of HD, and 89.3 parts of diphenyl carbonate, the same operation as in Example 1 was performed to obtain a polycarbonate resin. The specific viscosity, glass transition temperature, and melt viscosity 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, tear strength, and stretch resistance of the obtained unstretched film were 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 the retardation value and wavelength dispersion were measured. Further, in the same manner as in Example 1, evaluation of thermal unevenness and evaluation of light leakage of reflected light were performed. The results are shown in Table 2.

[Example 3]
<Manufacture of polycarbonate resin>
Except for using 74.2 parts of SPG, 54.4 parts of BCF, 1.1 parts of 1,4-butanediol (hereinafter abbreviated as BD) and 89.3 parts of diphenyl carbonate, the same operation as in Example 1 was performed, A polycarbonate resin was obtained. The specific viscosity, glass transition temperature, and melt viscosity 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, tear strength, and stretch resistance of the obtained unstretched film were 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 the retardation value and wavelength dispersion were measured. Further, in the same manner as in Example 1, evaluation of thermal unevenness and evaluation of light leakage of reflected light were performed. The results are shown in Table 2.

[Example 4]
<Manufacture of polycarbonate resin>
Except for using 74.2 parts of SPG, 51.4 parts of BCF, 1.8 parts of BD, and 89.3 parts of diphenyl carbonate, the same operation as in Example 1 was performed to obtain a polycarbonate resin. The specific viscosity, glass transition temperature, and melt viscosity 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, tear strength, and stretch resistance of the obtained unstretched film were 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 the retardation value and wavelength dispersion were measured. Further, in the same manner as in Example 1, evaluation of thermal unevenness and evaluation of light leakage of reflected light were performed. The results are shown in Table 2.

[Example 5]
<Manufacture of polycarbonate resin>
Except for using 70.5 parts of SPG, 51.4 parts of BCF, 2.9 parts of BD, and 89.3 parts of diphenyl carbonate, the same operation as in Example 1 was performed to obtain a polycarbonate resin. The specific viscosity, glass transition temperature, and melt viscosity 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, tear strength, and stretch resistance of the obtained unstretched film were 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 the retardation value and wavelength dispersion were measured. Further, in the same manner as in Example 1, evaluation of thermal unevenness and evaluation of light leakage of reflected light were performed. The results are shown in Table 2.

[Example 6]
<Manufacture of polycarbonate resin>
The same operation as in Example 1 was carried out except that 74.2 parts of SPG, 51.4 parts of BCF, 2.9 parts of 1,4-cyclohexanedimethanol (hereinafter abbreviated as CHDM), and 89.3 parts of diphenyl carbonate were used. A polycarbonate resin was obtained. The specific viscosity, glass transition temperature, and melt viscosity 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, tear strength, and stretch resistance of the obtained unstretched film were 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 the retardation value and wavelength dispersion were measured. Further, in the same manner as in Example 1, evaluation of thermal unevenness and evaluation of light leakage of reflected light were performed. The results are shown in Table 2.

[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, glass transition temperature, and melt viscosity 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 and stretch resistance of the obtained unstretched film were 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 the retardation value and wavelength dispersion were measured. Further, in the same manner as in Example 1, evaluation of thermal unevenness and evaluation of light leakage of reflected light were performed. The results are shown in Table 2.

[Comparative Example 2]
<Manufacture of polycarbonate resin>
In 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 are added, and 585 parts of BPA, 1969 parts of BCF and 4.5 parts of sodium hydrosulfite are dissolved, and chlorinated. After adding 6604 parts of methylene, 1000 parts of phosgene was blown in at 16 to 20 ° C. for 60 minutes while stirring. 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 methylene chloride was evaporated to obtain an aromatic polycarbonate resin. The specific viscosity, glass transition temperature, and melt viscosity 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 and stretch resistance of the obtained unstretched film were 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 the retardation value and wavelength dispersion were measured. Further, in the same manner as in Example 1, evaluation of thermal unevenness and evaluation of light leakage of reflected light were performed. The results are shown in Table 2.

[Comparative Example 3]
<Manufacture of polycarbonate resin>
Example 1 except that 7.67 parts of 1,4,3,6-dianhydro-D-sorbitol (hereinafter sometimes abbreviated as ISS), 2.4.2 parts of SPG, 6.81 parts of BCF, and 32.45 parts of diphenyl carbonate were used. The polycarbonate resin was obtained in exactly the same manner as in Example 1. The specific viscosity, glass transition temperature, and melt viscosity 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 measured in the same manner as in Example 1. The photoelastic constant, tear strength, and stretch resistance of the obtained unstretched film were 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 the retardation value and wavelength dispersion were measured. Further, in the same manner as in Example 1, evaluation of thermal unevenness and evaluation of light leakage of reflected light were performed. The results are shown in Table 2.

[Comparative Example 4]
Except for using 80.3 parts of SPG, 51.4 parts of BCF, and 89.3 parts of diphenyl carbonate, the same operation as in Example 1 was performed to obtain a polycarbonate resin. The specific viscosity, glass transition temperature, and melt viscosity 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, tear strength, and stretch resistance of the obtained unstretched film were 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 the retardation value and wavelength dispersion were measured. Further, in the same manner as in Example 1, evaluation of thermal unevenness and evaluation of light leakage of reflected light were performed. The results are shown in Table 2.

  In Table 1, BCF is 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, and SPG is 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10. -Tetraoxaspiro [5.5] undecane, HD is 1,6-hexanediol, BD is 1,4-butanediol, CHDM is 1,4-cyclohexanedimethanol, BPA is 2,2-bis (4-hydroxy Phenyl) propane, ISS represents 1,4,3,6-dianhydro-D-sorbitol.

  R in Table 2 indicates the retardation value in the film plane at each wavelength of the optical film.

  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. Polarizing plate 6. reflector

Claims (7)

The repeating unit is represented by the following formula (A)

[Wherein, R ₁ and R ₂ each independently represent a hydrocarbon group having 1 to 10 carbon atoms or a halogen atom, and m and n represent the same or different integers of 0 to 4. ]
The repeating unit (A) represented by the following formula (B)

[Wherein, R _{3 to} R ₆ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. ]
And a repeating unit (B) represented by the following formula (C):

[Wherein, R ₇ is an alkylene group derived from a linear aliphatic diol having 3 to 8 carbon atoms, or a cycloalkylene group derived from an alicyclic diol of the following formula (C1) . ]

[Wherein R ₈ represents an alkyl group having 1 to 12 carbon atoms or a hydrogen atom, and r represents 0 or 1. ]
And the repeating unit (A) is 20 to 40 moles based on the total number of moles of the repeating units (A), (B), and (C). %, Polycarbonate resin occupying 50 to 79 mol% of repeating units (B) and 1 to 10 mol% of repeating units (C). The resin according to claim ^1, wherein the melt viscosity at a temperature of 280 ° C and a shear rate of 122 s- ^{1 is} in the range of 10 to 500 Pa · s.   An unstretched film using the resin according to claim 1.   The unstretched film according to claim 3, which is used as a polarizing plate protective film or a transmission layer film for optical disks. The unstretched film according to claim 3 is stretched, and retardation values R (450), R (550), and R (650) in the film plane at wavelengths of 450 nm, 550 nm, and 650 nm are expressed by the following formula ( 1) and (2)
0.60 <R (450) / R (550) <1.00 (1)
1.01 <R (650) / R (550) <1.40 (2)
A stretched film that satisfies   The stretched film according to claim 5, which is used as a retardation film.   A liquid crystal display device comprising the retardation film according to claim 6.

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