JP2007009010A - Optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film, such as a retardation film or an optically isotropic film, using an amorphous polyolefin advantageous in an economical aspect, namely a cyclic olefin-ethylene copolymer. <P>SOLUTION: This optical film comprises an amorphous polyolefin which is (i) a copolymer comprising ethylene units and norbornene units, has (ii) a glass transition temperature in a range of 100 to 180°C, and has (iii) a meso type/racemo type existence ratio in a range of 0.2≤[meso type]/[racemo type]≤4 in respect to the stereoregularity of the diad sites of the norbornene units. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transparent optical film, and more particularly to an optical film such as a retardation film or an optically isotropic film for a liquid crystal display device using an amorphous polyolefin comprising an ethylene unit and a norbornene unit. Is.

In recent years, the progress of liquid crystal display devices has been remarkable, and not only small and medium-sized devices such as mobile phones and personal computer monitors but also large-sized devices for televisions are being used widely.
Various polymer films are used in liquid crystal display devices. For example, retardation films, polarizing plates and protective films used for improving display quality such as color compensation of liquid crystals, widening of viewing angle, and improvement of contrast. A substrate or the like. As the polymer material, polycarbonate, polyvinyl alcohol, triacetyl cellulose (hereinafter referred to as TAC), polyether sulfone, and the like have been often used so far. For example, polycarbonate and the like have been often used for retardation films. With regard to such a retardation film, a resin called amorphous polyolefin has recently attracted attention. Amorphous polyolefin is a polyolefin which has an alicyclic structure and is made amorphous by increasing heat resistance, and is characterized by excellent dimensional stability due to high transparency and low water absorption. Furthermore, since it does not contain an aromatic component, it has a feature that the photoelastic constant is extremely low, and its excellent physical properties are gradually attracting attention as the size of liquid crystal display devices such as televisions is increased. .

  Such amorphous polyolefins can be broadly classified into two in terms of structure. One is obtained by ring-opening polymerization of a cyclic olefin, and then hydrogenating the double bond of the main chain produced. Product names “ZEONEEX”, “ZEONOR”, JSR (manufactured by Nippon Zeon Co., Ltd.) Resins such as “ARTON” manufactured by Co., Ltd. are already on the market. The other is obtained by copolymerizing cyclic olefin with ethylene and vinyl, and is commercially available under the trade name “APEL” manufactured by Mitsui Chemicals, Inc., and the product name “TOPAS” manufactured by TICONA. Etc. Among these, the former type of ring-opening polymerization and hydrogenation type has a low photoelastic constant, but the birefringence is easily developed when a film is stretched and oriented, to a liquid crystal display device. Many studies have been made as retardation films, such as incorporation of (see, for example, Patent Documents 1 to 6).

  On the other hand, the latter copolymer of cyclic olefin and ethylene can be produced in one stage of polymerization as compared with the former, and although it is advantageous in terms of economy, the optical properties of the film have hardly been studied so far. . In the above-mentioned reports using the ring-opening polymerized and hydrogenated type resin, the latter resin of vinyl type copolymer is also described as a general term for thermoplastic polyolefin and cyclic polyolefin as desirable resins. There are many cases, but there are few examples that have been specifically examined. Until now, only one example of a retardation film obtained by stretching a sheet made of a copolymer of ethylene and tetracyclododecene to give birefringence has been reported (see Patent Document 7). It was not known whether birefringence was likely or difficult to occur with a simple structure. For example, when amorphous polyolefin is used as a retardation film, it is important that birefringence develops, that is, birefringence is easily generated, in addition to film forming properties and transparency. This is because amorphous polyolefin generally has a very low photoelastic constant, and has an essential characteristic that birefringence hardly occurs as compared with an aromatic polymer such as polycarbonate or polysulfone. Therefore, in the case of a resin that hardly exhibits birefringence even when the film is stretched, the film thickness must be considerably increased to obtain a retardation film having a desired retardation value, and thinness and lightness are required. The liquid crystal display device is not suitable as a member. On the other hand, unlike the retardation film, a film having a high optical isotropy in three dimensions is required for the protective film and substrate of the polarizing plate. For example, a TAC film is currently used as a protective film for a polarizing plate, and although the in-plane retardation is suppressed, it is known that the retardation in the thickness direction is high. In these applications, in addition to the low photoelastic constant, there is a demand for a resin that hardly causes birefringence as much as possible.

  By the way, in order to obtain a vinyl copolymer of ethylene and a cyclic olefin, several methods are known, but polymerization is performed using a Ziegler-Natta catalyst represented by a combination of a vanadium compound and an organoaluminum compound. Alternatively, a polymerization method using a metallocene catalyst comprising a metallocene which is a metal complex such as titanium or zirconium and a co-catalyst such as MAO (methylaluminoxane) is practical. Among them, the Ziegler-Natta catalyst is known to give an atactic polymer with poor stereoregularity by random copolymerization because it is difficult to control the composition and steric structure because of its polymerization mechanism. On the other hand, the metallocene catalyst has a uniform active site and can be controlled in various ways. For example, it has been confirmed that the stereoregularity of the resulting copolymer varies depending on the ligand of metallocene (see Non-Patent Document 1). Further, although it has been reported that the difference affects the mechanical properties and the melt properties of the copolymer (see Patent Documents 8 to 10), the difference in optical properties has not been studied so far.

  There are several methods for forming an optical film, such as a solution casting method, a melt extrusion method, a heat press method, and a calender method. In recent years, a melt extrusion method has been demanded from the viewpoint of production cost and environment. In such a melt extrusion method, it is preferable to use a resin having a melt viscosity as low as possible in order to produce a film having high homogeneity required for an optical film. Amorphous polyolefins are generally more susceptible to thermal degradation and gelation than aromatic polymers such as polycarbonate due to their structure, and have a high melt viscosity and a high extrusion temperature during film formation. This is because there are concerns about spots, die muscles, and gelation.

JP-A-4-245202 Japanese Patent No. 3273046 JP-A-6-59121 JP-A-8-43812 Japanese Patent No. 3470567 JP 2003-306557 A Japanese Patent No. 3497894 Japanese National Patent Publication No. 8-507800 JP-T 8-507801 JP-A-7-2953 Macromol. Rapid Commun. 20, 279 (1999)

  The present invention has been made in view of the above situation, and the latter type of amorphous polyolefin, which is advantageous in terms of economy, that is, using a copolymer of cyclic olefin and ethylene, a retardation film, An object of the present invention is to provide an optical film such as an optical isotropic film, preferably by a melt extrusion method.

  The present inventors comprehensively studied the structure and film properties of an ethylene-cycloolefin copolymer, particularly the expression of birefringence, melt viscosity, film-forming properties, and mechanical properties of the film. As a result, the ethylene-cyclic olefin copolymer in the range of stereoregularity in addition to the molecular structure and composition of the cyclic olefin has a good balance between optical properties and film-forming properties, mechanical properties of the film, etc. It has been found that an optical film having excellent film properties can be obtained, and that the copolymer can be obtained as a resin composition comprising two types of copolymers having different stereoregularities.

That is, the present invention is as follows.
[1] A copolymer comprising ethylene units and norbornene units, ii) having a glass transition temperature in the range of 100 ° C. to 180 ° C., and iii) stereoregularity of the two-chain sites (dyads) of norbornene units An optical film made of an amorphous polyolefin having a meso-type and racemo-type ratio of 0.2 ≦ [meso-type] / [rasemo-type] ≦ 4.
[2] The amorphous polyolefin is a resin composition containing the following (X) and (Y), and (X) / (Y) = 99/1 to 1/99 (weight ratio) Said optical film.
(X) i) a copolymer comprising an ethylene unit and a norbornene unit, ii) a glass transition temperature in the range of 60 ° C. to 200 ° C., and iii) a stereoregulation of a two-chain site (dyad) of the norbornene unit Amorphous polyolefin with a meso-type and racemo-type ratio of [meso-type] / [racemo-type]> 4 in terms of properties (i) a copolymer consisting of ethylene units and norbornene units, and ii) glass transition The temperature is in the range of 60 ° C. to 200 ° C., and iii) the abundance ratio of meso-type and racemo-type is [meso-type] / [rasemo-type] <0. 2. The above-mentioned optical film obtained by the amorphous polyolefin [3] melt extrusion method.
[4] Used as a retardation film, the retardation R (550) in the film plane at a wavelength of 550 nm is expressed by the following formula (1)
100 nm <R (550) <800 nm (1)
The above optical film having a thickness of 30 to 200 μm.
[5] Used as a retardation film, the in-plane retardation R (550) and the thickness direction retardation K (550) at a wavelength of 550 nm are represented by the following formulas (2) and (3):
0 nm <R (550) <100 nm (2)
50 nm <K (550) <400 nm (3)
(In the formula, K (550) is a thickness direction retardation value at a wavelength of 550 nm, and the following formula (4)
K = {(n _x + _ny ) / 2−n _z } × d (4)
Is as defined by, where, n _x, n _y is x-axis in the film plane, the y-axis, n _z is a refractive index in a thickness direction perpendicular to the x-axis and y-axis, d is the film Is the thickness. )
The above optical film having a thickness of 30 to 200 μm.
[6] i) a copolymer comprising an ethylene unit and a norbornene unit, ii) a glass transition temperature in the range of 100 ° C. to 180 ° C., and iii) a stereoregulation of a two-chain site (dyad) of the norbornene unit A method of using amorphous polyolefin as a retardation film in which the abundance ratio of meso-type and racemo-type is 0.2 ≦ [meso-type] / [racemo-type] ≦ 4.
[7] The above optical film wherein the absolute value of the retardation R (550) in the film plane at a wavelength of 550 nm and the retardation K (550) in the thickness direction are both 20 nm or less and the thickness is 10 to 300 μm. .

  According to the present invention, an optical film having a good balance between optical properties and film forming properties, film mechanical properties, etc., and excellent melt film forming properties can be obtained using an ethylene-cyclic olefin copolymer. It is useful for films and optically isotropic films.

  Such a retardation film has high moisture resistance and good dimensional stability, and is incorporated into a liquid crystal display device by a known method, and is effective in improving the display quality of a liquid crystal such as viewing angle improvement, contrast improvement, and color compensation. Used. The optically isotropic film has high moisture resistance and good dimensional stability, and has a low photoelastic constant. It is incorporated into a liquid crystal display device by a known method as a protective film, a substrate, etc. for a polarizing plate, and is useful. It is done.

Hereinafter, the present invention will be described in detail.
The amorphous polyolefin used in the present invention is a copolymer obtained by vinyl-type polymerization of ethylene and norbornene, and includes ethylene repeating units (A) and norbornene repeating units (A) and (B) represented by the following formulas (A) and (B). B).

[式（ｃ）中、ｎは０または１であり、ｍは０または正の整数であり、ｐは０または１であり、Ｒ^１〜Ｒ^２０は同一または異なり、水素原子、ハロゲン原子、または炭素数１〜１２の飽和あるいは不飽和脂肪族炭化水素基であり、また、Ｒ^１７とＲ^１８とで、あるいはＲ^１９とＲ^２０とでアルキリデン基を形成していてもよく、また、Ｒ^１７またはＲ^１８と、Ｒ^１９またはＲ^２０とが環を形成していてもよく、かつ該環が二重結合を有していてもよい。]
プロピレン、１−ブテン、１−ヘキセン、４−メチル−１−ペンテン、１−オクテン、１−デセン、１−ドデセン、１−テトラデセン、１−ヘキサデセン、１−オクタデセン等の炭素数３〜１８のα−オレフィン、シクロブテン、シクロペンテン、シクロペンテン、シクロヘキセン、３−メチルシクロヘキセン、シクロオクテン等のシクロオレフィン等を挙げることが出来る。この中で炭素数３〜１８のα−オレフィンは共重合の際の分子量調節剤として用いることが出来、中でも１−ヘキセンが好適に用いられる。かかるその他のビニルモノマーは単独であるいは２種類以上組み合わせて用いてもよく、またその繰り返し単位が全体の１０モル％以下が好ましく、より好ましくは５モル％以下である。 Furthermore, in the present invention, the glass transition temperature (Tg) of such a copolymer is in the range of 100 ° C to 180 ° C. When Tg is lower than 100 ° C., the heat stability is poor. On the other hand, if Tg is higher than 180 ° C., the toughness of the film tends to decrease, and the melt viscosity of the copolymer becomes too high, making it difficult to melt the film, which is not preferable. In the copolymer used in the present invention, the composition of the repeating units (A) and (B) and the glass transition temperature are substantially correlated, and the molar ratio thereof is (A) / (B) = 61/39 to 40/60. It is preferable to be in the range. A more preferable range of the glass transition temperature is 120 ° C. to 160 ° C., and a molar ratio (A) / (B) = 57/43 to 46/54. Such a composition can be determined by ¹³ C-NMR measurement. In the present invention, in addition to the above repeating units (A) and (B), a small amount of repeating units composed of other copolymerizable vinyl monomers may be contained within a range not impairing the object of the present invention. Specific examples of such other vinyl monomers include cyclic olefins represented by the following structural formula (C):

[In the formula (c), n is 0 or 1, m is 0 or a positive integer, p is 0 or 1, and R ^{1 to} R ²⁰ are the same or different and each represents a hydrogen atom, a halogen atom, or A saturated or unsaturated aliphatic hydrocarbon group having 1 to 12 carbon atoms, and R ¹⁷ and R ¹⁸ , or R ¹⁹ and R ²⁰ may form an alkylidene group, and R ¹⁷ Alternatively, R ¹⁸ and R ¹⁹ or R ²⁰ may form a ring, and the ring may have a double bond. ]
C3-C18 α such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, etc. -Cycloolefins such as olefin, cyclobutene, cyclopentene, cyclopentene, cyclohexene, 3-methylcyclohexene, cyclooctene and the like. Among these, an α-olefin having 3 to 18 carbon atoms can be used as a molecular weight regulator in the copolymerization, and 1-hexene is preferably used among them. Such other vinyl monomers may be used alone or in combination of two or more, and the repeating unit is preferably 10 mol% or less, more preferably 5 mol% or less of the whole.

The molecular weight of the ethylene-norbornene copolymer used in the present invention is a reduced viscosity η _sp / c measured in a cyclohexane solution at a temperature of 30 ° C. and a concentration of 1.2 g / dL, and within a range of 0.1 to 10 dL / g. Yes, and more preferably 0.3 to 3 dL / g. If the reduced viscosity η _sp / c is less than 0.1, the film becomes brittle, and if it is more than 10, the melt viscosity becomes too high, making it difficult to melt the film.

In general, an ethylene-norbornene copolymer depends on a polymerization method, a catalyst used, a composition, and the like, but in any case, some chain sites of norbornene units exist. It is known that there are two stereoisomers of the meso form of the following formula (D) and the racemo form of (E) for the stereoregularity in the two-chain site (hereinafter referred to as NN dyad) of the norbornene unit of vinyl polymerization type. ing.

The copolymer of the present invention is characterized in that the abundance ratio of meso-type and racemo-type is in the range of 0.2 ≦ [meso-type] / [racemo-type] ≦ 4 with respect to such stereoregularity. The larger the meso-type ratio, the more easily birefringence is developed, and the toughness of the film becomes higher. On the other hand, the more the racemo-type, the lower the melt viscosity and the higher the fluidity. What is necessary is just to select this existing ratio timely and optimal according to a use and a manufacturing method. For use as a retardation film, 0.8 ≦ [meso type] / [rasemo type] ≦ 4 is more preferable. The abundance ratio of the NN dyad stereoisomer here can be determined by ¹³ C-NMR from a report analyzing the stereoregularity of the ethylene-norbornene copolymer (see Non-Patent Document 1 above), in ¹³ C-NMR was measured in deuterated ortho dichlorobenzene solvent in the present invention, [meso] / [racemo type] = [peak area of 28.3ppm of ¹³ C-NMR spectrum] / ^[13 C-NMR spectrum 29 .7ppm peak area].

In the analysis by ¹³ C-NMR, the abundance ratio (molar fraction) of the NN dyad relative to the total amount of norbornene component, that is, how much the norbornene component forms a chain structure can be obtained. It is in the range of ~ 0.6. The molar fraction referred herein, ^[13 C-NMR peak area ⁺ 13 C-NMR peak area of 29.7ppm of the spectrum of 28.3ppm spectrum] / [peak area of one carbon atom of total norbornene component ] Is calculated.

  The method for synthesizing the ethylene-norbornene copolymer used in the present invention is not particularly limited as long as the glass transition temperature and the stereoregularity of the NN dyad satisfy the above ranges, and the combination of the vanadium compound and the organoaluminum compound is not limited. Copolymerization of ethylene and norbornene using a representative Ziegler-Natta catalyst, or polymerization using a metallocene catalyst consisting of a metallocene such as titanium or zirconium and a co-catalyst such as MAO (methylaluminoxane). Specific examples can be given. Among them, the method using a metallocene catalyst is preferable because it can obtain a highly homogenous polymer and the stereoregularity can be controlled by the type of metallocene.

  As the copolymer in the present invention obtained by a metallocene catalyst, it is possible to use a resin composition obtained by blending ethylene-norbornene copolymers (X) and (Y) having different stereoregularities obtained by different metallocene catalysts. It is preferable because the control of the properties is easy and practicality is high.

(X) is an ethylene having a glass transition temperature in the range of 60 ° C. to 200 ° C. and an abundance ratio of meso-type and racemo-type with respect to the stereoregularity of NN dyads: [meso-type] / [racemo-type]> 4 -Norbornene copolymer. As the metallocene used in the polymerization of the copolymer, those represented by the following formula (F) are preferable.

であり、このときＲ^２６〜Ｒ^２９は同一または異なっていて、水素原子、ハロゲン原子、炭素数１〜１２の飽和あるいは不飽和炭化水素基、炭素数１〜１２のアルコキシ基、または炭素数６〜１２のアリールオキシ基であるか、あるいはＲ^２６とＲ^２７またはＲ^２８とＲ^２９とが環を形成していていもよい。 In the above formula (F), M is a metal selected from the group consisting of titanium, zirconium or hafnium, and R ²⁴ and R ²⁵ are the same or different and are a hydrogen atom, a halogen atom, or a saturated or unsaturated group having 1 to 12 carbon atoms. A hydrocarbon group, an alkoxy group having 1 to 12 carbon atoms, or an aryloxy group having 6 to 12 carbon atoms, and R ²² and R ²³ are the same or different and can form a sandwich structure with the central metal M. A monocyclic or polycyclic hydrocarbon group, R ²¹ is a bridge connecting R ²² group and R ²³ group,

In this case, R ^{26 to} R ²⁹ are the same or different and are a hydrogen atom, a halogen atom, a saturated or unsaturated hydrocarbon group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or 6 carbon atoms. Or an aryloxy group of ˜12, or R ²⁶ and R ²⁷ or R ²⁸ and R ²⁹ may form a ring.

When R ²² and R ²³ which are ligands are the same, C ₂ symmetry with respect to the central metal M is preferable, and when they are different, those having C ₁ symmetry are preferable. R ²² and R ²³ are preferably a cyclopentadienyl group, an indenyl group, an alkyl or aryl substituent thereof, and the central metal M is most preferably zirconium in terms of catalytic activity. R ²⁴ and R ²⁵ may be the same or different, but are preferably an alkyl group having 1 to 6 carbon atoms or a halogen atom, particularly a chlorine atom. R ^{26 to} R ²⁹ are preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group, and as R ²¹ , a lower alkylene group such as a methylene group, an ethylene group, or a propylene group, an alkylidene group such as isopropylidene, Preferred examples include substituted alkylene groups such as diphenylmethylene, silylene groups, and substituted silylene groups such as dimethylsilylene and diphenylsilylene.

  Specific preferred metallocenes include isopropylidene- (cyclopentadienyl) (1-indenyl) zirconium dichloride, isopropylidene-[(3-methyl) cyclopentadienyl] (1-indenyl) zirconium dichloride, dimethylsilylene- (Cyclopentadienyl) (1-indenyl) zirconium dichloride, dimethylsilylene-bis (1-indenyl) zirconium dichloride, diphenylsilylene-bis (1-indenyl) zirconium dichloride, ethylene-bis (1-indenyl) zirconium dichloride, isopropyl Examples thereof include redene-bis (1-indenyl) zirconium dichloride. These may be used alone or in combination of two or more. As the metallocene promoter, a known catalyst such as methylaluminoxane, which is an organoaluminum oxy compound, or a combination of an ionic boron compound and an alkylaluminum compound can be used.

On the other hand, (Y) has a glass transition temperature in the range of 60 ° C. to 200 ° C., and the meso-type and racemo-type abundance ratio of NN dyads is [meso-type] / [racemo-type] <0. 2 is an ethylene-norbornene copolymer. The metallocene used in the polymerization of the copolymer has a Cs symmetry (mirror) with respect to the central metal M in the formula (F), unlike the case where the ligands R ²² and R ²³ are (X). Those having symmetry are preferred. R ²² and R ²³ are preferably a cyclopentadienyl group, a fluorenyl group, an alkyl- or aryl-substituted product thereof. Specific examples of preferred metallocenes include isopropylidene- (9-fluorenyl) (cyclopentadienyl) zirconium dichloride, diphenyl. Methylene- (9-fluorenyl) (cyclopentadienyl) zirconium dichloride, diphenylsilylene- (9-fluorenyl) (cyclopentadienyl) zirconium dichloride, dimethylsilylene- (9-fluorenyl) (cyclopentadienyl) zirconium dichloride, etc. Can be mentioned. These may be used alone or in combination of two or more. As the metallocene promoter, a known catalyst such as methylaluminoxane, which is an organoaluminum oxy compound, or a combination of an ionic boron compound and an alkylaluminum compound can be used.

  By using such a metallocene catalyst, the desired copolymer can be polymerized by a known polymerization method using a hydrocarbon solvent such as toluene, xylene, cyclohexane, etc. It can be isolated by removing the solvent after removing it by washing by reprecipitation in a solvent, or by adsorbing the catalyst to the adsorbent, adding some additive to agglomerate and depositing, etc. .

Each of the polymers constituting the (X) and (Y) may be one type of copolymer, or may be a blend of two or more types of copolymers having different compositions and molecular weights. In the case of a blend body, the glass transition temperature and the abundance ratio of NN dyads described above represent the entire blend body. When using such a blend, it is preferable to use a copolymer having a close copolymer composition from the viewpoint of compatibility. When the composition is too far, phase separation may occur due to blending, and the film may be whitened during film formation or stretching orientation. The molecular weights of (X) and (Y) are not particularly limited as long as they are within the range of the present invention described above when used as a resin composition, but in a cyclohexane solution having a temperature of 30 ° C. and a concentration of 1.2 g / dL. The reduced viscosity η _sp / c measured above is preferably in the range of 0.1 to 10 dL / g.

  The amorphous polyolefin in the present invention was blended in a ratio of (X) / (Y) = 99/1 to 1/99 (weight ratio) from the copolymers (X) and (Y) thus obtained. It is preferably formed using a resin composition. The composition of (X) and (Y) is determined by comprehensively considering the glass transition temperature, molecular weight, and NN dyad stereoregularity of (X) and (Y). More preferably, (X) / (Y) = 90/10 to 40/60, and more preferably (X) / (Y) = 75/25 when the optical film is used for an optical isotropic film. 10/90.

  The method for preparing the desired resin composition by blending copolymers (X) and (Y) is not particularly limited, and is isolated after being dissolved together in a good solvent such as cyclohexane, which is melt-kneaded in a ruder. For example, a known method can be used. Although (X) and (Y) in the present invention are completely different in the stereoregularity of the NN dyad, the compatibility is good and a transparent resin composition can be easily obtained.

  In the amorphous polyolefin (hereinafter sometimes referred to as “resin”) in the present invention, known antioxidants such as “Irganox” 1010 and 1076 (manufactured by Ciba Geigy), lubricants, plasticizers, and interfaces, as necessary. You may add additives, such as an activator, a ultraviolet absorber, and an antistatic agent.

  The optical film of the present invention can be produced (film-formed) by a known method such as a solution casting method, a melt extrusion method, a hot pressing method, or a calendar method. Of these, the melt extrusion method is preferable from the viewpoint of productivity and economy, and from the viewpoint of solvent-free environment. In the melt extrusion method, a method in which a resin is extruded to a cooling roll using a T die is preferably used. The resin temperature at the time of extrusion is determined in consideration of the fluidity, thermal stability and the like of the resin, but it is preferably performed in the range of 220 ° C. to 300 ° C. for the amorphous polyolefin used in the present invention. If it is less than 220 ° C., the melt viscosity of the resin becomes too high, and if it exceeds 300 ° C., there is a concern that the transparency and homogeneity of the film are impaired due to degradation and gelation of the resin. More preferably, it is in the range of 220 ° C to 290 ° C. In order to suppress oxidative degradation of the resin during melt extrusion, it is preferable to add an antioxidant.

In addition, when the amorphous polyolefin in the present invention is formed into a film by the solution casting method, a hydrocarbon solvent such as toluene, xylene, cyclohexane, decalin or the like is preferably used.
In the production of an optical film by these methods, it is preferable to reduce the thickness unevenness as much as possible. The thickness unevenness is preferably ± 8% or less, more preferably ± 5% or less, still more preferably ± 2% or less with respect to the film thickness. The thickness of the film is in the range of 10 to 400 μm, more preferably in the range of 30 to 300 μm.

  When used as a retardation film, the optical film of the present invention can be obtained by stretching and orientation of the unstretched film thus obtained. The stretching method is not particularly limited, and known methods such as longitudinal uniaxial stretching that stretches between rolls, lateral uniaxial stretching using a tenter, simultaneous biaxial stretching that combines them, and sequential biaxial stretching can be used. Moreover, although it is preferable from a point of productivity to perform continuously, you may carry out by a batch type and there is no restriction | limiting in particular. The stretching temperature is in the range of (Tg−20 ° C.) to (Tg + 30 ° C.), preferably (Tg−10 ° C.) to (Tg + 20 ° C.) with respect to the glass transition temperature (Tg) of the ethylene-norbornene copolymer. Is within the range. Although the draw ratio is determined by the target retardation value, it is 1.05 to 4 times, more preferably 1.1 to 3 times for each of the length and width.

  There are various types of liquid crystal display devices such as TN type, STN type, TFT type, transmissive type, reflective type, and transflective type, and various modes such as TN mode, vertical alignment mode, OCB mode, and IPS mode have been developed. ing. The properties of the retardation film required vary depending on the type of liquid crystal and mode used, but the ethylene-norbornene copolymer of the present invention has a good birefringence, so it is a thin film. It is possible to provide retardation films having various characteristics.

As one of the preferable optical films obtained in the present invention, the in-plane retardation R (550) at a wavelength of 550 nm is in the range of the following formula (1),
100 nm <R (550) <800 nm (1)
In addition, a retardation film having a thickness of 30 to 200 μm is exemplified. Here, the phase difference R is defined by the following formula (5), and is a characteristic representing a phase delay of light transmitted in a direction perpendicular to the film.
_{R = (n x -n y)} × d ··· (5)
Here, n _x is that the refractive index of the slow axis in the film plane (highest refractive index axis), n _y is a refractive index of n _x and the vertical direction in the film plane, d is the film Is the thickness.

  Here, R (550) is more preferably 100 to 600 nm. Moreover, as for thickness, 30-150 micrometers is more preferable, More preferably, it is 30-120 micrometers. Such a retardation film can be prepared by uniaxial stretching or biaxial stretching, and is suitably used for a 1 / 4λ plate, a 1 / 2λ plate, a λ plate, and the like.

As another preferable retardation film, an in-plane retardation R (550) at a wavelength of 550 nm and a retardation K (550) in the film thickness direction are represented by the following formulas (2) and (3):
0 nm <R (550) <100 nm (2)
50 nm <K (550) <400 nm (3)
And a retardation film having a thickness of 30 to 200 μm.

In the above formula, K (550) is a retardation value in the film thickness direction at a wavelength of 550 nm, and is defined by the following formula (4).
K = {(n _x + _ny ) / 2−n _z } × d (4)
In the above formula, n _x, n _y is x-axis in the film plane, the y-axis, n _z is a refractive index in a thickness direction perpendicular to the x-axis and y-axis, d is the thickness of the film.

  Here, the definition of the phase difference R is the same as that described above. R (550) is more preferably 10 to 80 nm, and further preferably 30 to 80 nm. K (550) is more preferably 100 to 250 nm. Moreover, as thickness, 30-150 micrometers is more preferable, More preferably, it is 30-120 micrometers. Such a retardation film can be prepared by biaxial stretching, has birefringence in the thickness direction of the film, and is particularly suitable for optical compensation in a vertical alignment (VA) mode.

  The optical film of the present invention can also be used as an optical isotropic film. In that case, an unstretched film obtained by the above-described film formation may be used as it is, or may be further stretched within a range in which optical isotropy is maintained. The toughness of the film can be improved by stretching.

  The stretching method in this case is not particularly limited, and a known method such as longitudinal uniaxial stretching that stretches between rolls, lateral uniaxial stretching using a tenter, simultaneous biaxial stretching that combines them, or sequential biaxial stretching can be used. From the viewpoint of improving optical isotropy and film toughness, biaxial stretching is most preferred. Moreover, although it is preferable from a point of productivity to perform continuously, you may carry out by a batch type and there is no restriction | limiting in particular. The stretching temperature is in the range of (Tg-10 ° C.) to (Tg + 40 ° C.) with respect to the glass transition temperature (Tg) of the ethylene-norbornene copolymer, preferably Tg to (Tg + 30 ° C.), more preferably ( Tg + 10 ° C.) to (Tg + 30 ° C.). The draw ratio is determined by the optical characteristics, the target film thickness, and the like, but is 1.05 to 4 times, more preferably 1.1 to 3 times for each of the length and width.

  As the retardation value of the optically isotropic film of the present invention, the absolute value of the retardation R (550) in the film plane at a wavelength of 550 nm and the retardation K (550) in the thickness direction are both 20 nm or less. Preferably, it is 10 nm or less. Here, the definitions of the phase difference R and the thickness direction phase difference K are the same as those described above. The film thickness is preferably 10 to 300 μm, more preferably 30 to 200 μm.

  Such an optical film has high three-dimensional optical isotropy including not only in the film plane but also in the thickness direction, and is suitably used for, for example, a protective film of a polarizing plate, a substrate, etc. in a liquid crystal display device.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to only these examples.

The raw materials used in Examples and Comparative Examples are as follows.
Toluene (solvent) and norbornene were all purified by distillation and sufficiently dried.
For metallocene, ethylene-bis (1-indenyl) zirconium dichloride purchased from Aldrich was used as it was. Isopropylidene- (9-fluorenyl) (cyclopentadienyl) zirconium dichloride is described in the literature [J. A. Ewen et al, J.A. Am. Chem. Soc. , 110, 6255-6266 (1988)].
As the ionic boron compound, trityl-tetrakis (pentafluorophenyl) borate was purchased from Tosoh Akzo Corporation and used as it was.
Triisobutylaluminum ^[(i _Bu) 3 Al] is purchased n- hexane concentration 1M from Kanto Chemical Co. and used as received.

The physical properties measured in Examples and Comparative Examples were measured by the following methods.
(1) Glass transition temperature (Tg): A 2920 type DSC manufactured by TA Instruments was used, and the temperature elevation rate was measured at 20 ° C./min.
(2) Molecular weight of copolymer: Reduced viscosity η _sp / c (dL / g) at 30 ° C. in a cyclohexane solution having a concentration of 0.5 g / dL was measured.
(3) ¹³ C-NMR measurement of copolymer: JNM-α400 type NMR apparatus manufactured by JEOL Ltd. was used. It was dissolved in deuterated dichlorobenzene solvent and measured at a temperature of 100 ° C. Tetramethylsilane was used as the standard for chemical shift. For quantification, 150 MHz ¹³ C-NMR spectrum was measured in reverse gated decoupling mode.
(4) Total light transmittance and haze value of the film: Measured using a turbidimeter NDH-2000 model manufactured by Nippon Denshoku Industries Co., Ltd.
(5) In-plane retardation value R of film and retardation value K in the film thickness direction: Measured at a light wavelength of 550 nm using a spectroscopic ellipsometer M150 manufactured by JASCO Corporation. The in-plane retardation value R is measured in a state where the incident light beam is perpendicular to the film surface. The thickness direction retardation value K is obtained by changing the angle between the incident light beam and the film surface little by little, measuring the retardation value at each angle, and performing curve fitting with a known refractive index ellipsoid equation to obtain a three-dimensional refractive index. N _x , n _y , and n _z are obtained and substituted by K = {(n _x + _ny ) / 2−n _z } × d. In this case, the average refractive index of the film is required, but it was separately measured using an Abbe refractometer (trade name “Abbe refractometer 2-T” manufactured by Atago Co., Ltd.).
(6) Film thickness: Measured with an electronic micro film thickness meter manufactured by Anritsu Corporation.
(7) Photoelastic constant of film: Measured with a spectroscopic ellipsometer M150 manufactured by JASCO Corporation. It was calculated from the change in retardation value when stress was applied to the film at a measurement wavelength of 550 nm.

[Reference Example 1: Synthesis of ethylene-norbornene copolymer (X)]
As a polymerization apparatus, a 3 L autoclave with a stirring blade and an ethylene line and a nitrogen line connected was used. Ethylene-bis (1-indenyl) zirconium dichloride was used as the metallocene, and ethylene and norbornene were co-polymerized as follows. A polymerization reaction was performed.

After replacing the inside of the autoclave with nitrogen gas, 1 L of toluene and 200 g of norbornene were charged into the container, and 1.2 mmol of triisobutylaluminum was added as a scavenger. Separately, 18 mmol of triisobutylaluminum and then 360 mg of trityl-tetrakis (pentafluorophenyl) borate were added to Schlenk in which 150 mg of ethylene-bis (1-indenyl) zirconium dichloride was dissolved in 20 mL of toluene under a nitrogen atmosphere. For 10 minutes at room temperature. This catalyst solution was added to the autoclave, and then the temperature was raised to 40 ° C. Then, the inside of the container was replaced with ethylene and the pressure was increased to 1.5 kg / cm ² to initiate polymerization. After 1 hour, the ethylene pressure was lowered to 1.0 kg / cm ² and the polymerization was continued for 1 hour, then the reaction was terminated by returning to a nitrogen atmosphere and adding a small amount of isopropanol. The reaction mixture was discharged into a large amount of methanol acidified with hydrochloric acid to precipitate a precipitate. The precipitate was separated by filtration, washed with acetone, methanol and water repeatedly and dried to obtain 213 g of resin powder. The ethylene-norbornene copolymer thus obtained had a molecular weight of reduced viscosity η _sp /c=0.95 dL / g. The Tg was 145 ° C. ^{In 13} C-NMR measurement, almost no racemo-type NN dyad at 29.7 ppm was observed, and it was found that it was only meso-type at 28.3 ppm. The abundance ratio (molar fraction) of the NN dyad relative to the total norbornene component amount was 0.42. The molar ratio of the ethylene component to the norbornene component was (A) / (B) = 49/51.

[Reference Example 2: Synthesis of ethylene-norbornene copolymer (Y)]
Polymerization was carried out in the same manner as in Example 1 except that the metallocene used in Reference Example 1 was replaced with isopropylidene- (9-fluorenyl) (cyclopentadienyl) zirconium dichloride to obtain 182 g of an ethylene-norbornene copolymer. . The obtained ethylene-norbornene copolymer had a molecular weight of reduced viscosity η _sp /c=0.60 dL / g. Moreover, it was Tg = 135 degreeC. ^{From the 13} C-NMR measurement, it was determined that [meso type] / [racemo type] = 0.04 / 0.50 = 0.08, and the abundance ratio (molar fraction) of the NN dyad relative to the total norbornene component amount was 0.38. there were. The molar ratio of the ethylene component to the norbornene component was (A) / (B) = 51/49.

[Example 1]
The synthesis of Reference Example 1 and Reference Example 2 was repeated to obtain the required amount of melt film formation. After the copolymer (X) of Reference Example 1 and the copolymer (Y) of Reference Example 2 were dry blended and mixed at a ratio of (X) / (Y) = 75/25 (weight ratio), biaxial Using a melt extruder (Nippon Steel Works TEX30SS-42BW-3V), a film was formed by melting and extruding from a T-die having a width of 15 cm and continuously winding with a cooling roller. The film forming conditions were a cylinder temperature of 260 ° C., a T die temperature of 270 ° C., a cooling roller temperature of 142 ° C., and a film forming speed of 2 m / min. The film has excellent transparency and homogeneity, and good surface properties. There were hardly any muscles or foreign bodies. Moreover, there was no problem in handling at the time of winding the roll and thereafter, and the film was sufficiently strong. Except for the 2.5 cm width at both ends of the film, the film thickness averaged 170 μm. Tg was 141 ° C., total light transmittance was 90.3%, and haze was 0.6%. The reduced viscosity η _{sp /} c of the film was 0.80 dL / g. Moreover, it was -7.3 * 10 < ^-12 > Pa < ^-1 > when the photoelastic constant of this film was calculated | required. From the ¹³ C-NMR measurement of the film, it was [meso type] / [racemo type] = 3.2. Further, retardation values R (550) and K (550) of the film were obtained. The results are shown in Table 1.

[Example 2]
The unstretched film obtained in Example 1 was stretched using a batch-type biaxial stretching apparatus in which the film end was fixed with a chuck. The horizontal direction was free, and longitudinal uniaxial stretching was performed under the conditions shown in Table 1, and the thickness of the film center portion after stretching and retardation R (550) and K (550) were measured. The results are shown in Table 1.

[Example 3]
The trade name “TOPAS” manufactured by TICONA is a cycloolefin copolymer obtained by copolymerizing ethylene and norbornene with a metallocene catalyst. When the ¹³ C-NMR measurement of the grade 6013 was performed, it was determined that [meso type] / [racemo type] = 0.36 / 0.04 = 9, and the abundance ratio of NN dyad relative to the total amount of norbornene component (molar fraction). The rate) was 0.40. The molar ratio of the ethylene component to the norbornene component was (A) / (B) = 50/50. Tg was 139 ° C. In addition, according to the same measurement, another grade 5013 of “TOPAS” has [Meso type] / [Lacemo type] = 0.05 / 0.41 = 0.12, and the ratio of NN dyads to the total amount of norbornene components (molar fraction). ) Was 0.46, and the molar ratio of the ethylene component to the norbornene component was (A) / (B) = 50/50. Tg was 138 ° C. This grade 6013 and grade 5013 were melt blended under the same conditions as in Example 1 except that the pellets were mixed by dry blending at a weight ratio of 6013/5013 = 50/50 and the film forming speed was changed to 1 m / min. And an unstretched film was obtained. The film was excellent in transparency and homogeneity, had good surface properties, and did not show any die streak or foreign matter. Moreover, there was no problem in handling at the time of winding the roll and thereafter, and the film was sufficiently strong. The average thickness was 280 μm, except for the 2.5 cm width at both ends of the film. Tg was 137 ° C., the total light transmittance was 90.7%, and haze was 0.5%. The reduced viscosity η _{sp /} c of the film was 0.72 dL / g. Moreover, it was -8.5 * 10 < ^-12 > Pa < ^-1 > when the photoelastic constant of this film was calculated | required. From the ¹³ C-NMR measurement of the film, it was [meso type] / [racemo type] = 1.0. Further, retardation values R (550) and K (550) of the film were determined. The results are shown in Table 1.

[Example 4]
The unstretched film obtained in Example 3 was subjected to sequential biaxial stretching of 1.5 times in length and 1.8 times in width using the batch-type biaxial stretching apparatus used in Example 2. The thickness, R (550), and K (550) at the center of the film after stretching were measured. The results are shown in Table 1.

Claims (7)

  A copolymer comprising an ethylene unit and a norbornene unit, ii) having a glass transition temperature in the range of 100 ° C. to 180 ° C., and iii) a meso-type with respect to the stereoregularity of the two-chain site (dyad) of the norbornene unit An optical film comprising an amorphous polyolefin having a racemo abundance ratio of 0.2 ≦ [meso type] / [rasemo type] ≦ 4. The amorphous polyolefin is a resin composition containing the following (X) and (Y), and (X) / (Y) = 99/1 to 1/99 (weight ratio). Item 2. The optical film according to Item 1.
(X) i) a copolymer comprising an ethylene unit and a norbornene unit, ii) a glass transition temperature in the range of 60 ° C. to 200 ° C., and iii) a stereoregulation of a two-chain site (dyad) of the norbornene unit Amorphous polyolefin with a meso-type and racemo-type ratio of [meso-type] / [racemo-type]> 4 in terms of properties (i) a copolymer consisting of ethylene units and norbornene units, and ii) glass transition The temperature is in the range of 60 ° C. to 200 ° C., and iii) the abundance ratio of meso-type and racemo-type is [meso-type] / [rasemo-type] <0. Amorphous polyolefin which is 2   The optical film according to claim 1, which is obtained by a melt extrusion method. It is used as a retardation film, and a retardation R (550) in the film plane at a wavelength of 550 nm is expressed by the following formula (1)
100 nm <R (550) <800 nm (1)
The optical film according to claim 1, which has a thickness of 30 to 200 μm. Used as a retardation film, the retardation R (550) in the film plane at a wavelength of 550 nm and the retardation K (550) in the thickness direction are represented by the following formulas (2) and (3):
0 nm <R (550) <100 nm (2)
50 nm <K (550) <400 nm (3)
(In the formula, K (550) is a thickness direction retardation value at a wavelength of 550 nm, and the following formula (4)
K = {(n _x + _ny ) / 2−n _z } × d (4)
Is as defined by, where, n _x, n _y is x-axis in the film plane, the y-axis, n _z is a refractive index in a thickness direction perpendicular to the x-axis and y-axis, d is the film Is the thickness. )
The optical film according to claim 1, which has a thickness of 30 to 200 μm.   i) a copolymer comprising ethylene units and norbornene units, ii) having a glass transition temperature in the range of 100 ° C. to 180 ° C., and iii) mesomorphism with respect to the stereoregularity of the two-chain sites (dyads) of the norbornene units. A method of using an amorphous polyolefin as a retardation film, wherein the abundance ratio between the mold and the racemo type is 0.2 ≦ [meso type] / [rasemo type] ≦ 4.   The absolute value of retardation R (550) in the film plane at a wavelength of 550 nm and retardation K (550) in the thickness direction are both 20 nm or less, and the thickness is 10 to 300 µm. An optical film as described in 1.