JP2009149720A - Method for producing cellulose ester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a cellulose ester film in order to improve the bleed out of an antioxidant contained in the cellulose ester film irrespective of the kinds of the antioxidants. <P>SOLUTION: This method for producing the cellulose ester film is characterized by comprising a process of producing a resin mixture by melting a resin consisting mainly of the cellulose ester with the antioxidant, a process of forming a film by melt extrusion-casting the resin mixture on a cooling drum, a process of humidification-treating the film and a process of stretching the humidification-treated film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a cellulose ester film used for optical applications, and more particularly to a method for producing an optical cellulose ester film containing an antioxidant and having excellent bleed-out resistance.

Conventionally, an optical film mainly composed of triacetyl cellulose has been preferably used for the polarizing plate protective film. In producing such a cellulose ester film, the solution casting method is the mainstream, but in recent years, production by the melt extrusion casting method (Patent Document 1) has also been tackled.
Since the cellulose ester has a melting temperature and a decomposition temperature close to each other, it is essential to impart heat resistance to the melt extrusion casting. Therefore, an antioxidant is usually added.

  However, since the cellulose ester has high hydrophilicity, the compatibility with a commercially available antioxidant developed for general-purpose plastics is not necessarily high. For this reason, depending on the additive formulation, the antioxidant often bleeds out, or the antioxidant is triggered to bleed out other additives (for example, ultraviolet absorbers).

  This phenomenon is more likely to occur when an acrylic polymer is contained, and an improvement means in this case has been desired.

There is a prior example of a method for producing an antioxidant-containing cellulose ester film for improving bleed-out (Patent Documents 2 and 3), but additional production equipment requiring special production conditions or a heavy load. Therefore, there is a need for a simpler solution with equipment.
JP 2000-352620 A JP 2007-56093 A JP 2007-216601 A

  This invention is made | formed in view of the said subject, and it aims at providing the manufacturing method for improving the bleeding out of antioxidant contained in the cellulose-ester film.

The object of the present invention has been achieved by the following means.
1. A step of melting a mixture of a resin mainly composed of cellulose ester and an antioxidant to prepare a resin mixture, a step of melt extrusion casting the resin mixture on a cooling drum to prepare a film, and a humidification treatment of the film And a step of stretching the humidified film, and a method for producing a cellulose ester film.

  According to the present invention, it is possible to provide a cellulose ester film having an improved antioxidant bleed-out.

  In the method for producing a cellulose ester film of the present invention, at least a step of melting a mixture of a resin mainly composed of cellulose ester and an antioxidant to prepare a resin mixture, the resin mixture is extruded and cast on a cooling drum. And a step of humidifying the film, and a step of stretching the humidified film.

  So far, the technology to improve the bleed-out of the antioxidant contained in the cellulose ester film has been exclusively changing the type and structure of the antioxidant, but the present invention is improved from the method for producing a cellulose ester film. It was something that was measured.

Even when the cellulose ester film contains another polymer, the effect is exhibited.
<Process of melting a mixture of a resin mainly composed of cellulose ester and an antioxidant to produce a resin mixture>
In the production method of the present invention, first, a resin mixture is prepared by melting a mixture of a resin mainly composed of cellulose ester and an antioxidant. In this case, the resin mixture may be moved to the next step while being melted, but is usually pelletized.

  Here, the resin containing cellulose ester as a main component means that 50% by mass or more of the resin to be melted is a cellulose ester resin.

  In the resin mixture, an antioxidant is melted with the cellulose ester resin, but it is preferable that other plasticizers and other additives are kneaded in advance and pelletized.

  Pelletization may be performed by a known method. For example, dry cellulose ester, plasticizer, and other additives (antioxidants, heat deterioration inhibitors, etc.) are fed to the extruder with a feeder, and a single or twin screw extruder is used. It can be kneaded, extruded from a die into a strand, cooled with water or air, and cut.

  It is important to dry the raw material before extruding to prevent decomposition of the raw material. In particular, since the cellulose ester is easy to absorb moisture, it is preferable to dry it at 70 to 140 ° C. for 3 hours or more with a dehumidifying hot air dryer or a vacuum dryer to keep the moisture content at 200 ppm or less, and further 100 ppm or less.

  The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. A small amount of an additive such as an antioxidant is preferably mixed in advance in order to mix uniformly.

  Mixing of the antioxidants may be performed by mixing solids, and if necessary, the antioxidant may be dissolved in a solvent, impregnated with cellulose ester and mixed, or sprayed and mixed. Also good.

  A vacuum nauter mixer or the like is preferable because drying and mixing can be performed simultaneously. Moreover, when touching with air, such as an exit from a feeder part or die | dye, it is preferable to set it as atmosphere, such as dehumidified air and dehumidified N2 gas.

  The extruder is preferably processed at as low a temperature as possible so that the shearing force is suppressed and the resin can be pelletized so as not to deteriorate (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

A film is formed using the pellets obtained as described above. It is also possible to feed the raw material powder as it is with a feeder to an extruder without forming into a pellet and form a film as it is.
<Process for producing a film by extruding and casting the resin mixture onto a cooling drum>
Using a single-screw or twin-screw type extruder, the melt temperature Tm during extrusion is about 200-300 ° C, filtered through a leaf disk filter, etc. Cast on the cooling roll, solidify on the cooling roll, and cast while pressing with the elastic touch roll.

  When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum or reduced pressure or in an inert gas atmosphere. Tm is the temperature at the die exit portion of the extruder.

  When foreign matter such as scratches or plasticizer aggregates adheres to the die, streak-like defects may occur. Such defects are also referred to as die lines, but in order to reduce surface defects such as die lines, it is preferable to have a structure in which the resin retention portion is minimized in the piping from the extruder to the die. . It is preferable to use a die that has as few scratches as possible inside the lip.

  The inner surface that contacts the molten resin such as an extruder or a die is preferably subjected to surface treatment that makes it difficult for the molten resin to adhere to the surface by reducing the surface roughness or using a material having a low surface energy. Specifically, a hard chrome plated or ceramic sprayed material is polished so that the surface roughness is 0.2 S or less.

  The cooling roll of the present invention is not particularly limited, but is a roll having a structure with a high-rigidity metal roll that allows a temperature-controllable heat medium or refrigerant to flow inside, and is not limited in size. It is sufficient that the film is large enough to cool the formed film, and the diameter of the cooling roll is usually about 100 mm to 1 m.

  Examples of the surface material of the cooling roll include carbon steel, stainless steel, aluminum, and titanium. Further, in order to increase the surface hardness or improve the releasability from the resin, it is preferable to carry out a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, or ceramic spraying.

  The surface roughness of the surface of the cooling roll is preferably 0.1 μm or less in terms of Ra, and more preferably 0.05 μm or less. The smoother the roll surface, the smoother the surface of the resulting film. Of course, it is preferable to further polish the surface that has been subjected to surface processing so as to have the surface roughness described above.

  As the elastic touch roll of the present invention, JP-A-03-124425, JP-A-08-224772, JP-A-07-1000096, JP-A-10-272676, WO97-028950, JP-A-11-235747, JP-A-11-235747 Although the surface as described in 2002-36332, Unexamined-Japanese-Patent No. 2005-172940, or Unexamined-Japanese-Patent No. 2005-280217 can use a thin-film metal sleeve covering silicon rubber roll, it is the following elastic touch rolls. preferable.

When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.
<Step of humidifying the film>
The step of humidifying the film of the present invention is provided after the step of extrusion casting on a cooling drum to form a film.

  It is preferable that the film is sufficiently cooled before the humidification step, and it is preferable that the film is cooled in a range of 50 to 80 ° C. so that moisture is reliably imparted to the film by humidification.

  As a method for humidification, it is most convenient to apply high-temperature water vapor, and it is preferable to spray a mixed gas of water vapor and air in the range of 80 to 150 ° C. on the film.

  For example, the humidification method described in JP-A-2002-52493 and JP-A-2002-179819 can be used for the entire film width.

  The amount of water vapor to be sprayed is preferably adjusted to an amount that does not cause condensation on the film surface, but if it occurs, it is preferably wiped off with a squeeze roll or the like. Alternatively, it can be volatilized in a subsequent hot stretching step.

  Another preferred method of humidification is to immerse the film in a water bath. It is preferable to wipe off water droplets on the surface by guiding the film in a water bath in the range of 30 to 100 ° C. and passing the film through a squeeze roll.

  When moisture is applied to the film in the humidifying process of the present invention by these methods, and the humidifying process is completed, the moisture content is preferably 0.1 to 3.0% by mass, and more preferably. It is 1.0-2.0 mass%.

  For the moisture content, the film immediately after the humidification treatment is cut into an appropriate size and weighed using a direct balance (L-160D PT, manufactured by Shimadzu Corporation) in a room at room temperature and humidity. Thereafter, drying is performed at 120 ° C. for 4 hours, and weighed again, and the moisture content is obtained from the following equation.

Moisture content (%) = (mass before drying−mass after drying) × 100 / mass after drying Further, the temperature of the film is preferably maintained at 50 to 80 ° C. The film temperature was measured with a non-contact infrared thermometer.

Although the details of the mechanism by which the effect of the present invention is obtained by the humidifying process are unknown, the present inventors presume as follows. The original film stretched without the humidification treatment has hydrophilic and hydrophobic domains dispersed relatively uniformly, but the hydrophilicity of the hydrophilic domain is advanced by the humidification treatment, and disproportionation proceeds by stretching. It is done. Since the stretching process is also a heat treatment process, it is believed that the hydrophobic antioxidant moves to the hydrophobic domain and is stabilized, and the bleedout resistance is improved.
<The process of extending | stretching the film which carried out the humidification process>
In the present invention, the film obtained as described above is stretched 1.01 to 3.0 times in at least one direction after the humidification treatment.

  Preferably, the film is stretched 1.1 to 2.0 times in both the longitudinal (film transport direction) and lateral (width direction) directions.

  As a method of stretching, a known roll stretching machine or tenter can be preferably used. In particular, when the polarizing plate protective film is a retardation film, it is preferable to stack the polarizing film with a polarizing film by setting the stretching direction to the width direction.

  By stretching in the width direction, the slow axis of the optical film made of the polymer film becomes the width direction. On the other hand, the transmission axis of the polarizing film is also usually in the width direction. A good viewing angle can be obtained by incorporating in a liquid crystal display device a polarizing plate laminated so that the transmission axis of the polarizing film and the slow axis of the polarizing plate protective film are parallel to each other.

  When the cellulose ester film of the present invention is used as a film having an optical compensation function, the temperature and magnification can be selected so that desired retardation characteristics can be obtained.

  Usually, the draw ratio is 1.1 to 3.0 times, preferably 1.2 to 1.5 times, and the drawing temperature is usually Tg to Tg + 50 ° C. of the resin constituting the film, preferably Tg to Tg + 40 ° C. In the temperature range.

  The stretching is preferably performed under a uniform temperature distribution controlled in the width direction. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C.

  For the purpose of reducing the retardation of the cellulose ester film produced by the above method and reducing the dimensional change rate, the film may be contracted in the longitudinal direction or the width direction.

  In order to shrink in the longitudinal direction, for example, there is a method in which the film is contracted by temporarily stretching out the width stretching and relaxing in the longitudinal direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching machine.

  The in-plane retardation (Ro) and thickness direction retardation (Rt) of the cellulose ester film of the present invention can be adjusted as appropriate, but when having a retardation function, Ro is 20 to 200 nm, and Rt is 90 to 400 nm. The ratio Rt / Ro of Rt and Ro is preferably 0.5 to 4, particularly preferably 1 to 3.

In addition, when the refractive index Nx in the slow axis direction of the film, the refractive index Ny in the fast axis direction, the refractive index Nz in the thickness direction, and the film thickness of the film are d (nm),
Ro = (Nx−Ny) × d
Rt = {(Nx + Ny) / 2−Nz} × d
Represented as: (Measurement wavelength 590nm)
The variation in retardation is preferably as small as possible, and is usually within ± 10 nm, preferably ± 5 nm or less, more preferably ± 2 nm or less.

  The uniformity in the slow axis direction is also important, and the angle is preferably −5 to + 5 ° with respect to the film width direction, more preferably in the range of −1 to + 1 °, and particularly −0. It is preferably in the range of 5 to + 0.5 °, particularly preferably in the range of −0.1 to + 0.1 °. These variations can be achieved by optimizing the stretching conditions.

  In the cellulose ester film of the present invention, it is preferable that the height from the top of the adjacent mountain to the bottom of the valley is 300 nm or more, and there is no streak continuous in the longitudinal direction with an inclination of 300 nm / mm or more.

  The shape of the streak was measured using a surface roughness meter. Specifically, using a Mitutoyo SV-3100S4, a stylus (diamond needle) having a tip shape of a cone of 60 ° and a tip curvature radius of 2 μm was used. The film is scanned in the width direction of the film at a measurement speed of 1.0 mm / sec while applying a load of 0.75 mN, and a cross-sectional curve is measured with a Z-axis (thickness direction) resolution of 0.001 μm.

  From this curve, the streak height reads the vertical distance (H) from the top of the mountain to the bottom of the valley. The slope of the streak is obtained by reading the horizontal distance (L) from the top of the mountain to the bottom of the valley and dividing the vertical distance (H) by the horizontal distance (L).

In the present invention, it suffices if there is a step of stretching after the step of humidifying the film. Therefore, there is a longitudinal stretching step before the step of humidifying treatment, and then the film subjected to the humidification treatment is then stretched laterally. The effects of the present invention can be obtained.
<Other processes>
In the manufacturing method of the cellulose-ester film of this invention, it has the process provided in a normal film manufacturing process other than the above, such as the ear | edge part deletion process of a film, and a winding-up process.
<Cleaning process>
It is preferable to add the process of automatically cleaning a belt and a roll to the process using the manufacturing method of this invention.

  There is no particular limitation on the cleaning device used in the cleaning process, for example, a method of niping a brush roll, a water absorbing roll, an adhesive roll, a wiping roll, an air blow method of blowing clean air, a laser incinerator, or There are combinations of these.

In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.
<Material constituting resin mixture>
The mixture of the resin mainly composed of the cellulose ester of the present invention and the antioxidant will be described in detail. Here, the resin containing cellulose ester as a main component means that 50% by mass or more of the resin to be melted is a cellulose ester.

<Cellulose ester>
Although it does not specifically limit as a cellulose ester of this invention, It is a C2-C22 carboxylic acid ester as a cellulose ester in which melt extrusion casting film formation is possible, An aromatic carboxylic acid ester may be sufficient, and especially carbon number Is preferably a lower fatty acid ester of 6 or less.

  The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms is large, and therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  Specifically, the cellulose ester includes cellulose acetate propionate, cellulose acetate butyrate, or a mixed fatty acid ester of cellulose to which a propionate group or a butyrate group is bonded in addition to an acetyl group such as cellulose acetate propionate butyrate. Can be used.

  The butyryl group forming butyrate may be linear or branched. As the cellulose ester preferably used in the present invention, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate phthalate are particularly preferably used.

  Preferred cellulose esters other than cellulose acetate phthalate for the present invention preferably satisfy the following formulas (1) and (2).

Formula (1) 2.0 <= X + Y <= 3.0
Formula (2) 0 ≦ Y ≦ 1.5
In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group, or a mixture thereof.

  Further, in order to obtain optical characteristics that meet the purpose, resins having different degrees of substitution may be mixed and used. The mixing ratio is preferably 10:90 to 90:10 (mass ratio).

  Of these, cellulose acetate propionate is particularly preferably used. In cellulose acetate propionate, 1.0 ≦ X ≦ 2.5, preferably 0.1 ≦ Y ≦ 1.5, and 2.0 ≦ X + Y ≦ 3.0.

  The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  The number average molecular weight of the cellulose ester used in the present invention is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 70000-200000 is used preferably.

  The weight average molecular weight Mw and number average molecular weight Mn of the cellulose ester were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The cellulose ester such as cellulose acetate phthalate of the present invention can be produced by a known method. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

<Resin other than cellulose ester>
Examples of the resin that can be used other than the cellulose ester of the present invention include the following acrylic polymers and sugar ester compounds. These resins can be used to adjust the birefringence of the cellulose ester film.

  These resins are used in an amount of 0 to 50% by mass based on the total amount of the resin.

(Acrylic polymer)
The acrylic polymer used in the present invention preferably exhibits negative birefringence in the stretching direction as a function when incorporated in an optical compensation film, and the structure is not particularly limited. A polymer having a weight average molecular weight of 500 or more and 30000 or less obtained by polymerizing a polymerizable unsaturated monomer is preferable.

(Test method for birefringence of acrylic polymers)
The acrylic polymer was dissolved in a solvent to form a cast film, and then dried by heating. The film having a transmittance of 80% or more was evaluated for birefringence.

  Refractive index measurement was performed using an Abbe refractometer-4T (manufactured by Atago Co., Ltd.) using a multiwavelength light source. The refractive index ny in the stretching direction and the refractive index in the in-plane direction perpendicular to each other were defined as nx. For a film where (ny-nx) <0 for each refractive index at 550 nm, the (meth) acrylic polymer is judged to be negatively birefringent with respect to the stretch direction.

  The acrylic polymer having a weight average molecular weight of 500 to 30,000 used in the present invention may be an acrylic polymer having an aromatic ring in the side chain or an acrylic polymer having a cyclohexyl group in the side chain.

  When the polymer has a weight average molecular weight of 500 or more and 30000 or less, and the composition of the polymer is controlled, for example, when the optical compensation film is a cellulose ester film particularly preferable in the present invention, the cellulose ester and the polymer The compatibility with can be improved.

  For an acrylic polymer having an aromatic ring in the side chain or an acrylic polymer having a cyclohexyl group in the side chain, if the weight average molecular weight is preferably 500 or more and 10,000 or less, in addition to the above, a cellulose ester film after film formation The film has excellent transparency and extremely low moisture permeability, and exhibits excellent performance as a protective film for polarizing plates.

  Since the polymer has a weight average molecular weight of 500 or more and 30000 or less, it is considered to be between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight too much.

  In particular, the acrylic polymer used in the optical compensation film of the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and hydroxyl group in the molecule, and an ethylenic group having no hydroxyl ring and having a hydroxyl group in the molecule. Polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerization of unsaturated monomer Xb and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb, or an ethylenic monomer having no aromatic ring The polymer Y is preferably a polymer Y having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing a saturated monomer Ya and an ethylenically unsaturated monomer copolymerizable with Ya.

[Polymer X, Polymer Y]
As a method for adjusting Ro and Rt of the optical compensation film of the present invention, an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxyl group or an amide group in the molecule, a hydroxyl group or an aromatic ring not having an aromatic ring in the molecule, A high molecular weight polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerizing an ethylenically unsaturated monomer Xb having an amide group and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb; and A low molecular weight polymer Y having a weight average molecular weight of 500 to 3,000 obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring and an ethylenically unsaturated monomer copolymerizable with Ya It is preferable to do.

  The polymer X used in the present invention is composed of an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxyl group or an amide group in the molecule, and an ethylenically unsaturated group having no aromatic ring in the molecule and a hydroxyl group or an amide group. It is a polymer having a weight average molecular weight of 2000 or more and 30000 or less obtained by copolymerizing the monomer Xb and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb.

  Preferably, Xa is an acrylic or methacrylic monomer that does not have an aromatic ring and a hydroxyl group or an amide group in the molecule, and Xb is an acrylic or methacrylic monomer that does not have an aromatic ring in the molecule and has a hydroxyl group or an amide group.

  The polymer X used in the present invention is represented by the following general formula (X).

Formula (X)
-[Xa] m- [Xb] n- [Xc] p-
In the general formula (X), Xa represents an ethylenically unsaturated monomer having no aromatic ring and a hydroxyl group or amide group in the molecule, and Xb does not have an aromatic ring in the molecule and has a hydroxyl group or an amide group. Represents an ethylenically unsaturated monomer, and Xc represents a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb. m, n, and p each represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

  Furthermore, the polymer X is preferably a polymer represented by the following general formula (X-1).

Formula (X-1)
_{- [CH 2 -C (-R1)} (- CO 2 R2)] m- [CH 2 -C (-R3) (- CO 2 R4-OH) -] n- [Xc] p-
In the general formula (X-1), R1 and R3 each represent a hydrogen atom or a methyl group. R2 represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. R4 is _{-CH 2 -, - C 2 H} 4 - or -C ₃ H ₆ - represents a. Xc _{is, [CH 2 -C (-R1)} (- CO 2 R2)] representing the a polymerizable monomer unit or _{[CH 2 -C (-R3) (} - - CO 2 R4-OH)]. m, n, and p represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

  Although the monomer as a monomer unit which comprises the polymer X of this invention is mentioned below, it is not limited to this.

  In X, the hydroxyl group means not only a hydroxyl group but also a group having an ethylene oxide chain.

  The ethylenically unsaturated monomer Xa having no aromatic ring and hydroxyl group or amide group in the molecule is, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i -, S-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n -, I-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), etc., or the above acrylic acid The thing which changed ester into methacrylic acid ester can be mentioned. Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

  The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydroxyl group or an amide group is preferably an acrylic acid or a methacrylic acid ester as a monomer unit having a hydroxyl group. For example, acrylic acid (2-hydroxyethyl) , Acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those obtained by replacing acrylic acid with methacrylic acid. Acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl) are preferable.

  As monomer units having an amide group in Xb, N-vinylpyrrolidone, N-acryloylmorpholine, N-methacryloylmorpholine, N-vinylpiperidone, N-vinylcaprolactam, acrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, N , N-dimethylaminopropylacrylamide, N, N-diethylacrylamide, N-hydroxyethylacrylamide, N-vinylacetamide and the like.

  Xc is not particularly limited as long as it is a monomer other than Xa and Xb and is a copolymerizable ethylenically unsaturated monomer, but preferably has no aromatic ring.

  The molar composition ratio m: n of Xa and Xb is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, the compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rt is high.

  Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  The molecular weight of the high molecular weight polymer X is more preferably 5,000 or more and 30,000 or less, and still more preferably 8,000 or more and 25,000 or less.

  By setting the weight average molecular weight to 5,000 or more, it is preferable because advantages such as little dimensional change of the optical compensation film under high temperature and high humidity and less curling as a polarizing plate protective film are preferable.

  When the weight average molecular weight is 30000 or less, compatibility with the cellulose ester is further improved, and bleeding out under high temperature and high humidity and further haze generation immediately after film formation are suppressed.

  The weight average molecular weight of the polymer X of the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like.

  The polymerization temperature is usually from room temperature to 130 ° C., preferably from 50 ° C. to 100 ° C., and this temperature or the polymerization reaction time can be adjusted.

  The measuring method of a weight average molecular weight can be calculated | required by the following method.

(Average molecular weight measurement method)
The weight average molecular weight Mw and the number average molecular weight Mn were measured using gel permeation chromatography (GPC). The measurement conditions are as described above.

  The low molecular weight polymer Y used in the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring. A weight average molecular weight of 500 or more is preferred because the residual monomer in the polymer is reduced.

  Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rt fall performance. Ya is preferably an acrylic or methacrylic monomer having no aromatic ring.

  The polymer Y used in the present invention is represented by the following general formula (Y).

General formula (Y)
-[Ya] k- [Yb] q-
In the general formula (Y), Ya represents an ethylenically unsaturated monomer having no aromatic ring, and Yb represents an ethylenically unsaturated monomer copolymerizable with Ya. k and q each represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

  The polymer Y of the present invention is more preferably a polymer represented by the following general formula (Y-1).

General formula (Y-1)
_{- [CH 2 -C (-R5)} (- CO 2 R6)] k- [Yb] q-
In the general formula (Y-1), R5 represents a hydrogen atom or a methyl group, respectively. R6 represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. Yb represents a monomer unit copolymerizable with [CH ₂ —C (—R 5) (— CO ₂ R 6)]. k and q each represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

Yb is a _{Ya [CH 2 -C (-R5)} (- CO 2 R6)] and is not particularly limited as long as it is copolymerizable ethylenically unsaturated monomers. Yb may be plural. k + q = 100, q is preferably 1-30.

  The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing the ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate ( i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), acrylic Acid heptyl (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid ( 2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid And maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural.

  In order to synthesize the polymers X and Y, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can make the molecular weights as uniform as possible without increasing the molecular weight.

  Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Used.

  In particular, the polymer Y is preferably a polymerization method using a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent. In this case, the terminal of the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. The compatibility of Y and cellulose ester can be adjusted by this terminal residue.

  The hydroxyl values of the polymers X and Y are preferably 30 to 150 [mg KOH / g].

(Measurement method of hydroxyl value)
The measurement of the hydroxyl value is based on JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated.

  Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C. After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid.

  Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point.

  Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained. The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
In the formula, B is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test, C is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for titration, f is a factor of a 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount 56.11 of potassium hydroxide.

  The above-mentioned polymer X and polymer Y are both excellent in compatibility with cellulose ester, excellent in productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and dimension stability. Excellent in properties.

The content of the polymer X and the polymer Y in the optical compensation film is preferably in a range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass% = (mass of polymer X / mass of cellulose ester) × 100) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of (Xg + Yg) in the formula (i) is 10 to 35% by mass. If the polymer X and the polymer Y are 5 mass% or more as a total amount with respect to the total mass of the cellulose ester, the polymer X and the polymer Y have a sufficient effect for adjusting the retardation value Rt. Moreover, if it is 35 mass% or less as a total amount, adhesiveness with polarizer PVA is favorable.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope solution described later, or can be added to the dope solution after being previously dissolved in an organic solvent for dissolving the cellulose ester.

(Sugar ester compound)
The cellulose ester film of the present invention may be obtained by melt-forming a molten composition containing a sugar ester compound obtained by esterifying a hydroxyl group of a sugar compound in which 1 to 12 at least one structure selected from a furanose structure and a pyranose structure is bonded. preferable.

  Examples of the sugar compound of the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose, etc., particularly those having both a furanose structure and a pyranose structure. preferable. An example is sucrose.

  The sugar ester compound of the present invention is one in which part or all of the hydroxyl groups of the sugar compound are esterified or a mixture thereof.

As a commercial item, monopet SB (Daiichi Kogyo Seiyaku Co., Ltd. product) etc. are mentioned, for example.
<Antioxidant>
In this invention, what is generally known can be used as an antioxidant. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.

  The effect of the present invention is particularly effective for phenolic antioxidants, and is effective for any antioxidant other than phenolic that has a phenol structure.

  For example, those including those commercially available from Ciba Specialty Chemicals under the trade names “IrgafosXP40” and “IrgafosXP60” are preferable.

  The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, Ciba Specialty Chemicals Co., Ltd., “Irganox 1076”, “Irganox 1010” (AO1), ADEKA “ADEKA STAB AO— What is marketed with the brand name of 50 "(AO6) is preferable.

  The phosphorous compounds are, for example, from Sumitomo Chemical Co., Ltd., “Sumilizer GP” (AO4), from ADEKA Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010”, Ciba Specialty -What is marketed with the brand name "IRGAFOS P-EPQ" from Chemicals Co., Ltd., and "GSY-P101" from Sakai Chemical Industry Co., Ltd. is preferable.

  The hindered amine compound is preferably, for example, commercially available from Ciba Specialty Chemicals Co., Ltd. under the trade names of “Tinuvin 144 (AO2)” and “Tinvin 770”, and from ADEKA Co., Ltd. as “ADK STAB LA-52”. .

  As the sulfur compound, for example, those commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer TPL-R” and “Sumilizer TP-D” are preferable.

  The above-mentioned double bond type compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer GM” (AO5) and “Sumilizer GS” (AO3).

  Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

  The amount of these antioxidants and the like to be appropriately added is determined in accordance with the process at the time of recycling, but generally 0.05 to 20% by mass, preferably with respect to the resin as the main raw material of the film Is added in the range of 0.1 to 1% by mass.

These antioxidants can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.
<Other additives>
In addition to the resin and the antioxidant, other additives such as a plasticizer, an ultraviolet absorber, and particles can be used for the resin mixture of the present invention.

<Plasticizer>
The plasticizer of the present invention is not particularly limited, but preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, and a polyhydric alcohol ester plasticizer, It is selected from polyester plasticizers, acrylic plasticizers and the like.

  Of these, when two or more plasticizers are used, at least one is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer composed of an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  In order to lower the melting temperature of the film constituent material, it can be achieved by adding a plasticizer having a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester.

  The cellulose ester film of the present invention preferably contains 1 to 25% by mass of an ester compound having a molecular weight of 350 to 1500, preferably 400 to 1000, having a structure in which an organic acid and a trivalent or higher alcohol are condensed. By adding 1% by mass or more, the effect of improving the flatness is recognized, and when it is less than 25% by mass, bleeding out is difficult and the temporal stability of the film is excellent, which is preferable.

  The organic acid in the ester compound having a structure in which the organic acid of the present invention and a trivalent or higher-valent alcohol are condensed is represented by the following general formula (1).

In the formula, R _{1 to} R ₅ represent a hydrogen atom or a cycloalkyl group, an aralkyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, a carbonyloxy group, an oxycarbonyl group, or an oxycarbonyloxy group. These may be further substituted. L represents a linking group and represents a substituted or unsubstituted alkylene group, an oxygen atom, or a direct bond.

The cycloalkyl group represented by R _{1 to} R ₅ is preferably a cycloalkyl group having 3 to 8 carbon atoms, and specifically, a group such as cyclopropyl, cyclopentyl, cyclohexyl and the like. These groups may be substituted, and preferred substituents include halogen atoms such as chlorine atom, bromine atom, fluorine atom, hydroxyl group, alkyl group, alkoxy group, cycloalkoxy group, aralkyl group (this phenyl group). The group may be further substituted with an alkyl group or a halogen atom), an alkenyl group such as a vinyl group or an allyl group, or a phenyl group (this phenyl group may be further substituted with an alkyl group or a halogen atom). Phenoxy group (this phenyl group may be further substituted by an alkyl group or a halogen atom), an acyl group having 2 to 8 carbon atoms such as an acetyl group or a propionyl group, an acetyloxy group, or a propionyloxy group. And an unsubstituted carbonyloxy group having 2 to 8 carbon atoms such as a group.

The aralkyl group represented by R _{1 to} R ₅ represents a group such as a benzyl group, a phenethyl group, and a γ-phenylpropyl group, and these groups may be substituted. Preferred substituents include The group which may be substituted with the said cycloalkyl group can be mentioned similarly.

Examples of the alkoxy group represented by R _{1 to} R ₅ include an alkoxy group having 1 to 8 carbon atoms, specifically, methoxy, ethoxy, n-propoxy, n-butoxy, n-octyloxy, isopropoxy. , Alkoxy groups such as isobutoxy, 2-ethylhexyloxy, or t-butoxy.

  These groups may be substituted, and preferred substituents include halogen atoms such as chlorine atom, bromine atom, fluorine atom, hydroxyl group, alkoxy group, cycloalkoxy group, aralkyl group (this phenyl group). May be substituted with an alkyl group or a halogen atom), an alkenyl group, a phenyl group (this phenyl group may be further substituted with an alkyl group or a halogen atom), an aryloxy group (for example, phenoxy) An acyl group such as an acetyl group or a propionyl group, or an aryl group such as an acetyloxy group or a propionyloxy group (the phenyl group may be further substituted with an alkyl group or a halogen atom). Arylcarbonyl groups such as unsubstituted acyloxy groups and benzoyloxy groups Shi group.

Examples of the cycloalkoxy group represented by R _{1 to} R ₅ include an unsubstituted cycloalkoxy group having 1 to 8 carbon atoms, specifically, cyclopropyloxy, cyclopentyloxy, cyclohexyl. And groups such as oxy.

  In addition, these groups may be substituted, and preferred substituents include the same groups that may be substituted with the cycloalkyl group.

Examples of the aryloxy group represented by R _{1 to} R ₅ include a phenoxy group, and the phenyl group includes a substituent that is exemplified as a group that may be substituted with the cycloalkyl group such as an alkyl group or a halogen atom. May be substituted.

Examples of the aralkyloxy group represented by R _{1 to} R ₅ include a benzyloxy group, a phenethyloxy group, and the like. These substituents may be further substituted. Preferred substituents include the above-mentioned cycloalkyl. The group which may be substituted with a group can be mentioned similarly.

Examples of the acyl group represented by R _{1 to} R ₅ include an unsubstituted acyl group having 2 to 8 carbon atoms such as an acetyl group and a propionyl group (the hydrocarbon group of the acyl group includes alkyl, alkenyl, alkynyl). These substituents may be further substituted, and preferred substituents include the same groups that may be substituted with the cycloalkyl group.

The carbonyloxy group represented by R _{1 to} R ₅ is an unsubstituted acyloxy group having 2 to 8 carbon atoms such as acetyloxy group and propionyloxy group (the hydrocarbon group of the acyl group is alkyl, alkenyl, alkynyl). And arylcarbonyloxy groups such as a benzoyloxy group, and these groups may be further substituted with the same groups as those which may be substituted with the cycloalkyl group.

The oxycarbonyl group represented by R _{1 to} R ₅ represents an alkoxycarbonyl group such as a methoxycarbonyl group, an ethoxycarbonyl group or a propyloxycarbonyl group, or an aryloxycarbonyl group such as a phenoxycarbonyl group.

  These substituents may be further substituted, and preferred examples of the substituent include the same groups that may be substituted with the cycloalkyl group.

The oxycarbonyloxy group represented by R _{1 to} R ₅ represents a C 1-8 alkoxycarbonyloxy group such as a methoxycarbonyloxy group, and these substituents may be further substituted and are preferably substituted. Examples of the group include the same groups that may be substituted on the cycloalkyl group.

Any one of R _{1 to} R ₅ may be connected to each other to form a ring structure.

The linking group represented by L represents a substituted or unsubstituted alkylene group, an oxygen atom, or a direct bond, and the alkylene group is a group such as a methylene group, an ethylene group, or a propylene group. These groups may be further substituted with the groups mentioned as the groups that may be substituted with the groups represented by R _{1 to} R ₅ .

  Among these, a direct bond and an aromatic carboxylic acid are particularly preferable as the linking group represented by L.

In addition, the organic acid represented by the general formula (1) constituting the ester compound serving as a plasticizer in the present invention includes at least R ₁ or R ₂ having the alkoxy group, acyl group, oxycarbonyl group, carbonyl group. Those having an oxy group or an oxycarbonyloxy group are preferred. A compound having a plurality of substituents is also preferred.

  In the present invention, the organic acid for substituting the hydroxyl group of the trivalent or higher alcohol may be a single type or a plurality of types.

  In the present invention, the trihydric or higher alcohol compound that reacts with the organic acid represented by the general formula (1) to form a polyhydric alcohol ester compound is preferably a 3-20 valent aliphatic polyhydric alcohol. In the present invention, the trihydric or higher alcohol is preferably represented by the following general formula (3).

Formula (3) R '-(OH) m
In the formula, R ′ represents an m-valent organic group, m represents a positive integer of 3 or more, and the OH group represents an alcoholic hydroxyl group. Particularly preferred is a polyhydric alcohol having 3 or 4 as m.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Adonitol, arabitol, 1,2,4-butanetriol, 1,2,3-hexanetriol, 1,2,6-hexanetriol, glycerin, diglycerin, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, ga Examples include lactitol, inositol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol.

  In particular, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol are preferable.

  The ester of the organic acid represented by the general formula (1) and a trihydric or higher polyhydric alcohol can be synthesized by a known method. In the examples, typical synthesis examples are shown. A method of condensing an organic acid represented by the general formula (1) and a polyhydric alcohol in the presence of an acid, for example, There are a method of reacting with a polyhydric alcohol by leaving it as a chloride or acid anhydride, a method of reacting a phenyl ester of an organic acid with a polyhydric alcohol, etc., and a method with a good yield is appropriately selected according to the target ester compound. It is preferable.

  As the plasticizer comprising an organic acid represented by the general formula (1) and an ester of a trihydric or higher polyhydric alcohol, a compound represented by the following general formula (2) is preferable.

In the formula, R _{6 to} R ₂₀ represent a hydrogen atom or a cycloalkyl group, an aralkyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, a carbonyloxy group, an oxycarbonyl group, or an oxycarbonyloxy group. These may be further substituted. R21 represents a hydrogen atom or an alkyl group.

The cycloalkyl group, aralkyl group, alkoxy group, cycloalkoxy group, aryloxy group, aralkyloxy group, acyl group, carbonyloxy group, oxycarbonyl group, and oxycarbonyloxy group of R _{6 to} R ₂₀ are represented by the above general formula ( The same group as R < ₁ > -R < ₅ > of 1) is mentioned.

  Below, the specific compound of the polyhydric alcohol ester concerning this invention is illustrated.

  Other plasticizers that can be used in the present invention are not particularly limited, but are preferably polycarboxylic acid ester plasticizers, glycolate plasticizers, phthalate ester plasticizers, fatty acid ester plasticizers, It is selected from polyester plasticizers and acrylic plasticizers.

  Among them, when two or more kinds of plasticizers are used, at least one kind is preferably a polyhydric alcohol ester plasticizer having a molecular weight of 350 to 1500 having a structure in which an organic acid and a trivalent or higher alcohol are condensed.

<Ultraviolet absorber>
As the ultraviolet absorber of the present invention, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, and triazine compounds are preferably used.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and also tinuvin 928, tinuvin 900, tinuvin 109, tinuvin 400, tinuvin 171, tinuvin 234, tinuvin There are tinuvins such as 326, tinuvin 327, tinuvin 328, etc., all of which are commercially available from Ciba Specialty Chemicals and can be preferably used.

  The cellulose ester film of the present invention preferably contains two or more ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The amount of UV absorber used is not uniform depending on the type of UV absorber, usage conditions, etc., but when the dry film thickness of the cellulose ester film is 30 to 200 μm, 0.5 to 10 mass relative to the cellulose ester. % Is preferable, and 0.6 to 4% by mass is more preferable.

<Fine particles>
The cellulose ester film of the present invention preferably contains fine particles.

  As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate.

  Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm.

  These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable.

  The content of these fine particles in the polarizing plate protective film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a polarizing plate protective film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the polarizing plate protective film low. In the polarizing plate protective film used in the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

The present invention will be specifically described below with reference to examples.
Example 1
The effect of the present invention was examined for a cellulose ester film production process having the following composition.

100 parts by mass of cellulose acetate propionate (dried at 80 ° C. for 6 hours (water content 200 ppm), acetyl group substitution degree 1.65, propionyl group substitution degree 1.21, weight average molecular weight 170000)
Pentaerythritol tetrabenzoate 5 parts by weight Tinuvin 928 0.8 part by weight Tinuvin 900 0.8 part by weight Antioxidant (described in Table 1) 1.0 part by weight Seahoster KEP-30 (manufactured by Nippon Shokubai Co., Ltd.) 0.1 part by weight Part The above mixture was further dried with mixing in a vacuum nauter mixer at 80 ° C. and 1 Torr for 3 hours.

  The obtained mixture was melted at 235 ° C. using a twin-screw extruder to produce resin mixture pellets. At this time, an all screw type screw was used in order to suppress heat generation due to shearing during kneading (corresponding to a step of preparing a resin mixture by melting a mixture of a resin mainly composed of cellulose ester and an antioxidant).

  In addition, evacuation was performed from the vent hole, and volatile components generated during kneading were removed by suction. The space between the feeder and hopper supplied to the extruder, the extruder die and the cooling tank was a dry nitrogen gas atmosphere to prevent moisture from being absorbed into the resin.

  The pellets were melted at 250 ° C. in a nitrogen atmosphere, passed through a filter from the extruder 1, and then extruded from the casting die 2 onto the first cooling roll 4, and the first cooling roll 4 and the touch roll 3. (Shown in FIG. 1) (corresponding to a step of extrusion casting the resin mixture onto a cooling drum to produce a film).

  The heat bolt was adjusted so that the gap width of the casting die 2 was 0.5 mm within 30 mm from the end in the width direction of the film and 1 mm at other locations. As the touch roll, an elastic touch roll was used, and oil at 120 ° C. was poured as cooling water therein.

  The first resin from the position where the resin extruded from the casting die 2 contacts the first cooling roll 4 to the position at the upstream end in the rotation direction of the first cooling roll 4 in the nip between the first cooling roll 3 and the elastic touch roll 3. The length L along the peripheral surface of the cooling roller 4 was set to 20 mm.

  Thereafter, the elastic touch roll 3 was separated from the first cooling roll 4, and the temperature T of the melted portion immediately before being sandwiched between the first cooling roll 4 and the elastic touch roll 3 was measured.

  In the present embodiment, the temperature T of the melted portion immediately before being sandwiched between the first cooling roll 4 and the elastic touch roll 3 is 1 mm upstream from the nip upstream end, and a thermometer (an independent meter). It was measured by HA-200E manufactured by Co., Ltd.

  As a result of measurement in this example, the temperature T was 230 ° C.

  The linear pressure of the elastic touch roll 3 against the first cooling roll 4 was 14.7 N / cm.

  First, the obtained film was stretched 1.7 times in the transport direction at 170 ° C. by a longitudinal stretching machine 5 utilizing the difference in peripheral speed of the roll.

Next, in the humidification treatment step, humidified air was applied to the film to perform a humidification treatment so as to obtain a desired moisture content. The humidified air was heated to 70 ° C. and blown into the process so as to be 10 m ³ / min (corresponding to the process of humidifying the film).

  After this, the ear part was deleted, introduced into a tenter part for lateral stretching, and stretched 1.7 times at 170 ° C. in the width direction (corresponding to a process of stretching a humidified film).

  Thereafter, it is cooled to 30 ° C. while relaxing 1% in the width direction, released from the clip, the clip gripping part is cut off, a knurling process with a width of 10 mm and a height of 5 μm is applied to both ends of the film, a winding tension of 220 N / m, The cellulose ester film 1 was wound around the core with a taper of 40%.

  In addition, the extrusion amount and the take-up speed were adjusted so that the cellulose ester film 1 had a thickness of 80 μm, and the finished film width was slit and wound up so as to have a width of 1430 mm.

  The winding core had an inner diameter of 152 mm, an outer diameter of 165 to 180 mm, and a length of 1550 mm.

  A prepreg resin obtained by impregnating glass fibers and carbon fibers with an epoxy resin was used as the core material for the core. The surface of the core was coated with an epoxy conductive resin, the surface was polished, and the surface roughness Ra was finished to 0.3 μm. The winding length was 2500 m.

  In addition, the conditions were changed as described in Table 1, and cellulose ester films 2 to 12 were obtained. The cellulose ester film 11 was passed through a tenter portion at 170 ° C. without being laterally stretched while holding both ends.

[Acrylic polymer composition Mass ratio Molecular weight Mw]
A1: MMA / MA / HEMA = 50/30/20 Mw5000
A2: MMA / ACMO = 70/30 Mw25000
A3: MMA / MA / VP = 50/20/30 Mw10000
MMA represents methyl methacrylate, MA represents methyl acrylate, HEMA represents 2-hydroxyethyl methacrylate, ACMO represents acryloylmorpholine, and VP represents N-vinylpyrrolidone.

  About the obtained cellulose-ester film, bleed-out was evaluated by the following method. The results are shown in Table 1.

<Bleed-out value>
A film sample was cut out in a size of 10 cm in the width direction and 10 cm in the longitudinal direction, treated for 48 hours under the conditions of 80 ° C. and 90% RH, and then TURBIDITY METER T-2600DA manufactured by Tokyo Denshoku Co., Ltd. The haze value measured using this was taken as the bleed-out value.

  From Table 1, it is clear that according to the production method of the present invention, the bleed-out can be improved by the humidification treatment.

It is Embodiment 1 of the manufacturing process of this invention. It is Embodiment 2 of the manufacturing process of this invention. It is Embodiment 3 of the manufacturing process of this invention. It is Embodiment 4 of the manufacturing process of this invention.

Explanation of symbols

B Process for producing a film by extruding and casting a resin mixture on a cooling drum C Process for humidifying a film D Process for stretching a film subjected to a humidification process a Film moisture content measurement point 1 Extruder 2 Die (including thickness adjusting means) )
DESCRIPTION OF SYMBOLS 3 Touch roll 4 1st cooling roll 5 Longitudinal stretch process 6 Humidification process 7 Ear part deletion process 8 Lateral stretch process 9 Winding process 10 Hot water bath

Claims (1)

  A step of melting a mixture of a resin mainly composed of cellulose ester and an antioxidant to prepare a resin mixture, a step of melt extrusion casting the resin mixture on a cooling drum to prepare a film, and a humidification treatment of the film And a step of stretching the humidified film. A method for producing a cellulose ester film, comprising:

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