JP2011123316A - Optical film, method for producing the same, polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film showing a good aptitude for handling, having such high optical expression properties as to improve viewing angle characteristics by itself upon being incorporated into a liquid crystal display, and capable of raising contrast in image display. <P>SOLUTION: The optical film is characterized in that: it comprises a thermoplastic resin; XRF intensity when performing XRF measurement of a film surface is 0.6-15; a total haze value is 0.1-1.0%; an internal haze value is <0.07%; a coefficient of dynamic friction at both surfaces of the film is 0.3-3.5; and formula (1): 25 nm≤Re≤140 nm is satisfied, wherein Re represents a retardation value in an in-plane direction of the film measured at a wavelength of 590 nm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical film, a method for producing the same, and a polarizing plate and a liquid crystal display device using the optical film. In particular, the present invention relates to an optical film that can be preferably used as an optical film such as a retardation film.

  In recent years, TV applications of liquid crystal display devices have progressed, and there has been an increasing demand for higher image quality, lower cost, and thinner thickness as the screen size increases. In particular, a VA mode liquid crystal display device is the most common liquid crystal display device for TV because it has a relatively high contrast and a relatively high manufacturing yield.

  However, when the VA mode liquid crystal display device displays black, an almost complete black display is possible in the normal direction of the liquid crystal display screen, but light leakage occurs when the black display screen is observed from an oblique direction of the liquid crystal display screen. Occurs and the viewing angle becomes narrow because the background cannot be displayed black. Therefore, in recent years, there has been a demand for an optical film that can further contribute to thinning by providing retardation to the polarizing plate protective film to provide optical compensation ability, and can independently compensate for the viewing angle when incorporated in a liquid crystal display device. It has been. Further, there is still a demand for further improvement in display performance of the liquid crystal display device, and there is a demand for an optical film that can further increase the contrast.

  On the other hand, various optical films have been conventionally used for liquid crystal display devices, and optical films to which various additives are added are known. Such optical films are manufactured by various film forming methods. As a typical method, there is known a solution film forming method in which a dope in which a thermoplastic resin is dissolved in a solvent is poured on a support to form a film. It has been. In the case of producing by such a solution casting method, a method using a dope to which a matting agent is added is known for the purpose of improving film transport characteristics. Such a matting agent closely corresponds to the handling suitability, and if the addition amount is small, wrinkles and creakings are generated on the film, which causes problems in transportability and tends to deteriorate the manufacturing yield. On the other hand, it is known that when the addition amount of the matting agent is increased, the haze of the manufactured optical film is increased according to the addition amount, and when an optical film having a high haze is used for a liquid crystal display device, contrast at the time of image display is increased. There was a problem that would decrease.

  In this way, an optical that has good handling aptitude, has high optical expression that can improve the viewing angle characteristics when incorporated in a liquid crystal display device, and can increase the contrast during image display. A film was sought.

  Here, the example which examined the characteristic of the optical film when controlling the addition amount of a mat agent is known (for example, refer patent documents 1-3). First, in Patent Document 1, a cellulose acetate dope having a substitution degree of 2.86 containing a matting agent is formed by co-casting, and a surface layer having a total thickness of about 40 μm is reduced to 0.1 parts by mass with respect to 100 parts by mass of cellulose acetate. An example is disclosed in which a film containing 026 parts by mass of a matting agent is stretched 1.41 times at 163 ° C. in a direction perpendicular to the film transport direction. In this document, 0.2 to 1.0 is described as a preferable dynamic friction coefficient. However, in a film having a matting agent concentration of 0.026% by mass, the dynamic friction coefficient is 3.5 or more when actually measured. Therefore, excellent transportability could not be obtained. Moreover, it does not mention about the haze value of the film obtained by the same literature, and when it actually measured, it was 1.5 or more, and it was unsuitable as an optical film. Furthermore, an anisotropic coating film is provided on one surface to develop a phase difference, and it has not been studied to improve handling suitability, reduce haze, and achieve optical properties. In addition, there is no mention of the influence on contrast when the film is incorporated in a liquid crystal display device.

  In Patent Literature 2, cellulose acetate having a total acyl substitution degree of 2.90 is used for the surface layer and the inner layer, and the surface layer having a total thickness of about 10 μm is 0.15 to 0.25 mass relative to the cellulose acylate. An example is disclosed in which a film containing 0.001 to 0.05 mass% of a matting agent in an inner layer is stretched 1.05 times in a direction perpendicular to the film conveying direction at 120 to 135 ° C. ing. In this document, although the total haze value can be reduced to 0.2% or less by such an aspect, the dynamic friction coefficient is as high as about 0.48 to 0.57, which is suitable for handling. It was found that improvement and low haze were not compatible. In addition, this document does not mention the expression of retardation of the obtained film. An example in which cellulose acylate propionate having a total acyl substitution degree of 2.65 was used for the surface layer and the inner layer was also described, but the same tendency was observed.

  In Patent Document 3, cellulose triacetate is used for the surface layer and the inner layer, and only a surface layer having a total thickness of about 10 to 20 μm contains a film containing 0.03 to 1.0% by mass matting agent with respect to cellulose triacetate. The example which dried at 140 degreeC and did not implement the extending | stretching process is disclosed. In the same document, it was described that the dynamic friction coefficient was suppressed to 0.001 to 0.36 by such an aspect, but the total haze value was not mentioned, and handling suitability was improved and low haze was reduced. No consideration was given to balancing. Further, since the document does not disclose or suggest that the film is stretched, the film described in the document is expected to exhibit almost no retardation.

  In this way, an optical that has good handling aptitude, has high optical expression that can improve the viewing angle characteristics when incorporated in a liquid crystal display device, and can increase the contrast during image display. The film was not known. In addition, since a film having the characteristics satisfying all the above requirements could not be produced only by forming the film by co-casting by specifying the addition amount of the matting agent, a method for producing a film having such characteristics is also known. There was no actual situation.

JP 2009-222994 A Patent No. 4036014 JP 2001-71418 A

  The object of the present invention is to obtain a film satisfying all of the above characteristics. That is, the problem to be solved by the present invention is that handling aptitude is good, it has high optical expression that can improve the viewing angle characteristics when incorporated in a liquid crystal display device, and at the time of image display. The object is to provide an optical film capable of increasing the contrast.

Under the above-mentioned problems, the present inventors have intensively studied and measured the matting agent concentration of the optical film obtained when manufactured by a special manufacturing method by fluorescent X-ray analysis (hereinafter referred to as XRF), Moreover, the dynamic friction coefficient was measured. As a result, the above-mentioned optical film in which the matting agent concentration is controlled in a specific XRF strength range and the dynamic friction coefficient is controlled in a specific range is surprisingly compatible with both handling suitability and low haze. I came to find out. It was also found that the optical film obtained when manufactured by the above special manufacturing method was able to achieve high optical expression at the same time.
That is, the present inventor has good handling aptitude, has high optical expression that can improve the viewing angle characteristics when incorporated in a liquid crystal display device, and increases the contrast at the time of image display. For the first time, the inventors have found that an optical film that can be manufactured can be produced, and have completed the present invention.
Specifically, the above problem has been solved by the following means.

[1] XRF intensity when thermoplastic film is included and XRF measurement of the film surface is performed is 0.6 to 15, the total haze value is 0.1 to 1.0%, and the internal haze value is 0. An optical film characterized by being less than 0.07% and having a dynamic friction coefficient of 0.3 to 3.5 on both surfaces of the film and satisfying the following formula (1).
Formula (1): 25 nm ≦ Re ≦ 140 nm
(In formula (1), Re represents the retardation value in the in-plane direction of the film measured at a wavelength of 590 nm.)
[2] The optical film according to [1], which satisfies the following formula (1 ′).
Formula (1 ′): 30 nm ≦ Re ≦ 100 nm
(In the formula (1 ′), Re represents the retardation value in the in-plane direction of the film measured at a wavelength of 590 nm.)
[3] The optical film according to [1] or [2], wherein the following formula (2) is satisfied.
Formula (2): 80 nm ≦ Rth ≦ 300 nm
(In Formula (2), Rth represents the retardation value in the film thickness direction measured at a wavelength of 590 nm.)
[4] The optical film according to any one of [1] to [3], wherein the thermoplastic resin is a cellulose acylate resin. [5] The total acyl substitution degree of the cellulose acylate resin. It is 2.1-2.6, The optical film as described in [4] characterized by the above-mentioned.
[6] The optical film according to any one of [1] to [5], wherein a core layer and at least one surface layer are laminated on both surfaces of the core layer.
[7] The optical film as described in [6], wherein the core layer and the surface layer both contain a cellulose acylate resin.
[8] The optical film as described in [6], wherein the core layer and the surface layer each contain a cellulose acylate resin having different degrees of total acyl substitution.
[9] The optical film as described in [7] or [8], wherein the cellulose acylate resin contained in the core layer has a total acyl substitution degree of 2.1 to 2.6.
[10] The optical film as described in any one of [1] to [9], wherein the internal haze is less than 0.03%.
[11] The optical film according to any one of [1] to [10], wherein an optically anisotropic layer is not laminated.
[12] A film that becomes at least one outermost layer of the optical film is formed by pouring a thermoplastic resin and a dope containing 0.03% by mass to 0.15% by mass of inorganic fine particles with respect to the thermoplastic resin. And a method of producing an optical film comprising a step and a step of stretching 20 to 40% of an optical film including a film to be the outermost layer in a direction perpendicular to the film conveying direction at a stretching temperature A ± 10 ° C. Where A represents the temperature (unit: ° C.) at which tan δ peaks when the dynamic viscoelasticity tan δ of cellulose acylate when the residual solvent amount is 0% is measured.
[13] The method for producing an optical film as described in [12], including a step of controlling the total film thickness of the optical film including the film to be the outermost layer to be 30 to 160 μm.
[14] The method for producing an optical film of [12] or [13], wherein a cellulose acylate resin is used as the thermoplastic resin.
[15] The surface layer dope and the core layer dope are sequentially cast or simultaneously co-cast so that the surface layer dope is laminated on both sides of the core layer dope. 14] The manufacturing method of the optical film as described in any one of 14.
[16] Any one of [12] to [14], wherein the surface layer dope and the core layer dope are simultaneously co-cast so that the surface layer dope is laminated on both sides of the core layer dope. The method for producing an optical film according to claim 1.
[17] The optical film as described in [15] or [16], wherein both of the surface layer dopes contain 0.03% to 0.15% by weight of inorganic fine particles with respect to the thermoplastic resin. Manufacturing method.
[18] The optical film as described in any one of [15] to [17], which includes a step of controlling the total thickness of the surface layers to be 0.5 to 9 μm.
[19] An optical film produced by the method for producing an optical film according to any one of [12] to [18].
[20] A polarizing plate using at least one optical film according to any one of [1] to [11] and [19].
[21] A liquid crystal display device using at least one optical film according to any one of [1] to [11] and [19].

  According to the present invention, the suitability for handling is good, the optical expression is high enough to improve the viewing angle characteristics when incorporated in a liquid crystal display device, and the contrast at the time of image display can be increased. An optical film and a method for producing the same can be provided. In addition, the liquid crystal display device of the present invention using the film of the present invention has improved viewing angle characteristics and high contrast during image display.

It is the schematic which shows an example when carrying out the fluent film formation of the laminated optical film of a 3 layer structure by simultaneous co-casting using the die for co-casting.

  Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value. In this specification, when the film of the present invention was produced by solution casting, the film surface on the side that was in contact with the support was called a band surface, and the film surface on the side that was not in contact with the support was The air side.

[Optical film]
The optical film of the present invention (hereinafter also referred to as the film of the present invention) contains a thermoplastic resin, has an XRF intensity of 0.6 to 15 when XRF measurement is performed on the film surface, and a total haze value of 0. 1 to 1.0%, the internal haze value is less than 0.07%, the dynamic friction coefficient on both surfaces of the film is 0.3 to 3.5, and satisfies the following formula (1) And
Formula (1): 25 nm ≦ Re ≦ 140 nm
(In formula (1), Re represents the retardation value in the in-plane direction of the film measured at a wavelength of 590 nm.)
Hereinafter, the film of the present invention will be described.

(XRF measurement of film surface)
The film of the present invention has an XRF intensity of 0.6 to 15 when XRF measurement is performed on the film surface. As the XRF intensity, two kinds of XRF intensity on the air surface side and XRF intensity on the band surface side can be measured, but the film of the present invention has an XRF intensity of 0 on both the air surface side and the band surface side. .6-15. When the XRF intensity is 0.6 or more, the total haze and dynamic friction coefficient of the optical film can be within the range of the present invention, and the handling ability can be improved. Furthermore, the contrast when incorporated in a liquid crystal display device can also be increased. When the XRF intensity is 15 or less, the dynamic friction coefficient can be within the range of the present invention while maintaining the entire haze of the optical film, the slipping of the optical film can be improved, and the handling ability can be improved.
The XRF intensity is preferably 0.6 to 10, and more preferably 0.6 to 5.

The XRF intensity in the present invention represents a value measured by the following method.
The amount of Si atoms (Si mg / m ² ) is measured by a calibration curve method using an X-ray fluorescence analyzer (XRF; X-ray Fluorescence Spectrometer). As a standard sample for preparing a calibration curve, a sodium silicate aqueous solution containing a known amount of Si atoms is uniformly dropped into an area of 30 mmφ on an aluminum substrate and then dried. There is no particular limitation on the model of the fluorescent X-ray analyzer, but in the present invention, the amount of Si atoms measured from the peak height of the Si-Kα spectrum under the following conditions using RIX3000 manufactured by Rigaku Denki Kogyo Co., Ltd. Adopted.
Equipment: RIX3000 manufactured by Rigaku Denki Kogyo Co., Ltd.
X-ray tube: Rh
Measurement spectrum: Si-Kα
Tube voltage: 50 kV
Tube current: 50 mA
Slit: COARSE
Spectroscopic crystal: RX4
Detector: F-PC
Analysis area: 30mmφ
Peak position (2θ): 144.75 deg.
Background (2θ): 140.70 deg. 146.85 deg.
Integration time: 80 seconds / sample
In the case of the above measurement conditions, the matting agent concentration that can be read by XRF measurement is an average value up to 20 μm from the film surface toward the film thickness direction.

(Haze)
The film of the present invention has a total haze value of 0.1 to 1.0%. When the total haze value is 0.1 to 1.0%, the contrast when the optical film is incorporated in a liquid crystal display device can be increased.
The total haze value is preferably 0.15 to 0.8%, and more preferably 0.2 to 0.7%. When the total haze is 0.2% or more, slipping with the handling roll can be ensured during handling for feeding and winding the roll film, scratches are less likely to occur, and handling suitability can be improved. In addition, the front and back surfaces do not adhere to each other during storage in a long roll state. Furthermore, the film also improves the adhesion between other substrates and films, and the saponification time for saponification treatment is shortened.

The film of the present invention has an internal haze of less than 0.07%. In the present specification, the internal haze is the surface scattering measured using an oil having a refractive index within ± 0.02 of the thermoplastic resin most contained in the film and covering both surfaces of the film with the oil. Haze value excluding components.
When the internal haze is less than 0.07%, the contrast when incorporated in the polarizing plate is increased, which is preferable. In order to suppress a decrease in contrast, the internal haze is more preferably less than 0.03%.

(Dynamic friction coefficient)
The film of the present invention has a dynamic friction coefficient of 0.3 to 3.5 on both surfaces of the film. If the dynamic friction coefficient is 0.3 or more, the creaking at the time of film conveyance can be improved, and the handling suitability can be improved. Moreover, if the said dynamic friction coefficient is 3.5 or less, the slipperiness at the time of film conveyance can be improved, and handling aptitude can be improved.
The dynamic friction coefficient is preferably 0.3 to 3.0 or less, and more preferably 0.3 to 2.0. In particular, it is preferable that the coefficient of dynamic friction is 3.0 or less because handling aptitude is remarkably improved.
In this specification, the dynamic friction coefficient is determined by adjusting the humidity of a film sample of 100 mm × 200 mm and 75 mm × 100 mm at 23 ° C. and a relative humidity of 65% for 2 hours, Tensilon tensile tester (RTA-100, manufactured by Orientec Co., Ltd.) ), A large film was fixed on a table, and a small film with a weight of 200 g was placed thereon. The weight F was measured by pulling the weight in the horizontal direction, and the dynamic friction coefficient μ _k was calculated from the following equation.
F = μ _k × W (W: weight of weight (Kgf))

(Retardation (Re, Rth))
The film of the present invention satisfies the following formula (1).
Formula (1): 25 nm ≦ Re ≦ 140 nm
In the formula (1), Re represents a retardation value in the in-plane direction of the film measured at a wavelength of 590 nm. When the film of the present invention has Re of 25 nm or more, viewing angle characteristics can be improved when incorporated in a liquid crystal display device.
In addition, the film of the present invention preferably satisfies the following formula (1 ′) from the viewpoint of increasing contrast and improving viewing angle characteristics.
Formula (1 ′): 30 nm ≦ Re ≦ 100 nm
Furthermore, it is more preferable to satisfy the following formula (1 ″) from the viewpoint of further increasing the contrast and improving the viewing angle characteristics.
Formula (1 ″): 40 nm ≦ Re ≦ 100 nm

The film of the present invention preferably satisfies the following formula (2) from the viewpoint of an increase in contrast when mounted on a VA liquid crystal display device.
Formula (2): 80 nm ≦ Rth ≦ 300 nm
(In Formula (2), Rth represents the retardation value in the film thickness direction measured at a wavelength of 590 nm.)
As for the film of this invention, it is more preferable that Rth is 90-270 nm, and it is especially preferable that it is 100-250 nm.

The preferred range of the retardation value of the film varies depending on the application.
The retardation value of the film of the present invention is preferably 25 nm ≦ Re ≦ 140 nm and 80 nm ≦ Rth ≦ 300 nm. Further, 30 nm ≦ Re ≦ 100 nm and 80 nm ≦ Rth ≦ 300 nm are more preferable, 40 nm ≦ Re ≦ 100 nm, and 90 nm <Rth <270 nm are particularly preferable, 45 nm <Re <80 nm, and More preferably, 100 nm <Rth <250 nm.

In this specification, Re (λ) and Rth (λ) respectively represent in-plane retardation and retardation in the thickness direction at a wavelength λ. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (when there is no slow axis, Rth (λ) With respect to the film normal direction (with an arbitrary direction as the rotation axis), the light of wavelength λ nm is incident from each inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side, and a total of 6 points are measured. KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), Rth can also be calculated from the following formula (A) and formula (B) based on the value, the assumed value of the average refractive index, and the input film thickness value.

注記：
上記のＲｅ（θ）は法線方向から角度θ傾斜した方向におけるレターデーション値を現す。
式（Ａ）におけるｎｘは面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘ及びｎｙに直交する方向の屈折率を表す。
式（Ｂ）
Ｒｔｈ＝（（ｎｘ＋ｎｙ）／２−ｎｚ）×ｄ

Note:
The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In formula (A), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, and nz represents the refractive index in the direction perpendicular to nx and ny. .
Formula (B)
Rth = ((nx + ny) / 2−nz) × d

When the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film without a so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) from −50 degrees to +50 degrees with respect to the film normal direction The light of wavelength λ nm is incident from each inclined direction in 10 degree steps and measured at 11 points. Based on the measured retardation value, the assumed average refractive index, and the input film thickness value, KOBRA 21ADH or WR is calculated.

In the above measurement, the assumed value of the average refractive index may be a value in a polymer handbook (John Wiley & Sons, Inc.) or a catalog of various optical films. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).
By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz.
In this specification, the measurement wavelength is 590 nm unless otherwise specified.

<Thermoplastic resin>
The optical film of the present invention contains a thermoplastic resin. The optical film of the present invention preferably contains a cellulose acylate resin as the thermoplastic resin.

(Cellulose acylate resin)
The cellulose acylate resin used in the present invention is not particularly defined. Examples of the cellulose as the acylate material include cotton linter and wood pulp (hardwood pulp, conifer pulp). Cellulose acylate obtained from any of the raw material celluloses can be used, and in some cases, they may be mixed and used. Detailed descriptions of these raw material celluloses can be found in, for example, Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, published by Nikkan Kogyo Shimbun (published in 1970), and the Japan Institute of Invention and Technology Publication No. 2001. The cellulose described in No.-1745 (pages 7 to 8) can be used.

First, the cellulose acylate preferably used in the present invention will be described in detail. Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio of the cellulose hydroxyl groups located at the 2nd, 3rd and 6th positions being esterified (100% esterification has a degree of substitution of 1).
The total degree of acyl substitution, that is, DS2 + DS3 + DS6 is preferably 2.1 to 2.9, more preferably 2.1 to 2.8, and particularly preferably cellulose contained in at least one layer from the viewpoint of expression of optical properties. The total acyl substitution degree of the acylate is 2.1 to 2.6. Further, DS6 / (DS2 + DS3 + DS6) is preferably 0.08 to 0.66, preferably 0.15 to 0.60, and more preferably 0.20 to 0.45. Here, DS2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with an acyl group (hereinafter also referred to as “degree of acyl substitution at the 2-position”), and DS3 is the degree of substitution of the hydroxyl group at the 3-position with an acyl group (hereinafter, referred to as “acyl group”). DS6 is the substitution degree of the hydroxyl group at the 6-position with an acyl group (hereinafter also referred to as “acyl substitution degree at the 6-position”). DS6 / (DS2 + DS3 + DS6) is the ratio of the acyl substitution degree at the 6-position to the total acyl substitution degree, and is hereinafter also referred to as “acyl substitution rate at the 6-position”.

Only one type of acyl group may be used in the film of the present invention, or two or more types of acyl groups may be used. The film of the present invention preferably has an acyl group having 2 to 4 carbon atoms as a substituent. When two or more kinds of acyl groups are used, one of them is preferably an acetyl group, and the acyl group having 2 to 4 carbon atoms is preferably a propionyl group or a butyryl group. DSA is the sum of the substitution degrees of the hydroxyl groups at the 2nd, 3rd and 6th positions by the acetyl group, and DSB is the sum of the substitution degrees of the 2nd, 3rd and 6th hydroxyl groups by the propionyl group or butyryl group. The value is preferably 2.3 to 2.6. The DSA + DSB value is preferably 2.35 to 2.55, and the DSB value is more preferably 0.10 to 1.70, more preferably the DSA + DSB value is 2.40 to 2.50, and the DSB value. Is 0.5 to 1.2. It is preferable that the DSA and DSB values be within the above ranges because a film having a small change in Re value and Rth value due to environmental humidity can be obtained.
That is, the cellulose acylate resin used in the film of the present invention is preferably cellulose acetate from the viewpoints of natural reducibility and environmental burden.
Further, 28% or more of DSB is a substituent at the 6-position hydroxyl group, more preferably 30% or more is a substituent at the 6-position hydroxyl group, and more preferably 31% or more is a substituent at the 6-position hydroxyl group. In particular, it is also preferred that 32% or more is a substituent of the 6-position hydroxyl group. With these films, a solution having preferable solubility can be prepared, and in particular, a non-chlorine organic solvent can be prepared with a good solution. Furthermore, it becomes possible to produce a solution having a low viscosity and good filterability.

  The acyl group having 2 or more carbon atoms of cellulose acylate in the present invention may be an aliphatic group or an allyl group, and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples thereof include propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, isobutanoyl group, tert -A butanoyl group, a cyclohexanecarbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, etc. can be mentioned. Among these, propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, tert-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like are more preferable, and propionyl group and butanoyl group are particularly preferable. is there.

  In the acylation of cellulose, when an acid anhydride or acid chloride is used as an acylating agent, an organic acid such as acetic acid or methylene chloride is used as an organic solvent as a reaction solvent.

As the catalyst, when the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acylating agent is an acid chloride (for example, CH ₃ CH ₂ COCl), Basic compounds are used.

  The most common industrial synthesis method of cellulose mixed fatty acid ester is to use cellulose corresponding to fatty acid corresponding to acetyl group and other acyl groups (acetic acid, propionic acid, valeric acid, etc.) or their anhydrides. This is a method of acylating with a mixed organic acid component.

  The cellulose acylate used in the present invention can be synthesized, for example, by the method described in JP-A-10-45804.

(Layer structure of film)
The film of the present invention may consist of one layer or two or more layers.
As for the film of this invention, it is more preferable that the surface layer of at least 1 layer is laminated | stacked on both surfaces of the core layer and this core layer. That is, the aspect of the film of the present invention having a laminated structure of three or more layers is preferable from the viewpoint of improving the degree of freedom in the step of realizing desired optical characteristics as an optical compensation film. The core layer refers to the thickest layer.
Moreover, when the film of this invention is a laminated film which consists of two or more layers, it is preferable that the film of this invention is co-cast.

The film of the present invention preferably contains inorganic fine particles in the surface layer from the viewpoint of increasing the total haze of the film and increasing the surface roughness of the film.
In the film of the present invention, the core layer preferably contains no inorganic fine particles from the viewpoint of lowering the internal haze of the film.

When the film of the present invention is composed of two or more layers, it is preferable not to include an adhesive or a pressure-sensitive adhesive between the respective layers from the viewpoint of reducing the production process. Can be manufactured by.
In addition, as an adhesive agent and an adhesive used when manufacturing the film of the multilayer structure adhere | attached through the adhesive agent or the adhesive, there exists description in Unexamined-Japanese-Patent No. 11-295527, for example.

In the case where the film of the present invention contains a cellulose acylate resin as the thermoplastic resin and consists of two or more layers, the core layer and the surface layer both contain a cellulose acylate resin from the viewpoint of optical characteristics. preferable. Moreover, the acyl group substitution degree of cellulose acylate in each layer may be uniform, or a plurality of cellulose acylates may be mixed in one layer. In the present invention, it is preferable that the core layer and the surface layer contain cellulose acylate resins having different degrees of total acyl substitution, from the viewpoint of achieving both expression of optical properties and handling suitability.
The average value of the total acyl substitution degree of the cellulose acylate resin contained in the film of the present invention is preferably 2.1 to 2.6, more preferably 2.2 to 2.5. Particularly preferred is 3 to 2.48.

When the film of the present invention comprises two or more layers, the average value of the total acyl substitution degree of the cellulose acylate resin contained in the core layer preferably satisfies 2.1 to 2.6, particularly from the viewpoint of expressing optical properties. preferable.
The average value of the total acyl substitution degree of the cellulose acylate resin contained in the core layer is more preferably 2.2 to 2.5, and particularly preferably 2.3 to 2.48.

In the film of the present invention, the core layer and the surface layer preferably contain cellulose acylate resins having different degrees of substitution.
The total acyl substitution degree of the cellulose acylate resin contained in the surface layer is more preferably 2.6 to 2.9, and particularly preferably 2.65 to 2.85.

  The film of the present invention preferably has no optically anisotropic layer laminated thereon. Since the film of the present invention expresses high retardation Re in the in-plane direction, viewing angle characteristics can be improved when incorporated in a liquid crystal display device even if an optically anisotropic layer is not laminated. Examples of the optically anisotropic layer generally include conventionally known optically anisotropic layers in optical film applications, and in particular, conventionally known optically anisotropic layers used in VA mode retardation films. For example, a layer obtained by polymerizing a polymerizable liquid crystalline compound.

(Film thickness)
The thickness of the film of the present invention (when it is composed of two or more layers) is preferably 30 to 160 μm. By controlling the total film thickness of the film, the Re expression level of the film and the total haze can be controlled within the scope of the present invention. Among them, the Re expression level of the film is particularly controlled within the scope of the present invention. It becomes important. The film thickness can be appropriately determined depending on the type of polarizing plate used, etc., preferably 35 to 155 μm, more preferably 40 to 140 μm, particularly preferably 40 to 100 μm, By making the thickness 60 μm or less, the cost can be reduced, which is preferable.

  When the film of the present invention comprises two or more layers, the film thickness ratio of the surface layer to the total film thickness (surface layer thickness + core layer thickness) is 0.005. It is preferable that it is -0.20, It is more preferable that it is 0.005-0.15, It is especially preferable that it is 0.01-0.10.

<Additives>
In the film of the present invention, as additives, inorganic fine particles (mat agent), non-phosphate ester compounds; retardation modifiers (retardation enhancers and retardation reducers); phthalate esters, phosphate esters Additives such as plasticizers such as series compounds; ultraviolet absorbers; antioxidants can also be added.

(Inorganic fine particles)
The film of the present invention preferably contains inorganic fine particles in at least one outermost layer from the viewpoint of controlling the XRF intensity within the range of the present invention, and more preferably contains inorganic fine particles in both outermost layers.

It is preferable to add inorganic fine particles (mat agent) to the film of the present invention. As inorganic fine particles used in the present invention, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Mention may be made of magnesium silicate and calcium phosphate. Inorganic fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. The silicon dioxide fine particles preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more. A primary particle having an average diameter of 5 to 30 nm is more preferable from the viewpoint of controlling the total haze of the film within the range of the present invention. The apparent specific gravity is preferably 10 to 100 g / liter or more, and more preferably 30 to 80 g / liter or more.
When the film of the present invention has a laminated structure of two layers, the inorganic fine particles are contained in at least one outermost layer. Moreover, when the film of this invention is a laminated structure of 3 or more layers, it is preferable that the said inorganic fine particle is contained in both the said surface layers.

  These fine particles usually form secondary particles having an average particle diameter of 0.1 to 3.0 μm, and these fine particles are present as aggregates of primary particles in the film, and 0.1 to 0.1 μm on the film surface. An unevenness of 3.0 μm is formed. The secondary average particle diameter is preferably 0.2 μm to 1.5 μm, more preferably 0.4 μm to 1.2 μm, and most preferably 0.6 μm to 1.1 μm. The primary and secondary particle diameters were determined by observing the particles in the film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle size. In addition, 200 particles were observed at different locations, and the average value was taken as the average particle size.

As fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used. The fine particles of zirconium oxide are commercially available under the trade names of Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.), and can be used.
Among these, Aerosil R972 is particularly preferable from the viewpoint of cohesiveness when preparing an inorganic fine particle dispersion.

In order to obtain a film having particles having a small secondary average particle size in the present invention, several methods are conceivable when preparing a dispersion of fine particles. For example, a method of preparing a fine particle dispersion in which a solvent and fine particles are mixed with stirring in advance, adding this fine particle dispersion to a small amount of cellulose acylate solution separately prepared, stirring and dissolving, and further mixing with the main cellulose acylate dope solution There is. This method is a preferable preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of cellulose ester to the solvent and dissolving with stirring, add fine particles to this and disperse with a disperser. This is used as a fine particle additive solution, and this fine particle additive solution is sufficiently mixed with the dope solution using an inline mixer. There is also a method of mixing. The present invention is not limited to these methods, but the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and 15 to 20%. Mass% is most preferred. A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved.
The matting agent concentration of the surface layer calculated from the XRF intensity measurement in the final cellulose acylate film is the case where the surface layer of at least one layer is laminated on both surfaces of the core layer and the core layer. The air surface side is preferably 0.6 to 12, more preferably 1.0 to 8.0, and particularly preferably 1.5 to 4.0. Moreover, it is preferable that it is 0.6-12 on a band surface side, It is more preferable that it is 1.0-8.0, It is especially preferable that it is 1.5-4.0.
The surface layer matting agent concentration calculated from the XRF intensity measurement in the final cellulose acylate film is preferably 0.6 to 12 on the air surface side in the case of a single-layer film. Is more preferably from 10 to 10, and particularly preferably from 4 to 8. Moreover, it is preferable that it is 0.6-12 on a band surface side, It is more preferable that it is 2-10, It is especially preferable that it is 4-8.

  The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of a cellulose ester.

(Non-phosphate compound)
The film of the present invention contains a phosphate ester compound or a non-phosphate ester polyester compound to suppress the phenomenon of the additive crying out of the film during wet heat durability, and the effect of the present invention Among these, it is also preferable from the viewpoint of reducing haze. Hereinafter, additives that can be used in the film of the present invention will be described in detail.

The film of the present invention preferably contains a non-phosphate ester compound in the low substitution degree layer. By including such a non-phosphate ester compound, the film of the present invention has an effect that it is difficult to whiten.
In the present specification, the “non-phosphate ester compound” refers to a “compound having an ester bond and the acid contributing to the ester bond other than phosphoric acid”. That is, the “non-phosphate ester compound” means a compound that does not contain phosphoric acid and is an ester compound.
Further, the non-phosphate ester compound may be a low molecular compound or a polymer (polymer compound). Hereinafter, a non-phosphate ester compound which is a polymer (polymer compound) is also referred to as a non-phosphate ester polymer.

  As the non-phosphate ester compound, known high molecular weight additives and low molecular weight additives can be widely employed as additives for cellulose acylate films. The content of the additive is preferably 1 to 35% by mass, more preferably 4 to 30% by mass, and still more preferably 10 to 25% by mass with respect to the cellulose resin.

  The high molecular weight additive used as the non-phosphate ester compound in the film of the present invention has a repeating unit in the compound, and preferably has a number average molecular weight of 700 to 10,000. The high molecular weight additive has a function of increasing the volatilization rate of the solvent and a function of reducing the residual solvent amount in the solution casting method. Furthermore, it exhibits useful effects from the viewpoint of film modification such as improvement in mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability.

Here, the number average molecular weight of the high molecular weight additive which is a non-phosphate ester compound in the present invention is more preferably a number average molecular weight of 700 to 8000, still more preferably a number average molecular weight of 700 to 5000, The number average molecular weight is preferably 1000 to 5000.
Hereinafter, the high molecular weight additive which is a non-phosphate ester compound used in the present invention will be described in detail with specific examples, but the high molecular weight which is a non-phosphate ester compound used in the present invention. Needless to say, the additives are not limited to these.

  Examples of the polymer additive that is a non-phosphate ester compound include polyester polymers (aliphatic polyester polymers, aromatic polyester polymers, etc.), copolymers of polyester components and other components, and the like. , Aliphatic polyester polymer, aromatic polyester polymer, polyester polymer (aliphatic polyester polymer, aromatic polyester polymer, etc.) and acrylic polymer and polyester polymer (aliphatic polyester polymer, aromatic A copolymer of an aromatic polyester polymer or the like) and a styrene polymer is preferable, and a polyester compound containing an aromatic ring as at least one of the copolymer components is more preferable.

  Examples of the aliphatic polyester-based polymer include at least one diol selected from aliphatic dicarboxylic acids having 2 to 20 carbon atoms, aliphatic diols having 2 to 12 carbon atoms, and alkyl ether diols having 4 to 20 carbon atoms. The both ends of the reaction product may be left as the reaction product, or the monocarboxylic acid, monoalcohol or phenol may be further reacted to carry out so-called end-capping. Good. It is effective in terms of storage stability that the end capping is performed in particular so as not to contain free carboxylic acids. The dicarboxylic acid used in the polyester polymer of the present invention is preferably an aliphatic dicarboxylic acid residue having 4 to 20 carbon atoms or an aromatic dicarboxylic acid residue having 8 to 20 carbon atoms.

  Examples of the aliphatic dicarboxylic acid having 2 to 20 carbon atoms preferably used in the present invention include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid. , Sebacic acid, dodecanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid.

  Among these, preferable aliphatic dicarboxylic acids are malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, and 1,4-cyclohexanedicarboxylic acid. Particularly preferably, the aliphatic dicarboxylic acid component is succinic acid, glutaric acid, or adipic acid.

  The diol utilized for the high molecular weight additive is selected from, for example, an aliphatic diol having 2 to 20 carbon atoms and an alkyl ether diol having 4 to 20 carbon atoms.

  Examples of the aliphatic diol having 2 to 20 carbon atoms include alkyl diols and alicyclic diols, such as ethane diol, 1,2-propanediol, 1,3-propanediol, and 1,2-butane. Diol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol) ), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3 -Methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl 1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Used as a mixture of two or more.

  Preferred aliphatic diols include ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1 , 4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, particularly preferred Is ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- Hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol.

  Preferred examples of the alkyl ether diol having 4 to 20 carbon atoms include polytetramethylene ether glycol, polyethylene ether glycol and polypropylene ether glycol, and combinations thereof. The average degree of polymerization is not particularly limited, but is preferably 2 to 20, more preferably 2 to 10, further 2 to 5, and particularly preferably 2 to 4. As examples of these, commercially useful polyether glycols typically include Carbowax, Pluronics and Niax resins.

In the present invention, a high molecular weight additive whose end is sealed with an alkyl group or an aromatic group is particularly preferable. This is because the terminal is protected with a hydrophobic functional group, which is effective against deterioration with time at high temperature and high humidity, and is due to the role of delaying hydrolysis of the ester group.
It is preferable to protect with a monoalcohol residue or a monocarboxylic acid residue so that both ends of the polyester additive of the present invention are not carboxylic acid or OH group.
In this case, the monoalcohol is preferably a substituted or unsubstituted monoalcohol having 1 to 30 carbon atoms, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol. , Octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, aliphatic alcohol such as dodecaoctanol, allyl alcohol, oleyl alcohol, benzyl alcohol, 3-phenyl Examples thereof include substituted alcohols such as propanol.

  End-capping alcohols that can be preferably used are methanol, ethanol, propanol, isopropanol, butanol, isobutanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, isooctanol, 2-ethylhexyl alcohol, isononyl alcohol, oleyl alcohol Benzyl alcohol, in particular methanol, ethanol, propanol, isobutanol, cyclohexyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol, benzyl alcohol.

  Moreover, when sealing with a monocarboxylic acid residue, the monocarboxylic acid used as a monocarboxylic acid residue is preferably a substituted or unsubstituted monocarboxylic acid having 1 to 30 carbon atoms. These may be aliphatic monocarboxylic acids or aromatic ring-containing carboxylic acids. Preferred aliphatic monocarboxylic acids are described, for example, acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid, and examples of the aromatic ring-containing monocarboxylic acid include Benzoic acid, p-tert-butylbenzoic acid, p-tert-amylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc. Yes, these can be used alone or in combination of two or more.

  The synthesis of the high molecular weight additive may be a hot melt condensation method using a polyesterification reaction or a transesterification reaction between the aliphatic dicarboxylic acid and a diol and / or a monocarboxylic acid or monoalcohol for end-capping by a conventional method. Alternatively, it can be easily synthesized by any of the interfacial condensation methods of acid chlorides of these acids and glycols. These polyester-based additives are described in detail in Koichi Murai, “Additives, Theory and Application” (Kokaibo Co., Ltd., first edition published on March 1, 1973). Also, JP-A Nos. 05-155809, 05-155810, JP-A-5-97073, JP-A-2006-259494, JP-A-07-330670, JP-A-2006-342227, JP-A-2007-003679. The materials described in each publication can also be used.

The aromatic polyester polymer is obtained by copolymerizing a monomer having an aromatic ring with the polyester polymer. The monomer having an aromatic ring is at least one monomer selected from aromatic dicarboxylic acids having 8 to 20 carbon atoms and aromatic diols having 6 to 20 carbon atoms.
Examples of the aromatic dicarboxylic acid having 8 to 20 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8- There are naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid. Among these, preferable aromatic dicarboxylic acids are phthalic acid, terephthalic acid, and isophthalic acid.

  Examples of the aromatic diol having 6 to 20 carbon atoms include, but are not limited to, bisphenol A, 1,2-hydroxybenzene, 1,3-hydroxybenzene, 1,4-hydroxybenzene, and 1,4-benzenedimethanol. Bisphenol A, 1,4-hydroxybenzene and 1,4-benzenedimethanol are preferred.

  In the present invention, the aromatic polyester-based polymer is used by combining at least one of each of aromatic dicarboxylic acid and aromatic diol with the above-mentioned polyester, but the combination is not particularly limited, and each component is not limited. There is no problem even if several types are combined. In the present invention, as described above, a high molecular weight additive whose end is sealed with an alkyl group or an aromatic group is particularly preferable, and the above-described method can be used for sealing.

  In the present invention, as the retardation reducing agent other than the non-phosphate ester compound, for example, a phosphate ester compound or a compound other than the ester ester known as an additive for the cellulose acylate film can be widely used. .

  The polymer retardation reducing agent is selected from phosphoric acid polyester polymers, styrene polymers, acrylic polymers, and copolymers thereof, and acrylic polymers and styrene polymers are preferred. Moreover, it is preferable that at least one polymer having negative intrinsic birefringence, such as a styrene polymer and an acrylic polymer, is included.

  Examples of the low molecular weight retardation reducing agent that is a compound other than a non-phosphate ester-based compound include the following. These may be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of an ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and a mixture of deterioration preventing agents are also possible. Furthermore, infrared absorbing dyes are described, for example, in JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the cellulose acylate solution (dope) preparation step, but it may be added by adding a preparation step to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested.

  Although it does not specifically limit as a low molecular weight retardation reducing agent which is compounds other than a non-phosphate ester type | system | group, The detail is described in Unexamined-Japanese-Patent No. 2007-272177 [0066]-[0085].

The compound described as the general formula (1) in [0066] to [0085] of JP-A-2007-272177 can be prepared by the following method.
The compound of the general formula (1) in the publication can be obtained by a condensation reaction between a sulfonyl chloride derivative and an amine derivative.

  JP, 2007-272177, A The compound of general formula (2) is a dehydration condensation reaction of carboxylic acids and amines using a condensing agent (for example, dicyclohexylcarbodiimide (DCC) etc.), or a carboxylic acid chloride derivative, It can be obtained by a substitution reaction with an amine derivative.

  The retardation reducing agent is more preferably an Rth reducing agent from the viewpoint of realizing a suitable Nz factor. Among the retardation reducing agents, examples of the Rth reducing agent include acrylic polymers and styrene polymers, and low molecular compounds represented by general formulas (3) to (7) in JP-A-2007-272177, and the like. Of these, acrylic polymers and styrene polymers are preferred, and acrylic polymers are more preferred.

The retardation reducing agent is preferably added at a rate of 0.01 to 30% by mass, more preferably 0.1 to 20% by mass, more preferably 0.1 to 10%, based on the cellulose resin. It is particularly preferable to add at a ratio of mass%.
By making the said addition amount 30 mass% or less, compatibility with a cellulose resin can be improved and whitening can be suppressed. When two or more types of retardation reducing agents are used, the total amount is preferably within the above range.

(Plasticizer)
As the plasticizer used in the present invention, many compounds known as cellulose acylate plasticizers can be usefully used. As the plasticizer, phosphate ester compounds or carboxylic acid esters are used. Examples of the phosphate ester-based compound include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.

(Retardation expression agent)
The film of the present invention can develop a retardation in a desired in-plane direction with or without a retardation enhancer, but may further include a retardation enhancer. By adopting a retardation developer, high Re developability can be obtained at a low draw ratio. The type of the retardation developing agent is not particularly defined, and examples thereof include those composed of a rod-like or discotic compound and compounds exhibiting retardation development among the non-phosphate ester compounds. As the rod-like or discotic compound, a compound having at least two aromatic rings can be preferably used as a retardation developer.
Two or more retardation developing agents may be used in combination.
The retardation developer preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

As the retardation developer, for example, compounds described in JP-A-2004-50516 and JP-A-2007-86748 can be used, but the present invention is not limited thereto.
Examples of the discotic compound include a compound described in European Patent Application No. 0911656A2, a triazine compound described in Japanese Patent Application Laid-Open No. 2003-344655, and a method described in Japanese Patent Application Laid-Open No. 2008-150592 [0097] to [0108]. The triphenylene compound to be used can also be preferably used.

  The discotic compound can be synthesized by a known method such as a method described in JP-A No. 2003-344655 and a method described in JP-A No. 2005-134484.

  In addition to the aforementioned discotic compound, a rod-shaped compound having a linear molecular structure can also be preferably used. For example, the rod-shaped compounds described in JP 2008-150592 A [0110] to [0127] are preferably used. it can.

Two or more rod-shaped compounds having a maximum absorption wavelength (λmax) longer than 250 nm in the ultraviolet absorption spectrum of the solution may be used in combination.
The rod-like compound can be synthesized with reference to methods described in the literature. References include Mol. Cryst. Liq. Cryst., 53, 229 (1979), 89, 93 (1982), 145, 111 (1987), 170, 43 Page (1989), J. Am. Chem. Soc., 113, 1349 (1991), 118, 5346 (1996), 92, 1582 (1970), J. Org Chem., 40, 420 (1975), Tetrahedron, 48, 16, 3437 (1992).

(Polarizer)
The film of the present invention can be applied to a polarizing plate using at least one film of the present invention.
The polarizing plate preferably has a polarizer and the film of the present invention on one surface of the polarizer. As with the optical compensation film of the present invention, the polarizing plate is not only a polarizing plate in the form of a film piece cut to a size that can be incorporated into a liquid crystal display device as it is, but also in a long form by continuous production. The polarizing plate of the aspect (for example, aspects with roll length 2500m or more, 3900m or more) wound up in roll shape is also contained. In order to use for a large-screen liquid crystal display device, the width of the polarizing plate is preferably 1470 mm or more as described above.
The specific configuration of the polarizing plate is not particularly limited and a known configuration can be adopted. For example, the configuration shown in FIG. 6 of Japanese Patent Application Laid-Open No. 2008-262161 can be adopted.

(Liquid crystal display device)
The film of the present invention can be applied to a liquid crystal display device having the polarizing plate.
The liquid crystal display device is a liquid crystal display device having a liquid crystal cell and a pair of polarizing plates disposed on both sides of the liquid crystal cell, wherein at least one of the polarizing plates is the polarizing plate of the present invention. An OCB or VA mode liquid crystal display device is preferable.
The specific configuration of the liquid crystal display device is not particularly limited, and a known configuration can be adopted. Further, the configuration described in FIG. 2 of JP-A-2008-262161 can also be preferably employed.

[Method for producing optical film]
The optical film manufacturing method of the present invention (hereinafter also referred to as the manufacturing method of the present invention) includes a thermoplastic resin and a dope containing 0.03% to 0.15% by weight of inorganic fine particles based on the thermoplastic resin. Fluently forming the film that is the outermost layer of at least one of the optical films and the optical film including the film that is the outermost layer at a stretching temperature A ± 10 ° C. in a direction perpendicular to the film transport direction 40% stretching step (where A represents the temperature at which tan δ shows a peak when the dynamic viscoelasticity tan δ of cellulose acylate when the residual solvent amount is 0% is measured) ).
According to the production method of the present invention, the handling ability, which has not been known so far, is good, and has a high optical expression so that the viewing angle characteristics can be improved independently when incorporated in a liquid crystal display device. The optical film of the present invention that can increase the contrast at the time of display can be produced.

  The film of the present invention is produced by a solution casting method (solvent casting method). About the manufacture example of the cellulose acylate film using a solvent cast method, U.S. Pat. Nos. 2,336,310, 2,367,603, 2,492,078, 2,492,977, 2,492,978, 2,607,704, 2,739,069 and 2,739,070, British Patent Nos. 640731 and 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, JP-A-60-203430, and JP-A-62-115035 can be referred to. Further, the film of the present invention is subjected to a stretching treatment. Regarding the stretching treatment methods and conditions other than those specified in the present specification, for example, JP-A-62-115035 and JP-A-4-152125. Gazettes, 4-284221, 4-298310, 11-48271, and the like.

<Preparation of dope>
In the solvent cast method, a film can be produced using a solution (dope) in which a thermoplastic resin is dissolved in an organic solvent.
The organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain. The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogenated hydrocarbon hydrogen atoms replaced with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. Methylene chloride is a typical halogenated hydrocarbon.
Two or more organic solvents may be mixed and used.

A thermoplastic resin solution can be prepared by a general method. The general method means that the treatment is performed at a temperature of 0 ° C. or higher (room temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly, methylene chloride) as the organic solvent.
The amount of the thermoplastic resin is preferably adjusted so as to be contained in the obtained solution in an amount of 10 to 40% by mass. The amount of the thermoplastic resin is more preferably 10 to 30% by mass. The thermoplastic resin is the same as the preferred range in the film of the present invention, preferably a cellulose acylate resin or a cyclic olefin resin, more preferably a cellulose acylate resin, and particularly preferably cellulose acetate. preferable. In the organic solvent (main solvent), arbitrary additives may be added from the additives mentioned as additives that can be preferably added to the film of the present invention. In the manufacturing method of the present invention, the dope contains inorganic fine particles.
The solution can be prepared by stirring the thermoplastic resin and the organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, a thermoplastic resin and an organic solvent are placed in a pressure vessel and sealed, and stirred while being heated to a temperature equal to or higher than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.
When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.
It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.
Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

<Casting method>
As a solution casting method, a method in which the prepared dope is uniformly extruded from a pressure die onto a metal support, and a method using a doctor blade in which the dope once cast on the metal support is adjusted with a blade is used. Although there is a method using a reverse roll coater that adjusts with a reverse rotating roll, a method using a pressure die is preferred. The pressure die includes a coat hanger type and a T die type, and any of them can be preferably used. Moreover, when using the method by a pressure die, the method which can adjust a film thickness highly among the well-known methods is more preferable. In addition to the methods mentioned here, it can be carried out by various known methods for casting a cellulose triacetate solution, and each condition is set in consideration of differences in the boiling point of the solvent used. Thus, the same effects as those described in the respective publications can be obtained.

In the production method of the present invention, a thermoplastic resin and a dope containing 0.03% to 0.15% by mass of inorganic fine particles are poured into the thermoplastic resin to form at least one outermost layer of the optical film. Form a film. When the film of the present invention is a single layer, this outermost film becomes the film of the present invention as it is. On the other hand, when the film of the present invention is composed of two or more layers, it is preferably at least one outermost layer of the film of the present invention and both outermost layers of the film of the present invention.
In addition, the inorganic fine particles contained in the dope for forming the outermost film is 0.03 relative to the thermoplastic resin in the dope when the film of the present invention is formed by co-casting. Mass% to 0.15 mass%, preferably 0.04 to 0.15 mass%, more preferably 0.05 mass% to 0.15 mass%, and 0.06 to 0.15 mass%. It is particularly preferably 14% by mass, and more preferably 0.06 to 0.12% by mass.
On the other hand, when the film of the present invention is formed as a single layer, it is 0.03% by mass to 0.15% by mass and 0.03 to 0.10% by mass with respect to the thermoplastic resin in the dope. It is preferably 0.03 to 0.07% by mass, particularly preferably 0.04 to 0.05% by mass.

It is preferable that the manufacturing method of this invention includes the process controlled so that the total film thickness of the optical film containing the film used as the said outermost layer may be set to 30-160 micrometers. A film to be at least one outermost layer of an optical film obtained by fluently irradiating a dope containing a thermoplastic resin and 0.03% by mass to 0.15% by mass of inorganic fine particles with respect to the thermoplastic resin in this range. By controlling the total film thickness of the film, it is possible to control the amount of Re expression of the film and the total haze within the scope of the present invention, and in particular, it is important for controlling the amount of Re expression of the film within the scope of the present invention. It becomes.
In the production method of the present invention, it is more preferable to control the total film thickness of the optical film including the outermost film to be 35 to 155 μm, particularly preferably 40 to 140 μm, and 40 to 100 μm. It is more particularly preferable.

(Co-casting)
When the film of the present invention comprises two or more layers, it is preferable to use a lamination casting method such as simultaneous co-casting (multilayer simultaneous casting) method, sequential casting method, coating method, etc. The casting method and the sequential casting method are more preferred, and the simultaneous co-casting method is particularly preferred from the viewpoints of stable production and production cost reduction.

When manufacturing by the co-casting method and the sequential casting method, first, a thermoplastic resin solution (dope) for each layer is prepared. In the production method of the present invention, the surface layer dope and the core layer dope are preferably sequentially or simultaneously co-cast so that the surface layer dope is laminated on both sides of the core layer dope. More preferably, it is cast.
That is, in the production method of the present invention, the thermoplastic resin, a dope containing 0.03% by mass to 0.15% by mass of inorganic fine particles with respect to the thermoplastic resin, and at least one kind of core containing the thermoplastic resin. The dope for the layer is sequentially flowed so that the thermoplastic resin and the dope containing the inorganic fine particles of 0.03 to 0.15% by mass with respect to the thermoplastic resin are laminated on both sides of the dope for the core layer. It is preferable to perform casting or simultaneous co-casting. In the production method of the present invention, the thermoplastic resin, a dope containing 0.03% by mass to 0.15% by mass of inorganic fine particles with respect to the thermoplastic resin, and at least one core layer containing a thermoplastic resin are used. Simultaneously co-casting the dope so that both sides of the core layer dope are laminated with the thermoplastic resin and a dope containing 0.03% by mass to 0.15% by mass of inorganic fine particles with respect to the thermoplastic resin. More preferably.

  In the production method of the present invention, it is sufficient that at least one of the surface layer dopes contains 0.03% to 0.15% by weight of inorganic fine particles with respect to the thermoplastic resin. In the production method of the present invention, both the surface layer dope is inorganic from the viewpoint of improving both the air surface side XRF intensity and the band surface side XRF intensity in matting agent concentration measurement using XRF and improving the dynamic friction coefficient. It is particularly preferable to contain 0.03% to 0.15% by weight of fine particles with respect to the thermoplastic resin.

  In the production method of the present invention, including the step of controlling the total thickness of the surface layer to be 0.5 to 9 μm improves the XRF intensity in the matting agent concentration measurement using XRF of the obtained optical film. From the viewpoint of increasing the contrast when the optical film is incorporated in a liquid crystal display device. The total film thickness of the surface layer is more preferably 0.5 to 8 μm, particularly preferably 1 to 7 μm, and particularly preferably 1.5 to 6 μm.

In the production method of the present invention, it is preferable to use a cellulose acylate resin as the thermoplastic resin. In that case, in the production method of the present invention, the dope containing 0.03% by mass to 0.15% by mass of inorganic fine particles with respect to the thermoplastic resin and the thermoplastic resin, and the dope for the core layer are substituted. It is more preferable to contain cellulose acylate resins having different from each other.
In the production method of the present invention, the average value of the total acyl substitution degree of the cellulose acylate resin contained in the core layer dope preferably satisfies 2.1 to 2.6, and the more preferable range is the film of the present invention. This is the same as the preferable range in the description of.

  In the simultaneous co-casting method (multi-layer simultaneous casting), the casting dope for each layer (which may be two layers or more) is provided on a casting metal support (band or drum) from another slit or the like. This is a casting method in which a dope is extruded from a casting gela which is extruded at the same time, and each layer is cast at the same time, peeled off from a metal support at an appropriate time, and dried to form a film. HYPERLINK "http://www6.ipdl.inpit.go.jp/Tokujitu/tjitemdrw.ipdl?N0000=231&N0500=4E#N/;=?=9=%3e9%3e///&N0001=4&N0552=9&N0553=000043 "\ t" tjitemdrw "Fig. 1 is a cross-sectional view of a state where a co-casting giesser 3 is used to extrude and cast three surface layer dopes 1 and a core layer dope 2 on a casting metal support 4 simultaneously. Shown in the figure.

  In the sequential casting method, the dope for the outermost layer is first extruded from a casting giusa on a casting metal support, cast, dried, or dried without being dried or dried. The dope for casting (for the core layer) is extruded by casting from the caster, and if necessary, the dope is cast and laminated sequentially up to the third layer and peeled off from the metal support at an appropriate time. And then casting to form a film.

  On the other hand, the coating method generally involves forming a core layer film into a film by a solution casting method, preparing a coating solution to be applied to the surface layer, and using a suitable coating machine, the film is applied one side at a time or simultaneously on both sides. Is a method of forming a laminated film by applying and drying a coating solution.

For example, it is possible to co-cast dopes having different additive concentrations such as the above-mentioned plasticizers, ultraviolet absorbers, inorganic fine particles (matting agents), etc., and to produce an optical film having a laminated structure having different additive concentrations in each layer. The inorganic fine particles can increase the concentration in the surface layer dope and decrease the concentration in the core layer dope. In the production method of the present invention, the surface layer dope preferably contains inorganic fine particles, and the core layer dope preferably contains no inorganic fine particles from the viewpoint of reducing the internal noise.
More plasticizers and UV absorbers can be added to the core layer dope than the surface layer dope, or only the core layer dope. Moreover, the kind of a plasticizer and a ultraviolet absorber can also be changed with the dope for core layers, and the dope for surface layers. Moreover, it is also a preferable aspect that a release agent is contained only in the surface layer dope on the metal support side. It is also preferable to add more alcohol, which is a poor solvent, to the surface layer dope than to the core layer dope in order to cool the metal support by the cooling drum method to gel the solution. The Tg of the surface layer dope may be different from the Tg of the core layer dope, and the Tg of the core layer dope is preferably lower than the Tg of the surface layer dope. Also, the viscosity of the solution containing the thermoplastic resin during casting may be different between the surface layer dope and the core layer dope, and the viscosity of the surface layer dope is preferably smaller than the viscosity of the core layer dope. The viscosity of the layer dope may be smaller than the viscosity of the surface layer dope.

  In the production method of the present invention, it is also preferred that the thermoplastic resins contained in the surface layer dope and the core layer dope are different. When the cellulose acylate resin is used as the thermoplastic resin, it is preferable that the total acyl substitution degree of the cellulose acylate resin contained in each of the surface layer dope and the core layer dope is different.

  The endlessly running metal support used for producing the film of the present invention includes a drum whose surface is mirror-finished by chrome plating and a SUS (stainless) belt (which is called a band) whose surface is mirror-finished by surface polishing. May be used). One or more pressure dies may be installed above the metal support. Preferably 1 or 2 groups. When two or more are installed, the amount of dope to be cast may be divided into various ratios for each die, or the dope may be fed to the dies from each of a plurality of precision quantitative gear pumps. The temperature of the cellulose acylate solution used for casting is preferably −10 to 55 ° C., more preferably 25 to 50 ° C. In that case, all solution temperatures in the process may be the same or different at different points in the process. If they are different, the temperature may be a desired temperature just before casting.

<Extension process>
The production method of the present invention is characterized in that it comprises a step of stretching 20 to 40% of the optical film including the film serving as the outermost layer in a direction perpendicular to the film conveying direction at a stretching temperature A ± 10 ° C. (however, A represents the temperature at which tan δ shows a peak when the dynamic viscoelasticity tan δ of cellulose acylate when the residual solvent amount is 0% is measured). In the method for producing a film of the present invention, at least one of an optical film obtained by pouring a dope containing a thermoplastic resin and 0.03% by mass to 0.15% by mass of inorganic fine particles with respect to the thermoplastic resin. By including a process of stretching the optical film including the film serving as the outermost layer under the above specific conditions, it is possible to achieve both improvement in transportability and reduction in haze, and high expression of Re.
In the film production method of the present invention, the film stretching direction under the above-mentioned specific conditions is a direction (width direction, TD direction) orthogonal to the film transport direction, but in the film transport direction unless it is contrary to the spirit of the present invention. May also be stretched.

  A is a temperature at which tan δ showed a peak when the dynamic viscoelasticity tan δ of cellulose acylate having a residual solvent amount of 0% was measured by vibron, and is a temperature specific to each film. Although there is no restriction | limiting in particular as a vibron used when measuring dynamic viscoelasticity, For example, IT measurement control Co., Ltd. make and brand name DVA200 can be used.

  In the production method of the present invention, a cellulose acylate resin is used as the thermoplastic resin, and the film is stretched by 25 to 40% in a direction orthogonal to the film transport direction in the stretching step, and the Re of the film of the present invention is controlled within a preferable range. It is more preferable from a viewpoint to do, and it is especially preferable to extend | stretch 30 to 40% in the direction orthogonal to a film conveyance direction.

  The temperature during stretching in the direction perpendicular to the film conveying direction is preferably from the stretching temperature A-10 ° C to the stretching temperature A + 10 ° C, and from the stretching temperature A-5 ° C to the stretching temperature A + 5 ° C. It is particularly preferred.

  Examples of the method of stretching in the direction perpendicular to the film conveying direction include, for example, JP-A-62-115035, JP-A-4-152125, JP-A-4284221, JP-A-4-298310, and JP-A-11-48271. It is described in the publication. In the case of stretching in the film transport direction (longitudinal direction), for example, the film is stretched by adjusting the speed of the film transport roller to make the film winding speed faster than the film stripping speed. In the case of stretching in the direction perpendicular to the film transport direction, the film can also be stretched by transporting the film while holding the film with a tenter and gradually widening the tenter. After the film is dried, it can be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine).

  When using an optical film as a protective film for a polarizer, the transmission axis of the polarizer and the slow axis in the plane of the optical film are placed in parallel to suppress light leakage when the polarizing plate is viewed from an oblique direction. There is a need to. Since the transmission axis of the roll film-shaped polarizer produced continuously is generally parallel to the width direction of the roll film, the protective film comprising the roll film-shaped polarizer and the roll film-shaped optical film. In order to continuously bond the film, the in-plane slow axis of the roll film-like protective film needs to be parallel to the width direction of the film. Therefore, it is preferable to stretch more in the width direction. In addition, the stretching treatment may be performed during the film forming process, or the raw film that has been formed and wound may be stretched, but in the production method of the present invention, the stretching is performed in a state containing a residual solvent. In order to carry out, it is preferable to extend | stretch in the middle of a film forming process.

<Drying>
The drying of the dope on the metal support involved in the production of the optical film is generally performed by applying hot air from the surface side of the metal support (drum or belt), that is, the surface of the web on the metal support, A method of applying hot air from the back surface of the drum or belt, contacting the temperature-controlled liquid from the back surface opposite the belt or drum dope casting surface, and heating the drum or belt by heat transfer to control the surface temperature. Although there is a liquid heat transfer method, the back surface liquid heat transfer method is preferable. The surface temperature of the metal support before casting may be any number as long as it is not higher than the boiling point of the solvent used for the dope. However, in order to promote drying and to lose fluidity on the metal support, the temperature should be set to 1 to 10 ° C. lower than the boiling point of the lowest boiling solvent. Is preferred. This is not the case when the cast dope is cooled and peeled off without drying.

  The film thickness may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap of the die base, the extrusion pressure from the die, the metal support speed, and the like so as to obtain a desired thickness.

<Winding>
The length of the optical film obtained as described above is preferably wound at 100 to 10,000 m per roll, more preferably 500 to 7000 m, and further preferably 1000 to 6000 m. The width of the optical film is preferably 0.5 to 5.0 m, more preferably 1.0 to 3.0 m, and still more preferably 1.0 to 2.5 m. When winding, it is preferable to give knurling to at least one end, the knurling width is preferably 3 mm to 50 mm, more preferably 5 mm to 30 mm, and the height is preferably 0.5 to 500 μm, more preferably 1 to 200 μm. is there. This may be a single push or a double push.

  In general, in a large-screen display device, since the contrast reduction and coloration in an oblique direction become remarkable, the film of the present invention is particularly suitable for use in a large-screen liquid crystal display device. When used as an optical compensation film for a large-screen liquid crystal display device, for example, the film width is preferably set to 1470 mm or more. In addition, the optical compensation film of the present invention is produced not only in the form of a film piece cut into a size that can be incorporated into a liquid crystal display device as it is, but also in a long shape by continuous production, and in a roll shape. The film of the aspect wound up by this is also included. The optical compensation film of the latter mode is stored and transported in that state, and is cut into a desired size and used when actually incorporated into a liquid crystal display device or bonded to a polarizer or the like. Similarly, it is cut into a desired size when it is actually assembled into a liquid crystal display device after being bonded together with a polarizer made of a polyvinyl alcohol film or the like that has been formed into a long shape. Used. As one mode of the optical compensation film wound up in a roll shape, a mode in which the roll length is rolled up to 2500 m or more can be mentioned.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

  In the present invention, measurement was performed by the following measurement method.

(XRF intensity and calculated matting agent concentration)
The XRF intensity was measured for each of the air surface side and the band surface side of the film sample 40 mm × 80 mm of the present invention in an environment of 60 ° C. and 90% relative humidity by the method described in this specification. The obtained XRF intensities are shown in Tables 6 and 7 below.
Moreover, based on the standard sample which prescribed | regulated the mat | matte agent density | concentration and the film thickness, the calibration curve of following Table 1 regarding XRF intensity | strength and a mat | matte agent density | concentration was created. From the measured values obtained above, the matting agent concentration was calculated for each of the air surface side and the band surface side using the calibration curve described in Table 1 below. The obtained results are shown in Tables 6 and 7 below.
In Table 1, X represents the intensity calculated by XRF, and Y represents the film thickness (unit: μm).

(All haze)
The total haze was measured by measuring a 40 mm × 80 mm film sample of the present invention at 25 ° C. and a relative humidity of 60% with a haze meter (HGM-2DP, Suga Test Instruments) according to JIS K-6714. The results are shown in Tables 6 and 7 below.

(Internal haze)
First, the refractive index of the film sample 40 mm × 80 mm of the present invention was measured by an Abbe refractometer (“Abbe refractometer 2-T” manufactured by Atago Co., Ltd.).
Next, a few drops of oil having a refractive index within ± 0.02 of the thermoplastic resin most contained in the film is added to the front and back surfaces of the film sample, and a 1 mm thick glass plate (microslide A glass haze meter (HGM-2DP) in which two glass plates and the obtained film are optically closely adhered and all hazes are removed by using two glass product numbers S 9111 (manufactured by MATAUNAMI). The haze was measured according to JIS K-6714 using a Suga test machine, and a value obtained by subtracting the haze measured by sandwiching only oil between two separately measured glass plates was calculated as the internal haze of the film.
Since the film samples using the cellulose acylate resins obtained in Examples and Comparative Examples had a refractive index of 1.48 to 1.49, the measurement was performed using liquid paraffin having a refractive index of 1.48.
Further, in the present invention, the measurement was performed 30 times by the above method, and the average value was defined as internal noise. The results are shown in Tables 6 and 7 below.

(Dynamic friction coefficient)
The dynamic friction coefficient of the obtained film was measured by the method described in this specification. The results are shown in Tables 6 and 7 below.

(Handling aptitude)
A film with a width of 1 m was prepared, a weight of 10 kg was applied to both sides, a 0.1 mΦ pass roll was reciprocated 50 cm, and then 5 times, and then the surface of the film was scratched and observed with respect to the film. The results of haze measurement were classified according to the following classification. The results are shown in Tables 6 and 7 below.
○: There is no scratch on the surface, and the haze value does not increase.
(Triangle | delta): Although the damage | wound of a surface is confirmed with a microscope, a haze value does not rise.
X: There are scratches on the surface, and the increase in haze value is less than 0.3%.
XX: There are scratches on the surface, and the increase in haze value is 0.3% or more.

(Optical expression)
Re and Rth were measured at a wavelength of 590 nm by KOBRA 21ADH (manufactured by Oji Scientific Instruments) by the above method. The results are shown in Tables 6 and 7 below.

[A: Co-cast film]
About the Example and comparative example which manufactured the film which consists of two or more layers, the optical film was formed with the following method.

(1) Preparation of Cellulose Acylate Resin by Synthesis Cellulose acylate having an acyl substitution degree shown in Table 1 was prepared. Sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, carboxylic acid was added, and an acylation reaction was performed at 40 ° C. Thereafter, the total substitution degree and the 6-position substitution degree were adjusted by adjusting the amount of sulfuric acid catalyst, the amount of water and the aging time. The aging temperature was 40 ° C. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.

(2) Dope Preparation <2-1> Dope for Core Layer The following composition is put into a mixing tank, stirred to dissolve each component, further heated to 90 ° C. for about 10 minutes, and then a filter paper having an average pore size of 34 μm and It filtered with the sintered metal filter with an average hole diameter of 10 micrometers.
――――――――――――――――――――――――――――――――――
Dope for core layer of Example 1 ――――――――――――――――――――――――――――――――――
・ Cellulose acetate (Substitution degree 2.41) 100.0 parts by mass Additive B 18.5 parts by mass Methylene chloride 365.5 parts by mass Methanol 54.6 parts by mass ―――――――――――――――――――――――

  Additive A is compound D-1 of JP-A-2009-222994. The structure of the additive A will be described below together with the structures of the additives H and I.

添加剤Ｂ〜Ｇについては下記表２に記載のものである。なお、下記表２中、ＥＧはエチレングリコールを、ＰＧはプロピレングリコールを、ＢＧはブチレングリコールを、ＴＰＡはテレフタル酸を、ＰＡはフタル酸を、ＡＡはアジピン酸を、ＳＡはコハク酸をそれぞれ示している。
また、前記添加剤の添加量は、各コア層用ドープ中に含まれる熱可塑性樹脂に対する質量％である。

Additives B to G are those described in Table 2 below. In Table 2 below, EG represents ethylene glycol, PG represents propylene glycol, BG represents butylene glycol, TPA represents terephthalic acid, PA represents phthalic acid, AA represents adipic acid, and SA represents succinic acid. ing.
Moreover, the addition amount of the said additive is the mass% with respect to the thermoplastic resin contained in each dope for core layers.

<2-2> Cellulose acylate dope for surface layer The following composition was put into a mixing tank, stirred to dissolve each component, further heated to 90 ° C. for about 10 minutes, and then a filter paper having an average pore size of 34 μm and an average pore size of 10 μm. And filtered with a sintered metal filter.
――――――――――――――――――――――――――――――――――
Surface layer dope of Example 1 ――――――――――――――――――――――――――――――――――
Cellulose acetate (substitution degree 2.81) 100.0 parts by mass Compound B 11.0 parts by mass Matting agent (Aerosil R972) 0.035 parts by mass Methylene chloride 365.5 parts by mass Methanol 54.6 parts by mass ――――――――――――――――――――――――――――――――――

  As shown in Tables 4 and 5 below, other surface layer dopes were prepared in the same manner as the surface layer dope of Example 1, except that the total acyl substitution degree of the cellulose acylate resin, the type of matting agent and the amount of matting agent added were changed. Was prepared.

(3) Co-casting The core layer dope and the surface layer dope were simultaneously co-cast so as to be a core layer and a surface layer having thicknesses described in Tables 4 and 5 below. The band was made of SUS.

(4) Stretching The obtained web (film) was peeled from the band, sandwiched between clips, and when the amount of residual solvent relative to the total film mass was 30 to 5% under the conditions of fixed end uniaxial stretching, the following Table 4 And it extended | stretched in the direction (lateral direction) orthogonal to a film conveyance direction using the tenter with the extending | stretching temperature and extending | stretching ratio of 5 described.
Thereafter, the clip was removed from the film and dried at 130 ° C. for 20 minutes. At this time, the cast film thickness was adjusted so that the film thickness after stretching became the film thickness (unit: μm) described in Tables 4 and 5. For the purpose of producing films having the compositions shown in Tables 4 and 5 and judging the suitability for production, 24 rolls having a roll width of 1280 mm and a roll length of 2600 mm were produced under the above conditions. About 1 roll in 24 rolls manufactured continuously, a 1-m long sample (width 1280 mm) was cut out at intervals of 100 m, and each measurement was performed.

[B: Single layer film]
About the other Example and comparative example which manufactured the single layer film, the optical film was formed with the following method.

(1) Preparation of Cellulose Acylate Resin Cellulose acylate resin was prepared by the same method as the production of the co-cast film. In addition, “propionyl” described in the following Tables 4 and 5 represents a cellulose acetate propionate resin having a total acyl substitution degree of 2.36 and a propionyl substitution degree of 0.8.

(2) Dope Preparation <2-1> Thermoplastic Resin Solution The following composition is put into a mixing tank, stirred to dissolve each component, further heated to 90 ° C. for about 10 minutes, a filter paper having an average pore size of 34 μm, and It filtered with the sintered metal filter with an average hole diameter of 10 micrometers.
――――――――――――――――――――――――――――――――――
Cellulose acylate solution of Comparative Example 9 ――――――――――――――――――――――――――――――――――
Thermoplastic resin described in Tables 4 and 5 below 100.0 parts by mass Additive B described in Tables 4 and 5 below 18.5 parts by mass Methylene chloride 403.0 parts by mass Methanol 60.2 parts by mass ―――――――――――――――――――――――――――――

<1-2> Matting Agent Dispersion Next, the following composition containing the cellulose acylate solution prepared by the above method was charged into a disperser to prepare a matting agent dispersion.
――――――――――――――――――――――――――――――――――――
Matting agent dispersion of Comparative Example 9 ――――――――――――――――――――――――――――――――――――
-Matting agent (Aerosil R972) 0.2 parts by mass-Methylene chloride 72.4 parts by mass-Methanol 10.8 parts by mass-Cellulose acylate solution 10.3 parts by mass ------- ―――――――――――――――――――――――

  100 parts by mass of the cellulose acylate solution of Comparative Example 9 and the matting agent dispersion of Comparative Example 9 were mixed in an amount of 0.02 parts by mass of inorganic fine particles with respect to the cellulose acylate resin, and the dope for film formation was mixed. Prepared.

  As shown in Table 5 below, the dopes of other examples and comparative examples were prepared in the same manner as the dope of Comparative Example 9, except that the type of thermoplastic resin, the additive addition amount, and the matting agent addition concentration were changed. did.

(3) Casting The above-described dope was cast using a band casting machine so as to have the film thicknesses shown in Table 5 below. The band was made of SUS.

(4) Stretching The obtained web (film) was peeled from the band, sandwiched between clips, and when the amount of residual solvent with respect to the mass of the entire film was in the state of 30 to 5% under the conditions of fixed end uniaxial stretching, the following Table 5 The film was stretched in the direction (lateral direction) perpendicular to the film conveying direction using a tenter at the stretching temperature and the stretching ratio described in 1.
Thereafter, the clip was removed from the film and dried at 130 ° C. for 20 minutes. At this time, the cast film thickness was adjusted so that the film thickness after stretching became the film thickness (unit: μm) described in Table 5. For the purpose of producing films having the compositions shown in Tables 5 and 7 and judging their production suitability, at least 24 rolls having a roll width of 1280 mm and a roll length of 2600 mm were produced under the above conditions. About 1 roll in 24 rolls manufactured continuously, a 1-m long sample (width 1280 mm) was cut out at intervals of 100 m, and each measurement was performed.

[C: Creation of polarizing plate]
A polarizer was produced by adsorbing iodine to a stretched polyvinyl alcohol film. The produced films of each Example and Comparative Example were attached to one side of a polarizer using a polyvinyl alcohol-based adhesive. The saponification treatment was performed under the following conditions.
A 1.5 mol / L aqueous sodium hydroxide solution was prepared and kept at 55 ° C. A 0.005 mol / L dilute sulfuric acid aqueous solution was prepared and kept at 35 ° C. The film produced in each Example and Comparative Example was immersed in the aqueous sodium hydroxide solution for 2 minutes, and then immersed in water to sufficiently wash away the aqueous sodium hydroxide solution. Subsequently, after being immersed in the above-mentioned dilute sulfuric acid aqueous solution for 1 minute, it was immersed in water to sufficiently wash away the dilute sulfuric acid aqueous solution. Finally, the sample was thoroughly dried at 120 ° C.
A commercially available cellulose triacylate film (Fujitac TD80UF, manufactured by Fuji Film Co., Ltd.) is saponified, and is attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive and dried at 70 ° C. for 10 minutes or more. did.
The transmission axis of the polarizer and the slow axis of the films of the examples and comparative examples were arranged in parallel. The transmission axis of the polarizer and the slow axis of the commercially available film were arranged so as to be orthogonal.

(Contrast during mounting after polarizing plate processing)
The polarizing plate was peeled off from the liquid crystal cell of BRAVIA-KDL40V5 (trade name, manufactured by Sony Corporation). Example: A pressure-sensitive adhesive is pasted on the polarizing plate obtained by preparing a polarizing plate on the side opposite to the polarizer of the film of each example and comparative example, and the film / adhesive / liquid crystal of each example or comparative example. The liquid crystal cells were bonded so that the cells were in the order. Contrast was measured for this liquid crystal display device. The results are shown in Tables 6 and 7 below.

From Tables 4 to 7, the film of the present invention has good handling suitability, has high optical expression that can improve the viewing angle characteristics independently when incorporated in a liquid crystal display device, and at the time of image display. It was found that the contrast could be increased.
On the other hand, Comparative Example 1 was such that the matting agent concentration in the surface layer dope was less than the range of the present invention, and the obtained optical film had all the XRF strength, total haze and dynamic friction coefficient within the range of the present invention. It was outside, and it was found that handling suitability and contrast at the time of mounting were poor.
In Comparative Example 2, the matting agent concentration in the surface layer dope was added in an amount exceeding the range of the present invention, and the obtained optical film had an XRF intensity outside the range of the present invention, and the contrast at the time of mounting was poor. I understood it.
In Comparative Example 3, the matting agent concentration in the surface layer dope was further reduced to 0 as compared with Comparative Example 1, and the obtained optical film had an XRF intensity and total haze outside the scope of the present invention. It was found that the aptitude and the contrast at the time of mounting were bad.
In Comparative Example 4, the stretching temperature was set to a temperature lower than the range of the present invention, and it was found that the obtained film had a total haze outside the range of the present invention, and the contrast at the time of mounting was poor.
In Comparative Example 5, the stretching temperature was set to a temperature exceeding the range of the present invention, and the obtained film had a coefficient of dynamic friction outside the range of the present invention, and it was found that handling suitability and contrast during mounting were poor.
Comparative Example 6 is a film production condition in which the matting agent concentration is 0.026% by mass. The obtained film has a dynamic friction coefficient outside the range of the present invention, and has poor handling suitability and mounting contrast. I understood it.
In Comparative Examples 9 and 11, in the single-layer casting, the matting agent concentration is an addition amount lower than the range of the present invention, and the obtained optical film has a total haze and a dynamic friction coefficient outside the range of the present invention. It turns out that handling aptitude is bad.
In Comparative Examples 10 and 12, in the single-layer casting, the matting agent concentration was an addition amount exceeding the range of the present invention, and the obtained optical film had an XRF strength and a dynamic friction coefficient outside the range of the present invention. It turned out that the contrast at the time of mounting was bad.
In Comparative Example 13, the draw ratio was set to be lower than the range of the present invention, and it was found that the obtained film had a Re of outside the range of the present invention and the contrast at the time of mounting was poor.
In Comparative Example 14, the draw ratio was set to a ratio exceeding the range of the present invention, and it was found that the obtained film had a total haze that was outside the range of the present invention, and the handling suitability and the contrast at the time of mounting were poor.
Comparative Examples 15 and 16 are film Nos. Described in JP-A-2009-222944. The film of Comparative Example 15 before application of the anisotropic layer thus obtained has a dynamic friction coefficient and optical properties that are out of the scope of the present invention, and Comparative Example 16 after application of the anisotropic layer. It was found that the dynamic friction coefficient on the coating side deviated from the range of the present invention.

1 Dope for surface layer 2 Dope for core layer 3 Co-casting Giesa 4 Casting support

Claims (21)

Including thermoplastics,
The XRF intensity when the XRF measurement of the film surface is performed is 0.6 to 15,
The total haze value is 0.1 to 1.0%,
The internal haze value is less than 0.07%, and the dynamic friction coefficient on both surfaces of the film is 0.3 to 3.5,
An optical film characterized by satisfying the following formula (1).
Formula (1): 25 nm ≦ Re ≦ 140 nm
(In formula (1), Re represents the retardation value in the in-plane direction of the film measured at a wavelength of 590 nm.) The optical film according to claim 1, wherein the following formula (1 ′) is satisfied.
Formula (1 ′): 30 nm ≦ Re ≦ 100 nm
(In the formula (1 ′), Re represents the retardation value in the in-plane direction of the film measured at a wavelength of 590 nm.) The optical film according to claim 1, wherein the following formula (2) is satisfied.
Formula (2): 80 nm ≦ Rth ≦ 300 nm
(In Formula (2), Rth represents the retardation value in the film thickness direction measured at a wavelength of 590 nm.)   The optical film according to claim 1, wherein the thermoplastic resin is a cellulose acylate resin.   The optical film according to claim 4, wherein the cellulose acylate resin has a total acyl substitution degree of 2.1 to 2.6.   The optical film according to any one of claims 1 to 5, wherein a core layer and at least one surface layer are laminated on both surfaces of the core layer.   The optical film according to claim 6, wherein the core layer and the surface layer both contain a cellulose acylate resin.   The optical film according to claim 6, wherein the core layer and the surface layer contain cellulose acylate resins having different degrees of total acyl substitution.   The optical film according to claim 7 or 8, wherein the total acyl substitution degree of the cellulose acylate resin contained in the core layer is 2.1 to 2.6.   Internal haze is less than 0.03%, The optical film as described in any one of Claims 1-9 characterized by the above-mentioned.   The optical film according to any one of claims 1 to 10, wherein an optically anisotropic layer is not laminated. A step of pouring a dope containing inorganic fine particles of 0.03% to 0.15% by mass with respect to the thermoplastic resin and the thermoplastic resin to form a film that is at least one outermost layer of the optical film;
A method for producing an optical film comprising the step of stretching the optical film including the film to be the outermost layer by 20 to 40% in a direction orthogonal to the film conveying direction at a stretching temperature A ± 10 ° C. A represents the temperature (unit: ° C.) at which tan δ peaks when the dynamic viscoelasticity tan δ of cellulose acylate when the residual solvent amount is 0% is measured.   The method for producing an optical film according to claim 12, comprising a step of controlling the total film thickness of the optical film including the outermost layer to be 30 to 160 μm.   The method for producing an optical film according to claim 12 or 13, wherein a cellulose acylate resin is used as the thermoplastic resin.   15. The surface layer dope and the core layer dope are sequentially or simultaneously co-cast so that the surface layer dope is laminated on both sides of the core layer dope. The manufacturing method of the optical film of one term.   The surface layer dope and the core layer dope are simultaneously co-cast so that the surface layer dope is laminated on both sides of the core layer dope. Manufacturing method of the optical film.   The method for producing an optical film according to claim 15 or 16, wherein both of the surface layer dopes contain 0.03% to 0.15% by weight of inorganic fine particles with respect to the thermoplastic resin.   The optical film according to any one of claims 15 to 17, comprising a step of controlling the total thickness of the surface layers to be 0.5 to 9 µm.   An optical film manufactured by the method for manufacturing an optical film according to any one of claims 12 to 18.   A polarizing plate comprising at least one optical film according to any one of claims 1 to 11 and 19.   A liquid crystal display device using at least one optical film according to any one of claims 1 to 11 and 19.

Images