JP2017219863A - Production method of cellulose acylate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a cellulose acylate film, which is a thin cellulose acylate film to be bonded to a polarizer by use of a photocurable adhesive to produce a polarizing plate, and which substantially prevents a failure such as breakage or increase in a haze value when the polarizing plate that has been adhered to a liquid crystal cell to constitute a liquid crystal panel is reworked from the liquid crystal panel.SOLUTION: The production method of a cellulose acylate film of the present invention aims to produce a cellulose acylate film having a film thickness of 10 μm or more and has the following characteristics. In first and second stretching steps for stretching a longitudinal direction and a width direction of the film, a stretching stress during stretching in the first stretching step is controlled to the range from 1 to 20 MPa, and a stretching stress during stretching in the second step is controlled to the range from 0.1 to 15 MPa; an elastic modulus in the longitudinal direction and an elastic modulus in the width direction of the cellulose acylate film are both within the range from 3.0 to 6.0 GPa; and an absolute value of the difference between the elastic modulus in the longitudinal direction and the elastic modulus in the width direction is within 2.0 GPa.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a cellulose acylate film. More specifically, it is a thinned cellulose acylate film, and the cellulose acylate film is bonded to a polarizer using a photocurable adhesive to produce a polarizing plate. The present invention relates to a method for producing a cellulose acylate film having excellent reworkability in which failure such as breakage or increase in haze value hardly occurs when reworking from a liquid crystal panel attached to a liquid crystal cell.

  In recent years, liquid crystal display devices such as liquid crystal televisions tend to be made thinner, and accordingly, cellulose acylate films that are generally used as members for polarizing plate protective films and the like are also required to be made thinner.

  However, a cellulose acylate film obtained by thinning a film produced by a solution casting method in the width direction at a high draw ratio is bonded to a polarizer using a photocurable adhesive. A polarizing plate is produced, and the produced polarizing plate is peeled off from the liquid crystal panel attached to the liquid crystal cell and re-attached (this operation is generally referred to as rework). It has been found that there is a problem in reworkability, such as a problem of breakage that is easy to tear, and an increase in haze estimated to be caused by bleeding out of additives due to stress during rework.

  In order to improve the strength of the polarizing plate, attempts have been made to improve the adhesion between the polarizer and the polarizing plate protective film, and to increase the strength of the polarizing plate protective film. Patent Document 1 uses an acrylic resin and a cellulose acylate resin, which are excellent in transparency and dimensional stability, and have a low hygroscopic property, and have improved brittleness, which is a defect of acrylic resin, and is suitable for a polarizing plate protective film. A film has been proposed. However, it has been found that this optical film does not have sufficient elongation at break and bending strength, causing problems in reworkability.

  With the reduction in thickness and size of displays, the technology has not provided sufficient reworkability, and a cellulose acylate film and a polarizing plate excellent in reworkability with further thin films have been desired.

International Publication No. 2009/047924

  The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is a thinned cellulose acylate film, which is polarized using a photocurable adhesive. When a polarizing plate is manufactured by pasting the polarizing plate, and the prepared polarizing plate is reworked from a liquid crystal panel attached to a liquid crystal cell, the rework property is less likely to cause failure such as breakage or increase in haze value. It is providing the cellulose acylate film excellent in, and the manufacturing method of the said cellulose acylate film. Furthermore, it is providing the thin-film polarizing plate and liquid crystal display device using the said cellulose acylate film.

  In order to solve the above problems, the present inventor is a cellulose acylate film formed by a solution casting method in the process of studying the cause of the above problems, and having a thickness in the range of 10 to 35 μm. When the absolute value of the difference between the modulus of elasticity in the longitudinal direction and the width direction and the modulus of elasticity is within a specific range, the cellulose acylate film uses a photocurable adhesive. Then, a polarizing plate is produced by bonding with a polarizer, and when the produced polarizing plate is reworked from a liquid crystal panel attached to a liquid crystal cell, a failure such as breakage or an increase in haze value occurs. I found it difficult.

  That is, the said subject which concerns on this invention is solved by the following means.

1. A cellulose acylate film production method for producing a cellulose acylate film having a thickness of 10 μm or more by a solution casting method,
The stretching stress at the time of stretching in the first stretching step when the web peeled from the casting support is stretched in the longitudinal direction and the width direction in the first stretching step and the second stretching step is 1 to Within the range of 20 MPa, the stretching stress during stretching in the second stretching step is within the range of 0.1-15 MPa,
When measured in an environment of 23 ° C. and 55 RH%, both the elastic modulus in the longitudinal direction and the elastic modulus in the width direction of the cellulose acylate film are within the range of 3.0 to 6.0 GPa, and the elastic modulus in the longitudinal direction. And a method for producing a cellulose acylate film, characterized in that an absolute value of a difference in elastic modulus in the width direction is within 2.0 GPa.

  2. The cellulose acylate film has an elongation at break in the longitudinal direction and an elongation at break in the width direction measured in an environment of 23 ° C. and 55 RH%, both within a range of 1 to 10%. The manufacturing method of the cellulose acylate film of Claim 1.

  3. The stretch ratio in the longitudinal direction and the stretch ratio in the width direction when the web peeled from the casting support is stretched in the longitudinal direction and the width direction in the first stretching step and the second stretching step. In each of the first and second items, wherein the ratio is 1.2 times or more and the product of the draw ratio in the longitudinal direction and the draw ratio in the width direction is within a range of 2.0 to 5.0 times The manufacturing method of the cellulose acylate film of description.

  4). When the amount of residual solvent in the web at the start of stretching in the first stretching step is in the range of 5 to 30% by mass, and the stretching temperature is Tg, the glass transition temperature of the cellulose acylate film is (Tg −30) to (Tg + 50) ° C., the residual solvent amount in the web at the start of stretching in the second stretching step is in the range of 1 to 20% by mass, and the stretching temperature is (Tg− The method for producing a cellulose acylate film according to any one of items 1 to 3, wherein the method is within a range of 10) to (Tg + 40) ° C.

  A cellulose acylate film thinned by the above means of the present invention, wherein the cellulose acylate film is bonded to a polarizer using a photocurable adhesive to produce a polarizing plate, and the produced film Production of a cellulose acylate film excellent in reworking property that is less likely to cause failure such as breakage or increase in haze value when reworking a polarizing plate from a liquid crystal panel attached to a liquid crystal cell, and the cellulose acylate film A method can be provided. In addition, a thin film polarizing plate and a liquid crystal display device using the cellulose acylate film can be provided.

  The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

  As described above, with the thinning of the polarizing plate and the liquid crystal display device, a high-quality and thin cellulose acylate film is required. As the film becomes thinner, the cellulose acylate film formed by a conventional method is required. Then, after processing a polarizing plate using a photocurable resin as an adhesive, it was found that there was a problem that the polarizing plate did not peel cleanly from the liquid crystal panel surface at the time of rework and was broken.

  As a result of examination, the cause of deterioration of reworkability is partly due to non-uniform adhesion between the cellulose acylate film and the polarizer by the photocurable adhesive, and the penetration of the photocurable adhesive into the film. This is presumed to be due to the fact that the film is biased or the film temperature locally rises due to heat at the time of photocuring, and the film becomes hung up.

  The former is presumed to be due to the fact that cellulose acylate molecules in the film tend to be in a non-uniform state by conventional stretching operations because the cellulose acylate film has been made thin.

  The latter is a thin film of cellulose acylate film that deforms even with a weak force, and the film when photocured is not smooth against the light-irradiated surface. it is conceivable that.

  As a result of further investigation, the problem of uneven penetration of the photocurable adhesive into the film and deformation of the film is that the elastic modulus of the cellulose acylate film is determined by the film longitudinal direction (MD direction) and the width direction (TD direction). ), The polarizing plate is presumed to be broken at the photocurable resin layer portion where the cellulose acylate film and the polarizer are bonded, depending on the peeling direction and the method of applying force during rework.

  As a result of repeated studies, the inventors of the present invention stretched the film in the longitudinal direction (MD direction) and the lateral direction (TD direction) at a high ratio in the longitudinal direction (MD direction) and the lateral direction (TD direction), respectively. As a result of adjusting the respective elastic modulus in the direction (TD direction) within a specific range, even in the case of a thin film, it is excellent in reworking property that does not easily cause failure such as breakage or increase in haze value at the time of polarizing plate rework. The present inventors have found that a cellulose acylate film can be provided.

Schematic diagram of an apparatus for producing the cellulose acylate film of the present invention

  The method for producing a cellulose acylate film of the present invention is a method for producing a cellulose acylate film by producing a cellulose acylate film having a film thickness in the range of 10 to 35 μm by a solution casting method. When the more peeled web is stretched in the longitudinal direction and the width direction in the first stretching step and the second stretching step, the stretching ratio in the longitudinal direction and the stretching ratio in the width direction are each 1.2 times or more. When the product of the draw ratio in the longitudinal direction and the draw ratio in the width direction is within the range of 2.0 to 5.0 times and measured in an environment of 23 ° C. and 55 RH%, the longitudinal direction of the cellulose acylate film The modulus of elasticity and the modulus of elasticity in the width direction are both within the range of 3.0 to 6.0 GPa, and the absolute value of the difference between the modulus of elasticity in the longitudinal direction and the modulus of elasticity in the width direction is 2.0 GPa. Characterized in that the inner. This feature is a technical feature common to the inventions according to claims 1 to 3.

  As an embodiment of the present invention, from the viewpoint of expression of the effect of the present invention, the elongation at break in the longitudinal direction and the elongation at break in the width direction of the cellulose acylate film are both in the range of 1 to 10%. The penetration of the photocurable adhesive into the film is not uneven, and the stress when reworking the produced polarizing plate from the liquid crystal panel attached to the liquid crystal cell is made uniform, such as breaking. This is preferable from the viewpoint of suppressing the occurrence of a failure and an increase in haze value.

  The method for producing a cellulose acylate film of the present invention is the stretch ratio in the longitudinal direction when the web peeled from the casting support is stretched in the longitudinal direction and the transverse direction in the first stretching step and the second stretching step. And the width direction draw ratio is 1.2 times or more, and the product of the longitudinal direction draw ratio and the width direction draw ratio is preferably in the range of 2.0 to 5.0 times. This is a manufacturing method for obtaining an elastic modulus.

  Furthermore, the stretching stress during stretching in the first stretching step is in the range of 1 to 20 MPa, and the stretching stress in stretching in the second stretching step is in the range of 0.1 to 15 MPa. The distribution of the resin molecules in the film in the longitudinal direction and the width direction is made uniform, and the force applied to the film when the produced polarizing plate is reworked from the liquid crystal panel attached to the liquid crystal cell in the above two directions. Is preferable because it can be made uniform.

  Further, when the amount of residual solvent in the web at the start of stretching in the first stretching step is in the range of 5 to 30% by mass, and the stretching temperature is Tg, the glass transition temperature of the cellulose acylate film, Within the range of (Tg-30) to (Tg + 50) ° C., the amount of residual solvent in the web at the start of stretching in the second stretching step is within the range of 1 to 20% by mass, and the stretching temperature is ( Tg-10) to (Tg + 40) C. is preferable from the viewpoint of preventing breakage during stretching and producing the desired cellulose acylate film with high productivity.

  Even if the polarizing plate in which the cellulose acylate film of the present invention is bonded to at least one surface of a polarizer using a photocurable resin is a thinned cellulose acylate film, breakage, etc. during polarizing plate rework Therefore, it is difficult to cause a failure and a haze value to increase, and it has excellent reworkability.

  Moreover, the polarizing plate which bonded the cellulose acylate film of this invention may be comprised suitably for a liquid crystal display device.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<Outline of Cellulose Acylate Film of the Present Invention>
The cellulose acylate film of the present invention is a cellulose acylate film formed by a solution casting method and having a film thickness in the range of 10 to 35 μm, and the cellulose measured in an environment of 23 ° C. and 55 RH% Both the elastic modulus in the longitudinal direction and the elastic modulus in the width direction of the acylate film are in the range of 3.0 to 6.0 GPa, and the absolute value of the difference between the elastic modulus in the longitudinal direction and the elastic modulus in the width direction With this configuration, a thin-film cellulose acylate film with excellent reworkability that is less prone to failure such as breakage and an increase in haze value during polarizing plate rework is provided. To do.

  Hereinafter, the longitudinal direction is referred to as the MD direction, and the width direction is referred to as the TD direction.

  In the present invention, the elastic modulus in both the MD direction and the TD direction is measured, and the elastic modulus is within a range of 3.0 to 6.0 GPa (measured in an environment of 23 ° C. and 55 RH%), and the elastic modulus The absolute value of the difference between the two values is within 2.0 in order to exhibit the effects of the present invention. The elastic modulus is more preferably in the range of 3.5 to 5.5 Gpa. Further, the absolute value of the difference in elastic modulus is more preferably within 1.0.

  If the elastic modulus is less than 3.0, the cellulose acylate film is not elastic and breakage and wrinkles are likely to occur during handling, and the film winding shape is also easily deteriorated at the center part to be transformed into a horse back.

  Moreover, it is difficult to produce a cellulose acylate film having an elastic modulus exceeding 6.0 GPa, and 6.0 GPa is considered the upper limit in the range of normal production conditions.

  When the absolute value of the difference in elastic modulus exceeds 2.0, the photocurable resin layer part where the cellulose acylate film and the polarizer are bonded depending on the direction of peeling or applying force during rework as described above Will break the polarizing plate.

  In order to adjust the elastic modulus within this range, there is no particular limitation. However, the cellulose acylate film may be stretched in the MD direction and the TD direction at a specific temperature and with a specific stretching ratio. It is preferable to take a means for axial stretching, and further, means for using a resin having a specific acyl group substitution degree and a specific weight average molecular weight range as cellulose acylate in order to perform the stretching in a method and a range preferable for the present invention, And a combination of means using an additive such as a plasticizer having a specific structure. Among these, a means for biaxial stretching in the MD direction and the TD direction at a specific stretching ratio at a specific temperature and a residual solvent is preferable.

(Measurement of elastic modulus)
The elastic modulus can be measured in accordance with JIS K 7127 by cutting a sample piece in the MD direction and the TD direction from the full width of the cellulose acylate film.

  Specifically, after leaving the sample in an environment of 23 ± 2 ° C. and 50 ± 5% RH for 24 hours, each sample has a width of 10 mm and a length of 200 mm so that the MD direction and the TD direction are respectively longer. Then, using the TG-2KN type tensile tester manufactured by Minebea, the above strip-shaped sample was set at a chucking pressure of 0.25 MPa and a distance between marked lines of 100 ± 10 mm. Pull at a speed of 100 ± 10 mm / min.

  Then, from the obtained tensile stress-strain curve, the elastic modulus calculation start point is 10 N, the end point is 30 N, and the tangent line drawn between them is extrapolated to obtain the elastic modulus in the MD direction and the TD direction.

  Further, the elongation at break in the MD direction and the elongation at break in the TD direction measured in an environment of 23 ° C. and 55 RH% of the cellulose acylate film of the present invention are both in the range of 1 to 10%. It is preferable. If it is in the said range, the said cellulose acylate film will be bonded with a polarizer using a photocurable adhesive agent, a polarizing plate will be produced, and the produced polarizing plate will be stuck to the liquid crystal cell. When reworking, the occurrence of failure such as breakage and the increase in haze value hardly occur, which is preferable. Among these, the range of 1 to 8% is more preferable, and the same means as the adjustment of the elastic modulus can be adopted for adjusting the elongation at break of the cellulose acylate film.

(Measurement of elongation at break)
First, the cellulose acylate film was cut into a size of 100 mm (MD direction) × 10 mm (TD direction) to obtain a sample film. The sample film was conditioned for 24 hours in an environment of 23 ° C. and 55% RH. In accordance with JIS K7127, the sample film after humidity adjustment was pulled in the MD direction using a Tensilon RTC-1225A manufactured by Orientec Co., Ltd., and the tensile strength was extended from the breaking point of the film to the breaking direction in the MD direction. Measure the degree. Further, the elongation at break in the TD direction is measured in the same manner except that the optical film is cut into a size of 10 mm (MD direction) × 100 mm (TD direction) and the direction in which the sample film is pulled is changed to the TD direction. The elongation at break was measured at 23 ° C. and 55% RH under the conditions of a tensile speed of 50 mm / min.

  Hereinafter, the present invention will be described in detail for each element.

<Cellulose acylate>
The cellulose acylate film of the present invention is an optical film for polarizing plate protective film and retardation film, containing cellulose acylate as a main component. A main component means that the content rate of the cellulose acylate in the said cellulose acylate film is 55 mass% or more. Preferably it is 70 mass% or more.

  The cellulose acylate according to the present invention preferably has an acyl group having 2 to 4 carbon atoms. Examples of the acyl group having 2 to 4 carbon atoms include an acetyl group, a propionyl group, and a butanoyl group.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxy groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by acylating part or all of these hydroxy groups with an acyl group. The total acyl group substitution degree means the ratio in which all the hydroxy groups of cellulose located at the 2nd, 3rd and 6th positions are acylated per one glucose unit (100% acylation has a degree of substitution of 3). .

  Examples of preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, Examples thereof include an isobutanoyl group, a tert-butanoyl group, a cyclohexanecarbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, and a cinnamoyl group. Among these, an acetyl group, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and an acetyl group is particularly preferable. A propionyl group and a butanoyl group (when the acyl group has 2 to 4 carbon atoms);

  The specific cellulose acylate is at least one selected from cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. Preferably there is.

  Among these, more preferred cellulose acylates are cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate and cellulose acetate butyrate, and particularly preferred cellulose acylate is cellulose triacetate. is there.

  Cellulose triacetate preferably has an average degree of acetylation (bound acetic acid amount) in the range of 54.0 to 62.5%, and more preferably has an average degree of acetylation in the range of 58.0 to 62.5%. Of cellulose triacetate.

  Cellulose diacetate preferably has an average degree of acetylation (bound acetic acid amount) in the range of 51.0% to 56.0%. Examples of commercially available products include L20, L30, L40, and L50 manufactured by Daicel Corporation, and Ca398-3, Ca398-6, Ca398-10, Ca398-30, and Ca394-60S manufactured by Eastman Chemical Japan Co., Ltd. .

  Cellulose acetate propionate or cellulose acetate butyrate has an acyl group having 2 to 4 carbon atoms as a substituent, the substitution degree of acetyl group is X, and the substitution degree of propionyl group or butyryl group is Y Those satisfying the following formulas (I) and (II) are preferred.

Formula (I) 2.0 ≦ X + Y ≦ 2.95
Formula (II) 0 ≦ X ≦ 2.5
Among them, it is preferable that 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9.

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

  The weight average molecular weight Mw of the cellulose acylate is preferably in the range of 80,000 to 300,000, and more preferably in the range of 120,000 to 200,000, from the viewpoint of controlling the elastic modulus and elongation at break. Within the above range, it is easy to control the elastic modulus by stretching during solution casting film formation, and it is possible to improve the elongation at break of the film and the bleed-out resistance.

  The number average molecular weight (Mn) of the cellulose acylate is preferably in the range of 30000 to 150,000 because the mechanical strength of the obtained cellulose acylate film is high. Further, cellulose acylate having a number average molecular weight of 40,000 to 100,000 is preferably used.

  The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose acylate is preferably in the range of 1.4 to 3.0.

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

  The measurement conditions are as follows.

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

  The cellulose acylate raw material cellulose used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferred. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

  For example, the ratio of cellulose acylate derived from cotton linter: cellulose acylate derived from wood pulp (conifer): cellulose acylate derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50. : 50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30 it can.

  The cellulose acylate according to the present invention can be produced by a known method. Generally, cellulose is esterified by mixing cellulose as a raw material, a predetermined organic acid (such as acetic acid or propionic acid), an acid anhydride (such as acetic anhydride or propionic anhydride), and a catalyst (such as sulfuric acid). The reaction proceeds until the triester is formed. In the triester, the three hydroxy groups of the glucose unit are substituted with an organic acid acyl acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose acylate such as cellulose acetate propionate or cellulose acetate butyrate can be produced. Next, cellulose acylate having a desired degree of acyl substitution is synthesized by hydrolyzing cellulose triester. Thereafter, cellulose acylate is completed through steps such as filtration, precipitation, washing with water, dehydration, and drying.

  The cellulose acylate according to the present invention has a pH of 6 when charged in 20 ml of pure water (electric conductivity 0.1 μS / cm or less, pH 6.8) and stirred in a nitrogen atmosphere at 25 ° C. for 1 hr. It is preferable that the electric conductivity is in the range of 1 to 100 μS / cm.

  Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

<Thermoplastic resin>
In the present invention, thermoplastic resins other than cellulose acylate can also be contained. Here, the “thermoplastic resin” refers to a resin that becomes soft when heated to the glass transition temperature or melting point and can be molded into a desired shape.

  It is preferable that the thermoplastic resin used in the present invention is easily manufactured and optically transparent.

  The term “transparent” as used in the present invention means that the total light transmittance of visible light is 60% or more, preferably 80% or more, and particularly preferably 90% or more.

  Although there is no particular limitation as long as it has the above properties, for example, acrylic resins such as polymethyl methacrylate, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polypropylene terephthalate, polyphenylene sulfide, polyphenylene oxide , Polycaprolactone, polycarbonate resin, norbornene resin, monocyclic olefin resin, cyclic conjugated diene resin, vinyl alicyclic hydrocarbon resin, and cyclic polyolefin resins such as hydrides thereof, polyarylate Resin, polysulfone (including polyethersulfone) resin, polyethylene, polypropylene, ABS resin, polylactic acid, cellophane, polyvinylidene chloride, polyvinyl alcohol, ethylene vinyl Examples include alcohols, syndiotactic polystyrene resins, norbornene resins, polymethylpentenes, polyether ketones, polyether ketone imides, polyamide resins such as nylon, fluorine resins, polyarylate, thermoplastic elastomers, silicones, etc. it can. Among these, an acrylic resin is preferable because the strength of the film can be improved and the optical characteristics can be adjusted.

<Additives>
(Sugar ester of disaccharide)
The cellulose acylate film of the present invention is a sugar ester of a disaccharide having a total average substitution degree represented by the following general formula (FA) in the range of 3.0 to 6.0 (hereinafter also simply referred to as a sugar ester). Is preferably used as a plasticizer from the viewpoint of controlling the elastic modulus during biaxial stretching and improving the tear strength.

（式中、Ｒ_１〜Ｒ_８は、各々独立に、水素原子、置換又は無置換のアルキルカルボニル基、若しくは、置換又は無置換のアリールカルボニル基を表し、Ｒ_１〜Ｒ_８は相互に同じであっても、異なっていてもよい。）
本発明に用いられる一般式（ＦＡ）で表される化合物の平均置換度は３．０〜６．０であることが、二軸延伸処理において本発明の効果を発現しやすく有効である。

(Wherein R _{1 to} R ₈ each independently represents a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group, and R _{1 to} R ₈ are the same as each other). Or it may be different.)
It is effective that the average substitution degree of the compound represented by the general formula (FA) used in the present invention is 3.0 to 6.0 because the effect of the present invention is easily manifested in the biaxial stretching treatment.

In the present invention, the degree of substitution of the compound represented by the general formula (FA) represents the number substituted with a substituent other than hydrogen among the eight hydroxy groups contained in the general formula (FA). Represents a number containing a group other than hydrogen among R _{1 to} R _{8 in} formula (FA). Therefore, when all of R _{1 to} R ₈ are substituted with a substituent other than hydrogen, the degree of substitution is 8.0, which is the maximum value, and when R _{1 to} R ₈ are all hydrogen atoms, 0.0 It becomes.

  The compound having the structure represented by the general formula (FA) is difficult to synthesize a single kind of compound in which the number of hydroxy groups and the number of OR groups are fixed. Since it is known that a compound in which several types of components having different groups are mixed is used, it is appropriate to use the average degree of substitution as the degree of substitution of the general formula (FA) in the present invention. The average substitution degree can be measured from the area ratio of the chart showing the substitution degree distribution by chromatography.

In General Formula (FA), R _{1 to} R ₈ represent a substituted or unsubstituted alkylcarbonyl group or a substituted or unsubstituted arylcarbonyl group, and R _{1 to} R ₈ may be the same or different. It may be.

  Examples of the sugar as a raw material for synthesizing the sugar ester according to the present invention include the following, but the present invention is not limited thereto.

  Glucose, galactose, mannose, fructose, xylose or arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose .

  In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.

  There is no restriction | limiting in particular as monocarboxylic acid used at the time of the synthesis | combination of the sugar ester used for this invention, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. The carboxylic acid used may be one kind or a mixture of two or more kinds.

  Examples of preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, Saturated lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, and laxaric acid Examples thereof include unsaturated fatty acids such as fatty acids, undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferable aromatic monocarboxylic acids include aromatic monocarboxylic acids having 1 to 5 alkyl groups or alkoxy groups introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, An aromatic monocarboxylic acid having two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid and tetralin carboxylic acid, or a derivative thereof can be mentioned, and benzoic acid is particularly preferable.

  Specific examples of the sugar ester used in the present invention will be given below. However, any one of R1 to R8 is the same substituent R, and the present invention is not limited thereto.

  The sugar ester used in the present invention can be produced by reacting a disaccharide with an acylating agent (also referred to as an esterifying agent, for example, an acid halide of acetyl chloride, an anhydride such as acetic anhydride). The distribution of the degree of substitution is made by adjusting the amount of acylating agent, the timing of addition, and the esterification reaction time, but it is possible to mix sugar esters with different degrees of substitution or purely isolated compounds with different degrees of substitution. By doing so, it is possible to adjust the target average substitution degree and components having a substitution degree of 4 or less.

(Synthesis Example: Synthesis of Compound Used in the Present Invention)

  Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube were charged with 34.2 g (0.1 mol) of sucrose, 135.6 g (0.6 mol) of benzoic anhydride, 284. 8 g (3.6 mol) was charged, the temperature was raised while bubbling nitrogen gas through a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours.

  Next, the inside of Kolben was depressurized to 4 × 10 2 Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of Kolben was depressurized to 1.3 × 10 Pa or less, the temperature was raised to 120 ° C., benzoic anhydride, Most of the produced benzoic acid was distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass aqueous sodium carbonate solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate a toluene layer. Finally, 100 g of water was added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer was collected, and toluene was distilled off at 60 ° C. under reduced pressure (4 × 10 2 Pa or less). The sugar ester 1 which is a mixture of 1, A-2, A-3, A-4, A-5, etc. was obtained.

  When the obtained mixture was analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS), A-1 was 1.2% by mass, A-2 was 13.2% by mass, and A-3 was 14.2% by mass. %, A-4 was 35.4% by mass, A-5 and the like were 40.0% by mass. The average degree of substitution was 5.2.

  Similarly, 158.2 g (0.70 mol) benzoic anhydride, 146.9 g (0.65 mol), 135.6 g (0.60 mol), 124.3 g (0.55 mol) and equimolar pyridine. To obtain sugar esters of components as shown in Table 1.

  Next, by purifying a part of the obtained mixture by column chromatography using silica gel, each of A-1, A-2, A-3, A-4, A-5 and the like having a purity of 100% is obtained. Obtained.

  A-5 or the like means a mixture of all components having a substitution degree of 4 or less, that is, compounds having a substitution degree of 4, 3, 2, 1. The average substitution degree was calculated with A-5 and the like being the substitution degree 4.

  In the present invention, the average degree of substitution was adjusted by adding in combination the sugar ester close to the desired degree of average substitution, isolated A-1 to A-5, and the like by the method prepared here.

<Measurement conditions for HPLC-MS>
1) LC section Device: JASCO Corporation column oven (JASCO CO-965), detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50)
Column: Inertsil ODS-3 Particle size 5 μm 4.6 × 250 mm (manufactured by GL Sciences Inc.)
Column temperature: 40 ° C
Flow rate: 1 ml / min
Mobile phase: THF (1% acetic acid): H2 O (50:50)
Injection volume: 3 μl
2) MS unit Device: LCQ DECA (manufactured by Thermo Quest Co., Ltd.)
Ionization method: Electrospray ionization (ESI) method Spray Voltage: 5 kV
Capillary temperature: 180 ° C Vaporizer temperature: 450 ° C
(Polyester compound)
In the present invention, in addition to the sugar ester, it is preferable to use a polyester compound represented by the following general formula (FB) as a plasticizer from the viewpoint of controlling the elastic modulus during biaxial stretching and improving the tear strength.

Formula (FB) B- (GA) n-GB
(Wherein B is a hydroxy group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms) A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In general formula (FB), a hydroxy group or a carboxylic acid residue represented by B, an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue represented by G, an alkylene dicarboxylic acid residue represented by A or It is composed of an aryl dicarboxylic acid residue and can be obtained by the same reaction as that of a normal ester compound.

  Examples of the carboxylic acid component of the polyester compound represented by the general formula (FB) include acetic acid, propionic acid, butyric acid, benzoic acid, p-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, and dimethylbenzoic acid. , Ethyl benzoic acid, normal propyl benzoic acid, aminobenzoic acid, acetoxybenzoic acid, aliphatic acid and the like, and these can be used as one kind or a mixture of two or more kinds.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester compound represented by the general formula (FB) include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, , 3-butanediol, 1,2-propanediol, 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-dimethylol) Heptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl-1,3-pen Diols, 2-ethyl 1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Is used as one or a mixture of two or more.

  In particular, alkylene glycols having 2 to 12 carbon atoms are particularly preferable because of excellent compatibility with cellulose acylate.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the polyester compound represented by the general formula (FB) include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Yes, these glycols can be used as one or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the polyester compound represented by the general formula (FB) include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecane. There exist dicarboxylic acid etc., and these are each used as a 1 type, or 2 or more types of mixture. Examples of the aryl dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and the like.

  The polyester compound represented by the general formula (FB) has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxy group (hydroxyl group) value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxy group (hydroxyl group) value is 15 mgKOH / g or less. Is.

  Although the specific compound of the polyester-type compound represented by general formula (FB) which can be used for this invention below is shown, this invention is not limited to this.

  The cellulose acylate film of the present invention preferably contains the sugar ester and the polyester-based compound in the range of 0.1 to 30% by mass, particularly in the range of 0.5 to 10% by mass of the cellulose acylate film. Is preferred.

(Plasticizer)
The cellulose acylate film of the present invention can contain other plasticizers as necessary to obtain the effects of the present invention.

  The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or an ester plasticizer. Agent, acrylic plasticizer and the like.

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

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

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (a).

Formula (a) R11- (OH) n
However, R11 represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxy group.

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

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

  In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with cellulose acylate is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as an alkyl group, a methoxy group or an ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. A higher molecular weight is preferable because it is less likely to volatilize, and a lower molecular weight is preferable in terms of moisture permeability and compatibility with cellulose acylate.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  As specific compounds of the polyhydric alcohol ester, compounds described in paragraphs [0058] to [0061] of JP-A-2006-113239 are preferable. The

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

Formula (b) R12 (COOH) m1 (OH) n1
In the formula, R12 represents an (m1 + n1) -valent organic group, m1 represents a positive integer of 2 or more, n1 represents an integer of 0 or more, a COOH group represents a carboxy group, and an OH group represents an alcoholic or phenolic hydroxy group.

  Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxy group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or derivatives thereof can be mentioned. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose acylate.

  The alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of the retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxy group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

(UV absorber)
The cellulose acylate film of the present invention preferably contains an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet rays of 400 nm or less, and in particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, and further Preferably it is 2% or less.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products made by BASF Japan and can be preferably used.

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

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

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

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition.

  For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose acylate to disperse and then added to the dope.

  The amount of UV absorber used is not uniform depending on the type of UV absorber, operating conditions, etc., but when the dry film thickness of the cellulose acylate film is 10 to 35 μm, it is 0.5% relative to the cellulose acylate film. The range of -10 mass% is preferable, and the range of 0.6-4 mass% is still more preferable.

(Phase difference increasing agent)
The cellulose acylate film of the present invention can contain a retardation increasing agent in order to adjust the retardation. For example, the phase difference increasing agent can be contained in a proportion in the range of 0.5 to 10% by mass, and more preferably in a proportion in the range of 2 to 6% by mass. The kind of the phase difference increasing agent is not particularly defined, but examples thereof include those made of a disk-like or rod-like compound. As the disk-like or rod-like compound, a compound having at least two aromatic rings can be preferably used as a retardation increasing agent.

  The discotic retardation increasing agent is preferably used in a range of 0.5 to 10 parts by mass, more preferably in a range of 1 to 8 parts by mass with respect to 100 parts by mass of the cellulose acylate. More preferably, it is used in the range of 2 to 6 parts by mass.

  As the discotic retardation increasing agent, compounds described in paragraphs [0143] to [0179] of JP-A-2006-113239 can be preferably used.

  The addition amount of the retardation increasing agent composed of the rod-shaped compound is preferably in the range of 0.5 to 10 parts by mass, more preferably in the range of 2 to 6 parts by mass with respect to 100 parts by mass of the cellulose acylate. . As the rod-like retardation increasing agent, compounds described in JP-A-2006-113239 can be preferably used.

  Further, two or more kinds of retardation increasing agents may be used in combination.

  The phase difference increasing agent preferably has maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

(Antioxidant)
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose acylate film may be deteriorated.

  The antioxidant has a role of delaying or preventing the cellulose acylate film from being decomposed by, for example, halogen in the residual solvent amount in the cellulose acylate film or phosphoric acid of the phosphoric acid plasticizer. It is preferable to make it contain in a cellulose acylate film.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably in the range of 1 ppm to 1.0% by mass with respect to the cellulose acylate, and more preferably in the range of 10 to 1000 ppm.

(Fine particles)
The cellulose acylate film of the present invention has, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, silicic acid in order to improve handleability. It is preferable to include a matting agent such as inorganic fine particles such as aluminum, magnesium silicate and calcium phosphate, and a crosslinked polymer. Of these, silicon dioxide is preferable because it can reduce the haze of the film.

  The primary average particle diameter of the fine particles is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm.

  These fine particles preferably form secondary particles having a particle size in the range of 0.1 to 5 μm and are contained in the cellulose acylate film, and the preferable average particle size is in the range of 0.1 to 2 μm, and more preferably. Is in the range of 0.2 to 0.6 μm. Thereby, the unevenness | corrugation about 0.1-1.0 micrometer high can be formed in the film surface, and this can give appropriate slipperiness to the film surface.

  The primary average particle size of the fine particles used in the present invention is measured by observing the particles with a transmission electron microscope (magnification of 500,000 to 2,000,000 times), observing 100 particles, measuring the particle size, and measuring the average value. The primary average particle diameter was determined.

<Production apparatus for cellulose acylate film>
First, an apparatus for producing a cellulose acylate film used for carrying out the method for producing a cellulose acylate film of the present invention will be described.

  As shown in FIG. 1, the cellulose acylate film manufacturing apparatus 1 according to this embodiment includes a casting apparatus 101, a first stretching apparatus 102, a second stretching apparatus 103, a drying apparatus 104, and a winding apparatus. 105, and while transporting the casting film (web) 3 formed by the casting apparatus 101, the longitudinal direction (MD direction) or the width direction (direction orthogonal to the conveying direction) by the first stretching apparatus 102, In the MD direction or TD direction in the second stretching device 103, dried (heat treatment) in the drying device 104, and wound up as a cellulose acylate film in the winding device 105. Yes. The web 3 may be dried by disposing a drying device between the first stretching device 102 and the second stretching device 103.

  Here, the cast film (web) refers to a state in which a dope in which a resin, an additive and the like are dissolved is cast on a cast support, formed into a film, and peeled off.

[Casting device]
The casting apparatus 101 is a metal endless belt having a mirror-finished surface (a metal cylindrical drum having a mirror-finished surface instead of an endless belt) 101a as a support, and a resin solution. The die 101b for casting the (dope) 2 on the endless belt 101a, the heating device 101c for removing the solvent from the dope 2 cast on the endless belt 101a, and the endless belt 101a were formed. And a peeling roller 4 for peeling the web 3 from the endless belt 101a. The endless belt 101a is wound around a driving roller 101a1 and a driven roller 101a2, and can travel in the direction of an arrow in the figure. The peeling roller 4 is disposed at an end portion on the side where the dope 2 is cast on the endless belt 101a. The casting apparatus 101 includes a casting process in which the resin solution (dope) 2 is cast on the endless belt 101a, and a casting film (web) 3 of the dope 2 formed on the endless belt 101a is peeled from the endless belt 101a. The peeling process to perform is performed.

  When the dope 2 is cast on the endless belt 101a from the die 101b, the dope 2 gels on the endless belt 101a to form a cast film (web) 3. The web 3 formed on the endless belt 101 a is peeled from the endless belt 101 a by the peeling roller 4. Here, the thickness of the web 3 on the endless belt 101a can be changed to various values so that the thickness of the cellulose acylate film wound up by the winding device 105 becomes a predetermined thickness. The thickness of the web 3 on the endless belt 101a is adjusted according to the casting amount of the dope 2, the traveling speed of the endless belt 101a, and the like.

  The heating device 101c includes a drying box 101c1, a first heating air supply device 101d disposed in the drying box 101c1, a second heating air supply device 101e, and an exhaust port 101f. The first heating air supply device 101d and the second heating air supply device 101e include heating air supply pipes 101d1 and 101e1 and headers 101d2 and 101e2, respectively.

  The temperature of the web 3 on the endless belt 101a on the first heating air supply device 101d side and the temperature of the web 3 on the endless belt 101a on the second heating air supply device 101e side are based on the time required for evaporation of the solvent, respectively. Considering the travel speed of the endless belt 101a to be determined, the degree of dispersion of fine particles in the dope 2, productivity, and the like, for example, a range of −5 ° C. to 70 ° C. is preferable, and a range of 0 ° C. to 60 ° C. is more preferable. .

  The wind pressure of the heating air supplied from the first heating air supply device 101d and the second heating air supply device 101e is, for example, from 50 Pa to 50 Pa in consideration of the uniformity of solvent evaporation, the degree of dispersion of fine particles in the dope 2, and the like. A range of 5000 Pa is preferred.

  The first heating air supply device 101d and the second heating air supply device 101e may supply only the heating air having a constant temperature, or stepwise the heating air having a plurality of temperatures along the traveling direction of the endless belt 101a. You may supply.

  The heating device 101c shown in FIG. 1 is for removing the solvent by heating the web 3 with heating air, but is not limited to this, for example, a device for heating the web 3 with an infrared heater, or the back surface of the endless belt 101a. It is also possible to heat the web 3 from the back side by spraying heated air.

  The time from casting the dope 2 on the endless belt 101a to peeling the web 3 from the endless belt 101a varies depending on the thickness of the produced cellulose acylate film, the type of solvent, etc. Considering good peelability from the belt 101a, for example, a range of 0.5 to 5 minutes is preferable.

  The endless belt 101a preferably has a mirror-finished surface. For example, a metal endless belt whose surface is plated with a casting is preferably used. The width of the endless belt 101a varies depending on the size of the cellulose acylate film to be produced, but is preferably in the range of 1700 mm to 2700 mm, for example. And the width | variety which casts dope 2 has the preferable range of 80%-99% among the width | variety of endless belt 101a, for example.

  When the web 3 formed on the endless belt 101a is peeled from the endless belt 101a, the residual solvent amount of the web 3 (the residual solvent amount of the web 3 at the time of peeling) is the peelability and peeling of the web 3 from the endless belt 101a. Considering the transportability of the subsequent web 3, retention by a tenter during stretching, the appearance and optical properties of the produced cellulose acylate film, for example, a range of 20 to 100% by mass is preferable, and 35 to 90% by mass. % Is more preferable, and the range of 45 to 80% by mass is more preferable. In addition, after peeling, the residual solvent amount of the web 3 when the web 3 starts to be stretched by the first stretching device 102 (the residual solvent amount of the web 3 when the first stretching device 102 starts stretching) depends on the tenter at the time of stretching. Considering retention, appearance and optical properties of the produced cellulose acylate film, for example, a range of 5 to 30% by mass is preferable, and the web is further dried until the first stretching device to adjust the residual solvent amount. It is preferable to do.

  Due to the tension (peeling tension) acting on the web 3 when the web 3 is peeled from the endless belt 101a and the tension acting on the web 3 (conveying tension) when the web 3 is transported after peeling, the web 3 Is stretched in the conveyance direction (MD direction) of the web 3. Considering this, the peeling tension and the transport tension are preferably in the range of 50 to 400 N / m, for example.

[First stretching device]
The first stretching device 102 includes an outer box 102a having a dry air intake port 102b and a discharge port 102c, and a stretching device 102d placed in the outer box 102a. The 1st extending | stretching apparatus 102 performs the 1st extending | stretching process of extending | stretching the web 3 peeled from the endless belt 101a to MD direction or TD direction.

  The stretching device 102d can stretch the web 3 in the MD direction or the TD direction as necessary. The dry air intake port 102b and the discharge port 102c may be reversed. Although the case where heated air is used is shown as the solvent removal means in the first stretching apparatus 102, the solvent removal means is not particularly limited, and other examples include means for heating with an infrared heater, for example.

  Drying in the first stretching apparatus 102 may be performed at a constant temperature, or may be divided into three to four stages of temperature and may be divided into several stages of temperature.

  The draw ratio in the MD direction in the first stretching step is expressed by the formula “stretch ratio in the MD direction in the first stretch process = web transport speed after the first stretch process / web transport speed before the first stretch process. Is required.

  Further, the stretching ratio in the TD direction is determined by the formula “stretching ratio in the TD direction in the first stretching process = width of the web after the first stretching process / width of the web before the first stretching process”. The width of the web is a value measured with a C-type JIS grade 1 steel scale.

  The tenter used in the stretching apparatus 102d is not particularly limited, and examples thereof include a clip tenter and a pin tenter from the viewpoint of versatility and ease of operation, and can be selected and used as necessary. For stretching in the MD direction, a conventionally known method, typically a heater heating method and an oven heating method, can be used.

  In the heater heating method, the temperature is instantaneously increased to the stretching temperature by a heater installed between the low-speed roller group and the high-speed roller group, and the stretching is performed with a relatively short stretching span.

  Since the width shrinkage due to stretching is reduced as the stretching span is shortened, the interval between the low speed roller group and the high speed roller group is preferably as short as possible. In the low-speed roller group, it is preferable to preheat to a temperature as close to the stretching temperature as possible within a range in which film adhesion and scratches do not occur.

  In the oven heating method, an oven is installed between a low-speed roller group and a high-speed roller group, and preheating, stretching, and cooling steps are included in the oven, and stretching is performed with a relatively long stretching span.

  The inside of the oven is preferably a floating that is stretched while being transported in a non-contact manner while the film is floated so that the hot air blown from nozzles arranged above and below the film passage does not come into contact with the nozzle. In addition, the upstream side from the entrance of the oven and the downstream side from the exit are generally held and conveyed by a suction roller and a guide roller at a holding angle capable of stably conveying the film.

  The heater heating method is advantageous in that the width shrinkage can be suppressed to be small, which is advantageous for forming a wide film, and that it can be installed in a relatively small space. The oven heating method has a uniform width of phase difference. There are advantages such as being high, and being hard to cause scratches and adhesion failures. The MD stretching method is appropriately selected in consideration of materials to be used and necessary physical properties.

[Second stretching device]
The second stretching device 103 has basically the same structure as the first stretching device 102. That is, the 2nd extending | stretching apparatus 103 is provided with the outer box 103a which has the dry wind inlet 103b and the discharge port 103c, and the extending | stretching apparatus 103d put in the outer box 103a. The second stretching device 103 performs a second stretching step of additionally stretching the web 3 stretched by the first stretching device 102 in a direction orthogonal to the stretching direction of the first stretching. The tenter used in the stretching apparatus 103d is not particularly limited, and examples thereof include a clip tenter and a pin tenter from the viewpoint of versatility and ease of operation, and can be selected and used as necessary. However, in this embodiment, in particular, in the second stretching step, it is preferable to use a clip tenter in order to grip and stretch the side portion of the web 3 that has been dried to some extent.

  The stretching device 103d can stretch the web 3 in the MD direction and the TD direction as necessary. Note that the dry air intake port 103b and the discharge port 103c may be reversed. Although the case where heated air is used is shown as the solvent removal means in the second stretching apparatus 103, the solvent removal means is not particularly limited, and other examples include means for heating with an infrared heater, for example.

  The drying conditions in the second stretching apparatus 103 vary depending on the residual solvent amount of the web 3 at the start of stretching by the second stretching apparatus 103, but considering the drying time, shrinkage unevenness, stability of the expansion and contraction, and the like. In addition, it achieves reasonable stretching and is consistent from the viewpoint of ensuring good dryness, flatness and film thickness uniformity without voids, and ensuring elastic modulus and optical properties of the produced cellulose acylate film. You may dry at the temperature of this, and it may divide into the temperature of 3-4 steps, and may divide into the temperature of several steps, and may dry.

  Here, the stretching ratio in the TD direction in the second stretching process is expressed by the formula “stretching ratio in the TD direction in the second stretching process = the width of the web after the second stretching process / the web before the second stretching process. It is calculated by “width”. The width of the web is a value measured with a C-type JIS grade 1 steel scale.

  Further, the draw ratio in the MD direction in the second stretching step is expressed by the formula “stretch ratio in the MD direction in the second stretch process = web transport speed after the second stretch process / web before the second stretch process. It is obtained by “conveying speed”.

[Drying equipment]
The drying device 104 includes a drying box 104a having a drying air intake port 104b and a discharge port 104c, an upper conveyance roller 104d that conveys the web 3, and a lower conveyance roller 104e. The drying device 104 performs a heat treatment step of drying the web 3 stretched in the MD direction and / or the TD direction in the first stretching step and the second stretching step. The upper conveyance roller 104d and the lower conveyance roller 104e are a set of upper and lower, and are composed of a plurality of sets. The number of transport rollers disposed in the second drying device 104 varies depending on the drying conditions, the drying method, the length of the cellulose acylate film 5 to be manufactured, and the like, and is appropriately set. The upper conveyance roller 104d and the lower conveyance roller 104e are free rotation rollers that are not rotationally driven by a drive source. In addition, a transport roller that freely rotates is not used between the drying device 104 and the winding device 105, and usually one to several transport drive rollers (rollers that are rotationally driven by a drive source). Requires installation. Basically, the purpose of the driving roller for conveyance is to convey the web 3 by its drive, so the conveyance of the web 3 and the rotation of the driving roller are synchronized by nip, suction (air suction), or the like. With the mechanism.

  In the drying device 104, drying may be performed using heated air, infrared rays, or the like alone, or drying may be performed using heated air and infrared rays in combination. It is preferable to use heated air from the viewpoint of simplicity. FIG. 1 shows a case where heated air is used. The drying temperature varies depending on the amount of residual solvent in the web when entering the drying process. However, considering the drying time, shrinkage unevenness, stability of the amount of stretching, etc., the drying temperature remains in the range of 30 ° C to 180 ° C, for example. What is necessary is just to select and decide suitably according to the amount of solvents. Moreover, it may be dried at a constant temperature, or may be divided into three to four stages of temperature and may be divided into several stages of temperature.

  The residual solvent amount of the web 3 after the drying process in the drying device 104 is 0.01 to 0.05% by mass in consideration of the load of the drying process (heat treatment process), the dimensional stability during storage, the expansion / contraction rate, and the like. The range of is preferable. In the present embodiment, the web 3 formed by the casting apparatus 101 is gradually removed of the solvent by the drying apparatus 104, and the web 3 having a total residual solvent amount of, for example, 2% by mass or less is referred to as a cellulose acylate film. There is a case.

[Winding device]
The winding device 105 winds the cellulose acylate film 5 having a predetermined residual solvent amount in a roll shape around a winding core to a required length by the drying device 104. The temperature at the time of winding is preferably cooled to room temperature in order to prevent scratches and loosening due to shrinkage after winding. The winder to be used can be used without any particular limitation, and may be a commonly used winder such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, or the like. Can be wound up.

  In the present embodiment, considering the use of the produced cellulose acylate film 5 as a thin film, the film thickness is 10 to 35 μm from the viewpoint of preventing the produced cellulose acylate film 5 from curling or wrinkling. A range of cellulose acylate films are produced.

<Method for producing cellulose acylate film>
According to the cellulose acylate film manufacturing apparatus 1 as shown in FIG. 1, a casting step of casting the resin solution 2 on the metal support 101a and the web 3 formed on the support 101a are supported. A peeling step for peeling from 101a, a first drawing step for drawing the peeled web 3 in the MD direction or the TD direction, and a second drawing for additionally drawing the web 3 in the MD direction or the TD direction after the first drawing step. A method for producing a cellulose acylate film by a solution casting film forming method is provided, comprising a step, a heat treatment step for drying the stretched web 3, and a winding step for winding the dried web 3 as a cellulose acylate film. The The method for producing a cellulose acylate film by such a solution casting film forming method is a preferred method for producing a cellulose acylate film from the viewpoints of suppression of coloring, suppression of foreign matter defects, suppression of optical defects such as die lines, and the like. In addition, you may make it dry the web 3 by performing a drying process between a 1st extending | stretching process and a 2nd extending | stretching process. Hereinafter, in addition to the contents described above, further description will be given.

[Dissolution process]
The dissolving step is a step of dissolving a cellulose acylate and other additives in an organic solvent mainly containing a good solvent for cellulose acylate while stirring, and forming a dope, or a cellulose acylate solution. Depending on the case, it is the process of mixing dope which is a main solution by mixing other additive solutions.

  For dissolving cellulose acylate, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9-95557 Alternatively, various dissolution methods such as a cooling dissolution method as described in JP-A-9-95538 and a high-pressure method as described in JP-A-11-21379 can be used. The method of pressurizing at a boiling point or higher is preferred.

  The total amount of cellulose acylate in the dope is preferably in the range of 15 to 45% by mass. An additive is added to the dope during or after dissolution to dissolve and disperse, then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  Filtration is preferably performed using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  In this method, a filter medium having a collected particle diameter in the range of 0.5 to 5 μm and a drainage time in the range of 10 to 25 sec / 100 ml is used for the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added. Only the aggregate can be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

  If necessary, remove large agglomerates from the acrylic particle charging kettle with a filter and feed it to the stock kettle. Thereafter, the acrylic particle additive liquid is added from the stock kettle to the main dope dissolving kettle.

  Thereafter, the main dope is filtered by a main filter, and an ultraviolet absorbent additive solution or the like may be further added in-line thereto.

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material. Since the return material contains an additive, in that case, it is preferable to control the amount of additive added in accordance with the amount of return material added.

  Recycled material is a finely pulverized cellulose acylate film, which is produced when a cellulose acylate film is formed, with both sides of the film cut off, or a cellulose acylate film that has been speculated out of scratches, etc. The original fabric is used.

  In addition, cellulose acylate and, optionally, additives kneaded and pelletized can be preferably used.

(Dope solvent)
A solvent useful for forming a dope when the cellulose acylate film of the present invention is produced by a solution casting film forming method is, for example, an organic solvent. As such an organic solvent, any organic solvent can be used without limitation as long as it can dissolve cellulose acylate and other additives simultaneously.

  For example, as a chlorinated organic solvent, methylene chloride (methylene chloride), and as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone , Ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3 -Hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Methylene chloride, methyl acetate, ethyl acetate, and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels, facilitating peeling from the metal support, and when the proportion of alcohol is small, the dissolution of cellulose acylate in a non-chlorine organic solvent system is promoted. There is also a role.

  In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, at least three types of acrylic resin, cellulose acylate, and acrylic particles are used in a total of 15 to 45. A dope composition dissolved in mass% is preferred.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

[Casting process]
A description will be given with reference to FIG. 1 again. In the casting process, the dope is fed to a pressure die through a liquid feed pump (for example, a pressurized metering gear pump), and is supported by an endless metal belt such as a stainless steel belt or a rotating metal drum. This is a step of casting a dope from a pressure die slit to a casting position on the body.

  A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

(Solvent evaporation process during casting process)
This is a step of heating the web on the support and evaporating the solvent.

  To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of -5 to 70 ° C.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 0.5 to 5 minutes.

[Peeling process]
A peeling process is a process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

  The temperature at the peeling position on the metal support is preferably in the range of 10 to 40 ° C, more preferably in the range of 11 to 30 ° C.

  In addition, the amount of residual solvent at the time of peeling of the web on the metal support at the time of peeling is in the range of 20 to 100% by mass depending on the strength of drying conditions, the length of the metal support, etc. in addition to the reasons described above. However, if the web is too soft, the flatness at the time of peeling will be lost, and slippage and vertical stripes due to the peeling tension are likely to occur. Therefore, the amount of residual solvent at the time of peeling is determined.

  The residual solvent amount of the web is defined by the following formula.

Residual solvent amount (mass%) = {(mass before heat treatment of web−mass after heat treatment of web) / (mass after heat treatment of web)} × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension at the time of peeling the metal support and the film is usually in the range of 196 to 245 N / m in addition to the values described above, but if wrinkles easily occur at the time of peeling, the tension is 190 N / m or less. It is preferable to peel at a minimum tension capable of peeling to 166.6 N / m, then to a minimum tension to 137.2 N / m, particularly preferably to a minimum tension of 100 N. It is peeling in the range of / m.

  In the present invention, the temperature at the peeling position on the metal support is preferably in the range of −5 ° C. to 70 ° C., more preferably in the range of 0 to 60 ° C., and in the range of 15 to 60 ° C. Most preferred.

[Stretching process (first stretching process, second stretching process)]
The stretching step (the first stretching step and the second stretching step performed after the first stretching step) is performed in the MD direction without the need to hold the side portions in the width direction of the web by the carrier after peeling. This is a step of stretching the web in the TD direction using a tenter stretching device that is stretched or held and conveyed by a pin tenter, a clip tenter or the like. The order of stretching in the MD direction and stretching in the TD direction may be either first or simultaneous, and may be repeated a plurality of times.

  In this invention, when extending | stretching the web peeled from the casting support body to MD direction and TD direction by the 1st extending process and the 2nd extending process, the draw ratio of MD direction and the draw ratio of TD direction are each set. The range is 1.2 times or more, more preferably 1.5 to 2.0 times. In order to bring the elastic modulus according to the present invention into the target range, it is preferable to stretch within the range of the magnification. In particular, in order to produce a thin film having a high elastic modulus without breakage and the like with good productivity, the film is preferably stretched within a range of 1.5 to 2.0 times.

  Moreover, it is necessary that the product of the draw ratio in the MD direction and the draw ratio in the TD direction be in the range of 2.0 to 5.0 times. This is a preferable range from the viewpoint of controlling the elastic modulus while taking a stretching balance in both directions, rather than controlling the elastic modulus by stretching in only one direction in the MD direction or the TD direction. The value of the product of the draw ratio is more preferably in the range of 2.0 to 4.0 times, and 2.5 to 3.5 times from the viewpoint of achieving the effect of the present invention and uniform stretching treatment. It is more preferable to make the range.

  The stretching stress during stretching in the first stretching step is in the range of 1 to 20 MPa, and the stretching stress in stretching in the second stretching step is in the range of 0.1 to 15 MPa. It is preferable because the force applied to the film when the manufactured polarizing plate is reworked from the liquid crystal panel attached to the liquid crystal cell can be made uniform in the two directions.

  The stretching stress is a factor controlled by the residual solvent amount, the temperature during stretching, the stretching ratio, and the like. The stretching stress decreases as the residual solvent amount increases and increases as the residual solvent amount decreases. Moreover, the temperature at the time of extending | stretching becomes low, so that it is high, and it becomes high, so that a draw ratio is high. From the viewpoint of reducing the occurrence of stretching unevenness and producing a film having a uniform elastic modulus without breakage or the like with good productivity, the first and second stretching steps are controlled by the above means within the range of the stretching stress. Is preferred.

  The stretching stress at the time of stretching in the first stretching step is more preferably in the range of 2 to 15 MPa, and is in the range of 3 to 10 MPa from the viewpoint of achieving the effect of the present invention and uniform stretching treatment. Particularly preferred.

  The stretching stress at the time of stretching in the second stretching step is more preferably within the range of 0.5 to 10 MPa, and the range of 1 to 8 MPa provides the effect of the present invention and uniform stretching treatment. It is preferable from the viewpoint.

  The stretching stress can be measured by the following method.

[Evaluation of stretching stress]
The following measurement is performed using a Tensilon tester (ORITC Corporation, RTC-1225A).

  A cellulose acylate film is cut out at 120 mm (MD: longitudinal direction) × 10 mm (TD: lateral direction), and the film is moved in the MD direction at a chuck length of 50 mm and a speed of 50 mm / min in a constant temperature bath maintained at a predetermined temperature. The tensile stress in the MD direction is determined by dividing the tensile load at that time by the film cross-sectional area (ie, film width × film thickness). Similarly, it is cut out by 10 mm (MD: longitudinal direction) × 120 mm (TD: lateral direction), the film is pulled in the TD direction, and the stretching stress in the TD direction is determined.

  In the first and second stretching steps, when a tenter stretching apparatus is used, it is preferable to use an apparatus that can independently control the holding position of the film by the tenter on the left and right. It is also preferable to create compartments with intentionally different temperatures to improve planarity. It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  In the first and second stretching steps, the stretching operation may be performed in multiple stages, or simultaneous biaxial stretching may be performed in the MD direction and the TD direction.

In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, in each of the first and second stretching steps, for example, the following stretching steps are possible.
(A) Stretch only in MD direction (b) Stretch only in TD direction (c) Simultaneous stretching in MD direction and TD direction (d) Stretch in MD direction-then stretch in TD direction (e) Stretch in TD direction-Then Stretching in the TD direction-Stretching in the MD direction-Thereafter stretching in the MD direction In addition, the simultaneous biaxial stretching includes stretching in one direction and shrinking the other while relaxing the tension.

  The amount of residual solvent of the web 3 when the web 3 starts to be stretched by the first stretching device 102 (the amount of residual solvent of the web 3 at the time of stretching by the first stretching device 102) is maintained and manufactured by the tenter during stretching. Taking into account the appearance and optical properties of the cellulose acylate film, for example, it is preferably in the range of 5 to 30% by mass at the start of the first stretching, and more preferably in the range of 6 to 25% by mass. . If it is in the above-mentioned range, it is preferable that the drying conditions are not excessive before stretching, and that the organic solvent evaporates during stretching and bubbles are not generated. A range of 7 to 20% by mass is particularly preferable.

  The amount of residual solvent at the start of the second stretching is preferably in the range of 1 to 20% by mass, more preferably in the range of 1.5 to 15% by mass, and in the range of 2 to 10% by mass. It is particularly preferred. If it is in the said range, a uniform elastic modulus can be provided in a film surface by extending | stretching, and it is preferable.

  After the second stretching, drying is preferably performed while applying a tenter until the residual solvent amount of the web becomes 10% by mass or less, and more preferably 5% by mass or less.

  In the first stretching step, the specific temperature for stretching may be within the range of (Tg-30) to (Tg + 50) ° C. when the glass transition temperature of cellulose acylate is Tg. Preferably, the second stretching step is preferably performed within the range of (Tg-10) to (Tg + 40) ° C. from the glass transition temperature of cellulose acylate.

  If it is in the said temperature range, it will become easy to control to the range of the above-mentioned extending | stretching stress, the film which provided the desired elasticity modulus uniformly can be manufactured, and is preferable.

  In the stretching step, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film, and the temperature distribution in the width direction in the stretching step is preferably within ± 5 ° C, more preferably within ± 2 ° C. Preferably, it is within ± 1 ° C.

[Heat treatment process]
The heat treatment step is a step of drying (heat treatment) while alternately passing the stretched web through rollers arranged in a drying apparatus.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from a residual solvent amount of about 8% by mass or less. Throughout, the drying is generally performed in the range of 40 to 250 ° C. It is particularly preferable to dry in the range of 40 to 160 ° C.

[Winding process]
The winding step is a step of winding the cellulose acylate film as a cellulose acylate film by a winder after the residual solvent amount in the web is 2% by mass or less. The cellulose acylate film of the present invention having good stability can be obtained. In particular, it is preferable to wind up in the range of 0.00 to 0.05 mass%.

  As a winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc., and these may be used properly.

  The cellulose acylate film of the present invention is preferably a long film. Specifically, the cellulose acylate film is about 100 m to 5000 m, and is usually in the form of a roll. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2.5m.

  The film thickness of the cellulose acylate film of the present invention is in the range of 10 to 35 μm in consideration of the use as a protective film for a polarizing plate of a thin film, more preferably 15 to 30 μm, and more preferably 20 to 30 μm. It is particularly preferred.

  The cellulose acylate film produced by the method as described above is a cellulose acylate film having low hygroscopicity, high transparency, and excellent weather resistance.

<Physical properties of cellulose acylate film>
The moisture permeability of the cellulose acylate film of the present invention is preferably in the range of 300 to 1800 g / m 2 · 24 h at 40 ° C. and 90% RH, more preferably in the range of 400 to 1500 g / m 2 · 24 h, and 40 to 1300 g / m 2 · A range of 24 h is particularly preferred. The moisture permeability can be measured according to the method described in JIS Z 0208.

  The visible light transmittance of the cellulose acylate film of the present invention is preferably 90% or more, and more preferably 93% or more.

  The haze of the cellulose acylate film of the present invention is preferably less than 1%, particularly preferably 0 to 0.1%.

<Uses of cellulose acylate film>
The cellulose acylate film of the present invention is preferably a functional film used for various display devices such as liquid crystal displays, plasma displays, and organic EL displays. Specifically, the cellulose acylate film of the present invention is a polarizing plate protective film for liquid crystal display devices, a retardation film, an antireflection film, a brightness enhancement film, a hard coat film, an antiglare film, an antistatic film, and a viewing angle. It may be an optical compensation film such as an enlargement. Typically, the cellulose acylate film of the present invention is a polarizing plate protective film, a retardation film, or an optical compensation film.

(Polarizing plate protective film)
The cellulose acylate film of the present invention is preferably used as a polarizing plate protective film that is bonded to at least one surface of a polarizer.

  The retardation value of the polarizing plate protective film is determined by the following formula, and the retardation value Ro in the in-plane direction is preferably in the range of 0 to 100 nm, more preferably in the range of 0 to 50 nm, and the thickness direction. The retardation value Rt is preferably in the range of −200 to 200 nm, more preferably in the range of −100 to 100 nm.

Formula (i): Ro = (nx−ny) × d (nm)
Formula (ii): Rt = {(nx + ny) / 2−nz} × d (nm)
(In the formula, Ro represents the in-plane retardation value in the film, Rt represents the retardation value in the thickness direction in the film, and d represents the thickness (nm) of the cellulose acylate film, nx Represents the maximum refractive index in the plane of the film, also referred to as the refractive index in the slow axis direction, ny represents the refractive index in the direction perpendicular to the slow axis in the film plane, and nz represents the film in the thickness direction. Represents refractive index, all measured values at a wavelength of 590 nm.)
The retardation value can be obtained at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH using, for example, KOBRA-21ADH (Oji Scientific Instruments).

(Optical compensation film)
Since liquid crystal displays use anisotropic liquid crystal materials and polarizing plates, there is a problem of viewing angle that even when good display is obtained when viewed from the front, display performance is degraded when viewed from an oblique direction. . Therefore, a viewing angle compensator is necessary to improve the performance of the liquid crystal display. The average refractive index distribution of the liquid crystal cell is larger in the cell thickness direction and smaller in the in-plane direction. Therefore, the viewing angle compensator must cancel this anisotropy. In other words, it is effective that the viewing angle compensation plate has a refractive index smaller than that in the in-plane direction, that is, a so-called negative uniaxial structure. The cellulose acylate film of the present invention can be an optical compensation film having such a function.

  When the cellulose acylate film of the present invention is used in a VA mode liquid crystal cell, a total of two cellulose acylate films may be used, one on each side of the cell (two-sheet type), or above and below the cell. A cellulose acylate film may be used only on either side (single sheet type).

  In the cellulose acylate film of the present invention, the retardation value Ro in the in-plane direction represented by the above formula is in the range of 40 to 150 nm at a measurement wavelength of 590 nm in an environment of 23 ° C. and 55% RH. Preferably, the range of 50 to 130 nm is more preferable. The retardation value Rt in the thickness direction is preferably in the range of 70 to 350 nm and more preferably in the range of 170 to 270 nm at a measurement wavelength of 590 nm in an environment of 23 ° C. and 55% RH.

  The cellulose acylate film of the present invention has a slow axis or a fast axis in the film plane, and the angle θ1 formed by the slow axis or the fast axis and the axis in the film forming direction is −1 ° or more and + 1 °. Or less, more preferably −0.5 ° or more and + 0.5 ° or less. θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). The cellulose acylate film in which θ1 satisfies the above relationship increases the luminance of the display image of the liquid crystal display device including the film, suppresses or prevents light leakage, and faithfully reproduces the color in the color liquid crystal display device.

<Polarizing plate>
The polarizing plate of the present invention can be produced by laminating the cellulose acylate film of the present invention on one surface of a polarizer using an active energy ray-curable adhesive.

  In addition, the cellulose acylate film of this invention may be used for the other surface of the polarizer which comprises a polarizing plate, and it is also preferable to paste another cellulose acylate film. Examples of such other cellulose acylate films include commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC4UE, KC8UE, KC8UY-X8, HC8UY-X8) KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, manufactured by Konica Minolta Co., Ltd.) are preferably used.

<Polarizer>
The polarizer, which is the main component of the polarizing plate, is an element that passes only light having a plane of polarization in a certain direction, and a typical known polarizer is a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

  As the polarizer, a polarizer obtained by forming a polyvinyl alcohol aqueous solution into a film and dyeing it by uniaxial stretching or dyeing and then uniaxially stretching and then preferably performing a durability treatment with a boron compound may be used. The thickness of the polarizer is preferably in the range of 5 to 30 μm, and particularly preferably in the range of 10 to 20 μm from the viewpoint of thinning.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. The ethylene-modified polyvinyl alcohol is also preferably used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used. A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has few color spots, and is particularly preferably used for a large-sized liquid crystal display device.

<Photocurable adhesive>
The bonding of the cellulose acylate film of the present invention and the polarizer is not particularly limited, but can be performed using a completely saponified polyvinyl alcohol adhesive, a photocurable adhesive, or the like. It is preferable to use a photocurable adhesive from the viewpoint that the obtained adhesive layer has a high elastic modulus and can easily suppress deformation of the polarizing plate.

  Preferred examples of the photocurable adhesive include (α) a cationic polymerizable compound, (β) a photo cationic polymerization initiator, and (γ) a wavelength longer than 380 nm, as disclosed in JP2011-08234A. And a photo-curable adhesive composition containing each component of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, other photocurable adhesives may be used.

  Hereinafter, an example of the manufacturing method of the polarizing plate using a photocurable adhesive agent is demonstrated. The polarizing plate includes (1) a pretreatment step for easily adhering the surface of the cellulose acylate film to which the polarizer is bonded, and (2) at least one of the adhesive surface between the polarizer and the cellulose acylate film, with the following light: An adhesive application step for applying a curable adhesive; (3) a bonding step for bonding a polarizer and a cellulose acylate film through the obtained adhesive layer; and (4) a polarization through an adhesive layer. It can manufacture by the manufacturing method including the hardening process which hardens an adhesive bond layer in the state by which the element | child and the cellulose acylate film were bonded together. What is necessary is just to implement the pre-processing process of (1) as needed.

(Pretreatment process)
In the pretreatment step, an easy adhesion treatment is performed on the adhesive surface of the cellulose acylate film with the polarizer. When the cellulose acylate film is adhered to both surfaces of the polarizer, easy adhesion treatment is performed on the adhesive surface of each cellulose acylate film with the polarizer. Examples of the easy adhesion treatment include corona treatment and plasma treatment.

(Adhesive application process)
In the adhesive application step, the photocurable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the cellulose acylate film. When the photocurable adhesive is directly applied to the surface of the polarizer or the cellulose acylate film, the application method is not particularly limited. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting a photocurable adhesive between a polarizer and a cellulose acylate film, the method of pressurizing with a roll etc. and spreading it uniformly can also be utilized.

(Bonding process)
Thus, after apply | coating a photocurable adhesive agent, it uses for a bonding process. In this bonding step, for example, when a photocurable adhesive is applied to the surface of the polarizer in the previous application step, a cellulose acylate film is superimposed thereon. When a photocurable adhesive is applied to the surface of the cellulose acylate film in the previous application step, a polarizer is superimposed thereon. Moreover, when a photocurable adhesive agent is cast between a polarizer and a cellulose acylate film, a polarizer and a cellulose acylate film are piled up in that state. When a cellulose acylate film is bonded to both sides of a polarizer and a photocurable adhesive is used on both sides, the cellulose acylate film is superimposed on each side of the polarizer via a photocurable adhesive. Is done. Usually, in this state, both sides (when a cellulose acylate film is overlaid on one side of the polarizer, when the cellulose acylate film is overlaid on both the polarizer side and the cellulose acylate film side, or on both sides of the polarizer) Is pressed between the two sides of the cellulose acylate film side) with a roll or the like. As the material of the roll, metal, rubber or the like can be used. The rolls arranged on both sides may be the same material or different materials.

(Curing process)
In the curing step, the active energy ray is irradiated to the uncured photocurable adhesive to cure the adhesive layer containing the epoxy compound or the oxetane compound. Thereby, the polarizer and the cellulose acylate film which are overlapped with each other are bonded through the photo-curable adhesive. When a cellulose acylate film is bonded to one side of the polarizer, the active energy ray may be irradiated from either the polarizer side or the cellulose acylate film side. Moreover, when bonding a cellulose acylate film on both surfaces of a polarizer, either cellulose acylate film is in a state in which the cellulose acylate film is superposed on both surfaces of the polarizer via a photocurable adhesive. It is advantageous to irradiate active energy rays from the side and simultaneously cure the photocurable adhesive on both sides.

  As the active energy ray, visible light, ultraviolet ray, X-ray, electron beam or the like can be used, and since it is easy to handle and has a sufficient curing speed, generally, an electron beam or ultraviolet ray is preferably used.

  Any appropriate condition can be adopted as the electron beam irradiation condition as long as the adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably in the range of 5 to 300 kV, more preferably in the range of 10 to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and may be insufficiently cured. If the acceleration voltage exceeds 300 kV, the penetration force through the sample is too strong and the electron beam rebounds, so that the cellulose acylate film Or damage the polarizer. The irradiation dose is in the range of 5 to 100 kGy, more preferably in the range of 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the adhesive becomes insufficiently cured, and when it exceeds 100 kGy, the cellulose acylate film and the polarizer are damaged, resulting in a decrease in mechanical strength and yellowing, thereby obtaining predetermined optical characteristics. I can't.

  Arbitrary appropriate conditions can be employ | adopted for the irradiation conditions of an ultraviolet-ray, if it is the conditions which can harden the said adhesive agent. The amount of UV irradiation is preferably 50 to 1500 mJ / cm @ 2, more preferably 100 to 500 mJ / cm @ 2 in terms of integrated light quantity.

  In the polarizing plate obtained as described above, the thickness of the adhesive layer is not particularly limited, but is usually in the range of 0.01 to 10 μm, and preferably in the range of 0.5 to 5 μm.

<Liquid crystal display device>
The liquid crystal display device of the present invention comprises a polarizing plate having the cellulose acylate film of the present invention. Specifically, the cellulose acylate film of the present invention is included in the polarizing plate disposed in at least one of the liquid crystal cells, and the film on the liquid crystal cell side of the polarizing plate is the cellulose acylate film of the present invention. As a result, the reworkability of the polarizing plate and the haze resistance during reworking are improved.

  In the liquid crystal display device of the present invention, it is preferable that the polarizing plate is bonded to one or both surfaces of the liquid crystal cell via an adhesive layer.

  In addition to the antiglare layer or the clear hard coat layer, the polarizing plate protective film used on the surface side of the liquid crystal display device of the present invention preferably has an antireflection layer, an antistatic layer, an antifouling layer, and a backcoat layer. .

  The cellulose acylate film and polarizing plate of the present invention can be used in liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB. In particular, it is preferably used for a VA (MVA, PVA) type liquid crystal display device. In particular, even when used in a liquid crystal display device having a large screen of 30 type or more, coloring during black display due to light leakage can be reduced and visibility such as front contrast can be improved. Thus, the liquid crystal display device of the present invention is excellent in various visibility.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Cellulose acylate used in Examples>
Cellulose acylate 1: Degree of substitution with acetyl group (total substitution degree of acyl group) 2.85, weight average molecular weight Mw = 152000, number average molecular weight Mn = 90000, Mw / Mn = 1.7, Tg = 169 ° C.
Cellulose acylate 2: Degree of acetyl group substitution (total substitution degree of acyl group) 2.45, weight average molecular weight Mw = 151000, number average molecular weight Mn = 100000, Mw / Mn = 1.5, Tg = 168 ° C.
<Preparation of Cellulose Acylate Film 101>
<Preparation of in-line additive solution>
10 parts by weight of Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd., average particle diameter of 16 nm, apparent specific gravity of 90 g / liter) and 90 parts by weight of methanol were stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. A fine particle dispersion was obtained.

  88 parts by mass of dichloromethane was added to the obtained fine particle dispersion while stirring, and the mixture was stirred and mixed with a dissolver for 30 minutes to dilute. The obtained solution was filtered with a polypropylene wind cartridge filter TCW-PPS-1N manufactured by Advantech Toyo Co., Ltd. to obtain a fine particle dispersion dilution.

  15 parts by mass of Tinuvin 928 (manufactured by BASF Japan Ltd.) and 100 parts by mass of dichloromethane were put into a sealed container, heated and stirred to completely dissolve, and then filtered. To the obtained solution, 36 parts by mass of the fine particle dispersion diluent was added with stirring, and further stirred for 30 minutes, and then 6 parts by mass of cellulose acylate 1 (acetyl group substitution degree 2.85, Mw = 152000, Mn = 90000, Mw / Mn = 1.7) was added with stirring, and the mixture was further stirred for 60 minutes. The obtained solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to obtain an in-line additive solution. The filter medium having a nominal filtration accuracy of 20 μm was used.

<Preparation of dope>
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. Filtration at 24 gave the main dope.

(Main dope composition)
Cellulose acetate 1 (acetyl group substitution degree 2.85, acetyl group substitution degree 2.9, Mw = 152000, Mn = 90000, Mw / Mn = 1.7) 100 parts by mass Additive 1: represented by formula (FA) Compound (Exemplary Compound FA-8) 8 parts by mass Additive 2: Compound represented by Formula (FB) (Exemplary Compound FB-15) 7 parts by mass Dichloromethane 430 parts by mass Methanol 40 parts by mass Main part of 100 parts by mass The dope and 2.5 parts by mass of the in-line additive solution were sufficiently mixed with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ) to obtain a dope.

  The obtained dope was uniformly cast on a stainless steel band support using a belt casting apparatus shown in FIG. 1 under conditions of a dope temperature of 35 ° C. and a width of 1.6 m. On the stainless steel band support, the solvent in the obtained dope film was evaporated until the residual solvent amount reached 100% to obtain a web, and then the web was peeled from the stainless steel band support. The obtained web was further dried at 35 ° C. and then slit so as to have a width of 1.4 m.

  Thereafter, the film was stretched in the MD direction at 190 ° C. at a stretching ratio of 2.0 times by the first stretching apparatus 102 shown in FIG. At that time, the residual solvent amount of the web at the start of stretching was 20%.

  Next, the film was stretched in the TD direction at 190 ° C. at a stretch ratio of 1.5 times by the second stretching apparatus 103 shown in FIG. At that time, the residual solvent amount of the web at the start of stretching was 5%.

  Thereafter, the obtained film was dried at 125 ° C. for 15 minutes while being transported by a number of rollers in the drying apparatus, then slit to 2.0 m width, and the height of the convex portion was 10 μm at both ends in the width direction. Were formed, and a long cellulose acylate film having a width of 2.0 m, a length of 4000 m, and a film thickness of 30 μm was produced.

<Preparation of cellulose acylate films 102-122>
In the production of the cellulose acylate film 101, as shown in Table 2, except that the cellulose acylate type, the temperature during stretching in the MD direction, the temperature during stretching in the TD direction, and the film thickness were changed. Cellulose acylate films 102 to 122 were produced.

≪Evaluation≫
<Measurement of elastic modulus>
The elastic modulus in the MD direction and TD direction of the produced cellulose acylate film was measured by the following method, and the absolute value of the difference was obtained.

[Measurement method of elastic modulus]
The elastic modulus was measured according to JIS K 7127 by cutting out a sample piece in the MD direction and the TD direction from the full width of the cellulose acylate film.

  After leaving the sample in an environment of 23 ± 2 ° C. and 50 ± 5% RH for 24 hours, the sample is cut into a strip of width 10 mm × length 200 mm so that the MD direction and the TD direction of each sample are respectively longer. Then, using the TG-2KN type tensile tester manufactured by Minebea, the above strip-shaped sample was set at a chucking pressure of 0.25 MPa and a distance between marked lines of 100 ± 10 mm, and the pulling speed was 100 ± 10 mm / min. Pull at the speed of.

  Then, from the obtained tensile stress-strain curve, the elastic modulus calculation start point was 10 N, the end point was 30 N, and the tangent line drawn between them was extrapolated to obtain the elastic modulus in the MD direction and the TD direction.

<Measurement of elongation at break>
The elongation at break in the MD direction and TD direction of the produced cellulose acylate film was measured by the following method.

[Measurement method of elongation at break]
The cellulose acylate film was cut into a size of 100 mm (MD direction) × 10 mm (TD direction) to obtain a sample film. The sample film was conditioned for 24 hours in an environment of 23 ° C. and 55% RH. In accordance with JIS K7127, the sample film after humidity adjustment was pulled in the MD direction using a Tensilon RTC-1225A manufactured by Orientec Co., Ltd., and the tensile strength was extended from the breaking point of the film to the breaking direction in the MD direction. The degree was measured. Further, the elongation at break in the TD direction was measured in the same manner except that the optical film was cut into a size of 10 mm (MD direction) × 100 mm (TD direction) and the direction in which the sample film was pulled was changed to the TD direction. The elongation at break was measured at 23 ° C. and 55% RH under the conditions of a tensile speed of 50 mm / min.

<Evaluation of reworkability>
A polarizing plate was produced using the produced cellulose acylate film, and the following reworkability was evaluated.

[Preparation of polarizing plate]
(1) Preparation of Polarizer A polyvinyl alcohol film having a thickness of 30 μm was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution at 45 ° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched in the MD direction under the conditions of a stretching temperature of 55 ° C. and a stretching ratio of 5 times. This uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 10 μm.

(2) Preparation of photocurable adhesive The following components were mixed and then defoamed to prepare a photocurable adhesive. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

(Composition of photocurable adhesive)
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries)
40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate
2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass (3) Preparation of polarizing plate The above prepared light on the cellulose acylate film The curable adhesive was applied using a micro gravure coater so as to have a dry thickness of 5 μm to form a photocurable adhesive layer. The application was performed under the conditions of gravure roller # 300, rotation speed 140% / line speed.

  Similarly, the photocurable adhesive prepared above was applied as a protective film on Konica Minolta Tac KC4UY (manufactured by Konica Minol Co., Ltd.) so as to have a dry thickness of 5 μm to form a photocurable adhesive layer.

  Arrange the acylate film on which the photocurable adhesive layer is formed on one side of the produced polarizer, and arrange the protective film on which the photocurable adhesive layer is formed on the other side, A laminate of an acylate film / a photocurable adhesive layer / a polarizer / a photocurable adhesive layer / a protective film was obtained. The obtained laminate was bonded with a roll-to-roll so that the longitudinal direction was matched with a roller machine.

  The polarizing plate 201 was obtained by irradiating an electron beam from both sides of the laminated laminate to cure the photocurable adhesive layer. The line speed was 20 m / min, the acceleration voltage was 250 kV, and the irradiation dose was 20 kGy.

  As described above, polarizing plates 101 to 122 using the cellulose acylate films 101 to 122 were produced.

[Evaluation of reworkability]
Each of the polarizing plates 101 to 122 was cut into a size of 100 mm × 100 mm, and attached to a glass plate using a substrate-less double-sided tape LUCIACS CS9621T (manufactured by Nitto Denko Corporation). After aging for 24 hours at 23 ° C. and 55%, the polarizing plate was peeled off from the glass plate by hand, and the state of the film at that time was evaluated as follows.

◎: Film can be peeled off without tearing ○: Film is sometimes shredded but can be peeled cleanly ○ △: Film is sometimes shredded but can be removed somehow △: Film is sometimes shredded and removed somehow, but peeled off Haze-like white unevenness appears in the film. ×: The film is torn immediately and cannot be removed.

  From the results of Table 2, the cellulose acylate film of the present invention satisfying the elastic modulus in the MD direction and the TD direction, the absolute value of the difference in the elastic modulus and the film thickness according to the present invention is excellent in the reworkability of the polarizing plate. I understood that.

  In addition, the cellulose acylate film of the present invention in which the elongation at break in the MD direction and the TD direction is in a preferable range was a result of better reworkability.

  The cellulose acylate films 101, 110 and 118 of comparative examples having a low elastic modulus with respect to the cellulose acylate film of the present invention, the cellulose acylate film 104 whose film thickness is outside the scope of the present invention, and the elastic modulus in the MD direction The cellulose acylate films 116 and 117 whose absolute values of the difference in elastic modulus in the TD direction are outside the scope of the present invention were both inferior in reworkability.

Example 2
In the production of the cellulose acylate film 103 of Example 1, the cellulose acylate film was prepared in the same manner except that the stretching ratio and stretching temperature in the MD direction and the stretching ratio and stretching temperature in the TD direction were changed as shown in Table 3. 201-214 were produced.

  Using the produced cellulose acylate films 201 to 214, in addition to the measurement of elastic modulus and the evaluation of reworkability performed in Example 1, the following stretching stress was measured.

<Measurement of stretching stress>
The stretching stress in the MD direction and TD direction of the produced cellulose acylate film was determined by the following measurement. The stretching in the MD direction is the first stretching step, and the stretching in the TD direction is the second stretching step.

[Measurement method of stretching stress]
The following measurements were performed using a Tensilon tester (ORICTEC, RTC-1225A).

  A cellulose acylate film is cut out at 120 mm (MD: longitudinal direction) × 10 mm (TD: lateral direction), and the film is moved in the MD direction at a chuck length of 50 mm and a speed of 50 mm / min in a constant temperature bath maintained at a predetermined temperature. The stretching stress in the MD direction was determined by dividing the tensile load at that time by the film cross-sectional area (that is, film width × film thickness). Similarly, 10 mm (MD: longitudinal direction) × 120 mm (TD: lateral direction) was cut out, the film was pulled in the TD direction, and the stretching stress in the TD direction was determined.

  Table 3 shows the structure of the cellulose acylate films 201 to 214, the evaluation results of the elastic modulus in the MD direction and the TD direction, stretching stress, and reworkability.

  From the results in Table 3, it is clear that the cellulose acylate film of the present invention satisfying the absolute value of the difference between the elastic modulus in the MD direction and the TD direction according to the present invention and the elastic modulus is excellent in the reworkability of the polarizing plate. It is.

  Moreover, the reworkability of the cellulose acylate film in which the product of the stretching stress, the stretching ratio, the absolute value of the difference in elastic modulus in the MD direction and the TD direction, and the like are in a preferable range was more excellent.

Example 3
In the production of the cellulose acylate film 103 of Example 1, as shown in Table 4, in the first stretching step, the stretching ratio in the MD direction, the stretching temperature, the residual solvent amount at the start of stretching, and the second stretching step Cellulose acylate films 301 to 311 were produced in the same manner except that the stretching ratio in a certain TD direction, the stretching temperature, and the residual solvent amount at the start of stretching were changed. The amount of residual solvent at the start of stretching was changed by adjusting the drying temperature condition in the previous step.

  Similarly, cellulose acylate films 312 to 316 were prepared in which the first stretching step was stretched in the TD direction and the second stretching step was stretched in the MD direction.

  Using the produced cellulose acylate films 301 to 316, in addition to the measurement of the elastic modulus and the evaluation of the reworkability performed in Example 1, the measurement of the stretching stress performed in Example 3 was performed.

  The residual solvent amount of the web was determined by the following formula.

Residual solvent amount (%) = {(mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment)} × 100
Note that the heat treatment for measuring the residual solvent amount was performed at 115 ° C. for 1 hour.

  Table 4 shows the structure of the cellulose acylate films 301 to 316, the evaluation results of the elastic modulus in the MD direction and the TD direction, stretching stress, and reworkability.

  From the results of Table 4, it is clear that the cellulose acylate film of the present invention satisfying the absolute values of the elastic modulus in the MD direction and the TD direction according to the present invention and the difference in the elastic modulus is excellent in the reworkability of the polarizing plate. It is.

  In addition, the cellulose acylate film in which the stretching temperature, the amount of residual solvent at the start of stretching, the elastic modulus, the absolute value of the difference in elastic modulus, and the like are in a preferable range has more excellent reworkability.

  The thinned cellulose acylate film of the present invention is bonded to a polarizer by using a photocurable adhesive to produce a polarizing plate, and the polarizing plate is reworked from a liquid crystal panel attached to a liquid crystal cell. In doing so, it can be suitably used as a member of a polarizing plate and a liquid crystal display device because failure such as breakage and increase in haze value hardly occur.

1 Cellulose acylate film production equipment 2 Dope (resin solution)
3 Web (casting membrane)
4 Peeling roller 5 Cellulose acylate film 101 Casting apparatus 101a Metal support (endless belt)
101b Die 101c Heating device 101d First heated air supply device 101e Second heated air supply device 101f Exhaust port 102 First stretching device 102d Stretching device 103 Second stretching device 103d Stretching device 104 Drying device 105 Winding device 105a Taken up Rolled cellulose acylate film

Claims (4)

A cellulose acylate film production method for producing a cellulose acylate film having a thickness of 10 μm or more by a solution casting method,
The stretching stress at the time of stretching in the first stretching step when the web peeled from the casting support is stretched in the longitudinal direction and the width direction in the first stretching step and the second stretching step is 1 to Within the range of 20 MPa, the stretching stress during stretching in the second stretching step is within the range of 0.1-15 MPa,
When measured in an environment of 23 ° C. and 55 RH%, both the elastic modulus in the longitudinal direction and the elastic modulus in the width direction of the cellulose acylate film are within the range of 3.0 to 6.0 GPa, and the elastic modulus in the longitudinal direction. And a method for producing a cellulose acylate film, characterized in that an absolute value of a difference in elastic modulus in the width direction is within 2.0 GPa.   The cellulose acylate film has an elongation at break in the longitudinal direction and an elongation at break in the width direction measured in an environment of 23 ° C. and 55 RH%, both within a range of 1 to 10%. The method for producing a cellulose acylate film according to claim 1.   The stretch ratio in the longitudinal direction and the stretch ratio in the width direction when the web peeled from the casting support is stretched in the longitudinal direction and the width direction in the first stretching step and the second stretching step. Each of them is 1.2 times or more, and the product of the draw ratio in the longitudinal direction and the draw ratio in the width direction is within a range of 2.0 to 5.0 times. The manufacturing method of the cellulose acylate film of description.   When the amount of residual solvent in the web at the start of stretching in the first stretching step is in the range of 5 to 30% by mass, and the stretching temperature is Tg, the glass transition temperature of the cellulose acylate film is (Tg −30) to (Tg + 50) ° C., the residual solvent amount in the web at the start of stretching in the second stretching step is in the range of 1 to 20% by mass, and the stretching temperature is (Tg− It is within the range of 10)-(Tg + 40) degreeC, The manufacturing method of the cellulose acylate film as described in any one of Claim 1- Claim 3 characterized by the above-mentioned.

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