WO2015001980A1

WO2015001980A1 - Polarizing plate and liquid crystal display device using same

Info

Publication number: WO2015001980A1
Application number: PCT/JP2014/066330
Authority: WO
Inventors: 真一郎鈴木
Original assignee: コニカミノルタ株式会社
Priority date: 2013-07-01
Filing date: 2014-06-19
Publication date: 2015-01-08
Also published as: KR20160013967A; KR101763509B1; JPWO2015001980A1

Abstract

[Problem] To provide a means for improving reworkability of a polarizing plate wherein a thin cellulose ester film is used as one of protective films. [Solution] A polarizing plate which comprises a protective film (A), a polarizer and a protective film (B) in this order. The protective film (A) is a polyester film that is formed from a polyester, and this polyester film has an elastic modulus of 5.0-8.0 GPa in the MD direction and/or in the TD direction. The protective film (B) is a cellulose ester film that is formed from a cellulose ester, and this cellulose ester film is characterized in that (1) the film thickness thereof is within the range of 15-60 μm, and (2) the toughness both in the MD direction and in the TD direction is 10-20.

Description

Polarizing plate and liquid crystal display device using the same

The present invention relates to a polarizing plate and a liquid crystal display device using the same.

Demand for liquid crystal display devices is expanding for applications such as liquid crystal televisions and personal computer liquid crystal displays. A liquid crystal display device is generally composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter and the like are sandwiched between glass plates, and two polarizing plates provided on both sides thereof. Each polarizing plate is usually configured to sandwich a polarizer between two transparent resin films. As one of such transparent resin films, a cellulose ester film such as cellulose acetate is often used for the purpose of protecting a polarizer (see, for example, International Publication No. 2011/016279 pamphlet). The cellulose ester film has a high transmittance, and by immersing it in an alkaline aqueous solution to saponify its surface and make it hydrophilic, excellent adhesion to a polarizer is realized.

In recent years, there has been a demand for thinner polarizing plates in response to demands for larger and thinner displays. Of course, there is a strong demand for thinning the cellulose ester film as a protective film, which is a constituent member of the polarizing plate. However, when the cellulose ester film which is a protective film is thinned, there is a problem that the reworkability of the polarizing plate is lowered. That is, when laminating a polarizing plate having a protective film made thin, to a liquid crystal cell, when the misalignment occurs at the time of laminating, when the polarizing plate is peeled off from the liquid crystal cell in order to re-paste, it cannot be peeled off well. Thus, there is a problem that the productivity of the liquid crystal display device is reduced.

By the way, conventionally, it has been proposed to use a resin film other than the cellulose ester film as a protective film for the polarizing plate. For example, in JP 2012-256057 A, when a polyester film made of polyethylene terephthalate or the like is used as a protective film for a polarizing plate, a film whose retardation is controlled to a predetermined value is used in combination with a specific light source. It is said that a polarizing plate excellent in durability and visibility is provided. However, it has not been known at all that reworkability as described above can be improved by using such a polyester film as a protective film for a polarizing plate.

The present invention has been made in view of the above problems, and a solution to the problem is to provide means capable of improving reworkability in a polarizing plate in which a thin cellulose ester film is used as one protective film. It is.

As a result of intensive studies in view of the above problems, the inventor of the present invention uses a polyester film made of polyester as the protective film A in the polarizing plate having the protective film A, the polarizer and the protective film B in this order. Has a modulus of elasticity of 5.0 to 8.0 GPa in at least one of the MD direction and the TD direction, and a cellulose ester film made of cellulose ester is used as the protective film B. The cellulose ester film is (1 ) The film thickness is in the range of 15 to 60 μm, and (2) the thinned cellulose ester film is used as the protective film B by assuming that the toughness is 10 to 20 in both the MD direction and the TD direction. Excellent reworkability even when It found that it is possible to realize a polarizer, a completed the invention.

That is, the above-mentioned problem of the present invention is solved by the following means.

1. A polarizing plate having a protective film A, a polarizer and a protective film B in this order,
The protective film A is a polyester film made of polyester,
The polyester film has an elastic modulus of 5.0 to 8.0 GPa in at least one of the MD direction and the TD direction,
The protective film B is a cellulose ester film made of cellulose ester,
The cellulose ester film is
(1) The film thickness is in the range of 15-60 μm,
(2) The toughness is 10 to 20 in both the MD direction and the TD direction.
A polarizing plate characterized by that;
2. The polarizing plate according to 1 above, wherein the polyester is polyethylene terephthalate;
3. 3. The polarizing plate according to 1 or 2 above, wherein the protective film A has a thickness in the range of 40 to 100 μm;
4). For the protective film B, the in-plane retardation value Ro defined by the following formulas (i) and (ii) is in the range of 30 to 70 nm, and the retardation value Rt in the thickness direction is 100 to 140 nm. The polarizing plate according to any one of claims 1 to 3, which is within a range:
Formula (i): Ro = (n _x −n _y ) × d (nm)
Formula (ii): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
Wherein, n _x represents a refractive index in the direction x in which the refractive index in the plane direction is maximized in the film. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. The measurement is performed at a measurement wavelength of 590 nm in an environment of 23 ° C. and 55% RH. ]
5. The polarizing plate according to any one of 1 to 4, wherein the cellulose ester contains cellulose acetate as a main component;
6). 6. The polarizing plate according to 5 above, wherein the cellulose acetate has a degree of acetyl group substitution of 2.1 to 2.95;
7). The polarizing plate according to any one of 1 to 6, wherein the protective film B contains a retardation increasing agent;
8). The retardation increasing agent is represented by the following general formula (1):

In the formula, R ¹ to R ⁴ each independently represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a halogen atom;
Each X independently represents —O— or —O—C (═O) — (wherein O is bonded to the phenyl skeleton in the general formula (1));
R ⁵ and R ⁶ are each independently
When X is —O—, it represents a hydroxyl group, an ester group or an alkyl group which may be substituted with an optionally substituted aromatic group; or a glycidyl group,
When X is —O—C (═O) —, a hydroxyl group, an ester group or an alkyl group which may be substituted with an optionally substituted aromatic group; or an optionally substituted aromatic group To express,
The polarizing plate of said 7 containing the compound represented by these;
9. The polarizing plate according to any one of 1 to 8, wherein the protective film A and the protective film B are both bonded to the polarizer with an ultraviolet curable adhesive;
10. 10. The polarizing plate according to any one of 1 to 9, wherein the polarizer has a thickness in the range of 2 to 15 μm;
11. 11. The polarizing plate according to any one of 1 to 10 above, which has a thickness in the range of 80 to 150 μm;
12 12. A liquid crystal display device comprising the polarizing plate according to any one of 1 to 11 above.

It is a schematic sectional drawing which shows an example of a structure of the polarizing plate of this invention. It is the figure which showed typically an example of the dope preparation process of the solution casting film forming method preferable for this invention, a casting process, and a drying process (solvent evaporation process).

The polarizing plate which concerns on this invention is a polarizing plate which has the protective film A, the polarizer, and the protective film B in this order, Comprising: The said protective film A is a polyester film which consists of polyester, The said polyester film is MD direction and TD. The elastic film has an elastic modulus of 5.0 to 8.0 GPa in at least one of the directions, and the protective film B is a cellulose ester film made of cellulose ester.
(1) The film thickness is in the range of 15-60 μm,
(2) The toughness is 10 to 20 in both the MD direction and the TD direction.
It is characterized by this. According to the polarizing plate concerning this invention, even if it is a case where a thin cellulose-ester film is used as one protective film, it becomes possible to improve rework property.

Although the details of the mechanism have not been clarified as to the technical reason for obtaining the intended effect of the present invention by the above configuration defined in the present invention, the present invention has the following hypothesis-verification process. It was completed after that.

That is, in view of the above-mentioned problems, the present inventor has eagerly studied the characteristics relating to the polarizing plate having the protective film A, the polarizer, and the protective film B in this order. In the process, it was hypothesized that a decrease in the tear strength of the polarizing plate might be the cause of the decrease in reworkability when a thinned cellulose ester film was used as the protective film B. On that basis, it was confirmed that the reworkability was improved when a polyester film having a high tear strength was used as the protective film A, and the hypothesis was verified. Thereafter, in order to obtain a polarizing plate with further improved reworkability, various properties of the polyester film constituting the protective film A were changed and the performance of the polarizing plate was examined. As a result, a polyester film having a predetermined range of elastic modulus was obtained. It has been found that particularly excellent reworkability can be achieved when used. On the other hand, if such a protective film A is used, it is confirmed that a cellulose ester film can be used as the protective film B as in the conventional case, and further, the lower limit of toughness as a physical property required for the cellulose ester film. The value was found and the present invention was completed.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present invention, “˜” is used to mean that the numerical values described before and after it are included as the lower limit value and the upper limit value.

"Polarizer"
Hereinafter, the detail of each component of the polarizing plate of this invention is demonstrated.

[Configuration of polarizing plate]
The polarizing plate of the present invention has a protective film A, a polarizer and a protective film B in this order, the protective film A is a polyester film (for example, polyethylene terephthalate film), and the protective film B is a cellulose ester film (for example, cellulose). Acetate film).

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of the polarizing plate of the present invention. In FIG. 1, a polarizing plate 101 of the present invention has a polyethylene terephthalate film 102, which is a protective film A, and a polarizer 104 from the surface side. The polyethylene terephthalate film 102 and the polarizer 104 are bonded to each other by ultraviolet curing. Bonded by the agent layer 103A. The ultraviolet curable adhesive layer 103A is made of a material that is cured by irradiating ultraviolet rays or the like. The details of the ultraviolet curable adhesive will be described later.

In the polarizing plate 101 shown in FIG. 1, the surface of the polarizer 104 opposite to the surface on which the polyethylene terephthalate film 102 that is the protective film A is further disposed, further through the ultraviolet curable adhesive layer 103B, A cellulose acetate film 105 as the protective film B is laminated.

Although not shown in FIG. 1, on the further outer side (outermost surface portion) of the polyethylene terephthalate film 102, for example, an antiglare layer, an antireflection layer, an antifouling layer, a hard coat layer, etc. May be provided.

[Protective film A]
The protective film A is a polyester film made of polyester. As a specific form of the polyester film, conventionally known knowledge can be appropriately referred to except that the elastic modulus is a value within a predetermined range. Specifically, the polyester film constituting the protective film A used for the polarizing plate according to the present invention is 5.0 to 8.0 GPa, preferably 5.5 to 7.0 GPa in at least one of the MD direction and the TD direction. More preferably, it has an elastic modulus of 5.8 to 6.5 GPa. If the elastic modulus is low, the reworkability of the polarizing plate deteriorates, and it is difficult to produce a film having a high elastic modulus. Moreover, it preferably has the predetermined elastic modulus in both the MD direction and the TD direction. In addition, as a value of the elasticity modulus of a polyester film, the value measured by the measuring method as described in the column of the Example mentioned later shall be employ | adopted.

As the polyester constituting the polyester film, polyethylene terephthalate or polyethylene naphthalate can be used, but other copolymer components may be included. These resins are excellent in transparency and excellent in thermal and mechanical properties, and the retardation can be easily controlled by stretching. In particular, polyethylene terephthalate is the most suitable material because it has a large intrinsic birefringence and relatively large retardation can be obtained even when the film is thin.

Further, for the purpose of suppressing deterioration of optical functional dyes such as iodine dyes, it is preferable that the light transmittance of light having a wavelength of 380 nm in the protective film A is 20% or less. The light transmittance is more preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less. If the light transmittance is 20% or less, the optical functional dye can be prevented from being deteriorated by ultraviolet rays. The transmittance in the present invention is measured by a method perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

Here, in order to reduce the light transmittance of the protective film A to 20% or less, it is desirable to appropriately adjust the type, concentration, and thickness of the ultraviolet absorber. The ultraviolet absorber used in the present invention is a known substance. Examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber, and an organic ultraviolet absorber is preferable from the viewpoint of transparency. When two or more kinds of ultraviolet absorbers are used in combination, ultraviolet rays having different wavelengths can be absorbed simultaneously, so that the ultraviolet absorption effect can be further improved.

Of the UV absorbers, UV absorbers having a molecular weight of 400 or more are not sublimated or are not easily volatilized at a high boiling point. From the viewpoint of improving weather resistance, it is preferable.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- ( Benzotriazoles such as 1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, Hindered amines such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butyl Bis (1,2,2,6,6-pentamethyl-4-piperidyl) malonate, 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionylo Xyl] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine The hybrid type | system | group which has the structure of a hindered amine is mentioned, These can be used individually or in combination of 2 or more types. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

As these ultraviolet absorbers, commercially available products may be used, for example, Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328, Tinuvin 928, etc. manufactured by BASF Japan, or 2, 2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (molecular weight 659; examples of commercially available products are manufactured by ADEKA Corporation LA31) can be preferably used.

The above ultraviolet absorbers can be used alone or in combination of two or more.

In addition to the ultraviolet absorber, it is also preferable to include various additives within a range not impeding the effects of the present invention. Examples of additives include inorganic particles, heat resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light proofing agents, flame retardants, thermal stabilizers, antioxidants, and antigelling agents. And surfactants. Moreover, in order to show high transparency, it is also preferable that a polyester film does not contain a particle | grain substantially. “Polyester film substantially does not contain particles” means, for example, in the case of inorganic particles, when inorganic elements are quantified by fluorescent X-ray analysis, 50 ppm by mass or less, preferably 10 ppm by mass or less, particularly preferably detection The content is below the limit.

Furthermore, the polyester film constituting the protective film A can be subjected to corona treatment, coating treatment, flame treatment or the like in order to improve the adhesion to the polarizer.

In addition, as described in Patent Document 2, when a white light emitting diode is used as a backlight light source of a liquid crystal display device, it is preferable to control the retardation value of the polyester film to a value within a predetermined range. Specifically, the polyester film used for the protective film A preferably has a retardation of 3000 to 30000 nm. When the retardation is less than 3000 nm, when used as a protective film, it exhibits a strong interference color when observed from an oblique direction, so the envelope shape is different from the emission spectrum of the light source, and it is difficult to ensure good visibility. There is a risk of becoming. The lower limit value of the preferred retardation is 4500 nm, the next preferred lower limit value is 5000 nm, the more preferred lower limit value is 6000 nm, the still more preferred lower limit value is 8000 nm, and the particularly preferred lower limit value is 10,000 nm.

On the other hand, the upper limit of the retardation of the polyester film is preferably 30000 nm, more preferably 20000 nm. Even if a polyester film having a retardation higher than that is used as the protective film A, the effect of improving the visibility is not substantially obtained, and the thickness of the film is considerably increased, so that it can be handled as an industrial material. May decrease.

In the present invention, the retardation value of the protective film A can be obtained by measuring the refractive index and thickness in the biaxial direction, or a commercially available automatic birefringence measurement such as KOBRA-21ADH (Oji Scientific Instruments). It can also be determined using an apparatus.

The polyester film constituting the protective film A can be manufactured according to a general polyester film manufacturing method. For example, the polyester resin is melted and the non-oriented polyester extruded and formed into a sheet shape is stretched in the longitudinal direction by utilizing the speed difference of the roll at a temperature equal to or higher than the glass transition temperature, and then stretched in the transverse direction by a tenter. The method of performing heat processing is mentioned.

The polyester film of the present invention may be a uniaxially stretched film or a biaxially stretched film, but when the biaxially stretched film is used as a polarizer protective film, it may be observed from directly above the film surface. Although rainbow-like color spots are not seen, caution is necessary because rainbow-like color spots may be observed when observed from an oblique direction. This phenomenon is because biaxially stretched films are composed of refractive index ellipsoids having different refractive indexes in the running direction, width direction, and thickness direction, and the retardation becomes zero depending on the direction of light transmission inside the film (refractive index). This is because there is a direction in which the ellipsoid looks like a perfect circle. Therefore, when the liquid crystal display screen is observed from a specific oblique direction, a point where the retardation becomes zero may be generated, and a rainbow-like color spot is generated concentrically around that point. When the angle from the position directly above the film surface (normal direction) to the position where the rainbow-like color spots are visible is θ, the angle θ increases as the birefringence in the film increases, and the rainbow-like color increases. Spots are difficult to see. The biaxially stretched film tends to reduce the angle θ, and therefore the uniaxially stretched film is more preferable because rainbow-like color spots are less visible.

However, a perfect uniaxial (uniaxial symmetry) film is not preferable from the viewpoint of improving the reworkability because the mechanical strength in the direction orthogonal to the orientation direction is significantly reduced. In the present invention, the polyester film is biaxial (biaxial symmetry) in a range that does not substantially cause rainbow-like color spots or a range that does not cause rainbow-like color spots in a viewing angle range required for a liquid crystal display screen. ) Is preferable.

The film thickness of the polyester film constituting the protective film A is not particularly limited, but is preferably 40 to 100 μm, more preferably 60 to 95 μm. When the film thickness of the polyester film is 40 μm or more, the anisotropy of the mechanical properties of the film is difficult to be exhibited, and the protective film A having excellent mechanical strength can be configured. Moreover, if the film thickness of a polyester film is 100 micrometers or less, since the increase in the thickness of a polarizing plate is prevented, it is preferable.

Subsequently, the film forming conditions of the polyester film will be specifically described.

In order to control the value of the elastic modulus of the polyester film within the above-described range, first, it is preferable to perform filtration treatment twice or more in a state where the polyester as a film forming raw material is melted. By performing such treatment, the polymer component (dama) contained in the raw material polyester can be removed, and the molecular weight distribution of the polyester can be made sharper. In addition, there is no restriction | limiting in particular about the specific means of a filtration process, What is necessary is just to perform a filtration process using filter media, such as a conventionally well-known stainless steel sintered compact. Here, the filter particle size (initial filtration efficiency 95%) of the filter medium is preferably 25 μm or less, and more preferably 10 μm or less.

Thereafter, the raw material polyester subjected to the filtration treatment is mixed with an additive such as an ultraviolet absorber if necessary, and is then introduced into an extruder, melted, extruded from a T-die, and adhered to a cooling roll. A stretched sheet is obtained. The unstretched sheet is stretched in the MD direction by stretching (roll stretching) between rolls having a speed difference, and further stretched by stretching (tenter stretching) or holding by a clip and expanding as needed. The film is also stretched in the TD direction by stretching (inflation stretching) or the like, and finally biaxially oriented.

Here, first, in the first stage longitudinal stretching step, stretching is performed between two or many rolls having different peripheral speeds. The draw ratio (longitudinal draw ratio) at this time is preferably 2 to 5 times, more preferably 3 to 5 times, and particularly preferably 3 to 4 times. As a heating means at this time, a method using a heating roll or a method using a non-contact heating method may be used, or they may be used in combination. Among these, the most preferable stretching method includes a method using both roll heating and non-contact heating. In this case, preheating the film to a relatively high temperature of 120 to 150 ° C. is important from the viewpoint of increasing the elastic modulus of the polyester film. Then, it can introduce | transduce into the horizontal extending process mentioned later by heating with an infrared heater. The importance of this preheating is similarly applied to the case where the transverse stretching step is performed first and then the longitudinal stretching step is performed. The stretching temperature in the longitudinal stretching step is preferably 90 to 180 ° C, more preferably 100 to 180 ° C.

Subsequently, the uniaxially stretched film thus obtained can be introduced into a tenter and stretched in the width direction. The draw ratio (transverse draw ratio) at this time is preferably 1 to 5 times, more preferably 2 to 5 times, still more preferably 2 to 4 times, and particularly preferably 3 to 4 times. . The stretching temperature in the transverse stretching step is preferably 90 to 180 ° C, more preferably 100 to 150 ° C. The biaxially stretched film thus obtained is subjected to heat treatment as necessary. The heat treatment is preferably carried out in a tenter, preferably in the range of the melting point Tm-50 ° C. to Tm of the polyester.

Furthermore, from the viewpoint of increasing the elastic modulus of the polyester film, it is preferable to control the total value of the longitudinal draw ratio and the transverse draw ratio. Specifically, the total value is preferably controlled to 6.0 to 9.0 times, more preferably 6.0 to 8.0 times, and more preferably 6.5 to 7.5 times. More preferably.

As a method of blending the ultraviolet absorber with the polyester film constituting the protective film A, a known method can be used in combination. For example, a preliminarily kneaded extruder is used to blend the dried ultraviolet absorber and the polymer raw material. A master batch can be prepared and blended by, for example, a method of mixing the predetermined master batch and polymer raw material during film formation.

At this time, the concentration of the UV absorber in the master batch is preferably 5 to 30% by mass in order to uniformly disperse the UV absorber and mix it economically. As a condition for producing the master batch, it is preferable to use a kneading extruder and to extrude at a temperature not lower than the melting point of the polyester raw material and not higher than 290 ° C. for 1 to 15 minutes. Above 290 ° C, the weight loss of the UV absorber is large, and the viscosity of the master batch is greatly reduced. When the extrusion temperature is -50 ° C. or lower, uniform mixing of the UV absorber becomes difficult. At this time, if necessary, a stabilizer, a color tone adjusting agent, and an antistatic agent may be added.

The polyester film may have a multilayer structure of at least three layers, and an ultraviolet absorber may be added to the intermediate layer of the film. A film having a three-layer structure containing an ultraviolet absorber in the intermediate layer can be specifically produced as follows. Polyester pellets alone for the outer layer, master batches containing UV absorbers for the intermediate layer and polyester pellets are mixed at a predetermined ratio, dried, and then supplied to a known melt laminating extruder, which is slit-shaped. Extruded into a sheet from a die and cooled and solidified on a casting roll to make an unstretched film. That is, using two or more extruders, a three-layer manifold or a merging block (for example, a merging block having a square merging portion), a film layer constituting both outer layers and a film layer constituting an intermediate layer are laminated, An unstretched film can be produced by extruding a three-layer sheet from a die and cooling it with a casting roll.

[Protective film B]
The protective film B is a cellulose ester film made of cellulose ester. As a specific form of the cellulose ester film, conventionally known knowledge can be appropriately referred to except that the film thickness and toughness are values within a predetermined range.

Specifically, the cellulose ester film constituting the protective film B used in the polarizing plate according to the present invention is characterized in that the film thickness is in the range of 15 to 60 μm, and more preferably 20 to 40 μm. Within range. If the film thickness of the cellulose ester film as the protective film B is 15 μm or more, it has sufficient rigidity and can be obtained with excellent handleability, and if it is 60 μm or less, it is easy to produce a thin film polarizing plate. Become.

In addition, the cellulose ester film constituting the protective film B used in the polarizing plate according to the present invention has a toughness of 10 to 20 in both the MD direction and the TD direction, and more preferably 15 to 20 Within range. By controlling the toughness value of the cellulose ester film in such a range, the inventor configures the polarizing plate in combination with the protective film A made of the polyester film having the elastic modulus as described above. It was found that even when a thin cellulose ester film was used as the protective film B, a polarizing plate excellent in reworkability could be realized. In addition, as a toughness value of the cellulose ester film, a value measured by the measuring method described in the column of Examples described later is adopted.

(Cellulose ester)
Cellulose ester (cellulose ester resin) is formed by acylating some or all of the hydrogen atoms of hydroxyl groups (—OH) at the 2nd, 3rd and 6th positions in β-1,4 bonded glucose units constituting cellulose. This is a cellulose acylate resin substituted with a group.

The cellulose ester contained in the film of this embodiment is not particularly limited, but is preferably an ester of a linear or branched carboxylic acid having about 2 to 22 carbon atoms. The carboxylic acid constituting the ester may be an aliphatic carboxylic acid, may form a ring, or may be an aromatic carboxylic acid. For example, the hydrogen atom of the hydroxyl group of cellulose is an acyl group having 2 to 22 carbon atoms such as acetyl, propionyl, butyryl, isobutyryl, valeryl, pivaloyl, hexanoyl, octanoyl, lauroyl, stearoyl, etc. Examples include substituted cellulose esters. The carboxylic acid (acyl group) constituting the ester may have a substituent. The carboxylic acid constituting the ester is particularly preferably a lower fatty acid having 2 to 6 carbon atoms, more preferably a lower fatty acid having 2 to 4 carbon atoms, and a lower fatty acid having 2 or 3 carbon atoms. More preferably it is. Note that the acyl group in the cellulose ester may be a single species or a combination of a plurality of acyl groups.

Specific examples of preferred cellulose esters include cellulose acetate (diacetyl cellulose (DAC), triacetyl cellulose (TAC)), cellulose acetate propionate (CAP), cellulose acetate butyrate, and cellulose acetate propionate butyrate. Examples thereof include mixed fatty acid esters of cellulose to which a propionate group or a butyrate group is bound in addition to such an acetyl group. Preferred is cellulose acetate, cellulose acetate butyrate or cellulose acetate propionate, and particularly preferred is cellulose acetate. In this invention, it is preferable that the cellulose ester which comprises the protective film B contains a cellulose acetate as a main component from a viewpoint of a handleability or film forming ability. Here, “including as a main component” means that the content of cellulose acetate is 50% by mass or more based on the total amount of cellulose ester. The cellulose acetate content is preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 98% by mass with respect to the total amount of cellulose ester. It is at least mass%, most preferably 100 mass%.

The butyryl group that can be contained in the cellulose ester may be linear or branched. Moreover, these cellulose esters may use a single kind, and may use it in combination of multiple types.

The total degree of acyl group substitution (total acyl group substitution degree) of the cellulose ester can be about 1.0 to 3.0. The total degree of substitution of the acyl group is preferably in the range of 2.0 to 2.95, more preferably 2.1 to 2.7 from the viewpoint of lowering moisture permeability. Further, when the cellulose ester contains cellulose acetate as a main component, from the viewpoint of film forming suitability and film strength, the degree of acetyl group substitution of the cellulose acetate is 2.1 to 2.95 from the viewpoint of film processing suitability. Preferably, it is 2.2 to 2.75, more preferably 2.2 to 2.6. In the range of 2.2 to 2.75, the film is hard and the tear strength is good, and in the range of 2.2 to 2.6, the visibility is particularly good when used as a phase difference. The acyl group substitution degree of cellulose ester can be measured by the method prescribed in ASTM-D817-96.

The degree of substitution of acyl groups indicates the average number of acyl groups per glucose unit, and how many hydrogen atoms of hydroxyl groups at the 2nd, 3rd and 6th positions of 1 glucose unit are substituted with acyl groups. Show. Therefore, the maximum degree of substitution is 3.0. In this case, it means that the hydrogen atoms of the hydroxyl groups at the 2nd, 3rd and 6th positions are all substituted with acyl groups. These acyl groups may be substituted on the 2nd, 3rd and 6th positions of the glucose unit on average, or may be substituted with a distribution. The degree of substitution is determined by the method prescribed in ASTM-D817-96.

In order to obtain desired optical characteristics, cellulose acetates having different degrees of substitution may be mixed and used. The mixing ratio of different cellulose acetates is not particularly limited.

The number average molecular weight of the cellulose ester is preferably in the range of 4 × 10 ⁴ to 3 × 10 ⁵ in order to increase the mechanical strength of the resulting film, and is 4.5 × 10 ⁴ to 2 × 10 ⁵ . The range is more preferable, and the range of 5 × 10 ⁴ to 7 × 10 ⁴ is particularly preferable. In the present specification, “weight average molecular weight (Mw)” and “number average molecular weight (Mn)” are values measured using gel permeation chromatography (GPC). The measurement conditions are as follows.

The content of residual sulfuric acid in the cellulose ester is preferably in the range of 0.1 to 45 ppm by mass in terms of elemental sulfur, and more preferably in the range of 1 to 30 ppm by mass. Sulfuric acid is considered to remain in the film in a salt state. When the content of the residual sulfuric acid exceeds 45 ppm by mass, the film tends to break when the film is stretched hot or when slitting is performed after the hot stretch. The content of residual sulfuric acid can be measured by the method prescribed in ASTM D817-96.

The content of free acid in the cellulose ester is preferably in the range of 1 to 500 ppm by mass, more preferably 1 to 100 ppm by mass, and further preferably in the range of 1 to 70 ppm by mass. preferable. When the content of the free acid is in the above range, it is difficult to break when the film is hot stretched or slitted after the hot stretch, as described above. The content of free acid can be measured by the method prescribed in ASTM D817-96.

Cellulose ester may contain a trace amount of metal components. It is thought that a trace amount metal component originates in the water used in the synthesis process of the cellulose derivative. Like these metal components, the content of components that can become insoluble nuclei is preferably as small as possible. In particular, metal ions such as iron, calcium, and magnesium may form an insoluble matter by forming a salt with a resin decomposition product or the like that may contain an organic acidic group. In addition, the calcium (Ca) component easily forms a coordination compound (that is, a complex) with an acidic component such as a carboxylic acid or a sulfonic acid, and many ligands. There is a risk of forming an insoluble starch or turbidity.

Specifically, the content of the iron (Fe) component in the cellulose ester is preferably 3 mass ppm or less, and more preferably 1 mass ppm or less. Further, the content of the calcium (Ca) component in the cellulose derivative is preferably 60 ppm by mass or less, and more preferably in the range of 0 to 30 ppm by mass. The content of the magnesium (Mg) component in the cellulose ester is preferably in the range of 0 to 70 ppm by mass, and particularly preferably in the range of 0 to 20 ppm by mass.

The content of metal components such as iron (Fe) component, calcium (Ca) component, and magnesium (Mg) component is pre-processed by microdigest wet cracking device (sulfuric acid decomposition) and alkali melting of completely dried cellulose ester. After the measurement, it can be measured using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

The contents of residual alkaline earth metal, residual sulfuric acid and residual acid can be adjusted by thoroughly washing the cellulose ester obtained by synthesis.

Cellulose esters such as cellulose acetate and cellulose acetate propionate can be produced by known methods. 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 (hydroxyl groups) of the glucose unit are substituted with an acyl acid of an organic acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose ester such as cellulose acetate propionate or cellulose acetate butyrate can be produced. Next, a cellulose ester resin having a desired degree of acyl substitution is synthesized by hydrolyzing the cellulose triester. Thereafter, the cellulose ester is completed through steps such as filtration, precipitation, washing with water, dehydration, and drying. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

The cellulose ester may be a commercially available product. Commercially available products include Daicel Corporation L20, L30, L40, and L50, Eastman Chemical Co. Ca398-3, Ca398-6, Ca398-10, Ca398-30, Ca394-60S, and the like.

(Retardation increasing agent)
The cellulose ester film as the protective film B preferably contains a retardation increasing agent. The “retardation increasing agent” means an additive having a function of increasing the retardation of the cellulose ester film by the addition thereof. There is no restriction | limiting in particular about the specific form of a retardation raising agent, A conventionally well-known knowledge can be referred suitably.

Here, as a preferable form of the retardation increasing agent, for example, a compound represented by the following general formula (1) may be mentioned. However, it goes without saying that other retardation increasing agents may be used. The compound of the following general formula (1) can raise the retardation value of the thickness direction of a cellulose-ester film especially, and can also reduce the moisture permeability of the said film. Moreover, the compound of the following general formula (1) has low volatility even under high temperature and high humidity. For this reason, the bleed resistance of the cellulose ester film can be improved, and as a result, the sharpness of the image can be improved.

In the general formula (1), R ¹ to R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a halogen atom. Here, R ¹ to R ⁴ may be the same or different from each other. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, a propyl group, and an isopropyl group. Among them, from the viewpoint of improving the retardation value (particularly the retardation value in the thickness direction of the film) and compatibility with the cellulose ester, hydrogen atoms, methyl groups, ethyl groups, fluorine atoms, chlorine atoms are A methyl group is preferable, and a methyl group is particularly preferable.

In the general formula (1), each X independently represents —O— or —O—C (═O) —. Here, when X represents —O—C (═O) —, the ether oxygen (—O—) of —O—C (═O) — is bonded to the phenyl skeleton in the general formula (1). . Among these, X is preferably —O—.

In the general formula (1), R ⁵ and R ⁶ each independently have the following definition.

When X is —O—, R ⁵ and R ⁶ each independently represents a hydroxyl group, an ester group or an alkyl group which may be substituted with an optionally substituted aromatic group; or a glycidyl group .

When X is —O—C (═O) —, R ⁵ and R ⁶ may each independently be substituted with a hydroxyl group, an ester group or an optionally substituted aromatic group. Represents an alkyl group; or an optionally substituted aromatic group.

The ester group capable of substituting the alkyl group is represented by the formula: —O—C (═O) —R or —C (═O) —O—R, wherein R is a straight chain having 1 to 8 carbon atoms. A chain or branched chain alkyl group or an aromatic group. The alkyl group and aromatic group are as defined below.

The alkyl group as R ⁵ and R ⁶ is not particularly limited, but is methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group. A linear or branched alkyl group having 1 to 8 carbon atoms, such as neopentyl group, hexyl group, heptyl group and octyl group. Among these, an alkyl group having 1 to 5 carbon atoms is preferable, and an alkyl group having 2 to 4 carbon atoms is preferable.

The aromatic group may be an aryl group having 6 to 24 carbon atoms. More specifically, a phenyl group, p-tolyl group, naphthyl group, biphenyl group, fluorenyl group, anthryl group, pyrenyl group, azulenyl group, acenaphthylenyl group, terphenyl group, phenanthryl group and the like can be mentioned. Of these, a phenyl group and a naphthyl group are preferable, and a phenyl group is more preferable. The aromatic group may have a substituent. Here, the substituent capable of substituting the aromatic group is not particularly limited, and examples thereof include an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a phenyl group, a methylphenyl group, and a phenylphenyl group. , Methylphenylphenyl group, cyano group, halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), nitro group and the like. Moreover, the said substituent may be one, or may be two or more, and in the latter case, each substituent may be the same or different. Among these, from the viewpoint of improving the retardation value (particularly the retardation value in the thickness direction of the film) and compatibility with the cellulose ester, the aromatic group is a phenyl group, a methylphenyl group, or a methylphenylphenyl group. It is preferable that

The method for producing the compound of the general formula (1) when R ⁵ and R ⁶ are alkyl groups having a substituent is not particularly limited. Specifically, the compound can be obtained by reacting an epoxy compound with an aromatic monocarboxylic acid. As said epoxy compound, the diglycidyl ether type epoxy compound obtained by reaction with biphenols and epichlorohydrin is mentioned. As a specific example of this epoxy compound, 3,3 ′, 5,5′-tetramethyl-4,4′-diglycidyloxybiphenyl (commercially available product is “jER YX-4000” manufactured by Japan Epoxy Resin Co., Ltd.) Biphenol type epoxy compounds such as epoxy equivalent of 180 to 192)) can be used.

Examples of the aromatic monocarboxylic acid include benzoic acid, dimethylbenzoic acid, trimethylbenzoic acid, tetramethylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, cumic acid, o-toluic acid, m-toluic acid, p-toluic acid, anisic acid, ethoxybenzoic acid, propoxybenzoic acid, cyanobenzoic acid, fluorobenzoic acid, nitrobenzoic acid, 4-phenylbenzoic acid, 4- (3-methylphenyl) benzoic acid, 4- (4- Methylphenyl) benzoic acid, 4- (3,5-dimethylphenyl) benzoic acid, 2-methyl-4-phenylbenzoic acid, 2,6-dimethyl-4-phenylbenzoic acid, 2,6-dimethyl-4- ( 3,5-dimethylphenyl) benzoic acid, naphthoic acid, nicotinic acid, furoic acid, 1-naphthalene carboxylic acid, 2-naphthalene carboxylic acid, etc. It is below. These aromatic monocarboxylic acids can be used alone or in combination of two or more.

In the above reaction, the epoxy group of the epoxy compound and the carboxyl group of the aromatic monocarboxylic acid react to synthesize the compound of the general formula (1). Here, the reaction conditions are not particularly limited as long as the reaction proceeds. For example, the reaction temperature is 80 to 130 ° C, more preferably 100 ° C to 115 ° C. The reaction time is preferably 10 to 25 hours. The mixing ratio (preparation ratio) of the epoxy compound and the aromatic monocarboxylic acid is not particularly limited as long as the reaction proceeds. For example, the ratio of the number of moles of epoxy groups in the epoxy compound to the number of moles of aromatic monocarboxylic acid (number of moles of epoxy group) / (number of moles of aromatic monocarboxylic acid) is 1 / 0.9 to 1.0. It is preferable that it is the range of these.

In the above reaction, a catalyst may be used as necessary. Examples of the catalyst include phosphine compounds such as trimethylphosphine, triethylphosphine, tributylphosphine, trioctylphosphine, and triphenylphosphine; 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-ethyl-4-methyl Imidazole compounds such as imidazole and 4-phenyl-2-methylimidazole; triethylamine, tributylamine, trihexylamine, triamylamine, triethanolamine, dimethylaminoethanol, tritylenediamine, dimethylphenylamine, dimethylbenzylamine, 2 -(Dimethylaminomethyl) phenol, amine compounds such as 1,8-diazabicyclo (5,4,0) undecene-7; Such as emission compounds. These catalysts are preferably used in an amount of 0.05 to 1 part by mass with respect to a total of 100 parts by mass of the epoxy compound and the aromatic monocarboxylic acid.

Among these, R ⁵ and R ⁶ are preferably an alkyl group having a hydroxyl group and an ester group as a substituent, or a glycidyl group. In this case, X is more preferably —O—. Further, as the compound of the general formula (1), the compounds described in JP 2011-140637 A and JP 2011-116912 A are included in the compound of the general formula (1). In addition, some of the compounds described in JP-A-2006-45468 are also included in the compound of the general formula (1). More specifically, the following is mentioned as a more preferable example of the compound of General formula (1). In addition, a compound is prescribed | regulated by the following number. That is, the following compound (1-1) is also referred to as “compound (1-1)”.

There is no restriction | limiting in particular about content of the retardation raising agent in the cellulose-ester film which comprises the protective film B, It can adjust suitably to content which can achieve the value of the desired retardation as mentioned in the form mentioned later. Is possible. As an example, the content of the retardation increasing agent in the cellulose ester film is preferably 0.5 to 30 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the cellulose ester contained in the cellulose ester film. Particularly preferred is 2 to 5 parts by mass. If it is such quantity, sufficient retardation can be provided to a cellulose-ester film. Moreover, when using the retardation raising agent represented by the above general formula (1), the tear strength of the film can be improved by adding such an amount, and the volatile property under high temperature and high humidity. Therefore, it is possible to improve the bleed resistance of the film and thus the sharpness of the image.

In addition, as a method for adding the retardation increasing agent, it may be added to the resin forming the cellulose ester film as a powder, or after being dissolved in a solvent, it may be added to the resin forming the cellulose ester film.

(Plasticizer)
The cellulose ester film as the protective film B may contain a plasticizer in order to improve the fluidity of the composition during film production and the flexibility and workability of the film. Examples of plasticizers include sugar ester plasticizers, polyester plasticizers, polyhydric alcohol ester plasticizers, acrylic compounds, polycarboxylic acid ester plasticizers (including phthalate ester plasticizers), glycosates. Examples include rate plasticizers, ester plasticizers (including citrate ester plasticizers, fatty acid ester plasticizers, phosphate ester plasticizers, trimellitic ester plasticizers, etc.), styrene compounds, and the like. Among the plasticizers, it is effective for moisture permeability to include at least one plasticizer selected from the group consisting of the following sugar ester plasticizers (sugar ester compounds), polyester plasticizers, and acrylic compounds. This is preferable from the viewpoint of achieving both high control and compatibility with the cellulose ester. These may be used alone or in combination of two or more.

The molecular weight of the plasticizer is preferably 5000 or less, and more preferably 3000 or less from the viewpoint of achieving both improvement in wet heat resistance and compatibility with the cellulose ester. When the compound having a molecular weight of 3000 or less is a polymer, the weight average molecular weight (Mw) is preferably 3000 or less. A preferable molecular weight (Mw) is in the range of 100 to 2500, and more preferably in the range of 300 to 2000.

Sugar ester plasticizer (sugar ester compound) is a compound having 1 to 12 furanose structures or pyranose structures, in which all or part of the hydroxy groups in the compound are esterified. The sugar ester plasticizer can be added for the purpose of preventing hydrolysis.

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

The monocarboxylic acid used for esterifying all or part of the OH group in the pyranose structure or furanose structure is not particularly limited, and is a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic A monocarboxylic acid or the like can be used. The carboxylic acid used may be one type or a mixture of two or more types.

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, Saturation of 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 preferable alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, and derivatives thereof.

Examples of preferred 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, phenylacetic acid, toluic acid, cinnamic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as benzylic acid, biphenylcarboxylic acid, naphthalenecarboxylic acid, tetralincarboxylic acid, or derivatives thereof, and benzoic acid is particularly preferable.

Preferred examples of such sugar esters include sucrose esters represented by the following general formula (FA).

R ₁ to R _{8 in} formula (FA) each independently represent a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group. R ₁ to R ₈ may be the same as or different from each other.

The substituted or unsubstituted alkylcarbonyl group is preferably a substituted or unsubstituted alkylcarbonyl group having 2 or more carbon atoms. Examples of the substituted or unsubstituted alkylcarbonyl group include a methylcarbonyl group (acetyl group). Examples of the substituent that the alkyl group has include an aromatic hydrocarbon ring group such as a phenyl group.

The substituted or unsubstituted arylcarbonyl group is preferably a substituted or unsubstituted arylcarbonyl group having 7 or more carbon atoms. Examples of the arylcarbonyl group include a phenylcarbonyl group. Examples of the substituent that the aromatic hydrocarbon ring group has include an alkyl group such as a methyl group, an alkoxyl group such as a methoxy group, and the like.

The compound represented by the general formula (FA) preferably has an average degree of substitution of 3.0 to 8.0, more preferably 4.0 to 7.5, and even more preferably 4.5 to 7.0. By taking this value, the moisture permeability control and the compatibility with the cellulose ester can be highly compatible.

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 hydroxyl groups contained in the general formula (FA). Of R ₁ to R _{8 in} the general formula (FA), this represents a number containing a group other than hydrogen. Therefore, when all of R ₁ to R ₈ are substituted with a substituent other than hydrogen, the degree of substitution is a maximum value of 8.0, 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 hydroxyl groups and the number of OR groups are fixed. Since it is known that it becomes a compound in which several different components are mixed, it is appropriate to use the average substitution degree as the substitution degree 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.

In the 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. (Hereinafter, R ₁ to R ₈ are also referred to as acyl groups). Specific examples of R ₁ to R ₈ include acyl groups derived from monocarboxylic acids used during the synthesis of the sugar ester compounds exemplified above.

Specific examples of the sugar ester compound according to the present invention will be given below, but any of R ₁ to R ₈ may be the same substituent R, and the present invention is not limited thereto. In the following examples, polyester compounds are defined by the following symbols. In the present invention, sugar ester compounds in which R ₁ to R ₈ are different groups can be used.

The sugar ester compound according to the present invention can be produced by reacting the sugar with an acylating agent (also referred to as an esterifying agent, for example, an acid halide such as 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 a mixture of sugar ester compounds with different degrees of substitution or purely isolated compounds with different degrees of substitution. Can be used to adjust components having a target average substitution degree and a substitution degree of 4 or less.

(Synthesis example: Synthesis example of sugar ester compound)

Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube was 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 the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were 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 is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A sugar ester compound 1 which is a mixture of A-1, A-2, A-3, A-4, A-5 and the like was obtained.

The obtained mixture was analyzed by high performance liquid chromatography mass spectrometry (HPLC-MS). As a result, 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 ester compounds having the components shown in Table A.

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

A-5 etc. means a mixture of all components having a substitution degree of 4 or less, that is, compounds having substitution degrees of 4, 3, 2, 1. The average degree of substitution was calculated with A-5 as the degree of substitution of 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 and the isolated A-1 to A-5 etc. by the method prepared here.

Examples of other sugar esters include compounds described in JP-A Nos. 62-42996 and 10-237084.

The polyester plasticizer is not particularly limited. For example, a polymer (polyester polyol) in which the terminal obtained by a condensation reaction of dicarboxylic acid or an ester-forming derivative thereof and glycol becomes a hydroxy group (hydroxyl group). Alternatively, a polymer in which the terminal hydroxy group of the polyester polyol is sealed with a monocarboxylic acid (end-capped polyester) can be used. The ester-forming derivative referred to here is an esterified product of dicarboxylic acid, dicarboxylic acid chloride, or dicarboxylic acid anhydride.

Preferably, it is preferable to use a polyester plasticizer represented by the following general formula (FB-1) from the viewpoint of high compatibility between moisture permeability control and compatibility with the cellulose ester.

In the above formula, B represents a linear or branched alkylene group having 2 to 6 carbon atoms or a cycloalkylene group, and A represents an aromatic ring group having 6 to 14 carbon atoms, or 4 to 12 carbon atoms. N represents a natural number of 1 or more.

The compound represented by the above formula is obtained from a dicarboxylic acid having an aromatic ring (also referred to as an aromatic dicarboxylic acid) and a linear or branched alkylene or cycloalkylene diol having 2 to 6 carbon atoms, at both ends. Is not sealed with a monocarboxylic acid.

Examples of the aromatic dicarboxylic acid having 6 to 16 carbon atoms include phthalic acid, isophthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3 -Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and the like. Of these, phthalic acid and terephthalic acid are preferred.

Examples of the aromatic dicarboxylic acid having 4 to 12 carbon atoms include 1,2-ethanedicarboxylic acid (succinic acid), 1,3-propanedicarboxylic acid (glutaric acid), 1,4-butanedicarboxylic acid (adipic acid), Examples include 1,5-pentanedicarboxylic acid (pimelic acid) and 1,8-octanedicarboxylic acid (sebacic acid), and adipic acid and succinic acid are particularly preferable.

In addition, it is also preferable from the viewpoint of improving film strength that the dicarboxylic acid is mixed with an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid.

Examples of the linear or branched alkylene or cycloalkylene diol having 2 to 6 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1,3-butane. Diol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexane Examples thereof include diol and 1,4-cyclohexanedimethanol. Of these, ethanediol, 1,2-propanediol, 1,3-propanediol, and 1,3-butanediol are preferable.

Among them, it is preferable for obtaining the effect of the present invention that A is a naphthalene ring or a biphenyl ring which may have a substituent. Here, the substituent is an alkyl group, alkenyl group, or alkoxyl group having 1 to 6 carbon atoms.

The hydroxyl value (OH value) of the polyester compound is preferably 100 mgKOH / g or more and 500 mgKOH / g or less, more preferably 170 mgKOH / g to 400 mgKOH / g. When the hydroxyl value is in this range, the compatibility with the cellulose ester and the cellulose ether becomes suitable.

When the hydroxyl value is 400 mgKOH / g or less, the hydrophobicity of the polyester compound does not increase too much, and when the hydroxyl value is 170 mgKOH / g or more, the intermolecular interaction (hydrogen bond, etc.) between the polyester compounds is excessively strong. It is thought that this is because precipitation in the film can be prevented.

In addition, for measurement of the hydroxyl value, the acetic anhydride method described in Japanese Industrial Standard JIS K1557-1: 2007 can be applied.

The number average molecular weight (Mn) of the polyester compound can be calculated from the following formula.

The polyester compound can be obtained by a conventional method such as a hot melt condensation method using a polyesterification reaction or a transesterification reaction between the dicarboxylic acid and a diol, or an interfacial condensation method between an acid chloride of these acids and a glycol. Easy to synthesize.

The following are examples of the above polyester compounds.

Preferably, it is preferable to use a polyester plasticizer represented by the following general formula (FB-2) from the viewpoint of high compatibility between moisture permeability control and compatibility with cellulose ester.

In the general formula (FB-2), B represents a hydroxy group or a carboxylic acid residue, G represents an alkylene glycol residue having 2 to 18 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or 4 carbon atoms. Represents an oxyalkylene glycol residue having ˜12, 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 the general formula (FB-2), a hydroxy group or carboxylic acid residue represented by B, an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue represented by G, and an alkylene dicarboxylic acid residue represented by A It is composed of a group or an aryl dicarboxylic acid residue, and can be obtained by a reaction similar to that of a normal ester compound.

Examples of the carboxylic acid component of the polyester compound represented by the general formula (FB-2) include acetic acid, propionic acid, butyric acid, benzoic acid, p-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, and dimethyl. There are benzoic 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, respectively.

Examples of the alkylene glycol component having 2 to 18 carbon atoms of the polyester compound represented by the general formula (FB-2) include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,2-butanediol. 1,3-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 -Dimethylolheptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl-1, -Pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. These glycols are used as one or a mixture of two or more.

Particularly, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with the cellulose ester resin. More preferred are alkylene glycols having 2 to 6 carbon atoms, and still more preferred are alkylene glycols having 2 to 4 carbon atoms.

Examples of the aryl glycol having 6 to 12 carbon atoms of the polyester plasticizer represented by the general formula (FB-2) include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, cyclohexanediethanol, 1,4 -There are cyclic glycols such as benzenedimethanol, and these glycols can be used as one kind or a mixture of two or more kinds.

Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the polyester compound represented by the general formula (FB-2) include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols can be used as one kind or a mixture of two or more kinds.

Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the polyester compound represented by the general formula (FB-2) include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, and sebacic acid. , Dodecanedicarboxylic acid and the like, and these are used as one kind or a mixture of two or more kinds, respectively.

Examples of the aryl dicarboxylic acid component having 6 to 12 carbon atoms of the polyester compound represented by the general formula (FB-2) include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, and 1,4-naphthalene. There are dicarboxylic acids and the like.

The polyester compound represented by the general formula (FB-2) has a weight average molecular weight of preferably 300 to 3000, more preferably 350 to 1500. 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.

The weight average molecular weight of the polyester plasticizer is calculated by measurement using gel permeation chromatography (GPC) under the following measurement conditions.

Hereinafter, specific compounds of the polyester compound represented by Formula (FB-2) that can be used in the present invention will be shown, but the present invention is not limited thereto. In the following Examples, polyester compounds are defined by the following symbols.

The viscosity of the polyester plasticizer depends on the molecular structure and molecular weight, but in the case of an adipic acid plasticizer, it has a high compatibility with the cellulose ester and has a high effect of imparting plasticity. It is preferably in the range of s (25 ° C.). One type of polyester plasticizer may be used, or two or more types may be used in combination.

The polyhydric alcohol ester plasticizer is an ester compound (alcohol ester) of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, preferably a divalent to 20-valent aliphatic polyhydric alcohol ester. The polyhydric alcohol ester compound preferably has an aromatic ring or a cycloalkyl ring in the molecule.

The acrylic compound is not particularly limited, but at least one selected from the group consisting of (meth) acrylic acid, (meth) acrylic acid ester, (meth) acrylamides, and (meth) acrylonitrile. Examples thereof include a polymer having a repeating unit derived from a certain acrylic monomer. These acrylic compounds can improve the water resistance of the film.

Among them, the acrylic compound is preferably one in which the methyl methacrylate unit is 50 to 99% by mass and the total amount of other monomer units copolymerizable therewith is 1 to 50% by mass.

Examples of other copolymerizable monomers include alkyl methacrylates having an alkyl group having 2 to 18 carbon atoms; alkyl acrylates having an alkyl group having 1 to 18 carbon atoms; amides such as acryloylmorpholine and N, N-dimethylacrylamide A vinyl monomer having a group; a methacrylic acid ester or an acrylic acid ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester moiety; an α, β-unsaturated carboxylic acid such as acrylic acid or methacrylic acid; Unsaturated group-containing divalent carboxylic acids such as fumaric acid and itaconic acid; aromatic vinyl compounds such as styrene and α-methylstyrene; α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, and the like. Two or more kinds of monomers can be used in combination.

The acrylic compound used in the present invention may have a ring structure, specifically, a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure and a maleic anhydride structure. And a pyran ring structure.

Among these, other monomers that can be copolymerized include alkyl acrylates having 1 to 18 carbon atoms in the alkyl group, amides such as acryloylmorpholine and dimethylacrylamide, from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. Preferred are a vinyl monomer having a group, a methacrylic acid ester or an acrylate ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion, an N-substituted maleimide structure, a pyran ring structure and the like.

Specific examples of the alkyl acrylate having 1 to 18 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, and 2-ethylhexyl acrylate. And methyl acrylate.

Specific examples of the vinyl monomer having an amide group include acrylamide, N-methylacrylamide, N-butylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, acryloylmorpholine, N-hydroxyethylacrylamide, acryloylpyrrolidine, Acryloylpiperidine, methacrylamide, N-methylmethacrylamide, N-butylmethacrylamide, N, N-dimethylmethacrylamide, N, N-diethylmethacrylamide, methacryloylmorpholine, N-hydroxyethylmethacrylamide, methacryloylpyrrolidine, methacryloylpiperidine, N-vinylformamide, N-vinylacetamide, vinylpyrrolidone and the like can be mentioned. Preferably, acryloylmorpholine, N, N-dimethylacrylamide, N-butylacrylamide, vinylpyrrolidone, 2-hydroxyethyl methacrylate are used.

Specific examples of the methacrylic acid ester or acrylate ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester moiety include, for example, cyclopentyl acrylate, cyclohexyl acrylate, methyl cyclohexyl acrylate, trimethylcyclohexyl acrylate, Norbornyl acrylate, norbornyl acrylate, cyano norbornyl acrylate, isobornyl acrylate, bornyl acrylate, menthyl acrylate, fentyl acrylate, adamantyl acrylate, dimethyladamantyl acrylate, tricycloacrylate [5.2 .1.0 ^2,6 ] dec-8-yl, tricyclo [5.2.1.0 ^2,6 ] dec-4-methyl acrylate, cyclodecyl acrylate, cyclopentyl methacrylate, cyclohexane methacrylate Xylyl, methyl cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, norbornyl methacrylate, norbornyl methyl methacrylate, cyano norbornyl methacrylate, phenyl norbornyl methacrylate, isobornyl methacrylate, bornyl methacrylate, menthyl methacrylate, methacryl Fentyl acid, adamantyl methacrylate, dimethyladamantyl methacrylate, tricyclo [5.2.1.0 ^2,6 ] dec-8-yl methacrylate, tricyclo [5.2.1.0 ^2,6 ] decyl methacrylate 4-methyl, cyclodecyl methacrylate, dicyclopentanyl methacrylate and the like.

Preferably, isobornyl methacrylate, dicyclopentanyl methacrylate, dimethyladamantyl methacrylate and the like can be mentioned.

Examples of the N-substituted maleimide include N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, Ni-propylmaleimide, N-butylmaleimide, Ni-butylmaleimide, Nt-butylmaleimide, N-laurylmaleimide, N-cyclohexylmaleimide, N-benzylmaleimide, N-phenylmaleimide, N- (2-chlorophenyl) maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromophenyl) phenylmaleimide, N -(2-methylphenyl) maleimide, N- (2-ethylphenylmaleimide), N- (2-methoxyphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N- (4-benzylphenyl) Maleimide, N- (2,4,6-tribromoph Yl) maleimide and the like. Preferably, N- methyl maleimide, N- cyclohexyl maleimide, etc. N- phenyl maleimide.

These monomers are commercially available.

The acrylic compound preferably has a weight average molecular weight (Mw) in the range of 15000 or less, more preferably in the range of 10,000 or less, from the viewpoint of achieving both moisture permeability control and compatibility with the cellulose ester. More preferably, it is in the range of 5000 to 10,000. In addition, the weight average molecular weight (Mw) of the acrylic compound according to the present invention is calculated by measurement using gel permeation chromatography (GPC) under the following measurement conditions.

Examples of the aliphatic polyhydric alcohol include ethylene glycol, propylene glycol, trimethylolpropane, pentaerythritol and the like.

The monocarboxylic acid can be an aliphatic monocarboxylic acid, an alicyclic monocarboxylic acid, an aromatic monocarboxylic acid, or the like. One kind of monocarboxylic acid may be used, or a mixture of two or more kinds may be used. Further, all of the OH groups contained in the aliphatic polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

The aliphatic monocarboxylic acid is preferably a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms. The number of carbon atoms of the aliphatic monocarboxylic acid is more preferably 1-20, and still more preferably 1-10. Examples of such aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, and the like, and acetic acid may be preferable in order to enhance compatibility with the cellulose ester.

Examples of the alicyclic monocarboxylic acid include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid and the like.

Examples of aromatic monocarboxylic acids include benzoic acid; one having 1 to 3 alkyl groups or alkoxy groups (for example, methoxy group or ethoxy group) introduced into the benzene ring of benzoic acid (for example, toluic acid); benzene ring Aromatic monocarboxylic acids having two or more (for example, biphenyl carboxylic acid, naphthalene carboxylic acid, tetralin carboxylic acid, etc.) are included, and benzoic acid is preferred.

The molecular weight of the polyhydric alcohol ester plasticizer is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. In order to make it hard to volatilize, the one where molecular weight is larger is preferable. In order to improve moisture permeability and compatibility with the cellulose ester, a smaller molecular weight is preferable.

Specific examples of the polyhydric alcohol ester plasticizer include trimethylolpropane triacetate, trimethylolpropane benzoate, pentaerythritol tetraacetate, and an ester represented by the general formula (I) described in JP-A-2008-88292. Compound (A) and the like are included.

The polyvalent carboxylic acid ester plasticizer is an ester compound of a divalent or higher, preferably 2 to 20 valent polycarboxylic acid and an alcohol compound. The polyvalent carboxylic acid is preferably a 2-20 valent aliphatic polyvalent carboxylic acid, a 3-20 valent aromatic polyvalent carboxylic acid, or a 3-20 valent alicyclic polyvalent carboxylic acid.

Examples of polyvalent carboxylic acids include 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 Contains aliphatic polycarboxylic acids such as fumaric acid, maleic acid and tetrahydrophthalic acid; oxypolycarboxylic acids such as tartaric acid, tartronic acid, malic acid and citric acid, etc., and suppresses volatilization from the film. For this, oxypolycarboxylic acids are preferred.

Examples of the alcohol compound include an aliphatic saturated alcohol compound having a straight chain or a side chain, an aliphatic unsaturated alcohol compound having a straight chain or a side chain, an alicyclic alcohol compound, or an aromatic alcohol compound. The carbon number of the aliphatic saturated alcohol compound or the aliphatic unsaturated alcohol compound is preferably 1 to 32, more preferably 1 to 20, and still more preferably 1 to 10. Examples of the alicyclic alcohol compound include cyclopentanol, cyclohexanol and the like. Examples of the aromatic alcohol compound include phenol, paracresol, dimethylphenol, benzyl alcohol, cinnamyl alcohol and the like. The alcohol compound may be one kind or a mixture of two or more kinds.

The molecular weight of the polyvalent carboxylic acid ester plasticizer is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. A larger molecular weight of the polyvalent carboxylic acid ester plasticizer is preferable from the viewpoint of suppressing bleeding out. From the viewpoint of moisture permeability and compatibility with cellulose ester, a smaller one is preferable.

The acid value of the polyvalent carboxylic acid ester plasticizer is preferably 1 mgKOH / g or less, more preferably 0.2 mgKOH / g or less. The acid value refers to the number of milligrams of potassium hydroxide necessary for neutralizing the acid (carboxy group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070 (1992).

Examples of the polyvalent carboxylic acid ester plasticizer include an ester compound (B) represented by the general formula (II) described in JP-A-2008-88292.

The polycarboxylic acid ester plasticizer may be a phthalate ester plasticizer. Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate and the like.

Examples of glycolate plasticizers include alkylphthalyl alkyl glycolates. 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 and the like. .

The ester plasticizer includes a fatty acid ester plasticizer, a citrate ester plasticizer, a phosphate ester plasticizer, a trimellitic acid plasticizer, and the like.

Examples of the fatty acid ester plasticizer include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate and the like. Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, acetyl tributyl citrate and the like. Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate (BDP), trioctyl phosphate, tributyl phosphate and the like. Examples of trimellitic acid plasticizers include octyl trimellitic acid, n-octyl trimellitic acid, isodecyl trimellitic acid, and isononyl trimellitic acid.

The styrene compound (styrene plasticizer) may be a homopolymer of a styrene monomer or a copolymer of a styrene monomer and another copolymer monomer. The content of the structural unit derived from the styrenic monomer in the styrenic compound may be preferably 30 to 100 mol%, more preferably 50 to 100 mol%, in order for the molecular structure to have a certain bulkiness.

The styrene monomer is preferably a compound represented by the following formula (A).

R ¹⁰¹ to R ¹⁰³ in the formula (A) each independently represent a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, or an aryl group. R ¹⁰⁴ is a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, a cycloalkyl group, an aryl group, an alkoxy group having 1 to 30 carbon atoms, an aryloxy group, an alkyloxycarbonyl group having 2 to 30 carbon atoms, an aryloxycarbonyl Group, an alkylcarbonyloxy group having 2 to 30 carbon atoms, an arylcarbonyloxy group, a hydroxyl group, a carboxyl group, a cyano group, an amino group, an amide group, and a nitro group. Each of these groups may further have a substituent (for example, a hydroxyl group, a halogen atom, an alkyl group, etc.). R ¹⁰⁴ may be the same as or different from each other, and may be bonded to each other to form a ring.

Examples of styrenic monomers include styrene; alkyl-substituted styrenes such as α-methylstyrene, β-methylstyrene, and p-methylstyrene; halogen-substituted styrenes such as 4-chlorostyrene and 4-bromostyrene; p-hydroxy Hydroxystyrenes such as styrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, 3,4-dihydroxystyrene; vinylbenzyl alcohols; p-methoxystyrene, p-tert-butoxystyrene, m Alkoxy substituted styrenes such as tert-butoxystyrene; vinyl benzoic acids such as 3-vinylbenzoic acid and 4-vinylbenzoic acid; 4-vinylbenzyl acetate; 4-acetoxystyrene; 2-butylamidostyrene, 4-methylamide Styrene, p-sul Amidostyrenes such as N-amidostyrene; Aminostyrenes such as 3-aminostyrene, 4-aminostyrene, 2-isopropenylaniline and vinylbenzyldimethylamine; Nitrostyrenes such as 3-nitrostyrene and 4-nitrostyrene; Examples include cyanostyrenes such as 3-cyanostyrene and 4-cyanostyrene; vinylphenylacetonitrile; arylstyrenes such as phenylstyrene, and indenes. The styrenic monomer may be one kind or a combination of two or more kinds.

The copolymerizable monomer combined with the styrenic monomer is a (meth) acrylic acid ester compound represented by the following formula (B), maleic anhydride, citraconic anhydride, cis-1-cyclohexene-1,2-dicarboxylic anhydride, Acid anhydrides such as 3-methyl-cis-1-cyclohexene-1,2-dicarboxylic anhydride and 4-methyl-cis-1-cyclohexene-1,2-dicarboxylic anhydride, and nitrile groups such as acrylonitrile and methacrylonitrile -Containing radical polymerizable monomers; amide bond-containing radical polymerizable monomers such as acrylamide, methacrylamide, trifluoromethanesulfonylaminoethyl (meth) acrylate; fatty acid vinyls such as vinyl acetate; chlorine such as vinyl chloride and vinylidene chloride Containing radical polymerizable monomer; 1,3-butadiene, a Puren, 1,4-dimethyl butadiene conjugated diolefins such as, etc. are included, it is preferably represented by the following formula (B) (meth) acrylic acid ester compound or maleic anhydride.

R ¹⁰⁵ to R ¹⁰⁷ in the formula (B) each independently represent a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, or an aryl group. R ¹⁰⁸ represents a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, a cycloalkyl group, or an aryl group. Each of these groups may further have a substituent (for example, a hydroxyl group, a halogen atom, an alkyl group, etc.).

Examples of (meth) acrylic acid ester compounds include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate (i-, n-), butyl (meth) acrylate (n- , I-, s-, tert-), pentyl (meth) acrylate (n-, i-, s-), hexyl (meth) acrylate (n-, i-), heptyl (meth) acrylate (n -, I-), octyl (meth) acrylate (n-, i-), nonyl (meth) acrylate (n-, i-), myristyl (meth) acrylate (n-, i-), (meta ) Acrylic acid (2-ethylhexyl), (meth) acrylic acid (ε-caprolactone), (meth) acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), (meth) acrylic acid (3-hydroxy) Propyl) (Meth) acrylic acid (4-hydroxybutyl), (meth) acrylic acid (2-hydroxybutyl), acrylic acid (2-methoxyethyl), (meth) acrylic acid (2-ethoxyethyl) phenyl acrylate, (meth ) Phenyl methacrylate, (meth) acrylic acid (2 or 4-chlorophenyl), (meth) acrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), (meth) acrylic acid (o or m or p-tolyl), Benzyl (meth) acrylate, phenethyl (meth) acrylate, (meth) acrylic acid (2-naphthyl), cyclohexyl (meth) acrylate, (meth) acrylic acid (4-methylcyclohexyl), (meth) acrylic acid ( 4-ethylcyclohexyl) and the like.

Specific examples of the styrene compound include styrene / maleic anhydride copolymer, styrene / acrylic ester copolymer, styrene / hydroxystyrene polymer, styrene / acetoxystyrene polymer, and the like. Of these, a styrene / maleic anhydride copolymer is preferable.

The content of the plasticizer is not particularly limited, but is preferably in the range of 0.1 to 30% by mass with respect to 100% by mass of the cellulose ester contained in the cellulose ester film. More preferably within the range. If it is such quantity, a cellulose-ester film will not produce bleeding out easily.

(Other additives)
Further, the retardation film of the present invention may further contain other additives, if necessary, instead of the plasticizer or in addition to the plasticizer. Examples of such other additives include, but are not limited to, hydrogen bonding compounds, activators, antioxidants, colorants, ultraviolet absorbers, matting agents, acrylic particles, hydrogen bonding solvents, ionic interfaces. An active agent etc. are mentioned.

The hydrogen bonding compound can reduce the fluctuation of the retardation value Rt with respect to the change in humidity. Here, the hydrogen bonding compound preferably has at least a plurality of functional groups selected from a hydroxy group, an amino group, a thiol group, and a carboxylic acid group in one molecule, and a plurality of different functional groups in one molecule. It is more preferable to have a hydroxy group and a carboxylic acid group in one molecule.

The hydrogen bonding compound preferably contains 1 to 2 aromatic rings as a mother nucleus, and the value obtained by dividing the number of functional groups contained in one molecule by the molecular weight of the compound is 0.00. It is preferably 01 or more.

The above effect is such that the hydrogen-bonding compound is bonded (hydrogen bond) to a site where the cellulose ester and water molecules interact (hydrogen bonds), thereby suppressing the change in charge distribution due to desorption of water molecules. For the reason.

Specific examples of the compound include Exemplified Compound E-104 described in JP2012-82235A.

The hydrogen bonding compound can be added in the range of 1 to 30 parts by mass with respect to 100 parts by mass of the cellulose ester.

Since the film of the present invention is preferably used on the viewing side or the backlight side of the polarizing plate, it preferably contains an ultraviolet absorber for the purpose of imparting an ultraviolet absorbing function. It does not specifically limit as a ultraviolet absorber, What was mentioned above as what can be contained in the polyester film as the protective film A can be used similarly.

The amount of the UV absorber used in the cellulose ester film as the protective film B is not uniform depending on the type of UV absorber, usage conditions, etc., but generally it is preferably 0.05 with respect to 100% by mass of the cellulose ester. It is added in a range of ˜10% by mass, more preferably 0.1 to 5% by mass.

The matting agent is fine particles imparting slipperiness of the film, and may be either an inorganic compound or an organic compound as long as it does not impair the transparency of the resulting film and has heat resistance during melting. These matting agents can be used alone or in combination of two or more. By using particles having different particle sizes and shapes (for example, acicular and spherical), both transparency and slipperiness can be made highly compatible. Among these, silicon dioxide, which is excellent in transparency (haze), is particularly preferably used because it has a refractive index close to that of the acrylic copolymer or cellulose ester used as a compatible resin.

Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP- 30, Seahoster KEP-50 (above, manufactured by Nippon Shokubai Co., Ltd.), Silo Hovic 100 (manufactured by Fuji Silysia), Nip Seal E220A (manufactured by Nippon Silica Industry), Admafine SO (manufactured by Admatechs) Goods etc. can be preferably used.

The shape of the particles can be used without particular limitation, such as indefinite shape, needle shape, flat shape, spherical shape, etc. However, the use of spherical particles is preferable because the transparency of the resulting film can be improved.

When the particle size is close to the wavelength of visible light, light is scattered and the transparency is deteriorated. Therefore, the particle size is preferably smaller than the wavelength of visible light, and more preferably ½ or less of the wavelength of visible light. . If the size of the particles is too small, the slipperiness may not be improved, so the range of 80 nm to 180 nm is particularly preferable. The particle size means the size of the aggregate when the particle is an aggregate of primary particles. Moreover, when a particle is not spherical, it means the diameter of a circle corresponding to the projected area.

The matting agent is added in an amount of 0.05 to 10% by mass, preferably 0.1 to 5% by mass with respect to the resin (cellulose ester).

The film of the present invention may contain, for example, acrylic particles described in International Publication No. 2010/001668 in an amount within a range where transparency can be maintained. The acrylic particles have an action of improving the brittleness of the film.

Examples of such commercially available acrylic particles include, for example, “Metablene W-341” manufactured by Mitsubishi Rayon Co., “Kane Ace” manufactured by Kaneka Corporation, “Paraloid” manufactured by Kureha Co., Ltd., “Roid and Haas Co.” “Acryloid”, “Staffroid” manufactured by Ganz Kasei Kogyo Co., Ltd., Chemisnow MR-2G, MS-300X (above, manufactured by Soken Chemical Co., Ltd.) and “Parapet SA” manufactured by Kuraray Co., Ltd. Or 2 or more types can be used.

The hydrogen bonding solvent can be added for the purpose of adjusting (reducing) the solution viscosity in a solvent for dissolving the constituent materials of the film when a film is produced by the solution casting method. The hydrogen bonding solvent is J.I. N. As described in Israel Ativili, “Intermolecular Forces and Surface Forces” (Takeshi Kondo, Hiroyuki Oshima, Maglow Hill Publishing, 1991) and electrically negative atoms (oxygen, nitrogen, fluorine, chlorine) An organic solvent capable of producing a hydrogen atom-mediated “bond” that occurs between an electronegative atom and a covalently bonded hydrogen atom, that is, a bond having a large bonding moment and containing hydrogen, such as OH (Oxygen hydrogen bond), N—H (nitrogen hydrogen bond), FH (fluorine hydrogen bond), and an organic solvent that can arrange adjacent molecules.

These form a stronger hydrogen bond between the resin and the hydrogen bonding solvent than the intermolecular hydrogen bond of the acrylic copolymer, cellulose ester resin, or other resin mixture for compatibilization itself. Thus, a change in solution viscosity can be expected.

In the solution casting method performed in the present invention, in addition to adjusting the solution viscosity with respect to the resin solution to be used, in order to reduce the peeling force at the time of film formation, a hydrogen bond is added to the solvent for dissolution. A part or all of the solvent may be used.

An ionic surfactant can be added for the purpose of reducing the peeling force during film formation.

Examples of the ionic surfactant that can be used in the present invention include a cationic surfactant, an anionic surfactant, and an amphoteric surfactant.

Examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like.

Examples of the anionic surfactant include higher alcohol (C ₈ -C ₂₂ ) sulfate salts (for example, sodium salt of lauryl alcohol sulfate, sodium salt of octyl alcohol sulfate, ammonium salt of lauryl alcohol sulfate, “Tepol-81” ( Trade name, manufactured by Shell Chemical Co., Ltd.), secondary sodium alkyl sulfate, etc.), aliphatic alcohol phosphate salts (eg, sodium salt of cetyl alcohol phosphate), alkylaryl sulfonates (eg, dodecylbenzenesulfonic acid) Sodium salt, isopropyl naphthalene sulfonic acid sodium salt, dinaphthalenedisulfonic acid sodium salt, metanitrobenzene sulfonic acid sodium salt), alkylamide sulfonates (eg Examples thereof include C ₁₇ H ₃₃ CON (CH ₃ ) CH ₂ SO ₃ Na) and sulfonates of dibasic fatty acid esters (for example, sodium sulfosuccinic acid dioctyl ester, sodium sulfosuccinic acid dihexyl ester, etc.). Of these, sulfates and sulfonates are particularly preferably used.

Examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like.

Among these, an anionic surfactant is preferable in the present invention. The above surfactant is 0.01% by mass or more and 5% by mass or less, preferably 0.05% by mass or more and 3% by mass or less, more preferably 0.2% by mass with respect to the total amount of the resin constituting the film. % To 2% by mass is preferable. When the addition amount is larger than this range, the surfactant is precipitated from the film, or the hygroscopicity of the film is increased, and a quality undesirable for the quality of the retardation film is exhibited. If the addition amount is less than this range, the effect of the present invention using a surfactant may not be obtained.

(Physical properties of film)
Hereinafter, the characteristic about the physical property etc. of the cellulose-ester film as the protective film B in this invention is demonstrated.

(transparency)
A haze value (turbidity) is used as an index for judging the transparency of the cellulose ester film. In particular, in a liquid crystal display device used outdoors, it is required that sufficient brightness and high contrast are obtained even in a bright place. Therefore, the haze value is preferably 0.6% or less, and is 0.4% or less. More preferably. When used as a scattering film, the haze value may exceed the above range. The internal haze of the film is preferably 0.01 to 0.1.

Further, the film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%.

The haze value and transmittance can be measured using a haze meter.

A film satisfying the above physical properties can be preferably used as a polarizing plate protective film for a large-sized liquid crystal display device or a liquid crystal display device for outdoor use.

(Retardation)
The retardation value in the cellulose ester film as the protective film B is not particularly limited, but the in-plane retardation value Ro defined by the following formulas (i) and (ii) is in the range of 30 to 70 nm, The retardation value Rt in the thickness direction is preferably in the range of 100 to 140 nm from the viewpoint of improving contrast and viewing angle when mounted on a VA display device. In particular, when the retardation value Ro in the in-plane direction is in the range of 45 to 60 nm and the retardation value Rt in the thickness direction is in the range of 110 to 135 nm, the contrast and viewing angle when mounted on the VA display device Is particularly improved and preferable.

Formula (i): Ro = (n _x −n _y ) × d (nm)
Formula (ii): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
In the formula (i) and (ii), n _x represents a refractive index in the direction x in which the refractive index in the plane direction is maximized in the film. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. The measurement is performed at a measurement wavelength of 590 nm in an environment of 23 ° C. and 55% RH.

(Method for producing cellulose ester film)
Next, the manufacturing method of a cellulose-ester film is demonstrated. The present invention is not limited to this.

As a method for producing a cellulose ester film, a usual inflation method, T-die method, calendar method, cutting method, casting method, emulsion method, hot press method and the like can be used. From the viewpoint of suppression, suppression of optical defects such as die lines, etc., the film forming method is preferably a solution casting film forming method and a melt casting film forming method. More preferred for obtaining.

<Solution casting film forming method>
In the case of forming a film by the solution pouring method, the cellulose ester film is produced by dissolving the cellulose ester and a desired additive in a solvent to prepare a dope (dissolution process; dope preparation process), and moving the dope indefinitely. The process of casting on an endless metal support (casting process), the process of drying the cast dope as a web (solvent evaporation process), the process of peeling from the metal support (peeling process), drying, stretching, It is preferable to include a step of holding the width (stretching / width holding / drying step) and a step of winding the finished film (winding step).

FIG. 2 is a diagram schematically showing an example of a dope preparation step, a casting step, and a drying step (solvent evaporation step) of a solution casting film forming method preferable for the present invention.

大きな Remove large agglomerates from the charging vessel 41 with the filter 44 and feed the solution to the stock vessel 42. Thereafter, various additive solutions are added from the stock kettle 42 to the main dope dissolving kettle 1.

After that, the main dope is filtered by the main filter 3, and the additive solution is added in-line from 16 to this. In many cases, the main dope may contain about 10 to 50% by mass of the recycled material. The return material is a product obtained by finely pulverizing a film, and is produced by forming a film by cutting off both sides of the film, or by using a film raw material that has been speculated out by scratches or the like.

In addition, as a raw material for the resin used for preparing the dope, a pellet obtained by pelletizing cellulose ester and a desired additive in advance can be preferably used.

Hereinafter, each process will be described.

1) Dissolution process (dope preparation process)
This step is a step of forming a dope by dissolving the cellulose ester and a desired additive in a dissolving kettle in a solvent mainly composed of a good solvent for the cellulose ester while stirring.

The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. The concentration for achieving both of these is preferably 10 to 35% by mass, more preferably 15 to 22% by mass.

Solvents used in the dope may be used alone or in combination of two or more. However, it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of solubility of cellulose acetate.

The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent. Therefore, a good solvent and a poor solvent change with the average substitution degree of a cellulose ester.

The good solvent used in the present invention is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

Further, the poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone and the like are preferably used. The dope preferably contains 0.01 to 2% by mass of water.

Also, the solvent used for dissolving the cellulose ester is used by collecting the solvent removed from the film by drying in the film-forming process and reusing it.

The recovery solvent may contain trace amounts of additives added to cellulose acetate, such as plasticizers, UV absorbers, polymers, monomer components, etc., but these are preferably reused even if they are included. Can be purified and reused if necessary.

A general method can be used as a method for dissolving the cellulose ester in preparing the dope described above. Specifically, 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, Various dissolution methods such as a method using a cooling dissolution method as described in Kaihei 9-95538 and a method using a high pressure as described in Japanese Patent Application Laid-Open No. 11-21379 can be used. Among them, a method of performing pressurization at a temperature equal to or higher than the boiling point of the main solvent is preferable.

In addition, a method of stirring and dissolving while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and does not boil under pressure is preferable in order to prevent the generation of massive undissolved material called gel or mamako.

Further, a method in which cellulose acetate is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

The heating temperature with the addition of the solvent is preferably higher from the viewpoint of the solubility of cellulose acetate, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

The preferred heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

Next, this cellulose ester solution (doping during or after dissolution) is preferably filtered using a suitable filter medium such as filter paper.

As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.007 mm is more preferable.

There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable.

It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose acetate by filtration.

A bright spot foreign object is placed when two polarizing plates are placed in a crossed Nicol state, a film or the like is placed between them, light is applied from one polarizing plate, and the opposite is observed when observed from the other polarizing plate. It is a point (foreign matter) where light from the side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. More preferably, it is 100 pieces / cm ² or less, further preferably 50 pieces / m ² or less, and further preferably 0 to 10 pieces / cm ² . Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable.

A preferable temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and further preferably 45 to 55 ° C.

A smaller filtration pressure is preferable. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

2) Casting step Subsequently, the dope is cast on a metal support. That is, in this step, the dope is fed to the pressurizing die 30 through a liquid feed pump (for example, a pressurized metering gear pump) and transferred indefinitely, for example, an endless metal belt 31 such as a stainless steel belt or a rotating metal drum. The dope is cast from the pressure die slit to the casting position on the metal support.

¡Pressure dies that can adjust the slit shape of the die base and make the film thickness uniform are preferred. 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 preferably 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.

The cast width is preferably 1.4 m or more from the viewpoint of productivity. More preferably, it is 1.4 to 4 m. When it exceeds 4 m, there is a risk of streaking in the manufacturing process or lowering of stability in the subsequent transport process. More preferably, it is 1.6 to 2.5 m in terms of transportability and productivity.

The metal support in the casting process is preferably a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support.

The surface temperature of the metal support in the casting step is −50 ° C. to less than the boiling point of the solvent, and a higher temperature is preferable because the web drying rate can be increased. May deteriorate.

The preferred support temperature is 0 to 55 ° C, more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

The method for controlling the temperature of the metal support is not particularly limited, but there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

3) Solvent evaporation step This step is a step of evaporating the solvent by heating the web (the dope is cast on the casting support and the formed dope film is called the web) on the casting support. It is.

In order 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. The drying efficiency is good 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 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat by means such as infrared rays.

From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds when forming a stainless steel belt film and within 5 to 40 seconds when forming a drum film.

4) Peeling step Next, the web is peeled from the metal support. That is, this step is a step of peeling the web where the solvent is evaporated on the metal support at the peeling position. The peeled web is sent to the next process.

The temperature at the peeling position on the metal support is preferably within the range of −50 to 40 ° C., more preferably within the range of 10 to 40 ° C., and within the range of 15 to 30 ° C. when the stainless steel belt is formed. Most preferably, it is −30 to 10 ° C. when forming a drum.

In addition, the residual solvent amount of the web on the metal support at the time of peeling is appropriately adjusted depending on the strength of drying conditions, the length of the metal support, and the like. In order for the cellulose ester film to exhibit a predetermined toughness value, it is preferable to control the residual solvent amount when peeling the web from the metal support to 15 to 40% by mass, more preferably 20 to 35%. % By mass.

In the present invention, the amount of residual solvent is defined by the following formula.

Note that M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

The peeling tension when peeling the metal support and the film is preferably 300 N / m or less. More preferably, it is within the range of 196 to 245 N / m. However, when wrinkles easily occur during peeling, peeling with a tension of 190 N / m or less, preferably 100 to 190 N / m is preferred.

5) Drying / stretching / width holding process (drying)
In the drying step of the cellulose ester film, the web is peeled from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, and particularly preferably. Is 0 to 0.01% by mass or less.

In the film drying process, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed. For example, after peeling, the web is fed using a drying device 35 that alternately conveys the web through rollers arranged in a drying device and / or a tenter stretching device 34 that clips and conveys both ends of the web with clips. dry.

The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but is preferably performed with hot air in terms of simplicity. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout, the drying is generally carried out in the range of 40-250 ° C. It is particularly preferable to dry within the range of 40 to 200 ° C. The drying temperature is increased stepwise and is preferably heated to about 100 to 150 ° C., preferably 5 to 30 minutes, more preferably 6 to 12 minutes.

When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

It is also preferable to provide a neutral zone between different temperature zones so that each zone does not cause interference.

(Stretching / width retention)
Subsequently, the web is preferably stretched in at least one direction from the metal support. The orientation of molecules in the film can be controlled by the stretching treatment. In order to obtain the target retardation values Ro and Rt in the present invention, even if the cellulose ester film has the configuration of the present invention and contains a retardation increasing agent, it is further refracted by controlling the conveying tension and stretching operation. It is preferable to perform rate control. For example, the retardation value can be changed by lowering or increasing the tension in the longitudinal direction.

As a specific stretching method, two axes are sequentially or simultaneously applied to the longitudinal direction (film forming direction; casting direction; MD direction) of the film and the direction orthogonal to the film plane, that is, the width direction (TD direction). Stretching or uniaxial stretching can be performed. Preferably, it is a biaxially stretched film that is biaxially stretched in the casting direction (MD direction) and the width direction (TD direction), but the cellulose ester film according to the present invention may be a uniaxially stretched film. And an unstretched film may be sufficient. The stretching operation may be performed in multiple stages. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. 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. Thus, for example, the following stretching steps are possible:
-Stretch in the casting direction-> Stretch in the width direction-> Stretch in the casting direction-> Stretch in the casting direction-Stretch in the width direction-> Stretch in the width direction-> Stretch in the casting direction-> Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension.

The draw ratios in the biaxial directions perpendicular to each other are preferably in the range of 0.01 to 2.0% in the casting direction (MD direction) and 10 to 50% in the width direction, respectively. A range of 0.1 to 1.0% in the extending direction and 20 to 40% in the width direction is preferable. The residual solvent amount at this time is preferably in the range of 15 to 40% so that the cellulose ester film exhibits a predetermined toughness value.

The stretching temperature is usually preferably performed in the temperature range of Tg to Tg + 60 ° C. of the resin constituting the film. Usually, the stretching temperature is preferably from 120 ° C. to 200 ° C., more preferably from 130 ° C. to 200 ° C., and more preferably from 140 ° C. to 190 ° C. or less.

The amount of residual solvent in the film at the time of stretching is not particularly limited, but in order for the cellulose ester film to exhibit a predetermined toughness value, the amount of residual solvent at the time of stretching in the width direction is 2 to 5 mass. % Is preferred.

There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination. Among them, it is particularly preferable to perform stretching in the width direction (lateral direction) by a tenter method in which both ends of the web are gripped by clips or the like.

Also, in the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

It is preferable to carry out the width maintenance or lateral stretching in the film forming step by a tenter, and it may be a pin tenter or a clip tenter.

The slow axis or the fast axis of the cellulose ester film according to the present invention exists in the film plane, and θ1 is −1 ° or more and + 1 ° or less when the angle formed with the film forming direction is θ1 in the entire film width and length. It is preferably −0.5 ° or more and + 0.5 ° or less, more preferably −0.2 ° or more and + 0.2 ° or less.

This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

6) Winding process Finally, a cellulose ester film is obtained by winding the obtained web (finished film). More specifically, it is a step of winding the film as a film by a winder 37 after the residual solvent amount in the web becomes 2% by mass or less, and the dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. A film having good properties can be obtained. In particular, it is preferable to wind in the range of 0.00 to 0.10% by mass.

As a winding method, a generally used one 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.

Before winding, the end may be slit and cut to the product width, and knurled (embossed) may be applied to both ends to prevent sticking and scratching during winding. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. Note that the clip holding portions at both ends of the film are usually cut off because the film is deformed and cannot be used as a product. If the material has not deteriorated due to heat, it is reused after recovery.

The cellulose ester film is preferably a long film. Specifically, the cellulose ester film has a thickness of about 100 m to 10000 m, and is usually in the form of a roll. Further, the width of the film is preferably 1.4 to 4 m, more preferably 1.4 to 4 m, and more preferably 1.6 to 4 m in order to meet demands for an increase in the size of liquid crystal display devices and production efficiency. More preferably, it is ˜3 m.

The cellulose ester film laminate produced by the above method is preferably subjected to aging treatment for 3 days or more under conditions of 50 ° C. or higher after the outer peripheral portion is packaged. By performing such treatment, it becomes possible to control the toughness of the cellulose ester film to a value within the above-mentioned preferable range, and it is preferable to control to a value within this range from the viewpoint of improving dimensional stability.

[Polarizer]
The polarizer, which is the main component of the polarizing plate of the present invention, 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 2 to 30 μm, more preferably 2 to 15 μm from the viewpoint of thin film suitability, and further preferably 3 to 10 μm from the viewpoint of further thin film suitability and handleability.

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. Of 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.

In addition, a coating-type polarizer is prepared by the method described in JP 2011-1000016 A, JP 4691205 A, JP 4751481 A, and JP 4804589 A and bonded to the cellulose ester film according to the present invention. It is also preferable to produce a polarizing plate.

[UV curable adhesive]
In the polarizing plate of this invention, as shown in FIG. 1, it is preferable that each of the protective film A and the protective film B demonstrated above and the polarizer are bonded by the ultraviolet curable adhesive.

In the present invention, by applying an ultraviolet curable adhesive to the bonding between the protective film A and the polarizer or the bonding between the protective film B and the polarizer, the productivity is high and the durability of the polarizer is increased. Excellent properties can be obtained.

[Composition of UV curable adhesive]
As the UV curable adhesive composition for polarizing plates, a photo radical polymerization composition using photo radical polymerization, a photo cation polymerization composition using photo cation polymerization, and photo radical polymerization and photo cation polymerization are used in combination. Hybrid type compositions are known.

The radical photopolymerizable composition includes a radically polymerizable compound containing a polar group such as a hydroxy group and a carboxy group described in JP-A-2008-009329 and a radically polymerizable compound not containing a polar group at a specific ratio. Composition) and the like are known. In particular, the radical polymerizable compound is preferably a compound having a radical polymerizable ethylenically unsaturated bond. Preferable examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include an N-substituted (meth) acrylamide compound and a (meth) acrylate compound. (Meth) acrylamide means acrylamide or methacrylamide.

In addition, as the cationic photopolymerization type composition, as disclosed in JP2011-08234A, (α) a cationic polymerizable compound, (β) a cationic photopolymerization initiator, and (γ) a wavelength longer than 380 nm. And an ultraviolet 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 ultraviolet curable adhesives may be used.

(Pretreatment process)
A pre-processing process is a process of performing an easily bonding process to the adhesive surface of a cellulose-ester film with a polarizer. In the case where the protective film A and the protective film B are bonded to both surfaces of the polarizer, an easy adhesion treatment is performed on the surface of each protective film that is bonded to the polarizer. Examples of the easy adhesion treatment include corona treatment and plasma treatment.

(Application process of UV curable adhesive)
In the step of applying the ultraviolet curable adhesive, the ultraviolet curable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the protective film. When the ultraviolet curable adhesive is applied directly to the surface of the polarizer or the protective film, the application method is not particularly limited. For example, various wet 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 an ultraviolet curable adhesive between a polarizer and a protective film, the method of pressurizing with a roll etc. and spreading it uniformly can also be utilized.

(Bonding process)
After apply | coating a ultraviolet curable adhesive by said method, it processes by a bonding process. In this bonding step, for example, when an ultraviolet curable adhesive is applied to the surface of the polarizer in the previous application step, a protective film is superimposed thereon. In the case of a system in which an ultraviolet curable adhesive is first applied to the surface of the protective film in the previous application step, a polarizer is superimposed thereon. Moreover, when the ultraviolet curable adhesive is cast between the polarizer and the protective film, the polarizer and the protective film A are superposed in that state. In the case where the protective film A and the protective film B are bonded to both surfaces of the polarizer, respectively, and both surfaces use an ultraviolet curable adhesive, the protective film is provided on both surfaces of the polarizer via an ultraviolet curable adhesive. A and protective film B are overlaid. Usually, in this state, both sides (when the protective film A is superposed on one side of the polarizer, the protective film A and the protective film B are superposed on the polarizer side and the protective film A side, and on both sides of the polarizer. In such a case, the pressure is sandwiched between a pressure roller or the like from the protective film A and the protective film B side). Metal, rubber, or the like can be used as the material of the pressure roller. The pressure rollers arranged on both sides may be made of the same material or different materials.

(Curing process)
In the curing step, an uncured ultraviolet curable adhesive is irradiated with ultraviolet rays, and a cationic polymerizable compound (for example, epoxy compound or oxetane compound) or a radical polymerizable compound (for example, acrylate compound, acrylamide compound, etc.) The ultraviolet curable adhesive layer that is included is cured, and the polarizer and the protective film A or the polarizer and the protective film B that are superposed with each other are bonded via the ultraviolet curable adhesive. When bonding the protective film A to the single side | surface of a polarizer, you may irradiate an active energy ray from either the polarizer side or the protective film A side. In addition, when the protective film A and the protective film B are bonded to both surfaces of the polarizer, ultraviolet rays are applied in a state where the protective film A and the protective film B are superimposed on the both surfaces of the polarizer via an ultraviolet curable adhesive, respectively. It is advantageous to irradiate and simultaneously cure the UV curable adhesive on both sides.

Any appropriate conditions can be adopted as the ultraviolet irradiation conditions as long as the ultraviolet curable adhesive applied to the present invention can be cured. Preferably the dose of ultraviolet is 50 ~ 1500mJ / cm ² in accumulated light quantity, and even more preferably 100 ~ 500mJ / cm ^2.

When the production process of the polarizing plate is performed in a continuous line, the line speed depends on the curing time of the adhesive, but is preferably 1 to 500 m / min, more preferably 5 to 300 m / min, and further preferably 10 to 100 m / min. is there. If the line speed is 1 m / min or more, productivity can be ensured, or damage to the protective film A can be suppressed, and a polarizing plate having excellent durability can be produced. If the line speed is 500 m / min or less, the ultraviolet curable adhesive is sufficiently cured, and an ultraviolet curable adhesive layer having a desired hardness and excellent adhesiveness can be formed.

<Display device>
The polarizing plate according to the present invention can be used for various display devices, but is particularly preferably applied to a liquid crystal display device.

As a liquid crystal display device having the polarizing plate of the present invention, a TN (Twisted Nematic) method, a STN (Super Twisted Nematic) method, an IPS (In-Plane Switched) method, an OCB (Optically Compensated Birefringence Vrefringence Virgent Affinity A nt Virgentence V irencement V irencement V irencement V irencement V irencement V refrenceence method. It can be preferably used for MVA (including Multi-domain / Vertical / Alignment and PVA; Patterned / Vertical / Alignment), HAN (Hybrid Aligned / Nematic), and the like. In order to increase the contrast, the VA (MVA, PVA) method is preferable.

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 "%" is used in an Example, unless otherwise indicated, "mass%" is represented.

<< Preparation of polyethylene terephthalate film as protective film A >>
(Production Example 1: Production of PET (A))
When the temperature of the esterification reactor was raised to 200 ° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged and 0.017 parts by mass of antimony trioxide as a catalyst while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Subsequently, the pressure was increased and the pressure esterification reaction was performed under conditions of a gauge pressure of 0.34 MPa and 240 ° C., and then the esterification reaction vessel was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, it heated up to 260 degreeC over 15 minutes, and 0.012 mass part of trimethyl phosphate was added. Then, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction can and subjected to polycondensation reaction at 280 ° C. under reduced pressure.

After completion of the polycondensation reaction, filtration is performed with a filter made of NASRON (registered trademark) with a 95% cut diameter of 5 μm, extruded into a strand form from a nozzle, and using cooling water that has been previously filtered (pore diameter: 1 μm or less). The mixture was cooled and solidified, and was cut into pellets (the resultant was also referred to as “PET (A)”).

(Production Example 2: Production of PET (B))
10 parts by weight of dried UV absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinon-4-one), 90 parts by weight of PET (A) containing no particles And a polyethylene terephthalate resin (B) containing an ultraviolet absorber was obtained using a kneading extruder (the obtained one is also referred to as “PET (B)”).

(Production Example 3: Preparation of Adhesive Modified Coating Solution)
A transesterification reaction and a polycondensation reaction were carried out by a conventional method, and as a dicarboxylic acid component (based on the total dicarboxylic acid component) 46 mol% terephthalic acid, 46 mol% isophthalic acid and 8 mol% sodium 5-sulfonatoisophthalate, A water-dispersible sulfonic acid metal base-containing copolymer polyester resin having a composition of 50 mol% ethylene glycol and 50 mol% neopentyl glycol as a glycol component (based on the entire glycol component) was prepared. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, 0.06 parts by mass of a nonionic surfactant were mixed and then heated and stirred. 5 parts by mass of a water-dispersible sulfonic acid metal base-containing copolymer polyester resin was added, and stirring was continued until the resin was no longer solidified. Thereafter, the resin water dispersion was cooled to room temperature to obtain a uniform water dispersible copolyester resin liquid having a solid concentration of 5.0% by mass. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (Silicia 310, manufactured by Fuji Silysia Co., Ltd.) in 50 parts by mass of water, 99.46 parts by mass of the water-dispersible copolyester resin solution was mixed with 99.46 parts by mass of the silicia 310. 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added with stirring to obtain an adhesive modified coating solution.

[Preparation of PET film 1]
A polyethylene terephthalate film having a three-layer structure was produced by the following method.

90 parts by weight of PET (A) resin pellets containing no particles and 10 parts by weight of PET (B) resin pellets containing an ultraviolet absorber were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and then an extruder (for intermediate layer) In addition, PET (A) was dried by a conventional method and supplied to an extruder (for both outer layers) and dissolved at 285 ° C. These two types of polymers were each filtered twice with a filter medium made of a sintered stainless steel (nominal filtration accuracy of 10 μm particles, 95% cut), laminated in a two-type, three-layer confluence block, and extruded into a sheet form from the die. Thereafter, the film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and solidified by cooling to obtain an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the thickness ratio of each layer was 10 (outer layer): 80 (intermediate layer): 10 (outer layer).

Next, after applying the above-mentioned adhesive property-modified coating solution on the both sides of this unstretched PET film by a reverse roll method so that the coating amount after drying becomes 0.08 g / m ² , it was dried at 80 ° C. for 20 seconds. .

The unstretched film on which this coating layer was formed was preheated to 145 ° C. using a heated roll group and an infrared heater, and then stretched 3 times in the running direction (MD direction) with a roll group having a difference in peripheral speed. Thereafter, the film was guided to a tenter stretching machine and guided to a hot air zone having a temperature of 135 ° C. while being gripped by a clip, and stretched 4 times in the width direction (TD direction). In this way, a biaxially oriented PET film 1 (film thickness 60 μm) was obtained.

[Preparation of PET films 2 to 17]
In the production of the PET film 1, the number of filtrations of the molten polymer before film formation by the electrostatic application casting method, the presence or absence of preheating before stretching in the MD direction, the stretching ratio in the MD direction and the TD direction, and the film thickness of the film PET films 2 to 17 were produced in the same manner except that the production conditions were changed as shown in Table 1 below.

[Evaluation of elastic modulus of PET film]
Each of the PET films produced above was conditioned for 24 hours in an environment of 23 ° C. and 55% RH, and the elastic modulus was measured according to the method described in JIS K7127. Tensilon RTC-1225 manufactured by Orientec Co., Ltd. is used as the tensile tester. The shape of the test piece is 120 mm (length) x 10 mm (width), and the upper and lower sides are sandwiched by 100 mm between the chucks (10 mm above and below the grip allowance). The test speed was 100 mm / min. The measurement was performed five times for each of the MD direction and the TD direction per sample, and the average value in each direction was calculated. The results are shown in Table 1 below.

<< Production of cellulose acetate film as protective film B >>
[Production of Cellulose Acetate Film 1]
(Preparation of fine particle dispersion)
10 parts by mass of Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 16 nm, apparent specific gravity of 90 g / L) and 90 parts by mass of ethanol were stirred and mixed with a dissolver for 30 minutes, and then high pressure disperser Manton Gorin Was used to prepare a fine particle dispersion.

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

(Preparation of inline additive solution)
15 parts by weight of Tinuvin 928 (manufactured by BASF Japan) and 100 parts by weight of dichloromethane as an ultraviolet absorber and 100 parts by weight of dichloromethane were put into a sealed container, and heated and stirred to completely dissolve, followed by filtration. To the obtained solution, 36 parts by mass of the fine particle dispersion diluted liquid was added with stirring, and further stirred for 30 minutes, and then 6 parts by mass of cellulose ester 1 (acetyl group substitution degree 2.80, Mn = 75000, Mw = 150,000, Mw / Mn = 2.0) 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.

<Composition of main dope>
Cellulose acetate (acetyl group substitution degree: 2.35, Mn = 80000, Mw = 135000, Mw / Mn = 1.68) 86 parts by mass Ester compound (above compound FB-16) 2 parts by mass Sugar ester (above compound FA- 20) 7 parts by mass Retardation increasing agent (compound 1-2) 2 parts by mass Dichloromethane 430 parts by mass Ethanol 11 parts by mass 100 parts by mass of main dope and 2.5 parts by mass of inline additive solution The dope was obtained by thoroughly mixing with a Toray static in-tube mixer Hi-Mixer, SWJ).

(Film forming process)
The obtained dope was uniformly cast on a stainless band support using a belt casting apparatus under the conditions of a dope liquid temperature of 35 ° C. and a width of 1.95 m. On the stainless steel band support body, the organic solvent in the obtained dope film | membrane was evaporated until the amount of residual solvents became 30 mass%, and the web was formed, Then, the web was peeled from the stainless steel band support body. The obtained web was further dried at 35 ° C. and then slit to have a width of 1.90 m. Thereafter, the web was stretched 0.5% in the running direction (MD direction) with a group of rolls having a difference in peripheral speed under the condition of 160 ° C. Subsequently, it extended | stretched 30% in TD direction (width direction of the film) with the tenter. The residual solvent amount of the web at the start of stretching in the TD direction was 3% by mass.

Thereafter, the obtained film was dried at 120 ° C. for 15 minutes while being conveyed by a number of rolls in the drying apparatus, and then slit to 1.6 m width to obtain a cellulose acetate film. The end was knurled. And the lengthy cellulose acetate film of width 1.6m, length 6000m, and thickness 30micrometer obtained in this way is wound up in the length direction, and the laminated roll body 1 of the cellulose acetate film 1 is obtained. It was.

(Aging treatment of laminated roll body)
Thereafter, the outer periphery of the laminated roll body 1 is double-wrapped using a moisture-proof film packaging material in which aluminum is deposited on a polyethylene resin film having a thickness of 50 μm, and the end of the core is fastened with a rubber band. A body 1A was produced.

Next, the produced laminated roll body 1A was subjected to an aging treatment for 3 days in a constant temperature environment of 50 ° C. to produce a cellulose acetate film 1.

[Production of Cellulose Acetate Films 2-28]
In the production of the cellulose acetate film 1, the amount of residual solvent at the time of web peeling from the stainless steel band support, the stretching ratio in the MD direction at the time of web peeling, the residual solvent amount at the start of stretching in the TD direction, Except for changing the production conditions of the presence or absence of aging treatment, the acetyl group substitution degree of the raw material cellulose acetate, the film thickness of the film, and the type of retardation increasing agent as shown in Table 2 below, Cellulose acetate films 2 to 28 were produced. Of the retardation increasing agents listed in Table 2, compounds (1-1) and (1-4) have the structures described above, and triazine compounds and rod-shaped compounds have the following structures. is there.

[Evaluation of retardation of cellulose ester film]
About each of the cellulose ester film produced above, the retardation value Ro in the in-plane direction and the retardation value Rt in the thickness direction were measured. The results are shown in Table 2 below.

[Evaluation of toughness of cellulose ester film]
About each of the cellulose-ester film produced above, it measured with the following measuring method and calculated each toughness of MD direction and TD direction.

1) Cut out five optical films into 120 mm (MD direction) × 10 mm (TD direction) to obtain test pieces for MD direction measurement. The obtained test piece is conditioned for 24 hours in an environment of 23 ° C. and 55% RH.

2) Next, the tensile elastic modulus of the test piece is measured by the method described in JISK7127. Tensilon RTC-1225 manufactured by Orientec Co., Ltd. is used as the tensile tester, and the upper end and the lower end in the longitudinal direction (MD direction) of the test piece are sandwiched by 100 mm between the chucks. The test piece is pulled in the longitudinal direction (MD direction) at a speed of 100 mm / min at a rate of 100 mm / min at the center and the lower end, and stress (breaking point stress T) and elongation (breaking point elongation E) when the test piece breaks. ) Are measured for a total of 5 times (for a total of 5 sheets). The measurement is performed in an environment of 23 ° C. and 55% RH.

3) The maximum value of five measured values of the stress at break T (N / mm ² or MPa) obtained, the maximum value of five measured values of the elongation at break E (%), and the film of the test piece The thickness t (mm) is applied to the following formula to calculate the toughness in the MD direction.

Toughness = stress at break T (N / mm ² or MPa) × cross-sectional area A (mm ² ) of test piece in a direction perpendicular to the tensile direction × (elongation at break E (%) / 100) ^1/2
Cross-sectional area A (mm ² ) of the test piece = width 10 (mm) of the test piece × film thickness t (mm) of the test piece
Similarly, for the TD direction toughness of the optical film, five optical films are cut into a size of 120 mm (TD direction) × 10 mm (MD direction) to prepare a test piece for TD direction measurement. The same measurement as described above is performed except that the test pieces are pulled in the longitudinal direction (TD direction) of the test piece, and the toughness in the TD direction is calculated.

The results obtained by the measurement are shown in Table 2 below.

<Production of polarizing plate>
(Production of polarizer)
A polyvinyl alcohol film having an average polymerization degree of 2400 and a saponification degree of 99.9 mol% and a thickness of 50 μm was immersed in warm water at 30 ° C. for 60 seconds to swell. Next, the obtained film was immersed in an aqueous solution of iodine / potassium iodide (mass ratio = 0.5 / 8) having a concentration of 0.3% and dyed while being stretched up to 3.0 times. Thereafter, the obtained film was stretched in a boric acid ester aqueous solution at 65 ° C. so that the total stretching ratio was 5.5. Thereafter, the obtained film was dried in an oven at 40 ° C. for 3 minutes to obtain a polarizer having a thickness of 10 μm.

In the production of the polarizer, the thickness of the unstretched polarizer was changed to 8 μm, 10 μm, 75 μm, and 90 μm, respectively, thereby further producing a polarizer having a thickness of 1.5 μm, 2 μm, 15 μm, or 18 μm. .
[Preparation of UV curable adhesive solution]
Each of the following components was mixed and then defoamed to prepare an ultraviolet curable adhesive solution. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

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 [Preparation of Polarizing Plate]
(Preparation of polarizing plate 1)
A polarizing plate 1 (101) having the configuration shown in FIG. 1 was produced according to the following method. The numerical value in parentheses indicates the number of each component described in FIG.

First, as the cellulose ester film (105) as the protective film B, the cellulose ester film 1 prepared above was used, and the surface thereof was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the ultraviolet curable adhesive liquid prepared above is applied to the corona discharge treated surface of the cellulose ester film 1 (105) with a bar coater so that the film thickness after curing is about 3 μm, and is photocurable. A resin layer (103B) was formed. The polyvinyl alcohol-iodine polarizer (104, thickness 10 μm) produced above was bonded to the obtained photocurable resin layer (103B).

Next, the PET film 1 produced above was used as the protective film A (102), and the surface was subjected to corona discharge treatment. The conditions of the corona discharge treatment were a corona output intensity of 2.0 kW and a speed of 18 m / min.

Next, the UV curable adhesive solution prepared above is applied to the corona discharge treated surface of the PET film 1 (102) with a bar coater so that the film thickness after curing is about 3 μm. An agent layer (103A) was formed.

A polarizer (104) bonded to one side of the cellulose ester film 1 (105) is bonded to the UV curable adhesive layer (103A), and a protective film A (PET film, 102) / UV curable type is bonded. A laminate in which the adhesive layer (103A) / polarizer (104) / ultraviolet curable adhesive layer (103B) / protective film B (cellulose ester film, 105) was laminated was obtained. In that case, it bonded so that the slow axis of a cellulose-ester film (105) and the absorption axis of a polarizer (104) might mutually orthogonally cross.

From both sides of this laminate, using a UV irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems), UV light was applied so that the integrated light amount was 750 mJ / cm ^2. The UV curable adhesive layers (103A, 103B) were cured to produce polarizing plate 1 (101).

[Preparation of polarizing plates 2 to 48]
In the production of the polarizing plate 1, the polarizing plates 2 to 48 were prepared in the same manner except that the type of the protective film A, the type of the protective film B, and the thickness of the polarizer were changed to the combinations shown in Table 3 below. Produced.

[Creation of liquid crystal display device]
The polarizing plate on the viewing side of the VA type liquid crystal display device was peeled off, and the polarizing plate prepared above was bonded to the liquid crystal cell via an adhesive mainly composed of butyl acrylate to produce a VA type liquid crystal display device.

[Evaluation of reworkability of polarizing plate]
For the polarizing plates 1 to 48 produced above, the reworkability was evaluated according to the following method.

The polarizing plates produced above were cut into squares each having a size of 20 cm × 20 cm and bonded to a glass substrate using an acrylic adhesive. Next, the bonded polarizing plate was peeled from the glass with a strength of 5N from the corner. This operation was performed with 10 polarizing plates for one type of sample, and the number of polarizing plates that were not peeled completely due to tears in the polarizing plate was counted. And it ranked by the following references | standards and evaluated the rework property of the polarizing plate. The results are shown in Table 3 below:
A: The number of polarizing plates that were not completely peeled was 0. ○: The number of polarizing plates that were not completely peeled was 1 to 2. Δ: The number of polarizing plates that were not completely peeled was 3 to 3. 4 sheets ×: The number of polarizing plates that were not completely peeled was 5 or more. Note that the reworkability of the polarizing plates is practically acceptable as long as it is at the level of Δ, but is preferably at least the level of ○. And ◎ are particularly preferred.

[Evaluation of suitability of thin film for polarizing plate]
The total film thickness of each produced polarizing plate was measured, and the suitability of the thin film was evaluated according to the following criteria. If it was a rank of △ or higher, it was determined that it had suitability as a polarizing plate in response to a request for thinning the display:
A: The total film thickness of the polarizing plate is less than 100 μm. O: The total film thickness of the polarizing plate is 100 μm or more and 150 μm or less. Δ: The total film thickness of the polarizing plate is thicker than 150 μm and less than 180 μm. X: The layer thickness of the polarizing plate is 180 μm or more. Each evaluation result obtained as described above is shown in Table 3 below.

As is clear from the results shown in Table 3, the polarizing plate of the present invention having the structure defined in the present invention is a case where a thinned cellulose ester film is used as the protective film B for the comparative example. (That is, while having thin film suitability), it is found to be excellent in reworkability. In addition, when the tear strength of the polarizing plate produced above was compared, the polarizing plate 28 (using cellulose ester film No. 12 using cellulose acetate having an acetyl group substitution degree of 2.45) was weak in strength. It was easy to tear. In addition, the display device on which the

polarizing plates

31, 37, and 44 are mounted has a large change in color when observed obliquely as compared with the other polarizing plates, and the polarizing plate 36 is also oblique compared with the other polarizing plates. The color change when observed from was slightly inferior.

This application is based on Japanese Patent Application No. 2013-138329 filed on July 1, 2013, the disclosure of which is incorporated by reference in its entirety.

DESCRIPTION OF SYMBOLS 1

Melting pot

3, 6, 12, 15

Filter

4, 13

Stock pot

5, 14

Liquid feed pump

8, 16 Conduit 10 Ultraviolet absorber preparation pot 20 Merge pipe 21 Mixer 30 Pressure die 31 Metal belt 32 Web 33 Peeling Position 34 Tenter stretching device 35 Drying device 41 Feeding pot 42 Stock pot 43 Pump 44 Filter

Claims

A polarizing plate having a protective film A, a polarizer and a protective film B in this order,
The protective film A is a polyester film made of polyester,
The polyester film has an elastic modulus of 5.0 to 8.0 GPa in at least one of the MD direction and the TD direction,
The protective film B is a cellulose ester film made of cellulose ester,
The cellulose ester film is
(1) The film thickness is in the range of 15-60 μm,
(2) The toughness is 10 to 20 in both the MD direction and the TD direction.
The polarizing plate characterized by the above-mentioned.
The polarizing plate according to claim 1, wherein the polyester is polyethylene terephthalate.
The polarizing plate according to claim 1 or 2, wherein the thickness of the protective film A is in the range of 40 to 100 µm.
For the protective film B, the in-plane retardation value Ro defined by the following formulas (i) and (ii) is in the range of 30 to 70 nm, and the retardation value Rt in the thickness direction is 100 to 140 nm. The polarizing plate according to any one of claims 1 to 3, which is within a range:
Formula (i): Ro = (n x −n y ) × d (nm)
Formula (ii): Rt = {(n x + n y ) / 2−n z } × d (nm)
Wherein, n x represents a refractive index in the direction x in which the refractive index in the plane direction is maximized in the film. n y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. The measurement is performed at a measurement wavelength of 590 nm in an environment of 23 ° C. and 55% RH. ]
The polarizing plate according to any one of claims 1 to 4, wherein the cellulose ester contains cellulose acetate as a main component.
The polarizing plate according to claim 5, wherein the cellulose acetate has a degree of acetyl group substitution of 2.1 to 2.95.
The polarizing plate according to any one of claims 1 to 6, wherein the protective film B contains a retardation increasing agent.
The retardation increasing agent is represented by the following general formula (1):

In the formula, R 1 to R 4 each independently represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a halogen atom;
Each X independently represents —O— or —O—C (═O) — (wherein O is bonded to the phenyl skeleton in the general formula (1));
R 5 and R 6 are each independently
When X is —O—, it represents a hydroxyl group, an ester group or an alkyl group which may be substituted with an optionally substituted aromatic group; or a glycidyl group,
When X is —O—C (═O) —, a hydroxyl group, an ester group or an alkyl group which may be substituted with an optionally substituted aromatic group; or an optionally substituted aromatic group To express,
The polarizing plate of Claim 7 containing the compound represented by these.
The polarizing plate according to any one of claims 1 to 8, wherein the protective film A and the protective film B are both bonded to the polarizer with an ultraviolet curable adhesive.
10. The polarizing plate according to claim 1, wherein the thickness of the polarizer is in the range of 2 to 15 μm.
The polarizing plate according to any one of claims 1 to 10, wherein the thickness is in the range of 80 to 150 µm.
A liquid crystal display device comprising the polarizing plate according to any one of claims 1 to 11.