KR101862974B1 - Method for producing optical film - Google Patents

Abstract

The method for producing an optical film using the solution soft film-forming method has a flexible peeling step and a stretching step. E _MD (MPa) is the mechanical strength in the transport direction of the flexible film or optical film, and E _TD (MPa) is the mechanical strength in the transverse direction perpendicular to the transport direction. In the flexible peeling process, the dope is stretched in the carrying direction by softening the dope on the support 9 so that 1 <E _MD / E _TD <1.5 when the flexible film is peeled from the support 9. In the stretching step, the flexible film is stretched in the width direction so that an optical film having E _MD ? E _TD is obtained.

Description

METHOD FOR PRODUCING OPTICAL FILM [0002]

The present invention relates to a process for producing an optical film using a solution casting method.

2. Description of the Related Art In recent years, the demand for thinning of mobile devices such as smart phones and tablets, particularly display devices, has been strengthened. Along with this, there has been a strong demand for thinning of each member constituting the display device. For example, in a liquid crystal display device, the demand for thinning of the polarizing plate and thinning of the glass substrate of the liquid crystal cell is getting stronger.

In the thinning of the polarizing plate, not only thinning of the polarizer but also reduction of the thickness of the protective film (optical film) covering the polarizer from both sides is strongly demanded. Further, the thickness of the glass substrate of the liquid crystal cell was 0.5 mm in the past, but it is 0.4 mm at present, and the thickness of the glass substrate is progressing, and the thinning of the glass substrate is likely to proceed further.

However, when the glass substrate of the liquid crystal cell is made thin, after the liquid crystal panel is manufactured by bonding the polarizing plate to the liquid crystal cell, the liquid crystal panel may be warped. The occurrence of the warpage in the liquid crystal panel is attributable to the dimensional fluctuation (elongation and shrinkage) in the polarizer due to the change in humidity or temperature (environment variation), and the glass substrate of the liquid crystal cell is bent due to the dimensional fluctuation of the polarizer I think. Until now, since the glass substrate of the liquid crystal cell is thick, the glass substrate does not warp to such a degree that the polarizing plate is somewhat stretched or shrunk. However, due to the remarkable thinning of the glass substrate of the above-mentioned conventional technique, the stretching and expansion of the polarizing plate bends the glass substrate. When the glass substrate is bent, when the liquid crystal cell to which the polarizing plate is bonded is incorporated in the display device, problems such as leakage of light (transmission of light even in a black display without being blocked by the polarizing plate) occur.

Therefore, in order to suppress the light leakage in the display device, it is very important to suppress the dimensional fluctuation of the polarizing plate. Here, since the polarizing plate is composed of the polarizer and the optical film, it is important to suppress both the dimensional fluctuation of the polarizer and the dimensional fluctuation of the optical film in order to suppress the dimensional fluctuation of the polarizing plate. However, since the polarizer is formed of, for example, a polyvinyl alcohol film having hygroscopicity and contains water in the production process of the polarizing plate (for example, water-flower bonding with the optical film), the dimensional change due to the function of the polarizer It is very difficult to suppress. Therefore, in order to suppress the dimensional fluctuation of the polarizing plate, it is necessary to suppress the dimensional fluctuation of the optical film bonded to the polarizer. In addition, in the optical film, the mechanical strength (rigidity, elastic modulus) for suppressing the dimensional fluctuation of the optical film itself following the dimensional change of the polarizer is also required.

Here, examples of the production method of the optical film include a melt softening film forming method and a solution softening film forming method. The solution casting method is superior to the melt casting film forming method in that an optical film having a large molecular weight and a high mechanical strength can be formed. Further, it is generally well known that in the film formation process of the optical film, the mechanical strength in the stretching direction is increased by stretching.

In view of this, for example, in Patent Document 1, it is important to prevent the residual strain (residual stress) from being collected in order to suppress the dimensional fluctuation of the optical film used in the polarizing plate. For this reason, , And that the optical film is stretched in the width direction (TD (Transverse Direction) direction) in a state where the residual solvent amount is 3 to 250 mass%. However, if the stretching direction is only one direction in the TD direction, the mechanical strength in the other direction (for example, MD (Machine Direction) in the transport direction of the optical film) can not be increased. In order to increase the mechanical strength of the optical film in each direction in the plane, it is necessary to elongate the optical film in both the MD and TD directions.

In the solution casting method, there are a simultaneous biaxial stretching and a sequential stretching as a method of stretching in the MD and TD directions after peeling the flexible film (optical film) from the support. The simultaneous biaxial stretching of electrons means that both ends of the optical film 100 in the TD direction are gripped by the gripping portions 101a and 101b and the optical film 100 is gripped by the gripping portions 101a and 101b 100 are arranged in the TD direction while the gap between the grip portions 101a, 101a arranged in the MD direction and the gap between the grip portions 101b, 101b are widened as shown in Fig. 7B during transportation in the MD direction By widening the gap between the grip portions 101a and 101b, the optical film 100 is simultaneously stretched in two directions, i.e., the MD direction and the TD direction. The latter method is a method in which unidirectional stretching is sequentially (sequentially) performed on an optical film peeled from a support. The order of performing the stretching is not specifically defined. For example, the stretching in the MD direction may be followed by the stretching in the TD direction, or the stretching in each direction may be performed in the reverse order.

However, in the above simultaneous biaxial stretching, since the interval between the grippers 101a and 101a and the gap between the grippers 101b and 101b are widened in the MD direction, in the optical film 100, And 101b, the width of the non-gripped region B becomes narrower than that of the region A gripped by the grippers 101a and 101b. When the neck-in occurs, the thickness of both end portions of the width of the optical film 100 becomes thicker than the central portion. In this case, the position where the quality of the optical film 100 is stable becomes only a narrow range at the center of the width, and the portion that becomes the product from the optical film 100 can not be efficiently obtained.

In the case of continuous stretching, the solvent concentration of the flexible film on the support must be maintained at a very high level in order to secure the residual solvent amount until the second stretching. As a result, a transfer risk due to condensation may occur, or a cost increase may occur in order to make the apparatus resistant to solvent, which is not a realistic method. Further, when the optical film is stretched in the MD direction after peeling from the support, it is necessary to keep the optical film in the TD direction in order to suppress shrinkage in the TD direction by stretching in the MD direction. However, as shown in Fig. 8, in the construction in which the optical film 100 is transported in the MD direction using the rolls 201 and 202, the optical film 100 can not be held in the TD direction, The shrinkage of the optical film 100 in the TD direction can not be controlled.

On the other hand, in the MD-direction stretching, there is a method of performing the stretching in the direction of the support on the dope in addition to the above-mentioned stretching of the flexible film from the support. For example, in Patent Documents 2 to 5, there is disclosed a method of performing stretching in the MD direction by increasing the moving speed (conveying speed) of the supporting body, compared with the discharging speed of the dope from the flexible die. The ratio (S / T) of the moving speed S of the supporting body to the discharging speed T is calculated by the following formula (1), where D (m / sec) represents the discharging speed of the dope and S Also called a ratio or draft ratio. As the ratio (S / T) increases, the draw magnification in the MD direction increases.

When stretching in the MD direction at the time of softening in this manner, it is considered that, after peeling from the support, only the stretching in the TD direction can increase the mechanical strength in each direction in the plane of the obtained optical film. Further, since the stretching after peeling from the support is completed in only one direction in the TD direction, it is considered that the above-mentioned problem that occurs in the case of simultaneous biaxial stretching or sequential stretching in which stretching in two directions is carried out after peeling is not caused.

Japanese Patent Application Laid-Open No. 2014-32386 (see paragraph [0124]), Japanese Patent Application Laid-Open No. 2002-28943 (Claim 7, paragraph [0055]) Japanese Patent Application Laid-Open No. 11-216732 (see claim 1, paragraphs [0028] and [0031]), Japanese Patent Laid-Open Publication No. 2013-203838 (see claim 4, paragraph [0065]). Japanese Patent Application Laid-Open No. 2014-223758 (see paragraph [0053]),

In the case of stretching in the MD direction (MD stretching) at the time of softening and stretching in the TD direction (TD stretching) after separation of the flexible film from the support, if the MD stretching and the TD stretching are small, The mechanical strength in the MD direction and the TD direction can not be increased. Therefore, in both the MD and TD directions, the dimensional fluctuation due to the fluctuation in wet heat of the optical film can not be suppressed. Even if the MD stretching is too large, that is, if the stretching magnification in the MD direction is excessively high, it is impossible to suppress the dimensional fluctuation due to the wet heat fluctuation of the optical film. This is because if the MD stretching is too large, the distance from the flexible die to the landing on the support tends to be long, the dope (ribbon) tends to vibrate and the film thickness tends to fluctuate in the MD direction. Fluctuates within the plane of the mechanical strength, and it is presumed that the fluctuation of the dimension due to the fluctuation of the heat of the optical film can not be suppressed. Therefore, in order to suppress the dimensional fluctuation due to the fluctuation of the heat of the optical film, it is necessary to appropriately set the magnitude of MD stretching and TD stretching.

DISCLOSURE OF THE INVENTION The present invention has been made in order to solve the above problems, and an object thereof is to provide an optical film which is excellent in both MD stretching and TD stretching when MD stretching is performed at the time of softening and TD stretching is performed after peeling of the flexible film from the support, The present invention is to provide a method of manufacturing an optical film capable of suppressing dimensional fluctuations in the MD and TD directions due to the fluctuation of wet heat.

The above object of the present invention is achieved by the following production method of an optical film.

The method for producing an optical film according to one aspect of the present invention is a method for producing an optical film using a solution casting method,

A flexible separation step of flexing the dope from a flexible die on a moving support and drying the dope on the support to form a flexible film and then peeling off the flexible film conveyed by the movement of the support from the support;

And a stretching step of stretching in the transverse direction perpendicular to the conveying direction of the flexible film while the peeled flexible film is conveyed to obtain the optical film,

When the mechanical strength of the flexible film or the optical film in the transport direction is E _MD (MPa) and the mechanical strength in the transverse direction is E _TD (MPa)

In the flexible separation step, at the time when the flexible film is peeled from the support,

1 < E _MD / E _TD < 1.5

The dope is stretched on the support so as to stretch in the carrying direction,

In the stretching step,

E _{MD &lt;} = E _TD

The stretchable film is stretched in the transverse direction so that the optical film is obtained.

According to the above manufacturing method, in the flexible peeling step, the dope is stretched on the support and stretched in the carrying direction (MD stretching) so that 1 <E _MD / E _TD <1.5 when the flexible film is peeled from the support. In the stretching step, stretching in the width direction (TD stretching) is performed so that an optical film having E _MD ? E _TD is obtained. As described above, in the flexible peeling step, the size of the MD stretching (the relationship between the mechanical strength E _MD and E _TD of the flexible film after MD stretching) is appropriately set, and in the stretching step, the size of the TD stretching The relationship between the mechanical strength E _MD and E _TD of the optical film of the present invention) can be appropriately set, thereby suppressing the dimensional fluctuation in the MD and TD directions due to the fluctuation of the humidity of the optical film.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view showing a schematic structure of a manufacturing apparatus to which an optical film manufacturing method according to an embodiment of the present invention is applied. FIG.
2 is a perspective view showing an example of a support used in the production apparatus.
3 is a perspective view showing another example of the support.
4 is an explanatory view schematically showing an example of a dope pouring method in the above production apparatus.
Fig. 5 is an explanatory view schematically showing another dipping method of the dope.
6 is an explanatory view schematically showing the relationship between the slit interval of the flexible die and the thickness of the dope on the support in the production apparatus.
7A is a plan view of an optical film before stretching by simultaneous biaxial stretching.
Fig. 7B is a plan view of the optical film after stretching by simultaneous biaxial stretching. Fig.
8 is a plan view of an optical film conveyed by two rolls.

An embodiment of the present invention will be described with reference to the drawings as follows. In the present specification, when numerical ranges A to B are represented, values of lower limit A and upper limit B are included in the numerical range. The present invention is not limited to the following contents. For convenience of explanation, the carrying direction of the flexible film or optical film in the plane perpendicular to the thickness direction of the flexible film or the optical film (within the film plane) is also referred to as the MD direction, and the width direction orthogonal to the MD direction is defined as TD direction ". Further, the MD direction stretching is also called MD stretching, and the TD stretching is also called TD stretching.

[Point of Manufacturing Method of Optical Film]

The method for producing an optical film of the present embodiment is a method for producing an optical film using a solution casting film forming method wherein a dope is made from a flexible die on a moving support and the dope is dried on the support to form a flexible film A flexible separation step of separating the flexible film conveyed by the movement of the support from the support, a stretching step of stretching the flexible film in the transverse direction orthogonal to the conveying direction of the flexible film while conveying the separated flexible film, Respectively. The mechanical strength of the flexible film or the optical film in the transport direction is E _MD (MPa), and the mechanical strength in the transverse direction is E _TD (MPa). In the flexible separation step, the dope is stretched in the carrying direction by softening the dope on the support so that 1 <E _MD / E _TD <1.5 when the flexible film is peeled from the support. In the stretching step, the flexible film is stretched in the width direction so that the optical film having E _MD ? E _TD is obtained. Further, the relationship between the mechanical strength E _MD and E _TD is determined by the ratio of the stretching magnification in the MD direction (the ratio of the moving speed of the support to the dope discharge speed) and the stretching magnification in the TD direction (the film width after stretching Ratio) can be appropriately set.

In the flexible peeling process, the MD is stretched by softening the dope on the support so that 1 < E _MD / E _TD . By this MD stretching, the mechanical strength E _MD in the _MD direction becomes higher than the mechanical strength E _{TD in the} TD direction. Then, in the subsequent stretching step, the TD stretching is performed so that an optical film having E _MD ? E _TD is obtained. That is, by stretching process, the mechanical strength in the MD direction E _MD, the magnitude relation of mechanical strength in the TD direction E _TD is reversed or as E _MD <E _{TD, MD} becomes E = E _TD.

As described above, in the case of softening, MD stretching satisfying 1 < E _MD / E _TD is performed, and TD stretching with E _MD ? E _TD is carried out after peeling. In the obtained optical film, Both the strength E _MD and the mechanical strength E _TD in the TD direction are improved and the balance of these mechanical strengths E _MD and E _TD is also good. This makes it possible to suppress the dimensional fluctuation in the MD and TD directions due to the fluctuation of the humidity of the optical film.

Further, when MD stretching is performed so as to satisfy E _MD / E _TD < 1.5 at the time of softening, the stretching magnification in the MD direction is not excessively increased so that the distance from the flexible die to landing on the support becomes long, (Ribbons) are vibrated, and fluctuation of the film thickness in the MD direction can be suppressed. Thus, it is possible to suppress the mechanical strength E _MD E _TD from fluctuating in the plane, and the dimensional fluctuation due to the fluctuation of the heat of the optical film can be reliably suppressed.

In this embodiment, when the drying rate (% / min) is defined as the rate at which the amount of the residual solvent in the dope decreases from an ejection amount from the flexible die to an arbitrary amount by drying, the flexible separation step , It is preferable to maintain a state in which the drying speed is not more than 100 (% / min) for at least one second from the time when the dope is discharged from the flexible die.

If the state in which the drying speed is 100 (% / min) or less from the discharge timing of the dope for 1 second or more is maintained, the dope is hardly dried and the dope can be maintained in the state of the residual solvent amount. In this state, even if the draw ratio in the MD direction at the time of softening is increased (even if the movement speed of the support is increased with respect to the dope discharge speed), the distance from the soft die to the dope landing on the support becomes longer than necessary And vibration of the dope (ribbon) is suppressed. Thereby, it is possible to reduce the film thickness nonuniformity in the MD direction (film thickness nonuniformity of transverse shapes) when the drawing magnification is increased. Therefore, when a liquid crystal display device is constituted by applying a formed optical film to a protective film of a polarizing plate (in particular, a protective film on the liquid crystal cell side with respect to a polarizer), light leakage due to unevenness in film thickness of the optical film can be reduced.

In the flexible separation step, the liquid with a solid content of 15% or less and the dope may be simultaneously flexed so that the liquid covers the dope in the direction of the film thickness by a shared lead.

Since the surface layer of the dope (the outermost layer on the opposite side of the support and the outermost layer on the support side) is covered with a liquid having a solid content of 15% or less by the coke oven, the dope becomes difficult to dry, (100% (% / min) or less) of the drying speed can be surely realized. As a result, it is possible to reliably reduce uneven film thickness in the MD direction and light leakage of the liquid crystal display device caused thereby.

It is preferable that the gap of the slit for discharging the dope in the flexible die is 2 to 10 times the thickness of the dope discharged from the slit and landed on the support.

If the width of the flexible film on the support in the TD direction is constant, the ratio of the thickness of the dope landed on the support to the gap of the slit of the flexible die corresponds to the stretching magnification in the MD direction. The stretching magnification in the MD direction at the time of softening is not less than 2 times and not more than 10 times so that the effect of suppressing the dimensional fluctuation of the optical film due to the fluctuation of the wet heat and the thickness unevenness in the MD direction at the high stretching magnification are suppressed to suppress light leakage Can be obtained in a well-balanced manner.

The moving speed of the support is preferably 30 m / min or more. By forming a flexible film on the support at such a moving speed and forming an optical film, the productivity of the optical film can be improved.

The moisture permeability of the optical film obtained in the stretching step is preferably 150 g / m &lt; 2 &gt; day or less. When the moisture permeability is in the above range, the dimensional change of the optical film due to the function can be suppressed. Thus, when the optical film is applied to the protective film of the polarizing plate and the polarizing plate is bonded to the glass substrate of the liquid crystal cell, warping of the glass substrate due to humidity fluctuation can be reliably reduced.

[Detailed Description of Manufacturing Method of Optical Film]

Hereinafter, the details of the production method of the optical film of the present embodiment will be described.

Fig. 1 is an explanatory view showing a schematic structure of a manufacturing apparatus 1 to which a manufacturing method of an optical film of the present embodiment is applied. The production apparatus 1 is an apparatus for producing an optical film by a solution casting film forming method and includes a melt mixing apparatus 2, a liquid feeding pump 3 and 6, a filtration apparatus 4 and 7, A flexible die 8, a support 9, a tenter 10, a drying device 11, and a winding device 12. In this manufacturing apparatus 1, the following liquid / laminating process, a softening process, a drying process on a support, a peeling process, a drying / stretching process, and a winding process are performed in this order. The above processes from the above-mentioned fusing step to the peeling step correspond to the above-mentioned flexible peeling step.

&Lt; Tank / Liquid feeding process >

In the dissolving and mixing apparatus 2, the film forming material of the optical film is introduced by blowing, conveying, feeding by pump, etc., and they are mixed and dissolved. As a mixing method, stirring may be performed with a stirring blade or the like, or stirring may be carried out non-contact using magnetic or the like. Further, as described in Japanese Patent Application Laid-Open No. 2002-241511, it is possible to dissolve by heating or pressurization at the time of mixing, but in this case, in the vicinity of the boiling point of the solvent in the dissolution / mixing device 2 having pressure resistance , It is preferable to perform depressurization or opening to replace the atmosphere in the apparatus with the solvent vapor.

It is preferable that the dissolving and mixing apparatus 2 is shielded again so that the concentration of the dissolving liquid does not change as the atmosphere in the interior is replaced with the solvent vapor. The substitution with the solvent vapor is preferably carried out near the boiling point of the solvent having a specific gravity higher than that of the atmosphere and the valve provided in the upper portion of the dissolution mixing apparatus 2 is opened.

It is also preferable to maintain the concentration of the dope to be prepared by cooling the gas removed from the solution mixing device 2 and adding the coagulated solvent into the dissolution mixing device 2.

From the viewpoint of promoting dissolution, the dissolving and mixing apparatus 2 preferably has a facility for temperature regulation on the wall surface portion. In addition, a method of bringing a liquid or gas whose temperature is adjusted into contact with the outer wall, or a method of heating by a high frequency or the like is also preferable because dissolution can be promoted.

From the standpoint of suppressing the separation of components, it is preferable that the components are always stirred during dissolution or during temperature change. The dope after the dissolution is completed is preferable to be less than the boiling point of the solvent before pouring, because foaming or the like as a cavitation source is suppressed.

After the completion of the dissolution, the dope is sent from the solution mixing device 2 to the filtration device 4 by the liquid delivery pump 3, and the foreign substance in the dope is removed by the filtration device 4. The foreign matter includes foreign matter mixed with the raw material, unharmed by the impurities in the raw material, and foreign matter agglomerated by drying a part of the dissolved product.

In the filtration device 4, it is preferable to make the filtration pressure as low as possible while ensuring the filtration amount required for production, because it is less likely to escape the foreign matter. Regarding the filter medium, among the various filters, a filter according to the foreign matter to be filtered may be appropriately selected and used. Although only two filtration devices 4 and 7 are shown in Fig. 1, it is also preferable to remove foreign substances using a plurality of filtration devices. In addition, the smaller the pressure difference between before and after the filtration becomes, the more difficult it is for the foreign matter to escape. Therefore, it is also possible to prevent the pressure difference from being generated before and after filtration by appropriately setting the pipe diameter, desirable.

There is a possibility that a foreign object is generated due to abrasion at the slidable portion of the liquid delivering apparatus or the like. Therefore, as shown in Fig. 1, it is preferable that the filtration device 7 is provided after the liquid delivery pump 6 which is the final liquid delivery device.

The dope filtered in the filtration device 4 is sent to a political kiln 5 containing a kiln or a tank, and is left there for one hour or more. This stabilizes the concentration of the dope, removes foaming, stabilizes the temperature, and suppresses fluctuations in the amount of liquid transferred due to the viscosity fluctuation at the time of pouring, and stabilizes the film thickness and quality of the optical film to be produced. In the political furnace 5, it is preferable to keep the dope at a temperature equal to or lower than the boiling point of the solvent.

It is more preferable that the pressure in the fixed furnace 5 is equal to or lower than the peripheral air pressure of the flexible die 8. [ This is because, when the pressure drops sharply after the discharge of the dope from the flexible die 8, foaming and volume fluctuation are suppressed, and a more uniform film can be obtained.

The dope set in the stationary furnace 5 is sent to the filtration device 7 by the liquid feed pump 6, filtered there and then sent to the flexible die 8. Stabilization of the dope temperature by a temperature adjusting mechanism (not shown) when the dope is fed to the flexible die 8 after the standing is suppressed to suppress disruption of the movement of the film after discharge due to a change in viscosity, Which is advantageous in that it is possible to improve confusion.

<Flexible Process>

The dope conveyed to the flexible die 8 is discharged from the flexible die 8 toward the moving support 9 and is plied onto the support 9. The support 9 is preferably an endless continuous support, for example, a stainless steel belt such as SUS316 or SUS304 generally used, or a metal drum coated with hard chrome plating or the like. When the support 9 is formed of a belt, if the length of the belt is 150 m or more, it is difficult to control the belt 9 due to inertia or expansion. Therefore, the length of the belt is preferably 150 m or less. It is preferable that the width of the belt is wide, but it is preferably 3 m or less in consideration of folding. The thickness of the belt is preferably 1 to 3 mm.

In the case of producing a product having a width exceeding 2 m, it is preferable that the support width is 2 m or more. As the belt having a width of 2 m or more, for example, a seam belt 9a having a welded portion T for one week in the manufacturing direction (MD direction) can be used as shown in Figs. 2 and 3. The shim belt 9a is manufactured by arranging a plurality of shim belts 9a ₁ in the width direction and welding the adjacent shim belts 9a ₁ . In the welded portion T, 1 to 10 pin holes having a long diameter of 70 mu m or more and a depth of 30 mu m or more may be present. Further, the welding portion T for one week in the manufacturing direction may be included in the central portion of the width of the belt or may be cut off. Seam (S) of the forming direction of each seam belt (9a ₁₎ is, and may be arranged to be between the respective seam belt (9a _1), in a straight line as shown in Figure 2, or may displaced in the production direction as shown in FIG. 3 .

In this embodiment, when the speed at which the dope is discharged is T (m / sec) and the speed at which the support 9 is moved is S (m / sec) (S / T) is greater than one. As a result, MD stretching is performed in which the dope is elongated in the MD direction at the time of softening. At this time, the moving speed of the support 9 is preferably 30 m / min or more from the viewpoint of improvement of the productivity of the optical film as described above.

The stretching ratio (ratio (S / T)) in the MD direction in the softening step is set so that 1 < E _MD / E _TD < 1.5 at the time of peeling the flexible film from the support 9 do.

In the flexible process, flexibility at a temperature higher than the dew point around the flexible die 8 is preferable in that condensation can be prevented from occurring due to cooling by volatilization heat. Further, the lower the temperature of the dope, the slower the drying and the lower the production rate. Therefore, it is preferable that the dope is 3 ° C or higher in practical use and the boiling point of the lowermost solvent contained in the dope is not more than the boiling point.

The dope supplied to the flexible die 8 may be a single layer or a laminated layer. In the case of the lamination, a plurality of the melt mixing device 2, the liquid feeding pumps 3 and 6, the filtration devices 4 and 7, and the stationary furnace 5 are provided to form a feed block immediately before the flexible die 8, In the flexible die 8, a method of joining (laminating) each dope is preferable. A flexible method of flexibly stacking a plurality of doughs at the same time is called a shared die.

Fig. 4 is an example of a dope softening method, and schematically shows a state in which the dope is flexed on the support 9 by the common streak from the flexible die 8. Fig. In this embodiment, the dope D1 for forming the optical film and the liquid L1 (for example, air side) and L2 (for example, the support side) having a solid content of 15% L2 so as to cover the dope D1 in the film thickness direction, they may be simultaneously poured on the support 9 from the flexible die 8. The liquids L1 and L2 may be the same composition (material) as the dope D1 or may be the same composition (material) as a part of the dope D1 if the liquid is a liquid having a solid fraction of 15% or less. The solid content refers to the ratio of solid content such as fine particles (matte) to the entire liquid.

The above-described drying speed (100 (% / min) or less) is reliably prevented because the surface and the back of the dope D1 are covered with the liquids L1 and L2 and the dope D1 is hardly dried It is possible to realize it. That is, the state of the residual solvent amount can be maintained for a predetermined time (for example, 1 second or more) after the discharge. As a result, even when the MD stretching is performed at a high stretching magnification at the time of softening, the vibration of the dope (ribbon) during discharge can be suppressed, and it is possible to suppress the film thickness nonuniformity of the transverse type.

Fig. 5 schematically shows another softening method of the dope. 5, the dope D1 from the flexible die 8 is softened on the support 9 as a single layer and is covered with the cover D1 so as to cover the surface of the dope D1 landed on the support 9. [ C may be provided. When the liquid L3 (for example, methylene chloride) the same as the liquid contained in the dope D1 is received in the cover C, the liquid L3 is filled in the cover C with the volatile vapor. This makes it difficult for the solvent (for example, methylene chloride) in the dope D1 to evaporate in the dope D1 on the support 9 covered with the cover C. As a result, it is possible to maintain a state in which the drying speed is 100 (% / min) or less in the same manner as described above for a predetermined period of time (for example, 1 second or more) after the dope is discharged from the flexible die 8, Even when the MD stretching is carried out at the stretching magnification, it becomes possible to suppress the film thickness non-uniformity of the transverse step.

It is also preferable that a plurality of dope supply ports to the flexible die 8 are provided in the TD direction so as to allow different dope to be flexible at the end portion and the center in the TD direction in order to improve the neck by MD stretching in the flexible state. In that case, it is preferable that the Doped viscosity of the end portion in the TD direction is higher than the central portion.

It is also preferable to supply a solvent containing a good solvent to the end portion in order to suppress the occurrence of a film at the end portion. As described in JP-A-05-086212 and the like, it is also preferable that the solvent supplied to the end portion contains not only good solvents but also poor solvents in an amount of 0 to 50%.

Typical poor solvents include alcohols such as methanol and ethanol, ketones such as acetone, and the like. These may be appropriately selected and adjusted depending on the time taken for drying and compatibility with the dope, and the concentration of the poor solvent is preferably 0% or more and 50% or less.

6 schematically shows the relationship between the slit interval P (占 퐉) of the flexible die 8 and the thickness M (占 퐉) of the dope D1 on the support 9. As described above, it is preferable that the slit interval P is not less than 2 times and not more than 10 times the thickness M of the dope D1. That is, it is preferable that the draw ratio in the MD direction is 2 times or more and 10 times or less. For example, if the thickness M of the doping D1 is 50 mu m, the slit spacing P is preferably 100 mu m or more and 500 mu m or less. When the slit interval P is within the above range with respect to the thickness M of the dope D1, as described above, the effect of suppressing the dimensional fluctuation of the optical film due to the humid heat fluctuation, The effect of suppressing the thickness unevenness and suppressing the light leakage can be obtained in a good balance.

As described above, the slit gap of the flexible die 8 may be adjusted according to the film thickness of the dope required. However, as described in Japanese Patent Application Laid-Open No. 2002-036266, You can. When forming the thin film, it is preferable that the gap is as narrow as possible. However, if the gap is less than 150 mu m, it is not preferable because control of the film thickness in the TD direction becomes difficult.

Further, as described in Japanese Patent Application Laid-Open No. 2002-028943, the angle formed by the center line of the die slit and the tangent line of the endless metal supporting body moving infinitely is set to 40 to 90 degrees, the linear velocity of the flexible film is set to 10 to 200 m / min, and the fluctuation of the linear velocity is set within 占 5%; the gap between the end of the die slit and the endless metal supporting body surface moving infinitely is set to 200 占 퐉 to 5 mm; the viscosity of the dope is set to 1 to 200 Pa sec.

<Drying Step on Support>

On the support 9, the flexible dope is dried and a flexible film (web) is formed. The flexible film is conveyed along with the movement of the support 9. Since the flexible film is peeled off from the support 9 in the subsequent peeling step, transfer inhibition is important, and the smoother the surface of the support 9 is, the better. That is, for example, it is preferable that the surface of the support 9 has no concavity and convexity or pinhole. Further, as described in Japanese Patent Application Laid-Open Nos. 2000-84960, 2002-234042 and 2002-001745, the centerline average roughness Ra of the surface of the support is 1 to 3 nm, (Ra: 1 to 5 nm, Rz: 10 to 50 nm, Ry: 10 to 50 nm), which is called mirror finish.

When the thickness of the support is measured at two points at intervals of 50 mm in an arbitrary place in the MD direction or the TD direction, if the thickness deviation is 1 占 퐉 or less, and more preferably 0.3 占 퐉 or less, So that the sticking and the convex distortion when the optical film is wound and stored as a roll can be eliminated.

The temperature of the supplied dope and the temperature of the supplied drying wind are higher than the dew point temperature of the peripheral gas to be discharged in the vicinity of the supporter 9 immediately after the supporter 9 and when the solvent is, for example, two kinds of solvents A and B, (A solvent boiling point x A solvent content + B solvent boiling point x B solvent content). If the temperature is lower than the dew point temperature, dew condensation occurs and a mark due to condensation is generated on the surface of the film. Further, when the temperature is higher than (A solvent boiling point x A solvent content + B solvent boiling point x B solvent content), a phenomenon occurs in which the flexible dope is foamed, thereby deteriorating the planarity of the film. The solvent A is, for example, a good solvent, and the solvent B is, for example, a poor solvent. (A solvent boiling point × A solvent content + B solvent boiling point × B solvent content + C solvent boiling point × C solvent content + D solvent boiling point × D solvent content ...) in the case where there are three or more kinds of solvents.

The surface roughness may intentionally be roughened on the support 9 other than the central portion of the width of the support on which the optical film to be the product portion is obtained. Normally, it is preferable that the mirror surface finish has an arithmetic average roughness Ra of 10 nm or less. However, for example, when the Ra is roughly 10 m or so in a range of about 300 mm from the end of the support, The peelability of the film is improved. This is because the adhesion between the unevenness of the surface of the support and the coherent film can not be fully attended to the shrinkage of the coherent film due to drying, and the adhesion area is partially reduced by peeling.

As described in Japanese Patent Application Laid-Open No. 2005-104148, on the support 9, it is preferable to change the wind speed of the drying wind according to the progress of drying. For example, the air velocity in the flexible portion is more preferably 0.5 m / sec or less, and more preferably 0.1 m / sec or less.

<Peeling process>

The solvent is evaporated on the support 9 and the formed flexible film is peeled off at the peeling position. The peeled flexible film is transported to the next process.

In the drying step on the support, the solvent in the flexible film is evaporated, but it is preferable that the residual solvent amount of the flexible film on the support 9 at the time of peeling is within the range of 15 to 100 mass%. The adjustment of the amount of the residual solvent can be exemplified by the amount of heat supplied (hot air, IR heater, microwave, etc.), the rate of removal of the volatilized solvent (blowing, coagulation, Dry hot wind is often used. In the case of using dry hot air, the amount of the residual solvent is preferably controlled by the drying temperature and the drying time in the drying step on the support. The factors other than the drying temperature and the drying time are often such that the adjustment value for avoiding deformation due to gas movement on the film surface is small in many cases. Here, the residual solvent amount of the flexible film is defined by the following formula.

(Mass%) = (mass (g) before the heat treatment of the flexible film-mass (g) after the heat treatment of the flexible film) / (mass (g)

The heat treatment at the time of measuring the amount of the residual solvent means that the heat treatment is carried out at 115 占 폚 for 1 hour while maintaining the pressure at 1 atm.

If the amount of the residual solvent is 15 mass% or more, the matte contained therein is not uniformly dispersed in the thickness direction in the drying process on the support (9). As a result, a desired concavo-convex structure is generated by stretching, and deformation of the wound shape of the optical film to be formed easily can be suppressed. Further, the drying time of the flexible film is not long, and the productivity is also improved. On the other hand, if the amount of the residual solvent is within 100 mass%, the flexible film has self-supporting property, the peeling failure of the flexible film can be avoided, and the mechanical strength of the flexible film can be maintained. As a result, the planarity at the time of peeling the flexible film is improved, and generation of crumples (creases) and vertical stripes due to the peeling tension can be suppressed.

When the flexible film is peeled from the support 9, the peeling tension is usually in the range of 100 to 200 N / m. In the case of a flexible film having a low strength at the time of peeling, peeling is preferably carried out with a tension of 100 N / m or less . In this case, a peeling aid may be added, or an air knife or the like may be provided at the peeling position so that even a storage force can be stably peeled off.

The film temperature at the peeling position of the support 9 is preferably in the range of 0 to 40 캜, more preferably in the range of 5 to 30 캜, and most preferably in the range of 10 to 25 캜.

<Drying / Stretching Step>

The coherent film peeled off from the support 9 in the peeling process is then dried in the drying process. The drying may be performed before or after the stretching in the tenter 10. That is, the drying step can be divided into a pre-drying step before the drawing (the first drying step) and a main drying step after the drawing (the second drying step).

(Preliminary drying step)

The coherent film peeled from the support 9 is preliminarily dried in a first drying apparatus (not shown). In the first drying apparatus, the flexible film may be conveyed by a plurality of rolls arranged vertically, or both ends of the flexible film may be fixed by a gripping device such as a clip or a pin, and the flexible film may be conveyed while being dried.

When the flexible film is to be dried while being transported by a plurality of rolls, the inter-roll distance is preferably narrower than the width of the flexible film to be transported, more preferably within 1 m. By shortening the distance between the rolls, curls such as wrinkles and curls during transportation can be improved.

Further, as the number of rolls is increased, the resistance for rotating the rolls increases to increase the tension for conveying the flexible film, or to add a control drive device. In addition, there is a possibility that a scratch or the like of a roll is transferred to enter the product . Therefore, the smaller the number of rolls, the better. As a result, the number of rolls is often from 100 to 10000, and the surface of the roll is preferably Ra &lt; = 10 nm, and it is preferable that pinholes, protrusions, and the like are not present. The roll diameter may be appropriately selected according to the wrap angle at the time of conveyance, and the range of 100 to 300 mm is frequently used.

The means for drying the flexible film is not particularly limited and generally can be performed by hot air, infrared rays, heating rolls, microwaves or the like, but for convenience, hot air is preferably used.

The drying temperature in the preliminary drying process of the flexible film is preferably -20 占 폚 or lower of the glass transition point of the flexible film. Particularly, it is effective to carry out heat treatment at a temperature of 30 占 폚 or more for 1 minute to 30 minutes. The drying temperature is preferably in the range of 30 to 120 占 폚, and more preferably in the range of 35 to 100 占 폚.

In this preliminary drying step, it is preferable to adjust the amount of the residual solvent in the flexible film at the time of stretching, but the amount of the residual solvent may be adjusted at the beginning of the drawing step described later. The residual solvent amount is preferably controlled by the drying temperature and the drying time in the preliminary drying step.

(Drawing step)

The flexible film is subjected to stretching treatment in a stretching apparatus (tenter 10) under a specific residual solvent amount to obtain an optical film. By the stretching treatment, it is possible to suppress the occurrence of minute creases caused by the matte or foreign matter of the optical film, and to promote the uniform distribution of the matting agent. In addition, by controlling the orientation of the molecules in the optical film, a target retardation value Ro in the in-plane direction and a retardation value Rt in the thickness direction can be obtained.

The amount of the residual solvent at the start of the stretching in the stretching step is preferably 10 mass% or more, more preferably 15 to 100 mass%. If the residual solvent amount exceeds 100 mass%, the strength of the grip portion may be insufficient.

In the stretching step, stretching can be performed in the MD direction and / or the TD direction. In the present embodiment, stretching in the TD direction in the stretching step after peeling is preferable from the viewpoint of improving dimensional stability and mechanical strength, because stretching in the MD direction is performed at the time of softening as described above. In particular, the optical film satisfying the E ≤E _{MD TD} is obtained, it is possible by stretching the yuyeonmak in the TD direction, to surely improve the dimensional stability and mechanical strength.

The stretching may include a step of widening the width, a step of maintaining the width and lowering the residual stress, and finally a step of reducing the width to relax a part of the residual stress. In this case, it is preferable that the step is carried out in the order of the step before the width is widened (the heat-releasing step), the step of widening the width (the step of stretching), the step of maintaining the widening width (the holding step), and the step of reducing the width of widening. In each of the above steps, the temperatures may be the same or different.

In order to reduce the residual stress, which is the purpose of the holding process and the relaxation process, in a shorter time, these steps may be performed at a higher temperature than the stretching step. In order to maintain the residual solvent, the reheat process may be performed at a lower temperature than the stretching process.

Further, after stretching in a region where the residual solvent amount is 10% by mass or more, further stretching may be performed for the purpose of adjusting the phase difference and the like.

Specifically, after the TD stretching (residual solvent 10% or more) in the stretching (MD stretching) step in the flexible separating step and in the stretching step, the stretching may be performed only in the MD direction alone or in the TD direction only, May be performed. In the case of biaxial stretching, simultaneous biaxial stretching may be performed or may be performed stepwise. The stepwise stretching includes, for example, sequential stretching in which stretching directions are different from each other, stretching in the same direction in multiple steps, and addition of stretching in different directions to any one of the steps. That is, for example, the following stretching steps are possible:

Stretching in the MD direction Stretching in the TD direction Stretching in the MD direction Stretching in the TD direction

Stretching in the TD direction stretching in the TD direction stretching in the MD direction stretching in the MD direction

Further, simultaneous biaxial stretching may include stretching in one direction and shrinking the other by relaxing the tension.

In the stretching step, stretching is preferably performed in a temperature range of (Tg-50) to (Tg + 50) deg. C, with the glass transition temperature of the dried film as Tg (DEG C) so that the film thickness after stretching becomes a desired range . If the stretching is carried out in the above-mentioned temperature range, the retardation can be easily adjusted and the stretching stress can be reduced, so that the haze is lowered. Further, the occurrence of breakage of the optical film is suppressed, and an optical film excellent in planarity and coloring property can be obtained. Further, the larger the amount of the residual solvent, the lower the Tg of the appearance, and therefore, the stretching at the low temperature side is preferable.

Here, the glass transition temperature Tg is the midpoint glass transition temperature (Tmg) measured according to JIS K7121 (1987), which is measured using a commercially available differential scanning calorimeter at a heating rate of 20 캜 / min. The specific glass transition temperature Tg of the optical film can be measured using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc. according to JIS K7121 (1987).

In the stretching step, after the stretching (MD stretching) at the time of stretching, the film is preferably stretched in the TD direction at a stretching ratio within a range of 101 to 200% with respect to the original width, and a stretching ratio within a range of 110 to 140% It is more preferable to stretch. Within this range, generation of minute creases on the product film surface or inside of the product film due to stretching at a high magnification can be suppressed. Particularly, when a composition contains a retardation increasing agent, not only a desired retardation value can be obtained but also the optical film can be made thin. The stretching magnification means the ratio (%) of the length of the optical film or the width of the optical film after stretching to the length or width of the optical film before stretching.

Further, in the case of MD stretching after TD stretching, the MD stretching method is not particularly limited. For example, there are a method in which a plurality of rolls are caused to have a major speed difference, and a roll is wound therebetween in the longitudinal direction (MD direction), and both ends of the web are fixed with clips or pins, A method of stretching in the machine direction in the longitudinal direction and a method of stretching in both longitudinal and transverse directions in both longitudinal and lateral directions. Of course, these methods may be used in combination.

As a method for stretching the optical film in the TD direction in the stretching process, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-46625, the both ends of the optical film are fixed with a clip or pin, There is a method in which the width of the fin is increased so as to extend (tenter method). The method of using the clip is called a clip tenter method, and the method of using the pin is called a pin tenter method.

When stretching in the TD direction, stretching at a stretching speed of 100 to 500% / min in the TD direction is preferable from the viewpoint of improving the planarity of the optical film.

When the stretching speed is 100% / min or more, formation of cracks is suppressed even at a low magnification, planarity is improved, and optical films can be processed at a high speed, which is preferable from the viewpoint of productivity. If the stretching speed is within 500% / min, it is preferable that the optical film can be processed without breaking.

The preferred stretching speed is in the range of 150 to 300% / min and is effective at the time of low stretching. The stretching speed is defined by the following formula.

Elongation speed (% / min) = [(d ₁ / d ₂ ) -1] × 100 (%) / t

Here, d ₁ is the width dimension (mm) of the optical film in the stretching direction after stretching, d ₂ is the width dimension (mm) of the stretching direction of the optical film before stretching, and t is the time (min) required for stretching.

The optical film of the present embodiment contains a retardation increasing agent or a retardation reducing agent and is stretched so that the in-plane retardation value Ro is in the range of 0 to 600 nm and the retardation value Rt in the thickness direction is in the range of 0 to 600 nm And may have a desired phase difference value within the range. The retardation value Ro in the in-plane direction and the retardation value Rt in the thickness direction were measured at a wavelength of 590 nm under an environment of 23 占 폚 and 55% RH using an automatic birefringence index liquid scanning (Axo Scan Mueller Matrix Polarimeter, Dimensional refractive index measurement, and can be calculated from the obtained refractive indices nx, ny, and nz.

The optical film of the present embodiment is characterized in that the in-plane retardation value Ro of the optical film represented by the following formulas (i) and (ii) is in the range of 40 to 60 nm, the retardation value Rt in the thickness direction is in the range of 110 to 140 nm Is preferable in view of improving the visibility such as the viewing angle and the contrast in the VA type liquid crystal display device. The optical film can be adjusted within the retardation value range by stretching while at least adjusting the stretching magnification in the TD direction.

(I): Ro = (nx-ny) xd (nm)

Rt = {(nx + ny) / 2-nz} xd (nm)

[In the formulas (i) and (ii), nx represents the refractive index in the direction x in which the refractive index becomes maximum in the in-plane direction of the film. ny represents the refractive index in the direction y perpendicular to the direction x in the in-plane direction of the film. nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film]

(This drying step)

In this drying step, the stretched optical film is heated and dried by the drying device 11 as the second drying device. In the case of heating the optical film by hot air or the like, means for preventing the mixing of hot air after use is provided by providing a nozzle capable of discharging hot air (air including solvent or air including wetting unit) . The hot air temperature is more preferably in the range of 40 DEG C or more and (Tg + 20) DEG C or less. The drying time is preferably about 5 seconds to 60 minutes, more preferably 10 seconds to 30 minutes.

In the drying step, it is preferable to dry the optical film in a short time until the residual solvent amount becomes 0.1 mass% or less from the viewpoint of productivity improvement. Further, drying at a temperature higher than (Tg + 20) DEG C is not preferable because the optical film becomes too soft and stuck to the conveying means (for example, the conveying roller).

The heating and drying means used in the drying step is not limited to hot air. For example, infrared ray, heating roller, microwave, or the like can be used. From the viewpoint of simplicity, it is preferable to carry out drying by hot air while conveying the film by the conveying rollers arranged in a staggered manner.

The transporting tension during drying is preferably set to a tension that does not cause elongation and shrinkage of the optical film, and is preferably set in a range of 20 N / m to 120 N / m so as to prevent wrinkling and curling during transportation.

&Lt; Slit process &

It is preferable that there is a slit process in which the end portion of the optical film is slit and removed so that deformation occurring in the grip portion after the stretching in the tenter 10 and deformation occurring in the end portion in the flexible state do not adversely affect the transport. Further, when the optical film is wound by the slit in the winding step to be described later, a good winding state can be obtained.

As described in Japanese Patent Application Laid-Open No. 196750/1993, when the width end portion of the optical film is cut into slitters (for example, rotary blades), fine fragments that are generated are mixed into the product, , And air may be jetted from the nozzles to the slitters. By this injection, it is possible to reduce the attachment of the cutting powder generated at the time of cutting to the edge of the blade of the slitter. At this time, it is preferable that the spraying angle of the air to the slitter (the angle between the slitter and the nozzle) is 15 ° or more. The temperature of the air to be sprayed is preferably lower than 50 占 폚 in order to suppress the temperature rise of the blade due to the frictional heat. In addition, since fragments are generated by cracking at the time of cutting, it is also preferable that means for softening the film so as to prevent cracking is provided for the film before cutting. As means for smoothing, heating or humidification and swelling by a solvent is known, and it is preferable that the smoothing is carried out immediately before the slit. In the case of heating, when the film is carried out at a temperature in the range of Tg-70 占 폚 or more and Tg-30 占 폚, deformation due to heating hardly occurs and generation of debris can be suppressed by sufficient softening.

&Lt; Winding step &

(Knurled)

It is preferable to perform knurling (concave-convex processing) on both ends of the width in order to suppress the blocking of the wound film and the occurrence of black bands before winding the optical film with the both ends slit.

The knurling can be formed by pressing a heated embossing roller against the film width end portion. Fine irregularities are formed on the surface of the embossing roller. By pressing the optical film against the surface of the embossing roller, concave and convex portions can be formed at both end portions of the optical film, and the volume of the end portion can be increased. At that time, since the shape of the concavities and convexities changes due to the temperature of the embossing roller, it is desirable that the amount of heat is sufficient so that the temperature does not change, and it is preferable that the diameter of the embossing roller is 100 mm or more. Further, since the temperature to be used is 100 DEG C or higher, it is preferable that the heat-releasing device of the embossing roller is provided at a position not contacting the film. The height of the region where the unevenness is formed in the optical film is preferably 2 to 10 mu m, and the width of the region is preferably 5 to 20 mm. Further, since the boundaries of the convex portion and the concave portion are not a straight line but a curved line, the occurrence of perforations and whiskers is suppressed, which is preferable.

It is preferable that the knurling is performed after the drying step and before the winding step in the film formation of the optical film. Also, as described in Japanese Patent No. 3947394, it is preferable to perform knurling after the stretching process because slip scratches due to transportation and transfer of marks on adhered objects can be improved.

(Winding process)

After the knurling process, a winding step is performed in which the optical film is wound in a roll form in the winding device (12). In the winding step, the amount of the residual solvent in the optical film becomes 0.1% by mass or less, and then the optical film is wound. When the amount of the residual solvent is preferably 0.05 mass% or less, an optical film having good dimensional stability can be obtained. At this time, it is preferable that the water content in the optical film is set to 50 to 80% of the saturated moisture content from the viewpoint that it can be hardly affected by ambient moisture during storage.

As a winding method in the winding device 12, a generally used method may be used. For example, there are a constant torque method, a constant tension method, a taper tension method, an internal stress constant program tension control method, and the like.

When the production speed (film transport speed) exceeds 30 m / min, the removal of the accompanying wind accompanying the transportation of the optical film becomes a big problem. In order to remove the accompanying wind, it is preferable to wind it while removing the wind accompanied by a touch roll or an air touch.

[Physical Properties of Optical Film]

&Lt; Modulus of elasticity &

The elastic modulus (mechanical strength) can be measured in the MD direction and the TD direction in accordance with JIS K 7127 (1999), which is one of the standards of the Japanese Industrial Standards Committee (JIS). As a specific measuring method, for example, a sample film was cut into 140 mm (measurement direction) × 10 mm (width) using a tensilon tester (RTC-1225A manufactured by ORIENTEC Co., Ltd.) The mechanical strength E _{MD in the} MD direction or the mechanical strength E in the TD direction was calculated from the slope at 0.05% to 0.25% elongation when the sample film was stretched in the MD direction or the TD direction at a measurement length of 100 mm and a tensile speed of 50 mm / _TD can be calculated.

<Planarity>

With respect to the planarity of the optical film, there is a large problem of thickness irregularity, and in particular, thickness irregularity continuous in the TD direction becomes prominent, which is problematic. The thickness unevenness can be evaluated using a point light source projection method. Concretely, in the dark room, an angle of 45 degrees with respect to the light axis of a commercially available point light source (a xenon lamp manufactured by Hamamatsu Photonics K.K., a xenon lamp made by USHIO, a MP160 manufactured by Sekisui Chemical Co., Ltd.) Can be determined at a position spaced from the light source by 200 to 300 mm and the thickness unevenness of the film can be judged by visually confirming the light and darkness projected on the projection plane orthogonal to the light beam axis spaced from the film by 1000 to 2000 mm.

&Lt; Film length, width, film thickness >

The optical film of the present embodiment is preferably long, and is preferably 100 to 10000 m in length, and is wound in a roll form. The width of the optical film is preferably 1 m or more, more preferably 1.3 m or more, and particularly preferably 1.3 to 4 m.

The film thickness of the optical film is preferably in the range of 5 to 30 mu m from the viewpoints of reduction in thickness of the display device and productivity. More preferably in the range of 10 to 20 mu m. If the film thickness is 5 mu m or more, it is possible to obtain a film strength of a certain level or more. When the film thickness is 30 mu m or less, it can be applied to a thin display device.

[Material of optical film]

(With respect to cellulose acylate)

The cellulose acylate film according to this embodiment contains cellulose acrosate as a main component. For example, the cellulose acylate film according to the present embodiment contains cellulose acylate in an amount of preferably 60 to 100 mass% with respect to the total mass (100 mass%) of the film. Further, the cellulose acylate has a total acyl group substitution degree of 2.0 or more and less than 3.0, more preferably 2.2 to 2.7.

Examples of the cellulose acylate include cellulose and an ester of an aliphatic carboxylic acid and / or an aromatic carboxylic acid having about 2 to 22 carbon atoms, and more preferably an ester of cellulose and a lower fatty acid having 6 or less carbon atoms.

The acyl group bonded to the hydroxyl group of cellulose may be linear or branched or may form a ring. Other substituents may also be substituted. When the number of carbon atoms is the same, the number of carbon atoms is preferably selected from an acyl group having from 2 to 6 carbon atoms, and the total sum of propionyl substitution degree and butyryl substitution degree is from 0 to less than 3.0 to be. The cellulose acylate preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

Concretely, examples of the cellulose acylate include acetyl groups such as cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate or cellulose acetate phthalate, mixed fatty acids of cellulose having a propionate group, a butyrate group or a phthalyl group bonded thereto Esters can be used. The butyryl group forming the butyrate may be linear or branched.

In the present embodiment, cellulose acetate, cellulose acetate butyrate or cellulose acetate propionate is particularly preferably used as the cellulose acylate.

In addition, in order to obtain optical properties meeting the purpose, resins having different degree of substitution may be mixed and used. The mixing ratio at that time is preferably 1:99 to 99: 1 (mass ratio).

Among the above-mentioned materials, cellulose acetate propionate is preferably used as the cellulose acylate. In cellulose acetate propionate, it is preferable that 0 < Y? 2.5 and 0.5? X? 3.0 (however, 2.0? X + Y? 3.0) is preferable, and 0.5? Y? 2.0 and 1.0? (Provided that 2.0? X + Y < 3.0). X represents the degree of substitution of the acetyl group, Y represents the substitution degree of the propionyl group, and X + Y represents the substitution degree of the total acyl group. The substitution degree of an acyl group can be measured in accordance with ASTM-D817-96, which is one of the standards formulated and issued by the American Society for Testing and Materials (ASTM).

The number average molecular weight of the cellulose acylate is preferably in the range of from 60000 to 300000 because the mechanical strength of the obtained film is increased. More preferably, a cellulose acylate having a number average molecular weight of 70,000 to 200,000 is used.

The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose acylate are measured using gel permeation chromatography (GPC). The measurement conditions are as follows. The present measuring method can also be used as a method for measuring other polymers in the present embodiment.

Solvent: methylene chloride;

Column: Three shodex K806, K805 and K803G (manufactured by Showa Denko K.K.) are connected and used;

Column temperature: 25 캜;

Sample concentration: 0.1 mass%;

Detector: RI Model 504 (manufactured by GL Science);

Pump: L6000 (manufactured by Hitachi Seisakusho Co., Ltd.);

Flow rate: 1.0 ml / min

Calibration curve: Standard curve of polystyrene STK standard Polystyrene (manufactured by TOSOH CORPORATION) Mw = 1000000 to 500 Using a calibration curve of 13 samples. 13 samples are used at almost equal intervals.

The residual sulfuric acid content in the cellulose acylate is preferably in the range of 0.1 to 45 mass ppm in terms of sulfur element. They are thought to be contained in salt form. If the content of residual sulfuric acid exceeds 45 mass ppm, it tends to be easily broken at the time of thermal stretching or slitting after heat elongation. The residual sulfuric acid content is more preferably in the range of 1 to 30 mass ppm. The residual sulfuric acid content can be measured by the method specified in ASTM-D817-96.

The free acid content in the cellulose acylate is preferably 1 to 500 mass ppm. If it is in the above-mentioned range, it is preferable because it is hard to break as in the above. Further, the free acid content is preferably in the range of 1 to 100 mass ppm, and it is more difficult to break. And particularly preferably in the range of 1 to 70 mass ppm. The free acid content can be determined by the method specified in ASTM-D817-96.

The cellulose acylate thus synthesized is preferably washed more thoroughly as compared with the solution used in the solution casting method, so that the residual alkaline earth metal content, residual sulfuric acid content and residual acid content can be set within the above range.

Cellulose as a raw material of cellulose acylate is not particularly limited, but cotton linter, wood pulp, kenaf and the like can be mentioned. Further, the cellulose acylates obtained therefrom may be mixed and used in any ratio.

The cellulose acylate can be produced by a known method. Specifically, it can be synthesized with reference to the method described in, for example, Japanese Patent Application Laid-Open No. 10-45804.

As the cellulose ester based resin film particularly preferred in the present embodiment, cellulose acylate satisfying the following formulas (1) and (2) can be mentioned.

2.0 < / RTI &gt; &lt; RTI ID =

(2) 0? X <3.0

(In the formulas (1) and (2), Z1 represents the total acyl substitution degree of the cellulose acylate, and X represents the sum of the propionyl substitution degree and the butyryl substitution degree of the cellulose acylate)

<Cycloolefin Resin>

The optical film of the present embodiment may be composed of a cycloolefin resin film. As the cycloolefin resin, there may be mentioned a polymer or copolymer of a monomer having a structure represented by the following formula (S).

Wherein R ¹ to R ⁴ each independently represents a hydrogen atom, a hydrocarbon group, a halogen atom, a hydroxyl group, a carboxyl group, an acyloxy group, an aryloxycarbonyl group, an alkoxycarbonyl group, an alkoxy group, a cyano group, Or a hydrocarbon group substituted with a polar group (i.e., a halogen atom, a hydroxy group, an acyloxy group, an aryloxycarbonyl group, an alkoxycarbonyl group, an alkoxy group, a cyano group, an amide group, an imide group or a silyl group).

Provided that at least two of R ¹ to R ⁴ may combine with each other to form an unsaturated bond, a monocyclic ring or a polycyclic ring, and the monocyclic or polycyclic ring may have a double bond or may form an aromatic ring. R ¹ and R ² , or R ³ and R ⁴ may form an alkylidene group. p and m are an integer of 0 or more.

The hydrocarbon group represented by R ¹ and R ^{3 in the} above formula (S) is preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 2 carbon atoms.

R ² and R ⁴ are each a hydrogen atom or a monovalent organic group, at least one of R ² and R ⁴ is preferably a polar group having a polarity other than a hydrogen atom and a hydrocarbon group, m is an integer of 0 to 3, p Is an integer of 0 to 3, more preferably m + p = 0 to 4, more preferably 0 to 2, particularly preferably m = 1 and p = 0.

Specific monomers having m = 1 and p = 0 are preferred in that the resulting cycloolefin resin has a high glass transition temperature and excellent mechanical strength. The glass transition temperature is a value obtained by a method based on JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

Examples of the polar group of the specific monomer include a carboxyl group, a hydroxy group, an alkoxycarbonyl group, an allyloxycarbonyl group, an amino group, an amide group and a cyano group, and these polar groups may be bonded through a connecting group such as a methylene group.

Further, a hydrocarbon group in which a divalent organic group having a polarity such as a carbonyl group, an ether group, a silyl ether group, a thioether group, or an imino group is bonded as a linking group may also be used as the polar group.

Among them, a carboxy group, a hydroxy group, an alkoxycarbonyl group or an allyloxycarbonyl group is preferable, and an alkoxycarbonyl group or an allyloxycarbonyl group is particularly preferable.

The monomers in which at least one of R ² and R ⁴ is a polar group represented by the formula - (CH ₂ ) _n COOR is a monomer having a high glass transition temperature, low hygroscopicity and excellent adhesion with various materials .

In the formula relating to the specific polar group, R is a hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 2 carbon atoms, preferably an alkyl group.

Specific examples of the copolymerizable monomers include cycloolefin resins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene and dicyclopentadiene.

The number of carbon atoms of the cycloolefin is preferably from 4 to 20, more preferably from 5 to 12.

In the present embodiment, the cycloolefin resin may be used singly or in combination of two or more.

The preferred molecular weight of the cycloolefin resin is 0.2 to 5 cm 3 / g, more preferably 0.3 to 3 cm 3 / g, and particularly preferably 0.4 to 1.5 cm 3 / g in terms of intrinsic viscosity [η] _inh and is measured by gel permeation chromatography The number average molecular weight (Mn) in terms of polystyrene measured by gel permeation chromatography (GPC) is 8000 to 100000, more preferably 10000 to 80000, particularly preferably 12000 to 50000, a weight average molecular weight (Mw) Preferably 30,000 to 250,000, and particularly preferably 40,000 to 200,000.

When the intrinsic viscosity [eta] _inh , the number average molecular weight and the weight average molecular weight are in the above ranges, heat resistance, water resistance, chemical resistance, mechanical properties and molding processability of the cycloolefin resin are improved.

The glass transition temperature (Tg) of the cycloolefin resin is usually 110 占 폚 or higher, preferably 110 to 350 占 폚, more preferably 120 to 250 占 폚, particularly preferably 120 to 220 占 폚. The Tg of 110 DEG C or more is preferable because it is hard to cause deformation by use under high temperature conditions or by secondary processing such as coating or printing.

On the other hand, by setting the Tg to 350 占 폚 or less, it is possible to avoid the case where the molding process becomes difficult and the possibility that the resin is deteriorated by heat at the time of molding can be lowered.

The cycloolefin resin may contain, for example, a specific hydrocarbon resin as described in Japanese Patent Application Laid-Open Nos. 9-221577 and 10-287732, A thermoplastic elastomer, a rubbery polymer, an organic fine particle, an inorganic fine particle and the like may be added, and additives such as a specific wavelength dispersant, a sugar ester compound, an antioxidant, a peel promoter, a rubber particle, a plasticizer and an ultraviolet absorber may be included.

As the cycloolefin resin, commercially available products can be preferably used. Examples of commercially available products are commercially available from JSR Corporation under the trade names ARTON (registered trademark) G, ATON F, ATON R and ATON RX. They are commercially available under the trade names ZEONOR (registered trademark) ZF14, ZF16, ZEONEX (registered trademark) 250 or Zeonex 280 from Nippon Zeon Co., Ltd. These can be used.

<Ultraviolet absorber>

The optical film of the present embodiment preferably contains an ultraviolet absorber in order to shield unnecessary ultraviolet rays irradiated to the polarizing plate or the liquid crystal display device.

Examples of the ultraviolet absorber include oxybenzophenone compounds, benzotriazole compounds, salicylic ester compounds, benzophenone compounds, cyanoacrylate compounds, and nickel complex salt compounds. Among them, benzotriazole Based compound is preferable. The ultraviolet absorber described in JP-A-10-182621, JP-A-8-337574, and JP-A-6-148430 are preferably used.

When the optical film of the present embodiment is used as a protective film of a polarizing plate in addition to an optical compensation film, ultraviolet absorbers are preferably used because they are excellent in the ability of absorbing ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of polarizers and liquid crystals, From the viewpoint of displayability, it is preferable that the light-emitting device has a characteristic that absorption of visible light having a wavelength of 400 nm or more is small.

The addition amount of the ultraviolet absorber is preferably in the range of 0.1 to 5.0 mass%, more preferably in the range of 0.5 to 5.0 mass% with respect to the polymer composition.

Examples of the benzotriazole ultraviolet absorber useful in the optical film of the present embodiment include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'- Benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, 2- 3'- (3 ', 4 ", 5", 6 "-tetrahydrophthalimidomethyl) -5-chlorobenzotriazole, Methylphenyl] benzotriazole, 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol- (2-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H- benzotriazol- Methylphenol and 2-ethylhexyl-3- [3-t-butyl-4-hydroxy-5- (chloro-2H-benzotriazol- 3-t-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate Only, but it is not limited to these.

TINUVIN 928 "," TINUVIN 109 "," TINUVIN 171 "," TINUVIN 326 "," TINUVIN 328 "(commercially available as" Trade name, manufactured by BASF Japan) can be preferably used.

<Mat>

The optical film of the present embodiment preferably contains a matting agent for imparting concavity and convexity to the film surface at the time of film formation, ensuring slidability, and achieving a stable winding shape. By containing the matting agent, scratches or deterioration in conveying property can be suppressed when the produced optical film is handled.

Examples of the matting agent include fine particles of an inorganic compound and fine particles of a resin. Examples of the fine particles of the inorganic compound include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate . It is preferable that the fine particles include silicon in that turbidity is lowered, and silicon dioxide is particularly preferable.

The average particle diameter of the primary particles of the fine particles is preferably in the range of 5 to 400 nm, more preferably in the range of 10 to 300 nm. These particles may be mainly contained as secondary aggregates having a particle diameter in the range of 0.05 to 0.3 탆 or may be contained as primary particles without aggregation if the particles have an average particle diameter within the range of 80 to 400 nm.

The content of these fine particles in the optical film is preferably in the range of 0.01 to 3.0 mass%, more preferably in the range of 0.01 to 2.0 mass%. When the optical film has a multilayer structure by a covalent bonding method, it is preferable that the optical film contains the added amount of fine particles on the surface.

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

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

Examples of the fine particles of the resin include a silicone resin, a fluororesin and an acrylic resin. Silicone resin is preferable, and it is particularly preferable to have a three-dimensional network structure. For example, they are commercially available under the trade names of TOPSPEAR 103, 105, 108, 120, 145, 3120 and 240 (manufactured by Toshiba Silicone Co., Ltd.), and these can be used.

Of these, Aerosil 200V, Aerosil R972V and Aerosil R812 are particularly preferably used since they have a large effect of lowering the friction coefficient while keeping the haze of the optical film low.

In the optical film of the present embodiment, it is preferable that the coefficient of dynamic friction of at least one surface is in the range of 0.2 to 1.0.

<Phase difference increasing agent>

The retardation increasing agent is a compound having a function of increasing the retardation value Rt in the thickness direction of the optical film by being added to the optical film. For example, when the retardation value Rt (measured at an optical wavelength of 590 nm) in the thickness direction of the optical film in which 3 parts by mass of the compound is added to 100 parts by mass of the resin shows a value of 1.1 times or more as compared with the optical film without compound, It can be said that the compound functions as a phase difference increasing agent.

The phase difference increasing agent is not particularly limited and includes, for example, a conventionally known discotic compound (1,3,5) having an aromatic ring described in paragraphs [0143] to [0179] of JP-A No. 2006-113239 -Triazine-based compounds, etc.), JP 2006-113239 A, and JP-A-2012-214682 paragraphs [0118] to [0133] Based compounds and the like can be used.

Examples of properties required for the phase difference increasing agent include excellent compatibility with a resin, excellent phase retardation when the optical film is made thin, excellent precipitation resistance, high moisture content, And the resistance to fluctuation of the retardation value is excellent. From this point of view, it is preferable to appropriately select the retardation increasing agent.

Among them, it is particularly preferable to contain a compound represented by the following formula (A).

Hereinafter, the formula (A) will be described in detail. In formula (A), L ₁ and L ₂ each independently represent a single bond or a divalent linking group. Examples of L ₁ and L ₂ include the following structures (in the following, R represents a hydrogen atom or a substituent).

L ₁ and L ₂ are preferably -O-, -COO-, and -OCO-.

R ₁ , R ₂ and R ₃ each independently represent a substituent. Specific examples of the substituent represented by R ₁ , R ₂ and R ₃ include a halogen atom (fluorine atom, chlorine atom, bromine atom and iodine atom), an alkyl group (methyl group, ethyl group, n- Cyclohexyl group, cyclopentyl group, 4-n-dodecylhexyl group, etc.), alkenyl group (vinyl group, allyl group, etc.) (Such as a phenyl group, a p-tolyl group, or a naphthyl group), an alkenyl group (e.g., an isopropyl group, an n-butyl group, , A heterocyclic group (2-furyl group, 2-thienyl group, 2-pyrimidinyl group, 2-benzothiazolyl group and the like), cyano group, hydroxyl group, nitro group, carboxyl group, Butoxy group, 2-methoxyethoxy group and the like), an aryloxy group (phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, Phenoxy group, 2- P-methoxyphenylcarbonyloxy group and the like), an amino group (an amino group (an amino group) such as an acyloxy group , An acylamino group (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group and the like), an amino group such as a methylamino group, a dimethylamino group, an anilino group, Alkyl and arylsulfonylamino groups such as methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group and p-methylphenylsulfonylamino group, mercapto group, alkylthio group (Methylthio group, ethylthio group, n-hexadecylthio group and the like), arylthio group (phenylthio group, p-chlorophenylthio group and m-methoxyphenylthio group), sulfamoyl group Sulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N- N-benzoylsulfamoyl group, N- (N'-phenylcarbamoyl) sulfamoyl group, etc.), sulfo group, acyl group (acetyl group, pivaloylbenzoyl group Etc.), a carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di- Etc.).

R ₁ and R ₂ are preferably a substituted or unsubstituted phenyl group or a substituted or unsubstituted cyclohexyl group, more preferably a phenyl group having a substituent or a cyclohexyl group having a substituent, more preferably a substituent And a cyclohexyl group having a substituent at the 4-position.

R ₃ is preferably a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, a hydroxyl group, a carboxyl group, an alkoxy group, an aryloxy group, an acyloxy group, a cyano group or an amino group, Is a hydrogen atom, a halogen atom, an alkyl group, a cyano group, or an alkoxy group.

Wa and Wb represent a hydrogen atom or a substituent,

(I) Wa and Wb may combine with each other to form a ring,

(II) at least one of Wa and Wb may have a cyclic structure, or

(III) At least one of Wa and Wb may be an alkenyl group or an alkynyl group.

Specific examples of the substituent represented by Wa and Wb include a halogen atom (fluorine atom, chlorine atom, bromine atom and iodine atom), an alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, (Vinyl group, allyl group and the like), cycloalkenyl group (2-ethylhexyl group and the like), cycloalkyl group (cyclohexyl group, cyclopentyl group, (Such as a phenyl group, a p-tolyl group, or a naphthyl group), a heterocyclic group (such as a cyclopenten-1-yl group or a 2-cyclohexene-1-yl group), an alkynyl group (an ethynyl group or a propargyl group) A cyano group, a hydroxyl group, a nitro group, a carboxyl group, an alkoxy group (a methoxy group, an ethoxy group, an isopropoxy group, an isopropoxy group, an isopropoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-methoxyphenoxy group, Tetradeca An aminophenoxy group and the like), an acyloxy group (formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group and p-methoxyphenylcarbonyloxy group) An amino group, an amino group, a dimethylamino group, an anilino group, an N-methyl-anilino group and a diphenylamino group), an acylamino group (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group and benzoylamino group) (Methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio group (E.g., methylthio, ethylthio, n-hexyldecylthio etc.), arylthio groups (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group etc.), sulfamoyl groups Di-, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethyl sulf (N-benzylsulfamoyl group, N- (N'-phenylcarbamoyl) sulfamoyl group and the like), sulfo group, acyl group (acetyl group, pivaloylbenzoyl group and the like) (Carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group and the like) .

The substituent may be further substituted with the above group.

(I) When Wa and Wb are bonded to each other to form a ring, the ring is preferably a nitrogen-containing 5-membered ring or a sulfur-containing 5-membered ring. The formula (A) is particularly preferably a compound represented by the following formula (1) or (2).

In formula (1), A ₁ and A ₂ each independently represent -O-, -S-, -NRx- (Rx represents a hydrogen atom or a substituent) or -CO-. Examples of the substituent represented by Rx are the same as the specific examples of the substituent represented by Wa and Wb. Rx is preferably a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group.

In the formula (1), X represents a nonmetal atom of Groups 14 to 16. X is preferably = O, = S, = NRc, = C (Rd) Re. Here, Rc, Rd and Re represent substituents, and examples thereof are the same as the specific examples of the substituent represented by Wa and Wb. _{L 1, L 2, R 1} , R 2, R 3, n , is _{L 1, L 2, R 1} , R 2, R 3, n and copper in the general formula (A).

In the formula (2), Q ₁ represents -O-, -S-, -NRy- (Ry represents a hydrogen atom or a substituent), -CRaRb- (wherein Ra and Rb represent a hydrogen atom or a substituent) -. Here, Ry, Ra and Rb represent a substituent, and examples thereof are the same as the specific examples of the substituent represented by Wa and Wb.

Y represents a substituent. Examples of the substituent represented by Y are the same as the specific examples of the substituent represented by Wa and Wb. Y is preferably an aryl group, a heterocyclic group, an alkenyl group or an alkynyl group.

Examples of the aryl group represented by Y include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group and a biphenyl group, and a phenyl group and a naphthyl group are preferable, and a phenyl group is more preferable.

Examples of the heterocyclic group include a heterocyclic group containing at least one hetero atom such as a nitrogen atom, an oxygen atom, and a sulfur atom such as a furyl group, a pyrrolyl group, a thienyl group, a pyridinyl group, a thiazolyl group and a benzothiazolyl group , A furyl group, a pyrrolyl group, a thienyl group, a pyridinyl group, and a thiazolyl group are preferable.

The aryl group or the heterocyclic group may have at least one substituent. Examples of the substituent include a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cyano group, a nitro group, an alkylsulfinyl group having 1 to 6 carbon atoms, an alkylsulfonyl group having 1 to 6 carbon atoms, a carboxyl group, a fluoroalkyl group having 1 to 6 carbon atoms, An alkylthio group having 1 to 6 carbon atoms, an alkylthio group having 1 to 6 carbon atoms, an N-alkylamino group having 1 to 6 carbon atoms, an N, N-dialkylamino group having 2 to 12 carbon atoms, an N-alkylsulfamoyl group having 1 to 6 carbon atoms , An N, N-dialkylsulfamoyl group having 2 to 12 carbon atoms, and the like.

_{L 1, L 2, R 1} , R 2, R 3, n , is _{L 1, L 2, R 1} , R 2, R 3, n and copper in the general formula (A).

(II) Specific examples of the case where at least one of Wa and Wb in the formula (A) has a ring structure is preferably the following formula (3).

In the formula (3), Q ₃ represents ═N- or ═CRz- (Rz represents a hydrogen atom or a substituent), and Q ₄ represents a nonmetal atom of Groups 14 to 16. Z represents a group of nonmetal atoms forming a ring together with Q ₃ and Q ₄ .

The ring formed from Q ₃ , Q _4, and Z may be further routed to another ring. The ring formed from Q ₃ , Q ₄ and Z is preferably a nitrogen-containing 5-membered ring or 6-membered ring condensed with a benzene ring.

_{L 1, L 2, R 1} , R 2, R 3, n , is _{L 1, L 2, R 1} , R 2, R 3, n and copper in the general formula (A).

(III) When at least one of Wa and Wb is an alkenyl group or an alkynyl group, they are preferably a vinyl group or an ethynyl group having a substituent.

Among the compounds represented by the above formulas (1), (2) and (3), the compounds represented by the formula (3) are particularly preferred.

The compound represented by the formula (3) is superior in heat resistance and light resistance to the compound represented by the formula (1), and has a solubility in an organic solvent and compatibility with a polymer Good.

The compound represented by the formula (A) may be contained in an appropriate amount to give a desired wavelength dispersibility and anti-smudge property. The amount of the compound represented by formula (A) is preferably 1 to 15% by mass relative to the cellulose derivative, By mass to 2% by mass to 10% by mass. Within this range, it is possible to impart sufficient wavelength dispersibility and anti-smudge property to the cellulose derivative.

The compound represented by the formula (A), the formula (1), the formula (2) and the formula (3) can be obtained by referring to a known method. Specifically, Journal of Chemical Crystallography (1997); 27 (9); 512-526, JP-A-2010-31223, JP-A-2008-107767, and the like.

<Other additives>

The optical film of the present embodiment may contain a retardation reducing agent, a plasticizer, an antioxidant, a light stabilizer, an antistatic agent, a releasing agent, a thickening agent, etc. in addition to additives such as ultraviolet absorber, matting agent and phase difference increasing agent. Details of the main additives are described below.

(Plasticizer)

As the plasticizer to be added to the optical film, a polyester resin can be used. The polyester resin is obtained by polymerizing a dicarboxylic acid and a diol, wherein 70% or more of the dicarboxylic acid constituent unit (constituent unit derived from the dicarboxylic acid) is derived from an aromatic dicarboxylic acid, 70% or more of units (constitutional units derived from a diol) are derived from an aliphatic diol.

The proportion of the structural unit derived from an aromatic dicarboxylic acid is 70% or more, preferably 80% or more, and more preferably 90% or more. The proportion of the constitutional unit derived from an aliphatic diol is 70% or more, preferably 80% or more, more preferably 90% or more. The polyester resin may be used in combination of two or more.

Examples of the aromatic dicarboxylic acid include naphthalene dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid and 2,7-naphthalene dicarboxylic acid, 4 , 4'-biphenyldicarboxylic acid, 3,4'-biphenyldicarboxylic acid, and ester-forming derivatives thereof.

As the polyester resin, aliphatic dicarboxylic acids such as adipic acid, azelaic acid and sebacic acid, and monocarboxylic acids such as benzoic acid, propionic acid and butyric acid can be used as long as the object of the present invention is not impaired.

Examples of the aliphatic diol include ethylene glycol, 1,3-propylene diol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and ester-forming derivatives thereof.

As the polyester resin, monohydric alcohols such as butyl alcohol, hexyl alcohol and octyl alcohol, and polyhydric alcohols such as trimethylol propane, glycerin and pentaerythritol may be used as long as the object of the present invention is not impaired.

For the production of the polyester resin, known methods such as a direct esterification method and an ester exchange method can be applied. Examples of the polycondensation catalyst to be used in the production of the polyester resin include known antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds such as germanium oxide, titanium compounds such as titanium acetate and aluminum compounds such as aluminum chloride But are not limited to these.

Preferable examples of the polyester resin include polyethylene terephthalate resin, polyethylene terephthalate-isophthalate copolymer resin, polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer resin, polyethylene-2,6-naphthalene dicarboxylate resin, polyethylene -2,6-naphthalenedicarboxylate-terephthalate copolymer resin, polyethylene-terephthalate-4,4'-biphenyldicarboxylate resin, poly-1,3-propylene-terephthalate resin, polybutylene terephthalate Phthalate resin, and polybutylene-2,6-naphthalenedicarboxylate resin.

Examples of the more preferable polyester resin include polyethylene terephthalate resin, polyethylene terephthalate-isophthalate copolymer resin, polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer resin, polybutylene terephthalate resin, and polyethylene- And naphthalene dicarboxylate resins.

The intrinsic viscosity of the polyester resin (value measured at 25 占 폚 in a mixed solvent of phenol / 1,1,2,2-tetrachloroethane = 60/40 mass ratio) is preferably in the range of 0.7 to 2.0 cm3 / g, More preferably 0.8 to 1.5 cm 3 / g. If the intrinsic viscosity is 0.7 cm 3 / g or more, the molded product containing the polyester resin composition obtained by using the polyester resin has a sufficiently high molecular weight, so that it has mechanical properties required as a molded product and good transparency. When the intrinsic viscosity is 2.0 cm 3 / g or less, moldability is improved. As the other plasticizer, the compounds described in the formulas (PEI) and (PEII) of paragraphs [0056] to [0080] of JP-A No. 2013-97279 may be used.

(Antioxidant)

The antioxidant is preferably contained in the optical film since it plays a role of retarding or preventing decomposition of the optical film by, for example, halogen, which is a residual solvent in the optical film, phosphoric acid of a phosphoric acid plasticizer or the like.

As such an antioxidant, a hindered phenolic compound is preferably used, and examples thereof include 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexane Di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4- Di-t-butyl anilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5- Propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5- (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5 Di-t-butyl-4-hydroxybenzyl) -isocyanurate.

Particularly preferred are 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t- butyl- Glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferable. Further, a hydrazine-based metal inactive agent such as N, N'-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, t-butylphenyl) phosphite, or the like may be used in combination.

[Polarizer]

The polarizing plate can be formed by disposing a polarizing plate protective film on both sides of the polarizer. It is also possible to arrange a polarizing plate protective film on one side of the polarizer and a retardation film on the other side. The optical film of the present embodiment can be used as either a polarizing plate protective film or a retardation film. For example, in the polarizing plate disposed on the viewer side with respect to the liquid crystal cell, the optical film of the present embodiment can be used as the polarizing plate protective film on the viewing side of the polarizer.

<Polarizer>

The polarizer is an element which allows only light of a polarization plane in a certain direction to pass, and examples thereof include a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes a polyvinyl alcohol film stained with iodine and a dichroic dye stained.

The polarizer can be obtained by uniaxially stretching a polyvinyl alcohol film, dyeing it, or dyeing a polyvinyl alcohol film, followed by uniaxially stretching, preferably by further performing a durability treatment with a boron compound.

The film thickness of the polarizer is preferably in the range of 5 to 30 mu m, more preferably in the range of 5 to 15 mu m.

Examples of the polyvinyl alcohol film include those having an ethylene unit content of 1 to 4% by mole, a degree of polymerization of 2000 to 4000, and a degree of saponification of 99.0 to 99.99% by mole as described in JP-A-2003-248123 and JP-A-2003-342322 Ethylene-modified polyvinyl alcohol is preferably used. In addition, a polarizer may be manufactured by the method described in Japanese Patent Application Laid-Open Nos. H11-100161, JP4691205, and H4804589, and the polarizing plate may be bonded to the optical film of the present embodiment.

<Adhesive>

The optical film of this embodiment is bonded to the polarizer with an adhesive. As the adhesive, a water-soluble or active energy ray-curable adhesive may be used. The active energy ray curable adhesive is preferably an ultraviolet curable adhesive.

(Watercolor)

As the water-shedding agent, a fully saponified polyvinyl alcohol aqueous solution may be used. A polarizing plate is obtained by bonding the optical film of this embodiment to a polarizer using a fully saponified polyvinyl alcohol aqueous solution and bonding another polarizing plate protective film to the other surface. The optical film of the present embodiment may be provided on the liquid crystal cell side with respect to the polarizer in the liquid crystal display device, or may be provided on the viewer side (opposite to the liquid crystal cell). The polarizing plate may be formed by bonding the optical film of the present embodiment and a conventional polarizing plate protective film to the respective surfaces with the polarizer interposed therebetween.

As the conventional polarizing plate protective film, commercially available cellulose ester films (for example, Konica Minolta Tact KC8UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC8UA, KC6UA, KC4UA, KC2UA, KC4UY, KC4CT1, KC2CT1, KC8UY- KC8UXW-RHA-NC, KC8UXW-RHA-C, KC8UXW-RHA-NC, and KC8UXW-RHA-NC.

(Active energy ray-curable adhesive)

The polarizing plate may be constituted by bonding the optical film and the polarizer of the present embodiment with an active energy ray curable adhesive. The optical film of the present embodiment is advantageous in that the generation of minute creases on the film surface due to stretching is suppressed and therefore the mechanical strength of the point is high and the peeling from the point is improved after bonding with an active energy ray- do.

As the active energy ray curable adhesive, it is preferable to use an ultraviolet curing type adhesive (hereinafter also referred to as UV paste). By applying a UV paste to the bonding of the optical film and the polarizer, a polarizing plate having high strength and excellent planarity can be obtained even in a thin film.

&Lt; Composition of UV paste &

As a UV paste composition for a polarizing plate, there are known a photo radical polymerization type composition using photo radical polymerization, a photo cation polymerization type composition using photo cation polymerization, and a hybrid type composition using photo radical polymerization and photo cation polymerization in combination.

Examples of the photo-radical polymerization type composition include compositions containing a radical polymerizing compound containing a polar group such as a hydroxyl group or a carboxyl group and a radical polymerizing compound not containing a polar group in a specific ratio as described in JP-A-2008-009329 It is known. In particular, the radical polymerizing compound is preferably a compound having a radically polymerizable ethylenic unsaturated bond. Preferable examples of the compound having a radically polymerizable ethylenically unsaturated bond include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include N-substituted (meth) acrylamide-based compounds, (meth) acrylate-based compounds and the like. (Meth) acrylamide means acrylamide or methacrylamide.

As the photo cationic polymerization type composition, there may be mentioned (a) a cationic polymerizable compound, (?) A photo cationic polymerization initiator, (?) A photoacid generator having a wavelength longer than 380 nm , A photosensitizer exhibiting maximum absorption in the ultraviolet curable adhesive agent, and (?) A naphthalene-based photosensitizer. However, other UV pools may be used.

<Junction using UV paste>

(a) Pretreatment process

The pretreatment step is a step of performing an adhesion facilitating treatment on the adhesion surface of the optical film to the polarizer. Examples of the adhesion facilitating treatment include corona treatment and plasma treatment.

(b) UV coating process

As the UV paste application process, the UV paste is applied to at least one of the bonding surfaces of the polarizer and the optical film. When the UV pulp is applied directly to the surface of the polarizer or optical film, there is no particular limitation on the coating method. 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. Also, a method may be used in which a UV paste is poured between the polarizer and the optical film, and then pressed with a roller or the like to spread out uniformly.

(c)

After the UV paste is applied by the above method, it is treated in the bonding process. In this bonding step, for example, when a UV paste is applied to the surface of the polarizer in the previous coating step, the optical film is superimposed thereon. In the case of a method of first applying a UV paste to the surface of an optical film, a polarizer is superimposed thereon. When a UV paste is softened between the polarizer and the optical film, the polarizer and the optical film overlap with each other in this state. Normally, in this state, the optical film is pressed between the pressure rollers and the like from both sides of the optical film side. As the material of the pressure roller, metal or rubber can be used. The pressure rollers disposed on both sides may be the same material or different materials.

(d) Curing process

In the curing step, an ultraviolet ray is irradiated to an uncured UV paste to form a cationic polymerizable compound (for example, an epoxy compound or an oxetane compound) or a radically polymerizable compound (for example, an acrylate compound or an acrylamide compound Etc.), and the optical film is adhered to the superimposed polarizer through the UV paste. When the optical film is bonded to one surface of the polarizer, the active energy ray may be irradiated on either the polarizer side or the optical film side. When an optical film is bonded to both surfaces of a polarizer, it is advantageous to irradiate ultraviolet rays and simultaneously cure the UV pulps on both surfaces in a state in which the optical film is superimposed on both surfaces of the polarizer via a UV paste.

Irradiation conditions for ultraviolet rays may be any appropriate conditions as long as the condition is such that the UV pulp can be cured. The dose of ultraviolet rays is preferably in the range of 50 to 1,500 mJ / cm2, more preferably in the range of 100 to 500 mJ / cm2 in terms of the accumulated light quantity.

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 in the range of 1 to 500 m / min, more preferably in the range of 5 to 300 m / min, To 100 m / min. When the line speed is 1 m / min or more, productivity can be ensured, or damage to the optical film can be suppressed, and a polarizer excellent in durability can be produced. Further, when the line speed is 500 m / min or less, the UV paste is sufficiently cured, and a UV paste layer having desired hardness and excellent adhesion can be formed.

<Other polarizing plate protective film>

The optical film of this embodiment may be used together with another polarizing plate protective film to constitute a polarizing plate. Examples of the polarizing plate protective film include a resin film such as polyethylene terephthalate, polyethylene naphthalate and polycarbonate, an alicyclic polyolefin (for example, Zeonoa (registered trademark), polyarylate (manufactured by Nippon Zeon Co., Polyether sulfone, polysulfone, cycloolefin copolymer, polyimide (for example, Neoprim TM manufactured by Mitsubishi Gas Kagaku Co., Ltd.), fluorene ring-modified polycarbonate, alicyclic modified polycarboxylic acid Polybutylene terephthalate, polyethylene naphthalate (abbreviated as &quot; polyethylene terephthalate &quot;), poly (ethylene terephthalate), poly : PEN), and polycarbonate (abbreviated as PC) are preferably used as a protective film.

The thickness of the other polarizing plate protective film is not particularly limited, but may be about 10 to 200 占 퐉, preferably within a range of 10 to 100 占 퐉, and more preferably within a range of 10 to 70 占 퐉.

[Liquid crystal display device]

By using a polarizing plate in which the optical film of the present embodiment is bonded to a polarizer in a liquid crystal display device, a liquid crystal display device having various visibility can be realized.

The polarizing plate described above can be used for liquid crystal display devices of various driving systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, and OCB. It is preferably a VA (MVA, PVA) type liquid crystal display device and an IPS type liquid crystal display device.

In a liquid crystal display device, normally, two polarizing plates, that is, a polarizing plate on the viewer side and a polarizing plate on the backlight side, are used. It is also preferable to use a polarizing plate provided with the optical film of the present embodiment as both polarizing plates, and it is also preferable to use the polarizing plate as a polarizing plate on one side. In particular, it is preferable that the polarizing plate provided with the optical film of the present embodiment is used as a polarizing plate on the viewer's side that is in direct contact with the external environment. At that time, when the optical film of the present embodiment is an optical compensation film, it is preferable that the optical film is disposed on the liquid crystal cell side with respect to the polarizer.

As the polarizing plate on the backlight side, a polarizing plate other than the polarizing plate of the present embodiment may be used. In this case, a commercially available cellulose ester film (for example, Konica Minolta Tac KC8UX, KC4UX, KC4UX, KC8BRCR, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC4UY, KC4CT1, KC2UA, KC4UA, KC6UA, KC8UA, KC2UAH, KC4UAH, KC6UAH, KC4UAH, KC6UAH, KC2UA, KC2UA, KC2UT, KC8UY-HA, KC2UA, KC4UA, KC2UA, KC8UA, KC2UAH, KC4UAH, KC6UAH, TD40UL, Fujitac R02, Fujitac R06, and others manufactured by Fuji Photo Film Co., Ltd.) are preferably used.

As the polarizing plate on the backlight side, the optical film of the present embodiment may be used on the liquid crystal cell side of the polarizer, and the commercially available protective film, retardation film, polyester film, acrylic film or polycarbonate film A bonded polarizing plate can also be preferably used.

By using the polarizing plate provided with the optical film of the present embodiment, a liquid crystal display device having excellent visibility such as display unevenness can be obtained even in a large-screen liquid crystal display having a screen of 30 or more in particular.

[Example]

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples. In the following, the notation &quot; part &quot; or &quot;% &quot; is used, but unless otherwise stated, they shall denote &quot; mass part &quot;

&Lt; Production of optical films 1-1 to 1-11 >

(Cellulose acylate resin)

First, cellulose acetate propionate (CAP) having substitution degree and molecular weight (number average molecular weight Mn and weight average molecular weight Mw) of an acyl group shown in Table 1 was prepared as a cellulose acylate resin. In Table 1, X represents the degree of substitution of the acetyl group, Y represents the substitution degree of the propionyl group, and X + Y represents the substitution degree of the total acyl group.

(Preparation of fine particle addition liquid)

Subsequently, 12 parts by mass of fine particles (Aerosil R812, manufactured by Nippon Aerosil Co., Ltd.) and 88 parts by mass of ethanol were mixed with a dissolver for 50 minutes with stirring, followed by dispersion using a mannitol dispersing machine to prepare a fine particle dispersion.

Then, 50 parts by mass of methylene chloride was added to the dissolution tank, and 50 parts by mass of the prepared fine particle dispersion was added slowly while methylene chloride was sufficiently stirred. The dispersion was carried out with an attritor so that the volume average particle diameter became 0.1 탆. The solution was filtered with Fine Mat NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle addition liquid.

(Preparation of dope)

Initially, methylene chloride and ethanol were added to the pressure-dissolving tank as the organic solvent in the following amounts. Then, the cellulose acylate resin was added to the pressurized dissolution tank containing the organic solvent with stirring. The solution was heated and completely dissolved with stirring, and the solution was filtered using Azumi Rosa No. 244 manufactured by Azumi Co., Ltd. to prepare a main dope. Subsequently, a compound (a), a sugar ester compound (sucrose benzoate having an average degree of substitution of 7.3) and a fine particle addition liquid prepared as described below as a compound represented by the formula (A) The mixture was sealed and dissolved while stirring to prepare a dope solution.

<Composition of Dope>

Methylene chloride 340 parts by mass

64 parts by mass of ethanol

100 parts by mass of cellulose acetate propionate

(Acetyl substitution degree: 1.4, propionyl substitution degree: 1.0)

Optical performance modifier (compound of formula (A): compound a) 3 parts by weight

A sugar ester compound (5 parts by mass of sucrose benzoate having an average degree of substitution of 7.3

2 parts by mass of the fine particle addition liquid

Compounds of formula (A): Compounds a

(Film Formation of Optical Film)

Using the above dope, optical films 1-1 to 1-11 having a film thickness of 50 mu m were formed by the solution softening method. That is, MD stretching (first stretching) was performed by softening the dope from a flexible die on a support having a thickness of 2 mm made of SUS316 which was driven at a speed of 80 m / min, and the dope was dried on the support to form a flexible film , And the flexible film conveyed by the movement of the support was peeled from the support (flexible peeling step). Thereafter, the peeled flexible film was stretched in the TD direction (second stretching) to obtain an optical film (stretching step).

The conditions (residual solvent amount, stretching magnification, temperature, mechanical strength E _MD, E _TD ) in the stretching (first stretching) at the time of softening and the stretching (second stretching) after peeling were as shown in Table 2 same. In Table 2, cellulose acetate propionate is abbreviated as CAP.

Further, since the elongation magnification in the first elongation at the time of softening is considered to be almost no volatilization of the solvent since the time from the ejection of the dope to the landing onto the support is 5 msec or less,

(%) = (Film thickness at the time of dope discharge (占 퐉) / film thickness (占 퐉) at the time of landing) 占 100

. The film thickness (slit interval of the flexible die) at the time of dope discharge and the film thickness of the dope landed on the support were measured using a micro head type spectroscopic interference laser displacement meter (model: SI-F80) manufactured by KEYENCE.

Further, after the dope is softened on the support, the dope (flexible film) is transported and dried so as not to expand and contract in both the MD and TD directions, and the film thickness of the flexible film when the residual solvent amount becomes less than 0.1% The amount of the residual solvent at an arbitrary film thickness on the support was calculated from the film thickness at the time of discharge measured as the presumed amount of the residual solvent existing at the time of discharging.

In addition, the first mechanical strength in the MD direction after stretching E _MD and mechanical strength measurements of E _TD in the TD direction, and a second mechanical strength measurement of E _TD of mechanical strength E _MD and TD directions of the MD direction after the stretching, the above-described Method, that is, a method in accordance with JIS K 7127 (1999).

For comparison with the optical films 1-1 to 1-11, the optical film 1-12 was produced using the above-described dope. The production conditions of the optical film 1-12 were the same as those of the optical film 1-3 except that the MD stretching was not performed at the time of softening but the TD stretching was performed after peeling. In addition, in order not to perform MD stretching at the time of softening, the amount of the residual solvent in the dope at the initial stage of softening was set at 300% by mass to prepare the optical film 1-12.

&Lt; Production of optical films 2-1 to 2-8 >

(Cycloolefin resin)

As the cycloolefin resin, a cycloolefin resin COP1 synthesized as follows was prepared.

(Synthesis of cycloolefin resin COP1)

50 g of 8-methoxycarbonyl-8-methyltetracyclo [4.4.0.1 ^2,5 .1 ^7,10 ] -3-dodecene represented by the above structural formula, 2.3 g of 1-hexene as a molecular weight regulator and 100 g of toluene were dissolved in a nitrogen Was charged into a substituted reaction vessel, and heated to 80 캜. And 0.09 ml of a toluene solution of triethyl aluminum (0.6 mol / L) and 0.29 ml of a toluene solution (0.025 mol / L) of methanol-denatured WCl ₆ were added and reacted at 80 ° C for 3 hours to obtain a polymer. Subsequently, the obtained ring-opening copolymer solution was placed in an autoclave, and 100 g of toluene was further added. The hydrogenation catalyst RuHCl (CO) [P (C ₆ H ₅ )] ₃ was added in an amount of 2500 ppm based on the amount of the monomer, and the hydrogen gas pressure was adjusted to 9 to 10 MPa for 3 hours at 160 to 165 ° C. After completion of the reaction, a large amount of methanol solution was precipitated to obtain a hydrogenated product. The cycloolefin resin COP1, which is a hydrogenated product of the ring opening polymer, had a glass transition temperature (Tg) of 167 占 폚, a weight average molecular weight (Mw) of 13.5 占⁰⁴ and a molecular weight distribution (Mw / Mn) of 3.06.

(Preparation of fine particle dispersion)

12 parts by mass of fine particles (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.) and 88 parts by mass of ethanol were mixed by stirring with a dissolver for 50 minutes and then dispersed with mannitol to prepare a fine particle dispersion.

Subsequently, 100 parts by mass of the fine particle dispersion was slowly added to dichloromethane (100 parts by mass) being stirred in the dissolution tank. In addition, the particles were dispersed in the attritor so that the particle size of the secondary particles became a predetermined size. The solution was filtered with Fine Mat NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle addition liquid.

(Preparation of main doping)

The main dope of the following composition was prepared. First, dichloromethane and ethanol were added to the pressure-melting tank. The cycloolefin resin COP1 and the fine particle addition liquid were added to a pressurized dissolution tank containing dichloromethane while stirring. This was heated, and the resin was dissolved with stirring, and this was filtered using Azumi-rosy No.244 manufactured by Azumi Co., Ltd. to prepare a main dope.

<The composition of main dop>

Cycloolefin resin COP1 100 parts by weight

302 parts by mass of dichloromethane

Ethanol 18 parts by mass

10 parts by mass of the fine particle addition liquid

(Film Formation of Optical Film)

Using the above-described dope, optical films 2-1 to 2-8 shown in Table 2 were formed by the solution softening method. The film formation conditions such as the moving speed of the support are the same as in the production of the optical films 1-1 to 1-11. In Table 2, the cycloolefin resin COP1 is referred to as COP.

For comparison with the optical films 2-1 to 2-8, optical films 2-9 were prepared using the dope. The production conditions of the optical film 2-9 were the same as those of the optical film 2-1 except that MD stretching was not performed at the time of softening and TD stretching was performed after peeling.

<Evaluation>

(Evaluation of dimensional fluctuation due to wet heat fluctuation)

The optical films prepared above were measured for dimensions A (mm) in the MD direction and dimensions B (mm) in the TD direction after the optical films were allowed to stand at 22 ° C and 55% RH for 24 hours. Then, the optical film was measured for the dimension A '(mm) in the MD direction and the dimension B' (mm) in the TD direction after the optical film was allowed to stand at 30 ° C. and 90% RH for 24 hours. Then, on the basis of the following formulas, the dimensional variation rate of the optical film in the MD direction and the TD direction due to the humid heat fluctuation was calculated.

Dimensional variation ratio (%) in the MD direction = {(A-A ') / A} 100

Dimensional variation ratio (%) in the TD direction = {(B-B ') / B} 100

The parameters and dimensional variation of each optical film are summarized in Table 2.

In the optical film 1-1, the dimensional change ratio was equal to that of the optical film 1-12 serving as a reference, and the dimensional variation did not improve (the dimensional variation rate did not decrease). This, the first did not done 1 performed the stretching is to <E _MD / E _TD stretching because (so small a stretching ratio in the MD direction), the first stretch after the MD orientation of the mechanical strength E _MD and TD direction of the machine It is considered that the strength E _TD becomes the same as that of the optical film 1-12 which is not subjected to the first stretching as a result. For the optical film 2-1, it is considered that the reason why the dimensional fluctuation is not improved from the reference optical film 2-9 is the same reason as described above.

Also in the optical films 1-9, the dimensional variation ratio is equal to that of the reference optical film 1-12, and the dimensional variation is not improved. This is considered to be due to the following reasons. That is, since the ratio of E _MD / E _TD after the first stretching exceeds 1.5 and the stretching ratio in the MD direction is excessively high, the distance from the flexible die to the landing on the support becomes longer, , And the film thickness fluctuates in the MD direction. It is considered that the fluctuation of the film thickness causes fluctuation in the plane of the mechanical strength E _MD · E _TD and as a result the effect of improving the dimensional fluctuation of the optical film is not obtained. In particular, from the results of the optical films 1-9 and 2-6, it can be said that when the ratio of E _MD / E _TD after the first stretching exceeds 1.5 according to the film material (resin) have.

In the optical film 1-11, the dimensional variation ratio in the TD direction is larger with respect to the reference optical film 1-12. This is considered to be because the mechanical strength E _TD in the TD direction after the second stretching is smaller than the mechanical strength E _MD in the MD direction, that is, the draw ratio in the TD direction is small (the stretching in the TD direction is weak). For the optical film 2-8, the optical film 2-9 as a reference is not particularly improved in dimension variation in the TD direction because the same reason as described above (since stretching in the TD direction is weak) I think.

In contrast, optical films 1-2 to 1-8 and 1-10, in the first after stretching, and satisfies a _{1 <E MD / E TD <} 1.5, the first, _MD E 2 after stretching in _TD ≤E As a result, the dimensional fluctuation of the optical film due to the wet heat fluctuation was improved in both the MD and TD directions. This also applies to the optical films 2-2 to 2-5 and 2-7.

Therefore, in the case of performing MD stretching at the time of softening and TD stretching after peeling of the flexible film from the support, MD stretching is performed so that 1 < E _MD / E _TD < 1.5 after the first stretching, TD stretching is performed so that _MD &amp; efDot; E _TD , it is possible to suppress dimensional fluctuations in the MD and TD directions of the optical film due to the fluctuation in wet heat.

<Reduction of Film Thickness Nonuniformity of Transverse Shape>

Subsequently, in the film formation of the optical films 1-2, 1-6, 2-3, and 2-4, the initial drying rate of the dope from the flexible die to the support is changed to obtain the thickness unevenness in the MD direction ) And light leakage were investigated. The results are shown in Table 3. The drying rate refers to the rate (% / min) at which the amount of the residual solvent in the dope is reduced from the time of discharging from the flexible die to an arbitrary amount by drying, wherein the amount of residual solvent The amount was reduced by 50% from the discharge time. That is, the drying speed is a speed determined by drying the time until the amount of the residual solvent in the dope is reduced by 50% from the value at the time of discharge from the flexible die (initial value). For example, when the amount of the residual solvent in the dope is 200% by mass at the time of discharging from the flexible die, and the time until the amount of residual solvent after discharging becomes 100% by mass, which is half thereof, is 1 minute, -100) / 1 = 100 (% / min).

The optical films 1-2 and 2-3 are formed by three types of films, ie, single-layer flexible film, shared film (see FIG. 4) and concatenated film (see FIG. 5) The film formation was carried out in two ways, that is, a coke oven and a concentration up. In this case, 90 parts by mass of dichloromethane (methylene chloride) as a good solvent and 10 parts by mass of ethanol as a poor solvent were mixed in the coke oven as liquids L1 and L2 shown in Fig. 4, (L1, L2) so as to be flexible on the support. Then, the time until the surface layer was completely dried was adjusted in accordance with the amount of the feed liquid. 5, a cover (C) filled with dichloromethane as the liquid (L3) is placed on the support, the solvent concentration around the support is raised, . In addition, the length of the area covered with the cover C in the MD direction was adjusted at an arbitrary time until completion of the passage.

The evaluation of the thickness unevenness of the trapezoidal shape in Table 3 was carried out as follows. That is, the formed optical film was placed at a position spaced apart from the light source by 200 mm so as to form an angle of 45 ° with respect to the light axis of a point light source (Xenon lamp: L2274 manufactured by Hamamatsu Photonics K.K.) Brightness and darkness projected on a smooth white projection plane were visually observed to check whether or not there was a variation in film thickness of the transverse mode. Then, on the basis of the following criteria, evaluation was made for the thickness irregularity of the trapezoidal shape.

<< Evaluation Criteria >>

○ ... Thickness variation of transverse shapes was not observed.

△ ... Thickness nonuniformity of the trapezoidal shape was slightly observed, but it is a level at which there is no problem in actual use.

× ... Thickness nonuniformity of the trapezoidal shape is considerably observed, and there is a problem in practical use.

Further, regarding the light leakage, the optical film was sandwiched between two polarizers (films) arranged so as to become Cross-Nicols to confirm light leakage, and evaluation was made based on the following criteria.

<< Evaluation Criteria >>

○ ... Little light leakage was observed.

△ ... Light leakage was slightly observed, but there was no problem in actual use.

× ... Light leakage is observed considerably, and there is a problem in practical use.

It can be seen from Table 3 that, in the flexible method using the cured lead or the concentration up, if the dope is plied on the support while maintaining the drying rate at 100% / min or less for one second or more after discharging the dope from the flexible die, It was confirmed that the effect of suppressing thickness irregularity and light leakage of the transverse shape was high.

Subsequently, the ratio (concentration, solid content ratio) of the solid content of the two kinds of liquids L1 and L2 covering the dope D1 in Fig. 4 is changed when the optical film 1-2 is formed by the covariance technique, Film thickness nonuniformity and light leakage in the transverse mode in the optical film were evaluated by the same method as described above. The results are shown in Table 4.

Table 4 shows prescriptions of the liquid L1 on the air side (the side opposite to the support) and the liquid L2 on the support side with respect to the dope D1. The solid content was calculated as a ratio (%) of the solid content to the entire liquid. In addition, the dispersion diluent (fine particle dispersion) contains fine particles which become solid components. Therefore, in the formulas (3) to (5), the solid content ratio of the resin (2) is added to the solid content ratio of the resin (0.6%).

From Table 4, it can be seen that the effect of suppressing the thickness irregularity and light leakage of the transverse shape becomes smaller when the common streak is performed by using a liquid having a solid fraction exceeding 15%. This is because, in a liquid having a solid content of more than 15%, the amount of solvent is small, so that even if the drying speed is low, the dope tends to be hardened by volatilization of the solvent and the ribbon tends to vibrate, . Therefore, it can be said that the solid fraction of the liquid used in the coke oven is preferably 15% or less.

Then, in the optical films 1-6, 1-7, 2-4, and 2-5, the thickness unevenness of the transverse mode and light leakage were evaluated in the same manner as described above. The results are shown in Table 5.

In the optical films 1-6 and 2-4, the stretching magnification in the MD direction at the time of softening is stretched to 1000% (10 times). Under such stretching conditions, if the dope is plied on the support while maintaining the drying rate at 100% / min or less for 1 second or more after ejection of the dope from the flexible die, the thickness irregularity of the cross- It can be seen that the effect of suppressing leakage is high. In contrast, in the optical films 1-7 and 2-5, the stretching magnification in the MD direction at the time of softening exceeds 1000% (10 times). Under such stretching conditions, if the dope is plied on the support while maintaining the drying rate at 100% / min or less for 1 second or more after ejection of the dope from the flexible die, the thickness irregularity of the cross- It can be seen that the effect of suppressing leakage is low. This is considered to be because when the draw ratio in the MD direction exceeds 10 times, the landing point of the dope on the flexible die and the support becomes longer and the ribbon tends to vibrate. When the stretching ratio in the MD direction is less than 2 times, the MD stretching is too weak to increase the mechanical strength E _MD in the MD direction and the dimensional fluctuation of the optical film can not be improved. 1-1 and 2-1.

From the above, it can be said that the stretching magnification in the MD direction at the time of softening is preferably 2 times or more and 10 times or less. In addition, as described above, the stretching magnification is the same as the ratio of the thickness of the dope landed on the support to the gap of the slit for discharging the dope in the flexible die, If the thickness of the dope is not less than 2 times and not more than 10 times the thickness of the landed dope on the support, it can be said that the effect of suppressing the film thickness nonuniformity and the light leakage of the traversing pattern is high.

&Lt; Relation between the moisture permeability of the resin and the warpage of the glass substrate >

Subsequently, the optical films 1-2 and 2-2 having a thickness of 50 mu m were adhered to one side of a square glass having a thickness of 0.3 mm and a side of 200 mm using a watercolor, and the adhered film was placed horizontally The sample was air-conditioned at 22 ° C and 55% RH for 24 hours, and the amount of exfoliation from the plane of installation of the glass end portion was measured by a goldsmith of JIS Class 1 standard and evaluated based on the following criteria. The results are shown in Table 6.

<< Evaluation Criteria >>

○ ... The deflection of the glass is less than 1 mm.

△ ... The deflection of the glass is not less than 1 mm and less than 3 mm.

× ... The deflection of the glass is 3 mm or more.

The cellulose acylate resin constituting the optical film 1-2 had a moisture permeability of 300 g / m &lt; 2 &gt; / day and a cycloolefin resin constituting the optical film 2-2 had a moisture permeability of 150 g / m &lt; day.

From Table 6, it can be seen that in the optical film 1-2, the glass warp occurred more than 3 mm. This is presumably because the moisture permeability of the cellulose acylate resin exceeds 150 g / m &lt; 2 &gt; .day and the dimensional fluctuation of the optical film due to the function is large, so that the glass is warped by the dimensional fluctuation of the optical film. On the other hand, in the optical film 2-2, the warping of the glass is less than 3 mm. This is presumably because the moisture permeability of the cycloolefin resin is 150 g / m &lt; 2 &gt; day or less and the dimensional fluctuation of the optical film due to the function is small.

From the above, it can be said that the moisture permeability of the optical film is preferably 150 g / m &lt; 2 &gt; day or less from the viewpoint of suppressing warping of the glass due to dimensional fluctuation of the optical film.

Further, the optical film may be composed of an acrylic resin. The moisture permeability of the acrylic resin is 50 g / m 2 · day and 150 g / m 2 · day or less. Therefore, even when the optical film is made of acrylic resin, it is considered that glass warpage due to dimensional fluctuation of the optical film can be suppressed.

The manufacturing method of the optical film of the present embodiment described above can be expressed as follows.

1. A method for producing an optical film using a solution casting film forming method,

A flexible separation step of flexing the dope from a flexible die on a moving support and drying the dope on the support to form a flexible film and then peeling off the flexible film conveyed by the movement of the support from the support;

And a stretching step of stretching in the transverse direction perpendicular to the conveying direction of the flexible film while the peeled flexible film is conveyed to obtain the optical film,

When the mechanical strength of the flexible film or the optical film in the transport direction is E _MD (MPa) and the mechanical strength in the transverse direction is E _TD (MPa)

In the flexible separation step, at the time when the flexible film is peeled from the support,

1 < E _MD / E _TD < 1.5

The dope is stretched on the support so as to stretch in the carrying direction,

In the stretching step,

E _{MD &lt;} = E _TD

Is stretched in the transverse direction so as to obtain the optical film of the present invention.

2. When the drying rate (% / min) is defined as the rate at which the amount of the residual solvent in the dope decreases from the time of discharging from the flexible die to an arbitrary amount by drying,

The method for producing an optical film according to 1 above, wherein the flexible release step maintains a state in which the drying speed is not more than 100 (% / min) from a point of time when the dope is discharged from the flexible die for not less than 1 second .

3. The optical film of claim 2, wherein in the flexible peeling step, the liquid is flexible so as to cover the dope in the film thickness direction simultaneously with the liquid having the solid content of 15% or less and the dope, &Lt; / RTI &gt;

4. The flexible die as described in 1 or 2 above, wherein the gap of the slit for discharging the dope in the flexible die is 2 to 10 times the thickness of the dope discharged from the slit and landed on the support Gt;

5. The process for producing an optical film according to any one of 1 to 4, wherein the support has a moving speed of 30 m / min or more.

6. The method for producing an optical film as described in any one of 1 to 5 above, wherein the optical film obtained in the stretching step has a moisture permeability of 150 g / m &lt; 2 &gt;

INDUSTRIAL APPLICABILITY The present invention is applicable to the production of an optical film used for a polarizing plate of a liquid crystal display.

8: Flexible die
9: Support
E _MD : Mechanical strength (MD direction)
E _TD : Mechanical strength (TD direction)

Claims (6)

A method for producing an optical film using a solution soft film forming method,
A flexible separation step of flexing the dope from a flexible die on a moving support and drying the dope on the support to form a flexible film and then peeling off the flexible film conveyed by the movement of the support from the support;
And a stretching step of stretching in the transverse direction perpendicular to the conveying direction of the flexible film while the peeled flexible film is conveyed to obtain the optical film,
When the mechanical strength of the flexible film or the optical film in the transport direction is E _MD (MPa) and the mechanical strength in the transverse direction is E _TD (MPa)
In the flexible separation step, at the time when the flexible film is peeled from the support,
1 < E _MD / E _TD < 1.5
The dope is stretched on the support so as to stretch in the carrying direction,
In the stretching step,
E _{MD &lt;} = E _TD
Is stretched in the transverse direction so as to obtain the optical film of the present invention. The method according to claim 1, wherein when the drying rate (% / min) is defined as the rate at which the residual solvent amount in the dope decreases by 50% from the discharge time from the flexible die by drying,
Wherein the flexible release step maintains a state in which the drying speed is not more than 100 (% / min) for at least one second from the time when the dope is discharged from the flexible die. 3. The method according to claim 2, wherein, in the flexible separation step, the liquid is flexible so as to cover the dope in the thickness direction at the same time as the liquid with the solid fraction of 15% &Lt; / RTI &gt; 3. The flexible die according to claim 1 or 2, characterized in that a gap of the slit for discharging the dope in the flexible die is 2 to 10 times the thickness of the dope discharged from the slit and landed on the support By weight based on the total weight of the optical film. delete 4. The method for producing an optical film according to any one of claims 1 to 3, wherein the optical film obtained in the stretching step has a moisture permeability of 150 g / m &lt; 2 &gt;

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