JP5458527B2 - Manufacturing method of optical film - Google Patents

Description

The present invention can be used for various functional films such as a protective film for a polarizing plate used for a liquid crystal display (LCD), a retardation film, a viewing angle widening film, and an antireflection film used for a plasma display. those concerning the method of producing a film.

  In recent years, liquid crystal display devices have come to be used in televisions and large monitors due to improvements in image quality and high definition technology. In particular, these liquid crystal display devices are costly due to their large size and efficient production. The demand for down and the like has become stronger in materials for liquid crystal display devices, and a wider optical film is required.

  In recent years, the demand for optical films has been increasing rapidly in response to the rapid growth of liquid crystal TVs, and there is a strong demand for improved productivity.

  There are roughly two methods for producing an optical film: a melt casting method and a solution casting method. The former is a method for producing a film by casting a molten liquid obtained by heating and melting a resin on a cooling metal support to cool and solidify, then peeling the web and further stretching it as necessary. On the other hand, in the latter, the resin is dissolved in a solvent, the solution (dope) is cast on the support, the solvent is evaporated with hot air, hot water, etc., and then peeled off from the support. This is a method for producing a film by stretching.

  In order to increase the production speed of optical films, when the production speed is increased, the melt casting film forming method extrudes a high-viscosity resin melt from the casting die. The liquid feeding pressure also increases, and as a result, the film thickness deviation in the film width direction increases. In addition, the casting film coming out of the casting die also has a strong streak in the conveying direction and deteriorates the flatness. Therefore, it is necessary to take measures to increase the temperature of the resin melt and lower the viscosity. It was.

  On the other hand, in the case of the solution casting film forming method, as the production rate of the film increases, the drying time on the metal support is shortened. There was a problem that it was necessary to dry in time, and it was necessary to raise the drying temperature.

  By the way, the resin solution (dope) in the solution casting film forming method and the resin melt in the melt casting film forming method are both free acid as a partially decomposed product, impurities, and impurities contained in the plasticizer. For example, in the case of a cellulose ester resin, the decomposition products thereof include acetic acid, propionic acid, butyric acid, and the like.

  In the case of the solution casting film forming method, if the plasticizer is an ester compound of an acid and an alcohol, the decomposition product or residue of the acid or methylene chloride decomposition product hydrochloric acid or methyl acetate (in the case of demethylene chloride) ), Acetic acid which is a decomposition product thereof.

  Here, usually, an oxidation reaction of a metal element naturally occurs on the surface of the metal support to form an oxide film. However, in the solution casting film forming method, a resin solution (dope) containing an extremely small amount of acid is used, and hot air is applied after casting. Particularly, the drying temperature needs to be high as the production rate increases. Also in the melt casting film forming method, if the production rate is increased, it is necessary to raise the temperature of the melt to lower the viscosity of the resin melt.

  Thus, when the film production rate is increased, it is necessary to increase the temperature of the dope or the melt, so that the oxide film formed on the surface of the metal support is reduced by the corrosion of the acid, and the surface is microscopic. It turned out that it became uneven by corrosion and became rough.

Even if the metal support is made of a highly corrosion-resistant material such as stainless steel or chrome plating, the above-mentioned corrosion occurs in a small amount of acid over a long period of time. The degree of corrosion, such as to the eye in personal, not like can be confirmed clearly by visual inspection, the surface of the metal support is corrosion are mirror state take place in the film for optical applications, the If such a minute surface is incorporated into a liquid crystal panel, the portion where the corrosion of the metal support is transferred appears uneven and emphasized.

  Such a metal support for film formation is difficult to apply, such as troubles during production and polishing of scratches caused by cleaning work, and even when processing the metal surface itself, A processing method for providing a high-density oxide film while maintaining a super-mirror surface state with a surface roughness Ra of several nanometers has not been known.

An object of the present invention is to solve the above problems of the prior art, while maintaining a very smooth surface state, the metal oxide skin layer with enhanced oxygen binding ratio than the oxide state of ordinary metal surface This makes it possible to improve the releasability (peelability) of the film from the metal support even during the continuous production of optical films, to obtain a very smooth peelability, and to allow variation in retardation (Re) value. It is possible to produce an optical film having greatly reduced optical properties with excellent transparency and flatness, and at the same time, the production speed can be increased and the productivity of the film can be improved. Another object of the present invention is to provide an optical film manufacturing method capable of meeting demands for thinning, widening, and improving the quality of protective films for polarizing plates.

Furthermore, by preventing the corrosion of the surface of the metal support, there is no quality failure such as unevenness that appears when the corrosion pattern is transferred to the film, and when the surface becomes rough due to corrosion, the anchor effect The releasability (peelability) is remarkably deteriorated, and it is possible to prevent the optical value such as retardation from being adjusted to the desired characteristics by increasing the stress applied to the web at the time of peeling. An optical film manufacturing method capable of meeting demands for thinning, widening, and high quality of a protective film for a polarizing plate, etc. by manufacturing an optical film having excellent optical properties There is to do.

  In particular, the present invention provides a method capable of producing a stable optical film without causing the above-described problems even in high-speed film formation at a film formation speed of 50 m / min or more.

  In order to achieve the above object, the invention of claim 1 is a method for producing an optical film by a melt casting film forming method or a solution casting film forming method, wherein iron (Fe) and In addition to containing the element of chromium (Cr), the component element composition ratio on the surface of the metal support satisfies the following relationship (i) and / or (ii), and on the surface of the metal support: It is characterized by casting a thermoplastic resin melt in the melt casting film forming method or a thermoplastic resin solution (dope) in the solution casting film forming method.

(I) (Fe ₂ O ₃ + FeO) / Fe = 5-50
(Ii) (CrO ₂ + CrO ₃ ) / Cr = 10-50
Invention of Claim 2 is a manufacturing method of the optical film of Claim 1, Comprising: Before casting a resin melt or dope on a metal support body, a metal support surface is irradiated with atmospheric pressure plasma or A metal oxide is formed by surface treatment by excimer ultraviolet irradiation.

  Invention of Claim 3 is a manufacturing method of the optical film of Claim 1 or 2, Comprising: The integration time of an atmospheric pressure plasma irradiation process or an excimer ultraviolet irradiation process is 0.1-3000 sec, It is characterized by the above-mentioned. Yes.

  Invention of Claim 4 is a manufacturing method of the optical film as described in any one of Claims 1-3, Comprising: Thermoplastic fat is a cellulose ester resin, It is characterized by the above-mentioned.

Invention of Claim 5 is a manufacturing method of the optical film as described in any one of Claims 1-4, Comprising: A metal support body is an endless belt for film forming, a drum, or a roll. It is characterized by being either .

  The invention of claim 1 is a method for producing an optical film by a melt casting film forming method or a solution casting film forming method, wherein an element of iron (Fe) and / or chromium (Cr) is applied to the surface of a metal support. And the component element composition ratio on the surface of the metal support satisfies the following relationship (i) and / or (ii), and the thermoplasticity in the melt casting film forming method is provided on the surface of the metal support. It is characterized by casting a resin melt or a thermoplastic resin solution (dope) in a solution casting film forming method.

(I) (Fe ₂ O ₃ + FeO) / Fe = 5-50
(Ii) (CrO ₂ + CrO ₃ ) / Cr = 10-50
According to the first aspect of the present invention, by forming the metal oxide film layer in which the oxygen bond ratio is higher than the oxide state of the normal metal surface while maintaining a very smooth surface state, Even during production, the release (removability) of the film from the metal support is improved, very smooth releasability is obtained, variation in retardation (Re) value is greatly reduced, and transparency In addition, it is possible to produce an optical film having optical properties with excellent flatness, to increase the production speed, to improve the productivity of the film, and as a result, a protective film for polarizing plates in recent years, etc. There exists an effect that it can respond to the request | requirement of film thinning, widening, and quality improvement.

Furthermore, it is possible to prevent corrosion of the surface of the metal support, with its corrosion pattern disappears failure of quality, such as unevenness expressed by transferring the film, when the rough come surface corrosion, an anchor effect Since the releasability (peelability) of the web is remarkably deteriorated and the stress applied to the web at the time of peeling increases, it is possible to prevent optical values such as retardation from being adjusted to the desired characteristics, and transparent An optical film having excellent optical properties and flatness can be produced, and there is an effect that it is possible to meet demands for thinning, widening, and high quality of a protective film for a polarizing plate.

  Invention of Claim 2 is a manufacturing method of the optical film of Claim 1, Comprising: Before casting a resin melt or dope on a metal support body, a metal support surface is irradiated with atmospheric pressure plasma or A metal oxide is formed by surface treatment by excimer ultraviolet irradiation. According to the invention of claim 2, oxygen is maintained more than the normal oxide state of the metal surface while maintaining a very smooth surface state. By creating a metal oxide film layer with a high bonding ratio, the mold release (peelability) of the film from the metal support is improved even during continuous production of optical films, resulting in a very smooth peelability. As a result, variation in retardation (Re) value is greatly reduced, and an optical film having optical properties excellent in transparency and flatness can be produced, and production speed can be increased. Living It can improve sexual, an effect that eventually recent thinning of the protective films for polarizing plate, it is possible to meet the demand for broadening, and higher quality.

  Invention of Claim 3 is a manufacturing method of the optical film of Claim 1 or 2, Comprising: The integration time of an atmospheric pressure plasma irradiation process or an excimer ultraviolet irradiation process is 0.1-3000 sec, According to the invention of Item 3, the super-mirror surface state can be maintained for a long period of time, and in the case of no conventional treatment, the surface is gradually attacked by impurities in the dope after several years of use. The support was replaced in a short period of time due to the cloudiness of the film, but the effect was that the cycle was extended several times.

  Invention of Claim 4 is a manufacturing method of the optical film as described in any one of Claims 1-3, Comprising: Thermoplastic fat is a cellulose ester resin.

Invention of Claim 5 is a manufacturing method of the optical film as described in any one of Claims 1-4, Comprising: A metal support body is an endless belt for film forming, a drum, or a roll. It is either one .

  Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  The method for producing an optical film according to the present invention is a method for producing an optical film by a melt casting film forming method or a solution casting film forming method, wherein iron (Fe) and / or chromium (Cr) is formed on the surface of a metal support. And the component element composition ratio on the surface of the metal support satisfies the following relationship (i) and / or (ii), and the melt casting film forming method is provided on the surface of the metal support: It is characterized by casting the thermoplastic resin melt in (1) or the thermoplastic resin solution (dope) in the solution casting film forming method.

  As a method for measuring the composition ratio of the component elements, X-ray photoelectron spectroscopy called XPS or ESCA is used.

(I) (Fe ₂ O ₃ + FeO) / Fe = 5-50
(Ii) (CrO ₂ + CrO ₃ ) / Cr = 10-50
Here, if the (Fe ₂ O ₃ + FeO) / Fe ratio of (i) of the component element composition ratios on the surface of the metal support is less than 5, the corrosion resistance is compared with that of the untreated one. It does not change so much, and the difference in treatment is partially large, which is not preferable because it becomes uneven as the surface corrosion progresses. Also, if the (Fe ₂ O ₃ + FeO) / Fe ratio exceeds 50, if something comes into contact with the surface and scratches are created, it becomes difficult to polish and repair it to a smooth surface. This is not preferable.

Further, if the (CrO ₂ + CrO ₃ ) / Cr ratio of (ii) is less than 10, the corrosion resistance is not much different from that of the untreated one, and the difference in treatment is partly large. Since unevenness is caused by the progress of surface corrosion, it is not preferable. Further, when the (CrO ₂ + CrO ₃ ) / Cr ratio exceeds 50, when something comes into contact with the surface to create a scratch, it becomes difficult to polish and repair it to a smooth surface. Therefore, it is not preferable.

  In the method for producing an optical film of the present invention, the surface of the metal support is preferably subjected to surface treatment by atmospheric pressure plasma irradiation or excimer ultraviolet irradiation before casting a dope or a resin melt on the metal support.

  In this case, the integrated time of the atmospheric pressure plasma irradiation process or the excimer ultraviolet irradiation process is 0.1 to 3000 sec, preferably 0.5 to 500 sec.

  Here, if the integrated time of the atmospheric plasma irradiation treatment or the excimer ultraviolet irradiation treatment is less than 0.1 sec, it is not preferable because sufficient surface modification is not performed and the surface corrosion resistance is not improved. Further, if the integrated time of the atmospheric pressure plasma irradiation process or the excimer ultraviolet irradiation process exceeds 3000 seconds, the surface becomes rough and rough, which is not preferable.

  According to the present invention, high-energy surface treatment is performed by a high-energy irradiation device (A) composed of an atmospheric pressure plasma device and an excimer ultraviolet device, and the surface of the metal support is more than the surface oxide film naturally formed in the atmosphere. By forming the metal oxide film layer having an increased oxygen bond ratio as described above, the releasability from the metal support is improved.

  In the method for producing an optical film of the present invention, the thermoplastic fat is preferably a cellulose ester resin.

  Moreover, in the manufacturing method of an optical film, a metal support body is either an endless belt for film forming, a drum, or a roll.

  Hereafter, the manufacturing method of the optical film by this invention is described in detail.

The optical film can be produced by a melt casting film forming method or a solution casting film forming method.

  First, the manufacturing method of the optical film by the melt casting film forming method of this invention is demonstrated.

  Melt casting film forming methods are classified into molding methods that are heated and melted, and melt extrusion molding methods, press molding methods, inflation methods, injection molding methods, blow molding methods, stretch molding methods, and the like can be applied. Among these, in order to obtain an optical film excellent in mechanical strength and surface accuracy, the melt extrusion method is excellent. Hereinafter, the method for producing the film of the present invention will be described by taking the melt extrusion method as an example.

  In the method for producing an optical film by the melt casting film forming method of the present invention, the film constituent material to be used is mainly a pellet-shaped material, and it is preferable to dry before film formation. The moisture content of the pellets after drying is preferably 500 ppm or less, more preferably 200 ppm or less.

  As the dryer, a dehumidifying hot air dryer, a ribbon-type heat transfer vacuum dryer, a screw-type heat transfer vacuum dryer, or the like can be preferably used, but is not limited thereto.

  When using a vacuum dryer, the degree of vacuum is preferably 0.01 Pa or less, more preferably 0.03 Pa or less. The temperature is preferably 50 ° C. or higher and 150 ° C. or lower. More preferably, it is 80 degreeC or more and 120 degrees C or less. It is preferable to put nitrogen gas into the dryer during drying. When returning from the vacuum state to the atmospheric pressure, it is preferable to add dehumidified air or nitrogen gas.

  When using a dehumidifying hot air dryer, the dew point of the dehumidified air is preferably −20 ° C. or lower, more preferably −40 ° C. or lower.

  Pneumatic transportation is preferred as a transfer method from the dryer to the extruder. The air used for transportation is preferably dehumidified. Pellets that are pneumatically transported from the dryer are placed in a hopper above the extruder, but there is a powder collector on the hopper to remove small debris and powder from the pellets that are transported along with the pellets Is preferred. In the collector, pellets and powder are separated by the force of air, and only the powder is removed. The hopper is preferably kept warm. The temperature is preferably 50 ° C. or higher and 150 ° C. or lower. More preferably, it is 80 degreeC or more and 120 degrees C or less. It is preferable to put dehumidified air into the hopper.

  FIG. 1 is a schematic flow sheet showing the overall configuration of an apparatus for carrying out the method for producing an optical film by the melt casting method of the present invention, and FIG. 2 is an enlarged view of a cooling roll portion from the casting die. . Note that the implementation of the present invention is not limited to the process of the drawings shown below.

  1 and 2, for example, a cellulose ester resin dried under hot air, vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C. using an extruder (1), and a leaf disk type filter (2) Filter through to remove foreign matter.

  When the feed hopper (not shown) is introduced into the extruder (1), it is preferable to prevent oxidative decomposition or the like by applying a vacuum, a reduced pressure, or an inert gas atmosphere.

  When additives such as a plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer (3).

  It is preferable to mix a resin such as a cellulose resin and other additives such as a stabilizer added as necessary before melting. Mixing may be performed by a mixer or the like, or as described above, mixing may be performed in a resin preparation process such as a cellulose resin. When a mixer is used, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, or the like can be used.

  After the film constituent materials are mixed as described above, the mixture may be directly melted and formed into a film using an extruder (1). Once the film constituent materials are pelletized, the pellets May be melted with an extruder (1) to form a film. Further, when the film constituent material includes a plurality of materials having different melting points, a so-called braided semi-melt is once produced at a temperature at which only a material having a low melting point is melted, and the semi-melt is extruded (1). ) To form a film. If the film component contains a material that is easily pyrolyzed, in order to reduce the number of times of melting, a method of directly forming a film without producing pellets, or after making a paste-like semi-molten material as described above A method of forming a film is preferred.

  As the extruder (1), various commercially available extruders can be used, but a melt-kneading extruder is preferable, and a single-screw extruder or a twin-screw extruder may be used. When forming a film directly without producing pellets from film constituent materials, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is required. However, even with a single-screw extruder, the screw shape is a Maddock type. By changing to a kneading type screw such as a unimelt type or a dull mage, moderate kneading can be obtained, so that it can be used. When a pellet or braided semi-melt is once used as a film constituent material, it can be used in either a single screw extruder or a twin screw extruder.

  In the extruder (1) and after the extrusion, the cooling step is preferably carried out by substituting with an inert gas such as nitrogen gas or reducing the pressure to reduce the oxygen concentration.

  Although the preferable conditions for the melting temperature of the film constituent material in the extruder (1) vary depending on the viscosity and discharge amount of the film constituent material, the thickness of the sheet to be produced, etc., in general, the glass transition of the film (resin mixture) The temperature (Tg) is Tg or more and Tg + 100 ° C. or less, preferably Tg + 10 ° C. or more and Tg + 90 ° C. or less. The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. Further, the residence time of the film constituting material in the extruder (1) is preferably short, and is within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. The residence time depends on the type of the extruder (1) and the extrusion conditions, but it can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, and the like. Is possible.

  The shape, rotation speed, etc. of the screw of the extruder (1) are appropriately selected depending on the viscosity of the film constituting material, the discharge amount, and the like. In this embodiment, the shear rate in the extruder (1) is 1 / second to 10000 / second, preferably 5 / second to 1000 / second, more preferably 10 / second to 100 / second. As the extruder (1), an extruder generally marketed as a plastic molding machine can be used.

  The film constituent material extruded from the extruder (1) is sent to the casting die (4), and is extruded from the casting die (4) into a film shape.

  The melt discharged from the extruder (1) is supplied to the casting die (4). The casting die (4) is not particularly limited as long as it is used for producing a sheet or a film. As the material of the casting die (4), hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. are sprayed or plated. Buffing as surface processing, lapping using a # 1000 or higher grinding wheel, plane cutting using a diamond grinding wheel of # 1000 or higher (cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. And the like.

  The preferred material of the lip portion of the casting die (4) is the same as that of the casting die (4). The surface accuracy of the lip is preferably 0.5S or less, and more preferably 0.2S or less.

In the method for producing an optical film by the melt casting film forming method of the present invention, after mixing film materials such as cellulose resin, the resin melt is discharged from the die lip of the casting die (4) using an extruder (1). To form a cast film on the surface of the cooling roll (5).

  While containing the element of iron (Fe) and / or chromium (Cr) on the surface of the cooling roll (5) as the metal support, the component element composition ratio on the surface of the metal support (5) is the following (i) and / Or satisfy the relationship (ii), on the surface of the metal support (5), a thermoplastic resin melt in the melt casting film forming method or a thermoplastic resin solution in the solution casting film forming method ( Dope).

(I) (Fe ₂ O ₃ + FeO) / Fe = 5-50
(Ii) (CrO ₂ + CrO ₃ ) / Cr = 10-50
In the present invention, before casting the resin melt on the surface of the cooling roll (5) as a metal support, the surface of the metal support is subjected to surface treatment by atmospheric pressure plasma irradiation or excimer ultraviolet irradiation, A metal oxide film as described above is formed.

  A high energy irradiation apparatus including an atmospheric pressure plasma irradiation apparatus and an excimer ultraviolet irradiation apparatus will be described later.

  Next, the cast film is brought into contact with the first cooling roll (5) subjected to the high-energy surface treatment as described above, and is brought into contact with the first cooling roll (5). Further, the second cooling roll ( 7) A third total of three cooling rolls (8) are sequentially circumscribed, and are cooled and solidified to form a film (10).

  In order to extrude the resin melt from the casting die (4) in the form of a film and to take out the extruded casting film (film), it is brought into close contact with at least two rotating bodies (cooling rolls) to form the film. To do.

  Here, in order to correct the flatness, a touch roll (6) is provided that clamps the molten film on the surface of the first cooling roll (5). The touch roll (6) has an elastic surface and forms a nip with the first cooling roll (5).

  The embodiment of the present invention shown in FIG. 1 and FIG. 2 is different in that the cast film first contacts the surface of the first cooling roll (5) and the film contacts the surface of the touch roll (6). The embodiment which has shown is shown.

  In addition, although illustration was abbreviate | omitted, the point which the casting film from an extruder (4) contacted the surface of the 1st cooling roll (5) first, and the casting film contacted the surface of the touch roll (6). The point may be the same.

  Furthermore, in the embodiment of the present invention shown in FIGS. 1 and 2, the cooled and solidified film (10) peeled from the third cooling roll (8) by the peeling roll (9) is a dancer roll (film tension adjusting roll). Through (11), the film is guided to a stretching device (12), where the film (10) is stretched in the transverse direction (width direction). By this stretching, the molecules in the film are oriented.

  As a method of stretching the film in the width direction, a known tenter or the like can be preferably used. In particular, it is preferable to set the stretching direction to the width direction because lamination with the polarizing film can be performed in a roll form. By stretching in the width direction, the slow axis of the optical film made of the cellulose ester resin film becomes the width direction.

  After stretching, the end of the film is slit to a product width by a slitter (13) and cut off, and then knurled (embossed) by a knurling device comprising an embossing ring (14) and a back roll (15). By applying to both ends of the film and winding by the winding device (16), sticking in the optical film (original winding) (F) and generation of scratches are prevented. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.

  FIG. 5 is an explanatory diagram for explaining the principle of the atmospheric pressure plasma irradiation apparatus. The atmospheric pressure plasma irradiation apparatus (atmospheric pressure plasma irradiation apparatus) (40) will be described in detail with reference to FIG.

  In the atmospheric pressure plasma apparatus (40) used in the present invention, a reactive gas is changed to a plasma state by applying a high frequency voltage between opposing electrodes to discharge it, and a metal support (first cooling roll) (5 ) Is modified to form a metal oxide film layer on the surface of the metal support (5).

  In the atmospheric pressure plasma irradiation device (40), a method called a direct type or a planer type in which high-frequency power is applied between electrodes opposed to each other so as to sandwich a substrate to be processed, and a supply gas is converted into plasma, and a reactive gas are supplied. There are methods called a remote method and a downstream method in which plasma is generated between electrodes to which a high-frequency voltage is applied, and both methods can be used in the present invention. However, in the method for producing an optical film of the present invention, It is desirable to use the latter method for high energy surface treatment.

In the figure, (a) and (b) are counter electrodes of the atmospheric pressure plasma irradiation apparatus (40), (g) is a reactive gas, and (5) is a surface of a metal support (first cooling roll) .

  Then, according to the atmospheric pressure plasma irradiation device (40), the reactive gas (g) is introduced between the counter electrodes (a) and (b) to which the high-frequency voltage is applied, and is converted into plasma, thereby forming a metal support. (5) A metal oxide layer is formed by spraying the surface.

While containing the element of iron (Fe) and / or chromium (Cr) in the 1st cooling roll (5) surface as a metal support body, the component element composition ratio of the metal support body (5) surface is the following (i ) And / or (ii).

(I) (Fe ₂ O ₃ + FeO) / Fe = 5-50
(Ii) (CrO ₂ + CrO ₃ ) / Cr = 10-50
In the embodiment of the present invention, it is necessary to apply an electrode capable of maintaining a uniform glow discharge state by applying such a high power voltage to the atmospheric pressure plasma irradiation apparatus (40).

  Such an electrode is preferably a metal base material coated with a dielectric. It is preferable to coat a dielectric on at least one side of the opposed application electrode and the ground electrode, and more preferably coat both of the opposed application electrode and the ground electrode with a dielectric. The dielectric is preferably an inorganic substance having a relative dielectric constant of 6 to 45. Examples of such a dielectric include ceramics such as alumina and silicon nitride, silicate glass, borate glass, and the like. Glass lining material and the like.

  In addition, when a cellulose ester film, which is a transparent film base material, is placed between electrodes or transported between electrodes and exposed to plasma, the transparent film base material has a roll electrode specification that can be transported in contact with one electrode. Furthermore, the dielectric surface and the gap between the electrodes can be kept constant by polishing the dielectric surface and setting the electrode surface roughness Rmax (JIS B 0601) to 10 μm or less. It is preferable because the discharge state can be stabilized, and further, the distortion and cracking due to the difference in thermal shrinkage and residual stress can be eliminated and the high-precision inorganic dielectric that is not porous can be coated to greatly improve the durability.

  In addition, the gap between the blowing slit for performing plasma supply and the surface of the metal support (5) is preferably 0.5 to 6 mm, and more preferably 1 to 4 mm. If it is too close, there is a risk of contacting or damaging the surface of the metal support (5). If it is too far, the effect of modifying the surface becomes weak.

  Various reactive gases (g) such as nitrogen, oxygen, argon, and helium can be used. Nitrogen is preferable from the viewpoints of environment, exhaust aftertreatment, and running cost. It is preferable to mix a small amount of oxygen. The mixing ratio of oxygen is preferably 2% by volume or less with respect to the volume of the source gas.

  In addition, as a raw material gas (g) for forming the surface treatment layer, for example, an organic solvent vapor such as methylene chloride or alcohol, or a monomer gas such as acetylene is mixed with nitrogen or oxygen of the reactive gas of the atmospheric pressure plasma. May be introduced. The mixing ratio is preferably in the range of 0.2 to 20% by volume with respect to the total volume of nitrogen and oxygen.

  When the source gas for forming the surface treatment layer is not mixed with the reactive gas of atmospheric pressure plasma, the source gas is sprayed on the surface of the casting film from the outside of the atmospheric pressure plasma irradiation device (40), It is also possible to carry out the reaction and form a film by feeding it under the atmospheric pressure plasma irradiation device (40).

  In that case, the gas concentration around the atmospheric pressure plasma irradiation apparatus (40) is preferably in the range of 500 ppm to 100,000 ppm, more preferably 1000 to 50,000 ppm.

  Further, the air volume of the source gas of atmospheric pressure plasma is desirably 20 to 5000 L / min per 1 m of the effective width of plasma irradiation. Furthermore, 40-2500 L / min is more preferable.

  FIG. 6 is an explanatory diagram for explaining the principle of the excimer ultraviolet irradiation device (50). The excimer ultraviolet irradiation device (50) will be described with reference to FIG.

In the figure, (u) is an excimer ultraviolet lamp, (r) is a reflector, (p) is a purge gas, and (5) is a metal support (first cooling roll) .

In this embodiment, the excimer ultraviolet lamp (u) shown in FIG. 6 is used to irradiate the surface of the metal support (5) mainly with ultraviolet light having a wavelength of 172 nm with a light quantity of 1 to 3000 mJ / cm ^2. Is. Under such ultraviolet irradiation, oxygen contained in the purge gas (p) generates active oxygen and ozone, contributes to the modification of the surface of the metal support (5), and on the surface of the metal support (5). A metal oxide film layer is formed.

  Further, if the gap between the excimer ultraviolet lamp (u) and the metal support (5) is too close, there is a risk of contact and damage to the surface of the metal support (5). Since the high energy of excimer ultraviolet rays is absorbed by water and the effect of modifying the surface of the metal support (5) is weakened, 0.5 to 4 mm is preferable, and 1 to 3 mm is more preferable.

While containing the element of iron (Fe) and / or chromium (Cr) in the 1st cooling roll (5) surface as a metal support body, the component element composition ratio of the metal support body (5) surface is the following (i ) And / or (ii).

(I) (Fe ₂ O ₃ + FeO) / Fe = 5-50
(Ii) (CrO ₂ + CrO ₃ ) / Cr = 10-50
In the method for producing an optical film of the present invention, various resins can be used as the film material. Among them, cellulose ester, particularly cellulose acylate is preferable.

Cellulose as a cellulose acylate raw material is not particularly limited, and examples thereof include cotton linter, wood pulp, and kefna. Moreover, you may mix and use the raw material cellulose obtained from these in arbitrary ratios. The cellulose acylate is preferably a cellulose acylate having an acetyl group or an acyl group having 3 to 22 carbon atoms. Examples of the acyl group having 3 to 22 carbon atoms, propionyl _{(C 2 H 5 CO -)} , n- butyryl _{(C 3} H 7 CO-), isobutyryl, valeryl _{(C 4} H 9 CO-), isovaleryl, Includes sec-valeryl, tert-valeryl, octanoyl, dodecanoyl, octadecanoyl and oleoloyl. Propionyl and butyryl are preferred. As the cellulose acylate, cellulose acetate is preferable, and cellulose triacetate is particularly preferable.

  When the acylating agent for the acyl group is an acid anhydride or acid chloride, an organic acid (eg, acetic acid) or methylene chloride is used as the organic solvent as the reaction solvent.

  In the cellulose acylate, the substitution degree of the hydroxyl group of cellulose is preferably 2.6 to 3.0. The degree of polymerization (average viscosity) of cellulose acylate is preferably 200 to 700, and particularly preferably 250 to 550.

  These cellulose acylates are commercially available from Daicel Chemical Industries, Ltd., Courtles, Hoechst, and Eastman Kodak. Photographic grade cellulose acylate is preferably used. The water content of the cellulose acylate is preferably 2% by weight or less.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acetic acid or other acids. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification is 1.00).

  The cellulose acylate used in the present invention has a cellulose acylate having a total acyl substitution degree of 2-position and 3-position of 1.70 to 1.95 and an acyl substitution degree of 6-position of 0.88 or more, It is obtained by blending cellulose acylate having a total acyl substitution degree at the 2nd and 3rd positions of 1.70 to 1.95 and an acyl substitution degree at the 6th position of less than 0.88. When the total of the 2- and 3-position acyl substitutions is 1.70 or less, the film is likely to absorb moisture and is susceptible to hydrolysis, so the durability of the film is lowered. In addition, the dimensional change due to humidity or the like becomes large. On the other hand, if it exceeds 1.95, the organicity of cellulose acylate increases, so the affinity with the solvent increases and the viscosity of the dope increases. Accordingly, the total of the 2- and 3-position acyl substitutions is preferably 1.70 to 1.95, and more preferably 1.75 to 1.88.

  By the way, since the hydroxyl group at the 6-position is a primary hydroxyl group, unlike the hydroxyl groups at the 2- and 3-positions, it has been found that hydrogen bonding of the hydroxyl group is extremely likely to occur. Therefore, by setting the acyl substitution degree at the 6-position to 0.88 or more, the solubility in a solvent is remarkably improved, and it is possible to obtain a dope that is preferable in terms of casting suitability. The range of the degree of acyl substitution at the 6-position is preferably from 0.88 to 0.99, more preferably from 0.89 to 0.98 in view of synthesis suitability and the like. However, when the degree of acyl substitution at the 6-position is improved, there is a problem that the film strength is lowered, and it is difficult to achieve both. On the other hand, if the acyl substitution degree is less than 0.88, the solubility in a solvent is remarkably lowered, which is not preferable.

  Further, a film made of cellulose acylate having a total acyl substitution degree of 2-position and 3-position of 1.70 to 1.95 and an acyl substitution degree of 6-position of 0.88 or more, or 2-position, 3-position In the roll state, an optical film in which a thin film is formed on a film made of cellulose acylate having a total acyl substitution degree of 1.70 to 1.95 and a acyl substitution degree of 6-position of less than 0.88. There has been a problem that flatness such as wrinkles and dents is liable to occur during storage, and the formed metal oxide layer is liable to crack, resulting in uneven film thickness.

  It has been found that these problems can be solved by blending cellulose acylate. In addition, cellulose acylate having an acyl substitution degree at the 6-position of 0.88 or more desirably has a smaller number of carbon atoms in the acyl substituent from the viewpoint of film strength, and is preferably all acetyl groups. In JP-A-11-5851, the total of acetyl substituents at the 2nd, 3rd and 6th positions is 2.67 or more, and the total of the acetyl substituents at the 2nd and 3rd positions is 1.97 or less. Although cellulose acetate is described, the range in which the sum of the 2nd and 3rd positions exceeds 1.90 is a preferred range from the optical suitability of the film, and the casting suitability is described in this specification. The range described is more preferable.

  The basic principle of the cellulose acylate synthesis method is described in Mita et al., Wood Chemistry pages 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using an acetic anhydride-acetic acid-sulfuric acid catalyst. Specifically, a cellulose raw material such as wood pulp is pretreated with an appropriate amount of an organic acid, and then it is esterified by adding it to a pre-cooled acylated mixture to complete cellulose acylate (2nd, 3rd and 6th positions). The total degree of acyl substitution is approximately 3.00). The acylated mixed solution generally contains an organic acid as a solvent, an anhydrous organic acid as an esterifying agent, and sulfuric acid as a catalyst. The organic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. After completion of the acylation reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess organic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide).

  Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid), and the desired acyl substitution degree and The cellulose acylate having a polymerization degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with the neutralizing agent as described above, or water or dilute sulfuric acid without neutralization. A cellulose acylate solution is introduced into the cellulose acylate solution (or water or dilute sulfuric acid is introduced into the cellulose acylate solution) to separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.

  In an ordinary cellulose acylate synthesis method, the acyl substitution degree at the 2-position or the 3-position is higher than the acyl substitution degree at the 6-position. Therefore, in order to make the total acyl substitution degree at the 2nd and 3rd positions 1.95 or less and the acyl substitution degree at the 6th position 0.88 or more, the above reaction conditions need to be specifically adjusted. . As specific reaction conditions, it is preferable to reduce the amount of the sulfuric acid catalyst and lengthen the time of the acylation reaction. When the amount of the sulfuric acid catalyst is large, the acylation reaction proceeds faster, but a sulfuric ester is formed between the cellulose and the cellulose according to the amount of the catalyst, and is released at the end of the reaction to form a residual hydroxyl group. Sulfate esters are more produced at the 6-position, which is highly reactive. Therefore, when there is much sulfuric acid catalyst, the acyl substitution degree of 6-position becomes small. Therefore, in order to synthesize the cellulose acylate used in the present invention, it is necessary to extend the reaction time in order to reduce the amount of sulfuric acid catalyst as much as possible and compensate for the reduced reaction rate.

(Plasticizer)
The following plasticizer may be contained in the optical film produced by the method of the present invention .

  An ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyvalent carboxylic acid and a monohydric alcohol are preferred because of their high affinity with the cellulose ester.

  An ethylene glycol ester plasticizer that is one of polyhydric alcohol esters: specifically, ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, ethylene glycol dicyclopropylcarboxylate And ethylene glycol cycloalkyl ester plasticizers such as ethylene glycol dicyclohexylcarboxylate, and ethylene glycol aryl ester plasticizers such as ethylene glycol dibenzoate and ethylene glycol di-4-methylbenzoate. These alkylate groups, cycloalkylate groups, and arylate groups may be the same or different, and may be further substituted. Moreover, the mix of an alkylate group, a cycloalkylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the covalent bond. Further, the ethylene glycol part may be substituted, the ethylene glycol ester partial structure may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber, etc. It may be introduced into a part of the molecular structure of the additive.

  Glycerin ester plasticizer that is one of polyhydric alcohol esters: Specifically, glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, glycerol tricyclopropylcarboxylate, glycerol Glycerin cycloalkyl esters such as tricyclohexylcarboxylate, glycerol aryl esters such as glycerol tribenzoate and glycerol-4-methylbenzoate, diglycerol tetraacetylate, diglycerol tetrapropionate, diglycerol acetate tricaprylate, diglycerol tetra Diglycerol alkyl esters such as laurate, diglycerol tetracyclobutylcarboxylate, diglycerol tetracycle Diglycerol cycloalkyl esters such as pentyl carboxylate, diglycerin tetrabenzoate, diglycerin aryl ester such as diglycerin 3-methylbenzoate or the like. These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Moreover, the mix of alkylate group, a cycloalkyl carboxylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the covalent bond. Furthermore, the glycerin and diglycerin part may be substituted, the partial structure of the glycerin ester and the diglycerin ester may be part of the polymer or regularly pendant, and the antioxidant, acid scavenger, You may introduce | transduce into a part of molecular structure of additives, such as a ultraviolet absorber.

  Specific examples of other polyhydric alcohol ester plasticizers include polyhydric alcohol ester plasticizers described in paragraphs 30 to 33 of JP-A No. 2003-12823.

  These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Moreover, the mix of alkylate group, a cycloalkyl carboxylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the covalent bond. Furthermore, the polyhydric alcohol part may be substituted, and the partial structure of the polyhydric alcohol may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber. May be introduced into a part of the molecular structure of the additive.

  Among the ester plasticizers composed of the polyhydric alcohol and the monovalent carboxylic acid, alkyl polyhydric alcohol aryl esters are preferred. Specifically, the above-mentioned ethylene glycol dibenzoate, glycerin tribenzoate, diglycerin tetrabenzoate, Exemplified compound 16 described in paragraph 32 of Kokai 2003-12823 can be mentioned.

  Dicarboxylic acid ester plasticizer that is one of polyvalent carboxylic acid esters: Specifically, alkyl dicarboxylic acid alkyl such as didodecyl malonate (C1), dioctyl adipate (C4), dibutyl sebacate (C8), etc. Ester plasticizers, alkyl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclopentyl succinate and dicyclohexyl adipate, and alkyl dicarboxylic acid aryl ester plasticizers such as diphenyl succinate and di-4-methylphenyl glutarate , Dicyclohexyl-1,4-cyclohexanedicarboxylate, didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, and other cycloalkyldicarboxylic acid alkyl ester plasticizers, dicyclohexyl-1,2- Cyclobutane Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as xylate, dicyclopropyl-1,2-cyclohexyl dicarboxylate, diphenyl-1,1-cyclopropyldicarboxylate, di-2-naphthyl-1,4- Cycloalkyldicarboxylic acid aryl ester plasticizers such as cyclohexane dicarboxylate, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate, dicyclopropyl Aryl dicarboxylic acid cycloalkyl ester plasticizers such as phthalate and dicyclohexyl phthalate, and aryl dicarboxylic acid aliquots such as diphenyl phthalate and di-4-methylphenyl phthalate Glycol ester-based plasticizers. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, or these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

Examples of other polycarboxylic acid ester plasticizers include alkyl polycarboxylic acid alkyl esters such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate. Plasticizer, tricyclohexyl-2-carbamate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate and other alkyl polycarboxylic acid cycloalkyl ester plasticizer, triphenyl-2-hydroxy -1,2,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate and other alkyl polyvalent carboxylic acid aryl ester plasticizers, tetrahexyl-1, 2,3,4-cyclobutanetetracarboxylate, tet Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as butyl-1,2,3,4-cyclopentanetetracarboxylate, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl- Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as 1,3,5-cyclohexyl tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2 , 3,4,5,6-cyclohexylhexacarboxylate and other cycloalkyl polycarboxylic acid aryl ester plasticizers, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2, Allies such as 4,5-tetracarboxylate Polycarboxylic acid alkyl ester plasticizers, aryl polycarboxylic acid cycloalkyl esters such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate Aryl polyvalent carboxylic acid aryl such as triphenylbenzene-1,3,5-tetracartoxylate, hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate An ester plasticizer may be mentioned. These alkoxy groups and cycloalkoxy groups may be the same or different, and may be monosubstituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, or these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or may be regularly pendant to the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  Among the ester plasticizers composed of the polyvalent carboxylic acid and the monohydric alcohol, dialkyl carboxylic acid alkyl esters are preferable, and specific examples include the dioctyl adipate and tridecyl tricarbalate.

  Further, phosphate ester plasticizers, carbohydrate ester plasticizers, polymer plasticizers and the like can be mentioned.

  Phosphate ester plasticizers: specifically, phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclobenthyl phosphate and cyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate And phosphoric acid aryl esters such as cresylphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate. These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Also alkylene bis (dialkyl phosphate) such as ethylene bis (dimethyl phosphate), butylene bis (diethyl phosphate), alkylene bis (diaryl phosphate) such as ethylene bis (diphenyl phosphate), propylene bis (dinaphthyl phosphate), phenylene bis (dibutyl phosphate) ), Arylene bis (dialkyl phosphate) such as biphenylene bis (dioctyl phosphate), phosphate esters such as arylene bis (diaryl phosphate) such as phenylene bis (diphenyl phosphate) and naphthylene bis (ditoluyl phosphate). These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Furthermore, the phosphate ester partial structure may be part of the polymer, or may be regularly pendant, and may be introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. May be. Among the above-mentioned compounds, phosphoric acid aryl ester and arylene bis (diaryl phosphate) are preferable, and specifically, triphenyl phosphate and phenylene bis (diphenyl phosphate) are preferable.

  Next, the carbohydrate ester plasticizer will be described. The carbohydrate means a monosaccharide, disaccharide or trisaccharide in which the saccharide is present in the form of pyranose or furanose (6-membered ring or 5-membered ring). Non-limiting examples of carbohydrates include glucose, saccharose, lactose, cellobiose, mannose, xylose, ribose, galactose, arabinose, fructose, sorbose, cellotriose and raffinose. The carbohydrate ester refers to an ester compound formed by dehydration condensation of a hydroxyl group of a carbohydrate and a carboxylic acid. Specifically, it means an aliphatic carboxylic acid ester or an aromatic carboxylic acid ester of a carbohydrate. Examples of the aliphatic carboxylic acid include acetic acid and propionic acid, and examples of the aromatic carboxylic acid include benzoic acid, toluic acid, and anisic acid. Carbohydrates have a number of hydroxyl groups depending on the type, but even if a part of the hydroxyl group reacts with the carboxylic acid to form an ester compound, the whole hydroxyl group reacts with the carboxylic acid to form an ester compound. Also good. In the present invention, it is preferable that all of the hydroxyl groups react with the carboxylic acid to form an ester compound.

  Specific examples of the carbohydrate ester plasticizer include glucose pentaacetate, glucose pentapropionate, glucose pentabtylate, saccharose octaacetate, saccharose octabenzoate, and of these, saccharose octaacetate is more preferable. preferable.

  Polymer plasticizer: Specifically, aliphatic hydrocarbon polymer, alicyclic hydrocarbon polymer, polyethyl acrylate, polymethyl methacrylate, copolymer of methyl methacrylate and 2-hydroxyethyl methacrylate (For example, an arbitrary ratio between copolymer ratios 1:99 to 99: 1), vinyl polymers such as polyvinyl isobutyl ether, poly N-vinyl pyrrolidone, polystyrene, poly 4-hydroxystyrene, etc. Examples thereof include styrene-based polymers, polybutylene succinates, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes, and polyureas. The number average molecular weight is preferably about 1,000 to 500,000, particularly preferably 5,000 to 200,000. If it is 1000 or less, a problem arises in volatility, and if it exceeds 500000, the plasticizing ability is lowered, and the mechanical properties of the cellulose ester film are adversely affected. These polymer plasticizers may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination.

In addition, since the optical film manufactured by the method of this invention will affect as an optical use when it colors, Preferably yellow degree (yellow index, YI) is 3.0 or less, More preferably, it is 1.0 or less. Yellowness can be measured based on JIS-K7103.

  The plasticizer preferably removes impurities such as residual acids, inorganic salts, organic low molecules, etc. that are carried over from production or generated during storage, and more preferably has a purity of 99% or more, like the cellulose ester described above. is there. The residual acid and water are preferably 0.01 to 100 ppm, and when melt-forming the cellulose resin, thermal degradation can be suppressed, and film-forming stability, optical properties of the film, and mechanical properties are improved. .

(Antioxidant)
Cellulose ester is accelerated not only by heat but also by oxygen in a high temperature environment where melt film formation is performed. Therefore, an antioxidant is used as a stabilizer in the optical film produced by the method of the present invention. It is also preferable to use it.

  The antioxidant useful in the present invention can be used without limitation as long as it is a compound that suppresses deterioration of the melt molding material due to oxygen, but among the useful antioxidants, phenolic compounds, hindered amine compounds, Examples thereof include phosphorus compounds, sulfur compounds, heat-resistant processing stabilizers, oxygen scavengers, etc. Among these, phenol compounds, hindered amine compounds, phosphorus compounds, and lactone compounds are particularly preferable.

  The hindered amine compound (HALS) is described, for example, in columns 5 to 11 of US Pat. No. 4,619,956 and columns 3 to 5 of US Pat. No. 4,839,405. Thus, 2,2,6,6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds are preferred. As a commercial item, LA52 (made by Asahi Denka Co., Ltd.) can be mentioned.

  As the lactone compound, compounds described in JP-A-7-233160 and JP-A-7-247278 are preferable.

  These stabilizers can be used singly or in combination of two or more, and the blending amount is appropriately selected within a range not impairing the object of the present invention, but is usually 0 with respect to 100 parts by weight of the cellulose ester. 0.001 to 10.0 parts by weight, preferably 0.01 to 5.0 parts by weight, and more preferably 0.1 to 3.0 parts by weight.

  By blending these compounds, it is possible to prevent coloring and strength reduction of the molded product due to heat and thermal oxidative degradation during melt molding without reducing transparency and heat resistance.

  The addition amount of the antioxidant is usually 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, and more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the cellulose ester.

(Acid scavenger)
The acid scavenger is an agent that plays a role of trapping an acid (protonic acid) remaining in the cellulose ester brought in from the production. Further, when the cellulose ester is melted, the hydrolysis of the side chain is accelerated by moisture and heat in the polymer, and acetic acid and propionic acid are generated in the case of CAP. A compound having an epoxy structure, a tertiary amine, an ether structure, or the like may be used as long as it can be chemically bonded to an acid, but is not limited thereto.

  Specifically, it is preferable to comprise an epoxy compound as an acid scavenger described in US Pat. No. 4,137,201. Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of diglycidyl ethers of various polyglycols, particularly about 8-40 moles of ethylene oxide per mole of polyglycol. Metal glycol compounds such as polyglycols, diglycidyl ethers of glycerol (eg, those conventionally used in and together with vinyl chloride polymer compositions), epoxidized ether condensation products, bisphenol A Diglycidyl ether (ie, 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of an alkyl of about 2 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms (e.g. Butyl epoxy stearate ), And various epoxidized long chain fatty acid triglycerides and the like (e.g., epoxidized vegetable oils and other unsaturated natural oils, which may be represented and exemplified by compositions such as epoxidized soybean oil, sometimes epoxidized natural) These are referred to as glycerides or unsaturated fatty acids, which generally contain 12 to 22 carbon atoms)).

(UV absorber)
As an ultraviolet absorber, from the viewpoint of preventing deterioration of a polarizer or a display device with respect to ultraviolet rays, the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, it absorbs visible light having a wavelength of 400 nm or more. Less is preferred.

  For example, salicylic acid ultraviolet absorbers (phenyl salicylate, p-tert-butyl salicylate, etc.) or benzophenone ultraviolet absorbers (2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, etc.), Benzotriazole UV absorber (2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′, 5′-di) -Tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, 2- (2'-hydroxy-3'-dodecyl- 5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-te t-butyl-5 '-(2-octyloxycarbonylethyl) -phenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-(1-methyl-1-phenylethyl) -5'- (1,1,3,3-tetramethylbutyl) -phenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di- (1-methyl-1-phenylethyl) -phenyl) benzotriazole ), Cyanoacrylate ultraviolet absorbers (2′-ethylhexyl-2-cyano-3,3-diphenyl acrylate, ethyl-2-cyano-3- (3 ′, 4′-methylenedioxyphenyl) -acrylate Etc.), triazine ultraviolet absorbers, or compounds described in JP-A Nos. 58-185777 and 59-149350, nickel complex compounds, Machine powder, and the like.

As the UV absorber used in the present invention, a benzotriazole UV absorber and a triazine UV absorber that are highly transparent and excellent in preventing the deterioration of the polarizing plate and the liquid crystal element are preferable, and the spectral absorption spectrum is more appropriate. Particularly preferred are benzotriazole ultraviolet absorbers.

The conventionally known benzotriazole-based ultraviolet absorber particularly preferably used together with the ultraviolet absorber used in the present invention may be bisified, for example, 6,6′-methylenebis (2- (2H-benzo [ d] [1,2,3] triazol-2-yl))-4- (2,4,4-trimethylpentan-2-yl) phenol, 6,6'-methylenebis (2- (2H-benzo [d ] [1,2,3] triazol-2-yl))-4- (2-hydroxyethyl) phenol and the like.

  Moreover, in this invention, it can also use in combination with a conventionally well-known ultraviolet absorbing polymer. Although it does not specifically limit as a conventionally well-known ultraviolet-absorbing polymer, For example, R ultraviolet-ray A-93 (made by Otsuka Chemical Co., Ltd.) and the R ultraviolet-ray A-93 and another monomer were copolymerized. Examples thereof include polymers. Specifically, P ultraviolet rays A-30M obtained by copolymerization of R ultraviolet rays A-93 and methyl methacrylate at a ratio (weight ratio) of 3: 7, and P ultraviolet rays obtained by copolymerization at a ratio of 5: 5 (weight ratio). A-50M etc. are mentioned. Furthermore, the polymer etc. which are described in Unexamined-Japanese-Patent No. 2003-113317 are mentioned.

  Moreover, as a commercial item, TINUVIN 109, TINUVIN 171, TINUVIN 360, TINUVIN 900, TINUVIN 900, TINUVIN 928 (all manufactured by Ciba Specialty Chemicals), LA-31 (Manufactured by Asahi Denka), R ultraviolet ray A-100 (manufactured by Otsuka Chemical Co., Ltd.) can also be used.

  Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy- 5-benzoylphenylmethane) and the like, but are not limited thereto.

  In the present invention, the ultraviolet absorber is preferably added in an amount of 0.1 to 20% by weight, more preferably 0.5 to 10% by weight, and further preferably 1 to 5% by weight. Two or more of these may be used in combination.

(Viscosity reducing agent)
In the present invention, a hydrogen bonding solvent can be added for the purpose of reducing the melt viscosity. The hydrogen bonding solvent is J.I. N. As described in Israel Ativili, “Intermolecular Forces and Surface Forces” (Takeshi Kondo, Hiroyuki Oshima, Maglow Hill Publishing, 1991) and electrically negative atoms (oxygen, nitrogen, fluorine, chlorine) An organic solvent capable of producing a hydrogen atom-mediated “bond” between a hydrogen atom covalently bonded to an electronegative atom, ie, a bond having a large bond moment and containing hydrogen, such as O—H (Oxygen hydrogen bond), N—H (nitrogen hydrogen bond), and organic solvent that can arrange adjacent molecules by including F—H (fluorine hydrogen bond). These have the ability to form stronger hydrogen bonds with cellulose than intermolecular hydrogen bonds of cellulose resin. In the melt casting film forming method performed in the present invention, the glass transition temperature of the cellulose resin used alone is used. In addition, the melting temperature of the cellulose resin composition can be lowered by the addition of a hydrogen bonding solvent, or the melt viscosity of the cellulose resin composition containing the hydrogen bonding solvent is lower than that of the cellulose resin at the same melting temperature. Can do.

  Examples of the hydrogen bonding solvent include alcohols: for example, methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, t-butanol, 2-ethylhexanol, heptanol, octanol, nonanol, dodecanol, ethylene glycol, Propylene glycol, hexylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, glycerin, etc., ketones: acetone, methyl ethyl ketone, etc., carboxylic acids: for example formic acid, acetic acid, propionic acid, Butyric acid, etc., ethers: eg, diethyl ether, tetrahydrofuran, dioxane, etc., Pyrrolidones: eg, N-methyl Pyrrolidone, etc., amines: for example, can be exemplified trimethylamine, pyridine, etc., and the like. These hydrogen bonding solvents can be used alone or in admixture of two or more. Among these, alcohol, ketone, and ether are preferable, and methanol, ethanol, propanol, isopropanol, octanol, dodecanol, ethylene glycol, glycerin, acetone, and tetrahydrofuran are particularly preferable. Furthermore, water-soluble solvents such as methanol, ethanol, propanol, isopropanol, ethylene glycol, glycerin, acetone, and tetrahydrofuran are particularly preferable. Here, water-soluble means that the solubility in 100 g of water is 10 g or more.

(Retardation control agent)
In the optical film produced by the method of the present invention , an orientation film may be formed to provide a liquid crystal layer, and polarizing plate processing may be performed by combining the cellulose acylate film and the retardation derived from the liquid crystal layer to provide optical compensation ability. . As the compound to be added for controlling the retardation, an aromatic compound having two or more aromatic rings as described in EP 911,656A2 can be used as a retardation control agent. . Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. An aromatic heterocyclic ring is particularly preferred, and the aromatic heterocyclic ring is generally an unsaturated heterocyclic ring. Of these, compounds having a 1,3,5-triazine ring are particularly preferred.

(Matting agent)
To the optical film produced by the method of the present invention, fine particles such as a matting agent can be added in order to impart slipperiness. Examples of the fine particles include fine particles of an inorganic compound or fine particles of an organic compound. The matting agent is preferably as fine as possible. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include inorganic fine particles such as magnesium silicate and calcium phosphate, and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. In many cases, fine particles such as silicon dioxide are surface-treated with an organic material, but such a material is preferable because it can reduce the haze of the film.

  Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazane, siloxane and the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency. The average particle size of the secondary particles of the fine particles is in the range of 0.05 to 1.0 μm. The average particle size of the secondary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used in the cellulose acylate film in order to produce an unevenness of 0.01 to 1.0 μm on the surface of the cellulose acylate film. The content of the fine particles in the cellulose ester is preferably 0.005 to 0.3% by weight with respect to the cellulose ester.

  Examples of the fine particles of silicon dioxide include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600, etc. manufactured by Nippon Aerosil Co., preferably Aerosil 200V, R972, R972V, R974, R202, and R812. Two or more kinds of these fine particles may be used in combination. When using 2 or more types together, it can mix and use in arbitrary ratios. In this case, fine particles having different average particle sizes and materials, for example, Aerosil 200V and R972V can be used in a weight ratio of 0.1: 99.9 to 99.9: 0.1.

The presence of fine particles in the film used as the matting agent can be used for another purpose to improve the strength of the film. The presence of the fine particles in the film can also improve the orientation of the cellulose ester itself constituting the optical film produced by the method of the present invention .

(Polymer material)
The optical film produced by the method of the present invention may be appropriately selected from polymer materials and oligomers other than cellulose ester and mixed. The polymer material or oligomer is preferably one having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and further preferably 92% or more. The purpose of mixing at least one of polymer materials and oligomers other than cellulose ester includes meanings for controlling viscosity at the time of heating and melting and improving film physical properties after film processing.

  Below, the manufacturing method of the optical film by the solution casting film forming method of this invention is demonstrated.

In the case where the method for producing an optical film according to the present invention is based on a solution casting film forming method, the solution casting film forming method uses a dope (resin solution) in which a thermoplastic resin is dissolved in a solvent as a metal from a casting die. The method includes a step of casting on a rotating drum or a metal rotating endless belt (support) to form a cast film, and peeling the cast film from the support.

  FIG. 3 is a flow sheet showing a specific example of an apparatus for carrying out the method for producing an optical film of the present invention by a solution casting film forming method.

  In the figure, first, in a dissolution vessel (21), for example, a cellulose ester resin is dissolved in a mixed solvent of a good solvent and a poor solvent, and an additive such as a plasticizer or an ultraviolet absorber is added to the resin solution. (Dope) is prepared.

  Next, a support comprising an endless belt made of, for example, a rotationally driven stainless steel, in which the dope adjusted in the melting pot is fed to the casting die (23) by a conduit through, for example, a pressurized metering gear pump (22) and transferred infinitely. (27) The dope is cast from the casting die (23) to the upper casting position.

In the present invention, the surface of a stainless steel endless belt (27) as a metal support contains elements of iron (Fe) and / or chromium (Cr) and component elements on the surface of the metal support (27). The composition ratio satisfies the following relationship (i) and / or (ii), and the thermoplastic resin solution (dope) in the solution casting film forming method is cast on the surface of the metal support (27). To do.

(I) (Fe ₂ O ₃ + FeO) / Fe = 5-50
(Ii) (CrO ₂ + CrO ₃ ) / Cr = 10-50
In the present invention, before casting the resin melt on the surface of a stainless steel endless belt (27) as a metal support, the surface of the metal support (27) is irradiated with atmospheric pressure plasma or excimer ultraviolet rays. The above-described metal oxide film is formed by performing a surface treatment.

  In addition, as a high energy irradiation apparatus which consists of a normal pressure plasma irradiation apparatus and an excimer ultraviolet irradiation apparatus, what was demonstrated in detail in above-mentioned FIG. 5 and FIG.

  For casting the dope by the casting die (23), there is a doctor blade method in which the film thickness of the cast dope film (web) is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll. However, it is preferable to use a pressure die that can adjust the slit shape of the die part and easily make the film thickness uniform. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used.

  In addition, as a casting die (23), the pressure die which can adjust the slit shape of a nozzle | cap | die part and is easy to make a film thickness uniform is preferable. The casting die (23) is usually provided with a decompression chamber (not shown).

  Here, it is preferable that the solid content concentration of the cellulose ester solution (dope) is 15 to 30% by weight. If the solid content concentration of the cellulose ester solution (dope) is less than 15% by weight, sufficient drying cannot be performed on the metal support (27), and a part of the dope film is on the metal support (27) during peeling. This leads to belt contamination and is not preferable. If the solid concentration exceeds 30%, the dope viscosity increases, filter clogging becomes faster in the dope adjustment process, or the pressure increases during casting on the metal support (27), and cannot be extruded. It is not preferable.

  Next, the cast film cast as described above is brought into contact with a metal support (27) made of a rotationally driven endless belt. The endless belt metal support (27) is held by a pair of front and rear drums (25) and (25) and a plurality of intermediate rolls (not shown), and is a drum at both ends of the metal support (27). (25) One or both of (25) is provided with a driving device for applying tension (not shown) to the metal support (27), whereby the metal support (27) is tensioned and stretched. Used in.

  Here, the width of the metal support (27) is preferably 1700 to 2500 mm, the casting width of the cellulose ester solution is preferably 1600 to 2400 mm, and the width of the film after winding is preferably 1400 to 2400 mm. Thereby, the wide optical film for liquid crystal display devices can be manufactured by a metal support body system.

  When an endless belt is used as the metal support (27), the belt temperature at the time of film formation is a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, and the mixed solvent is lower than the boiling point of the lowest boiling solvent. The film can be cast at a temperature, and more preferably in the range of 5 ° C to the boiling point of the solvent-5 ° C. At this time, it is necessary to control the ambient atmospheric humidity above the dew point. In addition, it is preferable that the peripheral speed of a metal support body (27) is 40-200 m / min.

  The dope cast on the surface of the metal support (27) as described above also increases the strength (film strength) of the gel film by promoting the drying until stripping.

  In the system using an endless belt as the metal support (27), on the metal support (27), the web (29) has a film strength that can be peeled from the metal support (27) by the peeling roll (28). In order to dry and solidify, the amount of residual solvent in the web (29) is preferably dried to 150% by weight or less, more preferably 80 to 120% by weight. Moreover, as for the web temperature when peeling a web (29) from a metal support body (27), 0-30 degreeC is preferable. Further, immediately after the web (29) is peeled off from the metal support (27), the temperature once decreases rapidly due to solvent evaporation from the metal support (27) adhesion surface side, and vapor such as water vapor or solvent vapor in the atmosphere is volatilized. Since the sex component tends to condense, the web temperature during peeling is more preferably 5 to 30 ° C.

  Here, the residual solvent amount can be expressed by the following equation.

Residual solvent amount (% by weight) = {(M−N) / N} × 100
In the formula, M is the weight of the web at an arbitrary time point, and N is the weight when a weight M is dried at a temperature of 110 ° C. for 3 hours.

  The dope film (web) (29) formed by the dope cast on the metal support (27) is heated on the metal support (27), and the release roll (28) is removed from the metal support (27). Until the web is peelable.

  To evaporate the solvent, there are a method of blowing air from the web side, a method of transferring heat from the back surface of the metal support (27) by a liquid, a method of transferring heat from the front and back by radiant heat, etc. What is necessary is just to use in combination.

  In the method using an endless belt for the metal support (27), the peeling tension when the metal support (27) and the web (29) are peeled off by the peeling roll (28) is measured by a peeling force as in JIS Z 0237. Peeling with a larger tension than the peeling force obtained in, but this may cause the peeling position to be taken downstream if the peeling tension is equal to the peeling force obtained by the JIS measurement method during high-speed film formation. Therefore, it is done at a high level for stabilization. However, even if the film is formed with the same peeling tension in the process, it is confirmed that the variation in the crossed Nicols transmittance (CNT) of the film is greatly reduced when the peeling force by the JIS measuring method is lowered.

  As the peeling tension value in the process, peeling is usually performed at 50 to 250 N / m. However, in the optical film produced according to the present invention which is made thinner than the conventional one, the web (29) is peeled off at the time of peeling. Since the amount of residual solvent is large and easily stretches in the transport direction, the film tends to shrink in the width direction, and when drying and shrinkage overlap, the edge curls and folds, making it easy to wrinkle, so it can be peeled off. Peeling at a tension of 170 N / m is preferable, and peeling at a minimum tension of 140 N / m is more preferable.

  In the present invention, after the web (29) is dried and solidified on the metal support (27) until it has a peelable film strength, the web (29) is peeled off by the peeling roll (28) and then stretched as described later. The web (29) is stretched in the process tenter (32).

  FIG. 4 is a flow sheet showing another specific example of an apparatus for carrying out the method for producing an optical film of the present invention by a solution casting film forming method. As a metal support, for example, the surface is subjected to a hard chrome plating treatment. The case where the rotational drive drum (26) made of stainless steel is used is illustrated.

  In the present invention, the surface of the rotary drive drum (26) made of stainless steel whose surface as a metal support is subjected to hard chrome plating contains iron (Fe) and / or chromium (Cr) elements. The composition ratio of component elements on the surface of the metal support (26) satisfies the following relationship (i) and / or (ii), and the melt casting film forming method is applied on the surface of the metal support (26). The thermoplastic resin melt or the thermoplastic resin solution (dope) in the solution casting film forming method is cast.

(I) (Fe ₂ O ₃ + FeO) / Fe = 5-50
(Ii) (CrO ₂ + CrO ₃ ) / Cr = 10-50
In the present invention, before casting the resin melt on the surface of the stainless steel rotary drive drum (26) subjected to hard chrome plating on the surface as the metal support, the surface of the metal support is The metal oxide film as described above is formed by surface treatment by atmospheric pressure plasma irradiation or excimer ultraviolet irradiation.

  Since the other points of the optical film manufacturing apparatus in FIG. 4 are the same as those in the optical film manufacturing apparatus in FIG. 3, the same components are denoted by the same reference numerals in the drawings.

  Further, as the high energy irradiation device including the normal pressure plasma irradiation device (40) and the excimer ultraviolet irradiation device (50), those described in detail with reference to FIGS. 5 and 6 are used.

  Next, in the method for producing an optical film by the solution casting method of the present invention, a resin solution (dope) containing a resin such as cellulose ester resin as a main material, a plasticizer, a retardation adjusting agent, an ultraviolet absorber, At least one kind of fine particles and low molecular weight substances and a solvent are included. Hereinafter, these will be described.

  In the method for producing an optical film by the solution casting film forming method of the present invention, various resins can be used as the film material, and among them, cellulose ester is preferable.

  A cellulose ester is a cellulose ester in which a hydroxyl group derived from cellulose is substituted with an acyl group or the like. Examples thereof include cellulose acylates such as cellulose acetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate, and cellulose acetate having an aliphatic polyester graft side chain. Among these, cellulose acetate, cellulose acetate propionate, and cellulose acetate having an aliphatic polyester graft side chain are preferable. Other substituents may be included as long as the effects of the present invention are not impaired.

  As an example of cellulose triacetate, the substitution degree of acetyl group is preferably 2.0 or more and 3.0 or less. By setting the degree of substitution within this range, good moldability can be obtained, and desired in-plane retardation (Ro) and thickness direction retardation (Rt) can be obtained. If the substitution degree of the acetyl group is lower than this range, the heat resistance as a retardation film, particularly the dimensional stability under wet heat may be inferior, and if the substitution degree is too large, the necessary retardation characteristics will not be exhibited. There is a case.

  The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  In the present invention, the number average molecular weight of the cellulose ester is preferably in the range of 60000 to 300000, since the mechanical strength of the resulting film is strong. Furthermore, 70000-200000 are preferable.

  In the present invention, various additives can be added to the cellulose ester.

  In the method for producing an optical film according to the present invention, it is preferable to use a dope composition containing a cellulose ester and an additive for reducing the thickness direction retardation (Rt).

  In the present invention, reducing the thickness direction retardation (Rt) of the cellulose ester film is important in terms of increasing the viewing angle of the liquid crystal display device operating in the IPS mode. In the present invention, such thickness direction retardation is used. The following are mentioned as an additive which reduces (Rt).

  In general, retardation of a cellulose ester film appears as the sum of retardation derived from a cellulose ester and retardation derived from an additive. Therefore, an additive for reducing the retardation of the cellulose ester is an additive that disturbs the orientation of the cellulose ester and is difficult to orient itself and / or has a small polarizability anisotropy. It is a compound that effectively reduces it. Therefore, as an additive for disturbing the orientation of the cellulose ester, an aliphatic compound is preferable to an aromatic compound.

  Here, as a specific retardation reducing agent, for example, a polyester represented by the following general formula (1) or (2) may be mentioned.

General formula (1) B1- (GA-) mG-B1
General formula (2) B2- (GA-) nG-B2
In the above formula, B1 represents a monocarboxylic acid component, B2 represents a monoalcohol component, G represents a divalent alcohol component, A represents a dibasic acid component, and these are synthesized. B1, B2, G, and A are all characterized by not containing an aromatic ring. m and n represent the number of repetitions.

  There is no restriction | limiting in particular as a monocarboxylic acid component represented by B1, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, etc. can be used.

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

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

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

  The monoalcohol component represented by B2 is not particularly limited, and known alcohols can be used. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12.

  Examples of the divalent alcohol component represented by G include the following, but the present invention is not limited thereto. For example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6- Hexanediol, 1,5-pentylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and the like can be mentioned. Among these, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, diethylene glycol, and triethylene glycol are preferred, and 1,3-propylene glycol, 1,4-butylene glycol Lumpur, 1,6-hexanediol, diethylene glycol is preferably used.

  The dibasic acid (dicarboxylic acid) component represented by A is preferably an aliphatic dibasic acid or an alicyclic dibasic acid. Examples of the aliphatic dibasic acid include malonic acid, succinic acid, glutaric acid, and adipic acid. , Pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid and the like, in particular, aliphatic carboxylic acid having 4 to 12 carbon atoms, at least one selected from these To do. That is, two or more dibasic acids may be used in combination.

  The number of repetitions m and n in the above general formula (1) or (2) is preferably 1 or more and 170 or less.

  The weight average molecular weight of the polyester is preferably 20000 or less, and more preferably 10,000 or less. In particular, polyesters having a weight average molecular weight of 500 to 10,000 have good compatibility with cellulose esters, and neither evaporation nor volatilization occurs during film formation.

  Polycondensation of polyester is carried out by a conventional method. For example, a direct reaction of the dibasic acid and glycol, a hot melt condensation method by the polyesterification reaction or transesterification reaction of the dibasic acid or alkyl esters thereof, for example, a methyl ester of dibasic acid and glycols, or Although it can be easily synthesized by any method of dehydrohalogenation reaction between acid chloride of these acids and glycol, it is preferable that polyester having a weight average molecular weight not so large is by direct reaction. Polyester having a high distribution on the low molecular weight side has a very good compatibility with the cellulose ester, and after forming the film, a moisture permeability is small, and a cellulose ester film rich in transparency can be obtained.

  The method for adjusting the molecular weight is not particularly limited, and a conventional method can be used. For example, although depending on the polymerization conditions, the amount of these monovalent compounds can be controlled by a method of blocking the molecular ends with a monovalent acid or monovalent alcohol. In this case, a monovalent acid is preferable from the viewpoint of polymer stability. For example, acetic acid, propionic acid, butyric acid, etc. can be mentioned, but during the polycondensation reaction, it is not distilled out of the system, but is stopped and such monovalent acid is removed from the reaction system. The one that is easy to accumulate is selected. These may be used in combination. In the case of direct reaction, the weight average molecular weight can also be adjusted by measuring the timing of stopping the reaction by the amount of water distilled off during the reaction. In addition, it can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged, or can be adjusted by controlling the reaction temperature.

  The polyester represented by the general formula (1) or (2) is preferably contained in an amount of 1 to 40% by weight based on the cellulose ester. It is particularly preferable to contain 5 to 15% by weight.

  In the present invention, examples of the additive for reducing the thickness direction retardation (Rt) include the following.

The dope used in the method for producing an optical film of the present invention is mainly a cellulose ester, a polymer as an additive for reducing retardation (Rt) (a polymer obtained by polymerizing an ethylenically unsaturated monomer, an acrylic polymer). And an organic solvent.

  In the present invention, in order to synthesize a polymer as an additive for reducing the thickness direction retardation (Rt), it is difficult to control the molecular weight in normal polymerization, and a method that can make the molecular weight as uniform as possible by a method that does not increase the molecular weight too much. It is desirable to use it. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method using a chain transfer agent such as carbon tetrachloride, a method using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and JP-A No. 2000-128911 or JP-A No. 2000-344823. Examples include a compound having a single thiol group and a secondary hydroxyl group as described in the publication, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. In particular, the method described in the publication is preferred.

  In the present invention, monomers as monomer units constituting a polymer as an additive for reducing useful thickness direction retardation (Rt) are listed below, but are not limited thereto.

  As the ethylenically unsaturated monomer unit constituting the polymer as an additive for reducing the thickness direction retardation (Rt) obtained by polymerizing an ethylenically unsaturated monomer, first, as a vinyl ester, for example, vinyl acetate, propionic acid, etc. Vinyl, vinyl butyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, Examples include vinyl crotonate, vinyl sorbate, vinyl benzoate, and vinyl cinnamate.

  Next, as acrylate ester, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate ( n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl) ), Acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2- Dorokishibuchiru) acrylate-p-hydroxymethylphenyl,-p-acrylic acid (2-hydroxyethyl) phenyl and the like; as methacrylic acid ester, the acrylic acid ester include those changed to methacrylic acid esters.

  Furthermore, examples of the unsaturated acid include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid, and the like.

  The polymer composed of the above monomers may be a copolymer or a homopolymer, and is preferably a vinyl ester homopolymer, a vinyl ester copolymer, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester.

  In the present invention, an acrylic polymer (simply referred to as an acrylic polymer) refers to a homopolymer or copolymer of acrylic acid or alkyl methacrylate having no monomer unit having an aromatic ring or a cyclohexyl group.

  Examples of the acrylate monomer having no aromatic ring and cyclohexyl group include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid 2-methoxy-ethyl), acrylic acid (2-ethoxyethyl), or the acrylic acid ester may include those obtained by changing the methacrylic acid ester.

  The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but it is preferable that the acrylic acid methyl ester monomer unit has 30% by weight or more, and the methacrylic acid methyl ester monomer unit has 40% by weight or more. It is preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  Polymers obtained by polymerizing the above ethylenically unsaturated monomers and acrylic polymers are both highly compatible with cellulose ester, excellent in productivity without evaporation and volatilization, and retainability as a protective film for polarizing plates The moisture permeability is small, and the dimensional stability is excellent.

  In the present invention, an acrylic acid or methacrylic acid ester monomer having a hydroxyl group is not a homopolymer but a constituent unit of a copolymer. In this case, the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is preferably contained in the acrylic polymer in an amount of 2 to 20% by weight.

  In the method for producing an optical film of the present invention, the dope composition contains a cellulose ester and an acrylic polymer having a weight average molecular weight of 500 or more and 3000 or less as an additive for reducing the thickness direction retardation (Rt). Is preferred.

  In the method for producing an optical film of the present invention, the dope composition contains a cellulose ester and an acrylic polymer having a weight average molecular weight of 5000 or more and 30000 or less as an additive for reducing the thickness direction retardation (Rt). It is preferable.

  In the present invention, if the weight average molecular weight of the polymer as an additive for reducing the thickness direction retardation (Rt) is 500 or more and 3000 or less, or if the polymer has a weight average molecular weight of 5000 or more and 30000 or less, the cellulose ester Is compatible with the material, and neither evaporation nor volatilization occurs during film formation. Moreover, the transparency of the cellulose ester film after film formation is excellent, the moisture permeability is extremely low, and it exhibits excellent performance as a protective film for polarizing plates.

  In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used as an additive for reducing the thickness direction retardation (Rt). The monomer unit having a hydroxyl group is the same as the monomer described above, but acrylic acid or methacrylic acid ester is preferable. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3 -Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, or these acrylic acids. The thing replaced by methacrylic acid can be mentioned, Preferably, it is 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. The acrylic acid ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is preferably contained in the polymer in an amount of 2 to 20% by weight, more preferably 2 to 10% by weight.

  The polymer as described above containing 2 to 20% by weight of the monomer unit having the above hydroxyl group, of course, is excellent in compatibility with cellulose ester, retention, dimensional stability, and low moisture permeability. It is particularly excellent in adhesion with a polarizer as a protective film for a polarizing plate, and has an effect of improving the durability of the polarizing plate.

  In the present invention, it is preferable that at least one terminal of the main chain of the polymer has a hydroxyl group. The method of having a hydroxyl group at the end of the main chain is not particularly limited as long as it has a hydroxyl group at the end of the main chain, but radical polymerization having a hydroxyl group such as azobis (2-hydroxyethylbutyrate). A method of using an initiator, a method of using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method of using a polymerization terminator having a hydroxyl group, a method of having a hydroxyl group at the terminal by living ion polymerization, Using a polymerization catalyst in which a compound having one thiol group and a secondary hydroxyl group as disclosed in JP-A No. 2000-128911 or JP-A No. 2000-344823, or a combination of the compound and an organometallic compound is used. It can be obtained by a polymerization method or the like, and the method described in the publication is particularly preferable. The polymer produced by the method related to the description in this publication is commercially available as Act Flow Series manufactured by Soken Chemical Co., Ltd., and can be preferably used.

  In the present invention, the polymer having a hydroxyl group at the terminal and / or the polymer having a hydroxyl group in a side chain has an advantage of significantly improving the compatibility and transparency of the polymer with respect to the cellulose ester.

  In the present invention, useful additives for reducing the thickness direction retardation (Rt) include, in addition to the above, for example, an ester compound of diglycerin polyhydric alcohol and fatty acid described in JP-A No. 2000-63560, An ester or ether compound of a hexose sugar alcohol described in JP-A-2001-247717, a trialiphatic alcohol phosphate compound described in JP-A-2004-315613, and a general formula (1) described in JP-A-2005-41911 A phosphoric acid ester compound described in JP-A No. 2004-315605, a styrene oligomer described in JP-A No. 2005-105139, and a polymer of a styrene monomer described in JP-A No. 2005-105140. .

  In the method for producing an optical film according to the present invention, an organic solvent having good solubility with respect to the cellulose derivative is referred to as a good solvent, and has a main effect on dissolution. Organic) solvent or main (organic) solvent.

  Examples of good solvents include ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethers such as tetrahydrofuran (THF), 1,4-dioxane, 1,3-dioxolane, 1,2-dimethoxyethane, formic acid Esters such as methyl, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride And 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferable.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by weight of an alcohol having 1 to 4 carbon atoms. After casting the dope on the support, the solvent starts to evaporate and the alcohol ratio increases, so that the web (referred to as the dope film after casting the cellulose derivative dope on the support is called web Is used as a gelling solvent that makes the web strong and makes it easy to peel off from the support, or when these ratios are small, dissolve the cellulose derivative of the non-chlorine organic solvent. There is also a role to promote.

  Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and propylene glycol monomethyl ether. Of these, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, good drying properties, and no toxicity. These organic solvents alone are not soluble in cellulose derivatives and are called poor solvents.

  The most preferable solvent for dissolving the cellulose derivative, which is a preferable polymer compound satisfying such conditions, at a high concentration is a mixed solvent having a ratio of methylene chloride: ethyl alcohol of 95: 5 to 80:20. Alternatively, a mixed solvent of methyl acetate: ethyl alcohol 60:40 to 95: 5 is also preferably used.

In the present invention, a plasticizer that imparts processability, flexibility, and moisture resistance to the film, fine particles (matting agent) that impart slipperiness to the film, an ultraviolet absorber that imparts an ultraviolet absorbing function, and an oxidation that prevents deterioration of the film An inhibitor or the like may be included.

  The plasticizer used in the present invention is not particularly limited. However, a cellulose derivative or a reactive metal compound capable of hydrolytic polycondensation can be used so as not to cause haze, bleed out or volatilize from the film. It preferably has a functional group capable of interacting with the condensate by hydrogen bonding or the like.

  Examples of such functional groups include hydroxyl groups, ether groups, carbonyl groups, ester groups, carboxylic acid residues, amino groups, imino groups, amide groups, imide groups, cyano groups, nitro groups, sulfonyl groups, sulfonic acid residues, Examples thereof include a phosphonyl group and a phosphonic acid residue, and a carbonyl group, an ester group and a phosphonyl group are preferred.

  Examples of such plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol ester plasticizers, glycolate plasticizers. Agents, citric acid ester plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, etc. can be preferably used, but polyhydric alcohol ester plasticizers, glycolate plasticizers are particularly preferred. And non-phosphate ester plasticizers such as polycarboxylic acid ester plasticizers.

  The polyhydric alcohol ester is composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

The polyhydric alcohol used in the present invention is represented by the following general formula (3) .

Formula (3) R1- (OH) n
(However, R1 represents an n-valent organic group, and n represents a positive integer of 2 or more.)
Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Examples of preferred polyhydric alcohols include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, gallium Examples include lactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

In the present invention, the monocarboxylic acid used in the polyhydric alcohol ester is not particularly limited, and known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid and the like can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

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

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

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

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

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. Examples thereof include aromatic monocarboxylic acids and derivatives thereof, and benzoic acid is particularly preferable.

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

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

  The glycolate plasticizer is not particularly limited, but a glycolate plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. As preferred glycolate plasticizers, for example, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like can be used.

  For phosphate plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenylbiphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, and the like can be used, but in the present invention, it is preferable that a phosphate ester plasticizer is not substantially contained.

  Here, “substantially does not contain” means that the content of the phosphoric ester plasticizer is less than 1% by weight, preferably 0.1% by weight, and particularly preferably not added.

  These plasticizers can be used alone or in combination of two or more.

  The amount of the plasticizer used is preferably 1 to 20% by weight. 6 to 16% by weight is further preferable, and 8 to 13% by weight is particularly preferable. If the amount of the plasticizer used is less than 1% by weight relative to the cellulose derivative, the effect of reducing the moisture permeability of the film is small, so this is not preferred. If it exceeds 20% by weight, the plasticizer bleeds out from the film, and the film This is not preferable because the physical properties of the resin deteriorate.

In the present invention, it is preferable to add fine particles such as a matting agent to the cellulose derivative in order to impart slipperiness. Examples of the fine particles include fine particles of an inorganic compound or fine particles of an organic compound.

  Examples of the fine particles of the inorganic compound include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide and the like. Of these, fine particles of a compound containing a silicon atom are preferred, and fine silicon dioxide particles are particularly preferred. Examples of the silicon dioxide fine particles include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, R805, OX50, and TT600 manufactured by Aerosil Co., Ltd.

  Examples of the organic compound fine particles include fine particles such as acrylic resin, silicone resin, fluorine compound resin, and urethane resin.

  The primary particle size of the fine particles is not particularly limited, but the average particle size in the film is preferably about 0.05 to 5.0 μm. More preferably, it is 0.1-1.0 micrometer.

  When the cellulose ester film is observed with an electron microscope or an optical microscope, the average particle diameter of the fine particles indicates an average value of the lengths in the major axis direction of the particles at the observation position of the film. As long as the particles are observed in the film, they may be primary particles or secondary particles in which the primary particles are aggregated, but most of the particles that are usually observed are secondary particles.

As an example of the measurement method, 10 vertical cross-sectional photographs are taken at random for each film, and the number of particles in 100 μm ² whose major axis length is in the range of 0.05 to 5 μm for each cross-sectional photograph. Count. The average value of the major axis lengths of the particles counted at this time is obtained, and a value obtained by averaging the average values of 10 locations is defined as the average particle size.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size added to the film often change, and what is important is that the fine particles are finally combined with the cellulose ester in the film to aggregate. And controlling the particle size formed.

  Here, if the average particle size of the fine particles exceeds 5 μm, haze deterioration or the like may be observed, or it may cause a failure in a wound state as a foreign matter. Moreover, when the average particle diameter of fine particles is less than 0.05 μm, it becomes difficult to impart slipperiness to the film.

  The fine particles are used by adding 0.04 to 0.5% by weight to the cellulose ester. Preferably, 0.05 to 0.3% by weight, more preferably 0.05 to 0.25% by weight is added. When the amount of fine particles added is 0.04% by weight or less, the film surface roughness becomes too smooth and blocking occurs due to an increase in the friction coefficient. If the amount of fine particles added exceeds 0.5% by weight, the coefficient of friction on the film surface will be too low, causing winding misalignment during winding, and the transparency of the film will be low and haze will be high. The above range is essential because it has no value as a film.

  For the dispersion of the fine particles, it is preferable to treat the composition in which the fine particles and the solvent are mixed with a high-pressure dispersion apparatus. The high-pressure dispersion apparatus used in the present invention is an apparatus that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.

It is preferable that the maximum pressure condition inside the apparatus is 980 N / cm ² or more in a thin tube having a tube diameter of 1 to 2000 μm, for example, by processing with a high-pressure dispersion apparatus. More preferably, the maximum pressure condition inside the apparatus is 1960 N / cm ² or more. Further, at that time, those having a maximum reaching speed of 100 m / sec or more and those having a heat transfer speed of 100 kcal / hr or more are preferable.

  Examples of the high-pressure dispersing device as described above include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer, and other manton gorin type high-pressure dispersing devices such as those manufactured by Izumi Food Machinery. A homogenizer etc. are mentioned.

  In the present invention, the fine particles are dispersed in a solvent containing 25 to 100% by weight of a lower alcohol, then mixed with a dope in which a cellulose ester (cellulose derivative) is dissolved in a solvent, and the mixed solution is allowed to flow on the support. A cellulose ester film is obtained which is formed by stretching and drying.

  Here, the content ratio of the lower alcohol is preferably 50 to 100% by weight, more preferably 75 to 100% by weight.

  Examples of lower alcohols preferably include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose ester.

  The fine particles are dispersed in the solvent at a concentration of 1 to 30% by weight. Dispersing at a concentration higher than this is not preferable because the viscosity increases rapidly. The concentration of the fine particles in the dispersion is preferably 5 to 25% by weight, more preferably 10 to 20% by weight.

  The ultraviolet absorbing function of the film is preferably imparted to various optical films such as a polarizing plate protective film, a retardation film, and an optical compensation film from the viewpoint of preventing deterioration of the liquid crystal. For such an ultraviolet absorbing function, a material that absorbs ultraviolet rays may be included in the cellulose derivative, and a layer having an ultraviolet absorbing function may be provided on a film made of the cellulose derivative.

  Examples of ultraviolet absorbers that can be used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. A benzotriazole-based compound with little coloring is preferable. In addition, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used.

  As the ultraviolet absorber, those having excellent absorption ability of ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer or liquid crystal and those having little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. preferable.

  Specific examples of useful UV absorbers in the present invention include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-). Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) ) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2- Methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, 2- (2'-hydroxy) 3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl -3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5 A mixture of-(5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  Further, as commercially available products of ultraviolet absorbers, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by Ciba Specialty Chemicals) can be preferably used.

  Specific examples of the benzophenone compounds that are ultraviolet absorbers that can be used in the present invention include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5- Examples thereof include, but are not limited to, sulfobenzophenone and bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane).

  In this invention, the compounding quantity of these ultraviolet absorbers has the preferable range of 0.01 to 10 weight% with respect to a cellulose ester (cellulose derivative), and also 0.1 to 5 weight% is preferable. If the amount of the UV absorber used is too small, the UV absorbing effect may be insufficient, and if the amount of the UV absorber used is too large, the transparency of the film may be deteriorated. The ultraviolet absorber is preferably one having high heat stability.

Moreover, the ultraviolet absorber which can be used for the manufacturing method of the optical film of this invention is a polymeric ultraviolet absorber (or ultraviolet-absorbing polymer) as described in Unexamined-Japanese-Patent No. 6-148430 and Unexamined-Japanese-Patent No. 2002-47357. Can be preferably used. In particular, it is represented by the general formula (1) described in JP-A-6-148430, the general formula (2), or the general formulas (3), (6), and (7) described in JP-A-2002-47357. A polymer ultraviolet absorber is preferably used.

  In general, the antioxidant is also referred to as a deterioration inhibitor, but is preferably contained in a cellulose ester film as an optical film. That is, when a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film as an optical film may be deteriorated. The antioxidant has a role of delaying or preventing the film from being decomposed by, for example, halogen in the residual solvent in the film or phosphoric acid of the phosphoric acid plasticizer, so that it is preferably contained in the film. .

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably 1 ppm to 1.0% by weight, more preferably 10 to 1000 ppm by weight with respect to the cellulose derivative.

  In addition, in the apparatus which implements the manufacturing method of the optical film of the present invention shown in FIG. 3 and FIG. 4, the stretching step is a film for a liquid crystal display device. A tenter method in which the film is fixed and stretched is preferable in order to improve the flatness and dimensional stability of the film.

  It is preferable that the residual solvent amount of the web (film) (29) immediately before entering the tenter (32) in the stretching step is 10 to 35% by weight.

In the present invention, the stretch ratio of the web in the tenter (32) in the stretching process is 3 to 100%, preferably 5 to 80%, and more preferably 5 to 60%. Moreover, the temperature of the warm air blown from the warm air blowing slit port in the tenter (32) is 100 to 200 ° C, preferably 110 to 190 ° C, and more preferably 115 to 185 ° C.

  A drying device (30) is preferably provided after the tenter (32) in the stretching step. In the drying device (30), the web (29) is meandered by a plurality of conveying rolls arranged in a staggered manner as viewed from the side, and the web (29) is dried in the meantime. The film transport tension in the drying apparatus (30) is affected by the physical properties of the dope, the amount of residual solvent in the peeling and film transport process, the drying temperature, etc., but the film transport tension during drying is 10 to 300 N. / M width, and 20 to 270 N / m width is more preferable.

  The means for drying the web (film) (29) is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to dry with hot air from the viewpoint of simplicity, for example, it is dried by the drying air (31) blown from the warm air inlet at the front portion of the bottom of the drying device (30), and is dried on the ceiling of the drying device (30). It is dried by exhaust air being discharged from the outlet of the rear portion. The temperature of the drying air (31) is preferably 40 to 160 ° C, and more preferably 50 to 160 ° C in order to improve the flatness and dimensional stability.

  These steps from casting to post-drying may be performed in an air atmosphere or in an inert gas atmosphere such as nitrogen gas. In this case, it goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  For example, a cellulose ester film that has finished the transport drying process is generally processed to form an emboss on the film by an embossing apparatus before the introduction to the winding process.

  Here, the height h (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. . Embossing may be formed on both sides of the film. In this case, the height h1 + h2 (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. For example, when the film thickness is 40 μm, the emboss height h1 + h2 (μm) is set to 2 to 12 μm. The emboss width is set to 5 to 30 mm.

  The film after drying is wound up by a winding device (33) to obtain the original roll of the optical film. A film having good dimensional stability can be obtained by setting the residual solvent amount of the film to be dried to 0.5% by weight or less, preferably 0.1% by weight or less.

  The winding method of the film may be a generally used winder, and there are methods for controlling the tension such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc. Use it properly.

  The film may be bonded to the winding core (winding core) by either a double-sided adhesive tape or a single-sided adhesive tape.

In the present invention, the optical film preferably has a width of 1200 to 2500 mm after winding.

  In this invention, the film thickness after drying of a cellulose-ester film has the preferable range of 20-150 micrometers as a finished film from a viewpoint of thickness reduction of a liquid crystal display device. Here, the film thickness after drying refers to a film in which the amount of residual solvent in the film is 0.5% by weight or less.

  Here, when the film thickness of the cellulose ester film after winding is too thin, for example, the required strength as a protective film for a polarizing plate may not be obtained. If the film thickness is too thick, the advantage of thinning the film becomes less than the conventional cellulose ester film. In order to adjust the film thickness, the dope concentration, the pumping amount, the slit gap of the die of the casting die, the extrusion pressure of the casting die, the speed of the support, etc. are controlled so as to obtain the desired thickness. Is good. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  In the process from immediately after casting through the solution casting film-forming method to drying, the atmosphere in the drying apparatus may be air, but may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. . However, of course, the danger of the explosion limit of the evaporating solvent in the dry atmosphere must always be considered.

  In the present invention, the cellulose ester film preferably has a moisture content of 0.1 to 5%, more preferably 0.3 to 4%, and even more preferably 0.5 to 2%.

  In the present invention, the cellulose ester film desirably has a transmittance of 90% or more, more preferably 92% or more, and further preferably 93% or more.

In addition, the optical film produced by the method of the present invention has a haze of 0.3 to 2.0 when three sheets are stacked. According to the present invention, the haze of the film is very low. It has optical properties with excellent transparency and flatness.

  Here, the haze of the optical film may be measured using, for example, a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.) according to a method defined in JIS K 7105.

  Moreover, the tensile elastic modulus in the machine direction (MD direction) of the cellulose ester film produced by the method for producing an optical film according to the present invention is 1500 to 3500 MPa, and the tensile elastic modulus in the direction perpendicular to the machine direction (TD direction) is It is preferably 3000 MPa to 4500 MPa, and the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction of the film is preferably 1.40 to 1.90.

  Here, if the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction of the optical film is less than 1.40, the sag of the central portion becomes large in winding a film having a width exceeding 1650 mm, and Since sticking increases, it is not preferable. Further, when the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction exceeds 1.90, warpage after overheating in the polarizing plate occurs, or the backlight is heated by the heat of the backlight when incorporated in a liquid crystal panel. Since the dimensional change behavior of the polarizing plate on the side and the surface side is greatly different, unevenness occurs at the corner, which is not preferable.

  As a specific method for measuring the tensile modulus of elasticity in the MD direction and TD direction of the film, for example, the method of JIS-K7217 can be mentioned.

  That is, using a tensile tester (TG-2KN, manufactured by Minebea Co., Ltd.), a sample was set at a chucking pressure: 0.25 MPa, a distance between marked lines: 100 ± 10 mm, and a pulling speed: 100 ± 10 mm / min. Pull on. As a result, from the obtained tensile stress-strain curve, the elastic modulus calculation start point is 10N, the end point is 30N, and the tangent line drawn between them is extrapolated to calculate the elastic modulus.

In the present invention, in the optical film, the in-plane retardation (Ro) defined by the following formula is 30 to 300 nm under the conditions of a temperature of 23 ° C. and a humidity of 55% RH, and the thickness direction retardation (Rt) is a temperature of 23 ° C. It is preferable that it is 70-400 nm on the conditions of humidity 55% RH.

Ro = (nx−ny) × d
Rt = {(nx + ny) / 2−nz} × d
In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, and nz is the film. The refractive index in the thickness direction (refractive index measured at a wavelength of 590 nm), d represents the thickness (nm) of the film.

  The retardation values Ro and Rt can be measured using an automatic birefringence meter. For example, using KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), the wavelength can be obtained at 590 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH.

As for the thickness of the film manufactured with the manufacturing method of said optical film of this invention , 30-200 micrometers is preferable.

The optical film manufactured by the method of the present invention is a film placed between two polarizing plates orthogonal to each other, the transmittance of the transmitted light having a wavelength of 600 nm is measured in a crossed Nicol state, and the transmission The variation in light transmittance is 2 × 10 ^{−5 to} 60 × 10 ⁻⁵ (%) .
Here, it is preferable that the variation in transmittance in the crossed Nicol state of the transmitted light having a wavelength of 600 nm of the optical film is smaller, and if the variation in transmittance exceeds 60 × 10 ⁻⁵ (%), transparency, flatness This is not preferable because the properties are lowered.

According to the optical film produced by the method of the present invention, the releasability (peelability) of the casting film (web) from the cooling roll or the support surface is improved, and a very smooth peelability is obtained. Since the variation in the width direction of the peeling position is reduced, the optical film is excellent in transparency and flatness because the variation in the crossed Nicols transmittance is greatly reduced.

  The optical film targeted by the present invention is a functional film used for various displays such as a liquid crystal display, a plasma display, and an organic EL display, particularly a liquid crystal display. A polarizing plate protective film, a retardation film, an antireflection film, It includes an optical compensation film such as a brightness enhancement film and a viewing angle expansion.

The optical film produced by the method of the present invention is preferably used for a liquid crystal display member, specifically a protective film for a polarizing plate. In particular, in a protective film for a polarizing plate that has strict requirements for both moisture permeability and dimensional stability, the optical film produced by the method of the present invention is preferably used.

By using the protective film for polarizing plates made of the optical film produced by the method of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning.

  By the way, the polarizing film is a film that has been conventionally stretched by treating a film that can be stretched and oriented, such as a polyvinyl alcohol film, with a dichroic dye such as iodine. Since the polarizing film itself does not have sufficient strength and durability, a polarizing plate is generally obtained by adhering a cellulose ester film having no anisotropy as a protective film to both surfaces thereof.

  The polarizing plate may be prepared by laminating the optical film produced by the method of the present invention as a retardation film, and the optical film produced by the method of the present invention is a retardation film and a protective film. Alternatively, it may be produced by directly bonding to a polarizing film. The method of bonding is not particularly limited, but can be performed with an adhesive composed of an aqueous solution of a water-soluble polymer. The water-soluble polymer adhesive is preferably a completely saponified polyvinyl alcohol aqueous solution. Furthermore, a long polarizing plate can be obtained by laminating a long polarizing film stretched in the longitudinal direction and treated with a dichroic dye and a long retardation film produced by the method of the present invention. . A polarizing plate is a sticking type in which a peelable sheet is laminated on one or both sides thereof via a pressure sensitive adhesive layer (for example, an acrylic pressure sensitive adhesive layer). Or the like can be easily attached).

  The polarizing plate thus obtained can be used for various display devices. In particular, a liquid crystal display device using a VA mode liquid crystal molecule in which liquid crystal molecules are substantially vertically aligned when no voltage is applied, or a TN mode liquid crystal cell in which liquid crystal molecules are substantially horizontal and twisted when no voltage is applied. Is preferred.

  By the way, a polarizing plate can be produced by a general method. For example, there is a method in which an optical film or a cellulose ester film is subjected to alkali saponification treatment, and a polyvinyl alcohol film is bonded to both surfaces of a polarizing film produced by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. is there. The alkali saponification treatment refers to a treatment of immersing the cellulose ester film in a high-temperature strong alkaline solution in order to improve the wetness of the water-based adhesive and improve the adhesiveness.

  The optical film produced by the method of the present invention includes a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optical anisotropic layer, a liquid crystal layer, an alignment layer, an adhesive layer, Various functional layers such as an adhesive layer and an undercoat layer can be provided. These functional layers can be provided by a method such as coating or vapor deposition, sputtering, plasma CVD, or atmospheric pressure plasma treatment.

  Thus, the obtained polarizing plate is provided in the one or both surfaces of a liquid crystal cell, and a liquid crystal display device is obtained using this.

A liquid crystal display device includes a liquid crystal cell in which rod-like liquid crystal molecules are sandwiched between a pair of glass substrates, a polarizing film disposed so as to sandwich the liquid crystal cell, and two polarizing plates each including a transparent protective layer disposed on both sides thereof. It is what you have.

  By using the protective film for polarizing plates made of the optical film produced by the method of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning. Furthermore, a liquid crystal display device using this polarizing plate or retardation film can maintain stable display performance over a long period of time.

  The optical film produced by the method of the present invention can also be used as a base material for an antireflection film or an optical compensation film.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

Examples 1-4
First, the manufacturing method of the optical film of this invention was implemented by the melt casting film forming method.

(Preparation of pellets)
Cellulose acetate propionate 100 parts by weight (acetyl group substitution degree 1.95, propionyl group substitution degree 0.7,
Number average molecular weight 75000, temperature 130 ° C., dried for 5 hours,
Glass transition temperature point Tg = 174 ° C.)
10 parts by weight of plasticizer [trimethylolpropane tris (3,4,5-trimethoxybenzoate)]
1 part by weight of antioxidant (IRGANOX-1010, manufactured by Ciba Specialty Chemicals)
1 part by weight of antioxidant (Sumilizer GP, manufactured by Sumitomo Chemical Co., Ltd.)
To the above material, 0.05 part by weight of silica particles (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.) and 0.5 part by weight of an ultraviolet absorber (TINUVIN360, manufactured by Ciba Specialty Chemicals) are added as a matting agent, and nitrogen gas is added. After mixing with an enclosed V-shaped mixer for 30 minutes, it was melted at 240 ° C. using a twin screw extruder (PCM30, manufactured by Ikegai Co., Ltd.) equipped with a strand die, and a cylindrical shape having a length of 4 mm and a diameter of 3 mm. A pellet was prepared. The shear rate at this time was set to 25 / second.

(Production of film)
Using the above molten resin, a cellulose acetate propionate film having a thickness of 40 μm was produced as follows.

  Film formation was performed with the manufacturing apparatus shown in FIG. Referring to the figure, the first cooling roll (5) and the second cooling roll (7) were made of stainless steel having a diameter of 40 cm, and the surface was hard chrome plated. Further, oil for temperature adjustment (cooling fluid) was circulated inside to control the roll surface temperature.

  Before casting the resin melt on the surface of the first chill roll (5) made of stainless steel plated with hard chrome as a metal support, the surface of the first chill roll (5) is exposed to atmospheric pressure plasma. Processed. The integrated time of the atmospheric pressure plasma irradiation treatment was 0.1 sec in Example 1, 10 sec in Example 2, 300 sec in Example 3, and 3000 sec in Example 4.

Here, the amount of reaction gas used in the atmospheric pressure plasma irradiation apparatus (40) was set to 1 m ³ per 1 m of irradiation width. The composition of the mixed gas (reactive gas) used for the plasma treatment is described below. The atmospheric pressure was 1.0 atm.

Nitrogen 99.8% by volume
Oxygen 0.2% by volume
Thereby, the component element composition ratio: (CrO ₂ + CrO ₃ ) / Cr on the surface of the first cooling roll (5) made of stainless steel subjected to hard chrome plating was as shown in Table 1.

  The elastic touch roll (6) had a diameter of 20 cm, the inner cylinder and the outer cylinder were made of stainless steel, and the outer cylinder surface was subjected to hard chrome plating. The wall thickness of the outer cylinder was 2 mm, and oil for cooling (cooling fluid) was circulated in the space between the inner cylinder and the outer cylinder to control the surface temperature of the elastic touch roll (6).

  The obtained pellets (water content 50 ppm) were melted in a single screw extruder (1) and subjected to pressure filtration using a leaf disk type metal filter (2).

  A casting die (4) having a lip clearance of 1.0 mm and a lip portion average surface roughness Ra of 0.01 μm was used as the casting die (4). Further, silica fine particles as a slip agent were added from the hopper opening in the middle of the extruder so as to be 0.1 parts by weight.

  The resin melt was melt-extruded from the casting die (4) into a film at a melting temperature of 250 ° C.

  And in this Example 1, the hard chromium plating stainless steel which irradiated the plasma by the said normal-pressure plasma irradiation apparatus (40) at the speed | rate of 20 m / min from the casting die (4). Cast on the surface of the first cooling roll (5). At this time, the cast film was brought into contact with the first cooling roll (5) having a surface temperature of 100 ° C. at a draw ratio of 10 to obtain a cast film having a thickness of 100 μm.

  The glass transition temperature (Tg) of the cellulose acetate propionate film of Example 1 is 136 ° C., and the glass transition temperature of the cast film extruded from the casting die (4) is determined by using DSC6200 manufactured by Seiko Corporation. It was measured by DSC method (in nitrogen, temperature rising temperature 10 ° C./min).

  Further, the cast film (film) was pressed on the first cooling roll (5) by the elastic touch roll (6) having a metal surface at a linear pressure of 10 kg / cm. The film temperature on the touch roll (6) side at the time of pressing was 180 ° C. ± 1 ° C.

  In addition, the surface temperature of the 2nd cooling roll (7) was 30 degreeC. And the surface temperature of each roll of an elastic touch roll (6), a 1st cooling roll (5), and a 2nd cooling roll (7) is with respect to a rotation direction from the position where a cast film (film) contact | connects a roll first. The average value obtained by measuring the temperature of the roll surface at a position 90 ° before 10 points in the width direction using a non-contact thermometer was defined as the surface temperature of each roll.

  The cooled and solidified film (10) peeled from the third cooling roll (8) by the peeling roll (9) is guided to a stretching device (12) through a dancer roll (film tension adjusting roll) (11), where the film ( 10) is stretched in the transverse direction (width direction). By this stretching, the molecules in the film are oriented.

  After stretching, the end of the film is slit to a product width by a slitter (13) and cut off, and then knurled (embossed) by a knurling device comprising an embossing ring (14) and a back roll (15). It applied to the both ends of the film, and it wound up with the winding apparatus (16), and produced three types of cellulose acetate propionate films with a film thickness of 40 micrometers.

Examples 5-8
(Excimer UV treatment)
In the same manner as in Example 1, cellulose acetate propionate films are produced. In these Examples, an excimer ultraviolet irradiation device (50) was used as a high energy irradiation device. The excimer ultraviolet irradiation device (50) is as shown in FIG. 6, and the irradiance is 40 mW / cm ^{2 in} quartz glass (q) having a length of about 300 mm in the transport direction of the first cooling roll (5). Used was an apparatus containing four excimer ultraviolet lamps having Xe ₂ wavelength of 172 nm.

  Before casting the resin melt on a stainless steel first cooling roll (5) subjected to hard chrome plating as a metal support, the surface of the first cooling roll (5) was surface-treated by excimer ultraviolet irradiation. . The accumulated time of the excimer ultraviolet irradiation treatment was 0.1 sec in Example 5, 10 sec in Example 6, 300 sec in Example 7, and 3000 sec in Example 8.

Thereby, the component element composition ratio: (CrO ₂ + CrO ₃ ) / Cr on the surface of the first cooling roll (5) made of stainless steel subjected to hard chrome plating was as shown in Table 1.

  Next, the cast film is brought into contact with the first cooling roll (5) subjected to the high-energy surface treatment as described above in the same manner as in Example 1, and a cast film having a thickness of 100 μm (cast) Film).

  Thereafter, this cast film was treated in the same manner as in Example 1 to prepare a cellulose acetate propionate film having a thickness of 40 μm.

Comparative Example 1
For comparison, a cellulose acetate propionate film is produced in the same manner as in Example 1 above. The difference from Example 1 is that Comparative Example 1 is the first metal support. The film is formed without performing high energy surface treatment on the surface of the cooling roll (5).

Examples 9-12
Next, the method for producing the optical film of the present invention was carried out by a solution casting film forming method.

(Preparation of dope)
The following materials were put into a closed container, heated, stirred and completely dissolved and filtered to prepare a dope. Silicon dioxide fine particles (Aerosil R972V) were added after being dispersed in ethanol.

(Dope composition)
Cellulose triacetate (acetyl substitution degree 2.88) 100 parts by weight Triphenyl phosphate 8 parts by weight Biphenyl diphenyl phosphate (liquid plasticizer) 4 parts by weight 5-chloro-2- (3,5-di-sec-butyl-2- Hydroxyphenyl)
-2H-benzotriazole (liquid UV absorber) 1 part by weight Methylene chloride 418 parts by weight Ethanol 23 parts by weight Aerosil R972V 0.1 part by weight (production of cellulose triacetate film)
Using the above dope, a cellulose triacetate film having a thickness of 40 μm was produced as follows.

  Film formation was performed with the manufacturing apparatus shown in FIG. Referring to the figure, the filtered dope was cast into a film from a casting die (23) made of a coat hanger die at a dope temperature of 35 ° C.

  In these examples, surface treatment was performed by atmospheric pressure plasma irradiation on the surface of a metal support (27) made of SUS316 and made of an endless belt polished to a super mirror surface before casting the dope. The integrated time of the atmospheric pressure plasma irradiation treatment was 0.1 sec in Example 9, 10 sec in Example 10, 300 sec in Example 11, and 3000 sec in Example 12.

Here, the amount of reaction gas used in the atmospheric pressure plasma irradiation apparatus (40) was set to 1 m ³ per 1 m of irradiation width. The composition of the mixed gas (reactive gas) used for the plasma treatment is described below. The atmospheric pressure was 1.0 atm.

Nitrogen 99.8% by volume
Oxygen 0.2% by volume
Thus, the component element composition ratios of the surface of the support (27) made of SUS316 and made of an endless belt polished to a super mirror surface: (Fe ₂ O ₃ + FeO) / Fe and (CrO ₂ + CrO ₃ ) / Cr It became what was shown in 1.

  Next, after the cast film was peeled off from the stainless steel endless belt (27) as the metal support subjected to the high energy surface treatment as described above, it was dried while being conveyed in a roll at 90 ° C. When the residual solvent amount is 10%, the film is stretched 1.06 times in the width direction in an atmosphere of 100 ° C., then the width is released, and the drying is finished in the 125 ° C. drying zone while carrying the roll. Was subjected to a knurling process having a width of 10 mm and a height of 8 μm to produce a cellulose triacetate film having a thickness of 40 μm. The film width was 1300 mm, and the winding length was 1500 m.

  Here, as the normal pressure plasma irradiation apparatus (40) which is a high energy irradiation apparatus, the thing shown in FIG. 5 was used like the case of the said Example 1. FIG.

Examples 13-16
(Excimer UV treatment)
Cellulose triacetate films are produced in the same manner as in Example 9. In these Examples, an excimer ultraviolet irradiation device (50) was used as the high energy irradiation device. The excimer ultraviolet irradiation device (50) is as shown in FIG. 6, and is made of quartz glass (SUS) made of SUS316 and made of an endless belt polished to an ultra-mirror surface and having a length in the transport direction of about 300 mm. In q), an apparatus containing four excimer ultraviolet lamps having an irradiance of 40 mW / cm ² and an Xe ₂ wavelength of 172 nm was used.

  Then, before the dope was cast on the surface of the endless belt metal support (27), surface treatment was performed by irradiation with an excimer ultraviolet lamp. The accumulated time of the excimer ultraviolet irradiation treatment was 0.1 sec in Example 13, 10 sec in Example 14, 300 sec in Example 15, and 3000 sec in Example 16.

Thus, the component element composition ratios of the surface of the support (27) made of SUS316 and made of an endless belt polished to a super mirror surface: (Fe ₂ O ₃ + FeO) / Fe and (CrO ₂ + CrO ₃ ) / Cr It became what was shown in 1.

  Thereafter, these cast films were treated in the same manner as in Example 9 to prepare three types of cellulose triacetate films having a film thickness of 40 μm.

Comparative Example 2
For comparison, a cellulose triacetate film is produced in the same manner as in Example 9. The difference from Example 9 is that in Comparative Example 2, film formation was performed without performing high-energy surface treatment. It is in the point which performed.

  Next, in order to evaluate the effect of the high energy surface treatment according to the present invention shown in Examples 1 to 8 above, the peel strength of the cast film, the crossed Nicol (CNT) permeation of the obtained cellulose acetate propionate film. Measurements were made for rate variation. Further, the film obtained in Comparative Example 1 was measured in the same manner.

  Further, in order to evaluate the effect of the high energy surface treatment according to the present invention shown in Examples 9 to 16, the peel strength of the cast film and the obtained cellulose triacetate were obtained as in Examples 1 to 8. The variation of the crossed Nicol (CNT) transmittance of the film was measured. Further, the film obtained in Comparative Example 2 was measured in the same manner.

  In Examples 9 to 16 and Comparative Example 2, when measuring the peeling force of the cast film, the solvent in the film evaporates momentarily and the residual solvent amount at the time of peeling decreases with time. The peeling force is also changed according to the amount of the residual solvent. Therefore, a sheet such as a food wrap was attached to the film surface side at the start of peeling to temporarily stop the evaporation of the solvent so that measurement with an arbitrary amount of residual solvent was possible. The method of each evaluation is shown below.

(Measurement method of peeling force)
About the various cast films in Examples 1 to 16 and Comparative Examples 1 and 2, the sample from which the release film was peeled was bonded to the object, and peeled off by 90 degrees in accordance with JIS Z 0237, peeling speed. The adhesive strength of 300 mm / min was measured.

[Method for measuring variation in crossed Nicols (CNT) transmittance]
About the various cellulose ester films obtained in Examples 1 to 16 and Comparative Examples 1 and 2, the width direction of the film was measured at a measurement wavelength of 600 nm using a polarizing film measuring device (VAP-7070) manufactured by JASCO Corporation. Cross nicol (CNT) transmittance was measured at intervals of 50 mm and at intervals of 50 mm in the longitudinal direction of 300 mm, and the difference between the average value of all the data and the most deviated value was taken as variation here.

(Preparation of polarizing plate)
Using the cellulose ester films produced in Examples 1 to 16 and Comparative Examples 1 and 2, a polarizing plate was produced and evaluated according to the method described below.

A polarizing plate using a cellulose ester film as a protective film for a polarizing plate was produced according to the following method.

1. Production of Polarizing Film A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and then immersed in an aqueous solution at 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. . This was washed with water and dried to obtain a polarizing film.

  Subsequently, according to the following processes 1-5, the polarizing film and the cellulose-ester film were bonded together and the polarizing plate was produced.

  Step 1: Examples 1 to 16 and Comparative Examples 1 and 2 The produced cellulose ester films were each immersed in a 2 mol / L sodium hydroxide solution at 50 ° C. for 90 seconds, then washed with water and dried. A protective film (made of polyethylene terephthalate) that can be removed again was attached to the surface provided with the antireflection film in advance for protection.

  Similarly, the cellulose ester film was immersed in a 2 mol / L sodium hydroxide solution at 50 ° C. for 90 seconds, then washed with water and dried.

  Process 2: The above-mentioned polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by weight for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizing film in Step 2 was lightly removed, and it was sandwiched between a cellulose ester film subjected to alkali treatment in Step 1 and a commercially available cellulose ester film, and laminated.

Process 4: It bonded together at the speed | rate of about 2 m / min with the pressure of 20-30 N / cm < ² > with the two rotating rollers. At this time, care was taken to prevent bubbles from entering.

  Step 5: The sample prepared in Step 4 in a dryer at 80 ° C. was dried for 2 minutes to prepare a polarizing plate.

(Evaluation of polarizing plate)
Next, the polarizing plate on the outermost surface of a commercially available liquid crystal display panel (NEC color liquid crystal display, MultiSync, LCD1525J, model name LA-1529HM) was carefully peeled off, and the polarization direction was adjusted here. 16 and the polarizing plates using the cellulose ester films of Comparative Examples 1 and 2 were pasted. Each liquid crystal display panel thus obtained was visually observed by a plurality of evaluators to look whitish when viewed from the front and obliquely.

Evaluation criteria for unevenness ◎ None of the evaluators can see the unevenness at all ○ Some evaluators may see slight unevenness, but the level that can be used as a product △ Many evaluators have seen unevenness slightly but × Many evaluations Unevenness was seen.

Table 1 below shows the types of high energy treatment by the high energy irradiation device comprising the atmospheric pressure plasma irradiation device (40) and the excimer ultraviolet irradiation device (50), the accumulated time of the high energy treatment, and the elemental composition ratio of the metal support surface. : (Fe ₂ O ₃ + FeO) / Fe and (CrO ₂ + CrO ₃ ) / Cr, variation in crossed Nicol (CNT) transmittance (%) of the obtained cellulose ester film, and production using the film The result of visual evaluation of the polarizing plate about the liquid crystal display panel equipped with the polarizing plate was described collectively.

  As is clear from the results in Table 1 above, in Examples 1 to 8 of the present invention, the resin melt was allowed to flow on the first cooling roll (5) made of stainless steel subjected to hard chrome plating as the metal support. Before extending, the surface of the first cooling roll (5) is subjected to a high energy surface treatment by a high energy irradiation device comprising an atmospheric pressure plasma irradiation device (40) or an excimer ultraviolet irradiation device (50), and a specific component element composition When a metal oxide film layer having a ratio is formed and then the casting film is brought into contact with the surface of the cooling roll (5), the casting film (film) is cooled with a low tension as a whole. The area that can be taken as production conditions has expanded. And since the release property (peelability) of the cast film from the cooling roll (5) was improved in this way, fluctuations in the peel position are reduced, thereby the width direction of the cellulose acetate propionate film. The longitudinal deviation of the expansion and contraction of the film was also reduced, and the variation in the crossed Nicol (CNT) transmittance of the film could be greatly reduced.

  On the other hand, in Comparative Example 1 in which the surface of the cooling roll (5) made of stainless steel subjected to hard chrome plating is not subjected to high energy surface treatment, the drop of the peel strength of the cast film is not so much seen, and the obtained cellulose acetate The variation in the crossed Nicol transmittance of the propionate film was not reduced.

  Moreover, the liquid crystal display panel equipped with the polarizing plate produced using the cellulose acetate propionate film obtained in Examples 1 to 8 of the present invention uses the cellulose acetate propionate film obtained in Comparative Example 1. It was confirmed that the liquid crystal display panel equipped with the polarizing plate produced in this way was excellent in display performance.

Furthermore, in Examples 9 to 16 of the present invention, before casting the dope on the surface of a metal support (27) made of SUS316 as a metal support and made of an endless belt polished to a super mirror surface, The surface of the support (27) is subjected to a high energy surface treatment by a high energy irradiation device comprising an atmospheric pressure plasma irradiation device (40) or an excimer ultraviolet irradiation device (50), and a specific element composition ratio: (Fe ₂ O ₃ + FeO ) / Fe and (CrO ₂ + CrO ₃ ) / Cr are formed, and then the dope is brought into contact with the surface of the metal support (27), the film has a low overall tension. Can be peeled off, and the area that could not be used as production conditions due to poor peeling has disappeared, and the area that can be taken as production conditions has expanded. Further, as described above, the release property of the cast film from the metal support (27) has been improved, so that the fluctuation of the peeling position is reduced, and thereby the longitudinal deviation of the stretching in the width direction of the cellulose triacetate film. The variation in crossed Nicol (CNT) transmittance could be greatly reduced.

  On the other hand, in Comparative Example 2 where no high-energy surface treatment was applied, the peel force was not significantly reduced, and the variation in crossed Nicol (CNT) transmittance was not reduced.

  Moreover, the liquid crystal display panel which attached the polarizing plate produced using the cellulose triacetate film obtained in Examples 9-16 of this invention is a polarizing plate produced using the cellulose triacetate film obtained in Comparative Example 2. It was confirmed that the mounted liquid crystal display panel was excellent in display performance.

It is a general | schematic flow sheet which shows 1st Embodiment of the apparatus which enforces the manufacturing method of the optical film of this invention. It is a principal part expansion flow sheet of the manufacturing apparatus of FIG. It is a flow sheet which shows 2nd Embodiment of the apparatus which enforces the manufacturing method of the optical film of this invention. It is a flow sheet which shows the modification of the apparatus of FIG. It is explanatory drawing for demonstrating the principle of the atmospheric pressure plasma irradiation apparatus used in the manufacturing method of the optical film of this invention. It is explanatory drawing for demonstrating the principle of the excimer ultraviolet irradiation apparatus used in the manufacturing method of the optical film of this invention.

1: Extruder 2: Filter 3: Static mixer 4: Casting die 5: First cooling roll 6: Touch roll 7: Second cooling roll 8: Third cooling roll 9: Peeling roll 10: Film (web)
12: Stretching device 13: Slitter 14: Embossing ring 15: Back roll 16: Winding device F: Optical film (original winding)
21: Melting pot 22: Pump 23: Casting die 24: Depressurization chamber 25: Front and rear winding drum 26: Casting rotationally driven stainless steel drum (support)
27: Stainless steel endless belt for casting (support)
28: peeling roll 29: web 30: roll transport drying device 31: warm air (dry air)
32: Tenter 33: Winder 40: Normal pressure plasma irradiation device 50: Excimer ultraviolet irradiation device a: Counter electrode of reactor of normal pressure plasma irradiation device b: Counter electrode of reactor of normal pressure plasma irradiation device g: Reaction gas s : Casting film u: excimer ultraviolet lamp of excimer ultraviolet irradiation device r: reflector p: purge gas q: quartz glass

Claims (5)

A method for producing an optical film by a melt casting film forming method or a solution casting film forming method, wherein an element of iron (Fe) and / or chromium (Cr) is contained on the surface of a metal support, and the metal support The component element composition ratio on the surface satisfies the following relationship (i) and / or (ii), and the thermoplastic resin melt or the solution flow in the melt casting film forming method is formed on the surface of the metal support. A method for producing an optical film, comprising casting a thermoplastic resin solution (dope) in a film-forming method.
(I) (Fe ₂ O ₃ + FeO) / Fe = 5-50
(Ii) (CrO ₂ + CrO ₃ ) / Cr = 10-50   Before casting the resin melt or dope on the metal support, the metal support surface is subjected to surface treatment by atmospheric pressure plasma irradiation or excimer ultraviolet irradiation to form a metal oxide, The manufacturing method of the optical film of Claim 1.   3. The method for producing an optical film according to claim 1, wherein the integrated time of the atmospheric pressure plasma irradiation treatment or the excimer ultraviolet irradiation treatment is 0.1 to 3000 seconds.   The method for producing an optical film according to any one of claims 1 to 3, wherein the thermoplastic fat is a cellulose ester resin.   The method for producing an optical film according to any one of claims 1 to 4, wherein the metal support is one of an endless belt, a drum, or a roll for film formation.

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