JP2014037064A - Method and apparatus for producing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of an optical film for controlling film, by which thickness irregularity due to disturbance (wind) is controlled and a thin film causing no display irregularity is obtained by controlling a stream of wind generating in a minute space in a casting process, which is conventionally supposed to give no influence in a production process of an optical film.SOLUTION: The production method of an optical film includes: a casting step of extruding a melt containing a thermoplastic resin into a film state from a cast die 4 onto a surface of a cast roller 5; and a compressing step of compressing the melt in a film state extruded in the casting step in a compressing part between the cast roller 5 and a touch roller 6. The shortest distance D1 between the cast die 4 and the cast roller 5 and the shortest distance D2 between the cast die 4 and the touch roller 6 are each within the range from 3 to 30 mm; and a ratio D1/D2 of the shortest distances is within the range from 0.5 to 2.0.

Description

  The present invention relates to an optical film manufacturing method and a manufacturing apparatus.

  In the melt casting method for producing optical films, it is known that the uniformity of film quality is greatly influenced by the ribbon stability of the molten resin from the die slip of the casting die to the cast roller or touch roller landing point. It has been.

  Usually, in order to avoid instability due to disturbance of the ribbon, it is common to adjust the dropping position of the molten resin and the air gap (referring to the distance from the die slip to the roller landing point). The drop position is on the contact point between the cast roller and touch roller, or the structure of the space around the die slip and roller is devised to prevent film thickness unevenness due to disturbance.

  Japanese Patent Application Laid-Open No. 2004-228688 discloses a technique for preventing thickness unevenness and phase difference unevenness due to external stress such as heat and humidity by surrounding the air gap with a shielding plate and exhausting the inside.

  Patent Document 2 discloses a technique for preventing unevenness in thickness by rectifying air near the surface of a film by installing a labyrinth structure casing and an end shielding plate around a casting die, and blowing or sucking air. Is disclosed.

  However, as the liquid crystal display device is made thinner, the optical film is also made thinner. When the thin optical film is provided in a liquid crystal display device, display unevenness that has not been a problem in the past occurs. I understood that.

  In the process of analyzing the cause of this display unevenness, the present inventor has found that the cause is minute film thickness unevenness of the optical film. Further, the cause of the film thickness unevenness is a casting die and a cast roller (also referred to as a rotation support body or a cooling roller) and a casting die and a touch roller (also referred to as a pinching rotation body) during film formation. It was found that the flow of wind accompanying the rotation of the roller entering from the gap caused temperature unevenness on the front and back of the ribbon, and caused slight film thickness unevenness on the cast roller.

  The cast roller takes up high-temperature molten resin and cools it to form a film, and the touch roller performs surface correction of the optical film. The flatness of the optical film is ensured by narrowing the film between the cast roller and the touch roller. Usually, the melt casting film forming method using a touch roller includes a step of cooling and peeling the narrow-pressed resin on the cast roller, but the cast roller requires a diameter of a certain degree or more in order to secure the cooling capacity, The diameter of the touch roller is not always the same. Also, the die structure has a slit adjustment mechanism (heat bolt) for discharging resin on one side, so the distance between the casting die and the cast roller, and the gap between the casting die and the touch roller is different, and the space is very small. Then, a difference occurs in the flow of the wind that enters from the cast roller side and the touch roller side as the roller rotates.

  The above-mentioned techniques have been proposed for the problem around the wind of the cast part in the melt casting film forming method, but these techniques pay attention to the wind flow in a relatively wide space of the cast part. This is a technology that does not consider the effect of ribbon due to the difference in wind flow caused by the rotation of the roller. Even with the above technology, the display unevenness that appears in the display device newly generated by the thinning of the optical film It was difficult to eliminate.

JP 2006-150806 A JP 2009-154518 A

  The present invention has been made in view of the above-described problems and situations, and its solution is to control the flow of wind generated in a minute space during casting that has not been affected in the optical film manufacturing process. Thus, it is to provide a method for producing an optical film which controls film thickness unevenness due to disturbance (wind) and has no display unevenness even if the film thickness is reduced.

  Moreover, it is providing the manufacturing apparatus which manufactures the optical film without the said film thickness nonuniformity.

  In order to solve the above-mentioned problems, the present inventor, in the process of examining the cause of the above-mentioned problem, sets the distance between the casting die and the cast roller and the gap between the casting die and the touch roller to a specific range and relationship, respectively. By adjusting, the instability of the ribbon due to the difference in wind flow entering from the rotation direction of each roller is eliminated to control the film thickness unevenness, and a method for producing an optical film that does not display unevenness even when it is thinned is found. The present invention has been reached.

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

  1. A casting process in which a melt containing a thermoplastic resin is extruded in the form of a film from a casting die onto the surface of the cast roller, and a film-like melt extruded in the casting process is sandwiched between the cast roller and the touch roller. A method of manufacturing an optical film having a clamping step of clamping at a portion, wherein the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller are 3 to 3, respectively. A method for producing an optical film, characterized in that the value is within a range of 30 mm and the ratio D1 / D2 of the shortest distance is within a range of 0.5 to 2.0.

  2. The shortest distances D1 and D2 are within a range of 3 to 30 mm, respectively, and the ratio of the shortest distances D1 / D2 is within a range of 0.5 to 2.0 by the gap adjusting means. The manufacturing method of the optical film of Claim 1.

  3. The second aspect is characterized in that the gap adjusting means is means for attaching and adjusting a member in at least one gap between the casting die and the cast roller, or the casting die and the touch roller. The manufacturing method of the optical film of description.

  4). 3. The method for producing an optical film according to claim 2, wherein the gap adjusting means is a means for adjusting the casting die by tilting within a range of ± 10 ° from the vertical direction.

  5. The apparatus for producing an optical film according to claim 2, wherein the gap adjusting means is a means for adjusting the height of at least one of the cast roller and the touch roller by varying it.

  6). 3. The method for producing an optical film according to claim 2, wherein the gap adjusting means is a means using a casting die having an asymmetric shape on the cast roller side and the touch roller side.

  7). The said touch roller is an elastic touch roller, The manufacturing method of the optical film as described in any one of Claim 1-6 characterized by the above-mentioned.

  8). The manufacturing method according to any one of claims 1 to 7, wherein a diameter of the cast roller is 1.1 times or more larger than a diameter of the touch roller.

  9. The optical film according to any one of items 1 to 8, wherein the thermoplastic resin is at least one selected from cellulose ester resins, acrylic resins, and cyclic olefin resins. Production method.

  10. It is a manufacturing apparatus of the optical film used for the manufacturing method of the optical film as described in any one of Claim 1-9, Comprising: The shortest distance D1 of the said casting die and the said cast roller, and the said casting die And a gap adjusting means for setting the shortest distance D2 between the touch roller and the touch roller within a range of 3 to 30 mm and a ratio D1 / D2 of the shortest distance within a range of 0.5 to 2.0. An apparatus for producing an optical film.

  11. 11. The optical film according to claim 10, wherein a member is mounted as at least one gap between the casting die and the cast roller or between the casting die and the touch roller as the gap adjusting means. Manufacturing equipment.

  12 11. The apparatus for producing an optical film as set forth in claim 10, wherein the casting die is inclined within a range of ± 10 ° from the vertical direction as the gap adjusting means.

  13. 11. The apparatus for producing an optical film according to claim 10, wherein the gap adjusting means has a variable height of at least one of the cast roller and the touch roller.

  14 The apparatus for producing an optical film according to claim 10, wherein the gap adjusting means includes a casting die having an asymmetric shape on the cast roller side and the touch roller side.

  The above-described means of the present invention controls the flow of wind accompanying the rotation of the cast roller and the touch roller, which occurs in a minute space during casting, which has not been affected in the optical film manufacturing process. The film thickness unevenness due to (wind) can be controlled, and a method for producing an optical film without display unevenness even when the film thickness is reduced can be provided. Moreover, the manufacturing apparatus which manufactures the optical film without the said film thickness nonuniformity can be provided.

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

  In the case of the melt casting film forming method, the flow of wind around the air gap is surrounded by a shielding plate or a casing, and the inside of the film is blown or exhausted to adjust the flow of the macro wind. Although it contributes to the reduction of film thickness unevenness, when the optical film is thinned, the slight film thickness unevenness that appears as display unevenness due to the slight flow of air around the casting die is eliminated. It is difficult.

  According to the method of manufacturing an optical film of the present invention, paying attention to the gap between the casting die and the cast roller and the casting die and the touch roller, the respective distances are adjusted to a specific range and relationship, thereby the roller. It is presumed that a method for producing a thinned optical film that has no film thickness unevenness due to disturbance (wind) can be provided by controlling the flow of wind entering from the rotation direction of the film.

Schematic showing the positional relationship between the casting die, cast roller and touch roller Schematic diagram of means for adjusting the distance between the casting die, cast roller and touch roller Schematic diagram of means for adjusting the distance between the casting die, cast roller and touch roller Schematic which shows embodiment of the manufacturing method of an optical film

  The method for producing an optical film according to the present invention includes the shortest distance D1 between the casting die and the cast roller, the shortest distance D2 between the casting die and the touch roller, and the ratio of the shortest distance in the melt casting method. Cast roller and touch roller, which are produced in a minute space at the time of casting that has not been affected in the manufacturing process of the optical film by this configuration, characterized by performing casting and clamping pressure within a specific range. By controlling the flow of wind accompanying the rotation of the roller, film thickness unevenness due to disturbance (wind) is controlled, and a method for producing an optical film without display unevenness even when the film thickness is reduced is provided. This feature is a technical feature common to the inventions according to claims 1 to 14.

  As an embodiment of the present invention, from the viewpoint of manifestation of the effect of the present invention, the optical film manufacturing method uses the gap adjusting means to set the shortest distances D1 and D2 within the range of 3 to 30 mm and the shortest distance. The value of the ratio D1 / D2 is preferably in the range of 0.5 to 2.0. The gap adjusting means is preferably adjusted by mounting a member in one of the gaps between the casting die and the cast roller or between the casting die and the touch roller. It is preferable to install it with an inclination within a range of ± 10 ° from the direction, and it is preferable to adjust by changing the height of one of the cast roller and the touch roller. It is also preferable to use a casting die having an asymmetric shape on the cast roller side and the touch roller side. In either case, by adjusting the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller, the flow of wind entering from the rotation direction of each roller is controlled, and the thin film The present invention also provides a method for producing an optical film having no film thickness unevenness due to disturbance (wind).

  The touch roller is preferably an elastic touch roller in order to improve the flatness of the optical film, and the diameter of the cast roller is 1.1 times or more larger than the diameter of the touch roller to efficiently cool the web. And it is preferable from the viewpoint of obtaining an optical film without unevenness by clamping.

  The thermoplastic resin according to the present invention is preferably at least one selected from a cellulose ester resin, an acrylic resin, and a cyclic olefin resin for obtaining an optical film used in a liquid crystal display device.

  In the optical film manufacturing apparatus for carrying out the optical film manufacturing method of the present invention, the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller are 3 to 30 mm, respectively. And having a gap adjusting means that makes the value of the shortest distance ratio D1 / D2 within the range of 0.5 to 2.0, the film thickness unevenness due to disturbance (wind) can be reduced. The present invention provides an apparatus for manufacturing an optical film that is controlled and has no display unevenness in thinning.

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

<Outline of optical film manufacturing method>
The method for producing an optical film of the present invention comprises a casting step of extruding a melt containing a thermoplastic resin from a casting die onto the surface of a cast roller, and a film-like melt extruded in the casting step. A method of manufacturing an optical film having a clamping step of clamping at a clamping portion between the cast roller and the touch roller, wherein the shortest distance D1 between the casting die and the casting roller, the casting die, and the The shortest distance D2 to the touch roller is in the range of 3 to 30 mm, respectively, and the value of the shortest distance ratio D1 / D2 is in the range of 0.5 to 2.0.

  The optical film manufacturing method of the present invention is characterized in that the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller are narrower than the conventional ones, and the shortest distance By adjusting the ratio within a specific range, the flow of wind entering from the rotation direction of each roller is controlled, and the influence of disturbance (wind) on film thickness unevenness is reduced. The “shortest distance” in the present invention refers to the distance of the shortest portion of the gap between the casing portion of the casting die and the roller surface.

  FIG. 1 is a schematic diagram showing the positional relationship among a casting die, a cast roller and a touch roller, which is a feature of the method for producing an optical film of the present invention. In addition, this figure is a figure drawn typically and does not prescribe | regulate the magnitude | size and shape of each apparatus, The magnitude | size and shape of a casting die, a cast roller, and a touch roller can be designed freely suitably. In the figure, an embodiment is shown in which the point (P) at which the film (melt) first contacts the surface of the cast roller B and the point (P) at which the film contacts the surface of the touch roller C are the same. In some cases, the point at which the film first contacts the surface of the cast roller B may be different from the point at which the film contacts the surface of the touch roller C. From the viewpoint of further improving the flatness, it is preferable that the point (P) that contacts the surface of the cast roller B and the point (P) that the film contacts the surface of the touch roller C are the same.

  FIG. 1A is a schematic diagram showing the positional relationship between a casting die A, a cast roller B, and a touch roller C used in a conventional melt casting film forming method. The lower end of the conventional casting die is located above the top of the cast roller B, and the shortest distance D1 between the casting die A and the cast roller B and the shortest distance D2 between the casting die A and the touch roller C are relatively It was long, so the air gap was some distance away. The air gap is preferably shortened in order to avoid instability due to disturbance of the ribbon, but as disclosed in Patent Document 1 and Patent Document 2, the periphery of the air gap is blocked to Although the means of rectifying by exhausting or blowing air has been proposed, the shortest distances D1 and D2 between the casting die and the roller are adjusted, and the difference in wind flow accompanying the rotation of each roller There was no technical idea to rectify the wind generated in a minute space.

FIG. 1B is a schematic diagram showing a positional relationship among the casting die, the cast roller, and the touch roller according to the present invention.
The positional relationship between the casting die A, the cast roller B and the touch roller C according to the present invention is such that the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller are 3 to 30 mm, respectively. It is within the range, and the value of the ratio D1 / D2 of the shortest distance is within the range of 0.5 to 2.0.

  In this way, the present invention adjusts the shortest distances D1 and D2 between the casting die and the roller to a specific range and relationship, thereby rectifying the wind entering from the rotation direction of each roller, and the difference in the flow of each wind. It is characteristic that the ribbon r is stabilized by adjusting the thickness to produce an optical film that does not cause film thickness unevenness even if it is a thin film.

  In the present invention, the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller are adjusted within a range of 3 to 30 mm, respectively. Considering the effect, it is preferably in the range of 5 to 20 mm, more preferably in the range of 5 to 10 mm.

  In the present invention, adjusting the value of the shortest distance ratio D1 / D2 within the range of 0.5 to 2.0 is important in adjusting the difference in the flow of wind accompanying the rotation of each roller. Yes, preferably in the range of 0.7 to 1.5, more preferably in the range of 0.9 to 1.1, and particularly preferably 1.0 (equal distance).

  By adjusting the shortest distance and the value of the shortest distance ratio D1 / D2 within the above range, it becomes possible to adjust the difference in the flow of wind entering from the rotation direction of each roller.

  In the present invention, from the viewpoint of manifestation of the effects of the present invention, the optical film manufacturing method includes the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller by the gap adjusting means. Is preferably adjusted within the range of 3 to 30 mm, and the value of the ratio D1 / D2 of the shortest distance is preferably set within the range of 0.5 to 2.0, and the optical film having the gap adjusting means is manufactured. It is preferable to use an apparatus.

  Although the preferable example of the said gap | interval adjustment means is shown below, this invention is not limited to these, Moreover, it is preferable to use a gap | interval adjustment means combining suitably.

  The gap adjusting means shown in FIG. 2 (a) is configured to install a member in one of the gaps between the casting die and the cast roller or between the casting die and the touch roller, and to generate wind generated in a minute space. It is a means to adjust to rectify. The thickness of the member is appropriately determined depending on the adjustment degree of the shortest distances D1 and D2 and the adjustment degree of the value of the ratio D1 / D2. Further, the shape of the member is not particularly limited, but is preferably a rust shape or an arch shape facing the roller shape as shown in FIG. Moreover, it is preferable to use any material such as metal or plastic as appropriate, but it is preferable from the viewpoint of wind rectification to use a material similar to the casting die and having a smooth surface.

  The gap adjusting means shown in FIG. 2B is a means for adjusting the casting die by inclining within a range of ± 10 ° when the vertical direction is 0 °. The term “inclined” as used in the present invention means that the vertical direction of the casting die is inclined and installed in a direction within a range of ± 10 ° excluding the vertical direction (0 °). A tilting range within the above range is preferable because it does not affect the stability of the ribbon that gravity falls from the die slip. The inclination angle is appropriately determined depending on the adjustment degree of the shortest distances D1 and D2 and the adjustment degree of the value of the ratio D1 / D2.

  The gap adjusting means shown in FIG. 3A is a means for adjusting by adjusting the height of one of the cast roller and the touch roller. In the figure, the shortest distance D2 is adjusted by raising the height of the touch roller C from the height of the cast roller B. How much the height is changed is appropriately determined depending on the adjustment degree of the shortest distances D1 and D2 and the adjustment degree of the value of the ratio D1 / D2. The device capable of changing the height of at least one of the cast roller and the touch roller preferably has a structure capable of moving up and down a bearing portion of the roller, for example.

  The gap adjusting means shown in FIG. 3B is a means using a casting die having an asymmetric shape on the cast roller side and the touch roller side. In the figure, the casting die shape on the touch roller side is an asymmetrical shape, and the shortest distance D2 is adjusted. The extent to which the shape is changed is appropriately determined depending on the adjustment degree of the shortest distances D1 and D2 and the adjustment degree of the value of the ratio D1 / D2.

<Method for producing optical film by melt casting method>
FIG. 4 is a schematic view showing an embodiment of the method for producing an optical film of the present invention.

  In the present embodiment, a film material containing a thermoplastic resin such as a cellulose ester resin is mixed to obtain a resin mixture, which is then melted at an extrusion temperature of about 200 to 300 ° C. using an extruder 1, and is a leaf disk type. The filter 2 is used to remove foreign matter. Next, the filtered melt is melt-extruded from the casting die 4 onto the cast roller 5. The extruded film-like melt circumscribes the cast roller 5 and is pressed against the surface of the cast roller 5 with a predetermined pressure by the touch roller 6 at the pinching portion. The film peeled from the touch roller 6 is conveyed by the cast roller 5, further circumscribed in the order of the cooling rollers 7 and 8, cooled and solidified, and peeled by the peeling roller 9. The peeled film 17 is stretched in the longitudinal (conveying direction) and lateral (lateral direction) of the film by the longitudinal stretching apparatus 10 and the lateral stretching apparatus 20 and then wound by the winding apparatus 60.

  The film extruded from the casting die 4 is cooled and surface-corrected by at least two rotating bodies (a cast roller and a touch roller) having a cooling function. The cast roller and the touch roller are not limited to rollers, and may be a drum or a belt.

  The cast roller 5 is made of a seamless steel pipe having a wall thickness of about 20 to 30 mm, and has a mirror finished surface. Inside, a pipe for flowing a coolant is arranged so that heat can be absorbed from the film on the roller by the coolant flowing through the pipe. Preferred materials for the cast roller 5 include carbon steel and stainless steel. The diameter of the cast roller 5 is not particularly limited, but it is preferably 1.1 times or more larger than the diameter of the touch roller described later, from the viewpoint of obtaining an optical film without unevenness by efficiently cooling and pinching the web. It is preferably in the range of 110 to 1000 mm, and more preferably in the range of 200 to 1000 mm.

  The temperature of the cast roller 5 is preferably set to be equal to or lower than the glass transition temperature (Tg) of the resin mixture and equal to or higher than the melting point of the additive. The temperature drop of the film after coming into contact with the surface of the cast roller 5 is preferably in the range of 20 to 50 ° C. If the temperature drop of the film at the cast roller 5 is too great, the film thickness unevenness will increase due to non-uniform shrinkage. It is preferable to install the cooling roller 7 and the cooling roller 8 subsequent to the cast roller 5 in order to improve the flatness of the film, and it is preferable that the temperature is lowered stepwise within a range of 5 to 30 ° C.

  On the other hand, the touch roller 6 is a rotating body for the purpose of pressing the film in the direction of the cast roller 5 from the opposite side of the cast roller 5 with respect to the film.

  The surface of the touch roller 6 is preferably a metal, and the thickness is in the range of 0.1 to 10.0 mm. Preferably it is the range of 0.2-6.0 mm. The surface of the touch roller is subjected to a treatment such as chrome plating, and the surface roughness is preferably 0.1 μm or less, and more preferably 0.05 μm or less, at the maximum height Ry. The smoother the roller surface, the smoother the surface of the resulting film.

  In the clamping step, the touch roller 6 is preferably made of an elastic roller (elastic metal roller) having a metal cylinder on the outer periphery.

  That is, when the pressure of the touch roller 6 is not uniform, uneven orientation occurs in the film, and this becomes uneven brightness in the display device. In order to correct the surface of the film with uniform pressure, an elastic touch roller having a metal cylinder on the outer periphery as described above is preferable.

  The metal material on the surface of the touch roller 6 is required to be smooth, moderately elastic, and durable. Carbon steel, stainless steel, titanium, nickel produced by electroforming, etc. can be preferably used. Further, in order to increase the hardness of the surface or improve the releasability from the resin, it is preferable to perform a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, or ceramic spraying. It is preferable that the surface processed is further polished to have the above-described surface roughness.

  The touch roller 6 has a double structure of a metal outer cylinder and an inner cylinder, and has a double cylinder configuration having a space so that a cooling fluid can flow between them.

  The inner cylinder is preferably a lightweight and rigid metallic inner cylinder such as carbon steel, stainless steel, aluminum, titanium or the like. By giving rigidity to the inner cylinder, it is possible to suppress the rotational shake of the roller. A sufficient rigidity can be obtained by setting the thickness of the inner cylinder to a range of 2 to 10 times that of the outer cylinder. The inner cylinder may be further coated with a resin elastic material such as silicone or fluororubber.

  The structure of the space through which the cooling fluid flows can be any structure as long as the temperature of the roller surface can be uniformly controlled. For example, the roller can be made to flow in the width direction and return alternately or in a spiral shape. Temperature control with a small surface temperature distribution is possible. The cooling fluid is not particularly limited, and water or oil can be used according to the temperature range to be used. The temperature of the touch roller 6 is preferably 60 to 160 ° C, more preferably 70 to 150 ° C.

  The touch roller 6 is preferably set in a drum shape in which the outer diameter at the center is larger than the outer diameters at both ends. The touch roller is generally pressed against the film by pressing means at both ends, but in this case, the touch roller bends, so that there is a phenomenon that the touch roller is strongly pressed toward the end. Highly uniform pressing is possible by using a drum-shaped roller.

  The diameter of the touch roller 6 (the diameter of the metal outer cylinder) is preferably in the range of 100 to 500 mm. The effective width of the touch roller 6 needs to be wider than the film width to be pinched. Due to the difference between the radius of the center portion of the touch roller 6 and the radius of the end portion (hereinafter referred to as the crowning amount), unevenness such as streaks generated at the center portion of the film can be prevented. The amount of crowning is preferably in the range of 50 to 300 μm.

  Examples of the elastic touch roller include JP-A-03-124425, JP-A-08-224772, JP-A-07-1000096, JP-A-10-272676, WO97 / 028950, JP-A-11-235747, JP-A-2002. A thin-film metal sleeve-covered silicon rubber roller as described in Japanese Patent No. 36332, Japanese Patent Application Laid-Open No. 2005-172940, or Japanese Patent Application Laid-Open No. 2005-280217 can be used.

  The cast roller 5 and the touch roller 6 are installed at positions opposite to the plane of the film so as to sandwich the film. The cast roller 5 and the touch roller 6 may be in contact with the film by a surface or by a line.

  In the method for producing an optical film according to the present embodiment, the conditions for melt extrusion can be performed in the same manner as the conditions used for other thermoplastic resins such as polyester. The material is preferably dried beforehand. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less, using a vacuum or reduced pressure drier or a dehumidifying hot air drier.

  For example, the resin dried under hot air, vacuum, or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C. using the extruder 1, filtered through a leaf disk type filter 2, and the foreign matter is removed.

  When introducing into the extruder 1 from a supply hopper (not shown), it is preferable to prevent oxidative decomposition and the like under vacuum, reduced pressure, or 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 that the thermoplastic resin and other additives such as a stabilizer added as necessary are mixed before melting. Mixing may be performed by a mixer or the like, or may be performed in the resin preparation process as described above. 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 melted directly using the extruder 1 to form a film. Once the film constituent materials are pelletized, the pellets are extruded. The film may be melted by the machine 1 to form a film. In addition, when the film constituent material includes a plurality of materials having different melting points, once at a temperature at which only the material having a low melting point melts, a semi-molten product (a material having a low melting point and a high melting point that remains solid) It is also possible to produce a film in which the materials are mixed, and to put the semi-melt into the extruder 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 extruders available on the market 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 necessary, but 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 a semi-molten material is used as the film constituent material, it can be used with either a single screw extruder or a twin screw extruder.

  In the extruder 1 and the cooling step after extrusion, it is preferable to reduce the oxygen concentration by replacing with an inert gas such as nitrogen gas or reducing the pressure.

  The melting temperature of the film constituent material in the extruder 1 varies depending on the viscosity and discharge amount of the film constituent material, the thickness of the sheet to be manufactured, etc., but generally the glass transition temperature of the film (resin mixture) It is Tg or more and Tg + 150 ° C. or less, preferably Tg + 10 ° C. or more and Tg + 120 ° C. or less with respect to Tg. The melt viscosity at the time of extrusion is in the range of 1 to 10000 Pa · s, preferably in the range of 10 to 1000 Pa · s. In addition, the residence time of the film constituent material in the extruder 1 is preferably short, and is within 60 minutes, preferably within 30 minutes, and more preferably within 20 minutes. The residence time depends on the type of the extruder 1 and the extrusion conditions, but can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, and the like. is there.

  The shape, rotation speed, and the like of the screw of the extruder 1 are appropriately selected depending on the viscosity, the discharge amount, and the like of the film constituent material. In this embodiment, the shear rate in the extruder 1 is in the range of 1 / second to 10000 / second, preferably in the range of 5 / second to 1000 / second, more preferably in the range of 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 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. Any of a commonly used T die, fish tail die, and hanger coat die may be used. The material of the casting die 4 is sprayed or plated with hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Processing includes buffing, lapping using a # 1000 or higher whetstone, flat cutting using a # 1000 or higher diamond whetstone (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, and electrolytic composite polishing. And the like.

  A preferred material for 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.

  The slit of the casting die 4 is configured such that the gap can be adjusted. Usually, one of the pair of lips forming the slit of the casting die 4 is a flexible lip having low rigidity and easily deformed, and the other is a fixed lip. A large number of heat bolts are arranged at a constant pitch in the width direction of the casting die 4, that is, in the length direction of the slit. Each heat bolt is provided with a block having an embedded electric heater and a cooling medium passage. While constantly cooling the block, the input of the embedded electric heater is increased or decreased to increase or decrease the temperature of the block. The film thickness is adjusted by thermal expansion and contraction and displacement of the flexible lip. The heat bolt preferably has a length of 20 to 40 cm and a diameter of 7 to 14 mm, and a plurality of, for example, several tens of heat bolts are preferably arranged in a pitch of 20 to 40 mm. The slit gap is usually in the range of 200 to 1000 μm, preferably in the range of 300 to 800 μm, more preferably in the range of 400 to 600 μm.

  In the present embodiment, the step of extruding the molten resin mixture from the casting die 4 attached to the extruder to the film-like resin, bringing the extruded film-like resin into close contact with at least two rotating bodies, and taking it out. Have.

  The surface accuracy of the cast roller 5 and the touch roller 6 is preferably high, and the surface roughness is preferably 0.1 μm or less, and more preferably 0.05 μm or less, at the maximum height Ry.

  The touch roller 6 preferably presses the film against the cast roller 5 by pressing means. The linear pressure with which the touch roller 6 presses the film at this time can be adjusted by a hydraulic piston or the like, and is preferably 0.1 to 100 N / mm, more preferably 1 to 50 N / mm.

  In addition, the cast roller 5 or the touch roller 6 can be reduced in diameter at both ends of the roller or provided with a flexible roller surface in order to improve the uniformity of adhesion with the film.

  When the portion from the opening (lip) of the casting die 4 to the cast roller 5 is depressurized to 70 kPa or less, the die line correction effect is more greatly manifested. The reduced pressure is preferably 50 kPa or more and 70 kPa or less. There is no particular limitation on the method of keeping the pressure of the portion from the lip of the casting die 4 to the cast roller 5 at 70 kPa or less, but there is a method of covering the roller periphery from the casting die 4 with a pressure-resistant member and reducing the pressure. . At this time, the suction device is preferably subjected to a treatment such as heating with a heater so that the device itself does not become a place where volatile matter discharged from the melt is attached. If the suction pressure is too small, the sublimate cannot be sucked effectively, so it is necessary to set the suction pressure appropriately.

  A molten film-like resin from the casting die 4 is brought into close contact with the cast roller 5, the cooling roller 7, and the cooling roller 8 in order to be cooled and solidified to obtain a resin film 17.

  In the embodiment of the present invention shown in FIG. 4, the cooled and solidified film 17 peeled from the cooling roller 8 by the peeling roller 9 is introduced into the longitudinal stretching device 10 and is stretched in the transport direction (MD direction).

  Next, the film after longitudinal stretching is guided to a lateral stretching apparatus (tenter) 20 where the film 17 is stretched in the lateral direction (width direction). By this transverse stretching, the molecules in the film are oriented.

  The draw ratio is preferably 1.0 to 2.0 times in the casting direction and 1.01 to 2.5 times in the width direction, and 1.01 to 1 in the casting direction. It is more preferable to obtain the required retardation value by 5 times and 1.05 to 2.0 times in the width direction.

  After lateral stretching, the end of the film 17 is slit to a product width by the slitter 19 and cut off, and then knurled (embossing) is applied to both ends of the film by a knurling device comprising an embossing ring 53 and a back roller 52. By applying and winding with the winding device 60, 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.

  The winder to be used may be a commonly used winder, and can be wound by a winding method such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress.

  In addition, you may perform the process of giving the knurling after horizontal stretching, and the slitter process process which cuts out the thick film part of a film edge part before a winding-up process.

  As described above, the optical film produced using the method for producing an optical film of the present invention has no film thickness unevenness and is of high quality. Therefore, the optical film is used for a liquid crystal display member, particularly a polarizing plate protective film. Can be used for plates.

  Next, the materials used in the method for producing an optical film of the present invention will be sequentially described.

<Thermoplastic resin>
The thermoplastic resin that is the main material of the optical film according to the present invention includes preferable requirements such as easy production, optical transparency, and easy control of the phase difference.

  The thermoplastic resin having the above properties is not particularly limited. For example, cellulose ester resins such as cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, and cellulose acetate propionate, polycarbonate resins, polyarylate Examples thereof include polyester resins, polysulfone (including polyether sulfone) resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins, cyclic olefin resins, polyamide resins, fluororesins, and nylons. Among these, cellulose ester resins, acrylic resins, and cyclic olefin resins are preferable, and cellulose ester resins are particularly preferable.

  The material constituting the optical film produced by the production method of the present invention includes these resins, and if necessary, stabilizers, plasticizers, ultraviolet absorbers, matting agents as slip agents, and retardation control agents. These materials are appropriately selected depending on the required characteristics of the target optical film.

<Cellulose ester resin>
The cellulose ester resin preferably used in the present invention is not particularly limited, but the ester group is preferably a linear or branched carboxylic acid ester having about 2 to 22 carbon atoms, and these carboxylic acids form a ring. It may be an ester of an aromatic carboxylic acid. In addition, these carboxylic acids may have a substituent. The cellulose ester resin is particularly preferably a lower fatty acid ester having 6 or less carbon atoms.

  Specific examples of preferred cellulose ester resins include, in addition to cellulose acetate, propionate groups or butyrate groups in addition to acetyl groups such as cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate. Mention may be made of mixed fatty acid esters of bound cellulose. Of these, cellulose acetate propionate is particularly preferred.

  The cellulose acetate propionate used in the present invention preferably satisfies the substitution degrees of the following formulas (i) and (ii) at the same time.

Formula (i): 2.0 ≦ X + Y ≦ 2.9
Formula (ii): 0 ≦ X ≦ 2.5
(In the formula, X represents the degree of substitution of the acetyl group. Y represents the degree of substitution of the propionyl group.)
The measuring method of the substitution degree of these acyl groups can be measured according to ASTM-D817-96.

  The larger the total acyl group substitution degree, the better the dimensional change, haze, and water absorption.

  The cellulose ester resins that can be used in the present invention may be mixed with resins having different degrees of substitution in order to obtain optical properties that meet the purpose. The mixing ratio is preferably in the range of 10:90 to 90:10 (mass ratio).

  The cellulose ester resin that can be used in the present invention can be used alone, but can also be used by mixing with two or more other resins. Examples of the resin to be mixed include acrylic resin, polyester resin, polycarbonate resin, polyamide resin, and vinyl resin. Among these, acrylic resins are preferably used.

  The mixing ratio of other resins that can be mixed with the cellulose used in the present invention is preferably within the range of 10:90 to 90:10 (mass ratio).

  The number average molecular weight of other resins that can be mixed with the cellulose used in the present invention is preferably in the range of 2000 to 150,000.

  The number average molecular weight of the cellulose ester resin used in the present invention is preferably in the range of 60,000 to 300,000, since the mechanical strength of the resulting film is strong. Furthermore, the thing of 70000-200000 is used preferably.

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

  The weight average molecular weight Mw and the number average molecular weight Mn of the cellulose ester resin and the resin to be mixed can be measured using gel permeation chromatography (GPC). An example of measurement conditions is as follows, but is not limited to this, and an equivalent measurement method can be used.

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

  Although there is no limitation in particular as a raw material of the cellulose ester-type resin used for this invention, Cotton linter, wood pulp, kenaf, etc. can be mentioned. Moreover, the cellulose ester-type resin obtained from them can be mixed and used in arbitrary ratios, respectively.

  Cellulose ester resins such as cellulose acetate and cellulose acetate propionate used in the present invention can be produced by known methods. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

  The cellulose ester-based resin used in the present invention preferably has a small amount of bright spot foreign matter when formed into a film. The bright spot foreign matter is considered to be one of the reasons that the esterification part of the hydroxy group contained in the cellulose resin is unreacted, and the cellulose resin with little bright spot foreign matter is used, and the heated and melted cellulose resin is filtered. As a result, foreign matter can be removed and bright spot foreign matter can be reduced.

<Acrylic resin>
The acrylic resin used in the present invention includes a methacrylic resin. Although it does not restrict | limit especially as an acrylic resin, The thing which a methylmethacrylate unit consists of 50-99 mass% and the total amount of the other monomer unit copolymerizable with this is 1-50 mass% is preferable. .

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

  The acrylic resin of the present invention may have a ring structure, specifically, a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure and a maleic anhydride structure, a pyran ring. Structure is mentioned.

  Among these, from the viewpoint of thermal decomposition resistance and fluidity of the copolymer, alkyl acrylate having 1 to 18 carbon atoms, vinyl monomer having an amide group such as acryloylmorpholine and dimethylacrylamide, and carbon number in the ester portion. A methacrylic acid ester or acrylic acid ester having 5 to 22 alicyclic hydrocarbon groups, an N-substituted maleimide structure, a pyran ring structure and the like are preferable.

  Specific examples of the alkyl acrylate having 1 to 18 carbon atoms are methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, etc., preferably And methyl acrylate.

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

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

  Preferable examples include isobornyl methacrylate, dicyclopentanyl methacrylate, dimethyladamantyl methacrylate and the like.

  Examples of the N-substituted maleimide include N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, Ni-propylmaleimide, N-butylmaleimide, Ni-butylmaleimide, Nt-butylmaleimide, N-laurylmaleimide, N-cyclohexylmaleimide, N-benzylmaleimide, N-phenylmaleimide, N- (2-chlorophenyl) maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromophenyl) phenylmaleimide, N -(2-methylphenyl) maleimide, N- (2-ethylphenylmaleimide), N- (2-methoxyphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N- (4-benzylphenyl) Maleimide, N- (2,4,6-tribromophe Le) maleimide and the like.

  Preferably, N-methylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, etc. are mentioned.

  Commercially available monomers can be used as they are.

  The acrylic resin used in the present invention preferably has a weight average molecular weight (Mw) of 20000 or more. The weight average molecular weight (Mw) of the acrylic resin is more preferably in the range of 20,000 to 1,000,000, particularly preferably in the range of 50,000 to 600,000, and most preferably in the range of 100,000 to 400,000. The upper limit of the weight average molecular weight (Mw) of the acrylic resin is preferably 1000000 or less from the viewpoint of production.

  The weight average molecular weight of the acrylic resin used in the present invention can be measured by the gel permeation chromatography described above.

  As a method for producing an acrylic resin that can be used in the present invention, any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used.

  Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

  In addition to the above acrylic resins, known acrylic resins can be used. For example, an acrylic resin having a lactone ring unit as described in JP-A-2008-9378 has high heat resistance and is preferably used. .

  Specific examples of the (meth) acrylic resin include, for example, Delpet 60N, 80N (manufactured by Asahi Kasei Chemicals Corporation), Dianal BR52, BR80, BR83, BR85, BR88 (manufactured by Mitsubishi Rayon Co., Ltd.), KT75 (Electricity). (Made by Chemical Industry Co., Ltd.), (Meth) acrylic resin having a ring structure in the molecule described in JP-A-2004-70296, high Tg (meth) acrylic obtained by intramolecular crosslinking or intramolecular cyclization reaction Resin system is mentioned.

<Cyclic olefin resin>
Specific examples of the cyclic olefin resin (also referred to as cycloolefin resin) preferably used in the present invention are preferably norbornene resins. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And the graft polymer which modified these by unsaturated carboxylic acid or its derivative (s), and those hydrides, etc. are mentioned. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as cyclic olefin resins. As specific examples, trade names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, product names “ARTON” manufactured by JSR Corporation, “TOPAS” manufactured by TICONA, and product names manufactured by Mitsui Chemicals, Inc. “APEL” may be mentioned.

  The content of the thermoplastic resin in the optical film is preferably in the range of 50 to 100% by mass, more preferably in the range of 50 to 99% by mass, still more preferably in the range of 60 to 98% by mass, and particularly preferably. Is in the range of 70 to 97% by mass. When the content of the thermoplastic resin is 50% by mass or more, high transparency and the like inherent in the thermoplastic resin can be sufficiently exhibited.

<Plasticizer>
The plasticizer is not particularly limited, and preferably used plasticizers include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, Tributyl phosphate, etc., phthalate ester type, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, etc. , Ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc. Preferred.

  Polyhydric alcohol ester plasticizers are also preferable. Examples of polyhydric alcohols include adonitol, arabitol, 1,2,4-butanetriol, 1,2,3-hexanetriol, 1,2,6- Hexanetriol, glycerin, diglycerin, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, galactitol, glucose, cellobiose, inositol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, tri Examples include methylolpropane, trimethylolethane, xylitol and the like. In particular, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol are preferable.

  Esters of organic acids and trihydric or higher polyhydric alcohols can be synthesized by known methods. For example, a method of condensing and esterifying an organic acid and a polyhydric alcohol in the presence of an acid, a method of previously reacting an organic acid with an acid chloride or acid anhydride and reacting with the polyhydric alcohol, a phenyl ester of an organic acid, and There are methods of reacting polyhydric alcohols, and it is preferable to select a method with good yield appropriately depending on the target ester compound.

  The organic acid is not particularly limited, but is preferably a monovalent carboxylic acid or a monovalent alcohol.

  The molecular weight of the polyhydric alcohol ester thus obtained is not particularly limited, but is preferably 300 to 1500, and more preferably 400 to 1000. 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 ester. Specific examples of other polyhydric alcohol ester plasticizers include polyhydric alcohol ester plasticizers described in JP-A-2003-12823, paragraphs [0030] to [0033].

  Two or more kinds of the above plasticizers may be used in combination as required. In this case, it is preferable to use a phosphate ester plasticizer at a ratio of 50% or less because, as a result, hydrolysis of the cellulose ester resin film hardly occurs and the durability is excellent.

  A smaller proportion of the phosphate ester plasticizer is more preferable, and it is particularly preferable to mainly use a phthalate ester or glycolate ester plasticizer.

  Further, the amount of the plasticizer to be added in order to make the water absorption rate and moisture content within a specific range is 3% to 30% by mass with respect to the thermoplastic resin, and more preferably 10 to 25%. It is in the range of 15% by mass, more preferably 15-25% by mass. Here, when the addition amount of the plasticizer is within 30% by mass, the mechanical strength and dimensional stability of the resin film are favorable, which is preferable.

<Antioxidant>
As the antioxidant, hindered phenol compounds are suitable. Specific examples thereof include 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-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadec -3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxy Benzyl) benzene and tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate. In particular 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] and 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. In order to obtain the effect, the addition amount of these compounds is preferably in the range of 1 ppm to 1.0%, particularly preferably in the range of 10 to 1000 ppm by mass ratio with respect to the thermoplastic resin.

<Acid scavenger>
The acid scavenger is an agent that plays a role of trapping an acid (protonic acid) remaining in the thermoplastic resin brought in from the time of manufacture. Further, when the thermoplastic resin is melted, hydrolysis of the side chain is promoted 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 and these fatty acids generally contain 12 to 22 carbon atoms)).

<Ultraviolet absorber>
It is preferable to add an ultraviolet absorber to the optical film. Here, as the ultraviolet absorber, the absorption ability of ultraviolet rays having a wavelength of 370 nm or less is excellent from the viewpoint of preventing deterioration of the liquid crystal, and the absorption of visible light having a wavelength of 400 nm or more is as little as possible from the viewpoint of good liquid crystal display properties. Those are preferably used.

  In particular, the transmittance of ultraviolet rays at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, and still more preferably 2% or less.

  Examples of the ultraviolet absorber used include, but are not limited to, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  It is preferable to use one or more of these ultraviolet absorbers, and two or more different ultraviolet absorbers may be contained.

  Preferably used ultraviolet absorbers include benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers. An embodiment in which a benzotriazole-based ultraviolet absorber with less unnecessary coloring is added to the cellulose ester-based resin film is particularly preferable.

  The ultraviolet absorber may be added by dissolving the ultraviolet absorber in an organic solvent such as alcohol, methylene chloride, dioxolane and the like, or adding it directly to the dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and the cellulose ester resin to disperse and then added to the dope.

  The use amount of the ultraviolet absorber is in the range of 0.1 to 2.5% by mass, preferably in the range of 0.5 to 2.0% by mass, more preferably in the range of 0.8 to 2.0% by mass relative to the thermoplastic resin. The range is 2.0% by mass. When the amount of the ultraviolet absorber used is 2.5% by mass or less, the transparency of the optical film is preferably high.

<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 ester resins, and in the melt casting film forming method performed in the present invention, the cellulose ester resins used alone The cellulose resin composition that can lower the melting temperature of the cellulose ester resin composition by addition of a hydrogen bonding solvent than the glass transition temperature of, or contains a hydrogen bonding solvent rather than the cellulose ester resin at the same melting temperature The melt viscosity of the product can be lowered.

  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>
An optical film manufactured using the method for manufacturing an optical film of the present invention has two or more aromatic rings as described in EP 911,656 A2 in order to control retardation. Aromatic compounds having can also 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.

<Fine particles>
Fine particles may be added to the optical film as a matting agent in order to make it easy to handle by preventing sticking between films or imparting slipperiness.

  The kind of fine particles may be an inorganic compound or 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. In this, it is preferable that it is a compound containing a silicon atom, and especially a silicon dioxide fine particle is preferable. As silicon dioxide fine particles, for example, Aerosil manufactured by Aerosil Co., Ltd. AEROSIL-200, 200V, 300, R972, R972V, R974, R976, R976S, R202, R812, R805, OX50, TT600, RY50, RX50, NY50, NAX50, NA50H, NA50Y, NX90, RY200S, RY200, RX200, R8200, RA200H, RA200HS, NA200Y, R816, R104, RY300, RX300, R106, and the like. Among these, AEROSIL-200V and R972V are preferable in terms of controlling dispersibility and particle size.

  The average particle size of the fine particles in the film is preferably in the range of 50 nm to 2 μm from the viewpoint of imparting slipperiness and ensuring transparency. Preferably, it is the range of 100-1000 nm, More preferably, it is the range of 100-500 nm. The average particle diameter in the film can be confirmed by taking and observing a cross-sectional photograph.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size after being added to a film often change. It is important that the fine particles are finally combined with the resin in the film. It is to control the particle size formed by aggregation.

  The addition amount of the fine particles is in the range of 0.02 to 0.5% by mass, preferably in the range of 0.04 to 0.3% by mass with respect to the optical film.

<Polarizer>
The optical film manufactured using the method for manufacturing an optical film of the present invention is suitable for a protective film for a polarizing plate. The polarizing plate is formed by pasting the optical film as a protective film on the front and back of a polarizer obtained by processing a stretchable film such as a polyvinyl alcohol film with a dichroic dye such as iodine. The

  The optical film includes a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optically anisotropic layer, a liquid crystal layer, an alignment layer, an adhesive layer, an adhesive layer, a lower layer Various functional layers such as a pulling 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.

<Liquid crystal display device>
By using a liquid crystal display device in which a polarizing plate having an optical film produced by using the production method of the present invention is bonded to at least one surface of a liquid crystal cell, a liquid crystal display having no display unevenness and excellent visibility. A device can be made. The optical film manufactured by the manufacturing method of the present invention includes various types such as a reflective type, a transmissive type, a transflective type LCD, a TN type, an STN type, an OCB type, a HAN type, a VA type (PVA type, MVA type), and an IPS type. It is preferably used in a drive type LCD. In particular, a large-screen display device with a 30-inch screen or more has the effect of less color unevenness and wavy unevenness, and eyes are not tired even during long-time viewing.

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

Example 1
(Preparation of pellet 1)
After the resin mixture 1 shown below was mixed for 30 minutes with a V-type mixer, it was melted at 230 ° C. under a nitrogen atmosphere using a twin screw extruder (PCM30, Ikegai Co., Ltd.) equipped with a strand die. A cylindrical pellet having a thickness of 4 mm and a diameter of 3 mm was prepared. 1-1. The obtained pellet had a glass transition point (Tg) of 135 ° C. The shear rate at this time was set to 25 (/ s).

(Resin mixture 1)
Cellulose acetate propionate (acetyl group substitution degree 1.4, propionyl group substitution degree 1.35, number average molecular weight 60000) 89% by mass
Trimethylolpropane tribenzoate (plasticizer, melting point 85 ° C.) 9% by mass
IRGANOX XP 420 / FD (Antioxidant, manufactured by BASF Japan)
0.25% by mass
TINUVIN 928 (UV absorber, manufactured by BASF Japan, melting point 115 ° C.)
1.6% by mass
Seahoster KEP-30 (matting agent (silica fine particles), manufactured by Nippon Shokubai Co., Ltd., average particle size 0.3 μm) 0.15% by mass
The degree of substitution of acyl groups such as acetyl group and propionyl group of cellulose acetate propionate was measured according to the method prescribed in ASTM-D817-96.

(Preparation of pellet 2)
The resin mixture 2 shown below was mixed for 30 minutes with a V-type mixer, then melted at 230 ° C. in a nitrogen atmosphere using a twin screw extruder 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 and no. 1-2. The obtained pellet had a glass transition point (Tg) of 135 ° C.

(Resin mixture 2)
Acrylic resin (acrylic polymer having lactone ring structure in resin) 89% by mass
Trimethylolpropane tribenzoate (plasticizer, melting point 85 ° C.) 9% by mass
IRGANOX XP 420 / FD (Antioxidant, manufactured by BASF Japan)
0.25% by mass
TINUVIN 928 (UV absorber, manufactured by BASF Japan, melting point 115 ° C.)
1.6% by mass
Seahoster KEP-30 (matting agent (silica fine particles), manufactured by Nippon Shokubai Co., Ltd., average particle size 0.3 μm) 0.15% by mass
(Synthesis of acrylic resin)
In a 30 L reaction kettle equipped with a stirrer, temperature sensor, cooling pipe, nitrogen introduction pipe, 8000 g of methyl methacrylate (MMA), 2000 g of methyl 2- (hydroxymethyl) acrylate (MHMA), 10000 g of 4-methyl- 2-Pentanone (methyl isobutyl ketone, MIBK), 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while passing nitrogen through this. When refluxed, 5.0 g of tertiary butyl peroxyisopropyl was used as an initiator. While adding carbonate (manufactured by Akzo Kayaku Co., Ltd., trade name: Kaya-Carbon Bic-75), a solution comprising 10.0 g of tertiary butyl peroxyisopropyl carbonate and 230 g of MIBK was added dropwise over 2 hours under reflux ( Solution polymerization at about 105 to 120 ° C.) Aging was carried out over a period of 4 hours in La.

  To the obtained polymer solution, 30 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemical Co., Ltd., trade name: Phoslex A-18) was added and cyclized under reflux (about 90 to 120 ° C.) for 5 hours. A condensation reaction was performed.

(Preparation of pellet 3)
The resin mixture 3 shown below was mixed with a V-type mixer for 30 minutes, then melted at 235 ° C. in a nitrogen atmosphere using a twin screw extruder 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 and no. 1-3. The obtained pellet had a glass transition point (Tg) of 131 ° C.

(Resin mixture 3)
Cycloolefin resin (Nippon Zeon Co., Ltd., ZEONOR 1420R, glass transition temperature 140 ° C.) 89% by mass
9% by mass of trimethylolpropane tribenzoate (plasticizer, melting point 85 ° C.)
IRGANOX XP 420 / FD (Antioxidant, manufactured by BASF Japan)
0.25% by mass
TINUVIN 928 (UV absorber, manufactured by BASF Japan, melting point 115 ° C.)
1.6% by mass
Seahoster KEP-30 (matting agent (silica fine particles), manufactured by Nippon Shokubai Co., Ltd., average particle size 0.3 μm) 0.15% by mass
<Manufacture of Optical Film 101: Present Invention>
Prepared pellet No. 1-1 was dried at 100 ° C. for 5 hours to have a water content of 100 ppm, and an optical film was produced under the conditions shown below using the film casting apparatus shown in FIG. At that time, the air gap is adjusted to 120 mm, and as shown in FIG. 2A, a metal member E is attached to the casting die A, and the position of the casting die and the thickness of the member E are adjusted. The shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller were 3 mm and D1 / D2 = 1.0, respectively.

  Next, under the following melt extrusion conditions, the pellet No. After extruding the 1-1 melt, it was peeled, the formed web was stretched and dried, and the stretched film was slit with a slitter so as to have a width of 2000 mm. An optical film having a length of 40 μm and a length of 5000 m was manufactured as an optical film sample 101.

(Melt extrusion conditions)
Single screw extruder: screw diameter 90 mm, L / D = 30 (L: indicates screw length)
Cast roller 5: The surface temperature was set to 100 ° C., the surface roughness was set to a maximum height Ry of 0.1 μm or less stainless steel, and the roller diameter was set to 400 mm.

  Touch roller 6: A metal outer cylinder, an inner cylinder, and a double cylinder structure having a gap are used. The material of the metal outer cylinder was stainless steel, the surface roughness was 0.05 μm or less at the maximum height Ry, and the wall thickness was 3 mm. The inner cylinder was aluminum and the wall thickness was 30 mm. The gap between the metal outer cylinder and the inner cylinder was 5 mm. Oil was allowed to flow into the gap, and the temperature of the surface of the metal outer cylinder was set to 120 ° C. The roller diameter was set to 200 mm.

  Extrusion environment: Nitrogen gas was sealed from the vicinity of the material supply port, and the inside of the extruder was kept in a nitrogen atmosphere.

Extrusion temperature: 240 ° C
Casting die: Coat hanger type, hard chrome plating is applied to the inner wall and finished to a mirror surface with a surface roughness of 0.1S. The lip gap of the casting die was set to 2 mm.

Touch roller pressing (linear pressure): 20 N / mm
The surface temperature of the second cooling roller is 30 ° C
Film transport speed: 30 m / min
TD stretching device: Pin tenter MD stretching ratio: 1.5 times TD stretching ratio: 1.5 times Tension during winding: 150 N / m
<Preparation of Optical Films 102 to 121: Present Invention>
In the production of the optical film 101, the type of the pellet is No. In addition to 1-1, no. 1-2 and No.1. 1-3, while adjusting the length of the air gap as shown in Table 1, a metal member E was mounted on the casting die A, and the position and height of the casting die and the thickness of the member E The optical film was adjusted in the same manner except that the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller were changed as shown in Table 1. 102-121 were produced. Each roller diameter was appropriately changed when adjusting the gap distance.

<Manufacture of optical films 122-124, 127-129, and 132-134: Comparative example>
In the production of the optical film 101, no member is attached, and the shortest distance D1 between the casting die and the cast roller, the casting die, and the touch roller while adjusting the length of the air gap as shown in Table 1 The optical films 122 to 124, 127 to 129, and 132 to 134 of Comparative Examples with different resin pellets were produced in the same manner except that the shortest distance D2 was adjusted to the distance shown in Table 1.

<Manufacture of optical films 125, 126, 130, 131, 135, and 136: comparative example>
In the production of the optical film 101, while adjusting the length of the air gap as shown in Table 1, the metal member E is mounted on the casting die A, and the position and height of the casting die and the member E are adjusted. The thickness is adjusted, and the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller are changed in the same manner as in Table 1, Optical films 125, 126, 130, 131, 135, and 136 of comparative examples with different resin pellets were produced.

<Evaluation>
(Evaluation of display unevenness of liquid crystal display devices)
<Preparation of polarizing plate>
A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 6 times at 50 ° C. in the transport direction to prepare a polarizer.

  The produced optical films 101 to 136 were bonded to both sides of the polarizer. The optical film using the cellulose ester resin was bonded using an alkali saponification treatment and a 5% by mass aqueous solution of a completely saponified polyvinyl alcohol as an adhesive. In addition, optical films using acrylic resins and cycloolefin resins are bonded using the following active energy ray-curable adhesive liquid (cationic type), and irradiated with ultraviolet rays to cure the adhesive and polarizing plate. Was made.

(Preparation of active energy ray-curable adhesive solution: cationic polymerization type)
Each of the following components was mixed and then defoamed to prepare an active energy ray-curable adhesive solution. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries) 40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass <Production of liquid crystal display device>
The polarizing plate on the viewing side of a commercially available 37-type TFT color liquid crystal display bravia (manufactured by Sony Corporation) was carefully peeled off, and the above-prepared polarizing plate was pasted with the polarization direction aligned to produce a liquid crystal display device.

<Evaluation method of display unevenness of display device>
Each liquid crystal display device produced in this way was visually observed according to the following evaluation criteria for the presence or absence of unevenness that appears whitish when viewed from the front and oblique directions.

◎: Unevenness is not visible at all ○: Unevenness at a level that can be used as a product is found △: Unevenness at a level that can be used as a product is observed ×: Unevenness that affects the product is observed Table 1 shows the results obtained Show.

表１に示した結果から、比較例に対して、本発明の光学フィルムの製造方法によって製造された光学フィルム１０１〜１２１は、流延ダイとキャストローラとの最短距離Ｄ１と流延ダイとタッチローラとの最短距離Ｄ２がそれぞれ３〜３０ｍｍの範囲内であり、かつ当該最短距離の比Ｄ１／Ｄ２の値が０．５〜２．０の範囲内に調整されることによって、外乱（風）によるリボンの安定性が向上し、液晶表示装置の表示ムラの問題が改善されることが確認された。

From the results shown in Table 1, with respect to the comparative example, the optical films 101 to 121 manufactured by the optical film manufacturing method of the present invention are the shortest distance D1 between the casting die and the cast roller, the casting die and the touch. The shortest distance D2 between the rollers is in the range of 3 to 30 mm, and the value of the shortest distance ratio D1 / D2 is adjusted to be in the range of 0.5 to 2.0. As a result, it was confirmed that the stability of the ribbon by the liquid crystal was improved and the problem of display unevenness of the liquid crystal display device was improved.

Example 2
As the gap adjusting means, while adjusting the length of the air gap as shown in Table 2, as shown in FIG. 2 (b), the casting die A is tilted within a range of ± 10 ° from the vertical direction. In the same manner as in the optical films 101 to 121 of the present invention, the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller were changed to produce an optical film. Similarly, display unevenness was evaluated and shown in Table 2.

表２に示した結果から、流延ダイを±１０°の範囲内で傾斜させて上記Ｄ１、Ｄ２及びその比Ｄ１／Ｄ２の値を、本発明の光学フィルムの製造方法の範囲内に調整することによって、外乱（風）によるリボンの安定性が向上し、液晶表示装置の表示ムラの問題が実施例１を再現し改善されることが確認された。

From the results shown in Table 2, the casting die is tilted within a range of ± 10 °, and the values of D1, D2 and the ratio D1 / D2 are adjusted within the range of the method for producing an optical film of the present invention. As a result, it was confirmed that the stability of the ribbon due to disturbance (wind) was improved, and the problem of display unevenness of the liquid crystal display device was reproduced by improving Example 1.

Example 3
As the gap adjusting means, the optical film 101 of the present invention was changed except that the height of the touch roller with respect to the cast roller was changed as shown in FIG. 3A while adjusting the length of the air gap as shown in Table 3. Optical films were prepared by changing the values of D1 and D2 in the same manner as in .about.121, and display unevenness was evaluated in the same manner as in Example 1 and shown in Table 3.

表３に示した結果から、タッチローラのキャストローラに対する高さを変えて、上記Ｄ１、Ｄ２及びその比Ｄ１／Ｄ２の値を、本発明の光学フィルムの製造方法の範囲内に調整することによって、外乱（風）によるリボンの安定性が向上し、液晶表示装置の表示ムラの問題が実施例１を再現し改善されることが確認された。

From the results shown in Table 3, by changing the height of the touch roller relative to the cast roller and adjusting the values of D1, D2 and the ratio D1 / D2 within the range of the optical film manufacturing method of the present invention. It was confirmed that the stability of the ribbon due to disturbance (wind) was improved, and the problem of display unevenness of the liquid crystal display device was reproduced by improving Example 1.

Example 4
As the gap adjusting means, the length of the air gap is adjusted as shown in Table 4, and the casting die A is made asymmetrical as shown in FIG. In the same manner as described above, the values of D1 and D2 were changed to produce an optical film having a film thickness of 30 μm, and display unevenness was evaluated in the same manner as in Example 1 and shown in Table 4.

表４に示した結果から、流延ダイ非対称形状にして上記Ｄ１、Ｄ２及びその比Ｄ１／Ｄ２の値を、本発明の光学フィルムの製造方法の範囲内に調整することによって、外乱（風）によるリボンの安定性が向上し、液晶表示装置の表示ムラの問題が実施例１を再現し改善されることが確認された。

From the results shown in Table 4, disturbance (wind) was obtained by adjusting the values of D1, D2 and the ratio D1 / D2 within the range of the method for producing an optical film of the present invention by making the casting die asymmetrical. It was confirmed that the stability of the ribbon due to the liquid crystal was improved, and the problem of display unevenness of the liquid crystal display device was reproduced by improving Example 1.

A Casting die B Cast roller C Touch roller E Member P Contact point between film and cast roller r Ribbon 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 Cast roller, rotating support, cooling roller 6 Touch roller, sandwiching Pressure rotating body 7, 8 Cooling roller 9 Peeling roller 10 Longitudinal stretching device 17 Film 19 Slitter 20 Horizontal stretching device 52 Back roller 53 Embossing ring 60 Winding device

Claims (14)

  A casting process in which a melt containing a thermoplastic resin is extruded from the casting die onto the surface of the cast roller in a film form, and the film-like melt extruded in the casting process is sandwiched between the cast roller and the touch roller. A method of manufacturing an optical film having a clamping step of clamping with a pressing part, wherein the shortest distance D1 between the casting die and the cast roller and the shortest distance D2 between the casting die and the touch roller are 3 respectively. A method for producing an optical film, which is in a range of ˜30 mm, and the value of the ratio D1 / D2 of the shortest distance is in a range of 0.5 to 2.0.   The shortest distances D1 and D2 are within a range of 3 to 30 mm, respectively, and the ratio of the shortest distances D1 / D2 is within a range of 0.5 to 2.0 by the gap adjusting means. The manufacturing method of the optical film of Claim 1.   3. The gap adjusting means is a means for adjusting by attaching a member to at least one gap between the casting die and the cast roller or between the casting die and the touch roller. The manufacturing method of the optical film of description.   3. The method for producing an optical film according to claim 2, wherein the gap adjusting means is means for adjusting the casting die by inclining within a range of ± 10 ° from the vertical direction.   The optical film manufacturing apparatus according to claim 2, wherein the gap adjusting unit is a unit that variably adjusts the height of at least one of the cast roller and the touch roller.   3. The method for producing an optical film according to claim 2, wherein the gap adjusting means is a means using a casting die having an asymmetric shape on the cast roller side and the touch roller side.   The said touch roller is an elastic touch roller, The manufacturing method of the optical film as described in any one of Claim 1- Claim 6 characterized by the above-mentioned.   The manufacturing method according to claim 1, wherein a diameter of the cast roller is 1.1 times or more larger than a diameter of the touch roller.   The optical film according to any one of claims 1 to 8, wherein the thermoplastic resin is at least one selected from a cellulose ester resin, an acrylic resin, and a cyclic olefin resin. Production method.   It is a manufacturing apparatus of the optical film used for the manufacturing method of the optical film as described in any one of Claim 1-9, Comprising: The shortest distance D1 of the said casting die and the said cast roller, and the said casting die And a gap adjusting means for setting the shortest distance D2 between the touch roller and the touch roller within a range of 3 to 30 mm and a ratio D1 / D2 of the shortest distance within a range of 0.5 to 2.0. An apparatus for producing an optical film.   11. The optical film according to claim 10, wherein a member is mounted as at least one gap between the casting die and the cast roller or between the casting die and the touch roller as the gap adjusting means. Manufacturing equipment.   The optical film manufacturing apparatus according to claim 10, wherein the casting die is inclined within a range of ± 10 ° from the vertical direction as the gap adjusting means.   The apparatus for producing an optical film according to claim 10, wherein as the gap adjusting means, a height of at least one of the cast roller and the touch roller is variable.   The optical film manufacturing apparatus according to claim 10, wherein the gap adjusting unit includes a casting die having an asymmetric shape on the cast roller side and the touch roller side.

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