JPWO2011027681A1 - Film production method - Google Patents

Abstract

The subject of this invention is providing the method of manufacturing the film which was excellent in smoothness (texture), and generation | occurrence | production of surface failures, such as peeling horizontal stage, was fully suppressed. The object is to continuously extrude a film-constituting material containing a molten thermoplastic resin from the casting die 4 in the form of a film, to circumscribe the film-like melt to the first rotating body 5 and to cool and solidify the film. The film-like melt is pressed against the surface of the first rotating body by the second rotating body 6 and then stretched, and the arithmetic average surface roughness Ra of the second rotating body 6 is 110 to 300 nm, and the width This is achieved by a film production method characterized in that the total draw ratio represented by the product of the draw ratio (times) in the hand direction and the draw ratio (times) in the transport direction is 2 to 9.

Description

  The present invention relates to a film manufacturing method, and more particularly to an optical film manufacturing method.

  A liquid crystal display device is widely used as a monitor because it saves space and energy compared to a conventional CRT display device. Furthermore, it is also spreading for TV. In such a liquid crystal display device, various optical films such as a polarizing plate protective film, a retardation film, and a viewing angle widening film are used.

  In addition, optical films such as an antireflection film, an antiglare film, and a protective form are also used in plasma displays, organic EL displays, and the like.

  These optical films are required to have excellent smoothness (texture) and no surface failure. In particular, as the size of monitors and TVs increases and the definition becomes higher, these required qualities are becoming stricter.

  As a method for producing an optical film, a melt casting film forming method is known. In the melt casting film forming method, a polymer is heated and melted and extruded into a film form from a casting die, and then the film melt is cooled and solidified by circumscribing a cast roll, and further stretched as necessary. This is a method of forming a film (Patent Documents 1 and 2). At this time, the film-like melt is pressed against the surface of the cast roll by the touch roll, thereby correcting the streaks generated in the film transport direction due to foreign matters (dust) adhering to the lip portion of the casting die. The surface of the touch roll or cast roll is preferably a mirror surface, and the surface roughness Ra is set to 100 nm or less.

  However, in such a melt casting film forming method, the adhesion with the film increases as the surface of the touch roll or cast roll becomes a mirror surface. Therefore, the peeling position from the touch roll or cast roll in the film was not stable, and a stepwise surface deformation called a peeling horizontal step occurred in the width direction of the film. The problem of the peeling step occurred remarkably when the film forming speed was increased.

  Therefore, a technique is disclosed in which a recess having a depth of 5 nm or more and 500 nm or less is formed in at least one of a touch roll or a cast roll with an area ratio of 0.5% or more and 20% or less (Patent Document 3). In this document, the roll in which the concave portion is formed has concave portions or convex portions distributed at a predetermined density in a smooth surface. However, with such a technique, local peeling failure cannot be improved, and the occurrence of peeling lateral stages cannot be sufficiently suppressed.

JP 2008-265167 A JP 2008-183849 A JP 2007-137027 A

  An object of this invention is to provide the method of manufacturing the film which was excellent in smoothness (texture) and in which generation | occurrence | production of surface failures, such as peeling horizontal stage, was fully suppressed.

The present invention continuously extrudes a film-constituting material containing a molten thermoplastic resin into a film shape from a casting die, makes the film-shaped melt circumscribing a first rotating body, and cools and solidifies the film-shaped melt. A method for producing a film that is stretched after pressing an object against the surface of the first rotating body by a second rotating body,
The arithmetic average surface roughness Ra of the second rotating body is 110 to 300 nm,
The present invention relates to a method for producing a film, characterized in that a total draw ratio represented by a product of a draw ratio (times) in the width direction and a draw ratio (times) in the transport direction is 2 to 9.

  According to this invention, while being excellent in smoothness (texture), the film by which generation | occurrence | production of surface failures, such as peeling horizontal stage, was fully suppressed can be manufactured. Moreover, such an effect can be effectively obtained even if the film forming speed is increased to 20 m / min or more.

It is a schematic block diagram of an example of the apparatus which enforces the manufacturing method of the film which concerns on this invention. It is a principal part enlarged view of the 1st rotary body in FIG. 1, and the 2nd rotary body vicinity. (A) is a perpendicular sectional view with respect to an axis about an example of the 2nd rotating body, and (B) is a perpendicular sectional view which passes along an axis about the 2nd rotating body shown in (A). It is a disassembled perspective view which shows the outline of the block diagram of a liquid crystal display device. It is a graph which shows the relationship between the total draw ratio in an Example / comparative example and the surface roughness of a touch roll with the result of comprehensive evaluation.

[Film Production Method]
The method for producing a film according to the present invention is based on a so-called melt casting method, that is, a film constituent material containing a molten thermoplastic resin is continuously extruded from a casting die into a film shape, and the film-like melt is produced. The object is circumscribed on the first rotating body to be cooled and solidified, and the film-like melt is pressed against the surface of the first rotating body by the second rotating body, and then stretched.

  Specifically, the film production method according to the present invention includes a melt extrusion process, a cooling process, and a stretching process, and usually further includes a winding process. Hereafter, each process is demonstrated in detail using FIGS. 1-3. FIG. 1 is a schematic configuration diagram of an example of an apparatus for carrying out the film manufacturing method of the present invention. FIG. 2 is an enlarged view of a main part in the vicinity of the first rotating body and the second rotating body in FIG. FIG. 3A is a vertical sectional view with respect to an axis of an example of the second rotating body, and FIG. 3B is a vertical sectional view passing through the axis of the second rotating body shown in FIG.

(Melting extrusion process)
In this step, the film constituent material containing the thermoplastic resin is melted using the extruder 1, and then the melt 42 is continuously extruded from the casting die 4 into a film shape. At this time, after the melt is melted by the extruder 1, it may be extruded from the casting die 4 into a film via the filter 2 and the static mixer 3 as shown in FIG. 1.

  It is preferable to mix the film constituent material containing the thermoplastic resin described in detail later before melting. Mixing may be performed by a mixer or the like, or may be performed in the process of preparing the thermoplastic resin. When a mixer is used, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, or the like can be used.

  After the film constituent materials are mixed, the mixture may be directly melted by the extruder 1 to form a film, but once the film constituent materials are pelletized, the pellets are melted by the extruder 1 A film may be formed. When the film constituent material includes a plurality of materials having different melting points, a so-called bowl-shaped semi-melt is once produced at a temperature at which only a material having a low melting point is melted, and the semi-melt is supplied to the extruder 1. It is also possible to form a film by introducing it. If the film component contains a material that is easily pyrolyzed, the film can be formed directly without making pellets for the purpose of reducing the number of times of melting, or after creating a bowl-shaped semi-melt as described above. A method of forming a film is preferred.

  The melt extrusion by the extruder 1 can be performed under the same conditions as those used for 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 dryer or a dehumidifying hot air dryer. For example, a thermoplastic 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 and filtered through a leaf disk type filter 2 to remove foreign matters.

  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 an additive such as a plasticizer is not mixed in advance, the additive 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.

  As the extruder 1, what is generally available as a plastic extruder is used, and various types of extruders available on the market can be used. However, a melt-kneading extruder is preferable, and a single screw extruder or a twin screw extruder is also used. An extruder may be used. When forming a film directly without producing pellets from a film constituting material, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is required. However, even with a single-screw extruder, the screw shape is a Maddock type. By changing to a kneading type screw such as a unimelt type or a dull mage, moderate kneading can be obtained, so that it can be used. When a pellet or bowl-shaped semi-melt is used as the film constituent material, it can be used with either a single screw extruder or a twin screw extruder. It is preferable to reduce the oxygen concentration by replacing the inside of the extruder 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 (Tg) of the film Tg to Tg + 150 ° C., preferably Tg + 10 ° C. to Tg + 130 ° C. The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. The residence time of the film constituting material in the extruder 1 is preferably shorter, and is within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. The residence time depends on the type of the extruder 1 and the extrusion conditions, but the material supply amount and L / D (ratio between the screw length and the cylinder inner diameter), the screw rotation speed, and the screw groove depth. It is possible to shorten it by adjusting etc.

  In the present specification, the Tg of a film is assumed to be equal to the Tg of a mixture obtained by uniformly mixing, melting and cooling a predetermined film constituent material in advance, and can be detected by measuring the Tg of the mixture. Tg uses the value measured by DSC method (in nitrogen, temperature rising temperature 10 ° C./min) using “DSC6200” manufactured by Seiko Co., Ltd.

  The shape, rotation speed, and the like of the screw of the extruder 1 are appropriately selected depending on the viscosity, discharge amount, and the like of the film constituent material. In the present invention, the shear rate in the extruder 1 is 1 / second to 10000 / second, preferably 5 / second to 1000 / second, more preferably 10 / second to 100 / second.

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

  The casting die 4 to which the melt discharged from the extruder 1 is supplied is not particularly limited as long as it is used for producing a sheet or a film. 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. I can give you.

  A preferred material for the lip portion of the casting die 4 is the same as that of the casting die 4.

(Cooling process)
In this step, the film-like melt 42 extruded from the casting die 4 is circumscribed by the first rotating body 5 to be cooled and solidified, and the film-like melt 42 is cooled by the second rotating body 6 to the first rotating body 5. Press the surface to correct the surface. The film obtained by cooling and solidifying and surface correction by the first rotating body 5 and the second rotating body 6 is further circumscribed by the third rotating body 7 and the fourth rotating body 8 in order as shown in FIG. It may be cooled while being conveyed.

  The discharge position of the film-like melt 42 on the first rotating body 5 is not particularly limited as long as the melt is sandwiched at a predetermined pressure between the first rotating body 5 and the second rotating body 6 after discharging. . For example, the film-like melt 42 may be discharged directly to the nip 43 between the first rotating body 5 and the second rotating body 6 as shown in FIG. After being discharged onto the surface and conveyed by the rotation of the first rotating body 5, it may be sandwiched by the nip portion 43.

  The entire outer peripheral surface of the second rotating body 6 is uniformly roughened, and the arithmetic average surface roughness Ra of the outer peripheral surface of the second rotating body 6 is 110 to 300 nm, preferably 140 to 210 nm. . While maintaining the Ra within the above-mentioned preferable range, by performing a combination of predetermined stretching, surface failure is further improved while further improving smoothness on the contact surface with the second rotating body in the film as the final product. This can be further effectively reduced. If the Ra of the second rotating body is too small, the adhesiveness with the film becomes excessively high, and thus a surface failure such as a peeling step occurs in the film as the final product. If Ra of the second rotating body is too large, the smoothness (texture) of the film surface as the final product is lowered.

  In the present specification, the arithmetic average surface roughness Ra is a value based on JIS-B-0601-1994, and an average value of values measured at arbitrary five points by Surfcom 130A (manufactured by Tokyo Seimitsu Co., Ltd.) is used. Yes.

  The surface roughness Ra can be controlled by selecting the abrasive when uniformly polishing the outer peripheral surface with the abrasive. For example, specifically, Ra is smaller as the average primary particle size of the abrasive is smaller, and Ra is larger as the particle size is larger.

  The temperature of the 2nd rotary body 6 is Tg-80 degreeC-TgdegreeC normally, Preferably it is Tg-50 degreeC-Tg-5 degreeC. Tg is the glass transition temperature of the film.

  The temperature of the 2nd rotary body 6 is the temperature of the outer peripheral surface of the said rotary body, and uses the temperature of the outer peripheral surface just before contacting a film-form melt. Specifically, when the rotating body repeats contact and peeling with the film-like melt by rotation, after the film-like melt peels from the rotating body, immediately before circumscribing, the time when the melt is not in contact with the melt. The temperature of the outer peripheral surface is set as the temperature of the second rotating body 6.

  The surface temperature of the rotating body can be measured with a non-contact type thermometer (manufactured by Hayashi Electric Works).

  The shape of the second rotating body 6 is not particularly limited as long as the Ra of the outer peripheral surface in contact with the film is controlled within the above range. For example, in FIG. 1 and FIG. 2, the second rotating body 6 has a roll shape, but may be a belt wound around two or more rotating rolls. The preferred second rotating body 6 has a roll shape from the viewpoints of rotational stability, temperature control stability, and ease of manufacture of a seamless rotating body. The second rotating body 6 having a roll shape (hereinafter sometimes referred to as a second roll 6) is generally also called a touch roll.

  The 2nd rotary body 6 is normally equipped with a temperature control means inside. The temperature control means may be, for example, a heater such as a heating wire, or a fluid such as liquid oil or water. In the present specification, the fluid as the temperature control means can be referred to as a “cooling fluid” based on the temperature of the film-like melt, and is considered based on the ambient temperature (for example, room temperature) at the time of film production. And “heating fluid”. The surface temperature of the second rotating body 6 can be controlled by adjusting the temperature of the fluid and the output of the heater.

  From the viewpoint of pressing the second rotating body 6 with a uniform and weak force so as not to leave residual stress on the film, the outer peripheral surface preferably has elasticity. For example, when the 2nd rotary body 6 has a roll shape, it is preferable that the 2nd rotary body 6 is equipped with the metallic outer cylinder which has flexibility on the surface. The second rotating body 6 is particularly preferably configured as a double cylinder having a cooling fluid flow space inside the outer cylinder and a metal inner cylinder that is coaxial with the outer cylinder.

  As an example of preferable embodiment of the 2nd rotary body 6, the roll described as Unexamined-Japanese-Patent No. 11-235747 as a pressing roll is mentioned, for example. Such a preferred second roll is shown in FIGS. 3 (A) and 3 (B). 3A is a vertical sectional view with respect to the axis of the second roll 6, and FIG. 3B is a vertical sectional view passing through the axis of the second roll 6 shown in FIG. 3A.

  The second roll 6 shown in FIGS. 3A and 3B is an elastic roll whose surface is elastically deformed. Specifically, the outer cylinder is made of a flexible seamless stainless steel pipe (thickness 4 mm). 601 and a high-rigidity metal inner cylinder 602 (for example, made of stainless steel) arranged in the same axial center inside the outer cylinder 601. The cooling liquid 64 flows in the space 63 between the outer cylinder 601 and the inner cylinder 602.

  Specifically, in the second roll 6, outer cylinder support flanges 66a and 66b are attached to the rotary shafts 65a and 65b at both ends, and a thin metal outer cylinder 601 is attached between the outer peripheral portions of the both outer cylinder support flanges 66a and 66b. ing. In addition, a fluid supply pipe 69 is disposed in the same axial center in a fluid discharge hole 68 that forms a fluid return passage 67 at the axial center of one rotary shaft 65a. It is connected and fixed to a fluid shaft cylinder 60 arranged at the axial center in the cylinder 601. Inner cylinder support flanges 61a and 61b are attached to both ends of the fluid shaft cylinder 60, respectively, and the wall thickness is about 15 to 20 mm from between the outer peripheral parts of the inner cylinder support flanges 61a and 61b to the outer cylinder support flanges 66a and 66b. A metal inner cylinder 602 having the structure is attached.

  A cooling liquid inflow space 63 of about 10 mm, for example, is formed between the metal inner cylinder 602 and the thin metal outer cylinder 601, and in the vicinity of both ends of the metal inner cylinder 602, An outflow port 602a and an inflow port 602b communicating with the intermediate passages 62a and 62b outside the inner cylinder support flanges 61a and 61b are formed.

  The diameter of the 2nd roll 6 is not restrict | limited in particular, For example, it is preferable that it is the range of 200 mm to 500 mm. It is preferable that the 2nd roll 6 is a drum type (crown roll type) whose outer diameter of a center part is larger than the outer diameter of both ends. The crowning amount at this time is set to 100 μm, but is preferably within the range of 50 μm to 300 μm. The first roll may be a drum type instead of the second roll. The thickness of the outer cylinder 601 is not particularly limited as long as it has flexibility, and may be, for example, 1 to 10 mm, and preferably 2 to 6 mm.

  The width of the second roll 6 needs to be wider than the film width to be pressed. In particular, the axial distance between the inner cylinder support flanges 61a and 61b is sufficiently wider than the width (axial length) of the first rotating body 5 from the viewpoint of forming the uniform nip portion 43 in the axial direction. preferable.

  If the neck-in of the film is large and the thickness of the film end is thicker than the thickness of the central part, it is preferable to scrape the outer cylinder at the part in contact with the film thick film part. The end of the second roll 6 is preferably shaved off for the purpose of avoiding contact with the first rotating body 5. The amount of cutting at this time is in the range of 50 μm to 1 mm. Instead of scraping the end portion of the second roll 6, the end portion of the first rotating body 5 may be shaved.

  The surface of the second rotating body 6 is preferably subjected to a treatment such as chrome plating.

  It is preferable that the 2nd rotary body 6 presses a film in the range of 0.01 N / mm to 100 N / mm.

  The second rotating body 6 is used by being rotated so that the peripheral speed becomes the same value as the film forming speed.

  The film forming speed of the film is the length of the film manufactured per unit time, and is not particularly limited, but is preferably 20 to 80 m / min, and more preferably 20 to 50 m / min. Conventionally, when the film forming speed is increased, the problem of the peeling step occurs remarkably. However, in the present invention, even if the film forming rate is increased as described above, the peeling step can be effectively suppressed. The film forming speed is the peripheral speed of the first rotating body 5.

  The first rotating body 5 achieves cooling and solidification of the melt by winding the film-like melt 42.

  The temperature of the 1st rotary body 5 is Tg-80 degreeC-TgC normally, Preferably it is Tg-50 degreeC-Tg-5 degreeC. Tg is the glass transition temperature of the film.

  The temperature of the 1st rotary body 5 is the temperature of the outer peripheral surface of the said rotary body, and uses the temperature of the outer peripheral surface just before contacting a film-form melt. Specifically, when the rotating body repeats winding and peeling of the film-like melt by rotation, after the film-like melt is peeled from the rotating body, immediately before circumscribing, when the melt is not wound The temperature of the outer peripheral surface of the first rotating body 5 is the temperature of the first rotating body 5.

  The arithmetic average surface roughness Ra of the outer peripheral surface of the first rotating body 5 is not particularly limited, and is preferably 20 to 200 nm, and more preferably 50 to 100 nm, for example. By setting the Ra of the first photoconductor 5 within the above range, smoothness (texture) is further improved on the contact surface with the first rotating body in the film as the final product, and surface failure is further increased. It can be effectively reduced.

  The shape of the first rotating body 5 is not particularly limited as long as the film-like melt 42 is wound to achieve cooling and solidification of the melt. For example, in FIG. 1 and FIG. 2, the first rotating body 5 has a roll shape, but may be a belt wound around two or more rotating rolls. The 1st rotary body 5 preferable from a viewpoint of temperature control has a roll shape. The first rotating body 5 having a roll shape (hereinafter sometimes referred to as a first roll 5) is generally also called a cast roll (first cooling roll).

  When the 1st rotary body 5 has a roll shape, the 1st rotary body 5 shall be equipped with the metallic outer cylinder which has comparatively high rigidity on the surface side from a viewpoint of the moldability of a film-form melt. Is preferred.

  Similarly to the second rotating body 6, the first rotating body 5 is also provided with temperature control means inside. An example of the temperature control means is the same temperature control means as that of the second rotating body 6. The temperature of the first rotating body 5 can be controlled by adjusting the temperature of the fluid and the output of the heater.

  As an example of a preferred embodiment of the first rotating body 5, except for the following, it is the same as the roll shown in FIGS. 3A and 3B exemplified as an example of the preferred embodiment of the second rotating body 6. Rolls.

  The first roll 5 is made of a seamless stainless steel pipe in which the outer cylinder 601 has a relatively high rigidity. The thickness of the outer cylinder 601 is not particularly limited as long as it has high rigidity, and may be, for example, 10 to 100 mm. The diameter in particular of the 1st roll 5 is not restrict | limited, For example, it is preferable that it is the range of 100 mm to 1000 mm. The first roll 5 may be a cylindrical type in which the outer diameter of the central part is equal to the outer diameters of both end parts, or may be a crown roll type in which the outer diameter of the central part is larger than the outer diameters of both end parts.

  The surface of the first rotating body 5 is preferably subjected to a treatment such as chrome plating.

  The specifications of the third rotator 7 and the fourth rotator 8 can be set independently, but may be within the same range as the first rotator 5.

  The peripheral speeds of the third rotating body 7 and the fourth rotating body 8 can be reduced by slowing the film by the thermal shrinkage of the film, or by increasing the peripheral speed to give a peeling force. You may adjust.

  The temperature of the third rotator 7 and the temperature of the fourth rotator 8 are usually independently Tg-150 to Tg ° C, and preferably Tg-100 to Tg-5 ° C.

  The temperature of the 3rd rotary body 7 and the temperature of the 4th rotary body 8 are the temperature of the outer peripheral surface of each rotary body similarly to the temperature of a 1st rotary body, and the temperature of the outer peripheral surface just before contacting a film-form melt. It shall refer to temperature.

(Stretching process)
In this step, the unstretched film 10 peeled off by the peeling roll 9 is guided to a stretching machine 12 through a dancer roll (film tension adjusting roll) 11 where the film 10 is stretched. The molecules in the film are oriented by stretching.

  In the stretching step, usually, at least stretching in the width direction of the film is performed, preferably stretching in the width direction and stretching in the transport direction (also referred to as a longitudinal direction or MD direction).

  In the present invention, the total draw ratio represented by the product of the draw ratio (times) in the width direction and the draw ratio (times) in the transport direction is 2 to 9, preferably 2.5 to 6.5, more preferably. Is 3.2 to 6.5. As a result, it is possible to produce a film that is excellent in smoothness (texture) and in which occurrence of surface failures such as peeling horizontal steps is sufficiently suppressed. If the total draw ratio is too small, the smoothness (texture) of the film may be reduced, or surface failure such as a peeling step may occur. If the total draw ratio is too large, the film breaks.

  The ratio between the stretching ratio in the width direction and the stretching ratio in the transport direction is not particularly limited as long as the object of the present invention is achieved, and may be set as appropriate according to the target optical characteristics or mechanical characteristics. For example, it may be equally stretched in both the width direction and the transport direction, or may be stretched in only one direction.

  The draw ratio in the width direction is usually 1.01 to 3.0 times, preferably 1.2 to 2.8 times, more preferably 1.8 to 2.5 times.

  The stretching ratio in the width direction is the ratio of the length in the width direction after stretching to the length in the width direction before stretching, and can be detected by measuring the length in the width direction before and after stretching.

  The draw ratio in the conveying direction is usually 1.01 to 3.0 times, preferably 1.2 to 2.8 times, more preferably 1.8 to 2.5 times.

  The draw ratio in the carrying direction is the ratio of the length in the carrying direction after drawing to the length in the carrying direction before drawing, and can be controlled by adjusting the ratio between the carrying speed before drawing and the carrying speed after drawing.

  The method for stretching the film in the width direction is not particularly limited, but preferably, a clip tenter method or the like in which both ends in the width direction of the film are held by clips and stretched by applying tension in the width direction can be employed. .

  The method for stretching the film in the conveying direction is not particularly limited, and for example, a roll stretching method for stretching between adjacent rolls, an oven stretching method, or the like can be adopted. A roll stretching method is preferably employed.

  The stretching in the width direction and the conveyance direction may be performed in the width direction and then in the conveyance direction, or may be performed in the reverse order, or the width may be performed. Stretching in the direction and stretching in the transport direction may be performed simultaneously.

  Stretching is usually performed under heating conditions. The stretching temperature in the width direction and the stretching temperature in the transport direction are independently (Tg-30) ° C. or more and (Tg + 100) ° C. or less, preferably Tg−20 ° C. or more and Tg + 70 ° C. or less. Tg is the same as Tg of the film (hereinafter the same).

  In the stretching step, the above-described stretching is performed in the stretching step, and before that, it is preferable to carry out a preheating step in which heating is performed up to the stretching temperature. After the stretching step, it is usually preferable to carry out a holding step and a cooling step.

  The holding stage is a heat setting stage in which the film stretched in the stretching stage is held at the same temperature as that of the stretching stage while tension is applied.

The cooling stage is a stage in which the film heat-set in the holding stage is cooled and relaxed. Usually, the film is held at Tg-100 ° C or higher and Tg ° C or lower, preferably Tg-80 ° C or higher and Tg-20 ° C or lower. Then cool to room temperature.
(Winding process)
The stretched film is usually subjected to a knurling process (embossing process) on both ends of the film by a knurling device comprising an embossing ring 14 and a back roll 15 after the film end is cut into a product width by a slitter 13. Winding is performed by a winder 16. By knurling, sticking in the film (original winding) F and scratches are prevented. As a method of knurl processing, it can be processed by heating or pressurization using a metal ring having an uneven pattern on its side surface. 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 film]
The film produced in the present invention is useful as an optical film. The optical film referred to in the present invention is a film used for an optical device such as a liquid crystal image display device, a plasma image display device, or an organic EL image display device. For example, a polarizing film, a protective film for a polarizing film, a phase difference Examples thereof include a film, a reflective film, an optical compensation film, a viewing angle improving film, an antiglare film, an antireflective film, and an antistatic film. Among the above description, it is preferably used as a functional film such as a protective film or a retardation film used in a liquid crystal image display device.

  When using the optical film of this invention as a functional film of a liquid crystal image display apparatus, the liquid crystal display element of a structure as shown in FIG. 4 can be manufactured, for example.

  In FIG. 4, 21a and 21b are protective films, 22a and 22b are retardation films, 25a and 25b are polarizers, 23a and 23b are slow axis directions of the film, 24a and 24b are transmission axis directions of the polarizer, and 27 is A liquid crystal cell 29 is a liquid crystal display element. Reference numerals 26a and 26b denote polarizing plates, which include a protective film, a retardation film, and a polarizer.

  In such a liquid crystal display element, the optical film of the present invention may be used as the protective films 21a and 21b, or may be used as the retardation films 22a and 22b.

[Film constituent materials]
The material constituting the film of the present invention contains at least a thermoplastic resin, and may contain a stabilizer, a plasticizer, an ultraviolet absorber, a matting agent as a slipping agent, and a retardation control agent as necessary. These materials are appropriately selected depending on the required characteristics of the target film. Hereinafter, although the film constituent material suitable when manufacturing an optical film is demonstrated, various film constituent materials may be used according to a use.

  As the thermoplastic resin, a resin conventionally used in the field of optical films can be used. For example, a cellulose resin is preferably used. The cellulose resin has a cellulose ester structure and is preferably a single or mixed acid ester of cellulose having at least one group selected from a fatty acid acyl group and a substituted or unsubstituted aromatic acyl group. is there.

  Specific examples of the cellulose resin include, for example, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. Among these, particularly preferable cellulose resins include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate. A cellulose resin may be used individually by 1 type, or may be used in combination of 2 or more type.

  Cellulose acetate propionate and cellulose acetate butyrate which are mixed fatty acid esters have an acyl group having 2 to 4 carbon atoms as a substituent, the substitution degree of acetyl group is X, and the substitution degree of propionyl group or butyryl group When Y represents Y, those satisfying the following formulas (I) and (II) are preferred. The degree of substitution is defined as a numerical value indicating the number of hydroxyl groups substituted by an acyl group in glucose units.

Formula (I) 2.6 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
In particular, cellulose acetate propionate is preferably used. Among them, 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9 are preferable. The portion not substituted with the acyl group usually exists as a hydroxyl group.

  The cellulose resin can be synthesized by a known method. The raw material cellulose of the cellulose resin used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferable. A cotton linter is preferably used from the viewpoint of peelability during film formation. Cellulose resins made from these can be used in appropriate mixture or independently.

  The molecular weight of the cellulose resin is not particularly limited. For example, the number average molecular weight is preferably 60,000 to 200,000, particularly preferably 70,000 to 120,000.

  In order to remove foreign substances in the cellulose resin, the melt of the film constituent material can be filtered with the filter 2.

  As the material of the filter 2, conventionally known materials such as ceramics, metal, glass fiber, cellulose fiber, filter paper, and fluororesin such as tetrafluoroethylene resin are preferably used, and ceramics, metal, and the like are particularly preferably used. The absolute filtration accuracy is 50 μm or less, preferably 30 μm or less, more preferably 10 μm or less, and still more preferably 5 μm or less. These can be used in combination as appropriate. The filter can be either a surface type or a depth type, but the depth type is preferable because it is relatively less clogged.

  Additives such as stabilizers, plasticizers, ultraviolet absorbers, matting agents, retardation control agents, etc., which may be contained in the film constituent materials, are those conventionally used as additives in the field of optical films. It can be used.

  The stabilizer suppresses generation of volatile components and deterioration of strength based on alteration or decomposition of the film constituent material. Examples of such stabilizers include hindered phenol antioxidants, acid scavengers, hindered amine light stabilizers, peroxide decomposers, radical scavengers, metal deactivators, amines, and the like.

  As the hindered phenol antioxidant, for example, those described in columns 12-14 of US Pat. No. 4,839,405 can be used. Specific examples include 2,6-dialkylphenol derivative compounds.

  The hindered phenol antioxidant is, for example, a product name “Irganox 1076” and “Irganox 1010” from BASF Japan Ltd. (formerly Ciba Specialty Chemicals). Available from Chemistry as Sumilizer GP.

  Examples of the acid scavenger include epoxy compounds described in US Pat. No. 4,137,201.

  Examples of hindered amine light stabilizers include those described in US Pat. No. 4,619,956, columns 5-11 and US Pat. No. 4,839,405, columns 3-5. Can be used. Specific examples include 2,2,6,6-tetraalkylpiperidine compounds, acid addition salts thereof, or complexes of these with metal compounds.

  The addition amount of the stabilizer is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.005% by mass or more and 3% by mass or less, and further preferably 0.01% by mass with respect to the thermoplastic resin. It is 0.8 mass% or less. Two or more kinds of stabilizers may be used as a mixture, and in that case, the total amount thereof may be within the above range.

  The plasticizer is preferably used in terms of film modification such as improvement of mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability. Further, by adding a plasticizer, the melting temperature of the film constituent material can be lowered, or the melt viscosity of the film constituent material containing the plasticizer can be lowered at the same heating temperature as compared with the thermoplastic resin alone. it can.

  As the plasticizer, for example, phosphate ester derivatives and carboxylic acid ester derivatives are preferably used. Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a mass average molecular weight of 500 or more and 10,000 or less as described in JP-A No. 2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or cyclohexyl An acrylic polymer having a group in the side chain is also preferably used.

  Examples of phosphate ester derivatives include triphenyl phosphate, tricresyl phosphate, phenyl diphenyl phosphate, and the like.

  Examples of carboxylic acid ester derivatives include phthalic acid esters and citric acid esters. Examples of the phthalic acid ester derivative include dimethyl phthalate, diethyl phthalate, dicyclohexyl phthalate, dioctyl phthalate, and diethyl hexyl phthalate. Citric acid esters include acetyl triethyl citrate and acetyl tributyl citrate.

  In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin, trimethylolpropane tribenzoate, and the like can also be mentioned. Alkylphthalylalkyl glycolates are also preferably used for this purpose. The alkyl in the alkylphthalylalkyl glycolate is an alkyl group having 1 to 8 carbon atoms. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl glycolate, Ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl glycolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl Phthalyl ethyl glycolate, propyl phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl Cholate, octyl phthalyl methyl glycolate, and an octyl phthalyl ethyl glycolate, and the like.

  The addition amount of the plasticizer is preferably 0.5% by mass or more and less than 20% by mass, more preferably 1% by mass or more and less than 11% by mass with respect to the thermoplastic resin. Two or more kinds of plasticizers may be used in combination, and in that case, the total amount thereof may be within the above range.

  The ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the polarizer and the display device with respect to ultraviolet rays, and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. Those are preferred. Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Less benzotriazole compounds are preferred. Moreover, you may use the ultraviolet absorber of Unexamined-Japanese-Patent No. 10-182621, Unexamined-Japanese-Patent No. 8-337574, and the polymeric ultraviolet absorber of Unexamined-Japanese-Patent No. 6-148430.

  Ultraviolet absorbers are available, for example, as commercially available TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by BASF Japan Ltd. (formerly Ciba Specialty Chemicals)).

  The addition amount of a ultraviolet absorber is 0.1-20 mass% with respect to a thermoplastic resin, Preferably it is 0.5-10 mass%, More preferably, it is 1-5 mass%. Two or more kinds of ultraviolet absorbers may be used in combination, and in that case, the total amount thereof may be within the above range.

  The matting agent improves the slipperiness, transportability, winding property and strength of the film. The matting agent is preferably as fine as possible. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include inorganic fine particles such as magnesium silicate and calcium phosphate, and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. In many cases, fine particles such as silicon dioxide are surface-treated with an organic material, but such a material is preferable because it can reduce the haze of the film.

  Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazane, siloxane and the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency. The average particle size of the secondary particles of the fine particles is in the range of 0.005 to 1.0 μm. The average particle size of the secondary particles of preferable fine particles is 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used for generating irregularities of 0.01 to 1.0 μm on the film surface. The content of the fine particles is preferably 0.005 to 0.3% by mass with respect to the thermoplastic resin.

  Examples of the fine particles of silicon dioxide include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Nippon Aerosil Co., Ltd., preferably Aerosil 200V, R972, R972V, R974, R202, and R812. Two or more kinds of these fine particles may be used in combination.

  It is preferable that the matting agent is added before the film constituent material is melted or is previously contained in the film constituent material. For example, after mixing and dispersing fine particles previously dispersed in a solvent and cellulose resin and / or other additives such as a plasticizer and an ultraviolet absorber, the solvent is volatilized or the matting agent is preliminarily formed into a film by a precipitation method. Included in the material. By using such a film constituent material, the matting agent can be uniformly dispersed in the thermoplastic resin.

  The retardation control agent is preferably used particularly as an optical film, for example, when producing a film. As the retardation control agent, an aromatic compound having two or more aromatic rings as described in European Patent No. 911,656A2 can be used. 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. Particularly preferred is an aromatic heterocycle, and the aromatic heterocycle is generally an unsaturated heterocycle. Of these, a 1,3,5-triazine ring is particularly preferred.

  When adding a stabilizer, a plasticizer, and the above-mentioned other additives to the thermoplastic resin, the total amount of additives including them is 1% by mass or more and 30% by mass or less, preferably 5 to 5% by mass. 20 mass%.

  As the film constituent material, a polymer material other than cellulose resin or an oligomer may be appropriately selected and mixed. Such a polymer material or oligomer preferably has excellent compatibility with the cellulose resin, and the transmittance is 80% or more, preferably 90% or more, more preferably over the entire visible region (400 nm to 800 nm) when formed into a film. Is 92% or more. The purpose of mixing at least one of polymer materials and oligomers other than the cellulose resin includes meanings for the purpose of improving viscosity control during heating and melting and improving film physical properties after film processing.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Example 1>
(Pellet creation)
100 parts by weight of cellulose acetate propionate (acetyl group substitution degree 1.95, propionyl group substitution degree 0.7, number average molecular weight 75000, dried at 100 ° C. for 5 hours)
Trimethylolpropane tris (3,4,5-trimethoxybenzoate) 10 parts by mass IRGANOX-1010 (manufactured by BASF Japan Ltd. (formerly Ciba Specialty Chemicals)) 1 part by weight Sumizer GP (manufactured by Sumitomo Chemical) 1 part by weight Silica particles (Aerosil R972V (produced by Nippon Aerosil Co., Ltd.)) 0.05 parts by mass as the matting agent and TINUVIN 360 (manufactured by BASF Japan Ltd. (former Ciba Specialty Chemicals)) 0.5 as the ultraviolet absorber. After adding a mass part, it mixed for 30 minutes with the V-type mixer which enclosed nitrogen gas, it was made to melt at 240 degreeC using the twin-screw extruder (PCM30 Co., Ltd. Ikegai Co., Ltd.) which attached the strand die, and length A cylindrical pellet having a diameter of 4 mm and a diameter of 3 mm was produced. The shear rate at this time was set to 25 (/ s). The Tg of the pellet was 135 ° C., and the temperature was defined as the Tg of the film.

(Film production)
The film was manufactured with the manufacturing apparatus shown in FIGS.

  A casting die having a lip clearance of 1.0 mm and a lip portion average surface roughness Ra of 0.01 μm was used. The temperature of the lip portion of the casting die was controlled at 250 ° C.

  The cast roll 5 was the same as the roll configuration shown in FIGS. 3A and 3B except that the outer cylinder was made of a seamless stainless steel pipe having high rigidity. The cast roll 5 had a diameter of 40 cm, and the outer peripheral surface of the outer cylinder was hard chrome plated. The surface roughness Ra of the cast roll 5 was 100 nm. The surface temperature of the cast roll 5 was controlled to 110 ° C. during film production by adjusting the temperature of temperature adjusting oil (cooling fluid) circulated inside.

  The elastic touch roll 6 was the same as the roll configuration shown in FIGS. 3 (A) and 3 (B). The elastic touch roll 6 has a diameter of 30 cm, and hard chrome plating was applied to the outer peripheral surface of the outer cylinder. The surface roughness Ra of the elastic touch roll 6 was 125 nm. The wall thickness of the outer cylinder was 5 mm. The surface temperature of the elastic touch roll 6 was controlled at 80 ° C. during film production by adjusting the temperature of temperature adjusting oil (cooling fluid) circulated inside.

  The second cooling roll 7 and the third cooling roll 8 were the same as the cast roll 5. The surface roughness Ra of the second cooling roll 7 and the third cooling roll 8 was 100 nm. The surface temperature of the second cooling roll 7 was controlled to 80 ° C. by adjusting the temperature of temperature adjusting oil (cooling fluid) circulated inside. The surface temperature of the third cooling roll 8 was controlled to 50 ° C. during film production by adjusting the temperature of temperature adjusting oil (cooling fluid) circulated inside.

  The surface temperature of each of the elastic touch roll 6, cast roll 5, second cooling roll 7, and third cooling roll 8 is the roll surface at a position 90 ° before the rotation direction from the position where the film first contacts the roll. The average value obtained by measuring 10 points in the width direction with a non-contact thermometer was defined as the surface temperature of each roll.

  The film-forming speed means the peripheral speed of the cast roll 5 and is 20 m / min.

  The peripheral speeds of the elastic touch roll 6, the second cooling roll 7, and the third cooling roll 8 were adjusted to the film forming speed.

  After the melt was discharged from the lip portion of the casting die, the distance until it contacted the rotating roll was 100 mm.

  The film manufacturing method will be specifically described below.

  The obtained pellets (water content 50 ppm) were melted in a single screw extruder 1 and subjected to pressure filtration using a leaf disk type metal filter 2. Thereafter, the film-like melt was directly extruded and pressed between the cast roll 5 and the touch roll 6 from the lip portion of the casting die 4 to obtain a cast film having a draw ratio of 10 and a film thickness of 100 μm. At the time of pressing, the film was pressed on the cast roll 5 with the touch roll 6 at a linear pressure of 5 N / mm. Thereafter, the film was cooled while being conveyed by the second cooling roll 7 and the third cooling roll 8.

  The unstretched film 10 peeled off by the peeling roll 9 was guided to a stretching machine 12 through a dancer roll (film tension adjusting roll) 11 where the film 10 was stretched. Specifically, the film was stretched in the longitudinal direction at 160 ° C. by a roll stretching method, and then stretched in the width direction at 150 ° C. by a clip tenter method (stretching stage). The stretched film was held at the same temperature as the stretching step and heat-set with the tension applied (holding step). The heat-set film was held at 100 ° C. and then cooled to room temperature (cooling stage). As a result, a stretching of 1.6 times in the width direction and 1.6 times in the conveying direction was achieved.

  A clip gripping part was cut off from the obtained film, a knurling process having a width of 10 mm and a height of 5 μm was applied to both ends of the film, and a film having a thickness of 40 μm slit to a width of 1430 mm was obtained.

<Examples 2 to 12 / Comparative Examples 1 to 6>
A film was produced in the same manner as in Example 1 except that the surface roughness Ra of the elastic touch roll 6 and the cast roll 5 and the stretching ratio were controlled to the predetermined values described in the table.

  The surface roughness Ra of the elastic touch roll 6 and the cast roll 5 was controlled by selecting and using an abrasive when the outer peripheral surface was polished with the abrasive.

  The draw ratio was controlled by adjusting the roll peripheral speed difference (MD stretch) and the (tenter) clip rail width (TD stretch).

<Evaluation>
The film before stretching and the film as the final product were evaluated for the following evaluation items. The total draw ratio was also evaluated.
(Total draw ratio)
A: The total draw ratio was sufficiently large;
○: Total stretch ratio was large;
X: The total draw ratio was small.
(Before stretching; peeling step)
The film was projected, and visual observation was performed on the peeling horizontal stage generated in the width direction. A: No horizontal stage was observed when the angle of the film was set to 30 ° with respect to the light source.
○: When the film angle was set to 30 ° with respect to the light source, a slight horizontal row was observed, but there was no practical problem;
Δ: When the angle of the film with respect to the light source was set to 45 °, a horizontal stage was observed, which was practically problematic as it was, but was at a level that could be recovered (no practical problem);
X: When the angle of the film with respect to the light source was set to 90 °, a horizontal stage was observed, which was a level that could not be recovered (practically problematic).
(Before stretching; smoothness)
Visual observation of the contact surface of the film with the touch roll ◎; The surface had excellent texture;
○: Although the surface was slightly satin-like, there was no practical problem;
Δ: The surface is satin-like, and there is a problem in practical use as it is, but it was at a level that can be recovered (no problem in practical use);
X: The surface was satin-like, and was a level that could not be recovered (practically problematic).
(Product; peeling horizontal)
The film was projected, and visual observation was performed on the peeling horizontal stage generated in the width direction. A: No horizontal stage was observed when the angle of the film was set to 20 ° with respect to the light source;
○: When the film was set at an angle of 20 ° with respect to the light source, horizontal rows were slightly observed, but there was no practical problem;
Δ: When the angle of the film with respect to the light source was set to 30 °, a horizontal row was slightly observed, but there was no problem in practical use;
X: When the angle of the film with respect to the light source was set to 45 °, a horizontal stage was observed, and there was a problem in practical use.
(Product; smoothness)
Visual observation of the contact surface of the film with the touch roll ◎; The surface had very good texture;
○: The surface was slightly satin but had good texture;
Δ: The surface was satin-like, but there was no practical problem;
X: The surface was satin-like, and there was a problem in practical use.
(Comprehensive evaluation)
Overall evaluation of peel horizontal and smoothness evaluation results for product ◎; Both evaluation results were ◎;
○: Both evaluation results were ○ or more;
Δ: Both evaluation results were Δ or more;
X: One or more of x were included in both evaluation results.

  FIG. 5 is a graph showing the relationship between the total draw ratio and the surface roughness of the touch roll in Examples / Comparative Examples, together with the results of comprehensive evaluation.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 1st rotary body (cast roll; 1st cooling roll)
6 Second rotating body (touch roll)
7 Third rotating body (second cooling roll)
8 Fourth rotating body (third cooling roll)
9, 11, 13, 14, 15 Transport roll 10 Unstretched film 12 Stretcher 16 Winding device 21a, 21b Protective film 22a, 22b Retardation film 23a, 23b Film slow axis direction 24a, 24b Polarizer transmission axis Direction 25a, 25b Polarizer 26a, 26b Polarizing plate 27 Liquid crystal cell 29 Liquid crystal display device 42 Melt 43 Nip part

Claims (4)

A film-constituting material containing a molten thermoplastic resin is continuously extruded from a casting die into a film shape, and the film-shaped melt is circumscribed by a first rotating body to be cooled and solidified. A method for producing a film that is stretched after being pressed against the surface of a first rotating body by a rotating body,
The arithmetic average surface roughness Ra of the second rotating body is 110 to 300 nm,
A method for producing a film, characterized in that a total draw ratio represented by a product of a draw ratio (times) in the width direction and a draw ratio (times) in the transport direction is 2 to 9.   The method for producing a film according to claim 1, wherein the second rotating body has an arithmetic average surface roughness Ra of 140 to 210 nm.   The method for producing a film according to claim 1 or 2, wherein the total draw ratio is 3.2 to 6.5.   4. The method for producing a film according to claim 1, wherein the arithmetic mean surface roughness Ra of the first rotating body is 110 to 300 nm.